Forklift drive-by-wire drum brake system control method and device based on rapid nonsingular terminal sliding mode

Abstract

The invention discloses a forklift drive-by-wire drum brake control method and device based on a rapid nonsingular terminal sliding mode, and the method comprises the steps: 1) carrying out mechanism analysis for a mechanical structure and dynamic characteristics of a forklift drive-by-wire drum brake system, and building a dynamic model of the forklift drive-by-wire drum brake system; 2) according to the dynamic model established in the step 1, designing a fast nonsingular terminal sliding mode surface and a power reaching law so as to realize fast convergence of a system state; (3) according to the sliding mode surface and the reaching law designed in the step (2), a rapid nonsingular terminal sliding mode control algorithm suitable for the forklift drive-by-wire drum brake system is designed; and 4) based on the Lyapunov stability theory, proving that the control algorithm designed in the step 3 can enable the system state to converge to a balance point within finite time, and performing simulation on an MATLAB / Simulink platform to verify the effectiveness of the control algorithm in the forklift drive-by-wire drum brake system. And the response speed and the control precision of the drive-by-wire drum brake system of the forklift can be obviously improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial vehicle wire-controlled brake control, and specifically relates to a control method and device for a forklift wire-controlled drum brake system based on Fast Non-singular Terminal Sliding Mode Control (FNTSMC). The method can be used to improve the response speed, control accuracy and robustness of the forklift wire-controlled drum brake system under complex working conditions. Background Art

[0002] Traditional forklift braking systems mostly use mechanical or hydraulic transmission structures, and their braking force transmission process relies on the mechanical linkage of the driver's pedal or changes in hydraulic line pressure. Such systems have a certain degree of lag in dynamic response, especially in complex scenarios and operating conditions such as emergency braking or frequent starts and stops. The mechanical transmission time from pedal signal input to the full establishment of braking force is long, resulting in increased braking distance and reduced safety. In addition, the nonlinear characteristics of the hydraulic system (such as line pressure loss and brake pad wear) further reduce the control accuracy of the braking force, making it difficult to meet the needs of high-precision and high-frequency material handling. In recent years, the introduction of electro-hydraulic braking (EHB) technology has provided a new direction for the innovation of forklift braking systems. By directly driving the master cylinder piston with a servo motor, the braking command is transitioned from mechanical hydraulic control to electronic signal closed-loop control, which can theoretically significantly improve the system's response speed and control accuracy. However, existing control algorithms (such as PID control and fuzzy control) still have certain limitations when facing the dynamic nonlinear characteristics of hydraulic systems, model parameter perturbations and external disturbances. The fixed gains 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 braking control effect and theoretical expectations.

[0003] Sliding mode control (SMC), renowned for its robustness to system uncertainties and external disturbances, has been increasingly applied to the braking of construction vehicles. Traditional sliding mode controllers employ switching functions to force the system state trajectory to converge to the sliding surface. However, these controllers suffer from two key drawbacks in practical engineering applications: First, frequent sign switching within the control law can lead 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 singularities. Under certain conditions, the controlled variable may approach infinity, leading to actuator saturation and even system instability. To address these issues, researchers at home and abroad have recently proposed a series of novel terminal sliding mode control methods. These methods, by constructing novel sliding surfaces and reaching laws, avoid singularities while accelerating system state convergence. While these methods have achieved some success in fields such as robotics and drones, their application in forklift brake-by-wire systems is limited.

[0004] In forklift-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 often design controllers based on simplified linearized dynamic models, failing to fully consider the nonlinear characteristics of the braking system (such as time-varying friction coefficient, mechanical clearance, etc.) and load dynamic coupling. This leads to insufficient dynamic model accuracy, which can easily lead to model mismatch and low tracking accuracy when deployed in physical systems. 2) Existing forklift-by-wire drum brake system control methods lack robustness to complex and variable operating conditions (such as forklift load fluctuations, uphill and downhill driving, and external interference). Control performance can easily degrade under complex operating conditions, even causing control system instability.

