Torque closed-loop aircraft brake control system

Abstract

The invention discloses a torque closed-loop aircraft brake control system which comprises the following steps: acquiring a target brake torque through a brake control unit, and receiving torque feedback data acquired by a torque sensor; based on the target braking torque, current magnitude is generated through a feedback control method according to torque feedback data; a stop valve is opened through the magnitude of current, corresponding brake pressure is generated through a brake servo valve, and the brake device is subjected to near-constant-torque brake state control according to the brake pressure; and the brake control unit receives wheel speed data acquired by the wheel speed sensor, judges according to the wheel speed data, and controls whether the brake servo valve outputs safety current or not to generate corresponding brake pressure according to a judgment result.

Description

Technical Field

[0001] The present invention belongs to the field of aircraft control technology, and relates to a torque closed-loop control braking scenario of a wheel brake system in the aviation field, and in particular to a torque closed-loop aircraft brake control system. Background Art

[0002] The wheel brake system is a vital component of aircraft flight, directly impacting critical phases such as takeoff, landing, taxiing, and emergency braking. Its core function is to stably stop the aircraft, prevent tire blowouts, and adjust the aircraft's braking deceleration rate in real time to ensure smooth and safe takeoff and landing.

[0003] Pressure-controlled braking in wheel brake systems is a traditional braking method that utilizes closed-loop pressure control technology to precisely regulate hydraulic pressure for efficient braking and anti-skid control. It is currently widely used on platforms such as civil airliners and military transport aircraft. Although pressure-controlled braking technology is relatively mature, it still has certain drawbacks. The braking torque corresponding to the braking pressure is not fixed, but rather a nonlinear, dynamically changing relationship. This makes it difficult to precisely control the braking torque by controlling the braking pressure, resulting in the inability to achieve more direct and effective control of the aircraft's braking process. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention proposes a torque closed-loop aircraft brake control system to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above objectives, the present invention provides a torque closed-loop aircraft brake control system, comprising:

[0006] The system includes a brake control unit, a cut-off valve, a brake servo valve, a brake device and an aircraft wheel connected in sequence; a wheel speed sensor is provided on the aircraft wheel, and a torque sensor is provided on the rear end of the aircraft brake wheel shaft;

[0007] A target braking torque is preset by a brake control unit, which receives torque feedback data from a torque sensor. Based on the target braking torque, a current is generated according to the torque feedback data using a feedback control method. A shut-off valve is opened according to the current, and a corresponding brake pressure is generated through a brake servo valve. The brake device is controlled to a near-constant torque braking state according to the brake pressure.

[0008] The brake control unit also receives wheel speed data obtained by the wheel speed sensor, makes a judgment based on the wheel speed data, and controls the brake servo valve to output a safety current to generate corresponding brake pressure based on the judgment result.

[0009] Optionally, a pedal displacement sensor is also included, wherein the pedal displacement sensor is connected to the brake control unit and is arranged on the brake pedal of the aircraft. Within the response time of the control system, the brake control unit processes the displacement data obtained by the pedal displacement sensor to obtain a corresponding electrical signal, opens the cut-off valve according to the electrical signal, and generates an electrical signal through torque control to control the brake servo valve to output a corresponding brake pressure, and controls the brake device according to the brake pressure corresponding to the electrical signal.

[0010] Optionally, test data is obtained in the brake control unit, where the test data includes the initial deceleration of the aircraft, the tire load and the braking capacity in the aborted takeoff state. Several sets of test data are analyzed to obtain the braking torque under the limit state, and the target braking torque is preset based on the braking torque under the limit state.

[0011] Optionally, in the brake control unit, a safety speed is obtained. When the wheel speed data is greater than the initial deceleration, it is determined whether the wheel speed data is less than the safety speed in a control cycle. When it is less than the safety speed, the brake servo valve is controlled to generate corresponding brake pressure according to the safety current.

[0012] Optionally, in the brake control unit, the brake pressure corresponding to the electrical signal is limited within the control system response time.

[0013] Optionally, the feedback control method adopts an incremental PID control method.

