Gain scheduled state feedback velocity control of hydrostatic drive transmissions

In this paper, a velocity tracking controller for hydrostatic drive transmissions is developed. The solution is based on a state dependent model that incorporates nonlinear characteristics of the system. A full state feedback controller is devised and the gains are scheduled on measured speed and pressures, together with approximated volumetric flow. The effects of uncertainties, especially those related to equilibrium values of pressures, are eliminated by utilizing so-called D implementation. This technique eliminates the need for equilibrium values, which are model based and thus uncertain.

To demonstrate the efficacy of the controller, the solution is implemented on a 4.5-ton wheel loader. For comparison purposes, a constant gain state feedback controller with integral action is devised, and also a linear PID controller is tuned. The results show that the benefits of the devised controller are significant when it is compared to these two controllers. Moreover, the controllability of the machine is maintained in every situation.