Convergence and robustness of the Hopf oscillator applied to an ABLE exoskeleton: reachability analysis and experimentation

In this paper, we consider an industrial exoskeleton called ABLE, which we controlled using an adaptive oscillator. In the context of periodic human movements around the elbow axis we show that the exoskeleton anticipates smoothly the human movement, converges towards a limit cycle, and is "robust" against non-deterministic bounded perturbations. In particular, the properties of stability and robustness are formally proven, at the model level, using a recent development of the method of "reachability analysis". These properties are then confronted to preliminary experimental data.