Torque closed loop aircraft brake control system

Abstract

The application discloses a torque closed-loop airplane brake control system, comprising: obtaining target brake torque through a brake control unit, and receiving torque feedback data obtained by a torque sensor; generating current amount based on the target brake torque and the torque feedback data through a feedback control method; opening a cut-off valve through the current amount, and generating corresponding brake pressure through a brake servo valve, and controlling the brake device in a near constant torque brake state according to the brake pressure; further receiving wheel speed data obtained by a wheel speed sensor through the brake control unit, judging according to the wheel speed data, and controlling whether the brake servo valve outputs a safety current to generate corresponding brake pressure according to the judgment result.

Description

Technical Field

[0001] This invention belongs to the field of aircraft control technology, and relates to the torque closed-loop control braking scenario of aircraft wheel braking system in the aviation field, and particularly to a torque closed-loop aircraft braking control system. Background Technology

[0002] The wheel braking system is a crucial 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 braking deceleration rate in real time to ensure smooth and safe takeoff and landing.

[0003] Pressure-controlled braking systems are a traditional braking method that employs closed-loop pressure control technology. It achieves efficient braking and anti-skid control by precisely adjusting hydraulic pressure and is currently widely used in civil airliners, military transport aircraft, and other platforms. 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 non-linear, dynamically changing relationship. This makes it difficult to precisely control the braking torque by controlling the braking pressure, resulting in less direct and effective control over the aircraft braking process. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a torque closed-loop aircraft braking control system to solve the problems existing in the prior art.

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

[0006] It includes a brake control unit, a cut-off valve, a brake servo valve, a brake device, and a wheel connected in sequence; a wheel speed sensor is installed on the wheel, and a torque sensor is installed on the rear end of the aircraft brake wheel axle;

[0007] The brake control unit presets the target braking torque and receives torque feedback data from the torque sensor; based on the target braking torque, a current is generated according to the torque feedback data through a feedback control method; the cut-off valve is opened according to the current and the corresponding braking pressure is generated through the brake servo valve; the braking device is controlled to a near-constant torque braking state according to the braking pressure.

[0008] It also receives wheel speed data from the wheel speed sensor through the brake control unit, makes judgments based on the wheel speed data, and controls the brake servo valve to output a safe current to generate the corresponding brake pressure based on the judgment result.

[0009] Optionally, a foot pedal displacement sensor is also included, wherein the foot pedal displacement sensor is connected to the brake control unit and is installed on the brake pedal of the aircraft. During the response time of the control system, the brake control unit processes the displacement data acquired by the foot pedal displacement sensor to obtain the corresponding electrical signal, opens the shut-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. The braking device is controlled according to the brake pressure corresponding to the electrical signal.

[0010] Optionally, in the brake control unit, test data is acquired, including the aircraft's initial deceleration, tire load and braking capacity under aborted takeoff conditions, and several sets of test data are analyzed to obtain the braking torque under extreme conditions. Based on the braking torque under extreme conditions, a target braking torque is preset.

[0011] Optionally, in the brake control unit, a safe 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 safe speed in a control cycle. When it is less than the safe speed, the brake servo valve is controlled to generate the corresponding brake pressure according to the safe current.

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

[0013] Optionally, the feedback control method may employ incremental PID control.

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

[0015] The torque feedback data and the error signal of the target braking torque are obtained. The torque increment is calculated based on the error signal using an incremental PID control method. The current current is obtained based on the torque increment. The current current is the sum of the previous current 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] This invention proposes adding a torque sensor to a traditional aircraft braking system. Through feedback from the torque sensor, an aircraft braking system with closed-loop torque control is constructed. By controlling the braking torque, the aircraft's deceleration rate can be controlled more directly and effectively. Using multiple sets of test data for a specific type of brake disc, the mathematical relationship between pressure and torque at different speed ranges was determined. A braking pressure threshold value was also set for the aircraft braking system response time T0 to prevent tire lock-up due to excessive pressure immediately upon ground contact. Under the same braking conditions, compared to a traditional pressure-controlled braking system, the aircraft braking system using a closed-loop torque control achieves a higher deceleration rate. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

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

[0020] Figure 2 This is a schematic diagram of a torque closed-loop aircraft braking control system according to an embodiment of the present invention;

[0021] Figure 3 This is a graph showing the relationship between the preset target torque and the actual braking torque in an embodiment of the present invention.

