U.S. patent application number 12/692559 was filed with the patent office on 2010-07-22 for feedforward control system for a solar tracker.
Invention is credited to Kenneth Oosting.
Application Number | 20100185333 12/692559 |
Document ID | / |
Family ID | 42335957 |
Filed Date | 2010-07-22 |
United States Patent
Application |
20100185333 |
Kind Code |
A1 |
Oosting; Kenneth |
July 22, 2010 |
FEEDFORWARD CONTROL SYSTEM FOR A SOLAR TRACKER
Abstract
A feedforward control system for a solar tracker that includes a
solar tracker apparatus including at least two actuators and having
a driver system for driving the actuators. The system includes a
means for acquiring solar position angles for a given location,
date and time. The system includes a computer including a program
for performing mathematical calculations, the program being capable
of: acquiring a plurality of solar position angles for a given day,
arranging timing of the solar position angles for use in at least
one spline curve that relates the solar position angles to the
plurality of actuators, calculating the spline curve and its
coefficients, calculating a first derivative of the spline curve,
using the spline curve and first derivative of the spline curve to
calculate drive requirements of the actuators, creating outputs,
and communicating the outputs to the driver system to drive the
actuators to desired positions.
Inventors: |
Oosting; Kenneth; (Rocklin,
CA) |
Correspondence
Address: |
Jones Day;Attn: Peter G. Thurlow
222 East 41st Street
New York
NY
10017
US
|
Family ID: |
42335957 |
Appl. No.: |
12/692559 |
Filed: |
January 22, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61146508 |
Jan 22, 2009 |
|
|
|
61171263 |
Apr 21, 2009 |
|
|
|
61254963 |
Oct 26, 2009 |
|
|
|
Current U.S.
Class: |
700/279 ;
700/275; 700/282; 702/94 |
Current CPC
Class: |
Y02E 10/47 20130101;
F24S 50/20 20180501; F24S 2030/11 20180501; F24S 2030/17 20180501;
F24S 30/455 20180501; F24S 2030/115 20180501; Y02B 10/20 20130101;
F24S 2030/134 20180501; F24S 25/617 20180501; F24S 25/10 20180501;
F24S 2030/15 20180501 |
Class at
Publication: |
700/279 ; 702/94;
700/282; 700/275 |
International
Class: |
G05D 3/20 20060101
G05D003/20; G01C 25/00 20060101 G01C025/00; G05D 7/06 20060101
G05D007/06; G01M 1/38 20060101 G01M001/38 |
Claims
1. A feedforward control system for a solar tracker comprising: a
solar tracker apparatus including a plurality of actuators having a
driver system for driving the actuators; means for acquiring solar
position angles for a given location, date and time; and a computer
including a program for performing mathematical calculations,
wherein the program is capable of performing the following steps:
acquiring a plurality of solar position angles for a given day,
arranging timing of the solar position angles for use in at least
one spline curve, wherein the spline curves relate the solar
position angles to the plurality of actuators, calculating the
spline curves including the spline curve's coefficients,
calculating a first derivative of the spline curves, using the
spline curves and the first derivative of the spline curves to
calculate drive requirements of the actuators, creating outputs,
and communicating the outputs to the driver system to drive the
actuators to desired positions.
2. The system according to claim 1, wherein the driver system
includes a hydraulic system.
3. The system according to claim 2, wherein the program further
comprises the step of calculating the fluid flow rate required to
drive the actuators.
4. The system according to claim 1, wherein the program further
comprises the step of accepting an input for the driver system to
drive the actuators in a fashion such that the drive is advanced to
compensate for system hysteresis.
5. The system according to claim 1, wherein the program further
comprises the step of calculating a delta-time value for the driver
system to drive the actuators in a fashion such that the drive is
advanced to compensate for system hysteresis.
6. The system according to claim 1, wherein the program further
comprises the steps of: acquiring expected position values of the
actuators; reading inputs to acquire actual position values of the
actuators; and comparing the actual position values of the
actuators to the expected position values of the actuators in real
time without a delta-time, and calculating an error.
7. The system according to claim 6, wherein the program further
comprises the step of accepting at least one input to modify the
spline curve's calculations.
8. The system according to claim 6, wherein the program further
comprises the step of calculating a gain to modify the spline
curve's calculations.
9. The system according to claim 1, wherein the program further
comprises the steps of: accepting sensor input data; and performing
calibration of solar position angles.
10. The system according to claim 1, wherein the program further
comprises the step of controlling the driver movement through
feedforward calculations with position feedback that is used to
verify and adjust driver movement to achieve a desired position
trajectory of the solar tracker apparatus.
11. The system according to claim 1, wherein the program further
comprises the step of using angular position feedback from at least
one actuator to modify the position of the solar tracker apparatus
and to update the feedforward control system.
12. The system according to claim 1, wherein the spline curves are
constrained to have continuous functions for at least the first
derivatives.
13. The system according to claim 1, wherein the computer stores
data tables that contain coefficients for the spline curves, and
wherein the coefficients are part of an equation showing the
positions of the actuators as a function of time.
14. The system according to claim 1, wherein the program further
comprises the step of acquiring inputs including time of day, date,
GPS coordinates, and orientation of the tracker apparatus.
15. A feedforward control system for a solar tracker comprising: a
solar tracker apparatus including a plurality of actuators having a
driver system for driving the actuators; means for acquiring solar
position angles for a given location, date and time; and a computer
including a program for performing mathematical calculations,
wherein the program is capable of performing the following steps:
acquiring a plurality of solar position angles for a given day,
arranging timing of the solar position angles for use in at least
one spline curve, wherein the spline curves relate the solar
position angles to the plurality of actuators, calculating the
spline curves including the spline curve's coefficients,
calculating a first derivative of the spline curves, using the
spline curves and the first derivative of the spline curves to
calculate drive requirements of the actuators, creating outputs,
communicating the outputs to the driver system to drive the
actuators to desired positions, receiving sensor data when the
solar tracker apparatus is aimed at the sun within a given
tolerance, communicating the sensor data to the computer,
calculating the error between expected solar tracker apparatus
positions and actual solar tracker apparatus positions, and
generating a plurality of offset angles for use in correcting error
for future movements of the solar tracker apparatus.
16. The system according to claim 15, wherein the sensor data is
obtained from a sensor disposed in a tube member connected to the
solar tracker.
17. The system according to claim 16, wherein the sensor is a
machine vision sensor.
18. The system according to claim 15, wherein the sensor data is
obtained from a measured output of energy from one or more solar
panels on the solar tracker.
19. The system according to claim 18, wherein the program further
comprises the step of communicating the energy output to the
computer.
20. The system according to claim 15, wherein the program further
comprises the step of determining the actual position of the solar
tracker by moving the solar tracker apparatus such that a line
orthogonal to a plane of the solar panel sweeps in circular search
patterns, with each iteration increasing the radius of the circle
until it detects the sun.
21. The system according to claim 15, wherein data including
position and time where the sun is first detected and last detected
is recorded, and used in calculations that use motion of the solar
tracker apparatus, motion of the sun across the sky, and size and
geometric characteristics of the sun.
22. The system according to claim 15, wherein the program further
comprises the step of adding the offset angles to the outputs.
23. The system according to claim 15, wherein the program further
comprises the step of using corrections as solar angle inputs such
that the outputs incorporate the corrections.
24. A calibration system for a solar tracker comprising: a solar
tracker apparatus including a plurality of actuators having a
driver system for driving the actuators; level sensors capable of
detecting when the apparatus is level within a given tolerance; a
computer including a program that communicates with the driver
system to drive the actuators to desired positions, wherein the
program is capable of performing the following steps: communicating
with the level sensors when the apparatus is level with a given
tolerance and communicating an actual position for level to the
control system, calculating the error between an expected position
for level and the actual position for level, generating a plurality
of offset angles for use in correcting error for future movements
of the solar tracker apparatus, creating outputs, and communicating
the outputs to the driver system to drive the actuators to desired
positions.
25. The system according to claim 24, wherein the program further
comprises the step of adding the offset angles to the outputs.
26. The system according to claim 24, wherein the program further
comprises the step of using the corrections as solar angle inputs
such that the outputs incorporate the corrections.
27. A feedforward control system for a solar tracker comprising: a
solar tracker apparatus including a plurality of actuators having a
driver system for driving the actuators, wherein the driver system
includes a hydraulic system; means for acquiring solar position
angles for a given location, date and time; and a computer
including a program for performing mathematical calculations,
wherein the program is capable of performing the following steps:
acquiring a plurality of solar position angles for a given day,
acquiring inputs including time of day, date, GPS coordinates, and
orientation of the tracker apparatus, arranging timing of the solar
position angles for use in at least one spline curve, wherein the
spline curves relate the solar position angles to the plurality of
actuators, and the spline curves are constrained to have continuous
functions for at least a first derivatives, calculating the spline
curves including spline curve coefficients, calculating the first
derivative of the spline curves, using the spline curves and the
first derivative of the spline curves to calculate drive
requirements of the actuators, calculating the fluid flow rate
required to drive the actuators, creating outputs, communicating
the outputs to the driver system to drive the actuators to desired
positions, acquiring expected position values of the actuators,
reading inputs to acquire actual position values of the actuators,
comparing the actual position values of the actuators to the
expected position values of the actuators in real time without a
delta-time, and calculating an error, calculating a gain to modify
the spline curve's calculations, using angular position feedback
from at least one actuator to modify the position of the solar
tracker apparatus and to update the feedforward control system,
generating a plurality of offset angles, using the offset angles as
inputs in the feedforward control system such that the outputs
incorporate the corrections, and calculating a delta-time value for
the driver system to drive the actuators in a fashion such that the
drive is advanced to compensate for system hysteresis.
