阅读说明：本技术 一种飞机刹车系统液压伺服驱动的双闭环控制系统 (Hydraulic servo-driven double-closed-loop control system of airplane brake system ) 是由 刘文胜 梁雪林 马运柱 许丰瑞 于 2021-11-22 设计创作，主要内容包括：本发明公开了一种飞机刹车系统液压伺服驱动的双闭环控制系统,包括电压控制器、电流控制器、数模转换器、恒流输出模块和反馈调理模块；所述电压控制器的两个输入端分别与刹车控制盒和反馈调理模块的第一输出端连接,输出端经数模转换器连接到电流控制器的第一输入端；所述电流控制器的第二输入端还与反馈调理模块的第二输出端连接,电流控制器的输出端连接至恒流输出模块的输入端；所述恒流输出模块的输出端连接至伺服阀；所述反馈调理模块的采集输入端连接至恒流输出模块的电流采集端。本发明对飞机刹车系统液压伺服驱动的控制快速、精确且鲁棒性好。(The invention discloses a hydraulic servo-driven double closed-loop control system of an airplane brake system, which comprises a voltage controller, a current controller, a digital-to-analog converter, a constant-current output module and a feedback conditioning module, wherein the voltage controller is connected with the current controller; two input ends of the voltage controller are respectively connected with the brake control box and a first output end of the feedback conditioning module, and the output ends of the voltage controller are connected to a first input end of the current controller through a digital-to-analog converter; the second input end of the current controller is also connected with the second output end of the feedback conditioning module, and the output end of the current controller is connected to the input end of the constant current output module; the output end of the constant-current output module is connected to the servo valve; and the acquisition input end of the feedback conditioning module is connected to the current acquisition end of the constant current output module. The invention has the advantages of quick and accurate control on the hydraulic servo drive of the aircraft brake system and good robustness.)

1. A hydraulic servo driven double closed loop control system of an airplane brake system is characterized by comprising a voltage controller, a current controller, a digital-to-analog converter, a constant current output module and a feedback conditioning module; two input ends of the voltage controller are respectively connected with the brake control box and a first output end of the feedback conditioning module, and the output ends of the voltage controller are connected to a first input end of the current controller through a digital-to-analog converter; the second input end of the current controller is also connected with the second output end of the feedback conditioning module, and the output end of the current controller is connected to the input end of the constant current output module; the output end of the constant-current output module is connected to the servo valve; the acquisition input end of the feedback conditioning module is connected to the current acquisition end of the constant current output module;

the voltage controller acquires a given brake instruction signal from the brake control box and a second feedback signal of the constant current output module from the feedback conditioning module, and performs PID control according to the brake instruction signal and the voltage feedback signal to obtain a digital voltage reference signal;

the current controller acquires an analog voltage reference signal from the digital-to-analog converter and a first feedback signal of the constant current output module from the feedback conditioning module, and performs closed-loop control according to the voltage reference signal and the first feedback signal to obtain a driving voltage signal;

and the constant current output module outputs the servo valve driving current according to the driving voltage signal.

2. The hydraulic servo driven dual closed loop control system for an aircraft brake system as claimed in claim 1, wherein the current controller is an operational amplifier based closed loop control circuit.

3. An aircraft braking system hydraulic servo driven dual closed loop control system as claimed in claim 2 wherein the current controller comprises resistor R2, resistor R3, capacitor C2, capacitor C3, capacitor C1 and operational amplifier U1; the anode of the operational amplifier U1 is connected with the first end of the resistor R3 and the first end of the capacitor C3; the second end of the resistor R3 is connected with the first end of the resistor R2 and the first end of the capacitor C2; a first end of the capacitor C1 is connected to a power supply VCC; the second end of the capacitor C3, the second end of the capacitor C2 and the second end of the capacitor C1 are all grounded;

a second end of the resistor R2, which is used as a first input end of the current controller, is connected with the output end of the digital-to-analog converter;

the negative electrode of the operational amplifier is used as a second input end of the current controller and is connected to the current acquisition output end of the feedback conditioning module;

and the output end of the operational amplifier is used as the output end of the current controller and is connected to the input end of the constant current output module.

