CN-120428536-B - Fork truck line control drum brake system control method and device based on rapid nonsingular terminal sliding mode

Abstract

A forklift drum brake control method and device based on a rapid nonsingular terminal sliding mode comprises the steps of 1) carrying out mechanism analysis on the mechanical structure and dynamics characteristics of a forklift drum brake system, establishing a dynamics model of the forklift drum brake system, 2) designing a rapid nonsingular terminal sliding mode surface and a power approach law according to the dynamics model established in the step 1 so as to achieve rapid convergence of a system state, 3) designing a rapid nonsingular terminal sliding mode control algorithm suitable for the forklift drum brake system according to the sliding mode surface and the approach law designed in the step 2, and 4) proving that the control algorithm designed in the step 3 can enable the system state to converge to a balance point in a limited time based on Lyapunov stability theory, and carrying out simulation on a MATLAB/Simulink platform so as to verify the effectiveness of the control algorithm in the forklift drum brake system. The response speed and the control precision of the forklift line-control drum brake system can be obviously improved.

Inventors

• SUN ZHE
• Wan Jiahao
• Li Shaping
• QIU ZHIGANG
• B. Li Yinbo

Assignees

• 杭州集世迈新能源智能装备股份有限公司

Dates

Publication Date

20260512

Application Date

20250427

Claims (3)

