Electrohydraulic servo valve control with input

Abstract

Among other things, the subject matter of the present specification may be implemented in a controller device comprising a digital controller configured to provide a digital position signal based on a set point and a differential analog feedback signal; and a converter circuit configured to provide a differential analog electro-hydraulic servo valve position control signal based on the digital position signal, and to provide a differential analog feedback signal based on the differential analog electro-hydraulic servo valve position control signal.

Description

[0001] Priority claim

[0002] This application claims priority to U.S. Patent Application No. 16 / 784,864, filed on February 7, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present description relates to a control system for an electrohydraulic servovalves. Background Art

[0004] Electrohydraulic servovalves (EHSVs) are used for electrohydraulic control of components such as fuel valves, actuators, or switch valves. In some applications, EHSVs can be configured to provide hydraulic power to translate the position of a linear or rotary actuator. Using position feedback, EHSVs can be configured to drive the position of an actuator.

[0005] The aircraft includes a hydraulic servo control system that controls one or more adjustable surface components (such as, for example, ailerons, rudders, and elevators). Conventional hydraulic servo control systems are based on an analog electronic topology that includes various analog electronics to measure one or more analog signals that indicate the current position of the surface component. The analog signal is then compared to an analog set point value. The error between the analog signal and the analog set point value is determined, and the surface component is actively adjusted to maintain a minimum error. Summary of the invention

[0006] In general, this document describes a control system for an electrohydraulic servovalves.

[0007] In a first aspect, a controller device includes a digital controller configured to provide a digital position signal based on a set point and a differential analog feedback signal; and a converter circuit configured to provide a differential analog electro-hydraulic servo valve position control signal based on the digital position signal, and to provide a differential analog feedback signal based on the differential analog electro-hydraulic servo valve position control signal.

[0008] In a second aspect, according to aspect 1, the digital controller is further configured to receive an electro-hydraulic servo valve spool position signal, and the digital position signal is further based on the electro-hydraulic servo valve spool position signal.

[0009] In a third aspect, according to aspect 2, the electro-hydraulic servo valve spool position signal is based on a linear position of a spool of the electro-hydraulic servo valve.

[0010] In a fourth aspect, according to aspect 2 or 3, the electro-hydraulic servo valve spool position signal is a linear variable differential transformer signal.

[0011] In a fifth aspect, according to any one of aspects 1-4, the digital controller is further configured to receive an output position signal, and the digital position signal is further based on the output position signal.

[0012] In a sixth aspect, according to aspect 5, the output position signal is based on the position of the actuator.

[0013] In a seventh aspect, according to aspect 6, the actuator is a hydraulic rotary piston actuator.

[0014] In an eighth aspect, according to aspect 5 or 6, the output position signal is a variable differential transformer signal.

[0015] In a ninth aspect, a method of position control includes: receiving a predetermined set point, receiving a differential analog feedback signal, determining a digital position signal based on the received predetermined set point and the received differential analog feedback signal, providing the determined digital position signal, determining a differential analog electro-hydraulic servo valve position control signal based on the digital position signal, and providing a differential analog electro-hydraulic servo valve position control signal.

[0016] In a tenth aspect, according to aspect 9, the method further comprises receiving an electro-hydraulic servo valve spool position signal, wherein the digital position signal is further based on the electro-hydraulic servo valve spool position signal.

[0017] In an eleventh aspect, according to aspect 10, the electro-hydraulic servo valve spool position signal is based on a linear position of a spool of the electro-hydraulic servo valve.

[0018] In a twelfth aspect, according to aspect 10 or 11, the electro-hydraulic servo valve spool position signal is a linear variable differential transformer signal.

[0019] In a thirteenth aspect, according to any of aspects 9-12, the digital controller is further configured to receive an output position signal, and the digital position signal is further based on the output position signal.

[0020] In a fourteenth aspect, according to aspect 13, the output position signal is based on the position of the actuator.

[0021] In a fifteenth aspect, according to aspect 14, the actuator is a hydraulic rotary piston actuator.

[0022] In a sixteenth aspect, according to aspect 14 or 15, the output position signal is a variable differential transformer signal.

