Control methods of hyper-flexible manipulators using their dynamical features

While conventional flexible systems were based on the assumption with elasticity at links and/or joints, much more flexible structures without elasticity such as strings, wires, ropes and tethers are considered - called "hyper-flexible" systems. One of their discrete dynamic models can be represented by underactuated manipulator with serial rigid links connected by free joints. However, even its controllability is difficult to be shown, possible control goals are considered for this system, for instance, dynamic stabilization and impedance control. These control methods are developed through the analysis of dynamic behaviors of a free-joint manipulator model using the averaging method. For the system under gravity, inclined configuration other than gravitational vertical ones is shown to be dynamically stabilizable by vibratory input. The sliding mode control is applied to achieve a faster approach to the destination. The dynamic stabilization also has impedance property and the impedance can be designed by the modulation of parameters of vibratory input.