Multi-Motor EV Torque Control for Temperature-Induced Motor Drift
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Solution Overview
Problem
Existing control systems for electric vehicles with multiple motors struggle to accurately control output torques due to varying motor characteristics caused by temperature changes, leading to reduced straight-running stability and turning performance.
Innovation Solution
A control system that includes a parameter estimator, reference motor selector, and motor torque controller to calculate and correct estimated parameters, reducing differences between motors to improve torque control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If motor output characteristics are controlled separately for each motor, then straight-running stability and turning performance are improved, but differences in motor characteristics due to temperature changes cause torque control errors
Solution Approach 1:
The system changes the parameter representation from absolute torque values to relative torque ratios between motors. The controller calculates the ratio of output torques between multiple motors and adjusts control commands to maintain consistent ratios, compensating for temperature-induced characteristic variations.
Solution Approach 2:
The system implements feedback by continuously monitoring the actual output torque of each motor and comparing it with the target torque. Based on this feedback, the controller adjusts the torque command for each motor to maintain the desired torque ratio, thereby compensating for characteristic differences caused by temperature changes.
2Measurement precision
If temperature compensation is applied to each motor individually, then motor output accuracy is improved, but individual motor model errors cause estimation inaccuracies
Solution Approach 1:
The system merges the control of multiple motors by managing them as a coordinated group rather than independent units. The controller calculates the torque ratio relationship between motors and applies unified control strategies, allowing errors in individual motor models to be compensated by the collective control approach.
Solution Approach 2:
The system transforms the control parameters from individual motor absolute values to relative ratios between motors. This parameter transformation allows the system to control torque distribution based on proportional relationships, reducing the impact of individual motor model errors and temperature variations.
Data Source
AI summary
A control system for an electric vehicle configured to control output torques of each motor independently so as to improve a running stability and a control stability. Each of the motors is connected individually to one of wheels so that drive forces established by the wheels are controlled independently by controlling output torques of motors independently. A control unit is configured to: calculate estimated parameters of the motors; select a reference motor; calculate a difference between the estimated parameters of the reference motor and other motor; and control the torques of the motors to reduce a difference between the torques of the reference motor and other motor.