Improving pushbelt continuously variable transmission efficiency via extremum seeking control

The control design for the variator in a pushbelt continuously variable transmission (CVT) is investigated. The variator enables a stepless variation of the transmission ratio within a finite range. A conventional control design for the variator is typically obtained by the use of a variator model, which incorporates large uncertainties and, therefore, limits the variator efficiency. In this paper, a control design for the variator is discussed, which improves the variator efficiency and limits the number of sensors. The relation between inputs and outputs of the variator is investigated, from which one input-output map is identified, which exhibits a maximum. This maximum indicates performance in terms of the variator efficiency. For this reason, this input-output map is maximized by means of extremum seeking control (ESC), which omits the use of a variator model. Experiments illustrate that the approach is feasible and show that a conventional control design for the variator is outperformed.