Friction characteristics of a multi-chamber cylinder for digital hydraulics

This paper deals with the issue of defining friction characteristics of a multi-chamber cylinder for digital hydraulics. Using a multi-chamber cylinder under a set of supply pressures, friction characteristics are experimentally investigated for a range of velocity according to load conditions. A binary digit-based pressure e.g., high pressure or low pressure has been applied to each chamber. The friction force is measured based on the equation of motion using measured values of the pressures in the chambers of the multi-chamber cylinder and the position of the piston. As a mechanism to load the multi-chamber cylinder, a 1-Degree of Freedom (DOF) boom mockup mimicking a medium-sized mobile machine boom has been constructed. Then it has been utilized to test the motion of the cylinder under different mass–load conditions. It is shown that the cylinder states do not dominantly affect the friction force of a multi-chamber cylinder, comparing the effect of other parameter such as mass load and velocity, which is expected to be useful for the secondary control of digital hydraulic systems.