Vehicle Steering Control Rate Limiting for Comfort
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Solution Overview
Problem
Existing driving support apparatuses for vehicles often cause abrupt changes in the running state when a driver's steering operation deviates from the controlled trajectory, leading to uncomfortable experiences for occupants due to large deviations and torque imbalances during running control.
Innovation Solution
A driving support apparatus that limits the time change rate of the steered angle of steerable wheels when deviations exceed a reference value, and adjusts the target change amount based on decreasing corrections as deviations increase, incorporating a power steering device with damping and friction torque control to moderate steering forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the steering torque of running control is increased to correct large deviations, then the vehicle can return to the target trajectory faster, but the running state changes abruptly causing occupant discomfort
Solution Approach 1:
The patent applies dynamics by making the steering torque characteristics variable based on operating conditions. Specifically, the maximum steering torque is dynamically adjusted based on vehicle speed and steering angular velocity, allowing the system to provide strong correction when needed while limiting abrupt changes that cause discomfort. This dynamic adjustment resolves the contradiction between fast correction and comfort.
Solution Approach 2:
The patent changes key parameters (steering torque magnitude, maximum steering torque limits) based on vehicle speed and steering rate conditions. By modifying these parameters dynamically, the system achieves both rapid trajectory correction when deviations are large and smooth, comfortable steering when the vehicle is near the target trajectory or moving at high speeds.
2Ease of operation
If the steering assist torque is reduced during driver steering, then the driver's steering operation is facilitated, but the running control authority is weakened when large deviations need correction
Solution Approach 1:
The patent dynamically adjusts the arbitration between driver steering torque and running control torque based on real-time conditions. The control device calculates both torques and determines their combination based on vehicle speed, steering angular velocity, and deviation magnitude, ensuring both driver ease of operation and running control authority are maintained appropriately for each situation.
Solution Approach 2:
The system changes the weighting and magnitude of steering assist torque and running control torque based on operational parameters. When driver steering is detected, the assist torque is reduced for ease of operation, but when large deviations exist, the running control torque is enhanced to maintain authority, with transitions managed smoothly through parameter-based control.
3Productivity
If the steering torque is increased to correct large lateral deviations, then the vehicle returns to target trajectory faster, but the steering force becomes excessive and uncomfortable
Solution Approach 1:
The patent implements dynamic steering torque control where the maximum steering torque is adjusted based on vehicle speed and steering angular velocity. This dynamic approach allows efficient trajectory correction while preventing excessive steering forces that would cause discomfort, as the torque limits adapt to current operating conditions.
Solution Approach 2:
The system modifies steering torque parameters (maximum torque limits, torque rate of change) based on vehicle speed and steering rate conditions. This parameter adjustment ensures that trajectory correction remains efficient while steering forces stay within comfortable ranges for occupants.
Data Source
AI summary
A driving support apparatus for a vehicle comprising a steering device that steers steerable wheels, and a control unit configured to execute a running control in which a steered angle of the steerable wheels is changed by controlling the steering device, the control unit being configured to calculate a deviation between an index value of a target running state of the vehicle and an index value of an actual running state, to calculate a target change amount of the steered angle based on the index value deviation, to control the steering device so that a change amount of the steered angle conforms to the target change amount, and to limit a magnitude of a time change rate of the steered angle changed by the running control when one of a magnitude of the index value deviation and a magnitude of the target change amount exceeds a reference value.