Actuator clamping force determination method, device and equipment and readable storage medium

Abstract

The invention provides an actuator clamping force determination method, device and equipment and a readable storage medium, and relates to the technical field of automobiles. The method comprises the steps that according to the stress conditions of a motor, a ball bearing, a planetary gear set, a thrust bearing, a ball screw and a brake pad in the forward clamping and reverse releasing process of the actuator, a stress analysis model of the actuator in the forward clamping and reverse releasing process is constructed; according to the stress analysis model, the equivalent coulomb friction coefficient during forward clamping and reverse releasing, the clamping force during forward clamping and the clamping force during reverse releasing are obtained; and according to the equivalent coulomb friction coefficients during forward clamping and reverse releasing, the clamping force during forward clamping and the clamping force during reverse releasing, the target clamping force of the actuator at the target angular displacement is determined. According to the method and the device, the estimation accuracy of the target clamping force of the actuator at the target angular displacement is improved, so that the accurate updating of the rigidity characteristic is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of automobiles, and particularly relates to a method, device, equipment and readable storage medium for determining the clamping force of an actuator. Background Art

[0002] An Electronic Mechanical Brake (EMB) uses an electronic controller and a mechanical actuator to directly apply a braking force to the wheel end, and precise control of the clamping force of the electronic mechanical brake is required during the braking process.

[0003] Currently, a pressure sensor-free control scheme is used to achieve precise control of the clamping force of the electronic mechanical brake, which mainly performs angle closed-loop control based on regularly updated stiffness characteristics.

[0004] However, for the current pressure sensor-free control scheme, the accuracy of stiffness characteristic update is poor, resulting in low control accuracy of the clamping force of the electronic mechanical brake. Summary of the Invention

[0005] Embodiments of the present invention provide a method, device, equipment and readable storage medium for determining the clamping force of an actuator, which can obtain accurate clamping force and improve the accuracy of stiffness characteristic update of the actuator.

[0006] In a first aspect, embodiments of the present invention provide a method for determining the clamping force of an actuator, where the actuator includes a motor, a ball bearing, a planetary gear set, a thrust bearing, a ball screw, and a brake pad; wherein, the motor is connected to the ball bearing, the ball bearing is connected to the planetary gear set, the planetary gear set is connected to the thrust bearing, and the thrust bearing is connected to the ball screw; when the motor rotates, the ball screw drives the nut to move on the nut guide rail to drive the brake pad to clamp or release the brake disc; the method includes:

[0007] According to the force conditions of the motor, ball bearing, planetary gear set, thrust bearing, ball screw, and brake pad during the process of the actuator clamping the brake disc forward and releasing it backward, establish a force analysis model of the actuator during the forward clamping and backward releasing processes;

[0008] According to the force analysis model, obtain the equivalent Coulomb friction coefficient during forward clamping and backward releasing, the clamping force during forward clamping, and the clamping force during backward releasing;

[0009] According to the equivalent Coulomb friction coefficient during forward clamping and backward releasing, the clamping force during forward clamping, and the clamping force during backward releasing, determine the target clamping force of the actuator at the target angular displacement.

[0010] In an implementable embodiment, obtaining the equivalent Coulomb friction coefficient during forward clamping and reverse release according to the force analysis model includes:

[0011] According to the force analysis model, obtain the first dynamic equation of the ball screw and nut during forward clamping, the second dynamic equation of the ball screw and nut during reverse release, the relationship between the ball screw rotation angle and nut displacement, and the total friction torque during forward clamping and reverse release. The total friction torque includes the equivalent friction torque generated by motor friction torque, thrust bearing friction torque, ball screw ramp inclined plane friction, contact force separation, and housing guide rail friction;

[0012] According to the relationship between the ball screw rotation angle and nut displacement, the first dynamic equation, the second dynamic equation, and the total friction torque during forward clamping and reverse release, determine the first mapping relationship between the motor current and the clamping force during forward clamping and the second mapping relationship between the motor current and the clamping force during reverse release;

[0013] According to the first mapping relationship and the second mapping relationship, obtain the equivalent Coulomb friction coefficient during forward clamping and reverse release.

[0014] In an implementable embodiment, obtaining the first dynamic equation and the second dynamic equation includes:

[0015] According to the force analysis model, determine the driving force applied by the planetary gear set to the ball screw, the thrust bearing friction force, the contact force between the screw and the nut, the clamping force, and the screw lead angle;

[0016] Obtain the inertia of the planet gear, the inertia of the sun gear, the inertia of the screw, the total transmission ratio of the planetary gear set, the translational displacement of the ball screw and nut along their axis, the total mass of the piston and brake pad in the actuator, the nut mass, and the pitch radius of the ball screw;

[0017] According to the driving force, thrust bearing friction force, contact force, clamping force, screw lead angle, inertia of the planet gear, inertia of the sun gear, inertia of the screw, total transmission ratio of the planetary gear set, translational displacement, total mass of the piston and brake pad, nut mass, and pitch radius, determine the first dynamic equation and the second dynamic equation.

[0018] In an implementable embodiment, the first dynamic equation is:

[0019]

[0020] The second dynamic equation is:

[0021]

[0022] In the above formula, J pg , J sg and J s are the inertia of the planet gear, the inertia of the sun gear, and the inertia of the lead screw respectively. i g is the total transmission ratio of the planetary gear set. x s and y n are the translational displacements of the ball screw and the nut along their axes. α is the lead angle of the lead screw. m n is the mass of the nut. m p is the total mass of the piston and the brake pad. F s is the driving force applied by the planetary gear set to the ball screw. f b is the frictional force of the thrust bearing. N s is the contact force between the screw and the nut. f s is the rolling frictional force of the ball. F p is the clamping force. f n is the frictional force between the nut and the housing guide rail.

[0023] In an achievable embodiment, the first mapping relationship is:

[0024]

[0025] In the above formula, F p,A is the clamping force during clamping. i g is the total transmission ratio of the planetary gear set. η g is the transmission efficiency of the planetary gear. r s is the pitch radius of the ball screw. K m is the motor torque coefficient. i q,A is the q-axis current of the motor during forward clamping. G t,A is the equivalent Coulomb friction coefficient during forward clamping;

[0026] The second mapping relationship is:

[0027]

[0028] In the above formula, F p,R is the clamping force during forward release. G t,B is the equivalent Coulomb friction coefficient during reverse release.

