Electric Vehicle Torque Control for Turning Stability
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Solution Overview
Problem
Electric vehicles experience reduced drivability and riding comfort when transitioning from acceleration to braking, particularly during turns, due to increased transverse acceleration and unstable vehicle posture.
Innovation Solution
A control apparatus gradually varies vehicle torque towards the brake side by using a smaller rate value when the accelerator is switched from the on-state to the off-state, especially during turns, and when the steering angle or transverse acceleration is large, to minimize sudden torque changes and maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the vehicle torque is evenly varied without considering whether the vehicle is traveling straight or turning, then the control system is simple, but the drivability deteriorates more in turning than in traveling straight
Solution Approach 1:
The control system dynamically adjusts the rate value based on vehicle operating conditions (steering angle, transverse acceleration) to vary torque gradually at different rates for straight vs. turning conditions, making the control adaptive rather than fixed
Solution Approach 2:
The system changes the rate value parameter based on detected vehicle state (steering angle magnitude, transverse acceleration magnitude), using different rate values for different operating conditions to optimize drivability across scenarios
2Ease of operation
If the rate value is set to be smaller when the absolute value of steering angle or transverse acceleration is large, then the transient torque varies more gradually improving drivability, but the control complexity increases
Solution Approach 1:
The control system continuously monitors steering angle and transverse acceleration, using this feedback to dynamically determine the appropriate rate value for torque variation, creating a closed-loop control system
Solution Approach 2:
The rate value acts as an intermediary parameter that translates vehicle state (steering angle, acceleration) into appropriate torque variation characteristics, mediating between sensor inputs and motor control outputs
Data Source
AI summary
In an electric vehicle including a motor for traveling, when an accelerator is switched from an on-state to an off-state, the motor is controlled such that a vehicle torque is varied more gradually toward a requested torque on a brake side (requested torque in the off-state) in turning than in traveling straight. Thereby, when the accelerator is switched from the on-state to the off-state in turning, drivability of the driver can be restrained from deteriorating.