Anti-skid braking system based on adaptive reference speed module and control method

Abstract

An anti-skid braking system based on an adaptive reference speed module and a control method. By means of the adaptive reference speed module, an aircraft speed is divided into three sections, i.e., a high section, a medium section and a low section, and an aircraft deceleration rate is calculated. On the basis of the aircraft deceleration rate, the aircraft speed and a wheel speed, a corresponding reference speed deceleration rate is calculated, and a reference speed for the next moment is output. Since the reference speed deceleration rate in the method is determined on the basis of a runway condition, the aircraft speed and the wheel speed, it can be ensured that a slip rate of a wheel relative to the aircraft is kept within an optimal slip rate range, and a ground adhesion torque is used to the maximum extent, thereby improving the braking efficiency and reducing the braking distance.

Description

Antiskid brake system and control method based on adaptive reference speed module TECHNICAL FIELD

[0001] The present application relates to the field of aircraft wheel brake, in particular to an antiskid brake system and control method based on adaptive reference speed module. BACKGROUND

[0002] The wheel brake system is the safety guarantee for the take-off and landing of the aircraft, and the core of its decision is the antiskid brake control method, which has a significant impact on the brake performance of the aircraft. During braking, the pilot steps on the rudder, the wheel brake system collects the rudder command and outputs the brake pressure corresponding to the rudder stroke, and the brake device applies the brake pressure to the brake disc and converts it into the brake torque acting on the wheel. The friction between the runway and the tire forms the ground combined torque. The combined action of the brake torque and the ground combined torque makes the wheel decelerate. The size of the ground combined torque is directly related to the runway / tire combined coefficient, and the size of the combined coefficient changes with the slip rate of the random wheel. As shown in FIG. 1, the combined coefficient μ and the slip rate λ corresponding diagram under dry, wet, and ice / snow runway, wherein 1 is a dry runway, the best slip rate is 0.22, and the corresponding maximum combined coefficient is 0.8; 2 is a wet runway, the best slip rate is 0.18, and the corresponding maximum combined coefficient is 0.5; 3 is an ice / snow runway, the best slip rate is 0.16, and the corresponding maximum combined coefficient is 0.25. The ultimate goal of the antiskid brake control method is to control the slip rate of the wheel relative to the aircraft to keep it near the optimal slip rate. However, during braking, the uncertainty of the runway / tire combined coefficient, the uncertain fluctuation of the wheel load, and the nonlinear decay of the brake disc friction characteristics all affect the stability of the brake system, leading to the occurrence of wheel skidding. At this moment, the antiskid brake control method is needed to reduce the brake pressure, prevent the wheel from locking, keep the slip rate of the wheel near the maximum combined coefficient, improve the antiskid brake efficiency, and reduce the brake distance.

[0003] Currently, the commonly used antiskid brake control method in China is the speed difference plus pressure bias modulation (PD+PBM) control with limited maximum brake pressure. Due to the large difference in the combined coefficient of different runways, in order to ensure that this antiskid brake control method can be used normally on slippery, snow-melting and other poor runways, the brake pressure is limited to a small value, which results in low brake efficiency of this control method on dry runway, and the combined torque provided by the ground cannot be fully utilized. Even when the brake pressure has reached the limited pressure, the combined coefficient of the wheel and the ground has not reached the optimal value. At the same time, since the speed difference, which is used as the wheel skid judgment index, is a fixed value, the antiskid effect is acceptable at high speed, but at low speed, skidding occurs frequently, and the antiskid protection at high, medium and low speed cannot be considered simultaneously. It is urgent to develop adaptive antiskid brake control technology to solve this problem.

[0004] In the prior disclosed patent documents, in the application number CN202311354504.9, a brake control method and system based on aircraft variable load are disclosed, characterized by: calculating the deceleration rate after the aircraft lands, dividing the aircraft speed into high, medium and low speed sections, and presetting the aircraft deceleration rate of different aircraft speed sections, and adjusting the brake pressure of the preset deceleration rate and the real-time deceleration rate control object. The method sets different brake pressures at different speed sections in the brake control process in order to prevent the wheels from slipping. However, this method is based on empirical values, and the operation condition of the aircraft wheel brake system is complex, and the system characteristics are complex. During the braking process, unpredictable conditions such as disturbances will always be encountered, and the wheels will inevitably enter the slipping state. This method does not have the self-adaptability of slip control.

[0005] To solve the above problems, the present application provides a slip-preventing brake system and control method based on an adaptive reference speed module. SUMMARY

[0006] To overcome the deficiencies of frequent slipping at medium and low speeds, low brake efficiency, and inability to fully utilize the ground-provided combined moment in the prior art, the present application provides a slip-preventing brake system and control method based on an adaptive reference speed module.

