Sensorless Motor Control via Envelope Detection and Non-Orthogonal PLL
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Solution Overview
Problem
Existing position sensorless control methods for fault-tolerant permanent magnet motors are ineffective at low speeds, as they rely on back-EMF signals that fail in asymmetrical operations and require coordinate transformation, making them unsuitable for fault conditions.
Innovation Solution
A position sensorless control method using envelope detection and a non-orthogonal phase-locked loop, where high-frequency voltage signals are injected into non-faulty phase windings to estimate inductances and extract rotor position and speed information without coordinate transformation, applicable in both normal and faulty operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If back-EMF based sensorless control method is used, then position and speed detection accuracy is improved at high speeds, but the method becomes ineffective at low speeds and in fault conditions
Solution Approach 1:
The patent changes the detection parameter from back-EMF to phase inductance. By injecting high-frequency voltage signals and detecting the resulting current responses, the system estimates phase inductances which vary with rotor position. This parameter change enables effective operation at low speeds and under fault conditions where back-EMF signals are insufficient or unavailable.
Solution Approach 2:
The patent replaces the conventional coordinate transformation approach with a direct inductance estimation method using envelope detection and non-orthogonal phase-locked loop. This substitution eliminates the requirement for symmetrical phase windings and coordinate transformation, making the system applicable to fault conditions with asymmetrical operations.
2Extent of automation
If conventional high-frequency injection method with coordinate transformation is used, then position sensorless control is achieved, but the method cannot handle asymmetrical operation states in fault conditions
Solution Approach 1:
The patent explicitly addresses asymmetrical operation by using a non-orthogonal phase-locked loop that does not require symmetrical phase windings. The method can handle asymmetrical inductance variations caused by phase winding faults, making the sensorless control applicable to fault conditions where conventional symmetrical methods fail.
Solution Approach 2:
The patent extracts rotor position and speed information directly from phase inductance variations without requiring coordinate transformation. By injecting high-frequency signals into individual phases and detecting the envelope of current responses, the system obtains position information directly, eliminating the need for symmetrical coordinate systems.
3Measurement precision
If position sensor is installed for accurate position detection, then detection accuracy is improved, but system hardware complexity, volume, weight increase and reliability decreases
Solution Approach 1:
The patent creates an electrical copy of the rotor position information by estimating phase inductances from current responses to injected voltage signals. Instead of using a physical position sensor, the system reconstructs position data through electrical measurements and signal processing, eliminating the need for additional hardware sensors.
Solution Approach 2:
The system uses its own phase windings and power electronics to perform position detection. By injecting high-frequency voltage signals through the existing power switches and measuring the resulting currents, the system self-diagnoses rotor position without external sensors, making the system self-sufficient for position detection.
4Measurement precision
If position sensor is installed for reliable position detection, then detection reliability is improved, but system reliability decreases due to additional failure points
Solution Approach 1:
The system performs self-diagnosis of rotor position using its own phase windings and power electronics. By monitoring the inductance variations through injected signals and measured currents, the system eliminates external position sensors that would introduce additional failure points, thereby improving overall system reliability while maintaining detection accuracy.
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
Enables high-precision position and speed detection of fault-tolerant permanent magnet motors at low speeds, improving reliability and accuracy by eliminating the need for sensors and symmetrical phase winding operations.
Implementation Method 1
extracting the amplitude information of the high-frequency current response signals by performing the envelope detection thereon
Implementation Method 2
inputting the estimated two phase inductances into the non-orthogonal phase-locked loop for resolving, so as to obtain the rotor position and speed information
Implementation Method 3
injecting the high-frequency voltage signals into any two non-faulty phase windings of the motor... acquiring the corresponding current signals of the phase windings
Data Source
AI summary
In the position sensorless control method in low-speed region of the fault-tolerant permanent magnet motor system based on the envelope detection and the non-orthogonal phase-locked loop of the present disclosure, the position sensorless control of the motor is implemented by injecting the high-frequency voltage signals into any two non-faulty phase windings of the motor, extracting the high-frequency response currents of the high-frequency injected phases by the digital bandpass filter, calculating the differential mode inductances of the two phase windings through the envelope detecting and signal processing, and extracting the rotor position and rotational speed signals from the estimated two phase inductances through the non-orthogonal phase-locked loop. In addition, the controller of the present disclosure is small in size, high in accuracy, and high in reliability, which can effectively meet the performance requirements of the onboard electric actuators.