A regenerative braking compound control method for an electromechanical brake system

Abstract

The application discloses a regenerative braking composite control method for an electromechanical braking system and relates to the technical field of electromechanical braking. In order to solve the problems existing in the prior art, the application specifically comprises the following steps: acquiring vehicle state information in real time; calculating total required braking force and current required deceleration a_req based on a vehicle brake pedal signal; calculating the maximum regenerative braking force currently available for a regenerative braking system in real time according to the vehicle state information; calculating a dynamic distribution coefficient K1 based on the required deceleration, vehicle speed, wheel slip rate and vehicle stability control signal; distributing braking force according to a preset multi-level threshold strategy; generating regenerative braking target force and compensation braking force instructions for each wheel end of an EMB based on the braking force distribution result; and establishing feedforward-feedback composite control logic. The application effectively solves the problems of uneven braking force distribution, switching jerk and low energy recovery efficiency in the composite braking process.

Description

Technical Field

[0001] This invention relates to the field of electromechanical braking technology, and in particular to a regenerative braking composite control method for electromechanical braking systems. Background Technology

[0002] With the development of new energy vehicle technology, regenerative braking technology has become a key technology for improving energy utilization and extending driving range. During braking, the drive motor transforms into a generator, converting the vehicle's kinetic energy into electrical energy stored in the battery, thereby achieving energy recovery.

[0003] Currently, electric vehicles typically employ a composite braking scheme combining regenerative braking and traditional friction braking. However, in practical applications, the coordinated operation of these two braking sources faces significant technical bottlenecks. Regenerative braking systems exhibit extremely fast response characteristics (response time is typically in the millisecond range), but their braking force is constrained by various factors such as motor external characteristics, battery SOC (State of Charge), vehicle speed, and temperature. Traditional friction braking systems (such as hydraulic and pneumatic braking systems) have inherent response delays (hydraulic systems typically have a pressure build-up time of 100-200 milliseconds, while pneumatic systems have a delay of 300-500 milliseconds). This delay leads to problems such as uneven braking force distribution, jerking sensations during braking transitions, and unsatisfactory energy recovery efficiency. Therefore, we propose a composite control method for regenerative braking in electromechanical braking systems. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a regenerative braking composite control method for electromechanical braking systems.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A regenerative braking composite control method for an electromechanical braking system includes the following steps:

[0007] S1: Real-time acquisition of vehicle status information;

[0008] S2: Calculate the total required braking force and the current required deceleration a_req based on the vehicle brake pedal signal;

[0009] S3: Calculate the maximum regenerative braking force currently available in the regenerative braking system in real time based on vehicle status information;

[0010] S4: Calculate the dynamic allocation coefficient K1 based on demand deceleration, vehicle speed, wheel slip ratio and vehicle stability control signal;

[0011] S5: Distribute braking force according to a preset multi-level threshold strategy;

[0012] S6: Based on the braking force distribution results, generate the regenerative braking target force and the compensation braking force command for each wheel end of the EMB;

[0013] S7: Establish feedforward-feedback composite control logic to predict and close-loop correct the EMB compensation braking force.

[0014] Preferably, the vehicle status information includes brake pedal signal, vehicle speed, battery state of charge (SOC), motor speed and torque capability, wheel speed signals, and vehicle stability control system intervention request signal.

[0015] Preferably, the maximum regenerative braking force is the minimum of the maximum available braking force of the motor of the regenerative braking system and the maximum friction force of the tire on the axle where the regenerative system is located.

[0016] Preferably, the preset content of the multi-level threshold strategy includes the following aspects:

[0017] A1: When the required deceleration a_req > the first deceleration threshold a1 and the vehicle speed > the first vehicle speed threshold V1, it is determined to be a light braking mode, and the regenerative braking system undertakes all braking tasks.

[0018] A2: When the required deceleration a_req is under the following conditions, it is determined to be a medium braking intensity mode: the second deceleration threshold a2 > the required deceleration a_req < the first deceleration threshold a1, and the vehicle speed > the first vehicle speed threshold V1. In this case, the regenerative braking system shall bear the minimum (total required braking force × K1, maximum available regenerative braking force) of the braking force, and the remaining compensation braking force shall be borne by the EMB system.

