Method for estimating clamping force of electromechanical braking system without force sensor

Abstract

The invention discloses a clamping force estimation method for an electromechanical brake system without a force sensor. A brake information acquisition module, an electromechanical brake evaluation calculation module, a brake disc contact point detection module and an electromechanical brake system clamping force estimation module are included. The purpose of the invention is to accurately estimate the electromechanical braking clamping force of the force-free sensor through a braking information acquisition module, an electromechanical braking evaluation calculation module, a brake disc contact point detection module and an electromechanical braking system clamping force estimation module.

Description

Technical Field

[0001] The invention relates to a clamping force estimation method for an electronic mechanical brake system without a force-sensitive sensor. Background Art

[0002] The electronic mechanical brake system is a brake system based on electronic control and mechanical execution. Unlike traditional hydraulic or pneumatic brake systems, the electronic mechanical brake system directly controls the actuator through electronic signals, eliminating the dependence on hydraulic oil or air pressure, and has higher response speed and accuracy. However, existing research on electronic mechanical brake systems is mostly based on precise control of clamping force with force sensors, which has the problems of high cost and reduced accuracy after long-term operation. The clamping force control method without force sensors can effectively avoid the above problems. Therefore, the present invention proposes a clamping force estimation method for an electronic mechanical brake system without force sensors. Summary of the invention

[0003] The object of the present invention is to provide a method for estimating the clamping force of an electromechanical brake system without a force sensor, so as to solve the problems faced in the above-mentioned background technology.

[0004] To achieve the above object, the present invention provides the following technical solutions: A method for estimating the clamping force of an electromechanical brake system without force sensor comprises a brake information acquisition module, an electromechanical brake evaluation calculation module, a brake disc contact point detection module and an electromechanical brake system clamping force estimation module;

[0005] The braking information acquisition module is used to collect the braking force request information allocated to a single wheel and the basic information of the single wheel braking system, including the expected braking force Fb of the single wheel. Target , road adhesion coefficient μ road , the vehicle's driving speed V, the wheel's longitudinal speed V x , Wheel brake disc temperature Temp b 、Ambient temperature Temp e , Brake motor temperature Temp m 、Brake motor moment of inertia J m , brake motor speed n and brake motor output torque T m ;

[0006] The electronic mechanical brake evaluation calculation module is used to collect various data and calculate corresponding influencing factors, including:

[0007] Calculate the brake disc temperature influence factor Z1 according to the following formula:

[0008]

[0009] Among them, V represents the speed of the car, V xIndicates the longitudinal speed of the wheel, Temp b Indicates the brake disc temperature, Temp e represents the ambient temperature, Mat represents the material stiffness of the brake disc, and C1, C2, and C3 represent weight coefficients;

[0010] Calculate the brake motor evaluation factor Z2 according to the following formula:

[0011] Z2=Z 21 Z 22 Z 23 Z 24

[0012] Among them, Z 21 represents the temperature influence factor, Z 22 Indicates the output torque influence factor, Z 23 represents the running time impact factor, Z 24 Indicates the influencing factor of motor cooling efficiency;

[0013]

[0014] Among them, Temp m Indicates the brake motor temperature, Temp e Indicates the ambient temperature;

[0015]

[0016] Among them, C m Represents the torque influence weight, T m Indicates the output torque of the brake motor;

[0017]

[0018] Among them, t m represents the time impact weight, T run Indicates the continuous running time of the brake motor;

[0019] Z 24 =η cool

[0020] Among them, η cool Indicates the motor cooling efficiency coefficient;

[0021] The electromechanical brake clamping force influence factor Z is based on the following formula:

[0022]

[0023] Among them, Z1 represents the brake disc temperature influence factor, Z2 represents the brake motor evaluation factor, and β1, β2, and β3 represent weight coefficients.

