A method and system for compensating for non-linear cascading of by-layer progressive drive-by-wire actuator control

Abstract

The application relates to a kind of layer-by-layer progressive compensation and nonlinear cascade's drive-by-wire actuator control method and system, and the current actual angle or displacement signal of motor is collected by drive-by-wire brake actuator, and pressure request signal;The actuator friction force and rough compensation torque are calculated by load self-adaptive LuGre friction model;The concave coefficient estimate of pressure-displacement curve, the estimate of concentrated disturbance and fine compensation torque are calculated using adaptive extended state disturbance observer;The fine control torque is calculated using cascade nonlinear controller;According to the superposition result of rough compensation torque, fine compensation torque and fine control torque, the action of drive-by-wire brake actuator is controlled, and the actual angle or displacement request and actual pressure request are obtained.Compared with prior art, the application has the advantages of high precision, strong robustness and good adaptability.

Description

Technical Field

[0001] This invention relates to the field of automotive braking technology, and in particular to a method and system for controlling a drive-by-wire actuator with progressive compensation and nonlinear cascading. Background Technology

[0002] With the continuous improvement of automotive safety, comfort, and intelligence, braking systems are gradually evolving from traditional hydraulic braking to brake-by-wire (BBW). BBW systems directly generate braking force or hydraulic pressure through a motor and its reduction / conversion mechanism, offering advantages such as fast response, high control precision, and ease of integration with energy recovery and vehicle stability control. Existing brake-by-wire systems mainly include two types: electromechanical braking (EMB) and electro-hydraulic braking (EHB). EMB completely eliminates hydraulic lines, while EHB, based on a mature hydraulic architecture, uses a motor-driven booster mechanism, offering better engineering compatibility and feasibility. Unlike the discrete pressure regulation method of traditional solenoid valves, brake-by-wire introduces the motor actuator into the closed-loop control circuit. This makes pressure or clamping force control highly susceptible to friction, hysteresis, dead zone, and the nonlinear relationship between pressure and displacement. Furthermore, uncertainties such as brake pad wear, temperature changes, or hydraulic characteristic drift can easily lead to problems such as low-speed creep, force fluctuations, steady-state deviations, and deterioration of dynamic tracking performance.

[0003] To obtain accurate control feedback, existing systems mostly rely on pressure sensors to construct pressure closed loops. However, due to space constraints in wheels and actuators, cost and reliability limitations, and operational requirements after failures, scenarios involving sensor absence or failure objectively exist. Therefore, sensorless control utilizing only motor information has become an important research direction. Existing sensorless methods are mainly divided into two categories: one is to estimate the pressure or clamping force first and then perform pressure control; the other is to construct a pressure and displacement cascade control by estimating the pressure and measuring the displacement, supplemented by adaptive mechanisms, disturbance observers, Kalman filtering or sliding mode, fuzzy logic, and other robust control methods to suppress disturbances. Meanwhile, some studies have used Coulomb friction models, viscous friction models, Karnopp models, or Tustin models for friction compensation. However, the above methods generally have the following shortcomings: insufficient characterization of friction dynamics and their correlation with the load; lack of systematic differentiation and processing of parameter uncertainties and external disturbances; and the tendency for estimation errors to accumulate, potentially leading to a decline in closed-loop control performance or even stability risks.

[0004] Therefore, how to perform hierarchical processing of modelable nonlinearity, estimable disturbance, unmodelable factors and unestimated factors in a wire-controlled actuator under sensorless conditions, so as to improve pressure tracking accuracy and robustness while ensuring system stability, is a technical problem that needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a step-by-step progressive compensation and nonlinear cascade control method and system for actuators controlled by wire. Through a step-by-step progressive three-layer architecture consisting of a load adaptive LuGre friction model in the coarse compensation layer, an adaptive extended state disturbance observer in the fine compensation layer, and a cascaded nonlinear controller in the fine control layer, layer-by-layer suppression and compensation are performed for modelable nonlinearity, estimable disturbance, unmodelable factors, and unestimateable factors, respectively, thereby realizing high-precision pressure tracking control of actuators controlled by wire under sensorless conditions.

[0006] The objective of this invention can be achieved through the following technical solutions: According to one aspect of the present invention, a method for controlling a drive-by-wire actuator with progressive compensation and nonlinear cascading is provided, the specific steps of which include: S1. Collect the current actual rotation angle or displacement signal of the motor, as well as the pressure request signal, through the wired brake actuator; S2. Based on the actual rotation angle or displacement signal, calculate the actuator friction force and coarse compensation torque using the load adaptive LuGre friction model; S3. Based on the actual rotation angle or displacement signal and the actuator friction force, use the adaptive extended state disturbance observer to calculate the estimated value of the concavity coefficient, the estimated value of the concentrated disturbance, and the fine compensation torque of the pressure-displacement curve. S4. Based on the pressure request signal, the estimated concavity coefficient and the estimated concentrated disturbance, calculate the fine control torque using a cascaded nonlinear controller; S5. Control the linear brake actuator to operate based on the superposition result of the coarse compensation torque, fine compensation torque and fine control torque, so as to obtain the actual rotation angle or displacement request and the actual pressure request.