4. The hydraulic servo driven double closed loop control system of the aircraft brake system according to claim 1, wherein the constant current output module comprises a resistor R1 and a transistor Q1; the first end of the resistor R1 is used as the input end of the constant current output module and is connected to the output end of the current controller; the base of the transistor Q1 is connected to the second end of the resistor R1; the collector of the triode Q1 is used as the output end of the constant current output module and outputs the servo valve driving current; and the emitter of the triode Q1 is used as the current acquisition end of the constant current output module and is connected to the acquisition input end of the feedback conditioning module.

5. The hydraulic servo driven dual closed loop control system of an aircraft brake system according to claim 1, wherein the feedback conditioning module comprises a resistor R7, a resistor R8, an operational amplifier U2, a resistor R4, a resistor R5, a capacitor C4, a capacitor C5 and a capacitor C6;

the resistor R7 and the resistor R8 are connected between the current acquisition end of the constant current output module and the ground in series, wherein the first end of the resistor R7 is connected to the current acquisition end of the constant current output module, the second end of the resistor R7 is connected with the first end of the resistor R8, and the second end of the resistor R8 is grounded;

a first end of the resistor R7 is connected to the anode of the operational amplifier; the second end of the resistor R7 is connected to the cathode of the operational amplifier; the second end of the resistor R7 is also used as a second output end of the feedback conditioning module, is connected with a second input end of the current controller, and is used for outputting a first feedback signal;

the output end of the operational amplifier U2 is sequentially connected in series with the resistor R4 and the resistor R5, then serves as a first output end of the feedback conditioning module, is connected with the second input end of the voltage controller, and is used for outputting a second feedback signal;

two ends of the resistor R5 are grounded after being respectively connected with the capacitors C5 and C6 in parallel;

the capacitor C4 is connected between the power supply and ground.

6. The hydraulic servo actuated dual closed loop control system for an aircraft brake system as claimed in claim 5 wherein the resistance of resistor R7 is less than the resistance of resistor R8.

7. The hydraulic servo-actuated double closed-loop control system for the aircraft brake system as claimed in any one of claims 1 to 6, further comprising a direct current bias module, wherein the direct current bias module comprises a resistor R6 and a diode D1, a first end of the resistor R6 is connected to a power supply VCC, a second end of the resistor R6 is connected to an anode of the diode D1, and a cathode of the diode D1 is connected to a ground GND;

the positive terminal of the diode D1, serving as all ground terminals of the feedback conditioning module and the voltage controller, is denoted as AGND; all power supply ends connected with the feedback conditioning module and the voltage controller are power supply VDD;

all power supply ends of the current controller and the direct current bias module are power supplies VCC; all grounding ends connected with the current controller and the direct current bias module are marked as GND;

the power supply VCC-ground GND and the power supply VDD-ground AGND are two different power supply grounding systems.

Technical Field

The invention belongs to the technical field of airplane brake control, and particularly relates to a hydraulic servo-driven double-closed-loop control system of an airplane brake system.

Background

The hydraulic servo valve drive is an extremely important brake actuating mechanism in an airplane brake system and is responsible for converting an electric signal given by a brake control box into a pressure signal required by the brake mechanism. The traditional hydraulic servo valve driving control system in China is a single constant current source structure with voltage converted into current, and the core component of the hydraulic servo valve driving control system is composed of an operational amplifier and a triode. The drive control system is characterized by simple circuit structure and has two main disadvantages, one is that the output valve current has dead zone, i.e. the current is not adjustable when the current is less than a certain value (usually 4 mA). Secondly, the accuracy of the output valve current is affected by external load disturbance and parameter drift of internal components, so that the accurate valve current cannot be obtained.

Disclosure of Invention

The invention provides a hydraulic servo-driven double-closed-loop control system of an aircraft brake system, which is fast and accurate in control and good in robustness.

