I need to do an impressive final physics project. This is due in June, so I've got time. But, I do not want to waste it! So, I think I've come up with a possible topic and method. The important thing is that we are testing. It can't just be building something. You've got to be testing for something; the presence of something, the effect of something, etc. Many trials should be run.
The effects of mechanical resonance on the accuracy and repeatability of a stepping motor.
Resonance is a phenomenon which has always intrigued and mystified me, this is a great chance to explore I think.
So basically I will make a linear positioning system, a stage, leadscrew driven and a stepper motor drives the screw. I will make all nuts antibacklash, so mechanical repeatability will be excellent. Since a stepper driven system is usually open loop, the motor is the biggest source of possible error. So, I will use a .0001" dial indicator to make a zero point. Then, I will write a program to drive the motor. The program will last about 15 miniutes, will have sporatic negative and positive accelerations, a little of everything. I will write the program to deliberately target the resonance zones of most stepper motors. Then, finally after 15 minutes of motor rigor, I will have the motor return to the original zero position. This will depress the plunger of the .0001" dial indicator, and the indicator should return right to zero. I will document my findings. I know that when the motor is in it's natural frequency range while operating, it makes noise. I suspect it stalls a tiny bit too, this is a way to find out how much. There is no way to know on the fly unless an encoder was used.
I will try several different motors. Higher end American brands, generic motors, some tiny motors, some large motors. Then I will try once more with a mechanical damper to suppress resonance, recording any improvements. Then once more with super high end stepper drives, which electronically suppress resonance. The first drive is a 50 dollar hobby level drive. The second drive to test is a 550 dollar Pacific Scientific, so it should offer a contrast.
My friend has just shown me a soundcard oscilloscope. You literally use your soundcard for dual channel operation with high frequency capacity. I can make a little circuit to bring down the voltage to appropriate levels. I could record the back EMF of the motor while it resonates, this should also allow me to compare the effects that the dampers have on the natural frequencies of the motor.
My lab report needs to be a good 30 pages, so this should fill it.