[0007] Furthermore, in S2, Convert the motor's current actual rotation angle or displacement signal into the master cylinder piston displacement. and master cylinder piston speed The load-adaptive LuGre friction model is then input into the model, which is specifically described as follows: , , , in, This indicates the average deformation of the elastic bristles. Represents Coulomb friction. Represents static friction. Indicates static friction speed. Indicates the bristle stiffness coefficient. This indicates the brush bristle damping coefficient. Indicates the coefficient of viscous friction. This represents the calculated actuator friction force. The rate of change of the average deformation of the brush bristles; Under static conditions, i.e., the rate of change of the average deformation of the bristles. When the friction force is simplified to a static friction model for parameter identification, the expression for calculating the actuator friction force is: ; Under dynamic operating conditions, as the system gradually comes to a stop, the brush stiffness coefficient is approximately calculated. ,in The steady-state displacement of the system within the static friction range is represented by a small step input signal; the damping ratio of the second-order model of the system is selected as 0.7, and the brush damping coefficient is calculated. ,in This is the sum of the masses of the rack and pinion and the master cylinder piston; The obtained actuator friction force is converted into coarse compensation torque; the coarse compensation torque is output to the linear brake actuator, and the actuator friction force is also output.

[0008] Furthermore, in step S3, the current actual rotation angle or displacement signal of the motor is converted into the displacement of the master cylinder piston. and master cylinder piston speed ; Displace the master cylinder piston Master cylinder piston speed Friction between actuator The input is fed into an adaptive extended state perturbation observer, which is specifically: , , in, Indicates the displacement of the master cylinder piston. Indicates the speed of the master cylinder piston. , , , These are the displacements of the master cylinder piston. Master cylinder piston speed Concentrated disturbance Concavity coefficient The estimated value, For the motor output torque, For force or torque conversion coefficient, The damping coefficient of the deceleration mechanism is... This is the sum of the masses of the rack and pinion and the master cylinder piston. Main cylinder spring stiffness, For actuator friction, , and For positive feedback gain, For the adaptive gain of the concavity coefficient, For the stability correction term gain, The cross-sectional area of ​​the main cylinder piston. This represents the dead zone length in the pressure-displacement relationship. The estimated value of the main cylinder pressure; Define the estimation error variable as , , The corresponding error dynamic equation is obtained; the parameter adaptive law with projection operator is adopted to ensure that the estimated value is bounded. The estimated value of the concavity coefficient is calculated and output by the extended state observer. and estimates of concentrated disturbances Calculate the fine compensation torque and output it to the linear brake actuator, while simultaneously outputting the estimated value of the concavity coefficient. and the estimated value of the concentrated disturbance .

[0009] Furthermore, in step S4, the pressure request signal is converted into the desired displacement of the master cylinder. Desired speed of master cylinder and the expected acceleration of the master cylinder ; The estimated value of the concavity coefficient Centralized disturbance estimates Master cylinder piston displacement Master cylinder piston speed Actuator friction The correlation quantity with the desired displacement of the main cylinder is input into a cascaded nonlinear controller; In a cascaded nonlinear controller, the displacement tracking error is defined. Constructing the sliding surface ,in Positive design parameters; Along the system trajectory for the sliding surface Differentiating and substituting into the system state-space expression, we obtain the discontinuous control law, and further obtain the expression for the complete control input torque: , in, , A positive control gain for Boundary layer thickness of the function, Represents the hyperbolic tangent function; The calculated complete control input torque The torque is output to the linear brake actuator as a fine control torque.

[0010] Furthermore, S1 also includes the step of establishing a model of the drive-by-wire actuator, specifically including: Based on the master cylinder piston displacement Master cylinder piston speed Master cylinder piston acceleration and motor output torque Establish a mathematical model for the pressure-displacement relationship: , , in, Indicates the master cylinder pressure. The concavity coefficient of the pressure-displacement curve. This represents the dead zone length in the pressure-displacement relationship. Indicates a concentrated disturbance term; Establish the following control-oriented model: , , in, This represents the frictional force in a brake-by-wire actuator system. This is the sum of the masses of the rack and pinion and the master cylinder piston. This indicates the damping coefficient of the reduction gear mechanism. Main cylinder spring stiffness, For force or torque conversion coefficient, The cross-sectional area of ​​the main cylinder piston; Assign the following values ​​to the system state variables: The state-space expression is obtained as follows: , in, Indicates the displacement of the master cylinder piston. Indicates the speed of the master cylinder piston. Indicates system output variables, This indicates the motor's output torque. This represents the frictional force of the actuator. This is the sum of the masses of the rack and pinion and the master cylinder piston. For force or torque conversion coefficient, The damping coefficient of the deceleration mechanism is... Main cylinder spring stiffness, The cross-sectional area of ​​the main cylinder piston. This represents the dead zone length in the pressure-displacement relationship. The concavity coefficient of the pressure-displacement curve. This represents a concentrated disturbance term.

[0011] According to another aspect of the present invention, a drive-by-wire actuator control system with progressive compensation and nonlinear cascading is provided, comprising: a coarse compensation layer, a fine compensation layer, a precision control layer, and a drive-by-wire actuator. The coarse compensation layer is connected to the signal acquisition unit in the brake-by-wire actuator to receive the actual rotation angle signal or displacement signal of the motor. The actual rotation angle or displacement signal is used to calculate the actuator friction force and coarse compensation torque through the load adaptive LuGre friction model. The fine compensation layer is connected to the signal acquisition unit and the coarse compensation layer in the brake-by-wire actuator, and receives the actual rotation angle signal or displacement signal of the motor and the friction force of the actuator. It is used to calculate the estimated value of the concavity coefficient, the estimated value of the concentrated disturbance and the fine compensation torque of the pressure-displacement curve using the adaptive extended state disturbance observer. The fine control layer is connected to the signal acquisition unit and fine compensation layer in the linear brake actuator, and receives pressure request signals, concavity coefficient estimates and concentrated disturbance estimates. It is used to calculate the fine control torque using a cascaded nonlinear controller based on the pressure request signals, concavity coefficient estimates and concentrated disturbance estimates. The brake-by-wire actuator is used to control the action of the brake-by-wire actuator according to the superposition result of the coarse compensation torque, the fine compensation torque and the fine control torque, so as to obtain the actual rotation angle or displacement request and the actual pressure request.

