Fractional Order Observer Control for Disturbance-Rejecting Setpoint Tracking
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Solution Overview
Problem
Existing control systems for integer high-order systems face challenges in robustness and dynamic performance, particularly in set point tracking, due to poor disturbance rejection and transient response, as seen in fractional order active disturbance rejection controllers and extended state observer-based controllers.
Innovation Solution
A set point tracking system and method utilizing an extended state observer-based fractional order controller design, incorporating a fractional order proportional-integral-derivative controller and Bode's ideal transfer function to enhance robustness and dynamic performance, with a Crone approximation for fractional order derivative implementation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fractional order active disturbance rejection controller is used, then disturbance rejection is improved, but transient response deteriorates
Solution Approach 1:
The controller is segmented into two independent parts: a fractional order extended state observer for disturbance estimation and rejection, and a fractional order proportional derivative controller for set point tracking. This segmentation allows each component to be optimized independently, resolving the contradiction between disturbance rejection and transient response.
Solution Approach 2:
The patent employs fractional order dynamics (non-integer order) in both the observer and controller, providing continuous adjustment capability beyond integer orders. This dynamic flexibility enables simultaneous optimization of disturbance rejection and transient response characteristics that cannot be achieved with fixed integer-order controllers.
2Reliability
If extended state observer-based controller is used, then robustness is improved, but dynamic performance deteriorates
Solution Approach 1:
The control system is divided into an extended state observer module for robust disturbance estimation and a fractional order proportional derivative controller module for high-performance set point tracking. This segmentation enables the observer to provide robustness while the controller delivers superior dynamic performance.
Solution Approach 2:
The patent changes the order parameter from integer to fractional order in the controller design, allowing continuous tuning of system dynamics. This parameter change enables achieving both robustness and high dynamic performance by optimizing fractional order parameters independently.
3Measurement precision
If fractional order controller is used, then tracking accuracy is improved, but system complexity increases
Solution Approach 1:
The fractional order extended state observer acts as an intermediary that estimates disturbances and provides compensation signals. This intermediary approach simplifies the overall control structure by handling complexity in the observation layer while maintaining a relatively simple fractional order proportional derivative controller for tracking.
Solution Approach 2:
The fractional order extended state observer serves multiple functions: disturbance estimation, disturbance rejection, and providing feedback for the controller. This multi-functionality reduces the need for separate components, thereby managing system complexity while achieving high tracking accuracy.
Data Source
AI summary
A method and system for set point tracking control of an nth order integer control system. A first feedback compensated input signal is generated from an input signal, r(t), and a first negative feedback signal. A fractional order controller generates a set point modified signal from the first feedback compensated input signal. A second feedback compensated input signal is generated from the set point modified signal and a second negative feedback signal. A process variable is generated from the second feedback compensated input signal and applied to a non-linear plant which is affected by a disturbance which carries over into an output signal, y(t). An extended state observer receives the process variable and the output signal and generates the first second negative feedback and the second negative feedback signal to cancel the disturbance.