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TECHNICAL PAPERS

# Modelling a Variable Displacement Axial Piston Pump in a Multibody Simulation Environment

[+] Author and Article Information
Alessandro Roccatello

Politecnico di Torino, The Fluid Power Research Laboratory (FPRL), Corso Duca degli Abruzzi 24, Torino, 10129, Italyalessandro.roccatello@polito.it

Salvatore Mancò

Politecnico di Torino, The Fluid Power Research Laboratory (FPRL), Corso Duca degli Abruzzi 24, Torino, 10129, Italysalvatore.manco@polito.it

Nicola Nervegna

Politecnico di Torino, The Fluid Power Research Laboratory (FPRL), Corso Duca degli Abruzzi 24, Torino, 10129, Italynicola.nervegna@polito.it

In ADAMS a marker defines a point integral with a given solid body.

Reaction forces are applied at the marker of the first item selected in the pair constrained by the joint. Accordingly, it is possible that these will be either acting on the piston (in axial translatory motion) or on the center of the cylinder (in rotational motion about the shaft’s axis), this depending on how selections have been made in the process leading to joint creation.

ADAMS allows definition of generic forces (GFORCE) through analytic relations or external subroutines.

The actuator is permanently connected to pump deliver through a pilot line.

Hydrostatic forces pushing pistons onto the swashplate also depend on pressure values in each cylinder that are in turn dependent on piston angular position $ϑ$ and ultimately on portplate geometry.

J. Dyn. Sys., Meas., Control 129(4), 456-468 (Dec 11, 2006) (13 pages) doi:10.1115/1.2745851 History: Received July 14, 2006; Revised December 11, 2006

## Abstract

Analysis of a variable displacement axial piston pump, as in other complex fluid power and mechanical systems, requires appropriate insight into three multidisciplinary domains, i.e., hydraulics, mechanics and tribology. In recent years, at FPRL, modelling of axial piston pumps has evolved in AMESim (one-dimensional code) where a three-dimensional mechanical approach has required generation of proprietary libraries leading to the evaluation of internal forces/reactions in all pump subsystems. Tribologic aspects in axial piston pumps modelling are also being investigated but AMESim, in this respect, does not appear as the appropriate computational environment. Consequently, a new approach has been initiated grounded on MSC.ADAMS. In this perspective, the paper details how the model has been developed through proprietary macros that automatically originate all pump subsystems parametrically and further apply required constraints and forces (springs, contacts and pressure forces). The ADAMS environment has also been selected due to co-simulation capabilities with AMESim. Accordingly, the paper elucidates how the entire modelling has been construed where hydraulics is managed in AMESim while ADAMS takes care of mechanics. A comparison between simulated and experimental steady-state characteristics of the axial pump is also presented. As such this paper indicates an innovative methodology for the analysis of complex fluid power systems in the hope that, eventually, tribology will also fit into the scene.

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## Figures

Figure 3

Reaction forces on the piston (from barrel)

Figure 4

Co-simulation process between ADAMS and AMESim

Figure 5

Pump model in AMESim with ADAMS co-simulation interface submodel

Figure 6

Macros for automatic generation of the multibody system

Figure 7

Dialog box (GUI) for the axial piston machines multibody library

Figure 1

AMESim model of the pump

Figure 2

Forces acting on the piston

Figure 15

AMESim vs ADAMS (cosimulation) results: swashplate tilt

Figure 16

Experimental swashplate tilt

Figure 17

Swashplate tilt measurement

Figure 18

Figure 8

Pump model automatically generated through macros in ADAMS

Figure 9

A feasible constraints layout

Figure 10

Pump details

Figure 11

Possible constraints for the piston

Figure 12

Example of end-stop force between piston and barrel

Figure 13

Comparison between simulation results: piston-barrel reaction

Figure 14

AMESim vs ADAMS (cosimulation) results: pressure and shaft torque

Figure 19

Figure 20

Geometric parameters for the pump

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