[0029] In an achievable embodiment, the obtaining of the total frictional torque during clamping and release includes:

[0030]

[0031] In the above formula, T f,A is the total frictional torque during clamping, Tf,R is the total frictional torque at release, G t1,A is the Coulomb friction corresponding to the motor output torque term during clamping, G t2,A is the Coulomb friction corresponding to the clamping force term during clamping, G t1,R is the Coulomb friction corresponding to the motor output torque term during release, G t2,R is the Coulomb friction corresponding to the clamping force term during release, K m is the motor torque coefficient, i q,A is the q-axis current of the motor during clamping, i q,R is the q-axis current of the motor during release, F p,A is the clamping force during clamping, F p,R is the clamping force during release.

[0032] In an implementable embodiment, determining the target clamping force of the actuator at the target angular displacement according to the equivalent Coulomb friction coefficients, the first clamping force, and the first clamping force during forward clamping and reverse release includes:

[0033]

[0034] In the above formula, G t,A and G t,R are the equivalent Coulomb friction coefficients during clamping and release respectively, F p,A is the clamping force during clamping, F p,B is the clamping force during release, F p is the target clamping force.

[0035] In a second aspect, an embodiment of the present invention provides a clamping force determination device for an actuator, including:

[0036] A model construction module, configured to construct a force analysis model of the actuator during forward clamping and reverse release according to the force conditions of the motor, ball bearings, planetary gear sets, thrust bearings, ball screws, and brake pads during the process of the actuator forward clamping and reverse releasing the brake disc;

[0037] An acquisition module, configured to acquire the equivalent Coulomb friction coefficients during forward clamping and reverse release, the clamping force during forward clamping, and the clamping force during reverse release according to the force analysis model;

[0038] A determination module, configured to determine the target clamping force of the actuator at the target angular displacement according to the equivalent Coulomb friction coefficients during forward clamping and reverse release, the clamping force during forward clamping, and the clamping force during reverse release.

[0039] In a third aspect, an embodiment of the present invention provides an electronic device, including: a processor and a memory storing computer program instructions, where when the processor executes the computer program instructions, the steps of the above method are implemented.

[0040] In a fourth aspect, an embodiment of the present invention provides a computer storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the method described above are implemented.

[0041] The method, device, equipment, and readable storage medium for determining the clamping force of the actuator provided by the embodiments of the present invention analyze the force conditions of the motor, ball bearing, planetary gear set, thrust bearing, ball screw, and brake pads during the process of the actuator clamping forward and releasing the brake disc in reverse, and construct a force analysis model, which can improve the estimation accuracy of the target clamping force of the actuator at the target angular displacement, so as to realize the accurate update of the stiffness characteristics and ensure the accuracy of the clamping force control without a pressure sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Brief introductions of the accompanying drawings to be used are provided. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0043] Figure 1 It is a schematic structural diagram of an actuator in the electro-mechanical braking system provided by the embodiments of the present application;

[0044] Figure 2 It is a working principle flowchart of the control system for stiffness characteristic update provided by the embodiments of the present application;

[0045] Figure 3A It is a schematic flowchart of the method for determining the clamping force of the actuator provided by the embodiments of the present application;

[0046] Figure 3B It is a schematic diagram of the plane motion force analysis model of the ball screw provided by the embodiments of the present application;

[0047] Figure 4 It is a schematic flowchart of the equivalent Coulomb friction coefficient estimation during forward clamping and reverse release provided by the embodiments of the present application;

[0048] Figure 5 It is a schematic flowchart of the control system implementing the stiffness update function provided by the embodiments of the present application;

[0049] Figure 6 It is a schematic structural diagram of the device for determining the clamping force of the actuator provided by the embodiments of the present application;

[0050] Figure 7Schematic diagram of the hardware structure of the electronic device provided by the embodiment of the present invention. Detailed implementation manners

[0051] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present invention, rather than to limit the present invention. For those skilled in the art, the present invention can be implemented without some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by showing examples of the present invention.

[0052] It should be noted that, in this document, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, elements defined by the statement "comprising..." do not preclude the existence of additional identical elements in the process, method, article or device comprising the said elements.

[0053] The Electronic Mechanical Brake (EMB) is one of the research hotspots in the field of by-wire chassis. It uses an electronic controller and a mechanical actuator to directly apply braking force to the wheel end, significantly reducing system components. At the same time, it has a faster response speed and higher wheel-end execution flexibility, which is a highly integrated solution for the braking system. To achieve precise control of the clamping force of the electronic mechanical brake, a pressure sensor needs to be integrated in the limited space of the actuator. However, its single cost is relatively high, and it is easily affected by factors such as temperature, friction hysteresis, and assembly neutrality, resulting in poor reliability. Therefore, sensorless control is a key technology that urgently needs to be broken through. Currently, the mainstream solution for sensorless control is to perform corner closed-loop control based on the stiffness characteristics updated regularly. An accurate and robust stiffness characteristic update method is a prerequisite for achieving clamping force control. In related technologies, the stiffness characteristic update mainly includes the following methods: (1) Using the torque balance equation or state observer to estimate and update the stiffness characteristics in real time requires accurate calibration of the system friction characteristics, and the estimation noise is relatively large. (2) The estimation method of superimposing high-frequency signals to eliminate friction will generate relatively serious jitter and noise. (3) The estimation method of using forward and reverse clamping and releasing to eliminate friction does not consider the friction asymmetry caused by the ball screw. At the same time, the automatic calibration and update of the friction coefficient and stiffness are also key issues.

[0054] In view of the above problems, based on the estimation method of using forward and reverse clamping and releasing to eliminate friction, the embodiment of the present application proposes a method for determining the clamping force of the actuator, which can more accurately determine the clamping force for stiffness update, consider the stiffness update with friction asymmetry, and design a stiffness update function module. The friction asymmetry caused by the actuator, especially the ball screw, is modeled, and its asymmetry change law is calibrated using endurance tests, so as to obtain the accurate target clamping force of the actuator at the target angular displacement, improve the robustness of the algorithm during the entire life cycle of the actuator, and achieve accurate update of the stiffness characteristics. Using the updated stiffness characteristics, accurate control of the clamping force of the actuator without a pressure sensor can be realized.

[0055] Next, the technical solution of the present application will be described in detail through specific embodiments. It should be noted that these specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments.

