Sensorless Rotor Position Detection Using Phase Voltage Peak Comparison
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Solution Overview
Problem
Conventional sensorless angle-of-rotation transmitters for brushless electric motors face challenges in accurately determining rotor position due to fluctuations from switching processes and require complex analog electronic circuits, which are costly and inefficient.
Innovation Solution
A method and device that detect the peak value of phase voltage after disconnection, compare it with a numerically determined comparison value, and generate a position signal, allowing for reduced structural outlay by using a microcontroller for numerical algorithms and eliminating the need for separate comparators and additional measurement of other phase voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional analog electronic circuits with filter circuits and comparators are used for sensorless position determination, then position determination can be achieved, but the device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical/analog electronic circuit system with a numerical evaluation system. Instead of using analog filter circuits and comparators, the invention uses a microcontroller to numerically evaluate phase voltages and determine rotor position through software algorithms, thereby simplifying the hardware structure while maintaining measurement precision
Solution Approach 2:
The invention creates a numerical model of the back-EMF characteristics and uses this model to determine position. By copying the essential characteristics of the back-EMF signal into numerical form and comparing it with calculated values, the system achieves accurate position determination without complex analog circuitry
2Measurement precision
If filter circuits are added to prevent fluctuations from switching processes, then position determination accuracy improves, but device complexity increases
Solution Approach 1:
The patent replaces physical filter circuits with numerical filtering algorithms implemented in software. The microcontroller applies digital signal processing techniques to filter out switching fluctuations and noise from the phase voltage measurements, achieving the same effect as analog filters without the associated hardware complexity
Solution Approach 2:
The invention changes the state of signal processing from analog domain to digital domain. By converting the filtering operation from a physical circuit parameter to a software algorithm parameter, the system gains flexibility and reduces hardware complexity while maintaining measurement precision
3Measurement precision
If separate circuits are added to enable position determination only when freewheeling current has decayed, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent replaces separate enable circuits with software-based timing control. The microcontroller uses its internal timing mechanisms to determine when freewheeling current has decayed and when position determination should be performed, eliminating the need for additional hardware circuits while maintaining measurement accuracy
Solution Approach 2:
The invention makes the microcontroller perform multiple functions: it controls the converter circuit, evaluates phase voltages, determines timing based on freewheeling current decay, and generates position signals. By consolidating these functions into a single device, the system reduces overall complexity while maintaining measurement precision
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 simplifies the position determination process, reduces costs, and enhances accuracy by filtering out switching overshoots and allowing position determination during freewheeling states without additional hardware, leveraging existing microcontroller capabilities.
Implementation Method 1
The position determination is effected by said angle-of-rotation transmitters by detection of the so-called back electromotive force (also referred to as back-EMF) of the electric motor. This expression denotes the voltage induced in the stator coils by the rotating rotor magnetic field.
Data Source
AI summary
The invention relates to a method carried out with simple means for determining the position of the rotor in a sensorless and brushless multi-phase electric motor (1) in addition to a device particularly suitable for carrying out said method. According to said method, a phase voltage (Uv) on the clamping side on said motor phase is to be detected after clamping a first motor phase (V) from the reference potentials (UZ,M) of an intermediate circuit (7) during a detection period (TE), via which the detection period (TE) determines a peak value (Uv*) of the detected phase voltage (Uv), the peak values (Uv*) are to be compared to the comparative value (Uc), and a positon signal (SP) is to be produced when the peak value (Uv*) exceeds the comparative value (U0). The comparative value (Uc) is then determined digitally such that it corresponds to the value of the phase voltage (Uv) at a zero crossing of a voltage (UVind) induced in the first motor phase (V) or an increased or lowered value in relation to a predefined correction value (ΔQ).