[0012] Furthermore, the coarse compensation layer includes a load-adaptive LuGre friction model. The coarse compensation layer receives the actual motor rotation angle signal or displacement signal transmitted by the signal acquisition unit, converts it into the master cylinder piston displacement and master cylinder piston speed, and then inputs it into the load-adaptive LuGre friction model to calculate the actuator friction force and coarse compensation torque. The coarse compensation torque of the coarse compensation layer is transmitted to the brake-by-wire actuator, and the actuator friction force is transmitted to the fine compensation layer.

[0013] Furthermore, the fine compensation layer includes an adaptive extended state disturbance observer. The fine compensation layer receives the actual motor rotation angle signal or displacement signal transmitted by the signal acquisition module, and the actuator friction force transmitted by the coarse compensation layer. After converting the actual motor rotation angle signal or displacement signal into the master cylinder piston displacement and master cylinder piston speed, it inputs them into the adaptive extended state disturbance observer. Combined with the actuator friction force, it calculates the estimated value of concavity coefficient, the estimated value of concentrated disturbance, and the fine compensation torque. The fine compensation layer transmits the fine compensation torque to the brake-by-wire actuator and transmits the estimated value of concavity coefficient and the estimated value of concentrated disturbance to the fine control layer.

[0014] Furthermore, the fine control layer includes a cascaded nonlinear controller. The fine control layer receives the pressure request signal transmitted by the signal acquisition module and the concavity coefficient estimate and lumped disturbance estimate transmitted by the fine compensation layer. It converts the pressure request signal into the desired displacement of the master cylinder and its derivative, and then inputs it into the cascaded nonlinear controller. The fine control torque is calculated by combining the concavity coefficient estimate and the lumped disturbance estimate. The fine control layer transmits the fine control torque to the brake-by-wire actuator.

[0015] Furthermore, the wire-controlled brake actuator is connected to the coarse compensation layer, the fine compensation layer, and the fine control layer respectively. It receives the coarse compensation torque transmitted by the coarse compensation layer, the fine compensation torque transmitted by the fine compensation layer, and the fine control torque transmitted by the fine control layer. After superimposing the coarse compensation torque, the fine compensation torque, and the fine control torque, it performs the action and outputs the actual motor rotation angle signal or displacement signal and the actual pressure.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) By setting a coarse compensation layer and adopting a load-adaptive LuGre friction model, the present invention identifies static and dynamic parameters under different load conditions, enabling the model to adjust the bristle stiffness coefficient and damping coefficient online according to the system operating point. This solves the problem that the existing methods are insufficient in characterizing the dynamic characteristics of friction and its correlation with the load. Compared with the existing technology that uses a single-parameter static friction model, this load-adaptive mechanism can more accurately compensate for the modelable friction nonlinearity in the system, effectively suppress low-speed crawling, force fluctuation and steady-state deviation caused by friction, thereby improving the pressure tracking steady-state accuracy of the linear brake actuator under sensorless conditions.

[0017] (2) This invention constructs an adaptive extended state disturbance observer through a fine compensation layer, and jointly estimates the concavity coefficient of the pressure-displacement curve and the concentrated disturbance as an extended state. It also introduces a parameter adaptive law with a projection operator to ensure that the estimated value is bounded, thereby realizing the systematic distinction and compensation of parameter uncertainty and external disturbance. The fine compensation layer in this invention can estimate and compensate for the uncertainty and disturbance in the system online without relying on the pressure sensor, avoiding the problem of the accumulation and transmission of estimation error to control error in the existing pressure estimation and control framework, and reducing the risk of closed-loop performance degradation or even instability caused by estimation error.

[0018] (3) This invention uses a cascaded nonlinear controller in the fine control layer to further suppress residual high-frequency unmodeled dynamics and unpredictable disturbance inputs in the system on the basis of coarse compensation and fine compensation. At the same time, a sliding mode surface is constructed and a discontinuous control law is designed to directly constrain the pressure tracking error. The three-layer structure is progressive and mutually coordinated, and is used to process modelable nonlinearity, predictable disturbance and unmodelable / unpredictable factors in a layered manner. Finally, in practical applications, the brake-by-wire actuator can still take into account the stability of control and dynamic response performance under the condition of no pressure sensor, realize high-precision pressure following control, and meet the engineering requirements of vehicle braking system for safety, comfort and reliability. Attached Figure Description

