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Triggering a subsystem to run for set duration

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Roger
Roger on 24 May 2011
Hello, I want to trigger a subsystem that will then run for 0.25 time units (more than once) at points through the simulation but I do not know how to trigger a clock. Can anyone help?
Roger

Accepted Answer

Roger
Roger on 20 Jun 2011
The solution to this problem can be solved using 'Reset clock' block written by Ravi Mravi which is very elegent and can be built out of standard blocks. This would be a clock that would be running from the start but could be set to zero at any point by a trigger. see: http://www.mathworks.com/matlabcentral/fileexchange/5761

More Answers (2)

Fangjun Jiang
Fangjun Jiang on 24 May 2011
I am not fully understand your question. Let's see if this is the case. Set your simulation step size as 0.01 second. Drag a "Pulse Generator" block, set the period as 1 second and the pulse width as 25 (percent). Use the output of the "Pulse Generator" to trig an "Enabled Subsystem". The subsystem will be running every 0.25 second out of 1 second.
  1 Comment
Roger
Roger on 25 May 2011
Thank you for taking the time to consider my problem. As Mark said in his reply I am not sure of the time between triggers - but this was not clarified.

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MarkB
MarkB on 24 May 2011
Fangjun's approach is probably the best way if the interval between the 0.25 pulses is also known in advance. If it is not, I would recommend using Stateflow instead.
The general idea is that you would still use an "Enabled Subsystem" like above, but in this case, Stateflow would output a Boolean signal to drive it. Inside Stateflow, you could read any relevant inputs, and use them to enter a state that sets the output as "true", only exits after 0.25 (check the documentation for "temporal logic" to see the Stateflow keywords for defining time intervals), and then sets the output to "false" upon exiting the state.
  5 Comments
Fangjun Jiang
Fangjun Jiang on 26 May 2011
The use of Matlab function block is not needed. You could just use a switch block.

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