Sensorless Electric Motor Control via Dynamic HF Signal
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Solution Overview
Problem
Existing electric motor control systems face challenges in accurately determining rotor position without sensors, especially at low speeds, due to limitations in sensor resolution and reliability, which affects motor performance and efficiency.
Innovation Solution
A method for sensorless control of electric motors involves injecting a high-frequency signal to estimate rotor position using a phase locked loop (PLL) with dynamic gain adjustments based on current and speed errors, and calibrating the system to reduce acoustic noise and power consumption by adjusting signal voltage and frequency according to operational thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-frequency signal is injected into the electric motor for sensorless control at low speeds, then rotor position estimation accuracy is improved, but acoustic noise increases
Solution Approach 1:
The patent applies dynamics by making the HF signal parameters (voltage and frequency) adjustable rather than fixed. The controller dynamically adapts the voltage magnitude and frequency of the injected HF signal based on operating conditions, allowing optimization of both position estimation accuracy and noise reduction across different motor operating ranges
Solution Approach 2:
The patent changes physical parameters of the HF signal (voltage magnitude and frequency) to resolve the contradiction. By adjusting these parameters based on motor speed and load conditions, the system maintains accurate rotor position estimation while minimizing acoustic noise generation during different operational phases
2Measurement precision
If a high-frequency signal with maximum voltage is injected for accurate rotor position estimation, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The system dynamically adjusts the voltage magnitude of the injected HF signal based on actual motor operating conditions. Rather than continuously applying maximum voltage, the controller adapts the signal strength to match the required measurement precision for current speed and load conditions, thereby reducing unnecessary power consumption
Solution Approach 2:
The patent changes the voltage parameter of the HF signal from a fixed maximum value to a variable parameter that adapts to operating conditions. This allows the system to maintain sufficient signal strength for accurate rotor position estimation while minimizing power consumption during light-load or steady-state operations
3Device complexity
If sensorless control is used to eliminate position sensors, then device complexity is reduced, but measurement precision deteriorates at low speeds
Solution Approach 1:
The patent uses mechanical vibration principles by injecting a high-frequency signal that creates detectable responses in the motor's magnetic circuit. The HF signal excites the motor windings and magnetic core, creating measurable current responses that reveal rotor position information without requiring physical sensors, thereby maintaining measurement precision while eliminating sensor complexity
Solution Approach 2:
The injected HF signal acts as an intermediary that enables indirect measurement of rotor position. Instead of directly sensing position with physical sensors, the system uses the HF signal's interaction with the motor's magnetic circuit as a mediator to extract position information from current measurements, achieving accurate low-speed control without sensors
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
This approach enables accurate rotor position estimation and control at low speeds, reduces acoustic noise, and optimizes power usage, enhancing motor performance and reliability without the need for position sensors.
Implementation Method 1
injecting a high frequency (HF) signal into the electric motor... estimating a position of the rotor relative to the stator based on the current
Data Source
AI summary
There is provided a method of controlling an electric motor having a rotor and a stator. The method includes controlling the motor in a low-speed mode by injecting a high frequency (HF) signal into the motor. The HF signal may have an initial voltage and an initial frequency. The method may also include obtaining a speed of the rotor relative to the stator, and obtaining a reference input being sent to the motor. Moreover, the method may include comparing the speed and the reference input with a speed threshold and a reference input threshold respectively. In addition, the method may include reducing at least one of the initial voltage and the initial frequency if the speed is below the speed threshold and the reference input is below the reference input threshold, to reduce an acoustic noise caused by injecting the HF signal into the electric motor.