Open Loop Temperature Controller


Thread Starter

The Student

I have finished designing a Closed loop temperature controller. Using labview I designed a VI where the user monitor and control the loop settings (i.e., PID/OnOFF, PID settings, setpoint, process variable….etc).

No I have been asked to include an open loop control in the VI. Now, I know in open loop the controller (which is PWM duty cycle 0-100% in my design) is manually controlled. My question is, is that mean to include a PWM control in the vi for the user or to use the setpoint controller to control the temperature? If its to control the setpoint how can you implement that?
Add a manual mode where the PWM (also called time proportional) output is defined by the operator, from 0-100%. Wherever the output is set, it stays there.

That provides open loop temperature control, where the automatic feedback provided the error generator in the PID is ignored, but the temperature can still be adjusted by manual means.


Michael Griffin

"Open loop" means without using feedback. If you try to control temperature, you are doing closed loop control. Open loop would be to allow the user to directly manipulate the PWM duty cycle (0 - 100%).

You should look through the list archives for "bumpless transfer" (or variations on that) for more information on transfer between open and closed loop control.