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| 7. |
- Berner, Josefin, et al.
(författare)
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An experimental comparison of PID autotuners
- 2018
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Ingår i: Control Engineering Practice. - : Elsevier BV. - 0967-0661. ; 73, s. 124-133
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Tidskriftsartikel (refereegranskat)abstract
- In this paper two novel autotuners are compared with two industrially available ones. The aim is to see if the research frontline can improve the industry standard of today. Experiments are made on three laboratory processes with different characteristics. Two lag-dominated processes of which one is a level control problem with fast dynamics, and one a temperature control problem with slow dynamics, as well as one delay-dominated level control process. Both the experiments and the obtained controller performances are evaluated and discussed. The results show that the performance of the stateof-the-art industrial autotuners can be significantly improved.
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| 8. |
- Berner, Josefin, et al.
(författare)
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Asymmetric relay autotuning - Practical features for industrial use
- 2016
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Ingår i: Control Engineering Practice. - : Elsevier BV. - 0967-0661. ; 54, s. 231-245
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Tidskriftsartikel (refereegranskat)abstract
- The relay autotuner provides a simple way of finding PID controller parameters. Even though relay autotuning is much investigated in the literature, the practical aspects are not that well-documented. In this paper an asymmetric relay autotuner with features such as a startup procedure and adaptive relay amplitudes is proposed. Parameter choices and handling of noise, disturbances, start in non-steady state and other possible error sources are discussed. The autotuner is implemented and tested in an industrial air handling unit to show its use in practice. The experiments show good results, and prove that the proposed simple autotuner is well-suited for industrial use. But the experiments also enlighten possible error sources and remaining problems.
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| 9. |
- Berner, Josefin, et al.
(författare)
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Autotuner identification of TITO systems using a single relay feedback experiment
- 2017
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Ingår i: IFAC-PapersOnLine. - : Elsevier BV. - 2405-8963. ; 50:1, s. 6619-6623
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Tidskriftsartikel (refereegranskat)abstract
- Relay autotuning has proven very successful for single-input single-output systems. This paper proposes an identification method for relay autotuning of systems with two inputs and two outputs (TITO systems). The combination of asymmetric relay feedback and output error identification admits short tuning time, without the need for limit cycle convergence. The method is successfully demonstrated on relevant system models, including the Wood-Berry distillation column.
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| 10. |
- Berner, Josefin, et al.
(författare)
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Improved Relay Autotuning using Normalized Time Delay
- 2016
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Ingår i: American Control Conference (ACC), 2016.
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Konferensbidrag (refereegranskat)abstract
- The relay autotuner provides a simple way offinding PID controllers of sufficient performance. By usingan asymmetric relay function the excitation of the process isimproved. This gives better models, and hence a better tuning,without increasing the time consumption or complexity of theexperiment. Some processes demand more accurate modelingand tuning to obtain controllers of sufficient performance.These processes can be singled out by their normalized timedelays and be subject to further modeling efforts. The autotunerproposed in this paper provides a simple way of findingthe normalized time delay from the experiment, and uses itfor model and controller selection. The autotuner has beenimplemented and evaluated both in a simulation environmentand by industrial experiments.
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| 11. |
- Berner, Josefin, et al.
(författare)
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Practical Evaluation of a Novel Multivariable Relay Autotuner with Short and Efficient Excitation
- 2017
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Ingår i: IEEE Conference on Control Technology and Applications, CCTA 2017. ; , s. 1505-1510
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Konferensbidrag (refereegranskat)abstract
- In this paper we propose an autotuning method that combines a setup for decentralized relay autotuning of two-input two-output systems with an identification method that uses short experiments to estimate up to second-ordertime-delayed systems. A small modification of the experiment gives better low-frequency excitation and improved models. The method is successfully demonstrated in simulations and on a quadruple tank process.
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| 12. |
- Berner, Josefin, et al.
(författare)
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Towards a New Generation of Relay Autotuners
- 2014
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Ingår i: 19th IFAC World Congress, 2014.
