SOURCE Week 3
Posted by Nicole Sharp on 21 June 2005 at 13:10I'm learning that getting an experiment ready is a long line of small successes that don't sound like much when you describe them to anyone else. All the same, things are moving along here in Glennan 809.
Having gotten LabView installed and a command line to the motion controller created (#), I started work on getting the existing DAQ hardware to communicate with LabView and its components. No go. At the suggestion of Dr. White, I invaded the undergraduate lab and swiped some NI data acquisition hardware and installed it. I think it's set up properly, but I only did a cursory test.
From there, I started to plan out my hardware and software to control and automate the experiment--or, as my sister put it, "to play God". Dr. White nixed the idea of sending a program to the motion controller and having it execute from the device's memory, so I started working on writing a LabView program that accepts basic input and generates the necessary commands for the motion controller. The idea is that, once I've written the program, I shouldn't have to remember anything about the motion controller's programming language.
After many baby steps, I've got a LabView program (with quite a complicated VI diagram) that accepts the X and Y coordinates (in inches) of the desired final position, and the number of data points to be taken. The program then divides the move into increments, executes each one with a pause between each, and reports the position of the motion controller at each position. Today I finally got the programming for the arrays that save the intermediate positions worked out, and writing those to a file should be easy from here. All of this means that I'm ready to start figuring out how to control the data acquisition through LabView.
There's really just one more major obstacle, I think, and that's a problem with the motion controller. I can tell it where to go and it will move and report that it's pretty close to where I told it to be. But, if I actually measure the distance it's moved myself, the two values are almost always vastly (as far as this experiment is concerned) different. Based on the sounds I'm hearing sometimes when the motor runs--especially when I slow the speed down--I suspect that the engines don't actually have enough torque to overcome the full inertia of the gantry they have to move. This leaves me with a bit of a sticky situation. I don't have money for larger motors, and I don't really want to take somebody else's motion controller apart to try to make it lighter. It's sort of the bridge I've been avoiding contemplating, but the problem with making progress on other things is that I come closer to having nothing but that bridge left.