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Research Papers

Design and Implementation of a Binary Redundant Manipulator With Cascaded Modules1

[+] Author and Article Information
Emmanouil Tzorakoleftherakis

Department of Mechanical Engineering,
Northwestern University,
Evanston, IL 60208-3111
e-mail: man7therakis@gmail.com

Anastasia Mavrommati

Department of Mechanical Engineering,
Northwestern University,
Evanston, IL 60208-3111

Anthony Tzes

Department of Electrical and Computer Engineering,
University of Patras,
Rio 26500, Greece

2Corresponding author.

Manuscript received July 5, 2014; final manuscript received April 7, 2015; published online August 18, 2015. Assoc. Editor: Satyandra K. Gupta.

J. Mechanisms Robotics 8(1), 011002 (Aug 18, 2015) (10 pages) Paper No: JMR-14-1157; doi: 10.1115/1.4030372 History: Received July 05, 2014

The subject of this paper is the design and implementation of a prototype snakelike redundant manipulator. The manipulator consists of cascaded modules eventually forming a macroscopically serial robot and is powered by shape memory alloy (SMA) wires. The SMAs (NiTi) act as binary actuators with two stable states and as a result, the repeatability of the manipulator's movement is ensured, alleviating the need for complex feedback sensing. Each module is composed of a customized spring and three SMA wires which form a tripod with three degrees of freedom (DOFs). Embedded microcontrollers networked with the I2C protocol activate the actuators of each module individually. In addition, we discuss certain design aspects and propose a solution that deals with the limited absolute stroke achieved by SMA wires. The forward and inverse kinematics of the binary manipulator are also presented and the tradeoff between maneuverability and computational complexity is specifically addressed. Finally, the functionality and maneuverability of this design are verified in simulation and experimentally.

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References

Figures

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Fig. 3

(a) Electronics architecture ((b) and (c)) forward kinematics parameters

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Fig. 4

(a) Tripod discrete states, with the activated SMAs drawn with dashes and (b) macroscopically serial robot

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Fig. 2

(a) Simplified model of a bending module, (b) SMA arrangement, and (c) worst case configuration

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Fig. 1

(a) The 3DOF spatial tripod, (b) the implemented SMA-based tripod, (c) link design, and (d) IC slot

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Fig. 7

Parametric evaluation of angle θ

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Fig. 5

Workspace of the manipulator for all 88 possible configurations. One can see that despite the binary nature of actuation, the discrete positions of the end-effector essentially form a continuous workspace due to the large number of discrete states. Different levels indicate the vertical distance from the robot base.

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Fig. 6

(a) Snapshots of the robot movement, (b) state variations, (c) actual robot path, and (d) position error

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Fig. 8

(a) Manufactured link, (b) slave IC, and (c) assembly details

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Fig. 9

Experimental results

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Fig. 10

Demonstration of repeatability

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Fig. 11

Additional configurations

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