Induced-Voltage Observer for Sensorless Motor Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In sensorless control of brushless DC motors, the convergence gain and response frequency of the estimation system are affected by motor speed, making it difficult to design and adjust control parameters effectively, especially at low speeds.
Innovation Solution
The use of an induced-voltage observer allows for unconditional determination of all control gains, enabling clear and quantitative design of the induced voltage and frequency characteristics of the magnetic pole position estimation system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If sensorless control based on current estimation error is used, then the magnetic pole position can be estimated without sensors, but the convergence gain and response frequency become dependent on motor speed, causing poor performance at low speeds
Solution Approach 1:
The patent transforms the speed-dependent estimation problem into a speed-independent solution by changing the fundamental approach: instead of using current estimation error directly, it introduces an induced voltage observer that observes the induced voltage model. This parameter transformation allows the estimation system to maintain consistent convergence characteristics across all motor speeds, particularly improving low-speed performance where the original method failed.
2Stability of the object's composition
If induced voltage estimation response time is increased to match current response time, then stable control axis can be maintained, but the response frequency of current and speed must be decreased
Solution Approach 1:
The patent introduces an induced voltage observer as an intermediary component between the current detection and the magnetic pole position estimation. This observer processes the induced voltage information separately and feeds it to the estimation system, allowing the current control loop to maintain its original high response frequency while the position estimation benefits from the additional induced voltage information, thus achieving both stability and fast response.
3Ease of operation
If control parameters are adjusted through trial and error, then the system can be tuned for specific operating conditions, but the design process becomes complex and time-consuming
Solution Approach 1:
The induced voltage observer structure provides self-tuning characteristics where the estimation system automatically adapts to different operating conditions through its inherent model-based structure. The observer gains and parameters can be determined theoretically from motor parameters without requiring extensive trial-and-error adjustment, making the system easier to design and more adaptable to varying conditions.
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 stabilizes the control axis for current and speed control, ensuring stable estimation and control gains, even at low motor speeds, without the need for trial-and-error parameter adjustments.
Implementation Method 1
the magnitude and the phase of an induced voltage generated in the motor are estimated and, from them, the magnetic pole position (the position of the dq axis) of the rotor is estimated
Data Source
AI summary
In a sensorless control of a motor, due to the characteristic of a response frequency, an induced voltage, a magnetic pole position estimation gain, a current control gain, and a speed control gain are closely related. An object of the invention is to enable the induced voltage and the frequency characteristic of a magnetic pole position estimation system to be clearly designed and to theoretically and quantitatively design all of the control gains necessary for the sensorless control so as to solve a problem that a method of designing those parameters cannot be established and the parameters have to be adjusted in a try and error manner. A control device has an estimator estimating an estimation induced voltage and a phase error of a motor by applying an induced-voltage observer and a controller controlling the motor on the basis of the estimation induced voltage and the phase error.