Motor Controller Circuit With Auto-Tuned PI Loop Bandwidth
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Solution Overview
Problem
Existing motor control systems employing PI compensators require complex adjustments of multiple parameters, leading to increased memory requirements and cumbersome tuning processes due to the interaction of six parameters in multi-loop systems.
Innovation Solution
A controller circuit with a major and minor controller, each incorporating a PI compensator and auto-tuning circuit, reduces parameters to four by optimizing the first and fourth coefficients using pole-zero cancellation, allowing automatic tuning of the first and second PI compensators, with the sixth coefficient relative to the third as a reference, facilitating simpler adjustments and reduced memory needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multi-loop control system with PI compensators is employed, then motor control precision is improved, but the number of parameters increases to six, leading to complex tuning processes and increased memory requirements
Solution Approach 1:
The patent extracts and eliminates redundant parameters from the control system by applying pole-zero cancellation. Specifically, it sets the zero of the PI compensator to cancel the pole of the motor transfer function, which allows removing two parameters (the integral time constant and one gain parameter) while maintaining control precision. This reduces the six parameters to four essential parameters.
Solution Approach 2:
The patent changes the parameter representation by expressing the PI compensator in terms of pole-zero form rather than traditional proportional-integral form. This parameter transformation allows the system to use fewer parameters (four instead of six) while achieving the same control objective, thereby simplifying the tuning process and reducing memory requirements.
2Reliability
If six parameters are used in PI compensators, then control performance is maintained, but manual tuning becomes cumbersome and time-consuming
Solution Approach 1:
The patent removes two parameters from the tuning process by applying pole-zero cancellation. The integral time constant is determined by the motor's pole location, and one gain parameter is determined by the desired closed-loop pole location. This extraction of redundant parameters reduces manual tuning from six parameters to four parameters, significantly reducing tuning time while maintaining control performance.
Solution Approach 2:
The patent performs preliminary determination of two parameters based on the motor's transfer function characteristics and desired closed-loop performance. By pre-calculating the integral time constant from the motor pole and determining one gain from the desired pole location, the system eliminates the need for manual tuning of these parameters, reducing overall tuning time.
3Loss of information
If six parameters are stored in memory, then complete control information is preserved, but memory requirements increase
Solution Approach 1:
The patent extracts and eliminates two parameters from the control information that needs to be stored. By applying pole-zero cancellation, the system determines that only four parameters are necessary to fully describe the control system behavior. This reduces memory requirements from storing six parameters to storing four parameters, while preserving all essential control information.
Solution Approach 2:
The patent changes the parameter representation to a more efficient form. Instead of storing six parameters in the traditional PI compensator form, the system stores four parameters in pole-zero form. This parameter transformation maintains complete control information while reducing memory requirements by eliminating redundant parameter storage.
Data Source
AI summary
A controller circuit includes a major controller and a minor controller. The major controller controls a major loop in which a rotational speed of a motor serves as a controlled variable. The minor controller controls a minor loop in which a current flowing through the motor serves as a controlled variable. A sixth coefficient that defines a bandwidth of the minor controller is determined relative to a third coefficient that defines a bandwidth of the major controller.