28. A feedforward control system for a solar tracker comprising: a
solar tracker apparatus including a plurality of actuators having a
driver system for driving the actuators, wherein the driver system
includes a hydraulic system; means for acquiring solar position
angles for a given location, date and time; level sensors capable
of detecting when the apparatus is level within a given tolerance;
sensors capable of measuring the energy output from at least one
solar panel mounted on the solar tracker apparatus that are aimed
within a specified tolerance of a line orthogonal to a plane of the
solar panel; a computer including a program for performing
mathematical calculations, wherein the program is capable of
performing the following steps: acquiring a plurality of solar
position angles for a given day, acquiring inputs including time of
day, date, GPS coordinates, and orientation of the tracker
apparatus, communicating the energy output to the computer, wherein
data including position and time where the sun is first detected
and last detected is recorded and used in calculations that use
motion of the solar tracker apparatus, motion of the sun across the
sky, and size and geometric characteristics of the sun, arranging
timing of the solar position angles for use in at least one spline
curve, wherein the spline curves relate the solar position angles
to the plurality of actuators, and the spline curves are
constrained to have continuous functions for at least the first
derivatives, communicating with the level sensors when the
apparatus is level with a given tolerance and communicating an
actual position for level to the control system, calculating the
error between an expected position for level and the actual
position for level, calculating the spline curves including the
spline curve's coefficients, calculating the first derivative of
the spline curves, using the spline curves and the first derivative
of the spline curves to calculate drive requirements of the
actuators, calculating the fluid flow rate required to drive the
actuators, creating outputs, communicating the outputs to the
driver system to drive the actuators to desired positions,
controlling the driver movement through feedforward calculations
with position feedback that is used to verify and adjust driver
movement to achieve a desired position trajectory of the solar
tracker apparatus, acquiring expected position values of the
actuators, reading inputs to acquire actual position values of the
actuators, comparing the actual position values of the actuators to
the expected position values of the actuators in real time without
a delta-time, and calculating an error, using angular position
feedback from at least one actuator to modify the position of the
solar tracker apparatus and to update the feedforward control
system, generating a plurality of offset angles, using the offset
angles as inputs in the feedforward control system such that the
outputs incorporate the corrections, and calculating a delta-time
value for the driver system to drive the actuators in a fashion
such that the drive is advanced to compensate for system
hysteresis; data tables stored in the computer that contain
coefficients for the spline curves, wherein the coefficients are
part of an equation showing the positions of the actuators as a
function of time.
29. A calibration system for a solar tracker comprising: a solar
tracker apparatus including a plurality of actuators having a
driver system for driving the actuators; means for acquiring solar
position angles for a given location, date and time; and a computer
including a program for performing mathematical calculations,
wherein the program is capable of performing the following steps:
acquiring a plurality of solar position angles for a given day,
creating outputs, communicating the outputs to the driver system to
drive the actuators to desired positions, receiving sensor data
when the solar tracker apparatus is aimed at the sun within a given
tolerance, communicating the sensor data to the computer,
calculating the error between expected solar tracker apparatus
positions and actual solar tracker apparatus positions, and
generating a plurality of offset angles for use in correcting error
for future movements of the solar tracker apparatus.
30. The system according to claim 29, wherein the sensor data is
obtained from a sensor disposed in a tube member connected to the
solar tracker.
31. The system according to claim 30, wherein the sensor is a
machine vision sensor.
32. The system according to claim 29, wherein the sensor data is
obtained from a measured output of energy from one or more solar
panels on the solar tracker.
33. The system according to claim 32, wherein the program further
comprises the step of communicating the energy output to the
computer.
34. The system according to claim 29, wherein the program further
comprises the step of determining the actual position of the solar
tracker by moving the solar tracker apparatus such that a line
orthogonal to a plane of the solar panel sweeps in circular search
patterns, with each iteration increasing the radius of the circle
until it detects the sun.
35. The system according to claim 29, wherein data including
position and time where the sun is first detected and last detected
is recorded, and used in calculations that use motion of the solar
tracker apparatus, motion of the sun across the sky, and size and
geometric characteristics of the sun.
36. The system according to claim 29, wherein the program further
comprises the step of adding the offset angles to the outputs.
37. The system according to claim 29, wherein the program further
comprises the step of using corrections as solar angle inputs such
that the outputs incorporate the corrections.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to provisional application
Nos. 61/146,508, which was filed in the U.S. Patent and Trademark
Office ("USPTO") on Jan. 22, 2009; 61/171,263, which was filed in
the USPTO on Apr. 21, 2009; and 61/254,963, which was filed in the
USPTO on Oct. 26, 2009.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] This application is not the subject of any federally
sponsored research or development.
THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT
[0003] There has been no joint research agreements entered into
with any third parties.
BACKGROUND OF THE EMBODIMENTS OF THE PRESENT INVENTION
[0004] Control systems for solar generation apparatuses and devices
for tracking the sun across the sky are known in the art. A number
of existing systems use simple control methodologies to enable
solar panels to track the sun periodically during daylight hours.
The systems described in this application improve upon existing
solar tracker systems by, among other things, using a complex
feedforward control system for smooth and continuous tracking of
the sun across the sky to improve reliability, efficiency, and
accuracy of solar trackers.
BRIEF SUMMARY OF THE EMBODIMENTS OF THE PRESENT INVENTION
[0005] An embodiment of the present invention is directed to a
feedforward control system for a solar tracker that includes a
solar tracker apparatus including at least two actuators and having
a driver system for driving the actuators. Further, the system
includes a means for acquiring solar position angles for a given
location, date and time. Additionally, the system includes a
computer including a program for performing mathematical
calculations, where the program is capable of performing the steps
of: acquiring a plurality of solar position angles for a given day,
arranging timing of the solar position angles for use in at least
one spline curve that relates the solar position angles to the
plurality of actuators, calculating the spline curve including
spline curve coefficients, calculating a first derivative of the
spline curve, using the spline curve and the first derivative of
the spline curve to calculate drive requirements of the actuators,
creating outputs, and communicating the outputs to the driver
system to drive the actuators to desired positions.
[0006] Another embodiment of the present invention is directed to a
feedforward control system for a solar tracker that includes a
solar tracker apparatus including at least two actuators and having
a driver system for driving the actuators. Further, the system
includes a means for acquiring solar position angles for a given
location, date and time. Additionally, the system includes a
computer including a program for performing mathematical
calculations, where the program is capable of performing the steps
of: acquiring a plurality of solar position angles for a given day,
arranging timing of the solar position angles for use in at least
one spline curve that relates the solar position angles to the
plurality of actuators, calculating the spline curve including
spline curve coefficients, calculating a first derivative of the
spline curve, using the spline curve and the first derivative of
the spline curve to calculate drive requirements of the actuators,
creating outputs, communicating the outputs to the driver system to
drive the actuators to desired positions, receiving sensor data
when the solar tracker apparatus is aimed at the sun within a given
tolerance, communicating the sensor data to the computer,
calculating the error between expected solar tracker apparatus
positions and actual solar tracker apparatus positions, and
generating a plurality of offset angles for use in correcting error
for future movements of the solar tracker apparatus.
[0007] Yet another embodiment of the present invention is directed
to a calibration system for a solar tracker that includes a solar
tracker apparatus including at least two actuators and having a
driver system for driving the actuators. Further, the system
includes level sensors capable of detecting when the apparatus is
level within a given tolerance. Additionally, the system includes a
computer including a program that communicates with the driver
system to drive the actuators to desired positions, where the
program is capable of performing the steps of: communicating with
the level sensors to detect when the apparatus is level with a
given tolerance and communicating the actual position for level to
the control system, calculating the error between an expected
position for level and the actual position for level, generating a
plurality of offset angles for use in correcting error for future
movements of the solar tracker apparatus, creating outputs, and
communicating the outputs to the driver system to drive the
actuators to desired positions.
[0008] Another embodiment of the present invention is directed to a
feedforward control system for a solar tracker that includes a
solar tracker apparatus including at least two actuators and having
a hydraulic driver system for driving the actuators. Further, the
system includes a means for acquiring solar position angles for a
given location, date and time. Additionally, the system includes a
computer including a program for performing mathematical
calculations, where the program is capable of performing the steps
of: acquiring a plurality of solar position angles for a given day,
acquiring inputs including time of day, date, GPS coordinates, and
orientation of the tracker apparatus, and arranging timing of the
solar position angles for use in at least one spline curve that
relates the solar position angles to the plurality of actuators,
where the spline curve is constrained to have continuous function
for at least a first derivative. The program is also capable of
performing the steps of: calculating the spline curve including
spline curve coefficients, calculating the first derivative of the
spline curve, using the spline curve and the first derivative of
the spline curve to calculate drive requirements of the actuators,
calculating the fluid flow rate required to drive the actuators,
creating outputs, communicating the outputs to the driver system to
drive the actuators to desired positions, acquiring expected
position values of the actuators, reading inputs to acquire actual
position values of the actuators, comparing the actual position
values of the actuators to the expected position values of the
actuators in real time without a delta-time, and calculating an
error, calculating a gain to modify spline curve calculations,
using angular position feedback from at least one actuator to
modify the position of the solar tracker apparatus and to update
the feedforward control system, generating a plurality of offset
angles, using the offset angles as inputs in the feedforward
control system such that the outputs incorporate the corrections,
and calculating a delta-time value for the driver system to drive
the actuators in a fashion such that the drive is advanced to
compensate for system hysteresis.
