Dynamics identification of kinematically redundant parallel robots using the direct search method

This paper addresses both modeling and dynamics identification of kinematically redundant parallel robots. Based on the Lagrangian equations of the first kind and using the coordinate partitioning method the dynamic equations of the regarded mechanism are derived analytically in a reduced symbolic form. The set of minimal dynamic parameters is automatically obtained thanks to the Lagrange function and the virtual work. The direct pattern search technique is applied to calculate optimal excitation trajectories to obtain reliable dynamic parameters. The direct pattern search technique is further used to identify the dynamic parameters. The proposed algorithms can be applied on both serial and parallel mechanisms in order to solve the parameter identification problem. Exemplarily, the redundant 3-(P)RRR mechanism of the Institute of Mechatronic Systems is introduced and described in detail. In order to achieve kinematic redundancy, a prismatic actuator is added to the structure allowing one base joint to move linearly. As a result, the mechanism can be able to reconfigure its geometry according to different optimization criteria and strategies. Several experimental results demonstrate the effectiveness and, therefore, the capability of the introduced identification procedure.