[0014] Optionally, in the brake control unit, the current generation process includes:

[0015] The error signal between the torque feedback data and the target braking torque is obtained, and the torque increment is calculated based on the error signal using the incremental PID control method. The current amount is obtained based on the torque increment. The current amount is the sum of the previous current amount and the incremental current. The incremental current is calculated based on the fitting relationship of the torque increment.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects:

[0017] The present invention proposes adding a torque sensor to a conventional aircraft braking system. Through feedback from the torque sensor, an aircraft braking system with closed-loop torque control is constructed. Braking torque control enables a more direct and effective control of the aircraft's deceleration rate. Using multiple sets of test data for a specific brake disc model, the mathematical relationship between pressure and torque at different speeds was determined. A brake pressure threshold value is set for the aircraft braking system's response time T0 to prevent the aircraft tires from locking due to excessive pressure just as they contact the ground. Under the same braking environment, an aircraft braking system employing a closed-loop torque control system can achieve a higher deceleration rate than a conventional pressure-controlled braking system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings:

[0019] Figure 1 This is a logic block diagram of a traditional wheel brake closed-loop pressure control system according to an embodiment of the present invention;

[0020] Figure 2 Schematic diagram of a torque closed-loop aircraft brake control system according to an embodiment of the present invention;

[0021] Figure 3 A diagram showing the relationship between the preset target torque and the actual braking torque according to an embodiment of the present invention;

[0022] Figure 4 In the embodiment of the present invention, t A schematic diagram showing the relationship between the actual torque and target torque of the pressure limiting control is added at all times;

[0023] Figure 5 This is an incremental PID control logic block diagram of an aircraft brake control system according to an embodiment of the present invention;

[0024] Figure 6 This is a state curve diagram of a constant pressure control aborted takeoff test of an aircraft brake system according to an embodiment of the present invention.

[0025] Figure 7 This is a state curve diagram of a constant torque control aborted takeoff test of an aircraft braking system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0027] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0028] Regarding the pressure control brake of the wheel brake system, the traditional brake system consists of: brake control unit (BCU), wheel speed sensor, pressure sensor, pedal displacement sensor, cut-off valve and brake servo valve, etc. The logic of the traditional wheel brake pressure closed-loop control system is as follows: Figure 1 As shown in the figure, the operating principle is that the pilot operates the brake pedal. When braking, the pedal displacement sensor outputs an electrical signal proportional to its travel to the BCU. The BCU controls the opening of the shut-off valve, connects the hydraulic oil circuit, and controls the brake servo valve to output brake pressure to the brake device. At the same time, the wheel speed sensor sends the wheel speed signal to the BCU. The BCU uses anti-skid calculations to control the current signal output to the brake servo valve, thereby controlling the brake pressure and bringing the aircraft to a smooth stop. However, in the above description, the braking torque is not fixed, making it difficult to accurately control the braking torque by controlling the brake pressure, resulting in the inability to directly and effectively control the brakes. For the braking system, braking torque is the ultimate control target.

[0029] In order to solve the problems existing in the above-mentioned prior art, the present invention provides a torque closed-loop aircraft brake control system, comprising:

[0030] Brake control unit, pedal displacement sensor, wheel speed sensor, torque sensor, cut-off valve and brake servo valve, etc., its torque closed-loop control logic diagram is as follows Figure 2 shown.

[0031] The driver operates the brake pedal, which is provided with a pedal displacement sensor, which is subsequently connected to a brake control unit, a cut-off valve, a brake servo valve, a brake device and an aircraft wheel;

[0032] A torque sensor is installed on the rear end of the aircraft brake axle and is connected to the brake control unit to provide brake torque feedback to the brake control unit, which is used as feedback data for PID control adjustment and torque closed-loop control;

[0033] A wheel speed sensor is set on the wheel and connected to the brake control unit to provide the wheel speed to the brake control unit as the basic data of the speed corresponding threshold to further limit the brake control.

