| 1. |
- García-Mañas, Francisco, et al.
(author)
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A practical solution for multivariable control of temperature and humidity in greenhouses
- 2024
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In: European Journal of Control. - 0947-3580. ; 77
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Journal article (peer-reviewed)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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| 2. |
- García-Mañas, Francisco, et al.
(author)
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Multivariable control of nighttime temperature and humidity in greenhouses combining heating and dehumidification
- 2023
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In: IFAC-PapersOnLine. - 2405-8963. ; 56:2, s. 9900-9905
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Journal article (peer-reviewed)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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| 3. |
- Guzmán, José Luis, et al.
(author)
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Feedforward Control Concepts through Interactive Tools
- 2011
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In: 18th IFAC World Congress, 2011.
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Conference paper (peer-reviewed)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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| 4. |
- Guzmán, José Luis, et al.
(author)
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Interactive Learning Module: Basic Modelling and Identification Concepts
- 2008
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In: 17th IFAC World Congress, 2008.
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Conference paper (peer-reviewed)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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| 5. |
- Guzmán, José Luis, et al.
(author)
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Interactive Learning Module for Control Interaction Understanding
- 2009
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In: European Control Conference, 2009.
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Conference paper (peer-reviewed)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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| 6. |
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| 7. |
- Guzmán, José Luis, et al.
(author)
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Interactive Tool for Analysis of Time-Delay Dystems with Dead-Time Compensation
- 2006
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Conference paper (peer-reviewed)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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| 8. |
- Guzman, Jose Luis, et al.
(author)
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Interactive tool for analysis of time-delay systems with dead-time compensators
- 2008
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In: Control Engineering Practice. - : Elsevier BV. - 0967-0661. ; 16:7, s. 824-835
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Journal article (peer-reviewed)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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| 9. |
- Pawlowski, Andrzej, et al.
(author)
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Generalized Predictive Control With Actuator Deadband for Event-Based Approaches
- 2014
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In: IEEE Transactions on Industrial Informatics. - 1941-0050. ; 10:1, s. 523-537
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Journal article (peer-reviewed)abstract
- This work presents an event-based control structure using the generalized predictive control (GPC) algorithm with actuator deadband. The main objective of this work is to limit the number of controlled system updates. In this approach, the controlled process is sampled with a constant sampling time and is updated in an asynchronous way that depends on the obtained control signal value. To achieve the desired control properties, a hybrid system framework is used to model the virtual actuator deadband. The deadband is modeled as system input constraints in the GPC's optimization procedure, exploring mixed integer quadratic programming (MIQP) techniques. The presented control structure considers adjustable actuator deadband as an additional tuning parameter and allows a tradeoff between control performance and the number of events/updates. This fact is very important for the lifetime of the actuators and minimizes their wear, especially for mechanical and electromechanical systems. The minimization of actuator usage can be also understood as an economical saving. Other benefits can be found in distributed control systems, where various control system agents are connected through computer networks, and where a reduction in communication is always welcome.
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| 10. |
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