[0024] The brake disc contact point detection module is used to determine whether the brake caliper reaches the brake disc contact point, including:

[0025] Calculate the target braking torque Tu according to the following formula:

[0026] Tu=Fb Target R road

[0027] Among them, Fb Target represents the expected braking force of a single wheel, R represents the rolling radius of the wheel, μ road It represents the road adhesion coefficient;

[0028] The target clamping force Fn of the electromechanical brake system is calculated according to the following formula:

[0029]

[0030] Where Tu represents the target braking torque, μ represents the friction coefficient of the brake friction pad, and R b Indicates the brake disc radius;

[0031] When the target clamping force Fn is sent to the controller, the controller generates a motor drive signal to make the motor speed n = n max At this time, the chi-square test abnormal data detection method is used to detect the brake motor speed data, and the chi-square test factor X is calculated according to the following formula 2 :

[0032]

[0033] Among them, N a Indicates that a total of N a The motor speed data at each moment, the value can be set freely, E i represents theoretical data, E i =n max , O i Represents the motor speed data collected at the i-th moment, i∈N a .

[0034] The brake disc contact point detection module determines whether the brake caliper reaches the brake disc contact point according to the following formula:

[0035]

[0036] Among them, X 2 represents the chi-square test factor, Cp represents the contact state of the contact point, when Cp=1, it means that the brake caliper reaches the brake disc contact point, when Cp=0, it means that the brake caliper does not reach the brake disc contact point, Δ represents the chi-square test threshold, and the value is obtained by looking up the table.

[0037] The electronic mechanical brake system clamping force estimation module is used to estimate the actual clamping force of the electronic mechanical brake system according to a recursive least squares algorithm, and includes:

[0038] Calculate the friction torque T of the brake motor according to the following formula f :

[0039]

[0040] Among them, T m Indicates the output torque of the brake motor, T c is the Coulomb friction torque, T s represents the maximum static friction torque, w represents the angular velocity of the brake motor, w s represents the Stribeck speed, B v represents the viscous friction coefficient, w s , γ represents the empirical constant;

[0041] The brake motor torque balance model is established according to the following formula:

[0042]

[0043] Among them, J m Indicates the inertia constant of the brake motor, represents the angular acceleration of the brake motor, T m Indicates the output torque of the brake motor, T f Represents the friction torque of the brake motor, T L represents the load torque caused by the estimated clamping force, k cl Indicates the clamping force gain, F cl Indicates the estimated clamping force.

[0044] The electronic mechanical brake system clamping force estimation module establishes the brake motor torque balance model state equation according to the following formula:

[0045]

[0046] Among them, y represents the output value, A represents the state transition, x represents the estimated value, and J m Indicates the inertia constant of the brake motor, represents the angular acceleration of the brake motor, T m Indicates the output torque of the brake motor, T f Represents the friction torque of the brake motor, T L represents the load torque caused by the estimated clamping force, k cl Indicates the clamping force gain, F cl Indicates the estimated clamping force.

[0047] The electronic mechanical brake system clamping force estimation module establishes a cost function V according to the following formula:

[0048]

[0049] Where y(i) represents the output value at the i-th moment, A(i) represents the state transition at the i-th moment, x(k) represents the estimated value at the k-th moment, and λ represents the forgetting factor, which ranges from 0 to 1. When λ=0, it means that the estimation result has nothing to do with the historical data. When 0<λ<1, it means that the influence of the historical data on the estimation is weakened. When λ=1, it means that there is no weakening effect. When λ>1, it means that the influence of the historical data on the estimation is enhanced.

[0050] The expression of the system gain matrix L(k) is obtained according to the following formula:

[0051] L(k)=P(k)A(k)=P(k-1)A(k)(λ+A(k)P(k-1)A(k)) -1

[0052] Among them, A(k) represents the state transfer at the kth moment, P(k) represents the system covariance matrix at the kth moment, P(k-1) represents the system covariance matrix at the k-1th moment, and λ represents the forgetting factor;

[0053] The expression of the system covariance matrix P(k) is obtained according to the following formula:

[0054]

[0055] Among them, A(k) represents the state transition at the kth moment, P(k) represents the system covariance matrix at the kth moment, P(k-1) represents the system covariance matrix at the k-1th moment, L(k) represents the system gain matrix, and λ represents the forgetting factor.