[0007] The slip-preventing brake system based on an adaptive reference speed module includes a footrest, a footrest displacement sensor, a brake control unit, a servo valve, a front wheel speed sensor and a main wheel speed sensor. The end of the footrest is connected to the input end of the footrest displacement sensor, and the stroke of the footrest is used as the input of the footrest displacement sensor. The signal output end of the footrest displacement sensor is connected to the first signal input end of the brake control unit. The footrest displacement sensor outputs the voltage signal of the collected footrest displacement to the brake control unit. The front wheel speed sensor collects the front wheel speed as the aircraft speed. The main wheel speed sensor collects the main wheel speed.

[0008] The output end of the brake control unit is connected to the electrical signal input end of the servo valve, and the servo valve controls the wheel brake.

[0009] It is characterized in that, further comprising an adaptive reference speed module; the first signal output end and the second signal output end of each output end of the adaptive reference speed module are connected with the second signal input end of the brake control unit and the third signal input end of the brake control unit respectively. The voltage signals of the aircraft speed and the wheel speed are collected through the adaptive reference speed module, and the obtained voltage signals of the aircraft speed and the wheel speed are converted into the aircraft speed and the wheel speed respectively, and the wheel reference speed is obtained according to the aircraft speed and the wheel speed; the wheel reference speed and the wheel speed are output to the brake control unit respectively.

[0010] The front wheel speed sensor output end is connected with the first signal input end of the adaptive reference speed module. The main wheel speed sensor output is connected with the second signal input end of the adaptive reference speed module.

[0011] The adaptive reference speed module comprises a frequency-voltage conversion circuit, a voltage collection circuit, a CPU, a memory and a voltage output circuit. The 0-6khz voltage signals transmitted by the front wheel speed sensor and the main wheel speed sensor are converted into 0-5v voltage signals through the frequency-voltage conversion circuit. The 0-5v voltage signals are converted into 0-80m / s speed values through the voltage collection circuit. The aircraft speed is segmented by the CPU, and the aircraft deceleration rate, the reference speed deceleration rate and the reference speed of the current period are calculated. The current period main wheel speed and the reference speed are output to the brake control unit through the voltage output circuit.

[0012] The control process of the anti-skid brake system based on the adaptive reference speed module is:

[0013] Step one, determine the anti-skid control period K n :

[0014] The determined anti-skid control period K n , n is the period number, n=1, 2, …, m; from the start of braking to the stopping of the aircraft.

[0015] Determine the anti-skid control period K n , the aircraft lands and the wheel starts to rotate completely under the drive of the aircraft after landing, and the brake starts to work; the brake starts to work after the aircraft lands 2mm, and the starting time of the brake is determined as the starting point of the first brake period K1; each brake period t is 20ms.

[0016] Step two, calculate the anti-skid front instruction of the current period:

[0017] The pilot steps on the foot pedal, the brake control unit collects the voltage signal of the foot pedal stroke captured by the foot pedal displacement sensor, and converts it into the anti-skid front instruction C bp .

[0018] Step three, collect the airplane speed of current period and the main wheel speed of current period:

[0019] The adaptive reference speed module collects the front wheel speed through the speed sensor installed on the front wheel, and takes the collected front wheel speed as the airplane speed.

[0020] The adaptive reference speed module collects the main wheel speed through the speed sensor installed on the main wheel.

[0021] The front wheel speed is equivalent to the airplane speed.

[0022] Step four, calculate the reference speed of the main wheel of current period:

[0023] The airplane speed is segmented by the CPU in the adaptive reference speed module; the airplane speed is divided into high speed section, medium speed section and low speed section; when the airplane speed < 5m / s, no longer anti-skid.

[0024] The airplane speed of the high speed section is 80m / s~55m / s; the airplane speed of the medium speed section is 55m / s~30m / s; the airplane speed of the low speed section is 30m / s~5m / s.

[0025] The difference between the airplane speed of the previous period K n-1 and the airplane speed of current period K n is defined as the airplane speed difference Δ of current period K n . Divide the airplane speed difference Δ by the interval time of K n and K n-1 start time, and get the airplane deceleration rate V j of current period K n .

[0026] According to the airplane deceleration rate V j of current period, the runway state is identified:

[0027] If the airplane deceleration rate V j of current period ≥ 4.5m / s 2 , it is determined that the runway is dry runway.

[0028] If the airplane deceleration rate V j of current period < 4.5m / s 2 > 2.5m / s 2 , it is determined that the runway is wet runway.

[0029] If the airplane deceleration rate V j of current period ≤ 2.5m / s 2 , it is determined that the runway is ice and snow runway.

[0030] The adaptive reference speed module obtains the reference speed deceleration rate V jc .

[0031] If the aircraft speed is in the high speed section and the runway is a dry runway, the reference speed deceleration rate V jcg 1 is set to 4.5 m / s 2 ; if the aircraft speed is in the medium speed section and the runway is a dry runway, the reference speed deceleration rate V jcg 2 is set to 4 m / s 2 ; if the aircraft speed is in the low speed section and the runway is a dry runway, the reference speed deceleration rate V jcg 3 is set to 3.5 m / s 2 .