[0023] In the seventeenth aspect, a control system includes: a controller, the controller is configured to provide a predetermined set point and receive a first differential analog feedback signal; an electric hydraulic servo valve, the electric hydraulic servo valve is configured to receive a differential analog electric hydraulic servo valve position control signal; and a conversion device, the conversion device includes a circuit system, the circuit system is configured to perform operations including the following: receiving a predetermined set point; receiving a second differential analog feedback signal; determining a digital position signal based on the received predetermined set point and the second differential analog feedback signal; determining a differential analog electric hydraulic servo valve position control signal based on the determined digital position signal; providing a differential analog feedback signal to the electric hydraulic servo valve based on the differential analog electric hydraulic servo valve position control signal; determining a first differential analog feedback signal based on the second differential analog feedback signal; and providing the first differential analog feedback signal to the controller.

[0024] In an eighteenth aspect, according to aspect 17, the control system further includes a position sensor, which is configured to sense the position of the valve spool of the electric hydraulic servo valve and provide an electric hydraulic servo valve spool position signal representing the position, wherein the controller is further configured to receive the electric hydraulic servo valve spool position signal, and the digital position signal is further based on the electric hydraulic servo valve spool position signal.

[0025] In a nineteenth aspect, according to aspect 17 or 18, the control system further includes a hydraulic actuator and a position sensor, the hydraulic actuator is configured to be actuated by the hydraulic output of the electro-hydraulic servo valve, and the position sensor is configured to sense the position of the hydraulic actuator and provide an actuator position signal representing the position, wherein the controller is further configured to receive the actuator position signal, and the digital position signal is further based on the actuator position signal.

[0026] In a twentieth aspect, according to any one of aspects 17-19, the conversion device further comprises an amplifier configured to selectively amplify the differential analog electro-hydraulic servo valve position control signal based on an amplification signal provided by the controller.

[0027] In a general aspect, a controller device includes a digital controller configured to provide a digital position signal based on a set point and a differential analog feedback signal; and a converter circuit configured to provide a differential analog electro-hydraulic servo valve position control signal based on the digital position signal, and to provide a differential analog feedback signal based on the differential analog electro-hydraulic servo valve position control signal.

[0028] Various embodiments may include some, all, or none of the following features. The digital controller may be further configured to receive an electrohydraulic servo valve spool position signal, and the digital position signal may be further based on the electrohydraulic servo valve spool position signal. The electrohydraulic servo valve spool position signal may be based on a linear position of a spool of the electrohydraulic servo valve. The electrohydraulic servo valve spool position signal may be a linear variable differential transformer signal. The digital controller may be further configured to receive an output position signal, and the digital position signal may be further based on the output position signal. The output position signal may be based on a position of an actuator. The actuator may be a hydraulic rotary piston actuator. The output position signal may be a variable differential transformer signal.

[0029] In another general aspect, a method of position control includes: receiving a predetermined set point, receiving a differential analog feedback signal, determining a digital position signal based on the received predetermined set point and the received differential analog feedback signal, providing the determined digital position signal, determining a differential analog electro-hydraulic servo valve position control signal based on the digital position signal, and providing the differential analog electro-hydraulic servo valve position control signal.

[0030] Various implementations may include some, all, or none of the following features. The method may also include receiving an electrohydraulic servo valve spool position signal, wherein the digital position signal is further based on the electrohydraulic servo valve spool position signal. The electrohydraulic servo valve spool position signal may be based on a linear position of a spool of the electrohydraulic servo valve. The electrohydraulic servo valve spool position signal may be a linear variable differential transformer signal. The method may also include receiving an output position signal, wherein the digital position signal is further based on the output position signal. The output position signal may be based on a position of an actuator. The actuator may be a hydraulic rotary piston actuator. The output position signal may be a variable differential transformer signal.

[0031] In another general aspect, a control system includes: a controller, the controller being configured to provide a predetermined set point and receive a first differential analog feedback signal; an electrohydraulic servo valve, the electrohydraulic servo valve being configured to receive a differential analog electrohydraulic servo valve position control signal; and a conversion device, the conversion device including a circuit system, the circuit system being configured to perform operations including the following: receiving a predetermined set point; receiving a second differential analog feedback signal; determining a digital position signal based on the received predetermined set point and the second differential analog feedback signal; determining a differential analog electrohydraulic servo valve position control signal based on the determined digital position signal; providing a differential analog feedback signal to the electrohydraulic servo valve based on the differential analog electrohydraulic servo valve position control signal; determining a first differential analog feedback signal based on the second differential analog feedback signal; and providing the first differential analog feedback signal to the controller.

