Continuously variable chain drives, which transmit the power through frictional forces, consist of a chain and two movable and thus controllable pulleys. Consequently, we have to deal with the motion of chain elements having contact with these pulleys and with chain elements as part of the strands. Mechanically this results in different force budgets. In the strand case only joint forces act on the chain links, whereas in the contact situation we must also consider frictional forces generated in the contact zones between each chain link and the tapered surfaces of the cone pulley. To obtain the chain's dynamics due to the polygonal action in the chain, the chain is modeled link by link. Hence mechanical and mathematical models are extremely costly. When modeling the contact between the link and the pulley, unilateral constraints have to be taken into account. Two contact models are presented. By means of comparison of the two models, it is shown that both yield to very similar results.
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