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Research Papers

Development of an Insect-Inspired Hexapod Robot Actuated by Soft Actuators

[+] Author and Article Information
Canh Toan Nguyen

Robotics Innovatory Laboratory,
School of Mechanical Engineering,
Sungkyunkwan University,
Suwon 440-746, South Korea
e-mail: toannguyen@me.skku.ac.kr

Hoa Phung

Robotics Innovatory Laboratory,
School of Mechanical Engineering,
Sungkyunkwan University,
Suwon 440-746, South Korea
e-mail: phunghoa@skku.edu

Phi Tien Hoang

Robotics Innovatory Laboratory,
School of Mechanical Engineering,
Sungkyunkwan University,
Suwon 440-746, South Korea
e-mail: phitien@skku.edu

Tien Dat Nguyen

Robotics Innovatory Laboratory,
School of Mechanical Engineering,
Sungkyunkwan University,
Suwon 440-746, South Korea
e-mail: tiendat@me.skku.ac.kr

Hosang Jung

Robotics Innovatory Laboratory,
School of Mechanical Engineering,
Sungkyunkwan University,
Suwon 440-746, South Korea
e-mail: jhsx1004@skku.edu

Hyouk Ryeol Choi

Professor
Robotics Innovatory Laboratory,
School of Mechanical Engineering,
Sungkyunkwan University,
Suwon 440-746, South Korea
e-mail: hrchoi@me.skku.ac.kr

1Corresponding author.

Contributed by the Mechanisms and Robotics Committee of ASME for publication in the JOURNAL OF MECHANISMS AND ROBOTICS. Manuscript received December 14, 2017; final manuscript received August 12, 2018; published online October 10, 2018. Assoc. Editor: Robert J. Wood.

J. Mechanisms Robotics 10(6), 061016 (Oct 10, 2018) (8 pages) Paper No: JMR-17-1419; doi: 10.1115/1.4041258 History: Received December 14, 2017; Revised August 12, 2018

Insects are one of the most diverse group of animals on the planet and are almost ubiquitous. Their walking locomotion has inspired engineers and provided effective solutions for designing transport methods for legged robots. In this paper, we introduce a hexapod walking robot that mimics the design and walking motions of insects. The robot is characterized by small size, light weight, simple structure, and considerably fast walking speed. Three pairs of its legs are driven by three five-degrees-of-freedom (5DOF) soft actuators based on dielectric elastomer (DE) actuators which can provide up to five movements (including three translations and two rotations) within a compact structure. The robot imitates the crawling motion of an insect using the alternating tripod gait. The experiments show that the robot can achieve an average walking speed of 5.2 cm/s (approximately 21 body-lengths per minute) at 7 Hz of actuation frequency on flat rigid surfaces. Furthermore, the robot also demonstrates the omnidirectional capabilities of walking sideways and rotating its body direction, which enhance the potential of applying the proposed robot in practical uses.

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Figures

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Fig. 1

Simple model of a 3DOF stick insect leg with three hinge joints. Adapted from reference [15].

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Fig. 2

S-Hex II robot design and its main mechanical components

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Fig. 3

Overall design of the 5DOF soft actuator

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Fig. 4

Typical movements of the 5DOF soft actuator: (a) passive state, (b) the Z-axis translation, (c) the X/Y-axis translation, and (d) rotation around the X/Y-axis [14] (Reprinted with permission from Elsevier, ScienceDirect, Sensors and Actuators A: Physical © 2017)

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Fig. 5

Walking cycle of the S-Hex II robot's legs for forward motion (left side view): (a) passive state, (b) pushing downward, (c) swinging backward, (d) lifting upward, and (e) swinging forward [20] (Reprinted with permission from IEEE/RSJ IROS © 2017)

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Fig. 6

Walking cycle of the S-Hex II robot's legs for sideways movement (top view): (a) passive state, (b) first pair of legs moving sideways, (c) second pair of legs moving sideways, and (d) third pair of legs moving sideways

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Fig. 7

Walking cycle of the S-Hex II robot's legs for rotating motion (top view): (a) passive state, (b) first and third pairs of legs oppositely moving sideways, (c) rotating three pairs of legs counter clockwise, and (d) three pairs of legs returning to the passive state

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Fig. 8

Fabrication of the S-Hex II robot: (a) front and top view of one 5DOF soft DEA, (b) assemblage of three soft actuators into a single platform, and (c) the completed hands-on S-Hex II robot

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Fig. 9

Comparison of two robot legs' design

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Fig. 10

Schematic of controller system for the S-Hex II robot [20] (Reprinted with permission from IEEE/RSJ IROS © 2017)

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Fig. 11

(a) Main controller circuit and (b) high voltage amplifier module

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Fig. 12

Displacement performances of the 5DOF soft actuator: (a) translations along the Z- and X/Y-axis, and (b) rotation around the X/Y-axis. Blocking force and torque performances of the proposed actuator: (c) blocking forces along the Z-axis at z = 0 and along the X/Y-axis at x = 0, y = 0, respectively, and (d) blocking torque around the X/Y-axis at θ = 0. Frequency responses of the soft actuator: (e) translations along the Z- and X/Y-axis, and (f) rotation around the X/Y-axis [20]. (Reprinted with permission from IEEE/RSJ IROS © 2017).

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Fig. 13

The locomotion of the S-Hex II with walking speed of 5.2 cm/s at 7 Hz frequency of the applied voltages, using the alternating tripod gait [20] (Reprinted with permission from IEEE/RSJ IROS © 2017)

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Fig. 14

Sideways walking of the S-Hex II robot

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Fig. 15

Rotating the S-Hex II robot body direction

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Fig. 16

Walking speed results of the S-Hex II robot using two units of mm/s and body-length/s at different actuation frequencies of 1–7 Hz [20] (Reprinted with permission from IEEE/RSJ IROS © 2017)

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