Sensorless Rotor Position Detection Using Slowly Rising Test Voltage
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Solution Overview
Problem
Existing sensorless methods for determining the rotor position of electronically commutated synchronous machines, such as EC motors, face challenges in accuracy at low speeds and noise generation, particularly during startup and low-speed operations, and require a minimum speed for reliable position determination.
Innovation Solution
A method using a slowly rising test voltage signal with a voltage vector that can be continuously differentiated, allowing for low-noise position determination by evaluating current responses to determine the rotor position based on the smallest inductance, which minimizes noise excitation and enables accurate position detection up to 10% of rated speed without feedback from flywheel voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional test voltage signal is used for sensorless position determination, then position information can be obtained, but noise is excited and measurement precision deteriorates at low speeds
Solution Approach 1:
The patent applies parameter changes by using a slowly rising test voltage signal instead of a conventional abrupt test signal. The voltage signal rises gradually over a predetermined time period before reaching its test amplitude, which reduces noise excitation while maintaining measurement precision for rotor position determination at low speeds
2Adaptability or versatility
If sensorless commutation is used during motor startup, then no position sensors are required, but reliable position determination is impossible below minimum speed
Solution Approach 1:
The patent applies preliminary action by pre-rising the voltage signal to test amplitude before actually applying the test voltage for position measurement. This preliminary voltage build-up phase allows the system to maintain adaptability for sensorless commutation at startup while ensuring reliable position determination even at very low speeds by avoiding abrupt signal changes that would cause noise
3Device complexity
If back EMF measurement is used for sensorless position detection, then position information can be obtained without sensors, but a minimum speed is required for reliable evaluation
Solution Approach 1:
The patent replaces the conventional back EMF measurement method with an alternative approach using a slowly rising test voltage signal. This substitution maintains the simplicity of the sensorless commutation system while eliminating the minimum speed requirement, as the controlled voltage rise provides sufficient signal quality for position determination even when the rotor is stationary or moving very slowly
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 provides reliable and low-noise determination of the rotor position, reduces noise excitation, and allows for time-optimized position determination while maintaining high accuracy, even at low speeds, effectively addressing the limitations of existing methods.
Implementation Method 1
A test voltage signal u1 is imprinted into the coil system, wherein the test voltage signal u1 represents a voltage phasor with angular frequency ω and the voltage amplitude A of the voltage phasor initially rises to a test voltage UTEST during a rising phase PHan
Implementation Method 2
Determination of the rotor position γ0 by evaluating the current response, utilizing the effect that, as a result of the voltage excitation in step a), the largest current response is generated where the inductance is lowest
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The invention relates to a method for sensor-free position determination of the rotor position of an electronically commutated multiple-phase EC motor (1) comprising a rotor (2) and a stator (3) and comprising a commutation device (4) for generating string currents in the coil system (5) of the stator (3) by applying a test signal in the coil system (5), measuring the current value i in the strand during the measurement phase (PHMess) as a current response to the test signal, calculating |i| for the envelope determining of the current response and determining the rotor position therefrom.