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Konferensbidrag (refereegranskat)abstract
- The relay autotuner for PID control is based on the simple idea of investigating process dynamics by the oscillation obtained when the PID controller is replaced by a relay unction. In this paper an asymmetric relay function is used, which provides an equation for the static gain of the process. A method to find the normalized time delay is proposed and the benefits of this is discussed. Ways to find low-order models from the experiment are described. Considerations of how to choose the relay parameters are made and some examples are given.
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| 17. |
- Cederqvist, Lars, et al.
(författare)
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Cascade control of the friction stir welding process to seal canisters for spent nuclear fuel
- 2012
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Ingår i: Control Engineering Practice. - : Elsevier BV. - 0967-0661. ; 20:1, s. 35-48
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Tidskriftsartikel (refereegranskat)abstract
- This article presents the development to reliably seal copper canisters containing the Swedish nuclear waste, using friction stir welding. To avoid defects and welding tool fractures, it is important to control the welding temperature within a span of 790–910 degrees C. A cascade controller is used to efficiently suppress fast power input disturbances reducing their impact on the temperature. The controller is tuned using a recently presented method for robust PID control. Results show that the controller keeps the temperature within 710 degrees C during the 40 min long joint line sequences. Apart from the cascaded control structure, good process knowledge and control strategies adapted to different weld sequences have contributed to the successful results.
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| 18. |
- Cederqvist, Lars, et al.
(författare)
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Cascaded control of power input and welding temperature during sealing of spent nuclear fuel canisters
- 2010
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Konferensbidrag (refereegranskat)abstract
- The friction stir welding procedure to seal copper canisters requires variable power input throughout the 45 minute long weld cycle to keep the welding temperature within the process window. This is due to variable thermal boundary conditions throughout the weld cycle which, together with fast disturbances in the spindle torque, requires control of both the power input and the welding temperature to achieve a stable and robust process. By using a cascaded loop that determines the power input requirement, the regulator will not be dependent on repeatability in the necessary power input between weld cycles. As a result, a more accurate and reliable closed-loop control of the welding temperature is acquired.
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| 19. |
- Ekvall, Jenny, et al.
(författare)
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Improved web break strategy using a new approach for steam pressure control in paper machines
- 2008
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Ingår i: Control Engineering Practice. - : Elsevier BV. - 0967-0661 .- 1873-6939. ; 16:10, s. 1151-1160
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a new strategy for steam pressure control during web breaks in the paper machine. The aim was to restart paper production with the same drying properties of the cylinder as before the break. A detailed physical dynamic model of the drying cylinder has been developed. The accuracy of the model has been verified through experiments made at the M-real paper mill in Husum, Sweden. Verifications are made both during normal operation and during web breaks. The dynamic model has been reduced in order to derive simple transfer functions which were used to find the optimal steam pressure trajectory during web breaks. The resulting strategy has been tested on a paper machine with good results and it has been well received at the mill. (C) 2008 Elsevier Ltd. All rights reserved.
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| 20. |
- Ekvall, Jenny, et al.
(författare)
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Steam Pressure Control During Web Breaks in the Paper Machine
- 2004
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Ingår i: Preprints Control Systems 2004 Conference. - 1897023014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A new control strategy for steam pressure control inthe drying cylinders during web breaks is presented. The developmentis performed using a new physical model implemented inSimulink. The goal of the control strategy is that thecylinder temperatures are retained whenthe production is restarted after the web break.
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| 21. |
- Ericsson, Stefan, et al.
(författare)
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Implementation of an on-line detection procedure for oscillating control loops
- 2002
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Ingår i: Proceedings : control systems 2002 (SPCI-meddelande ; 76). - 0280-6800.
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Konferensbidrag (refereegranskat)abstract
- This paper describes a method for online supervision of control loops that automatically detects oscillations in the loops. The paper describes the method, its implementation in a Honeywell TDC3000 system, and experiences obtained from its use in the mill AssiDomän Frövi.
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| 22. |
- García-Mañas, Francisco, et al.
