P.A.C.E.: Exploratory design and evaluation of a Passive, Arm-Controlled Exoskeleton for gait assistance of paraplegic users

Abstract

Background: Passive gait orthoses (GOs) for paraplegic users face stagnating technology development. Current devices have issues with high energy expenditure, poor control and requiring crutches to maintain stability. The powered GOs that do tackle these issues effectively are highly expensive and require complex control systems.

Objective: The goal of this research is to design, build, and test a proof-of-concept prototype of a passive, upper-body-powered GO. This should allow users to walk without their lower limb function or the use of hand operated crutches for stability. The device should be usable, stable, and affordable to make it accessible to a wide demographic of users.

Methods: Design requirements and criteria were formulated according to the desired functions of the device. Several feasible solutions were ideated for each function, from which three distinct workable concepts were generated. The most promising concept was selected based on the performance criteria and developed further for prototyping. A one-legged stance test and a gait test were executed using the proof-of-concept lower limb paralysis simulator with one able bodied trial user.

Results: The P.A.C.E. was designed to let users walk using only upper body power. The able-bodied user successfully walked without their lower limb function using the P.A.C.E. LLPS prototype, taking consecutive steps over 5 minutes without falling. From limited testing, the user was able to achieve an average step length of 0.12m and a cadence of 11 steps/min.

Conclusions: According to current findings from the literature, P.A.C.E. is the first functioning passive, upper-body-driven and -controlled gait orthosis that does not require the use of crutches. By incorporating design improvements such as spring-loaded ankle joints and a more efficient body power transmission design, along with additional tests to investigate learning effects, the device may achieve faster walking speeds with lower energy expenditure. This research opens opportunities for future developments in passive GOs.