Technical Brief

Robotic Modular Leg: Design, Analysis, and Experimentation

[+] Author and Article Information
Wael Saab

Robotics and Mechatronics Laboratory,
Mechanical Engineering,
Virginia Tech,
Blacksburg, VA 24061
e-mail: waelsaab@vt.edu

William S. Rone

Robotics and Mechatronics Laboratory,
Mechanical Engineering,
Virginia Tech,
Blacksburg, VA 24061
e-mail: wsrone@vt.edu

Pinhas Ben-Tzvi

Robotics and Mechatronics Laboratory,
Mechanical Engineering,
Virginia Tech,
Blacksburg, VA 24061;
Electrical and Computer Engineering,
Virginia Tech,
Blacksburg, VA 24061
e-mail: bentzvi@vt.edu

Manuscript received October 6, 2016; final manuscript received December 23, 2016; published online March 9, 2017. Assoc. Editor: Hai-Jun Su.

J. Mechanisms Robotics 9(2), 024501 (Mar 09, 2017) (6 pages) Paper No: JMR-16-1293; doi: 10.1115/1.4035685 History: Received October 06, 2016; Revised December 23, 2016

This paper presents the design and analysis of a reduced degree-of-freedom (DOF) robotic modular leg (RML) mechanism. The RML is composed of a two serially connected four-bar mechanisms that utilize mechanical constraints between articulations to maintain a parallel orientation between the foot and body without the use of an actuated ankle. Kinematic and dynamic models are developed for the leg mechanism and used to analyze actuation requirements and aid motor selection. Experimental results of an integrated prototype tracking a desired foot trajectory are analyzed to improve the accuracy and repeatability of the mechanism. The prototype weighs 4.7 kg and measures 368 mm in a fully extended configuration and exhibits a maximum deviation from the straight line support phase equivalent to 5.2 mm.

Copyright © 2017 by ASME
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Fig. 1

Side view schematic diagram of the RML

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Fig. 2

Single-leg model: (a) kinematic variables and (b) dynamic variables

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Fig. 3

Motor speed analysis for varying hip speeds

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Fig. 4

Motor torque analysis for varying hip speeds

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Fig. 5

Integrated RML prototype tracking a foot trajectory at key points A, B, C, D, E, and F

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Fig. 6

Measured results of joint angle mean and standard deviation at the key points compared with desired joint trajectories



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