Rear Wheel Toe Angle Control Thermal Protection
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Solution Overview
Problem
Rear wheel toe angle control systems with electric actuators face issues where frequent adjustments under extreme conditions lead to increased motor load and brush temperature, potentially damaging the electric motor, and existing protective logic can cause undesirable vehicle behavior by abruptly changing the toe angle back to neutral.
Innovation Solution
A rear wheel toe angle control system that progressively reduces the manipulated variable of the electric actuator based on temperature detected by a sensor, rather than abruptly stopping it at a protective temperature, to prevent thermal damage and maintain smooth vehicle operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric actuator operates under extreme conditions with frequent toe angle adjustments, then the cornering performance and motion stability are improved, but the brush temperature rises and motor damage risk increases
Solution Approach 1:
The control device performs preliminary thermal protection by detecting actuator temperature and proactively reducing the manipulated variable before the motor reaches damaging temperatures. This preventive approach allows the system to operate under extreme conditions while avoiding brush overheating and motor failure.
2Reliability
If the controller performs protective logic by gradually returning toe angle to zero when brush temperature reaches protection temperature, then motor damage is prevented, but vehicle operator experiences unfamiliar steering impression
Solution Approach 1:
The control device applies local quality by differentiating the protection response based on operating conditions. When temperature reaches the protection threshold, the system reduces the manipulated variable proportionally rather than forcing toe angle to zero, maintaining steering smoothness while protecting the motor. The reduction ratio is adjusted according to whether the vehicle is cornering or not, providing condition-specific protection.
Solution Approach 2:
The control system dynamically adjusts the manipulated variable reduction based on real-time temperature measurements and operating conditions. Rather than using a fixed protective response, the system continuously adapts the reduction ratio to maintain both motor protection and steering naturalness under varying conditions.
3Reliability
If the controller abruptly resumes toe angle control when brush temperature falls below protection temperature, then motor protection is maintained, but vehicle operator experiences unfamiliar impression again
Solution Approach 1:
The control device dynamically resumes toe angle control based on the current operating condition when temperature drops below the protection threshold. Rather than abrupt resumption, the system gradually increases the manipulated variable according to whether the vehicle is cornering or traveling straight, ensuring smooth and natural steering recovery.
Data Source
AI summary
An electric actuator (electric motor) is thermally protected without causing any unfamiliar impression in steering a vehicle. A temperature compensation gain computing unit (25) reduces the manipulated variable of the electric actuator (40L, 40R) by using a gain that diminishes with the rise in the temperature of the actuator.