[0032] Various embodiments may include some, all, or none of the following features. The control system may also include a position sensor configured to sense the position of a valve spool of an electrohydraulic servo valve and provide an electrohydraulic servo valve spool position signal representing the position, wherein the controller is further configured to receive the electrohydraulic servo valve spool position signal, and the digital position signal is further based on the electrohydraulic servo valve spool position signal. The control system may also include a hydraulic actuator and a position sensor, the hydraulic actuator being configured to be actuated by the hydraulic output of the electrohydraulic servo valve, and the position sensor being configured to sense the position of the hydraulic actuator and provide an actuator position signal representing the position, wherein the controller is further configured to receive the actuator position signal, and the digital position signal is further based on the actuator position signal. The conversion device may also include an amplifier configured to selectively amplify the differential analog electrohydraulic servo valve position control signal based on an amplified signal provided by the controller.

[0033] The systems and techniques described herein may provide one or more of the following advantages. First, the system may provide position control in harsh operating environments. Second, the system may operate with greater immunity to electromagnetic interference and reduced electromagnetic interference emissions. Third, the system may have greater immunity to the effects of temperature changes. Fourth, the system may operate with lower power requirements and greater power efficiency.

[0034] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic diagram illustrating an example of a system for hydraulic position control.

[0036] Figure 2 It shows Figure 1 Block diagram of an example variation of the power stage of a system.

[0037] Figure 3 is a flow chart illustrating an example of a process for hydraulic position control.

[0038] Figure 4 is a schematic diagram of an example of a general purpose computer system. DETAILED DESCRIPTION

[0039] This document describes a control system for an electrohydraulic servo valve. The analog devices used in previous designs to generate and measure analog signals are susceptible to temperature changes. Therefore, in some implementations (such as aircraft applications), these components are subject to different temperature effects during operation, and various characteristics of the analog devices (such as gain, error, and phase margin) may change, thereby reducing the accuracy of such analog control systems. Some of these previous designs also require the use of multiple power sources to power individual analog components and to define analog set points. Therefore, such previous analog control systems require increased power, which reduces the overall power efficiency of the aircraft.

[0040] In general, the control system described in this document implements closed-loop control that remains in the digital domain and uses a position feedback system that is resistant to the effects of temperature changes and other adverse operating conditions that may be encountered in certain applications (such as aircraft control). The control system described in this document also implements analog control signals instead of pulse width modulation (PWM) control signals used in some previous designs. By using analog signals instead of PWM, electromagnetic interference that may be caused by PWM signals can be avoided.

[0041] Figure 1 is a schematic diagram illustrating an example of a system 100 for hydraulic position control. The system 100 includes an electrohydraulic servo valve (EHSV) 102. The EHSV 102 is configured to move to a plurality of bipolar positions sensed by a sensor 104. In some implementations, the sensor 104 may be a resolver. In some implementations, the sensor 104 may be a variable differential transformer (VDT), such as a rotary VDT or a linear VDT. For example, a VDT has few or no internal contact parts that may experience temperature-related issues, and thus the VDT may be used in operating environments with a wide operating temperature range that may damage, degrade, or destroy other types of position sensors (e.g., near an engine). The VDT also has mechanical stability, with few or no moving parts in frictional contact to wear out due to mechanical cycling and / or vibration.

[0042] The EHSV 102 controls the flow of hydraulic fluid to an actuator 106 (e.g., a linear hydraulic piston actuator, a hydraulic rotary piston actuator) through one or more hydraulic lines 105. The actuator 106 is configured to drive the position of a physical or mechanical load (e.g., an aircraft flight control surface, a valve). The position of the actuator 106 is sensed by a sensor 108. In some implementations, the sensor 108 may be a VDT or a resolver.

