Backup Torque Calculation for EPS Sensor Failure
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Solution Overview
Problem
The sudden failure of the torsion bar torque sensor in electric power steering systems leads to a loss of power steering assistance, making it difficult for drivers to steer vehicles effectively.
Innovation Solution
An electric power steering system that includes an electric motor, a torsion bar torque sensor, a vehicle speed sensor, and a steering angle sensor, with an electronic controller that determines the failure of the torsion bar torque sensor and calculates a steering assistance torque based on vehicle speed and steering angle, summing it with a hysteresis torque to generate an output torque for the electric motor to maintain steering assistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the torsion bar torque sensor is used to determine driver input torque, then the power steering assistance can be provided accurately, but the system reliability deteriorates when the sensor fails
Solution Approach 1:
The electronic controller continuously monitors the torsion bar torque sensor signal and pre-calculates alternative steering assistance torque values based on vehicle speed and steering angle. When sensor failure is detected, the backup calculation method is already prepared and can be immediately activated without interrupting power steering assistance.
Solution Approach 2:
The patent introduces an intermediary calculation method that uses vehicle speed and steering angle as intermediate parameters to derive steering assistance torque when the direct torsion bar torque sensor measurement is unavailable. This intermediary approach maintains the power steering function through a different computational pathway.
2Ease of operation
If the torsion bar torque sensor fails, then the system complexity reduces, but the power steering assistance is lost making steering difficult
Solution Approach 1:
The patent changes the input parameters for calculating steering assistance torque from direct torsion bar torque sensor measurements to vehicle speed and steering angle measurements. This parameter substitution allows the system to maintain steering assistance functionality using different, redundant measurement sources that are already present in the vehicle.
3Reliability
If a backup calculation method is implemented, then the reliability improves during sensor failure, but the device complexity increases
Solution Approach 1:
The electronic controller is designed with multi-functionality, capable of performing both normal torque-based steering assistance calculation and backup speed-angle-based calculation. This universal controller consolidates multiple functions into a single device, avoiding the need for separate backup hardware systems and minimizing overall device complexity.
Data Source
AI summary
Systems and methods for controlling an electric power steering system. The system includes an electric motor configured to provide a torque to a steering mechanism of a vehicle, a torsion bar torque sensor, a vehicle speed sensor, and a steering angle sensor. The system also includes an electronic controller configured to determine a failure of the torsion bar torque sensor, receive a vehicle speed from the vehicle speed sensor and a steering angle from the steering angle sensor, calculate a steering assistance torque based on the vehicle speed and the steering angle, calculate a hysteresis torque based on the steering angle, sum the steering assistance torque and the hysteresis torque to determine a turning torque, calculate a return torque and sum the turning torque and return torque to obtain an output torque, and generate a command for the electric motor to provide the output torque to the steering mechanism.