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

[0006] To overcome the problems of existing forklift-by-wire drum brake systems, such as slow response and insufficient control accuracy under complex operating conditions, the present invention provides a forklift-by-wire drum brake control method and device based on fast non-singular terminal sliding mode control (FNTSMC). Compared with traditional control methods, this invention utilizes a fast non-singular terminal sliding mode control algorithm to not only improve the braking system's response speed and control accuracy, but also enhance the system's robustness under uncertain and complex operating conditions. It can maintain a certain level of control performance under multiple operating conditions, thereby improving the operational safety and handling efficiency of new energy forklifts.

[0007] In order to solve the above technical problems, the first aspect of the present invention relates to a fast non-singular terminal sliding mode control method for a forklift wire-controlled drum brake system, which specifically comprises the following steps:

[0008] Step 1: Analyze the mechanical structure and dynamic characteristics of the forklift's wire-controlled drum brake system and establish a dynamic model of the forklift's wire-controlled drum brake system.

[0009] Step 2: Based on the dynamic model established in step 1, a fast non-singular terminal sliding mode surface and power reaching law are designed to achieve rapid convergence of the system state;

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

[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 within a finite time, and perform simulation on the MATLAB / Simulink platform to verify the effectiveness of the control algorithm in the forklift wire-controlled drum brake system.

[0012] A second aspect of the present invention relates to a fast non-singular terminal sliding mode control device for a forklift wire-controlled drum brake system, which integrates an electronic hydraulic brake (EHB) system, an electronic control unit (ECU) and a data communication system.

[0013] This invention takes into account the operational requirements of forklifts under complex operating conditions and provides a new control method that effectively addresses the lack of robustness of traditional control methods in the face of system nonlinearities, model uncertainties, and external disturbances. Compared with existing technologies, the present invention has the following beneficial effects: by designing a fast non-singular terminal sliding mode control algorithm, the present invention successfully improves the response speed, braking accuracy, and adaptability of the forklift's brake-by-wire system to complex operating conditions. This ensures stable operation of the brake-by-wire system under conditions such as heavy loads, no loads, and frequent starts and stops, thereby improving the operating efficiency and safety of the forklift. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] To more clearly illustrate the technical solution of the present invention, the following briefly describes the drawings mentioned in the technical description of the present invention. It is apparent that the drawings described below are only schematic diagrams of some embodiments of the present invention. Those skilled in the art can derive other similar diagrams based on these drawings without requiring creative effort.

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

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

[0017] Figure 3 This is the master cylinder piston position tracking effect diagram under the first working condition (emergency braking) simulated by the MATLAB / Simulink software platform;

[0018] Figure 4 This is the master cylinder piston position tracking error diagram under the first working condition simulated and tested on the MATLAB / Simulink software platform;

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

[0020] Figure 6 This is the master cylinder piston position tracking effect diagram under the second working condition (smooth braking) simulated by the MATLAB / Simulink software platform;

[0021] Figure 7 This is the master cylinder piston position tracking error diagram under the second working condition simulated and tested on the MATLAB / Simulink software platform;

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

[0023] Figure 9 is the phase locus diagram of the system;

[0024] Figure 10 Flow chart of the method of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is 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 wire-controlled drum brake system. The specific implementation steps are as follows:

[0028] Step 1: Describe the dynamic equations of the forklift's wire-controlled drum brake system based on the mechanism, and establish the dynamic models of the mechanical and hydraulic parts of the system;

[0029] Assume that the actual displacement of the master cylinder piston in the system is x, and the actual speed of the master cylinder piston is The actual acceleration of the master cylinder piston is i represents the gear ratio, η is the transmission efficiency, r is the gear radius, p is the internal hydraulic pressure of the system, A sc is the cross-sectional area of the master cylinder piston, T m is the motor torque. Analyzing the internal physical relationship of the forklift's wire-controlled drum brake system, according to Newton's second law, the dynamic equation of the forklift's wire-controlled drum brake system is as follows:

[0030]

[0031] Among them, c is the damping coefficient and k is the stiffness coefficient; is the rack force, denoted as F r ; A sc p is the internal hydraulic pressure of the system, denoted as F h ; kx is the spring force, denoted as F s ; is the friction force, denoted as F f .

