Design and Control of a Size-Adjustable Pediatric Lower-Limb Exoskeleton Based on Weight Shift

Abstract

Lower-limb exoskeletons have been proven to be beneficial for motor function disability patients, in both clinical rehabilitation settings and daily activities. However, exoskeletons for the pediatric field are still very limited. In this paper, a novel lower-limb exoskeleton design for children is presented. Based on the anthropometric data of the target group, the size of the exoskeleton is designed adjustable to suit children from 8 to 12 years old. It employs six active joints on the knee and hip, actuated by Brushless DC motors and Harmonic Drive gears. The controller is based on a finite state machine model and the weight shift between two feet to generate the gait trajectory. An innovative automatic step-triggering mechanism is also proposed, based on the feedback from the ground reaction force sensor on the foot. Two user interfaces on the exoskeleton and the host PC are designed for easily operating the exoskeleton by clinicians and engineers. Experiments have been conducted with three healthy volunteers following the predesigned rehabilitation session protocol. Results show that the exoskeleton can well follow the gait trajectory generated by the control algorithm. All volunteers can fulfill all tasks in the test protocol with reduced efforts and the steps are automatically triggered by the presented controller.

Pediatric Robotic Lower-Limb Exoskeleton: An Innovative Design and Kinematic Analysis

“…The configuration of the actuation unit for the three actuated joints is detailed in Table II. The table demonstrates that each of the three actuation units is capable of achieving the maximum power, torque, and velocity, as specified in the literature related to pediatric gait analysis [30,31,14,26].…”

“…in this context, 𝒜 and ℬ are extracted from ( 29) and ( 30), while the parameter 𝒫 is obtained from equation (26).…”

“…They simulated the LLE using ADAMS ™ ; however, their findings lacked subsequent kinematic validation. Zhang et al [26] conducted forward and inverse kinematic analysis for each leg of a full LLE. However, forward kinematics were individually derived for each plane, specifically the frontal and sagittal planes, and the derived inverse kinematics were not subsequently verified.…”

An Unpowered Knee Exoskeleton for Walking Assistance and Energy Capture

“…Their purpose is to improve the performance of the human body, reducing energy consumption, delaying fatigue, and increasing body speed. Wearable exoskeleton devices have a high development space in medical rehabilitation, power assistance and military fields [2,3]. One example is the IHMC exoskeleton or BLEEX [4,5].…”

Design and Control of a Single-Leg Exoskeleton with Gravity Compensation for Children with Unilateral Cerebral Palsy

“…Meanwhile, Atlas2030 (multi-joint exoskeleton) [18] and Trexo (exoskeletonplus-walker) [19] are commercialized devices in this field [11]. In exoskeleton-plus-walker devices, the walker carries the weight of the exoskeleton and ensures balance; however, the walker limits mobility and maneuverability, causing the patient to follow a fixed gait pattern, and their ability to maintain balance is not trained [20]. The literature reveals that brushless DC motors combined with harmonic drive gears are frequently employed as actuators in LLEs for children with CP.…”