[0019] Figure 1 A flowchart of a control method for a drive-by-wire actuator that combines progressive compensation and nonlinear cascading; Figure 2 Data flow diagram for a wire-controlled actuator control system with progressive compensation and nonlinear cascading; Figure 3 The figure shows the experimental results of the system in Example 2 under driver braking conditions. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0021] Example 1 In online control braking systems, the control accuracy of actuators directly affects vehicle braking safety and comfort. Due to limitations in installation space, cost, and reliability, it is often difficult to deploy pressure sensors in practical applications, forcing control systems to rely solely on motor rotation angle or displacement information for sensorless pressure control. Therefore, internal frictional nonlinearity, pressure-displacement nonlinearity, parameter uncertainty, and external disturbances become the main factors affecting control accuracy. Existing sensorless control methods often employ static friction models, which fail to characterize the dynamic characteristics of friction and its correlation with the load, resulting in insufficient friction compensation accuracy. Furthermore, they lack systematic differentiation and processing of parameter uncertainties and external disturbances, typically estimating them together, which easily leads to the accumulation and propagation of estimation errors. Simultaneously, they lack effective means to suppress high-frequency unmodeled dynamics and unpredictable disturbances, which can easily cause pressure overshoot, oscillations, or even closed-loop instability under dynamic operating conditions. To address the aforementioned issues, this embodiment provides a linear brake actuator control method based on progressive compensation and nonlinear cascading. By setting up a coarse compensation layer, a fine compensation layer, and a precise control layer, it respectively handles modelable nonlinearities, estimable disturbances, and unmodelable / unestimateable factors. The three-layer structure progresses step by step and cooperates with each other, achieving high-precision and highly robust pressure tracking control under sensorless conditions. like Figure 1 As shown, this embodiment provides a method for controlling a drive-by-wire actuator with progressive compensation and nonlinear cascading. The specific steps include: S1. Collect the current actual rotation angle or displacement signal of the motor, as well as the pressure request signal, through the wired brake actuator; S2. Calculate the actuator friction force and coarse compensation torque based on the actual rotation angle or displacement signal using the load adaptive LuGre friction model; S3. Based on the actual rotation angle or displacement signal and the actuator friction force, use the adaptive extended state disturbance observer to calculate the estimated value of the concavity coefficient, the estimated value of the concentrated disturbance, and the fine compensation torque of the pressure-displacement curve. S4. Based on the pressure request signal, the estimated concavity coefficient and the estimated lumped disturbance, calculate the fine control torque using a cascaded nonlinear controller; S5. Based on the superposition result of coarse compensation torque, fine compensation torque and fine control torque, control the linear actuator to obtain the actual rotation angle or displacement request and the actual pressure request.

[0022] S1 also includes the step of establishing a model of the drive-by-wire actuator, specifically including: Based on the master cylinder piston displacement Master cylinder piston speed Master cylinder piston acceleration and motor output torque Establish a mathematical model for the pressure-displacement relationship: , , in, Indicates the master cylinder pressure. The concavity coefficient of the pressure-displacement curve. , This represents the dead zone length in the pressure-displacement relationship. This represents a concentrated disturbance term; it is used to describe frictional hysteresis characteristics, unmodeled dynamics, and the effects of external disturbances.

[0023] Establish the following control-oriented model: , , in, This represents the frictional force in a brake-by-wire actuator system. This is the sum of the masses of the rack and pinion and the master cylinder piston. This indicates the damping coefficient of the reduction gear mechanism. Main cylinder spring stiffness, For force or torque conversion coefficient, The cross-sectional area of ​​the main cylinder piston; Assign the following values ​​to the system state variables: The state-space expression is obtained as follows: , in, Indicates the displacement of the master cylinder piston. Indicates the speed of the master cylinder piston. Indicates system output variables, This indicates the motor's output torque. This represents the frictional force of the actuator. This is the sum of the masses of the rack and pinion and the master cylinder piston. For force or torque conversion coefficient, The damping coefficient of the deceleration mechanism is... Main cylinder spring stiffness, The cross-sectional area of ​​the main cylinder piston. This represents the dead zone length in the pressure-displacement relationship. The concavity coefficient of the pressure-displacement curve. This represents a concentrated disturbance term.

[0024] In S2, Convert the motor's current actual rotation angle or displacement signal into the master cylinder piston displacement. and master cylinder piston speed This data is then input into the load-adaptive LuGre friction model, which is specifically as follows: , , , in, This indicates the average deformation of the elastic bristles. Represents Coulomb friction. Represents static friction. Indicates static friction speed. Indicates the bristle stiffness coefficient. This indicates the brush bristle damping coefficient. Indicates the coefficient of viscous friction. This represents the calculated actuator friction force. The rate of change of the average deformation of the brush bristles; Under static conditions, i.e., the rate of change of the average deformation of the bristles. When the friction force is simplified to a static friction model for parameter identification, the expression for calculating the actuator friction force is: ; Under dynamic operating conditions, as the system gradually comes to a stop, the brush stiffness coefficient is approximately calculated. ,in The steady-state displacement of the system within the static friction range is represented by a small step input signal; the damping ratio of the second-order model of the system is selected as 0.7, and the brush damping coefficient is calculated. ,in This is the sum of the masses of the rack and pinion and the master cylinder piston; The obtained actuator friction force is converted into coarse compensation torque; the coarse compensation torque is output to the linear brake actuator, and the actuator friction force is also output.

[0025] In S3, the current actual rotation angle or displacement signal of the motor is converted into the displacement of the master cylinder piston. and master cylinder piston speed ; Displace the master cylinder piston Master cylinder piston speed Friction between actuator The input is fed into the adaptive extended state perturbation observer, which is specifically: , , in, Indicates the displacement of the master cylinder piston. Indicates the speed of the master cylinder piston. , , , These are the displacements of the master cylinder piston. Master cylinder piston speed Concentrated disturbance Concavity coefficient The estimated value, For the motor output torque, For force or torque conversion coefficient, The damping coefficient of the deceleration mechanism is... This is the sum of the masses of the rack and pinion and the master cylinder piston. Main cylinder spring stiffness, For actuator friction, , and For positive feedback gain, For the adaptive gain of the concavity coefficient, For the stability correction term gain, The cross-sectional area of ​​the main cylinder piston. This represents the dead zone length in the pressure-displacement relationship. The estimated value of the main cylinder pressure; Define the estimation error variable as , , The corresponding error dynamic equation is obtained, and its expression is: , An adaptive law with a projection operator is used to ensure that the estimated value is bounded. The expression is as follows: , , By employing the projection operator, the following inequality can be guaranteed to hold: , The estimated value of the concavity coefficient is calculated and output using an extended state observer. and estimates of concentrated disturbances ; Calculate the fine compensation torque and output it to the linear brake actuator, while also outputting the estimated value of the concavity coefficient. and concentrated disturbance estimates .

