Motor Torque Control for Shorted Phase Coils
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Solution Overview
Problem
In electric power steering systems, when phase coils of a motor become shorted, the motor acts as a generator, applying braking torque to the shaft, making it difficult for the vehicle operator to steer the vehicle.
Innovation Solution
A method and system that determine a motor position and phase advance angles, adjust voltage amplitude and duty cycle values based on calibration values, and apply modified voltages to the phase coils to minimize or eliminate the braking torque, ensuring a desired torque output even during shorted operational conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase coils are shorted together, then the motor acts as a generator and produces braking torque, but this makes it difficult for the operator to steer the vehicle
Solution Approach 1:
The patent detects when a phase coil is shorted and converts this harmful condition into a beneficial one by adjusting the control strategy. Instead of shutting down the motor, the system modifies the duty cycle values and phase advance angles to compensate for the shorted phase, allowing the motor to continue providing steering assistance torque rather than generating braking torque.
Solution Approach 2:
The patent changes control parameters (duty cycle values and phase advance angles) in response to the shorted phase condition. By dynamically adjusting these parameters based on the detected fault, the system maintains motor functionality and prevents the shorted phase from causing braking torque, thus preserving steering ease.
2Reliability
If the motor acts as a generator during shorted phase condition, then braking torque is applied to the shaft, but this increases the force required by the operator to turn the steering wheel
Solution Approach 1:
The system converts the harmful braking torque effect into useful steering assistance by detecting the shorted phase condition and adjusting control parameters. The modified duty cycle values and phase advance angles enable the motor to continue producing assistive torque even with a shorted phase, eliminating the braking effect that would otherwise increase steering force requirements.
Solution Approach 2:
The patent implements a feedback mechanism where the controller continuously monitors motor phase conditions and adjusts control parameters in real-time. When a shorted phase is detected, the system uses feedback from this detection to modify duty cycle values and phase advance angles, ensuring the motor maintains proper torque characteristics and prevents excessive steering force requirements.
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 system effectively controls torque by determining and adjusting voltage duty cycles to maintain motor operation and assist steering, reducing the impact of shorted phase coils on vehicle steering.
Implementation Method 1
The motor has first, second, and third phase coils... applying first, second, and third voltages having first, second, and third duty cycles, respectively, based on the modified first, second, and third duty cycle values, respectively, to the first, second, and third phase coils, respectively, to obtain a desired torque from the motor
Data Source
AI summary
A system and a method for controlling torque of a motor are provided. The method includes modifying a phase advance angle based on an identified phase coil that has a faulted condition, a type of fault condition, and a polarity of a commanded torque to obtain a desired output torque from a motor.