Steering Yaw Rate Control on μ-Split Roads During Braking
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Solution Overview
Problem
When a vehicle traverses a μ-split road where the friction coefficients differ between the right and left road wheels, applying braking force can cause the vehicle to swerve towards the side with higher friction, leading to driver discomfort and reduced operation stability due to mismatched vehicle behavior.
Innovation Solution
A steering apparatus control system that compares target and actual yaw rates, using a microcontroller to adjust steering actuators to align actual yaw rates with driver intention by correcting steering angles, thereby canceling out yaw rate differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If braking force is applied on a μ-split road, then braking effectiveness is improved, but vehicle stability deteriorates due to swerving
Solution Approach 1:
The control apparatus applies preliminary counteracting steering torque to the steering wheel before and during braking on μ-split roads. This preliminary anti-action compensates for the expected yaw moment generated by braking force differences, preventing vehicle swerving and maintaining stability while preserving braking effectiveness
Solution Approach 2:
The control apparatus introduces an intermediary steering torque through the steering wheel that mediates between the driver's steering input and the vehicle's actual motion. This intermediary torque cancels out the harmful yaw moment caused by asymmetric braking forces, allowing the driver to maintain steering control while braking on μ-split surfaces
2Stability of the object's composition
If braking force difference control is applied, then vehicle swerving is reduced, but driver operation comfort deteriorates
Solution Approach 1:
The control apparatus uses the steering wheel as an intermediary to transmit compensatory torque to the driver. By acting through the familiar steering interface rather than directly controlling brake forces, the system maintains vehicle stability while preserving the driver's sense of control and operation comfort
Solution Approach 2:
The control apparatus continuously monitors vehicle state (yaw rate, steering angle, braking force) and dynamically adjusts the compensatory steering torque in real-time. This feedback mechanism ensures that the counteracting torque is applied only when and where needed, maintaining stability without creating unnecessary interference with driver operation
3Ease of operation
If steering actuator control is applied to cancel yaw rate, then vehicle behavior aligns with driver intention, but control system complexity increases
Solution Approach 1:
The control apparatus integrates multiple functions into a single control system that simultaneously manages braking coordination, steering torque compensation, and yaw rate control. By making the control system multi-functional rather than adding separate systems, the patent achieves vehicle behavior alignment without proportionally increasing complexity
Solution Approach 2:
The control apparatus uses the steering wheel and steering actuator as an intermediary mechanism to achieve yaw rate control. Rather than directly controlling vehicle motion through multiple actuators, the system works through the existing steering interface, leveraging the steering actuator's capability to provide both normal steering assistance and compensatory torque for yaw cancellation
Data Source
AI summary
A steering apparatus control apparatus, a steering apparatus control method, and a steering system according to the present invention are applied to a vehicle including a steering apparatus configured to be able to control a steering angle of road wheels independently of an operation quantity of a steering operation input member, compare a target yaw rate based on a physical quantity about a running state of the vehicle and the operation quantity of the steering operation input member with an actual yaw rate based on the physical quantity about the running state of the vehicle, and control a steering actuator in a direction in which a yaw rate of the vehicle is cancelled out such that the actual yaw rate approximates the target yaw rate. In this way, vehicle behavior that agrees with driver intention can be realized.