U.S. patent application number 11/977657 was filed with the patent office on 2008-05-01 for method, controller and system providing techniques for control of an air loaded regulator and cascaded control loops.
This patent application is currently assigned to Enfield Technologies, LLC. Invention is credited to Daniel S. Cook.
Application Number | 20080099069 11/977657 |
Document ID | / |
Family ID | 39474993 |
Filed Date | 2008-05-01 |
United States Patent
Application |
20080099069 |
Kind Code |
A1 |
Cook; Daniel S. |
May 1, 2008 |
Method, controller and system providing techniques for control of
an air loaded regulator and cascaded control loops
Abstract
A method for controlling a dome-operated pressure regulator is
disclosed. The pressure at a dome side of the pressure regulator is
measured. The operation of the pressure regulator is controlled
based upon at least a received command signal and the measurement.
A proportional control valve may be used to control the pressure on
at the dome side of the pressure regulator. A controller and a
system are also disclosed.
Inventors: |
Cook; Daniel S.;
(Terryville, CT) |
Correspondence
Address: |
HARRINGTON & SMITH, PC
4 RESEARCH DRIVE
SHELTON
CT
06484-6212
US
|
Assignee: |
Enfield Technologies, LLC
|
Family ID: |
39474993 |
Appl. No.: |
11/977657 |
Filed: |
October 24, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60854562 |
Oct 25, 2006 |
|
|
|
Current U.S.
Class: |
137/14 ;
137/101.19; 137/487.5; 251/129.04 |
Current CPC
Class: |
H01F 7/1844 20130101;
F16K 31/02 20130101; Y10T 137/87217 20150401; F16K 31/04 20130101;
Y10T 137/7761 20150401; F16K 27/041 20130101; F15B 13/0402
20130101; F16K 11/07 20130101; F15B 13/0446 20130101; Y10S 251/905
20130101; F16K 31/0613 20130101; Y10T 137/86622 20150401; F16K
27/048 20130101; Y10T 137/86614 20150401; Y10T 137/0396 20150401;
Y10T 137/2529 20150401; F16K 37/0041 20130101 |
Class at
Publication: |
137/14 ;
137/101.19; 137/487.5; 251/129.04 |
International
Class: |
G05D 16/02 20060101
G05D016/02; G05D 16/20 20060101 G05D016/20 |
Claims
1. A method comprising: taking a pressure measurement at a dome
side of a dome-operated pressure regulator; receiving a command
signal; and controlling operation of the pressure regulator based
upon at least the command signal and the measurement.
2. The method of claim 1, wherein the operation of the pressure
regulator is controlled by a proportional control valve that
affects the dome side.
3. The method of claim 2, wherein the controlling of the
proportional control valve includes at least one of dead band
elimination and dither amplitude and frequency control.
4. The method of claim 2, wherein the controlling of the
proportional control valve includes using a pulse width modulation
drive signal.
5. The method of claim 4, wherein the pulse width modulation drive
signal has a switching frequency of 40 kHz.
6. The method of claim 2, wherein the proportional control valve is
a bi-directional valve and further controls a venting of dome
pressure.
7. The method of claim 1, wherein the controlling the operation of
the air loaded pressure regulator utilizes electronic circuitry to
calculate a command for the proportional valve; wherein the
circuitry utilizes a proportional, integral, and derivative based
topology with a feed forward path.
8. The method of claim 1, wherein the controlling of the operation
of the pressure regulator is further based upon the history of the
command signal and the measurements.
9. The method of claim 1, wherein the controlling of the operation
of the pressure regulator is further based upon a pressure
difference in a fluid pressure.
10. A controller comprising: circuitry configured to receive a
pressure measurement taken at a dome side of a dome operated
pressure regulator; circuitry configured to receive a command
signal; and circuitry configured to generate a control signal for
controlling the operation of the pressure regulator based upon at
least the command signal and the measurement.
11. The controller of claim 10, further comprising circuitry
configured to provide at least one of dead band elimination and
dither amplitude and frequency control.
12. The controller of claim 10, wherein controlling the
proportional control valve includes using a pulse width modulation
drive signal.
13. The controller of claim 12, wherein the pulse width modulation
drive signal has a switching frequency of 40 kHz.
14. The controller of claim 10, wherein controlling the operation
of the pressure regulator utilizes proportional, integral, and
derivative based topology with a feed forward path.
15. The controller of claim 10, wherein the controlling the
operation of the pressure regulator is further based upon the
history of the command signal and the measurements.
16. The controller of claim 10, wherein controlling the operation
of the pressure regulator is further based upon a pressure
difference in a fluid pressure.
