阅读说明：本技术 一种飞机自适应防滑刹车控制方法 (Self-adaptive anti-skid brake control method for airplane ) 是由 操虹 张天闯 李卫 姚伟士 刘阳 王连波 丰四清 于 2020-12-09 设计创作，主要内容包括：本发明公开了一种飞机自适应防滑刹车控制方法。本发明包括以下步骤：步骤1,平均减速率计算,步骤2,前向电流计算,步骤3,输出电流计算,本发明由开环控制方式改为闭环控制方式,以飞机机轮减速率为控制目标,通过对输入速度信号的分析,计算飞机的减速率并找到飞机最适合的刹车控制条件,通过不断调节输入刹车电流,使刹车系统对机轮的刹车控制接近防滑状态的点,以找到前向刹车最优状态,并根据判断出的最优减速率,对刹车电流进行控制,使系统处于最优控制状态。(The invention discloses a self-adaptive anti-skid brake control method for an airplane. The invention comprises the following steps: the method comprises the steps of 1, average deceleration rate calculation, 2, forward current calculation, 3 and output current calculation, wherein an open-loop control mode is changed into a closed-loop control mode, the deceleration rate of an airplane wheel of the airplane is taken as a control target, the deceleration rate of the airplane is calculated and the optimal brake control condition of the airplane is found through analysis of an input speed signal, the brake current is continuously adjusted and input, so that the brake control of a brake system on the airplane wheel is close to the point of an anti-skid state, the optimal forward brake state is found, and the brake current is controlled according to the judged optimal deceleration rate, so that the system is in the optimal control state.)

1. An aircraft self-adaptive anti-skid brake control method is characterized by comprising the following steps:

step 1, calculating an average deceleration rate:

the self-adaptive algorithm is characterized in that a self-adaptive function is added on the basis of the original anti-skid braking algorithm, the calculation of the deceleration rate is added, the deceleration rate of the anti-skid braking control system is calculated through the speed change value of the airplane wheel in a non-skid state and in an equal period and is used as a control input, and the calculation formula is as the following formula (1):

Rate_Speed_dec＝(Speed_dec_last-Speed_dec)/n……(1)，

in the above formula (1): rate _ Speed _ dec: a rate of deceleration; speed _ dec _ last: the upper cycle average speed;

speed _ dec: average speed of the period; n: calculating the number of cycles of the average speed;

calculating the average speed by adopting a method of calculating the average speed in n periods, and calculating the actual deceleration rate of the previous period by using the average speed of the period and the average speed of the previous period every n periods;

step 2, calculating forward current:

the change of the braking current is controlled by adopting a PID control method through self-adaptive identification, and the maximum forward braking pressure is adjusted, so that the airplane realizes a fixed deceleration rate under different working conditions in the braking process;

and step 3, calculating output current:

in the adaptive anti-skid control, in the adaptive control output current, the sum of an input command current, an anti-skid regulating current and a deceleration rate regulating current is used as a forward braking current, the difference value of the forward braking current and the anti-skid current is used as the final servo valve control current output, the output current value is equal to the forward current minus the anti-skid current value, and the calculation formula is as the following formula (6):

Io＝I_brake-If……(6)，

in the above formula (6): io is output current; i _ break is a forward current; if is the antiskid current.

2. The adaptive antiskid brake control method for aircraft according to claim 1, wherein the step 2 comprises the steps of:

step 2.1, input current calculation:

when the anti-skid regulation and the deceleration rate regulation are not carried out, the forward braking current is equal to the input command current, and when the anti-skid regulation or the deceleration rate regulation is carried out, the anti-skid regulation current and the deceleration rate regulation current are regulated by taking the input command current as initial values;

converting the input instruction into input current for calculating forward input current according to the relation curve of the input instruction and the output current;

when the reference speed of the airplane is lower than the failure speed, the upper limit of the input current is 20mA, when the reference speed is higher than 20m/s, the maximum upper limit of the input current is set to be 12.5mA, and other speeds are set to be 14.6 mA;

when the command is larger than 90% for the first time, the input current smoothly rises within 1 s;

step 2.2, calculating an initial value of the forward current:

calculating a forward current initial value by analyzing the working state of the last period, recording the current output at the time as an anti-skid adjusting current when the software judges that the system is in an anti-skid state from a normal braking state, outputting the current as the forward current after the anti-skid is finished, and simultaneously calculating the target deceleration rate of the current control according to the magnitude of the current anti-skid current and finding a proper non-skid critical point;