[0056] The electronic mechanical brake system clamping force estimation module calculates the estimated value of x at the kth moment according to the following formula:

[0057] x(k)=x(k-1)+L(k)y(k)-A(k)x(k-1)

[0058] Among them, y(k) represents the output value at the kth moment, A(k) represents the state transition at the kth moment, x(k) represents the estimated value at the kth moment, x(k-1) represents the estimated value at the k-1th moment, and L(k) represents the system gain matrix.

[0059] The electronic mechanical brake system clamping force estimation module calculates the weighted clamping force estimation value Fk according to the following formula cl :

[0060] F cl =x(k)W

[0061] Wherein, x(k) represents the estimated value at the kth moment, and W represents the influencing factor of the electronic mechanical brake clamping force.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] 1. A clamping force estimation method for an electromechanical brake system without a force sensor comprises a brake information acquisition module, an electromechanical brake evaluation calculation module, a brake disc contact point detection module and an electromechanical brake system clamping force estimation module;

[0064] 2. The brake disc contact point detection module of the present invention determines whether the brake caliper reaches the brake disc contact point based on the chi-square detection algorithm, so as to accurately determine the start time of clamping force estimation;

[0065] 3. The clamping force estimation module of the electronic mechanical brake system of the present invention estimates the actual clamping force of the electronic mechanical brake system based on a recursive least squares algorithm, thereby realizing the clamping force estimation without a force sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The present invention will be further described below in conjunction with the accompanying drawings:

[0067] Figure 1 This is a framework diagram of a clamping force estimation method for an electromechanical brake system without a force sensor proposed in the present invention. DETAILED DESCRIPTION

[0068] The present invention is further described in detail below based on the accompanying drawings and specific embodiments.

[0069] like Figure 1 As shown, the present invention is a clamping force estimation method for an electronic mechanical brake system without force sensor, comprising a brake information acquisition module, an electronic mechanical brake evaluation calculation module, a brake disc contact point detection module and an electronic mechanical brake system clamping force estimation module;

[0070] The braking information acquisition module is used to collect the braking force request information allocated to a single wheel and the basic information of the single wheel braking system, including the expected braking force Fb of the single wheel. Target , road adhesion coefficient μ road , the vehicle's driving speed V, the wheel's longitudinal speed V x , Wheel brake disc temperature Temp b 、Ambient temperature Temp e , Brake motor temperature Temp m 、Brake motor moment of inertia J m , brake motor speed n and brake motor output torque T m ;

[0071] The electronic mechanical brake evaluation calculation module is used to collect various data and calculate corresponding influencing factors, including:

[0072] Calculate the brake disc temperature influence factor Z1 according to the following formula:

[0073]

[0074] Among them, V represents the speed of the car, V x Indicates the longitudinal speed of the wheel, Temp b Indicates the brake disc temperature, Temp e represents the ambient temperature, Mat represents the material stiffness of the brake disc, and C1, C2, and C3 represent weight coefficients;

[0075] Calculate the brake motor evaluation factor Z2 according to the following formula:

[0076] Z2=Z 21 Z 22 Z 23 Z 24

[0077] Among them, Z 21 represents the temperature influence factor, Z 22 Indicates the output torque influence factor, Z 23 represents the running time impact factor, Z 24 Indicates the influencing factor of motor cooling efficiency;

[0078]

[0079] Among them, Temp m Indicates the brake motor temperature, Temp e Indicates the ambient temperature;

[0080]

[0081] Among them, C m Represents the torque influence weight, T m Indicates the output torque of the brake motor;

[0082]

[0083] Among them, t m represents the time impact weight, T run Indicates the continuous running time of the brake motor;

[0084] Z 24 =η cool

[0085] Among them, η cool Indicates the motor cooling efficiency coefficient;

[0086] The electromechanical brake clamping force influence factor Z is based on the following formula:

[0087]

[0088] Among them, Z1 represents the brake disc temperature influence factor, Z2 represents the brake motor evaluation factor, and β1, β2, and β3 represent weight coefficients.

