EMB clamping force control method based on high-order all-wheel-drive system

Abstract

The invention discloses an EMB clamping force control method based on a high-order all-wheel-drive system. The EMB clamping force control method comprises the following steps that S1, a target clamping force value # imgabs0 # is obtained; s2, establishing a three-order EMB system simplified dynamic model for corner control; S3, through clamping force separation processing, converting the model for corner control into a high-order all-drive model for clamping force control; s4, designing a controller based on the high-order all-drive control method, designing the controller of the electronic mechanical braking system based on the high-order all-drive control method, synthesizing the control law in a simple explicit mode to obtain an expected linear closed-loop system with any specified pole position, and only adjusting one parameter to obtain an expected linear closed-loop system with any specified pole position. And the tuning task is greatly simplified. The EMB clamping force control method based on the high-order all-wheel-drive system has the effect of effectively overcoming nonlinear rigidity and friction load disturbance existing in an electronic mechanical braking system.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile manufacturing, and in particular to an EMB clamping force control method based on a high-order all-wheel drive system. Background Art

[0002] The electronic mechanical brake system completely eliminates the hydraulic system and is an electronically controlled pure mechanical brake system. It has outstanding advantages such as compact structure, rapid response, precise control, and strong compatibility. It is considered to be the best solution for future automotive brake systems. Under the condition of accurately obtaining the braking command, how to accurately and quickly control the clamping force of each wheel under external interference and efficiently design the controller of the closed-loop system with arbitrary pole position expectation are the current research focuses and difficulties of the electronic mechanical brake system.

[0003] In the study of electronic mechanical brake control methods, most of them use traditional three-loop control, sliding mode control, linear anti-disturbance control, neural network control, etc. However, some of the above control methods have complex adjustment parameters, and some use state space models. The state space model emphasizes the state vector, which is suitable for state solution and estimation, and does not provide sufficient convenience for solving the control input. In addition, the nonlinear stiffness and friction load disturbance problems in the electronic mechanical brake system seriously hinder the realization of its high-precision control effect. Therefore, there is an urgent need for a control method with simple adjustment parameters and precise control to achieve fast and accurate follow-up of the clamping force to the target value. Summary of the invention

[0004] In view of the above problems, a method for controlling the EMB clamping force based on a high-order all-wheel drive system is provided to solve the problems existing in the prior art.

[0005] The specific technical solutions are as follows: A method for controlling EMB clamping force based on a high-order all-wheel drive system comprises the following steps: S1. Get the target clamping force value ; S2. Establish a simplified dynamic model of the third-order EMB system for corner control; S3, through the clamping force separation process, transforming it from a model oriented to the corner control to a high-order all-wheel drive model oriented to the clamping force control; S4. Design a controller based on a high-order all-wheel drive control method to obtain the primary composite control law; S5. Design a LESO extended state observer to estimate the unmodeled dynamic and external disturbance variables in the system to obtain a lumped disturbance, and use the lumped disturbance to correct the primary composite control law to obtain a corrected composite control law; S6. Input the modified composite control law into the actual EMB system to control the driver to output the target clamping force value.

[0006] The above-mentioned EMB clamping force control method based on the high-order all-wheel drive system also has the following characteristics: the simplified dynamic model of the EMB system for corner control includes a mechanical subsystem model and an electrical subsystem model, wherein the mechanical subsystem model is: ; The electrical subsystem model is: ; In the formula, and are the position and speed of the motor shaft respectively; is the moment of inertia; is the viscous friction coefficient; is the load moment including the clamping force, external disturbance variables and nonlinear friction; is the number of motor pole pairs; is the magnetic flux; and are the dq axis stator currents respectively; and are the corresponding stator voltages respectively; is the stator resistance; and are the dq axis stator inductances, Output torque for the motor.

[0007] Replace the electrical subsystem model with a first-order inertial system model; ; In the formula, It is the control input of the motor servo driver; for arrive The transfer function of and are the equivalent gain and time constant respectively, which are obtained by using the MATLAB system identification toolbox; the state space equation of the simplified dynamic model of the EMB system for corner control is: .

