This project was made for a final project for a class (SE 423) at the University of Illinois at Urbana-Champaign.
It is designed to sort US coins. The user presents the robot a coin, which will be identified. The robot will then drive a path, and release the coin at the appropriate location. Afterwards, it will drive back to the starting point to await another coin.
The basis of this is the car itself. It consists of a Texas Instruments F28379D Launchpad microcontroller board on top of a custom board developed by the professor. This large board features components to allow the F28379D to drive motors, as well as other components for various labs. This board also serves as the chassis to which everything is mounted, including the wheels, motors, and coin handling components. The layout of the powertrain are two motors driving wheels mounted to the back of the robot car, and one undriven swiveling caster wheel on the center of the front.
To this car, a plate of thin poly carbonate is mounted. This is stiffened using thin aluminum strips attached using 3M VHB double sided tape. To this, an industry standard arcade style electronic multi coin acceptor is mounted. This coin acceptor does all the necessary tests to determine which coin was inserted, and if it is a valid coin, will send a number of "pulses", or short the signal wire to ground a number of times. To the output of the coin acceptor, a chute is added to catch the inserted and validated coin. At the end of this chute is mounted a servomotor, which holds the coin in the end of the chute until the car is at the correct spot, at which point it will release the coin. At the front of the car, 3 microswitches are mounted. At each drop off station, there is a can or similar object, with which the car collides. These switches serve to tell the car where the can is, and if it is off center. If so, the car can then correct, allowing it to correct the errors from the dead reckoning navigation.
During operation, the car waits at the starting line until a coin is inserted into the coin acceptor. The acceptor identifies the coin. If it is invalid, it is rejected into the return. If it is valid, the acceptor sends pulses accordingly. (1 pulse for a nickle, 2 for a dime, 5 for a quarter). The coin then drops out the bottom of the acceptor, onto the chute, where it is stopped by the servo arm. The car drives to the first can, where it will use the front microswitches to detect the can. Once it is there, if the switch activated was not the center switch, the car will backup and turn slightly to correct, and try again. This will repeat until only the center switch is depressed by the can. At this point, if the coin is a nickle, the servo will rotate the arm to release the coin from the chute. Then, it will turn 90 degrees and continue onto the next can, where it will repeat the above process, but releasing only dimes. For the third can, it will release quarters there. After then, it will repeat the process, where it gets to the fourth can, or back to where it started (the path looks like a square). At that point, it will stop and wait for another coin.
Videos of Operation:
https://uofi.box.com/s/qqaez9k3bsntl9xba8nczwscwlwmzzct
https://uofi.box.com/s/cbfy6rrzdaoy7izkw560yavwy8jahrzp
Video explanation:
https://uofi.box.com/s/y07jf688ihowu8jscmppv2ncg9org0j1
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