Electronic Gearing

[Mo_AB_4EVER]

Hi everybody, this is my first post on this forum, I hope you can help me with this one! Does anyone know a reliable and easy method for gearing to axes electronically with a servo drive? Basically, what I want to do is buy a servo drive with two encoders: One on the servo motor itself and one on a "master" shaft. The Servo motor shaft (later called the slave shaft) will follow the rotation (forward and reverse) of the Master shaft. The Master shaft is already controlled by a motor, but that does not change the project. It could as well be turned by hand, the slave shaft should respond. I need to be able to jog the slave shaft and to "enable/disable" the electronic gearing as needed. I also want to be able to change the gearing ratio easily, with a keypad o simple visual basic program or some other easy way. The motor power will be under 1HP and the 1000 pulses/rev on the master encoder should be more than enough. I should be kept in mind that I want to do electronic gearing for now, but later I could want to do more "acrobatic" stuff with it. But much later. So, does anyone have a good idea?

[GerryM]

Yes, electronic gearing is standard in most motion controllers. Your setup sounds reasonable and correct. One thing to point out is the gear ratio. Your slave should move 1:1 or less than your master if you want nice smooth motion. If you have a large ratio you can get jumpy movements on the slave. In other words say you want the slave to move 5 counts per every 1 count of the master, its movements may not be that smooth. I had a tapping application once on a home brew piece of equipment. I tied the rotational movement with the axial movement electronically. I was using the axial movement as the master, and I experienced jerky motion. It was because this axis moved much slower, so for every 1 count of error it was multiplied on the rotational movement. So I switched which was the master and the motion was smooth. I used the Emerson drives with an MEI motion controller. I believe Emerson, or Control Techniques, sells a drive with an add on card that will do both the motion control and the drive function, similar to this FM-3. If you want maximum flexibility then go with an external motion controller.

[Mo_AB_4EVER]

The Slave Shaft will move slower than the master, that is for sure, and also all speeds are relatively slow, like under 20 rpm. I know most motion controllers do electronic gearing, but what I mainly need is a pointer for buying one cheap that works good. The only motion controller that I ever worked with are Galil servo amps and Indramat feeders for stamping applications. Anyone knows where I could find (In Canada) used or refurbished equipment? I know I could find tons on ebay, but since I don't know what I should look for, this could take a while... Thanks for your help! Mo

[Peter Nachtwey]

The trick is to have virtual masters and gear them. Then each each axis tries to follow its own virtual master. This can be done whenever both axes are controlled from the same controller. True gearing should only be done when the motion controller doesn't have control over the master axis.

[OIDMBTRTECH]

You might take a look at the products from Contrex. www.contrexinc.com They have a variety of controllers. I am fairly certain one of them will fit your needs.

[panic mode]

you can also look at any motion processor or controller (control logix from AB, Q from Mitsubishi etc.)

[panic mode]

Danaher catalog D203 lists some standalone motion controler that look like panel meter. I never used this type but they are supposedly inexpencive.