[0056] In the electronic mechanical braking system, the motor drives a speed reduction and torque increasing mechanism (such as a planetary gear set), and the speed reduction and torque increasing mechanism drives a motion conversion mechanism (such as a ball screw). The lead screw nut moves linearly to push the brake pad and press the brake disc. Exemplarily, Figure 1 is a schematic structural diagram of the actuator in the electronic mechanical braking system provided by the embodiment of the present application, as Figure 1As shown in the figure, it includes a motor, a ball bearing 11, a planetary gear set 12, a force sensor 13, a thrust bearing 14, a ball screw, a brake pad 15 and a caliper 17. Among them, the motor drives the ball bearing 11 to drive the planetary gear set 12 to move. The planetary gear set 12 drives the thrust bearing 14 to push the ball screw to move on the nut guide, so that the brake pad 15 clamps or releases the brake disc 16, thereby realizing braking.

[0057] In this embodiment, the stiffness update scheme of the actuator can run in the control system for stiffness characteristic update. Exemplarily, Figure 2 is the working principle flowchart of the control system for stiffness characteristic update provided by the embodiment of the present application. As Figure 2 shown, the control system for stiffness characteristic update mainly includes the following functional modules:

[0058] (1) Upper-level control system: It can judge whether to enable according to the friction coefficient calibration and stiffness curve update requirements and the current states of the vehicle and the actuator. When the function is enabled, it sends a clamping / releasing instruction to the execution control system.

[0059] (2) Piston position calculation: Calculate the current piston position according to the motor angle and the parameters of the brake actuator. Since the motor position sensor can sense the motor angle in real time, the piston position can be obtained by integrating according to the actuator parameters:

[0060]

[0061] In the above formula, S is the piston position, Θ is the mechanical angle of the motor rotation, K is the transmission ratio of the speed reduction and torque increase mechanism, p is the thread pitch, and r is the pitch circle radius.

[0062] (3) Contact point identification: Select to enable / disable the contact point identification function according to the clamping / releasing instruction of the upper-level control system. When the function is enabled, refresh the contact point according to the actuator current and the piston position.

[0063] (4) Clamping / releasing control: When the upper-level control system issues a clamping / releasing instruction, drive the motor to rotate forward / backward according to the piston position and the actuator clamping force to complete the closed-loop clamping / releasing control of the actuator position.

[0064] (5) Clamping force estimation: Estimate the motor torque according to the motor current, and estimate the clamping force by the transmission ratio of the gear set and the lead of the ball screw.

[0065] (6) Friction coefficient estimation: Before the actuator is taken offline, perform several clamping and releasing operations, use an external force sensor to obtain the clamping force signal, estimate the friction coefficient from the current and the actual clamping force, and store the friction coefficients of different current segments during the clamping / releasing process respectively.

[0066] (7) Stiffness update: After the actuator is powered on, it performs several clamping and releasing operations, reads the friction coefficients at different current segments, superimposes the estimated clamping forces at the same piston displacement according to the asymmetric friction coefficients of clamping / releasing, eliminates the forward and reverse friction terms, obtains the accurate stiffness curve and stores it for subsequent closed-loop control without a pressure sensor.

[0067] In this embodiment, the stiffness update function is divided into three stages: ① Clamping and releasing; ② Data point storage; ③ Online fitting. First, perform a clamping and releasing operation according to the displacement ramp command and identify the contact point. Secondly, select several data points of the relative displacement according to the identified contact point. Finally, read the data points, eliminate the friction according to the calibrated asymmetric friction relationship to obtain the estimated clamping force, and perform an online fit to obtain the coefficients of the cubic curve of the stiffness characteristic. This will be described in detail through some embodiments below.

[0068] Exemplarily, Figure 3A is a schematic flowchart of the method for determining the clamping force of the actuator provided in the embodiment of the present application. Combining the above Figure 1 , this actuator is mainly used to clamp or release the brake disc of the wheel. This actuator can be mounted on a vehicle for braking the wheels on the vehicle. Specifically, this actuator includes a motor, a ball bearing, a planetary gear set, a thrust bearing, a ball screw, and a brake pad; wherein, the motor is connected to the ball bearing, the ball bearing is connected to the planetary gear set, the planetary gear set is connected to the thrust bearing, and the thrust bearing is connected to the ball screw; when the motor rotates, the ball screw drives the nut to move on the nut guide rail to drive the brake pad to clamp or release the brake disc. As Figure 3A shown, the method specifically includes the following steps:

[0069] Step S310: According to the force conditions of the motor, ball bearing, planetary gear set, thrust bearing, ball screw, and brake pad during the forward clamping and reverse releasing of the brake disc by the actuator, construct a force analysis model of the actuator during the forward clamping and reverse releasing processes.

[0070] In this embodiment, during the vehicle driving process, when the actuator clamps the brake disc, the wheel speed slowly decreases, and when the actuator releases the brake disc, the wheel speed slowly recovers.

[0071] In this embodiment, the control instruction can be issued by the driver or the intelligent driving system to control the actuator to clamp or release. Among them, clamping and releasing are two relative states. After the clamping state is completed, it enters the releasing state, and after the releasing state is completed, it enters the clamping state.

[0072] In this embodiment, referring to the above Figure 1, the force sensor can be arranged close to the thrust bearing. The electromechanical brake needs to achieve braking by adjusting the pressing degree between the brake disc and the brake pads. At this time, the force sensor will display the braking force of the current wheel end actuator, that is, the actual clamping force. In addition, the current-estimated clamping force can refer to a clamping force estimated according to the current of the motor in the actuator during the clamping or releasing process of the actuator.

[0073] Exemplarily, Figure 3B is a schematic diagram of the planar motion force analysis model of the ball screw provided by the embodiment of the present application. As Figure 3B shown, the ball 32 rolls in the nut guide 31, resulting in friction asymmetry of the ball screw.

[0074] Among them, except for the pad and the caliper stiffness, it is assumed that all mechanical components are rigid. The electrical equation and mechanical equation of the motor are as follows:

[0075]

[0076] In the above formula, u d and u q are the d-axis (excitation axis) and q-axis (torque axis) voltages of the motor respectively, i d and i q are the d-axis and q-axis currents of the motor respectively, L d and L q are the d-axis and q-axis inductances of the motor respectively, R s is the stator resistance, K m is the motor torque coefficient, K m =3 / 2P n Ψ f ,Ψ f is the permanent magnet flux linkage, θ e and θ m are the electrical angle and mechanical angle of the motor respectively, θ e =θ m P n ,P n is the number of poles, J m is the moment of inertia of the motor, T mf and T L are the friction torque and load torque of the motor respectively, B m and τ m are the viscous friction coefficient of the motor and the Coulomb friction torque independent of the load respectively.

