Blended Motion. What Controller?

I have a Automated wet bench project coming up where the motion requirement (in addition to a typical point to point motion), is to move the wafer boeat smoothly in a figure eight motion while it is in the etch bath.
Now, I have completed several poin-to-point robotic transfer systems but have a feeling that blended motion where you go from one curve to the next without slowing down is a bit more complicated. Any ideas on: what type of motion controller I should be shopping for? What kind of features and functions should be on the controller for blended motion?

I am leaning towards using PARKER equipment for the motion and a AB or Koyo PLC to feed the recipies to the controller and for general system supervision.

Any comments appreciated,
OJ

I just finished a Delta project.
Blended motion is very doable, the product is solid, well supported.
Take a look at http://www.deltacompsys.com/

I Have used Delta RMC controllers in the past for comlex point to point Hydraulic Motion Control and really liked how logical and userfrienly they were. Did not realize that they did blended motion.
Do you reccomend any Servo specific drives to use with the Delta Controllers. I really want this one to be easy and yet solid.

Thanks

I used an Automation Direct Servo drive, DL-06 controller, & a Delta RMC.

I was quite happy with the system performance.

Thanks for your quick reply,

Was your system a blended 2 or more axis motion?
Did you use Ethernet/IP?
C-More touch screen with Ethernet/IP?

How about monitoring the status of the drives? I know that I can monitor following error etc. on the RMC100 but if the drive has any problems, I would like to know that as well.

Did you use Drive amplifyers or Drives with internal control?

Thanks,

Orn, there are examples interfacing RMC75s with CMore displays and Control Logix PLCs here
http://www.deltamotion.com/dloads/downloads.php?category=rmc70&subcategory=Examples

The motion profile is not a problem. Two synchronized cam tables or splines can make a figure 8 or any x y motion profile you want. Just about any controller is capable of this. Blended moves are basic features, but basic point to point moves are not what you need because you must must move through a series of points while moving smoothly. The means that the velocity and accelerations at each point must be continuous. You must either use a cyclic cam table or have the means of specifying the position, velocity, acceleration and time interval between points. Both are possible and easy to do. Actually the second option takes a litle math to calculate the position, velocity and acceleration at each point, but these can be calculated on the controller.

Another idea, this should be easy.

http://en.wikipedia.org/wiki/Lissajous_curve

By changing the amplitude, frequncy and phase you can get mix just about any way you want.

Lineat transfer vs. CNC

When does a linear transfer system become a CNC machine. Is it a matter of a sophisticated Controller and software or is there more to it.
Seems to me that when you have set up a 3 or more axis system you pretty much have the same hardware as a CNC Machine, but are restricted to some cumbersome OEM programming software. What do you need before you can start using G code.

Thanks,

Good question. I don't think there is a rule for whats CNC and what is not. Its almost became a generic term. I think of a CNC as a G-code program controller. I think a lot of machines are called CNC even though they are not. A lot of people think as long as it has closed loop motion it is CNC.

I think CNC is the way to go if you have to be very flexible and able to do anything. However it does require someone who can program G-code. I think a lot of machines can just have a few programs with different parameters and do most everything. For what your talking about CNC is going to be more $.

You are talking about doing 8's. Is there another pattern you need? If you use the RMC 70 you can have several programs and just call the one you need for that pattern.

Another option could be using the RMC100 and using the (curve)spline tool to let the operator make the motion they want. It will be a little advanced but no more than having someone learn G-code.


edit:
Note the Delta motion controllers don't support G-code. However I know Peter has shown some interest in G-code.

When it comes to motion, there is little better than GE Fanuc.
www.gefanuc.com

Figure Eights.



Also attached is the program that is used to generate the figure 8.
I made use of one of our low level motion control routines which we call the advanced gear move. This allows one to specify the position, velocity and acceleration as a function of the master position. The x ( axis 0 ) and y ( axis 1 ) axes are both synchronized or geared to the virtual master ( axis 2 ). This allows one to increase the frequency by just increasing the master velocity. Note that axis 0, the x axis, always does a sine wave. The gray line is axis 1 and you can see it makes one loop of the top and one loop on the bottom. The xAmplitude and yAmplitude etc can are variables that can be edited from the c-more display.

I didn't comment the program but it is only two steps for the x and y axes and 1 for the master virtual axis which I didn't show because it just controls velocity. Most of the effort is in calculating the xPos, xVel, xAcc and yPos, yVel, yAcc. This involves taking the derivatives of the equation for position. Actually the Vel and Acc values are really gear ratios and gear ratios rates.

That is very cool Peter. I have a few projects going out the door right now. But in a week or so I may set this up on my test machine. I have been wanting to "play" with a virtual axis. I have looked at the adv. gearing but have not worked with that either. So your example will be a good place to start.

Perhaps and easier way would have been to use the sine and cosine to generate the cam table and then start the cam. The difference is that the Advanced Gear Move uses fifth order polynomials to go from point to point whereas the cam table uses only cubic interpolation. However, it wouldn't make much difference because the points are rather close together because there are 100 points per cycle.

Another difference is that advanced gear move doesn't require as much memory and the parameters can be changed on-the-fly.