[0043] The controller 110 (e.g., a digital controller, a processor, a field programmable gate array) is configured to provide a digital control signal 112 to a digital-to-analog converter (DAC) 120. The digital control signal 112 represents a target (e.g., desired) configuration or position of the EHSV 102 and / or the actuator 106. The DAC 120 converts the digital control signal 112 into a differential analog control signal including an analog control signal 122a and an analog control signal 122b. In some embodiments, the digital control signal 112 can be transmitted and received as a serial peripheral interface (SPI) signal (e.g., the controller 110 and the DAC 120 can communicate with each other via an SPI port). The digital control signal 112 is based in part on a received (e.g., user-provided or automatically provided) or determined (e.g., calibrated, calculated) set point 111, and one or more feedback signals to be described in subsequent paragraphs.

[0044] System 100 includes a power stage 101, which includes an amplifier 130a and an amplifier 130b. The analog control signal 122a is amplified by amplifier 130a to provide an amplified analog control signal 132a. The analog control signal 122b is amplified by amplifier 130b to provide an amplified analog control signal 132b. The amplified analog control signals 132a and 132b form an amplified differential analog control signal, which is provided to drive the configuration of the EHSV 102. In some embodiments, the analog output current required to drive the motor of the EHSV is about + / -10mA. In some implementations, a DAC with an output buffered by an operational amplifier can provide a tight, digitally controlled differential analog output. Compared to the PWM method, the DAC method is inherently less noisy (e.g., EMC).

[0045] Portion 142a of the amplified analog control signal 132a is amplified by amplifier 140a to provide a buffered analog control signal 144a. Portion 142b of the amplified analog control signal 132b is amplified by amplifier 140b to provide an amplified analog control signal 144a. Amplified analog control signals 144a and 144b form an amplified differential analog control signal, which is provided to receiver 150. Receiver 150 is an analog-to-digital converter (ADC). Receiver 150 converts the amplified differential analog signal provided by amplified analog control signals 144a and 144b into a digital signal that can be processed by controller 110. In use, amplified analog control signals 144a and 144b provide feedback used in a control loop that can be used to determine digital control signal 112. In the example shown, receiver 150 is integrated with controller 110, but in some embodiments, receiver 150 can be a separate module that communicates with controller 110.

[0046] The sensor 104 provides a position signal 162 to the signal demodulator 160, and the signal demodulator 160 provides a demodulated signal 164 based on the position signal 162. The receiver 170 is configured to receive the position signal 162. In some embodiments, the receiver may be configured to receive analog and / or digital signals and convert or otherwise provide them in a format that can be used by the controller 110. For example, the sensor 104 may be a VDT, and the position signal 162 may be an analog differential output signal of the VDT that varies with the position or configuration of the EHSV 102. In such an example, the signal demodulator 160 may be an ADC configured to convert the VDT signal into a digital signal that can be received by the receiver 170. In another example, the sensor 104 may be a decomposer, and the position signal 162 may be a digital signal that varies with the position or configuration of the EHSV 102. In such an example, the signal demodulator 160 may be a protocol converter configured to convert the digital signal into a format that can be received by the receiver 170.

[0047] In use, the demodulated signal 164 provides feedback for use in a control loop that can be used to determine the digital control signal 112. In the example shown, the receiver 170 is integrated with the controller 110, but in some embodiments, the receiver 170 may be a separate module in communication with the controller 110.

[0048] The sensor 108 provides a position signal 182 to the signal demodulator 180, and the signal demodulator 180 provides a demodulated signal 184 based on the position signal 182. The receiver 190 is configured to receive the position signal 182. In some embodiments, the receiver 190 may be configured to receive analog and / or digital signals and convert or otherwise provide them in a format that can be used by the controller 110. For example, the sensor 108 may be a VDT, and the position signal 182 may be an analog differential output signal of the VDT that varies with the position or configuration of the EHSV 102. In such an example, the signal demodulator 180 may be an ADC configured to convert the VDT signal into a digital signal that can be received by the receiver 190. In another example, the sensor 108 may be a decomposer, and the position signal 182 may be a digital signal that varies with the position or configuration of the EHSV 102. In such an example, the signal demodulator 180 may be a protocol converter configured to convert the digital signal into a format that can be received by the receiver 190.

