A control method and device for a forklift linear control drum brake system based on a fast non-singular terminal sliding mode

Abstract

A forklift linear control drum brake control method and device based on a fast non-singular terminal sliding mode, the method comprising: 1) for the mechanical structure and dynamics characteristics of the forklift linear control drum brake system, mechanism analysis is carried out, and a dynamics model of the forklift linear control drum brake system is established; 2) according to the dynamics model established in step 1, a fast non-singular terminal sliding surface and a power approaching law are designed to realize the fast convergence of the system state; 3) according to the sliding surface and the approaching law designed in step 2, a fast non-singular terminal sliding mode control algorithm suitable for the forklift linear control drum brake system is designed; 4) based on Lyapunov stability theory, it is proved that the control algorithm designed in step 3 can make the system state converge to the equilibrium point in a finite time, and simulation is carried out on the MATLAB / Simulink platform to verify the effectiveness of the control algorithm in the forklift linear control drum brake system. The response speed and control accuracy of the forklift linear control drum brake system can be significantly improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of industrial vehicle line control brake control, and particularly relates to a forklift line control drum brake system control method and device based on fast non-singular terminal sliding mode control (FNTSMC), which can be used to improve the response speed, control accuracy and robustness of the forklift line control drum brake system under complex working conditions. BACKGROUND

[0002] The traditional forklift brake system mostly adopts mechanical or hydraulic transmission structure, and its brake force transmission process depends on the mechanical linkage of the driver stepping on the pedal or the change of the hydraulic pipeline pressure. Such system has certain hysteresis in dynamic response, especially in complex scenes and working conditions such as emergency braking or frequent start-stop, and it needs to go through a long mechanical transmission time from the pedal signal input to the complete establishment of the brake force, resulting in increased braking distance and reduced safety. In addition, the nonlinear characteristics of the hydraulic system (such as pipeline pressure loss, brake pad wear, etc.) will further reduce the control accuracy of the brake force, making it difficult to meet the high-precision and high-frequency material handling requirements. In recent years, the introduction of electro-hydraulic braking (EHB) technology provides a new direction for the innovation of forklift brake systems. By directly driving the master cylinder piston with a servo motor, the brake command is converted from mechanical and hydraulic control to electronic signal closed-loop control, which can theoretically significantly improve the system response speed and control accuracy. However, the existing control algorithms (such as PID control, fuzzy control) still have certain limitations when facing the dynamic nonlinear characteristics of the hydraulic system, model parameter perturbation and external disturbances. The fixed gain or empirical rules of these algorithms are difficult to adapt to the complex time-varying working conditions faced by forklifts in engineering applications, resulting in a large gap between the actual brake control effect and the theoretical expectation.

[0003] Sliding mode control (SMC) is renowned for its robustness against system uncertainties and external disturbances, and is increasingly being applied in the braking field of engineering vehicles. Traditional sliding mode controllers force the system state trajectory to converge to the sliding surface by designing switching functions. However, in practical engineering applications, two key drawbacks exist: first, frequent switching of the sign function in the control law leads to high-frequency chattering in the actuator, accelerating wear of mechanical components and causing hydraulic pressure fluctuations; second, while terminal sliding mode control can achieve finite-time convergence, its sliding surface design suffers from singularity issues, meaning that the control quantity may tend towards infinity under certain states, leading to actuator saturation or even system instability. To address these problems, researchers both domestically and internationally have proposed a series of novel terminal sliding mode control methods in recent years. By constructing novel sliding surfaces and reaching laws, these methods accelerate system state convergence while avoiding singularities. Although such methods have achieved some success in fields such as robotics and drones, their application in forklift line braking systems is rare.

[0004] In forklift drive-by-wire drum brake systems, although traditional control methods can achieve basic braking functions, they still have significant limitations in practical applications: 1) Existing solutions mostly design controllers based on simplified linearized dynamic models, failing to fully consider the nonlinear characteristics of the braking system (such as time-varying friction coefficients, mechanical clearances, etc.) and load dynamic coupling, resulting in insufficient accuracy of the dynamic model. When deployed to a physical system, problems such as model mismatch and low tracking accuracy easily occur; 2) Existing control methods for forklift drive-by-wire drum brake systems lack robustness in dealing with complex and variable working conditions (such as forklift load changes, uphill and downhill driving, and the presence of external interference). When faced with complex working conditions, control performance is prone to degradation, and may even lead to instability of the control system.

