Steer-by-Wire Mode Switching with Gradual Turning Current Control
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Solution Overview
Problem
In steer-by-wire type steering systems, switching from a virtual mode to a normal mode can cause abnormal sounds and vibrations due to a sudden increase in current supplied to the turning device when the operation member state does not correspond to the actual wheel state.
Innovation Solution
A controller is configured to execute specific turning control or reaction force control when switching from virtual to normal mode, gradually adjusting the turning device and operation member to match the actual wheel state, thereby suppressing sudden current changes and vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the turning current is set to a current value at which the wheels are not turned in virtual mode, then power consumption is reduced, but abnormal sound and vibration are generated when switching to normal mode
Solution Approach 1:
The controller performs preliminary action by detecting the operation member state before mode switching and preparing the appropriate turning current value in advance. When switching from virtual to normal mode, the controller has already determined the required turning current based on the operation member state, enabling a smooth transition without sudden current changes that cause abnormal sounds and vibrations.
Solution Approach 2:
The controller changes the turning current parameter smoothly during mode transition. Instead of abruptly changing from zero current (virtual mode) to full current (normal mode), the controller adjusts the turning current value progressively based on the operation member state, preventing sudden current changes that generate abnormal sounds and vibrations while still achieving the desired wheel turning effect.
2Loss of substance
If the wheels are prevented from turning in virtual mode, then tire wear is reduced, but the operation member state does not correspond to the actual wheel state when switching to normal mode
Solution Approach 1:
The controller performs preliminary detection of the operation member state (operation angle) before mode switching. This preliminary action allows the controller to know the desired wheel position in advance, so when normal mode is activated, the wheels can be positioned correctly without sudden adjustments, maintaining state correspondence between the operation member and actual wheels.
Solution Approach 2:
The patent replaces the mechanical connection between the operation member and wheels with an electrical control system. The controller uses electrical signals to detect the operation member state and control the turning current to the wheels, allowing independent control of operation member position and wheel position. This substitution enables the wheels to remain stationary in virtual mode while maintaining the capability to achieve correct positioning in normal mode without mechanical coupling constraints.
Data Source
AI summary
A steer-by-wire type steering system includes an operation device, a turning device, and a controller. The controller is configured to switch between a normal mode and a virtual mode, and executes, when a control mode is switched from the virtual mode to the normal mode, at least one of specific turning control or specific reaction force control.