[0008] The above-mentioned EMB clamping force control method based on the high-order all-wheel drive system also has the following characteristics: the EMB system model is transformed as follows: the classical relationship between the clamping force and the motor angle is often expressed in the form of a cubic polynomial: ; According to the above relationship, the clamping force is separated as follows: ; In the formula, is the clamping force; is the linear part of the clamping force; is the nonlinear part of the clamping force; is the linear proportionality coefficient of the clamping force; is the motor angle corresponding to the EMB braking clearance; combined with the state space equation of the EMB system model for angle control, the state space equation of the simplified dynamic model of the EMB system for clamping force control can be obtained: ; After the EMB system model is transformed accordingly, it is converted into a high-order all-wheel drive model for clamping force control: ; In the formula, the first-order derivative coefficient ; Second-order derivative coefficient ; Non-zero coefficients of control input ; Lumped disturbances including unmodeled dynamics within the system and external disturbance variables .

[0009] The above-mentioned EMB clamping force control method based on the high-order all-wheel drive system also has the following characteristics: based on the high-order all-wheel drive control method, the composite control law of the EMB high-order all-wheel drive model Feedforward compensation controller and feedback closed loop controller constitute: ; The feedforward compensation controller is: ; The feedback closed-loop controller is: ;in, Indicates the clamping force tracking error.

[0010] The above-mentioned EMB clamping force control method based on the high-order all-wheel drive system also has the following characteristics: the feedback closed-loop controller is designed as a feedback closed-loop controller with a dynamic compensator, and the feedback closed-loop controller with a first-order dynamic compensator is: ;in, Represents the vector group consisting of the clamping force error and its derivative, expressed as ; The state vector of a dynamic compensator of order 1 (can be designed to be higher order); Both represent parameter matrices.

[0011] The above-mentioned EMB clamping force control method based on the high-order all-wheel drive system also has the following characteristics: the process of designing the LESO extended state observer is as follows, and the dynamic state space model of the EMB system can be expressed as: ;in ; , , for , , Estimated value of; concentrated disturbance It can estimate the lumped disturbance of unmodeled dynamics and external disturbance variables in the system .

[0012] The state space model can be expanded to the following model: ;in, ; Then the linear extended state observer is: .

[0013] The above-mentioned EMB clamping force control method based on the high-order all-wheel drive system also has the following characteristics: the lumped disturbance is estimated by using the extended state observer to correct the feedforward compensation controller, and the feedforward compensation controller is corrected to: ; The feedback closed-loop controller with a first-order dynamic compensator is modified to: ;in, ; ; .

[0014] In summary, the beneficial effects of this scheme are: In the EMB clamping force control method based on a high-order all-wheel drive system provided by the present invention, the design of the electronic mechanical brake system controller is performed based on the high-order all-wheel drive control method, and its control law can be synthesized in a simple explicit manner to obtain a desired linear closed-loop system with any specified pole position, and only one parameter needs to be determined, which greatly simplifies the tuning task. The EMB clamping force control method based on a high-order all-wheel drive system provided by the present invention has the effect of effectively overcoming the nonlinear stiffness and friction load disturbances existing in the electronic mechanical brake system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the classic relationship between clamping force and motor angle; Figure 2 Block diagram of a high-order all-wheel drive controller based on LESO with a first-order dynamic compensator. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0018] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0019] Figure 1 This is a schematic diagram of the classic relationship between clamping force and motor angle. Figure 2The block diagram of a high-order all-wheel drive controller based on LESO and with a first-order dynamic compensator is shown in Figure 1 and Figure 2 As shown, the EMB clamping force control method based on the high-order all-wheel drive system provided in this embodiment includes the following steps: S1. Get the target clamping force value ; S2. Establish a simplified dynamic model of the third-order EMB system for corner control; S3, through the clamping force separation process, transforming it from a model oriented to the corner control to a high-order all-wheel drive model oriented to the clamping force control; S4. Design a controller based on a high-order all-wheel drive control method to obtain the primary composite control law; S5. Design a LESO extended state observer to estimate the unmodeled dynamic and external disturbance variables in the system to obtain a lumped disturbance, and use the lumped disturbance to correct the primary composite control law to obtain a corrected composite control law; S6. Input the modified composite control law into the actual EMB system to control the driver to output the target clamping force value.