[0049] In use, the demodulated signal 184 provides feedback used in a control loop that can be used to determine the digital control signal 112. In the example shown, the receiver 190 is integrated with the controller 110, but in some embodiments, the receiver 190 can be a separate module that communicates with the controller 110. In some embodiments, the controller 110 can be an FPGA or a microprocessor. For example, both FPGAs and microprocessors are well suited to reading feedback from the sensor 104 and / or the sensor 108 (e.g., VDT or resolver signals) and driving the digital control signal. The controller 110 closes the current control loop and the position control loop, allowing configuration in range, Ki / Kp values, and software-imposed limits.

[0050] The advantage of this approach is that the closed loop control can be maintained in the digital domain. Current control in the digital domain allows configurability, for example, when different motors are connected. The power stage can remain analog, and the absence of PWM switching provides the advantage of inherent low radiated emissions. The DAC 120 with differential analog output allows precise control in the low current domain. The differential voltage of the amplified analog control signals 144a and 144b allows the analog to digital conversion within the receiver 150 to sample to sense the current at almost any time (essentially without time constraints).

[0051] The system 100 can be used in a harsh operating environment (e.g., an environment that can degrade, destroy, or otherwise negatively affect the life and / or performance of a previous control system). In some implementations, the controller 110 can be remotely located from the other components of the system 100. For example, the controller 110 can be located in or near the cockpit of an aircraft, and the actuator 106 can be located in an aircraft wing or engine. In such examples, the digital nature of the digital control signal 112 can allow the digital control signal 112 to be transmitted from near the cockpit to near the actuator 106, relatively more unaffected by noise and / or signal degradation that may negatively affect the generation of analog control signals. In another example, as described in the previous paragraph, the sensor 104 and / or the sensor 106 can be a ratiometric VDT or resolver, which is an inherently frictionless stable absolute position sensor with an almost unlimited cycle life and can operate in a harsh environment.

[0052] In some implementations, the EHSV 102 can be located remotely from the DAC 120. For example, because the analog control signals 122a and 122b and the amplified analog control signals 132a and 132b are differential analog signals, they are substantially immune to electrical noise over distance (e.g., unlike non-differential signals). In another example, because the analog control signals 122a and 122b and the amplified analog control signals 132a and 132b are differential analog signals, these signals can emit much less electromagnetic interference over long interconnects than PWM signals used in other designs.

[0053] In some implementations, the actuator 106 may be located remotely from the DAC 102. For example, the hydraulic line 105 between the EHSV 102 and the actuator 106 provides a fluid connection that is immune to electrical noise and can withstand high temperatures that might otherwise damage an electrical connection (e.g., melt insulation on wires).

[0054] In some implementations, the sensor 104 may be remotely located from the controller 110 and / or the signal demodulator 160. For example, the sensor 104 may be a VDT, and the position signal 162 may be a VDT signal. Some types of VDT signals are differential analog signals that vary as the sensed position changes. The differential signal is highly immune to electrical noise and signal attenuation that may otherwise occur over long transmission distances. In some implementations, the sensor 108 may be remotely located from the controller 110 and / or the signal demodulator 180 for similar reasons.

[0055] In some embodiments, the power stage 101 can be replaced or modified based on specific applications and / or user needs. For example, the power of amplifiers 130a and 130b can be controlled based on current requirements. In such examples, if the current is low, the track can be reduced, and if high current is required, the track can be increased. In another example, a larger output drive current can be achieved by connecting the two amplifiers in parallel to have a higher supply voltage to the amplifiers. In such examples, the second operational amplifier can be changed to a differential voltage follower. The follower configuration allows a single DAC output to drive a differential current, thereby reducing the complexity of digital control. In another example, the amplifier configuration can also be replaced with an H-bridge topology to obtain higher power current.

[0056] Figure 2 is a block diagram illustrating an example power stage 200. In some embodiments, the power stage 200 may be Figure 11. The power stage 200 is a variation of the example power stage 101 of the system 100. In general, the power stage 200 is configured so that the power to the amplifiers 130a and 130b can be controlled, and the power stage 200 includes amplifiers in parallel to drive the amplified analog control signals 132a and 132b.

[0057] Power stage 200 includes amplifiers 130a and 130b in the illustrated view and EHSV 102. Analog control signals 122a and 122b are received from DAC 120 (not shown in this view) and portions 142a and 142b are provided to amplifiers 140a and 140b (not shown in this view).

