Methods, systems, equipment and media for controlling the clamping force of electronic parking brake systems

Abstract

This application relates to the field of automotive braking technology, and discloses a method, system, device, and medium for controlling the clamping force of an electronic parking brake system. The method includes: acquiring a target clamping force; determining a target position of a brushless motor based on the target clamping force and a preset clamping force-position mapping relationship; determining a target speed of the brushless motor based on the target position and the actual position of the brushless motor; determining a target current of the brushless motor based on the target speed and the actual speed of the brushless motor; and generating a pulse width modulation signal for driving the brushless motor based on the target current and the actual current of the brushless motor, thereby generating an actual clamping force corresponding to the target clamping force. Its beneficial effects include suppressing brake shudder and improving the smoothness of vehicle braking.

Description

Technical Field

[0001] This application relates to the field of automotive braking technology, and in particular to methods, systems, devices and media for controlling the clamping force of electronic parking brake systems. Background Technology

[0002] Electronic Park Brake (EPB), a key component of brake-by-wire technology, commonly employs brushed DC motors as actuators and relies on a current-based single-loop control strategy to regulate clamping force. However, this technology suffers from significant drawbacks: the inherent mechanical commutation structure of brushed motors causes periodic fluctuations in output torque, directly leading to braking jitter and severely impacting the smoothness of braking. Furthermore, the nonlinear relationship between current and torque limits the accuracy of clamping force estimation in the absence of direct force sensors, making high-precision closed-loop control difficult to achieve. Summary of the Invention

[0003] This application provides a method, system, device and medium for controlling the clamping force of an electronic parking brake system, which solves the technical problem of insufficient clamping force control accuracy in related technologies and achieves the technical effect of suppressing brake vibration and improving the smoothness of vehicle braking.

[0004] To achieve the above objectives, the main technical solutions adopted in this application include:

[0005] In a first aspect, embodiments of this application provide a clamping force control method for an electronic parking brake system. The method includes: acquiring a target clamping force; determining a target position of a brushless motor based on the target clamping force and a preset clamping force-position mapping relationship; determining a target speed of the brushless motor based on the target position and the actual position of the brushless motor; determining a target current of the brushless motor based on the target speed and the actual speed of the brushless motor; and generating a pulse width modulation signal for driving the brushless motor based on the target current and the actual current of the brushless motor to generate an actual clamping force corresponding to the target clamping force.

[0006] The clamping force control method for the electronic parking brake system provided in this application transforms the abstract target clamping force into a physical drive command executable by the motor through a preset clamping force-position mapping relationship. By coordinating the control of the target position, target speed, and target current, the brushless motor is driven to accurately and smoothly reach the target position. Based on the established linear relationship between the motor position and the output clamping force, an actual clamping force corresponding to the height of the target clamping force is generated. This fundamentally avoids the periodic jitter of the clamping force caused by direct torque control fluctuations in traditional single-current-loop control, improving the control accuracy of the clamping force and the smoothness of the braking process.

[0007] Optionally, determining the target position of the brushless motor based on the target clamping force and a preset clamping force-position mapping relationship includes: obtaining the initial contact point position of the brushless motor, where the initial contact point position is the position of the brushless motor when the brake pad and brake disc are in initial contact; calculating the corresponding displacement increment based on the target clamping force and the overall stiffness of the brake caliper; and determining the target position of the brushless motor based on the initial contact point position and the displacement increment.

[0008] By precisely calibrating the initial contact point as the mechanical zero point and combining it with the calculation of displacement increments based on Hooke's Law, the abstract target clamping force is linearly converted into a precise and unique physical position command executable by the brushless motor. Through the clamping force-position mapping relationship, the nonlinear errors of traditional indirect force control are avoided, ensuring the accuracy of clamping force control and laying the foundation for improving the control precision and smoothness of the braking system.

[0009] Optionally, the initial contact point position is determined as follows: during the process of the brushless motor driving the brake pad to move toward the brake disc, the current and speed of the brushless motor are acquired; if the rate of increase of the current exceeds the current threshold and the rate of decrease of the speed exceeds the speed threshold, it is determined that the initial contact state has been reached; the position of the brushless motor in the initial contact state is determined as the initial contact point position.

[0010] By real-time collaborative monitoring of the current and speed change rate during the brushless motor drive process and setting dual thresholds for joint judgment, the reference drift caused by human intervention error and mechanical wear is eliminated, and the automatic and accurate identification of the initial contact state between the brake pads and the brake disc is achieved.