when the previous period is normal, the slippage phenomenon occurs in the current period, and the input instructions are all larger than 90%, the initial value of the forward current in the current period is equal to the adjustment quantity of the output value-1 mA in the previous period;

when the previous period is normal, the slippage phenomenon occurs in the current period, and any one of the input commands is less than 90%, the initial value of the forward current in the current period is equal to the output value of the previous period, the relation coefficient between the forward current and the input current is calculated, and when the command is not full, the numerical value of the forward current is converted according to the input current according to the relation coefficient;

when no slip phenomenon exists in the period, the initial value of the forward current is equal to the instruction input current multiplied by a forward current calculation coefficient;

step 2.3, forward current increment control calculation:

when the braking instruction is maximum, calculating a difference value between a target deceleration rate and an actual deceleration rate according to continuously adjusted output current, performing PID control, adjusting the magnitude of forward current through the deceleration rate, searching a system adaptation ground condition and load condition down-regulation node, and adjusting nearby the regulation point to enable the system to be in a non-slip critical state;

calculating a target deceleration rate and an actually measured deceleration rate to obtain a deceleration rate control error, and multiplying the deceleration rate error by a KP coefficient to obtain an incremental regulation current;

when any wheel is in an anti-skid state or the input command current in the period is not maximum, the incremental adjustment current is cleared, incremental control is carried out until the wheel does not skid and the command input reaches more than 90%, and the actual deceleration rate calculation formula is as the following formula (2):

Rate_Speed_dec＝Rate_speed_dec_plane-Rate_Speed_dec……(2)，

in the above formula (2): rate _ speed _ dec _ plane: a target deceleration rate;

rate _ Speed _ dec: an actual deceleration rate;

the delta adjustment current I _ dec is calculated as the following formula (3):

I_dec＝Rate_Speed_dec*Kp……(3)，

in the above formula (3): i _ dec: incrementally adjusting the current; kp: a Kp coefficient;

step 2.4, calculating forward current:

when the left and right commands are greater than 90%, the pilot is considered to need to increase from the initial current;

when the current value of the forward incremental current is larger than zero, the current is increased upwards, the incremental value of the control period is calculated, the incremental adjustment current calculated by adding the initial value of the forward current and the deceleration rate control period is divided by the deceleration rate period 10, namely the forward output current of the period is obtained, the deceleration rate calculation period is n periods, and the incremental current is slowly increased by n periods;

when the forward incremental current value is less than zero, the current is required to be adjusted downwards when the deceleration is larger, the output value is adjusted in place in the first period, and the other n-1 deceleration rate calculation periods are kept unchanged;

when any one of the left and right commands is less than 90%, the forward current is equal to the input command current multiplied by a forward current regulation coefficient and linearly changes along with the change of the input command, the regulation coefficient recovers a linear coefficient of 1.0 after the command input is the minimum value and is kept for 1s, and the calculation is carried out at other times according to the calculated coefficient during the slipping and incremental regulation so as to ensure that the change of the pedal can linearly follow the pedal stroke of a pilot; the cycle delta current is calculated as follows (4):

I_delta＝I_dec/n……(4)，

in the above formula (4): i _ delta is a periodic delta adjustment current; i _ dec is the delta adjust current;

the forward current in this cycle is calculated as follows (5):

I_brake＝I_brake_last+I_delta……(5),

in the above formula (5): i _ crack is the forward current of the period; i _ break _ last is the last cycle forward current.

Technical Field

The invention belongs to the technical field of airplane brake control, and particularly relates to an airplane self-adaptive anti-skid brake control method.

Background

Currently, during the braking process of an airplane, the wheels of the airplane are subjected to the torque generated by the braking pressure and the combined torque generated by the friction force between the runway and the tires. The magnitude of the braking torque depends on the magnitude of the braking pressure and the performance of a friction material, the magnitude of the combined torque depends on the magnitude of the load on the wheel and the magnitude of the friction coefficient between the tire and the runway, the magnitude of the friction coefficient between the tire and the runway is changed according to the sliding rate of the wheel relative to the runway, and the anti-skid braking system aims to adjust the magnitude of the braking pressure to keep the friction coefficient between the tire and the runway close to the maximum value so as to fully utilize the friction coefficient between the tire and the runway, thereby improving the braking efficiency and shortening the sliding distance.

