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Research Papers

Singularity-Based Four-Bar Linkage Mechanism for Impulsive Torque With High Energy Efficiency

[+] Author and Article Information
Tomoaki Mashimo

Assistant Professor
Electronics-Inspired Interdisciplinary Research
Institute,
Toyohashi University of Technology,
Toyohashi, Aichi 441-8580, Japan
e-mail: mashimo@eiiris.tut.ac.jp

Takateru Urakubo

Assistant Professor
Graduate School of System Informatics,
Kobe University,
Kobe, Hyogo 657-8501, Japan
e-mail: t.urakubo@silver.kobe-u.ac.jp

Takeo Kanade

U.A. and Helen Whitaker Professor
The Robotics Institute,
Carnegie Mellon University,
Pittsburgh, PA 15213
e-mail: Takeo.Kanade@cs.cmu.edu

1Corresponding author.

Manuscript received December 17, 2012; final manuscript received October 22, 2014; published online December 4, 2014. Assoc. Editor: Xilun Ding.

J. Mechanisms Robotics 7(3), 031002 (Aug 01, 2015) (8 pages) Paper No: JMR-12-1209; doi: 10.1115/1.4028930 History: Received December 17, 2012; Revised October 22, 2014; Online December 04, 2014

We propose a mechanism that exploits the singular configuration in a closed-loop four-bar linkage that can produce a high impulsive torque (a high torque for a short period in time) at the start of motion and high angular velocity during the successive motion. Such characteristics make the mechanism suitable for executing with high energy efficiency a certain class of tasks, such as lifting heavy objects. In this paper, we define the singularity-based linkage mechanism (SLM), analyze its characteristics of torque generation and energy efficiency theoretically, and then confirm them experimentally by using an SLM prototype. The performance of the SLM is compared with that of a comparable size parallelogram mechanism (PM). It is shown that the energy efficiency of the SLM comes from the fact that it achieves the high acceleration of the output link in the neighborhood of the singular configuration by providing energy with low current and high voltage to the motor; whereas the typical PM requires high current to produce the comparable impulsive torque.

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References

Figures

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Fig. 1

SLM that is a four-bar closed-loop linkage with fixed link 0. When links 1 and 2 form a straight line (θ2=0), the SLM takes the singular configuration and generates impulsive torque.

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Fig. 2

Time history of the angular displacements and the output torque TD of link 3 when a unit step input torque τI is given to link 1

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Fig. 3

Actual device of the experimental SLM system: before lifting (left side) and after lifting (right side)

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Fig. 4

Time history of the torque-based lifting experiment (a constant motor torque is applied): (a) the angle and (b) the dynamic output torque of link 3

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Fig. 5

Time history of the angle-based lifting experiment (an optimized motor torque to achieve a desired angle is applied): (a) the angle and (b) the dynamic output torque of link 3

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Fig. 6

(a) The electric energy Ee (input) and the mechanical energy Em (output), and (b) the conversion efficiency ε in the angle-based lifting experiment

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Fig. 7

Initial configuration of the SLM and PM (the configuration of the SLM is singular)

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Fig. 8

Comparison of the SLM and PM when a step motor torque is applied: (a) the angle and (b) the task torque of link 3

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Fig. 9

Time history of the SLM and PM when the optimized motor torque is applied: (a) the optimized motor torque, (b) the angle of link 3, (c) the output task torque, (d) the angular velocity of link 1, (e) the energy consumption, and (f) the energy efficiency

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Fig. 10

Energy consumption of the SLM (solid lines) and PM (dotted lines) by the tasks with the desired angle and the load mass. The plot shows the task, mL = 3 kg and φT=135 deg, shown in Fig. 9.

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Fig. 11

Energy efficiency of the SLM (solid lines) and PM (dotted lines) by the tasks with the desired angle and the load mass. The plot shows the task, mL = 3 kg and φT=135 deg, shown in Fig. 9.

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Fig. 12

Characteristic of SLM related to the mass of load: (a) the output dynamic torque and (b) the angular acceleration of link 3

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Fig. 13

Initial singular configuration (left) and ending singular configuration (right) of the experimental SLM system

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Fig. 14

Relation of the range of motion Φ, initial angle φ0, and ending angle φe with respect to the length l2. The positions marked as (a), (b), and (c) correspond to the three configurations of SLM shown in Fig. 15.

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Fig. 15

Examples of the SLM with three ranges of motion Φ (narrow (a), middle (b), and wide (c)): parameters (top table) and the initial and ending angles of the SLM (bottom figures)

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Fig. 16

Characteristic of output SLM’s torque TD related to its range of motion Φ

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