[0077] Among them, the planetary gear set is modeled with an ideal transmission ratio including transmission efficiency as follows:

[0078] T s =i g η g T L

[0079]

[0080] In the above formula, T s is the driving torque of the lead screw, i g is the total transmission ratio of the planetary gear set, η g is the gear transmission efficiency, θ s is the rotation angle of the lead screw.

[0081] Step S320: According to the force analysis model, obtain the equivalent Coulomb friction coefficient during forward clamping and reverse release, the clamping force during forward clamping, and the clamping force during reverse release.

[0082] In this embodiment, the friction coefficient of the ball screw during the clamping and releasing processes of the actuator is asymmetric, which affects the accuracy of the final clamping force control. Referring to the above Figure 1 , assuming that the friction coefficient at a certain position point W1 where the thrust bearing pushes the ball screw to translate forward to drive the brake pad to clamp the brake disc is A, and the friction coefficient at the same position point W1 where the thrust bearing drives the ball screw to translate backward to drive the brake pad to release the brake disc is B, then A and B are asymmetric.

[0083] In this embodiment, after several automatic clamping and releasing operations, the friction coefficient can be estimated and averaged from the clamping force and the actual clamping force by the current, and the positive and negative asymmetric friction coefficients in different current segments are stored.

[0084] Exemplarily, the motor current during the clamping and releasing processes of the actuator can be obtained, and at the same time, the average value of the clamping force estimated according to the current and the actual clamping force is taken to obtain the average clamping force, and then the friction coefficient corresponding to the current is determined according to the mapping relationship between the clamping force and the current.

[0085] Step S330: Determine the target clamping force of the actuator at the target angular displacement according to the equivalent Coulomb friction coefficient during forward clamping and reverse release, the clamping force during forward clamping, and the clamping force during reverse release. In this embodiment, after the actuator is powered on, the stiffness update is enabled, and the target clamping force is estimated using the motor current and the friction coefficient.

[0086] Among them, several automatic clamping and releasing operations are performed, and the estimated clamping forces at the same piston position are superimposed according to the asymmetric friction coefficient to eliminate the positive and negative friction terms and take the average value to obtain a more accurate target clamping force at this angular displacement, and an accurate stiffness curve is obtained and stored based on this target clamping force.

[0087] In this embodiment, the stiffness characteristic reflects the relationship between the force applied to the actuator and its deformation. By continuously updating the stiffness characteristic, the clamping force state can be indirectly understood. Combining with the angular position closed-loop control (i.e., adjusting the actuator's action according to the deviation between the set target angular position and the actual angular position), the control of the clamping force can be achieved. In an electromechanical brake, there is an inherent relationship between the stiffness characteristic of the actuator and the clamping force it outputs. For example, when a certain driving signal is input to the actuator, the relationship between the displacement generated and the corresponding clamping force reflects the stiffness situation. If the stiffness is large, a greater clamping force can be generated under the same displacement; conversely, the clamping force is smaller.

[0088] In this embodiment, since the electromechanical brake will be affected by various factors during actual operation, such as the change in environmental temperature may cause the material to expand or contract, the wear between components will change the structure, and the fatigue caused by long-term use, etc., these will all change the stiffness characteristic of the actuator. Therefore, it is necessary to update it regularly to ensure the accuracy and reliability of inferring the clamping force based on the stiffness characteristic. For example, when using an electromechanical brake in an environment with a large temperature difference, if the stiffness characteristic is not updated in time, there may be a large deviation when controlling the clamping force according to the initially set stiffness value, and precise control cannot be achieved.

[0089] In this embodiment, the angular position closed-loop control can be performed based on the regularly updated stiffness characteristic to achieve the braking of the wheel. Among them, the angular position closed-loop control is a control method that adjusts the actuator's action in real time by monitoring the rotation angle of the actuator to achieve precise control of the clamping force. Specifically, the angular position closed-loop control can set a target angular position, corresponding to the expected clamping force magnitude. During the execution process, the sensor will feedback the actual angular position of the actuator in real time, and the control system will compare the actual angular position with the target angular position, and adjust the actuator's action according to the deviation between the two. For example, if the actual angular position is smaller than the target angular position, it means that the predetermined clamping degree has not been reached, and the control system will drive the actuator to continue rotating to increase the clamping force; conversely, if the actual angular position exceeds the target angular position, it means that the clamping force is too large, and the control system will correspondingly reduce the actuator's action to lower the clamping force.

[0090] Among them, the corner closed-loop control combined with the stiffness characteristic update can closely link the corner with the clamping force by using the stiffness characteristic. Through the accurate stiffness characteristic updated regularly, the corresponding clamping force magnitude can be calculated more precisely according to the current corner situation, and then high-precision adjustment of the clamping force can be achieved in the closed-loop control. For example, given the currently updated stiffness value and the angle of rotation of the actuator, the clamping force acting on the braking object at this time can be accurately determined based on the mathematical relationship between them (determined by the stiffness characteristic), and then the subsequent actions of the actuator can be adjusted according to the difference between the target clamping force and the actually feedback clamping force (reflected by the corner), so as to achieve the purpose of accurately controlling the clamping force.

[0091] In addition, in some embodiments, the stiffness update after the actuator is powered on needs to judge the states of the actuator, the brake disc and the vehicle. To ensure the accuracy of the update, the stiffness update should be carried out when the actuator reports no fault, the temperature of the brake disc is normal, and the vehicle is in a stationary state.

[0092] In the embodiments of the present application, by analyzing the force conditions of the motor, ball bearing, planetary gear set, thrust bearing, ball screw and brake pads during the forward clamping and reverse release of the brake disc by the actuator, a force analysis model is constructed, which can improve the estimation accuracy of the target clamping force of the actuator at the target angular displacement, so as to realize the accurate update of the stiffness characteristic and ensure the accuracy of the clamping force control without a pressure sensor.

[0093] In some embodiments, Figure 4 is a schematic diagram of the equivalent Coulomb friction coefficient estimation process during forward clamping and reverse release provided by the embodiments of the present application. In order to obtain the dynamic mapping relationship between the motor current and the clamping force during forward and reverse directions, especially the friction asymmetry caused by the ball screw, it is necessary to perform partial modeling on the actuator. As Figure 4 shown, it includes the following steps:

[0094] Step S410: According to the force analysis model, obtain the first dynamic equation of the ball screw and the nut during the clamping process and the second dynamic equation of the ball screw and the nut during the release process.

