Adaptive Impedance Control of a Robotic Orthosis for Gait Rehabilitation

Abstract

Intervention of robotic devices in the field of physical gait therapy can help in providing repetitive, systematic, and economically viable training sessions. Interactive or assist-as-needed (AAN) gait training encourages patient voluntary participation in the robotic gait training process which may aid in rapid motor function recovery. In this paper, a lightweight robotic gait training orthosis with two actuated and four passive degrees of freedom (DOFs) is proposed. The actuated DOFs were powered by pneumatic muscle actuators. An AAN gait training paradigm based on adaptive impedance control was developed to provide interactive robotic gait training. The proposed adaptive impedance control scheme adapts the robotic assistance according to the disability level and voluntary participation of human subjects. The robotic orthosis was operated in two gait training modes, namely, inactive mode and active mode, to evaluate the performance of the proposed control scheme. The adaptive impedance control scheme was evaluated on ten neurologically intact subjects. The experimental results demonstrate that an increase in voluntary participation of human subjects resulted in a decrease of the robotic assistance and vice versa. Further clinical evaluations with neurologically impaired subjects are required to establish the therapeutic efficacy of the adaptive-impedance-control-based AAN gait training strategy.

Adaptive Patient-Cooperative Control of a Compliant Ankle Rehabilitation Robot (CARR) With Enhanced Training Safety

“…The patient's disability level and active engagement have been also considered for more advanced adaptation laws. Hussain, et al [22] designed an adaptive impedance controller that adjusts the assistance of a robotic gait orthosis according to the disability level and voluntary participation of human subjects. Jamwal, et al [23] applied a similar control strategy on a compliant parallel ankle robot.…”

Recent Trends in Lower-Limb Robotic Rehabilitation Orthosis: Control Scheme and Strategy for Pneumatic Muscle Actuated Gait Trainers

“…Recently, in 2013, Hussain et al, invented a six degree of freedom robotic orthosis for gait rehabilitation to encourage patients' voluntary contribution in the robotic gait training process, as shown in Figure 8c [51,52]. It implements four pneumatic muscle actuators, which are arranged as two pairs of antagonistic mono-articular muscles at the hip and knee joint angles.…”

“…Additionally, the result findings demonstrated that an increase/decrease in the human's voluntary participation during gait training will result in a decrease/increase of robotic assistance. Adaptive impedance control using boundary-layer-augmented sliding mode control (BASMC) [51,52] Table 1 shows the comparison of existing pneumatic muscle actuated lower-limb rehabilitation orthosis systems. Based on the evaluations of these systems for the past 10 years, it can be concluded that researchers' interests shifted to the implementation of the natural compliant-type actuators (i.e., McKibben muscle, rubbertuators, air muscle, PAM, PMA, etc.).…”

Review of EMG-based neuromuscular interfaces for rehabilitation: elbow joint as an example

“…This EMG-based neuromuscular interface not been limited to elbow joint only, but also other different anatomical locations, such as elbow (Buchanan et al, 1998), shoulder (Laursen et al, 1998), knee (Lloyd and Buchanan, 1996;Lloyd and Besier, 2003;Lloyd and Buchanan, 2001), ankle (Ferris et al, 2006;Hussain et al, 2012), jaw, lower back (Nussbaum and Chaffin, 1998) and wrist (Buchanan et al, 1993). The theoretical basis is that: if the EMG signals can be measured precisely and processed adequately to reflect the activation of each muscle crossing the joint and if the activation can be modulated properly by models, it is possible to accurately estimate individual muscle forces over a wide range of tasks and contraction modes.…”