[0019] A3: When the required deceleration a_req < the second deceleration threshold a2, it is determined to be a high braking intensity mode, and the EMB system undertakes all braking tasks.

[0020] A4: When the vehicle speed is lower than the first speed threshold V1 and higher than the second speed threshold V2, it enters the low-speed transition mode, and the dynamic allocation coefficient K2 decreases as the vehicle speed decreases.

[0021] A5: When the vehicle speed is lower than the second speed threshold V2, it is determined to be in low-speed braking mode, and the EMB system will take over all braking tasks.

[0022] Preferably, the value of the first deceleration threshold a1 is calibrated through vehicle dynamics simulation and real vehicle testing, and its range is between -2 and 0 m / s².

[0023] The value of the first vehicle speed threshold V1 is calibrated by testing the external characteristics of the motor, and the range is between 8 and 15 km / h.

[0024] Preferably, the remaining compensating braking force is preferentially allocated to the EMB actuator on the non-regenerative braking axis;

[0025] The second deceleration threshold a2 is the critical deceleration value when the vehicle is about to trigger the anti-lock braking function (ABS) or the electronic stability control system (ESC) function. Its value is obtained through the calibration of the chassis control system.

[0026] K1 is a dynamic variation coefficient, and its value ranges from 0 to 1. When the demand deceleration a_req is closer to a2, the value of K1 is smaller.

[0027] Preferably, A4 further includes judging the decreasing trend of motor torque in the regenerative braking system and the increasing trend of torque in the EMB system by using motor torque characteristic coefficients K3 and K4, so as to ensure that the decreasing torque of the regenerative braking system and the increasing torque of the EMB system are consistent within the same cycle.

[0028] K3 and K4 are the braking torque characteristic coefficients of the regenerative braking system motor and the EMB system motor, respectively.

[0029] The torque characteristic coefficient is obtained by: obtaining the torque response curves of the motor when it receives different torque commands under different initial torque conditions through bench testing; combining the motor's current actual speed, actual torque, and historical operating data to establish a motor torque change rate prediction model; and predicting the actual torque output value of the motor in the next control cycle based on this model.

[0030] Preferably, the second speed threshold V2 is the critical speed at which the regenerative braking system can hardly provide effective braking force for energy recovery at the current speed;

[0031] K2 is a dynamic variation coefficient, which ranges from 0 to 1 and decreases linearly as the vehicle speed decreases. The relationship that K2 satisfies is: K2=(V-V2) / (V1-V2), where V is the current vehicle speed, V1 is the first vehicle speed threshold, and V2 is the second vehicle speed threshold.

[0032] Preferably, the feedforward control is based on the pre-compensation amount predicted by the rate of change of demand braking force, and the feedback control corrects the deviation between the actual output force and the target value through a PID algorithm.

[0033] A composite control system for implementing the regenerative braking composite control method includes a signal detection module for acquiring vehicle status information, a control unit for executing the composite control method, a regenerative braking execution module for executing regenerative braking target force commands, an EMB braking execution module for executing EMB compensation target force commands, and a communication network. The control unit is a vehicle controller (VCU), an EMB main controller, or a dedicated composite braking controller.

[0034] The EMB braking execution module includes an EMB controller and EMB actuators distributed at each wheel end, wherein the EMB actuator includes a drive motor, a reduction mechanism and a brake caliper.

[0035] The communication network is a CAN FD bus.

[0036] The beneficial effects of this invention are as follows:

[0037] This invention provides a regenerative braking composite control method for electromechanical braking systems. This method achieves precise coordinated control of regenerative braking and EMB braking through a multi-level threshold control strategy and motor torque characteristic information, effectively solving problems such as uneven braking force distribution, switching jerks, and low energy recovery efficiency in the composite braking process. Attached Figure Description

[0038] Figure 1 This is a schematic flowchart of a regenerative braking composite control method for an electromechanical braking system proposed in this invention.

