Adaptive oscillators with human-in-the-loop: Proof of concept for assistance and rehabilitation

Abstract

Abstract-Most recent findings in robot-assisted therapy suggest that the therapy is more successful if the patient actively participates to the movement ("assistance-as-needed"). In the present contribution, we propose a novel approach for designing highly flexible protocols based on this concept. This approach uses adaptive oscillators: a mathematical primitive having the capacity to learn the high-level features of a quasi-sinusoidal signal (amplitude, frequency, offset). Using a simple inverse model, we demonstrate that this method permits to synchronize with the torque produced by the user, such that the effort associated with the movement production is shared between the user and the assistance device, without specifying any arbitrary reference trajectory. Simulation results also establish the method relevance for helping patients with movement disorders. Since our method is specifically designed for rhythmic movements, the final target is the assistance/rehabilitation of locomotory tasks. As an initial proof of concept, this paper focuses on a simpler movement, i.e. rhythmic oscillations of the forearm about the elbow.

Augmented visual, auditory, haptic, and multimodal feedback in motor learning: A review

“…In a recent control concept, the haptic controller does not rely on reference trajectories and supports arbitrary rhythmic movements of the user. To do so, the controller uses adaptive oscillators that synchronize with the sinusoidal high-level features of the user's movements (Ronsse, Koopman et al, 2011;Ronsse et al, 2010;Ronsse, Vitiello, et al, 2011). Such strategies can be seen as a trade-off between leaving the user in full control of the movement features-that is, trajectory and movement frequency-while still providing a certain amount of assistance/guidance.…”

“…The control of most haptic guidance feedback strategies is based upon reference trajectories, except for zero impedance control and a few model-based control algorithms (Ronsse, Koopman, et al, 2011;Ronsse et al, 2010;Ronsse, Vitiello, et al, 2011). The reference trajectories are either recorded and postprocessed or artificially generated.…”

Oscillator-based assistance of cyclical movements: model-based and model-free approaches

“…Nonetheless, we asked the participants to perform the movement around the vertical position, mimicking the inverted pendulum configuration of the leg during the stance phase of walking [15]. This experiment was already published in [31,33,34] and is only surveyed here. Experiment 2 extends the approach to walking assistance, and therefore specifically addresses the related challenges.…”

A general family of morphed nonlinear phase oscillators with arbitrary limit cycle shape

“…Having the decoupling of the radial dynamics from the phase dynamics, one can control radial dynamics stable point and convergence properties separately and leave the phases for eigenfrequency control or for inter-agents phase synchronization. This motivates applications like CPGs, or more applied examples like model-free tracking in assistance and rehabilitation robotics like [40,41] when the frequency coupling can be stably separated from radial coupling.…”