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A passively regulated full-toroidal continuously variable transmission


This work presents a novel self-regulated toroidal continuously variable transmission (ART-CVT) that features a passive control of the speed ratio, achieved with no need for supplementary actuation system. The proposed transmission system is based on a full-toroidal CVT topology which combines a specially shaped geometry of the conjugate profiles with a pre-load system to create a correlation between the speed ratio and the input torque. Such a solution is conceived to reduce the complexity that is usually associated with active regulated systems and it is envisaged to be applicable to low-power/low-cost systems such as small wind turbines, powered-two-wheelers, or bicycles. We illustrate a simplified mathematical model that is able to describe the response of the proposed ART-CVT in quasi-static steady-state operational conditions. Additionally, we propose a case-study in a realistic scenario: a design for an ART-CVT that matches the requirements of a low-power wind turbine coupled with a synchronous generator directly connected to the grid without additional power converters. The achieved results show that an ART-CVT is able to reach working conditions close to the maximum theoretical aerodynamic performance without any active regulation.

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This research received funds from Tuscany Region (Italy) under the project EOLO no. 646436 (FAR FAS 2014-A).

Author information

AB and DM originated the idea for the ART-CVT layout. MM and GM carried out the mechanical analysis and set up the case study. MM, GM, CMO, and MF analyzed the case study data and drafted the manuscript. CMO, CS and MF provided scientific supervision. MM and GM equally contributed to this work.

Correspondence to Marco Fontana.

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AB and DM belong to ACTA, a company with a financial interest in the subject discussed in this manuscript. All the other authors declare no conflict of interest.

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Milazzo, M., Moretti, G., Burchianti, A. et al. A passively regulated full-toroidal continuously variable transmission. Meccanica 55, 211–226 (2020). https://doi.org/10.1007/s11012-019-01096-y

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