Assist On-Ankle: a reconfigurable ankle exoskeleton with series-elastic actuation

Abstract

We present the kinematics, optimal dimensional synthesis, series-elastic actuation, control, characterization and user evaluation of AssistOn-Ankle, a reconfigurable, powered exoskeleton for ankle rehabilitation. AssistOnAnkle features reconfigurable kinematics for delivery of both range of motion (RoM)/strengthening and balance/ proprioception exercises. In particular, through lockable joints, the underlying kinematics can be configured to either a self-aligning parallel mechanism that can naturally cover the whole RoM of the human ankle, or another parallel mechanism that can support the ground reaction forces/torques transferred to the ankle. Utilizing a single device to treat multiple phases of treatment is advantageous for robotic rehabilitation, since not only does it decrease the device cost and help with the space requirements, but also shorten the time it takes for patients to familiarize with the device. Bowden cable-based series-elastic actuation of AssistOn-Ankle allows for a remote placement of the motors/drivers to result in a compact design with low apparent inertia, while also enabling high-fidelity force/impedance control and active backdriveability of the device. This is one of several papers published in Autonomous Robots comprising the "Special Issue on Assistive and Rehabilitation Robotics". B Volkan Patoglu

Special Issue on Assistive and Rehabilitation Robotics

“…In this Special Issue, Erdogan et al (2016) propose a powered exoskeleton for the ankle joint that performs this information gathering as well as optimal dimensional synthesis and series-elastic actuation mode control. In their approach, the authors present a self-alignment parallel mechanism for the configuration of the prototype kinematics and another parallel mechanism that can support the ground reaction force and torque transferred to the ankle.…”

Connected Elbow Exoskeleton System for Rehabilitation Training Based on Virtual Reality and Context-Aware

“…The vast majority of these works are focused on the recovery of injuries and problems of the upper limbs. There are other works that focus on the study of injuries from other areas such as the ankle [7][8][9]. Other works focused on one of the Sensors 2020, 20, 858 3 of 17 most important joints of the lower extremities such as the knee [10][11][12][13][14][15].…”

Design and Performance Evaluation of a Novel Wearable Parallel Mechanism for Ankle Rehabilitation

“…A typical instance is the active ankle-foot orthosis proposed by Blaya and Herr (2004), by employing series elastic actuator (SEA), rotary potentiometer, and ground reaction force sensors, a gait pathology known as drop-foot can be treated via variableimpedance control. Similarly, exoskeletons (Kim et al, 2011;Zhu et al, 2011;Lopez et al, 2013;Meijneke et al, 2014;Witte et al, 2015;Dijk et al, 2017;Erdogan et al, 2017) were also developed with the concept of SEA to provide push-off assistance. Moreover, robotic tendons, i.e., a DC motor in series with a spring, were used in ankle-foot orthoses (Hollander et al, 2006;Boehler et al, 2008;Oymagil et al, 2008;Ward et al, 2011) to provide sufficient energy and peak power saving for systems; pneumatic muscle actuators (PMA), due to their intrinsically compliant and high power/weight ratio, were also widely selected as the actuation technology of the ankle exoskeletons Gordon et al, 2006;Kinnaird and Ferris, 2009;Sawicki and Ferris, 2009;Park et al, 2014).…”

“…Fan and Yin (2009) presented an ankle exoskeleton with a 3-RPS (revolute-prismatic-spherical) parallel mechanism as the main mechanical structure in cooperation with an electromyographic-based neuro-fuzzy controller. A reconfigurable ankle exoskeleton (Erdogan et al, 2017) was proposed for multiple phases of treatment, in which the 3-RPS structure and the 3-UPS (universal-prismatic-spherical) structure can be interconverted via lockable joints. Stewart platform (Takemura et al, 2012;Nomura et al, 2015) was also utilized for ankle exoskeletons.…”