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Technical Brief

Developing a Mobile Lower Limb Robotic Exoskeleton for Gait Rehabilitation

[+] Author and Article Information
Zhao Guo

State Key Laboratory of Mechanism System
and Vibration, Institute of Robotics,
Shanghai Jiao Tong University,
Shanghai 200240, China;
Department of Biomedical Engineering,
National University of Singapore,
Singapore 117575, Singapore
e-mail: guozhao@sjtu.edu.cn

Haoyong Yu

Department of Biomedical Engineering,
National University of Singapore,
Singapore 117575, Singapore
e-mail: bieyhy@nus.edu.sg

Yue H. Yin

State Key Laboratory of Mechanism System
and Vibration, Institute of Robotics,
Shanghai Jiao Tong University,
Shanghai 200240, China
e-mail: yhyin@sjtu.edu.cn

1Corresponding author.

Manuscript received August 8, 2013; final manuscript received February 17, 2014; published online xx xx, xxxx. Assoc. Editor: Venketesh N. Dubey.

J. Med. Devices 8(4), 044503 (Aug 19, 2014) (6 pages) Paper No: MED-13-1189; doi: 10.1115/1.4026900 History: Received August 08, 2013; Revised February 17, 2014

A new compact mobile lower limb robotic exoskeleton (MLLRE) has been developed for gait rehabilitation for neurologically impaired patients. This robotic exoskeleton is composed of two exoskeletal orthoses, an active body weight support (BWS) system attached to a motorized mobile base, allowing over-ground walking. The exoskeletal orthosis is optimized to implement the extension and flexion of human hip and knee joints in the sagittal plane. The motor-driven BWS system can actively unload human body weight and track the vertical displacement of the center of mass (COM). This system is compact and easy for therapist to help patient with different weight (up to 100 kg) and height (150–190 cm). Experiments were conducted to evaluate the performance of the robot with a healthy subject. The results show that MLLRE is a useful device for patient to achieve normal over-ground gait patterns.

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Figures

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Fig. 1

Schematic graph of the MLLRE: (a) robotic gait orthosis, (b) mobile base combining with BWS system, and (c) the integrated structure of the robotic system

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Fig. 2

CAD models of the MLLRE: (a) robotic gait orthosis, (b) mobile base incorporating with BWS system, and (c) the integrated robotic system

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Fig. 3

Schematic graph of three different robotic orthosis: four-bar linkage mechanism in LOKOMAT (a), in ALEX (b), offset slider-crank mechanism in our MLLRE (c), and (d) the definition of knee and hip joint angles with the positive direction indicated

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Fig. 4

Robotic orthosis: (a) the side view and (b) the 45 deg view of the CAD model

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Fig. 5

(a) A labeled schematic of the offset slider-crank mechanism, x is the slider displacement, l1 is the crank length, l2 is the connecting rod length, l3 is the length from the slider center to the rotation center along the x direction, e is the eccentricity, and H is the stroke of the slider. θ, ϕ, and γ are the crank angle, connecting rod angle, and transmission angle, respectively. F1 is the active force produced by the ball screw and F2 is the force acted on the connecting rod. (b) Relationship between the crank angle and the joint angle, we define θch, θck as the crank angle in the hip and knee, respectively. (c) The mechanical diagram of the robotic orthosis. dt is the distance between the hip joint and the mass center of the thigh, dc is the distance between the knee joint and the mass center of the calf, α and β are eccentric angles of the mass center away from the centerline of the thigh and calf, Th and Tk are the joint required torques, Ft and Fc are the interaction forces, lt and lc are the interaction force arms, mt is the mass of the thigh(including the motor), and mc is the mass of the calf.

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Fig. 6

CAD models of the BWS system

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Fig. 7

Pressure and sEMG sensors

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Fig. 8

(a) The limit switches in trunk segment and (b) the width adjustable device designed to adjust the distance between two orthoses

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Fig. 9

(a) The gait angle and required torque on hip and knee joints, and (b) the flow diagram of the position control

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Fig. 10

Prototype of the MLLRE, its major components labeled

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Fig. 11

Experiments with two gait cycles on a healthy subject, (solid line and dotted line represent the reference and real angles), (a) hip joint tracking, (b) knee joint tracking, and (c) COM tracking

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