[0009] Yet another embodiment of the present invention is directed
to a feedforward control system for a solar tracker that includes a
solar tracker apparatus including at least two actuators and having
a hydraulic driver system for driving the actuators. Further, the
system includes a means for acquiring solar position angles for a
given location, date and time. The system also includes level
sensors capable of detecting when the apparatus is level within a
given tolerance and sensors capable of measuring the electrical
output from at least one solar panel mounted on the solar tracker
apparatus that are aimed within a specified tolerance of the
central axis of the solar panel and orthogonal to the solar panel.
Additionally, the system includes a computer including a program
for performing mathematical calculations, where the program is
capable of performing the steps of: acquiring a plurality of solar
position angles for a given day, acquiring inputs including time of
day, date, GPS coordinates, and orientation of the tracker
apparatus, and communicating the electrical output to the computer,
where data including position and time where the sun is first
detected and last detected is recorded and used in calculations
that use motion of the solar tracker apparatus, motion of the sun
across the sky, and size and geometric characteristics of the sun.
The program is also capable of performing the step of arranging
timing of the solar position angles for use in at least one spline
curve that relates the solar position angles to the plurality of
actuators, where the spline curve is constrained to have continuous
function for at least a first derivative. Further, the program is
capable of performing the steps of: communicating with the level
sensors when the apparatus is level with a given tolerance and
communicating an actual position for level to the control system,
calculating the error between an expected position for level and
the actual position for level, calculating the spline curve
including spline curve coefficients, calculating the first
derivative of the spline curve, using the spline curve and the
first derivative of the spline curve to calculate drive
requirements of the actuators, calculating the fluid flow rate
required to drive the actuators, creating outputs, communicating
the outputs to the driver system to drive the actuators to desired
positions, controlling the driver movement through feedforward
calculations with position feedback that is used to verify and
adjust driver movement to achieve a desired position trajectory of
the solar tracker apparatus, acquiring expected position values of
the actuators, reading inputs to acquire actual position values of
the actuators, and comparing the actual position values of the
actuators to the expected position values of the actuators in real
time without a delta-time, and calculating an error. The program is
also capable of performing the steps of: using angular position
feedback from at least one actuator to modify the position of the
solar tracker apparatus and to update the feedforward control
system, generating a plurality of offset angles, using the offset
angles as inputs in the feedforward control system such that the
outputs incorporate the corrections, and calculating a delta-time
value for the driver system to drive the actuators in a fashion
such that the drive is advanced to compensate for system
hysteresis. Additionally, the system includes data tables stored in
the computer that contain coefficients for the spline curves, where
the coefficients are part of an equation showing the positions of
the actuators as a function of time.
[0010] Another embodiment of the present invention is directed to a
calibration system for a solar tracker that includes a solar
tracker apparatus including at least two actuators and having a
driver system for driving the actuators. Further, the system
includes a means for acquiring solar position angles for a given
location, date and time. Additionally, the system includes a
computer including a program that is capable of performing the
steps of acquiring a plurality of solar position angles for a given
day, creating outputs, communicating the outputs to the driver
system to drive the actuators to desired positions, receiving
sensor data when the solar tracker apparatus is aimed at the sun
within a given tolerance, communicating the sensor data to the
computer, calculating the error between expected solar tracker
apparatus positions and actual solar tracker apparatus positions,
and generating a plurality of offset angles for use in correcting
error for future movements of the solar tracker apparatus.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0011] Preferred features of embodiments of the present invention
are disclosed in the accompanying drawings, wherein similar
reference characters denote similar elements throughout the several
views, and wherein:
[0012] FIG. 1 is a front perspective view of a feedforward
controlled solar tracker, according to an embodiment of the present
invention;
[0013] FIG. 2 is a front/side perspective view of a feedforward
controlled solar tracker in the early morning position, according
to an embodiment of the present invention;
[0014] FIG. 2A is a detail showing the joint connector of a
feedforward controlled solar tracker, according to an embodiment of
the present invention;
[0015] FIG. 2B is a detail showing the linking mechanism of a
feedforward controlled solar tracker, according to an embodiment of
the present invention;
[0016] FIG. 3 is a side perspective view of a feedforward
controlled solar tracker in the mid afternoon position, according
to an embodiment of the present invention;
[0017] FIG. 3A is a detail showing the joint connector of a
feedforward controlled solar tracker, according to an embodiment of
the present invention;
[0018] FIG. 3B is a detail showing the linking mechanism of a
feedforward controlled solar tracker, according to an embodiment of
the present invention;
[0019] FIG. 4 is a front/side perspective view of a feedforward
controlled solar tracker, according to an embodiment of the present
invention;
[0020] FIG. 5 is a side plan view of a feedforward controlled solar
tracker, according to an embodiment of the present invention;
[0021] FIG. 6A is a depiction of the location of the bases of a
feedforward controlled solar tracker configured in a right angle
triangle position, according to an embodiment of the present
invention;
[0022] FIG. 6B is a depiction of the location of the bases of a
feedforward controlled solar tracker configured in an isosceles
triangle position, according to an embodiment of the present
invention;
[0023] FIG. 6C is depiction of the location of the bases of a
feedforward controlled solar tracker configured in an equilateral
triangle position, according to an embodiment of the present
invention;
[0024] FIG. 7 is a front/side perspective view of a linking
mechanism used to connect the post to a platform/sub-frame of a
feedforward controlled solar tracker, according to an embodiment of
the present invention;
[0025] FIG. 8 is a front perspective view of a linking mechanism in
the form of a pillow block bearing assembly used to connect the
post to a platform/sub-frame of a feedforward controlled solar
tracker, according to an embodiment of the present invention;
[0026] FIG. 9A is a depiction of the actuator bases and post base
of a feedforward controlled solar tracker, which are stabilized by
torsion resistance bars, according to an embodiment of the present
invention;
[0027] FIG. 9B is a side plan view of the post base and an actuator
base of a feedforward controlled solar tracker, which are
stabilized by a diagonal brace and a torsion resistance bar,
according to an embodiment of the present invention;
[0028] FIG. 10 is a front/side perspective view of a feedforward
controlled solar tracker with a pedestal connected to an actuator
base, according to an embodiment of the present invention;
[0029] FIG. 11 is a flowchart illustrating the hydraulic system
process of a feedforward controlled solar tracker, according to an
embodiment of the present invention;
[0030] FIG. 12A is a front perspective view of an inverted single
acting actuator cylinder of a feedforward controlled solar tracker,
according to an embodiment of the present invention;
[0031] FIG. 12B is a front perspective view of an inverted single
or double acting actuator cylinder of a feedforward controlled
solar tracker, according to an embodiment of the present
invention;
[0032] FIG. 13 is a front/side perspective view of a feedforward
controlled solar tracker with two posts, according to an embodiment
of the present invention;
[0033] FIG. 14 is a front perspective view of a feedforward
controlled solar tracker with two posts, according to an embodiment
of the present invention;
[0034] FIG. 15 is a side plan view of a feedforward controlled
solar tracker with two posts, according to an embodiment of the
present invention;
[0035] FIG. 16 is a side perspective view of a feedforward
controlled solar tracker with a third actuator, according to an
embodiment of the present invention;
[0036] FIG. 16A is a detail further showing the mechanics of a
feedforward controlled solar tracker with a third actuator,
according to an embodiment of the present invention;
[0037] FIG. 17 is a side plan view of a feedforward controlled
solar tracker, according to an embodiment of the present
invention;
[0038] FIG. 18 is a front perspective view of a feedforward
controlled solar tracker, according to an embodiment of the present
invention;
[0039] FIG. 19 is a front/side perspective view of a feedforward
controlled solar tracker that utilizes a constant moment lever for
actuation through a sprocket gear and a rack gear, according to an
embodiment of the present invention;
[0040] FIG. 20 is a side perspective view of a feedforward
controlled solar tracker that utilizes a constant moment lever for
actuation through a sprocket gear and a rack gear, according to an
embodiment of the present invention;
[0041] FIG. 20A is a detail of the sprocket gear of a feedforward
controlled solar tracker that utilizes a constant moment lever for
actuation, according to an embodiment of the present invention;
[0042] FIG. 21 is a front plan view of a feedforward controlled
solar tracker that utilizes a constant moment lever for actuation
through a sprocket gear and a rack gear, according to an embodiment
of the present invention;
[0043] FIG. 22 is a front/side perspective view of a feedforward
controlled solar tracker that utilizes a third ground mounted
actuator to pull a chain or cable to provide a constant moment for
the positions of the actuators, according to an embodiment of the
present invention;
[0044] FIG. 22A is a front plan view of a feedforward controlled
solar tracker that utilizes a third ground mounted actuator to pull
a chain or cable to provide a constant moment for the positions of
the actuators, according to an embodiment of the present invention;
and
[0045] FIG. 22B is a side plan view of a feedforward controlled
solar tracker that utilizes a third ground mounted actuator to pull
a chain or cable to provide a constant moment for the positions of
the actuators, according to an embodiment of the present
invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION
[0046] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings, in which
preferred embodiments of the invention are shown. This invention
may, however, be embodied in many different forms and should not be
construed as limited to the illustrated embodiments set forth
herein.
[0047] In the following description, like reference characters
designate like or corresponding parts throughout the figures.
Additionally, in the following description, it is understood that
terms such as "first," "second," and the like, are words of
convenience and are not to be construed as limiting terms.
[0048] The embodiments of the present invention are directed to a
platform for aiming solar power generating systems (and components,
such as mirrors or photovoltaic cells "PV" and the like) such that
the platform's sub-frame is positioned to optimize the capture of
energy from the sun for conversion into electricity or other useful
forms of energy. The embodiments of the present invention are
optimized for strength, reliability, efficiency and
maintainability. The embodiments of the present invention are also
well suited for high wind conditions and can continue tracking the
sun even in strong winds.
