When you think of an industrial robot, you may picture the very capable six-axis variety welding a car body together, but there are, of course, a variety of styles from which to choose. One such robot is known as a SCARA, or Selective Compliance Assembly Robot Arm. These robots themselves come in several styles, and use a pair of motors to control the X/Y position of an end effector that itself may move in the Z direction and possibly rotate itself.
While still in the prototype stages, electromechanical engineer and robotics aficionado “Proto G” has put together his own little SCARA setup, employiing a pair of DYNAMIXEL continuous rotation servos. These are arranged hub-to-hub to allow the arm to swing rapidly in 360 degrees.
Unlike what are normally (and perhaps incorrectly) termed continuous rotation servos, with angular feedback removed, the devices he’s using can still read their angular position while making full revolutions. They also have onboard PID control, meaning that while his setup moves at a speed that’s difficult to track with the naked eye (the motors are capable of 470 RPM rotation), after bouncing around, the arms do eventually settle into the correct position.
Hardware includes custom linkages that Proto G plans to share in an upcoming video, and carbon fiber rods that form the bulk of the linkage-arms. He’s using an OpenCM9.04 board for control, which conveniently features plug-in mounting points for the servos he’s using. These motors can even be daisy-chained together as needed, further simplifying wiring required.
Be sure to view it in action in the video below, or check out his color sorting delta robot for another impressive project by “Mr. G” that’s much further along in its development.