17. A system comprising: a dome operated pressure regulator; a
sensor configured to take a pressure measurement at a dome side of
the pressure regulator; circuitry configured to receive a command
signal; and a controller configured to generate a control signal
for controlling the operation of the pressure regulator based upon
at least the command signal and the measurement.
18. The system of claim 17, further comprising a proportional
control valve that affects the pressure at the dome side of the
dome-operated pressure regulator.
19. The system of claim 17, wherein generating the control signal
is further based upon the history of the command signal and the
measurements.
20. The system of claim 17, wherein generating the control signal
is further based upon a pressure difference in a fluid
pressure.
21. The system of claim 17, wherein generating the control signal
is further based on measurements taken on the high pressure signal.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS:
[0001] This patent application claims priority under 35 U.S.C.
.sctn.119(e) from Provisional Patent Application No. 60/854,562,
filed Oct. 25, 2006, the disclosure of which is incorporated by
reference herein in its entirety.
TECHNICAL FIELD
[0002] This invention relates generally to control systems and,
more specifically, relates to controllers and systems using
electronically controlled valves, electronically controlled valves,
and portions thereof.
BACKGROUND
[0003] Control systems for electronically controlled valves control
many different types of fluids for many different purposes. While
control systems, their controllers, and the associated
electronically controlled valves have many benefits, these control
systems, controllers, electronically controlled valves and portions
thereof may still be improved.
[0004] It is desired to control very high pressure (e.g., 1,500
PSI) air through the use of air loaded mechanical pressure
regulator. Classical single loop control methods do not meet the
demanding performance criteria. Such methods result in the output
being oscillatory with higher gains or faster responses, but
performing too slowly with stable gains. Such classical approaches
tolerate the performance limitations.
[0005] A method to control the output of a air loaded high pressure
regulator to a very fine degree was needed.
[0006] The air loaded regulator functions by applying air pressure
to the control dome of an appropriate level of apply a force on a
countering piston. This piston is sized appropriately such that the
down stream high pressure acts on the piston and in direct
opposition to the dome pressure. Because of the area ratio of the
low pressure and high pressure sides, the pressures required to
exert equal forces are equivalent to the inverse of this area
ratio. Because of this, a relative low pressure air source (e.g.
100 psig) may be controlled which will in turn control a relatively
high pressure air source (e.g. 1500 psig).
SUMMARY
[0007] An exemplary embodiment in accordance with this invention is
a method for controlling a dome-operated pressure regulator. The
pressure at a dome side of the pressure regulator is measured. A
command signal is received. The operation of the pressure regulator
is controlled based upon at least the command signal and the
measurement.
[0008] A further exemplary embodiment in accordance with this
invention is a controller. The controller includes circuitry
configured to receive a pressure measurement taken at a dome side
of a dome operated pressure regulator. There is circuitry
configured to receive a command signal. The controller also has
circuitry configured to generate a control signal for controlling
the operation of the pressure regulator based upon at least the
command signal and the measurement.
[0009] Another exemplary embodiment in accordance with this
invention is a system that includes a dome operated pressure
regulator. A sensor is provided that is configured to take a
pressure measurement at a dome side of the pressure regulator.
There is circuitry configured to receive a command signal. The
system includes a controller that is configured to generate a
control signal for controlling the operation of the pressure
regulator based upon at least the command signal and the
measurement.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The attached Drawing Figures include the following:
[0011] FIG. 1 is a block diagram of a system including a portion
for controlling an electronically controlled valve and the
electronically controlled valve;
[0012] FIG. 2 is a cutaway, perspective view of an exemplary
pneumatic valve;
[0013] FIG. 3 is a view of the motor housing retainer coupled to
the motor housing and also of the coil header assembly and
spool;
[0014] FIG. 4 shows a block diagram of a rheometer pneumatic
pressure control system;
[0015] FIG. 5 shows a block diagram of a rheometer pneumatic
pressure control system;
[0016] FIG. 6 shows a block diagram of an air loaded high pressure
regulator;
[0017] FIG. 7 shows a logic flow diagram of a method in accordance
with an embodiment of this invention; and
[0018] FIG. 8 shows a diagram of an Tescom air loaded pressure
regulator.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0019] Referring now to FIG.1, a block diagram is shown of an
exemplary system 100 having a portion for controlling an
electronically controlled valve 120. System 100 also includes in
this example the electronically controlled valve 120. FIG. 1 is a
simplistic, high-level view of a system 100 that includes a control
input 105, an adder 10, a spool position controller 115, the
electronically controlled valve 120, and a feedback sensor module
150 that takes an input from one or more feedback sensors (not
shown) and that produces one or more feedback signals 151. A valve
controller 160 includes the adder 110, the spool position
controller 115, and the feedback sensor module 150. The
electronically controlled valve 120 includes a spool actuator 125,
such as a voice coil, a spool 130, a body 135, an input 140, and an
output 145.