[0049] As depicted in FIGS. 1-5 and 17-18, in an embodiment of the
present invention, the solar tracking apparatus 2 includes a
foundation system 1 comprising an I-beam cross 4 and adjustable
foundation mountings 6 (such as screws, metal foundations, or the
like) that secure the I-beam cross 4 to the mounting surface 8 to
which the solar tracking apparatus 2 is affixed. One skilled in the
art will readily understand that the foundation mountings 6 may be
adjustable or non-adjustable in embodiments of the present
invention. Additionally, one skilled in the art will readily
understand that different I-beam foundation systems may be
utilized, including, but not limited to, a T-cross. Connected to
the I-beam cross 4 are two linear actuators 10, 12 and a post 14.
In an embodiment of the present invention, the linear actuators 10,
12 are preferably comprised of an east-west actuator 10 and a
north-south actuator 12. The bottom end of the linear actuators 10,
12 are preferably connected to the I-beam cross 4 via pinned
connections 15, joint connections, or the like. These pinned
connections 15 allow the linear actuators 10, 12 to achieve two
degree of freedom movement, relieve strain in the linear actuators,
and they assure proper, free motion of the actuators. One of
ordinary skill in the art will understand that, as used in the
description of embodiments of the present invention, two degree of
freedom movement refers to a manipulation that can cause motion in
two independent forms such as two orthogonal axes or two orthogonal
lines of motion, or one axis and one line. Additionally, a person
of ordinary skill in the art will readily understand that the
pinned connection can be a connection made by the use of a link
with two pins, such that the link allows two degree of freedom
movement. In a preferred embodiment of the invention as shown in
FIGS. 1-5, the bottom end of the post 14 is rigidly anchored to the
I-beam cross 4. This creates a two-pinned system in an embodiment
of the invention. However, a three-pinned system in an embodiment
of the invention may be preferred in which the post 14 is connected
to the I-beam cross 4 via a pinned connection (not shown in
figures). In a preferred embodiment of the present invention, the
top end of the linear actuators 10, 12 and the top end of the post
14 are connected to a sub-frame 16, which holds a platform 18 that
tracks the sun. In a preferred embodiment of the present invention,
the platform holds or consists of a solar array. The linear
actuators 10, 12 are connected to the sub-frame 16 via a joint
connection 20 that allows the actuators 10, 12 to achieve two
degree of freedom movement. In fact, both the pinned connections 15
at the bottom of the linear actuators 10, 12 and the joint
connection 20 at top of the linear actuators 10, 12 are two degree
of freedom pinned connections or the like that relieve strain in
the actuators and assure proper, free motion. The post 14 is
preferably connected to the sub-frame 16 via a linking mechanism 22
that allows the platform 18 to rotate about the post 14 with two
degrees of freedom. In another embodiment of the invention the post
14 may be connected to the sub-frame 16 via a joint, similar to the
joint connection 20 between the actuators 10, 12 and the sub-frame
16. A person of ordinary skill in the art will readily understand
that there are different means for connecting both the post 14 and
the actuators 10, 12 to the sub-frame. All embodiments described
above creates a three-pinned system of connection between the
sub-frame 16 and the tops of the post 14 and actuators 10, 12. In
yet another embodiment of the invention, the actuators 10, 12 and
the post 14 are connected directly to the platform 18 via pinned
joints or linkages without a sub-frame 16.
[0050] The solar tracker's two or three-pinned connections 15 to
the foundation system 1 and joint connection 20 and/or linking
mechanism 22 connections to the sub-frame 16 provide adequate
strength to withstand substantial forces while minimizing or
avoiding transmission of certain torques into its foundation system
1. The lower torques associated with the connection points of the
post 14 and actuators 10, 12 to the foundation system 1 and
sub-frame 16 also provide for the capability of installing the
system on rooftops. Most embodiments of the system are well suited
for commercial roof truss spacing because the solar tracker's
foundation system 1 is capable of spanning two or more trusses
(which are typically eight to ten feet apart).
[0051] In a preferred embodiment of the present invention, the
linear actuators 10, 12 also function as structural members. Use of
the actuators 10, 12 as structural members creates operating
strength while also reducing production costs. In a preferred
embodiment of this invention the linear actuators 10, 12 are
hydraulic cylinders that are driven by a hydraulic pump.
[0052] As can be seen in the figures, and more specifically FIGS.
6A-6C, the connections of both the bottom and the top of the linear
actuators 10, 12 and the post 14 to the foundation system 1 and
sub-frame 16, respectively, preferably create a triangle shape. The
dimensions of the triangles formed by the connections to the
foundation 1 and the connections to the sub-frame 16 can be
adjusted for different requirements in different embodiments. For
example, standard PV panels have greater tolerance than mirrored or
focused systems (i.e., concentrators). Standard panels can be
controlled with a smaller system with smaller triangles and smaller
actuators than focused systems, which require more exact aiming.
FIG. 6A depicts a right angle triangle position ("RA" model solar
tracker) 24; FIG. 6B depicts an isosceles triangle position ("ISO"
model solar tracker) 25; and FIG. 6C depicts an equilateral
triangle position ("EQ" model solar tracker) 27.
[0053] As shown in FIGS. 1-5, in an embodiment of the present
invention, the foundation system 1 is comprised of an I-beam cross
4 and a number of removable, adjustable foundation mountings 6
(pilings, ground screws, helical ground anchors, or the like). In
yet another embodiment of the present invention, the foundations
under the three separate bases (post 14 and two actuators 10, 12)
are replaced with a single foundation designed to support the three
mounting locations. For example, a large concrete slab or the like
could be used. In this embodiment the foundation system 1 comprises
a concrete slab with adjustable mountings for an I-beam cross 4 or
the like, or the three separate bases. The I-beam cross 4 is
mounted such that its bases face north-south and east-west and is
leveled by the adjustable foundation mountings 6. The actuators 10,
12 and center post 14 are preferably mounted to the I-beam cross 4.
This system provides for rapid, strong, and inexpensive
installations while also providing for inexpensive and total
clean-up after the system is decommissioned after twenty to thirty
years of service.
[0054] As can be seen in FIG. 10, in a preferred embodiment of the
present invention, a pedestal 44 is added under the actuator 12,
which causes the lower joints or pinned connections 15 of the
actuators 10, 12 to be at levels different from one another.
Causing the lower joint or pinned connection 15 to be higher on the
base (of which actuator 12 is part) is desirable as it improves
stability and strength of the solar tracking apparatus for certain
angles of the east-west degree of freedom at the beginning and
ending of solar days. Additionally, the pedestal 44 under the
actuator 12 helps reduce strain and interference, and allow the
solar tracker apparatus 2 to efficiently reach angles required to
align the platform 18 orthogonal to the rays of the sun.
[0055] As depicted in FIGS. 9A and 9B, in a preferred embodiment of
the present invention, diagonal braces 38 attach to the post 14 at
some height above the foundation 1 and to the foundation mountings
of the actuators 10, 12 (cylinders in the hydraulic embodiment).
These braces 38 provide additional strength and/or reduce the
amount of material needed in the post 14 and thus reduce the cost
of the post 14. In embodiments where the I-beam cross 4 is not
used, braces or torsion resistance bars 40 may be used to connect
the foundation mountings of the actuators 10, 12 and post 14 such
that they are constrained from rotating. These connections act as
long levers on the post base 17 while using the actuator 10, 12
foundation mountings as anchors to resist movement. Using the
actuator 10, 12 foundation mountings in this way is particularly
effective as the load on the actuator 10, 12 base would be
perpendicular to the primary axis of the screw foundations 42 (or
the like) giving the maximum resistance.
[0056] Turning back to a preferred embodiment depicted in FIGS.
1-5, the orientation of the linking mechanism 22 or joint at the
top of the post 14 is fixed and capable of resisting rotational
forces about its center axis. The post 14 itself is also designed
to be capable of resisting such rotational forces transferred from
the linking mechanism 22. This resistance keeps the solar tracking
apparatus 2 standing erect and in calibration.
[0057] The mounting of the linking mechanism 22 at the top of the
post 14 as well as the joints 20 at the top of each actuator 10, 12
is at an angle to optimize use of the linking mechanism 22 or joint
20 within their mechanical limits. Joints 20 at the tops of the
actuators 10, 12 can optionally have some rotational freedom in
addition to what is provided by the free rotation of the actuators
10, 12.
[0058] FIGS. 7 and 8 further depict the two degree of freedom
linking mechanism 22 at the top of the post 14 in greater detail.
The two degree of freedom linking mechanism 22 at the top of the
post 14 is designed to be sufficiently strong to withstand very
large torque forces. A preferred embodiment depicted in FIG. 7
shows a linking mechanism 22 designed to compensate for the maximum
torque that might be caused by high winds. The linking mechanism 22
includes a body member 31 that connects a first axle 33 and a
second axle 35. The first axle 33 and second axle 35 preferably
include bearing assemblies 28, that are mounted orthogonal to each
other to allow the linking mechanism 22 to achieve two degree of
freedom movement. The radius "r" of the body member 31 causes the
torque to be distributed into forces in each of two bearings/axle
assemblies 28 such that the torque is resisted by each bearing
30.
[0059] A preferred embodiment of the post linking mechanism 22
depicted in FIG. 7 also provides an offset 32 comprised of the
distance between the first axle 33 and the second axle 35 of the
linking mechanism 22, center to center. This offset 32 acts to
assure the sub-frame 16 has clearance past the post 14 even at
sunset when the sub-frame 16 is oriented to point close to the
horizon. The offset 32 also provides greater angular movement of
the sub-frame 16 near the end of the linear actuator's 10, 12
stroke. The offset 32 also provides leverage for the actuator 12
when the actuator is near its retracted position.
