5. Tuning
Once the electronics have been assembled and mounted on the robot, it is necessary to calibrate the creature. Start by angling the infrared emitter and detector about 30 degrees away from the robot's direction of travel. Carefully align the emitter and detector so that they point exactly parallel to each other. Then turn the robot on by pushing the "Power" switch up while leaving the "Level" switch in the deactivated down position. Check to see that robot runs forward when it is in an open space. If the red obstacle detection indicator is always on when you put the robot on the floor, tilt the IR components slightly upwards until the light goes off. Next, hold the robot and move it to within 8" of an obstacle. Verify that the red LED lights up and that the robot's motor runs in reverse in this situation.
If you now let the creature loose, it should try to avoid things in its path. Muramator works best on wood or smooth tiled floors; it has a hard time plowing through carpeting. If it seems to lurch a lot or has trouble turning, shift the batteries forward or back to change the creature's balance. At this point, you might try designing an obstacle course for the vehicle to see what it can and can not do. For instance, if it encounters an obstacle which juts out, such as a convex corner, it will swerve away from it but never come back toward it. It has no of memory which direction it used to be travelling so it can not get back on track in this case. You might also want to experimentally change the direction the IR components, or purposely mis-align them, to see how these parameters alter the creature's behavior.
Next switch in the second layer of control by sliding the "Level" switch forward. Start with both potentiometers midway through their ranges by making the arrows on the dials point toward the edge of the circuit board. If you keep Muramator in a large open area, the green LED should flash at regular intervals. When this light is on, the robot should perform some sort of spin. Once the circuitry appears to be working properly, adjust the "Forward" dial until the robot goes about 8" between turns. Then adjust the "Turn" dial so that the robot makes about 3/4 of a revolution (270 degrees) every time it turns. Muramator should now not only avoid objects, but turn around if it hasn't seen anything in a while. Together, these reflexes make it follow along walls and circle any post-like objects it sees.
Changing the values of these two potentiometers can produce noticeably different results as shown in the paths above. You can explore these interactions with your own robot, or you might try writing a computer graphics simulation of the events. Notice, as shown on the right, if the turn timer is set for too long an interval, the robot will only regain the wall after a number of turns. If the obstacle had been a post rather than a corner, the robot might not have found it again. On the other hand, consider the scene on the left in which the travel distance is set too long. Here, the robot may wander off into the middle of the room when it encounters a corner. The first travel leg after an AVOID turn is often longer than the succeeding ones. Thus, even though the robot heads back toward the wall, it will be too far away to see the obstacle again. This, however, can be a useful feature if there is more than one robot in the world. With this tuning, corners become a natural meeting place for creatures.
Another interesting set-up involving two identical vehicles is shown above. Here, the travel distances are set very short and the turn angle is set to 180 degrees. If you send the two robots head-to-head, they will veer off from each other and then turn around for another pass. Robot jousting! It helps if you cover both opponents with commercially available Scotch-lite retro-reflective tape. This increases the sighting distance for other robots to about 18". To achieve the maximum range, make sure each robot's infrared beam is pointing level with respect to the floor. This is just one example of how robots can interact in the world. With a larger number of individuals, there may be even more interesting patterns.
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