Design Innovation Paper

Design, Modeling, and Experimental Validation of a Novel Infinitely Variable Transmission Based on Scotch Yoke Systems

[+] Author and Article Information
X. F. Wang

Department of Mechanical Engineering,
University of Maryland,
Baltimore County,
1000 Hilltop Circle,
Baltimore, MD 21250

W. D. Zhu

Fellow ASME
Division of Dynamics and Control,
School of Astronautics,
Harbin Institute of Technology,
Harbin 150001, China;
Department of Mechanical Engineering,
University of Maryland,
Baltimore County,
1000 Hilltop Circle,
Baltimore, MD 21250

1Corresponding author.

Contributed by the Power Transmission and Gearing Committee of ASME for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received July 25, 2014; final manuscript received August 21, 2015; published online November 16, 2015. Assoc. Editor: Shapour Azarm.

J. Mech. Des 138(1), 015001 (Nov 16, 2015) (8 pages) Paper No: MD-14-1446; doi: 10.1115/1.4031499 History: Received July 25, 2014; Revised August 21, 2015

A novel infinitely variable transmission (IVT) based on scotch yoke systems is designed to provide a continuously varied output-to-input speed ratio from zero to a specified value. By changing the crank length of scotch yoke systems, the speed ratio of the IVT can be continuously adjusted. The IVT consists of a pair of noncircular gears and two modules: an input-control module and a motion conversion module. The input-control module employs two planetary gear sets to combine the input speed of the IVT with the control speed from the stepper motor that changes the crank length of scotch yoke systems. The motion conversion module employs two scotch yoke systems to convert the combined speeds from the input-control module to translational speeds of yokes, and the translational speeds are converted to output speeds through rack–pinions. The speed ratio between the output of the motion conversion module and the input of the input-control module has a shape of a sinusoidal-like wave, which generates instantaneous variations. Use of scotch yoke systems provides a benefit to isolate the interaction between the crank length and the shape of the speed ratio, and a pair of noncircular gears can be used to eliminate the instantaneous variations of the speed ratio for all crank lengths. A prototype of the IVT was built and instrumented, and its kinematic behavior was experimentally validated. A driving test was conducted to examine the performance of the IVT.

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Grahic Jump Location
Fig. 4

(a) 3D model and (b) schematic diagram of the input-control module

Grahic Jump Location
Fig. 5

Structure of the second planetary gear set; the first planetary gear set has the same structure

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Fig. 3

Schematic diagram of the SGIVT. 1—Output gear of the first planetary gear set, 2—output gear of the second planetary gear set, 3—gear on the control shaft, 4—gear on the idler shaft, 5—carrier, 6—ring gear, 7—sun gear, 8—planet gear, 9—input gears of scotch yoke systems driven by the first planetary gear set, 10—input gear of scotch yoke systems driven by the second planetary gear set, 11–pin, 12—yoke, 13—crank gear, 14(a–d)—racks meshed with crank gears in four directions, 15—output gear, 16—rack meshed with the output gear on the top side of the yoke represented by a solid line, 17—rack meshed with the output gear on the bottom side of the yoke represented by a dashed line

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Fig. 2

Layout of the SGIVT

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Fig. 1

Schematic illustrating the principle of the SGIVT with scotch yoke systems

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Fig. 8

Schematic of the first and second scotch yoke systems

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Fig. 14

Block diagram of the controller for the SGIVT

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Fig. 15

Slope of linear regression from the measured speed of the DC motor and the angle of the stepper motor

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Fig. 7

Structure of the first scotch yoke system; the second scotch yoke system has the same structure

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Fig. 6

(a) 3D model of the motion conversion module and (b) schematic diagram of the input motion conversion part

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Fig. 9

Structure of the output motion conversion part of a scotch yoke system

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Fig. 12

Comparison of experimental and theoretical average speed ratios

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Fig. 13

Experimental speed ratio of the noncircular gears, experimental speed ratios of the SGIVT with and without the noncircular gears, and the theoretical speed ratio of the noncircular gears or that of the SGIVT without the noncircular gears

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Fig. 16

Driving test results of the SGIVT; values of the angle of the stepper motor are scaled down by 100, and those of the input voltage are scaled up by 5

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Fig. 10

Tooth profiles based on approximated pitch profiles

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Fig. 11

Experimental setup of the SGIVT




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