[0032] Assuming that the fluid volume in the system is not affected by the movement of the master cylinder piston, the dynamic equation of the hydraulic part of the system can be expressed as:

[0033]

[0034] in, is defined as the first-order differential of p with respect to time, Q represents the volume flow of brake fluid inside the system, β e Indicates the bulk modulus of brake fluid.

[0035] The wheel cylinder hydraulic pressure model of the system is described below:

[0036]

[0037] Among them, p sc Indicates wheel cylinder hydraulic pressure. Considering Substituting formula (4) into formula (3) yields:

[0038]

[0039] By integrating equation (5), the mapping relationship between the pressure in the master cylinder and the position of the master cylinder piston can be described as:

[0040]

[0041] Among them, p0 is the initial pressure in the cylinder.

[0042] In practice, the nonlinear relationship between master cylinder internal pressure p and piston displacement x is affected by factors such as dead zone, friction, temperature fluctuations, and brake pad wear. In dynamic modeling, these nonlinear factors can be treated as system perturbations, and a second-order polynomial is used to fit the relationship between master cylinder internal pressure p and master cylinder piston position x. This not only reflects the relationship between master cylinder internal pressure and piston displacement but also facilitates subsequent controller design. The fitted second-order relationship between master cylinder internal pressure p and piston displacement x is as follows:

[0043] p=μx 2 (7)

[0044] Among them, μ represents the key characteristic parameter of the relationship between the internal pressure p of the master cylinder and the piston displacement x. Its physical meaning is related to the system stiffness, hydraulic fluid characteristics, etc.

[0045] The core purpose of the above processing is to provide a dynamic model with a certain degree of accuracy and convenient controller design for the design of the forklift wire brake control system, rather than a completely accurate physical description.

[0046] At this point, the complete dynamic model of the forklift wire brake system is given as follows:

[0047]

[0048] Where d is the lumped model parameter uncertainty and external disturbance. According to the mechanical structure and dynamic properties of the forklift wire brake system, it can be assumed that the lumped perturbation has an upper bound, that is, in, For its upper bound.

[0049] Step 2: Design a fast non-singular terminal sliding surface for the forklift's wire-controlled drum brake system to improve the error convergence characteristics of the forklift's wire-controlled drum brake system.

[0050] The master cylinder piston position tracking error e is defined as follows:

[0051] e=xx r (9)

[0052] Among them, x and x r Represent the actual piston position and the expected piston position respectively. The fast non-singular terminal sliding surface is defined as follows:

[0053]

[0054] Where λ>0,1<γ<2, and the function sig(x) α is defined as follows:

[0055] sig(x) α =|x| α sgn(x) (11)

[0056] For the initial conditions e(0) and In a finite time t s Converges to zero, and t s The expression is as follows:

[0057]

[0058] In order to attract the system state to the sliding surface, a power reaching law is designed as follows:

[0059]

[0060] Among them, the parameters ε>0,0<ρ<1.

[0061] Step 3: Based on the dynamic model of the forklift's wire-controlled drum brake system established in Step 1 and the sliding mode surface and reaching law designed in Step 2, further design a sliding mode controller for the forklift's wire-controlled drum brake system.

[0062] First, the sliding surface is derived according to formula (10):

[0063]

[0064] and From step 1, we can see that:

[0065]

[0066] Substituting formula (1) into the above formula, we can get:

[0067]

[0068] According to the definition of equivalent control input, temporarily ignore the influence of the lumped perturbation d in Eq. (15) and solve Get the equivalent control quantity u eq as follows:

[0069]

[0070] On this basis, in order to ensure the robustness of the control system to d, the arrival segment control variable u is designed based on the power reaching law. r as follows:

[0071]

[0072] Among them, L is a positive parameter.

