Research Papers

Design and Performance Evaluation of a Bio-Inspired and Single-Motor-Driven Hexapod Robot With Dynamical Gaits

[+] Author and Article Information
Ke-Jung Huang

Department of Mechanical Engineering,
National Taiwan University,
Taipei 106, Taiwan
e-mail: b95502111@ntu.edu.tw

Shen-Chiang Chen

Department of Mechanical Engineering,
National Taiwan University,
Taipei 106, Taiwan
e-mail: b94501023@ntu.edu.tw

Haldun Komsuoglu

Robolit LLC,
1829 Pine Street, Suite 404,
Philadelphia, PA 19103
e-mail: haldun.komsuoglu@gmail.com

Gabriel Lopes

Delft Center for Systems and Control,
Delft University of Technology,
Delft 2628, The Netherlands
e-mail: G.A.DelgadoLopes@tudelft.nl

Jonathan Clark

Department of Mechanical Engineering,
Florida State University,
Tallahassee, FL 32310
e-mail: jeclark@fsu.edu

Pei-Chun Lin

Department of Mechanical Engineering,
National Taiwan University,
Taipei 106, Taiwan
e-mail: peichunlin@ntu.edu.tw

1Corresponding author.

Manuscript received July 17, 2014; final manuscript received March 3, 2015; published online April 14, 2015. Assoc. Editor: Jaydev P. Desai.

J. Mechanisms Robotics 7(3), 031017 (Aug 01, 2015) (12 pages) Paper No: JMR-14-1171; doi: 10.1115/1.4029975 History: Received July 17, 2014; Revised March 03, 2015; Online April 14, 2015

Over its lifetime, the hexapedal robot RHex has shown impressive performance. Combining preflexes with a range of control schemes, various behaviors such as leaping, running, bounding, as well as running on rough terrain have been exhibited. In order to better determine the extent to which the passive and mechanical aspects of the design contribute to performance, a new version of the hexapedal spring-loaded inverted pendulum (SLIP)-based runner with a novel minimal control scheme is developed and tested. A unique drive mechanism is utilized to allow for operation (including steering) of the robot with only two motors. The simplified robot operates robustly and it exhibits walking, SLIP-like running, or high-speed motion profiles depending only on the actuation frequency. In order to better capture the critical nonlinear properties of the robot’s legs, a more detailed dynamic model termed R2-SLIP is presented. The performance of the robot is compared to the basic SLIP, the R-SLIP, and this new R2-SLIP model. Furthermore, these results suggest that, in the future, the R2-SLIP model can be used to tune/improve the design of the leg compliance and noncircular gears to optimize performance.

Copyright © 2015 by ASME
Topics: Robots , Motors , Design , Gears , Springs
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Fig. 1

The model and the robot. (a) The SLIP model with its intrinsic parameters, ICs, and motion profile. (b) The robot performs dynamic motion similar to the SLIP model, which includes a stance phase and a flight phase. (c) The leg motion profile, which includes a stance phase and an aerial phase.

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Fig. 2

The hexapod robot: (a) three-dimensional (3D) model which shows key components and (b) photo of the robot

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Fig. 3

Design of the noncircular gear pair. (a) The normalized angular speed profiles of the input gear (red solid line) and the output gear (base design: green dashed-dotted line segments; after smoothing: blue dashed curve). (b) The designed pitch circles and the final appearance of gear.

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Fig. 4

Two types of legs used on the robot. (a) Linear spring leg and (b) compliant circular leg. (c) Method and notation of deriving equivalent linear spring stiffness of the compliant circular leg. (d) Plot of force versus deformation of the compliant circular leg with different contact points. (e) Plot of stiffness of the compliant circular leg versus different contact points. The matched torsion spring stiffness of the R-SLIP model and R2-SLIP is plotted in solid red curve and dashed green curve, respectively.

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Fig. 5

(a) The R-SLIP and (b) R2-SLIP models with their intrinsic parameters, ICs, and motion profiles, respectively. The notations of the R-SLIP model (c) and the R2-SLIP model (d), which are used to determine the parameters of the models with best fit to the characteristics of the circular legs.

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Fig. 6

Photos of the robot walking (a) and jogging (b). (c) Experimental setup for robot performance evaluation.

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Fig. 7

Mean and standard deviations of the legs’ actual (blue) and designed (red with arrow) rotational speeds

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Fig. 8

The states of the robot (blue) and models (red). The robot is operated with different stride frequencies: 3.6(0.3) Hz in (a), 5.2(0.4) Hz in (b), and 9.1(0.4) Hz in (c).

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Fig. 9

The robot COM trajectories (blue solid) and model mass trajectories (red dashed). The robot is operated with different stride frequencies: 3.6(0.3) Hz in (a), 5.2(0.3) Hz in (b), and 9.1(0.4) Hz in (c).




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