Minimal-model for robust control design of large-scale hydraulic machines

Abstract

Hydraulic machines are in use where the large forces, at relatively low velocities, are required by varying loads and often hazardous and hard-to-reach environments, like e.g. offshore, mining, forestry, cargo logistics, and others industries. Cranes and excavators equipped with multiple hydraulic cylinders are typical examples for that. For design of the robust feedback controls of hydraulic cylinders, already installed into large-scale machines, there is a general lack of reliable dynamic models. Also the suitable and feasible identification techniques, especially in frequency domain, yield limited. This paper proposes a minimal-modeling approach for determining the most relevant open-loop characteristics of hydraulic cylinders installed on a bulk loader crane. The resulted model allows for robust control design without knowledge of the overall complex system behavior. The total system gain, non-negligible input dead-zone, and aggregated phase lag are identified from the simple openloop experiments. An aggregated phase lag is captured for the assumed bandwidth of the system, and that without knowledge of the higher-order residual system dynamics. Based thereupon, the robust feedback position regulator is designed and extended by the velocity feed-forwarding. The proposed modeling approach, together with the designed control system, are evaluated on the third axis of a hydraulic loader crane.

Validation of a Limited Information Shared Controller: A Comparative Study

“…The full automation of a hydraulic manipulator with a fixed base is investigated in the literature, see e.g. [7], [8] or [9]. In these works, detailed and simplified models are developed to control the position and the velocity of the end-effector.…”

Use of second-order sliding mode observer for low-accuracy sensing in hydraulic machines

“…Further we note that the input dead-band can be estimated either by an off-or on-line identification approach, see e.g. [11], [12], and that by various quasi-static openloop control experiments. The overall identified dead-band of hydraulic system, used in this work, is W = 0.6.…”