(författare)
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A practical solution for multivariable control of temperature and humidity in greenhouses
- 2024
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Ingår i: European Journal of Control. - 0947-3580. ; 77
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a simple and effective control solution to regulate temperature and humidity inside a greenhouse, which are the main climatic variables affecting crop growth and health. A multivariable control strategy with inverted decoupling is proposed in two schemes. The nighttime control scheme uses heating and dehumidification, and the daytime control scheme uses natural ventilation, dehumidification, and humidification. A system identification methodology is used to obtain low-order linear models from data measured in a greenhouse. This simplifies the design of proportional–integral (PI) controllers and allows the use of well-known control techniques. For instance, anti-windup is used to deal with the saturation of the actuators and for a bumpless transfer mechanism to switch between the nighttime and the daytime control schemes. Setpoint weighting is used for the humidity controllers to attenuate undesired effects on the temperature control loop when the humidity setpoint is changed. Furthermore, split range control is used for the first time to control humidity by combining a heat-pump dehumidifier and a fogging system. The control solution presented in this work allows the integral absolute error to be reduced, on average, by 88.5% for the interactions affecting the temperature control loop, and by 85.6% for the humidity control loop, compared to decentralized PI control. The control schemes have been tested in simulation with real disturbance data from a Mediterranean greenhouse and in preliminary form in a real facility to conclude that the proposed multivariable control strategy could be effective in decoupling the temperature and the humidity control loops.
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| 23. |
- García-Mañas, Francisco, et al.
(författare)
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Multivariable control of nighttime temperature and humidity in greenhouses combining heating and dehumidification
- 2023
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Ingår i: IFAC-PapersOnLine. - 2405-8963. ; 56:2, s. 9900-9905
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Tidskriftsartikel (refereegranskat)abstract
- This work presents a multivariable control strategy to regulate nighttime temperature and relative humidity inside a greenhouse, using a pipe heating system and a dehumidification system. The greenhouse is modeled as a two-input two-output (TITO) process with a system identification methodology to calculate low-order linear models. Proportional-integral (PI) controllers with anti-windup are used, and an inverted decoupling scheme is adopted. The strategy was tested in simulation with real data. Results suggest that it is attractive for real implementation and show for the first time that the use of dehumidification systems can be applied as part of a combined control strategy.
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| 24. |
- Garcia, Pedro, et al.
(författare)
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Control of unstable non-minimum-phase delayed systems
- 2006
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Ingår i: Journal of Process Control. - : Elsevier BV. - 1873-2771 .- 0959-1524. ; 16:10, s. 1099-1111
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Tidskriftsartikel (refereegranskat)abstract
- The control of systems with long delays, by considering the option of stable/unstable and minimum/non-minimum-phase processes, is a challenging one. Most of the existing solutions do not cover all the situations and, in any case, they lead to complex controllers. Simple controllers, easy to design and tune, are very important in the process industry. In this paper, some control schemes based on a new but very simple Smith Predictor are presented, the tuning of the controllers being done on a delay-free model. Internal stability and robust stability analysis for these control structures is provided. Several illustrative examples taken from previous works are included to demonstrate the simplicity and superiority of the proposed method over those already published both for robust stability and to reject load disturbance. (C) 2006 Elsevier Ltd. All rights reserved.
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| 25. |
- Garpinger, Olof, et al.
(författare)
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A Software Tool for Robust PID Design
- 2008
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Konferensbidrag (refereegranskat)abstract
- This paper presents a fast, interactive and easily modifiable software tool for robust PID design. The Matlab based program is supposed to give people with moderate knowledge on PID control a possibility to learn more and also be a future part of an autotuner. The PID design is made by minimizing the integrated absolute error value during a load disturbance on the process input. The optimization is performed with H-infinity constraints on the sensitivity and complementary sensitivity function, providing a robust closed loop system. Nelder Mead optimization is used with the AMIGO method providing an initial controller. The proposed method works well, and is very efficient, on a large batch of systems common in process industry. The design tool is also shown to work on a highly oscillatory process model.
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| 26. |
- Garpinger, Olof, et al.