[0060] The linking mechanism 23 depicted in FIG. 8 provides a more
compact link than that of the linking mechanism 22 shown in FIG. 7,
and provides fewer singularities for angles near the horizon. The
linking mechanism 23 in an alternative embodiment of the present
invention is substantially a pillow block bearing assembly. The
fundamental differences between the linking mechanism 22 in FIG. 7
and the linking mechanism 23 in FIG. 8 are that the linking
mechanism 23 in FIG. 8 has no axles (the axles are part of the post
14 and sub-frame 16), whereas the linking mechanism 22 in FIG. 7
has the axles 33, 35 as part of the link and the linking mechanism
22 has an elongated offset between axles compared to the linking
mechanism 23 in FIG. 8. The linking mechanism 23 depicted in FIG. 8
includes a steel plate 29 or the like to assure proper orientation
of the bearing assemblies 28. The disadvantage of the linking
mechanism 23 in FIG. 8 is that it requires a slightly longer
actuator to achieve the same angles as the post link 22 shown in
FIG. 7. The linking mechanism 23 in FIG. 8 is not preferable in
that it is not capable of reaching certain angles that are required
to point at the sun for some locations and days of the year.
Linking mechanism 22 is preferred as it provides the capability to
reach extreme angles in order to align the sub-frame 16/platform 18
to a position orthogonal to the rays of the sun, particularly
during sunrise and sunset.
[0061] As can be seen in FIGS. 7 and 8, the linking mechanisms 22,
23 are designed to provide minimal strain displacement even under
heavy wind loads. The linking mechanism 22 preferably provides
minimal clearance requirements for the bearings 30 and bearing/axle
assembly 28 to minimize costs and strains in these components. The
offset 32 distance between the axles 33, 35 causes the system to
move in a fashion that closely resembles the solar system, thus one
actuator 10 preferably provides time of day positioning while the
other actuator 12 preferably provides day of the year positioning.
The linking mechanism 22 body member 31 length determines the
amount of angular movement that can be achieved without binding.
Linking mechanism 22 length is optimized to provide the required
freedom of movement at the lowest possible loading conditions for
the actuators 10, 12. The linking mechanism 22 may be constructed
of welded components rather than being formed of a solid piece of
metal. The axles 33, 35 of the linking mechanism 22 are typically
separate components that are welded or fastened into place in the
twisted or fabricated component. The body member 31 of the linking
mechanism 22 may also be fabricated from square stock, twisted flat
bar, casting or the like.
[0062] A person of ordinary skill in the art will readily
understand that, in alternate embodiments, ball joints or other
types of joints may be used in place of the joints 20 and/or pinned
connections 15. This is because the joints on the actuators 10, 12
may allow rotation. However, the joint/linking mechanism 22, 23 at
the top of the post 14 cannot be replaced by a ball joint because
it must hold the system in place resisting rotation, and it
preferably has an offset length 32 (or joint/linking mechanism
length) greater than zero. However, an alternative embodiment of
the invention may allow for a linking mechanism with an offset
length equal to zero.
[0063] FIGS. 16 and 16A depict the solar tracking apparatus 2 with
the addition of a third actuator 34. Additional accuracy is
achieved in the early morning or late evening by adding the
additional actuator 34 to the sub-frame 16 such that the mounts 36
on one end of the platform 18 are raised at an angle to the
sub-frame 16 such that this additional degree of freedom sweeps
across the horizon (for the ISO model solar tracker) or down to the
horizon (for the RA model solar tracker) to the exact position of
sunrise or sunset for any given day of the year. Fixed or actuated
elevation is added to the sub-frame 16 to optimize the solar
tracking apparatus 2 for early morning or late afternoon/evening
aiming. This added capability is desirable for certain types of
solar panels and/or cases where power generation at or near
sunrise/sunset is critical.
[0064] The solar tracking apparatus 2 is designed for rapid and
cost effective deployments. The assembly process is aided by the
system design in that multiple assembly steps can take place
simultaneously: foundation system 1, sub-frame 16, structural
component assembly (actuators 10, 12 and post 14) and the
positioning and orientation of the foundation system 1. These
simultaneous operations culminate in final assembly wherein a crane
(or similar) is used to place the components so that they can be
fastened together efficiently. The power supply to the solar
tracker apparatus is any form of stable, clean power. In a
preferred embodiment of the present invention, any electronic
components in the system are provided with an enclosure for
protection from weather and the like.
[0065] Several different embodiments of the solar tracking
apparatus 2 are available for different uses. Each embodiment
provides specific features for its specific function. As shown in
FIGS. 6A-6C, these embodiments vary the triangle from a standard
isosceles triangle 25 (FIG. 6B) to a preferable right angle
triangle 24 (FIG. 6A) to an equilateral triangle 27 (FIG. 6C). Post
14 height and actuator 10, 12 and 34 lengths also vary to change
performance characteristics.
Feedforward Control System:
[0066] A person skilled in the art would readily understand that
there are different means that may be utilized to create a
feedforward control system in embodiments of the present invention,
including, but not limited to, having inputs of time of day, date,
GPS coordinates, and foundation orientation. In a preferred
embodiment of the invention, a computer control platform will use
these inputs to acquire several sets of solar position angles for a
given day. The computer control platform in the present invention
preferably has input and output capabilities typical of a
Programmable Logic Controller (PLC). Additionally, in a preferred
embodiment of the present invention, the feedforward control system
makes use of polynomial spline curves to drive the linear actuator
10, 12 and 34 positions. These spline curves are created by taking
multiple known angular positions of the sun during the day and
translating those angles into linear actuator 10, 12 and 34
positions based on the a relationship between the angular positions
of the sun and the mechanical configuration of the particular
embodiment of the present invention. These linear actuator 10, 12
and 34 positions become data points for the creation of the spline
curve which is a function of "t"--time from sunrise to sunset. In
some embodiments additional spline curves are also used to map the
angles of the linking mechanism 22 axles 33, 35 and the
time-function ratio of those angular positions and angular
velocities are related to the linear positions and linear
velocities of the actuators 10, 12 and 34.
[0067] Either a central computer or a computer located on each
solar tracker is capable of calculating these spline curves
overnight for the next day's use using previously stored data. In
the case where a central computer is used to calculate the spline
curves for all the solar trackers in an application area or all the
solar trackers in more than one application area, each solar
tracker has the ability to store a data table. This data table
contains the coefficients for spline curves indicating actuator
cylinder positions (or associated angles) and related motor speeds
(or on-off cycles and valve positions) as a function of time and
delta-t (time shift for GPS longitude location within time zone).
Alternatively, each solar tracker could be equipped with
sufficiently large memory capacity to store up to several years'
worth of data tables. In some embodiments, multiple curve sets are
provided in the data table with the correct curve set selected
based on certain factors such as the date or the latitude as given
by GPS coordinates with the associated time offset (location), or
both date and location.
[0068] In an alternate embodiment of the present invention, data
tables are used to control the system by using stored data for
input versus time, without the use of spline curves. Another
alternate embodiment of the present invention uses full solar
calculations done in real-time. This embodiment uses feedforward
control based on actuator positions and/or linking mechanism 22
angular positions, and rates of change directly translated from
elevation and azimuth angles in real-time rather than using spline
curves to indicate actuator positions and velocities. Yet another
embodiment of the present invention uses neither feedforward
control nor spline curves but rather uses a series of rules
together with actuator positions translated from standard elevation
and azimuth angles for solar position.
[0069] A preferred embodiment of the present invention utilizes the
spline curve method for building the feedforward model. This is
because the mathematics of real-time solar calculations and their
respective derivatives requires much greater computational power
and generates a significant error as well as potential for a
plethora of singularities. This increase in complexity leads to an
increase in hardware costs and reduces the accuracy and stability
of the control system.
[0070] In a preferred embodiment, the spline curve method provides
for incremental adjustments to the actuator 10, 12 and 34
velocities throughout the day with position adjustments being
continuous (or so frequent and small that the motion increment is
imperceptible or nearly imperceptible).
[0071] The spline curve used in a preferred embodiment of the
present invention is typically a multi-segment, third degree
polynomial in the form:
f.sub.1(t)=a.sub.1t.sup.3+a.sub.2t.sup.2+a.sub.3t+a.sub.4 for t=0
to t.sub.a
f.sub.2(t)=b.sub.1t.sup.3+b.sub.2t.sup.2+b.sub.3t+b.sub.4 for
t=t.sub.a to t.sub.b
f.sub.3(t)=c.sub.1t.sup.3+c.sub.2t.sup.2+c.sub.3t+c.sub.4 for
t=t.sub.b to t.sub.c
f.sub.4(t)=d.sub.1t.sup.3+d.sub.2t.sup.2+d.sub.3t+d.sub.4 for
t=t.sub.c to t.sub.final
[0072] Methods for solving such systems of equations are well known
to those skilled in the art. The above example is a system composed
of a sixteen by sixteen set of position equations that requires
sixteen data points to define a unique solution. A combination of
position requirements (for certain values of "t") and continuity
constraints (between f.sub.1, f.sub.2, f.sub.3, and f.sub.4) define
these data points. Higher degree polynomials with correspondingly
larger systems of equations are used to make the linear actuator
10, 12 and 34 positions increasingly accurate for achieving desired
angles of the sub-frame 16 and/or platform 18. The spline curves
indicating the desired angles of the axis of the post linking
mechanism 22 are used to produce a feedforward modification loop.
The actual angles of the post linking mechanism 22 are compared
with the desired angles to calculate the measured error. This error
is multiplied by a gain that is used in the feedback loop to modify
the feedforward control system.
