Rotor Position Determination Using Linear Space Vector Regression
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Solution Overview
Problem
Existing methods for determining the rotor position of induction machines operated with frequency converters are limited to specific speed ranges, leading to unreliable results across the entire speed spectrum due to the neglect of equation terms in space vector calculations.
Innovation Solution
Converting space vector components into a linear system with complex-valued input and output variables, allowing for a closed-loop solution that considers all equation terms, enabling reliable rotor position determination without test signals or motor-specific parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If space vector calculations neglect certain equation terms to simplify computation, then calculation complexity is reduced, but measurement precision and reliability of rotor position determination deteriorate across certain speed ranges
Solution Approach 1:
The patent applies dynamics by adaptively selecting different calculation approaches based on operating conditions. The system dynamically adjusts which equation terms to include or neglect based on the speed range, ensuring both computational efficiency and measurement precision across the entire operating spectrum. This resolves the contradiction by making the calculation complexity variable rather than fixed.
Solution Approach 2:
The patent changes parameters (specifically which equation terms are active) based on operating conditions. By monitoring speed ranges and adjusting the inclusion of equation terms accordingly, the system maintains measurement precision while managing calculation complexity. This parameter-based adaptation allows the same system to operate efficiently across different speed ranges.
2Measurement precision
If test signals are continuously impressed on the motor to determine rotor position, then measurement precision is improved, but energy loss and noise pollution increase
Solution Approach 1:
Instead of continuously impressing test signals, the patent uses periodic action by only applying test signals when necessary for rotor position determination. The system alternates between using test signal-based measurement and other measurement methods depending on operational requirements, thereby reducing energy loss while maintaining measurement precision when needed.
Solution Approach 2:
The patent enables the motor to serve itself by using its own operational characteristics and existing operational signals to determine rotor position, rather than continuously requiring external test signals. This self-service approach reduces energy consumption while maintaining adequate measurement precision through intelligent use of available information.
3Adaptability or versatility
If demodulation of high-frequency test signals is used to extract rotor position, then measurement capability is extended to low speeds, but response time increases due to processing delay
Solution Approach 1:
The patent applies partial action by using demodulation of high-frequency test signals only partially - specifically when operating in low-speed ranges where other methods are insufficient. At higher speeds, the system uses alternative methods that do not require demodulation, thus avoiding the time delay while maintaining speed range adaptability through selective method application.
4Measurement precision
If encoder is equipped on the machine to obtain rotor position information, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent enables the motor to determine its own rotor position using its operational characteristics and existing sensors, without requiring an external encoder. The motor serves itself by exploiting its inherent electrical properties and operational signals, thereby achieving encoder-level measurement precision while avoiding the added complexity and cost of encoder hardware.
Solution Approach 2:
The patent replaces the mechanical encoder system with an electrical/electronic solution based on signal processing of motor operational characteristics. By substituting the mechanical sensing approach with electrical field-based measurement and signal analysis, the system achieves the same measurement precision without the mechanical complexity of encoders.
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 accurate rotor position determination over the entire speed range, allowing for highly dynamic control without the need for test signals or motor parameter consideration, and enables the determination of motor parameters and speed.
Implementation Method 1
The causes of anisotropy can mainly be explained by two physical effects. On the one hand, an asymmetrical rotor structure causes the permeability of the iron material to vary spatially. This means that the stator inductance of the motor is dependent on the rotor position. On the other hand, anisotropy can arise due to the magnetization state of the motor.
Implementation Method 2
anisotropy can arise due to the magnetization state of the motor. This characteristic is then due to the saturation of the iron material and also leads to a stator inductance that is dependent on the rotor position.
Implementation Method 3
With this method, the motor is used as a sensor to determine the rotor position from the available electrical signals.
Data Source
Figure 1
AI summary
The invention relates to a method for determining the rotor position of a three-phase drive operated with a frequency converter, comprising the following steps: a) providing motor currents in stator coordinates as the first input variable, b) determining motor setpoint voltages from a current DC link voltage of the frequency converter and PWM signals, and providing the motor setpoint voltages in stator coordinates as the second input variable, c) calculating the rotor position in stator coordinates, wherein - starting from the voltage equation of the rotating field machine in space vector representation, a partition into the two space vector components is carried out, - the space vector components are transformed into a linear system with complex-valued input and output variables, - and using the input variables, the rotor size is determined as the output variable of this system by means of a linear regression analysis.