[0005] To address the aforementioned issues, a non-singular terminal sliding mode surface and a power-law approach can be designed for forklift drive-by-wire drum brake systems to avoid chattering and singularity risks associated with traditional sliding mode control methods. Furthermore, a globally convergent closed-loop control system is constructed based on Lyapunov stability theory, enabling precise control of the master cylinder piston position and ensuring smooth braking of engineering forklifts under complex conditions. Compared to existing technologies, the fast non-singular terminal sliding mode control method for forklift drive-by-wire drum brake systems offers significant technical advantages in response speed, control accuracy, and adaptability to complex conditions, demonstrating considerable engineering application value and practical significance in the field of drive-by-wire braking for new energy forklifts. Summary of the Invention

[0006] To overcome the problems of insufficient response and control precision in existing forklift drive-by-wire drum brake systems under complex working conditions, this invention provides a forklift drive-by-wire drum brake control method and device based on fast non-singular terminal sliding mode control. Compared with traditional control methods, this invention, through the design of a fast non-singular terminal sliding mode control algorithm, not only improves the response speed and control precision of the braking system, but also enhances the system's robustness under uncertain and complex working conditions. It can maintain a certain level of control performance under multiple working conditions, thereby improving the operational safety and handling efficiency of new energy forklifts.

[0007] To address the aforementioned technical challenges, the first aspect of this invention relates to a fast non-singular terminal sliding mode control method for a forklift drive-by-wire drum brake system, comprising the following steps:

[0008] Step 1: Conduct a mechanism analysis on the mechanical structure and dynamic characteristics of the forklift drive-by-wire drum brake system, and establish a dynamic model of the forklift drive-by-wire drum brake system;

[0009] Step 2: Based on the dynamic model established in Step 1, design a fast non-singular terminal sliding surface and a power-law approaching law to achieve fast convergence of the system state.

[0010] Step 3: Based on the sliding surface and reaching law designed in Step 2, design a fast non-singular terminal sliding mode control algorithm suitable for forklift drive-by-wire drum brake system;

[0011] Step 4: Based on Lyapunov stability theory, prove that the control algorithm designed in Step 3 can make the system state converge to the equilibrium point in a finite time, and perform simulation on the MATLAB / Simulink platform to verify the effectiveness of the control algorithm in the forklift drive-by-wire drum brake system.

[0012] A second aspect of the invention relates to a fast non-singular terminal sliding mode control device for a forklift drive-by-wire drum brake system, which integrates an electro-hydraulic braking system, an electronic control unit, and a data communication system.

[0013] This invention considers the operational needs of forklifts under complex working conditions and provides a novel control method that effectively addresses the insufficient robustness of traditional control methods when facing system nonlinear characteristics, model uncertainties, and external disturbances. Compared with existing technologies, the beneficial effects of this invention are reflected in: by designing a fast nonsingular terminal sliding mode control algorithm, this invention successfully improves the response speed, braking accuracy, and adaptability to complex working conditions of the forklift's brake-by-wire system. It ensures stable operation of the brake-by-wire system even under heavy load, no-load, and frequent start-stop conditions, thereby improving the forklift's working efficiency and safety. Attached Figure Description

[0014] To more clearly illustrate the technical solution of the present invention, the accompanying drawings mentioned in the technical description of the present invention will be briefly described below. Obviously, the drawings described below are only schematic diagrams of some embodiments of the present invention. For those skilled in the art, other similar illustrations can be derived from these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the dynamic model of the forklift drive-by-wire drum brake system of the present invention;

[0016] Figure 2 This is a simulation program diagram of the MATLAB / Simulink software platform of the present invention;

[0017] Figure 3 The image shows the effect of master cylinder piston position tracking under the first working condition (emergency braking) simulated and tested in the MATLAB / Simulink software platform.

[0018] Figure 4 The image shows the master cylinder piston position tracking error under the first working condition simulated and tested using the MATLAB / Simulink software platform.