[0011] Optionally, based on the target current and the actual current of the brushless motor, a pulse width modulation signal is generated to drive the brushless motor to produce an actual clamping force corresponding to the target clamping force. This includes: calculating the current error between the target current and the actual current; calculating the duty cycle of the pulse width modulation signal based on the current error to drive the brushless motor to produce a corresponding output torque; and determining the actual clamping force based on the output torque.

[0012] By leveraging the smooth torque characteristics of the brushless motor and the rapid response of the PWM current closed loop, the clamping force fluctuations caused by torque pulsation and nonlinearity in traditional brushed motors are resolved, ensuring the overall accuracy, smoothness, and anti-interference capability of clamping force control.

[0013] Optionally, the method further includes: calculating an estimated clamping force based on the actual current, the actual position, and the actual speed of the brushless motor; and correcting the target position according to the force deviation between the target clamping force and the estimated clamping force, so that the actual clamping force approaches the target clamping force.

[0014] By continuously collecting the actual current, position, and speed of the motor, the clamping force is estimated. The new force deviation is obtained by comparing it with the target clamping force. The target position is then corrected until the force deviation is reduced to within the error range allowed by the system, thereby achieving a precise match between the actual clamping force and the target clamping force.

[0015] Optionally, determining the target speed of the brushless motor based on the target position and the actual position of the brushless motor includes: calculating the position error between the target position and the actual position; and performing at least one of proportional, integral, and differential operations on the position error to calculate the target speed.

[0016] By using the position error between the target position and the actual position as the core input of the position loop PID controller, and employing at least one of the proportional, integral, and derivative control algorithms for real-time calculation, a smooth, stable, and fast-responding target speed command can be intelligently generated. This process enables precise planning of the motor's motion trajectory, ensuring that the motor's approach from the current position to the target position is not only rapid but also effectively avoids overshoot and oscillation.

[0017] Optionally, based on the target speed and the actual speed of the brushless motor, the target current of the brushless motor is determined by: calculating the speed error between the target speed and the actual speed; and performing at least one of proportional, integral, and differential operations on the speed error to calculate the target current.

[0018] By constructing a precise speed closed-loop control, dynamic matching between the target speed and the actual speed is achieved. On the one hand, the proportional term is used to quickly respond to speed deviations, the integral term to eliminate static errors, and the derivative term to suppress speed overshoot, dynamically outputting an appropriate target current to ensure that the motor speed stably tracks the target speed. On the other hand, through closed-loop adjustment at the speed level, the transmission of speed fluctuations caused by load disturbances to torque and clamping force fluctuations is blocked, laying the foundation for precise torque control in the subsequent current loop.

[0019] Secondly, embodiments of this application provide a clamping force control system for an electronic parking brake system. The system includes: an acquisition module for acquiring a target clamping force; a first determination module for determining a target position of a brushless motor based on the target clamping force and a preset clamping force-position mapping relationship; a second determination module for determining a target speed of the brushless motor based on the target position and the actual position of the brushless motor; a third determination module for determining a target current of the brushless motor based on the target speed and the actual speed of the brushless motor; and a driving module for generating a pulse width modulation signal for driving the brushless motor based on the target current and the actual current of the brushless motor, so as to generate an actual clamping force corresponding to the target clamping force.

[0020] Thirdly, embodiments of this application provide a computer device, including: a memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the computer instructions to perform the above-described clamping force control method of the electronic parking brake system.

[0021] Fourthly, embodiments of this application provide a computer-readable storage medium storing computer instructions, which are used to cause a computer to execute the above-described clamping force control method for an electronic parking brake system.

[0022] Fifthly, embodiments of this application provide a computer program product, including computer instructions, which are used to cause a computer to execute the above-described clamping force control method for an electronic parking brake system. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 A flowchart illustrating a clamping force control method for an electronic parking brake system provided in this application embodiment;

[0025] Figure 2 This is a schematic diagram of the electronic parking brake system architecture provided in the embodiments of this application;

[0026] Figure 3 A schematic diagram of a clamping force control system for an electronic parking brake system provided in this application embodiment;

