U.S. patent application number 16/194294 was filed with the patent office on 2019-05-30 for heliostat correction system based on celestial body images and its method.
The applicant listed for this patent is SHANGHAI PARASOL RENEWABLE ENERGY CO., LTD. Invention is credited to Yuda Chen, Ping Shen, Nan Sun, Siliang You.
Application Number | 20190162449 16/194294 |
Document ID | / |
Family ID | 61150600 |
Filed Date | 2019-05-30 |
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United States Patent
Application |
20190162449 |
Kind Code |
A1 |
Sun; Nan ; et al. |
May 30, 2019 |
Heliostat Correction System Based on Celestial Body Images and Its
Method
Abstract
A heliostat correction system includes an image acquisition
module for acquiring the image of a celestial body in a field of
view and sending the image to a data analysis module which analyzes
the deviation value between the celestial body image and the image
center in an image coordinate system and transmits the deviation
value to a correction calculation module which decomposes the
deviation to a corresponding rotation axis according to the
rotation mode of a heliostat to obtain the deviation angle of each
rotation axis; a data storage module is used to store the
correction result of the heliostat and the single correction period
control command list of the heliostat; a communication module reads
the single correction period control command list from the data
storage module, sends the list to the heliostat, and simultaneously
controls the image acquisition module to shoot according to the
rotation period of the heliostat.
Inventors: |
Sun; Nan; (Shanghai, CN)
; Shen; Ping; (Shanghai, CN) ; You; Siliang;
(Shanghai, CN) ; Chen; Yuda; (Shanghai,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHANGHAI PARASOL RENEWABLE ENERGY CO., LTD |
Shanghai |
|
CN |
|
|
Family ID: |
61150600 |
Appl. No.: |
16/194294 |
Filed: |
November 17, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/CN2018/081854 |
Apr 4, 2018 |
|
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16194294 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F24S 50/20 20180501;
G06K 9/209 20130101; G05D 3/12 20130101; G05B 23/02 20130101; G06K
9/3216 20130101; G05D 3/105 20130101; G05B 19/402 20130101; F24S
20/20 20180501 |
International
Class: |
F24S 50/20 20060101
F24S050/20; F24S 20/20 20060101 F24S020/20; G05B 23/02 20060101
G05B023/02; G05D 3/12 20060101 G05D003/12; G06K 9/20 20060101
G06K009/20 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 27, 2017 |
CN |
201711209150.3 |
Claims
1. A heliostat correction system based on celestial body images,
provided on a reflecting surface of a heliostat which is fixed on a
rotation axis, comprising: an image acquisition module, a data
analysis module, a correction calculation module, a data storage
module, and a communication module; wherein the image acquisition
module is in a same direction as the reflecting surface of the
heliostat, the image acquisition module and the heliostat both
facing celestial bodies or other markers; a deviation angle between
an optical axis vector of the image acquisition module and a normal
vector of the heliostat is known; the image acquisition module is
used for acquiring images of the celestial bodies moving regularly
in a field of view and having a certain brightness, and then
sending the images to the data analysis module, which analyzes a
deviation value between the celestial body image and an image
center in an image coordinate system and transmits the deviation
value to the correction calculation module, which decomposes the
deviation value to a corresponding rotation axis according to a
rotation mode of the heliostat to obtain the deviation angle of
each rotation axis; the data storage module is used for storing a
correction result of the heliostat and a single correction period
control command list of the heliostat; the communication module is
used for reading the single correction period control command list
from the data storage module, and then sending the list to the
heliostat while controlling the image acquisition module to shoot
according to a rotation period of the heliostat.
2. The heliostat correction system of claim 1, wherein the image
acquisition module comprises a light intensity adjusting device, an
imaging light path and a digital image sensor.
3. The heliostat correction system of claim 2, wherein the light
intensity adjusting device is a neutral attenuation sheet or other
device capable of adjusting an incident light intensity of a
celestial body, and the imaging light path is a lens or a
pinhole.
4. The heliostat correction system of claim 1, wherein the
correction calculation module adopts two correction methods
according to all deviation angle data of a single correction
period: method 1: an error correction model based on various error
parameters is derived from a theoretical mathematical model of the
heliostat, and error angle data corresponding to a time sequence is
substituted into the error correction model to obtain better error
parameter values; method 2: an exact position of a celestial body
is determined according to an image acquisition time; an ideal
rotation angle sequence of each axis based on time in a single
correction period is obtained, and then a connection is established
between the ideal rotation angle and an error angle sequence
through the acquired time sequence to generate an error angle
compensation table for each rotation axis.