[0026] In S4, the pressure request signal is converted into the desired displacement of the master cylinder. Desired speed of master cylinder and the expected acceleration of the master cylinder ; Based on the state-space expression of the system, we obtain: , in, This represents the expected value of the system output. This indicates the desired displacement of the master cylinder. Describe a symbolic function that satisfies (When the independent variable) (time) or (When the independent variable) hour), This represents the dead zone length in the pressure-displacement relationship. The concavity coefficient of the pressure-displacement curve. Indicates a concentrated disturbance term. This represents an estimated value of the concavity coefficient. This represents an estimate of the concentrated disturbance.

[0027] Estimated value of concavity coefficient Centralized disturbance estimates Master cylinder piston displacement Master cylinder piston speed Actuator friction The correlation quantity with the desired displacement of the main cylinder is input into a cascaded nonlinear controller.

[0028] Therefore, we obtain the identity: , This leads to the desired displacement of the main cylinder: , In a cascaded nonlinear controller, the displacement tracking error is defined. Constructing the sliding surface ,in For positive design parameters, the expression for constructing the sliding surface is: , in, Indicates the displacement of the master cylinder piston. This indicates the desired displacement of the master cylinder. Indicates displacement tracking error. The derivative representing the displacement tracking error, Represents the sliding surface variable. The design parameters are positive. This reduces the displacement tracking error. Approaching 0 is equivalent to making the sliding surface Approaching 0, the focus of subsequent control design is to ensure the sliding surface convergence.

[0029] Along the system trajectory for the sliding surface Taking the derivative and substituting it into the system state-space expression, we obtain the discontinuous control law, which is expressed as: , This leads to the complete control input torque, expressed as: , in, , A positive control gain for Boundary layer thickness of the function, Represents the hyperbolic tangent function; item Positive control gain used to compensate for disturbance estimation errors. The value must meet the following conditions: , Substituting the control law into the expression for the derivative of the sliding surface, we get: , The calculated complete control input torque The torque is output to the linear brake actuator as a fine control torque.

[0030] Example 2 Based on the method provided in Example 1, this example provides a linear actuator control system with progressive compensation and nonlinear cascading, such as... Figure 2 As shown, the system includes: a coarse compensation layer, a fine compensation layer, a precision control layer, and a linear brake actuator. The coarse compensation layer is connected to the signal acquisition unit in the brake-by-wire actuator to receive the actual rotation angle signal or displacement signal of the motor. It is used to calculate the friction force and coarse compensation torque of the actuator through the load adaptive LuGre friction model based on the actual rotation angle or displacement signal. The fine compensation layer is connected to the signal acquisition unit and the coarse compensation layer in the brake-by-wire actuator. It receives the actual rotation angle signal or displacement signal of the motor and the friction force of the actuator. It is used to calculate the estimated value of the concavity coefficient of the pressure-displacement curve, the estimated value of the concentrated disturbance, and the fine compensation torque using the adaptive extended state disturbance observer. The fine control layer is connected to the signal acquisition unit and fine compensation layer in the linear brake actuator. It receives pressure request signals, concavity coefficient estimates, and concentrated disturbance estimates. Based on the pressure request signals, concavity coefficient estimates, and concentrated disturbance estimates, it uses a cascaded nonlinear controller to calculate the fine control torque. The brake-by-wire actuator is used to control the action of the brake-by-wire actuator based on the superposition result of coarse compensation torque, fine compensation torque and fine control torque, so as to obtain the actual rotation angle or displacement request and the actual pressure request.

[0031] The coarse compensation layer includes a load-adaptive LuGre friction model. The coarse compensation layer receives the actual motor rotation angle signal or displacement signal transmitted by the signal acquisition unit, converts it into the master cylinder piston displacement and master cylinder piston speed, and then inputs it into the load-adaptive LuGre friction model to calculate the actuator friction force and coarse compensation torque. The coarse compensation torque of the coarse compensation layer is transmitted to the brake-by-wire actuator, and the actuator friction force is transmitted to the fine compensation layer.

[0032] The fine compensation layer includes an adaptive extended state disturbance observer. The fine compensation layer receives the actual motor rotation angle signal or displacement signal transmitted by the signal acquisition module, and the actuator friction force transmitted by the coarse compensation layer. After converting the actual motor rotation angle signal or displacement signal into the master cylinder piston displacement and master cylinder piston speed, it inputs them into the adaptive extended state disturbance observer. Combined with the actuator friction force, it calculates the estimated value of concavity coefficient, the estimated value of concentrated disturbance, and the fine compensation torque. The fine compensation layer transmits the fine compensation torque to the brake-by-wire actuator and transmits the estimated value of concavity coefficient and the estimated value of concentrated disturbance to the fine control layer.

