A Critical Analysis of Valve-Compensated Hydrostatic Actuators: Qualitative Investigation

Abstract

Hydrostatic actuation has gained interest from both academia and industry due to the unquestionable energetic advantages when compared to valve-controlled actuators; the main feature being the absence of throttling losses due to the direct control of the cylinder by the pump. However, the fact that the great majority of applications are based on single-rod cylinders has been both a challenge and a source of inspiration for a variety of different circuit designs. In an attempt to compensate for the uneven flows coming in and out of differential cylinders, several solutions have been proposed, including the use of hydraulic transformers, individual pumps connected to the cylinder ports or pumps with unmatched input and output flows. The simplest approach, however, seems to be the use of compensation valves in the circuit, which is the focus of this paper. Here, we analyse some representative circuits proposed along the years in a direct and elucidative manner, showing that the definitive solution to the single-rod actuator control problem has been established, paving the road for introducing stable and trustworthy circuits, which can be commercially used in the near future.