Electric Motor Control System Torque Management During Abnormality
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Solution Overview
Problem
The existing electric motor control system for vehicle steering mechanisms experiences a significant drop in torque during abnormal conditions, making steering difficult, especially at low speeds, and increases the risk of irreversible demagnetization of the permanent magnet when trying to compensate by increasing supply current to the normal set of windings.
Innovation Solution
The system distributes current to both sets of windings when normal and sets the supply current to zero for the abnormal set while increasing the current to the normal set up to an irreversible demagnetizing current, ensuring higher torque and maintaining steering performance during abnormalities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the supply current to the normal set of windings is increased to compensate for torque drop during abnormality, then the torque of the electric motor can be maintained, but the irreversible demagnetizing factor of the permanent magnet increases
Solution Approach 1:
The control system dynamically adjusts the supply current to the normal set of windings based on the abnormality state. During abnormality, the system increases the current beyond normal operating levels to maintain torque, while continuously monitoring to prevent irreversible demagnetization. This dynamic current adjustment allows the system to optimize torque output while managing the risk to the permanent magnet.
Solution Approach 2:
The system changes the operating parameters (supply current magnitude) in response to abnormality conditions. By increasing the current to the normal winding set from normal levels to elevated levels (but below irreversible demagnetization thresholds), the system compensates for the lost torque capacity while staying within safe operational boundaries for the permanent magnet.
2Force
If the supply current to the normal set of windings is increased from normal time, then the torque can be maintained, but the irreversible demagnetizing factor increases and replacement of the electric motor is required
Solution Approach 1:
The control system implements protective measures before irreversible damage occurs. By establishing and enforcing current limits during abnormal operation, the system cushions against conditions that would cause irreversible demagnetization. This prior protection allows the motor to continue operating through multiple abnormality events without requiring replacement, thereby extending service life while maintaining torque capability.
3Reliability
If the supply current to the normal set of windings is not increased, then the permanent magnet is protected from demagnetization, but the steering assistance becomes insufficient at low vehicle speeds
Solution Approach 1:
The system applies partial excessive action by increasing the current to levels higher than normal operating conditions but deliberately below the threshold of irreversible demagnetization. This partial increase in current provides sufficient additional torque to maintain acceptable steering assistance during low-speed abnormality conditions, while the excessive current is limited to prevent permanent damage to the magnet.
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 steering performance during abnormalities by increasing torque without excessive irreversible demagnetization, prioritizing driving performance over potential magnetic deterioration.
Implementation Method 1
an electric motor which drives a steering mechanism of a vehicle... the electric motor is provided with a stator equipped with 2 sets of plural phase windings and a rotor equipped with a permanent magnet
Implementation Method 2
a rotor equipped with a permanent magnet... increases the supply current to a normal set of the windings up to an irreversible current that increase an irreversible demagnetizing factor of the permanent magnet
Data Source
AI summary
To provide an electric motor control system and an electric power steering apparatus that torque of the electric motor can be increased for ensuring of steering performance even at the time of abnormality occurrence. The controller is provided with 2 sets of control systems which control a supply current to each set of the windings. When abnormality occurs in one set of the windings and the control system, the electric motor control system sets 0 to supply current to all phase or partial phase windings of abnormality occurrence set, and increase supply current to normal set of the windings up to an irreversible current that increase an irreversible demagnetizing factor of the permanent magnet more than the normal time.