[0027] Figure 4 This is a schematic diagram of the structure of a computer device provided in an embodiment of this application. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] Electronic Parking Brake (EPB), as an important component of brake-by-wire technology, has gradually replaced traditional mechanical handbrakes and become a standard feature in modern vehicles. The EPB system drives an actuator motor through an electronic control unit. This motor, via a reduction and torque amplification mechanism and a motion conversion device (such as a lead screw and nut pair), converts the motor's rotational torque into the linear clamping force of the brake caliper, thereby achieving functions such as parking braking, automatic parking, and dynamic braking assistance. Currently, most mainstream EPB systems on the market use brushed DC motors as actuators. These motors are widely used due to their simple structure, mature drive circuitry, and low cost. In terms of control strategy, related technologies typically employ a current-based single-loop control method. The basic principle is that the controller, based on the target clamping force command, maps a corresponding target current value through a lookup table or simple calculation. Then, by adjusting the motor drive current, the actual current tracks this target value, thereby indirectly controlling the motor's output torque and ultimately achieving the desired clamping force. However, this solution based on brushed motors and single-loop current control has gradually revealed the following inherent defects and limitations when applied to vehicle braking scenarios with higher requirements for smoothness and precision: 1) Low clamping force control precision and poor braking smoothness. Due to the mechanical commutator and brush structure, the output torque of a brushed DC motor has inherent periodic fluctuations. These torque fluctuations are directly transmitted to the brake disc through the transmission mechanism, causing the actual clamping force to oscillate around the target value, resulting in brake jitter and severely affecting the smoothness of vehicle braking and ride comfort. 2) Limited system reliability and short lifespan. Continuous mechanical friction between the brushes and commutator not only reduces motor efficiency and generates noise, but also causes brush wear and carbon dust. Wear accumulation changes the motor's electrical parameters, affecting control stability; while carbon dust accumulation may lead to commutator short circuits or poor contact, reducing the long-term reliability of the system. In addition, mechanical wear also directly limits the lifespan of the actuator. 3) Difficulty in clamping force estimation and monitoring. Under cost constraints when direct force sensors (such as pressure sensors) are unavailable, related solutions rely on current values ​​to indirectly estimate clamping force. However, the relationship between current and output torque in a brushed motor is not ideally linear; its characteristics are affected by various nonlinear factors such as temperature, wear conditions, and commutation processes. Therefore, relying solely on current parameters makes it difficult to establish an accurate and robust clamping force estimation model. This results in the system being unable to achieve precise closed-loop feedback control and effective monitoring of the clamping force, and the control performance is prone to degradation under conditions such as changes in the friction coefficient or system wear.Although existing research has explored the introduction of more efficient and reliable actuator configurations such as brushless direct current motors (BLDC) or permanent magnet synchronous motors (PMSM) into EPB systems and proposed corresponding actuator models, the performance potential of brushless motors has not yet been fully explored at the control strategy level. In particular, how to design a core algorithm that matches the characteristics of brushless motors and can achieve high-precision, high-smoothness clamping force closed-loop control to completely solve the technical problems caused by the aforementioned actuator and control strategy deficiencies remains a technical challenge for those skilled in the art.

[0030] This application provides a clamping force control method for an electronic parking brake system. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Also, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0031] Please refer to Figure 1 , Figure 1 A flowchart of a clamping force control method for an electronic parking brake system provided in this application embodiment is shown below. Figure 1 As shown, the process includes the following steps:

[0032] Step S1: Obtain the target clamping force.

[0033] Clamping force refers to the normal pressure generated between the contact surfaces of the electromechanical brake pads and the brake disc during braking. Target clamping force refers to the theoretical clamping force value that the electromechanical brake is expected to achieve, calculated and issued by the main controller of the electronic parking brake (EPB) system. The target clamping force is used to drive the electromechanical brake to generate the corresponding actual clamping force.

[0034] Step S3: Determine the target position of the brushless motor based on the target clamping force and the preset clamping force-position mapping relationship.

[0035] The clamping force-position mapping relationship refers to a pre-calibrated linear correspondence between the clamping force and the position of the brushless motor. By using a brushless motor as the actuator, periodic torque pulsations caused by mechanical commutation can be eliminated. Through the clamping force-position mapping relationship, the abstract target clamping force requirement is transformed into a physical position command that the motor can execute. Since the conversion from motor position to braking clamping force is linear and deterministic, by controlling the brushless motor to precisely operate to the target position, the brake caliper is indirectly driven to generate the actual clamping force corresponding to the target clamping force. Through high-precision position control, high-precision control of the clamping force is equivalently achieved, eliminating periodic jitter in the clamping force caused by fluctuations in direct torque control, and improving the smoothness and control accuracy of vehicle braking.