[0034] According to the analysis of the brake disc characteristics, during the braking and deceleration process, there will be a large initial peak torque when the aircraft tire just touches the ground, which may cause the tire to lock. In response to this problem, the purpose of setting the pressure limit control within the system response time T0 is to skip the aircraft tire lock caused by excessive initial peak torque. The core principle of the above system of the present invention is: preset the target braking torque, and perform limit control on the braking pressure within the system response time T0, introduce the feedback value of the torque sensor, and control the output torque to quickly respond to the target torque through incremental PID control to improve braking efficiency; at the same time, introduce the speed value of the wheel speed sensor, set the speed response flag, and judge whether the wheel speed drops t 速 The anti-skid threshold within the aircraft is set to a safety threshold for the brake servo valve to reduce the risk of aircraft tire lock. The system of the present invention combines fly-by-wire control and hydraulic actuation through a control algorithm to effectively increase system response speed while ensuring control accuracy, thereby improving the braking deceleration rate of the aircraft braking system. It mainly includes the following steps:

[0035] Based on the above preset target braking torque, the brake pressure limit control at time T0 is:

[0036] The braking torque and braking pressure of an aircraft braking system typically exhibit nonlinear characteristics, requiring consideration of factors such as aerodynamic drag, tire friction coefficient, and thermal load. The braking system provided by this invention fits a brake pressure-torque characteristic curve to multiple sets of test data from a certain type of brake disc on an aviation power test bench, determining the mathematical relationship between the brake pressure (MPa) and braking torque (KN·m) for that model at different speeds. After analyzing multiple sets of test curves, taking the aborted takeoff test state as an example, the initial deceleration V is set. ZZQF (km / h), the system can preset the target braking torque as KN 目标值 .

[0037] Initial deceleration V ZZQF km / h is the speed at which the aircraft begins braking during a terminated takeoff (RTO). A terminated takeoff (RTO) is a state where the aircraft decelerates to zero to complete the braking process. The key parameters for calculating braking torque are related to the dynamic friction coefficient μ1 between the brake disc and the friction pad, the brake pressure P1 acting on the brake mechanism, and the effective torque radius r1 of the brake friction surface. Braking torque = dynamic friction coefficient μ1 × hydraulic pressure P1 applied to the brake mechanism × effective torque radius r1. This system uses a terminated takeoff test as an example. After determining the aircraft's initial deceleration (km / h), the tire load (kN) and braking capacity (MJ) during a terminated takeoff, multiple sets of test data for a specific brake disc model are analyzed to determine the ultimate braking torque. The target torque is selected based on empirical data, slightly lower than the ultimate braking torque. The target torque can be obtained by reducing the ultimate braking torque by a fixed percentage or value based on empirical data or by a fixed ratio, in order to achieve the optimal braking state.

[0038] Under the condition that other relevant parameters of the system are consistent, it is found through the verification of the aviation power test bench that the preset braking target torque and the actual braking torque curve are as follows Figure 3 As shown:

[0039] pass Figure 3 It can be seen that at the time T0 when the braking current is established, the actual braking torque value collected exceeds the target braking torque KN 目标值 . The reason is that during the moment T0 when the brake current climbs, the initial peak torque is too large, and the aircraft brake system instantly applies the maximum brake pressure (about 90% of the peak torque), causing the aircraft tire to lock. In constant torque braking mode, the system will quickly respond to the target torque output, but in the high-speed stage, the friction coefficient μ between the brake disc and the tire will decrease with increasing speed. If the initial brake pressure is too high, the tire slip rate will instantly exceed the critical value, causing the tire to lock. In order to prevent the initial torque from overshooting, under this condition, the control system response time is increased within T0 seconds. The limit control of the brake pressure is increased. Through the analysis of multiple groups of test curves of a certain type of brake disc on an aviation power test bench, the brake pressure of the aircraft tire at the edge of locking was determined, and this brake pressure was set as the brake pressure threshold value P 初始 After adding the brake pressure limit control at time T0, the aviation power test bench verification curve is as follows Figure 4 shown.