5. A heliostat correction method based on celestial body images,
comprising: (1) installing the heliostat correction system of claim
1 on the heliostat to ensure that the image acquisition module in
the heliostat correction system is in a same direction as the
reflecting surface of the heliostat, and calibrating the image
acquisition module; (2) importing the single correction period
control command list of the heliostat to be corrected into the data
storage module; when correction is performed for a first time,
substituting initial parameters obtained from surveying and
measurement into a heliostat mathematical model to generate an
initial control command list; when the correction has been made, a
new control command list is generated according to a previous
correction result; (3) when environmental conditions meet
correction requirements, reading, by the communication module, the
single correction period control command list of the data storage
module and sending the single correction period control command
list to the heliostat, so that the heliostat adjusts a rotation
angle of each axis according to a preset period; (4) sending, by
the heliostat, feedback to the communication module every time the
heliostat completes adjustment, and controlling, by the
communication module, the image acquisition module to shoot the
celestial body images; (5) transmitting, by the image acquisition
module, the celestial body images to the data analysis module, and
calculating, by the data analysis module, the deviation
.DELTA.d.sub.x' and .DELTA.d.sub.y' between the celestial body
image center and the image center in the image coordinate system;
(6) decomposing, by the correction calculation module, the
deviation into corresponding rotation axes according to the
rotation mode of the heliostat to obtain the deviation angle of
each rotation axis, and then correcting the deviation angle of two
axes according to the deviation angle between the optical axis
vector of the image acquisition module and a normal vector of a
mirror surface of the heliostat; (7) after accumulating all the
deviation angle data of a single correction period, performing, by
the correction calculation module, correction on the heliostat; (8)
storing, by the correction calculation module, the correction
results of the heliostat in the data storage module, and
iteratively replacing the original single correction period control
command list of the heliostat to generate the control command list
of a next correction period; and (9) after the correction period
ends, notifying, by the communication module, the heliostat to
switch to a normal working state.
6. The heliostat correction method of claim 5, wherein the
correction method for the deviation angle in step (6) is as
follows: the mirror surface of the heliostat rotates around
orthogonal X axis and Y axis, where a position of the Y axis
remains fixed and the X axis rotates with the mirror surface around
the Y axis; a deviation angle of the X axis .DELTA..theta..sub.x
and a deviation angle of the Y axis .DELTA..theta..sub.y, satisfy
following relations: { .DELTA..theta. y = arctan ( .DELTA. d y '
Pix f ) .DELTA..theta. x = arctan ( .DELTA. d x ' Pix ( .DELTA. d y
' Pix ) 2 + f 2 ) ##EQU00005## Where, Pix represents a pixel size
of the image acquisition module and f represents a focal length of
the image acquisition module.
7. The heliostat correction method of claim 5, wherein the
correction method for the deviation angle in step (6) is as
follows: the mirror surface of the heliostat rotates around
orthogonal Z axis and Y axis, where a position of the Z axis
remains fixed and the Y axis rotates with the mirror surface around
the Z axis; a deviation angle of the Z axis .DELTA..theta..sub.z
and a deviation angle of the Y axis .DELTA..theta..sub.y, satisfy
following relations: { .DELTA..theta. y = arctan ( .DELTA. d y '
Pix f ) .DELTA..theta. z = arctan ( .DELTA. d x ' Pix f cos .theta.
y ) ##EQU00006## Where, Pix represents a pixel size of the image
acquisition module and f represents a focal length of the image
acquisition module.
8. The heliostat correction method of claim 5, wherein step (7)
adopts following two correction methods: method 1: an error
correction model based on various error parameters is derived from
a theoretical mathematical model of the heliostat, and error angle
data corresponding to a time sequence is substituted into the error
correction model to obtain better error parameter values, so that a
revised heliostat mathematical model is closer to an actual
mechanical motion; method 2: an exact position of a celestial body
is determined according to an image acquisition time; an ideal
rotation angle sequence of each axis based on time in a single
correction period is obtained, and then a connection is established
between the ideal rotation angle and an error angle sequence
through the acquired time sequence to generate an error angle
compensation table for each rotation axis, so that an angle between
the normal vector of the heliostat and an incident vector of the
celestial body is as small as possible.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a Continuation-In-Part
application of PCT Application No. PCT/CN2018/081854 filed on Apr.