In order to achieve the technical purpose, the invention adopts the following technical scheme:

a double closed-loop control system driven by a hydraulic servo of an airplane brake system comprises a voltage controller, a current controller, a digital-to-analog converter, a constant current output module and a feedback conditioning module; two input ends of the voltage controller are respectively connected with the brake control box and a first output end of the feedback conditioning module, and the output ends of the voltage controller are connected to a first input end of the current controller through a digital-to-analog converter; the second input end of the current controller is also connected with the second output end of the feedback conditioning module, and the output end of the current controller is connected to the input end of the constant current output module; the output end of the constant-current output module is connected to the servo valve; the acquisition input end of the feedback conditioning module is connected to the current acquisition end of the constant current output module;

the voltage controller acquires a given brake instruction signal from the brake control box and a second feedback signal of the constant current output module from the feedback conditioning module, and performs PID control according to the brake instruction signal and the voltage feedback signal to obtain a digital voltage reference signal;

the current controller acquires an analog voltage reference signal from the digital-to-analog converter and a first feedback signal of the constant current output module from the feedback conditioning module, and performs closed-loop control according to the voltage reference signal and the first feedback signal to obtain a driving voltage signal;

and the constant current output module outputs the servo valve driving current according to the driving voltage signal.

Further, the current controller adopts a closed-loop control circuit based on an operational amplifier.

Further, the current controller comprises a resistor R2, a resistor R3, a capacitor C2, a capacitor C3, a capacitor C1 and an operational amplifier U1; the anode of the operational amplifier U1 is connected with the first end of the resistor R3 and the first end of the capacitor C3; the second end of the resistor R3 is connected with the first end of the resistor R2 and the first end of the capacitor C2; a first end of the capacitor C1 is connected to a power supply VCC; the second end of the capacitor C3, the second end of the capacitor C2 and the second end of the capacitor C1 are all grounded;

a second end of the resistor R2, which is used as a first input end of the current controller, is connected with the output end of the digital-to-analog converter;

the negative electrode of the operational amplifier is used as a second input end of the current controller and is connected to the current acquisition output end of the feedback conditioning module;

and the output end of the operational amplifier is used as the output end of the current controller and is connected to the input end of the constant current output module.

Further, the constant current output module comprises a resistor R1 and a triode Q1; the first end of the resistor R1 is used as the input end of the constant current output module and is connected to the output end of the current controller; the base of the transistor Q1 is connected to the second end of the resistor R1; the collector of the triode Q1 is used as the output end of the constant current output module and outputs the servo valve driving current; and the emitter of the triode Q1 is used as the current acquisition end of the constant current output module and is connected to the acquisition input end of the feedback conditioning module.

Further, the feedback conditioning module comprises a resistor R7, a resistor R8, an operational amplifier U2, a resistor R4, a resistor R5, a capacitor C4, a capacitor C5 and a capacitor C6;

the resistor R7 and the resistor R8 are connected between the current acquisition end of the constant current output module and the ground in series, wherein the first end of the resistor R7 is connected to the current acquisition end of the constant current output module, the second end of the resistor R7 is connected with the first end of the resistor R8, and the second end of the resistor R8 is grounded;

a first end of the resistor R7 is connected to the anode of the operational amplifier; the second end of the resistor R7 is connected to the cathode of the operational amplifier; the second end of the resistor R7 is also used as a second output end of the feedback conditioning module, is connected with a second input end of the current controller, and is used for outputting a first feedback signal;

the output end of the operational amplifier U2 is sequentially connected in series with the resistor R4 and the resistor R5, then serves as a first output end of the feedback conditioning module, is connected with the second input end of the voltage controller, and is used for outputting a second feedback signal;

two ends of the resistor R5 are grounded after being respectively connected with the capacitors C5 and C6 in parallel;

the capacitor C4 is connected between the power supply and ground.

Further, the resistance value of the resistor R7 is smaller than that of the resistor R8.

Furthermore, the double closed-loop control system driven by the hydraulic servo of the aircraft brake system further comprises a direct current bias module, wherein the direct current bias module comprises a resistor R6 and a diode D1, the first end of the resistor R6 is connected with a power VCC, the second end of the resistor R6 is connected with the anode of the diode D1, and the cathode of the diode D1 is connected to the ground GND;

the positive terminal of the diode D1, serving as all ground terminals of the feedback conditioning module and the voltage controller, is denoted as AGND; all power supply ends connected with the feedback conditioning module and the voltage controller are power supply VDD;

all power supply ends of the current controller and the direct current bias module are power supplies VCC; all grounding ends connected with the current controller and the direct current bias module are marked as GND;

the power supply VCC-ground GND and the power supply VDD-ground AGND are two different power supply grounding systems.