[0036] Step S5: Determine the target speed of the brushless motor based on the target position and the actual position of the brushless motor.

[0037] By dynamically and in real-time tracking the positional deviation between the actual and target positions of the brushless motor, this deviation is translated into precise control of the brushless motor speed. This ensures both rapid system response and smooth motor approach to the target position, laying the foundation for high-precision positioning without overshoot or jitter, and ensuring stable clamping force output. In practical applications, if the positional deviation is large, a higher motor speed is used for rapid approach and response. If the positional deviation is small, a lower motor speed is used for smooth approach, preventing overshoot.

[0038] Step S7: Determine the target current of the brushless motor based on the target speed and the actual speed of the brushless motor.

[0039] The speed variation of a brushless motor directly reflects the matching effect between its torque output and the load torque. A dynamic match between torque demand and current supply is established through speed feedback. The torque matching is determined by the speed deviation between the actual speed and the target speed, and the current is then dynamically adjusted to accurately correct the torque deviation. Specifically, the speed deviation is input into a speed loop PID controller to calculate the target current for the brushless motor.

[0040] In practical applications, if the actual speed is lower than the target speed, the current needs to be increased to boost the motor torque and bring the brushless motor's actual speed up to match the target speed. If the actual speed is higher than the target speed, the current needs to be decreased to reduce the motor torque and prevent speed overshoot. If the actual speed matches the target speed, the current is maintained.

[0041] Step S9: Based on the target current and the actual current of the brushless motor, generate a pulse width modulation signal to drive the brushless motor, so as to generate an actual clamping force corresponding to the target clamping force.

[0042] Based on the current difference between the actual current and the target current of the brushless motor, a precise pulse width modulation (PWM) signal is generated, which directly drives the brushless motor to output the corresponding instantaneous electromagnetic torque. This provides the physical basis for ultimately generating the actual clamping force that corresponds to the target clamping force through the transmission mechanism.

[0043] Pulse Width Modulation (PWM) signals are used to drive brushless motors. In practical applications, when the actual current is lower than the target current, the PWM duty cycle is increased to improve output torque. When the actual current is higher than the target current, the PWM duty cycle is decreased to reduce output torque.

[0044] The clamping force control method for the electronic parking brake system provided in this application transforms the abstract target clamping force into a physical drive command executable by the motor through a preset clamping force-position mapping relationship. By coordinating the control of the target position, target speed, and target current, the brushless motor is driven to accurately and smoothly reach the target position. Based on the established linear relationship between the motor position and the output clamping force, an actual clamping force corresponding to the height of the target clamping force is generated. This fundamentally avoids the periodic jitter of the clamping force caused by direct torque control fluctuations in traditional single-current-loop control, improving the control accuracy of the clamping force and the smoothness of the braking process.

[0045] In some specific embodiments, please refer to Figure 2 , Figure 2 This is a schematic diagram of the electronic parking brake system architecture provided in an embodiment of this application. Figure 2As shown, the electronic parking brake system adopts a distributed control architecture, mainly including: a main controller, a left rear wheel domain controller, a right rear wheel domain controller, a left rear wheel electromechanical brake, and a right rear wheel electromechanical brake. All components are connected via an in-vehicle network (e.g., CAN bus). The main controller, as the vehicle's braking strategy unit, receives signals from brake pedal travel sensors, pedal speed sensors, wheel speed sensors, etc. Based on the driver's braking request and vehicle status signals, the main controller calculates the total braking force required for the entire vehicle and distributes it to each wheel according to regulations and stability control requirements, generating target clamping forces for the left and right rear wheels, and sending this information via the bus. The left and right rear wheel domain controllers are independently responsible for the braking control of the rear wheels on their respective sides. Each domain controller has an embedded microprocessor that receives the target clamping force from the main controller and executes a three-loop clamping force control algorithm consisting of a position loop, a speed loop, and a current loop. Domain controllers typically integrate peripherals such as a PWM generator module, an encoder interface, and a current sampling ADC. Both the left and right rear electromechanical brakes include a brushless direct current motor (BLDC), a reduction gear, a threaded pair (such as a ball screw) to convert rotary motion into linear motion, and a brake caliper. The PWM signal generated by the domain controller is amplified by the power drive circuit (typically a three-phase full-bridge inverter) to drive the brushless motor, ultimately pushing the brake piston to press the friction pads against the brake disc. Each electromechanical brake is also equipped with: an encoder for high-precision detection of the motor rotor's actual position; and a current sensor for real-time sampling of the actual phase current of the motor windings.

