Experimental Validation of Motor Primitive-Based Control for Leg Exoskeletons during Continuous Multi-Locomotion Tasks

Abstract

An emerging approach to design locomotion assistive devices deals with reproducing desirable biological principles of human locomotion. In this paper, we present a bio-inspired controller for locomotion assistive devices based on the concept of motor primitives. The weighted combination of artificial primitives results in a set of virtual muscle stimulations. These stimulations then activate a virtual musculoskeletal model producing reference assistive torque profiles for different locomotion tasks (i.e., walking, ascending stairs, and descending stairs). The paper reports the validation of the controller through a set of experiments conducted with healthy participants. The proposed controller was tested for the first time with a unilateral leg exoskeleton assisting hip, knee, and ankle joints by delivering a fraction of the computed reference torques. Importantly, subjects performed a track involving ground-level walking, ascending stairs, and descending stairs and several transitions between these tasks. These experiments highlighted the capability of the controller to provide relevant assistive torques and to effectively handle transitions between the tasks. Subjects displayed a natural interaction with the device. Moreover, they significantly decreased the time needed to complete the track when the assistance was provided, as compared to wearing the device with no assistance.

Assessing User Transparency with Muscle Synergies during Exoskeleton-Assisted Movements: A Pilot Study on the LIGHTarm Device for Neurorehabilitation

“…As proposed in many papers [ 7 , 23 ], transparency is a key feature that a robotic device should have to provide valuable assistance to patients in rehabilitation. While remarkable efforts have been done in the literature to design devices and controllers for achieving transparency [ 23 , 24 , 42 ], few works have investigated the potential of a modular description of the neuromuscular system in evaluating the properties of a device. In this paper, it is suggested that muscle synergies may be considered for comparing motor modules underlying movement in free movements and robot-assisted ones, providing a user-centered view of the transparency properties of the device.…”

A Review on Human–exoskeleton Coordination Towards Lower Limb Robotic Exoskeleton Systems

“…The sensitive amplification control (SAC) method is a kind of zero torque control method that is widely used for load-carrying exoskeleton robots. Kazerooni and Huang et al [144]- [146] are renowned for their design of the human augmentation exoskeleton robot BLEEX. To simplify the control, they gave the BLEEX three distinct states that manifest three different dynamic models: single support; double support; and double support with redundancy.…”

“…A PI-based motor current regulator is used to provide low-level control. Garate et al [144,145] have presented a gait phase estimation-based control structure that is intended to help pilots in complicated terrain. The gait phase is estimated by an AFO whilst, at the same time, the walking intention is estimated to determine the terrain.…”

A Knee–Ankle–Foot Orthosis to Assist the Sound Limb of Transfemoral Amputees

“…The third experimental activity was carried out in seven healthy subjects [46]. The orthotic devices were controlled based on a novel motor primitives approach based on an adaptive-oscillator phase detector.…”