Mechanical Overview
The mechanical design of the robot consisted of three major subsystems: the drive train, the bumpers, and the MINER transport system. The frame of the robot was constructed with laser cut Duron pieces, with layers connected by standoffs. We divided the robot into three layers: a bottom layer which contained the drive train and color sensor, a middle layer which contained the MINER funnel, electromagnet, and various circuit boards, and a top layer that contained the TIVA, SPUD, accelerometer, switches, indicator LED's, and IR sensor. The two 7.2 V batteries that powered the robot were mounted to the bottom layer using adjustable straps, allowing for both the lowest possible center of mass and easy access for replacement.
Drive Train
The drive train was powered by two Maxon motors with a 50:1 gear reduction. The motors were attached to the drive shaft via a flexible coupling to reduce side loads caused by shaft misalignment. We used two skate wheels as drive wheels and a ball caster as the third point of contact with the field. The wheels were positioned in the center of the robot to allow it to turn on a dime. We mounted encoders to the back of each motor to allow for PID position and velocity control. A color sensor was also mounted underneath the drive train facing downward, allowing our robot to know which square on the grid it was in.
BumpersWe place bumpers on the front and back of the robot to detect collisions. Each bumper consisted of a piece of Duron mounted to a lightweight hinge. A limit switch was placed behind the panel so that causing the hinge to fold downward resulted in a switch press. Gray foam was attached to the outside of the bumper to dampen collisions.
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Localization
In order for the robot to know its position and orientation on the field at any given time, a color sensor and accelerometer were used. The color sensor was mounted on the bottom of the robot facing downward, while the accelerometer was mounted to a plate on the top level.
MINER Transport
In order to allow for misalignment of the robot with the MINER, the robot was constructed with a large cutout in the front containing a funnel to guide the beacon to the center of the robot. A beam break sensor was embedded into this funnel to detect whether or not a MINER was inside the cutout. To secure the MINER during transport, we mounted a 5V electromagnet to the center of the robot such that it contacted the ferrous MINER flange when it was fully within the robot. Finally, in order to locate the MINER, we attached an IR sensor to a 3D printed mount that both secured the IR transistor and served as a shroud to narrow the detection range for more precise alignment.