4, 2018, which claims the benefit of Chinese Patent Application No.
201711209150.3 filed on Nov. 27, 2017. All the above are hereby
incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a heliostat correction
system based on celestial body images and its method, and belongs
to the technical field of heliostat correction.
BACKGROUND OF THE INVENTION
[0003] In a solar thermal power station, a certain number of
heliostats are used to reflect the sunlight in an area into a heat
absorber area, and the energy required for power generation is
obtained by concentrating the sunlight. However, the position of
the sun changes continuously with time, so the heliostats need to
move continuously to correct the exit direction of the reflected
light, so that the light spot can accurately fall in the area of
the heat absorber, thus improving the working efficiency of the
whole solar thermal power station.
[0004] The positions of celestial bodies (such as the sun, the
moon, first-class stars, etc.) that move regularly and have a
certain brightness can be accurately calculated by the
corresponding astronomical formulas, that is, the incident vector
at any given moment is known. The space positions of the heat
absorber area and the heliostat are relatively fixed, i.e. the
reflection vector at any moment is known. Therefore, in theory, for
the heliostat with a fixed installation position, its mirror
surface normal vector at any given moment can be accurately
calculated, which is then decomposed into the rotation angle of the
corresponding rotation axis according to the rotation mode of the
heliostat, so as to realize the accurate mechanical motion of the
heliostat.
[0005] Although sufficient mechanical motion accuracy of the
heliostat has been ensured in design, various new errors will be
introduced in the process of processing, manufacturing,
transportation and installation as well as daily operation, such as
tilt of the rotation axis of the heliostat, foundation deformation,
installation attitude deviation, deformation of the supporting
structure, etc., making the newly installed heliostat unable to
meet the design requirements and its reflected spot position will
shift, thus directly affecting the power generation efficiency.
Therefore, after installation, the heliostat needs to be corrected
to ensure the accuracy of its mechanical motion before it can meet
the requirements of normal operation, which is also a routine
workflow of the solar thermal power station.
[0006] At present, the heliostat correction technology mainly
involves identification and processing of the reflected light spot.
Chinese Patent (CN102937814B) first irradiates the light spot on a
carrier, then calculates the precision of the heliostat by means of
image acquisition and processing, and finally corrects the
heliostat according to the result. Chinese Patent (CN103345261B)
sets up a photosensitive array directly under the heat collector in
the same direction, calculates the deviation of the light spot
center according to the intensity of the output signal, and finally
corrects the rotation corner of the heliostat. Chinese Patent
(CN103728983A) installs an image acquisition device on the top of
the tower to photograph a specific heliostat, and calculates the
deviation between the actual rotation angle and the theoretical
rotation angle from the light spot position obtained by
acquisition. Although the above three methods are all traditional
methods of heliostat correction, the number of heliostats that can
be corrected at the same time is limited because the light spot
carriers (white boards, photosensitive arrays, image acquisition
devices, etc.) they use are installed on the tower.
[0007] In modern solar thermal power stations, there are usually
thousands of heliostats, and the data points for heliostat
correction need to cover the range of mechanical motion as much as
possible in order to obtain the best correction effect. Obviously,
the traditional correction methods with low efficiency usually take
a long time to make the heliostats in the whole solar thermal power
station reach the optimal working state, which can no longer meet
the operational requirements of modern solar thermal power
stations. Therefore, there is a need for a high-efficiency,
high-precision and convenient method to correct heliostats, which
can accurately correct any number of heliostats at the same
time.
SUMMARY OF THE INVENTION
[0008] The purpose of the present invention is to provide a
heliostat correction system based on celestial body images and its
method, in view of the fact that the current technology cannot meet
the existing needs, which takes celestial bodies (such as the sun,
the moon, first-class stars, etc.) that move regularly and have a
certain brightness as markers, and can carry out correction during
the day and at night, thus reducing the influence on the power
generation efficiency and improving the correction efficiency.
