Contact force control of flexible link manipulators: A combined approach to robust control and identification

Due to their superior weight to payload ratio, flexible link robots have been employed in space operations and industrial applications where long reach manipulators are required. As automation technologies advance, there will be increased demand for flexible link manipulators for contact task operations. Examples include satellite capturing space robots and industrial operations that require contact with delicate objects. In these cases, the robots are required to make contact with environments whose locations may not be known in advance. Thus, collision during contact is unavoidable.; This thesis deals with the modeling, system identification and robust control of flexible link manipulators that are required to perform contact task operations. For a single flexible link in contact with rigid and compliant surfaces, two novel infinite dimensional models are developed and evaluated experimentally. Dynamic differences of the models with respect to the force sensing devices are examined.; A coherent system identification and robust control methodology is proposed. Recent results in system identification using generalized orthonormal basis functions are adopted and new algorithms are developed that improve the identification of resonant systems. The identification results are combined with estimated measures of model uncertainties which can be directly used in the design of robust controllers, satisfying a priori specifications for stability, tracking, and disturbance rejection. The proposed methodology is used to develop force and contact transition controllers that are easy to implement, and at the same time, are robust to modeling uncertainties. For the contact transition control, a switching condition is proposed based on robust position and force controllers. The stability of the switching controller is examined using a piecewise quadratic Lyapunov approach. Both simulation and experimental results have been carried out showing the effectiveness of the proposed technique.