Units for constants in simscape custom module

Question

Steven 2017-2-3

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/323290-units-for-constants-in-simscape-custom-module

评论： Steven 2017-2-6

I have a constant that I have declared in the variables section. I'm assuming that everything needs units. Some papers use constants that use equations with units that don't match (on one side of the equation its a constant and on the other side might be V/K)

variables(Access=private)
    cm = { 0, '' };
    i = { 2, 'A' };
    V1= { 0, 'V' };
    T1 = { 0, 'K' }; 
end

in the equations section if I mix up the units will it throw an error?

equations
 i == V1*T1;
end

is there some way to have a unitless constant that doesn't have units?

equations
 cm == V1*T1;
end

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Steven 2017-2-6

在 MATLAB Online 中打开

Found some help : https://www.mathworks.com/help/physmod/simscape/lang/declaring-domains-and-components.html#bruso4j-1

To declare a unitless parameter, you can either use the same syntax:

par1 = { value , '1' };

Steven 2017-2-6

编辑：Steven 2017-2-6

在 MATLAB Online 中打开

This doesn't solve my problem right now however, because I have Kelvin/Kelvin and its not going to unitless. Example:

nodes %conserving ports
 Ta = foundation.thermal.thermal; % H:top 
 Tb = foundation.thermal.thermal; % C:bottom
end
variables
   R  = {334, '1'};
end
parameters
   cTemp = {3.2342, '1'}; 
end
equations
   R == (Th.T - cTemp)/Th.T;
end

This will not compile. Even changing R and cTemp to units of K will not compile

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Answer 1

Nirja Mehta 2017-2-6

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/323290-units-for-constants-in-simscape-custom-module#answer_253583

Assign '1' as the unit of "cm".

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Steven 2017-2-6

That compiles, but I can't combine a that is set with R = {334, '1'}; value with any other unit in an equation so it doesn't have that much use. I need a true unitless value that will compile

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