1. 1. A rapid nonsingular terminal sliding mode control method applied to a forklift drive-by-wire drum brake system comprises the following specific implementation steps: step 1, carrying out mechanism analysis on the mechanical structure and the dynamics characteristic of a forklift brake system, and establishing a dynamics model of the forklift brake system; Step 2, designing a quick nonsingular terminal sliding mode surface and a power approach law according to the dynamics model established in the step 1 so as to realize quick convergence of a system state; Step 3, designing a rapid nonsingular terminal sliding mode control algorithm suitable for a forklift drive-by-wire drum brake system according to the sliding mode surface and the approach law designed in the step 2; Step 4, based on Lyapunov stability theory, the control algorithm designed in the step 3 is proved to be capable of converging the system state to a balance point in a limited time, and simulation is carried out on a MATLAB/Simulink platform to verify the effectiveness of the control algorithm in the forklift line control drum brake system; The step 1 specifically comprises the following steps: the mass of the rack and the master cylinder piston in the system is The actual displacement of the master cylinder piston is The actual speed of the master cylinder piston is The actual acceleration of the master cylinder piston is , The gear ratio is indicated as such, In order to achieve a transmission efficiency, the transmission, For the radius of the gear wheel, For the internal hydraulic pressure of the system, Is the cross-sectional area of the master cylinder piston, For motor torque, the internal physical relationship of the forklift brake system is analyzed, and the dynamic equation of the forklift brake system is as follows, wherein the dynamic equation is obtained according to Newton's second law: (1) (2) Wherein, the In order to achieve a viscous coefficient of friction, Is a rigidity coefficient; Is recorded as rack force ; Is the internal hydraulic pressure of the system, and is recorded as ; Is recorded as spring force ; Is recorded as friction force , Assuming that the fluid volume in the system is not affected by the master cylinder piston motion, the kinetic equation for the hydraulic portion of the system can be expressed as: (3) Wherein, the Is defined as With respect to the first-order differentiation of time, Representing the brake fluid volume flow within the system, The bulk modulus of the brake fluid is indicated, Indicating the volume of the master cylinder, The wheel cylinder pressure model of the system is described below: (4) Wherein, the The rate of change of the wheel cylinder hydraulic pressure is indicated, Representing wheel cylinder and brake pipe volumes, taking into account Substituting formula (4) into formula (3) to obtain: (5) by integrating equation (5), the mapping between the master cylinder pressure and the master cylinder piston position can be described as: (6) Wherein, the As the initial pressure in the cylinder is set, In actual case, the master cylinder internal pressure With displacement of the piston The nonlinear relation between the two is influenced by dead zone, friction, temperature change and brake pad abrasion, and the nonlinear factors can be regarded as system disturbance in dynamic modeling, and a second-order polynomial is adopted to control the internal pressure of the master cylinder With master cylinder piston position The relation curve between the two is subjected to fitting treatment, so that the relation that the pressure in the main cylinder changes along with the increase of the displacement of the piston can be reflected, the design of a subsequent controller is facilitated, and the hydraulic pressure in the main cylinder is fitted With displacement of the piston The second order relation is as follows: (7) Wherein, the Characterizing master cylinder internal pressure With displacement of the piston The key characteristic parameters of the relation, the physical meaning of which is related to the system rigidity and the hydraulic fluid characteristic, The core objective of the above process is to provide a dynamic model for forklift brake-by-wire control system design that has a degree of accuracy and facilitates controller design, rather than a completely accurate physical description, So far, the complete dynamics model of the forklift brake-by-wire system is given as follows: (8) Wherein, the For lumped model parameter uncertainty and external disturbances, it can be assumed that the lumped perturbation has an upper bound, i.e., based on the mechanical structure and dynamics of the truck brake-by-wire system , wherein, Is the upper bound thereof; The step 2 specifically comprises the following steps: defining master cylinder piston position tracking error The following are provided: (9) Wherein, the And The fast nonsingular terminal sliding mode is defined as follows, representing the actual piston position and the expected piston position respectively, and being uniformly second-order conductive: (10) Wherein, the As the first derivative of the displacement error, And a function of Is defined as the following formula: (11) For the initial conditions And Can be used for a limited time Inner convergence to zero, and The expression is as follows: (12) in order to attract the system state to the slip plane, a power approach law is designed as follows: (13) Wherein the parameters are ; The step 3 specifically comprises the following steps: first, the slip form surface is derived according to equation (10): (14) Wherein, the Is the second derivative of the displacement error, and As can be seen from step 1: (15) substituting formula (1) into the above formula can obtain: (16) lumped perturbation in (15) is temporarily ignored based on the definition of equivalent control inputs Is to solve for the influence of (1) Obtaining the equivalent control quantity The following are provided: (17) Wherein the equivalent control amount For the control law of the sliding section, on the basis, for ensuring the control system to control Is to design the arrival segment control quantity based on the power approach law The following are provided: (18) Wherein, the 、 All are positive parameters, and the positive parameters are used for the control of the power supply, In summary, the final control law of the forklift brake-by-wire system is as follows: i.e. a fast nonsingular terminal sliding mode controller.
2. 2. The control method according to claim 1, wherein step 4 specifically includes: the lyapunov function is defined as follows: The first derivative of formula (20) is obtained: (21) substituting formula (9) and formula (14) into formula (21) yields: Wherein when In the time-course of which the first and second contact surfaces, , It can be seen that in this way, When the control system meets the Lyapunov stabilization condition, Substituting the formula (14) and the formula (17) The method can obtain: When (when) When formula (23) can be expressed as follows: When (when) At the time, there are When (1) At the time, there are From the phase trajectory of the system, when When it is implemented in a limited time The convergence time of the arrival segment is given below : Wherein, the In order to be the initial condition of the system, This indicates that the system state may be in a limited time Inner convergence to steady state: To sum up, the designed fast nonsingular terminal sliding mode controller Can make the master cylinder piston position trace error During a limited time Inner convergence to zero, i.e. actual position of master cylinder piston During a limited time Inner convergence to the intended position of the master cylinder piston 。
3. 3. The utility model provides a be applied to quick nonsingular terminal slipform controlling means of fork truck drive-by-wire drum brake system, through carrying footboard displacement sensor, data acquisition module, built-in upper computer core computing platform, servo motor encoder, CAN data bus, as the electronic control unit of system lower computer, master cylinder servo motor, brake liquid pipeline, in-cylinder pressure sensor, data communication unit etc. of being responsible for carrying out quick nonsingular terminal slipform control algorithm as set forth in claim 1, realize the accurate closed loop tracking control to anticipated master cylinder piston position, the concrete implementation steps are as follows: Step 1, completing the input of a forklift braking demand signal through a pedal displacement sensor and a data acquisition module; step 2, completing calculation of a forklift target braking signal through an upper computer core calculation platform with a built-in rapid nonsingular terminal sliding mode control algorithm and a servo motor encoder; step 3, finishing control signal transmission through the CAN data bus and an electronic control unit serving as a lower computer of the system; step 4, executing braking action through the electronic control unit and the master cylinder servo motor; Step 5, completing the generation of the braking force of the forklift through a braking liquid pipeline; Step 6, completing closed loop feedback control through an in-cylinder pressure sensor, a servo motor encoder, an electronic control unit, a CAN data bus, a data communication unit and an upper computer core computing platform, and meeting the braking requirement of a forklift; The step 1 specifically comprises the following steps: When a driver presses a brake pedal, the pedal displacement sensor converts a displacement signal into an electric signal, and the electric signal is transmitted to an upper computer through a data acquisition module; The step 2 specifically comprises the following steps: After receiving the displacement signal, the upper computer calculates the expected piston displacement according to the mapping relation between the fork truck pedal stroke and the target master cylinder piston displacement, and takes the expected piston displacement as a reference signal of the rapid nonsingular terminal sliding mode control system, and the upper computer is responsible for executing the rapid nonsingular terminal sliding mode control algorithm and calculating the control signal according to the braking requirement and the system state I.e. servomotor torque signal, wherein the master cylinder piston is in actual position Acquiring motor angular displacement through a measuring servo motor encoder, and establishing according to a mapping relation between the motor angular displacement and the piston displacement; the step 3 specifically comprises the following steps: the upper computer sends signals to the electronic control unit through the CAN data bus, wherein the signals comprise master cylinder piston target position signals and servo motor torque signals; the step4 specifically comprises the following steps: After receiving a control signal from the upper computer, the electronic control unit drives a servo motor in the EHB, and the servo motor drives a master cylinder piston to do feeding movement through a reduction gear transmission mechanism in the system; the step 5 specifically comprises the following steps: The feeding motion of the master cylinder piston can cause the compression of brake fluid in the cylinder, so that the brake fluid is transmitted to a brake fluid pipeline, and the brake fluid acts on wheel cylinders, so that braking force required by forklift tire braking is generated; The step 6 specifically comprises the following steps: The master cylinder internal pressure sensor is responsible for collecting pressure, the servo motor encoder is responsible for measuring angular position change in real time, the electronic control unit feeds the sensor signals back to the upper computer through the CAN data bus, the data communication unit adjusts control quantity in real time according to feedback signals and a rapid nonsingular terminal sliding mode control algorithm, and then the data communication unit sends signals to the lower computer electronic control unit to correct braking actions, so that closed loop feedback control is formed, the position of a master cylinder piston is ensured to accurately track an expected target position, and the expected hydraulic pressure is maintained in the master cylinder, so that the braking requirement of a forklift is met.

