Sensorless Commutation Control for High-Inductance Motor Drives
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Solution Overview
Problem
Existing methods for electronically commutating drive motors in motor vehicle auxiliary units, such as water circulation pumps, require significant computing power and are not suitable for small drive motors with high inductances, as they rely on separate sensors or complex signal processing to detect rotor position.
Innovation Solution
A motor current tap generates a voltage signal proportional to the motor current, which is filtered using a high-pass filter to produce peak signals indicating rotor pole jumps, allowing for simple and low-power control unit operation by triggering polarity reversals based on these signals, with optional redundancy from additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless rotor position detection is used by evaluating EMF during forced breaks in motor current supply, then separate sensors can be avoided, but significant computing power is required and the method is not suitable for small drive motors with high inductances
Solution Approach 1:
The patent replaces the complex computational EMF evaluation method with a simple analog electronic filtering approach. The high-pass filter circuit physically processes the motor current signal to generate peak signals, substituting mechanical/computational signal processing with an electronic analog system that requires minimal computing power.
Solution Approach 2:
The patent changes the signal processing approach from time-domain EMF analysis during current breaks to frequency-domain filtering of continuous motor current. By using a high-pass filter with a specific cutoff frequency, the system transforms the motor current signal to extract pole position information through peak detection, adapting the parameter evaluation method to suit high-inductance motors.
2Device complexity
If EMF evaluation during forced current breaks is used for rotor position detection, then sensorless operation is achieved, but the current supply pause must be very long for large inductances which reduces productivity
Solution Approach 1:
The patent enables continuous motor current supply while simultaneously performing rotor position detection. The high-pass filter processes the continuous motor current signal without requiring current interruptions, allowing the motor to operate continuously at full power while the control unit determines pole positions from the filtered peak signals.
Solution Approach 2:
The patent replaces the mechanical current interruption method with an electronic signal processing approach. Instead of physically breaking the current to measure EMF, the system uses a high-pass filter to extract position information from the continuous current waveform, eliminating the need for productivity-reducing current pauses.
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 reduces computing requirements, enabling efficient commutation control with low-power processors and improving suitability for small drive motors by eliminating the need for complex signal evaluation and separate sensors, while maintaining reliability through dead time settings.
Implementation Method 1
The voltage signal drops at the motor current tap, which is the input signal for an electrical high-pass filter, which is arranged electrically between the motor current tap and the control unit. The voltage signal U M , which is proportional to the motor current I M, is differentiated in the mathematical sense by the high-pass filter
Implementation Method 2
So-called sensorless rotor position detection can be carried out by evaluating the induction voltage induced in the stator coils by the permanent-magnetic rotor, so-called EMF, during forced breaks in the motor current supply
Data Source
Figure 1
Figure 2
AI summary
An electric motor vehicle auxiliary unit (13) comprising an electronically commutated drive motor (16), the motor coils (17) thereof being energized by an electronic commutator arrangement (14), wherein the commutator arrangement (14) has a control unit (30) and multiple power semiconductors (T1-T4) which are controlled by the control unit (30), a motor current tap (23) is arranged in the course of the motor current path (21) at which current tap a voltage signal UM proportional to the motor current IM drops during motor energization, and a high-pass filter (22) is arranged between the motor current tap (23) and the control unit (30), the input signal of which high-pass filter is the voltage signal UM and the output signal of the high-pass filter is a control signal for the control unit (30), by means of which, following the input of a peak signal (T), the following pole reversal (K) is triggered after a delay (dt).