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lamboom

Sine Wave motion

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Hi I'm wondering if anyone has been successful using stepper motor actuators, designed for simple positioning (like IAI RCP2 actuators), to move in a simple sine wave motion .. back and forth .. and, be able to select various strokes and frequencies.

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We did a setup using a wave generator for testing apps, the generator is not a very cheap solution but you can set various frequencies and can change from sine to square wave. We did acceleration tests with the square wave, accelerometers measured backlash and we charted acceleration, current, and actual position vs command position. If you are working in a lab, not much can outperform that setup for simplicity sake. Assuming your stepper motor has a controller, the stroke can be set up in there, and then the generator does the rest via 0-10v or a variety of scaled analog signals. http://www.bitscope.com/software/dso/guide/1.3/?p=wavegen

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Thanks for the info .. interestingly, the application is for a wave generator ... ocean waves, in a small tank ... & yes, the RCP2 actuator has a pulse motor .. however the driver is not an analog input type... that would be too easy. It looks like I have to use something like the Mitsubishi FX2N-10GM? That has a programmable pulse train output. AIA suggested using a PCON-PO driver for the actuator. We are still looking into a solution. Certainly there are solutions to produce sine wave motions (you couldn't draw a circle without that ability. But, I'm not using that type of equipment .. I'm probably coming at this way wrong.. but, that's OK ... it's part of the learning curve. I want to see if I can do it without using integrated path equipment. The IAI actuator and it's controller (not the PCON) was designed to move from A to B in a trapezoid motion. I care not about "positioning" .. just the movement ..a sine wave. I love that wave generator you used! Edited by lamboom

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We have a motion controller that can generate sine waves and we have a stepper motor output. See the step and direction, QST, module. http://www.deltamotion.com/products/motion/rmc100/

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This would work for an app if the actuator has limit switches which will be used to enable fwd/reverse. I have also used a programmable relay to do the fwd/rev portion and then count the number of strokes for a test. Most drives and controllers have an accel/decel function which will "curve off" the ends of the linear motion. If you combine that with the S-curve adjustment, you can make a pretty fair sine wave as well. I didn't mention it because you said you need to change waveform on a regular basis and it would become a tedious thing to do this way. But example, if you have a motion that lasts 20 seconds. 10 seconds of that is above the zero line of your scale, so set the decel and accel for about 1/3 of that time, so the ramp up will now angle off the bottom and top of the wave. Now if you about double that accel/decel time and put that in as your s-curve time, it will smooth out the changes and make things look much more like a sine wave. You can play with this and see what kind of results you get till you get something a little more flexible in. BTW, eaton (CH) ELC has a pretty inexpensive controller that has pulse output.

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Thanks for the info on Eaton/Cutler Hammer ... I'll look into it .. An' you are quite correct the "s-curve" modifications aren't gonna do it. I wonder if there's a controller out there that takes an analog signal .. converts it to a pulse train .. then drives a stepper motor in an actuator .. A lot like todays hydraulic actuators with position feedback .. the servo amplifier gets an analog waveform, then drives a servo valve... and the actuator does what the waveform looks like (as best it can...

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Hi again.. do you know of a PLC.. or controller that could communicate with the RCP2 actuator by IAI... and... here's the hard part.. accept an analog signal? I don't think IAI has anything that can input an analog signal. Edited by lamboom

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