A coordinated control method and system for brake energy recovery of commercial vehicles

Abstract

The application relates to new energy vehicle control technology and discloses a coordination control method and system for brake energy recovery of a commercial vehicle, which improves the smoothness of an electrical coordination process, compensates for the delay and deficiency of air pressure brake torque caused by system response problems with motor torque in the process of motor torque reduction and air pressure torque increase, improves the drivability of the electrical coordination process, adjusts and controls the speed difference between the two ends of a transmission system, namely a wheel end and a motor output end, with the motor when torsional vibration is caused by the rapid reduction of motor torque, so that the control target is zero, so that the purpose of reducing torsional vibration and improving drivability is achieved, and the time of the electrical coordination is shortened and the energy saving contribution rate is improved through the method combining theoretical calculation and experiments.

Description

Technical Field

[0001] This invention relates to new energy vehicle control technology, and more particularly to a method and system for coordinated control during the electric braking switching process of regenerative braking in commercial vehicles. Background Technology

[0002] New energy vehicles are generally equipped with a braking energy recovery system, which uses an electric motor to convert some or all of the kinetic energy into electrical energy and store it during braking.

[0003] During regenerative braking, many operating conditions require coordinated control of motor braking and pneumatic braking. For example, when entering low speeds, to prevent motor stalling, motor braking disengages, and all braking is performed by pneumatic braking. In this situation, without coordinated control, the motor's rapid response allows it to instantly reduce braking force to zero, while the pneumatic braking response is slower. Especially before mode switching, when all braking is done by motor braking, the pneumatic braking process requires a series of physical processes such as inflation, gap elimination, and pressure build-up, causing the vehicle to instantly lose braking force before gradually engaging. This results in a noticeable jolt for the driver, severely impacting ride comfort. Simultaneously, the rapid torque reduction of the motor can induce torsional vibration in the transmission system shafts, causing low-frequency lurching in the front-to-back direction and affecting drivability. Because of the significant difference in response speed and process between motor braking and pneumatic braking, affecting vehicle ride comfort and drivability, coordinated control is necessary.

[0004] As in prior art 1, CN110126628B, the coordinated control method is the slope control method, also known as the gradient control method. This means that the changes in motor braking and air braking are controlled within a certain range. With this setting, the changes in motor braking and air braking are not significant in each working cycle. Although there are differences in execution, the overall braking force fluctuates, but because the entire process takes a long time, the driver does not feel it very noticeably. Prior art 2, CN112848907B, uses a formula to calculate the moment of energy recovery exit, i.e., the electrical switching, and increases the pressure of the basic brake in advance. By using a calculation method to obtain the energy recovery exit switching moment, the basic brake is increased in advance, thereby improving the jerkiness during the brake actuator switching process and enhancing vehicle smoothness. Summary of the Invention

[0005] This invention addresses the problems in existing technologies where the timing obtained from coordinated control is inaccurate due to complex actual operating conditions, making the pre-pressurization method impractical in real-world applications. Furthermore, the slow response speed of basic braking, especially air pressure, means that reaching the target pressure still requires a considerable amount of time, failing to improve smoothness. This invention provides a coordinated control method and system for regenerative braking of commercial vehicles.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A coordinated control method for regenerative braking in commercial vehicles, the method comprising: Step 1: Obtaining the motor exit time Tt. After the commercial vehicle brakes, monitor the current motor speed St obtained by the speed sensor installed on the motor output shaft, and calculate the time Tt required for the motor to decelerate to the required exit speed S0 with the current braking force Ft. Step 2: Compare the time Tt from Step 1 with the time Tq required for the air pressure to rise to the target air pressure Pt, thus obtaining the current braking force Ft. The set time is Tq+T0; where T0 is the calibrated time. If Tt≤Tq+T0, proceed to Step 3 to obtain the torque; otherwise, further compare the time Tt with the time Tq+T0. Step 3: Torque acquisition. The motor's compensation torque Trq_s for air pressure is obtained through air pressure feedback compensation control, and the motor's compensation torque Trq_c for torsional vibration is obtained through speed difference torsional vibration control. Step 4: Torque superposition. The motor compensation torque Trq_s for air pressure and the motor compensation torque Trq_c for torsional vibration obtained in Step 3 are superimposed, and the superimposed torque is transmitted to the controller. Step 5: Determine the air pressure. Based on the torque in Step 4, determine the air pressure P. Compare the air pressure P with the target air pressure Pt. If the air pressure P reaches the target air pressure Pt, determine the braking force Ft corresponding to the target air pressure. Otherwise, return to Step 3.