[0019] Figure 5 The output torque diagram of the servo motor under the first working condition simulated and tested using the MATLAB / Simulink software platform;

[0020] Figure 6 The image shows the master cylinder piston position tracking effect under the second working condition (smooth braking) simulated and tested on the MATLAB / Simulink software platform.

[0021] Figure 7 The image shows the master cylinder piston position tracking error under the second working condition simulated and tested using the MATLAB / Simulink software platform.

[0022] Figure 8 The output torque diagram of the servo motor under the second working condition simulated and tested in the MATLAB / Simulink software platform;

[0023] Figure 9 The phase trajectory diagram of the system;

[0024] Figure 10 This is a flowchart of the method of the present invention. Detailed Implementation

[0025] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0026] Example 1

[0027] This embodiment relates to a fast non-singular terminal sliding mode control method applied to a forklift drive-by-wire drum brake system. The specific implementation steps are as follows:

[0028] Step 1: Describe the dynamic equations of the forklift drive-by-wire drum brake system based on the mechanism, and establish the dynamic model of the mechanical and hydraulic parts of the system;

[0029] Assume the mass of the rack and 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 , Indicates the gear ratio. For transmission efficiency, For the gear radius, For the internal hydraulic system, The cross-sectional area of ​​the master cylinder piston. Let be the motor torque. Analyzing the internal physical relationships of the forklift's drive-by-wire drum brake system, according to Newton's second law, the dynamic equations of the forklift's drive-by-wire drum brake system are as follows:

[0030] (1)

[0031] (2)

[0032] in, The coefficient of viscous friction is... This is the stiffness coefficient; For rack force, denoted as ; The internal hydraulic pressure of the system is denoted as . ; The spring force is denoted as . ; Friction force, denoted as .

[0033] Assuming the fluid volume in the system is unaffected by the piston movement of the master cylinder, the dynamic equations of the hydraulic system can be expressed as:

[0034] (3)

[0035] in, Defined as The first differential of time Represents the internal brake fluid volume flow rate. This indicates the bulk modulus of brake fluid. This indicates the volume of the master cylinder.

[0036] The following describes the wheel cylinder pressurization model of the system:

[0037] (4)

[0038] in, Indicates the rate of change of hydraulic pressure in the wheel cylinder. This indicates the volume of the wheel cylinder and brake line, taking into account... Substituting equation (4) into equation (3) yields:

[0039] (5)

[0040] By integrating equation (5), the mapping relationship between the pressure inside the master cylinder and the position of the master cylinder piston can be described as follows:

[0041] (6)

[0042] in, This represents the initial pressure inside the cylinder.

[0043] In practice, the internal pressure of the master cylinder With piston displacement The nonlinear relationship between them is affected by dead zone, friction, temperature changes, and brake pad wear. In dynamic modeling, these nonlinear factors can be regarded as system disturbances, and a second-order polynomial can be used to represent the internal pressure of the master cylinder. Relative to the position of the master cylinder piston The relationship curves are fitted to reflect the relationship between the pressure inside the master cylinder and the increase in piston displacement. This not only reflects the change in pressure inside the master cylinder with the increase in piston displacement, but also facilitates the design of the subsequent controller. The fitted hydraulic pressure inside the master cylinder... With piston displacement The second-order relation between them is as follows:

[0044] (7)

[0045] in, Characterizing the internal pressure of the master cylinder With piston displacement The key characteristic parameters of the relationship between the two systems are related to the system stiffness and hydraulic fluid characteristics.

[0046] The core purpose of the above processing is to provide a dynamic model with a certain degree of accuracy and ease of controller design for the forklift drive-by-wire brake control system, rather than a completely accurate physical description.

[0047] Therefore, the complete dynamic model of the forklift's brake-by-wire system is given below:

[0048] (8)

[0049] in, To account for the uncertainties in the lumped model parameters and external disturbances, based on the mechanical structure and dynamic properties of the forklift's steer-by-wire braking system, it can be assumed that the lumped perturbation has an upper bound, i.e. ,in, Its upper limit.

