Pressure closed-loop control system for electro-hydraulic pressure servo valve of airplane brake system

Abstract

The invention discloses a pressure closed-loop control system for an electro-hydraulic pressure servo valve of an aircraft braking system. The pressure closed-loop control system comprises a braking instruction sensor, an FPGA module, a DSP module, a pressure sensor and the electro-hydraulic pressure servo valve. The FPGA module is connected with the DSP module, the brake instruction sensor, the pressure sensor and the electro-hydraulic pressure servo valve. By adopting the incremental PID algorithm and adding the transparent transmission link, the response speed and the control precision of the system are effectively improved, and meanwhile, the problem of brake failure caused by the fault of the pressure sensor is avoided. According to the method, the command pressure change can be quickly responded, and accurate control of the brake pressure is ensured, so that the brake efficiency is improved, the risk of uneven temperature of a brake disc of an aircraft wheel and aircraft yawing is reduced, and the reliability and the safety of an aircraft brake system are enhanced.

Description

Technical Field

[0001] The invention relates to the field of aircraft brake systems, and in particular to a pressure closed-loop control system for an electro-hydraulic pressure servo valve of an aircraft brake system. Background Art

[0002] At present, the mainstream aircraft brake system on aircraft is electric-hydraulic type, which is mainly composed of pedal command sensor, speed sensor, electro-hydraulic pressure servo valve, digital brake control unit, etc. Its working principle is that the digital brake control unit receives the command signal of the pedal command sensor, collects the wheel speed signal at the same time, outputs the control signal after anti-skid calculation, controls the electro-hydraulic pressure servo valve to output hydraulic pressure, and acts on the brake device to complete braking.

[0003] However, the existing electro-hydraulic pressure servo valves in China are all open-loop controlled, relying on the performance index control of the electro-hydraulic pressure valve (generally controlling the rated pressure ±0.5Mpa) to control the actual output, and there is a deviation between the output pressure and the command pressure. Inaccurate control pressure will lead to reduced braking efficiency, uneven brake disc temperature of each wheel of the aircraft, and aircraft yaw.

[0004] The utility model with publication number CN202624192 discloses an aircraft anti-skid wheel brake system, which proposes a method of reducing the error caused by the zero bias of the electro-hydraulic pressure servo valve by feeding back the pressure sensor signal to the anti-skid brake control box, thereby improving the aircraft anti-skid brake control accuracy. However, the utility model only connects the systems, and neither quantifies the control accuracy nor proposes a method for calibrating the brake pressure of the wheel brake system.

[0005] In the invention with publication number CN105644543A, a brake pressure correction method for a wheel brake system is disclosed. In the invention, the pressure sensor signal is fed back to the anti-skid brake control box, and the brake pressure command after anti-skid control and the pressure fed back by the pressure sensor signal are differentially calculated to output the adjusted brake pressure. However, in the invention, when the pressure sensor signal fails, the wheel brake system will lose its braking ability, and the pressure adjusted by the differential calculation based on the feedback pressure signal and the anti-skid pressure are synchronously adjusted, which may cause deviation in anti-skid control.

[0006] The invention with publication number CN113879267A discloses a method and system for increasing the dynamic response of an aircraft wheel brake system. By using FPGA to complete the pressure closed-loop control at the front end, the brake algorithm control and closed-loop control can be effectively isolated. However, the hydraulic pressure servo valve is a high-order system based on first-order inertia, and the standard PID control cannot achieve good control effects, especially frequency response. Summary of the invention

[0007] In order to solve the technical problems in the above background, the present invention uses FPGA to perform PID closed-loop control on the electro-hydraulic pressure servo valve, and effectively increases the system response while ensuring the control accuracy by adding a transparent transmission link and adopting incremental PID control.

[0008] To achieve the above-mentioned purpose, the present invention provides a pressure closed-loop control system for an electro-hydraulic pressure servo valve of an aircraft brake system, comprising: a brake command sensor, an FPGA module, a DSP module, a pressure sensor and an electro-hydraulic pressure servo valve; the FPGA module is respectively connected to the DSP module, the brake command sensor, the pressure sensor and the electro-hydraulic pressure servo valve.

