ADAPTIVE-CONTROL OF FLEXIBLE MULTILINK MANIPULATORS

An adaptive self-tuning control scheme is developed for end-point posi tion control of flexible manipulators. The proposed scheme has three c haracteristics. First, it is based on a dynamic model of a flexible ma nipulator described in cartesian coordinates, which eliminates the bur den and inaccuracy of translating a desired end-point trajectory to jo int coordinates using inverse kinematic relations. Second, the effect of flexibility is included in the dynamic model by approximating flexi ble links with a number of rigid sublinks connected at fictitious join ts. The relatively high stiffness of the fictitious joints is shown to result in a decomposition of the model into two subsystems operating at different rates. This allows for stabilization of the oscillatory m odes associated with the flexible links by a fast feedback control in addition to a slower control for trajectory tracking. Third, the contr ol is constructed from measurements of the end-point position and defo rmations of the flexible links, with the manipulator parameters requir ed to form the control obtained using a recursive least-squares estima tion algorithm, which is fast enough for on-line applications. Satisfa ctory results are obtained from digital simulation of a two-link flexi ble manipulator.