Its a general question.
For example, I want to design a controller for a nonlinear system to cope with certain periodic disturbance. In order to get a linearized state space model, I linearize the system about certain operating region and state space linear model has no information of this periodic disturbance. how to remove or minimize it. One solution is to use model predictive control where a real system posed to this periodic disturbance is tracking a reference system model (this reference model doesn't included this disturbance into account). I would appreciate if you can suggest a solution other than this.
(Edited)
Hi Kamran
For controller circuit designing you need to model your system and get all differential equations related to your capacitors voltage and inductors currents. After that there are very different structures to design your controller.
Regards
Hi Kamran,
To reject a disturbance, you may try to design a Disturbance Observer.
Good luck!
Dear Kamran,
In fact there are several approaches to solve this problem, among these techniques we can note some that are the most used: Modeling of periodic disturbances and compensation by conventional control methods; Rejection and Compensation of Periodic Disturbance in Control System; Adaptive Rejection of Periodic Disturbances Acting; Indirect Periodic Disturbance Compensator using Feedforward Control; Compensation of periodic disturbances model using Observer...
For more details and informations about this subject i suggest you to see links and attached files in topics.
-Dealing with periodic disturbances in controls of mechanical systems ...
www.sciencedirect.com/science/article/pii/S1367578808000321
-Adaptive Compensation of Periodic Disturbance in ... - EE, Technion
webee.technion.ac.il/control/info/Projects/.../daniel_fernando.pdf
-Dynamic and Closed-Loop Control
https://ai2-s2-pdfs.s3.amazonaws.com/.../72e1b0d3357562e22b65...
-System Identification in the Presence of Completely Unknown Periodic ...
people.duke.edu/~hpgavin/SystemID/.../Phan-JGDC-2000a.pdf
-Measurable Disturbances Compensation: Analysis and Tuning ... - MDPI
www.mdpi.com/2227-9717/4/2/12/pdf
-An Online Observer for Minimization of Pulsating Torque in SMPM ...
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4835102/
Best regards
Thank you all for your replies especially @Mohamed-Mourad Lafifi for such a detailed answer.
You can see integral adaptation principle of synergetic control theory or
synergetic sliding mode control.
I personally like Sliding Mode Controllers (SMC), because they can compensate for any bounded disturbance (including periodic one). SMC can compensate also for un-modeled dynamics. Observers for estimating disturbance is also very useful specially if you know the nature of this disturbance.
Good luck.
Dear Kamran Ali Shah,
Please find attached this papers. We have successfully reduce periodic disturbances using this algorithms. Detailed theoretical explanation, for the developed controllers, is available at the following papers:
http://www.mdpi.com/1424-8220/13/3/3831/pdf
In this paper, a new self-tuning algorithm is developed for determining the Fourier Series Controller coefficients with the aim of reducing the torque ripple in a PMSM. This algorithm adjusts the controller parameters based on the component’s harmonic distortion in time domain of the compensation signal.
http://www.mdpi.com/2076-3417/6/9/254/pdf
A new Fourier Series Learning Controller (FSLC) for velocity control on a Permanent Magnet Synchronous Motor (PMSM) is proposed and implemented. An analysis of the error convergence for the FSLC is presented, and the update law for the Fourier series coefficients is specified.
Regards,
Alfonso Gómez
Hi Kamran,
If you are working with linear systems, I'd advise you to explore some Linear Robust Controllers, such as the following:
- High-gain feedback
- Linear Quadratic Gaussian (LQG) controller with loop transfer recovery
- H∞ controller synthesis
- Quantitative Feedback Theory (QFT)
before moving to the nonlinear realm or advanced disturbance rejection techniques. These linear robust controllers have good disturbance attenuation attributes, though each has pros and cons.
Good luck!
Since Kamran Ali linearize his non-linear model, I think he is designing a linear control that he will apply to the non-linear system subject to periodic un-know disturbance. Regarding Yew-Chung suggestions, LQG/LTR and H-inf techniques both requires first to build a generalized plant that includes the nominal plant, filters, disturbance model (if available), and all the interconnections to disturbance input, control input, regulated output and measured output (see for instance the book of K. Zhou, Robust and Optimal Control). After that you should verify the existence conditions and remove singularities (if needed). Then you will get the controller using the robust control toolbox of MatLab.
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