[0009] Preferably, the brake command sensor receives pilot input, and transmits it to the DSP module after AD acquisition; the DSP module obtains a command pressure signal after anti-skid calculation, and transmits the command pressure signal to the FPGA module; the FPGA module performs closed-loop calculation based on the command pressure signal and the pressure feedback value fed back by the pressure sensor, and outputs a brake current signal to the electro-hydraulic pressure servo valve.

[0010] Preferably, a transparent transmission link is added during the closed-loop operation of the FPGA module, and an incremental PID algorithm is used to ensure a smooth transition. The specific method includes: when the pressure is not close to the effective range of the command pressure, the command pressure is directly output without closed-loop control; when the pressure rises and enters the effective range, the deviation control is performed through the incremental PID algorithm based on the command pressure.

[0011] Preferably, the workflow of the FPGA module specifically includes:

[0012] Step 1: Determine the input command pressure data P C Is it within the valid range? If not, report an error to the upper level. If yes, continue to execute downwards.

[0013] Step 2: Determine whether there is a pressure sensor fault. The fault determination condition of the pressure sensor is: detect whether the signal of the pressure sensor is within the effective range;

[0014] If the pressure sensor fails, closed-loop control is not performed and the FPGA directly outputs the input command pressure P out =P C , proceed to step 7;

[0015] If the pressure sensor is not faulty, proceed to step 3;

[0016] Step 3: Calculate the difference between the input command pressure and the feedback pressure:

[0017] e=P C-P D

[0018] In the formula, e represents the difference; P C Indicates command pressure; P D Indicates feedback pressure;

[0019] Step 4: If the feedback pressure is within the command pressure △a range, closed-loop control is performed, otherwise the command pressure is directly transmitted;

[0020] If e>△a, FPGA directly outputs the input command pressure P out =P C , proceed to step 7;

[0021] If e<△a, FPGA performs PID operation and executes step 5;

[0022] Step 5: Perform incremental PID calculation and use the difference e to perform PID calculation:

[0023] △P pid =K P *(e k -e k-1 )+K I *e k +K D *(e k -2e k-1+ e k-2 )

[0024] P pid =P outk-1 +△P pid

[0025] In the formula, K P , K I , K D Indicates PID coefficient; e k Indicates the current difference; e k-1 Indicates the difference value of the previous beat; e k-2 Indicates the difference between the previous and previous beats; P outk-1 Indicates the output of the previous beat; △P pid Indicates PID control increment;

[0026] Step 6: Make a valid value judgment after calculation and limit the calculated value P pid The effective range is set to avoid over-limit output, and the pressure closed-loop adjustment boundary is also limited. The electro-hydraulic pressure servo valve whose adjustment value exceeds the use boundary will not be controlled.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention effectively improves the response speed and control accuracy of the system by adopting an incremental PID algorithm and adding a transparent transmission link, while avoiding the problem of brake failure caused by pressure sensor failure. The present invention can quickly respond to command pressure changes, ensure accurate control of brake pressure, thereby improving braking efficiency, reducing the risk of uneven brake disc temperature of aircraft wheels and aircraft yaw, and enhancing the reliability and safety of the aircraft braking system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0030] Figure 1 A schematic diagram of the system structure of an embodiment of the present invention;

[0031] Figure 2 A conventional electric-by-wire hydraulic aircraft anti-skid brake system according to an embodiment of the present invention;

[0032] Figure 3 A closed-loop control flow chart of an electro-hydraulic pressure servo valve according to an embodiment of the present invention;

[0033] Figure 4 A schematic diagram of conventional direct output current control according to an embodiment of the present invention;

[0034] Figure 5 For the embodiment of the present invention Figure 3 Based on the schematic diagram of PID control;

[0035] Figure 6 The present invention is a schematic diagram of an embodiment of the present invention that adds transparent transmission to the PID control. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] like Figure 1As shown, it is a schematic diagram of the system structure of an embodiment of the present invention, including: a brake command sensor, an FPGA module, a DSP module, a pressure sensor and an electro-hydraulic pressure servo valve; the FPGA module is respectively connected to the DSP module, the brake command sensor, the pressure sensor and the electro-hydraulic pressure servo valve.

[0039] Among them, the brake command sensor receives the pilot's input, and transmits it to the DSP module after AD acquisition; the DSP module obtains the command pressure signal after anti-skid calculation, and transmits the command pressure signal to the FPGA module; the FPGA module performs closed-loop calculation based on the command pressure signal and the pressure feedback value from the pressure sensor, and outputs the brake current signal to the electro-hydraulic pressure servo valve.

