Research On Underactuated Overhead Crane Control Strategy

An underactuated system is the system that has fewer independent control actuators than degrees of freedom to be controlled. Because the underactuated system has many advantages such as light weight, low cost and low energy consumption, it has wide application prospect in the field of industrial production. However, due to the lack of driving characteristics, it has brought great challenges for the control of such systems. In recent years the underactuated system is considered as one of the most active fields of control theory.An overhead crane is a typical nonlinear underactuted system with strong states coupling. Due to such merits as strong load ability and simple operation, it is widely used for industrial production, port transportation, and so on. To improve the efficiency of the overhead crane system, there is a great need for an effective control strategy. The control targets of the overhead crane can be divided into two parts: on one hand, the trolley is required to arrive at the desired position quickly; on the other hand, the payload swing should be suppressed as small as possible. It is of great importance and value to solve the two problems in the control theory. Thus, to achieve both precise trolley positioning and load swing elimination during the load transport process of the overhead crane system, this paper makes a deep study. The main issues are as follows:The dynamic model of the overhead crane system is established through the Lagrange's equation of mechanics system, and then the model is simplified and analyzed in order to lay the foundation for the design of the controller in the following chapters.For the coupling problem of the overhead crane system, a parameter self-tuning decoupled sliding mode controller is designed through a new saturated function. In addition, to alleviate the chattering phenomena, a parameter self-tuning strategy is introduced. The parameter self-tuning decoupled sliding mode controller improves the dynamic characteristics of the system by simulations.For the unknown nonlinear function in the overhead crane system, an adaptive fuzzy sliding mode controller is designed. The unknown nonlinear function is estimated through the adaptive fuzzy algorithm. By transforming the sliding mode surface of the payload swing angle, load swing angle can converge to zero in finite time after reaching the sliding surface. Simulation results show the good performance of the controller.Because partial state of the overhead crane system cannot be measured and some unknown external disturbance exist, an extended state observer(ESO) based sliding mode control strategy is proposed. All states of the system and the external disturbance system states are estimated by the extended state observer. By adding the compensation of the disturbance to the control input, the anti-interference ability of the system is improved. Simulation results demonstrate the effectiveness of the proposed controller.