[0020] In the above embodiment, the simplified dynamic model of the EMB system for corner control includes a mechanical subsystem model and an electrical subsystem model, wherein the mechanical subsystem model is: (1); The electrical subsystem model is: (4); where and are the position and speed of the motor shaft respectively; is the moment of inertia; is the viscous friction coefficient; is the load moment including the clamping force, external disturbance variables and nonlinear friction; is the number of motor pole pairs; is the magnetic flux; and are the dq axis stator currents respectively; and are the corresponding stator voltages respectively; is the stator resistance; and are the dq axis stator inductances, Output torque for the motor.

[0021] Replace the electrical subsystem model with a first-order inertial system model; (5); where It is the control input of the motor servo driver; for arrive The transfer function of and are the equivalent gain and time constant respectively, which are obtained by using the MATLAB system identification toolbox; the state space equation of the simplified dynamic model of the EMB system for corner control is: .

[0022] In the above embodiment, the EMB system model is transformed as follows: the classical relationship between the clamping force and the motor angle is often expressed in the form of a cubic polynomial: (2) According to the above relationship, the clamping force is separated as follows: ; In the formula, is the clamping force; is the linear part of the clamping force; is the nonlinear part of the clamping force; is the linear proportionality coefficient of the clamping force; is the motor angle corresponding to the EMB braking clearance; combined with the state space equation of the EMB system model for angle control, the state space equation of the simplified dynamic model of the EMB system for clamping force control can be obtained: ; After the EMB system model is transformed accordingly, it is converted into a high-order all-wheel drive model for clamping force control: (6); where the first-order derivative coefficient is ; Second-order derivative coefficient ; Non-zero coefficients of control input ; Lumped disturbances including unmodeled dynamics within the system and external disturbance variables .

[0023] In the above embodiment, based on the high-order all-wheel drive control method, the composite control law of the EMB high-order all-wheel drive model Feedforward compensation controller and feedback closed loop controller constitute: (7); The feedforward compensation controller is: (8); The feedback closed-loop controller is: (9); among them, Indicates the clamping force tracking error.

[0024] It should be noted that in order to achieve fast, accurate and stable tracking of the clamping force, a composite control law is designed under the high-order all-wheel drive control method to obtain the ideal clamping force error tracking dynamics, and a dynamic compensator is used to provide additional degrees of freedom for improving the control performance. In order to achieve stable tracking of the clamping force, LESO is designed for online clamping force state estimation and compensation of the nonlinear part of the clamping force, the load torque including nonlinear friction, and external disturbances.

[0025] It should also be noted that the above control law is combined with the high-order all-wheel drive model to obtain: (10); The pole positions of the closed-loop system (10) can be determined by choosing To arbitrarily allocate, the characteristic polynomial of (10) is designed as: (11); the control gain can be obtained explicitly as: (12); Order , we can get: (13); among which Representative from arrive The transfer function of .

[0026] It can be clearly seen from the above formula that is a low-pass filter whose filter bandwidth is given by definition. for The filtering value satisfies . Convergence to 0 indicates Converges to 0.

[0027] So far, we have obtained arrive The transfer function of .

[0028] In the above embodiment, the process of designing the LESO extended state observer is as follows, and the EMB system dynamics state space model can be expressed as: ;in ; , , for , , Estimated value of; concentrated disturbance It can estimate the lumped disturbance of unmodeled dynamics and external disturbance variables in the system .

[0029] The state space model can be expanded to the following model: ;in, ; Then the linear extended state observer is: .

