Steer-By-Wire Steering Shaft Locking to Prevent Phase Shift
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Solution Overview
Problem
In steer-by-wire systems, when the ignition switch is turned off, the steering wheel freely rotates due to its own weight, causing a phase shift between the steering wheel and steered wheel, leading to uncomfortable sensations for the driver and limited vehicle travel until the shift is corrected, and the absence of steering reaction force results in an uncomfortable driving experience.
Innovation Solution
A steering input device that increases reaction torque from a reaction force motor after the ignition switch is turned off, locking the steering shaft to prevent unwanted rotation and maintain alignment between the steering wheel and steered wheel, thereby suppressing phase shifts and uncomfortable sensations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the power supply of the steering reaction force actuator is turned off when the ignition switch is switched to OFF state, then power consumption is reduced, but the steering wheel freely rotates causing phase shift between steering wheel and steered wheel
Solution Approach 1:
The lock mechanism is activated in advance before the ignition switch is completely turned off. The control unit receives the OFF signal and immediately engages the lock mechanism to secure the steering shaft, preventing any subsequent rotation that would cause phase shift. This preliminary locking action ensures alignment is maintained without requiring continuous power to the reaction force actuator.
Solution Approach 2:
The patent replaces the electrical control system (reaction force actuator) with a mechanical locking system. Instead of relying on continuous electrical power to maintain steering wheel position, a mechanical lock mechanism physically constrains the steering shaft, eliminating the need for sustained electrical power while preventing phase shift.
2Loss of energy
If the power supply of the steering reaction force actuator is turned off when the ignition switch is switched to OFF state, then power consumption is reduced, but the driver experiences uncomfortable sensation due to absence of steering reaction force
Solution Approach 1:
The lock mechanism engages in advance before the driver would notice any discomfort from loss of reaction force. By securing the steering shaft position mechanically before power is completely cut, the system eliminates the need to maintain electrical power for the reaction force actuator, reducing consumption while preventing the uncomfortable sensation of free rotation.
3Reliability
If the lock mechanism is activated immediately when ignition is turned off, then phase shift is prevented, but the driver experiences uncomfortable sensation during steering operation
Solution Approach 1:
The lock mechanism is activated in advance during the transition period when the ignition switch is turned off, but before the driver would notice any discomfort. This timing ensures the steering shaft is secured while the driver is still operating the vehicle, preventing phase shift without causing the uncomfortable sensation of sudden locking during normal steering.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses driver discomfort and phase shifts between the steering wheel and steered wheel, ensuring smooth vehicle travel by maintaining alignment and reaction force when the ignition is turned off, and reducing power consumption by adjusting torque levels.
Implementation Method 1
a reaction force motor 321 that applies, to the steering shaft 310, a steering load (steering reaction force) in accordance with a steering operation by a driver
Implementation Method 2
a lock mechanism 330 for regulating rotation of the steering shaft 310
Data Source
AI summary
A steering input device for steer-by-wire, according to the present invention, includes a steering shaft that is mechanically separated from a steered wheel, a reaction force motor that applies a steering load to the steering shaft, a lock mechanism that regulates rotation of the steering shaft, a steering amount sensor that detects an operation amount of the steering shaft and outputs an operation amount signal, and a controller. The controller increases the reaction torque generated by the reaction force motor after the starting switch of the vehicle is switched to an OFF state, and after the reaction torque is increased, switches the lock mechanism to a locked state. Thereby, it is possible to suppress an uncomfortable sensation of the driver in steering, while suppressing occurrence of a phase shift between the steering wheel and the steered wheel when the starting switch of the vehicle is switched to the OFF state.