[0033] The fine control layer includes a cascaded nonlinear controller. The fine control layer receives the pressure request signal transmitted by the signal acquisition module and the estimated concavity coefficient and concentrated disturbance value transmitted by the fine compensation layer. It converts the pressure request signal into the desired displacement of the master cylinder and its derivative, and then inputs it into the cascaded nonlinear controller. The fine control torque is calculated by combining the estimated concavity coefficient and concentrated disturbance value. The fine control layer transmits the fine control torque to the brake-by-wire actuator.

[0034] The wire-controlled brake actuator is connected to the coarse compensation layer, the fine compensation layer, and the precision control layer respectively. It receives the coarse compensation torque transmitted by the coarse compensation layer, the fine compensation torque transmitted by the fine compensation layer, and the precision control torque transmitted by the precision control layer. After superimposing the coarse compensation torque, the fine compensation torque, and the precision control torque, it performs the action and outputs the actual motor rotation angle signal or displacement signal and the actual pressure.

[0035] To better illustrate the hydraulic pressure tracking performance of the system in this embodiment, the hardware-in-the-loop experiment adopted the following approach: a pressure target tracking experiment based on the driver's braking intention, the results of which are as follows. Figure 3 As shown.

[0036] In the experiment, the electromechanical wire-controlled actuator layer-by-layer progressive high-precision control method and system control parameters proposed in this invention were selected as follows: brush stiffness coefficient Damping coefficient viscous friction coefficient Coulomb friction Static friction static friction speed All parameters vary with the load. The symbols, names, units, and values ​​of other relevant control parameters are shown in Table 1. Table 1. Control parameters in the experiment of Example 2 Figure 3 The experimental results of the system in this embodiment under driver braking conditions include curves showing pressure versus time and brake pedal travel versus time. The pressure versus time curves include actual pressure, estimated pressure, and requested pressure. Although rapidly changing pressure targets can cause parameter variations and external disturbances in the pressure-displacement relationship, the estimated pressure still approximates the actual pressure, indicating that this method can achieve good implicit pressure response. Creep, dead zone, oscillation, and waveform distortion caused by friction are almost eliminated, thus avoiding pressure overshoot and undesirable vehicle deceleration. Throughout the test, the root mean square error (RMSE) of pressure control was 1.68 bar; while in the steady-state pressure setpoint phase, the error remained within 0.5 bar, demonstrating that the sensorless control system proposed in this invention still provides good pressure tracking performance.

[0037] Therefore, the coarse compensation layer in this embodiment adopts a load-adaptive LuGre friction model, which is based on brush bristle modeling theory and can characterize the dynamic characteristics of friction. At the same time, a load-adaptive mechanism is introduced to identify the brush bristle stiffness coefficient under different load conditions. Brush damping coefficient viscous friction coefficient Coulomb friction Static friction and static friction speed This invention enables the friction model parameters to be adjusted online according to the system's operating point. Compared with existing technologies that use a single-parameter static friction model, this invention can significantly improve the accuracy of friction compensation, effectively compensate for modelable frictional nonlinearities in linear brake actuator systems, and suppress low-speed crawling, force fluctuations, and steady-state deviations caused by friction.

[0038] Furthermore, existing technologies in pressure sensorless solutions often employ a framework of first estimating pressure and then controlling it, which is prone to the transmission and accumulation of estimation errors to control errors, inducing instability. Therefore, an adaptive extended state disturbance observer in the fine compensation layer outputs an estimated value of the concavity coefficient. and concentrated disturbance estimates The estimated value is then directly input into the fine control layer to participate in the control law calculation of the cascaded nonlinear controller, so that the pressure estimation is implicitly integrated into the control law, which weakens the transmission link of the estimation error and reduces the risk of closed-loop performance degradation or even instability caused by the accumulation of estimation error.

[0039] Meanwhile, addressing the issues of parameter uncertainty, lack of system suppression for external disturbances, and high-frequency unmodeled dynamics in existing technologies, this invention uses an adaptive extended state disturbance observer in the fine compensation layer to separate, estimate, and compensate for concentrated disturbances. Combined with a cascaded nonlinear controller in the fine control layer, it further suppresses residual high-frequency unmodeled dynamics and unpredictable disturbance inputs in the system, building upon the coarse and fine compensation layers. The three-layer structure is progressive and mutually supportive, addressing modelable nonlinearities, predictable disturbances, and unmodelable and unpredictable factors in a tiered manner. Experimental results show that the overall performance of this invention is superior to comparative methods, achieving high-precision and highly robust pressure tracking control under sensorless conditions.

[0040] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the described module can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0041] The electronic device of this invention includes a central processing unit (CPU), which can perform various appropriate actions and processes according to computer program instructions stored in read-only memory (ROM) or loaded from a storage unit into random access memory (RAM). The RAM may also store various programs and data required for device operation. The CPU, ROM, and RAM are interconnected via a bus. Input / output (I / O) interfaces are also connected to the bus.

[0042] Multiple components in the device are connected to an I / O interface, including: input units such as a keyboard, mouse, etc.; output units such as various types of displays, speakers, etc.; storage units such as disks, optical disks, etc.; and communication units such as network interface cards, modems, wireless transceivers, etc. The communication unit allows the device to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks. The processing unit performs the various methods and processes described above, such as the method of the present invention. For example, in some embodiments, the method of the present invention may be implemented as a computer software program tangibly contained in a machine-readable medium, such as a storage unit. In some embodiments, part or all of the computer program may be loaded and / or installed on the device via ROM and / or the communication unit. When the computer program is loaded into RAM and executed by the CPU, one or more steps of the method of the present invention described above may be performed. Alternatively, in other embodiments, the CPU may be configured to execute the method of the present invention by any other suitable means (e.g., by means of firmware).