[0020] The electronically controlled valve 120 controls fluid
(e.g., air, gas, water, oil) 141 flow through the electronically
controlled valve 120 by operating the spool 130. The spool actuator
125 controls movement of the spool 130 based on one or more control
signals 116 from the spool position controller 115. The spool
position controller 115 modifies the one or more control signals
116 based on the one or more input signals 111, which include
addition of the control input signal 105 and the one or more
feedback signals 151. The feedback sensor module 150 can monitor
the spool actuator 120 (e.g., current through the spool actuator),
a sensor indicating the position of the spool 130, or sensors
indicating any number of other valve attributes (e.g., pressure or
flow rate of the fluid 141). Aspects of the present invention are
related to a number of the elements shown in FIG. 1.
[0021] Now that an introduction has been given with regard to an
exemplary system 100, descriptions of exemplary aspects of the
invention will now be given.
[0022] Turning to FIG. 2 in addition to FIG. 1, a cutaway,
perspective view is shown of an exemplary pneumatic valve 200. The
pneumatic valve 200 includes an electronics cover 205, a motor
housing retainer 207, a motor housing 210, an upper cavity 215, a
lower cavity 216, a coil header assembly 220, a spool 230, a sleeve
260, a lower spring 240, an upper spring 245, external ports 270,
271, 280, 281, and 282, circumferentially spaced internal ports
270a, 271a, 280a, 281a, and 282a, and a valve body 290. Coil header
assembly 220 includes a voice coil portion 222 having a voice coil
221 and an overlap portion that overlaps a portion of the spool 230
and connects the spool 230 to the coil header assembly 220. The
spool actuator 125 of FIG. 1 includes, in the example of FIG. 2,
motor housing 210, coil header assembly 220, upper spring 245, and
lower spring 240. It is noted that a view of the motor housing 210
is also shown in, e.g., FIG. 3 and that at least a portion of the
motor housing 210 is magnetized in order to be responsive to the
voice coil 221. A cable 1720 couples the motor housing retainer 207
to the voice coil 221.
[0023] In this example, a top surface 211 of the motor housing 210
contacts a bottom surface 208 of motor housing retainer 207. The
motor housing 210 is therefore held in place by the motor housing
retainer 207, and the motor housing retainer 207 is a printed
circuit board.
[0024] Patent application Ser. No. ______, filed on Sep. 19, 2007
and titled "Retaining Element for a Mechanical Component" describes
the motor housing retainer 207 in further detail. Patent
application Ser. No. ______ is assigned to the assignee of the
present application, and is hereby incorporated by reference in its
entirety.
[0025] The spool 230 includes in this example a passage 265. The
passage 265 has a number of purposes, including equalizing pressure
between the upper cavity 215 and the lower cavity 216, as described
in more detail below. The passage 230 is included in an exemplary
embodiment herein, but the spool 230 may also be manufactured
without passage 265.
[0026] An exemplary embodiment in accordance with this invention is
a method which includes formation and control of a dual loop (e.g.,
cascaded loops) system.
[0027] A rheometer may be used to empirically determine properties
of various fluids (e.g., viscosity and its derivatives). To
accomplish this task, a pump forces fluid through a restrictive
passage where transducers are placed. These transducers serve as a
fluid/air interface and output a signal proportional to the
difference in pressure between the fluid side and air side. A
rheometer pneumatic pressure control system (RPPCS) can control the
air pressure so as to minimize this difference between fluid
pressure and air pressure so that fluid pressure may be measured
indirectly rather than directly so that the sensors don't get
contaminated and so that the pressure sensors themselves are not
affected by dynamic random fluid forces.
[0028] A simple block diagram of such as the system is shown in
FIG. 4. As shown in diagram, a source of high pressure 410 and a
source of low pressure 420 air is supplied in addition to a vacuum
source. There is an inner loop that includes a low-level signal
sensor amplifier 440, e.g., the LS-C30, which is responsive to a
dome pressure of a high pressure regulator 445, and an outer loop
that is controlled by a high performance RPPCS controller 450. The
dome pressure valve 480, e.g., the LS-V15, shown in FIG. 4 is
similar to the valve shown in FIG. 2.