[0009] The technical proposal of the present invention is as
follows: a heliostat correction system based on celestial body
images, comprising a heliostat fixed on a rotation axis; the
reflecting surface of the heliostat is provided with a heliostat
correction system; the heliostat correction system comprises an
image acquisition module, a data analysis module, a correction
calculation module, a data storage module and a communication
module; the image acquisition module is in the same direction as
the reflecting surface of the heliostat, i.e. both facing celestial
bodies or other markers; the deviation angle between the optical
axis vector of the image acquisition module and the normal vector
of the heliostat is known; the image acquisition module is used for
acquiring images of celestial bodies moving regularly in the field
of view and having a certain brightness, and then sending them to
the data analysis module, which analyzes the deviation value
between the celestial body image and the image center in the image
coordinate system and transmits the deviation value to the
correction calculation module, which decomposes the deviation value
to the corresponding rotation axis according to the rotation mode
of the heliostat to obtain the deviation angle of each rotation
axis; the data storage module is used for storing the correction
result of a single heliostat and the single correction period
control command list of the heliostat; the communication module
reads the single correction period control command list from the
data storage module and then sends the list to the heliostat while
controlling the image acquisition module to shoot according to the
rotation period of the heliostat.
[0010] In the present invention: the image acquisition module
comprises a light intensity adjusting device, an imaging light path
and a digital image sensor, wherein the light intensity adjusting
device is a neutral attenuation sheet or other device capable of
adjusting the incident light intensity of a celestial body, and the
imaging light path is a lens or a pinhole.
[0011] In the present invention: the correction calculation module
adopts two correction methods according to all deviation angle data
of a single correction period:
[0012] Method 1: The error correction model based on various error
parameters is derived from the theoretical mathematical model of
the heliostat, and the error angle data corresponding to a time
sequence is substituted into the error correction model to obtain
better error parameter values;
[0013] Method 2: The exact position of a celestial body is
determined according to the image acquisition time; the ideal
rotation angle sequence of each axis based on time in a single
correction period is obtained, and then a connection is established
between the ideal rotation angle and the error angle sequence
through the acquired time sequence to generate an error angle
compensation table for each rotation axis.
[0014] A heliostat correction system based on celestial body
images, comprising the following steps:
[0015] (1) Installing the heliostat correction system on the
heliostat to ensure that the image acquisition module in the
heliostat correction system is in the same direction as the
reflecting surface of the heliostat; the deviation angle between
the optical axis vector of the image acquisition module and the
normal vector of the mirror surface of the heliostat is known; the
image acquisition module is calibrated;
[0016] (2) Importing the single correction period control command
list of the heliostat to be corrected into the data storage module;
if correction is performed for the first time, substituting the
initial parameters obtained from surveying and measurement into the
heliostat mathematical model to generate the initial control
command list; if correction has been made, a new control command
list is generated according to the previous correction result
instead;
[0017] (3) When the environmental conditions meet the correction
requirements, the communication module reads the single correction
period control command list of the data storage module and sends it
to the heliostat, so that the heliostat adjusts the rotation angle
of each axis according to the preset period;
[0018] (4) The heliostat to be corrected sends feedback to the
communication module every time the heliostat completes adjustment,
and the communication module controls the image acquisition module
to shoot celestial body images;
[0019] (5) The image acquisition module transmits the celestial
body images to the data analysis module, and the data analysis
module calculates the deviation .DELTA.d.sub.x' and .DELTA.d.sub.y'
between the celestial body image center and the image center in the
image coordinate system;
[0020] (6) The correction calculation module decomposes the
deviation into the corresponding rotation axes according to the
rotation mode of the heliostat to obtain the deviation angle of
each rotation axis, and then corrects the deviation angle of the
two axes according to the deviation angle between the optical axis
vector of the image acquisition module and the normal vector of the
mirror surface of the heliostat;
[0021] (7) After accumulating all the deviation angle data of a
single correction period, the correction calculation module
performs correction on the heliostat;
[0022] (8) The correction calculation module stores the correction
results of the heliostat in the data storage module, and
iteratively replaces the original single correction period control
command list of the heliostat to generate the control command list
of the next correction period; and
[0023] (9) After the correction period ends, the communication
module notifies the heliostat to switch to the normal working
state.