[0030] In the above embodiment, the extended state observer is used to estimate the lumped disturbance and to modify the feedforward compensation controller. The feedforward compensation controller is modified as: ; The feedback closed-loop controller is corrected to: ;in, ; ; .

[0031] In the above embodiment, the feedback closed-loop controller is designed as a feedback closed-loop controller with a dynamic compensator: (14); among which represents the vector group consisting of the clamping force error and its derivative, expressed as ; The state vector of a dynamic compensator of order 1 (can be designed to be higher order); Both represent parameter matrices.

[0032] Under the composite control law (7) of (8) and (9), the system (6) has the following closed-loop dynamic system: (15); among which ; The high-order all-wheel drive model corresponding to the closed-loop dynamic system (15) is: (16); among which (17); Assume that the expected characteristic polynomial of model (16) is: (18); get The display solution is as follows: (19); from arrive The transfer function is expressed as follows: (20); Then, when and When , the closed-loop characteristic polynomials given by the composite control law (7) and (18) based on (14) and (8) can ensure that the system (6) reaches consistent final stability and boundedness. Moreover, The dynamics of (21); Proof: From arrive The transfer function (13) and arrive The transfer function (20) can be obtained: (22); when When (23); integrating over [0, t] yields (24); The proof is completed.

[0033] It should also be noted that the LESO is designed as follows: The dynamic state space model of the EMB system can be expressed as: (26); among them ; for Estimated value of; concentrated disturbance The load moment including nonlinear friction, the nonlinear part of the clamping force, external disturbances, etc. can be estimated.

[0034] The state space model can be expanded to the following model: (27); among them ; Then the linear extended state observer can be designed as: (28); Through the pole placement method, the observer coefficients can be obtained as follows: (29); among them is the bandwidth parameter of the linear extended state observer.

[0035] When the derivative of the concentrated disturbance When bounded, there is a finite time and constant , so that (30); where c is a positive integer.

[0036] when The bigger, The smaller the boundary of Estimate the first-order derivative of the clamping force , the second-order derivative and concentrated disturbance , which can greatly reduce the burden of the closed-loop controller and thus achieve higher control accuracy.

[0037] At this point, the LESO design is complete.

[0038] The high-order all-wheel drive controller based on LESO and with first-order dynamic compensator is modified as follows: The feedforward compensation controller is modified as follows: (31); The feedback closed-loop controller with a first-order dynamic compensator is modified to (32); among them ; ; ; So far, the design of the high-order all-wheel drive controller based on LESO and with a first-order dynamic compensator has been completed. The overall control structure of the controller is as follows: Figure 2 As shown; Stability analysis of a high-order all-wheel drive controller based on LESO with a first-order dynamic compensator.

[0039] When the derivative of the concentrated disturbance In EMB, the composite control law (7) is formed by equations (31) and (32), and the controller gain and observer gain are obtained by equations (25) and (29), which can ensure the consistent final stability of the system (6). In addition, The dynamics of (33) Proof: When When , the system (6) under the composite control law (7) composed of equations (31) and (32) has the following closed-loop system dynamics: (34) Among them .

[0040] By analogy with formula (15), the high-order all-wheel drive model corresponding to formula (34) is: (35) From equations (13) and (19), the Laplace form of equation (35) is: (36) When and When (37) Based on (30), [ ,t], we can get (38) The proof is completed; so far, the stability analysis of the high-order all-wheel drive controller based on LESO and with a first-order dynamic compensator is completed.

[0041] Working principle: A high-order full-drive model is used to obtain the composite control law. Since the composite control law is composed of a feedforward compensation controller and a feedback closed-loop controller, the extended state observer is used to correct the feedforward compensation controller and the feedback closed-loop controller to obtain a corrected composite control law. The corrected composite control law is input into the actual EMB system to control the clamping force corresponding to the drive output. Under a certain size of step disturbance, the target clamping force value can also be quickly restored.