At present, the existing antiskid control adopts reference deceleration-speed difference control and bias regulation, a reference speed is arranged in a system, and antiskid control is carried out through the difference between the reference speed and the speed of a wheel. When the airplane wheel rotates in an accelerating way, the system generates a reference speed according to the speed of the airplane wheel, and in the braking process, when the deceleration of the airplane wheel is smaller than the set parameter deceleration, the reference speed is changed according to the change rule of the speed of the airplane wheel; when the wheel deceleration is larger than the set reference deceleration, the reference speed is changed according to the set reference deceleration and compared with the wheel speed, and if the reference speed is larger than the wheel speed, an anti-skid signal is output to reduce the brake pressure. When the speed of the airplane wheel is recovered, the antiskid signal disappears, and the brake pressure is controlled to rise by the bias regulation rule. The reference deceleration-speed difference control method can correct the set reference deceleration by the feedback unit according to different runway surface states. The reference deceleration of the system is adapted to the current runway surface condition in order to obtain the best anti-skid braking effect. In the traditional anti-skid braking system, the maximum main braking pressure is limited under the rated pressure, and the pressure limit value cannot meet the requirement of anti-skid control under a special working condition.

In the traditional antiskid brake system, the maximum main brake pressure is limited under the rated pressure, and the pressure limit value cannot meet the requirement of antiskid control under special working conditions. The self-adaptive anti-skid control is realized by adjusting the control current on the basis of inputting the instruction current, searching the critical point of non-skid of the system, controlling the system to enter a stable state near the critical point, achieving the principle of optimal control of the system, reducing the skid of the system and enabling the brake to be more stable. The brake device has different processes and different brake torque characteristics, so that in the actual use process, under the rated brake pressure, system control parameters must be adjusted according to the characteristics of the brake device, different control systems are used to achieve better matching with the brake device, the brake is stable, and the efficiency meets the index requirement. Under plateau and wet conditions, due to the limitation of rated pressure, even if the whole course is full, the command output deceleration rate can not meet the index requirement, and even the situation of braking out of the runway occurs; in order to deal with the situation, the braking torque of the braking device is designed to be higher in the design process, but a new problem is caused, the braking system can frequently slip due to the excessively high braking torque, the control difficulty of a pilot is increased, and the stability of the whole braking process is influenced; this problem is particularly pronounced in small aircraft, the underlying reason for which is the poor adaptation of the reference deceleration-speed difference control method to the brake device as the core actuating element.

The traditional reference linear velocity-bias voltage regulation control method is divided into two parts:

1) and (3) normal braking current control: normal brake current is in direct proportion to an input brake instruction, a pilot steps on a pedal, the control box calculates the brake current according to the signal size of a pedal instruction sensor, and the brake current is subtracted from the anti-skid current and then sent to the servo valve for control.

2) Normal anti-slip current control: the control box calculates the reference speed of the airplane wheel by acquiring a speed signal, judges whether the airplane wheel is in a slipping stage or a bias stage according to the relation between the reference speed and the speed signal, and calculates the speed difference between the reference speed and the speed of the airplane wheel when the airplane wheel is judged to slip, calculates the anti-slip current and adjusts the slipping of the airplane wheel;

the principle of the traditional reference linear velocity-bias voltage regulation control method can be analyzed as follows:

1) the maximum normal brake control current is determined in control systems of different types, and once the maximum normal brake control current is determined, the maximum normal anti-skid brake current cannot be changed, and the determination of the maximum normal anti-skid brake current is determined according to relevant factors of the load condition of the airplane and the characteristics of the airplane wheels and is verified through tests, so that the maximum normal brake control current is not an optimal scheme and is determined by integrating the state of the whole airplane, and the requirement of re-adapting and adjusting for replacing different brake discs and different airplane parameters is met.

2) The anti-skid current is calculated and adjusted according to the reference speed difference, and is most used for determining the skidding condition of the airplane wheel, indirectly reflecting the skidding rate of the airplane wheel relative to the ground, and not actually reflecting the reference deceleration rate of the airplane. The speed difference reaches the coefficient of antiskid current calculation, and the coefficient is obtained through system test matching optimization, so that the method has certain limitation, and different systems need to be adapted and adjusted.