[0095] In this embodiment, the above Figure 3B can be continued to be referred to, and the ball screw is expanded into a planar motion force analysis model as shown in Figure 3B . The rotational motion of the ball screw is converted into planar translation. During forward clamping and reverse release, the external forces of the ball screw include the driving force F s applied by the gear set, the thrust bearing friction f b , the contact force N s between the screw and the nut, and the ball rolling friction f s . The external force of the nut also includes the clamping force Fp and the frictional force f between the nut and the housing guide rail n .

[0096] Among them, r s is the pitch radius of the ball screw, r s = L / 2π, where L is the lead of the ball screw.

[0097] In some embodiments, according to the force analysis model, the driving force Fs applied by the planetary gear set to the ball screw, the frictional force fb of the thrust bearing, the contact force Ns between the screw and the nut, the clamping force Fp and the lead angle α of the screw rod can be analyzed. At the same time, further combined with the inertia J of the planet gear pg , the inertia J of the sun gear sg , the inertia J of the screw rod s , the total transmission ratio i of the planetary gear set g , the translational displacement of the ball screw and the nut along their axes, the total mass m of the piston and the brake pad in the actuator p , the mass m of the nut n and the pitch radius r of the ball screw s , the first dynamic equation and the second dynamic equation are constructed.

[0098] Exemplarily, when clamping forward, the first dynamic equation of the ball screw and the nut is expressed as:[[]]

[0099]

[0100] When releasing in reverse, the second dynamic equations of the ball screw and the nut are respectively expressed as:[[]]

[0101]

[0102] In the above formula, J pg , J sg and J s are the inertia of the planet gear, the inertia of the sun gear and the inertia of the screw rod respectively, i g is the total transmission ratio of the planetary gear set, x s and y n are the translational displacements of the ball screw and the nut along their axes, α is the lead angle of the screw rod, m n is the mass of the nut, m p is the total mass of the piston and the brake pad, F s is the driving force applied by the planetary gear set to the ball screw, f b is the frictional force of the thrust bearing, N s is the contact force between the screw and the nut, f s is the rolling frictional force of the ball, F p is the clamping force, f n is the frictional force between the nut and the housing guide rail.

[0103] Step S420: Obtain the relationship between the ball screw rotation angle and the nut displacement.

[0104] In this embodiment, the thrust bearing friction and the guide rail friction are respectively modeled (for example, using the Karnopp friction model):

[0105]

[0106] In the above formula, D b , C b and G b are respectively the viscous friction coefficient of the thrust bearing, the Coulomb friction torque independent of the load, and the Coulomb friction coefficient. D n , C n and G n are respectively the viscous friction coefficient of the guide rail, the Coulomb friction force independent of the load, and the Coulomb friction coefficient. T nb and F ns are the maximum static friction torque of the thrust bearing and the maximum static friction of the guide rail independent of the load. θ s is the rotation angle of the ball screw.

[0107] In some embodiments, the lead angle of the lead screw, the ball screw, and the translational displacement of the nut along its axis can be obtained; then, based on the lead angle of the lead screw, the ball screw, and the translational displacement of the nut along its axis, the relationship between the ball screw rotation angle and the nut displacement is determined. Exemplarily, the relationship between the screw rotation angle and the nut displacement:

[0108] y n = x s tanα = θ s r s tanα

[0109] In the above formula, θ s is the rotation angle of the ball screw, r s is the pitch radius of the ball screw, α is the lead angle of the screw, x s and y n are the translational displacements of the screw and the nut along their axes.

[0110] Step S430: Obtain the total friction torque during the clamping and releasing processes.

[0111] Among them, the total friction torque includes the motor friction torque, the thrust bearing friction torque, the ball screw ramp inclined plane friction, the equivalent friction torque generated by the separation of the contact force, and the housing guide rail friction.

[0112] In this embodiment, by combining the dynamic equations of the ball screw and the nut for the relationship between the screw rotation angle and the nut displacement, eliminating the internal ball contact force and the friction force, the dynamic mapping relationship between the motor current and the clamping force during forward clamping and reverse release is obtained:

[0113]

[0114] In the above formula, i g is the total transmission ratio of the planetary gear set, η g is the gear transmission efficiency, r s is the pitch radius of the ball screw, K m is the motor torque coefficient, i q,A is the q-axis current of the motor during clamping, i q，R is the q-axis current of the motor during release, θ m，A is the mechanical angle of the motor during clamping, θ m，R is the mechanical angle of the motor during release, T f,A is the total friction torque during forward clamping, T f，R is the total friction torque during reverse release, J eq,A and J eq,R are the equivalent moments of inertia during forward clamping and reverse release respectively, F p,A and F p,R are the clamping forces during forward clamping and reverse release respectively.

[0115] Among them, the equivalent moment of inertia includes the motor moment of inertia, the planetary gear moment of inertia, the sun gear moment of inertia, the screw moment of inertia, and the moment of inertia equivalent to the translational masses of the nut, piston, and brake pads:

[0116]

[0117] In the above formula, J eq,A and J eq,R are the equivalent moments of inertia during forward clamping and reverse release respectively.

[0118] In addition, in the above formula:

[0119]

[0120] Exemplarily, the total friction torque T f,A during the clamping process and the total friction torque T f,R during the release process can be calculated by the following formula:

[0121]

[0122] Furthermore, by considering the entire ball screw along the x s , y nPerform a force analysis on the shaft. Since it is in an approximately constant low-speed motion state during the stiffness update process, the relatively small viscous friction and Coulomb friction independent of the load are ignored:

[0123]

[0124] In this way, the friction torque of the thrust bearing and the friction force of the housing guide rail during forward clamping and reverse release can be sorted out:

[0125]

[0126] Substitute back into the total friction torque equation, and similarly ignore the relatively small viscous friction and Coulomb friction independent of the load, and sort out to get:

[0127]

[0128] In the above formula, T f,A is the total friction torque during clamping, T f,R is the total friction torque during release, G t1,A is the Coulomb friction corresponding to the item related to the motor output torque during clamping, G t2,A is the Coulomb friction corresponding to the item related to the clamping force during clamping, G t1,R is the Coulomb friction corresponding to the item related to the motor output torque during release, G t2,R is the Coulomb friction corresponding to the item related to the clamping force during release, K m is the motor torque coefficient, i q,A is the q-axis current of the motor during clamping, i q,R is the q-axis current of the motor during release, F p,A is the clamping force during clamping, F p,R is the clamping force during release.

