A Novel Precision Measuring Parallel Mechanism for the Closed-Loop Control of a Biologically Inspired Lower Limb Exoskeleton

Abstract

The knee joint of the human body involves both rotation and translation, while the magnitude of anterior-posterior translation during flexion/extension movement of the knee joint is very small compared with the length of the human lower limb. It is therefore desirable for an exoskeleton leg to have two degrees of freedom to accommodate the motion of the human knee joint, and for there to be a precision measuring method to obtain its trajectory. This paper presents a novel parallel mechanism which can be used as a precise measuring device to realize closed-loop control for a biologically inspired 3-degree of freedom (DOF) lower limb exoskeleton (BLLE-3) for human gait rehabilitation. In this work, mechanical design and kinematics of the exoskeleton are described. Errors of exoskeleton motion are modelled and analyzed. Closed-loop control law is implemented to enable accurate trajectory following the motions of the exoskeleton. Simulations and experimental results are included to show the effectiveness of the new measuring and control method.

A Pediatric Knee Exoskeleton With Real-Time Adaptive Control for Overground Walking in Ambulatory Individuals With Cerebral Palsy

“…For example, the EXOTrainer (Cestari et al, 2018) and WAKE-Up use series elastic actuation (SEA) to enhance joint compliance in human and robot interactions as the elastic element helps reduce the interface stiffness and mechanical impedance, and increase the capacity for energy storage, all of which can aid in the use of wearable robots for rehabilitation of individuals who still have some voluntary movement (Kong et al, 2012). However, SEAs and other mechanisms designed to reduce interaction forces on the user (Zhou et al, 2018) increase system complexity and reduce dynamic responsiveness and may therefore limit their utility in children who are ambulatory and require relatively low levels of assistance at specific times during walking. Furthermore, these exoskeletons are primarily laboratory-based and not yet available for home and communitybased gait training.…”

Design of a powered full-body exoskeleton for physical assistance of elderly people

“…The details of the study can be seen in Virk et al 38 It is noted that the knee joint can also be modelled as a joint involving both rotating and sliding motions, 40 but this also implies a complicated design of joints. 41 We thus consider the knee as a revolute joint to make the design simple and compact.…”

Motion intensity modeling and trajectory control of upper limb rehabilitation exoskeleton robot based on multi-modal information

“…Compared with the traditional rehabilitation training, the rehabilitation exoskeleton robots can provide more scientific and reasonable rehabilitation training for patients while reducing the workload of the therapists [1,2], which have become one of the most popular research topics [3][4][5]. Many research groups over the world have worked in this area [6][7][8], and the exoskeleton robots for different rehabilitation parts have been presented [9][10][11].…”