Steer-By-Wire Current Limiting Under Temperature Sensor Drift
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Solution Overview
Problem
In steer-by-wire steering systems, temperature sensors can malfunction, leading to inaccurate current limiting controls that reduce motor torque and affect turning accuracy, even when the motor is not overheated.
Innovation Solution
A steering system with dual microcomputers and temperature sensors that independently calculate current limits based on their respective temperature readings, switching to independent calculation mode when a temperature difference threshold is exceeded, ensuring accurate torque control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current limiting control is executed based on temperature sensor detection, then motor overheating is prevented, but turning accuracy deteriorates when sensor drift occurs
Solution Approach 1:
The patent divides the temperature monitoring function into multiple independent temperature sensors (first temperature sensor and second temperature sensor) positioned at different locations. Each sensor independently monitors temperature in its local area, and the system selects the higher temperature reading for current limiting control. This segmentation ensures that if one sensor drifts, the other can compensate, preventing false current limiting while maintaining accurate overheating protection.
2Reliability
If current limiting control is executed when temperature exceeds threshold, then motor protection is achieved, but motor torque is reduced
Solution Approach 1:
The patent implements dynamic current limiting control where the current limit value is adjusted based on real-time temperature readings from multiple sensors. The system continuously monitors temperatures and dynamically adjusts the current limit threshold rather than using a fixed limit. This allows the system to maintain high torque output when temperatures are acceptable while automatically reducing current limits only when actual overheating conditions are detected, preventing unnecessary torque reduction.
3Device complexity
If single temperature sensor is used for current limiting control, then system complexity is reduced, but measurement reliability decreases when sensor drift occurs
Solution Approach 1:
The patent combines multiple temperature sensors and their monitoring functions into a unified control system. The control unit integrates readings from both temperature sensors, applies drift detection algorithms, and coordinates current limiting control based on combined information. This merging approach maintains relatively simple system architecture while significantly improving measurement reliability through cross-validation of sensor readings and intelligent selection of temperature data for control decisions.
Data Source
AI summary
A steer-by-wire steering system including a steering device including a steering motor and a controller configured to supply a steering current to the steering motor based on a steering request. The controller includes a plurality of microcomputers, a plurality of drive circuits, and a plurality of temperature sensors. When a detection temperature difference that is a difference between detection temperatures of any two of the plurality of temperature sensors is greater than a predetermined threshold, each of the plurality of microcomputers executes an independent calculation control to independently calculate and set a current limit value, which is an upper limit value of the steering current, based on a detection temperature of one of the plurality of temperature sensors corresponding to itself, irrespective of detection temperatures of one or more of the plurality of temperature sensors other than the one of the plurality of temperature sensors corresponding to itself.