Kinematic Creep in a Continuously Variable Transmission: Traction Drive Mechanics for Cobots

[+] Author and Article Information
R. Brent Gillespie

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109e-mail: brentg@umich.edu

Carl A. Moore

Department of Mechanical Engineering, Florida State University, Tallahasee, FL 32310email: camoore@eng.fsu.edu

Michael Peshkin, J. Edward Colgate

Department of Mechanical Engineering, Northwestern University, Evanston, Illinois 60208e-mail: peshkin,colgate@nwu.edu

J. Mech. Des 124(4), 713-722 (Nov 26, 2002) (10 pages) doi:10.1115/1.1517560 History: Received September 01, 1999; Online November 26, 2002
Copyright © 2002 by ASME
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The sideslip angle α predicted by the elastic model in response to an applied lateral force F
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Model of the CVT, with sphere S represented by two coaxial cones making line contact with drive rollers W1 and W2
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Normalized tractive force versus creep ξ and spin ψ
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Torque as a function of creep ξ and spin ψ
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Photograph of the prototype CVT. The drive rollers with axes in the vertical plane are visible on the left while the steering rollers with axes in the horizontal plane are visible on the right.
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Thin wheel with heading b1 and steering axis b3. The steering angle is γ.
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Two views of the CVT with sphere S caged between drive rollers W1 and W2 and steering rollers R1 and R2.
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The rotational axis of the sphere oriented by angle γ
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The governing relationships are drawn graphically around a circle so as to indicate the range of γ in which they are valid. In concentric regions starting at the center, the signs of the spin parameters, the relationships between the creep to spin ratios and the drive roller torques, and the drive roller torque values at limiting friction are noted.
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The transmission ratio of speeds as a function of the transmission angle γ with a/R=0.2
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Sideslip angle α as a function of the disallowed force τand the transmission angle γ. Beyond the limiting curve, α will increase without regard to τ applied.



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