Steer-By-Wire Reaction Torque Feedback for Output-Limited Steering
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Solution Overview
Problem
In steer-by-wire systems, drivers cannot recognize when the output torque of the turning device is limited due to overheating or power limitations, leading to a lack of feedback on the vehicle's steering state.
Innovation Solution
A steering control device that calculates a current limit presentation command value to convey the output-limited state to the driver by adjusting the current flowing to the reaction-force-use rotary electric machine, based on the difference between the angles of the reaction force device and the turning device, and increases the absolute value of this command when the turning device is in an output-limited state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output torque of the turning device is limited due to overheating or power limitations, then the turning device can operate within safe parameters, but the driver cannot recognize the output-limited state leading to lack of feedback on steering performance
Solution Approach 1:
The patent implements a feedback mechanism by calculating a current limit presentation command value based on the angle difference between the reaction force device and turning device. When the turning device is in an output-limited state, the system increases the absolute value of this command value, creating increased resistance that feeds back to the driver. This resolves the contradiction by maintaining reliable operation within limits while providing the driver with sensory feedback about the limited state through the steering wheel resistance.
2Loss of information
If the current limit presentation command value is increased when the turning device is output-limited, then the driver can recognize the limited state through increased resistance, but this requires additional control complexity
Solution Approach 1:
The reaction force device serves multiple functions: it provides normal reaction force to the driver during regular operation and simultaneously acts as a feedback mechanism to indicate the output-limited state by increasing resistance. This multi-functionality resolves the contradiction by using existing system components for dual purposes, avoiding additional complex hardware while still providing the necessary driver feedback about steering performance limitations.
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
Enables the driver to recognize the output-limited state of the turning device through increased resistance and feedback, ensuring safe operation by clearly indicating when the device is operating within its limits.
Implementation Method 1
a reaction force device including a reaction-force-use rotary electric machine and a reaction-force-use power converter that drives the reaction-force-use rotary electric machine
Data Source
AI summary
A steering control device in a seer-by-wire system calculates a current limit presentation command value so as to convey an output-limited state of a turning device to a driver, calculates a steering torque command value on a basis of a physical quantity corresponding to an output torque of the turning device, and calculates a basic reaction force torque command value being a basic value of a reaction force torque command value so that a detection value of a torque sensor follows a target value that is based on the steering torque command value. The control device controls a current flowing to a reaction-force-use rotary electric machine on a basis of the basic reaction force torque command value and the end presentation command value, and increases an absolute value of the current limit presentation command value when the turning device is in the output-limited state.