Experiments on Rest-to-rest Motion of a Flexible Arm

We present an experimental validation of a recently proposed solution to the problem of finding the input torque command that provides rest-to-rest motion in a given time for a one-link flexible arm. The basic idea is to design an auxiliary output such that the associated input-output transfer function has no zeros. Planning a smooth interpolating trajectory for this output imposes a unique rest-to-rest motion to the whole arm, with automatically bounded link deformations. The nominal torque is then obtained by standard inverse dynamics computation. The method is presented for a linear model of an Euler-Bernoulli flexible beam, satisfying dynamic boundary conditions and taking into account also modal damping. We illustrate the dynamic identification of the experimental flexible arm, the handling of static/viscous joint friction within the proposed method, and the way to include a stabilizing feedback based only on joint measurements. Finally, we report on comparative experimental results.