[0058] The power to the amplifiers 130a and 130b is controlled by the power control circuit 210. Constant power is supplied to the amplifiers 130a and 130b by the power source 212. Additional power from the power source 214 is supplied to the amplifiers 130a and 130b based on an amplification control signal 216 (e.g., provided by the controller 110). When the signal 216 goes high, the switch 218a and the switch 218b allow the additional power from the power source 214 to flow to the amplifiers 130a and 130b. When the signal 216 goes low, the switch 218a and the switch 218b prevent the additional power from the power source 214 from flowing to the amplifiers 130a and 130b.

[0059] In addition to the current provided by amplifier 130a, the output drive current is provided by amplifier 230a to EHSV 102. Amplifier 230a is configured to follow the amplified analog control signal 132a output by amplifier 130a and provide the output of amplifier 230a in parallel with the amplified analog control signal 132a to form an amplified analog controller signal 232a provided to EHSV 102. Similarly, amplifier 230b is configured to follow the amplified analog control signal 132b output by amplifier 130b and provide the output of amplifier 230b in parallel with the amplified analog control signal 132b to form an amplified analog controller signal 232b provided to EHSV 102. Amplified analog control signals 232a and 232b together form a differential analog control signal that drives the operation of EHSV 102.

[0060] Figure 3 is a flow chart showing an example of a process 300 for hydraulic position control. Figure 1 The processes are performed by a system such as the example system 100 of FIG. 10A . For clarity of presentation, the following description uses the system 100 and the power stage 200 as examples to describe the processes. However, another system or combination of systems may be used to perform the processes.

[0061] At 310 , a predetermined set point is received. For example, the example controller 110 may receive the set point 111 from a human operator (eg, a pilot) or from another circuit (eg, an autopilot) representing a desired configuration of the EHSV 102 , the actuator 106 , or a mechanical load actuated by the actuator 106 .

[0062] At 320, a differential analog feedback signal is received. For example, controller 110 receives an amplified differential analog signal provided by amplified analog control signals 144a and 144b.

[0063] At 330, a digital position signal is determined based on the received set point and the received differential analog feedback signal.For example, controller 110 may determine digital control signal 112 based on set point 111 and amplified analog control signals 144a and 144b.

[0064] At 340 , the determined digital position signal is provided. For example, the digital control signal 112 may be provided from the controller 110 to the DAC 120 .

[0065] At 350, a differential analog electrohydraulic servo valve position control signal is determined based on the digital position signal. For example, DAC 120 provides amplified analog control signals 132a and 132b that together form an amplified differential analog control signal.

[0066] At 360 , a differential analog electro-hydraulic servo valve position control signal is provided. For example, the amplified differential analog control signal formed by the amplified analog control signals 132 a and 132 b is provided by DAC 120 .

[0067] In some implementations, process 300 may also include receiving an electro-hydraulic servo valve spool position signal, wherein the digital position signal is further based on the electro-hydraulic servo valve spool position signal. For example, controller 110 may receive a demodulated signal 164 based on position signal 162, and controller 110 may determine digital control signal 112 based on demodulated signal 164.

[0068] In some implementations, the electro-hydraulic servo valve spool position signal can be based on the linear position of the spool of the electro-hydraulic servo valve. For example, the position signal 162 can be provided by the sensor 104, which is configured to sense the linear position of the EHSV 102. In some implementations, the electro-hydraulic servo valve spool position signal can be a variable differential transformer signal. For example, the sensor 104 can be a linear VDT or a rotary VDT.

[0069] In some implementations, process 300 may also include receiving an output position signal, wherein the digital position signal is further based on the output position signal. For example, controller 110 may receive a demodulated signal 184 based on position signal 182, and controller 110 may determine digital control signal 112 based on demodulated signal 184. In some implementations, the output position signal may be a variable differential transformer signal. For example, sensor 108 may be a linear VDT or a rotary VDT that may provide position signal 182 as a VDT signal.

[0070] In some implementations, the output position signal can be based on the position of the actuator. For example, the position signal 182 is provided by the sensor 108, which is configured to sense the position of the actuator 106 or the position of a load positioned by the actuator 106 or otherwise controlled by the actuator 106. In some implementations, the actuator can be a hydraulic rotary piston actuator (RPA). For example, the actuator 106 can be a hydraulic RPA.

