Hybrid Modeling And Analysis Of Greenhouse Control Systems

Hybrid systems theory has roots in several different fields of science,such as computer science and the control theory,etc.. It is defined as the modeling, analysis, and control of systems which involve the interaction of both discrete state systems, represented by finite automata, and continuous state dynamics, represented by differential equations. Hybrid control system comprise continuous control laws combined with discrete mode logic, and can be used to implement the intelligent control system in a more unified and systematic manner.Greenhouse systems have become very complex and require equally complex control structures to maintain optimal growth conditions and to justify the significant investments involved. Information technologies play an essential role in the greenhouse climate control systems.The overall goal of this dissertation is to model and analysis the greenhouse system in a hybrid systems approach. The solutions based on the hybrid systems for the complexity, nonlinear, multiple time scale problems in the greenhouse climate control system are given. This dissertation also contributes to the development of the hybrid systems simulation platform for the greenhouse climate control system. The main research works of this dissertation are as followings:Summarizing reviews of the hybrid systems related theory and approaches are given. The hybrid systems related conception and basic theory are introduced. The general hybrid systems modeling and analysis approaches are summarized. Finite automata and regular language are used to model and analyze discrete event systems. The features and modeling of the continuous state dynamical systems in the hybrid systems are investigated. The Nerode-Kohn model for hybrid systems is refined and the hybrid automata modeling for hybrid systems are proposed.The structure, approaches and design of the hybrid control system are investigated. According to the features of the hybrid systems, the hybrid control-loop and architecture structure for the control system in hybrid system are proposed. Separated closed-loop controllers are synthesized for the continuous dynamical systems and discrete-event systems. RW supervisor control theory and approaches for discrete event systems closed-loop control is studied. Several advanced control technology are applied to the hybrid systems. The event driven internal model controller, feed-forward control and anti-windup algorithm are proposed. The implementation of the intelligent control based on the hybrid control systems framework are discussed and proposed. The hybrid systems simulation frameworks and related modulars are designed and developed. Based on the Hybrid Systems, greenhouse systems are studied and analyzed. The control and production activites in the greenhouse system are goal oriented and the control goals tree is proposed. The control goals and activities are classified. In hybrid systems framework an architecture structure, in which the low levels perform physical control and high levels do decision-making and cognitive control, for the control system is designed. Several solutions for greenhouse climate control problems, such as the applications of plant growth model and disturbances compensation, are discussed and studied. The simulation framework for greenhouse climate control system is disigned. For research purpose the greenhouse micro-climate and plant growth model are studied and their simulation modulars are implemented and the simulation researches are carried out.In hybrid systems framework, the study and design on the greenhouse climate control system are given. The greenhouse environment temperature control system is designed and implemented. Based on the internal model control theory method, the heating process and ventilation process controller are designed and tested in the greenhouse fields. The fields test results show that the controllers satisfy the requirements of the greenhouse system. In the greenhouse environment temperature hybrid control system the hybrid control loops are designed. In the hybrid control loop, all components, such as the temperature setpoints, the controllers and disturbances compensators are designed and implemented as hybrid dynamical system. As part of the control loop the temperature setpoints, which is a hybrid dynamical system, interact with the plants growth models and disturbances compensators through the continuous IO variables and discrete events. The heating and ventilation process control strategies are implemented in discrete event systems and supervisor controllers. The study shows that the hybrid systems are suitable to implement the greenhouse climate intelligent control systems.