First Experience - Emerson - Control Techniques FM-3 Servo Drive
For those of you that aren't familiar with my writing style, this article is what I call my first experiences. This does not mean this product is brand new on the market, but rather the first time I've personally had an integration application using this product. I will also share my learning curve ratings at the end of my first experience articles. I gave this device a "1" learning curve rating. Very easy to integrated to a PLC. You can download my electrical drawing for the Emerson FM-3 here: Watch this servo in action, download the application video:
One of our suppliers Allied Automation out of Indianapolis, Indiana, has been trying for quite some time to get us to use the Emerson servo drive products. Of course like anyone else, sometimes you get tunnel vision with certain types of products you may encounter. In my case, I was using Allen Bradley Ultra Drive servos and was pretty much blinded. I try to always caution others about this tunnel vision problem that Controls Engineers can get. If this happens to you, stop, take a deep breath and open your mind.
One day we had an application come up that we felt an Ultra Drive product couldn't handle, so I was told at the time that we might have problems using an Ultra Drive in an indexing table application because the resolver doesn't roll over automatically, or we would have to reset the resolver with a sensor every revolution of the table. At first, we really didn't want to hassle with this reset and thought that surely someone else has come up with a servo that can be used in a one-way only indexing table application. Right? Without much thinking we called up our buddies in Indy and talked about that Emerson servo again. After a couple of phone calls we found out that the Emerson drives have an automatic resolver roll over for our indexing table application so we decided to give the servo a try.
With out much further a-do, we ordered one of these drives and it arrived pretty quickly. Of course like any other servo motor I've seen, it looks pretty standard as you can see from the pictures below. The servo motor cables are "armu" grade.
The motor is long, but I don't think dimensionally it's any longer than most servo motors. Our application uses an 8:1 inline gearbox to bring the ratio down on our index table application.
The dial table that was designed is rather small and contains 72 stop positions, or in a 360 degree table at 8:1 equals 40 degrees of motion every time the motor was told to index.
What makes me smile about this Emerson drive is of course the servo controller. We used the FM-3 model with our indexing table package. This controller is a drive and indexer all built into one unit. Which means you can do all your programming inside the controller and just send a "go" signal from the PLC to this controller and it will handle the motion move program. It's a low powered unit and accepts any range of voltage from 90-230 VAC single phase. I think anything that has such a wide range of input voltage must be pretty flexible. The controller has some I/O that you can program to anything you want inside the controller. It's virtually all drag and drop to assign I/O to any of the physical I/O outside the controller.
The software that comes with the Emerson servo is called Power Tools Pro version 3.0. Let me tell you what, I was really tickled how easy this software is to used. It's a menu tree based software that I found very intuitive and easy to use. Everything makes sense what you need to access in the servo controller. From assigning I/O, to setting up your homing motion, to finally writing a simple program. Once you use this software I think you'll agree. The controller saves everything inside the controller flash. So if you don't have the original program, it's ok because you can upload the program and all the comments direct from the drive. I wouldn't never recommend relying on this method of uploading software from any device, because the device could fail any time, then your not going to be your bosses best friend anymore. However at any point, if you need to, you can upload everything from the controller and not lose any monetary value in your program or comments at development time.
I found it very easy to assign I/O points from internal status bits in the controller to real world physical I/O points on the controller. This was very handy to send signals from the servo controller to the PLC so the PLC knows the status of the controller at all times. You can even assign I/O or conditions within the controller to stop other internal signal. For example, there is a flag in the controller under RAMPS>STOP which if active will stop the current motion program and end your program. I needed my application to stop executing the program if the drive enable went low, so I dragged the status bit from DriveEnableStatus to the Ramp>Stop function. Now when the drive enable drops out, my program stopped executing. This servo indexer still executes code when the drive enable goes low by default. I can see where this is extremely handy in some applications. You'll probably want to use this feature when you hit an e-stop but you don't want to lose your program. Of course if your program comes to a point that it needs to issue a motion command while the drive is disabled, I think your going to be stuck. But if you have a desire to keep executing your program even after an e-stop occurs, you have the option to do so out of the box on this controller. In my case, I wanted the program to end no matter what on an e-stop so I used the internal mappings of two internal bits to accomplish what I needed.
Setting up the index move was nothing more than double clicking on the first index0 profile tree menu and filling in the wizard form for what I wanted that index0 to do. Since I only have one motion profile for an index table, I only needed to setup one index profile. In my case, I need to move the motor 40 degrees for each of the 72 stations.
Last but not least is the programming itself. It's a structured text language similar to basic or visual basic. Very easy to use, you can even drag and drop conditions from any of the tree menus right into your conditional statements. When you do this, the software automatically comments the programming lines. This makes it pretty fast and easy for you guys who forget to comment your programs.
In summary, I thought this servo package was easy to use for a first timer. I'll definitely use it again in another application. I don't recall having any issues with the drive at all. I didn't have any tuning problems, nor did I have to adjust any tuning parameters to get the drive to run. Everything worked out of the box with no known problems.
Technical support from Emerson was good since I only called once to the tech guy asking about stopping the program on an e-stop, which I used his suggestion above.
Learning curve rating:
Curve 0 = Walk in the park.
Curve 10 = Get out the scholastic cap and crash in the classroom.
I gave this device a "1" learning curve rating. Very easy to integrated to a PLC.
You can download my electrical drawing for the Emerson FM-3 here:
Watch this servo in action, download the application video:
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