Establishment of steering circuits and evaluation of oil temperature

Abstract: The master thesis has been performed for Volvo 3P on the site of Lyon in France, andin the premises of the design office front and rear axle installation of the productdevelopment department. This unit is in charge of the conception, the design and theproduction of the chassis and of the power steering system of all the trucks of theVolvo AB group.The sizing of the circuits is currently grounded on the experience of the member ofthe design office. Each new steering circuit has to follow a serial of test in differentcondition of utilization in order to be validated by Volvo and its suppliers. To securethe design process, the introduction of a simulation method in the design process ofsteering circuits has been wished. The simulation tool is intended to need input datasimple enough so that it can be used in the early development stage of a designprocess. It has been decided to simulate static tests, when the engine runs at constantspeed without air circulation. The tool has to be able to predict the oil temperaturewith an error of 10%. To validate the tool, the results need to be correlated ondifferent circuit architectures. Finally the tool needs to be confronted to reality bycomparing the prediction with measurement lead on a prototype vehicle.The software Amesim has been chosen to develop the simulation tool. In fact a prestudy of the problem has shown that different scientific domains have to be taken inaccount to model the steering oil temperature evolution. In particular the heat transfersand the fluid mechanic have to be considered. Based on the bond graph theory,Amesim is a convenient software to model complex physical phenomena. To modelcorrectly a steering circuit, the key components have to be identified andcharacterized in static functioning. The pump, the oil tank, the pipes and the steeringgear are the principle components of interest. Their pressure losses and heat transfershave been thoroughly defined in static condition so as to obtain pertinent results.The Simulations have been realized on two completely different steering circuits, andthe results obtain are encouraging. Four test cases have been studied on a PremiumLancer LC 8x4 MD 11 with results differences inferior to 5% with tests. Two testcases have also been studied on a Premium 4x2 MD11 and have given results witherrors inferior to 7% compared to reality. Nevertheless it has been impossible toconfront the models with the reality due to delaying of testing because of theinternational financial crisis. Then the steering gear hydraulic path has been identifiedas an influencing parameter on the oil temperature and has been approximated. Aclose work with the suppliers must lead in the future to a better knowledge of thatcomponent. Finally the influence of the surrounding temperature has also beenhighlighted. The next step is to consider the fan strategy in the modelling of steeringcircuit so as to enhance the accuracy of the model. Finally it is necessary to confrontthe simulation to the reality in order to validate the modelling method.