(författare)
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Criteria and Trade-offs in PID Design
- 2012
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Ingår i: 2nd IFAC Conference on Advances in PID Control 2012. - 9783902823182 ; , s. 47-52
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Konferensbidrag (refereegranskat)abstract
- Control design is a rich problem which requires that many issues such as load disturbances and set-point responses, model uncertainty, and measurement noise are taken into account. These issues are discussed for design of PI and PID controllers. The purpose is to give insight into the different criteria and their trade-offs, not to give specific tuning methods.
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| 27. |
- Garpinger, Olof, et al.
(författare)
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Modeling for Optimal PID Design
- 2014
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Konferensbidrag (refereegranskat)abstract
- Even though PID controllers have been around for a long time, few industrial controllers use derivative action and the remaining PI controllers are often designed with formula-based tuning rules rather than through computer-based optimization. This paper will delve into some of the reasons behind these choices and show potential benefits of instead using software-based PID tuning. Three commonly used tuning rules are compared to software tuning with respect to performance and robustness over a large process batch. The study shows the importance of combining a fast, accurate modeling tool with the software design method and gives guidelines for future modeling tools with regards to desired process information. With moderate process knowledge it is possible to design controllers that are much closer to optimal than the three tuning rules, with significant performance improvements as a result.
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| 28. |
- Garpinger, Olof, et al.
(författare)
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Performance and robustness trade-offs in PID control
- 2014
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Ingår i: Journal of Process Control. - : Elsevier BV. - 1873-2771 .- 0959-1524. ; 24:5, s. 568-577
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Tidskriftsartikel (refereegranskat)abstract
- Control design is a rich problem which requires consideration of many issues such as load disturbance attenuation, set-point tracking, robustness with respect to process variations and model uncertainty, and effects of measurement noise. The purpose of this paper is to provide insight into the trade-offs between performance and robustness explicitly. This is accomplished by introducing plots that show the trade-offs for PI and PID control. These also provide valuable understanding of design compromises used for common PI design methods.
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| 29. |
- Garpinger, Olof, et al.
(författare)
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Software-based optimal PID design with robustness and noise sensitivity constraints
- 2015
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Ingår i: Journal of Process Control. - : Elsevier BV. - 1873-2771 .- 0959-1524. ; 33:9, s. 90-101
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Tidskriftsartikel (refereegranskat)abstract
- Even though PID control has been available for a long time, there are still no tuning methods including derivative action that have gained wide acceptance in industry. Also, there is still no general consensus for when one should use PID, PI or even I control on a process. The focus of this article is to present a new method for optimal PID control design that automatically picks the best controller type for the process at hand. The proposed PID design procedure uses a software-based method to find controllers with optimal or near optimal load disturbance response subject to robustness and noise sensitivity constraints. It is shown that the optimal controller type depends on maximum allowed noise sensitivity as well as process dynamics. The design procedure thus results in a set of PID, PI and I controllers with different noise filters that the user can switch between to reach an acceptable control signal activity. The software is also used to compare PI and PID control performance with equivalent noise sensitivity and robustness over a large batch of processes representative for the process industry. This can be used to show how much a particular process benefits from using the derivative part.
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| 30. |
- Garpinger, Olof, et al.
(författare)
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Software for PID design: benefits and pitfalls
- 2012
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Ingår i: 2nd IFAC Conference on Advances in PID Control 2012. - 9783902823182 ; , s. 140-145
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Konferensbidrag (refereegranskat)abstract
- The most common PID design methods in industry are based on formulas. This article will present some major advantages of instead using the power of computer based softwares for PID controller design. The Matlab based software used in this work was developed in 2007 and derives robust, IAE minimizing, PID controllers. The experiences of using this software are collected in this article and include control signal activity limitation due to measurement noise, controller design on an industrial Friction Stir Welding process and fast controller design for large batches of processes. It is shown that the properties of the software make it suitable for design of PID controllers and in PID research. There are, however, some possible design pitfalls that the user needs to be aware of. Some of these are presented as well.
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| 31. |
- Garrido, Juan, et al.
