LDT for hydraulic cylinders

[ZBTB]

Hello, I am raising and lowering a platform with four hydraulic cylinders with a height tolerance +/- 1mm. I was looking for the best possible solution for an LDT, and if anyone would recommend using a Siemens SM334 analog I/O module or an SM335 fast analog I/O module for processing the feedback from the LDT. Any suggestions would be appreciated.

 

[Peter Nachtwey]

The easy way.

http://www.mtssensors.com/ and
http://www.balluff.com

I would recommend one of these hydraulic motion controller
http://www.deltamotion.com/products/motion/rmc100/index.php
You it costs more but you will save so much time because commands like SyncMoveAbs, SyncMoveRel and SyncStop are built in which allows you to keep your axes synchronized. It has graphing that will allow you to plot the positions, velocities etc of the actuators real time and programming capability that allows one to synchronously move 4 axes in just one command.

I prefer SSI rods because they don't drift as much as the analog rods do. The SSI also provides feedback at regulator intervals which is necessary for fine velocity control. Analog data is asynchronous to the motion controller. One can easily get 5 micron resolution which allows for more accurate speed estimates.

If you use the motion controller you may not even need the PLC.
Just add the HMI of your choice. Red Lions work well. If you decide you do need the PLC you can communicate with the motion conroller using Profibus DP to transfer up to 32 32 bit registers back and forth which is probably many more than you need.

What will make your project more 'interesting' is the tuning. Auto tuning makes life easy but that ususally can't be done unless the actuators can be moved separately.

Note, I sell the controllers but it is the best solution for what you want to do. I don't see how you will maintain 1mm with PID control unless you are moving, accelerating and decelerating very slowly. The motion controller includes things you probably haven't even thought of.

One more note. There are on-line training classes and controllers. The training classes don't cost that much and you will definitely save the cost of training by reducing the time it takes to set up a system. A four actuator project should take no more than 4 hours to get going one the wiring and plumbing is done right.

 

[CharlesM]

I second what Peter said.

I like the MTS SSI sensors the best however I have used the Balluff. I have seen some from Turck that looked good as well but have never used them.

I am using RMC controllers with my Siemens PLC's. They have a Profibus option for all their controllers. You may also want to check out their online forum.

http://forum.deltamotion.com/index.php