[0046] In some specific embodiments, determining the target position of the brushless motor based on the target clamping force and a preset clamping force-position mapping relationship includes: obtaining the initial contact point position of the brushless motor, wherein the initial contact point position is the position of the brushless motor when the brake pad and brake disc are in initial contact; calculating the corresponding displacement increment based on the target clamping force and the overall stiffness of the brake caliper; and determining the target position of the brushless motor based on the initial contact point position and the displacement increment.

[0047] The initial contact state refers to the critical state during braking where the brake pads, driven by the motor, have just contacted the brake disc surface but have not yet generated any clamping force. In this state, the specific angular position of the brushless motor rotor is the initial contact point. The displacement increment refers to the additional linear displacement the brake pads need to press against the brake disc relative to the brake disc to generate a specific target clamping force, starting from the initial contact point. According to Hooke's Law, force is proportional to deformation; the corresponding displacement increment can be obtained by calculating the ratio of the target clamping force to the overall stiffness of the brake caliper.

[0048] By precisely calibrating the initial contact point as the mechanical zero point and combining it with the calculation of displacement increments based on Hooke's Law, the abstract target clamping force is linearly converted into a precise and unique physical position command executable by the brushless motor. Through the clamping force-position mapping relationship, the nonlinear errors of traditional indirect force control are avoided, ensuring the accuracy of clamping force control and laying the foundation for improving the control precision and smoothness of the braking system.

[0049] In some specific embodiments, the initial contact point position is determined as follows: during the process of the brushless motor driving the brake pad to move toward the brake disc, the current and speed of the brushless motor are acquired; if the rate of increase of the current exceeds the current threshold and the rate of decrease of the speed exceeds the speed threshold, it is determined that the initial contact state has been reached; the position of the brushless motor in the initial contact state is determined as the initial contact point position.

[0050] When the brake pads make physical contact with the brake disc, the system load increases suddenly and significantly. This abrupt change in load will simultaneously cause a rapid increase in the motor phase current and a sudden decrease in motor speed.

[0051] By real-time collaborative monitoring of the current and speed change rate during the brushless motor drive process and setting dual thresholds for joint judgment, the reference drift caused by human intervention error and mechanical wear is eliminated, and the automatic and accurate identification of the initial contact state between the brake pads and the brake disc is achieved.

[0052] In some specific embodiments, the domain controller controls the brushless motor to drive the brake pads slowly toward the brake disc at a constant low speed (e.g., 100 RPM). Simultaneously, the actual motor current (via a current sensor) and actual speed (obtained by differentiating the encoder position signal to obtain the angular velocity) are acquired in real time. When the system detects that the rate of increase of the current exceeds a preset current threshold (e.g., 0.8 A / ms) and the rate of decrease of the speed simultaneously exceeds a preset speed threshold (e.g., 400 RPM / s), it determines that the brake pads are just making contact with the brake disc but have not yet generated a significant clamping force; this state is the initial contact state. The domain controller immediately records the actual motor position fed back by the encoder at this time and stores it in non-volatile memory as a key parameter, namely the initial contact point position (…). ).

[0053] In some specific embodiments, the assembly stiffness of the brake caliper is calibrated as follows: Calibration is performed on a production line or dedicated bench using high-precision force and displacement sensors. The control motor pushes the piston forward slowly from the initial contact point, recording the actual clamping force corresponding to multiple displacement points. A linear fit is performed on the "displacement-force" data sequence, and the slope of the resulting straight line is calibrated as the assembly stiffness (K_brake), typically in N / mm or N / rad, and this parameter is embedded in the domain controller.

[0054] In some specific embodiments, a pulse width modulation signal for driving the brushless motor is generated based on the target current and the actual current of the brushless motor to produce an actual clamping force corresponding to the target clamping force. This includes: calculating the current error between the target current and the actual current; calculating the duty cycle of the pulse width modulation signal based on the current error to drive the brushless motor to produce a corresponding output torque; and determining the actual clamping force based on the output torque.

[0055] The output torque of a brushless motor is proportional to its phase current, which can be precisely controlled by adjusting the PWM duty cycle. By calculating the current error between the target current and the actual current in real time, and quickly calculating the corresponding PWM duty cycle using a PI (Proportional-Integral) controller in the current loop, the power circuit is driven to output the required precise electromagnetic torque. This torque, after being amplified by the reduction mechanism, is converted by the lead screw and nut pair into a linear thrust of the brake caliper piston, ultimately pushing the brake pads to press against the brake disc. Because the transmission chain from motor current to output torque, then to piston thrust, and finally clamping force has a definite and linear mapping relationship, precise control of the current is equivalent to indirect, high-precision control of the clamping force.

