Switch LookUp Table during start-up and shut-down mode

Hello,

I am modeling a process with startup and shutdown mode. The output temperature depends on an input value via two lookup tables (blue curve = startup, red curve = shutdown).

My idea was to switch between those two tables using two points:

• at Point 1 switch startup to shutdown
• at Point 2 switch shutdown to startup

My first thought was to solve this with logical operators but i am struggling to construct the proper logic in Simulink.

Any block diagram example or the correct logic pattern would help a lot.

Answer 1

[Shashank]

Hi @Alexander,

From the diagram, it looks like you're trying to model a hysteresis relationship, where the selected lookup table depends not only on the current input but also on the previous operating mode.

If the transition between the two curves is based on fixed input thresholds, one option to consider is the Relay block, since it supports separate switch-on and switch-off thresholds. The Relay output could then be used to control a Switch block that selects between the two lookup tables.

Just to clarify, are Point 1 and Point 2 fixed input thresholds, or do they depend on both the input and the current output temperature? That would help determine whether a Relay block is sufficient or whether a state-based approach would be more appropriate.

References

• Relay Block: https://www.mathworks.com/help/simulink/slref/relay.html
• Switch Block: https://www.mathworks.com/help/simulink/slref/switch.html

[Alexander]

Hi @Shashank

thank you very much for your answer. I think the Relay Block is exactly what i need. I will try it with this approach.