Before doing any machine work, the first step is use a computer aided design program, CAD, so that different types of changes can be made before having the final work done. The base chassis was modeled on the computer, so that all of the developers can see what the final product will look like when it is finished. Below are CAD images of what changes we wanted to make to the platform to add our DGPS, compass, computer, custom electronics, power distribution circuitry, etc. The CAD work done here was created by Chase Hansel. The CAD images also take into account the placement of the SICK LIDAR on the front of the vehicle.

  Once all project leaders were satisfied with the work Chase did, we sent off the wheel chair chassis and CAD files to the machine shop to have the modifications made. In addition to what is seen in the CAD images is the addition of a pole in the center of the vehicle to mount the DGPS antenna, camera, and digital compass. The pole and additional metal added are made from aluminum. The reason for using aluminum is because it us non-ferrous and will not interfere with our sensors. The DGPS antenna and compass get mounted on the pole, so that they are as far away as possible from other electronics that may interfere with it.

  One more step that needed to be done is the mounting of the magnetic encoders on the wheels. Unfortunately, the space between the motor gear box and the wheel was not wide enough to fit the encoder ring on the axle and reader above it. To resolve this issue, a quarter inch layer on the plastic rim of the wheel was removed. Two levels were cut out, one to fit the encoder ring on, and then a deeper level around the ring to make room for the reader. This worked out very well and everything fit perfectly. Note: Make sure to check the encoder ring periodically to make sure it has not cracked. Since it is placed on a plastic wheel and not the metal axle, it has more stress forces placed on it, which may lead to breaks. Additional magnetic rings are available for replacement.

  The final steps in the chassis modifications was the creation of an electronics drawer, and computer mount. The electronics drawer is mounted on the back of the vehicle, and contains all custom circuits, power distribution components, and has all cable connections. On the back panel of the drawer are power switches for turning the vehicle on and off. The computer mount is made out of lexand and is mounted on the back section of Calculon. It was made four inches high, so that additional electronics and excess cables can be stored underneath the notebook computer.