[0042] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. An EMB clamping force control method based on a high-order all-wheel drive system, characterized in that: The following steps are involved: S1. Get the target clamping force value ; S2. Establish a simplified dynamic model of the third-order EMB system for corner control; S3, through the clamping force separation process, transforming it from a model oriented to the corner control to a high-order all-wheel drive model oriented to the clamping force control; S4. Design a controller based on a high-order all-wheel drive control method to obtain the primary composite control law; S5. Design a LESO extended state observer to estimate the unmodeled dynamic and external disturbance variables in the system to obtain a lumped disturbance, and use the lumped disturbance to correct the primary composite control law to obtain a corrected composite control law; S6. Input the modified composite control law into the actual EMB system to control the driver to output the target clamping force value.

2. The EMB clamping force control method based on a high-order all-wheel drive system according to claim 1, characterized in that: The simplified dynamic model of the EMB system for corner control includes a mechanical subsystem model and an electrical subsystem model, where the mechanical subsystem model is: ； The electrical subsystem model is: ; In the formula, and are the position and speed of the motor shaft respectively; is the moment of inertia; is the viscous friction coefficient; is the load torque including the clamping force, external disturbance variables and nonlinear friction; is the number of motor pole pairs; is the magnetic flux; and They are Shaft stator current; and are the corresponding stator voltages respectively; is the stator resistance; and They are Shaft stator inductance, Output torque for the motor; Replace the electrical subsystem model with a first-order inertial system model; ; In the formula, It is the control input of the motor servo driver; for arrive The transfer function of and are the equivalent gain and time constant, respectively, which are obtained using the MATLAB system identification toolbox; The state space equation of the simplified dynamic model of the EMB system for corner control is: .

3. The EMB clamping force control method based on a high-order all-wheel drive system according to claim 2, characterized in that: The EMB system model is transformed as follows: The classic relationship between clamping force and motor angle is often expressed in cubic polynomial form: ; According to the above relationship, the clamping force is separated as follows: ; In the formula, is the clamping force; is the linear part of the clamping force; is the nonlinear part of the clamping force; is the linear proportionality coefficient of the clamping force; The EMB brake clearance corresponds to the motor rotation angle; Combining the state space equations of the EMB system model for angle control mentioned above, the state space equations of the simplified dynamic model of the EMB system for clamping force control can be obtained: ; After the EMB system model is transformed accordingly, it is converted into a high-order all-wheel drive model for clamping force control: ; In the formula, the first-order derivative coefficient ; Second-order derivative coefficient ; Non-zero coefficients of control input ; Lumped disturbances including unmodeled dynamics within the system and external disturbance variables .

4. The EMB clamping force control method based on a high-order all-wheel drive system according to claim 3, characterized in that: Based on high-order all-wheel drive control method, composite control law of EMB high-order all-wheel drive model Feedforward compensation controller and feedback closed loop controller constitute: ; The feedforward compensation controller is: ; The feedback closed-loop controller is: ;in, Indicates the clamping force tracking error.

5. The EMB clamping force control method based on a high-order all-wheel drive system according to claim 4, characterized in that: The feedback closed-loop controller is designed as a feedback closed-loop controller with a dynamic compensator: The feedback closed loop controller with first order dynamic compensator is; ;in, represents the vector group consisting of the clamping force error and its derivative, expressed as ; represents the state vector of a dynamic compensator of order 1; Both represent parameter matrices.

6. The EMB clamping force control method based on a high-order all-wheel drive system according to claim 5, characterized in that: The process of designing the LESO extended state observer is as follows, The EMB system dynamics state space model can be expressed as: ； in ; , , for , , Estimated value of; concentrated disturbance It can estimate the lumped disturbance of unmodeled dynamics and external disturbance variables in the system ; The state space model can be expanded to the following model: ； in, ; Then the linearly extended state observer is: 。 7. The EMB clamping force control method based on a high-order all-wheel drive system according to claim 6, characterized in that: The extended state observer is used to estimate the lumped disturbance and to modify the feedforward compensation controller. The feedforward compensation controller is modified as: ； The feedback closed-loop controller with a first-order dynamic compensator is modified to: ； in, ; ; .

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