sample error in simulink if else statement

When i am using if loop in matlab simulink it shows the error Sample time 1 of 'bdc_2_CL/Subsystem/If Action Subsystem/PID Controller/u' does not match the sample time [0, 0] of the If block 'bdc_2_CL/Subsystem/If' controlling its execution. this error is coming only when i am trying to connect closed loop simulation. In open loop it is perfectly working.In closed loop i have just added one adder and discrete PID controller

[ashwani gupta]

i will suggest a very crude way to tackle this problem. Just add one rate transition block before all the input signals of if block and it will resolve your problems.

Answer 1

[Sebastian Castro]

Conditionally executed subsystems like your "If" block are not guaranteed to execute at every time step.

According to your error message, the PID Controller block inside this subsystem is set to Discrete mode with at sample time of 1. However, the PID Controller block inside cannot take a deterministic rate because it's inside the "If" block.

Go to the PID Controller block and change its sample time to -1, for "Inherit". Does that work?

- Sebastian

Answer 2

[kpb]

No , I tried it before still it is not working , while in a closed loop system it works perfectly wid sample time -1.

[Sebastian Castro]

Looking at your error again, there seems to be some block "u" in that subsystem set to a sample time of 1. Maybe an Inport/Outport block?