Abstract
The ratio and the pressure of a CVT are usually controlled using linear control. However due to the non-linearity of the system gain scheduling becomes necessary to guarantee an accurate control. This tuning can take time due to the high number of gains that need to be set. This paper describes a non-linear control strategy that avoids the high number of gains and enables a faster tuning of the controller. Hydraulic servo-pumps are used instead of valves to set the primary and secondary pulley pressure. Using state-feedback, the servo-pumps control the flow going in and out of the pulleys such that the dynamics become fast enough to be neglected. The primary and secondary pressures are linearised by an Input-Output feedback linearization. An output loop controls the ratio through a table where the ratio and the primary torque are the inputs and the primary and secondary pressures are the outputs.
Keywords: CVT, non-linear control, hydraulic servo-pump, state-feedback, flow control