MATLAB Simulink中的Simscape模块可以针对不同的物理场进行建模，由Simscape language编写的 .ssc 文件所定义。
例如，对于 Reluctance Force Actuator 模块：
它所对应的 reluctance_force_actuator.ssc 文件如下：
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component reluctance_force_actuator
% Reluctance Force Actuator :2.0
% Represents a generic magnetomotive device based on the reluctance force
%
% F = -0.5 * PHI^2 * dR/dx
%
% where R is the reluctance dependent on the thickness of, or length of,
% the air gap x, and PHI is the flux in the magnetic circuit.
%
% The magnetic force produced acts to close the air gap, i.e. the
% resulting force is negative acting from the mechanical C to R ports.
% Copyright 2009-2016 The MathWorks, Inc.
nodes
N = foundation.magnetic.magnetic; % N:top
S = foundation.magnetic.magnetic; % S:bottom
R = foundation.mechanical.translational.translational; % R:top
C = foundation.mechanical.translational.translational; % C:bottom
end
parameters
x0 = { 2, 'mm' }; % Initial air gap
xmin = { 1e-4, 'mm' }; % Minimum air gap
CSA = { 0.01, 'm*m' }; % Cross-sectional area
mur = { 1, '1' }; % Relative permeability of material
K_contact = { 1e6, 'N/m'}; % Contact stiffness
D_contact = { 500, 'N*s/m'}; % Contact damping
end
variables
mmf = { 0, 'A' }; % MMF
phi = { 0, 'Wb' }; % Flux
f = { 0, 'N' }; % Force
u = { 0, 'm/s' }; % Velocity
end
variables(Access=private)
x = {value=x0, priority=priority.high}; % Air gap
end
branches
phi : N.phi -> S.phi;
f : C.f -> R.f;
end
equations
assert(x0>=xmin)
assert(xmin>0)
assert(CSA>0)
assert(mur>0)
assert(K_contact>0)
assert(D_contact>0)
mmf == N.mmf - S.mmf;
u == R.v - C.v;
u == x.der;
if x > xmin
mmf == phi*x/(N.mu0*mur*CSA);
f == -0.5*phi^2*1/(N.mu0*mur*CSA);
else
mmf == phi*xmin/(N.mu0*mur*CSA);
f == -0.5*phi^2*1/(N.mu0*mur*CSA) + K_contact*(xmin-x) - D_contact*u;
end
end
end
其中，声明 nodes 的部分：
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nodes
N = foundation.magnetic.magnetic; % N:top
S = foundation.magnetic.magnetic; % S:bottom
R = foundation.mechanical.translational.translational; % R:top
C = foundation.mechanical.translational.translational; % C:bottom
end
可以看到这个部件是关于 magnetic domain 和 translational domain 的建模。在定义关系的 equations 部分中，该模块用到了 N.mu0 来调用真空磁导率：
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equations
assert(x0>=xmin)
assert(xmin>0)
assert(CSA>0)
assert(mur>0)
assert(K_contact>0)
assert(D_contact>0)
mmf == N.mmf - S.mmf;
u == R.v - C.v;
u == x.der;
if x > xmin
mmf == phi*x/(N.mu0*mur*CSA);
f == -0.5*phi^2*1/(N.mu0*mur*CSA);
else
mmf == phi*xmin/(N.mu0*mur*CSA);
f == -0.5*phi^2*1/(N.mu0*mur*CSA) + K_contact*(xmin-x) - D_contact*u;
end
end
这样的操作在 MATLAB 命令行中是无效的，它只有在 .ssc 文件中才是可行的。所以，如果我们想要查看这个常数的具体值，可以电脑中的 magnetic.ssc 文件中找到，还可以在官方文档中找到：Magnetic Domain - MathWorks：
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domain magnetic
% Magnetic Domain
% Copyright 2009 The MathWorks, Inc.
parameters
mu0 = { 4*pi*1e-7 'Wb/(m*A)' }; % Permeability constant
end
variables
mmf = { 0 , 'A' }; % MMF
end
variables(Balancing = true)
phi = { 0 , 'Wb' }; % Flux
end
end
可以看到，在 paramaters 部分，该文件定义了 mu0 具体的值。
按照这个方法，同样可以查看其他物理域的内置常数，详见： Foundation Domain Types and Directory Structure - MathWorks。