[0029] FIG. 5 shows a block diagram of a rheometer control system,
including an outer loop controller and an inner loop controller. By
sensing and using information from the high pressure side (e.g., as
received via the D/P Xducer feedback signal) and dome pressure on
the dome of a high pressure regulator (where the dome pressure is
controlled is controlled by the RPPCS controller `inner` loop where
the inner control loop is the dome pressure control loop which may
include the LS-V15 pneumatic valve), the system can control the
output of the high pressure regulator to a very fine degree.
[0030] The RPPCS utilizes an air loaded high pressure regulator 470
(e.g., Tescom Model 26-2015) to control pressure on the air side of
the air/fluid transducer. Air is constantly vented to the
atmosphere through a small orifice 460 in the high pressure side
through an isolations valve (with an orifice flow coefficient is
approximately C.sub.V=0.012).
[0031] FIG. 6 shows a block diagram of a dome-operated pressure
regulator 470. The high pressure supply is provided to the inlet
side 610 of the regulator 470; a vent valve at the inlet may be
provided for convenience. The regulator 470 uses dome pressure on
the dome side 620 to control the flow from the inlet side 610
(having high pressure) to the outlet side 615. This in turn
regulates the pressure at the outlet side 615. An approximate
pressure gain of, for example, 16.8 psig/psig (i.e. 100 psig in the
dome will cause the regulator to maintain approximately 1680 psig
at the outlet port) may be had.
[0032] In an non-limiting example, a dome-operated pressure
regulator has a diaphragm 630 within the dome. The diaphragm moves
in response to pressure changes on the dome side 620. Movement of
the diaphragm 630 moves a piston 640 with an opening 645. The
opening 645 affects the fluid flow from the inlet side 610 to the
outlet side 615. It should be appreciated that other methods of
controlling fluid flow based on dome pressure exist, e.g., using a
valve and valve seat.
[0033] FIG. 8 shows a diagram of an air loaded high pressure
regulator 470 made by Tescom Corporation.
[0034] The rheometer requires very precise pressure balancing of
the transducers beyond what is possible by using an air loaded
regulator alone. For this reason, a proportional pneumatic control
valve (e.g., Enfield Technologies Model LS-V15) controls the air
flow from a low pressure supply (typically 100 psig) into the dome
to increase or decrease the pressure.
[0035] Due to the bi-directional nature of some control valves
(e.g., the Enfield Technologies control valve), the venting of dome
pressure to atmosphere can also be controlled. Dome pressure is
monitored with a pressure transducer mounted as close to the dome
volume as possible. The low level sensor signal is amplified by
using a low-level signal sensor amplifier 440 (e.g., Enfield
Technologies LS-C30) to scale and offset the pressure signal; for
example, such that 0-100 psig equals 0-10V. The output from
low-level signal sensor, amplifier is provided to the rheometer
controller board for control.
[0036] The rheometer pneumatic pressure control board uses a pulse
width modulation (PWM) device and supporting circuitry (which may
include a pressure controller with may be implemented as analog or
digital circuitry, a combination of analog and digital circuitry or
with software and suitable hardware) to regulate the application of
power to the pneumatic control valve 480. The PWM device may
utilize a switching frequency of approximately 40 kHz to
efficiently apply valve power proportionally. For various circuit
topologies the switching frequency may be anywhere from a few kHz
to a few thousand kHz. The valve drive circuits may incorporate
advanced valve enhancement electronics (e.g., Dead Band
Elimination, Dither Amplitude and Frequency Control).
[0037] For further information see: Dead Band Elimination--patent
application Ser. No. ______, filed on Oct. 5, 2007 and titled "Dead
Band Reduction in Electronically Controlled Valves"; and Dither
Amplitude and Frequency Control--patent application Ser. No.
______, filed on Oct. 5, 2007 and titled "Variable Frequency and
Amplitude Dither for Electronically Controlled Valves". Patent
applications Ser. Nos. ______ and ______ are assigned to the
assignee of the present application, and are hereby incorporated by
reference in its entirety.
[0038] The dome pressure of the regulator 470 is controlled by a
rheometer pneumatic pressure control board. The dome pressure
signal is connected to an input of the control board. The outer
loop controller 450 generates a desired dome pressure signal for
the nested loop dome pressure controller. The nested loop
controller serves to actuate the proportional pneumatic valve 480
as necessary to achieve and maintain the requested dome pressure
command objective.
[0039] The outer loop controller 450 is provided a command
reference signal at the control board ("CMD") that represents the
expected transducer output with 0 psid across the air/fluid
interface. The outer loop controller 450 may utilize a
proportional, integral, and derivative (PID) based topology with a
feed forward (FF) path.
