Motor Controller Phase Offset Compensation for Steering
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Solution Overview
Problem
Conventional electric power steering systems experience performance issues due to torque ripple and increased steering effort when a phase current-carrying failure occurs, leading to poor steering feel and motor performance.
Innovation Solution
A motor controller that adjusts current control to follow a secant or cosecant curve in phases adjacent to a failed phase, compensates for phase offset, and advances rotational angle compensation based on motor direction and speed to maintain smooth operation and high output performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor controller stops motor control immediately after detecting a current-carrying failure, then safety is improved, but steering performance deteriorates significantly
Solution Approach 1:
The system prepares a backup control mode in advance where current can be supplied to the remaining two healthy phases when a current-carrying failure is detected. This pre-planned alternative ensures that steering assistance is maintained without interruption, cushioning the impact of the failure on steering performance while still ensuring safety through controlled operation in a degraded mode.
2Productivity
If the motor controller carries current in the remaining two phases during current-carrying failure, then steering assistance is maintained, but torque ripple increases causing poor steering feeling
Solution Approach 1:
The controller dynamically changes the current waveform parameters in the remaining two phases based on the motor's rotational position. By adjusting the amplitude and timing of the current supplied to phases V and W according to the rotor angle, the system optimizes torque output and minimizes torque ripple, maintaining smooth steering feeling even during two-phase operation.
Solution Approach 2:
The control system continuously adapts the current characteristics in real-time based on motor rotation angle and operational conditions. The current magnitude and phase are dynamically adjusted to compensate for the missing phase, creating a balanced torque distribution that reduces ripple and maintains steady motor rotation despite operating in a degraded two-phase mode.
3Duration of action of moving object
If sine wave current is carried in the remaining two phases during failure, then motor control continues, but steering feeling deteriorates due to torque ripple
Solution Approach 1:
The system transitions from standard sine wave current to a modified current waveform with dynamically adjusted parameters. The current amplitude, frequency, and phase angle are continuously adapted based on the motor's rotational position and the specific failure condition, optimizing torque production while minimizing harmful torque ripple in the degraded two-phase operating mode.
Data Source
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AI summary
The micro computer 17 continue an output of a motor control signal to execute a current control to carry to each of two phases a phase current changing like a secant curve or a cosecant curve at making a predetermined rotational angle according to the phase generated the current-carrying failure as an asymptote at the generation of the current-carrying failure. The micro computer 17 provides a rotational angle compensating section 40 compensating an input rotational angle θ to correct a phase offset between a phase current command value Ix* as a current command value and an actual phase current value Ix as an actual current value in the current control.