State-of-the-art research in robotic hip exoskeletons: A general review

Abstract

Ageing population is now a global challenge, where physical deterioration is the common feature in elderly people. In addition, the diseases, such as spinal cord injury, stroke, and injury, could cause a partial or total loss of the ability of human locomotion. Thus, assistance is necessary for them to perform safe activities of daily living. Robotic hip exoskeletons are able to support ambulatory functions in elderly people and provide rehabilitation for the patients with gait impairments. They can also augment human performance during normal walking, loaded walking, and manual handling of heavy-duty tasks by providing assistive force/torque. In this article, a systematic review of robotic hip exoskeletons is presented, where biomechanics of the human hip joint, pathological gait pattern, and common approaches to the design of robotic hip exoskeletons are described. Finally, limitations of the available robotic hip exoskeletons and their possible future directions are discussed, which could serve a useful reference for the engineers and researchers to develop robotic hip exoskeletons with practical and plausible applications in geriatric orthopaedics.

The translational potential of this article: The past decade has witnessed a remarkable progress in research and development of robotic hip exoskeletons. Our aim is to summarize recent developments of robotic hip exoskeletons for the engineers, clinician scientists and rehabilitation personnel to develop efficient robotic hip exoskeletons for practical and plausible applications.

Keywords: Ageing population; Gait rehabilitation; Hip dysfunction; Human performance augmentation; Robotic hip exoskeletons.

Fig. 1

Normal gait cycle. The green lines represent the right leg, and the blue lines represent the left leg. The gait cycle is composed of the alternating stance phase and swing phase, and it starts when one foot contacts the ground and ends when the same foot contacts the ground again.

Fig. 2

The human hip joint angles and torques during a gait cycle with a normal gait pattern. The stance phase is from 0% to 62% of a gait cycle, and the swing phase is from 62% to 100% of a gait cycle. (A) Hip joint angle; (B) hip joint torque.

Fig. 3

Essential components of a robotic hip exoskeleton. The essential components include ​the mechanical structure for transferring assistive force/torque, actuator for generating assistive force/torque, multisensor system for motion data collection, controller for controlling the exoskeleton, and power source for providing power for the exoskeleton.

Fig. 4

Robotic hip exoskeletons for gait rehabilitation. (A) The robotic hip exoskeleton APO actuated by SEAs that comprise electric motors, custom torsional springs, harmonic drive, and a four-bar mechanism (Image credit: Elsevier); (B) the robotic hip exoskeleton actuated by electric motors through flexible Bowden cable transmission ​(Image credit: Professor Wang of the Southeast University, Nanjing, China).

Fig. 5

Robotic hip exoskeletons for human performance augmentation. (A) The robotic hip exoskeleton developed for reducing the metabolic cost of healthy individuals during walking (Image credit: Professor Kang of the Georgia Institute of Technology, Atlanta, GA, USA); (B) the robotic hip exoskeleton developed for assisting individuals with heavy-duty tasks, especially for the assistance of lift movement (Image credit: Professor Chen of the BioRobotics Institute, Scuola Superiore Sant’Anna, Pisa, Italy).