[0050] Step 2: Design a fast non-singular terminal sliding surface for the forklift drive-by-wire drum brake system to improve the error convergence characteristics of the forklift drive-by-wire drum brake system;

[0051] Define master cylinder piston position tracking error as follows:

[0052] (9)

[0053] in, and Let represent the actual piston position and the expected piston position, respectively, and both be second-differentiable. The fast nonsingular terminal sliding surface is defined as follows:

[0054] (10)

[0055] in, The first derivative of the displacement error. And the function The definition is as follows:

[0056] (11)

[0057] For the initial conditions and It can be done in a limited time. It converges to zero, and The expression is as follows:

[0058] (12)

[0059] To attract the system state to the sliding surface, a power-law approach is designed as follows:

[0060] (13)

[0061] Among them, parameters .

[0062] Step 3: Based on the dynamic model of the forklift drive-by-wire drum brake system established in Step 1 and the sliding surface and reaching law designed in Step 2, a sliding mode controller for the forklift drive-by-wire drum brake system is further designed.

[0063] First, differentiate the sliding surface according to equation (10):

[0064] (14)

[0065] in, Let be the second derivative of the displacement error, and As can be seen from step 1:

[0066] (15)

[0067] Substituting equation (1) into the above equation, we get:

[0068] (16)

[0069] Based on the definition of equivalent control input, the lumped perturbation in equation (15) is temporarily ignored. The impact and solution To obtain the equivalent control quantity as follows:

[0070] (17)

[0071] Among them, equivalent control quantity This is the control law for the sliding section. Based on this, to ensure the control system's... To enhance robustness, a control variable for the arrival segment based on a power-law approach is designed. as follows:

[0072] (18)

[0073] in, , All are positive parameters.

[0074] In summary, the final control law of the forklift's steer-by-wire braking system is as follows:

[0075] That is, a fast non-singular terminal sliding mode controller.

[0076] Step 4: Based on Lyapunov stability theory, prove that the sliding mode equivalent control law designed in Step 3 can enable the forklift drive-by-wire drum brake system to reach a stable state, and perform performance analysis and simulation verification of the designed fast non-singular terminal sliding mode control algorithm on the MATLAB / Simulink software platform.

[0077] The Lyapunov function is defined as follows:

[0078]

[0079] Taking the first derivative of equation (20) yields:

[0080] (twenty one)

[0081] Substituting equations (9) and (14) into equation (21), we get:

[0082] Among them, when hour, .

[0083] Therefore, At that time, the control system satisfies the Lyapunov stability condition.

[0084] Substituting equations (14) and (17) into We can obtain:

[0085]

[0086] when Then, equation (23) can be expressed as follows:

[0087]

[0088] when Sometimes, ;when Sometimes, From the phase trajectory of the system, when At that time, to achieve The convergence time of the arrival segment is given below. :

[0089]

[0090] in, These are the initial conditions for the system.

[0091] This indicates that the system state can be determined in a finite time. Converging to a steady state:

[0092]

[0093] In summary, the designed fast non-singular terminal sliding mode controller It can make the master cylinder piston position tracking error In a limited time The internal convergence reaches zero, which is the actual position of the master cylinder piston. In a limited time Converging to the expected position of the master cylinder piston .

[0094] The dynamic model parameters of the forklift drive-by-wire drum brake system are given below:

[0095]

[0096] Two verification scenarios were designed in the simulation. The first was an emergency braking scenario, where the expected master cylinder piston position of the forklift's drive-by-wire braking system was determined. It is its extreme position, that is =0.05m. The second type is smooth braking, with the expected master cylinder piston position... The expression is as follows:

[0097] (27)

[0098] Simulation programs built on the MATLAB / Simulink software platform, such as Figure 2 As shown, the simulation results are as follows: Figures 3 to 8 As shown.

[0099] Simulation results show that the designed fast non-singular terminal sliding mode control algorithm enables the master cylinder piston to achieve stable reference position tracking. In the first operating condition, the tracking error of the master cylinder piston position is almost zero, and the servo motor output torque is also stable at... Furthermore, the tracking error is relatively smooth, meeting the requirements for tracking control. In the second operating condition, the tracking error of the master cylinder piston position is limited to a bounded region, with a boundary range of approximately... The output torque range of the servo motor is Furthermore, the path is relatively smooth with no obvious high-frequency chattering, thus meeting the tracking control requirements. This demonstrates that the designed fast non-singular terminal sliding mode control algorithm for forklift drive-by-wire braking systems exhibits good tracking control performance for various master cylinder piston expected trajectories, verifying the algorithm's effectiveness.

