Steering Control Device Guard Process for Oversteering
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Solution Overview
Problem
In a steer-by-wire steering system, when a vehicle is in an oversteering state due to centrifugal force exceeding frictional force, counter-steering can lead to an excessive steering reaction force, causing the driver to feel heaviness and worsening the steering experience.
Innovation Solution
A steering control device with an electronic control unit that calculates a target reaction torque and controls a steering-side motor to generate a motor torque corresponding to this target. The unit also calculates an angle axial force and performs a guard process to prevent this force from becoming excessive, thereby limiting the steering reaction force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the angle axial force is calculated based on target turning angle during counter-steering, then the steering reaction force increases to provide stability, but the driver feels heaviness and steering feeling deteriorates
Solution Approach 1:
The patent applies dynamics by making the axial force calculation adaptive to the vehicle's actual turning state. The system dynamically switches between using target turning angle (for stability) and actual turning angle (for responsiveness) based on whether the vehicle is in normal steering or counter-steering mode, resolving the contradiction between stability and ease of operation
Solution Approach 2:
The patent changes the parameter used for axial force calculation from target turning angle to actual turning angle during counter-steering. This parameter substitution allows the steering reaction force to reflect the vehicle's actual state rather than the driver's input, preventing excessive force and maintaining steering feel while preserving stability through appropriate force levels
2Reliability
If the steering reaction force is increased to counteract oversteering, then vehicle control is improved, but the driver experiences excessive force and worsened steering feel
Solution Approach 1:
The patent uses feedback by comparing the target turning angle with the actual turning angle to detect counter-steering conditions. Based on this feedback, the system adjusts the axial force calculation to use actual turning angle, ensuring the steering reaction force is appropriate for the vehicle's actual state while maintaining control capability
Solution Approach 2:
The patent applies partial action by using only the actual turning angle (rather than target turning angle) to calculate axial force during counter-steering. This partial use of turning angle information provides sufficient force for vehicle control while avoiding the excessive force that would result from using target turning angle, thus maintaining both control and acceptable steering feel
Data Source
AI summary
A steering control device includes an electronic control unit configured to calculate a target reaction torque that is a target value of a steering reaction force that is a force against steering input to a steering unit and to control operation of a steering-side motor provided in the steering unit such that a motor torque corresponding to the target reaction torque is generated. The electronic control unit is configured to calculate an angle axial force, as an axial component based on an axial force acting on a turning shaft that operates to turn turning wheels, the angle axial force being an axial force in which road-surface information is not reflected, and the angle axial force being determined according to an angle convertible to a turning angle of the turning wheels. The electronic control unit is configured to perform a guard process such that the angle axial force is not excessive.