[0073] A preferred embodiment of the feedforward control system
includes the use of a time differential to minimize or eliminate
motion hysteresis. By advancing time by a small increment
("delta-t") in the spline curve calculations, the time delay caused
by the physics of the solar tracking apparatus' response and a
circuit's response can be virtually eliminated. A "delta-t" term is
used in each spline curve used for driving the solar tracking
apparatus such that the drive and sensor feedback match more
precisely. Real-time without the "delta-t" term is used for
checking position and measuring error. This use of "delta-t"
effectively reduces control error by one order of magnitude.
[0074] In alternate embodiments of the present invention, the
spline curves may be 2nd, 3rd or higher degree polynomials in one
or more segments.
[0075] The first derivative of the position equation is then used
to determine the desired time rate of change for the actuator 10,
12 and 34. If hydraulic cylinders are used for the linear actuators
10, 12 and 34, this time rate of change is easily converted into
fluid flow rate requirements by the computer and subsequent
pump-motor speed/current requirements for the feed forward control
system.
[0076] The feedforward control system provides very accurate and
smooth control (such as pump motor speed control, pulse modulation
to the drive(s) or valve fluttering) for the linear actuators 10,
12 and 34. This control strategy minimizes or eliminates
overdriving of the actuators 10, 12 and 34, which reduces wear and
strain on the actuators 10, 12 and 34 and other mechanical
components and minimizes the electrical current draw and energy
use.
[0077] Constraining the first, second, third and fourth derivative
to be continuous between functions provides the smoothest operation
and lowest wear for the mechanical components of the solar tracking
apparatus 2. With these constraints the equipment has greater
reliability.
[0078] In a preferred embodiment of the present invention, sensor
feedback on actuator 10, 12 and 34 positions, linking mechanism 22
angles, or both is required to modify and update the feedforward
control system. This creates a feedback control system. A person
skilled in the art would readily understand that means for a
feedback control system include, but are not limited to, having
inputs of linear actuator positions, angular positions of the
linking mechanism 22 axles 33, 35, and solar tracking sensor data.
Wind resistance and changes in friction will change with
environmental conditions and time. Compensation for these small
changes is accomplished by multiplying the error times a small gain
to adjust the actuator 10, 12 and 34 speed until the actual
position matches the expected position. This error information is
also multiplied by an even smaller gain to adjust power to the
actuators 10, 12 and 34 for future movements thus making the
feedforward model increasingly accurate over time for the then
current environmental and mechanical conditions.
[0079] Communications capabilities help assure maximum up time. In
another alternate embodiment the control system is equipped with
secure interne communications for sending maintenance requests
and/or responding to status inquiries.
[0080] The embodiments of the present invention preferably include
one of the following categories for the configuration of the solar
tracking apparatus: [0081] 1. Optimized for PV panel, ground
installations between 30.degree. and 50.degree. latitude; [0082] 2.
Optimized for PV panel, ground installations between 0.degree. and
30.degree. latitude; [0083] 3. Optimized for PV panel, ground
installations with extreme latitudes greater than 50.degree.;
[0084] 4. Optimized for PV panel, rooftop installations between
30.degree. and 50.degree. latitude; [0085] 5. Optimized for PV
panel, rooftop installations between 0.degree. and 30.degree.
latitude; [0086] 6. Optimized for PV panel, rooftop installations
with extreme latitudes greater than 50.degree.; [0087] 7. Optimized
for concentrated PV panel, ground installations between 30.degree.
and 50.degree. latitude; [0088] 8. Optimized for concentrated PV
panel, ground installations between 0.degree. and 30.degree.
latitude; [0089] 9. Optimized for concentrated PV panel, ground
installations with extreme latitudes greater than 50.degree.;
[0090] 10. Optimized for concentrated PV panel, rooftop
installations between 30.degree. and 50.degree. latitude; [0091]
11. Optimized for concentrated PV panel, rooftop installations
between 0.degree. and 30.degree. latitude; and [0092] 12. Optimized
for concentrated PV panel, rooftop installations with extreme
latitudes greater than 50.degree..
[0093] It should be noted that some embodiments optimize at angles
other than 0.degree., 30.degree. or 50.degree.. In an alternate
embodiment of the present invention, an additional level of
optimization is added to provide maximum wind resistance for each
of the above twelve categories.
[0094] In each of these categories, the triangle dimensions,
platform 18 or solar array size, actuator 10, 12 and 34 lengths,
and/or the post 14 height are adjusted to accommodate the specific
needs of the particular embodiment. For example, standard PV panel
installations require a lower cost system but have a greater angle
of tolerance. Focused/concentrated systems have a small tolerance
for error but are less costly than standard PV systems on a per
watt basis.
[0095] For locations in North America, the latitude requires that
the PV panels are preferably elevated above the horizon between a
minimum and maximum angle at mid-day, specific to the particular
location and day of the year. For ISO models (based on an isosceles
triangle 25) all locations between certain latitudes require a
specific post 14 height while a different post 14 height is
required when outside of this particular range. Locations closer to
the equator require a taller post 14 and locations farther north
require a shorter post 14. In all cases for the ISO model solar
tracker, the post 14 height is adjusted relative to the fully
retracted actuator 10, 12 and 34 (cylinder) height.
[0096] Extra height may be added to all three bases to gain ground
clearance for the solar panel array and frame mounted to the
sub-frame. In an embodiment of the present invention, risers can be
added under post 14 and actuators 10, 12 to provide extra height
for ground clearance, or so a larger platform 18 may be mounted on
a solar tracker. Risers may also be added under the entire
foundation system 1, for example under the I-beam cross 4 to bring
I-beams to level or to raise the height of the entire foundation.
This use for leveling is preferred and of particular value for
locations where the ground is sloped.
[0097] In an embodiment of the present invention, torsion
resistance bars 40 are used to diagonally tie risers to the ends of
the I-beam cross 4 component not passing over or under the riser.
These torsion resistance bars 40 provide the risers with additional
stability and resistance to torque.
[0098] Actuator 10, 12 and 34 capabilities can also be adjusted to
meet different height requirements of the solar tracker. In any
case, larger systems require larger components, including larger
actuators 10, 12 and 34.
[0099] ISO systems (based on isosceles triangles 25) operating in
northern regions of the northern hemisphere or far southern regions
of the southern hemisphere benefit from an embodiment with a
reverse orientation where the post 14 is taller than the retracted
actuators 10, 12. In such a case the orientation would preferably
position the post 14 away from the equator for an ISO model
embodiment of the present invention. This is because the sunrise
will appear farther north and south away from the equator during
the summer and winter as the system installation location moves
away from the equator.
[0100] As discussed above, in a preferred embodiment of the present
invention, the linear actuators 10, 12 and 34 are hydraulic
cylinders because hydraulic systems are well known for reliability
and strength. Components are readily available and the supply of
technicians capable of working on hydraulics is ample. In alternate
embodiments, screw drives, pneumatics, or other linear actuators
and the like may be used in place of hydraulic cylinders. In these
alternate embodiments a motor is preferably used to drive the
actuators. However, a person skilled in the art will readily
understand that there are many means that may be used to drive the
actuators, including, but not limited to, using pumps with valves,
motors with gears, and motors with belts and pulleys.
[0101] The control system in a preferred embodiment of the present
invention is a feedforward system based on expected angles for the
position of the sun at a given time on a given date for a given set
of coordinates. Inputs to the system may include (but are not
limited to) time of day, date, GPS coordinates, foundation
orientation, cylinder/angular position feedback, and solar tracking
sensor data. The feedforward output controls motor speed and fluid
flow rate. In certain preferred embodiments where hydraulics are
utilized, the system also manipulates valve positions to control
fluid flow directions. One adjustable valve or one or more binary
valves function as dump valves to release excess fluid (if any) to
flow back to a hydraulic reservoir. The control system causes the
motor to drive the pump to produce nearly the exact amount of fluid
needed to cause the required movements. Excess fluid flow will only
be produced in cases where the fluid demand is so small that the
motor and pump cannot accurately produce the desired flow rate.
There are also times when excess fluid flow is produced when motion
is stopped and the pump is running in stand-by mode (such as in a
warm-up cycle).
[0102] As for the inputs in the system described above for an
embodiment of the present invention, the time of day and date are
acquired from a radio frequency ("RF") signal, a local server, a
GPS system, an onboard clock, or the like. The GPS coordinates are
acquired from an onboard GPS system, or are input by/from an
external GPS and stored in flash memory. Alternatively, the GPS
coordinates are acquired from a local server, or the like. The
foundation orientation is input at setup and stored in flash
memory, or input via sensors or the like. The cylinder positions
are acquired in real-time or input via sensors or the like. The
solar tracking sensor data is acquired in real-time or input via
sensors or the like.
[0103] Expected sensor readings for actuator 10, 12 and 34
(cylinder) positions or linking mechanism 22 angles are also output
by the feedforward system and are measured against actual readings
of their positions to find control errors used in the feedback
portion of the control system. These errors are then multiplied by
relatively small gains to dynamically modify the pump speed (or
motor speed) and valve positions to accomplish desired movements of
the solar tracker. In a preferred embodiment of the present
invention, the feedback system compensates for mechanical system
changes over time, including, but not limited to, those in
friction, and environmental condition changes, including, but not
limited to, temperature changes.
[0104] For embodiments with solar feedback optimization, the
outputs from the solar sensor(s) detecting the position of optimal
solar input relative to the position of the platform 18 are
multiplied by a relatively small, time cumulative gain to create
slow and stable adjustments to the feedforward positioning within
predefined limits from the feedforward values. This output is then
translated into an adjustment to the actuator 10, 12 and 34
(cylinder) positions and finally converted to pump and valve
signals. A sensor similar to a single two dimensional Charged
Couple Device ("2D CCD") sensor with minimal optics and computing
capability is used to find the center of brightness in this
embodiment. However, other sensors with similar capabilities may
also be used.