According to the research and development conditions of a plurality of current antiskid braking systems, the antiskid braking control rate of the reference speed difference-bias control has poor adaptability to the system, wherein the reason is that the adaptability to the system is poor:

1) the braking torque of the airplane wheel is greatly changed, and the torque characteristics of different materials are different, so that the braking current changes to the braking torque of the airplane wheel differently;

2) the speed difference cannot reflect the actual airplane wheel deceleration rate, the conventional closed-loop control is not adopted, the final control target of the braking system is the deceleration rate of the airplane, the reference speed difference-bias control can only be calculated as speed closed-loop control, and the deceleration rate is open-loop control.

3) Under the conditions of 1/2 load and 1/4 load, the combination coefficient of the wheels of the airplane and the ground is reduced, and the current-moment coefficient of the wheels is larger, so that the antiskid braking slipping frequency is higher under the condition of low load, and the smoothness of the braking process of the airplane is caused.

The reference speed difference-bias control has certain advantages, is used on a plurality of machine types at present, has higher maturity, has verified system safety and no obvious defects, and sacrifices certain performance for different runway conditions and airplane load conditions to ensure the adaptability of the airplane wheel brake to the runway. The research goal of the adaptive control method is to develop the potential of the control method step by step on the basis of the traditional reference speed difference-bias control and improve the control method from the following aspects:

1) the deceleration rate of the antiskid brake control system of the airplane under various airplane working conditions is improved;

2) the wheel slipping frequency under the low load condition is reduced, so that the brake is more stable;

3) the adaptability of the antiskid brake control system to wheels made of different brake materials;

in order to solve the above problem, improvements in algorithms are required.

Disclosure of Invention

The invention aims to provide an aircraft self-adaptive anti-skid brake control method which can overcome the technical problems. The method comprises the following steps:

step 1, calculating an average deceleration rate:

the self-adaptive algorithm is characterized in that a self-adaptive function is added on the basis of the original anti-skid braking algorithm, the calculation of the deceleration rate is added, the deceleration rate of the anti-skid braking control system is calculated through the speed change value of the airplane wheel in a non-skid state and in an equal period and is used as a control input, and the calculation formula is as the following formula (1):

Rate_Speed_dec＝(Speed_dec_last-Speed_dec)/n……(1)，

in the above formula (1): rate _ Speed _ dec: a rate of deceleration; speed _ dec _ last: the upper cycle average speed;

speed _ dec: average speed of the period; n: calculating the number of cycles of the average speed;

calculating the average speed by adopting a method of calculating the average speed in n periods, and calculating the actual deceleration rate of the previous period by using the average speed of the period and the average speed of the previous period every n periods;

step 2, calculating forward current:

the change of the braking current is controlled by adopting a PID control method through self-adaptive identification, and the maximum forward braking pressure is adjusted, so that the airplane realizes a fixed deceleration rate under different working conditions in the braking process; the method specifically comprises the following steps:

step 2.1, input current calculation:

when the anti-skid regulation and the deceleration rate regulation are not carried out, the forward braking current is equal to the input command current, and when the anti-skid regulation or the deceleration rate regulation is carried out, the anti-skid regulation current and the deceleration rate regulation current are regulated by taking the input command current as initial values;

converting the input instruction into input current for calculating forward input current according to the relation curve of the input instruction and the output current;

when the reference speed of the airplane is lower than the failure speed, the upper limit of the input current is 20mA, when the reference speed is higher than 20m/s, the maximum upper limit of the input current is set to be 12.5mA, and other speeds are set to be 14.6 mA;

when the command is larger than 90% for the first time, the input current smoothly rises within 1 s;

step 2.2, calculating an initial value of the forward current:

calculating a forward current initial value by analyzing the working state of the last period, recording the current output at the time as an anti-skid adjusting current when the software judges that the system is in an anti-skid state from a normal braking state, outputting the current as the forward current after the anti-skid is finished, and simultaneously calculating the target deceleration rate of the current control according to the magnitude of the current anti-skid current and finding a proper non-skid critical point;

when the previous period is normal, the slippage phenomenon occurs in the current period, and the input instructions are all larger than 90%, the initial value of the forward current in the current period is equal to the adjustment quantity of the output value-1 mA in the previous period;