[0039] Figure 2 This is a schematic diagram of the framework of a regenerative braking composite control method for an electromechanical braking system proposed in this invention.

[0040] Figure 3 This is a schematic diagram of the regenerative braking system and EMB system for a regenerative braking composite control method for an electromechanical braking system proposed in this invention.

[0041] In the diagram: 1. EMB wheel-end motor, 2. EMB main controller, 3. Non-drive shaft, 4. CAN bus one, 5. Regenerative braking system, 6. Reducer, 7. Drive shaft, 8. Wheel, 9. CAN bus two. Detailed Implementation

[0042] The technical solution of this patent will be further described in detail below with reference to specific embodiments.

[0043] The embodiments of this patent are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this patent, and should not be construed as limiting this patent.

[0044] Example 1: A regenerative braking composite control method for an electromechanical braking system, such as... Figure 1-2 As shown, it includes the following steps:

[0045] S1: Real-time acquisition of vehicle status information;

[0046] Preferably, the vehicle status information includes brake pedal signal, vehicle speed, battery state of charge (SOC), motor speed and torque capability, wheel speed signals, and vehicle stability control system intervention request signal.

[0047] S2: Calculate the total required braking force and the current required deceleration a_req based on the vehicle brake pedal signal; this calculation is based on the brake pedal signal.

[0048] S3: Calculate the maximum regenerative braking force currently available in the regenerative braking system in real time based on vehicle status information;

[0049] Preferably, the maximum regenerative braking force is the minimum of the maximum available braking force of the motor of the regenerative braking system and the maximum friction force of the tire on the axle where the regenerative system is located.

[0050] S4: Calculate the dynamic allocation coefficient K1 based on demand deceleration, vehicle speed, wheel slip ratio and vehicle stability control signal;

[0051] S5: Distribute braking force according to a preset multi-level threshold strategy;

[0052] Furthermore, the preset content of the multi-level threshold strategy includes the following aspects:

[0053] A1: When the required deceleration a_req > the first deceleration threshold a1 and the vehicle speed > the first vehicle speed threshold V1, it is determined to be a light braking mode, and the regenerative braking system undertakes all braking tasks.

[0054] As a supplement, if the regenerative braking system fails to respond to the braking request in a timely manner, the EMB system will compensate for the insufficient braking force.

[0055] Furthermore, the first deceleration threshold a1 in A1 is the critical deceleration value that determines whether the vehicle will exhibit an unstable trend when braking is performed solely on the axle where regenerative braking is located. Its value is calibrated through vehicle dynamics simulation and real vehicle testing, and its range is between -2 and 0 m / s².

[0056] Furthermore, the first vehicle speed threshold V1 in A1 is the critical vehicle speed at which the regenerative braking system's braking capacity is significantly reduced under low-speed conditions, but it can still provide effective regenerative braking. Its value is calibrated through motor external characteristic testing and ranges from 8 to 15 km / h.

[0057] A2: When the required deceleration a_req is under the following conditions, it is determined to be a medium braking intensity mode: the second deceleration threshold a2 > the required deceleration a_req < the first deceleration threshold a1, and the vehicle speed > the first vehicle speed threshold V1. In this case, the regenerative braking system shall bear the minimum (total required braking force × K1, maximum available regenerative braking force) of the braking force, and the remaining compensation braking force shall be borne by the EMB system.

[0058] Preferably, the remaining compensating braking force is preferentially allocated to the EMB actuator on the non-regenerative braking axis;

[0059] Furthermore, the second deceleration threshold a2 in A2 is the critical deceleration value when the vehicle is about to trigger the anti-lock braking function (ABS) or the electronic stability control system (ESC) function, and its value is obtained through the calibration of the chassis control system.

[0060] Furthermore, in A2, K1 is a dynamic variation coefficient, with a value range of 0 to 1. When the demand deceleration a_req is closer to a2, the value of K1 is smaller.

[0061] For example, when the demand reduction rate a_req reaches 0.9*a2, K1 can take the value 0.

[0062] A3: When the required deceleration a_req < the second deceleration threshold a2, it is determined to be a high braking intensity mode, and the EMB system undertakes all braking tasks; in order to ensure braking stability.

