Prototype design for autonomous vehicle

University essay from KTH/Maskinkonstruktion (Inst.); KTH/Maskinkonstruktion (Inst.)


This thesis describes the mechanical design of a prototype vehicle developed for a company located in California. The project was based on an earlier vehicle located at KTH, Transport Labs, and investigated if the existing concept for the vehicle would work as a concept for an autonomous prototype, with focus on component layout and increased forces. The design of the vehicle is based on a concept with a carbon fiber bottom plate, two separate suspension modules with electric hub motors and steer by wire. In addition a steering interface, seats and a roll cage is added to the base. Quadrant symmetric design and four wheel steering/drive makes the vehicle move equally good forward and reverse. The steering is controlled by individual rotating actuators mounted at each wheel, meaning that the vehicle, apart from acquiring a low turning radius also can angle the wheel in the same direction and drive with so called crab steer where the car is moving sideways without rotating itself. The brake system contains a regular manual hydraulic brake system in parallel with an autonomous brake system. The project was started by generating a list of requirements. This was then considered when doing the design in CAD (Solid Edge). The design was validated with ADAMS (MBS) and ANSYS Workbench (FEA). The majority of the project was carried out in Sweden at KTH where the driveline of the vehicle was designed and assembled. The driveline was then transported to California where the vehicle was finalized and tested. The test carried out indicated that the concept was working as a prototype but that some of the components needed to be upgraded. All tests needed was not carried out which led to that the maximum speed of the vehicle was limited to 40 km/h Further durability-, and high load tests will be carried out in order to, with suitable safety, raise the maximum speed. The maximum steering angle of each wheel acquired was 23 degrees that, with four wheel steering, means an effective steering angle of 46 degrees. The cars minimum turning radius was around 5 meters.

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