Styrtransmission för bandfordon
The purpose of this master thesis is to construct a steering transmission, for a trackedvehicle, containing two hydraulic circuits which are connected. The steeringtransmission should be mechanical to avoid steer-by-wire.BAE Systems Hägglunds has in an earlier study examined a system with two hydraulicpumps and one hydraulic motor, but the safety of the system wasn?t sufficient.To achieve sufficient redundancy there must be two hydraulic motors, which arecontrolled separately. When the two systems are connected in one point, this point is acritical part of the system because it directly affects both circuits. If one of the hydrauliccircuits fails the other should be able to operate independently as a steeringtransmission. 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 meansthat the use of a brake or a bidirectional no-back control is necessary to prevent the driveshaft from going backwards.The tracked vehicle should be able to make a pivot turn in less then 12 s, with a vehicleweight of 17500 kg. That combined with lack of space set high demands on thehydraulic system. The hydraulic components which are used must withstand pressure upto 450 bar and flows up to 170 l/min. The hydraulic pumps must cope with the drivecircuit?s speed of 4400 rpm. The hydraulic pumps must have a variable displacement sothat the vehicle will be able to turn in both directions. The hydraulic motor have a fixeddisplacement, this makes construction of the mechanical linkage from the steering wheelto 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 theconcept to a differential style if any problems appear during testing. The system is a partof a component test that will be carried out during 2006.