Identification and Decoupling Control of Flexure Jointed Hexapods

By exploiting properties of the joint space mass-inertia matrix of flexure jointed hexapods, a new decoupling method is proposed. The new decoupling method, through a static input-output mapping, transforms the highly coupled 6 input 6 output dynamics into 6 independent single-input single-output (SISO) channels. Controls for these SISO channels are far simpler than their multiple-input multiple-output counterparts. Prior decoupling control algorithms imposed severe constraints on the allowable geometry, workspace, and payload. This paper derives a new algorithm which removes these constraints, thus greatly expanding the applications. Based on the new decoupling algorithm, an identification algorithm is introduced to identify the joint space mass-inertia matrix using payload accelerations and base forces. This algorithm can be used for precision payload calibration, thus improving performance and removing the labor required to design the control for different payloads. The new decoupling algorithm is experimentally compared to earlier techniques. These experimental results indicate that the new approach is practical, and improves performance.