Sensorless Rotor Position Estimation via Resonance
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Solution Overview
Problem
Existing methods for controlling salient electrical machines are unreliable in harsh environments due to mechanical sensor failures from temperature variations and vibrations, and they require external excitation hardware, leading to noise and torque disturbances.
Innovation Solution
A sensorless control system that estimates rotor position using a voltage test pulse and measures the damped resonance response, allowing for accurate position determination without external sensors or excitation hardware, reducing noise and torque disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical sensors (encoders, resolvers, hall-sensors) are mounted on the shaft to measure rotor position, then position measurement accuracy is improved, but reliability deteriorates in harsh environments due to temperature variations and mechanical vibrations
Solution Approach 1:
The patent replaces mechanical position sensors with an electrical measurement system. Instead of using mechanical encoders, resolvers, or hall-sensors mounted on the shaft, the invention measures rotor position by detecting the resonance frequency of the motor's inductance, which varies with rotor position. This substitution eliminates mechanical sensors from the harsh environment, improving reliability while maintaining measurement capability.
2Difficulty of detecting and measuring
If external excitation circuits are used to generate resonance for position detection, then position detection capability is improved, but device complexity increases
Solution Approach 1:
The patent makes the motor's power conversion system perform multiple functions. The same inverter that drives the motor for normal operation is also used to generate the test signals needed for position detection. By utilizing the existing power conversion hardware for both motor control and position sensing, the invention eliminates the need for separate external excitation circuits, reducing device complexity while maintaining position detection capability.
3Measurement precision
If voltage pulses with non-negligible current amplitude are applied to estimate position, then position information is obtained, but torque disturbance increases
Solution Approach 1:
The patent uses periodic test signals at the resonance frequency of the motor's inductance to excite the system for position measurement. By applying sinusoidal test currents at the resonant frequency rather than arbitrary voltage pulses, the measurement process becomes more efficient and requires smaller signal amplitudes, thereby reducing the disturbance torque while still obtaining accurate position information.
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
The system provides reliable rotor position estimation and control in harsh conditions, with high resolution and low component count, reducing costs and electromagnetic compatibility issues.
Implementation Method 1
A voltage test pulse is applied to a motor phase and a damped resonance response is measured
Implementation Method 2
The phase inductance L forms a resonant circuit with a known capacitance C of the power conversion system. A voltage test pulse is applied to the motor phase and a damped resonance response is measured
Data Source
Figure 1~2
Figure 3(A)~4
Figure 5~6A
AI summary
The present invention relates to sensorless rotor position estimation of a salient machine, such as a switched reluctance machine or a salient brushless DC machine. The invention relates to a test system (200) for a salient machine (230) to be driven using an inverter (220). Periods of zero current may occur in the phases of the salient machine. The test system (200) comprises a test pulse generator (210) for applying a voltage test pulse with the inverter of the salient machine. The voltage test pulse may be applied in an idle phase of the machine. The test system furthermore may comprise a measurement circuit (240) for determining a damped resonance response following the end of the voltage test pulse at which moment at least one terminal of a phase winding of the machine is decoupled, and a processor (250) for deriving therefrom a position of a rotor of the salient machine (230).