EV Drive Torque Split Control for Backlash Shock Reduction
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Solution Overview
Problem
Existing torque control systems in electric vehicles face challenges in managing backlash and backlash vibrations, leading to drivability issues and NVH problems, with existing methods focusing on post-correction rather than preventive measures.
Innovation Solution
A torque control system that distributes torque commands between front-wheel and rear-wheel motors, allowing sequential zero-crossing through backlash bands, with controlled change rates and compensation to maintain smooth torque transitions, thereby reducing backlash shock and improving drivability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the torque change rate is set large to improve acceleration responsiveness, then the acceleration/deceleration responsiveness is improved, but backlash shock and drivability deterioration occur
Solution Approach 1:
The patent segments the torque change process into multiple stages with different torque change rates. During normal operation, a larger torque change rate is used for responsiveness, while during backlash occurrence periods (identified through sensors), a smaller torque change rate is applied to prevent shock, thus resolving the contradiction between responsiveness and backlash prevention
Solution Approach 2:
The patent employs feedback control by monitoring drive system conditions (such as motor speed, wheel speed, and acceleration) to detect when backlash is occurring. Based on this feedback, the controller dynamically adjusts the torque change rate to appropriate levels, preventing backlash shock while maintaining acceleration responsiveness
2Object-generated harmful factors
If gradient limits and filters are used to reduce backlash vibration, then NVH performance is improved, but acceleration/deceleration responsiveness deteriorates
Solution Approach 1:
The patent dynamically adjusts the torque change rate based on real-time drive system conditions rather than using fixed gradient limits. The controller increases the torque change rate when backlash is not occurring to maintain responsiveness, and decreases it when backlash is detected, thus improving NVH performance without sacrificing acceleration responsiveness
Solution Approach 2:
The patent changes the torque change rate parameter dynamically based on drive system state. By switching between different torque change rate values (larger for normal operation, smaller for backlash prevention), the system achieves both reduced backlash vibration and maintained acceleration responsiveness, resolving the contradiction
3Object-generated harmful factors
If active feedback torque correction control is applied to suppress vibration, then backlash vibration is reduced, but low responsiveness due to hardware characteristics cannot be prevented
Solution Approach 1:
The patent takes preliminary action by detecting backlash occurrence in advance through sensor monitoring and proactively adjusting the torque change rate before significant vibration occurs. This preventive approach reduces backlash vibration without the time loss associated with reactive correction control, maintaining responsiveness while suppressing vibration
Data Source
AI summary
A torque control system for a drive system of an electric vehicle includes a controller that generates a front-wheel torque command and a rear-wheel torque command having torque values distributed from required torque for vehicle driving, a front-wheel motor, wherein operation of the front-wheel motor is controlled according to the front-wheel torque command, and a rear-wheel motor, wherein operation of the rear-wheel motor is controlled according to the rear-wheel torque command. The controller determines whether there is a change request of a direction of the required torque, and determines, in a case where there is the change request of the direction of the required torque, the front-wheel torque command and the rear-wheel torque command determined from the required torque as values for sequential zero-crossing while the required torque determined in real time changes while performing zero-crossing of passing through 0 torque for direction change.