[0063] A4: When the vehicle speed is lower than the first speed threshold V1 and higher than the second speed threshold V2, it enters the low-speed transition mode, and the dynamic allocation coefficient K2 decreases as the vehicle speed decreases.

[0064] As a supplement, the decreasing trend of motor torque in the regenerative braking system and the increasing trend of torque in the EMB system are determined by the motor torque characteristic coefficients K3 and K4, ensuring that the decreasing torque of the regenerative braking system and the increasing torque of the EMB system are consistent within the same cycle; thus enabling seamless switching between the regenerative braking system and the EMB system.

[0065] Preferably, K3 and K4 are the braking torque characteristic coefficients of the regenerative braking system motor and the EMB system motor, respectively;

[0066] The torque characteristic coefficient is obtained by: obtaining the torque response curves of the motor under different initial torque conditions when it receives different torque commands (increased torque / decreased torque) through bench testing; combining the motor's current actual speed, actual torque and historical operating data to establish a motor torque change rate prediction model; and predicting the actual torque output value of the motor in the next control cycle based on the model.

[0067] Furthermore, the second speed threshold V2 in A4 is the critical speed at which the regenerative braking system can hardly provide effective braking force for energy recovery at the current vehicle speed;

[0068] Furthermore, in A4, K2 is a dynamic variation coefficient, which ranges from 0 to 1 and decreases linearly as the vehicle speed decreases; the lower the vehicle speed, the smaller the value of K2.

[0069] Preferably, the relationship that K2 satisfies is: K2=(V-V2) / (V1-V2), where V is the current vehicle speed, V1 is the first vehicle speed threshold, and V2 is the second vehicle speed threshold;

[0070] For example, when the vehicle speed drops to 1.2*V2, K2 can take the value of 0.

[0071] A5: When the vehicle speed is lower than the second speed threshold V2, it is determined to be in low-speed braking mode, and the EMB system will take over all braking tasks.

[0072] S6: Based on the braking force distribution results, generate the regenerative braking target force and the compensation braking force command for each wheel end of the EMB;

[0073] S7: Establish feedforward-feedback composite control logic to predict and close-loop correct the EMB compensated braking force;

[0074] Furthermore, the feedforward control predicts the pre-compensation amount based on the rate of change of the demand braking force, and the feedback control corrects the deviation between the actual output force and the target value through a PID algorithm.

[0075] In use, this embodiment provides a regenerative braking composite control method for an electromechanical braking system. By using a multi-level threshold control strategy and motor torque characteristic information, it achieves precise coordinated control of regenerative braking and EMB braking, effectively solving problems such as uneven braking force distribution, switching jerks, and low energy recovery efficiency in the composite braking process.

[0076] Example 2: A composite control system capable of implementing a regenerative braking composite control method for electromechanical braking systems, such as... Figure 3As shown, the composite control system is based on the EMB system and regenerative braking, and includes a signal detection module for collecting vehicle status information, a control unit for executing the composite control method, a regenerative braking execution module for executing the regenerative braking target force command, an EMB braking execution module for executing the EMB compensation target force command, and a communication network;

[0077] Preferably, the signal detection module, control unit, regenerative braking execution module, and EMB braking execution module are all connected through a communication network;

[0078] Furthermore, the control unit is a vehicle controller (VCU), an EMB main controller, or a dedicated composite brake controller.

[0079] Furthermore, the EMB braking execution module includes an EMB controller and EMB actuators distributed at each wheel end, wherein the EMB actuator includes a drive motor, a reduction mechanism, and a brake caliper.

[0080] Furthermore, the communication network is a CAN FD bus.

[0081] In addition, a storage medium storing a computer program is included, which, when executed by a processor, is used to implement the regenerative braking composite control method.

[0082] Furthermore, the electromechanical braking system includes an EMB system, a non-drive shaft 3, a regenerative braking system 5, four wheels 8, a drive shaft 7 for driving the wheels 8, a reducer 6 located between the regenerative braking system 5 and the drive shaft 7, a CAN bus 4 for communication between the EMB system and the regenerative braking system 5, and a CAN bus 9; this is prior art and will not be described in detail.

