SP_RampUP Logic Block Documentation

Overview

The fn_SP_RampUP function block is designed to smoothly increase a set point (SP) from its current value to a desired target over a predefined time period. This is especially important in automation systems where sudden jumps in set point can lead to system instability, overshoot, or even equipment damage.

By utilizing the fn_SP_RampUP block, the increase is linear, controlled, and safe, ensuring system integrity during ramp transitions.

In the above picture we are showing the fn_SP_RampUP block.

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Functional Description

• This block gradually ramps up the set point over the time duration defined by TM_PT.
• It ensures a predictable and smooth transition from the initial to the target set point.
• Once the target is reached, the output Finish becomes TRUE, signaling the completion of the ramp-up process.

Here is an illustration showing how the block behaves with real-time data and calculated outputs.

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Signal Connection Example

Below is a typical example showing how the pins are connected to the fn_SP_RampUP block within a control logic diagram.

In the above picture we are showing the example of connecting the pins.

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Pins Information

Signal Name	Type	Description
TM_PT	WORD	Time duration over which the set point will be increased
Last_SP	REAL	The previous set point value before ramping started
Init_SP	REAL	The current initial set point from which ramping begins
Final_SP	REAL	The desired target set point after ramping
Final_SP_Fctr	REAL	A multiplier applied to the target set point for scaling (use 1.0 for exact)
Calc_SP	REAL	The intermediate set point calculated during the ramp-up
Finish	BOOL	FALSE = Ramp-up not completed, TRUE = Ramp-up cycle completed

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Operational Behavior

1. Initialization:
   The block reads Init_SP as the starting point and calculates the final target using Final_SP × Final_SP_Fctr.

2. Ramping:
   It linearly increases Calc_SP over time, based on TM_PT, moving from Init_SP to the scaled Final_SP.

3. Completion:
   Once the target set point is reached, the Finish signal becomes TRUE, indicating ramping is done.

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Example Use Case

For instance, in a flow control application, where the pump speed needs to be increased gradually over 10 seconds, set TM_PT = 10, Init_SP = 0.0, Final_SP = 100.0, and Final_SP_Fctr = 1.0.
This allows a smooth and safe increase in flow rate, avoiding system shocks.

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Best Practices

• Choose TM_PT appropriately based on how quickly the system can respond without oscillations.
• Set Final_SP_Fctr = 1.0 if no scaling of Final_SP is required.
• Reset and update Init_SP and Last_SP correctly each time the ramping is triggered.
• Use the Finish output to trigger downstream logic only after the set point has reached the desired value.
• Ideal for applications such as temperature increases, motor start ramps, gradual pressure build-up, etc.

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The fn_SP_RampUP block provides a structured and safe way to implement set point ramp-up functionality, minimizing disturbances and ensuring a smooth and reliable process transition.