Limiting the derivative of a flow to a maximum (increase) and minimum (decrease) value. This avoids jumps in the primitives by limiting the rates of change.
The first derivative of the [Flow required] is compared to the maximum increase rate limit and minimum decrease rate limit. If it is outside the specified range, the state jumps to "limited" (either for increase or decrease). Then the slew rate is set as the respective limit, integrated ([flow_limited]) and used as for the [Flow]. When [Flow] intersects with [Flow required] the state jumps back to "unlimited". Then the [Flow] equals the [Flow required].