Robust gain scheduling control of an earthmoving vehicle powertrain

The inter-load coupling and the nonlinear ties make the control of a multivariable electro-hydraulic system a challenging problem, which has a practical significance in applications such as the earthmoving industry. In previous work, the nonlinear powertrain was locally modeled as an LTI MIMO system and a local LTI MIMO controller was designed at each operating point using an H_∞ algorithm. In this paper, to cover the entire operating range of the nonlinear system, a gain-scheduled global controller is designed by scheduling different local controllers on the system flow rate and the power demand. A local controller network scheduling strategy is utilized to simplify the closed-loop robust analysis. Different portions of outputs form different local controllers are combined into the total control by using interpolation-weighting functions. To guarantee the stability and the performance, the robustness of the closed-loop global system is analyzed by modeling the dynamics of the scheduling variables as an uncertainty. The design procedure is presented for a multivariable hydraulic control problem; the achieved stability and performance are demonstrated by both analytical and experimental results.