Asymmetries in the Disturbance Compensation Methods for the Stable and Unstable First Order Plants
This paper analyzes the first-order and first-order time-delayed systems control approaches, focusing mainly on unstable systems. First, it discusses asymmetries between the disturbance observer-based (DOB) control with decoupled tracking and the disturbance rejection responses, stressing applicatio...
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| Format: | Article |
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MDPI AG
2020-09-01
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| Series: | Symmetry |
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| Online Access: | https://www.mdpi.com/2073-8994/12/10/1595 |
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| author | Mikulas Huba Pavol Bistak Damir Vrancic Katarina Zakova |
| author_facet | Mikulas Huba Pavol Bistak Damir Vrancic Katarina Zakova |
| author_sort | Mikulas Huba |
| collection | DOAJ |
| description | This paper analyzes the first-order and first-order time-delayed systems control approaches, focusing mainly on unstable systems. First, it discusses asymmetries between the disturbance observer-based (DOB) control with decoupled tracking and the disturbance rejection responses, stressing applications to stable and unstable plants. The paper analyzes some DOB-based control solutions for unstable systems which do not use internal closed-loop stabilization. The novelty of the paper is thorough study accompanied with a comprehensive explanation of the differences between two distinct approaches: the transfer-function- and the closed-loop-based feedforward control approach from the point of view of control constraints. It is clearly illustrated that the main cause of instability of DOB-based approaches, applied to unstable systems, is given by their effort to impose on the system the unstable dynamics of the chosen nominal process model. It is also shown that the closed-loop stability of the DOB-based control, applied to the unstable systems, can be restored by using the supervising reference model control (RMC). The main novelty of the proposed approach is that its eliminates the mentioned stability problems while maintaining the full functionality of the chosen control structures. RMC has so far only been implemented for generating a setpoint feedforward signal. However, by generalization of this approach for disturbance rejection, the methodology of DOB design, based on nominal models, can be extended to the control of unstable systems. Without the use of disturbance reference models, the interactions of the master stabilizer with disturbance compensation cannot be eliminated. Without the internal stabilization, the stable transients can only be achieved by designing controllers based on stable models, instead of unstable ones. The existing modifications of DOB-based schemes for unstable plants, proposed in some references, are shown to lead to traditional Proportional-Integrative (PI) control, thus losing all the advantages over the PI controllers. In all the considered structures, the role of integrating models is also emphasized. |
| first_indexed | 2024-03-10T16:03:45Z |
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| id | doaj.art-8008dbb988f14b80a3c791c48d00d02a |
| institution | Directory Open Access Journal |
| issn | 2073-8994 |
| language | English |
| last_indexed | 2024-03-10T16:03:45Z |
| publishDate | 2020-09-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Symmetry |
| spelling | doaj.art-8008dbb988f14b80a3c791c48d00d02a2023-11-20T15:04:17ZengMDPI AGSymmetry2073-89942020-09-011210159510.3390/sym12101595Asymmetries in the Disturbance Compensation Methods for the Stable and Unstable First Order PlantsMikulas Huba0Pavol Bistak1Damir Vrancic2Katarina Zakova3Institute of Automotive Mechatronics, Faculty of Electrical Engineering and Information Technology, Slovak University of Technology in Bratislava, 812 19 Bratislava, SlovakiaInstitute of Automotive Mechatronics, Faculty of Electrical Engineering and Information Technology, Slovak University of Technology in Bratislava, 812 19 Bratislava, SlovakiaDepartment of Computer Automation and Control, J. Stefan Institute, SI-1000 Ljubljana, SloveniaInstitute of Automotive Mechatronics, Faculty of Electrical Engineering and Information Technology, Slovak University of Technology in Bratislava, 812 19 Bratislava, SlovakiaThis paper analyzes the first-order and first-order time-delayed systems control approaches, focusing mainly on unstable systems. First, it discusses asymmetries between the disturbance observer-based (DOB) control with decoupled tracking and the disturbance rejection responses, stressing applications to stable and unstable plants. The paper analyzes some DOB-based control solutions for unstable systems which do not use internal closed-loop stabilization. The novelty of the paper is thorough study accompanied with a comprehensive explanation of the differences between two distinct approaches: the transfer-function- and the closed-loop-based feedforward control approach from the point of view of control constraints. It is clearly illustrated that the main cause of instability of DOB-based approaches, applied to unstable systems, is given by their effort to impose on the system the unstable dynamics of the chosen nominal process model. It is also shown that the closed-loop stability of the DOB-based control, applied to the unstable systems, can be restored by using the supervising reference model control (RMC). The main novelty of the proposed approach is that its eliminates the mentioned stability problems while maintaining the full functionality of the chosen control structures. RMC has so far only been implemented for generating a setpoint feedforward signal. However, by generalization of this approach for disturbance rejection, the methodology of DOB design, based on nominal models, can be extended to the control of unstable systems. Without the use of disturbance reference models, the interactions of the master stabilizer with disturbance compensation cannot be eliminated. Without the internal stabilization, the stable transients can only be achieved by designing controllers based on stable models, instead of unstable ones. The existing modifications of DOB-based schemes for unstable plants, proposed in some references, are shown to lead to traditional Proportional-Integrative (PI) control, thus losing all the advantages over the PI controllers. In all the considered structures, the role of integrating models is also emphasized.https://www.mdpi.com/2073-8994/12/10/1595disturbance observerunstable plantreference model control |
| spellingShingle | Mikulas Huba Pavol Bistak Damir Vrancic Katarina Zakova Asymmetries in the Disturbance Compensation Methods for the Stable and Unstable First Order Plants Symmetry disturbance observer unstable plant reference model control |
| title | Asymmetries in the Disturbance Compensation Methods for the Stable and Unstable First Order Plants |
| title_full | Asymmetries in the Disturbance Compensation Methods for the Stable and Unstable First Order Plants |
| title_fullStr | Asymmetries in the Disturbance Compensation Methods for the Stable and Unstable First Order Plants |
| title_full_unstemmed | Asymmetries in the Disturbance Compensation Methods for the Stable and Unstable First Order Plants |
| title_short | Asymmetries in the Disturbance Compensation Methods for the Stable and Unstable First Order Plants |
| title_sort | asymmetries in the disturbance compensation methods for the stable and unstable first order plants |
| topic | disturbance observer unstable plant reference model control |
| url | https://www.mdpi.com/2073-8994/12/10/1595 |
| work_keys_str_mv | AT mikulashuba asymmetriesinthedisturbancecompensationmethodsforthestableandunstablefirstorderplants AT pavolbistak asymmetriesinthedisturbancecompensationmethodsforthestableandunstablefirstorderplants AT damirvrancic asymmetriesinthedisturbancecompensationmethodsforthestableandunstablefirstorderplants AT katarinazakova asymmetriesinthedisturbancecompensationmethodsforthestableandunstablefirstorderplants |