[0032] If the aircraft speed is in the high speed section and the runway is a wet runway, the reference speed deceleration rate V jcs 1 is set to 3.5 m / s 2 ; if the aircraft speed is in the medium speed section and the runway is a wet runway, the reference speed deceleration rate V jcs 2 is set to 3 m / s 2 ; if the aircraft speed is in the high speed section and the runway is a wet runway, the reference speed deceleration rate V jcs 3 is set to 2.5 m / s 2 .

[0033] If the aircraft speed is in the high speed section and the runway is an icy runway, the reference speed deceleration rate V jcb 1 is set to 2.5 m / s 2 ; if the aircraft speed is in the medium speed section and the runway is an icy runway, the reference speed deceleration rate V jcb 2 is set to 2 m / s 2 ; if the aircraft speed is in the low speed section and the runway is an icy runway, the reference speed deceleration rate V jcb 3 is set to 1.5 m / s 2 .

[0034] The aircraft speed and the main wheel speed V n of the current period K w are input into the adaptive reference speed module, and the reference speed V n of the current period K cn is obtained, which is specifically:

[0035] If the aircraft speed is in the high speed section and the runway is a dry runway, the reference speed of the current cycle is obtained by formula (1)

[0036] If the aircraft speed is in the medium speed section and the runway is a dry runway, the reference speed of the current cycle is obtained by formula (2)

[0037] If the aircraft speed is in the low speed section and the runway is a dry runway, the reference speed of the current cycle is obtained by formula (3)

[0038] If the aircraft speed is in the high speed section and the runway is a wet runway, the reference speed of the current cycle is obtained by formula (4)

[0039] If the aircraft speed is in the medium speed section and the runway is a wet runway, the reference speed of the current cycle is obtained by formula (5)

[0040] If the aircraft speed is in the low speed section and the runway is a wet runway, the reference speed of the current cycle is obtained by formula (6)

[0041] If the aircraft speed is in the high speed section and the runway is an icy runway, the reference speed of the current cycle is obtained by formula (7)

[0042] If the aircraft speed is in the high speed section and the runway is an icy runway, the reference speed of the current cycle is obtained by formula (8)

[0043] If the aircraft speed is in the high speed section and the runway is an icy runway, the reference speed of the current cycle is obtained by formula (9)

[0044] The reference speed of the current cycle and the main wheel speed are transmitted to the brake control unit.

[0045] Step five, anti-skid state judgment of the current cycle:

[0046] The brake control unit receives the reference speed of the current cycle and the main wheel speed. The difference between the reference speed of the current cycle and the main wheel speed is the reference speed difference of the current cycle.

[0047] The brake control unit determines the state of the current wheel through the reference speed difference of the current cycle: if the reference speed difference of the current cycle is greater than or equal to the anti-skid entering threshold, the main wheel has entered the slipping state during the current brake process, and the anti-skid needs to be intervened to reduce the anti-skid command C ap to reduce the brake pressure and release the wheel to make it roll; otherwise, the anti-skid does not need to be entered, and the brake continues.

[0048] The threshold value is set to 0.3.

[0049] The post-slip instruction C ap is determined.

[0050] The difference between the pre-slip instruction and the slip instruction of the current period is calculated by formula (10) to obtain the post-slip instruction C ap C ap of the current period. bp C as (10)

[0051] In the formula, C bp is the pre-slip pressure instruction; C as is the slip instruction of the current period.

[0052] When the slip instruction C as of the current period is determined, the difference between the reference speed difference of the current period and the slip entry threshold value is taken as the slip amount A n of the current period, and the slip instruction C as of the current period is determined by formula (11).

[0053] Wherein, K p is the proportional level coefficient of the slip amount; K i is the integral level coefficient of the slip amount; K d is the differential level coefficient of the slip amount; K p , K i , K d are all real numbers greater than 0, and are obtained by slip brake test.

[0054] m is the number of periods in the slip process from when the slip amount A n > 0 to when the slip amount ≤ 0; when the slip amount A n ≤ 0, the number of previous periods is cleared.

[0055] The slip instruction C as of the current period is less than or equal to the pre-slip pressure instruction C bp .

[0056] Step six, output the control instruction of the current period:

[0057] The brake control unit converts the obtained post-slip instruction C ap into the value of the brake control current C v by formula (12), and outputs the brake control current C vOutput to servo valve, through the servo valve adjustment brake pressure, and implement anti-skid brake C v =1 / p*C ap (12)

[0058] Wherein, p is the gain coefficient of servo valve.

[0059] Step seven, continuous anti-skid brake:

[0060] Cyclically repeat steps two to six until the plane stops.

[0061] The present application realizes the most suitable reference speed under various runway conditions and operating conditions by the adaptive reference speed module, maximizes the utilization of the ground combined moment, shortens the braking distance and improves the braking efficiency.

