Research Papers

Modeling and Control of an Infinitely Variable Speed Converter

[+] Author and Article Information
W. D. Zhu

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

X. F. Wang

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

1Corresponding author.

Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received February 6, 2013; final manuscript received December 20, 2013; published online February 24, 2014. Assoc. Editor: Luis Alvarez.

J. Dyn. Sys., Meas., Control 136(3), 031015 (Feb 24, 2014) (10 pages) Paper No: DS-13-1065; doi: 10.1115/1.4026411 History: Received February 06, 2013; Revised December 20, 2013

Traditional transmission in a vehicle has low efficiency and that in a wind turbine has a constant output-to-input speed ratio, which needs a power converter to regulate the current frequency that can be fed into the grid. Different types of continuously variable transmission (CVT) have been developed for vehicle and wind turbine applications, which allow optimal engine speeds to be selected for different driving conditions in the former and can generate constant-frequency current without using a power converter in the latter. An infinitely variable speed converter (IVSC) is a specific type of CVT that can achieve a zero speed ratio and transmit a large torque at a low speed ratio. An IVSC with drivers that convert an eccentric motion of cams to a concentric motion of the output shaft through one-way bearings is introduced, and an active control system with a combined feedback and feed-forward control that can automatically adjust the eccentricity of outer cams to control the speed ratio of the transmission is developed. The kinematic model of the IVSC is derived and fitted by a polynomial function to serve as the feed-forward function in the control law. The feedback control is used to reduce the system error. A dynamic model of the IVSC is derived to investigate the effect of the dynamic load on the input and output speeds. Static and dynamic tests were conducted to validate the kinematic model of the IVSC. The variation of the average output speed per revolution of the output shaft is 0.56% with respect to the desired output speed in the simulation and 0.91% in the experiments.

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Fig. 1

(a) Two-dimensional, (b) three-dimensional layouts of the IVSC, and (c) the power flow of the IVSC

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Fig. 2

Configuration of the motion conversion module: (a) concentric and (b) eccentric with the maximum outer cam eccentricity

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Fig. 3

Layout of the driver module

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Fig. 4

Layout of the control module

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Fig. 5

Speed relations of the planetary gear set: (a) the left view, (b) the front view, and (c) the right view

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Fig. 6

Outer cam eccentricity; after the inner cam rotates clockwise by θc relative to the outer cam, the relative position of the outer cam to the inner cam will change from (a) to (b)

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Fig. 7

Speed relation of the driver module

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Fig. 8

(a) The inner and outer cams of the first group and (b) those of the second group

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Fig. 9

Output-to-input speed ratio of one driver

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Fig. 10

Speed ratios of the first and second drivers

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Fig. 11

Output-to-input speed ratio of the IVSC

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Fig. 12

Average output-to-input speed ratio versus the control angle

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Fig. 13

System consisting of an input motor, the IVSC, and an output load

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Fig. 14

Influence of the input power and output inertia on the input and output speeds: (a) the input speeds, (b) the output speeds with varied input powers and the constant output inertia Ig = 149.8631Nms2, (c) the input speeds, and (d) the output speeds with the constant input power P = 0.1130W and varied output inertias

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Fig. 15

Block diagram of the active control system of the IVSC

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Fig. 16

Schematic diagram of the block Ctrl in Fig. 15

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Fig. 17

Average input and output speeds of the IVSC over 0.4 s for a desired output speed of 20 RPM with the active control system in Fig. 15

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Fig. 18

Prototype of the IVSC and experimental devices

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Fig. 19

Dynamic test of the feed-forward function

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Fig. 20

Block diagram of the open-loop control system for the dynamic test

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Fig. 21

Implementation of the closed-loop controller in labview

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Fig. 22

Experimental results of the prototype of the IVSC with the active control system



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