when the previous period is normal, the slippage phenomenon occurs in the current period, and any one of the input commands is less than 90%, the initial value of the forward current in the current period is equal to the output value of the previous period, the relation coefficient between the forward current and the input current is calculated, and when the command is not full, the numerical value of the forward current is converted according to the input current according to the relation coefficient;

when no slip phenomenon exists in the period, the initial value of the forward current is equal to the instruction input current multiplied by a forward current calculation coefficient;

step 2.3, forward current increment control calculation:

when the braking instruction is maximum, calculating a difference value between a target deceleration rate and an actual deceleration rate according to continuously adjusted output current, performing PID control, adjusting the magnitude of forward current through the deceleration rate, searching a system adaptation ground condition and load condition down-regulation node, and adjusting nearby the regulation point to enable the system to be in a non-slip critical state;

calculating a target deceleration rate and an actually measured deceleration rate to obtain a deceleration rate control error, and multiplying the deceleration rate error by a KP coefficient to obtain an incremental regulation current;

when any wheel is in an anti-skid state or the input command current in the period is not maximum, the incremental adjustment current is cleared, incremental control is carried out until the wheel does not skid and the command input reaches more than 90%, and the actual deceleration rate calculation formula is as the following formula (2):

Rate_Speed_dec＝Rate_speed_dec_plane-Rate_Speed_dec……(2)，

in the above formula (2): rate _ speed _ dec _ plane: a target deceleration rate;

rate _ Speed _ dec: an actual deceleration rate;

the delta adjustment current I _ dec is calculated as the following formula (3):

I_dec＝Rate_Speed_dec*Kp……(3)，

in the above formula (3): i _ dec: incrementally adjusting the current; kp: a Kp coefficient;

step 2.4, calculating forward current:

when the left and right commands are greater than 90%, the pilot is considered to need to increase from the initial current;

when the current value of the forward incremental current is larger than zero, the current is increased upwards, the incremental value of the control period is calculated, the incremental adjustment current calculated by adding the initial value of the forward current and the deceleration rate control period is divided by the deceleration rate period 10, namely the forward output current of the period is obtained, the deceleration rate calculation period is n periods, and the incremental current is slowly increased by n periods;

when the forward incremental current value is less than zero, the current is required to be adjusted downwards when the deceleration is larger, the output value is adjusted in place in the first period, and the other n-1 deceleration rate calculation periods are kept unchanged;

when any one of the left and right commands is less than 90%, the forward current is equal to the input command current multiplied by a forward current regulation coefficient and linearly changes along with the change of the input command, the regulation coefficient recovers a linear coefficient of 1.0 after the command input is the minimum value and is kept for 1s, and the calculation is carried out at other times according to the calculated coefficient during the slipping and incremental regulation so as to ensure that the change of the pedal can linearly follow the pedal stroke of a pilot; the cycle delta current is calculated as follows (4):

I_delta＝I_dec/n……(4)，

in the above formula (4): i _ delta is a periodic delta adjustment current; i _ dec is the delta adjust current;

the forward current in this cycle is calculated as follows (5):

I_brake＝I_brake_last+I_delta……(5),

in the above formula (5): i _ crack is the forward current of the period; i _ crack _ last is the forward current of the last period;

and step 3, calculating output current:

in the adaptive anti-skid control, in the adaptive control output current, the sum of an input command current, an anti-skid regulating current and a deceleration rate regulating current is used as a forward braking current, the difference value of the forward braking current and the anti-skid current is used as the final servo valve control current output, the output current value is equal to the forward current minus the anti-skid current value, and the calculation formula is as the following formula (6):

Io＝I_brake-If……(6)，

in the above formula (6): io is output current; i _ break is a forward current; if is the antiskid current.

The invention has the following advantages:

1. the method breaks through the limit of rated braking pressure, can adjust the braking pressure within the full pressure range, can automatically improve the braking pressure under the conditions of plateau and wet state, can ensure that the deceleration rate reaches the standard, and simultaneously can reduce the output to ensure the safety and the stability of the whole braking process when the braking torque is higher.

2. Aiming at the design characteristics of the existing antiskid brake control system, the method comprehensively considers the maturity of product design, and carries out system design on the basis of the method for upgrading the original system and under the condition of reducing the change of the system architecture as much as possible.

3. And changing an open-loop control mode into a closed-loop control mode, taking the deceleration rate of the airplane wheel of the airplane as a control target, calculating the deceleration rate of the airplane and finding the optimal brake control condition of the airplane by analyzing the input speed signal.

