Tuesday, September 25, 2012

What I Do at Work

This summer I have been working at a small company called Wells Research doing engineering design work. The company builds testing equipment for the optics industry.  The stuff that I am working on is really cool and I wanted to share a little about my experiences with the world.

Currently, I am working on a project to control a motor.  The motor controls the y position of a linear stage. Normally this setup is used to move a camera back and forth to adjust the focus.  Over the past month, I have been able to successfully model the position of the lens with MatLAB code.  The input of the system is kind of an odd function.  Instead introducing a force, the feedback control is done by inputting a trapezoidal or triangular velocity profile into the system's state space.  The input is essentially a curve that accelerates to a certain speed, holds that speed and then decelerates.  This tells the dynamic system to move a precise distance and then decelerate rapidly. It works quite well.

The biggest problem that I had was determining how the computer sends a signal to the motor.  There are constants that are defined in the program and the motor has a specific code developed by the company that gives it commands.  Determining what number to input in order to get a specific result was rather tricky, but eventually, after a lot of testing, I was able to get a suitable result.

The precise motor position was analyzed with an eddy current sensor.  I thought it was rather cool.  I attached a steel block to the top of the lens mount and then faced the sensor towards the block.  The sensor can read between 0 and 2 mm extremely precisely and the result can be measured with an oscilloscope and then converted to millimeters.  I really enjoyed testing and analyzing this system.  It was a lot of fun!

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