(författare)
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Practical advantages of inverted decoupling
- 2011
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control. - : SAGE Publications. - 0959-6518 .- 2041-3041. ; 225:7, s. 977-992
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a study of the main advantages of inverted decoupling in 2×2 processes. Two simulation examples and an experimental process are used to show these advantages in comparison with simplified decoupling. The study focuses on the following practical advantages: the apparent process is the same as that obtained if one loop changes to manual; bumpless transfer and anti-windup are achieved easily using a feed-forward input in the controllers; and abnormalities of secondary loops do not affect the opposite loop. Because of this, inverted decoupling may be a good and easy way to improve the performance of industrial TITO (two inputs and two outputs) processes with interaction problems (when it can be applied).
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| 32. |
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| 33. |
- Guzmán, José Luis, et al.
(författare)
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Feedforward Control Concepts through Interactive Tools
- 2011
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Ingår i: 18th IFAC World Congress, 2011.
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Konferensbidrag (refereegranskat)abstract
- This paper presents an interactive software tool for basic and advanced concepts of feedforward control. The ideal compensator is analyzed to show how the effects of the load disturbances are eliminated from the process output. Furthermore, it is also shown that the ideal compensator is seldom realizable, since the compensator may be non-causal, it may be unstable, it may have infinite high-frequency gain because of derivative action, and it may require a more complicated structure than what is available. The drawback of not taking the feedback controller into account during the typical open-loop feedforward design is also studied. The proposed software tool helps to evaluate all these situations in an interactive way, enabling users to find possible design solutions to these problems.
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| 34. |
- Guzman, Josè Luis, et al.
(författare)
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Give us PID controllers and we can control the world
- 2024
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Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 2405-8963.
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this paper is to emphasize the importance of PID control for our society in general and for the control engineering community in particular. To this end, we first equate the relevance of PID controllers with other inventions in history to remark how PID control has contributed to revolutionizing our world as the main ambassador of the automatic control field. Afterwards, the PID control resilience is provided by showing a brief historical evolution to realize its timely adaptation, and how nowadays it is much more than just the three terms; P, I, and D. Moreover, it is summarized how PID control has been demonstrated to be equivalent to other optimal control solutions and how the recurrent comparison with Model Predictive Control (MPC) is not necessary at all, as both control algorithms should be considered as complementary approaches. Finally, encouragements and suggestions are summarized to continue working on PID control topics.
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| 35. |
- Guzmán, José Luis, et al.
(författare)
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Interactive Learning Module: Basic Modelling and Identification Concepts
- 2008
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Ingår i: 17th IFAC World Congress, 2008.
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Konferensbidrag (refereegranskat)abstract
- This paper describes an interactive tool focused on teaching and learning basic concepts about modelling and identification. Modelling and identification play fundamental roles in the field of automatic control, since it is not possible to perform a control system design without having a model describing the dynamics of the process to be controlled. The tool presented in this work is dedicated to describe the most important aspects of basic modelling centralized on first and second order systems with dead-time and zero effects.
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| 36. |
- Guzmán, José Luis, et al.
(författare)
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Interactive Learning Module for Control Interaction Understanding
- 2009
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Ingår i: European Control Conference, 2009.
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Konferensbidrag (refereegranskat)abstract
- This paper describes an interactive tool focused on teaching and learning basic concepts on multivariable control systems. Most industrial processes are represented by multivariable systems and thus the teaching and learning of basic concepts on multivariable control is a key factor in control engineering education. In this sense, the interactive tool presented in this paper is aimed to introduce basic ideas on multivariable control systems mainly focused on interaction and pairing concepts.
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| 37. |
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| 38. |
- Guzmán, José Luis, et al.
(författare)
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Interactive Learning Modules for PID Control
- 2006
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Ingår i: 7th IFAC Symposium on Advances in Control Education, 2006.
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Konferensbidrag (refereegranskat)abstract
- This paper describes a collection of interactive learning modules for PID control based on the graphical spread sheet metaphor. The modules are designed to speed up learning and to enhance understanding of the behaviour of loops with PID controllers. The modules are implemented in Sysquake, a Matlab dialect with strong support of interaction. Executable versions of the modules for Mac and PC are available on the web.
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| 39. |
- Guzmán, José Luis, et al.