[0129] Among them, the Coulomb friction consists of two parts, the item related to the motor output torque and the item related to the clamping force, and has strong asymmetry:

[0130]

[0131] Step S440: Determine the first mapping relationship between the motor current and the clamping force during the forward clamping process and the second mapping relationship between the motor current and the clamping force during the reverse release process according to the relationship between the ball screw rotation angle and the nut displacement, the first dynamic equation, the second dynamic equation, and the total friction torque during the forward clamping and reverse release processes.

[0132] In this embodiment, according to the relationship between the ball screw rotation angle and the nut displacement, the first dynamic equation, the second dynamic equation, and the total frictional torque during the clamping and releasing processes, substituting them back into the dynamic mapping relationship between the motor current and the clamping force, and neglecting the inertial force, the first mapping relationship and the second mapping relationship can be obtained.

[0133] Exemplarily, the first mapping relationship is:

[0134]

[0135] In the above formula, F p,A is the clamping force during clamping, i g is the total transmission ratio of the planetary gear set, η g is the planetary gear transmission efficiency, r s is the pitch radius of the ball screw, K m is the motor torque coefficient, i q,A is the q-axis current of the motor during clamping, G t,A is the equivalent Coulomb friction coefficient during clamping;

[0136] The second mapping relationship is:

[0137]

[0138] In the above formula, F p,R is the clamping force during release, G t,B is the equivalent Coulomb friction coefficient during release.

[0139] Step S450: According to the first mapping relationship and the second mapping relationship, obtain the equivalent Coulomb friction coefficients during forward clamping and reverse release.

[0140] Exemplarily, the equivalent Coulomb friction coefficient is:

[0141]

[0142] In the above formula, G t,A and G t,B are the equivalent Coulomb friction coefficients during forward clamping and reverse release, respectively.

[0143] In some embodiments, when determining the target clamping force, the motor currents during M times of clamping and releasing of the brake disc by the actuator can be used to obtain the motor currents at the same relative angular displacement of the relative contact point during clamping and releasing; then, according to the motor currents at the same relative angular displacement of the relative contact point during clamping and releasing, and the friction coefficients in different current segments, the target clamping force can be determined.

[0144] In this embodiment, when updating the stiffness, the currents at the same relative angular displacement of the relative contact point during forward clamping and reverse release are taken into account, considering the friction asymmetry.

[0145] For example, the forward and reverse friction can be eliminated according to the following formula to obtain a relatively accurate clamping force at the angular displacement as the target clamping force:

[0146]

[0147] In the above formula, G t,A and G t,R are the equivalent Coulomb friction coefficients during clamping and release, i g is the total transmission ratio of the planetary gear set, η g is the gear transmission efficiency, r s is the pitch radius of the screw, K m is the motor torque coefficient, i q，A is the q-axis current of the motor during clamping, i q，R is the q-axis current of the motor when released, F p,A is the clamping force during clamping, F p,B is the clamping force when released, F p is the target clamping force.

[0148] Furthermore, in some embodiments, the wear of the contact surface of mechanical parts is generally divided into three stages: the running-in stage, the stable wear stage, and the severe wear stage. Under normal operating conditions, the actuator should work in the stable wear stage, with a low wear rate and basically unchanged. The friction parameters of each part of the actuator are identified by bench durability testing, and the change law is calibrated, as follows:

[0149]

[0150] In the above formula, t m is the wear estimation time step, G b0 , G n0 and μ s0 are the initially calibrated Coulomb friction coefficients of thrust bearing, housing guide and ball respectively.

[0151] In some embodiments, after a vehicle has traveled a long distance, the stiffness curve changes due to wear of the pads, and errors occur in the clamping force control, so it is necessary to update the stiffness characteristics. Before the long-distance travel, the first stiffness curve of the actuator can be obtained according to the target clamping force, and then the pressure sensor-free position closed-loop control can be performed according to the first stiffness curve. After the long-distance travel, the actuator will go offline first, and then the stiffness update can be enabled after it is powered on again. At this time, the second stiffness curve of the actuator after powering on is obtained. If the deviation between the first stiffness curve and the second stiffness curve is greater than the set threshold, the stiffness characteristics of the actuator are updated according to the second stiffness curve.

[0152] For example,Figure 5 The flowchart shows the process of the control system provided by the embodiments of this application to implement the stiffness update function. As Figure 5 shown, it includes the following steps:

[0153] Step S510: Enable the friction coefficient calibration before the actuator goes offline, and obtain the real clamping force signal using an external force sensor.

[0154] Step S520: Automatically perform several clamping and releasing operations, estimate the friction coefficient based on the current and the actual clamping force, and take the average. Store the positive and negative asymmetric friction coefficients for different current segments.

[0155] Step S530: Enable the stiffness update after the actuator is powered on, and estimate the clamping force using the motor current and the friction coefficient.

[0156] Step S540: Automatically perform several clamping and releasing operations, superimpose the estimated clamping forces at the same piston position according to the asymmetric friction coefficient, eliminate the positive and negative friction terms, and take the average to obtain and store the accurate stiffness curve.

[0157] Step S550: Perform position closed-loop control without a pressure sensor according to the stiffness curve.

[0158] Step S560: After a long-distance driving, due to the wear of the spacer block, the stiffness curve changes, resulting in an error in the clamping force control.

[0159] Step S570: Enable the stiffness update after the actuator is powered on again, and automatically perform several clamping and releasing operations. If there is a large deviation between the average value of the stiffness curve and the stored value, update the stiffness characteristics.

[0160] Furthermore, in some embodiments, after the stiffness characteristics are updated, position closed-loop control without a pressure sensor can be performed on the actuator according to the updated stiffness characteristics. Specifically, refer to step S580 above Figure 5 to perform position closed-loop control without a pressure sensor according to the updated stiffness curve.

[0161] The stiffness update method considering friction asymmetry provided by the embodiments of this application models the friction asymmetry caused by the actuator, especially the ball screw, and calibrates the variation law of its asymmetry using durability tests, improving the robustness of the algorithm during the entire life cycle of the actuator. This patent designs a corresponding stiffness update function module, which can automatically update the stiffness characteristics when the vehicle is powered off, ensuring the accuracy of the clamping force control without a pressure sensor.

[0162] The following is the device embodiment of this application, which can be used to execute the method embodiment of this application. For the details not disclosed in the device embodiment of this application, please refer to the method embodiment of this application.

