Looking for simple solution for s5 PID control problem.


Thread Starter


I am in the process of trying to more or less commision a control loop designed to control steel level in a tundish for a caster.

The system is relatively simple, an hydraulically operated slidegate is used to control the flow of steel from a ladle to a tundish. Tundish level is measured with a scale. The original control loop used the siemens "K-Controller" function block to drive the position of the slidegate with it's output being sent to a proportional directional valve and feedback was going to be gotten from a slave following cylinder with an LVDT.

We have over time, however, scrapped the idea of using the proprtional valve and decided to go with a simple directional valve and manual flow control valve (ie converting to pulsed digital outputs) We have also determined that the cylinder positon feedback is too unrelialble to trust.(ie need to go to an "open loop" arangement) Crude attempts have been made to program a simple controller using ladder logic with timers and counters etc. but I continue to find that solving the problems to get it to work involves writing function blocks to calculate rate of change, distance from setpoint over time.... You probably see where I'm going, Im basically trying to write my own loop for no real reason.

If anyone has a simple elegant solution to make this transition or if anyone knows if siemens already sells a function block designed for a system like this, I would greatly appreciate it.

Also if anyone has any information on where i can get the documentation to program the data blocks associated with siemens function blocks "K-Controller", "S-Controller" , "PIDR" etc.... I can't seem to find them on the net and since this software was all part of an original commisioning about 3 years ago, no specific documentation for these special blocks was given to us (Perhaps they thought it would just work forever)

Thanks [email protected]