robotmatrix.org

 Introduction

• Objective: This arm uses the wrist and gripper assembly, and maneuvers a plastic pipette (which is something like an eyedropper) between different flasks and test tubes to mix solutions with different colors.
• Parts:
  • Robix Rascal Robot Kit/Construction Set
  • The solutions are water and food coloring.
  • The glassware and pipette are available at chemistry supply stores. Other glassware or plastic-ware may be used as well, of course, and a large plastic eyedropper may be substituted for the pipette.
  • The test tubes are .3? (8 mm) in inner diameter.
  • Stands.
• To learn: This project shows the repeatability of the system and servo drive tuning.

 Step 1: Assemble and build the Chemist Robot Body and Muscle

 Step 2: Chemist Robot Teaching and Macro Programming

When programming the chemist robot ? in particular, the lifting and lowering motion in order to insert the pipette (it's like a large eye dropper) into the flask and pick up some liquid, it is recommended to move servos 1, 2, 3 and 4 in a single move. This can keep the pipette vertical as it moves up and down, minimizes side motion and eliminates possible pipette rotation. Do this by teaching the top point of the motion and then the bottom point, with axes 1-4.

To further reduce the side movement, you can add one or more additional points between the top and bottom points. To achieve this, you will need to move to each point on the way down, un-squeeze the dropper, and then move to each point, in reverse order, on the way up again. You may want to make the points into macros for convenience.

 Step 3: Servo Drive Tuning

You can tune the servo to reduce oscillation by adjusting accelerations, speeds, and joint tightness. Once the tuning is successful, thus reduces the oscillation, it however does not affect the positional accuracy of the robot.