[0056] By leveraging the smooth torque characteristics of the brushless motor and the rapid response of the PWM current closed loop, the clamping force fluctuations caused by torque pulsation and nonlinearity in traditional brushed motors are resolved, ensuring the overall accuracy, smoothness, and anti-interference capability of clamping force control.

[0057] In some specific embodiments, the method further includes: calculating an estimated clamping force based on the actual current, the actual position, and the actual speed of the brushless motor; and correcting the target position according to the force deviation between the target clamping force and the estimated clamping force, so that the actual clamping force approaches the target clamping force.

[0058] By leveraging the linear relationship between clamping force and motor position, force control deviations are converted into position adjustment commands, enabling adaptive correction of the clamping force. This eliminates control errors caused by mechanical wear, load disturbances, and other factors without requiring additional hardware. In practical applications, if the estimated clamping force is less than the target clamping force, the target position needs to be increased to drive the brake pads to further press against the brake disc and increase the clamping force. If the estimated clamping force is greater than the target clamping force, the target position needs to be decreased to reduce the brake pad pressure and decrease the clamping force.

[0059] By continuously collecting the actual current, position, and speed of the motor, the clamping force is estimated. The new force deviation is obtained by comparing it with the target clamping force. The target position is then corrected until the force deviation is reduced to within the error range allowed by the system, thereby achieving a precise match between the actual clamping force and the target clamping force.

[0060] In some specific embodiments, the method for calculating the estimated clamping force is as follows:

[0061]

[0062] In the above formula, This is an estimated value for the clamping force; It is the motor torque constant. It is the measured phase current; It is the total frictional torque of the system, which is a function of the motor position θ and angular velocity ω, and is used to correct for frictional losses during transmission. It is the gain of the transmission mechanism, where, is the transmission efficiency, and p is the lead screw pitch.

[0063] In some specific embodiments, determining the target speed of the brushless motor based on the target position and the actual position of the brushless motor includes: calculating the position error between the target position and the actual position; and performing at least one of proportional, integral, and differential operations on the position error to calculate the target speed.

[0064] By using the position error between the target position and the actual position as the core input of the position loop PID controller, and employing at least one of the proportional, integral, and derivative control algorithms for real-time calculation, a smooth, stable, and fast-responding target speed command can be intelligently generated. This process enables precise planning of the motor's motion trajectory, ensuring that the motor's approach from the current position to the target position is not only rapid but also effectively avoids overshoot and oscillation.

[0065] In some specific embodiments, the target current of the brushless motor is determined based on the target speed and the actual speed of the brushless motor: the speed error between the target speed and the actual speed is calculated; at least one of proportional, integral and differential operations is performed on the speed error to calculate the target current.

[0066] By using a PID (Proportional-Integral-Derivative) controller in the speed loop to adjust the speed error, a precise closed-loop speed control is constructed, achieving dynamic matching between the target speed and the actual speed. On one hand, the proportional term quickly responds to speed deviations, the integral term eliminates static errors, and the derivative term suppresses speed overshoot, dynamically outputting an appropriate target current to ensure that the motor speed stably tracks the target speed. On the other hand, through closed-loop adjustment at the speed level, the transmission of speed fluctuations caused by load disturbances (such as changes in brake disc friction resistance) to torque and clamping force fluctuations is blocked, laying the foundation for precise torque control in the subsequent current loop.

[0067] In some specific embodiments, the core function of the position loop is to: invoke a preset clamping force-position mapping relationship through the domain controller, and then transfer the received target clamping force... Substitute the values ​​into the following formula to calculate the target position that the motor needs to reach. :

[0068]

[0069] The actual position of the motor is obtained by reading the encoder. Calculate the target location. With actual location The difference yields the position error. The position error is input into the position loop PID controller. This controller performs proportional, integral, and derivative operations on the error. The proportional term provides a fast response, the integral term eliminates steady-state error, and the derivative term suppresses overshoot and oscillation. The output value of the position loop controller is the target speed required to achieve accurate position tracking. This serves as the instruction for the next cycle (speed cycle).

