Steering Torque Control for Noticeable Autonomous Lane Changes
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Solution Overview
Problem
In autonomous driving systems, the reduction of additional reaction torque when a turn signal is activated can make it unclear to drivers when and how the target travel lane will be switched, leading to discomfort and difficulty in noticing lane changes.
Innovation Solution
A motor control device that includes a manual steering command value generation unit, an integrated angle command value calculation unit, and a motor control unit, which adjusts road reaction force characteristics to enhance the driver's perception of lane changes by increasing specific coefficients when a direction change command is input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If additional reaction torque is reduced when turn signal switch is ON to facilitate lane change, then ease of operation is improved, but driver awareness of lane change timing deteriorates
Solution Approach 1:
The system applies periodic modulation to the road reaction force characteristic coefficients at specific intervals during the lane change process. The coefficients are increased at predetermined timing points (when turn signal is ON and when lane change is completed) to create periodic noticeable changes in steering reaction force, allowing drivers to detect lane change timing while maintaining smooth operation.
Solution Approach 2:
The system dynamically changes the road reaction force characteristic coefficients (k1, k2, c1, c2) based on driving conditions and lane change status. By increasing these coefficients at specific timing, the system creates noticeable steering reaction force changes that inform drivers of lane change timing, while keeping the coefficients adjustable to maintain operational smoothness.
2Productivity
If additional reaction torque is reduced during autonomous driving lane change, then productivity is improved, but measurement precision of lane change event deteriorates
Solution Approach 1:
The system prepares for lane change notification by monitoring the turn signal switch status and predetermined conditions in advance. When the turn signal is activated and conditions are met, the system proactively increases the road reaction force coefficients to notify drivers of upcoming or completed lane changes, ensuring timely perception without delaying the lane change execution.
3Loss of information
If road reaction force characteristic coefficients are increased when direction change command is input, then driver awareness of lane change is improved, but force requirement for steering operation increases
Solution Approach 1:
The system applies different road reaction force characteristic coefficients to different operational phases locally. During normal autonomous driving, lower coefficients are used for smooth operation. When turn signal is ON or lane change is completed, coefficients are increased locally at these specific timing points to provide noticeable feedback, creating local quality variations that inform drivers without requiring high force throughout the entire operation.
Data Source
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AI summary
A motor control device includes: a steering member; an electric motor that drives a steering operation mechanism; a manual steering command value generation unit that generates a manual steering command value using steering torque; an integrated angle command value calculation unit that calculates an integrated angle command value by adding the manual steering command value to an automatic steering command value for driving assistance; and a motor control unit that controls the electric motor based on the integrated angle command value. The manual steering command value generation unit is configured to generate the manual steering command value based on an equation of motion including road reaction force characteristic coefficients. The motor control device further includes a road reaction force characteristic change unit that, when a direction change command is input by a driver operation, increases a value of at least one road reaction force characteristic coefficient out of the road reaction force characteristic coefficients as compared to a value before the direction change command is input.