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Abstract



Faster Locking Differential Through Active Brake-Control


When a vehicle with wheels aligned in pairs turn, the wheel traveling around the outside of the curve has to roll farther than the wheel on the inside. This means that some sort of device must must be used to allow the drive wheels to rotate at different speeds to prevent wear on the tires. This is usually a mechanical device where the input rotation controls the sum of the two output rotations, this is known as a differential. This solution however has some shortcomings, the biggest one is that the total amount of force that can be transferred between the tires and the road surface is limited by the tire with the least traction. In slippery conditions this can be a big problem since it only takes one wheel to lose traction in order to prevent the vehicle from accelerating. In this thesis a locking differential is used to overcome this shortcoming, this gives the driver the option to lock the shafts of the driving wheels together. This is done by pushing two cogwheels, one attached to each shaft, together. The aim of this thesis is to shorten the lock- and unlock-time of the locking differential by aligning the cogwheels using the service brakes and available sensors. The results were evaluated by implementing the software in a truck and doing test runs on Scanias test track. These tests showed that the system greatly improved both lock- and unlock-times but at cost of lower driver comfort. With additional work with some fine tuning of the system, the overall performance could probably be increased even more.

Joakim Hallqvist

2014

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