Research On Water Hydraulic Jet Pipe Servo Valve Driven By Self-sensing Actuator

Water hydraulic electro-hydraulic servo valve as a new type hydraulic component which is inosculated of mechanical, electronic and hydraulic technology, it is one core control component of ware hydraulic servo control system, and has many merits such as small volume, light weight, high control precision and fast response speed, it has also become a very important research object in the forefront of international fluid power transmission and control field at present. Based on the advantages of the jet-pipe servo valve, the water hydraulic features, and the Giant Magnetostrictive Material(GMM) self-sensing driving technology, the working mechanism, design theory and performance simulation of water hydraulic jet pipe servo valve driven by self-sensing actuator are carried out.In a water hydraulic jet pipe servo valve, the overall performance of the valve is directly influenced by the structure dimension of the receiver and the jet pipe amplifier. The influence rules of the structure dimension parameters and performance parameters on the buildup pressure in the two receiving holes are researched by using numerical simulation, computer emulation and experiment analysis methods. Through analyzing the characteristics of the flow field, a mathematics relation between the jet nozzle offset and the pressure ratio inside the two receiver holes is established, which reveals the energy distribution and conversion mechanism.When high velocity water flowing through the jet pipe nozzle, cavitation happens very easily in the nozzle and its downstream. At the same time due to the existence of the jet shear layer and the narrow spacing between the nozzle and the receiver, the high-frequency cavitation self-oscillation is much more apt to occur, which seriously affecting the performance of the servo valve.The cavitation flow field characteristics in the jet pipe amplifier are simulated with commercial Computational Fluid Dynamics(CFD) software. The influence of operating parameters and structural parameters of jet nozzles on cavitation jet have been researched systematically. These parameters mainly include inlet pressure, outlet pressure, temperature of water, nozzle convergence angle, length of the nozzle cylindrical section, nozzle diameter and nozzle export chamfer angle. The methods to limit the emergence and development of the nozzle jet internal cavitations are proposed.Taking the powerstage spool as the driving object and spool displacement as sensing parameter, the transfer functions and block diagrams of various aspects of the self-sensing jet pipe servo valve are established. The relationship between the drive current/voltage and the spool displacement, and the doubleaction transfer law in the servo valve system are analyzed and studied systematically. The mathematical model reflecting servo valve control features is finally established.The characteristics index system of water hydraulic servo valve is established, with currently existing oil hydraulic servo valve characteristics index system as a source of reference. Using AMESim software, the system simulation and parameters sensibility disquisition of self-sensing jet pipe servo valve are completed to find out the variational trend, these parameters mainly include the clearance between valve spool and sleeve, overlap length of slide valve orifice and valve spool.