[0089] The brake disc contact point detection module is used to determine whether the brake caliper reaches the brake disc contact point, including:

[0090] Calculate the target braking torque Tu according to the following formula:

[0091] Tu=Fb Target R road

[0092] Among them, Fb Target represents the expected braking force of a single wheel, R represents the rolling radius of the wheel, μ road It represents the road adhesion coefficient;

[0093] The target clamping force Fn of the electromechanical brake system is calculated according to the following formula:

[0094]

[0095] Where Tu represents the target braking torque, μ represents the friction coefficient of the brake friction pad, and R b Indicates the brake disc radius;

[0096] When the target clamping force Fn is sent to the controller, the controller generates a motor drive signal to make the motor speed n = n max At this time, the chi-square test abnormal data detection method is used to detect the brake motor speed data, and the chi-square test factor X is calculated according to the following formula 2 :

[0097]

[0098] Among them, N a Indicates that a total of N a The motor speed data at each moment, the value can be set freely, E i represents theoretical data, E i =n max , O i Represents the motor speed data collected at the i-th moment, i∈N a .

[0099] The brake disc contact point detection module determines whether the brake caliper reaches the brake disc contact point according to the following formula:

[0100]

[0101] Among them, X 2 represents the chi-square test factor, Cp represents the contact state of the contact point, when Cp=1, it means that the brake caliper reaches the brake disc contact point, when Cp=0, it means that the brake caliper does not reach the brake disc contact point, Δ represents the chi-square test threshold, and the value is obtained by looking up the table.

[0102] The electronic mechanical brake system clamping force estimation module is used to estimate the actual clamping force of the electronic mechanical brake system according to a recursive least squares algorithm, and includes:

[0103] Calculate the friction torque T of the brake motor according to the following formula f :

[0104]

[0105] Among them, T m Indicates the output torque of the brake motor, T c is the Coulomb friction torque, T s represents the maximum static friction torque, w represents the angular velocity of the brake motor, w s represents the Stribeck speed, B v represents the viscous friction coefficient, w s , γ represents the empirical constant;

[0106] The brake motor torque balance model is established according to the following formula:

[0107]

[0108] Among them, J m Indicates the inertia constant of the brake motor, represents the angular acceleration of the brake motor, T m Indicates the output torque of the brake motor, T f Represents the friction torque of the brake motor, T L represents the load torque caused by the estimated clamping force, k cl Indicates the clamping force gain, F cl Indicates the estimated clamping force.

[0109] The electronic mechanical brake system clamping force estimation module establishes the brake motor torque balance model state equation according to the following formula:

[0110]

[0111] Among them, y represents the output value, A represents the state transition, x represents the estimated value, and J m Indicates the inertia constant of the brake motor, T m Indicates the output torque of the brake motor, represents the angular acceleration of the brake motor, T f Represents the friction torque of the brake motor, T L represents the load torque caused by the estimated clamping force, k cl Indicates the clamping force gain, F cl Indicates the estimated clamping force.

[0112] The electronic mechanical brake system clamping force estimation module establishes a cost function V according to the following formula:

[0113]

[0114] Where y(i) represents the output value at the i-th moment, A(i) represents the state transition at the i-th moment, x(k) represents the estimated value at the k-th moment, and λ represents the forgetting factor, which ranges from 0 to 1. When λ=0, it means that the estimation result has nothing to do with the historical data. When 0<λ<1, it means that the influence of the historical data on the estimation is weakened. When λ=1, it means that there is no weakening effect. When λ>1, it means that the influence of the historical data on the estimation is enhanced.

[0115] The expression of the system gain matrix L(k) is obtained according to the following formula:

[0116] L(k)=P(k)A(k)=P(k-1)A(k)(λ+A(k)P(k-1)A(k)) -1

[0117] Among them, A(k) represents the state transfer at the kth moment, P(k) represents the system covariance matrix at the kth moment, P(k-1) represents the system covariance matrix at the k-1th moment, and λ represents the forgetting factor;

[0118] The expression of the system covariance matrix P(k) is obtained according to the following formula:

[0119]

[0120] Among them, A(k) represents the state transition at the kth moment, P(k) represents the system covariance matrix at the kth moment, P(k-1) represents the system covariance matrix at the k-1th moment, L(k) represents the system gain matrix, and λ represents the forgetting factor.