(författare)
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Interactive Tool for Analysis of Time-Delay Dystems with Dead-Time Compensation
- 2006
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Konferensbidrag (refereegranskat)abstract
- This paper presents an interactive tool which allows to study the problem of systems with delays. The developed tool provides several examples in order to compare PI control and Smith Predictor approaches for processes with delay. Robustness problems due to presence of model uncertainties can also be studied, as well as other control structures to face the different problems that the original Smith Predictor has with integrator and unstable processes.
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| 40. |
- Guzman, Jose Luis, et al.
(författare)
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Interactive tool for analysis of time-delay systems with dead-time compensators
- 2008
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Ingår i: Control Engineering Practice. - : Elsevier BV. - 0967-0661. ; 16:7, s. 824-835
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Tidskriftsartikel (refereegranskat)abstract
- The problem of controlling delayed systems has been widely studied in the control community. The Smith predictor (SP) scheme was the most famous and efficient technique to cope with this problem. Afterwards, robustness problems and those related to the control of integrating and unstable delayed processes were resolved. This work presents an interactive tool for studying and understanding the different alternatives available for controlling systems with large delays. Interactive tools have provided excellent support for the control community during recent years. In this sense, the tool developed here helps to compare easily the performance of PID controllers and SP approaches for processes with delay, as well as other control structures used to solve different problems that the original SP has when integrator and unstable models are employed. Robustness problems due to presence of model uncertainties can also be analyzed. Furthermore, some real industrial processes are also described as motivation in the study of the problems presented in the paper. The tool incorporates a set of typical transfer functions based on these real industrial processes.
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| 41. |
- Guzmán, José Luis, et al.
(författare)
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Performance indices for feedforward control
- 2015
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Ingår i: Journal of Process Control. - : Elsevier BV. - 1873-2771 .- 0959-1524. ; 26, s. 26-34
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a performance benchmark for the assessment of two feedforward control architectures for the load disturbance compensation problem is proposed. In particular, two indices are devised so that the advantage of using a feedforward compensator with respect to the use of a feedback controller only is quantified. Furthermore, these metrics will help to make quantitative comparisons among different feedforward control schemes and tuning rules. Analysis and simulation results are given to demonstrate the effectiveness of the proposed approach.
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| 42. |
- Guzman, Josè Luis, et al.
(författare)
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Selecting control schemes and tuning rules in feedforward control
- 2023
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Ingår i: IFAC-PapersOnLine. - 2405-8963. ; 56:2, s. 3253-3258
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Tidskriftsartikel (refereegranskat)abstract
- This paper treats the problem of feedforward control from measurable load disturbances. Most of the tuning rules based on IAE or ISE optimization for feedforward compensators that have been presented in recent years are compared with each other as well as with optimal compensators. There are two different feedforward control schemes that may be used, and these schemes are also compared and analyzed. The paper gives recommendations for selection of both control schemes and tuning rules.
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| 43. |
- Guzmán, José Luis, et al.
(författare)
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Simple tuning rules for feedforward compensators
- 2011
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Ingår i: Journal of Process Control. - : Elsevier BV. - 1873-2771 .- 0959-1524. ; 21:1, s. 92-102
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes new simple tuning rules for design of feedforward compensators. The problem of feedforward from load disturbances is analyzed, and it is shown that the feedback controller should be taken into account in the feedforward design process. Simple rules based on IAE minimization with restrictions on the process output overshoot and the high-frequency gain of the compensator are then derived. Several simulations are presented along the paper to show the advantages of the proposed design rules.
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| 44. |
- Guzmán, José Luis, et al.
(författare)
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Understanding PID design through interactive tools
- 2014
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Ingår i: 19th IFAC World Congress, 2014.
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Konferensbidrag (refereegranskat)abstract
- Hundreds of PID design methods are available in literature. Many of them are very similar and sometimes it is not straightforward to understand their purposes. This paper presents an interactive software tool to help in the study and understanding of several wellknown PID tuning rules. Frequency- and time-domain responses are analyzed in order to show the robustness and performance properties of each method. Furthermore, a free tuning option is available to provide comparisons with user-defined rules or other existing tuning methods. A wide range of stable process models are included in the tool, where model-reduction techniques are applied for high-order processes to obtain simple models for design purposes.
