Electric Motor Torque Slope Control for Backlash Shock Reduction
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Solution Overview
Problem
Electric motor vehicles experience acceleration shock due to backlash in the transition from regenerative braking to acceleration, which current methods fail to adequately address, resulting in delays and reduced acceleration performance.
Innovation Solution
A system and method that determine the backlash torque range based on a coast down value, adjusting the motor torque slope to mitigate shock by using a motor controller with backlash torque determination, correction, and shock determination units to optimize torque application according to vehicle speed and acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the motor torque is set to a backlash torque range between +10 Nm and -10 Nm to reduce gear backlash shock, then the shock due to backlash is reduced, but the start-up of the vehicle is delayed and acceleration is reduced
Solution Approach 1:
The patent applies dynamics by making the backlash torque range adjustable rather than fixed. The control unit dynamically adjusts the backlash torque range based on motor speed, expanding it at higher speeds where backlash occurs and reducing or eliminating it at lower speeds where acceleration performance is critical. This resolves the contradiction by adapting the torque control strategy to operating conditions.
Solution Approach 2:
The patent changes the parameter of backlash torque range based on motor speed. At motor speeds above a predetermined threshold, the backlash torque range is set to a first range (e.g., +10 Nm to -10 Nm) to reduce shock. At speeds below the threshold, the range is set to a second range (e.g., +5 Nm to -5 Nm) or zero to improve start-up and acceleration performance. This parameter adjustment resolves the contradiction between shock reduction and acceleration performance.
2Device complexity
If a fixed backlash torque range is used to mitigate shock, then the shock reduction is simplified, but the shock at acceleration is insufficiently reduced because motor torque is applied beyond the backlash torque range according to vehicle speed
Solution Approach 1:
The patent makes the backlash torque range dynamic by adjusting it according to motor speed. The control unit receives motor speed information and automatically adjusts the torque range threshold accordingly. This dynamic adjustment increases control sophistication to reduce acceleration shock more effectively while managing complexity through automated speed-based logic.
Solution Approach 2:
The patent changes the backlash torque range parameter based on motor speed conditions. When motor speed exceeds a predetermined value, the control unit sets the backlash torque range to a first value (e.g., +10 Nm to -10 Nm). When motor speed is below the threshold, it sets the range to a second value (e.g., +5 Nm to -5 Nm) or zero. This parameter change strategy effectively reduces acceleration shock across different operating conditions while maintaining manageable control complexity.
Data Source
AI summary
A system and a method for reducing the acceleration shock of an electric motor vehicle are provided. A backlash torque range is determined based on a coast down value indicating the motor torque for maintaining a vehicle speed. A slope of the motor torque that falls within a backlash torque range is reduced and corrected, considering that the motor torque for causing backlash is changed as the motor speed changes, thereby reducing the shock due to the backlash at the acceleration (start-up) of a vehicle.