Electric Motor Winding Fault Torque Control
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Solution Overview
Problem
In electric power steering systems, malfunctions of the electric motor's windings, such as short circuits or open phases, lead to unpredictable torque delivery, increasing the steering effort required from the driver and potentially causing safety issues due to abrupt changes in steering assistance.
Innovation Solution
A control method that reduces the set-point torque for steering assistance while maintaining or increasing the set-point torque for damping, using a monitoring circuit to detect winding malfunctions and adjust torques dynamically, ensuring continued safety and smooth transition during faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric motor continues to operate with a defective winding, then steering assistance is maintained, but the torque becomes non-constant and unpredictable, causing abrupt steering deflections
Solution Approach 1:
The control system dynamically adjusts the set-point torque for steering assistance based on the actual motor torque characteristics. When a winding defect is detected, the system continuously adapts the torque command to match the actual torque delivery, transforming the static torque expectation into a dynamic adjustment process that compensates for the defective winding's non-constant torque output.
Solution Approach 2:
The system implements feedback by continuously monitoring the actual motor torque and comparing it with the set-point torque for steering assistance. When discrepancies are detected due to winding defects, the control unit adjusts the set-point torque accordingly, creating a closed-loop control system that maintains stable steering assistance despite the defective winding.
2Force
If the set-point torque for steering assistance is increased to compensate for driver effort, then steering support is improved, but abrupt torque availability causes steering deflections and reduces safety
Solution Approach 1:
The control system applies preliminary anti-action by proactively reducing the set-point torque for steering assistance when a winding defect is detected. This preventive measure counteracts the potential harmful effect of abrupt torque availability before it can cause steering deflections, prioritizing safety over maximum steering support.
Solution Approach 2:
The system changes the torque parameter dynamically by adjusting the set-point torque for steering assistance based on the detected winding defect. Instead of maintaining a fixed high torque value that could cause abrupt deflections, the control unit modifies the torque parameter to match the actual motor capabilities, ensuring smooth and predictable steering behavior.
3Reliability
If the relay is opened to disconnect windings upon defect detection, then motor safety is protected, but steering assistance is completely lost, requiring increased driver effort
Solution Approach 1:
The control system takes preliminary action by detecting the winding defect and adjusting the set-point torque for steering assistance before the relay is opened. This advance preparation ensures a smooth transition of steering assistance levels, preventing abrupt changes that would require sudden increases in driver effort while still protecting the motor through eventual disconnection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances driving safety by maintaining damping torque and reducing steering assistance torque proportionally, allowing the system to better counteract steering deflections and prevent abrupt losses of assistance, thus ensuring stable vehicle control even with winding malfunctions.
Implementation Method 1
a control unit applies a current to the windings of the electric motor to generate a total torque
Data Source
AI summary
A method of controlling an electric motor of a power steering system having at least three windings is described, wherein a control unit applies a current to the windings of the electric motor to generate a total torque having a value which is ascertained by the control unit from a set-point torque for steering assistance and a set-point torque for damping. A damping set-point circuit ascertains the set-point torque for damping and a steering assist set-point circuit ascertains the set-point torque for steering assistance. A monitoring circuit monitors the function of the windings of the electric motor. In the event of a malfunction of any of the windings, the monitoring circuit outputs an error signal, upon which the set-point torque for steering assistance is reduced.