[0007] Preferably, the motor exit time Tt is obtained by including: Differentiate the monitored St to obtain the current deceleration at, and the time Tt required for the current braking force Ft to reduce the speed to the speed S0 that the motor needs to exit, Tt = (St – S0) / at; The current electric motor's power source is Ft, where Ft = Trq_m*i / Rd; Where Trq_m is the motor output shaft torque, i is the transmission ratio between the motor output shaft and the drive wheel, and Rd is the radius of the drive wheel.

[0008] As a preferred method, the time Tq required for the air pressure to rise to the target air pressure Pt to obtain the current braking force Ft is obtained by looking up a table; A two-dimensional table is established for the pressurization time of the air pressure system. The two dimensions of the table are the initial pressure P0 and the final pressure Pt. The pressurization time Tq is measured by experiment when the two dimensions change, i.e., Tq = Tab(P0, Pt); where Tab(P0, Pt) is a two-dimensional table; P0 is the initial pressure and Pt is the final pressure.

[0009] Preferably, the compensation torque Trq_c for torsional vibration of the motor is obtained by: obtaining the compensation torque Trq_c for torsional vibration of the motor through PID control. ; Where Trq_c is the motor's compensation torque for torsional vibration. This refers to the motor's rotational speed. Let be the rotational speed of the wheel, and i be the transmission ratio between the motor output shaft and the drive wheel.

[0010] To address the aforementioned technical problems, the present invention also provides a coordinated control system for regenerative braking in commercial vehicles, comprising: The module for obtaining the motor exit time Tt monitors the current motor speed St obtained by the speed sensor installed on the motor output shaft after the commercial vehicle brakes, and calculates the time Tt required for the motor to decelerate to the required exit speed S0 with the current braking force Ft. The module for obtaining the time required for braking force compares time Tt with the time Tq required for the air pressure to rise to the target air pressure Pt, thus obtaining the time Tq required for the current braking force Ft. The set time is the relationship between Tq and T0; where T0 is the calibrated time. If Tt ≤ Tq + T0, then step three, torque acquisition, is executed; otherwise, time Tt is further compared with time Tq + T0. The torque acquisition module obtains the motor's compensation torque Trq_s for air pressure through air pressure feedback compensation control, and obtains the motor's compensation torque Trq_c for torsional vibration through speed difference torsional vibration control. The torque superposition module superimposes the motor's compensation torque Trq_s for air pressure and the motor's compensation torque Trq_c for torsional vibration obtained by the torque acquisition module, and transmits the superimposed torque to the controller. The air pressure determination module determines the air pressure P based on the torque from the torque superposition module. It then compares the air pressure P with the target air pressure Pt. If the air pressure P reaches the target air pressure Pt, the braking force Ft corresponding to the target air pressure is determined. Otherwise, it returns to the torque acquisition module.

[0011] This invention, by adopting the above technical solutions, has significant technical effects: This invention compensates for the delay and insufficiency of the pneumatic braking torque caused by system response issues by using motor torque to compensate for the decrease in motor torque and the increase in pneumatic torque during the process of motor torque reduction and pneumatic torque increase; thus improving the smoothness of the electrical coordination process. When torsional vibration occurs in the transmission system due to a rapid decrease in motor torque, this invention uses a motor to adjust and control the speed difference between the two ends of the transmission system—the wheel end and the motor output end—so that the control target is zero, thereby reducing torsional vibration and improving the drivability of the electrical coordination process. This invention combines theoretical calculations and experiments to accurately calculate the time required for the motor to reach its operating speed under current speed and braking force. It also experimentally obtains the time required for air pressure to reach the target braking force. By comparing these two times, the time required to initiate electrical coordination can be accurately determined. This improves drivability, shortens electrical coordination time, and increases energy-saving contribution. Attached Figure Description

[0012] Figure 1 This is a flowchart of Embodiment 1 of the present invention; Figure 2 This is a flowchart of Embodiment 2 of the present invention; Figure 3 This is a schematic diagram of the torsional vibration compensation control algorithm of the present invention. Detailed Implementation

