Control System Design on a Power-Split CVT for High-Power Agricultural Tractors

Savaresi S.M., A. Taroni, F. Previdi, S. Bittanti

The problem considered in this paper is the design and tuning of the control system of a power-split continuously variable transmission (CVT) used in high-power tractors. Power-split
CVTs are characterized by the combination of a traditional mechanical transmission and by a continuously-variable transmission. This guarantees, at the same time, smooth variations of
the transmission-ratio and high efficiency of the overall transmission system. The control architecture of an hydrostatic power-split CVT is constituted by three main parts: 1) servo-controller on
the current of the valve which drives the hydraulic transmission; 2) a servo-controller on the hydraulic transmission-ratio; and 3) a synchronizer which coordinates the hydraulic and the mechanical
parts of the CVT. In this work, these three controllers are fully developed, including: design, implementation, and evaluation on an experimental system.

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