Electric Power Steering Torque Fault Handling
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Solution Overview
Problem
Existing electric power steering systems fail to provide comfortable and reasonable steering behavior when encountering faulty or incorrect steering torque information, leading to potential driver discomfort and safety issues.
Innovation Solution
A method where a control unit cyclically checks the steering torque information for plausibility and reduces the support torque by a definable value immediately upon detecting a fault, with the reduction being monotonic and based on the development of the steering angle information, and further adjusted stepwise or linearly over time, ensuring smooth operation even when steering angle information is 'frozen' or incorrect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the support torque is maintained at normal levels when steering torque information is faulty, then the steering assistance remains strong, but the driver experiences discomfort and irritation
Solution Approach 1:
The control unit proactively reduces the support torque as soon as a fault in the steering torque information is detected, preventing the harmful effect of incorrect torque application to the driver. This preliminary counter-action ensures that faulty information does not lead to uncomfortable or unsafe steering assistance.
Solution Approach 2:
The fault condition, which would normally cause harmful steering behavior, is converted into a beneficial outcome by systematically reducing the support torque. This transformation ensures that even though the steering torque information is faulty, the system adapts to provide safe and comfortable steering operation.
2Reliability
If the support torque is reduced immediately and significantly upon fault detection, then steering safety is improved, but the driver may be irritated by abrupt changes
Solution Approach 1:
The control unit dynamically adjusts the support torque based on the detected fault condition and current steering angle. Instead of a fixed reduction, the system continuously adapts the torque level, making the transition smooth and context-dependent, which prevents abrupt changes that would irritate the driver while maintaining safety.
Solution Approach 2:
The control unit changes the support torque parameter systematically based on the steering angle and fault condition. By adjusting this parameter dynamically rather than applying a sudden fixed reduction, the system maintains steering safety while ensuring the change is perceptible but not irritating to the driver.
3Ease of operation
If the support torque is reduced as a function of steering angle development, then comfortable steering behavior is maintained, but the response time to fault conditions increases
Solution Approach 1:
The control unit immediately detects the fault condition and initiates the torque reduction process without delay. By taking preliminary action to reduce torque as soon as the fault is detected, the system maintains fast response speed while subsequently adjusting the torque smoothly as a function of steering angle development to ensure comfort.
Data Source
Figure 1
AI summary
The method involves superimposing a steering torque guided on the steering handle by steering drive and applying a motor torque from the servomotor for producing a steering movement. An electronic control device contains, as input value, an information, appropriate for describing a steering angle and a steering torque acting on the steering line. A target specification is determined for the reinforcing torque applied by the servomotor. The target specification for the reinforcing torque is influenced depending on the angle information, if a torque information is diagnosed as defective. An independent claim is also included for a control unit for an electrical power steering system with a unit for storing and execution of a program module.