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High-Performance Mechanical Transmissions

We are currently developing a new generation of mechanical transmissions, intended to replace gears in applications where backlash, friction, and flexibility cannot be tolerated. Speed-o-Cam is a speed-reduction mechanism based on cams and pure-rolling contact, that is capable of producing, in one single stage, a reduction of N:1, where N is an integer that can be as high as 8 for planar mechanisms, and 12 for spherical mechanisms. The limit here is imposed by the maximum pressure-angle value, which is commonly accepted as around tex2html_wrap_inline3330 . We have produced one prototype that is intended for the coupling of parallel shafts; a second prototype, in its final stages of production, is aimed at coupling shafts with intersecting axes. Although the prototype of the latter was designed for shafts intersecting at right angles, virtually any angle can be accommodated, from tex2html_wrap_inline3332 to tex2html_wrap_inline3334 . In the extreme cases, an angle of tex2html_wrap_inline3332 produces an external plate cam; an angle of tex2html_wrap_inline3334 - an internal plate cam. Planar Speed-o-Cam is intended to replace spur and helical gears, while its spherical counterpart is targeted at bevel gears. One more transmission under development, Slide-o-Cam, is aimed at replacing rack-and-pinion mechanisms, and follows the same principle of power transmission under pure-rolling conditions for minimum friction losses, high stiffness and zero backlash. (Figures 6.9 and 6.10).
 


Figure 6.9: Planar Speed-o-Cam prototype



Figure 6.10: Virtual prototype of Slide-o-Cam

One more task in this project is the structural optimization of the transmissions. The major issue here is that cam mechanisms are subject to periodically-varying loads. Results available for structural optimization concern mostly the case in which the structure is optimum for one single given load. Within the framework of this project, we are developing novel structural optimization criteria and techniques to meet them. The purpose is to obtain mechanisms that are both light and structurally robust.

As mentioned above, cam transmissions induce periodically-varying loads, which, under steady-state conditions and small perturbations, lead to linear dynamical systems with periodically-varying coefficients. Results from classical control theory for time-invariant systems cannot directly be extended to this kind of systems. Using Floquet-Lyapunov theory, we are developing novel techniques for the stability analysis and the feedback control of these systems.

J. Angeles, L. Slutski, M. A. González-Palacios, R. Spiteri, P. Montagnier, C. Teng, O. Navarro, C. J. Wu, D. Wang, S. Asamoah


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Annual Report

Mon Jun 26 21:22:20 GMT 2000