[0022] Figure 4 For the embodiments of the present invention in K t A schematic diagram showing the relationship between the actual torque and the target torque of the pressure limiting control at all times;

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

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

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

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

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

[0028] For pressure-controlled braking systems of aircraft wheels, the traditional braking system comprises: a brake control unit (BCU), wheel speed sensors, pressure sensors, pedal displacement sensors, shut-off valves, and brake servo valves. The logic of a traditional closed-loop pressure control system for aircraft wheels is as follows: Figure 1 As shown, its working principle is as follows: the pilot operates the brake pedal, and when braking, the pedal displacement sensor outputs an electrical signal proportional to its travel to the BCU. The BCU controls the shut-off valve to open, connecting the hydraulic circuit, and controls the brake servo valve to output braking pressure to the braking device. At the same time, the wheel speed sensor sends the wheel speed signal to the BCU. The BCU, through anti-slip calculations, controls the magnitude of the current signal output to the brake servo valve, thereby controlling the braking pressure and bringing the aircraft to a smooth stop. However, in the above description, since the braking torque is not constant, it is difficult to accurately control the braking torque by controlling the braking pressure, resulting in the inability to directly and effectively control the brakes; while for the braking system, the braking torque is the ultimate control target.

[0029] To address the problems existing in the prior art, the present invention provides a torque closed-loop aircraft braking control system, comprising:

[0030] The brake control unit, pedal displacement sensor, wheel speed sensor, torque sensor, shut-off valve, and brake servo valve, etc., are illustrated in the torque closed-loop control logic diagram below. Figure 2 As shown.

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

[0032] A torque sensor is installed on the rear end of the aircraft brake wheel axle and connected to the brake control unit to provide braking torque feedback to the brake control unit. This feedback data is used for PID control adjustment and torque closed-loop control.

[0033] Wheel speed sensors are installed on the wheels and connected to the brake control unit to provide the wheel speed as the basic data for the speed response threshold, thereby further limiting the brake control.

[0034] Based on brake disc characteristics, during braking deceleration, the aircraft tires experience a significant initial peak torque upon contact with the ground, potentially leading to tire lock-up. To address this issue, the pressure limiting control within the system response time T0 aims to prevent excessive initial peak torque from causing tire lock-up. The core principle of the system described in this invention is as follows: a target braking torque is preset, and braking pressure is limited within the system response time T0. Feedback from a torque sensor is incorporated, and incremental PID control is used to ensure the output torque responds quickly to the target torque, improving braking efficiency. Simultaneously, the speed value from a wheel speed sensor is used, and a speed response flag is set to determine the wheel speed decrease t. 速 The system incorporates an internal anti-slip threshold and sets a safety threshold for the brake servo valve to reduce the risk of aircraft tire lock-up. The system in this invention combines fly-by-wire control and hydraulic actuation with a control algorithm to effectively increase system response speed and improve the braking deceleration rate of the aircraft braking system while ensuring control accuracy. The main steps include:

[0035] To achieve the aforementioned preset target braking torque, the braking pressure is limited and controlled within time T0:

[0036] The braking torque and braking pressure of aircraft braking systems typically exhibit nonlinear characteristics, requiring consideration of factors such as aerodynamic drag, tire friction coefficient, and thermal load. The braking system provided in this invention, by fitting braking pressure-torque characteristic curves to multiple sets of test data from an aero-engine test bench for a specific brake disc model, determines the mathematical relationship between braking pressure (MPa) and braking torque (KN·m) at different speed ranges. Through analysis of multiple sets of test curves, taking aborted takeoff test conditions as an example, and setting the initial deceleration V... ZZQF (km / h), this system can preset the target braking torque to KN. 目标值 .

[0037] Initial deceleration V ZZQF km / h is the speed at which braking begins when the aircraft aborts takeoff. Aborted takeoff (RTO) is the process of decelerating to 0 to complete the braking process. The core parameters for calculating braking torque are mainly related to the dynamic friction coefficient μ1 of the brake disc and friction pads, the braking pressure P1 applied to the braking device, and the effective torque radius r1 of the braking friction surface. Braking torque = dynamic friction coefficient μ1 × hydraulic pressure P1 applied to the braking device × effective torque radius r1. Taking the aborted takeoff test state as an example, this system analyzes multiple sets of test data for a certain type of brake disc to obtain the braking torque under extreme conditions, based on determined initial deceleration Km / h, tire load KN, and braking capacity MJ under the aborted takeoff state. The selected target torque is obtained based on empirical values, slightly lower than the braking torque under extreme conditions. The target torque can be obtained by reducing the target torque by a fixed percentage or a fixed value from the braking torque under extreme conditions, with the aim of achieving the most ideal braking state.