[0073] In summary, the final control law of the forklift wire brake system is as follows:

[0074]

[0075] Step 4: Based on Lyapunov stability theory, prove that the sliding mode equivalent control law designed in step 3 can make the forklift wire-controlled drum brake system 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.

[0076] The Lyapunov function is defined as follows:

[0077]

[0078] Taking the first-order derivative of formula (20) we can get:

[0079]

[0080] Substituting equations (9) and (14) into equation (21), we obtain:

[0081]

[0082] Among them, when hour,

[0083] From this we can see that When , the control system satisfies the Lyapunov stability condition.

[0084] Substitute equation (14) and equation (17) into We can get:

[0085]

[0086] when When , formula (23) can be expressed as follows:

[0087]

[0088] When s>0, there is When s<0, there is According to the phase trajectory of the system, when When s=0 is achieved in a finite time, the convergence time t of the arrival segment is given below r :

[0089]

[0090] Among them, V0=V(s(0)) is the initial condition of the system.

[0091] Therefore, the system state can converge to the equilibrium point within a finite time t, and the expression of time t is:

[0092]

[0093] In summary, the designed fast non-singular terminal sliding mode control law u can make the master cylinder piston position tracking error e converge to zero within a finite time t, that is, the actual position x of the master cylinder piston converges to the expected position x of the master cylinder piston within a finite time t. r .

[0094] The dynamic model parameters of the forklift wire-controlled drum brake system are given as follows:

[0095] name symbol Numerical Rack and master cylinder piston mass m 0.60kg Viscous friction coefficient c 38000N·s / m Stiffness coefficient k 4980N / m gear ratio i 25 Gear radius r 0.012m Mechanical efficiency η 0.75 Master cylinder cross-sectional area <![CDATA[A sc ]]> <![CDATA[0.000385m 2 ]]> Master cylinder volume <![CDATA[V a ]]> 7.85ml Wheel cylinder and brake pipe volume <![CDATA[V b ]]> 20ml Pressure-position characteristic parameters μ 0.372 Brake fluid bulk modulus <![CDATA[β e ]]> 1680MPa

[0096] In the simulation, two verification conditions are designed. The first is the emergency braking condition, where the expected master cylinder piston position x r is its extreme position, that is, x r =0.05m. The second is smooth braking, the expected master cylinder piston position x r The expression is as follows:

[0097]

[0098] The simulation program built on the MATLAB / Simulink software platform is as follows Figure 2 The simulation results are shown in Figures 3 to 8 shown.

[0099] The simulation results show that the designed fast non-singular terminal sliding mode control algorithm can enable the master cylinder piston to achieve stable reference position tracking. Under the first working condition, the tracking error of the master cylinder piston position is almost close to zero, and the servo motor output torque is also stable at 0.1Nm and relatively smooth, meeting the tracking control requirements. Under the second working condition, the tracking error of the master cylinder piston position is limited to a bounded area, and its boundary range is approximately ±0.001m. The servo motor output torque range is -0.05~0.05Nm, and is relatively smooth, without obvious high-frequency vibration, which also meets the tracking control requirements. It shows that the designed fast non-singular terminal sliding mode control algorithm for forklift wire brake system has good tracking control effect for various expected trajectories of master cylinder pistons, verifying the effectiveness of the algorithm.

