Vehicle Steering Device Torque Adjustment for Driver Comfort
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Solution Overview
Problem
In electric power steering systems, when a vehicle speed signal is not available, using a high alternative vehicle speed can result in excessive assist force at low speeds, causing discomfort to the driver during wheel operation.
Innovation Solution
A vehicle steering device that adjusts the target steering torque based on the absolute difference between actual and estimated vehicle motion parameters when an alternative vehicle speed is used, thereby reducing excessive steering torque at low speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high alternative vehicle speed is used when vehicle speed signal is not available, then the steering control can be maintained, but excessive assist force is generated in low speed range causing driver discomfort
Solution Approach 1:
The patent applies dynamics by making the target steering torque dynamically adjustable based on vehicle motion state. When alternative vehicle speed is used, the system detects large deviations in yaw rate or lateral acceleration and automatically reduces the torque gain, allowing the assist force to adapt to actual vehicle conditions rather than using a fixed high-speed torque characteristic
Solution Approach 2:
The patent changes the parameter of target steering torque by introducing a torque gain coefficient that modifies the basic map output. When alternative vehicle speed is detected, the torque gain is reduced based on the magnitude of deviation between actual and estimated motion parameters, effectively transforming the torque characteristic from high-speed to low-speed range
2Ease of operation
If the target steering torque is reduced to prevent excessive assist force, then driver comfort is improved, but the steering torque may become insufficient at high speeds
Solution Approach 1:
The patent applies local quality by applying different torque gain adjustments to different vehicle speed ranges. The torque gain is selectively reduced only when alternative vehicle speed is used and deviation is detected, while maintaining normal torque characteristics when vehicle speed is accurately known or deviation is small, thus providing locally optimized torque for different operating conditions
Data Source
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AI summary
When a vehicle speed Vs of a vehicle is a predetermined alternative vehicle speed, a target steering torque Tref is reduced in accordance with the absolute value of the difference between a physical quantity generated through turning motion of the vehicle and an estimated value of the physical quantity at an alternative vehicle speed.