Advantageous effects

The current controller in the invention simultaneously receives the output of the digital-to-analog converter and the output of the feedback conditioning module, carries out closed-loop feedback control after comparison, forms a coarse adjustment loop of valve current output from hardware, takes the integrated operational amplifier as a core controller, and has almost real-time operation process, so the speed of the adjustment loop is fast.

The voltage controller receives a given brake command signal and the output of the feedback conditioning module at the same time, and a valve current closed-loop control system is formed inside, so that valve current fluctuation caused by parameter drift or load disturbance on hardware is compensated on software.

The feedback conditioning module mainly comprises two parts, wherein the first part is a low-end current sampling circuit used for the current control module to perform coarse adjustment, and the second part is a current sampling circuit used for a DSP to perform software fine adjustment and comprising a precision resistor and a differential operational amplifier. Through the cooperation of the two valve current sampling circuits, the control precision and speed of the servo valve current can be considered.

Because the conventional precise operational amplifier cannot really realize rail-to-rail output, in order to avoid a dead zone that the output of the constant current source is close to a zero point, the conventional method adopts a non-zero reference voltage or adopts a positive and negative dual power supply to supply power. Both of these schemes complicate the system and add many additional components. According to the invention, through arranging the direct current bias module, a relatively stable non-zero reference voltage can be obtained only through one power diode and one power resistor which provide bias voltage, and a direct current bias voltage is provided for the power triode with constant current output, so that the reference working point of the power triode is raised to the voltage value, and the dead zone of the output current is indirectly eliminated. The problem that the current of the servo valve cannot be adjusted from zero in a dead zone is solved.

The constant current output module takes a power triode as a core, a base electrode of the constant current output module receives instruction voltage from a current controller, and servo valve current with beta multiple relation is output between a collector and an emitter after the base electrode current amplification function of the triode, so that conversion from weak current to strong current is completed.

Compared with the traditional DSP analog output method which adopts PWM to output pulse signals with adjustable duty ratio and then obtains direct current voltage signals after low-pass filtering, the method has the advantages that the DAC module is arranged behind the voltage controller, accurate analog voltage can be directly output, and the control precision is improved compared with the traditional scheme.

Drawings

FIG. 1 is a schematic structural diagram of a dual closed-loop control system according to an embodiment of the present application;

FIG. 2 is a control schematic block diagram of a dual closed-loop control system according to an embodiment of the present application;

FIG. 3 is a schematic diagram of a voltage closed loop in a dual closed loop control system according to an embodiment of the present application;

fig. 4 is a schematic diagram of current closed loop, feedback conditioning and dc bias in a dual closed loop control system according to an embodiment of the present application.

Detailed Description

The following describes embodiments of the present invention in detail, which are developed based on the technical solutions of the present invention, and give detailed implementation manners and specific operation procedures to further explain the technical solutions of the present invention.

The embodiment provides a hydraulic servo-driven double closed-loop control system of an aircraft brake system, which is shown in fig. 1 and comprises a voltage controller, a current controller, a digital-to-analog converter, a constant-current output module and a feedback conditioning module; two input ends of the voltage controller are respectively connected with the brake control box and a first output end of the feedback conditioning module, and the output ends of the voltage controller are connected to a first input end of the current controller through a digital-to-analog converter; the second input end of the current controller is also connected with the second output end of the feedback conditioning module, and the output end of the current controller is connected to the input end of the constant current output module; the output end of the constant-current output module is connected to the servo valve; and the acquisition input end of the feedback conditioning module is connected to the current acquisition end of the constant current output module.

In a more preferred embodiment, the double closed-loop control system for the hydraulic servo drive of the aircraft braking system further comprises a direct current bias module, wherein the direct current bias module comprises a resistor R6 and a diode D1, a first end of the resistor R6 is connected with a power VCC, a second end of the resistor R6 is connected with an anode of a diode D1, and a cathode of a diode D1 is connected to the ground GND; the positive terminal of the diode D1, serving as all ground terminals of the feedback conditioning module and the voltage controller, is denoted as AGND; all power supply ends connected with the feedback conditioning module and the voltage controller are power supply VDD; all power supply ends of the current controller and the direct current bias module are power supplies VCC; all grounding ends connected with the current controller and the direct current bias module are marked as GND; the power supply VCC-ground GND and the power supply VDD-ground AGND are two different power supply grounding systems.