[0100] Example 2

[0101] This embodiment relates to a fast non-singular terminal sliding mode control device for a forklift's drive-by-wire drum brake system. It utilizes a pedal displacement sensor, a data acquisition module, a host computer core computing platform with a built-in fast non-singular terminal sliding mode control algorithm, a servo motor encoder, a CAN data bus, an electronic control unit (servo motor) as the system's lower-level unit, a master cylinder servo motor, brake fluid lines, an in-cylinder pressure sensor, and a data communication unit to achieve precise closed-loop tracking control of the expected master cylinder piston position. The specific implementation steps are as follows:

[0102] Step 1: Input the forklift braking demand signal through the pedal displacement sensor and data acquisition module;

[0103] When the driver presses the brake pedal, the pedal displacement sensor converts the displacement signal into an electrical signal, which is then transmitted to the host computer via the data acquisition module.

[0104] Step 2: The target braking signal of the forklift is calculated by the host computer core computing platform with built-in fast non-singular terminal sliding mode control algorithm and servo motor encoder;

[0105] After receiving the displacement signal, the host computer calculates the expected piston displacement based on the mapping relationship between the forklift pedal travel and the target master cylinder piston displacement, and uses this displacement as the reference signal for the fast non-singular termination sliding mode control system. The host computer is responsible for executing the fast non-singular termination sliding mode control algorithm, calculating the control signal based on braking requirements and system status. This refers to the servo motor torque signal. Specifically, it includes the actual position of the master cylinder piston. The angular displacement of the motor is acquired by measuring the encoder of the servo motor, and then a mapping relationship between the motor angular displacement and the piston displacement is established.

[0106] Step 3: Control signals are sent via the CAN data bus and the electronic control unit, which acts as the lower-level machine in the system.

[0107] The host computer sends signals to the electronic control unit via the CAN data bus, including the target position signal of the master cylinder piston and the torque signal of the servo motor.

[0108] Step 4: The braking action is performed through the electronic control unit and the master cylinder servo motor;

[0109] After receiving the control signal from the host computer, the electronic control unit will drive the servo motor inside the EHB. The servo motor then drives the master cylinder piston to perform feed motion through the reduction gear transmission mechanism within the system.

[0110] Step 5: Generate braking force for the forklift through the brake fluid lines;

[0111] The feed motion of the master cylinder piston compresses the brake fluid inside the cylinder, thereby transmitting the brake fluid to the brake fluid lines. The brake fluid acts on the wheel cylinders, thus generating the braking force required for the forklift tires.

[0112] Step 6: Closed-loop feedback control is completed through the cylinder pressure sensor, servo motor encoder, electronic control unit, CAN data bus, data communication unit, and host computer core computing platform to meet the braking requirements of the forklift.

[0113] The pressure sensor inside the master cylinder is responsible for collecting pressure data, while the servo motor encoder is responsible for measuring angular position changes in real time. The electronic control unit feeds back the sensor signals to the host computer via the CAN data bus. The data communication unit adjusts the control input in real time based on the feedback signal and the fast non-singular terminal sliding mode control algorithm, and then sends a signal to the lower-level electronic control unit to correct the braking action, thus forming a closed-loop feedback control. This ensures that the master cylinder piston position can accurately track the expected target position and maintain the expected hydraulic pressure inside the master cylinder, thereby meeting the braking requirements of the forklift.

[0114] The above description represents only one embodiment of the present invention and does not limit the scope of its application. Those skilled in the art will recognize that the present invention can be modified and altered in many different ways. Any adjustments, substitutions, or improvements made within the core concepts and principles of the present invention should be considered part of the scope of protection of the present invention.