[0105] The known relationship recorded in the mathematical model
between the actuator 10, 12 and 34 (cylinder) position's "time rate
of change" (or first derivative) and motor speed for driving the
hydraulic pump is a component of the control system. The first
derivative of the spline curve equations provides the velocity of
the rod that drives the actuators 10, 12 and 34 (cylinder). For
hydraulic systems, knowing the cylinder bore and rod diameter
allows the control system to calculate the fluid flow rate required
to move the actuators 10, 12 and 34 (cylinder) at that speed. With
the required flow rate the control system can use the cubic inch
per rotation rating of the pump to calculate the required pump
speed. The driver calculations for controlling the motor speed to
drive the pump are then derived from the pump speed requirements to
create the desired flow rate.
[0106] Because of the speed of the system the requirements for the
motor size are minimal. A small but durable motor (similar in size
to a vacuum cleaner motor) is all that is required to drive the
system. Additionally, minimizing motor startups helps reduce wear
on the motor. A small motor rated and regulated for continuous use
is better than a larger motor that must be started and stopped
frequently. The feedforward control system balances the drive so
that on/off cycles are minimized. Minimizing valve cycles is also
important to assure maximum reliability. The balance provided by
the feedforward control system provides for minimal valve
cycles.
[0107] In certain embodiments of the present invention, sensors are
mounted to the actuator 10, 12 and 34 (cylinder) bodies or are
mounted inside the cylinder bodies such that they detect the
measurement of the total cylinder length from center of one joint
to the center of the other joint. These sensors provide feedback
data on the position of each actuator 10, 12 and 34 (cylinder) that
is used in the control algorithm discussed above. However, a
preferred embodiment of this invention calculates actuator
positions based on linking mechanism angles as measured by encoders
on each angle as it is more accurate and cost effective than
measuring the actuator positions directly.
[0108] In the RA embodiment or the ISO embodiment of the solar
tracker the sub-frame 16 of the present invention has multiple
mounting holes for the attachment of the universal joints at the
top of each actuator 10, 12 such that the adjustments can be made
to accommodate various latitude and tolerance requirements. Using
mounting holes that are spaced close together provides a greater
reach for extreme sunrise and sunset angles while positions farther
from the post 14 or other actuator 10, 12 offer greater
accuracy.
[0109] In an embodiment of the present invention, full 360.degree.
rotation is achieved by using linear actuators 10, 12 with longer
strokes (relative to the triangle height) and making the post 14
height equal to the actuator's 10 mid-stroke length.
[0110] Sensors: In certain embodiments the control system has one
or more types of sensors for each degree of freedom. These sensors
include, but are not limited to, encoders, linear sensors, level
sensors, and vision sensors. Encoders may be used to measure angles
directly from the linking mechanism axles 33, 35. Linear position
measurement sensors such as Magnetostictive, laser, Ultrasonic
(e.g., those manufactured by MTS), or the like may be used to
measure linear actuator 10, 12 and 34 lengths. A gyroscope, mercury
switch or other device is used to measure when the platform 18 is
level. A machine vision system and/or photocell (or similar) can
optionally be included as part of the control system in certain
embodiments. The vision system is used to measure the angular error
between the solar tracker position and the actual position of the
sun. This measured error is used to modify or calibrate the control
system and reduce error.
[0111] In an embodiment of the present invention, sensors to
measure elevation and azimuth angles may replace or augment sensors
on the linear actuators. These angle measuring devices will help
assure the system operates within the tighter tolerances of
focused, concentrated, or mirrored collectors. Additionally, in an
embodiment of the present invention, integrated data from the
energy system may be added to the other data inputs mentioned above
and made available to owners and maintenance providers through the
present invention's optional internet connection. In certain
embodiments of the present invention, solar sensor feedback may be
added to verify tracking is correct. This involves directly sensing
the position of the sun relative to the line orthogonal to the face
of the platform 18 by measuring system power output.
[0112] In alternate embodiments, solar angles may be provided in
real-time and translated directly into linear actuator positions
with derivatives extracted by use of difference calculations. These
translations and calculations are used as an alternative to the
spline curves described above.
[0113] Day time calibration: In an embodiment with a photocell or
similar detector being used, the sensors are located at the bottom
of a hollow tube mounted such that the tube's main axis is aimed
orthogonal to the plane of the platform 18. The tube size and
length is selected to assure the desired degree of accuracy is
confirmed when the sensor can and cannot detect the sun.
Alternatively, the measured output of electrical energy from one or
more solar panels on the tracker may be used to sense that the sun
is within the acceptance angle of the platform 18 and solar panel.
In the case of using electrical output, the ramp up and ramp down
of power provides additional information about the sun's position
relative to the current calibration of the control system. If the
sensing strategy does not detect the sun for more than a given
amount of time, the control program moves the platform 18 outward
in concentric circles (the central axis orthogonal to the platform
18 sweeps out circular search patterns with each iteration
increasing the radius of the circle) from its original position
until it detects the sun or reaches a preset maximum angular offset
from its then current calibration. If the maximum allowable offset
is reached the solar tracker goes back to the original trajectory
and continues tracking for a set amount of time. If the sun is
again detected by the sensor, tracking continues as normal. If not,
the search sequence is initiated again. If the sun is found during
a search, calibration offsets are set for the angles associated
with each axle 33, 35 of the linking mechanism 22. If the sun is
not located before a set number of search sequences are completed,
the tracker sends a message requesting maintenance for
recalibration. To find the center of the sun the tracker continues
its then circular path until it reaches the farthest point along
the path where the sun is detected. The time and length of the
arched path where the sun is detected are measured and this
geometric information is used to calculate the center of the sun
based on the known expected geometry of the appearance of the sun
for the given day and GPS coordinates.
[0114] An embodiment of the present invention uses a machine vision
sensor that operates in a similar way but is faster because its
concentric circles are performed in software rather than on the
solar tracker apparatus. In alternative embodiments of the present
invention, sensors measuring the electrical output of the solar
panel system are used in lieu of optical sensors or the like that
detect the sun.
[0115] In a preferred embodiment of the present invention, the
positions and times of where and when the sun is first detected and
last detected are recorded and used in calculations that take
advantage of the known circular pattern of the solar tracker's
motion, the known motion of the sun across the sky, and the known
apparent size and geometric characteristics of the sun to find the
center of the sun.
[0116] Nightly calibration: Each night the solar tracker goes into
a position where its platform 18 is level and the system checks its
position against the level sensor (gyroscope or similar). If the
level position is confirmed within a certain tolerance the sequence
is complete. If the system is out of tolerance, a search sequence
similar to a daytime search is conducted to find the level position
and offset angles are set as discussed above, or as applied to
azimuth and elevation inputs to the spline curve generation only
with a greater maximum search area.
[0117] Communication: In a preferred embodiment the system is
equipped with a combination of fiber optic, wireless, and/or wired
local ethernet networking or the like to communicate with a local
server which possesses an internet connection. Depending on the
number of trackers within a solar field, a number of local servers
act as a supervisory control system and data acquisition systems
("SCADA system") for a group of solar trackers. The SCADA system
uses an internet connection to sync its local clocks to remote
atomic clocks on a daily basis. The SCADA system then syncs its
real-time clock to the real-time clocks of the solar trackers on a
nightly basis or at power-up. In addition, the SCADA system relays
any additional information required for the nightly spline curves
wherein inputs such as time, position coordinates of the solar
tracker, and angular position of the sun or spline curve
coefficients can be acquired. The SCADA system also acts as a data
concentrator, as well as performing functions such as monitoring
alarms, collecting data and the like. Messages and reports can also
be sent from this connection (e.g., a request for maintenance).
[0118] In any of the calibration methods mentioned above, the
corrections may be used as output in the control system to improve
performance or as inputs to a feedforward control system such that
the outputs of the planned trajectory incorporate the calibration
corrections.
[0119] Wind relief: In a preferred embodiment the solar tracking
apparatus 2 is designed such that its actuators 10, 12 and 34 moves
in order to comply with the force of heavy winds in order to
prevent any system components from breaking or bending. In systems
with hydraulic actuators 10, 12 and 34 this is accomplished through
the use of counterbalance valves mounted on each cylinder. The
counterbalance valves are set to relieve the hydraulic pressure
that exceeds the pressure needed for normal wind conditions. Fluid
relieved under this condition flows between both sides of the
cylinder and a reservoir tank. This relief function of the
counterbalance valves is proportional to the force of the wind. The
valve will open only as needed resulting in a minimal cylinder
displacement. After the wind gust subsides, the drive system brings
the cylinder back to recover its position within a certain
tolerance. Recovery time will vary with the amount of displacement
but will always be accomplished within a few minutes. This feature
protects the system from damage in high winds and allows for the
capture of solar energy at much higher wind speeds than has been
possible with other solar trackers.
[0120] In an embodiment of the present invention the hydraulic
reservoir is in the post. A portion of the interior of the main
post is used to house the hydraulic fluid.
[0121] A person of ordinary skill in the art will readily
understand that bumpers or the like may be used in embodiments of
the present invention as a means to prevent the solar tracking
apparatus from being driven past its mechanical limits. As such, in
an embodiment of the present invention, bumpers are provided to
prevent the solar tracking apparatus from being driven past its
mechanical limits. These bumpers keep the solar tracking apparatus
from being damaged or moving in an undesirable direction in
windstorms. In the event of a power failure during heavy winds, the
wind relief system and bumpers preference the system to move toward
a horizontal position where wind loading will be at a minimum. If
heavy winds are not present during a power failure, the system
holds its position until power is restored.
[0122] Balance: The solar tracking apparatus 2 is preferably
balanced about the linking mechanism 22 such that ground clearances
are maximized and wind loading is channeled to promote moving the
platform 18 to a horizontal position. These conditions also help
minimize actuator 10, 12 and 34 loads under most circumstances.