[0062] Compared with the prior art, the present application has the following advantages:

[0063] The adaptive reference speed module is designed, which divides the aircraft speed into three segments, i.e., high speed of 80 m / s to 55 m / s, medium speed of 55 m / s to 30 m / s and low speed of 30 m / s to 5 m / s, and first defines the three different speed segments, and calculates the aircraft deceleration rate, and calculates the corresponding reference speed deceleration rate according to the aircraft deceleration rate, the aircraft speed and the wheel speed, and outputs the reference speed at the next moment, since the reference speed deceleration rate in the method is determined according to the runway state, the aircraft speed and the wheel speed, thus the slip rate of the wheel relative to the aircraft can be kept in the optimal slip rate range, the ground combined moment is maximized, the braking efficiency is improved and the braking distance is reduced. The braking efficiency is calculated according to the acceleration calculation method required in chapter 5.2.4 of AIR 1739B, Fig. 5 is a braking efficiency calculation diagram of the aircraft anti-skid brake control method based on the adaptive reference speed module under a dry runway, wherein 18 is the acceleration during the aircraft braking process, 19 is the selected acceleration for calculating the braking efficiency, and the calculated braking efficiency is 96.97%. Fig. 6 is a braking efficiency calculation diagram of the aircraft anti-skid brake control method limiting the maximum braking pressure under a dry runway, wherein 20 is the acceleration during the aircraft braking process, 21 is the selected acceleration for calculating the braking efficiency, and the calculated braking efficiency is 83.53%.

[0064] The optimal slip rate range is shown in Fig. 7. Fig. 8 is the ground combined moment of the aircraft anti-skid brake control method based on the adaptive reference speed module under a dry runway, and Fig. 9 is the ground combined moment of the aircraft anti-skid brake control method limiting the maximum braking pressure under a dry runway, and it can be seen that the aircraft anti-skid brake control method based on the adaptive reference speed module utilizes a higher ground combined moment on a dry runway. BRIEF DESCRIPTION OF DRAWINGS

[0065] Figure 1 is a graph of the relationship between the coefficient of friction μ and the slip ratio λ on dry, wet, and icy runways.

[0066] Figure 2 is a block diagram of the control system of the present application.

[0067] Figure 3 is a block diagram of the adaptive reference speed module

[0068] Figure 4 is a flowchart of the present application.

[0069] Figure 5 is a graph of the efficiency of the anti-skid brake control method based on the adaptive reference speed module on a dry runway

[0070] Figure 6 is a graph of the efficiency of the anti-skid brake control method with a limited maximum brake pressure on a dry runway

[0071] Figure 7 is a diagram of the optimal slip ratio range

[0072] Figure 8 is the ground bonding moment of the anti-skid brake control method based on the adaptive reference speed module for an airplane on a dry runway

[0073] Figure 9 is the ground bonding moment of the anti-skid brake control method with a limited maximum brake pressure for an airplane on a dry runway

[0074] In the figures: 1. Relationship between the coefficient of friction μ and the slip ratio λ on a dry runway; 2. Relationship between the coefficient of friction μ and the slip ratio λ on a wet runway; 3. Relationship between the coefficient of friction μ and the slip ratio λ on an icy runway; 4. Footrest; 5. Footrest displacement sensor; 6. Adaptive reference speed module; 7. Brake control unit; 8. Servo valve; 9. Front wheel speed sensor; 10. Main wheel speed sensor; 11. Front wheel; 12. Main wheel; 13. Frequency-voltage conversion circuit; 14. Voltage acquisition circuit; 15. CPU; 16. Memory; 17. Voltage output circuit; 18. Aircraft deceleration rate of the anti-skid brake control method based on the adaptive reference speed module; 19. Aircraft deceleration rate selected when calculating the brake efficiency of the anti-skid brake control method based on the adaptive reference speed module; 20. Aircraft deceleration rate of the anti-skid brake control method with a limited maximum brake pressure; 21. Aircraft deceleration rate selected when calculating the brake efficiency of the anti-skid brake control method with a limited maximum brake pressure; 22. Optimal slip ratio range; 23. Optimal slip ratio. DETAILED DESCRIPTION

[0075] Example One

[0076] This example provides an anti-skid brake control system based on an adaptive reference speed module, which includes a footrest 4, a footrest displacement sensor 5, an adaptive reference speed module 6, a brake control unit 7, a servo valve 8, a front wheel speed sensor 9, and a main wheel speed sensor 10. As shown in Figure 2.

[0077] The end of the pedal is connected with the input end of the pedal displacement sensor, and the stroke of the pedal is taken as the input of the pedal displacement sensor. The signal output end of the pedal displacement sensor is connected with the first signal input end of the brake control unit. The pedal displacement sensor outputs the voltage signal of the collected pedal displacement to the brake control unit.

[0078] The front wheel speed sensor is installed on the front wheel of the airplane, and the speed of the front wheel is collected as the speed of the airplane. The output end of the front wheel speed sensor is connected with the first signal input end of the adaptive reference speed module. The main wheel speed sensor is installed on the main wheel of the airplane, and the speed of the main wheel is collected. The output of the main wheel speed sensor is connected with the second signal input end of the adaptive reference speed module.

