Abstract
Hydraulic control of the Continuously Variable Transmission (CVT) is the focus of this paper. To attain different gear ratios, axial pulley forces have to be realized by applying pressures at primary and secondary cylinder. These pressures can be obtained from the line pressure in various ways, depending on the number, type and location of the valves incorporated. Four possible configurations are investigated, one of which is the setup as it is applied in current VDT transmissions. For a qualitative comparison, transfer functions of linearized models in a number of operating points are used. Results show that, for one thing, certain choices may lead to high levels of interaction between the separate control circuits, often rendering effective control difficult. Final remarks and recommendations concerning 'optimal' hydraulic CVT control conclude the paper.