[0163] Figure 6 is a schematic structural diagram of a clamping force determination device for an actuator provided by an embodiment of the present application. As Figure 6 shown, the clamping force determination device 600 may include a model construction module 610, an acquisition module 620, and a determination module 630.

[0164] Among them, the model construction module 610 is used to construct a force analysis model of the actuator during forward clamping and reverse release according to the force conditions of the motor, ball bearing, planetary gear set, thrust bearing, ball screw, and brake pad during the forward clamping and reverse release of the actuator. The acquisition module 620 is used to obtain the equivalent Coulomb friction coefficient during forward clamping and reverse release, the clamping force during forward clamping, and the clamping force during reverse release according to the force analysis model. The determination module 630 is used to determine the target clamping force of the actuator at the target angular displacement according to the equivalent Coulomb friction coefficient during forward clamping and reverse release, the clamping force during forward clamping, and the clamping force during reverse release.

[0165] The device provided by the embodiment of the present application can be used to execute the method in the above embodiment, and its implementation principle and technical effect are similar, which will not be elaborated here.

[0166] Figure 7 is a schematic hardware structure diagram of an electronic device provided by an embodiment of the present invention. The electronic device can be integrated on a vehicle. As Figure 7 shown, the electronic device 700 may include a processor 701 and a memory 702 storing computer program instructions.

[0167] Specifically, the above-mentioned processor 701 may include a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present invention.

[0168] The memory 702 may include a mass storage for data or instructions. By way of example and not limitation, the memory 702 may include a hard disk drive (HDD), a floppy disk drive, a flash memory, an optical disc, a magneto-optical disc, a magnetic tape, or a universal serial bus (USB) drive, or a combination of two or more of these. In one example, the memory 702 may include removable or non-removable (or fixed) media, or the memory 702 is a non-volatile solid state memory. The memory 702 may be inside or outside the integrated gateway disaster recovery device.

[0169] In one example, the memory 702 can be a Read Only Memory (ROM). In one example, the ROM can be a mask-programmed ROM, a Programmable ROM (PROM), an Erasable PROM (EPROM), an Electrically Erasable PROM (EEPROM), an Electrically Alterable ROM (EAROM), or a flash memory, or a combination of two or more of these.

[0170] The memory 702 can include a read only memory (ROM), a random access memory (RAM), a magnetic disk storage media device, an optical storage media device, a flash memory device, an electrical, optical, or other physical / tangible memory storage device. Thus, generally, the memory includes one or more tangible (non-transitory) computer-readable storage media (e.g., memory devices) encoded with software including computer-executable instructions, and when the software is executed (e.g., by one or more processors), it is operable to perform the operations described with reference to the method according to one aspect of the present disclosure.

[0171] The processor 701 reads and executes the computer program instructions stored in the memory 702 to implement the methods in the above embodiments.

[0172] In one example, the electronic device 700 may further include a communication interface 703 and a bus 704. Among them, as Figure 7As shown, a processor 701, a memory 702, and a communication interface 703 are connected via a bus 704 to complete communication with each other. The communication interface 703 is mainly used to implement communication between various modules, devices, units, and / or apparatuses in the embodiments of the present invention. The bus 704 includes hardware, software, or both, and couples the components of the online data flow charging device to each other. By way of example and not limitation, the bus may include an Accelerated Graphics Port (AGP) or other graphics bus, an Extended Industry Standard Architecture (EISA) bus, a Front Side Bus (FSB), a Hyper Transport (HT) interconnect, an Industry Standard Architecture (ISA) bus, an InfiniBand interconnect, a Low Pin Count (LPC) bus, a memory bus, a Micro Channel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCI-X) bus, a Serial Advanced Technology Attachment (SATA) bus, a Video Electronics Standards Association Local (VLB) bus, or other suitable buses or a combination of two or more of these. In a suitable case, the bus 704 may include one or more buses. Although the embodiments of the present invention describe and illustrate specific buses, the present invention contemplates any suitable bus or interconnect.

[0173] In addition, in combination with the method in the above embodiments, an embodiment of the present invention may provide a braking system, and the braking system includes the above-mentioned electronic device.

[0174] It should be clear that the present invention is not limited to the specific configurations and processes described above and illustrated in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and illustrated as examples. However, the method process of the present invention is not limited to the specific steps described and illustrated, and those skilled in the art can make various changes, modifications, and additions, or change the order between steps after understanding the spirit of the present invention.

[0175] The functional blocks shown in the above structural block diagram can be implemented as hardware, software, firmware, or a combination thereof. When implemented in hardware, it can be, for example, an electronic circuit, an application specific integrated circuit (ASIC), appropriate firmware, a plug-in, a functional card, and so on. When implemented in software, the elements of the present invention are programs or code segments for performing the required tasks. The program or code segment can be stored in a machine-readable medium or transmitted via a data signal carried in a carrier wave over a transmission medium or a communication link. A "machine-readable medium" can include any medium that can store or transmit information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, read-only memory (ROM), flash memory, erasable read-only memory (EROM), floppy disks, compact disc read-only memory (CD-ROM), optical discs, hard disks, fiber optic media, radio frequency (RF) links, and so on. The code segment can be downloaded via a computer network such as the Internet, an intranet, and so on.

[0176] It should also be noted that the exemplary embodiments mentioned in the present invention describe some methods or systems based on a series of steps or devices. However, the present invention is not limited to the order of the above steps, that is, the steps can be executed in the order mentioned in the embodiments, or different from the order in the embodiments, or several steps can be executed simultaneously.

[0177] Aspects of the present disclosure have been described above with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present disclosure. It should be understood that each block in the flowcharts and / or block diagrams, and the combinations of blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device to produce a machine, such that the instructions executed by the processor of the computer or other programmable data processing device enable the implementation of the functions / actions specified in one or more blocks of the flowcharts and / or block diagrams. Such a processor can be, but is not limited to, a general-purpose processor, a special-purpose processor, a special application processor, or a field programmable logic circuit. It should also be understood that each block in the block diagrams and / or flowcharts, and the combinations of blocks in the block diagrams and / or flowcharts, can also be implemented by dedicated hardware for performing the specified functions or actions, or by a combination of dedicated hardware and computer instructions.