[0083] The EMB system includes an EMB main controller 2 and four EMB wheel-end motors 1.

[0084] Among them, CAN bus 29 is used for communication between EMB master controller 2 and wheel-end motor.

[0085] Example 3: A regenerative braking composite control method for an electromechanical braking system, such as... Figure 1-3 As shown, the execution process of the regenerative braking composite control method includes the following specific steps:

[0086] S100: Signal Acquisition and Processing: After the vehicle goes online, the system is powered on and initialized, and various sensors begin to work continuously.

[0087] The working functions of various sensors are as follows:

[0088] ① Brake pedal opening sensor: Collects pedal travel signal at a sampling frequency of 100Hz. The signal is directly obtained from the EMB main controller.

[0089] ② Wheel speed sensor: Collects the real-time rotational speed of the four wheels to calculate vehicle speed and identify wheel slip ratio;

[0090] ③ Motor controller (MCU): Periodically reports the real-time speed of the drive motor and the current maximum available torque (limited by factors such as battery SOC, temperature, and motor temperature) via the bus.

[0091] ④ Battery Management System (BMS): Reports the total voltage, current, SOC (state of charge), and temperature information of the battery pack;

[0092] ⑤ Electronic Stability Control (ESC) function within the EMB system: Reports the current status, such as whether it is in an active intervention state such as ABS, TCS or VDC;

[0093] ⑥ The EMB main controller receives all the above signals and uses the Kalman filter algorithm to perform data fusion and filtering to eliminate signal noise and improve control accuracy.

[0094] S200: Calculates the total demand braking force and demand deceleration;

[0095] Specifically, the EMB main controller determines the correspondence between the pedal travel and the driver's expected total deceleration based on the foot feel curve, and then performs subsequent calculations to obtain the driver's total braking force F_total and current deceleration a_req.

[0096] S300: Calculate the maximum available regenerative braking force;

[0097] The maximum available regenerative braking force F_regen_max is constrained by two factors: the capacity of the motor itself and the adhesion between the axle where regenerative braking is located and the ground.

[0098] Regarding point 1: Maximum available braking force of the motor F_motor_max: Based on the current maximum available torque of the motor T_motor_max reported by the MCU, combined with the reduction ratio i of the reducer and the rolling radius r of the wheel, it is calculated by the formula F_motor_max=T_motor_max*i*η / r, where η is the transmission efficiency;

[0099] Regarding point two: the maximum ground adhesion force F_road_max: is calculated using the formula F_road_max=M_axle*g*μ based on the axle load M_axle of the axle where regenerative braking is located (usually the front axle) and the real-time estimated road adhesion coefficient μ.

[0100] Finally, F_regen_max = min(F_motor_max, F_road_max); ensuring that the request for regenerative braking force will not cause motor overload or wheel lock-up.

[0101] S400: Calculate the dynamic allocation coefficient K1;

[0102] The dynamic allocation coefficient K1 is a variable between [0, 1], and its core function is to coordinate energy recovery and braking stability.

[0103] Base value calculation: The EMB pre-stores a two-dimensional lookup table K1_Map(a_req) based on the demand deceleration a_req. Generally, the smaller the absolute value of a_req (mild braking), the closer the base value of K1 is to 1 (prioritizing energy recovery); the larger the absolute value of a_req (emergency braking), the smaller the base value of K1 (prioritizing braking stability and reserving more braking force for a more reliable EMB system).

[0104] Stability Correction: The system monitors the slip ratio λ of each wheel in real time. If the slip ratio λ of any wheel exceeds the preset stability threshold (e.g., 0.15), or if an intervention request from the ESC function is received, the system will quickly reduce the request for regenerative braking until the regenerative braking system disengages. At the same time, the EMB system will quickly increase the braking force to meet the total braking demand, ensuring that the vehicle stability control function can quickly and accurately adjust vehicle stability and ensure safety.

