The Bug. Things that Think Spring Brandon Leffert Erich Hacker Andrew Boehm

Transcription

1 The Bug Things that Think Spring 2007 Brandon Leffert Erich Hacker Andrew Boehm

2 The Bug: A Computational Automaton For the computational automata project, our team chose to make a mobile crawler entitled The Bug. This bug would walk around, responding to its surroundings. We chose light as the best medium to respond to, as it is a bug. The project went through several development phases. First, our planning phase involved designing the actual bug as well as discussing through the programming. Once the planning was complete, prototyping could begin. This automaton consisted of two main parts: the physical element and the computational element. We started the physical element out with a simple wood prototype with plastic legs made in the rapid prototyper. The prototype provided insight on design capabilities and correct movement of the legs. The following is the prototype model. The prototype showed the weaknesses of the ABS-plastic that is used by the rapid prototyper. As a result, the designed was modified to strengthen the axels to support the weight. The drive system between the motors and gears was also changed from a friction drive system with belts to a positive drive system with sprockets and chains. Once the prototype proved the design concept, several other prototypes of the legs and gears were created to display the capacity of the strengthened axels and backings on the legs themselves. When we were satisfied that the design was complete we started work on the final project. A close-up of the final project design is shown to the right.

3 The plastic body took forty-four hours to produce on the rapid prototyper. However, due to the fragility of the plastic from the prototyper, all of the axels on the prototyped product broke even though they were redesigned to be strengthened. A rather large aesthetic aspect of the body did not even form in the prototyper. As a result of the unfortunate breaking and faulty modeling, each axel was further reinforced by having small nails driven through them. The main drive axels were upgraded to wood dowels to support the torque needed to turn the gear train. Even with all the modifications and reinforcing, every time any weight was placed on the legs the gears would bind up and not move. As a result, we used a remote control car to act as the movement system of the bug. The cricket was spliced into the motors of the car for control, and the remote control part of the car was removed so the crickets themselves controlled the car. We utilized two crickets for the final product; one cricket controlled the sensors and the bug motors and the other controlled the movement of the car. The sensor cricket would send the same information used to drive the legs via IR to the second cricket that would control the car. Light sensors were placed on the top of the bug at the front and back. The bug was programmed to follow the light, and if both sensors saw the same amount of light it would sit comfortably still. If there was a shadow in front of the bug, it would do a five point turn and reverse direction, running away from the shadow. The following picture illustrates the bug in all its glory:

4 The picture shows the implementation and integration of all the systems on the bug. The remote control car gives the illusion that the bug is walking on its own when in fact it is the car that provides the motion. Throughout this project, there were many aspects that could have been changed to better ensure success. As many groups will say, to improve the project we could have started the final design sooner than we did. We had thought, through all of the prototyping that the final bug would have worked better than it had. The rapid-prototyper was not nearly as reliable as we had hoped, however. If the design changed earlier or our team had more time, we could have replaced all of the ABS-plastic prototyped gears with acrylic plastic gears; gears made out of acrylic have a much lower friction factor between them and do not break as easily, as one of our smaller gears had. Also, the Lego motors we used were just barely strong enough to move the legs. As a result, the gears were greased down extremely to improve their ease of movement, but this could have not been an issue with stronger motors. The legs themselves were strong enough to support the weight of the bug, but we could have improved them by making them out of a more inelastic material to prevent binding of the gears. Throughout this project, though there were many aspects that needed to be redesigned or rebuilt, overall The Bug turned out to be a marvelous success. It performed almost exactly as intended with few modifications from the original design. The sensors saw what they where supposed to see and the bug responded in the correct manner.

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