Balance in this case is by geometry rather than mass.
[0123] Fluid: In an embodiment utilizing hydraulic cylinders, the
system is preferably well suited to use biodegradable oils because
of the design for low operating pressures and duty cycles. These
environmentally friendly fluids also reduce costs for clean-up and
maintenance.
[0124] Hose failure: As discussed above, in an embodiment of the
invention, counterbalance valves are mounted directly to the
cylinders. In the event of hose failure, the counterbalance valves
hold the cylinders in place until hydraulic power can be restored.
If the hydraulic fluid supply drops to the point that no cylinder
movement is possible, then the control system will sense this
condition and automatically shutdown. In any case the amount of
fluid spilled will be minimized. All fittings and seals and hoses
in the system are made with the latest technology and best quality
to assure minimal maintenance requirements and lowest probability
of leakage or spills.
[0125] In an embodiment of the solar tracker apparatus, separate
pumps and motors (or bi-directional pumps and motors) are used for
each cylinder as an alternative to valve controls from one pump to
multiple cylinders.
[0126] Another embodiment of the present invention makes use of
multiple layers of manipulation where a second, third, or fourth
base system is mounted on top of other systems such that the
manipulation is cumulative. This stacked approach provides greater
freedom of manipulation and reduces the impact of the mechanical
limits of the joints.
[0127] In an embodiment of the present invention, auxiliary
actuation of the sub-frame along a single axis or multiple axes
offers greater freedom and accuracy on the chosen axis. For
example, some embodiments of the present invention have minimal or
no articulation across the horizon (azimuth axis). These
configurations benefit from being able to rotate north-south for
the location of the sunrise/sunset on the horizon.
[0128] Further, an embodiment of the present invention may utilize
auxiliary actuation of the base as an alternate way of adding
flexibility and accuracy. In such a case the foundation mountings
of the actuators and post are each attached to a single rotating
base.
[0129] An embodiment of the present invention may utilize damping
such as struts or the like that are added to eliminate vibrations
and further reduce wear.
[0130] Additionally, an embodiment of the present invention may be
used for alternate purposes such as for aiming a satellite dish,
drive mechanism (such as a propeller or jet engine), or as a
mounting/aiming system for weapons.
[0131] An embodiment of the present invention does not use feed
forward control. In this alternate configuration the spline curve
positions are used as inputs for standard
Proportional-Integral-Derivative ("PID") control.
[0132] In alternate embodiments, additional articulation may be
added to rotate the linking mechanism 22 at the top of the post 14,
rotate the entire post 14, or rotate the entire apparatus 2. The
primary reason for doing so is to increase the accuracy of the
system in the early morning and/or late afternoon. For certain
conversion equipment to be mounted on an embodiment of the present
invention, the power generation opportunity increases by one to two
hours for both sunrise and sunset if the additional articulation is
added.
[0133] In alternate embodiments of the present invention, the solar
tracking apparatus may be mounted in orientations other than
horizontal. For example, the system may be mounted on the side of a
building, on a hillside, or the like. These locations will offer
less exposure to the sun in total but will benefit by a greater
efficiency from tracking the sun when there is exposure.
[0134] In another alternate embodiment of the present invention the
post height is actuated. A linear actuator or the like is used to
move the top of the post up and down while the joint is held from
rotating about the axis of the post by the actuator or framing
external to the actuator. This embodiment provides greater range of
motion for the platform with less stroke length in each
actuator.
[0135] A person of ordinary skill in the art will readily
understand that embodiments of the present invention are not
limited to only two actuators. In an embodiment of the present
invention, a third actuator may also be attached in a fashion
similar to actuators 10, 12 directly to the sub-frame 16 such that
it is on the opposite side of the post 14 and symmetric to the
east-west actuator. This third actuator would serve the same
purpose as the east-west actuator, thus increasing strength and
stability.
[0136] As shown in FIGS. 12A and 12B, in an embodiment of the
present invention, the system utilizes one or more inverted
cylinders 76. These cylinder configurations provide a pulling force
only, and have the advantage of gravity pulling debris away from
the rod seals 78.
[0137] Further, as shown in FIGS. 13-15, in an embodiment of the
present invention a second post 80 (fourth leg) is used to create
greater stability and torque resistance. In this version the second
post 80 is aligned with the axis of the lower rotation of the
linking mechanism 22 and the axle of the lower joint 82 is extended
to span the distance between the posts 14 and 80. The linking
mechanism 22 is further supported by link supports 81.
[0138] As depicted in FIGS. 19-21, another embodiment of the
present invention provides a constant moment lever 46 for actuation
through a sprocket gear 48 and rack gear 50. This configuration
also allows multiple trackers to share a single actuator 52 for the
east-west actuation. The single actuator 52 pushes and pulls a rod
54 with a rack gear 50 attached to the rod 54 at each solar tracker
56. The rack gear 50 interfaces with a sprocket gear 48 segment on
each tracker 56. The post-top link 58 is directly connected to the
sprocket gear 48 such that the link 58 rotates east and west (or
along the orientation desired at setup) as the rod 54 is pushed and
pulled. The rod 54 runs at or near ground level so as to provide
clearance for the solar tracker motion. The sprocket gear 48
segment has a radius R1 from the center of the rotational axis 60
of the lower axle of the post-top link 58 down to the rack gear 50
on the rod 54. In certain embodiments, the post 64 can be split
such that the rod 54 and sprocket gear 48 run between the two parts
of the post 64 or the rod 54 and sprocket gear 48 may run adjacent
to the post 64. The second actuator 66 for each solar tracker can
be moved continuously or may be moved periodically as needed to
meet performance requirements. In other embodiments the second
actuator 66 is replaced with a fixed length member or a manually
adjusted length member. This embodiment would be much less costly
to build and would provide advanced performance over other solar
trackers.
[0139] In yet another alternate embodiment the east-west actuator
is positioned horizontally and moves a gear rack which turns a spur
gear that is an integral part of the post link. The center of the
spur gear is the bottom axle of the link. The top axle of the link
is attached to the spur gear joining two points on the outer
circumference of the gear such that the axle has a sufficiently
long connection to the gear as to assure strength and stability,
and is sufficiently far from the other axle as to provide adequate
angular freedom to assure all positions of the sun can be reached
by the tracker. The axles would preferably be orthogonal to one
another. The two ends of the top axle and the second actuator on
the sub-frame would form stability triangles. The horizontal
actuator would be supported by a short post at its fixed end and it
would be supported by the center post at the rod end. The short
post, main post, and base of the second actuator would form the
stability triangle on the ground. The main post could either be
comprised of a two post system or a single post with a passage for
the actuated gear rack and actuator support though its center.
[0140] As depicted in FIGS. 22, 22A and 22B, in another alternate
embodiment a third ground-mounted actuator 68 is used to pull a
chain or cable 70 across a sprocket or non-slip pulley 72 in
opposition to the east-west control actuator 74 of a right angle
with sprocket ("RAS") model tracker. This embodiment provides a
constant moment for all positions of the actuators 74 driving the
east-west angular position and provides a greater stability factor
at and near the horizons. The chains or cable 70 can run over the
top or under the bottom of the sprocket or non-slip pulley 72.
[0141] Although preferred embodiments of the present invention and
modifications thereof have been described in detail herein, it is
to be understood that this invention is not limited to the
embodiments and modifications described herein, and that other
modifications and variations may be effected by one skilled in the
art without departing from the spirit and scope of the invention as
defined by the appended claims. For example, the present invention
may include four or more actuators, three or more posts, angled
posts, as well as other features.
LIST OF REFERENCE NUMBERS INCLUDED IN FIGURES
[0142] The following is a list of reference numbers used in the
attached figures for embodiments of the present invention: [0143]
(1) Foundation System [0144] (2) Solar Tracking Apparatus [0145]
(4) I-Beam Cross [0146] (6) Foundation Mountings [0147] (8)
Mounting Surface [0148] (10) Actuator [0149] (12) Actuator [0150]
(14) Post [0151] (15) Joint/Pinned Connection [0152] (16) Sub-frame
[0153] (17) Post Base [0154] (18) Platform [0155] (20) Joint
Connection [0156] (22) Linking Mechanism [0157] (23) Linking
Mechanism [0158] (24) Right Angle Triangle [0159] (25) Isosceles
Triangle [0160] (26) Center Axis [0161] (27) Equilateral Triangle
[0162] (28) Bearing Assembly [0163] (29) Steel Plate [0164] (30)
Bearing [0165] (31) Body Member [0166] (32) Offset [0167] (33)
First Axle [0168] (34) Third Actuator [0169] (35) Second Axle
[0170] (36) Mounts [0171] (38) Braces [0172] (40) Torsion
Resistance Bars [0173] (42) Foundations [0174] (44) Pedestal [0175]
(46) Constant Moment Lever [0176] (48) Sprocket Gear [0177] (50)
Rack Gear [0178] (52) East-West Actuator [0179] (54) Rod [0180]
(56) Solar Tracker [0181] (58) Post Top Link [0182] (60) Rotational
Axis [0183] (64) Post [0184] (66) Second (North-South) Actuator
[0185] (68) Ground Mounted Actuator [0186] (70) Chain [0187] (72)
Sprocket [0188] (74) East-West Actuator [0189] (76) Inverted
Cylinder [0190] (78) Rod Seals [0191] (80) Second Post [0192] (81)
Link Supports [0193] (82) Lower Joint [0194] (84) Pull Bar [0195]
(86) Chain Connection [0196] (88) Mounting Pins [0197] (90) Torsion
Bars [0198] (92) Push Bar [0199] (94) Guide Pins [0200] (96)
Foundation Plate
* * * * *