Steer-By-Wire Wheel Alignment Control During Parking
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Solution Overview
Problem
The steer-by-wire steering system may fail to steer the wheels to the correct angle due to reduced actuator output or overheating, leading to unexpected vehicle acceleration when the steering angle deviates from the prescribed relationship with the steered angle, especially during parking.
Innovation Solution
A control unit manages the steering and reaction force actuators to maintain a prescribed relationship between the steering and steered angles, setting speed or acceleration limits when deviations occur, and performing phase matching controls to align the angles, including passive, opposite, and active phase matching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the steering actuator output is reduced due to failure or overheating, then the steering system reliability deteriorates, but the vehicle may start traveling before wheels are properly steered, causing sudden unexpected acceleration
Solution Approach 1:
The control unit applies preliminary anti-action by detecting steering angle deviations before the vehicle starts moving and actively correcting them. When the steering member is operated while the vehicle is stationary, the control unit monitors whether the wheels are properly steered and prevents vehicle movement until alignment is achieved, thereby counteracting the potential harmful effect of sudden unexpected acceleration
Solution Approach 2:
The system implements feedback control by continuously monitoring the relationship between the steering member angle and wheel angle, and adjusting the steering actuator output accordingly. The control unit compares the actual wheel position with the expected position based on steering member input, and makes real-time corrections to ensure proper alignment before vehicle movement
2Reliability
If the steering actuator maximum output is reduced due to overheating or failure, then the steering correction capability deteriorates, but setting speed or acceleration limits may prevent the vehicle from accelerating as intended by the driver
Solution Approach 1:
The system applies dynamics by making the speed and acceleration limits dynamic rather than static. The control unit adjusts these limits based on the detected steering angle deviation and the correction status. When alignment is achieved or deviation is within acceptable ranges, the limits are relaxed or removed, allowing normal vehicle acceleration. When misalignment is detected, limits are applied temporarily until correction is complete
Solution Approach 2:
The control unit continuously monitors steering angle alignment and provides feedback to adjust vehicle motion constraints. Based on the real-time relationship between steering member angle and wheel angle, the system dynamically modifies acceleration and speed limits, ensuring safety during misalignment while restoring full performance when alignment is achieved
Data Source
AI summary
Provided is a steer-by-wire steering system for a vehicle that can prevent the vehicle from suddenly accelerating in a direction which the drive did not anticipate even when the steering angle of the steering member was changed while the vehicle was parked. When the steered angle deviates from the prescribed relationship to the steering angle (ST2: Yes), immediately or upon satisfaction of a trigger condition, the control unit drives the steering actuator to bring the steered angle to come closer to the prescribed relationship to the steering angle (ST16, ST17, ST20, ST21), and sets an upper limit to a speed or an acceleration of the vehicle (ST7).