Electric Motor Torque Control for Vibration Suppression
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Solution Overview
Problem
Conventional regenerative brake control systems for electric vehicles generate vibration in the front-back direction when decelerating, particularly when the regenerative braking force is set high and the vehicle comes to a stop.
Innovation Solution
A control device for electric motor vehicles that calculates a first torque target value based on acceleration and motor rotation speed, and a second torque target value by adding motor rotation speed feedback torque and disturbance torque, switching between these values to manage regenerative braking and minimize vibration during deceleration and stopping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a large regenerative braking force is applied to decelerate the vehicle, then the deceleration performance is improved, but vibration in the front-back direction of the vehicle body is generated when the vehicle stops
Solution Approach 1:
The control device dynamically switches between two torque control modes based on the vehicle's stopping state. During deceleration, the first torque target value provides strong regenerative braking. When the vehicle approaches stop (determined by the just-before-stop moment determining unit), the system transitions to the second torque target value that incorporates disturbance torque estimation, thereby adapting the control strategy to eliminate vibration while maintaining deceleration performance throughout the stopping process
Solution Approach 2:
The system changes the torque command parameters based on the vehicle's operational phase. The first torque target value is used during active deceleration, while the second torque target value (incorporating motor rotation speed feedback torque and disturbance torque estimation) is applied when the vehicle is about to stop. This parameter switching resolves the contradiction by optimizing torque characteristics for each phase of the stopping process
2Use of energy by moving object
If the regenerative braking force is increased to improve energy efficiency, then the energy recovery is improved, but the vehicle requires additional mechanical braking systems to prevent vibration at stop
Solution Approach 1:
The electric motor serves multiple functions: it acts as a drive motor during acceleration, a regenerative brake during deceleration, and a vibration-suppressing actuator during stopping. The control device enables the motor to perform both energy recovery and vibration suppression functions by switching between the first and second torque target values, eliminating the need for separate mechanical braking systems while maintaining energy efficiency
Solution Approach 2:
The control system uses the motor's own rotational kinetic energy and inertia to suppress vibration during stopping. By applying the second torque target value that includes disturbance torque estimation and speed feedback, the motor self-regulates to prevent vibration without requiring external mechanical braking components, thereby simplifying the overall braking system while maintaining high energy recovery
Data Source
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AI summary
A control device for electric motor vehicle using an electric motor 4 as a traveling drive source and configured to decelerate by a regenerative braking force of the electric motor 4 calculates a first torque target value on the basis of vehicle information and calculates a second torque target value which converges to zero with a reduction in a speed parameter proportional to a traveling speed of the electric motor vehicle. If the vehicle is determined to have not reached a just-before-stop moment, the first torque target value is set as a motor torque command value. If the vehicle is determined to stop shortly, the second torque target value is set as the motor torque command value. The electric motor 4 is controlled on the basis of the set motor torque command value.