The direct current bias module provides a bias voltage for the feedback conditioning module, and a constant voltage bias circuit is formed by a power diode which works constantly and a current-limiting resistor which keeps the diode on working. The bias circuit raises the reference point of the operational amplifier U1, and reduces the parameter characteristic requirement of the operational amplifier.

Referring to fig. 2, the voltage controller receives a brake command signal from the brake control box and feeds back a second feedback signal acquired by the conditioning module, outputs a digital voltage reference signal after operation of the software closed-loop control algorithm, and sends the digital voltage reference signal to the digital-to-analog conversion module through the SPI bus. The current controller synthesizes an analog voltage signal given by the DAC and a first feedback signal (representing a voltage signal fed back by the rough current) given by feedback, outputs a corresponding voltage signal after operation, and sends the voltage signal to the constant current output module after passing through the current limiting resistor. The base of the constant current output module receives the signal after passing through the current-limiting resistor, and after internal current amplification, a desired valve current signal is obtained between the collector and the emitter of the constant current output module. The expected valve current flows out from the positive electrode of the power supply, flows into the collector of the power triode of the constant current output module after passing through the servo valve coil, flows into the direct current bias module through the emitter, and finally returns to the negative electrode of the power supply.

The above modules are specifically described as follows in the present embodiment:

the constant current output module comprises a resistor R1 and a triode Q1; the resistor R1 is used for limiting current, the first end of the resistor R1 is used as the input end of the constant current output module, is connected to the output end of the current controller, and obtains a driving voltage signal from the current controller; the base electrode of the triode Q1 is connected to the second end of the resistor R1, and a base current signal is obtained; the collector of the triode Q1 is used as the output end of the constant current output module and outputs the servo valve driving current; and the emitter of the triode Q1 is used as the current acquisition end of the constant current output module and is connected to the acquisition input end of the feedback conditioning module. The triode amplifies the current signal flowing into the base stage of the triode, obtains large current output between the collector and the emitter of the triode and is used for driving the servo valve coil.

The feedback conditioning module is shown in fig. 4 and includes a resistor R7, a resistor R8, an operational amplifier U2, a resistor R4, a resistor R5, a capacitor C4, a capacitor C5, and a capacitor C6; the resistor R7 and the resistor R8 are connected between the current acquisition end of the constant current output module and the ground in series, wherein the first end of the resistor R7 is connected to the current acquisition end of the constant current output module, the second end of the resistor R7 is connected with the first end of the resistor R8, and the second end of the resistor R8 is grounded; a first end of the resistor R7 is connected to the anode of the operational amplifier; the second end of the resistor R7 is connected to the cathode of the operational amplifier; the second end of the resistor R7 is also used as the second output end of the feedback conditioning module, connected with the second input end of the current controller, and used for outputting a current feedback signal; the output end of the operational amplifier U2 is sequentially connected in series with the resistor R4 and the resistor R5, then serves as a first output end of the feedback conditioning module, is connected with the second input end of the voltage controller, and is used for outputting a voltage feedback signal; two ends of the resistor R5 are grounded after being respectively connected with the capacitors C5 and C6 in parallel; the capacitor C4 is connected between the power supply and ground. Wherein, the resistance value of the resistor R7 is smaller than that of the resistor R8.

The feedback conditioning module consists of a large low-side sampling resistor R8 for rough collection and a precise resistor R7+ a precise operational amplifier U2 for precise collection, wherein the large low-side sampling resistor R8 directly outputs a voltage feedback signal If (which is marked as a first feedback signal representing rough current feedback) to the current controller to participate in hardware closed-loop regulation. The precise sampling resistor R7 collects weak differential signals, voltage feedback signals Uf (marked as second feedback signals representing fine current feedback) of 0-3V are obtained after precise differential operational amplification, and the voltage feedback signals Uf are sent to a voltage controller in the DSP module to participate in software closed-loop control operation.