[0105] S500: Multi-level door-restricted power distribution;

[0106] S510 - Light Braking Mode: When a_req>a1 (e.g., a1=-0.15g) and V>V1 (e.g., V1=12km / h), it indicates that the braking intensity is low and the vehicle speed is high, and regenerative braking is sufficient to handle it alone.

[0107] At this point, the regenerative braking target force F_regen_target = F_total and the EMB target force F_emb_target = F_total - F_regen_actual are set; this mode can maximize energy recovery.

[0108] S520 - Medium braking intensity mode: When a2 < a_req ≤ a1 (for example, a2 = -0.6g, that is, before the ABS trigger threshold) and V > V1, enter the compound braking mode. The regenerative braking target force: F_regen_target = min(F_total * K1, F_regen_max); the remaining braking force F_emb_comp = F_total - F_regen_actual is preferentially allocated to the EMB actuator of the axle where non-regenerative braking is located (usually the rear axle); this allocation method conforms to the characteristic of the axle load shifting forward during braking, can optimize the braking force distribution between the front and rear axles, and improve braking efficiency.

[0109] S530 - High braking intensity mode: When a_req ≤ a2, enter the high-intensity braking mode. At this time, the regenerative braking system completely exits (F_regen_target = 0), and all braking forces are provided by the EMB system (F_emb_target = F_total) to ensure the braking stability of the vehicle.

[0110] S540 - Low-speed transition mode: When V2 < V ≤ V1 (for example, V2 = 5 km / h), the motor energy recovery efficiency drops sharply, and the system enters the smooth switching transition zone.

[0111] Vehicle speed proportionality factor K2: K2 = (V - V2) / (V1 - V2); as the vehicle speed V decreases from V1 to V2, K2 linearly decreases from 1 to 0.

[0112] Calculate the new target value: The new regenerative braking target force F_regen_new = F_regen_target * K2.

[0113] Torque coordination control (core): Calculate the torque ΔF_regen that needs to be reduced for regenerative braking = F_regen_old - F_regen_new.

[0114] At the same time, based on the torque characteristic coefficients (K3, K4) for accurate prediction:

[0115] K3 (rate of change of regenerative braking motor torque increase / decrease): The EMB queries the pre-stored torque characteristic coefficient table (see Table 1 below), and based on the current motor speed, current torque, and the amount of requested torque decrease ΔF_regen, predicts the amount of actual increase / decrease of the motor torque ΔF_regen_actual in the next control cycle (such as 10 ms).

[0116] K4 (rate of change of EMB motor torque increase / decrease): Similarly, the EMB queries the characteristic coefficient table of the EMB wheel-end motor and predicts the amount of torque increase / decrease it can achieve in the next control cycle based on its current state.

[0117] To ensure that the total braking force remains unchanged, the EMB system is instructed to immediately increase the braking force by ΔF_emb = ΔF_regen_actual. Through this "prediction-matching" mechanism, the reduction of regenerative braking force and the increase of EMB braking force are precisely synchronized in time and magnitude, achieving a completely seamless mode switch.

[0118] S550 - Low-speed braking mode: When V<=V2, the regenerative braking system is completely disengaged (F_regen_target=0), and all braking force is provided by the EMB system (F_emb_target=F_total), ensuring braking reliability at low speeds.

[0119] S600: Instruction generation and execution;

[0120] The EMB sends the calculated F_regen_target to the MCU, which then distributes F_emb_target to the EMB controllers at each wheel end. Each actuator receives the instructions and begins its operation.

[0121] S700: Feedforward-feedback composite control; this step runs in parallel with the steps above to ensure control accuracy.

[0122] Feedforward control: The EMB monitors the changing trends of F_total and F_regen_max in real time. For example, when it detects that the driver rapidly depresses the pedal (F_total increases sharply) or the battery SOC suddenly increases (causing F_regen_max to suddenly decrease), the feedforward channel will predict in advance the amount of additional compensation that the EMB system needs and issue instructions in advance to overcome the mechanical inertia of the EMB system and significantly reduce the system response delay.

[0123] Feedback Control: The EMB continuously acquires the actual output torque value from the MCU and EMB wheel-end motor controller via the bus and compares it with the target value. Any deviations (due to system errors, wear, etc.) are input to the PID controller. The PID controller's output fine-tunes the EMB target force command for the next cycle, thereby eliminating static errors and ensuring that the actual braking force is highly consistent with the driver's needs.

