Simulation Research On Three Typical Model Free Control Methods

It is no doubtful that a mathematical model of a plant plays a central role in the synthesis of a control system.It is almost impossible to obtain a complete model thatreflects the dynamics of a plant. Model-free control is a new control method, which only needs system I/O data. Because of this key point, model-free control becomes the hotspot of control theory research nowadays. This paper focuses on the comparison studies of three kinds of model-free algorithms for a general discrete time nonlinear system and three-tank liquid-level control system. Model-free control technologies which adopted in this paper are model-free adaptive control (MFAC), iterative feedback tuning (IFT), and virtual reference feedback tuning (VRFT). It needs to be emphasized that liquid-level is an important parameter in industrial process control, and liquid-level control system possess some characteristics various other systems, such as large-lag, time-varying parameters, coupling and strong nonlinear. Three-tank water system is a more typical liquid-level control system, and many industrial process control systems can be abstracted as mathematical model of three-tank system. The main works of this paper are summarized as the following threepoints.1. Introducing the basic algorithm of the three model-free control technologies, MFAC, IFT and VRFT;2. Comparison studies of three kinds of model-free algorithms for a general discrete time nonlinear system was given, the control performance and factors which affect the system performance were analyzed also.3. Introducing the hardware components of the three-tank system, describing the dynamic characteristics of the liquid-level control system and showing the transfer function of the liquid-level control system; Comparison studies of three kinds of model-free algorithms for three-tank liquid-level control system were given.