[0024] In the present invention: the correction method for the
deviation angle in Step (6) is as follows:
[0025] The mirror surface of the heliostat rotates around the
orthogonal X axis and Y axis, where the position of the Y axis
remains fixed and the X axis rotates with the mirror surface around
the Y axis. The deviation angles of this rotation mode, i.e. the
deviation angle of the X axis .DELTA..theta..sub.x and the
deviation angle of the Y axis .DELTA..theta..sub.y, satisfy the
following relations:
{ .DELTA..theta. y = arctan ( .DELTA. d y ' Pix f ) .DELTA..theta.
x = arctan ( .DELTA. d x ' Pix ( .DELTA. d y ' Pix ) 2 + f 2 )
##EQU00001##
[0026] Where Pix represents the pixel size of the image acquisition
module and f represents the focal length of the image acquisition
module.
[0027] In the present invention: the correction method for the
deviation angle in Step (6) is as follows:
[0028] The mirror surface of the heliostat rotates around the
orthogonal Z axis and Y axis, where the position of the Z axis
remains fixed and the Y axis rotates with the mirror surface around
the Z axis. The deviation angles of this rotation mode, i.e. the
deviation angle of the Z axis .DELTA..theta..sub.z and the
deviation angle of the Y axis .DELTA..theta..sub.y, satisfy the
following relations:
{ .DELTA..theta. y = arctan ( .DELTA. d y ' Pix f ) .DELTA..theta.
z = arctan ( .DELTA. d x ' Pix f cos .theta. y ) ##EQU00002##
[0029] Where, Pix represents the pixel size of the image
acquisition module and f represents the focal length of the image
acquisition module.
[0030] In the present invention: Step (7) adopts the following two
correction methods:
[0031] Method 1: The error correction model based on various error
parameters is derived from the theoretical mathematical model of
the heliostat, and the error angle data corresponding to a time
sequence is substituted into the error correction model to obtain
better error parameter values, so that the revised heliostat
mathematical model is closer to the actual mechanical motion.
[0032] Method 2: The exact position of a celestial body is
determined according to the image acquisition time; the ideal
rotation angle sequence of each axis based on time in a single
correction period is obtained, and then a connection is established
between the ideal rotation angle and the error angle sequence
through the acquired time sequence to generate an error angle
compensation table for each rotation axis, so that the angle
between the normal vector of the heliostat and the incident vector
of the celestial body is as small as possible.
[0033] Beneficial effects of the present invention:
[0034] 1. The present invention takes celestial bodies (such as the
sun, the moon, first-class stars, etc.) that move regularly and
have a certain brightness as markers, and can carry out correction
during the day and at night, thus reducing the influence on the
power generation efficiency and improving the correction
efficiency.
[0035] 2. The present invention takes celestial bodies that move
regularly and have a certain brightness as markers, aligns the
surface normal of the heliostat with the center of the celestial
body, and then calculates the included angle between the surface
normal vector and the incident vector through the image acquisition
module, and calculates the deviation of the mechanical motion of
the heliostat, so that all the heliostats to be corrected can be
corrected simultaneously and concurrently by an independent
heliostat correction system, thus greatly improving the correction
efficiency.
[0036] 3. A single heliostat correction system is only responsible
for the correction of one heliostat and the correction systems on
different heliostats are independent of each other. Therefore,
failure of a certain heliostat correction system will only affect
the heliostat to which it belongs and will not affect the heliostat
correction progress of the solar thermal power station.
[0037] 4. The heliostat correction system comprises an image
acquisition module, a data analysis module, a correction
calculation module, a data storage module and a communication
module. A single heliostat correction system can independently
complete all the correction work of a single heliostat, and can
ensure the efficiency of heliostat correction.
[0038] 5. The communication module can send the updated single
correction period control command list to the heliostat without
sending the data back to the upper computer for processing and then
sending by the upper computer, thus reducing the possibility of
error.
[0039] 6. The heliostat correction system can be directly installed
on the reflecting surface of the heliostat, and the modularized
heliostat correction system can be replaced directly in case of
failure, so the equipment maintenance is of low difficulty and
cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 is a schematic view of the system of the present
invention;
[0041] FIG. 2 is a schematic view of the detection of the present
invention;
[0042] FIG. 3 is a schematic view of deviation calculation of the
image coordinate system of the present invention;
[0043] FIG. 4 is a schematic view of the rotation mode of the
heliostat of the present invention;
[0044] FIG. 5 is an exploded view of the deviation angle of the
rotation mode of FIG. 4;
[0045] FIG. 6 is a schematic view of another rotation mode of the
heliostat of the present invention;
[0046] FIG. 7 is an exploded view of the deviation angle of the
rotation mode of FIG. 6;
[0047] In the figures: 1. heliostat; 2. heliostat correction
system; 3. celestial body; 4. image acquisition module; 5. data
analysis module; 6. correction calculation module; 7. data storage
module; and 8. communication module.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0048] The present invention will now be described in detail with
reference to the accompanying drawings and embodiments.