[0040] The main program control cycle of this brake system is T (ms), through Figure 4 It can be seen that when the braking current is K I When the rate climbs, the control system responds to the brake pressure within a threshold limit of (T0 / T) seconds. At this time, the actual braking torque is also limited, avoiding the risk of the aircraft brake system locking due to excessive initial peak torque during high-speed deceleration. When the aircraft speed transitions from the high-speed stage to the medium-speed stage, the brake pressure is no longer limited, and the actual braking torque smoothly approaches the target torque, achieving a constant torque braking state. Figure 4 As can be seen, during the period from 85 to 127 on the horizontal axis (actually 65 to 127), the left valve current is limited to a certain value, so the brake pressure corresponding to the brake current is also limited. This pressure limitation is intended to prevent excessive initial peak torque and locking during high-speed operation. The speed range for pressure limiting is set as the high-speed stage V1. Beyond the period 127, the pressure limit is no longer applied, and the speed range is set as the medium-speed stage V2.

[0041] Regarding the above wheel speed threshold control design:

[0042] This system collects wheel speed signals through wheel speed sensors and outputs them to the brake control unit. The speed threshold control principle is that the wheel speed signal collected by the wheel speed sensor is greater than V ZZQF(km / h) speed state, the speed control monitoring flag SPEED_FLAG is valid and set to 1; when the control cycle T 速 (ms), the wheel speed signal collected by monitoring is in the control period T 速 Is it less than V within (ms) 安全速度阈值 (km / h), if less than V 安全速度阈值 (km / h), it is judged that the aircraft tire is losing speed too quickly, and the torque control should be immediately exited, and the brake servo valve safety current should be output to control the brake pressure to avoid tire wear or other damage due to locking.

[0043] For incremental PID control design:

[0044] The incremental PID controller is an algorithm commonly used in closed-loop control systems. It controls the output by calculating the proportional, integral, and differential deviations to achieve stability and accuracy in the control objective. Its core characteristic is the "incremental output control variable Δuk" rather than the absolute value. The incremental PID algorithm formula is as follows:

[0045] Δuk=K p (e k -e k-1 )+K i e k +K d (e k -2e k-1 +e k-2 ) ①;

[0046] Where: K p , K I and K D Indicates PID coefficient; e k Indicates the error of the current k;

[0047] e k-1 Indicates the last error; e k-2 Indicates the previous error;

[0048] This system is based on the test data of a certain model of multiple sets of brake discs in an aerospace power test bench for aborted takeoff brake tests. It collects brake pedal signals for switch control. When the pedal stroke exceeds a specific voltage value, it enters the constant torque control working mode. By presetting the target brake torque value KN 目标值 , set the initial brake pressure threshold value P 初始 , select the speed value V based on the aircraft brake system abort takeoff test state ZZQF (km / h) is the initial deceleration, and KN of the torque sensor is collected. 实时值Through incremental PID control, the error between the current target torque and the real-time torque is calculated. The corresponding increment of the output control quantity is calculated based on the error at different times. The final output control quantity KN is obtained by adding the real-time torque of the current torque sensor to the corresponding increment. pid The value is converted into current to control the final brake pressure. At the same time, it is determined whether the aircraft tire speed is less than V in the main program control cycle T (ms) during the braking process. 安全速度阈值 (km / h) threshold. If it is less than the safe speed, the torque closed-loop control is exited and the brake pressure of the servo valve dead zone current threshold is output.

[0049] The present invention is directed to a process of finding an optimal deceleration rate in a test state of a rejected takeoff (RTO) of an aircraft, that is, a braking process of the aircraft at a maximum deceleration rate.

[0050] Multiple test conditions for this system are conducted under aborted takeoff conditions. The target torque and critical threshold of the braking system are related but not equivalent concepts. The target torque represents a theoretical requirement, while the critical threshold represents a physical limitation. The target torque for an aborted takeoff should be the ideal braking torque to maximize the aircraft's deceleration rate. It should be slightly lower than the maximum braking torque before tire lock to meet the maximum deceleration rate requirement.

[0051] In the RTO test state, V ZZQF In the high-speed stage from V1 (Km / h) to V2 (Km / h), the pressure limit is set under the influence of the initial peak torque; in the medium-speed stage from V1 (Km / h) to V2 (Km / h) and in the medium-speed stage from V2 (Km / h), when the vehicle decelerates to 0 (i.e., the braking process is completed), the current torque should be adjusted in real time through PID control to approach the target torque infinitely to achieve the braking state with the most ideal deceleration rate.

[0052] With this design, the incremental PID workflow of the aircraft brake control system is as follows: Figure 5 shown.

