International Review on Modelling and Simulations (I.RE.MO.S.), Vol. 4, n. 2 April 2011 Manuscript received January 2007, revised January 2007 Copyright © 2007 Praise Worthy Prize S.r.l. - All rights reserved Modelling of an electro-hydraulic forklift in Matlab Simulink Tatiana A. Minav 1 , Denis M. Filatov 2 , Lasse I.E. Laurila 3 , Juha J. Pyrhönen 4 , Victor B.Vtorov 5 Abstract – Evaluation of an electro-hydraulic system of a working machine is carried out by a Matlab Simulink model. Modelling of the total forklift system is presented. Analysis and verification of the Simulink model with practical results are also performed for an internal gear and axial piston hydraulic machine drive. Practical results are presented to demonstrate the energy efficiency of the proposed electro-hydraulic forklift arrangement with potential energy recovery feature. Keywords: Drives, pumps, permanent magnet machines, energy efficiency, energy recovery, model Nomenclature B e bulk module C s Stribeck friction F co Coulomb friction in cylinder F f friction force F load force created by load F so static friction i current i a , i b , i c currents in the phases a, b, c i d direct-axis components of the stator current i D direct-axis current of the damper winding i q quadrature-axis component of the stator current i sd direct-axis components of the stator current i sq quadrature-axis components of the stator current J eq combined inertia of the load J m total equivalent inertia of the motor J p total equivalent inertia of the pump K d derivative gain K e motor voltage constant K i integral gain K p proportional gain L cyl length of cylinder piston L Ds direct-axis leakage inductances of the damper winding L md direct-axis magnetising inductance L mq quadrature-axis magnetising inductance L Qs quadrature-axis leakage inductances of the damper winding L sd direct-axis stator inductance L sq quadrature-axis stator inductance L ss stator leakage inductance m load mass m p mass of the cylinder piston m t total mass p number of pole pairs p rtn tank pressure p s system pressure Q in input flow R D direct-axis resistances of the damper winding R Q quadrature-axis resistances of the damper winding R s stator resistance S p cross sectional area of a hydraulic piston T co Coulomb friction T e electromagnetic torque T f,p frictional torque T L load torque T motor drive torque T p,th theoretical torque required for compressing fluid T so static friction T v viscous friction u d direct-axis components of the stator voltage u sd stator voltage for d-axis u sq stator voltage for q-axis V cylinder volume V 0 dead volume of cylinder V th theoretical pump displacement per revolution η vol volumetric efficiency of the pump σ viscous friction ȥ d direct-axis components of the stator flux linkage Ȍ PM permanent magnet created flux linkage ȥ q quadrature-axis components of the stator flux linkage Ȍ sd stator d-winding flux linkages Ȍ sq stator q-winding flux linkages Ȧ m electrical angular velocity ȍ rotation speed of the shaft p p p , , x x x & & & piston position, velocity and acceleration I. Introduction Recently, energy saving requirements in heavy machines and, especially, battery-operated working machines have been highlighted from the CO 2 reduction and energy efficiency points of view [1, 2]. There are different traditional technologies that improve the energy efficiency of hydraulic systems. Load Sensing (LS) valves, variable displacement pumps and pure pump control [3], pump-controlled actuators (PCA) [4] and