Rotating Machine Control Device for Rotor Position Estimation
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Solution Overview
Problem
Existing control devices for rotating electric machines face challenges in accurately estimating the rotor position, especially at zero speed or low speeds, due to low induced voltage and precision issues, leading to inefficiencies and potential demagnetization of permanent magnets, and are affected by manufacturing errors and environmental changes.
Innovation Solution
A control device that includes a magnetic pole position estimation unit, vector calculation unit, current command correction unit, current control unit, voltage application unit, and voltage control unit, which corrects d-axis and q-axis current commands by superimposing a high-frequency voltage component to enhance estimation precision and stability, ensuring the current amplitude of electrical angle frequency components is at least half of the specific frequency component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position sensor or speed sensor is provided for a rotating machine, then it is possible to accurately obtain the rotor speed information or the rotor position information, but there is an increase in cost, a need for wires, and a decrease in reliability due to sensor failure
Solution Approach 1:
The patent extracts the position detection function from a physical sensor and implements it through signal processing of existing motor phase currents. The rotor position is estimated by analyzing the back-EMF or current characteristics without requiring a dedicated position sensor, thereby eliminating sensor-related reliability issues while maintaining measurement precision
Solution Approach 2:
The patent uses phase current signals as an intermediary to indirectly obtain rotor position information. Instead of directly measuring position with a sensor, the system uses the existing current signals that already flow through the motor windings and processes them to extract position data, avoiding the need for additional sensors and wires
2Device complexity
If induced voltage is used to estimate rotor position, then the control method is simple, but the induced voltage is low at zero speed or low-speed range causing poor S/N ratio and difficult position estimation
Solution Approach 1:
The patent applies preliminary action by injecting a high-frequency voltage signal before attempting to measure rotor position at low speeds. This injected signal creates a detectable response in the phase currents that allows position estimation to proceed even when the natural back-EMF is too weak, effectively preparing the system with an artificial signal source before the measurement problem occurs
Solution Approach 2:
The patent uses electrical vibration by superimposing a high-frequency voltage signal on the motor phase windings. This high-frequency excitation creates corresponding current vibrations that can be detected and used to estimate rotor position, similar to how mechanical vibration is used in tactile sensors, but in the electrical domain to overcome the low signal level at low speeds
3Measurement precision
If magnetic saliency is used to superimpose a high-frequency signal for position estimation, then the rotor position can be estimated independently of speed, but the method requires additional high-frequency signal input and has precision deterioration at no load or low load due to small current amplitude and deadtime voltage error
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the amplitude and frequency of the injected high-frequency voltage signal based on the operating conditions. At no load or low load conditions, the system modifies these parameters to ensure sufficient current amplitude for accurate detection while compensating for deadtime effects, thereby maintaining measurement precision without excessive complexity
Solution Approach 2:
The patent implements feedback by using the detected rotor position information to adjust the injection strategy and control parameters. The system continuously monitors the response to the injected signal and uses this feedback to refine position estimation accuracy, particularly adapting to no load or low load conditions where current amplitude is small and deadtime errors are significant
4Measurement precision
If d-axis current command value is offset toward negative direction to correct c-axis current command, then estimation precision is improved, but torque production may be reduced
Solution Approach 1:
The patent applies dynamics by making the d-axis current offset dynamic rather than fixed. The offset amount is adjusted in real-time based on operating conditions such as speed, load, and estimated position accuracy requirements. This allows the system to apply sufficient offset to improve position estimation precision while minimizing the impact on torque production by reducing the offset when it is not needed or when torque requirements are high
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 solution effectively suppresses the deterioration of rotor position estimation precision, improves control efficiency, and prevents demagnetization, allowing for precise control across various operating conditions and machine types, reducing costs and increasing reliability.
Implementation Method 1
there is a control method of using magnetic saliency of the rotor to superimpose a high-frequency signal for estimating the position
Data Source
AI summary
Provided is a control device for a rotating machine including a magnetic pole position estimation unit, a vector calculation unit, a current command correction unit configured to correct a first d-axis current command and a first q-axis current command, to thereby output a second d-axis current command and a second q-axis current command, a voltage application unit configured to superimpose a high-frequency voltage including a specific frequency component on voltage commands on rotational coordinates. The magnetic pole position estimation unit is configured to estimate the position of the magnetic pole based on a state quantity of the specific frequency component. The current command correction unit is configured to correct the current commands so that a current amplitude of electrical angle frequency components is equal to or larger than a half of a current amplitude of the specific frequency component.