Modeling And Control Of Hybrid System

While the industrial objects become more complex and the precision control becomes higher and higher, the coupled relation between the continuous variables dynamic systems (CVDS) and the discrete event dynamic systems(DEDS) which are in the process of industrial control is increasing obviously. Focusing on the coupled relation and the exceptive dynamics, the research of hybrid system attracted the attention of the international control sector.The hybrid system means that the system contains both continuous subsystem and discrete subsystem. The discrete part often acts as the scheduler or monitor managers in the control system, such as the ON/OFF switches, valves, gearings, limiters or selectors, and the continuous part is evolved with the elapse of time. The interaction of the two parts makes the trajectory of the system presents a transition of discrete position on the whole and a gradual evolution of continuous states in local. The hybrid system, narrowly, refers to a system which contains both discrete variables and continuous variables; while broadly it means a system which contains two interactional processes, continuous process and discrete process.Around of the modeling of the hybrid system and the design of optimization controller, from the characteristics of the hybrid system, some new methods from discrete modeling and continuous control on the traditional system are shown in this article. Many methods for discrete event system like as Automata, Petri net, Projection Construct and many methods for continuous time system like as Generalized Predictive Control algorithm (GPC), Multi-Model Control and Fuzzy Supervisory are discussed and analyzed deeply from the construct of a system model and designing of optimal controller.1. Aimed at the hybrid system which can incarnate the characters of the discrete event system and based on the automata modeling theory, an extended automata model for the hybrid system is developed. The projection construct is used to solve the interface problem between the discrete event dynamic subsystems and the continuous variable dynamic subsystems. The model obtained by this way is described by graphs, so it is easy to understand. And the modeling process is illustrated by two examples and the stateflow toolbox in matlab is introduced for simulation. The simulation results show the extended automata model is good at solving the synchronous problem between the two subsystems of hybrid systems.2. Aiming at the object's properties of the hybrid system, digital variables which represents the discrete event is imported to enlarge the classical GPC's object. Using mixed integer quadratic programming algorithm to solve this control system, and on this basis, the solution of control the hybrid systems which contain constrained conditions is studied.3. Based on switching system model of hybrid system, the idea of hybrid system control by using Multi-Model Control is developed. In virtue of the design rule of the fuzzy monitor in the fuzzy supervisory control, a monitor which can be used in the hybrid system control has been designed, and on the function of the monitor, the transitions of local controllers and the minimum disturbance have been achieved. And then using the Lyapunov stability theory and its reasoning to solve the matrix inequalities and developed the decision method of its global stability.4. The control method which combined with MLD model and GPC is applied in the multi-model control systems. In this theoretic, multi-model control systems are equivalent to switch model in the hybrid system, importing corresponding logic variable, using a uniform expression with a linear inequality which contains constraints to replace models in representative conditions. In this way, we can get the biggest advantage that the disturbance which is produced in switching models is debased and the amount of controllers is reduced too. It shows that the effect of this control method is very good through the simulation.5. Combined with the characteristic of wind turbine, aiming at its characteristic of hybrid, the control methods are shown above are used in the control of the wind turbine in all condition.