Sensorless Permanent Magnet Motor Control via Current Feedback
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Solution Overview
Problem
Existing control schemes for permanent magnet motors rely on mechanical position sensors, which reduce mechanical reliability, or require high frequency injection and back electromotive force (EMF), and do not function effectively for both surface-mount and interior permanent magnet motors without saliency.
Innovation Solution
A motor control system that uses an inverter to output power waveforms to a permanent magnet motor based on current feedback, employing a proportional and integral regulator to generate correction voltages and control signals, allowing for torque and speed control without mechanical position sensors, high frequency injection, or reliance on saliency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical position sensors are used to track rotor position, then position information is effectively provided, but mechanical reliability is reduced
Solution Approach 1:
The patent replaces mechanical position sensors with an electronic control system that determines rotor position indirectly through current feedback and mathematical modeling. The control circuitry uses measured phase currents and motor parameters to calculate rotor position without any mechanical sensing components, thereby eliminating the reliability issues associated with mechanical sensors while maintaining position measurement capability.
Solution Approach 2:
The patent introduces current measurements and mathematical models as intermediary elements to indirectly determine rotor position. Instead of directly measuring position with mechanical sensors, the system uses phase current measurements combined with motor electrical characteristics to infer rotor position through computational methods, serving as a non-mechanical intermediary between the motor control and position information.
2Measurement precision
If high frequency injection or back EMF techniques are used to identify rotor position without mechanical sensors, then position information can be obtained, but the system depends on motor saliency and does not function for both surface-mount and interior permanent magnet motors
Solution Approach 1:
The patent employs parameter-based control where the control circuitry adapts to different motor types by utilizing fundamental electrical parameters (resistance, inductance, back EMF constants) that exist across both surface-mount and interior permanent magnet motor configurations. The system modifies control parameters and mathematical models based on detected motor characteristics rather than relying on fixed saliency-based techniques, enabling universal applicability across different motor topologies.
Solution Approach 2:
The patent creates a universal control system that can operate with both surface-mount permanent magnet motors and interior permanent magnet motors through a unified current-feedback approach. The control circuitry is designed to handle various motor configurations by using general electrical parameters and adaptive mathematical models that work across different motor types, eliminating the need for type-specific control algorithms.
3Reliability
If current feedback with proportional and integral regulator is used for torque control, then torque and speed control is achieved without mechanical sensors, but complex control signal processing is required
Solution Approach 1:
The patent implements a feedback control system where phase current measurements are continuously monitored and fed back to the control circuitry. The proportional and integral regulator processes these feedback signals to generate corrective control actions that maintain accurate torque and speed control. This closed-loop feedback mechanism enables reliable sensorless operation by continuously adjusting control based on actual system state while managing the complexity through systematic control theory application.
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 and speed of permanent magnet motors without mechanical sensors, maintaining reliability and functionality across different motor types, regardless of saliency, by using current feedback for position determination and dynamic correction.
Implementation Method 1
an inverter configured to receive direct current (DC) power and output a power waveform to a permanent magnet motor
Implementation Method 2
A three phase permanent magnet motor may be controlled by supplying three phase power to stator windings in the motor
Data Source
AI summary
Systems and methods of controlling a permanent magnet motor without a mechanical position sensor are provided. In accordance with one embodiment, a motor control system includes an inverter configured to receive direct current (DC) power and output a power waveform to a permanent magnet motor, driver circuitry configured to receive control signals and drive the inverter based upon the control signals, a current sensor configured to determine a sampled current value associated with the power waveform, and control circuitry configured to generate the control signals based at least in part upon a comparison of a flux-producing component of the sampled current value and a flux-producing component of a command reference current value.