Most current hip exoskeletons emphasize assistance for walking rather than stability. The goal of this paper is to develop a novel, high-power, self-balancing, and passively and software-controlled actively compliant hip exoskeleton that can assist with movement and maintain balance in both the sagittal and frontal planes. The developed hip exoskeleton includes powered hip abduction/adduction (HAA) and hip flexion/extension (HFE) joints. Each actuation unit employs a modular and compact series elastic actuator (SEA) with a high torque-to-weight ratio. It provides mechanical compliance at the interface between the exoskeleton and the wearer to ensure safety and a natural gait in the coupled wearer-exoskeleton system. A new balance controller based on the “extrapolated center of mass” (XCoM) concept is presented for maintaining walking stability. This controller reacts to perturbations in balance and produces a compliant guidance force through a combination of the passive elasticity of the SEA and active compliant control based on adaptive admittance control. The function of the hip exoskeleton is not to override human control but rather to involve the wearer in movement control in order to avoid conflicts between wearer and exoskeleton. Our preliminary experiments on a healthy subject wearing the hip exoskeleton demonstrate the potential effectiveness of the proposed hip exoskeleton and controller for walking balance control.

A lower-back exoskeleton prototype designed to provide back support for industrial workers who manually handle heavy materials is presented in this article. Reducing spinal loads during these tasks can reduce the risk of work-related back injuries. Biomechanical studies show that compression of the lumbar spine is a key risk factor for musculoskeletal injuries. To address this issue, we present a wearable exoskeleton designed to provide back support and reduce lumbar spine compression. To provide effective assistance and avoid injury to muscles or tendons, we apply a continuous torque of approximately 40 Nm on both hip joints to actively assist both hip abduction/adduction (HAA) and hip flexion/extension (HFE). Each actuation unit includes a modular and a compact series-elastic actuator (SEA) with a clutch. The SEA provides mechanical compliance at the interface between the exoskeleton and the user, and the clutches can automatically disengage the torque between the exoskeleton and the user. These experimental results show that the exoskeleton can lower lumbar compression by reducing the need for muscular activity in the spine. Furthermore, powering both HFE and HAA can effectively reduce the lumbar spinal loading user experience when lifting and lowering objects while in a twisted posture.

Transparency and guaranteed safety are important requirements in the design of wearable exoskeleton actuators for individuals who have lower limb deficits but still maintain a certain level of voluntary motor control. Specifically, precision in torque delivery timing and magnitude, robustness, disturbance rejection, and repeatability are desired in the actuator design and control. Motivated by these needs, this study aims to develop a series of elastic actuators with clutch (SEAC) that can precisely generate the desired assistance in terms of both timing and torque magnitude for a wearable hip exoskeleton and guarantee the wearer's safety at the same time. The proposed mechanical design improves actuator transparency and safety by a mechanical clutch that automatically disengages the transmission when needed. New torque control for the SEAC, based on singular perturbation theory with flexible compensation techniques, is proposed to precisely control the assistive torque by rejecting the undesired human motion disturbance. The mechanical design of the proposed device and the design of a singular perturbation control algorithm are discussed, and the SEAC performance is verified by experiments. Experimental results, derived from a test with a human subject, are presented to demonstrate the precision of the assistive torque and timing control of the SEAC while interacting with a human wearer.

This paper presents the design, tactile sensor, characterization, and control system of a new dexterous myoelectric hand prosthesis to overcome the limitations of state-of-the-art myoelectric prostheses (e.g., limited functionality, controllability, and sensory feedback). Our dexterous myoelectric hand allows independent finger movement and thumb abduction/adduction, with a motor for each finger and an additional motor for the thumb (i.e., 6 total motors). Each fingertip has a biomimetic tactile sensor with 13 tactile units, each of which can detect normal and tangential forces. The hand controller uses an electromyography (EMG) pattern recognition controller and a tactile sensor feedback-based grasping controller to automatically and dynamically adjust the finger grasp force to prevent objects from slipping. This closed-loop controller structure will allow users to safely and effectively grasp complex objects with varying densities and shapes. In addition, the electronic hardware is integrated into the hand, and the pattern recognition controller can be implemented in the hand embedded system.

To overcome the limitations of a traditional soft hip exosuit directly driven by Bowden cables or winding belts at two points, in this article, we propose a new soft hip exosuit design concept based on series-wedge-structures for energy-efficient walking and running during daily activities for elderly individuals. The series-wedge-structure is designed to improve the comfort of the wearer–exosuit interface and to passively adapt to the user's body curvature, with no hindrance during movement. The design and function, including the series-wedge-structure belt, series elastic cable drive actuator, and control scheme, are described. The presented soft exosuit, which is lightweight (1.4 kg) and comfortable, provides assistive torque for hip flexion by folding series-wedge-structures driven by Bowden cables. The series-wedge-structure-based hip exosuit adopts single actuation coupled to the Bowden cable pull mechanism with a series elastic actuator to drive both hip flexions based on the out-of-phase nature of the human legs during walking and running. The exosuit performance test results show that the proposed exosuit improves the comfort of the wearer–exoskeleton interface by minimizing the shear force and maximizing the exosuit–skin interaction force contact area. Three healthy subjects walked at a fixed speed of 1.25 m/s and ran at a fixed speed of 2.2 m/s while wearing the proposed exosuit with/without assistance and without wearing the exosuit to evaluate the biomechanical and physiological effects of the proposed exosuit assistance on locomotion. The metabolic rate with exosuit assistance was reduced by 10.9% for walking and by 6.2% for running compared with not wearing the exosuit.