[0013] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0014] Example 1 A coordinated control method for regenerative braking in commercial vehicles. Figure 1 The methods include: Step 1: Obtaining the motor exit time Tt. After the commercial vehicle brakes, monitor the current motor speed St obtained by the speed sensor installed on the motor output shaft, and calculate the time Tt required for the motor to decelerate to the required exit speed S0 with the current braking force Ft. Step 2: Compare the time Tt from Step 1 with the time Tq required for the air pressure to rise to the target air pressure Pt, thus obtaining the current braking force Ft. The set time is Tq+T0; where T0 is the calibrated time. If Tt≤Tq+T0, proceed to Step 3 to obtain the torque; otherwise, further compare the time Tt with the time Tq+T0. Step 3: Torque acquisition. The motor's compensation torque Trq_s for air pressure is obtained through air pressure feedback compensation control, and the motor's compensation torque Trq_c for torsional vibration is obtained through speed difference torsional vibration control. Step 4: Torque superposition. The motor compensation torque Trq_s for air pressure and the motor compensation torque Trq_c for torsional vibration obtained in Step 3 are superimposed, and the superimposed torque is transmitted to the controller. Step 5: Determine the air pressure. Based on the torque in Step 4, determine the air pressure P. Compare the air pressure P with the target air pressure Pt. If the air pressure P reaches the target air pressure Pt, determine the braking force Ft corresponding to the target air pressure. Otherwise, return to Step 3.

[0015] The acquisition of the motor exit time Tt includes: Differentiate the monitored St to obtain the current deceleration at, and the time Tt required for the current braking force Ft to reduce the speed to the speed S0 that the motor needs to exit, Tt = (St – S0) / at; The current electric motor's power source is Ft, where Ft = Trq_m*i / Rd; Where Trq_m is the motor output shaft torque, i is the transmission ratio between the motor output shaft and the drive wheel, and Rd is the radius of the drive wheel.

[0016] The time Tq required for the air pressure to rise to the target air pressure Pt, thus obtaining the current braking force Ft, is obtained by looking up a table. Calculating Tq theoretically requires establishing an air-pressure braking system model. However, due to significant differences in the length and layout of braking system pipes across different vehicle models, the model parameters are difficult to obtain, resulting in low accuracy and slow calculation speed, which cannot meet the requirements for rapid calculation within the controller. Therefore, this invention employs a pre-experimental table lookup method, where Tq is obtained by looking up a table before use within the controller.

[0017] A two-dimensional table is established for the pressurization time of the air pressure system. The two dimensions of the table are the initial pressure P0 and the final pressure Pt. The pressurization time Tq is measured by experiment when the two dimensions change, i.e., Tq = Tab(P0, Pt); where Tab(P0, Pt) is the two-dimensional table; P0 is the initial pressure and Pt is the final pressure.

[0018] Example 2 Based on Example 1, Figure 2 In this embodiment, to reduce torsional vibration in the transmission system, the speed difference between the wheels and the motor at both ends of the transmission system shaft caused by torsional vibration is controlled, using a traditional PID controller. For example... Figure 3 As shown, the acquisition of the motor's torsional vibration compensation torque Trq_c includes: obtaining the torque Trq_s through PID control. ; Where Trq_c is the motor's compensation torque for torsional vibration. This refers to the motor's rotational speed. Let be the rotational speed of the wheel, and i be the transmission ratio between the motor output shaft and the drive wheel.

[0019] PID represents a controller function that primarily uses a linear combination of three parts—proportional adjustment, integral accumulation, and derivative prediction—to address the error, specifically the speed difference caused by torsional vibration. This allows for feedback control of the torsional vibration phenomenon in the transmission system. The controlled objects in the diagram refer to the motor controller, the motor, and the entire transmission system.

[0020] Example 3 Based on the above embodiments, this embodiment is a coordinated control system for regenerative braking of commercial vehicles, which includes: The module for obtaining the motor exit time Tt monitors the current motor speed St obtained by the speed sensor installed on the motor output shaft after the commercial vehicle brakes, and calculates the time Tt required for the motor to decelerate to the required exit speed S0 with the current braking force Ft. The module for acquiring the time required for braking force compares time Tt with the time Tq required for the air pressure to rise to the target air pressure Pt, thus obtaining the time Tq required for the current braking force Ft. The time is set to a relationship of Tq + T0, where T0 is the calibrated time. If Tt ≤ Tq + T0, step three, torque acquisition, is executed; otherwise, time Tt is further compared with time Tq + T0. T0 is taken as 1% to 5% of the time T required for the maximum air pressure to rise, determined based on actual experimental conditions, ensuring that the air pressure can rise to the target air pressure Pt within the time Tq + T0. The maximum air pressure is the air pressure generated when the brake pedal is at its maximum position.

[0021] The torque acquisition module obtains the motor's compensation torque Trq_s for air pressure through air pressure feedback compensation control, and obtains the motor's compensation torque Trq_c for torsional vibration through speed difference torsional vibration control. The torque superposition module superimposes the motor's compensation torque Trq_s for air pressure and the motor's compensation torque Trq_c for torsional vibration obtained by the torque acquisition module, and transmits the superimposed torque to the controller. The air pressure determination module determines the air pressure P based on the torque from the torque superposition module. It then compares the air pressure P with the target air pressure Pt. If the air pressure P reaches the target air pressure Pt, the braking force Ft corresponding to the target air pressure is determined. Otherwise, it returns to the torque acquisition module.

