Patent Application
20080099069
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.
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.
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.
A method to control the output of a air loaded high pressure regulator to a very fine degree was needed.
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).
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.
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.
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.
The attached Drawing Figures include the following:
Referring now to
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
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.
Turning to
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.
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.
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.
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.
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.
A simple block diagram of such as the system is shown in
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 CV=0.012).
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.
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.
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.
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).
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.
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.
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.
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.
A basic block diagram of the control system is provided as
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.
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.
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.
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.
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.
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.
Optionally the sensor amplifier 440 may include light emitting diodes (LEDs) for power status and minor troubleshooting.
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.
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.
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.
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.
This patent application claims priority under 35 U.S.C. §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.
| Number | Date | Country | |
|---|---|---|---|
| 60854562 | Oct 2006 | US |