[0070] In some specific embodiments, the core function of the speed loop is to obtain the actual speed of the motor by performing differential calculations on continuous encoder position signals. Calculate the target velocity. Compared with actual speed The speed error is input to the speed loop PID controller. The controller calculates the speed error and outputs the target motor current (I_target, usually corresponding to the q-axis current) required for the actual speed to accurately track the target speed. This current directly corresponds to the electromagnetic torque that the motor should output.

[0071] In some specific embodiments, the core function of the current loop is to obtain the actual phase current I_actual of the motor windings through sampling by a current sensor. It then calculates the current error Current_Error between the target current I_target and the actual current I_actual. This Current_Error is input to the fastest-responding current loop PI controller. The controller outputs a control quantity, which is directly converted into the duty cycle of a pulse-width modulation (PWM) signal. This PWM signal controls the on / off time of the switching devices in the power drive circuit, thereby precisely adjusting the average voltage applied to the motor, forcing the actual current to quickly and accurately track the target current.

[0072] The power drive circuit drives the brushless motor to output precise torque based on the PWM signal. This torque is amplified by the reduction mechanism and then converted by the lead screw into a linear thrust of the brake piston, ultimately causing the brake pads to press against the brake disc. Since the conversion from "motor position" to "clamping force" is based on a calibrated linear relationship, when the motor is servoed to the target position under the control of the aforementioned position loop, speed loop, and current loop, the system generates an actual clamping force corresponding to the target clamping force height.

[0073] Accordingly, please refer to Figure 3 , Figure 3 A schematic diagram of a clamping force control system for an electronic parking brake system provided in this application embodiment is shown below. Figure 3 As shown, the system includes: an acquisition module for acquiring a target clamping force; a first determination module for determining a target position of the brushless motor based on the target clamping force and a preset clamping force-position mapping relationship; a second determination module for determining a target speed of the brushless motor based on the target position and the actual position of the brushless motor; a third determination module for determining a target current of the brushless motor based on the target speed and the actual speed of the brushless motor; and a driving module for generating a pulse width modulation signal for driving the brushless motor based on the target current and the actual current of the brushless motor, so as to generate an actual clamping force corresponding to the target clamping force.

[0074] Further functional descriptions of the above modules and units are the same as those in the corresponding embodiments described above, and will not be repeated here.

[0075] In this embodiment, the clamping force control system of the electronic parking brake system is presented in the form of a functional unit. Here, a unit refers to an ASIC (Application Specific Integrated Circuit) circuit, a processor and memory that execute one or more software or fixed programs, and / or other devices that can provide the above functions.

[0076] Please see Figure 4 , Figure 4 This is a schematic diagram of the structure of a computer device provided in an embodiment of this application, such as... Figure 4 As shown, the computer device includes one or more processors 10, memory 20, and interfaces for connecting the components, including high-speed interfaces and low-speed interfaces. The components communicate with each other via different buses and can be mounted on a common motherboard or otherwise installed as needed. The processors can process instructions executed within the computer device, including instructions stored in or on memory to display graphical information of a GUI on external input / output devices (such as display devices coupled to the interfaces). In some alternative implementations, multiple processors and / or multiple buses can be used with multiple memories and multiple memory modules, if desired. Similarly, multiple computer devices can be connected, each providing some of the necessary operations (e.g., as a server array, a group of blade servers, or a multiprocessor system). Figure 4 Take a processor 10 as an example.

[0077] Processor 10 may be a central processing unit, a network processor, or a combination thereof. Processor 10 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The programmable logic device may be a complex programmable logic device (CAMP), a field-programmable gate array (FPGA), a general-purpose array logic (GDA), or any combination thereof.

[0078] The memory 20 stores instructions executable by at least one processor 10 to cause the at least one processor 10 to perform the method shown in the above embodiments.

[0079] The memory 20 may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created based on the use of the computer device. Furthermore, the memory 20 may include high-speed random access memory and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some alternative embodiments, the memory 20 may optionally include memory remotely located relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0080] The memory 20 may include volatile memory, such as random access memory; the memory may also include non-volatile memory, such as flash memory, hard disk or solid-state drive; the memory 20 may also include a combination of the above types of memory.

[0081] The computer device also includes a communication interface 30 for communicating with other devices or communication networks.