[0053] In the above content, the final output control quantity KN pid The current corresponding to the value is obtained by fitting the relationship between the control torque and the current.

[0054] In the above content, the current used to control the final brake pressure at the current moment is calculated by summing the previous output and the current incremental current.

[0055] Comparison of constant pressure control and constant torque control examples:

[0056] Figure 6 This is the aborted takeoff test curve of a certain type of aviation power test bench under constant pressure control; Figure 7This is the aborted takeoff test curve of a certain type of aviation power test bench using constant torque control.

[0057] pass Figure 6 and Figure 7 The test curve analysis shows that when the system parameters are basically the same, the average torque of the constant torque control method is higher than that of the constant pressure brake, so the average deceleration rate of the aircraft is higher, the braking system can be controlled more accurately, and nonlinear errors can be reduced.

[0058] Compared with the constant pressure control of some existing aircraft wheel brake systems, this control algorithm has the following differences: 1. Precise control: It directly uses the braking torque as the control target, reducing the nonlinear error between constant pressure oils; 2. Strong adaptability: It uses "PID" control logic and speed threshold control to enhance the safety and reliability of the aircraft braking system.

[0059] In the above scheme, the present invention optimizes the braking efficiency and improves the deceleration rate of the aircraft by presetting the target torque based on the characteristics of the aircraft brake carbon disc; in the present invention, initial brake pressure threshold control and speed threshold control are added to avoid the risk of aircraft locking to a great extent, thereby increasing the safety of the system; the system function logic set by the present invention is clear, the algorithm is easy to control, and the response speed of the servo valve is improved.

[0060] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A torque closed-loop aircraft brake control system, characterized in that: include: The system includes a brake control unit, a cut-off valve, a brake servo valve, a brake device and an aircraft wheel connected in sequence; a wheel speed sensor is provided on the aircraft wheel, and a torque sensor is provided on the rear end of the aircraft brake wheel shaft; A target braking torque is preset by a brake control unit, which receives torque feedback data from a torque sensor. Based on the target braking torque, a current is generated according to the torque feedback data using a feedback control method. A shut-off valve is opened according to the current, and a corresponding brake pressure is generated through a brake servo valve. The brake device is controlled to a near-constant torque braking state according to the brake pressure. The brake control unit also receives wheel speed data obtained by the wheel speed sensor, makes a judgment based on the wheel speed data, and controls the brake servo valve to output a safety current to generate corresponding brake pressure based on the judgment result.

2. The system according to claim 1, wherein: It also includes a pedal displacement sensor, which is connected to the brake control unit and is arranged on the brake pedal of the aircraft. Within the response time of the control system, the brake control unit processes the displacement data obtained by the pedal displacement sensor to obtain a corresponding electrical signal, opens the cut-off valve according to the electrical signal, and generates an electrical signal through torque control to control the brake servo valve to output the corresponding brake pressure, and controls the brake device according to the brake pressure corresponding to the electrical signal.

3. The system according to claim 1, wherein: In the brake control unit, test data is obtained, where the test data includes the initial deceleration of the aircraft, the tire load and the braking capacity in the aborted takeoff state. Several sets of test data are analyzed to obtain the braking torque under the limit state, and the target braking torque is preset based on the braking torque under the limit state.

4. The system according to claim 3, characterized in that In the brake control unit, the safety speed is obtained. When the wheel speed data is greater than the initial deceleration, it is determined whether the wheel speed data is less than the safety speed during the system control cycle. When it is less than the safety speed, the brake servo valve is controlled to generate the corresponding brake pressure according to the safety current.

5. The system according to claim 2, wherein: In the brake control unit, the brake pressure corresponding to the electrical signal is limited within the control system response time.

6. The system according to claim 1, wherein: The feedback control method adopts the incremental PID control method.

7. The system according to claim 1, wherein: In the brake control unit, the current generation process includes: The error signal between the torque feedback data and the target braking torque is obtained, and the torque increment is calculated based on the error signal using the incremental PID control method. The current amount is obtained based on the torque increment. The current amount is the sum of the previous current amount and the incremental current. The incremental current is calculated based on the fitting relationship of the torque increment.

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