[0100] Example 2

[0101] This embodiment relates to a fast non-singular terminal sliding mode control device for a forklift drive-by-wire drum brake system. This device implements precise closed-loop tracking of the desired master cylinder piston position by using 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 (FNTSMC) algorithm, a servo motor encoder, a CAN data bus, an electronic control unit (ECU) serving as the system's slave computer, a master cylinder servo motor, brake fluid lines, an in-cylinder pressure sensor, and a data communication unit. The specific implementation steps are as follows:

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

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

[0104] Step 2: The forklift’s target braking signal is calculated using the host computer core computing platform with a built-in fast non-singular terminal sliding mode control (FNTSMC) algorithm and the 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 stroke and the target master cylinder piston displacement, and uses it as the reference signal for the fast non-singular terminal sliding mode control system. The host computer is responsible for executing the fast non-singular terminal sliding mode control algorithm (FNTSMC), which adjusts the braking demand and system status (actual position x and speed of the piston in the master cylinder) according to the braking demand and system status (actual position x and speed of the piston in the master cylinder). ) calculates the control signal u, which is the servo motor output torque. The actual position x of the master cylinder piston is indirectly measured by measuring the angular displacement of the servo motor encoder and then based on the mapping relationship between the motor angular displacement and the piston displacement.

[0106] Step 3: Control signal transmission is completed through the CAN data bus and the electronic control unit (ECU) as the system lower computer;

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

[0108] Step 4: Braking is performed through the electronic control unit (ECU) and the master cylinder servo motor.

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

[0110] Step 5: Generate the forklift's braking force through the brake fluid pipeline;

[0111] The feed movement of the master cylinder piston causes the compression of the brake fluid in the cylinder, thereby transferring 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 tire braking.

[0112] Step 6: Complete closed-loop feedback control through the in-cylinder pressure sensor, servo motor encoder, electronic control unit (ECU), CAN data bus, data communication unit, and host computer core computing platform to meet the forklift braking requirements.

[0113] The in-cylinder pressure sensor and servo motor angular displacement sensor monitor the system status, specifically the master cylinder piston position, in real time. The electronic control unit (ECU) transmits these sensor signals to the host computer via the CAN data bus. The data communication unit adjusts the control variable (servo motor torque) in real time based on the feedback signals and the fast non-singular terminal sliding mode control algorithm. This signal is then sent to the lower-level electronic control unit (ECU) to correct the braking action, thus forming a closed-loop feedback control system. This ensures that the master cylinder piston position accurately tracks the target position and maintains the desired hydraulic pressure within the master cylinder to meet the forklift's braking requirements.

[0114] The foregoing merely represents one embodiment of the present invention and does not limit the scope of application of the present invention. It will be appreciated by those skilled in the art that the present invention may be modified and altered in various ways. Any adjustments, substitutions, or improvements made within the core concepts and principles of the present invention shall be considered part of the scope of protection of the present invention.

Claims

1. A fast non-singular terminal sliding mode control method for a forklift wire-controlled drum brake system. The specific implementation steps are as follows: Step 1: Analyze the mechanical structure and dynamic characteristics of the forklift's wire-controlled drum brake system and establish a dynamic model of the forklift's wire-controlled drum brake system. Step 2: Based on the dynamic model established in step 1, a fast non-singular terminal sliding mode surface and power reaching law are designed to achieve rapid convergence of the system state; Step 3: Based on the sliding surface and reaching law designed in step 2, a fast non-singular terminal sliding mode control algorithm for the forklift drive-by-wire drum brake system is designed. 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 within a finite time, and perform simulation on the MATLAB / Simulink platform to verify the effectiveness of the control algorithm in the forklift wire-controlled drum brake system.

