Oscillator-based walking assistance: A model-free approach

Abstract

In this paper, we further develop our framework to design new assistance and rehabilitation protocols based on motor primitives. In particular, we extend our recent results of oscillator-based assistance to the case of walking. The adaptive oscillator used in this paper is capable of predicting the angular position of the user's joints in the future, based on the pattern learned during preceding cycles. Assistance is then provided by attracting the joints to this future position using a force field in a compliant lower-limb exoskeleton. To demonstrate the method efficiency, we computed the rate of metabolic energy expended by the participants during a walking task, with and without assistance. Results show a significant decrease of energy expenditure with the assistance switched on, although not to a point to entirely compensate for the burden due to the exoskeleton lack of transparency. The results further show changes in the kinematics: with assistance, the participants walked with a faster cadence and ampler movements. These results tend to prove the relevance of designing assistance protocols based on adaptive oscillators (or primitives in general) and pave the way to the design of new rehabilitation protocols.

A light-weight active orthosis for hip movement assistance

“…hip or knee angle profile during gait), even when it slowly changes its main features such as frequency and envelope over cycles [18], [48]- [49]. While a detailed analysis of the mathematical formulation of the algorithm is available in [18], hereafter we briefly recap its working principle and how we implemented it on the APO.…”

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

“…Experiment 2 extends the approach to walking assistance, and therefore specifically addresses the related challenges. Preliminary results were recently published in [35]. Both experiments deal with movement assistance of healthy participants.…”