Clamping Strategies for Belt-Type Continuously Variable Transmissions: An Overview

Since pushbelt and chain type continuously variable transmissions (CVTs) are friction-based systems, their actuation entails a trade-off: while sufficient actuation (clamping) forces are required to ensure safe operation, excess forces would result in inefficient operation due to frictional losses and increased power consumed for actuation. Early works on CVT control focused mainly on operating the CVT such that optimal gear ratios are tracked, while employing only simple conservative strategies for clamping. In later works, to maintain competition with manual transmissions, the clamping strategies have received increased attention. In this paper, the clamping objective of a belt-type CVT is discussed and the works on it are reviewed.