A review on belt and chain continuously variable transmissions (CVT): Dynamics and control

Over the last two decades, significant research effort has been directed towards developing vehicle transmissions that reduce the energy consumption of an automobile. This effort has been a direct consequence of the growing environmental concern imposing the directives of reduced exhaust emissions and increased vehicle efficiency on current vehicle manufacturers and users. A continuously variable transmission (CVT) offers a continuum of gear ratios between desired limits, which consequently enhances the fuel economy and dynamic performance of a vehicle by better matching the engine operating conditions to the variable driving scenarios. Although a CVT plays a crucial role in the plan to improve vehicle fuel economy, its complete potential has not been realized in a mass-production vehicle. The current paper reviews the state-of-the-art research on dynamic modeling and control of friction-limited continuously variable transmissions. The basic concepts, mathematical models, and computational schemes are extensively discussed. Challenges and critical issues for future research on modeling and control of such CVTs are also discussed.