Sensor-Free Initial Rotor Angle Detection in Electric Machines
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Solution Overview
Problem
Determining the initial rotor angle of a stationary electric machine without angular position sensors is challenging due to the complexity and low precision of existing methods, which is essential for sensor-free control in electric machines like BLDCM and PMSM.
Innovation Solution
A method using a power supply module, switch circuit, and feedback circuit to determine the initial rotor position by analyzing current values through different power supply modes and applying a similar triangle method for precise angle calculation, with error compensation using a piecewise linearization method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If angular position sensors are used to detect rotor position, then control performance is improved, but cost increases and installation becomes difficult
Solution Approach 1:
The patent extracts and eliminates the angular position sensor from the system by using sensor-free control methods. It determines rotor position indirectly through mathematical models and electrical measurements (currents and voltages) rather than direct physical sensing, thereby removing the costly and complex sensor component while maintaining control functionality.
Solution Approach 2:
The patent replaces the mechanical/angular position sensor system with an electrical/mathematical system. Instead of using physical sensors to detect rotor position, the system uses electrical measurements (phase currents and voltages) combined with mathematical algorithms to calculate rotor position, substituting a mechanical sensing approach with an electrical computation approach.
2Ease of operation
If simple methods are used to determine initial angle by running the electric machine, then ease of operation is improved, but reliability deteriorates due to inability to operate in stationary state
Solution Approach 1:
The patent performs preliminary action by determining the initial rotor angle while the motor is in a stationary state before starting operation. This allows the system to calculate and store the initial position information in advance using electrical measurements taken with the motor stationary, eliminating the need to physically rotate the motor to establish initial position.
Solution Approach 2:
The patent replaces mechanical rotation methods with electrical measurement methods. Instead of physically running or rotating the motor to determine initial angle, the system uses electrical measurements (currents and voltages) taken while the motor is stationary, combined with mathematical calculations to determine the initial rotor position.
3Device complexity
If previous methods for determining rotor angle in stationary state are used, then sensor-free control is achieved, but precision and simplicity deteriorate
Solution Approach 1:
The patent applies dynamics by iteratively optimizing the initial angle determination process. It uses multiple measurement cycles with different voltage vectors, calculates initial angles from each cycle, compares results, and refines the determination through iterative calculation. This dynamic, multi-step process improves precision while maintaining simplicity by using basic electrical measurements and mathematical operations.
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 precise determination of the initial rotor angle in a stationary state with reduced complexity and cost, improving the accuracy and reliability of sensor-free electric machine control.
Implementation Method 1
a feedback circuit, which detects an electric machine winding current and generates a corresponding feedback signal
Data Source
AI summary
An apparatus and method for determining initial rotor position in a stationary state of an electric machine. The apparatus and method for determining initial rotor position in a stationary state of an electric machine include: a power supply module being used for supplying power at least to a motor; a switch circuit being used for switching motor power supply modes, wherein each power supply mode corresponds to a different electrical angle; a feedback circuit detecting a motor winding current and generating a corresponding feedback signal to feed back to a controller; and the controller determining a rotor angle on the basis of currents passing through the motor in different power supply modes, wherein the controller performs the following operations: (a) weighting and then comparing fed-back current values of currents passing through the motor in different power supply modes; (b) based on a maximum current value and current values for two power supply modes before and after the power supply mode corresponding to the maximum current value, calculating a position angle PA corresponding to the position of the maximum current value by using a similar triangle approximation method.