4. The brake current is continuously adjusted to enable the brake system to control the brake of the airplane wheel to be close to the point of the antiskid state, so that the optimal state of forward brake is found.

5. And controlling the braking current according to the judged optimal deceleration rate to enable the system to be in an optimal control state.

Drawings

FIG. 1 is a schematic diagram of an adaptive braking control method according to the present invention;

FIG. 2 is a flow chart of an average deceleration rate calculation of the method of the present invention;

FIG. 3 is a flow chart of the input current calculation of the method of the present invention;

FIG. 4 is a flow chart of the calculation of the initial value of the forward current in the present cycle of the method of the present invention;

FIG. 5 is a flow chart of the present cycle forward current delta value calculation of the method of the present invention;

FIG. 6 is a flow chart of the present cycle forward current value calculation of the method of the present invention;

FIG. 7 is a flow chart of the output current value calculation of the method of the present invention;

FIG. 8 is a brake command curve for the method of the present invention.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The method comprises the following steps:

step 1, calculating an average deceleration rate:

the self-adaptive algorithm is characterized in that a self-adaptive function is added on the basis of the original anti-skid braking algorithm, the calculation of the deceleration rate is added, the deceleration rate of the anti-skid braking control system is calculated through the speed change value of the airplane wheel in a non-skid state and in an equal period and is used as a control input, and the calculation formula is as the following formula (1):

Rate_Speed_dec＝(Speed_dec_last-Speed_dec)/n……(1)，

in the above formula (1): rate _ Speed _ dec: a rate of deceleration; speed _ dec _ last: the upper cycle average speed;

speed _ dec: average speed of the period; n: calculating the number of cycles of the average speed;

calculating the average speed by adopting a method of calculating the average speed in n periods, and calculating the actual deceleration rate of the previous period by using the average speed of the period and the average speed of the previous period every n periods;

FIG. 2 is a flow chart of an average deceleration rate calculation of the method of the present invention;

step 2, calculating forward current:

the change of the braking current is controlled by adopting a PID control method through self-adaptive identification, and the maximum forward braking pressure is adjusted, so that the airplane realizes a fixed deceleration rate under different working conditions in the braking process; the method specifically comprises the following steps:

step 2.1, input current calculation:

when the anti-skid regulation and the deceleration rate regulation are not carried out, the forward braking current is equal to the input command current, and when the anti-skid regulation or the deceleration rate regulation is carried out, the anti-skid regulation current and the deceleration rate regulation current are regulated by taking the input command current as initial values;

according to the relation curve between the input command and the output current, as shown in fig. 8, converting the input command into the input current for calculating the forward input current;

when the reference speed of the airplane is lower than the failure speed, the upper limit of the input current is 20mA, when the reference speed is higher than 20m/s, the maximum upper limit of the input current is set to be 12.5mA, and other speeds are set to be 14.6 mA;

when the command is larger than 90% for the first time, the input current smoothly rises within 1 s;

FIG. 3 is a flow chart of the input current calculation of the method of the present invention;

step 2.2, calculating an initial value of the forward current:

calculating a forward current initial value by analyzing the working state of the last period, recording the current output at the time as an anti-skid adjusting current when the software judges that the system is in an anti-skid state from a normal braking state, outputting the current as the forward current after the anti-skid is finished, and simultaneously calculating the target deceleration rate of the current control according to the magnitude of the current anti-skid current and finding a proper non-skid critical point;

when the previous period is normal, the slippage phenomenon occurs in the current period, and the input instructions are all larger than 90%, the initial value of the forward current in the current period is equal to the adjustment quantity of the output value-1 mA in the previous period;

when the previous period is normal, the slippage phenomenon occurs in the current period, and any one of the input commands is less than 90%, the initial value of the forward current in the current period is equal to the output value of the previous period, the relation coefficient between the forward current and the input current is calculated, and when the command is not full, the numerical value of the forward current is converted according to the input current according to the relation coefficient;

when no slip phenomenon exists in the period, the initial value of the forward current is equal to the instruction input current multiplied by a forward current calculation coefficient;

