I’ve had an old MiniMover5 trainer arm (1982) for about a year now, and hadn’t done nearly enough to get it up and running. I also just took an electromechanical systems course, and to motivate myself to make some progress (and get some help) I was able to make it into a group final project:
Basically we take the accelerometer, button, and sensor bar data from a Nintendo Wiimote, transferred over Bluetooth to a laptop, through which the user moves a virtual point in space. The computer finds an inverse kinematic solution for the arm to try to reach that point. If the point is outside of the arm’s workspace, the Wiimote even vibrates!
Anyway, the laptop commands the appropriate joint angles over a Pololu USB to Serial adapter and a Pololu Micro Serial Servo Controller, to six HS-311 servos. The arm originally used stepper motors, but they had gotten kind of wonky and the control electronics were shot.
Each servo has been modified for continuous rotation, and their potentiometers have been moved to the actual joints on the arm they control. This was really nice, since the joints are driven by a redundant cable mechanism from motors at the base. That means if you adjust the shoulder, without compensating with the elbow, two wrist, and hand motors, all the joints move in unintended ways. With the potentiometers measuring the actual joint angles, not just the motor positions, when we command one joint to move, the other motors correct for the unintended effects, and drive all the other joints to maintain their positions.
We also built a huge (world’s largest?) “sensor bar” out of a science-fair presentation board, and 50 IR LED’s, which looks really cool on a webcam viewed through an IR-pass filter:
We just presented it to the class this morning, and one of my group members felt the need to post a video of our work on you tube, check it out:
It still needs a lot of work, particularly faster motors (it would be nice to keep the servo electronics). Then tracks to make it mobile. Then wireless control. Then true autonomy. Then artificial intelligence…