Multiphase Motor Control via Phase Switching and Mask Signals
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Solution Overview
Problem
Conventional control systems for multiphase electric rotating machines face challenges in suppressing noise, accurately controlling rotation angles, and detecting position signals without complicating the system configuration, particularly when using pulse width modulation (PWM) and sensorless operation.
Innovation Solution
A control system that alternately switches phases in a power conversion circuit to modulate voltage, adjusts energization processes to control rotation angles, and uses a mask signal to manage PWM transitions and position signal detection, thereby reducing noise and improving position signal accuracy without adding complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If pulse width modulation (PWM) is conducted in synchronism with the changeover timing of switching elements, then switching noises are suppressed, but the neutral point potential changes in synchronism with PWM causing current flow through insulators and generating noise
Solution Approach 1:
The patent applies periodic action by conducting PWM processing in synchronism with the changeover timing of switching elements. The control unit coordinates the PWM switching timing with the phase switching timing, creating a periodic synchronization pattern that suppresses switching noises while managing neutral point potential variations through timed intervention.
2Reliability
If the rotation angle is controlled to the final rotation angle through two energization processes, then the rotation angle can be controlled even when starting close to the dead point, but the convergence time depends on inertia and friction making the process lengthy
Solution Approach 1:
The patent applies preliminary action by conducting the first energization process to bring the rotation angle close to the target before executing the second energization process. The control unit performs preliminary positioning operations that prepare the system for the final positioning, reducing the burden on the second process and optimizing the overall convergence time while ensuring reliable control even from dead point conditions.
3Measurement precision
If a mask signal is generated to mask comparison signals during PWM on-state and ringing occurrence period, then position signal detection accuracy is improved, but the system complexity increases
Solution Approach 1:
The patent applies the intermediary principle by introducing a mask signal as a mediator between the PWM control signals and the position signal detection system. The mask signal temporarily invalidates comparison signals during the PWM on-state and ringing period, preventing erroneous position detections without requiring hardware modifications. This software-based intermediary approach maintains detection accuracy while avoiding additional physical components.
Data Source
AI summary
A control system controls a multiphase rotating machine by a 120° energization process and a PWM process. In the 120° energization process, respective ones of switching elements of a high side arm and switching elements of a low side arm of a power conversion circuit are turned on. In the PWM process, the switching elements of the power conversion circuit turn on/off so that two phases that are connected to the switching elements that are in the on-state are alternately rendered conductive to the high potential side input terminal and the low potential side input terminal of the power conversion circuit.