Volitional control of ankle plantar flexion in a powered transtibial prosthesis during stair-ambulation

Abstract

Abstract-Although great advances have been made in the design and control of lower extremity prostheses, walking on different terrains, such as ramps or stairs, and transitioning between these terrains remains a major challenge for the field. In order to generalize biomimetic behaviour of active lowerlimb prostheses top-down volitional control is required but has until recently been deemed unfeasible due to the difficulties involved in acquiring an adequate electromyographic (EMG) signal. In this study, we hypothesize that a transtibial amputee can extend the functionality of a hybrid controller, designed for level ground walking, to stair ascent and descent by volitionally modulating powered plantar-flexion of the prosthesis. We here present data illustrating that the participant is able to reproduce ankle push-off behaviour of the intrinsic controller during stair ascent as well as prevent inadvertent push-off during stair descent. Our findings suggest that EMG signal from the residual limb muscles can be used to transition between level-ground walking and stair ascent/descent within a single step and significantly improve prosthesis performance during stair-ambulation.

Current overview of the state of disabled population, regarding the use of transtibial prosthesis

“…The use of electromyography will enable the development of prosthesis which adjust to the patient's walking pace without previous adjustment required (Chen, Wang and Wang, 2014;Chen et al, 2015;Kannape, Member, Herr and Member, 2014). Placement of electrodes on certain muscles of the limb will deliver useful signals to determine the natural position of the limb (Chen et al, 2014(Chen et al, , 2015Kannape et al, 2014).…”

“…Placement of electrodes on certain muscles of the limb will deliver useful signals to determine the natural position of the limb (Chen et al, 2014(Chen et al, , 2015Kannape et al, 2014). This response from the limb to changes in the muscles will help patients to adapt to the prosthesis (Kannape et al, 2014).…”

Split-belt adaptation and gait symmetry in transtibial amputees walking with a hybrid EMG controlled ankle-foot prosthesis

“…state machines that are intrinsically driven using on-board sensors [3], [4] to direct proportional myoelectric control [5], as well as hybrid designs [6]- [8]. However, none of these prostheses or interfaces have thus far been used to investigate long term locomotor adaptation.…”

“…Gait adaptation was imposed by asking participants to walk on a split-belt treadmill, with the belt on the affected side running at twice the speed of the contralateral belt. Extending our previous work on the hybrid EMG controller [6], [8] we hypothesized that transtibial amputees would be able to i) adjust their residual limb muscle EMG according to treadmill velocity and ii) adapt to the split-belt walking condition by normalizing temporal gait characteristics over the 10minute adaptation trial, but iii) show reduced sensorimotor learning as evidenced by the wash-out phase immediately following the adaptation trial. Finally, we compared amputee gait symmetry pre-and post-adaptation.…”

Engineered embodiment: Comment on “The embodiment of assistive devices—from wheelchair to exoskeleton” by M. Pazzaglia and M. Molinari

“…Amputees, at least in the laboratory, are now able to use their residual muscles to control ankle push-off [11,12], stiffness over the gait-cycle [13], and even the movement of a biarticulate prosthesis [14].…”