The voltage controller adopts a DSP module, a part of area inside the DSP module runs closed-loop control software, a given signal of the voltage controller comes from an operation result of an area where a brake control program runs, a feedback signal of the voltage controller comes from an analog signal output by a feedback conditioning module, the difference between the given signal and the feedback signal is obtained to obtain the input of the controller, the input is output after an advanced PID control algorithm runs, the output is output to a digital-to-analog conversion chip U3 after a certain gain, and the output is converted into an analog signal Uin by a digital-to-analog conversion chip U3 and is output.

Referring to fig. 3, the DSP module uses a single-channel output of the SPI communication interface to the digital-to-analog conversion module, and can update its analog output signal using the digital communication bus, thereby making up for the defect that the DSP chip cannot generate an analog signal, and improving the problem of poor accuracy of the conventional PWM output + low-pass filtering output analog voltage.

The current controller adopts a closed-loop control circuit based on an operational amplifier, and as shown in fig. 4, the current controller comprises a resistor R2, a resistor R3, a capacitor C2, a capacitor C3, a capacitor C1 and an operational amplifier U1; the anode of the operational amplifier U1 is connected with the first end of the resistor R3 and the first end of the capacitor C3; the second end of the resistor R3 is connected with the first end of the resistor R2 and the first end of the capacitor C2; a first end of the capacitor C1 is connected to a power supply VCC; the second end of the capacitor C3, the second end of the capacitor C2 and the second end of the capacitor C1 are all grounded; a second end of the resistor R2, which is used as a first input end of the current controller, is connected with the output end of the digital-to-analog converter; the negative electrode of the operational amplifier is used as a second input end of the current controller and is connected to the current acquisition output end of the feedback conditioning module; and the output end of the operational amplifier is used as the output end of the current controller and is connected to the input end of the constant current output module.

The current controller obtains an analog voltage reference signal from the digital-to-analog converter, and then realizes the conversion from constant voltage to constant current through the negative feedback control of the current according to a voltage signal If which is output by the feedback conditioning module and represents the current feedback. Specifically, the DAC module outputs an analog voltage signal to the anode of an operational amplifier in the current controller, the cathode of the DAC module obtains a servo valve current signal through a sampling resistor in the feedback conditioning module, and an output driving voltage is obtained through the closed-loop conditioning function of the operational amplifier and then sent to the constant current output module through a current limiting resistor R1.

The technical difficulty of the invention is to ensure the speed and the precision of the double closed-loop control system and the robustness of load disturbance and parameter perturbation. The invention belongs to a hydraulic servo valve driving control technology in the field of airplane brake control, but the system architecture and the design scheme of the invention are completely suitable for application occasions of other types of servo valve driving, and the universality and the compatibility of the invention can be adjusted by software. The invention can accurately adjust the current of the servo valve according to the instruction, has wide adjusting range, no output dead zone, high adjusting speed and high adjusting precision, and can ensure the stability under the conditions of external load disturbance and internal parameter perturbation of the output valve current.

The invention solves the problem of control speed through a control structure of a hardware closed loop, solves the problem of control precision through a software closed loop mode, solves the problem of output dead zone through a direct current bias circuit, and solves the robust control problem of load disturbance and parameter perturbation through an advanced PID algorithm operated in a DSP. The double closed-loop control system has high measurement precision and control precision, and can reach the adjustment precision of 0.01 mA; the adjusting range is flexible, the current can be adjusted within 0-40 mA at will, the adjusting range is convenient to change, and only the feedback gain coefficient needs to be modified; the brake instruction given by a brake control system is strictly executed, stable and reliable driving current is provided for the hydraulic servo valve, and the current is timely adjusted by DSP control software when the load is changed and the parameters of elements in the system are changed, so that the current of an output valve is ensured to be kept unchanged; the double closed-loop control system eliminates the dead zone of the traditional valve current driving circuit, and the output is adjustable from zero, so that the double closed-loop control system can be compatible with hydraulic servo valves of different models; the system adopts a good grounding technology and an EMC management technology at the PCB level, has good EMC performance, and can resist the interference of space electromagnetic waves and the influence of external noise; through software setting, the system can work in any one of three modes of open loop, single closed loop or double closed loop, thereby being compatible with different servo valve control requirements.

The above embodiments are preferred embodiments of the present application, and those skilled in the art can make various changes or modifications without departing from the general concept of the present application, and such changes or modifications should fall within the scope of the claims of the present application.