Dynamic Modeling And Internal Model Control Of Lifting Mechanism For Forging Manipulator

Forging manipulator,the major ancillary equipment for the forging press, is much powerful in increasing the efficiency of the forging processes. To fulfill the working requirement of specific tasks in integrated open-die or free forging process, a forging manipulator generally need to achieve several motions and the lifting motion is one of the major motions for forging manipulator. The lifting system is comprised of a complex multiple closed-loop mechanism and a large flow hydraulic driving system, and the dynamic behaviors are highly nonlinear and time-varying uncertainties, therefore, it is difficult to meet the requirements of smooth start-stop and precise positioning by using the conventional control methods.In this thesis, by combining the working demands and system’s features, the dynamic behaviors were analyzed and an approximate internal model controller was designed for the lifting system of forging manipulator with a carrying capacity of10KN. Moreover, the feasibility of the control method was verified by simulations and experiments. The main works and achievements are shown as follows:(1) Based on the modular approach combined with equivalent dynamic method, the dynamic equations of lifting system were deduced, and all the equations were verified by the ADAMS software and experiments.(2) After analyzing the structure, principle and characteristics of the hydraulic driving system of lifting mechanism, the nonlinear mathematical model was established. Besides, the reasonableness of the model was validated by experiments.(3) An approximate internal model control which can compensate the system’s nonlinearity and uncertainties was designed. Furthermore, the simulation comparison between internal model control and PID control was presented.(4) The PID control and internal model control experimental platform for the lifting system were developed. The comparison of control performance between PID control and internal model control were carried out.Simulation and experiment results show that the internal model controller achieves a better performance and robustness than PID controller due to its less steady-state error, shorter rise time and better anti-interference ability. The internal model controller can overcome the disadvantage of the PID controller and the working demands which require smooth start-stop and precise positioning can be better met.The research presented in this paper is generic and can be adapted to dynamic modeling of complex1-dof with multi-closed-loop mechanism as well as control of large flow hydraulic driving system with uncertainties and time-varying features.