Continuous control generally implies that a steady-state condition is reached in a process and that feedback stabilizes the operation over some prolonged period of time. Single-loop controllers, PLCs, and other programmable devices are well suited to continuous control tasks, or you can program LabVIEW to perform the low-level feedback algorithms and have it orchestrate the overall control scheme. LabVIEW has some advantages, particularly in experimental systems, because it's so easy to reconfigure. Also, you can handle tricky linearizations and complex situations that are quite difficult with dedicated controllers. Not to mention the free user interface.

Most processes use some form of the PID algorithm as the basis for feedback control. Gary wrote the original PID VIs in the LabVIEW PID Control Toolkit with the goal that they should be easy to apply and easy to modify. Every control engineer has personal preferences as to which flavor of PID algorithm should be used in any particular situation. You can easily rewrite the supplied PID functions to incorporate your favorite algorithm. Just because he programmed this particular set (which he personally trusts) doesn't mean it's always the best for every application. The three algorithms in the package are

• PID an interacting positional PID algorithm with derivative action on the process variable only

• PID (Gain Schedule) similar to the PID, but adds a tuning schedule that helps to optimize response in nonlinear processes

• PID with Autotuning adds an autotuning wizard feature that guides you through the...