Claims

1. A fast non-singular terminal sliding mode control method applied to a forklift drive-by-wire drum brake system, the specific implementation steps of which are as follows: Step 1: Conduct a mechanism analysis on the mechanical structure and dynamic characteristics of the forklift drive-by-wire drum brake system, and establish a dynamic model of the forklift drive-by-wire drum brake system; Step 2: Based on the dynamic model established in Step 1, design a fast non-singular terminal sliding surface and a power-law approaching law to achieve fast convergence of the system state. Step 3: Based on the sliding surface and reaching law designed in Step 2, design a fast non-singular terminal sliding mode control algorithm suitable for forklift drive-by-wire drum brake system; Step 4: Based on Lyapunov stability theory, prove that the control algorithm designed in Step 3 can make the system state converge to the equilibrium point in a finite time, and perform simulation on the MATLAB / Simulink platform to verify the effectiveness of the control algorithm in the forklift drive-by-wire drum brake system. Step 1 specifically includes: Assume the mass of the rack and 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 , Indicates the gear ratio. For transmission efficiency, For the gear radius, For the internal hydraulic system, The cross-sectional area of ​​the master cylinder piston. Given the motor torque, analyzing the internal physical relationships of the forklift's drive-by-wire drum brake system, and applying Newton's second law, the dynamic equations of the forklift's drive-by-wire drum brake system are as follows: (1) (2) in, The coefficient of viscous friction is... This is the stiffness coefficient; For rack force, denoted as ; The internal hydraulic pressure of the system is denoted as . ; The spring force is denoted as . ; Friction force, denoted as , Assuming the fluid volume in the system is unaffected by the piston movement of the master cylinder, the dynamic equations of the hydraulic system can be expressed as: (3) in, Defined as The first differential of time Represents the internal brake fluid volume flow rate. This indicates the bulk modulus of brake fluid. Indicates the volume of the master cylinder. The following describes the wheel cylinder pressurization model of the system: (4) in, Indicates the rate of change of hydraulic pressure in the wheel cylinder. This indicates the volume of the wheel cylinder and brake line, taking into account... Substituting equation (4) into equation (3) yields: (5) By integrating equation (5), the mapping relationship between the pressure inside the master cylinder and the position of the master cylinder piston can be described as follows: (6) in, This is the initial pressure inside the cylinder. In practice, the internal pressure of the master cylinder With piston displacement The nonlinear relationship between them is affected by dead zone, friction, temperature changes, and brake pad wear. In dynamic modeling, these nonlinear factors can be regarded as system disturbances, and a second-order polynomial can be used to represent the internal pressure of the master cylinder. Relative to the position of the master cylinder piston Fitting the relationship curve between the two cylinders not only reflects the change in pressure within the master cylinder as piston displacement increases, but also facilitates the design of subsequent controllers. The fitted hydraulic pressure within the master cylinder... With piston displacement The second-order relation between them is as follows: (7) in, Characterizing the internal pressure of the master cylinder With piston displacement The key characteristic parameters of the relationship between the two systems are related to the system stiffness and hydraulic fluid properties in terms of their physical meaning. The core purpose of the above processing is to provide a dynamic model with a certain degree of accuracy and ease of controller design for the forklift drive-by-wire brake control system, rather than a completely accurate physical description. Therefore, the complete dynamic model of the forklift's brake-by-wire system is given below: (8) in, To account for the uncertainties in the lumped model parameters and external disturbances, based on the mechanical structure and dynamic properties of the forklift's steer-by-wire braking system, it can be assumed that the lumped perturbation has an upper bound, i.e. ,in, Its upper boundary; Step 2 specifically includes: Define master cylinder piston position tracking error as follows: (9) in, and Let represent the actual piston position and the expected piston position, respectively, and both be second-differentiable. The fast nonsingular terminal sliding surface is defined as follows: (10) in, The first derivative of the displacement error. And the function The definition is as follows: (11) For the initial conditions and It can be done in a limited time. It converges to zero, and The expression is as follows: (12) To attract the system state to the sliding surface, a power-law approach is designed as follows: (13) Among them, parameters ; Step 3 specifically includes: First, differentiate the sliding surface according to equation (10): (14) in, Let be the second derivative of the displacement error, and As can be seen from step 1: (15) Substituting equation (1) into the above equation, we get: (16) Based on the definition of equivalent control input, the lumped perturbation in equation (15) is temporarily ignored. The impact and solution To obtain the equivalent control quantity as follows: (17) Among them, equivalent control quantity This is the control law for the sliding section. Based on this, to ensure the control system's... To enhance robustness, a control variable for the arrival segment based on a power-law approach is designed. as follows: (18) in, , All are positive parameters. In summary, the final control law of the forklift's drive-by-wire braking system is as follows: That is, a fast non-singular terminal sliding mode controller.