[0121] The electronic mechanical brake system clamping force estimation module calculates the estimated value of x at the kth moment according to the following formula:

[0122] x(k)=x(k-1)+L(k)y(k)-A(k)x(k-1)

[0123] Among them, y(k) represents the output value at the kth moment, A(k) represents the state transition at the kth moment, x(k) represents the estimated value at the kth moment, x(k-1) represents the estimated value at the k-1th moment, and L(k) represents the system gain matrix.

[0124] The electronic mechanical brake system clamping force estimation module calculates the weighted clamping force estimation value Fk according to the following formula cl :

[0125] F cl =x(k)W

[0126] Wherein, x(k) represents the estimated value at the kth moment, and W represents the influencing factor of the electronic mechanical brake clamping force.

Claims

1. A method for estimating the clamping force of an electromechanical brake system without a force sensor, characterized in that: The method includes the following: Braking information acquisition module, electronic mechanical braking evaluation calculation module, brake disc contact point detection module and electronic mechanical braking system clamping force estimation module; The braking information acquisition module is used to collect the braking force request information allocated to a single wheel and the basic information of the single wheel braking system, including the expected braking force Fb of the single wheel. Target , road adhesion coefficient μ road , the vehicle's driving speed V, the wheel's longitudinal speed V x , Wheel brake disc temperature Temp b 、Ambient temperature Temp e , Brake motor temperature Temp m 、Brake motor moment of inertia J m , brake motor speed n and brake motor output torque T m ; The electronic mechanical brake evaluation calculation module is used to collect various data and calculate corresponding influencing factors, including: Calculate the brake disc temperature influence factor Z1 according to the following formula: Among them, V represents the speed of the car, V x Indicates the longitudinal speed of the wheel, Temp b Indicates the brake disc temperature, Temp e represents the ambient temperature, Mat represents the material stiffness of the brake disc, and C1, C2, and C3 represent weight coefficients; Calculate the brake motor evaluation factor Z2 according to the following formula: Z2=Z 21 WITH 22 WITH 23 WITH 24 Among them, Z 21 represents the temperature influence factor, Z 22 Indicates the output torque influence factor, Z 23 represents the running time impact factor, Z 24 Indicates the influencing factor of motor cooling efficiency; Among them, Temp m Indicates the brake motor temperature, Temp e Indicates the ambient temperature; Among them, C m Represents the torque influence weight, T m Indicates the output torque of the brake motor; Among them, t m represents the time impact weight, T run Indicates the continuous running time of the brake motor; WITH 24 =η cool Among them, η cool Indicates the motor cooling efficiency coefficient; The electromechanical brake clamping force influence factor Z is based on the following formula: Among them, Z1 represents the brake disc temperature influence factor, Z2 represents the brake motor evaluation factor, and β1, β2, and β3 represent weight coefficients.

2. The method for estimating the clamping force of an electromechanical brake system without a force sensor according to claim 1, characterized in that: The brake disc contact point detection module is used to determine whether the brake caliper reaches the brake disc contact point, including: Calculate the target braking torque Tu according to the following formula: Your Facebook Target Rμ road Among them, Fb Target represents the expected braking force of a single wheel, R represents the rolling radius of the wheel, μ road It represents the road adhesion coefficient; The target clamping force Fn of the electromechanical brake system is calculated according to the following formula: Where Tu represents the target braking torque, μ represents the friction coefficient of the brake friction pad, and R b Indicates the brake disc radius; When the target clamping force Fn is sent to the controller, the controller generates a motor drive signal to make the motor speed n = n max At this time, the chi-square test abnormal data detection method is used to detect the brake motor speed data, and the chi-square test factor X is calculated according to the following formula 2 : Among them, N a Indicates that a total of N a The motor speed data at each moment, the value can be set freely, E i represents theoretical data, E i =n max , O i Represents the motor speed data collected at the i-th moment, i∈N a .