Claims

1. A coordinated control method for regenerative braking in commercial vehicles, the method comprising: Step 1: Obtaining the motor exit time Tt. After the commercial vehicle brakes, monitor the current motor speed St obtained by the speed sensor installed on the motor output shaft, and calculate the time Tt required for the motor to decelerate to the required exit speed S0 with the current braking force Ft. Step 2: Compare the time Tt from Step 1 with the time Tq required for the air pressure to rise to the target air pressure Pt, thus obtaining the current braking force Ft. The set time is Tq+T0; where T0 is the calibrated time. If Tt≤Tq+T0, proceed to Step 3 to obtain the torque; otherwise, further compare the time Tt with the time Tq+T0. Step 3: Torque acquisition. The motor's compensation torque Trq_s for air pressure is obtained through air pressure feedback compensation control, and the motor's compensation torque Trq_c for torsional vibration is obtained through speed difference torsional vibration control. Step 4: Torque superposition. The motor compensation torque Trq_s for air pressure and the motor compensation torque Trq_c for torsional vibration obtained in Step 3 are superimposed, and the superimposed torque is transmitted to the controller. Step 5: Determine the air pressure. Based on the torque in Step 4, determine the air pressure P. Compare the air pressure P with the target air pressure Pt. If the air pressure P reaches the target air pressure Pt, determine the braking force Ft corresponding to the target air pressure. Otherwise, return to Step 3.

2. The coordinated control method for brake energy recovery of a commercial vehicle according to claim 1, characterized in that, The acquisition of the motor exit time Tt includes: Differentiate the monitored St to obtain the current deceleration at, and the time Tt required for the current braking force Ft to reduce the speed to the speed S0 that the motor needs to exit, Tt = (St – S0) / at; The current electric motor's power source is Ft, where Ft = Trq_m*i / Rd; Where Trq_m is the motor output shaft torque, i is the transmission ratio between the motor output shaft and the drive wheel, and Rd is the radius of the drive wheel.

3. The coordinated control method for brake energy recovery of a commercial vehicle according to claim 1, characterized in that, The time Tq required for the air pressure to rise to the target air pressure Pt, thus obtaining the current braking force Ft, is obtained by looking up a table; A two-dimensional table is established for the pressurization time of the air pressure system. The two dimensions of the table are the initial pressure P0 and the final pressure Pt. The pressurization time Tq is measured by experiment when the two dimensions change, i.e., Tq = Tab(P0, Pt); where Tab(P0, Pt) is a two-dimensional table; P0 is the initial pressure and Pt is the final pressure.

4. The coordinated control method for regenerative braking of commercial vehicles according to claim 1, characterized in that, Obtaining the motor's torsional vibration compensation torque Trq_c includes: acquiring the motor's torsional vibration compensation torque Trq_c through PID control. ； Where Trq_c is the motor's compensation torque for torsional vibration. This refers to the motor's rotational speed. Let be the rotational speed of the wheel, and i be the transmission ratio between the motor output shaft and the drive wheel.

5. A coordinated control system for regenerative braking in commercial vehicles, characterized in that, include: The module for obtaining the motor exit time Tt monitors the current motor speed St obtained by the speed sensor installed on the motor output shaft after the commercial vehicle brakes, and calculates the time Tt required for the motor to decelerate to the required exit speed S0 with the current braking force Ft. The module for obtaining the time required for braking force compares time Tt with the time Tq required for the air pressure to rise to the target air pressure Pt, thus obtaining the time Tq required for the current braking force Ft. The set time is the relationship between Tq and T0; where T0 is the calibrated time. If Tt ≤ Tq + T0, then step three, torque acquisition, is executed; otherwise, time Tt is further compared with time Tq + T0. The torque acquisition module obtains the motor's compensation torque Trq_s for air pressure through air pressure feedback compensation control, and obtains the motor's compensation torque Trq_c for torsional vibration through speed difference torsional vibration control. The torque superposition module superimposes the motor's compensation torque Trq_s for air pressure and the motor's compensation torque Trq_c for torsional vibration obtained by the torque acquisition module, and transmits the superimposed torque to the controller. The air pressure determination module determines the air pressure P based on the torque from the torque superposition module. It then compares the air pressure P with the target air pressure Pt. If the air pressure P reaches the target air pressure Pt, the braking force Ft corresponding to the target air pressure is determined. Otherwise, it returns to the torque acquisition module.

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