2. The control method according to claim 1, characterized in that, Step 4 specifically includes: The Lyapunov function is defined as follows: Taking the first derivative of equation (20) yields: (21) Substituting equations (9) and (14) into equation (21), we get: Among them, when hour, , Therefore, At that time, the control system satisfies the Lyapunov stability condition. Substitute equations (14) and (17) into We can obtain: when Then, equation (23) can be expressed as follows: when Sometimes, ;when Sometimes, From the phase trajectory of the system, when At that time, to achieve The convergence time of the arrival segment is given below. : in, These are the initial conditions of the system. This indicates that the system state can be determined in a finite time. Converging to a steady state: In summary, the designed fast non-singular terminal sliding mode controller It can make the master cylinder piston position tracking error In a limited time The piston converges to zero, which is the actual position of the master cylinder piston. In a limited time Converging to the expected position of the master cylinder piston .

3. A fast non-singular terminal sliding mode control device for a forklift drive-by-wire drum brake system, comprising a pedal displacement sensor, a data acquisition module, a built-in host computer core computing platform responsible for executing the fast non-singular terminal sliding mode control algorithm as described in claim 1, a servo motor encoder, a CAN data bus, an electronic control unit as the system's lower-level machine, a master cylinder servo motor, brake fluid lines, an in-cylinder pressure sensor, and a data communication unit, etc., to achieve precise closed-loop tracking control of the expected master cylinder piston position. The specific implementation steps are as follows: Step 1: Input the forklift braking demand signal through the pedal displacement sensor and data acquisition module; Step 2: The target braking signal of the forklift is calculated by the host computer core computing platform with built-in fast non-singular terminal sliding mode control algorithm and servo motor encoder; Step 3: Control signals are sent via the CAN data bus and the electronic control unit, which acts as the lower-level machine in the system. Step 4: The braking action is performed through the electronic control unit and the master cylinder servo motor; Step 5: Generate braking force for the forklift through the brake fluid lines; Step 6: Closed-loop feedback control is completed through the in-cylinder pressure sensor, servo motor encoder, electronic control unit, CAN data bus, data communication unit, and host computer core computing platform to meet the braking requirements of the forklift. Step 1 specifically includes: When the driver presses the brake pedal, the pedal displacement sensor converts the displacement signal into an electrical signal, which is then transmitted to the host computer via the data acquisition module. Step 2 specifically includes: After receiving the displacement signal, the host computer calculates the expected piston displacement based on the mapping relationship between the forklift pedal travel and the target master cylinder piston displacement. This calculated displacement is then used as the reference signal for the fast non-singular termination sliding mode control system. The host computer is responsible for executing the fast non-singular termination sliding mode control algorithm, calculating the control signal based on braking requirements and system status. This refers to the servo motor torque signal, where the actual position of the master cylinder piston is... The angular displacement of the motor is acquired by measuring the encoder of the servo motor, and then a mapping relationship between the motor angular displacement and the piston displacement is established. Step 3 specifically includes: The host computer sends signals to the electronic control unit via the CAN data bus, including the target position signal of the master cylinder piston and the torque signal of the servo motor; Step 4 specifically includes: After receiving the control signal from the host computer, the electronic control unit will drive the servo motor inside the EHB. The servo motor will then drive the master cylinder piston to perform feed motion through the reduction gear transmission mechanism in the system. Step 5 specifically includes: The feed motion of the master cylinder piston will cause the brake fluid in the cylinder to be compressed, thereby transmitting the brake fluid to the brake fluid line. The brake fluid acts on the wheel cylinder, thereby generating the braking force required for the forklift tires. Step 6 specifically includes: The pressure sensor inside the master cylinder is responsible for collecting pressure, and the servo motor encoder is responsible for measuring the angular position change in real time. The electronic control unit feeds back the above sensor signals to the host computer through the CAN data bus. The data communication unit adjusts the control quantity in real time according to the feedback signal and the fast non-singular terminal sliding mode control algorithm, and then sends a signal to the lower-level electronic control unit to correct the braking action, thereby forming a closed-loop feedback control to ensure that the piston position of the master cylinder can accurately track the expected target position and maintain the expected hydraulic pressure inside the master cylinder, thereby meeting the braking requirements of the forklift.

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