Hello there, Can anyone help me with the switch of Simscape toolbox in Simulink??

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shravya ked
shravya ked on 8 Feb 2017
Edited: Hannes Daepp on 13 Feb 2017
Hello sir/madam, I am unable to simulate the Switch of simscape toolbox. I have attached a screenshot of the model done in simulink. Problem faced - I am unable to understand the switch operation. I have simulated the Switch, switch is always closed whatever the external signal value is(i.e less than or greater than the threshold value). Parameters given -
  1. Threshold - 3
  2. External Physical signal(PS constant)- 1
  3. DC voltage - 2
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Please find the attachment(image) and please help me out in this!!
Thanks & Regards,
Shravya

Answers (1)

Hannes Daepp
Hannes Daepp on 13 Feb 2017
Edited: Hannes Daepp on 13 Feb 2017
In the model above, the output will be 2 regardless of whether the switch is open or closed. This is caused by the fact that the switch is not actually completely open; rather, it still has some impedance that is specified by the open conductance in the block’s dialog.
To get behavior that is more indicative of the switch utility, you could use a switch to open or close a short circuit. The following model demonstrates how the switch can be used, and the circuit that it represents:
As illustrated in the screenshot above, the models on the left use a switch (threshold 3), while those on the right use resistors with resistances set to match the resistance/conductance specified for closed and open circuit values of the corresponding switch. In the top models, the switch is open -- represented on the left by a very high resistance. In the bottom case, the switch is closed, as represented on the right by a very low resistance. In both cases, the resistances on the right match those specified in the corresponding Switch Block parameters.
Depending on the specific application, the PS Switch block may be closer to what you are trying to model. Additionally, you may find more information on the switch block in the documentation: http://www.mathworks.com/help/physmod/simscape/ref/switch.html.

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