Robots make good toys!    

Completing the usual “welcome to the job” training, my first task as an intern at Labman has been to test and evaluate the Epson E2L SCARA robot.

A key job that the robot will have to do when it is ultimately incorporated into the system is to draw the 15*17 Lissajous pattern.

Lissajous Pattern (or, What I Made My Robot Draw)

The Lissajous pattern is created by two sine waves, one for the X coordinate and one for the Y. By varying the frequencies and phase of the two waves, one can vary the pattern drawn. Using some sample code from the robot’s suppliers, I set out to make the robot draw a variety of patterns.
Before I could do this, however, I needed a whistle-stop tour of the Labman workshop, to fabricate a pen-holder for the robot’s arm. I machined a small grooved cylinder to hold the pen, and a larger cylinder to fit the robot arm. These two parts were joined together with a short spring and retaining screws. The springs ensured that the pen was able to rest on paper with the ideal amount of force. Along the way I gained more experience using a variety of machine tools.

The required cycle time for the machine to draw the pattern is <20 seconds. However, due to the sharp corners in the 15*17 Lissajous pattern, the speed that the robot can be driven at is limited, due to the necessity of sudden acceleration/deceleration at the corners of the pattern. I tested a number of different approximations to the pattern, gradually increasing the speed to find the optimal trade-off between shortest cycle time and most accurate reproduction of the pattern. My parameters will be used in the program for the robot in the completed project.

Video to follow shortly!

This week has been a lot of fun to start my summer at Labman. I have learnt and will continue to learn a lot!

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