Description

Fork truck line control drum brake system control method and device based on rapid nonsingular terminal sliding mode Technical Field The invention belongs to the technical field of industrial vehicle brake-by-wire Control, and particularly relates to a forklift brake-by-wire system Control method and device based on Fast Non-singular TERMINAL SLIDING Mode Control (FNTSMC), which can be used for improving the response speed, control precision and robustness of a forklift brake-by-wire system under complex working conditions. Background The traditional forklift braking system mostly adopts a mechanical or hydraulic transmission structure, and the braking force transmission process depends on mechanical linkage of stepping on a pedal by a driver or pressure change of a hydraulic pipeline. The system has certain hysteresis in dynamic response, particularly under complex scenes and working conditions such as emergency braking or frequent start and stop, long mechanical transmission time is required to be experienced from pedal signal input to complete establishment of braking force, and the braking distance is increased and the safety is reduced. In addition, the non-linear characteristics of the hydraulic system (such as pipeline pressure loss, brake pad abrasion, etc.) further reduce the control accuracy of braking force, and it is difficult to meet the high-accuracy and high-frequency material handling requirements. In recent years, the introduction of Electro-hydraulic brake (Electro-Hydraulic Braking, EHB) technology has provided a new direction for the innovation of forklift brake systems. The servo motor directly drives the master cylinder piston to transition the braking command from mechanical hydraulic control to electronic signal closed-loop control, so that the response speed and control accuracy of the system can be obviously improved theoretically. However, existing control algorithms (such as PID control and fuzzy control) still have certain limitations in the face of dynamic nonlinear characteristics, model parameter perturbation and external disturbance of a hydraulic system, and fixed gains or experience rules of the algorithms are difficult to adapt to complex time-varying working conditions of a forklift in engineering application, so that a great difference exists between actual braking control effects and theoretical expectations. Slip-form control (Sliding Mode Control, SMC) is known for its strong robustness to system uncertainty and external disturbances and is increasingly being applied in the field of engineering vehicle braking. The traditional sliding mode controller forces the system state track to converge to the sliding mode surface by designing a switching function, but has two key defects in practical engineering application, namely, firstly, the frequent switching of a symbol function in a control law can cause a high-frequency buffeting phenomenon of an executing mechanism to accelerate the abrasion of mechanical parts and cause the fluctuation of hydraulic pressure, secondly, the terminal sliding mode control can realize limited time convergence, but the sliding mode surface design has the singularity problem, namely, the control quantity can tend to infinity under a specific state, so that the executor is saturated and even the system is unstable. In order to solve the problems, researchers at home and abroad in recent years propose a series of novel terminal sliding mode control methods, and the system state convergence is accelerated while avoiding singularities by constructing novel sliding mode surfaces and approach laws. Although such methods have achieved some success in the fields of robotics, unmanned aerial vehicles, etc., they have found little application in forklift line control systems. In a forklift brake-by-wire system, although a traditional control method can realize a basic braking function, the traditional control method still has remarkable limitations in practical application, namely 1) the existing scheme is mainly based on a simplified linearization dynamic model design controller, nonlinear characteristics (such as time-varying friction coefficient, mechanical clearance and the like) and load dynamic coupling of a braking system are not fully considered, so that the dynamic model precision is insufficient, the problems of model mismatch, lower tracking precision and the like are easy to occur when the dynamic model is deployed to a real object system, and 2) the existing forklift brake-by-wire system control method is insufficient in robustness for complex and variable working conditions (such as forklift load change, ascending and descending slopes, external interference and the like). When facing complex working conditions, the control performance decline phenomenon is easy to occur, and even instability of a control system can be caused. In order to solve the problems, a nonsingular terminal sliding mode surface and a power approach law can be desi