In many cases, your Controller may not be able to perform its function. This is because Controllers can have constraints that impact their behavior. It is worthwhile to summarize these constraints here:
Flow Capacity: Each Controller has a capacity (a maximum value that cannot be exceeded regardless of what the Controller wants to output. This is typically associated with some physical limitation (e.g., the size of a pump).
On/Off: Controllers can be turned off (e.g., if there is a power failure). When they are off, their output is zero.
Limitation of Outflows at the Lower Bound: The output of an Outflow Controller could be limited by its priority within the list of Outflow Requests for a Pool A stock element that integrates and conserves flows of materials. A Pool is a more powerful version of a Reservoir (it has additional features to more easily accommodate multiple inflows and outflows). element representing the Process Variable. In this case, if the Pool reaches its Lower Bound, the total outflow cannot exceed the total inflow, and the requested output from the Controller could be reduced.
Learn more
- Basic Controller Inputs
- Browser View of a Controller
- Comparing the Different Methods: Which Type of Controller Should I Use?
- Constraints on the Output of Controllers
- Controlling a Process Using Multiple Controllers
- Defining a Deadband Controller
- Defining a Proportional Controller
- Defining a Proportional Integral Derivative (PID) Controller
- Defining a Target that Represents an Upper or Lower Limit
- Turning a Controller On and Off
- Understanding Controllers
- Using a Proxy for the Process Variable When Defining a Controller
- Using Controller Elements