FIG. 4 is a flow chart of the calculation of the initial value of the forward current in the present cycle of the method of the present invention;

step 2.3, forward current increment control calculation:

when the braking instruction is maximum, calculating a difference value between a target deceleration rate and an actual deceleration rate according to continuously adjusted output current, performing PID control, adjusting the magnitude of forward current through the deceleration rate, searching a system adaptation ground condition and load condition down-regulation node, and adjusting nearby the regulation point to enable the system to be in a non-slip critical state;

calculating a target deceleration rate and an actually measured deceleration rate to obtain a deceleration rate control error, and multiplying the deceleration rate error by a KP coefficient to obtain an incremental regulation current;

when any wheel is in an anti-skid state or the input command current in the period is not maximum, the incremental adjustment current is cleared, incremental control is carried out until the wheel does not skid and the command input reaches more than 90%, and the actual deceleration rate calculation formula is as the following formula (2):

Rate_Speed_dec＝Rate_speed_dec_plane-Rate_Speed_dec……(2)，

in the above formula (2): rate _ speed _ dec _ plane: a target deceleration rate;

rate _ Speed _ dec: an actual deceleration rate;

the delta adjustment current I _ dec is calculated as the following formula (3):

I_dec＝Rate_Speed_dec*Kp……(3)，

in the above formula (3): i _ dec: incrementally adjusting the current; kp: a Kp coefficient;

FIG. 5 is a flow chart of the present cycle forward current delta value calculation of the method of the present invention;

step 2.4, calculating forward current:

when the left and right commands are greater than 90%, the pilot is considered to need to increase from the initial current;

when the current value of the forward incremental current is larger than zero, the current is increased upwards, the incremental value of the control period is calculated, the incremental adjustment current calculated by adding the initial value of the forward current and the deceleration rate control period is divided by the deceleration rate period 10, namely the forward output current of the period is obtained, the deceleration rate calculation period is n periods, and the incremental current is slowly increased by n periods;

when the forward incremental current value is less than zero, the current is required to be adjusted downwards when the deceleration is larger, the output value is adjusted in place in the first period, and the other n-1 deceleration rate calculation periods are kept unchanged;

when any one of the left and right commands is less than 90%, the forward current is equal to the input command current multiplied by a forward current regulation coefficient and linearly changes along with the change of the input command, the regulation coefficient recovers a linear coefficient of 1.0 after the command input is the minimum value and is kept for 1s, and the calculation is carried out at other times according to the calculated coefficient during the slipping and incremental regulation so as to ensure that the change of the pedal can linearly follow the pedal stroke of a pilot; the cycle delta current is calculated as follows (4):

I_delta＝I_dec/n……(4)，

in the above formula (4): i _ delta is a periodic delta adjustment current; i _ dec is the delta adjust current;

the forward current in this cycle is calculated as follows (5):

I_brake＝I_brake_last+I_delta……(5),

in the above formula (5): i _ crack is the forward current of the period; i _ crack _ last is the forward current of the last period;

FIG. 6 is a flow chart of the present cycle forward current value calculation of the method of the present invention;

and step 3, calculating output current:

in the adaptive anti-skid control, in the adaptive control output current, the sum of an input command current, an anti-skid regulating current and a deceleration rate regulating current is used as a forward braking current, the difference value of the forward braking current and the anti-skid current is used as the final servo valve control current output, the output current value is equal to the forward current minus the anti-skid current value, and the calculation formula is as the following formula (6):

Io＝I_brake-If……(6)，

in the above formula (6): io is output current; i _ break is a forward current; if is the antiskid current.

The method of the invention is to control the deceleration rate of the airplane wheel, find the optimal deceleration rate control of the airplane wheel braking system under various conditions, and adjust the servo valve control current through the identification of the input signal to enable the airplane wheel brake to be in the most appropriate control point, and the method of the invention adopts the self-adaptive control method shown in figure 1 to adjust the main brake pressure, and comprises the following steps: the device comprises a controller, a controlled object, an adaptive device, a feedback control loop and an adaptive loop. The self-adaptive controller carries out system parameter identification and interference parameter identification according to the reference input, feedback loop information and control quantity, and carries out real-time control on the dynamic performance of the system on the basis. The self-adaptive anti-skid control is realized by adjusting the control current on the basis of inputting the instruction current, searching the critical point of non-skid of the system, controlling the system to enter a stable state near the critical point, achieving the principle of optimal control of the system, reducing the skid of the system and enabling the brake to be more stable.

The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the present disclosure should be covered within the scope of the present invention claimed in the appended claims.