[0079] The first signal output end and the second signal output end of the adaptive reference speed module are connected with the second signal input end of the brake control unit and the third signal input end of the brake control unit, respectively. The adaptive reference speed module collects the voltage signals of the speed of the airplane and the speed of the wheel, converts the voltage signals into the speed of the airplane and the speed of the wheel, respectively, and obtains the reference speed of the wheel according to the speed of the airplane and the speed of the wheel. The reference speed of the wheel and the speed of the wheel are output to the brake control unit.

[0080] The output end of the brake control unit is connected with the electric signal input end of the servo valve. The brake control unit calculates the anti-skid instruction according to the reference speed and the speed of the wheel, converts the anti-skid instruction into the control current of the servo valve, and controls the wheel brake according to the brake pressure proportional to the control current output by the servo valve.

[0081] As shown in FIG. 3, the adaptive reference speed module includes a frequency-voltage conversion circuit 13, a voltage collection circuit 14, a CPU 15, a memory 16, and a voltage output circuit 17. The 0-6khz voltage signal transmitted by the front wheel speed sensor and the main wheel speed sensor is converted into a 0-5v voltage signal by the frequency-voltage conversion circuit. The 0-5v voltage signal is converted into a 0-80m / s speed value by the voltage collection circuit. The speed of the airplane is segmented by the CPU, and the airplane deceleration rate, the reference speed deceleration rate, and the reference speed of the current period are calculated. The main wheel speed and the reference speed of the current period are output to the brake control unit by the voltage output circuit.

[0082] Embodiment Two

[0083] The present example provides an adaptive reference speed module anti-skid brake control method, and the specific process is as follows:

[0084] Step One, determine the anti-skid control period Kn :

[0085] The determined anti-skid control period K is n, from the start of braking until the airplane stops.

[0086] After the airplane lands, the wheels start to rotate under the drive of the airplane, and the braking starts after the wheels completely rotate; the braking starts after the airplane lands 2 mm, and the starting time of the braking is determined as the starting point of the first braking period K1; each braking period t is 20 ms.

[0087] Step two, calculate the anti-skid front instruction of the current period:

[0088] The pilot steps on the rudder, and the brake control unit collects the voltage signal of the rudder stroke captured by the rudder displacement sensor, and converts it into the anti-skid front instruction C bp .

[0089] The anti-skid front pressure instruction C bp is converted in proportion to the rudder displacement voltage signal by a conventional method, and the collected rudder displacement voltage signal is converted into the anti-skid front pressure instruction C bp by the brake control unit. In this embodiment, the collected 0-3V rudder displacement voltage signal is converted into the 0-3000Psi anti-skid front pressure instruction C bp .

[0090] Step three, collect the airplane speed of the current period and the main wheel speed of the current period:

[0091] The adaptive reference speed module collects the front wheel speed through the speed sensor installed on the front wheel, and takes the collected front wheel speed as the airplane speed.

[0092] The adaptive reference speed module collects the main wheel speed through the speed sensor installed on the main wheel.

[0093] The front wheel speed is equivalent to the airplane speed.

[0094] Step four, calculate the reference speed of the main wheel of the current period:

[0095] And the reference speed of the current period is transmitted to the brake control unit and the memory 16, respectively.

[0096] The airplane speed is segmented by the CPU in the adaptive reference speed module; the airplane speed is divided into high-speed, medium-speed and low-speed segments; the airplane speed in the high-speed segment is 80m / s-55m / s; the airplane speed in the medium-speed segment is 55m / s-30m / s; the airplane speed in the low-speed segment is 30m / s-5m / s. When the airplane speed is <5m / s, the anti-skid is no longer performed.

[0097] Define the previous cycle K during braking. n-1 The aircraft speed and the current period K n The difference in aircraft speed is the current period K. n The aircraft speed difference Δ. Divide the aircraft speed difference Δ by K. n With K n-1 The interval between the start and end times is used to obtain the current period K. n aircraft deceleration rate V j .

[0098] Based on the aircraft deceleration rate V of the current cycle j Identify the runway status:

[0099] If the aircraft deceleration rate V in the current period j ≥4.5m / s 2 At that time, the runway was determined to be a dry runway.

[0100] If the aircraft deceleration rate V in the current period j <4.5m / s 2 >2.5m / s 2 At that time, the track was determined to be a wet track.

[0101] If the aircraft deceleration rate V in the current period j ≤2.5m / s 2 At that time, the track was determined to be an ice and snow track.

[0102] The adaptive reference speed module obtains the reference speed deceleration rate V for the current cycle based on the aircraft speed and deceleration rate in the current cycle, according to the segmentation of the aircraft speed and the identification of the runway. jc .

[0103] If the aircraft is traveling at high speed and the runway is dry, then set the reference speed deceleration rate V. jcg 1 4.5 m / s 2 If the aircraft speed is in the medium speed range and the runway is a dry runway, then set the reference speed deceleration rate V. jcg 2 4m / s 2 If the aircraft speed is in the low-speed range and the runway is a dry runway, then set the reference speed deceleration rate V. jcg 3 3.5 m / s 2 .