[0049] As shown in FIGS. 1 to 7, a heliostat correction system
based on celestial body images comprising a heliostat 1 which is
fixed on the rotation axis; the reflecting surface of the heliostat
1 is provided with a heliostat correction system 2; in the present
invention, the heliostat correction system 2 comprises an image
acquisition module 4, a data analysis module 5, a correction
calculation module 6, a data storage module 7 and a communication
module 8, and is used for the daily correction of the heliostat 1
in the solar thermal power station. The image acquisition module 4
comprises a light intensity adjusting device (a neutral attenuation
sheet or other device capable of adjusting the incident light
intensity of a celestial body), an imaging light path (a lens or a
pinhole) and a digital image sensor; the image acquisition module 4
is in the same direction as the reflecting surface of the heliostat
1; the deviation angle between the optical axis vector of the image
acquisition module 4 and the normal vector of the mirror surface of
the heliostat 1 is known; the image acquisition module 4 is used
for acquiring images of celestial bodies (such as the sun, the
moon, first-class stars, etc.) moving regularly in the field of
view and having a certain brightness, and then sending the images
to the data analysis module 5. The data analysis module 5 analyzes
the deviation value between the celestial body image and the image
center in the image coordinate system and transmits the deviation
value to the correction calculation module 6. The correction
calculation module 6 decomposes the deviation value to the
corresponding rotation axis according to the rotation mode of the
heliostat 1 to obtain the deviation angle of each rotation axis.
There are at least two correction methods:
[0050] (1) The error correction model based on various error
parameters
(x.sub.1,x.sub.2,x.sub.3,x.sub.4,x.sub.5,x.sub.6,x.sub.7,x.sub.8,x.sub.9,-
x.sub.10,x.sub.11,x.sub.12) is derived from the mathematical model
of the heliostat 1, where x.sub.1 and x.sub.2 represent the tilt
error of the two rotation axes; x.sub.3 represents the included
angle between the two rotation axes; x.sub.4 and x.sub.5 represent
the zero error of the two rotation axes; x.sub.6 and x.sub.7
represent the proportionality coefficient of the two rotation axes;
x.sub.8 and x.sub.9 represent the normal error of the mirror
surface of the heliostat; x.sub.10, x.sub.11 and x.sub.12 represent
the relative position error between the center of the heliostat
correction system and the center of the heliostat. The error angle
data corresponding to a time sequence is substituted into the error
correction model to obtain better error parameter values, so that
the revised heliostat mathematical model is closer to the actual
mechanical motion.
[0051] (2) The exact position of a celestial body is determined
according to the image acquisition time; the ideal rotation angle
sequence of each axis based on time in a single correction period
is obtained, and then a connection is established between the ideal
rotation angle and the error angle sequence through the acquired
time sequence to generate an error angle compensation table for
each rotation axis, so that the angle between the normal vector of
the heliostat and the incident vector of the celestial body is as
small as possible.
[0052] The data storage module 7 is used for storing the correction
result of a single heliostat 1 and the single correction period
control command list of the heliostat 1, where an initial value is
set for the single correction period control command list of the
heliostat 1 which is replaced and corrected in an iterative manner
according to the correction result. The communication module 8
reads the single correction period control command list from the
data storage module 7 and then sends the list to the heliostat 1
while controlling the image acquisition module 4 to shoot according
to the rotation period of the heliostat 1.