[0038] While ensuring that other relevant system parameters remain consistent, verification through an aerospace power test bench revealed that the preset braking target torque and the actual braking torque curves are as follows: Figure 3 As shown:

[0039] pass Figure 3 It can be seen that during 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 brake current ramp-up time T0, the initial peak torque is too large, causing the aircraft braking system to apply maximum braking pressure (approximately 90% of the peak torque) instantaneously, resulting in tire lock-up. In constant torque braking mode, the system responds quickly to the target torque output. However, at high speeds, the friction coefficient μ between the brake disc and tire decreases with increasing speed. If the initial braking pressure is too high, the tire slip ratio will instantaneously exceed the critical value, causing tire lock-up. To prevent initial torque overshoot, under these conditions, a limiting control of the braking pressure is added within the control system response time T0 seconds. Through analysis of multiple test curves of a certain type of brake disc on an aero-engine test bench, the braking pressure at the edge of tire lock-up was determined, and this braking pressure was set as the braking pressure threshold value P. 初始 Implement amplitude limiting control. After adding brake pressure amplitude limiting control at time T0, the verification curve on the aero-engine test bench is as follows: Figure 4 As shown.

[0040] The main program control cycle of this braking system is T (ms), through... Figure 4 It can be seen that when the braking current is K I During speed ramp-up, the control system sets a threshold limit on braking pressure within a response time (T0 / T) seconds. At this time, the actual braking torque is also limited, preventing the risk of the aircraft braking system locking up due to excessive initial peak torque during high-speed deceleration. Once the aircraft speed transitions from high-speed to medium-speed, braking pressure limiting is no longer applied, 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. Therefore, the braking pressure corresponding to the braking current is also limited at this time. This is to prevent excessive initial peak torque and subsequent brake lock-up during the high-speed phase, thus limiting the pressure. The speed range for setting the pressure limit is designated as the high-speed phase V1. Once the time range exceeds 127, the limit is lifted and designated as the medium-speed phase V2.

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

[0042] This system collects wheel speed signals via wheel speed sensors and outputs them to the brake control unit. The speed threshold control principle is based on the wheel speed signal collected by the wheel speed sensor being greater than V. ZZQFWhen the speed is (km / h), the speed regulation monitoring flag SPEED_FLAG is set to 1; when the control period T 速 Within (ms), the wheel speed signal collected by monitoring is within 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 If the speed drops too quickly (km / h), it is determined that the aircraft tires are slowing down too fast. Torque control should be disengaged immediately, and the brake servo valve should be output with a safe current to control the brake pressure, so as to avoid tire wear or other damage caused by locking up.

[0043] Design for incremental PID control:

[0044] Incremental PID controllers are a common algorithm used in closed-loop control systems. They achieve stability and accuracy by calculating the proportional, integral, and derivative values ​​of the deviation in the control output. Their core characteristic is the "incremental value Δuk" of the output control quantity, rather than its absolute value. The incremental PID algorithm formula is shown below:

[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] In the formula: K p K I and K D Represents the PID coefficients; e k This represents the error of the current iteration k;

[0047] e k-1 Indicates the previous error; e k-2 This indicates the error from the previous time step.

[0048] This system is based on test data from aero-engine test benches conducted on multiple sets of brake discs of a certain model during takeoff abort braking tests. It collects brake pedal signals for on / off control, and enters constant torque control mode when the pedal travel exceeds a specific voltage value. The system operates by presetting a target braking torque value (KN). 目标值 Set the initial braking pressure threshold value P 初始 The speed value V was selected based on the aircraft braking system's abort takeoff test state. ZZQF (km / h) is the initial deceleration, and the torque sensor's KN is collected. 实时值By using incremental PID control, the error between the current target torque and the real-time torque is calculated. The increment of the corresponding output control quantity is calculated based on the error at different times. The final output control quantity KN is obtained by adding the corresponding increment to the real-time torque of the torque sensor. pid The value is then converted into a current quantity to control the final braking pressure. Simultaneously, it is determined whether the aircraft tire speed during braking is less than V within the main program control cycle T (ms). 安全速度阈值 If the speed is less than the safe speed (km / h), the torque closed-loop control is exited, and the braking pressure of the dead zone current threshold of the output servo valve is applied.

