Motor Controller Phase Switching for Electric Power Steering
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Solution Overview
Problem
Conventional motor controllers for electric power steering systems face challenges in continuous operation during short-circuit failures, leading to electromagnetic braking, overheating, and reduced steering assist performance due to increased current requirements to cancel braking torque, and complex configurations that increase size and component count.
Innovation Solution
A motor controller with a main drive circuit and a backup drive circuit in parallel, an abnormality diagnosis unit that switches motor current to a backup phase when an abnormality is detected in the main circuit, preventing electromagnetic braking and ensuring continuous operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional motor controller continues to supply current to a motor phase with a short-circuit failure, then the motor can maintain operation, but electromagnetic braking occurs and the motor and inverter overheat
Solution Approach 1:
The patent extracts the faulty phase from the motor control system by detecting short-circuit failures and isolating the affected phase through the inverter circuit. This allows the motor to continue operating with the remaining healthy phases while preventing the electromagnetic braking and overheating that would occur if current continued to be supplied to the faulty phase
Solution Approach 2:
The patent implements preliminary failure detection by continuously monitoring the motor phases for short-circuit conditions before they can cause harmful effects. The control unit detects abnormalities and switches to a failure mode operation proactively, preventing electromagnetic braking and overheating from occurring in the first place
2Reliability
If a duplex system with separate inverter units is used to enable continuous driving, then reliability improves, but device complexity and size increase
Solution Approach 1:
The patent merges the failure detection and control functions into the existing inverter unit rather than requiring separate inverter units for each phase. The inverter detects short-circuit failures and controls the switching elements to isolate faulty phases, combining redundancy and control in a single integrated system that reduces complexity while maintaining continuous operation capability
Solution Approach 2:
The inverter unit is designed to perform multiple functions: normal motor control, failure detection, and failure mode operation. By making the inverter universal and capable of handling both healthy and faulty conditions, the patent eliminates the need for separate inverter units and reduces overall system complexity
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
The solution prevents electromagnetic braking and ensures continuous motor operation during short-circuit failures, maintaining steering assist performance and reducing overheating, while simplifying the configuration to minimize size and component count.
Implementation Method 1
a motor current of a phase output unit where the abnormality occurs is cut off and the phase output unit that has been cut off is switched to another phase output unit of a same phase in the backup motor drive circuit to drive the multi-phase electric motor
Data Source
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AI summary
Even when an abnormality occurs at a motor driver circuit, the driving of the electric motor is continuously controllable, so that a multi-phase electric motor does not generate the electromagnetic braking. A motor controller includes: a main motor drive circuit configured to control driving of a multi-phase electric motor; a backup motor drive circuit configured to control driving of the multi-phase electric motor, when an abnormality occurs at the main motor drive circuit; and an abnormality diagnosis unit configured to diagnose the abnormality of the main motor drive circuit and the backup motor drive circuit. In a normal drive state, only the main motor drive circuit is configured to drive the multi-phase electric motor, and in a backup drive state, when the abnormality diagnosis unit diagnoses that the abnormality occurs at the main motor drive circuit as a diagnoses result, a motor current of a phase output unit where the abnormality occurs is cut off, and the phase output unit that has been cut off is replaced with another phase output unit of a same phase in the backup motor drive circuit to drive the multi-phase electric motor.