EV Drive Torque Control to Evade Backlash Band
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Solution Overview
Problem
Existing drive systems in electric vehicles face issues with backlash, leading to vibration, noise, and harshness (NVH) due to rapid torque changes, which current methods fail to prevent effectively, and result in reduced responsiveness and stability.
Innovation Solution
A torque control method that evades the backlash band by separating operating regions of front and rear wheel motors, allowing active switching between power and responsiveness priority modes to minimize torque direction changes, thereby preventing backlash occurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the torque change rate is set too high, then the acceleration responsiveness is improved, but backlash occurs causing vibration, noise, and torsion of driveshaft
Solution Approach 1:
The control method predicts future torque requirements and proactively adjusts the torque command to evade the backlash band before backlash occurs. By calculating predicted torque values and comparing them with the backlash band range, the system takes preliminary action to prevent backlash rather than reacting after it occurs.
Solution Approach 2:
When the predicted torque would enter the backlash band, the control method skips through the problematic torque region by limiting the torque change rate. This allows the system to rush through the transition by taking a different path (through the backlash band) rather than directly entering it, thereby avoiding the harmful effects of backlash.
2Object-affected harmful factors
If the torque change rate is limited too small, then backlash is avoided, but the acceleration responsiveness deteriorates and vehicle behavior differs from driver intention
Solution Approach 1:
The control method dynamically adjusts the torque change rate based on real-time operating conditions. By continuously monitoring the predicted torque, current torque, and vehicle state, the system adapts the torque command profile to evade the backlash band while maintaining maximum possible responsiveness. This dynamic adjustment allows the system to be aggressive when safe and conservative when necessary.
Solution Approach 2:
The method changes the torque command parameters to avoid the backlash band. By calculating the backlash band range based on current torque and predicted torque, the system modifies the torque command parameters (magnitude and rate of change) to skip through or avoid the problematic parameter region, thereby preventing backlash while maintaining responsiveness.
3Object-affected harmful factors
If active feedback torque correction control is applied to suppress vibration, then NVH is reduced, but vehicle responsiveness deteriorates due to chronic torque correction delays
Solution Approach 1:
Instead of correcting vibration after it occurs, the method takes preliminary action to prevent backlash from occurring in the first place. By predicting future torque requirements and proactively evading the backlash band, the system eliminates the root cause of vibration before it can manifest, thereby avoiding the need for corrective actions that would cause delays.
Solution Approach 2:
The method converts the potential harm of torque correction delays into a benefit by preventing the need for correction altogether. By accepting a slightly more conservative torque command profile that evades the backlash band, the system eliminates vibration at its source, transforming what would have been a harmful corrective action into a beneficial preventive measure.
Data Source
AI summary
A method of controlling a drive system torque of an electric vehicle for generating a torque by evading a backlash band to prevent the occurrence of backlash in the drive system includes determining, by a controller, whether a plurality of predetermined entry conditions for entering a responsiveness priority mode of the vehicle are satisfied in a predetermined order based on vehicle driving information in a state in which control of a power priority mode is performed, and transitioning, by the controller, a mode to the responsiveness priority mode when it is determined that the plurality of entry conditions are sequentially satisfied and performing control of the responsiveness priority mode.