We commonly use proportional pressure relief valves to control hydraulic system pressure. These valves are driven by an analog output card in our PLC rack. Now, most proportional relief valves that I've used are pretty non-linear, especially at the lower end. Something like this:
What are some ways that one could use to linearize the control in the logic? For this example, let's assume we are using a SLC 5/03 and it is totally open loop control, with no pressure feedback.
The best I've been able to come up with is multiple SCP instructions, each preceeded with a comparsion that only allows one SCP to be active at a time. See attached.
Anybody have a better way to do this?
(In real life, I wouldn't typically hard-code all the values and would instead use values from a populated data table. For clarity in this example, I didn't do that...)
Aaron
What are some ways that one could use to linearize the control in the logic? For this example, let's assume we are using a SLC 5/03 and it is totally open loop control, with no pressure feedback.
The best I've been able to come up with is multiple SCP instructions, each preceeded with a comparsion that only allows one SCP to be active at a time. See attached.
Anybody have a better way to do this?
(In real life, I wouldn't typically hard-code all the values and would instead use values from a populated data table. For clarity in this example, I didn't do that...)
Aaron