Modeling and Trajectory Tracking Control of a New Parallel Flexible Link Robot

A completely new compliant lightweight robot is presented with a kinematic loop and a highly flexible link. It is explained how to model such parallel robots accurately but still computationally efficient. The elastic deformations are described with the floating frame of reference approach. For the flexible components this allows to use linear finite element models, which can represent arbitrary geometries. These models are further reduced by modal truncation and a Component Mode Synthesis minimizing the number of elastic degrees of freedom, which is necessary for real-time control purposes. The obtained model of the underactuated robot is non-minimum phase for the end-effector as output. Thus, for the applied trajectory tracking controller which is based on servo constraints, the concept of stable inversion is used. The performance is compared to a relocated minimum phase output. Corresponding simulations are validated by first experimental results showing the need for and high accuracy of the flexible model and the trajectory tracking control.