2. The method according to claim 1, wherein Step 1 specifically includes: assuming that the actual displacement of the master cylinder piston in the system is x, and the actual speed of the master cylinder piston is The actual acceleration of the master cylinder piston is i represents the gear ratio, η is the transmission efficiency, r is the gear radius, p is the internal hydraulic pressure of the system, A sc is the cross-sectional area of the master cylinder piston, T m is the motor torque. Analyzing the internal physical relationship of the forklift's wire-controlled drum brake system, according to Newton's second law, the dynamic equation of the forklift's wire-controlled drum brake system is as follows: Among them, c is the damping coefficient and k is the stiffness coefficient; is the rack force, denoted as F r ; A sc p is the internal hydraulic pressure of the system, denoted as F h ; kx is the spring force, denoted as F s ; is the friction force, denoted as F f , Assuming that the fluid volume in the system is not affected by the movement of the master cylinder piston, the dynamic equation of the hydraulic part of the system can be expressed as: in, is defined as the first-order differential of p with respect to time, Q represents the volume flow of brake fluid inside the system, β e represents the bulk modulus of brake fluid, The wheel cylinder hydraulic pressure model of the system is described below: Among them, p WC Indicates wheel cylinder hydraulic pressure, taking into account Substituting formula (4) into formula (3) yields: By integrating equation (5), the mapping relationship between the pressure in the master cylinder and the position of the master cylinder piston can be described as: Among them, p0 is the initial pressure in the cylinder, In actual situations, the nonlinear relationship between the master cylinder internal pressure p and the piston displacement x is affected by factors such as dead zone, friction, temperature changes, and brake pad wear. When dynamic modeling, these nonlinear factors can be regarded as system disturbances. A second-order polynomial is used to fit the relationship curve between the master cylinder internal pressure p and the master cylinder piston position x. This not only reflects the relationship between the master cylinder internal pressure and the increase of piston displacement, but also facilitates the design of subsequent controllers. The fitted second-order relationship between the master cylinder internal pressure p and the piston displacement x is as follows: p=μx 2 (7) Among them, μ is the key characteristic parameter that represents the relationship between the internal pressure p of the master cylinder and the piston displacement x. Its physical meaning is related to the system stiffness, hydraulic fluid characteristics, etc. The core purpose of the above processing is to provide a dynamic model with a certain degree of accuracy and convenient controller design for the design of forklift wire brake control system, rather than a completely accurate physical description. At this point, the complete dynamic model of the forklift wire brake system is given as follows: Where d is the lumped model parameter uncertainty and external disturbance. According to the mechanical structure and dynamic properties of the forklift wire brake system, it can be assumed that the lumped perturbation has an upper bound, that is, in, For its upper bound.

3. The method according to claim 1, wherein Step 2 specifically includes: The master cylinder piston position tracking error e is defined as follows: e=x-x r (9) Among them, x and x r Represent the actual piston position and the expected piston position respectively, and define the fast non-singular terminal sliding surface as follows: Where λ>0,1<γ<2, and the function sig(x) α is defined as follows: sig(x) α =|x| α sgn(x) (11) For the initial conditions e(0) and In a finite time t s Converges to zero, and t s The expression is as follows: In order to attract the system state to the sliding surface, a power reaching law is designed as follows: Among them, the parameters ε>0,0<ρ<1.

4. The method according to claim 1, wherein Step 3 specifically includes: First, the sliding surface is derived according to formula (10): and From step 1, we can see that: Substituting formula (1) into the above formula, we can get: According to the definition of equivalent control input, temporarily ignore the influence of the lumped perturbation d in Eq. (15) and solve Get the equivalent control quantity u eq as follows: On this basis, in order to ensure the robustness of the control system to d, the arrival segment control variable u is designed based on the power reaching law. r as follows: Among them, L is a positive parameter, In summary, the final control law of the forklift wire brake system is as follows:

5. The method according to claim 1, wherein Step 4 specifically includes: The Lyapunov function is defined as follows: Taking the first-order derivative of formula (20) we can get: Substituting equations (9) and (14) into equation (21), we obtain: Among them, when hour, From this we can see that When , the control system satisfies the Lyapunov stability condition. Substitute equation (14) and equation (17) into We can get: when When , formula (23) can be expressed as follows: When s>0, there is When s<0, there is According to the phase trajectory of the system, when When s=0 is achieved in a finite time, the convergence time t of the arrival segment is given below r : Among them, V0=V(s(0)) is the initial condition of the system, Therefore, the system state can converge to the equilibrium point within a finite time t, and the expression of time t is: In summary, the designed fast non-singular terminal sliding mode control law u can make the master cylinder piston position tracking error e converge to zero within a finite time t, that is, the actual position x of the master cylinder piston converges to the expected position x of the master cylinder piston within a finite time t. r .