[0043] The functions described above in this document can be performed, at least in part, by one or more hardware logic components. For example, exemplary types of hardware logic components that can be used, without limitation, include: Field Programmable Gate Arrays (FPGAs), Application-Specific Integrated Circuits (ASICs), Application Standard Products (ASSPs), System-on-Chip (SoCs), Complex Programmable Logic Devices (CPLDs), and so on.

[0044] The program code used to implement the methods of the present invention can be written in any combination of one or more programming languages. This program code can be provided to a processor or controller of a general-purpose computer, special-purpose computer, or other programmable data processing device, such that when executed by the processor or controller, the program code causes the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code can be executed entirely on the machine, partially on the machine, as a standalone software package partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0045] In the context of this invention, a machine-readable medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. Machine-readable media can include, but are not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0046] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for controlling a drive-by-wire actuator with progressive compensation and nonlinear cascading, characterized in that, The specific steps include: S1. Collect the current actual rotation angle or displacement signal of the motor, as well as the pressure request signal, through the wired brake actuator; S2. Based on the actual rotation angle or displacement signal, calculate the actuator friction force and coarse compensation torque using the load adaptive LuGre friction model; S3. Based on the actual rotation angle or displacement signal and the actuator friction force, use the adaptive extended state disturbance observer to calculate the estimated value of the concavity coefficient, the estimated value of the concentrated disturbance, and the fine compensation torque of the pressure-displacement curve. S4. Based on the pressure request signal, the estimated concavity coefficient and the estimated concentrated disturbance, calculate the fine control torque using a cascaded nonlinear controller; S5. Control the linear brake actuator to operate based on the superposition result of the coarse compensation torque, fine compensation torque and fine control torque, so as to obtain the actual rotation angle or displacement request and the actual pressure request.

2. The method for controlling a wire actuator with progressive compensation and nonlinear cascading as described in claim 1, characterized in that, In S2, Convert the motor's current actual rotation angle or displacement signal into the master cylinder piston displacement. and master cylinder piston speed The load-adaptive LuGre friction model is then input into the model, which is specifically described as follows: ， ， ， in, This indicates the average deformation of the elastic bristles. Represents Coulomb friction. Represents static friction. Indicates static friction speed. Indicates the bristle stiffness coefficient. This indicates the brush bristle damping coefficient. Indicates the coefficient of viscous friction. This represents the calculated actuator friction force. The rate of change of the average deformation of the brush bristles; Under static conditions, i.e., the rate of change of the average deformation of the bristles. When the friction force is simplified to a static friction model for parameter identification, the expression for calculating the actuator friction force is: ； Under dynamic operating conditions, as the system gradually comes to a stop, the brush stiffness coefficient is approximately calculated. ,in The steady-state displacement of the system within the static friction range is represented by a small step input signal; the damping ratio of the second-order model of the system is selected as 0.7, and the brush damping coefficient is calculated. ,in This is the sum of the masses of the rack and pinion and the master cylinder piston; The obtained actuator friction force is converted into coarse compensation torque; the coarse compensation torque is output to the linear brake actuator, and the actuator friction force is also output.

3. The method for controlling a wire actuator with progressive compensation and nonlinear cascading as described in claim 1, characterized in that, In step S3, the current actual rotation angle or displacement signal of the motor is converted into the displacement of the master cylinder piston. and master cylinder piston speed ; Displace the master cylinder piston Master cylinder piston speed Friction between actuator The input is fed into an adaptive extended state perturbation observer, which is specifically: ， ， in, Indicates the displacement of the master cylinder piston. Indicates the speed of the master cylinder piston. , , , These are the displacements of the master cylinder piston. Master cylinder piston speed Concentrated disturbance Concavity coefficient The estimated value, For the motor output torque, For force or torque conversion coefficient, The damping coefficient of the deceleration mechanism is... This is the sum of the masses of the rack and pinion and the master cylinder piston. Main cylinder spring stiffness, For actuator friction, , and For positive feedback gain, For the adaptive gain of the concavity coefficient, For the stability correction term gain, The cross-sectional area of ​​the main cylinder piston. This represents the dead zone length in the pressure-displacement relationship. The estimated value of the main cylinder pressure; Define the estimation error variable as , , The corresponding error dynamic equation is obtained; the parameter adaptive law with projection operator is adopted to ensure that the estimated value is bounded. The estimated value of the concavity coefficient is calculated and output by the extended state observer. and estimates of concentrated disturbances Calculate the fine compensation torque and output it to the linear brake actuator, while simultaneously outputting the estimated value of the concavity coefficient. and the estimated value of the concentrated disturbance .

4. The method for controlling a wire actuator with progressive compensation and nonlinear cascading as described in claim 1, characterized in that, In step S4, the pressure request signal is converted into the desired displacement of the master cylinder. Desired speed of master cylinder and the expected acceleration of the master cylinder ; The estimated value of the concavity coefficient Centralized disturbance estimates Master cylinder piston displacement Master cylinder piston speed Actuator friction The correlation quantity with the desired displacement of the main cylinder is input into a cascaded nonlinear controller; In a cascaded nonlinear controller, the displacement tracking error is defined. Constructing the sliding surface ,in Positive design parameters; Along the system trajectory for the sliding surface Differentiating and substituting into the system state-space expression, we obtain the discontinuous control law, and further obtain the expression for the complete control input torque: ， in, , A positive control gain for Boundary layer thickness of the function, Represents the hyperbolic tangent function; The calculated complete control input torque The torque is output to the linear brake actuator as a fine control torque.

