A method for realizing slope holding by combining VCU creep torque control with EPB parking

Abstract

The present invention discloses a method for realizing slope holding by combining VCU creep torque control with EPB parking, which includes the following steps: In the Ready state, release the handbrake, and then while starting to release the brake pedal, the creep PID control will be enabled and start to output torque; According to the signal sent by the VCU and the feedback torque value of the drive motor, the EPB gradually reduces the braking torque output by the EPB. When the drive torque of the motor is greater than the braking torque of the EPB, the EPB completely cancels the braking force; While the VCU outputs torque, it is detected by the VCU whether the motor speed matches the gear; A PID feedforward torque and a PID coefficient of the slope slip state are obtained by looking up a table with the data detected by the VCU; According to the detected feedforward torque and the PID coefficient, the torque output of the VCU is seamlessly switched from the creep torque to the torque calculated by the slope holding strategy; When driving uphill, after the driver steps on the accelerator pedal to start accelerating, the creep and slope holding strategies exit; The present invention ensures the stability of the vehicle when starting or reversing on a slope and reduces the possibility of slope slip.

Description

Technical Field

[0001] The present invention relates to a method for realizing slope holding by combining VCU creep torque control with EPB parking, and belongs to the technical field of vehicle driving slope holding. Background Art

[0002] The drive torque control of a pure electric vehicle is controlled by a VCU (vehicle control unit). When the vehicle is at a low speed and there is no throttle pedal opening and the brake opening is less than a certain value, the VCU enters the creep PID control mode according to the current state of the vehicle, and makes the vehicle automatically creep forward or backward according to the gear. When the driver is driving forward uphill or reversing downhill, the driver's operation is to step on the brake and release the handbrake, and then release the brake and step on the accelerator. During the process of stepping on the accelerator, the vehicle has no forward drive torque and no braking force, and at this time, the vehicle will slip.

[0003] In the prior art, creep and slope holding strategies are separated, and it is impossible to well balance creep and slope holding strategies in the control strategy. And for slope holding, the creep torque control will make the torque gradient larger.

[0004] In view of the above problems, a method for realizing slope holding by combining VCU creep torque control with EPB parking is specifically proposed. Summary of the Invention

[0005] In view of the problems existing in the above prior art, the present invention provides a method for realizing slope holding by combining VCU creep torque control with EPB parking. The method for realizing slope holding by combining VCU creep torque control with EPB parking controls the ramp start through the combination of the VCU creep anti-slip strategy and the EPB parking control. During the ramp start process, the state of the handbrake, the state of the brake pedal, and the torque of the drive motor are detected, and the output torques of the VCU and the EPB are controlled according to the detection results. At the same time, by comparing and analyzing the vehicle speed difference with the PID feedforward torque and the PID coefficient, the output torque is seamlessly switched with the torque calculated by the slope holding strategy, ensuring the stability of the vehicle when starting or reversing on a ramp and reducing the possibility of slipping.

[0006] To achieve the above object, the technical solution adopted by the present invention is: A method for realizing slope holding by combining VCU creep torque control with EPB parking, comprising the following steps:

[0007] S1. In the Ready state, release the handbrake, and then while starting to release the brake pedal, the creep PID control will be enabled and start to output torque;

[0008] S2. The Electronic Parking Brake (EPB) starts to gradually reduce the braking torque output by the EPB according to the signals sent by the Vehicle Control Unit (VCU) and the feedback torque value of the drive motor. When the drive torque of the motor is greater than the braking torque of the EPB, the EPB completely cancels the braking force.

[0009] S3. While the VCU outputs torque, it detects whether the motor speed matches the gear through the VCU.

[0010] S4. The VCU looks up a PID feedforward torque and a PID coefficient for the slope state by detecting data through the VCU.

[0011] S5. According to the detected feedforward torque and PID coefficient, the torque output of the VCU seamlessly switches from the creep torque to the torque calculated by the slope holding strategy.

[0012] S6. When driving uphill, after the driver steps on the accelerator pedal to start accelerating, the creep and slope holding strategies exit.

[0013] Preferably, the signals sent by the Vehicle Control Unit (VCU) in step S2 are the Ready state, the handbrake state, and the brake pedal state signals.

[0014] Preferably, in step S3, when the vehicle is in the forward gear and the drive motor has a negative speed, or when the vehicle is in the reverse gear and the drive motor has a positive speed, the slope holding strategy of the VCU is enabled.

[0015] Preferably, in step S4, the slope holding strategy of the VCU looks up a PID feedforward torque through the difference between the current vehicle speed and the target creep vehicle speed limit, and at the same time looks up the PID coefficient according to the vehicle speed difference.

[0016] Preferably, in step S4, the VCU has a built-in PID feedforward torque data table and a PID coefficient table.

[0017] Preferably, in step S5, the feedforward torque and the PID coefficient are greater than the values when the vehicle is driving on a flat road.

[0018] The beneficial effects of the present invention are:

[0019] This method of combining the VCU creep torque control with the EPB parking to achieve slope holding controls the hill start by combining the VCU creep anti-rollback strategy and the EPB parking control. During the hill start process, it detects the handbrake state, the brake pedal state, and the torque of the drive motor, and controls the output torque of the VCU and the EPB according to the detection results. At the same time, by comparing and analyzing the vehicle speed difference with the PID feedforward torque and the PID coefficient, the output torque is seamlessly switched to the torque calculated by the slope holding strategy, ensuring the stability of the vehicle when starting or reversing on a slope and reducing the possibility of rollback. Brief Description of the Drawings

[0020] Figure 1 This is a flowchart of a method for realizing slope holding by combining VCU creep torque control with EPB parking in the present invention. Detailed Embodiment

[0021] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the drawings and embodiments.

