Experimental Study of 3D Movement in Cushioning of Hydraulic Cylinder

Abstract

A double acting cylinder operation has been fully monitored in its key functional parameters, focused on characterization of end-of-stroke cushioning and starting phases. Being the cylinder performance reliant in the piston constructive geometry, the number and location of piston circumferential grooves is a significant parameter affecting the internal cushioning system performance. An eddy current displacement sensor assembled in the piston allows assessment of piston radial displacement inside the cylinder tube, which is directly related with the studied operating phases. Due to such 3D displacements, the piston becomes as an active and self-adjusting element along the functional cycle of the cylinder. Mechanical joints orientation and operating pressure are also relevant parameters affecting piston radial displacement and, thus, the cushioning and starting performance. Computational Fluid Dynamics (CFD) results confirm the observed functional role of the perimeter grooves; the flow and pressure distributions, where develops a significant radial force, are also in accordance with the registered radial displacement.

Bond Graph Simulation of Error Propagation in Position Estimation of a Hydraulic Cylinder Using Low Cost Accelerometers

“…The experimental assembly described in our previous work [8] has been updated by installing a triaxial accelerometer inside the piston. This sensor is able to monitor the accelerations generated by the extension and retraction movement (Z axis) and transversal displacements of the piston inside the cylinder body (X and Y axes), as described in Figure 15.…”

“…It should be noted that, the nature of both displacements are very different, where Y axis displacement is several orders of magnitude lower that Z axis displacement. Further description of the operational cycle of the studied hydraulic cylinder and its displacements can be found in our previous experimental work [8]. The generated irregularities in the displacement by the gear pump (Pump_Ripple), as a consequence of the transmitted vibrations and pressure pulses over the piston, are simulated adding a sinusoidal signal into the main displacement value.…”

“…In our previous work, the 3D movement of a piston inside a hydraulic cylinder during cushioning were assessed thanks to an Eddy current displacement sensor [8]. Unfortunately, these sensors are costly and have a limited measurement range and difficult installation.…”

Simulation of Hydraulic Cylinder Cushioning

“…As the cylinder approaches to its end of stroke, the piston closes the fluid outlet port, starting to narrow the flow section and producing a resulting cushioning pressure. The performance of this type of cushioning devices has been experimentally assessed in detail in our previous work [4].…”

“…One is the use of peripheral mobile rings, which actuate like a check valve during the cushion and starting phases [1][2][3]; the other is the use of peripheral grooves, whose number and design modulate the outlet section. Until now, this last design had garnered low levels of interest by academic studies, and it is therefore the object of our research; certain key operating factors, like the radial displacement of the piston, have already been experimentally identified in our previous work [4].…”