[0082] This application also provides a computer-readable storage medium. The methods described in this application can be implemented in hardware or firmware, or implemented as recordable on a storage medium, or implemented as computer code downloaded over a network and originally stored on a remote storage medium or a non-transitory machine-readable storage medium and subsequently stored on a local storage medium. Thus, the methods described herein can be processed by software stored on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; further, the storage medium can also include combinations of the above types of memory. It is understood that computers, processors, microprocessor controllers, or programmable hardware include storage components capable of storing or receiving software or computer code. When the software or computer code is accessed and executed by the computer, processor, or hardware, the methods shown in the above embodiments are implemented.

[0083] This application provides a computer program product including computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the computer device to perform the method of any embodiment of this application.

[0084] The systems and modules described in the above embodiments can be implemented by computer chips or physical entities, or by products with certain functions. A typical implementation device is a computer. Specifically, a computer can be, for example, a personal computer, laptop computer, cellular phone, camera phone, smartphone, personal digital assistant, media player, navigation device, email device, game console, tablet computer, wearable device, or any combination of these devices.

[0085] For ease of description, the above devices are described separately by function as various units. Of course, in implementing this application, the functions of each unit can be implemented in one or more software and / or hardware.

[0086] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0087] This application is described with reference to flowchart illustrations and / or block diagrams of methods, systems, and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations 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, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0088] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0089] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0090] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0091] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on its differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0092] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

[0093] Although embodiments of this application have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of this application, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method for controlling the clamping force of an electronic parking brake system, characterized in that, The method includes: Obtain the target clamping force; Based on the target clamping force and the preset clamping force-position mapping relationship, the target position of the brushless motor is determined, including: obtaining the initial contact point position of the brushless motor, where the initial contact point position is the position of the brushless motor in the initial contact state between the brake pad and the brake disc; calculating the corresponding displacement increment based on the target clamping force and the overall stiffness of the brake caliper; and determining the target position of the brushless motor based on the initial contact point position and the displacement increment. Based on the target position and the actual position of the brushless motor, the target speed of the brushless motor is determined; Based on the target speed and the actual speed of the brushless motor, the target current of the brushless motor is determined; Based on the target current and the actual current of the brushless motor, a pulse width modulation signal is generated to drive the brushless motor to produce an actual clamping force corresponding to the target clamping force. This includes: calculating the current error between the target current and the actual current; calculating the duty cycle of the pulse width modulation signal based on the current error to drive the brushless motor to produce a corresponding output torque; and determining the actual clamping force based on the output torque.

2. The method according to claim 1, characterized in that, The initial contact point position is determined as follows: During the process of the brushless motor driving the brake pads to move toward the brake disc, the current and speed of the brushless motor are acquired; If the rate of increase of the current exceeds the current threshold and the rate of decrease of the speed exceeds the speed threshold, then the initial contact state is determined to have been reached. The position of the brushless motor in the initial contact state is determined as the initial contact point position.

3. The method according to claim 1, characterized in that, The method further includes: Based on the actual current, actual position, and actual speed of the brushless motor, calculate the estimated clamping force. Based on the force deviation between the target clamping force and the estimated clamping force, the target position is corrected so that the actual clamping force approaches the target clamping force.

4. The method according to claim 1, characterized in that, Determining the target speed of the brushless motor based on the target position and the actual position of the brushless motor includes: Calculate the position error between the target position and the actual position; The target velocity is calculated by performing at least one of proportional, integral, and differential operations on the position error.

5. The method according to claim 1, characterized in that, Based on the target speed and the actual speed of the brushless motor, determine the target current of the brushless motor: Calculate the speed error between the target speed and the actual speed; The target current is calculated by performing at least one of proportional, integral, and differential operations on the speed error.

6. A clamping force control system for an electronic parking brake system, employing the clamping force control method for an electronic parking brake system as described in any one of claims 1-5, characterized in that, The system includes: The acquisition module is used to acquire the target clamping force; The first determining module is used to determine the target position of the brushless motor based on the target clamping force and the preset clamping force-position mapping relationship; The second determining module is used to determine the target speed of the brushless motor based on the target position and the actual position of the brushless motor; The third determining module determines the target current of the brushless motor based on the target speed and the actual speed of the brushless motor. The drive module generates a pulse width modulation signal to drive the brushless motor based on the target current and the actual current of the brushless motor, so as to generate an actual clamping force corresponding to the target clamping force.

7. A computer device, characterized in that, include: A memory and a processor are interconnected, the memory stores computer instructions, and the processor executes the computer instructions to perform the clamping force control method of the electronic parking brake system according to any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to execute the clamping force control method of the electronic parking brake system according to any one of claims 1 to 5.

Images