Can i run two PIDs at the same time?

Hi
I want to control speed of the rotating shaft and force applied by the pneumatic cylinder using two different PIDs from the same program.
I managed to get two PIDs to work separatly using PID control loop VI`s supplied with labview 6.1 (I got Kc, I and D right, so there is no overshoot). When I try to run both PIDs within my vi they don`t work. I again tried various gains and managed to get one PID to work but not the other. Then through trial and error I managed to get a second PID to work but I had to change refresh time of the FOR loop from 100msec to 1msec.
Does anyone have experience with running two PIDs in the same program? Does the timing of the FOR loop influence PID contorller? Does equiring of other data while
running PID has effect on the PID?
I would really appreciate any comments/help. I am pretty thrustrated at this time
Thanks

I don't know whcih PID vi's you are using but I had similar problems. I
solved it by going to the VI properties of the PID subvi, select category
execution and make sure that reentrant execution is selected. Only then two
instances of the PID vi can run without interfering each other.
Martien
solved by setting the execution mode
"smartlander" wrote in message
news:[email protected]..
> Hi
>
> I want to control speed of the rotating shaft and force applied by the
> pneumatic cylinder using two different PIDs from the same program.
> I managed to get two PIDs to work separatly using PID control loop
> VI`s supplied with labview 6.1 (I got Kc, I and D right, so there is
> no overshoot). When I try to run
both PIDs within my vi they don`t
> work. I again tried various gains and managed to get one PID to work
> but not the other. Then through trial and error I managed to get a
> second PID to work but I had to change refresh time of the FOR loop
> from 100msec to 1msec.
> Does anyone have experience with running two PIDs in the same program?
> Does the timing of the FOR loop influence PID contorller? Does
> equiring of other data while running PID has effect on the PID?
> I would really appreciate any comments/help. I am pretty thrustrated
> at this time
> Thanks

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