[0040] The following will explain in detail how the present invention solves technical problems in real life in conjunction with this embodiment.

[0041] like Figure 2 As shown, the common electric-by-wire hydraulic aircraft anti-skid brake system is composed of a brake control unit that collects speed sensor signals and command signals, and after anti-skid calculations, outputs control signals to the electro-hydraulic pressure servo valve to output hydraulic pressure, which acts on the brake device to complete braking.

[0042] The closed-loop control flow chart of the electro-hydraulic pressure servo valve in this embodiment is as follows: Figure 3 shown.

[0043] The brake command sensor receives the command pressure signal transmitted by the aircraft after anti-skid operation, and transmits the command pressure signal to the FPGA module; the FPGA module performs closed-loop operation based on the command pressure signal and the pressure feedback value fed back by the pressure sensor, and outputs the brake current signal to the electro-hydraulic pressure servo valve. In the closed-loop operation process of the FPGA module, a transparent transmission link is added, and an incremental PID algorithm is used to ensure a smooth transition. The specific method includes: when the pressure is not close to the effective range of the command pressure, the command pressure is directly output without closed-loop control; when the pressure rises and enters the effective range, the incremental PID algorithm is used to perform deviation control based on the command pressure.

[0044] The workflow of the FPGA module includes:

[0045] Step 1: Determine the input command pressure data P C Is it within the valid range? If not, report an error to the upper level. If yes, continue to execute downwards.

[0046] Step 2: Determine whether there is a pressure sensor fault. The fault determination condition of the pressure sensor is: whether the signal of the pressure sensor is within the effective range;

[0047] If the pressure sensor fails, closed-loop control is not performed and the FPGA directly outputs the input command pressure P out =P C , proceed to step 7;

[0048] If the pressure sensor is not faulty, proceed to step 3;

[0049] Step 3: Calculate the difference between the input command pressure and the feedback pressure:

[0050] e=P C -P D

[0051] In the formula, e represents the difference; P C Indicates command pressure; P D Indicates feedback pressure;

[0052] Step 4: If the feedback pressure is within the command pressure △a range, closed-loop control is performed, otherwise the command pressure is directly transmitted;

[0053] If e>△a, FPGA directly outputs the input command pressure P out =P C , proceed to step 7;

[0054] If e<△a, FPGA performs PID operation and executes step 5;

[0055] Step 5: Perform incremental PID calculation and use the difference e to perform PID calculation:

[0056] △P pid =K P *(e k -e k-1 )+K I *e k +K D *(e k -2e k-1+ e k-2 )

[0057] P pid =P outk-1 +△P pid

[0058] In the formula, K P , K I , K D Indicates PID coefficient; e k Indicates the current difference; e k-1 Indicates the difference value of the previous beat; e k-2 Indicates the difference between the previous and previous beats; P outk-1 Indicates the output of the previous beat; △P pid Indicates PID control increment;

[0059] Step 6: Make a valid value judgment after calculation and limit the calculated value P pid The effective range is set to avoid over-limit output, and the pressure closed-loop adjustment boundary is also limited. The electro-hydraulic pressure servo valve whose adjustment value exceeds the use boundary will not be controlled.

[0060] Embodiment 2

[0061] The advantages of the present invention compared with the prior art will be described in detail below in conjunction with this embodiment.

[0062] The traditional pressure closed-loop control calculation method is as follows:

[0063] I L =(P CL -P dL )×PID

[0064] I R =(P CR -P dR )×PID

[0065] In the formula, I L The brake current output by the pressure closed-loop control of the left wheel, I R The brake current output by the pressure closed loop control of the right wheel. The formula shows that the difference between the command pressure and the actual feedback pressure is used for standard PID closed loop control. Through experiments, it was found that this method is difficult to achieve good control effect on the electro-hydraulic pressure servo valve.

[0066] Figure 4 and Figure 5 These are the test data of an electro-hydraulic pressure servo valve inputting an 8Mpa command pressure step signal through current control and PID control respectively. Figure 4 In the direct output current control, the time from control input to output 2Mpa is 102ms, and after adding PID control, it is 165ms, and the response of the initial pressure is obviously slower. Although the speed of the initial pressure increase can be adjusted by adjusting the PID parameters, the impact of the initial pressure output after adding control cannot be ruled out. Moreover, it is difficult to use a set of parameters to adapt and match each input in the range.