[0124] Example 4: A regenerative braking composite control method for an electromechanical braking system, such as... Figure 1-2 As shown, the method for obtaining the torque characteristic coefficients (K3, K4) to achieve accurate prediction and control is as follows:

[0125] 1. Bench Test Setup: Install the motor under test (regenerative brake motor or EMB motor) on the test bench.

[0126] The platform includes:

[0127] 1) Dynamometer: Used to simulate load and apply different initial torques to the motor.

[0128] 2) High-precision torque sensor: measures the actual torque of the motor output shaft, with a sampling frequency ≥10kHz.

[0129] 3) Temperature control box: controls the motor to operate in different temperature environments.

[0130] 4) Data acquisition system: Records all test data.

[0131] II. Testing Procedure:

[0132] 1) Set a series of initial torque points (e.g., 0 Nm, 50 Nm, 100 Nm, ..., 300 Nm).

[0133] 2) At each initial torque point, send a series of torque step commands (such as +10Nm, +20Nm, -15Nm, -30Nm, etc.) to the motor controller.

[0134] 3) Record the complete response curve of the motor as it transitions from the current torque to the target torque.

[0135] 4) Repeat the above process to conduct tests under different motor speeds, different ambient temperatures, and different battery voltages (simulating different SOCs) to fully cover the possible operating range of the vehicle.

[0136] III. Data Processing and Modeling:

[0137] 1) Extract key characteristic parameters from the response curve, mainly the torque change rate (Nm / s) and response delay time (ms).

[0138] 2) Using all test data, establish a multi-dimensional lookup table model, namely the torque characteristic coefficient table. The input dimensions of this table include: initial torque, torque command difference, current speed, and current temperature. The output is the predicted torque change rate.

[0139] Initial torque (Nm) The instruction ΔTorque(Nm) Rotational speed (RPM) Temperature (°C) Predicted rate of change (Nm / s) ... ... ... ... ... 100 +20 2000 25 1250 100 +20 2000 -20 980 100 -30 2000 25 -1400 150 -40 1000 80 -1100 ... ... ... ... ...

[0140] Mass production application: The final calibrated torque characteristic coefficient table is burned into the Flash memory of each vehicle's EMB. During actual vehicle operation, the EMB queries this table in real time based on the motor's real-time status (current torque, speed, temperature) and the received torque command changes to obtain the predicted torque change rate (K3, K4), thereby predicting the torque value at the next moment.

[0141] In this embodiment, after adopting this technology in the EMB system, precise coordinated control of regenerative braking and EMB braking is achieved, effectively solving problems such as uneven braking force distribution, switching jerks, and low energy recovery efficiency in the compound braking process.

