Electric Vehicle Torque Control for Backlash Band Evasion
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Solution Overview
Problem
Existing torque control methods in electric vehicles fail to effectively prevent backlash in the drive system, leading to issues such as driveshaft torsion, gear backlash strikes, and impulsive drivability deterioration, while also failing to minimize noise, vibration, and harshness (NVH) issues.
Innovation Solution
A torque control method that separates the operating torque regions of front-wheel and rear-wheel motors to evade the backlash band, utilizing contra-directional and co-directional torque distribution modes to maintain gear alignment and minimize torque direction changes, thereby preventing backlash occurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If torque change rate is set to be large, then acceleration responsiveness is improved, but driveshaft torsion and gear backlash strike occur
Solution Approach 1:
The controller performs preliminary action by determining whether the motor torque is within the backlash band before torque is applied to the drive system. When the torque is within the backlash band, the controller limits the torque change rate in advance to prevent backlash strike and driveshaft torsion, while allowing higher torque change rates when torque is outside the backlash band, thus maintaining acceleration responsiveness without causing harmful effects.
2Object-affected harmful factors
If torque change rate is set to be small, then NVH issues are reduced, but acceleration responsiveness deteriorates
Solution Approach 1:
The controller applies local quality by implementing different torque change rate limits in different torque regions. When motor torque is within the backlash band, a first (stricter) torque change rate limit is applied to reduce NVH issues. When motor torque is outside the backlash band, a second (more relaxed) torque change rate limit is applied to maintain acceleration responsiveness. This localized approach ensures NVH reduction only where necessary without compromising overall performance.
3Stability of the object's composition
If torque is applied to eliminate backlash, then gear alignment is improved, but torque direction changes cause backlash strike
Solution Approach 1:
The controller applies dynamics by continuously monitoring the motor torque value and dynamically adjusting the torque change rate limit based on whether the current torque is within the backlash band. The system transitions between different control states (stricter limit when in backlash band, relaxed limit when outside) to maintain gear alignment while preventing backlash strike caused by torque direction changes.
Data Source
AI summary
In a torque control method for a drive system of an electric vehicle configured for generating torque by evading a backlash band to prevent occurrence of backlash in the drive system, torque control modes include a contra-directional distribution mode in an acceleration direction in which a front-wheel torque command is determined to be a maximum front-wheel torque threshold value set as a negative (−) torque value in a regenerative direction and a rear-wheel torque command is determined to be a positive (+) torque value in a driving direction and a contra-directional distribution mode in a regenerative direction in which the rear-wheel torque command is determined to be a minimum rear-wheel torque threshold value set as a positive (+) torque value in the driving direction and the front-wheel torque command is determined to be a negative (−) torque value in the regenerative direction thereof.