[0022] However, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the scope of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0024] As Figure 1 shown, a method for realizing slope holding by combining VCU creep torque control with EPB parking includes the following steps:

[0025] S1. In the Ready state, release the handbrake, and then while starting to release the brake pedal, the creep PID control will be enabled and torque will start to be output.

[0026] S2. The electronic parking brake system (EPB) starts to gradually reduce the braking torque output by the EPB according to the signals sent by the vehicle control unit (VCU) and the feedback torque value of the drive motor. When the drive torque of the motor is greater than the braking torque of the EPB, the EPB completely cancels the braking force; the signals sent by the vehicle control unit (VCU) are the Ready state, handbrake state and brake pedal state signals.

[0027] S3. While the VCU outputs torque, the VCU detects whether the motor speed matches the gear; when the vehicle is in the forward gear and the drive motor has a negative speed, or when the vehicle is in the reverse gear and the drive motor has a positive speed, the VCU slope holding strategy will be enabled.

[0028] S4. The VCU detects data to look up a PID feedforward torque and a PID coefficient for the slope sliding state; the VCU slope holding strategy looks up a PID feedforward torque according to the difference between the current vehicle speed and the target creep vehicle speed limit, and at the same time looks up the PID coefficient according to the vehicle speed difference; the VCU internally stores a PID feedforward torque data table and a PID coefficient table.

[0029] S5. According to the detected feedforward torque and PID coefficients, the torque output of the VCU seamlessly switches from the creep torque to the torque calculated by the slope hold strategy; the feedforward torque and PID coefficients are greater than the values when the vehicle is driving on a flat road.

[0030] S6. When driving uphill, after the driver steps on the accelerator pedal to start accelerating, the creep and slope hold strategies exit.

[0031] When the whole vehicle is in the Ready state, the throttle opening is equal to zero, and the brake opening is less than a certain value, the creep PID control strategy is entered, and torque output starts. When the feedback torque of the drive motor is greater than the braking torque of the EPB, the throttle pedal opening is greater than a certain value, and the vehicle movement direction and gear are matched, the creep and slope start hold strategy is entered.

[0032] Embodiment 1:

[0033] For the method of the VCU creep torque control combined with the EPB parking to achieve slope hold, when the whole vehicle is in the Ready state, release the handbrake, and then start to release the brake pedal. At the same time, the creep PID control is enabled and torque output starts. At the same time, the EPB gradually reduces the braking torque output according to the Ready state, handbrake state, brake pedal state, and the feedback torque value of the drive motor sent by the VCU. When the driving torque of the motor is greater than the braking torque of the EPB, the EPB completely cancels the braking force. While the VCU outputs torque, it also detects whether the motor speed matches the gear. When the forward gear is engaged and the motor has a negative speed, or when the reverse gear is engaged and the motor has a positive speed, the VCU slope hold strategy is enabled. A larger PID feedforward torque is looked up from the difference between the current vehicle speed and the target creep vehicle speed limit. At the same time, the PID coefficient corresponding to the current slope state is looked up according to the vehicle speed difference. Due to the feedforward torque and PID coefficients being larger than those on a flat road, the torque output of the VCU seamlessly switches from the creep torque to the torque calculated by the slope hold strategy. This ensures that when the vehicle starts or reverses on a slope, the possibility of slope slip is reduced. When the driver steps on the accelerator pedal to start accelerating, the creep and slope hold strategies exit.

[0034] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising one" does not exclude the presence of additional identical elements in the process, method, article or device comprising said element.

[0035] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements or improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for realizing slope holding by combining VCU creep torque control with EPB parking, characterized in that, Including the following steps: S1. In the Ready state, release the parking brake. Then, while starting to release the brake pedal, the creep PID control will be enabled and start to output torque. S2. The Electronic Parking Brake (EPB) system gradually reduces the braking torque output by the EPB according to the signals sent by the Vehicle Control Unit (VCU) and the feedback torque value of the drive motor. When the driving torque of the motor is greater than the braking torque of the EPB, the EPB completely cancels the braking force. S3. While the VCU outputs torque, it detects whether the motor speed matches the gear through the VCU. S4. The VCU slope holding strategy looks up a PID feedforward torque and a PID coefficient for the rollback state by checking the data detected by the VCU. S5. According to the detected feedforward torque and PID coefficient, the torque output of the VCU seamlessly switches from the creep torque to the torque calculated by the slope holding strategy. S6. When driving uphill, after the driver steps on the accelerator pedal to start accelerating, the creep and slope holding strategies exit.

2. A method for realizing slope holding by combining VCU creep torque control with EPB parking according to claim 1, characterized in that , in step S2, the signals sent by the Vehicle Control Unit (VCU) are the Ready state, parking brake state, and brake pedal state signals.

3. A method for realizing slope holding by combining VCU creep torque control with EPB parking according to claim 1, characterized in that , in step S3, when the vehicle is in the forward gear and the drive motor has a negative speed, or when the vehicle is in the reverse gear and the drive motor has a positive speed, the VCU slope holding strategy will be enabled.

4. A method for realizing slope holding by combining VCU creep torque control with EPB parking according to claim 1, characterized in that, In step S4, the VCU slope holding strategy looks up a PID feedforward torque by the difference between the current vehicle speed and the target creep vehicle speed limit, and at the same time looks up the PID coefficient by the vehicle speed difference.

5. A method for realizing slope holding by combining VCU creep torque control with EPB parking according to claim 1, characterized in that, In step S4, the VCU has a built-in PID feedforward torque data table and a PID coefficient table.

6. A method for realizing slope holding by combining VCU creep torque control with EPB parking according to claim 1, characterized in that, In step S5, the feedforward torque and PID coefficient are greater than the values when the vehicle is driving on a flat road.

Images