[0104] If the aircraft is traveling at high speed and the runway is wet, then set the reference speed deceleration rate V. jcs 1 3.5 m / s 2 If the aircraft speed is in the medium speed range and the runway is wet, then set the reference speed deceleration rate V.jcs 2 is 3 m / s 2 ; if the aircraft speed is in the high speed section and the runway is a wet runway, the reference speed reduction rate V jcs 3 is 2.5 m / s 2 .

[0105] if the aircraft speed is in the high speed section and the runway is an icy and snowy runway, the reference speed reduction rate V jcb 1 is 2.5 m / s 2 if the aircraft speed is in the medium speed section and the runway is an icy and snowy runway, the reference speed reduction rate V jcb 2 is 2 m / s 2 if the aircraft speed is in the low speed section and the runway is an icy and snowy runway, the reference speed reduction rate V jcb 3 is 1.5 m / s 2 .

[0106] The aircraft speed and the main wheel speed V n of the current period K w are input into the adaptive reference speed module, and the reference speed V n of the current period K cn is obtained, which is specifically:

[0107] if the aircraft speed is in the high speed section and the runway is a dry runway, the reference speed of the current period is obtained through formula (1)

[0108] if the aircraft speed is in the medium speed section and the runway is a dry runway, the reference speed of the current period is obtained through formula (2)

[0109] if the aircraft speed is in the low speed section and the runway is a dry runway, the reference speed of the current period is obtained through formula (3)

[0110] if the aircraft speed is in the high speed section and the runway is a wet runway, the reference speed of the current period is obtained through formula (4)

[0111] if the aircraft speed is in the medium speed section and the runway is a wet runway, the reference speed of the current period is obtained through formula (5)

[0112] if the aircraft speed is in the low speed section and the runway is a wet runway, the reference speed of the current period is obtained through formula (6)

[0113] If the aircraft speed is in the high speed section and the runway is icy, the reference speed of the current cycle is obtained by formula (7)

[0114] If the aircraft speed is in the high speed section and the runway is icy, the reference speed of the current cycle is obtained by formula (8)

[0115] If the aircraft speed is in the high speed section and the runway is icy, the reference speed of the current cycle is obtained by formula (9)

[0116] And the main wheel reference speed of the current cycle and the main wheel speed of the current cycle are transmitted to the brake control unit and the memory 16 respectively.

[0117] Step five, anti-skid state judgment of the current cycle:

[0118] The brake control unit receives the reference speed and the main wheel speed of the current cycle. The difference between the reference speed and the main wheel speed of the current cycle is the reference speed difference of the current cycle.

[0119] The brake control unit determines the state of the current wheel through the reference speed difference of the current cycle: if the reference speed difference of the current cycle is greater than or equal to the anti-skid entering threshold, the main wheel has entered the skid state during the current brake process, and the anti-skid needs to be intervened to reduce the anti-skid post-command C ap , so as to reduce the brake pressure and release the wheel to make it roll; otherwise, the anti-skid does not need to be entered, and the brake continues.

[0120] The anti-skid threshold is 0.3.

[0121] The specific process of determining the anti-skid post-command C ap is as follows:

[0122] The anti-skid post-command C ap is determined by formula (10) ap C bp =C as (10)

[0123] In the formula, C bp is the pre-anti-skid pressure command; C as is the anti-skid command of the current cycle.

[0124] When determining the anti-skid command C as of the current cycle, the difference between the reference speed difference of the current cycle and the anti-skid entering threshold is taken as the anti-skid amount A n of the current cycle, and the anti-skid command C as of the current cycle is determined by formula (11).

[0125] K p is a proportional level coefficient of the anti-skid amount; K i is an integral level coefficient of the anti-skid amount; K d is a differential level coefficient of the anti-skid amount; K p , K i , K d are all real numbers greater than 0, and are obtained through anti-skid brake test.

[0126] m is the number of periods in the anti-skid process starting from when the anti-skid amount A n > 0 to when the anti-skid amount ≤ 0; when the anti-skid amount A n ≤ 0, the number of previous periods is reset to 0.

[0127] The anti-skid instruction C as of the current period is calculated according to the following formula (10) C bp = K ap p * (C v - C v ) + C v .

[0128] Step six, output the control instruction of the current period:

[0129] The anti-skid instruction C ap after the anti-skid is converted into the value of brake control current C v through formula (12), and the brake control current C v is output to the servo valve to adjust the brake pressure and implement the anti-skid brake C v = 1 / p*C ap (12)

[0130] In the formula, p is the gain coefficient of the servo valve.

[0131] Step seven, continue the anti-skid brake:

[0132] Steps two to six are repeated in a loop until the airplane stops.

