Vehicle Steering Device Dual Motor Current Comparison
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Solution Overview
Problem
Existing vehicle steering devices with by-wire systems face challenges in rapid abnormality diagnosis of steering motors, leading to potential vehicle behavior errors due to error signals generated by current sensors and the need for waiting times in diagnosis processes.
Innovation Solution
The implementation of a vehicle steering device with first and second motors having common electric characteristics, connected through a steering force transmission mechanism, and equipped with current detecting units for rapid abnormality diagnosis, allowing for instantaneous detection of deviations in current values to prevent abnormal vehicle behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If abnormality diagnosis is performed using operation process on error signals from current sensor, then diagnosis can be made, but waiting time is necessary up to determination of abnormality diagnosis
Solution Approach 1:
The patent uses a second current sensor to create a redundant copy of the current detection function. By comparing the output signals from both current sensors, the system can rapidly determine abnormalities without requiring time-consuming operation processes, thus resolving the contradiction between diagnosis reliability and diagnosis speed.
2Ease of operation
If steering current command value is calculated from steering command angle and motor angle sensor signal, then steering control is achieved, but given time period is required for calculation
Solution Approach 1:
The patent implements a dual-sensor system where the second motor angle sensor provides a redundant measurement copy. This allows the system to perform rapid comparison-based abnormality diagnosis without requiring complex calculation processes, thereby reducing the time needed while maintaining steering control functionality.
3Device complexity
If abnormality diagnosis is made on basis of difference between command values without using current magnitude, then diagnosis process is simplified, but vehicle behavior may fall into error state during diagnosis
Solution Approach 1:
The patent uses redundant current sensors to provide real-time current magnitude measurements for immediate abnormality detection. This allows the system to maintain simple diagnosis processes while simultaneously monitoring actual current values to prevent vehicle behavior errors, thus resolving the contradiction between diagnostic simplicity and system reliability.
4Device complexity
If single motor is used for steering, then device structure is simplified, but rapid abnormality diagnosis cannot be performed
Solution Approach 1:
The patent divides the steering motor function into two separate motors (first motor and second motor), each with its own current sensor. This segmentation enables independent monitoring and rapid abnormality diagnosis by comparing the operational states of both motors, thereby achieving both structural feasibility and diagnostic reliability.
Data Source
AI summary
The steering device includes first and second motors for steering which have common electric characteristics; first and second current sensors detecting first and second current values in the first and second motor, respectively; and abnormality diagnosis units. The abnormality diagnosis units make an abnormality diagnosis indicating that the steering device is abnormal when difference between the first and second current values exceeds a predetermined threshold value. When some abnormality occurs in the current detecting units for detecting the magnitudes of a current flowing through the steering motor, an abnormality diagnosis is rapidly made by comparing the difference with the predetermined value.