[0178] The above are only specific embodiments of the present invention. Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the above-described systems, modules, and units can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein. It should be understood that the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. A method for determining the clamping force of an actuator, characterized in that, The actuator includes a motor, a ball bearing, a planetary gear set, a thrust bearing, a ball screw, and a brake pad; wherein, the motor is connected to the ball bearing, the ball bearing is connected to the planetary gear set, the planetary gear set is connected to the thrust bearing, and the thrust bearing is connected to the ball screw; when the motor rotates, the ball screw drives the nut to move on the nut guide rail to drive the brake pad to clamp or release the brake disc; the method includes: According to the force conditions of the motor, ball bearing, planetary gear set, thrust bearing, ball screw, and brake pad during the process of the actuator clamping the brake disc forward and releasing it backward, construct a force analysis model of the actuator during the forward clamping and backward release processes; According to the force analysis model, obtain the equivalent Coulomb friction coefficient during forward clamping and backward release, the clamping force during forward clamping, and the clamping force during backward release; According to the equivalent Coulomb friction coefficient during forward clamping and backward release, the clamping force during forward clamping, and the clamping force during backward release, determine the target clamping force of the actuator at the target angular displacement.

2. The method according to claim 1, wherein The obtaining of the equivalent Coulomb friction coefficient during forward clamping and backward release according to the force analysis model includes: According to the force analysis model, obtain the first dynamic equation of the ball screw and the nut during the forward clamping process, the second dynamic equation of the ball screw and the nut during the backward release process, the relationship between the ball screw rotation angle and the nut displacement, and the total friction torque during the forward clamping and backward release processes. The total friction torque includes the equivalent friction torque generated by motor friction torque, thrust bearing friction torque, ball screw ramp inclined plane friction, contact force separation, and housing guide rail friction; According to the relationship between the ball screw rotation angle and the nut displacement, the first dynamic equation, the second dynamic equation, and the total friction torque during the forward clamping and backward release processes, determine the first mapping relationship between the motor current and the clamping force during the forward clamping process and the second mapping relationship between the motor current and the clamping force during the backward release process; According to the first mapping relationship and the second mapping relationship, obtain the equivalent Coulomb friction coefficient during forward clamping and backward release.

3. The method according to claim 2, wherein The obtaining of the first dynamic equation and the second dynamic equation includes: According to the force analysis model, determine the driving force applied by the planetary gear set to the ball screw, the thrust bearing friction force, the contact force between the screw and the nut, the clamping force, and the screw lead angle; Obtain the planetary gear inertia, sun gear inertia, screw inertia, total transmission ratio of the planetary gear set, the translational displacement of the ball screw and the nut along their axes, the total mass of the piston and the brake pad in the actuator, the nut mass, and the pitch radius of the ball screw; According to the driving force, thrust bearing friction force, contact force, clamping force, screw lead angle, planetary gear inertia, sun gear inertia, screw inertia, total transmission ratio of the planetary gear set, translational displacement, total mass of the piston and the brake pad, nut mass, and pitch radius, determine the first dynamic equation and the second dynamic equation.

4. The method according to claim 3, wherein The first dynamic equation is as follows: The second dynamic equation is as follows: In the above formula, J pg , J sg and J s are the inertia of the planet gear, the inertia of the sun gear, and the inertia of the lead screw respectively. i g is the total transmission ratio of the planetary gear set. x s and y n are the translational displacements of the ball screw and the nut along their axes. α is the lead angle of the lead screw. m n is the mass of the nut. m p is the total mass of the piston and the brake pad. F s is the driving force applied by the planetary gear set to the ball screw. f b is the frictional force of the thrust bearing. N s is the contact force between the screw and the nut. f s is the rolling frictional force of the ball. F p is the clamping force. f n is the frictional force between the nut and the housing guide rail.

5. The method according to claim 2, wherein The first mapping relationship is as follows: In the above formula, F p,A is the clamping force during clamping, i g is the total transmission ratio of the planetary gear set, η g is the transmission efficiency of the planetary gear, r s is the pitch radius of the ball screw, K m is the motor torque coefficient, i q,A is the q-axis current of the motor during forward clamping, G t,A is the equivalent Coulomb friction coefficient during forward clamping; The second mapping relationship is as follows: In the above formula, F p,R is the clamping force during forward release, and G t,B is the equivalent Coulomb friction coefficient during reverse release.

6. The method according to claim 3, wherein The obtaining of the total frictional torque during the clamping and releasing processes includes: In the above formula, T f,A is the total frictional torque during clamping, and T f,R is the total frictional torque during release. G t1,A is the Coulomb friction corresponding to the item related to the motor output torque during clamping, and G t2,A is the Coulomb friction corresponding to the item related to the clamping force during clamping, and G t1,R is the Coulomb friction corresponding to the item related to the motor output torque during release, and G t2,R is the Coulomb friction corresponding to the item related to the clamping force during release. K m is the motor torque coefficient, and i q,A is the q-axis current of the motor during clamping, and i q,R is the q-axis current of the motor during release. F p,A is the clamping force during clamping, and F p,R is the clamping force during release.

7. The method according to claim 1, characterized in that, The determining of the target clamping force of the actuator at the target angular displacement according to the equivalent Coulomb friction coefficients during the forward clamping and reverse releasing, the clamping force during the forward clamping, and the clamping force during the reverse releasing includes: In the above formula, G t,A and G t,R are the equivalent Coulomb friction coefficients during clamping and releasing respectively, F p,A is the clamping force during clamping, F p,B is the clamping force during releasing, and F p is the target clamping force.

8. A clamping force determination device for an actuator, characterized in that, It includes: A model construction module, configured to construct a force analysis model of the actuator during the forward clamping and reverse releasing processes according to the force conditions of the motor, ball bearing, planetary gear set, thrust bearing, ball screw, and brake pads during the processes of the actuator clamping and releasing the brake disc forward and backward; An obtaining module, configured to obtain the equivalent Coulomb friction coefficients during the forward clamping and reverse releasing, the clamping force during the forward clamping, and the clamping force during the reverse releasing according to the force analysis model; A determining module, configured to determine the target clamping force of the actuator at the target angular displacement according to the equivalent Coulomb friction coefficients during the forward clamping and reverse releasing, the clamping force during the forward clamping, and the clamping force during the reverse releasing.

9. An electronic device, characterized in that, It includes: A processor and a memory storing computer program instructions, and when the processor executes the computer program instructions, the steps of the method according to any one of claims 1-7 are implemented.

10. A computer storage medium, characterized in that, A computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the steps of the method according to any one of claims 1-7 are implemented.

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