Claims

1. An anti-skid braking system based on an adaptive reference speed module, comprising a pedal (4), a pedal displacement sensor (5), a brake control unit (7), a servo valve (8), a front wheel speed sensor (9), and a main wheel speed sensor (10), wherein, The end of the pedal is connected to the input terminal of the pedal displacement sensor, and the pedal stroke is used as the input of the pedal displacement sensor. The signal output terminal of the pedal displacement sensor is connected to the first signal input terminal of the brake control unit. The pedal displacement sensor outputs the voltage signal of the collected pedal displacement to the brake control unit. The speed of the front wheel, collected by the front wheel speed sensor, is taken as the aircraft speed; the speed of the main wheel, collected by the main wheel speed sensor, is taken; the output of the brake control unit is connected to the electrical signal input of the servo valve; the wheel brakes are controlled by the servo valve. The feature is that it further includes an adaptive reference speed module (6); among the output terminals of the adaptive reference speed module, the first signal output terminal and the second signal output terminal are respectively connected to the second signal input terminal and the third signal input terminal of the brake control unit; the voltage signal of the aircraft speed and the voltage signal of the wheel speed are collected through the adaptive reference speed module, and the obtained voltage signals of the aircraft speed and the wheel speed are converted into aircraft speed and wheel speed respectively, and the wheel reference speed is obtained according to the aircraft speed and the wheel speed; the wheel reference speed and the wheel speed are respectively output to the brake control unit; The output of the front wheel speed sensor is connected to the first signal input of the adaptive reference speed module; the output of the main wheel speed sensor is connected to the second signal input of the adaptive reference speed module. The adaptive reference speed module (6) includes a frequency-to-voltage conversion circuit (13), a voltage acquisition circuit (14), a CPU (15), a memory (16), and a voltage output circuit (17). The frequency-to-voltage conversion circuit converts the 0-6kHz voltage signal transmitted from the front wheel speed sensor and the main wheel speed sensor into a 0-5V voltage signal. The voltage acquisition circuit converts the 0-5V voltage signal into a speed value of 0-80m / s. The CPU segments the aircraft speed and calculates the aircraft deceleration rate, reference speed deceleration rate, and reference speed for the current cycle. The voltage output circuit outputs the main wheel speed and reference speed for the current cycle to the brake control unit.

2. A control method for an anti-skid braking system based on an adaptive reference speed module as described in claim 1, characterized in that, The specific process is as follows: Step 1: Determine the anti-slip control cycle K n : The determined anti-slip control period K n n is the number of cycles, n = 1, 2, ..., m; from the start of braking until the aircraft comes to a complete stop; Step 2: Calculate the anti-slip command for the current cycle: When the pilot depresses the pedals, the brake control unit collects the voltage signal of the pedal travel captured by the pedal displacement sensor and converts it into an anti-skid command C. bp ; Step 3: Collect the aircraft speed and the main engine wheel speed for the current cycle: The adaptive reference speed module collects the speed of the nose wheel through a speed sensor installed on the nose wheel and uses the collected nose wheel speed as the aircraft speed; The adaptive reference speed module acquires the speed of the main engine wheel through a speed sensor installed on the main engine wheel; The speed of the nose wheel is equivalent to the speed of the aircraft. Step 4: Calculate the reference speed of the main wheel in the current cycle: The aircraft speed is segmented by the CPU in the adaptive reference speed module, which divides the aircraft speed into high-speed, medium-speed, and low-speed segments; when the aircraft speed is <5m / s, anti-skid measures are no longer applied. Define the previous cycle K during braking. n-1 The aircraft speed and the current period K n The difference in aircraft speed is the current period K. n The aircraft speed difference Δ; divide the aircraft speed difference Δ by K. n With K n-1 The interval between the start and end times is used to obtain the current period K. n aircraft deceleration rate V j ; Based on the aircraft deceleration rate V of the current cycle j Identify the runway status: If the aircraft deceleration rate V in the current period j ≥4.5m / s 2 At that time, the runway was determined to be a dry runway; If the aircraft deceleration rate V in the current period j <4.5m / s 2 >2.5m / s 2 At that time, the track was determined to be a wet track; If the aircraft deceleration rate V in the current period j ≤2.5m / s 2 At that time, the track was determined to be an ice and snow track; The adaptive reference speed module obtains the reference speed deceleration rate V for the current cycle based on the aircraft speed and deceleration rate in the current cycle, according to the segmentation of the aircraft speed and the identification of the runway. jc ; If the aircraft is traveling at high speed and the runway is dry, then set the reference speed deceleration rate V. jcg 1 4.5 m / s 2 If the aircraft speed is in the medium speed range and the runway is a dry runway, then set the reference speed deceleration rate V. jcg 2 4m / s 2 If the aircraft speed is in the low-speed range and the runway is a dry runway, then set the reference speed deceleration rate V. jcg 3 3.5 m / s 2 If the aircraft is traveling at high speed and the runway is wet, then a reference speed deceleration rate V is set. jcs 1 3.5 m / s 2 ; If the aircraft speed is in the medium speed range and the runway is wet, then set the reference speed deceleration rate V. jcs 2 3m / s 2 If the aircraft is traveling at high speed and the runway is wet, then a reference speed deceleration rate V should be set. jcs 3 2.5 m / s 2 If the aircraft is traveling at high speed and the runway is icy or snowy, then a reference speed deceleration rate V should be set. jcb 1 2.5 m / s 2 If the aircraft speed is in the medium speed range and the runway is icy or snowy, then the reference speed deceleration rate V is set. jcb 2 2m / s 2 If the aircraft speed is in the low-speed range and the runway is icy or snowy, then the reference speed deceleration rate V is set. jcb 3 1.5m / s 2 ; Set the current period K n Aircraft speed, main wheel speed V w By inputting the adaptive reference velocity module, the current period K can be obtained. n Reference speed V cn Specifically: If the aircraft is traveling at high speed and the runway is dry, the reference speed for the current cycle can be obtained using formula (1). If the aircraft speed is in the medium speed range and the runway is a dry runway, the reference speed for the current cycle can be obtained using formula (2). If the aircraft speed is in the low-speed range and the runway is a dry runway, the reference speed for the current cycle can be obtained using formula (3). If the aircraft is traveling at high speed and the runway is wet, the reference speed for the current cycle can be obtained using formula (4). If the aircraft speed is in the medium speed range and the runway is wet, the reference speed for the current cycle can be obtained using formula (5). If the aircraft speed is in the low-speed range and the runway is wet, the reference speed for the current cycle can be obtained using formula (6). If the aircraft is traveling at high speed and the runway is icy or snowy, the reference speed for the current cycle can be obtained using formula (7). If the aircraft is traveling at high speed and the runway is icy or snowy, the reference speed for the current cycle can be obtained using formula (8). If the aircraft is traveling at high speed and the runway is icy or snowy, the reference speed for the current cycle can be obtained using formula (9). The reference speed of the main wheel in the current cycle and the speed of the main wheel in the current cycle are transmitted to the brake control unit and the memory (16), respectively. Step 5: Determine the anti-slip condition for the current cycle: The brake control unit receives the reference speed and the main wheel speed of the current cycle; the difference between the reference speed and the main wheel speed of the current cycle is the reference speed difference of the current cycle. The brake control unit determines the current wheel status based on the reference speed difference of the current cycle: if the reference speed difference of the current cycle is greater than or equal to the anti-skid entry threshold, then the main wheel has already slipped during the current braking process, requiring anti-skid intervention and reducing the anti-skid command C. ap To reduce braking pressure, release the wheels and allow them to roll; conversely, if the pressure is too high, anti-skid entry is not needed, and braking continues. The threshold is set to 0.3; Step 6: Output control commands for the current cycle: The brake control unit uses formula (12) to process the anti-skid command C. ap Converted to brake control current C v The value of the brake control current C is then used to control the braking current. v The output is sent to a servo valve, which adjusts the brake pressure and applies anti-slip braking. C v =1 / p*C ap (12) In the formula, p is the gain coefficient of the servo valve; Step 7: Continuous anti-skid braking: Repeat steps two through six until the aircraft comes to a complete stop.