[0049] This invention addresses the process of finding the optimal deceleration rate during an aircraft abort takeoff (RTO) test, i.e., the braking process of an aircraft with the maximum deceleration rate.

[0050] The multiple test states of this system were conducted under aborted takeoff conditions. The target torque and critical threshold of the braking system are related but not identical concepts. The target torque is a theoretical requirement, while the critical threshold is a physical limitation. The target torque for aborted takeoff should be the ideal braking torque, with the aim of maximizing the aircraft's deceleration rate. It should be slightly lower than the maximum braking torque before the tires lock up to meet the maximum deceleration rate requirement.

[0051] Under RTO test conditions, for V ZZQF Pressure limiting is set under the influence of initial peak torque during the high-speed stage (V1(Km / h)~V2(Km / h)); during the medium-speed stages (V1(Km / h)~V2(Km / h) and V2(Km / h)) and deceleration to 0 (i.e., completion of braking process), the current torque should be adjusted in real time through PID control to infinitely approach the target torque in order to achieve the braking state with the most ideal deceleration rate.

[0052] Based on this design, the incremental PID control system flowchart for aircraft braking control is as follows: Figure 5 As shown.

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

[0054] In the above, the current used to control the final braking 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 The abort takeoff test curve under constant pressure control on a certain type of aircraft power test bench; Figure 7This is the takeoff abort test curve of a certain type of aircraft power test bench under constant torque control.

[0057] pass Figure 6 and Figure 7 Analysis of the test curves shows that, with the system parameters being basically the same, the constant torque control method produces a higher average torque than the constant pressure braking method. Therefore, the aircraft has a higher average deceleration rate and can control the braking system more precisely, while reducing nonlinear errors.

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

[0059] In the above scheme, the present invention optimizes braking efficiency and improves the aircraft deceleration rate by using a "PID control + feedforward composite control" method based on the characteristics of the aircraft brake carbon disc and by setting a target torque. The present invention adds initial brake pressure threshold control and speed threshold control, which greatly avoids the risk of aircraft lock-up and increases 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 this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A torque closed loop aircraft brake control system, characterized by, The system comprises: The system comprises a brake control unit, a cut-off valve, a brake servo valve, a brake device and a wheel; a wheel speed sensor is arranged on the wheel, and a torque sensor is arranged on the rear end of the aircraft brake wheel shaft; The brake control unit presets a target brake torque, receives torque feedback data obtained by the torque sensor, generates an electric current based on the target brake torque and the torque feedback data through a feedback control method, opens the cut-off valve according to the electric current, and generates corresponding brake pressure through the brake servo valve, and controls the brake device in 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, judges according to the wheel speed data, and controls whether the brake servo valve outputs a safety current to generate corresponding brake pressure according to the judgment result. In the brake control unit, test data is obtained, wherein the test data includes an initial deceleration of the aircraft, a tire load in a take-off abort state, and brake capacity, a plurality of sets of test data are analyzed to obtain a brake torque in a limit state, and the target brake torque is preset according to the brake torque in the limit state. In the brake control unit, a safety speed is obtained, and when the wheel speed data is greater than the initial deceleration, it is judged whether the wheel speed data is less than the safety speed in a system control cycle, and when the wheel speed data is less than the safety speed, the brake servo valve is controlled to generate corresponding brake pressure according to the safety current. In the brake control unit, the generation process of the electric current includes: An error signal of the torque feedback data and the target brake torque is obtained, and a torque increment is calculated according to the error signal through an incremental PID control method, and the current electric current is obtained according to the torque increment. The current electric current is the sum of the last electric current and the incremental current, and the incremental current is calculated according to the fitting relationship of the torque increment.

2. The system of claim 1, further comprising a foot pedal displacement sensor, wherein the foot pedal displacement sensor is connected to the brake control unit and arranged on the brake foot pedal plate of the aircraft, displacement data obtained by the foot pedal displacement sensor is processed by the brake control unit within the response time of the control system to obtain a corresponding electric signal, the cut-off valve is opened according to the electric signal, and the brake servo valve is controlled to output corresponding brake pressure through torque control to generate an electric signal, and the brake device is controlled to brake according to the electric signal corresponding to the brake pressure.

3. The system of claim 2, wherein in the brake control unit, the electric signal corresponding to the brake pressure is limited in amplitude within the response time of the control system.

4. The system of claim 1, wherein the feedback control method adopts an incremental PID control method. ​ ​ ​

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