[0053] As shown in FIG. 2, each heliostat 1 in the solar thermal
power station has an independent heliostat correction system 2, and
each heliostat correction system 2 performs a correction process
for the celestial body 3. Relative to the distance from the
celestial body to the earth, the influence of the position change
of the heliostat correction system 2 on the mirror surface on the
correction accuracy is negligible, so the heliostat correction
system 2 can be installed at any position of the reflecting surface
of the heliostat 1, but it needs to be ensured that: 1) the
deviation angle between the optical axis vector of the image
acquisition module 4 in the heliostat correction system 2 and the
normal vector of the mirror surface of the heliostat 1 is known; 2)
the image acquisition module 4 in the heliostat correction system 2
is in the same direction as the reflecting surface of the heliostat
1, i.e. both facing celestial bodies or other markers; 3) the
coordinate system of the image acquisition module 4 corresponds to
the coordinate system of the heliostat 1 or the deviation angle is
known.
[0054] The correction process of a single heliostat 1 in the
present invention comprises the following steps:
[0055] (1) Installing the heliostat correction system 2 on the
heliostat 1 to ensure that the deviation angle between the optical
axis vector of the image acquisition module 4 in the heliostat
correction system 2 and the normal vector of the mirror surface of
the heliostat 1 is known; the image acquisition module 4 is in the
same direction as the reflecting surface of the heliostat 1; the
coordinate system of the image acquisition module 4 corresponds to
the coordinate system of the heliostat 1 or the deviation angle is
known; the image acquisition module 4 is calibrated;
[0056] (2) Importing the single correction period control command
list of the heliostat 1 to be corrected into the data storage
module 7; if correction is performed for the first time,
substituting the initial parameters obtained from surveying and
measurement into the heliostat mathematical model to generate the
initial control command list; if correction has been made, a new
control command list is generated according to the previous
correction result instead;
[0057] (3) When the environmental conditions meet the correction
requirements, the communication module 8 reads the single
correction period control command list of the data storage module 7
and sends it to the heliostat 1, so that the heliostat 1 adjusts
the rotation angle of each axis according to the preset period;
[0058] (4) The heliostat 1 to be corrected sends feedback to the
communication module 8 every time the heliostat completes
adjustment, and the communication module 8 controls the image
acquisition module 4 to shoot celestial body images;
[0059] (5) As shown in FIG. 3, the image acquisition module 4
transmits the celestial body images to the data analysis module 5,
and the data analysis module 5 calculates the deviation
.DELTA.d.sub.x' and .DELTA.d.sub.y' between the celestial body
image center and the image center in the image coordinate
system;
[0060] (6) The correction calculation module 6 decomposes the
deviation into the corresponding rotation axes according to the
rotation mode of the heliostat 1 to obtain the deviation angle of
each rotation axis, and then corrects the deviation angle of the
two axes according to the deviation angle between the optical axis
vector of the image acquisition module and the normal vector of the
mirror surface of the heliostat;
[0061] FIG. 4 is a schematic view of the rotation mode of the
heliostat 1. The mirror surface of the heliostat 1 rotates around
the orthogonal X axis and Y axis, where the position of the Y axis
remains fixed and the X axis rotates with the mirror surface around
the Y axis. The decomposition of the deviation angles of this
rotation mode is shown in FIG. 5; the deviation angle of the X axis
.DELTA..theta..sub.x and the deviation angle of the Y axis
.DELTA..theta..sub.y satisfy the following relations:
{ .DELTA..theta. y = arctan ( .DELTA. d y ' Pix f ) .DELTA..theta.
x = arctan ( .DELTA. d x ' Pix ( .DELTA. d y ' Pix ) 2 + f 2 )
##EQU00003##
[0062] Where, Pix represents the pixel size of the image
acquisition module and f represents the focal length of the image
acquisition module.
[0063] FIG. 6 is a schematic view of another rotation mode of the
heliostat 1. The mirror surface of the heliostat 1 rotates around
the orthogonal Z axis and Y axis, where the position of the Z axis
remains fixed and the Y axis rotates with the mirror surface around
the Z axis. The decomposition of the deviation angles of this
rotation mode is shown in FIG. 7; the deviation angle of the Z axis
.DELTA..theta..sub.z and the deviation angle of the Y axis
.DELTA..theta..sub.y satisfy the following relations:
{ .DELTA..theta. y = arctan ( .DELTA. d y ' Pix f ) .DELTA..theta.
z = arctan ( .DELTA. d x ' Pix f cos .theta. y ) ##EQU00004##
[0064] Where, Pix represents the pixel size of the image
acquisition module and f represents the focal length of the image
acquisition module.