5. The method for controlling a wire actuator with progressive compensation and nonlinear cascading as described in claim 1, characterized in that, S1 also includes the step of establishing a model of the drive-by-wire actuator, specifically including: Based on the master cylinder piston displacement Master cylinder piston speed Master cylinder piston acceleration and motor output torque Establish a mathematical model for the pressure-displacement relationship: ， ， in, Indicates the master cylinder pressure. The concavity coefficient of the pressure-displacement curve. This represents the dead zone length in the pressure-displacement relationship. Indicates a concentrated disturbance term; Establish the following control-oriented model: ， ， in, This represents the frictional force in a brake-by-wire actuator system. This is the sum of the masses of the rack and pinion and the master cylinder piston. This indicates the damping coefficient of the reduction gear mechanism. Main cylinder spring stiffness, For force or torque conversion coefficient, The cross-sectional area of ​​the main cylinder piston; Assign the following values ​​to the system state variables: Thus, the state-space expression is obtained: ， in, Indicates the displacement of the master cylinder piston. Indicates the speed of the master cylinder piston. Indicates system output variables, This indicates the motor's output torque. This represents the frictional force of the actuator. This is the sum of the masses of the rack and pinion and the master cylinder piston. For force or torque conversion coefficient, The damping coefficient of the deceleration mechanism is... Main cylinder spring stiffness, The cross-sectional area of ​​the main cylinder piston. This represents the dead zone length in the pressure-displacement relationship. The concavity coefficient of the pressure-displacement curve. This represents a concentrated disturbance term.

6. A control system for a drive-by-wire actuator with progressive compensation and nonlinear cascading, used in the drive-by-wire actuator control method with progressive compensation and nonlinear cascading as described in any one of claims 1 to 5, characterized in that, The system includes: a coarse compensation layer, a fine compensation layer, a precision control layer, and a linear braking actuator. The coarse compensation layer is connected to the signal acquisition unit in the brake-by-wire actuator to receive the actual rotation angle signal or displacement signal of the motor. The actual rotation angle or displacement signal is used to calculate the actuator friction force and coarse compensation torque through the load adaptive LuGre friction model. The fine compensation layer is connected to the signal acquisition unit and the coarse compensation layer in the brake-by-wire actuator, and receives the actual rotation angle signal or displacement signal of the motor and the friction force of the actuator. It is used to calculate the estimated value of the concavity coefficient, the estimated value of the concentrated disturbance and the fine compensation torque of the pressure-displacement curve using the adaptive extended state disturbance observer. The fine control layer is connected to the signal acquisition unit and fine compensation layer in the linear brake actuator, and receives pressure request signals, concavity coefficient estimates and concentrated disturbance estimates. It is used to calculate the fine control torque using a cascaded nonlinear controller based on the pressure request signals, concavity coefficient estimates and concentrated disturbance estimates. The brake-by-wire actuator is used to control the action of the brake-by-wire actuator according to the superposition result of the coarse compensation torque, the fine compensation torque and the fine control torque, so as to obtain the actual rotation angle or displacement request and the actual pressure request.

7. A linear actuator control system with progressive compensation and nonlinear cascading as described in claim 6, characterized in that, The coarse compensation layer includes a load-adaptive LuGre friction model. The coarse compensation layer receives the actual motor rotation angle signal or displacement signal transmitted by the signal acquisition unit, converts it into the master cylinder piston displacement and master cylinder piston speed, and then inputs it into the load-adaptive LuGre friction model to calculate the actuator friction force and coarse compensation torque. The coarse compensation torque of the coarse compensation layer is transmitted to the brake-by-wire actuator, and the actuator friction force is transmitted to the fine compensation layer.

8. A linear actuator control system with progressive compensation and nonlinear cascading as described in claim 6, characterized in that, The fine compensation layer includes an adaptive extended state disturbance observer. The fine compensation layer receives the actual motor rotation angle signal or displacement signal transmitted by the signal acquisition module, and the actuator friction force transmitted by the coarse compensation layer. After converting the actual motor rotation angle signal or displacement signal into the master cylinder piston displacement and master cylinder piston speed, it inputs them into the adaptive extended state disturbance observer. Combined with the actuator friction force, it calculates the estimated value of concavity coefficient, the estimated value of concentrated disturbance, and the fine compensation torque. The fine compensation layer transmits the fine compensation torque to the brake-by-wire actuator and transmits the estimated value of concavity coefficient and the estimated value of concentrated disturbance to the fine control layer.

9. A linear actuator control system with progressive compensation and nonlinear cascading as described in claim 6, characterized in that, The fine control layer includes a cascaded nonlinear controller. The fine control layer receives the pressure request signal transmitted by the signal acquisition module and the estimated concavity coefficient and concentrated disturbance value transmitted by the fine compensation layer. It converts the pressure request signal into the desired displacement of the master cylinder and its derivative, and then inputs it into the cascaded nonlinear controller. The fine control torque is calculated by combining the estimated concavity coefficient and concentrated disturbance value. The fine control layer transmits the fine control torque to the brake-by-wire actuator.

10. A linear actuator control system with progressive compensation and nonlinear cascading as described in claim 6, characterized in that, The linear brake actuator is connected to the coarse compensation layer, the fine compensation layer, and the fine control layer respectively. It receives the coarse compensation torque transmitted by the coarse compensation layer, the fine compensation torque transmitted by the fine compensation layer, and the fine control torque transmitted by the fine control layer. After superimposing the coarse compensation torque, the fine compensation torque, and the fine control torque, it performs the action and outputs the actual motor rotation angle signal or displacement signal and the actual pressure.

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