3. The control method for the anti-skid braking system based on an adaptive reference speed module as described in claim 2, characterized in that, Determine the anti-slip control cycle K n When the aircraft lands and the wheels begin to rotate fully under the aircraft's drive, braking begins; braking is initiated 2mm after the aircraft lands, and the starting time of braking is determined as the start of the first braking cycle K1; each braking cycle t is 20ms.

4. The control method for the anti-skid braking system based on an adaptive reference speed module as described in claim 2, characterized in that, The high-speed range is 80m / s to 55m / s; the medium-speed range is 55m / s to 30m / s; and the low-speed range is 30m / s to 5m / s.

5. The control method for the anti-skid braking system based on an adaptive reference speed module as described in claim 2, characterized in that, In step five, the anti-slip command C is determined. ap The specific process is as follows: The difference between the pre-anti-slip command and the anti-slip command of the current cycle is calculated using formula (10) to obtain the post-anti-slip command C for the current cycle. ap C ap =C bp -C as (10) In the formula, C bp For anti-slip pressure command; C as This is the anti-slip instruction for the current cycle.

6. The control method for the anti-skid braking system based on the adaptive reference speed module as described in claim 5, characterized in that, In step five, the anti-slip command C for the current cycle is determined. as At that time, the difference between the reference speed difference of the current cycle and the anti-slip entry threshold is used as the anti-slip amount A of the current cycle. n The anti-slip command C for the current cycle is determined by formula (11). as ; Among them, K p It is the proportional coefficient of the anti-slip amount; K i It is the integral coefficient of the anti-slip amount; K d It is the micro-grading coefficient of anti-slip amount; K p K i K d All are real numbers greater than 0, and all were obtained through anti-skid braking tests; m is the self-anti-slip amount A n The number of cycles in the anti-slip process from when the anti-slip amount is >0 to when it is ≤0; when the anti-slip amount A n When the value is ≤0, the previous cycle number is reset to zero.

7. The control method for the anti-skid braking system based on the adaptive reference speed module as described in claim 5, characterized in that, The anti-slip command C for the current cycle as ≤Anti-slip pressure command C bp .

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