3. The method for estimating the clamping force of an electromechanical brake system without a force sensor according to claim 1, characterized in that: The brake disc contact point detection module determines whether the brake caliper reaches the brake disc contact point according to the following formula: Among them, X 2 represents the chi-square test factor, Cp represents the contact state of the contact point, when Cp=1, it means that the brake caliper reaches the brake disc contact point, when Cp=0, it means that the brake caliper does not reach the brake disc contact point, Δ represents the chi-square test threshold, and the value is obtained by looking up the table.

4. The method for estimating the clamping force of an electromechanical brake system without a force sensor according to claim 1, characterized in that: The electronic mechanical brake system clamping force estimation module is used to estimate the actual clamping force of the electronic mechanical brake system according to a recursive least squares algorithm, and includes: Calculate the friction torque T of the brake motor according to the following formula f : Among them, T m Indicates the output torque of the brake motor, T c is the Coulomb friction torque, T s represents the maximum static friction torque, w represents the angular velocity of the brake motor, w s represents the Stribeck speed, B v represents the viscous friction coefficient, w s , γ represents the empirical constant; The brake motor torque balance model is established according to the following formula: Among them, J m Indicates the inertia constant of the brake motor, represents the angular acceleration of the brake motor, T m Indicates the output torque of the brake motor, T f Represents the friction torque of the brake motor, T L represents the load torque caused by the estimated clamping force, k cl Indicates the clamping force gain, F cl Indicates the estimated clamping force.

5. The method for estimating the clamping force of an electromechanical brake system without a force sensor according to claim 1, characterized in that: The electronic mechanical brake system clamping force estimation module establishes the brake motor torque balance model state equation according to the following formula: Among them, y represents the output value, A represents the state transition, x represents the estimated value, and J m Indicates the inertia constant of the brake motor, T m Indicates the output torque of the brake motor, represents the angular acceleration of the brake motor, T f Represents the friction torque of the brake motor, T L represents the load torque caused by the estimated clamping force, k cl Indicates the clamping force gain, F cl Indicates the estimated clamping force.

6. The method for estimating the clamping force of an electromechanical brake system without a force sensor according to claim 1, characterized in that: The electronic mechanical brake system clamping force estimation module establishes a cost function V according to the following formula: Where y(i) represents the output value at the i-th moment, A(i) represents the state transition at the i-th moment, x(k) represents the estimated value at the k-th moment, and λ represents the forgetting factor, which ranges from 0 to 1. When λ=0, it means that the estimation result has nothing to do with the historical data. When 0<λ<1, it means that the influence of the historical data on the estimation is weakened. When λ=1, it means that there is no weakening effect. When λ>1, it means that the influence of the historical data on the estimation is enhanced. The expression of the system gain matrix L(k) is obtained according to the following formula: L(k)=P(k)A(k)=P(k-1)A(k)(λ+A(k)P(k-1)A(k)) -1 Among them, A(k) represents the state transfer at the kth moment, P(k) represents the system covariance matrix at the kth moment, P(k-1) represents the system covariance matrix at the k-1th moment, and λ represents the forgetting factor; The expression of the system covariance matrix P(k) is obtained according to the following formula: Among them, A(k) represents the state transition at the kth moment, P(k) represents the system covariance matrix at the kth moment, P(k-1) represents the system covariance matrix at the k-1th moment, L(k) represents the system gain matrix, and λ represents the forgetting factor.

7. The method for estimating the clamping force of an electromechanical brake system without a force sensor according to claim 1, characterized in that: The electronic mechanical brake system clamping force estimation module calculates the estimated value of x at the kth moment according to the following formula: x(k)=x(k-1)+L(k)y(k)-A(k)x(k-1) Among them, y(k) represents the output value at the kth moment, A(k) represents the state transition at the kth moment, x(k) represents the estimated value at the kth moment, x(k-1) represents the estimated value at the k-1th moment, and L(k) represents the system gain matrix.

8. The method for estimating the clamping force of an electromechanical brake system without a force sensor according to claim 1, characterized in that: The electronic mechanical brake system clamping force estimation module calculates the weighted clamping force estimation value Fk according to the following formula cl : Fk cl =x(k)W Wherein, x(k) represents the estimated value at the kth moment, and W represents the influencing factor of the electronic mechanical brake clamping force.

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