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|Here at the University of Alabama we take two design classes, ME489 and ME490. In ME490 a team of students must design and build something that a company needs to solve an engineering problem. In order to participate in the program, the client must pay a $750 fee to the student design clinic to help cover overhead of the program. Our project was unusual in that our client was a comic book store that needed a storefront display.
We decided that in order to keep costs down we would use stepper motors instead of servo systems. This eliminated all the feedback sensors that we would need for each motor. It also meant that we could use a digital i/o board instead of a more expensive analog board. Each arm has 3 independent axes of movement (rotation, elevation, and bending at the elbow). The head can rotate as well, giving the robot 7 independent movement axes.
We used a simple 286-16 with 640k of memory to control the stepper motors. This helped keep costs down and provided more than enough computing power to run the software. All software was written in Turbo C++ for DOS. To help simplify moving the robot, a very simple script language was used. A teaching program was developed to write the scripts. To generate a script, the robot was moved one motor at a time using a simple interface until it was in the desired position. Once this position was attained, the user tells the robot to learn that position and the required movements are then calculated to move the robot from the last position learned (or the starting position) to the new learned position. There is no limit to the number of positions that can be included in a script. Once the final position has been learned, the program will determine its position relative to the neutral starting position and then return the apparatus to "zero".
I think the project turned out very well. I have nicknamed him "Lurch" because he is almost 7 feel tall and never seems to smile! If you can think of a better name, email me and let me know!