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| 45. |
- Hang, Chang C., et al.
(författare)
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Automatic Tuning and Adaptation for PID Controllers—A Survey
- 1992
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Ingår i: Adaptive Systems in Control and Signal Processing 1992.
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Konferensbidrag (refereegranskat)abstract
- Adaptive techniques such as gain scheduling, automatic tuning and continuous adaptation have been used in industrial single-loop controllers for about ten years. This paper gives a survey of the different adaptive techniques, the underlying process models and control designs. The paper ends with an overview of industrial adaptive single-loop controllers.
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| 46. |
- Hansson, Jonas, et al.
(författare)
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Next generation relay autotuners—analysis and implementation
- 2021
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Ingår i: Proceedings of the 5th IEEE Conference on Control Technologies and Applications (CCTA) 2021. ; , s. 1075-1982
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Konferensbidrag (refereegranskat)abstract
- In order to produce models for automatic controller tuning, this paper proposes a method that combines a short experiment with a novel scheme for approximating processes using low-order time-delayed models. The method produces models aimed to tune PI and PID controllers, but they could also be used for other model-dependent controllers like MPC. The proposed method has been evaluated in simulations on benchmark processes. It has also been implemented in an industrial controller and tested experimentally on a water-tank process. It is shown that our method is successful in estimating models for a variety of processes such as lag-dominated, delay-dominated, balanced, and integrating processes. We also demonstrate that the experiment time is both shorter and more predictable than currently used autotuners.
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| 47. |
- Hast, Martin, et al.
(författare)
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Design of Optimal Low-Order Feedforward Controllers
- 2012
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Ingår i: 2nd IFAC Conference on Advances in PID Control 2012. - 9781627483247 ; , s. 483-488
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Konferensbidrag (refereegranskat)abstract
- Design rules for optimal feedforward controllers with lead-lag structure in the presence of measurable disturbances are presented. The design rules are based on stable first-order models with time delays, FOTD, and are optimal in the sense of minimizing the integrated-squared error. The rules are derived for an open-loop setting, considering a step disturbance. This paper also discusses a general feedforward structure, which enables decoupling in the design of feedback and feedforward controllers, and justifies the open-loop setting.
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| 48. |
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| 49. |
- Hast, Martin, et al.
(författare)
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Low-order feedforward controllers: Optimal performance and practical considerations
- 2014
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Ingår i: Journal of Process Control. - : Elsevier BV. - 1873-2771 .- 0959-1524. ; 24:9, s. 1462-1471
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Tidskriftsartikel (refereegranskat)abstract
- Feedforward control from measurable disturbances can significantly improve the performance in control loops. However, tuning rules for such controllers are scarce. In this paper design rules for how to choose optimal low-order feedforward controller parameter are presented. The parameters are chosen so that the integrated squared error, when the system is subject to a step disturbance, is minimized. The approach utilizes a controller structure that decouples the feedforward and the feedback controller. The optimal controller can suffer from undesirable high-frequency noise characteristics and tuning methods for how to filter the control signal are also provided. For scenarios where perfect disturbance attenuation in theory is achievable but where noise-filtering is needed, the concept of precompensation is introduced as a way to shift the controller time-delay to compensate for the low-pass filtering.
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| 50. |
- Hast, Martin, et al.
(författare)
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Optimal proportional–integral–derivative set-point weighting and tuning rules for proportional set-point weights
- 2015
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Ingår i: IET Control Theory and Applications. - : Institution of Engineering and Technology (IET). - 1751-8652. ; 9:15, s. 2266-2272
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Tidskriftsartikel (refereegranskat)abstract
- In this study, design of low-order feedforward controllers from both reference signal and measurable disturbance for proportional–integral–derivative (PID) controllers is considered. The feedforward controllers from reference are equivalent to the use of a PID controller with set-point weighting. The design problem is formulated as a convex optimisation problem and then solved for a batch of process models. The optimal proportional set-point weights are then used to derive tuning rules that minimise the integrated absolute error. Examples illustrate the usefulness of the proposed method and tuning rules
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