IPMSM Rotor Position Estimation Using Nonlinear Observer Filtering
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Solution Overview
Problem
Existing electric drive systems for IPM motors rely on electromechanical sensors, which increase cost, size, and complexity, and are prone to failures in harsh environments, while conventional sensorless methods face challenges with back EMF tracking and voltage injection techniques assuming constant DC bus voltage.
Innovation Solution
A system that uses a nonlinear observer to estimate rotor position by generating high-frequency voltage across a DC bus capacitor, filtering current measurements, and determining rotor position without a high power supply, employing a matched filter and synchronous reference frame filter to extract position information and control the motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electromechanical sensors (resolvers, optical encoders, hall-effect sensors) are used to obtain rotor position, then rotor position and speed can be accurately measured, but cost, size, weight, and hardware wiring complexity increase
Solution Approach 1:
The patent replaces electromechanical position sensors with a sensorless control system that uses electrical measurements (currents and voltages) and mathematical observers to estimate rotor position. This substitutes mechanical sensing components with electrical field-based measurement and computation, eliminating the need for physical sensors on the rotor.
Solution Approach 2:
The patent introduces mathematical observers (such as sliding mode observers or extended Kalman filters) as intermediaries that process electrical measurements and infer rotor position information. These observers act as computational mediators between the electrical measurements and the control system, enabling position estimation without direct mechanical sensing.
2Measurement precision
If electromechanical sensors are mounted on the rotor, then rotor position can be obtained, but the robustness of the IPMSM decreases due to sensor failures in harsh environments
Solution Approach 1:
The patent extracts the position sensing function from the mechanical rotor structure and relocates it to the stator-side control system. By removing sensors from the rotor and implementing sensorless estimation using stator current and voltage measurements, the system eliminates the vulnerability of mounted sensors to harsh environmental conditions while maintaining position measurement capability.
3Measurement precision
If conventional voltage injection techniques are used for initial rotor position detection, then position can be determined at standstill, but the technique assumes constant DC bus voltage which limits applicability
Solution Approach 1:
The patent implements adaptive voltage injection techniques that dynamically adjust injection parameters based on actual DC bus voltage conditions. The system modifies injection amplitude, frequency, and timing according to varying voltage levels, enabling reliable initial position detection across different operating conditions rather than assuming constant voltage.
Solution Approach 2:
The patent changes the parameters of the voltage injection technique (amplitude, frequency, pulse width) based on the actual DC bus voltage level. By adapting these parameters to match varying voltage conditions, the system maintains detection accuracy and reliability across different power supply scenarios.
Data Source
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AI summary
At least one example embodiment discloses a drive system (100) including a motor (155) including a rotor, the motor (155) configured to receive a measured current, a controller (102) configured to generate a voltage for the motor (155) at a stationary reference frame, the measured current being based on the voltage, a filter (168) configured to obtain position information of the rotor based on the measured current and a nonlinear observer (170) configured to estimate a rotor position of the motor (155) during the stationary reference frame based on the position information. The controller (102) is configured to control the motor (155) based at least in part on the estimated rotor position.