6. A fast non-singular terminal sliding mode control device for a forklift drive-by-wire drum brake system implements precise closed-loop tracking of the desired master cylinder piston position. This device 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 (FNTSMC) algorithm, a servo motor encoder, a CAN data bus, an electronic control unit (ECU) serving as the system's slave computer, a master cylinder servo motor, brake fluid lines, an in-cylinder pressure sensor, and a data communication unit. The device implements this control in the following steps: Step 1: Complete the forklift braking demand signal input through the pedal displacement sensor and data acquisition module; Step 2: The forklift’s target braking signal is calculated using the host computer core computing platform with a built-in fast non-singular terminal sliding mode control (FNTSMC) algorithm and the servo motor encoder. Step 3: Control signal transmission is completed through the CAN data bus and the electronic control unit (ECU) as the system lower computer; Step 4: Braking is performed through the electronic control unit (ECU) and the master cylinder servo motor. Step 5: Generate the forklift's braking force through the brake fluid pipeline; Step 6: Complete closed-loop feedback control through the in-cylinder pressure sensor, servo motor encoder, electronic control unit (ECU), CAN data bus, data communication unit, and host computer core computing platform to meet the forklift braking requirements.

7. The device according to claim 6, characterized in that Step 1 specifically includes: when the driver steps on the brake pedal, the pedal displacement sensor converts the displacement signal into an electrical signal, and transmits the electrical signal to the host computer through the data acquisition module.

8. The device according to claim 6, wherein Step 2 specifically includes: after the host computer receives the displacement signal, it calculates the expected piston displacement based on the mapping relationship between the forklift pedal stroke and the target master cylinder piston displacement, and uses it as the reference signal of the fast non-singular terminal sliding mode control system. The host computer is responsible for executing the fast non-singular terminal sliding mode control algorithm (FNTSMC) and adjusting the braking demand and system status (actual position x and speed of the piston in the master cylinder) according to the actual braking demand and system status (actual position x and speed of the piston in the master cylinder). ) calculates the control signal u, that is, the output torque of the servo motor, where the actual position x of the master cylinder piston is indirectly measured by measuring the motor angular displacement collected by the servo motor encoder and then based on the mapping relationship between the motor angular displacement and the piston displacement.

9. The device according to claim 6, wherein Step 3 specifically includes: the host computer sends a signal to the electronic control unit (ECU) via the CAN data bus, including the master cylinder piston target position signal and the control signal (servo motor torque signal).

10. The device according to claim 6, wherein Step 4 specifically includes: after the electronic control unit (ECU) receives the control signal from the host computer, it will drive the servo motor inside the EHB, and the servo motor will then push the master cylinder piston to perform feed motion through the reduction gear transmission mechanism in the system.

11. The device according to claim 6, wherein Step 5 specifically includes: the feeding movement of the master cylinder piston causes the brake fluid in the cylinder to be compressed, thereby transferring the brake fluid to the brake fluid pipeline, and the brake fluid acts on the wheel cylinder, thereby generating the braking force required for braking the forklift tire.

12. The device according to claim 6, wherein Step 6 specifically includes: the in-cylinder pressure sensor and the servo motor angular displacement sensor are responsible for real-time monitoring of the system status, that is, the master cylinder piston position. The electronic control unit (ECU) feeds back the above sensor signals to the host computer through the CAN data bus. The data communication unit adjusts the control variable (servo motor torque) 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-computer electronic control unit (ECU) to correct the braking action, thereby forming a closed-loop feedback control to ensure 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.

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