Water hydraulics - A novel design of spool-type valves for enhanced dynamic performance

Hydraulic systems provide the most powerful actuators available. In the last decades however, their use in mechatronic systems has decreased, mainly because of two factors: the nature of the actuators themselves (such as noise, cleanliness, size) and the ease of use of electric systems. Water hydraulics, which use water instead of oil as working medium, have several advantages and could not only improve the system performance but also the general acceptance of hydraulics. This paper addresses the flow force inside water hydraulic spool valves, which directly controls the dynamic performance of the entire system. Simulations have been carried out to study the efflux angles (strongly related to flow force) and anti-cavitation ability of different spool valves. In details, the effects of the geometry, opening width and the pressure drop on the efflux angles have been analyzed. The results show that: 1) the geometry and opening width exert significant influence on the efflux angles, while the pressure drop and cavitation have little effect; 2) The arc spool valve has good anti-cavitation ability, and it can increase the efflux angles greatly, thus improving performance. The results provide a basis for developing high performance, light weight and compact water hydraulic control valves for robot actuation systems.