[0065] (7) After accumulating all the deviation angle data of a
single correction period, the correction calculation module 6
performs correction on the heliostat 1;
[0066] There are two correction methods:
[0067] Method 1: The error correction model based on various error
parameters
(x.sub.1,x.sub.2,x.sub.3,x.sub.4,x.sub.5,x.sub.6,x.sub.7,x.sub.8,x.sub.9,-
x.sub.10,x.sub.11,x.sub.12) is derived from the mathematical model
of the heliostat 1, where x.sub.1 and x.sub.2 represent the tilt
error of the two rotation axes; x.sub.3 represents the included
angle between the two rotation axes; x.sub.4 and x.sub.5 represent
the zero error of the two rotation axes; x.sub.6 and x.sub.7
represent the proportionality coefficient of the two rotation axes;
x.sub.8 and x.sub.9 represent the normal error of the mirror
surface of the heliostat; x.sub.10, x.sub.11 and x.sub.12 represent
the relative position error between the center of the heliostat
correction system and the center of the heliostat. The error angle
data corresponding to a time sequence is substituted into the error
correction model to obtain better error parameter values, so that
the revised heliostat mathematical model is closer to the actual
mechanical motion.
[0068] Method 2: The exact position of a celestial body is
determined according to the image acquisition time; the ideal
rotation angle sequence of each axis based on time in a single
correction period is obtained, and then a connection is established
between the ideal rotation angle and the error angle sequence
through the acquired time sequence to generate an error angle
compensation table for each rotation axis, so that the angle
between the normal vector of the heliostat and the incident vector
of the celestial body is as small as possible.
[0069] (8) The correction calculation module 6 stores the
correction results of the heliostat 1 in the data storage module 7,
and iteratively replaces the original single correction period
control command list of the heliostat 1 to generate the control
command list of the next correction period; and
[0070] (9) After a single correction period ends, the communication
module 8 notifies the heliostat 1 to switch to the normal working
state.
[0071] According to the above embodiments:
[0072] I. The heliostat correction system of the present invention
takes celestial bodies (such as the sun, the moon, first-class
stars, etc.) that move regularly and have a certain brightness as
markers, aligns the mirror surface of the heliostat with the center
of the celestial body, and then calculates the included angle
between the normal vector of the mirror surface and the incident
vector through the image acquisition module, to obtain the
deviation of the mechanical motion of the heliostat. Therefore, all
the heliostats to be corrected can be corrected simultaneously and
concurrently by an independent heliostat correction system, thus
greatly improving the correction efficiency;
[0073] II. The heliostat correction system of the present invention
takes celestial bodies (such as the sun, the moon, first-class
stars, etc.) that move regularly and have a certain brightness as
markers, and can carry out correction during the day and at night,
thus reducing the influence on the power generation efficiency and
improving the correction efficiency.
[0074] III. In the present invention, a single heliostat correction
system is only responsible for the correction of one heliostat and
the correction systems on different heliostats are independent of
each other. Therefore, failure of a certain heliostat correction
system will only affect the heliostat to which it belongs and the
modularized heliostat correction system can be replaced directly in
case of failure, causing no influence on the heliostat correction
progress of the whole solar thermal power station.
[0075] IV. The heliostat correction system of the present invention
comprises an image acquisition module, a data analysis module, a
correction calculation module, a data storage module and a
communication module. A single heliostat correction system can
independently complete all the correction work of a single
heliostat and the modularized heliostat correction system can be
replaced directly in case of failure, causing no influence on the
heliostat correction progress of the whole solar thermal power
station.
[0076] V. The heliostat correction system of the present invention
comprises a communication module which can send the updated single
correction period control command list to the heliostat without
sending the data back to the upper computer for processing and then
sending by the upper computer, thus reducing the possibility of
error.
[0077] VI. The heliostat correction system of the present invention
can be directly installed on the reflecting surface of the
heliostat, and the modularized heliostat correction system can be
replaced directly in case of failure, so the equipment maintenance
is of low difficulty and cost.
[0078] The above is a description of embodiments of the present
invention, but the present invention is not limited to the above
description. It is within the scope of the present invention for
persons skilled in the art to make any equivalent modifications and
substitutions to this technical proposal. Therefore, all equivalent
changes and modifications made without departing from the spirit
and scope of the present invention shall fall within the scope of
the present invention.
* * * * *