Simulation of self induced oscillations in four wheel drive train
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
In 1992 the Haldex group bought Sigvard Johansson’s patent from 1988. The original design is based on a rotational speed difference dependent pump that creates a hydraulic pressure to engage the clutch that locks up the rotational difference. From the originally rather simple solution this has developed to gain in controllability and engagement speed to become a market leading system. The traction division of the Haldex group was recently sold to BorgWarner. When designing a four wheel drive system in a car the goal is to get the desired speed on all four wheels. For example, when cornering on pavement the requested speed of the rear wheels is lower than the speed of the front wheels, which requires the coupling between the differentials to allow speed differences. When trying to maintain a controlled slip during specific conditions vibrations may occur. The goal is to foresee when this will happen, create greater understanding and possibilities to avoid them. In later years the benefits with simulation has become more and more obvious, what to expect from a physical system and when to expect it. This is one of the major differences between high-end products and those built in a shed. The goals of this thesis are to •Create a dynamics model of the drive train. •Verify the simulated results and improve the simulation based on the testing results. •Make it possible to foresee when dynamic problems will occur and how to avoid them. A simplified model of the drive train was created in Simulink. Parts like drive shafts are assumed to be constant torsion beams and other components stiff; moment of inertia and damping were measured and taken in consideration. Friction models with various lubricants were created and implemented into the simulation. Both simulation and verification in testing rig were performed with data and driving case taken from a real car. The driving case was also used in a testing rig in order to verify the results and improve the simulation model. To be able to compare results from both methods the simulation was modified to the configuration of the rig. Thermal and friction models have been confirmed in rig testing and vibrations in the drive train have been linked to variations in sliding velocity. However when simulating a complex system, like the drive train of a car, there are lots of factors that affects vibrations, neither does rig testing with the very same setup give the same result every time. The simulation time is a big success since it takes less than a minute to simulate a simple drive case and if the user has an overview of the programming changes can be made easily without complications or error messages. The simulation instrument can be used to initially evaluate a new drive train setup or new friction characteristics of a friction system.
Place, publisher, year, edition, pages
2011. , 54 p.
Teknik, LSC, Haldex, lameller, koppling, vibrationer, simulink
IdentifiersURN: urn:nbn:se:ltu:diva-55576Local ID: c6da0107-7fe9-4497-8141-46e5a62c1779OAI: oai:DiVA.org:ltu-55576DiVA: diva2:1028960
Subject / course
Student thesis, at least 30 credits
Mechanical Engineering, master's level
Validerat; 20110524 (anonymous)2016-10-042016-10-04Bibliographically approved