[0071] Figure 4 is a schematic diagram of an example of a general purpose computer system 400. According to one implementation, system 400 may be used for the operations described in connection with process 300. For example, system 400 may be included as Figure 1 example controller 110 of part or all of the example.

[0072] System 400 includes processor 410, memory 420, storage device 430 and input / output device 440. Each of components 410, 420, 430 and 440 are interconnected using system bus 450. Processor 410 is capable of processing instructions for execution within system 400. In one implementation, processor 410 is a single-threaded processor. In another implementation, processor 410 is a multi-threaded processor. Processor 410 is capable of processing instructions stored in memory 420 or on storage device 430 to display graphical information of a user interface on input / output device 440.

[0073] The memory 420 stores information within the system 400. In one implementation, the storage device 420 is a computer-readable medium. In one implementation, the memory 420 is a volatile memory unit. In another implementation, the memory 420 is a non-volatile memory unit.

[0074] The storage device 430 can provide mass storage for the system 400. In one implementation, the storage device 430 is a computer-readable medium. In various implementations, the storage device 430 can be a floppy disk device, a hard disk device, an optical disk device, or a tape device.

[0075] The input / output device 440 provides input / output operations for the system 400. In one implementation, the input / output device 440 includes a keyboard and / or a pointing device. In another implementation, the input / output device 440 includes a display unit for displaying a graphical user interface.

[0076] The features described may be implemented in digital electronic circuits, or in computer hardware, firmware, software, or in a combination thereof. The apparatus may be implemented in a computer program product tangibly embodied in an information carrier, for example, in a machine-readable storage device for execution by a programmable processor; and the method steps may be performed by a programmable processor executing a program of instructions to perform the functions of the described implementation by operating on input data and generating output. The features described may advantageously be implemented in one or more computer programs executable on a programmable system comprising at least one programmable processor coupled to receive data and instructions from and transmit data and instructions to a data storage system, at least one input device, and at least one output device. A computer program is a set of instructions that can be used directly or indirectly in a computer to perform certain activities or bring about certain results. A computer program may be written in any form of programming language including compiled or interpreted languages, and it may be deployed in any form including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in an evaluation environment.

[0077] Suitable processors for executing a program of instructions include, for example, both general-purpose and special-purpose microprocessors, and the sole processor or one of multiple processors of any kind of digital computer. In general, the processor will receive instructions and data from a read-only memory or a random access memory or both. The basic elements of a computer are a processor for executing instructions, and one or more memories for storing instructions and data. In general, a computer will also include one or more mass storage devices for storing data files, or be operably coupled to the mass storage device to communicate with the mass storage device; such devices include: magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, which include, by way of example: semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and memory may be supplemented by, or incorporated into, an ASIC (Application Specific Integrated Circuit) and / or a Field Programmable Gate Array (FPGA).

[0078] To provide interaction with the user, these features can be implemented on a computer having a display device (such as a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user, and a keyboard and pointing device (such as a mouse or trackball) through which the user can provide input to the computer. User interaction can be command line based, or by using register reads and writes to input and / or output information to the system.

[0079] These features can be implemented in a computer system including a back-end component (such as a data server), or in a computer system including a middleware component (such as an application server or an Internet server), or in a computer system including a front-end component (such as a client computer with a graphical user interface or an Internet browser), or in any combination thereof. The components of the system can be connected by any form or medium of digital data communication (such as a communication network). Examples of communication networks include, for example, a LAN, a WAN, and the computers and networks that form the Internet.

[0080] A computing system may include clients and servers. Clients and servers are generally remote from each other and typically interact through a network (such as the one described). The relationship of client and server arises from computer programs running on the respective computers and having a client-server relationship to each other.

[0081] Although several embodiments have been described in detail above, other modifications are possible. In addition, the logic flow depicted in the accompanying drawings does not require the particular order or sequential order shown to achieve the desired results. In addition, other steps can be provided, or steps can be eliminated from the described flow, and other components can be added to the described system or removed from the described system. Accordingly, other implementations are also within the scope of the appended claims.