[0142] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A regenerative braking composite control method for an electromechanical braking system, characterized in that, Includes the following steps: S1: Real-time acquisition of vehicle status information; S2: Calculate the total required braking force and the current required deceleration a_req based on the vehicle brake pedal signal; S3: Calculate the maximum regenerative braking force currently available in the regenerative braking system in real time based on vehicle status information; S4: Calculate the dynamic allocation coefficient K1 based on demand deceleration, vehicle speed, wheel slip ratio and vehicle stability control signal; S5: Distribute braking force according to a preset multi-level threshold strategy; S6: Based on the braking force distribution results, generate the regenerative braking target force and the compensation braking force command for each wheel end of the EMB; S7: Establish feedforward-feedback composite control logic to predict and close-loop correct the EMB compensated braking force; The preset content of the multi-level threshold strategy includes the following aspects: A1: When the required deceleration a_req > the first deceleration threshold a1 and the vehicle speed > the first vehicle speed threshold V1, it is determined to be a light braking mode, and the regenerative braking system undertakes all braking tasks. A2: When the required deceleration a_req is under the following conditions, it is determined to be a medium braking intensity mode: the second deceleration threshold a2 > the required deceleration a_req < the first deceleration threshold a1, and the vehicle speed > the first vehicle speed threshold V1. In this case, the regenerative braking system shall bear the minimum (total required braking force × K1, maximum available regenerative braking force) of the braking force, and the remaining compensation braking force shall be borne by the EMB system. A3: When the required deceleration a_req < the second deceleration threshold a2, it is determined to be a high braking intensity mode, and the EMB system undertakes all braking tasks. A4: When the vehicle speed is lower than the first speed threshold V1 and higher than the second speed threshold V2, it enters the low-speed transition mode, and the dynamic allocation coefficient K2 decreases as the vehicle speed decreases. A5: When the vehicle speed is lower than the second vehicle speed threshold V2, it is determined to be a low-speed braking mode, and the EMB system will take over all braking tasks. The remaining compensating braking force is preferentially allocated to the EMB actuator on the non-regenerative braking axis. The second deceleration threshold a2 is the critical deceleration value when the vehicle is about to trigger the anti-lock braking function (ABS) or the electronic stability control system (ESC) function. Its value is obtained through the calibration of the chassis control system. K1 is a dynamic variation coefficient, and its value ranges from 0 to 1. When the demand deceleration a_req is closer to a2, the value of K1 is smaller. The A4 also includes judging the decreasing trend of motor torque in the regenerative braking system and the increasing trend of torque in the EMB system by using motor torque characteristic coefficients K3 and K4, so as to ensure that the decreasing torque of the regenerative braking system and the increasing torque of the EMB system are consistent within the same cycle. K3 and K4 are the braking torque characteristic coefficients of the regenerative braking system motor and the EMB system motor, respectively. The torque characteristic coefficient is obtained by: obtaining the torque response curves of the motor when it receives different torque commands under different initial torque conditions through bench testing; combining the motor's current actual speed, actual torque and historical operating data to establish a motor torque change rate prediction model; and predicting the actual torque output value of the motor in the next control cycle based on the model. The second speed threshold V2 is the critical speed at which the regenerative braking system can no longer provide effective braking force for energy recovery at the current vehicle speed; K2 is a dynamic variation coefficient, which ranges from 0 to 1 and decreases linearly as the vehicle speed decreases. The relationship that K2 satisfies is: K2=(V-V2) / (V1-V2), where V is the current vehicle speed, V1 is the first vehicle speed threshold, and V2 is the second vehicle speed threshold.

2. The regenerative braking composite control method for an electromechanical braking system according to claim 1, characterized in that, The vehicle status information includes brake pedal signal, vehicle speed, battery state of charge (SOC), motor speed and torque capability, wheel speed signals, and vehicle stability control system intervention request signal.

3. The regenerative braking composite control method for an electromechanical braking system according to claim 1, characterized in that, The maximum regenerative braking force is the minimum of the maximum available braking force of the motor of the regenerative braking system and the maximum friction force of the tire on the axle where the regenerative system is located.

4. The regenerative braking composite control method for an electromechanical braking system according to claim 1, characterized in that, The value of the first deceleration threshold a1 is calibrated through vehicle dynamics simulation and real vehicle testing, and its range is between -2 and 0 m / s². The value of the first vehicle speed threshold V1 is calibrated by testing the external characteristics of the motor, and the range is between 8 and 15 km / h.

5. A regenerative braking composite control method for an electromechanical braking system according to claim 1, characterized in that, The feedforward control is based on the pre-compensation amount predicted by the rate of change of demand braking force, and the feedback control corrects the deviation between the actual output force and the target value through the PID algorithm.

6. A composite control system for implementing the regenerative braking composite control method according to claim 1, comprising a signal detection module for acquiring vehicle state information, a control unit for executing the composite control method, a regenerative braking execution module for executing a regenerative braking target force command, an EMB braking execution module for executing an EMB compensation target force command, and a communication network, characterized in that, The control unit is a vehicle controller (VCU), an EMB main controller, or a dedicated composite brake controller. The EMB braking execution module includes an EMB controller and EMB actuators distributed at each wheel end, wherein the EMB actuator includes a drive motor, a reduction mechanism and a brake caliper. The communication network is a CAN FD bus.

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