Experimental Investigation on a Power Supply Control System for Hydraulic Actuators

Hydraulics is a technology widely used whenever high power is required with relatively small dimensions of the components. However, despite the high power density that characterizes the hydraulic components, they are intrinsically dissipative due to pressure drops across them. One of the possible adoptable solutions to increase the efficiency of the system is to control the power supply at the aim to tailor the generated power to the load demand. Many of the proposed solutions retrievable in literature lead to significant modifications of the hydraulic circuit, and are not of general validity for other kinds of systems. The present paper focuses exactly on a new kind of power supply control system, with a low impact on a hydraulic plant, and applicable to different kinds of systems. It is based on the regulation of the supply pressure by means of a servo valve. This new power supply control system is analysed through preliminary experimental activities conducted on a test rig, where the pressure of the fluid within a constant volume is controlled. Firstly, the bandwidth of the transfer function between the servo valve command and the supply pressure is evaluated. Secondly, a closed loop control of the supply pressure is realized, considering a pressure set-point drawn from a real case, already studied by the authors in a previous work. The experimental results show that the system is able to follow the set-point with a very small error. At the same time, a system model where the fluid is considered incompressible has been set-up. The relevant transfer function obtained shows remarkable differences with respect to the experimental one. Hence, the model needs to be reviewed including other effects, like fluid's compressibility, at the moment neglected. Besides the model improvement, authors have been planning other experimental activities in different conditions to confirm the preliminary results obtained.