[0067] This embodiment adopts the method of adding a transparent transmission link in the control process and using an incremental PID algorithm to ensure a smooth transition. The specific method is that when the pressure is not close to the effective range of the command pressure, the command pressure is directly output without closed-loop control; after the pressure rises and enters the effective range, the incremental PID algorithm is used to perform deviation control based on the command pressure.

[0068] from Figure 6The experimental results show that before the pressure rises, the control does not intervene and the pressure can rise quickly (84ms to 2Mpa). At the same time, after the pressure rises, the pressure deviation can be effectively controlled to within 0.2Mpa. This not only improves the response, but also ensures the steady-state error.

[0069] In actual application scenarios, the closed-loop control of the pressure of the electro-hydraulic pressure servo valve also needs to set an effective range. The valve with deviation beyond the range will no longer be controlled but replaced. Therefore, the range control proposed by this method can also be well applied to the use scenarios of voltage pressure servo valves.

[0070] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A pressure closed-loop control system for an electro-hydraulic pressure servo valve of an aircraft brake system, characterized in that: include: A brake command sensor, an FPGA module, a DSP module, a pressure sensor and an electro-hydraulic pressure servo valve; the FPGA module is connected to the DSP module, the brake command sensor, the pressure sensor and the electro-hydraulic pressure servo valve respectively.

2. The closed-loop pressure control system of the electro-hydraulic pressure servo valve of the aircraft brake system according to claim 1, characterized in that: The brake command sensor receives pilot input and transmits it to the DSP module after AD acquisition; the DSP module obtains a command pressure signal after anti-skid calculation, and transmits the command pressure signal to the FPGA module; the FPGA module performs closed-loop calculation based on the command pressure signal and the pressure feedback value fed back by the pressure sensor, and outputs a brake current signal to the electro-hydraulic pressure servo valve.

3. The closed-loop pressure control system of the electro-hydraulic pressure servo valve of the aircraft brake system according to claim 1, characterized in that: A transparent transmission link is added during the closed-loop operation of the FPGA module, and an incremental PID algorithm is used to ensure a smooth transition. The specific method includes: when the pressure is not close to the effective range of the command pressure, the command pressure is directly output without closed-loop control; when the pressure rises and enters the effective range, the deviation control is performed through the incremental PID algorithm based on the command pressure.

4. The closed-loop pressure control system for the electro-hydraulic pressure servo valve of the aircraft brake system according to claim 3, characterized in that: The workflow of the FPGA module specifically includes: Step 1: Determine the input command pressure data P C Is it within the valid range? If not, report an error to the upper level. If yes, continue to execute downwards. Step 2: Determine whether there is a pressure sensor fault. The fault determination condition of the pressure sensor is: whether the signal of the pressure sensor is within the effective range; If the pressure sensor fails, closed-loop control is not performed and the FPGA directly outputs the input command pressure P out =P C , proceed to step 7; If the pressure sensor is not faulty, proceed to step 3; Step 3: Calculate the difference between the input command pressure and the feedback pressure: e=P C -P D In the formula, e represents the difference; P C Indicates command pressure; P D Indicates feedback pressure; Step 4: If the feedback pressure is within the command pressure △a range, closed-loop control is performed, otherwise the command pressure is directly transmitted; If e>△a, FPGA directly outputs the input command pressure P out =P C , proceed to step 7; If e<△a, FPGA performs PID operation and executes step 5; Step 5: Perform incremental PID calculation and use the difference e to perform PID calculation: △P pid =K P *(e k -e k-1 )+K I *e k +K D *(e k -2e k-1+ e k-2 ) P pid =P outk-1 +△P pid In the formula, K P , K I , K D Indicates PID coefficient; e k Indicates the current difference; e k-1 Indicates the difference value of the previous beat; e k-2 Indicates the difference between the previous and previous beats; P outk-1 Indicates the output of the previous beat; △P pid Indicates PID control increment; Step 6: Make a valid value judgment after calculation and limit the calculated value P pid The effective range is set to avoid over-limit output, and the pressure closed-loop adjustment boundary is also limited. The electro-hydraulic pressure servo valve whose adjustment value exceeds the use boundary will not be controlled.

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