Claims

1. A controller device, comprising: a digital controller configured to provide a digital position signal based on a set point and a differential analog feedback signal; as well as A converter circuit is configured to provide a differential analog electro-hydraulic servo-valve position control signal to an electro-hydraulic servo-valve based on the digital position signal and to provide a portion of the differential analog electro-hydraulic servo-valve position control signal as the differential analog feedback signal.

2. The controller device according to claim 1, characterized in that The digital controller is further configured to receive an electro-hydraulic servo valve spool position signal, and the digital position signal is further based on the electro-hydraulic servo valve spool position signal.

3. The controller device according to claim 2, characterized in that The electro-hydraulic servovalve spool position signal is based on a linear position of a spool of the electro-hydraulic servovalve.

4. The controller device according to claim 2, characterized in that The electro-hydraulic servo valve spool position signal is a linear variable differential transformer signal.

5. The controller device according to claim 3, characterized in that The electro-hydraulic servo valve spool position signal is a linear variable differential transformer signal.

6. The controller device according to any one of claims 1 to 5, characterized in that: The digital controller is further configured to receive an output position signal, and the digital position signal is further based on the output position signal.

7. The controller device according to claim 6, characterized in that: The output position signal is based on the position of the actuator.

8. The controller device according to claim 7, characterized in that The actuator is a hydraulic rotary piston actuator.

9. The controller device according to claim 6, characterized in that The output position signal is a variable differential transformer signal.

10. The controller device according to claim 7, characterized in that The output position signal is a variable differential transformer signal.

11. A method for position control, comprising: receiving a predetermined set point; receiving a differential analog feedback signal; determining a digital position signal based on the received predetermined set point and the received differential analog feedback signal; providing a determined digital position signal; determining a differential analog electro-hydraulic servo valve position control signal based on the digital position signal; as well as providing the differential analog electro-hydraulic servo valve position control signal to the electro-hydraulic servo valve; as well as A portion of the differential analog electro-hydraulic servo valve position control signal is provided as the differential analog feedback signal. 12 . The method of claim 11 , further comprising receiving an electro-hydraulic servo valve spool position signal, wherein the digital position signal is further based on the electro-hydraulic servo valve spool position signal.

13. The method according to claim 12, characterized in that The electro-hydraulic servovalve spool position signal is based on a linear position of a spool of the electro-hydraulic servovalve.

14. The method according to claim 12, characterized in that The electro-hydraulic servo valve spool position signal is a linear variable differential transformer signal.

15. The method according to claim 13, characterized in that The electro-hydraulic servo valve spool position signal is a linear variable differential transformer signal.

16. The method of any of claims 11-15, further comprising receiving an output position signal, wherein the digital position signal is further based on the output position signal.

17. The method according to claim 16, characterized in that: The output position signal is based on the position of the actuator.

18. The method according to claim 17, characterized in that The actuator is a hydraulic rotary piston actuator.

19. The method according to claim 17, characterized in that The output position signal is a variable differential transformer signal.

20. The method of claim 18, wherein: The output position signal is a variable differential transformer signal.

21. A control system comprising: The controller device as claimed in claim 1; as well as; An electrohydraulic servo valve is configured to receive a differential analog feedback signal.

22. The control system of claim 21, further comprising a position sensor configured to sense the position of a valve spool of the electro-hydraulic servo valve and provide an electro-hydraulic servo valve spool position signal representing the position, wherein the controller is further configured to receive the electro-hydraulic servo valve spool position signal, and the digital position signal is further based on the electro-hydraulic servo valve spool position signal.

23. The control system of claim 21 or 22, further comprising a hydraulic actuator and a position sensor, wherein the hydraulic actuator is configured to be actuated by the hydraulic output of the electro-hydraulic servo valve, and the position sensor is configured to sense the position of the hydraulic actuator and provide an actuator position signal representing the position, wherein the controller is further configured to receive the actuator position signal, and the digital position signal is further based on the actuator position signal.

24. The control system according to any one of claims 21 or 22, characterized in that: The converter circuit includes an amplifier configured to selectively amplify the differential analog feedback signal based on an amplification signal provided by the digital controller.

25. The control system according to claim 23, characterized in that The converter circuit includes an amplifier configured to selectively amplify the differential analog feedback signal based on an amplification signal provided by the digital controller.

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