Research On Dynamics And Control Of Hydraulically Driven Flexible Robot Manipulators

Comparing with the conventional rigid robotic manipulator, there are a number of potential advantages stemming from the use of light-weight flexible-link manipulator such as faster operation, lower energy consumption, and higher load-carrying capacity for the amount of energy expended. Modeling and controlling are very important issues for robot flexible manipulators. Many researchers have put much more efforts on studying the two problems. For instance, dynamic modeling of flexible links by using Newton-Euler and Lagrange equations, and robust control, adaptive control and intelligent control techniques have been proposed for the flexible manipulators. However, mostly of these achievements are focus on the flexible manipulators driven by DC-motor, there are few studies of controlling hydraulically driven flexible manipulators. This research project focuses on the hydraulically driven flexible robot manipulators. Based on analyzing and modeling of the dynamics system of flexible-links, which is a strongly non-linear tight-coupling and time-varying system, and controlling of an electro-hydraulic position servo system, a new adaptive robust controller design theory and methodology for the hydraulically driven flexible robot manipulators has been proposed. In order to demonstrate the effectiveness of controlalgorithm introduced in this paper, numerical simulations and experiments have been performed. The research works described in this dissertation mainly consist of following topics. The dynamic characteristics of flexible robot manipulators have been analyzed, and introduced different methods that have been proposed for modeling of flexible link, namely, assume modes method, finite element method and lump mass method. A variety of robust controlling design approaches used for the non-linear system, such as, variable structure sliding mode control, adaptive control and "backstepping control" have been applied in the research work. Using backstepping control design methodology, an adaptive robust controller is adopted for the electro-hydraulic servo systems. The controller is able to take into account not only the effect of parameter variations but also the effect of hard-to-model non-linearity. The proposed controller is proven to be asymptotically stable via rigorous mathematical consequence; simulation results demonstrate the effectiveness of the approach. The kinetic and dynamic experiments of a single-link flexible manipulator have been given to verify the validity of the dynamic model and effect of the sliding control combining with the pole placement technique. The experiments of electro-hydraulic servo system with a flexible load carried out in hydraulic test rig showed that adaptive robust controller mentioned above is strongly robust in maintaining the same level of dynamic performance as the studied servo systems. The interactions betweenhydraulic cylinders and flexible robot mechanism have been analyzed, and proposed a special matrix, termed drive Jacobian. An example is also given for the calculation of drive Jacobian. A robust adaptive controller for the two-link hydraulically driven robot manipulators has been put forward, and it has been confirmed by means of dynamic simulations. The control strategy also can be used for multi-link flexible robot manipulators. Employing the dynamic modeling and controller design method previously addressed, an automatic tree-trimming robot has been designed.