[0040] The outer loop controller 450 provides a dome pressure
signal to the dome pressure valve 480 based on the current values
of "CMD", "FBK", and the history of each. A fluid pressure increase
may cause the air/fluid transducer to output a negative signal
proportional to the pressure difference (1V/psid). This is compared
to the CMD reference signal to generate a control error signal. The
error signal is modified by the PID gain settings to obtain a dome
pressure set point signal. The dome pressure set point signal may
also be modified by the FF path.
[0041] A basic block diagram of the control system is provided as
FIG. 5.
[0042] The high performance pneumatic device controller 450 is a
high speed, high accuracy analog control solution for use with
pneumatic valve products. The pneumatic controller 450 provides for
`Nested Loop` control architecture where more complex control
solutions are required.
[0043] The main loop or outer loop incorporates a flexible PID
control with an optional and selectable FF path. Several control
configurations may be available by adjusting control gains or
through DIP switch settings.
[0044] The input signals may be true differential inputs. The input
signals for control command (CMD) and feedback (FBK & AUX FBK)
signals may be coordinated. A PWM based valve drive may be built-in
to provide the necessary power required to position the valve.
Optional, DC/DC converters allow for a single power supply
connection.
[0045] The pneumatic controller 450 may feature DIP switches and/or
potentiometers that allow for a wide variety of control systems
configurations for a variety of applications. Some example
configurations include P-type control, PD-type control, PD-type
control, PI control, and PID control. Several test points may also
be provided on the controller for tuning analysis and
troubleshooting.
[0046] The high performance sensor amplifier 440 may be a dual
channel small signal differential signal amplifier with channels of
optically isolated, switched outputs that function as trip level
indications (such as Enfield Technologies LS-C30 high performance
sensor as shown). A wide dynamic calibration range and low noise
may allow amplification of signals from very low level sensors
(e.g., .+-.12.5 mV full scale) to medium range sensor outputs
(e.g., .+-.250 mV full scale) to provide a full scale output. The
signal amplifier may function with a variety of input
configurations and signal levels, for example bridge-type resistive
sensors that provide a differential voltage output.
[0047] Channels of optically isolated switched outputs may provide
for alarm or control functions. Outputs may be NPN type switches
(current sink) with common emitters (ICOM). The optical isolation
allows for connection to systems operating on differing voltage
references with little risk of ground loop or ground noise
problems. The output switches may be reverse polarity such that
when a switch condition is true (e.g., higher than the set-point),
the output voltage level from the switch will be a low voltage.
[0048] Optionally the sensor amplifier 440 may include light
emitting diodes (LEDs) for power status and minor
troubleshooting.
[0049] Channels of the sensor amplifier 440 may provide for offset
and gain adjustments via turn potentiometers to accommodate a wide
range of sensor inputs. Course and fine adjustment for the gain
setting allow for a wider gain range while maintaining adjustment
precision.
[0050] FIG. 7 shows a logic flow diagram of a method for
controlling a dome-operated pressure regulator in accordance with
an embodiment of this invention. In step 710, the pressure at a
dome side of the pressure regulator is measured. A command signal
is received in step 720. In step 730 the operation of the pressure
regulator is controlled based upon at least the command signal and
the measurement.
[0051] Certain embodiments of the disclosed invention may be
implemented by hardware (e.g., one or more processors, discrete
devices, programmable logic devices, large scale integrated
circuits, or some combination of these), software (e.g., firmware,
a program of executable instructions, microcode, or some
combination of these), or some combination thereof. Aspects of the
disclosed invention may also be implemented on one or more
semiconductor circuits, comprising hardware and perhaps software
residing in one or more memories. Aspects of the disclosed
invention may also include computer-executable media tangibly
embodying one or more programs of computer-readable instructions
executable by one or more processors to perform certain of the
operations described herein.
[0052] The foregoing description has provided by way of exemplary
and non-limiting examples a full and informative description of the
best techniques presently contemplated by the inventors for
carrying out embodiments of the invention. However, various
modifications and adaptations may become apparent to those skilled
in the relevant arts in view of the foregoing description, when
read in conjunction with the accompanying drawings and the appended
claims. All such and similar modifications of the teachings of this
invention will still fall within the scope of this invention.
[0053] Furthermore, some of the features of exemplary embodiments
of this invention could be used to advantage without the
corresponding use of other features. As such, the foregoing
description should be considered as merely illustrative of the
principles of embodiments of the present invention, and not in
limitation thereof.
* * * * *