Cerberus was constructed using a standard VEX Robotics kit, 3mm particleboard and 4mm foam core poster board. The VEX kit and one sheet of 30cm by 30cm sheet of particle board was provided Saint Mary's University. Additional components and materials were purchased with team budgets.
Chassis
The chassis is constructed solely from VEX components. The original design utilized a sprocket to drive the chain which would drive the wheels. This concept was abandoned as damage to chain would immobilize the robot. THe current desgin employs a reduction gear to power the rear axles. If the chain breaks in this scenario only the front wheel on the affected side will lose power.
The rear wheels are larger than the front wheels on Cerberus as the standard kit provides on set of each. The front and rear wheels are connected by a chain to give the robot all wheel drive. Different sized sprockets are used in order that the front and rear wheels provide the same velocity.
Arm and Extension Boom
The extension boom is a laminated I-beam constructed from foam core poster board. This is a cost effective solution that increases the range of the claw without sacrificing strength. Testing of the prototype beam has proven with an excessive load on the fully extended boom will tip the robot long before the I-beam will bend.
The extension boom is mounted to the vertical arm by a large gear driven by a reduction and worm gears. This configuration provides a smooth controlled movement of the extension boom assembly. The arm only has one range of motion. This adequate for removing the probes from the storage rack and deploying the probes. This motion will also be effective with the chassis on a slope in relation to the target soil as long as top of the vertical arm rises above the crest of the slope.
Claw and Carrier
The claw has three pincers located 60 degrees apart. The pincers rely on elastic bands for the closing force. Large pads with high friction sponge grippers provide a large surface area to grasp the probes thus reducing the time needed for alignment. The sponge grippers act like a suspension system and allow the probe limited movement to prevent damaging the needle. The pincers pads can be replaced with different attachments to increase versitility of Cerberus.
The claw is mounted in a carrier that proveds rotational motion. The claw can be rotated bringing each pincer into the ready position. This concept can be modified to allow for a claw more pincers thus increasing probe carrying capacity.
Production
