As from STEP 7 V15 it available a new instruction for ramp generation: RampFunction (Intructions > Technology > PID Control > Auxiliary Functions)

The RampFunction block enable to limiting the rate of change and the limit values of a signal with different gradients for positive/ negative/rising/falling signals

With this block, it is possible, for example, to generate a ramp for PID set points and so, to get soft and controlled changes of the process variable even with step changes in the original set points.

The gradients express how many “unitis” will increase / decrease per second.

These gradients could be found in the block instance DB, with the names:

• PositiveRisingSlewRate
• PositveFallingSlewRate
• NegativeRisingSlewRate
• NegativeFallingSlewRate

The substitute value input, together with the reset button, could be used to “turn off” the rum function.

In the attached example, the same variable was used in the Input and SubstituteOutput inputs. At this way, when Reset = true, the ramp function is deactivated. It should be useful, for example, in the PID tuning phase.