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Styrtransmission för bandfordon
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
2006 (Swedish)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Steering transmission for a tracked vehicle (English)
Abstract [en]

The purpose of this master thesis is to construct a steering transmission, for a tracked

vehicle, containing two hydraulic circuits which are connected. The steering

transmission should be mechanical to avoid steer-by-wire.

BAE Systems Hägglunds has in an earlier study examined a system with two hydraulic

pumps and one hydraulic motor, but the safety of the system wasn’t sufficient.

To achieve sufficient redundancy there must be two hydraulic motors, which are

controlled separately. When the two systems are connected in one point, this point is a

critical part of the system because it directly affects both circuits. If one of the hydraulic

circuits fails the other should be able to operate independently as a steering

transmission. This is possible by disconnecting the defect circuit with a tooth clutch.

Separating the systems can also be done with a differential. Using a differential means

that the use of a brake or a bidirectional no-back control is necessary to prevent the drive

shaft from going backwards.

The tracked vehicle should be able to make a pivot turn in less then 12 s, with a vehicle

weight of 17500 kg. That combined with lack of space set high demands on the

hydraulic system. The hydraulic components which are used must withstand pressure up

to 450 bar and flows up to 170 l/min. The hydraulic pumps must cope with the drive

circuit’s speed of 4400 rpm. The hydraulic pumps must have a variable displacement so

that the vehicle will be able to turn in both directions. The hydraulic motor have a fixed

displacement, this makes construction of the mechanical linkage from the steering wheel

to the hydraulic system easier. Push/pull wires will be used as linkage.

The system can easily be redimensioned to fit a heavier vehicle. It’s easy to shift the

concept to a differential style if any problems appear during testing. The system is a part

of a component test that will be carried out during 2006.

Abstract [sv]

I detta examensarbete konstrueras en komplett styrtransmission till ett bandfordon.

Systemet ska bestå av två hydraulkretsar som kopplas samman. Styrtransmissionen ska

vara helt mekanisk för att undvika ”steer-by-wire”.

BAE Systems Hägglunds har tidigare undersökt ett koncept bestående av två

hydraulpumpar och en hydraulmotor, men säkerheten i detta system var inte tillräcklig.

För att uppnå graden av redundans som krävs måste det finnas två hydraulmotorer som

kan styras oberoende av varandra. När hydraulkretsarna kopplas ihop i en punkt blir

denna en mycket kritisk detalj i systemet eftersom den direkt påverkar bägge kretsarna.

Om den ena hydraulkretsen havererar skall den andra obehindrat arbeta som

styrtransmission. Detta möjliggörs genom att koppla bort den trasiga kretsen med en

hydrauliskt styrd tandkoppling. Delningen av systemen kan även göras med en

differential. Då behövs en hydraulisk broms eller en tvåvägs backspärr som hindrar

drivaxeln från den trasiga hydraulkretsen att gå baklänges.

Kravet att klara en pivotsväng på mindre än 12 s, om bandfordonet väger 17500 kg,

kombinerat med bristen på utrymme i ett bandfordon medför att det ställs stora krav på

hydraulsystemet. De hydraulkomponenter som används måste klara tryck upp till 450

bar och flöden upp till 170 l/min. Hydraulpumparna måste klara drivkällans maximala

varvtal på 4400 rpm. För att svänga åt bägge håll krävs det att hydraulpumpen har ett

variabelt deplacement. Hydraulmotorn har ett fast deplacement, det gör konstruktionen

av det mekaniska styrlänkaget från ratten till hydraulsystemet enklare. Som styrlänkage

används push/pull-vajrar.

Styrsystemet kan enkelt dimensioneras om för att passa ett tyngre fordon. Det är enkelt

att skifta koncept till en differentiallösning om det framkommer problem under

provning.

Systemet är en del i ett komponentprov som kommer att utföras under 2006.

Place, publisher, year, edition, pages
2006.
Series
MMK 2006:36 MME 780
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-102003OAI: oai:DiVA.org:kth-102003DiVA: diva2:550278
External cooperation
BAE Systems Hägglunds,Hans Nordin
Uppsok
Technology
Supervisors
Examiners
Available from: 2012-09-06 Created: 2012-09-06 Last updated: 2012-09-06Bibliographically approved

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