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Technical Brief

MotionGen: Interactive Design and Editing of Planar Four-Bar Motions for Generating Pose and Geometric Constraints

[+] Author and Article Information
Anurag Purwar

Computer-Aided Design and Innovation Lab,
Department of Mechanical Engineering,
Stony Brook University,
Stony Brook, NY 11794-2300
e-mail: anurag.purwar@stonybrook.edu

Shrinath Deshpande

Computer-Aided Design and Innovation Lab,
Department of Mechanical Engineering,
Stony Brook University,
Stony Brook, NY 11794-2300

Q. J. Ge

Computational Design Kinematics Lab,
Department of Mechanical Engineering,
Stony Brook University,
Stony Brook, NY 11794-2300

1Corresponding author.

Manuscript received October 17, 2016; final manuscript received January 13, 2017; published online March 9, 2017. Assoc. Editor: Venkat Krovi.

J. Mechanisms Robotics 9(2), 024504 (Mar 09, 2017) (10 pages) Paper No: JMR-16-1317; doi: 10.1115/1.4035899 History: Received October 17, 2016; Revised January 13, 2017

In this paper, we have presented a unified framework for generating planar four-bar motions for a combination of poses and practical geometric constraints and its implementation in MotionGen app for Apple's iOS and Google's Android platforms. The framework is based on a unified type- and dimensional-synthesis algorithm for planar four-bar linkages for the motion-generation problem. Simplicity, high-utility, and wide-spread adoption of planar four-bar linkages have made them one of the most studied topics in kinematics leading to development of algorithms and theories that deal with path, function, and motion generation problems. Yet to date, there have been no attempts to develop efficient computational algorithms amenable to real-time computation of both type and dimensions of planar four-bar mechanisms for a given motion. MotionGen solves this problem in an intuitive fashion while providing high-level, rich options to enforce practical constraints. It is done effectively by extracting the geometric constraints of a given motion to provide the best dyad types as well as dimensions of a total of up to six four-bar linkages. The unified framework also admits a plurality of practical geometric constraints, such as imposition of fixed and moving pivot and line locations along with mixed exact and approximate synthesis scenarios.

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References

Figures

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Fig. 1

Five stamping poses; the stamping tool in first pose is almost horizontal, while in the fourth pose it is almost vertical

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Fig. 2

Stamping: Grashof crank–rocker solution; two curves shown are coupler curves in two different circuits

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Fig. 3

Excavator bucket motion through four positions

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Fig. 4

Excavator: Grashof crank–rocker linkage obtained by selecting two dyads

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Fig. 5

Poses for landing gear

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Fig. 6

Landing gear: non-Grashof triple-rocker linkage

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Fig. 7

Landing gear: Grashof crank–rocker linkage

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Fig. 8

Simulation of planar four-bar film-advancing mechanism in Motiongen

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Fig. 9

Reverse-engineered four-bar film-advancing mechanism satisfying a practical line constraint in MotionGen

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