Vehicle Steering Torque Estimation for Sensor Failure
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Solution Overview
Problem
Conventional vehicle steering control devices face difficulties in promptly judging torque sensor abnormality, leading to challenges in continuing torque assist efficiently when main and sub torque sensors are switched due to trouble.
Innovation Solution
A vehicle steering control device that includes an angle superimposing unit, a steering torque estimation unit, a torque sensor, and a comparison unit to compare detection values with estimated values, allowing for prompt judgment of torque sensor abnormality and control of the electric power assist unit based on estimated values, thereby ensuring reliable torque assist without requiring a double system type torque sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a double system type torque sensor is used to continue torque assist when one sensor fails, then reliability is improved, but device complexity increases and cost rises
Solution Approach 1:
The patent introduces a steering torque estimation unit as an intermediary mechanism that estimates steering torque based on driving current of the electric actuator. This estimation serves as a backup when the torque sensor fails, allowing the system to continue torque assist without requiring a complex double system type torque sensor configuration
Solution Approach 2:
The patent creates a virtual copy of the torque sensor function through the steering torque estimation unit. Instead of physically duplicating the torque sensor (which would increase complexity), the system replicates the torque detection capability through estimation based on electric actuator current, maintaining reliability while reducing device complexity
2Reliability
If a double system type torque sensor is implemented for failsafe design, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces the expensive torque sensor with a computationally-based estimation method that uses existing sensor data (driving current) to calculate steering torque. This estimation approach is more cost-effective while providing the same failsafe functionality needed for torque sensor abnormality handling
Solution Approach 2:
The steering torque estimation unit serves multiple functions: it provides torque estimation for normal operation and acts as a backup when the torque sensor fails. This multi-functionality eliminates the need for separate redundant torque sensors, reducing manufacturing cost while maintaining reliability
3Device complexity
If torque sensor abnormality judgment is delayed, then system simplicity is maintained, but productivity decreases due to inefficient torque assist continuation
Solution Approach 1:
The patent implements a feedback mechanism where the comparison unit continuously compares the torque sensor detection value with the steering torque estimation unit's estimated value. When they diverge beyond a threshold, the system promptly identifies torque sensor abnormality and switches to using the estimation value, ensuring efficient torque assist continuation without complex additional judgment systems
Data Source
AI summary
In a vehicle steering control device, a steering torque estimation unit estimates steering torque of a steering wheel based on driving current of an electric actuator; a torque sensor detects the steering torque of the steering wheel; an electric power assist unit is controlled based on the steering torque detected by the torque sensor; and a comparison unit compares the torque detected by the torque sensor with the steering torque estimated by the steering torque estimation unit. The electric power assist unit is controlled based on the estimated steering torque in place of being controlled based on the torque detected by the torque sensor when the torque sensor is judged to be abnormal, based on a comparison.