How to plot a implicit function for different values with different constraints?

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Misi 2022-12-13

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https://ww2.mathworks.cn/matlabcentral/answers/1877602-how-to-plot-a-implicit-function-for-different-values-with-different-constraints

评论： Misi 2022-12-14

Greeting guys

I want to plot the ''f'' function for different values of -20, -25, -30, -35, -40 and the different constraints of g1, g2 ,g3, g4 also my variables of Rd, Rb and bd are between LB and UB respectively. My function and variables and constrains are as follows:

dR=(Rd-Rb)
Td=4/3*pi*40000*dR^3+pi*3.8*45/0.001*dR^4+2*pi*Rd^2*bd*[15+0.1*(45*Rd/0.001)]
Td0=4/3*pi*15*dR^3+pi*0.1*45/0.001*dR^4+2*pi*Rd^2*bd*[15+0.1*(45*Rd/0.001)]
muJ=Rd^4*bd/[(0.069)^4*0.022-(0.065)^4*(bd+0.002)]
f=-Td
g1=1-Td/(50*Td0)
g2=1-muJ/0.25
g3=muJ/0.5-1
g4=Rb/Rd-1
LB = [0.030;0.010;0.003];
UB = [0.068;0.020;0.012];

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John D'Errico 2022-12-13

编辑：John D'Errico 2022-12-14

Very confusing.

I think what you are saying is that you want to see a 3-d level surface, with the variables {Rd, Rb, bd} as variables, and then want to see that 3-d level surface for several different levels, perhaps [-20, -25, -30, -35, -40].

However, the constraints you mention, g1, for example, are not constraints, or at least it is not clear what they are. If you are telling us that g1 is an EQUALITY constraint, say g1==0, then it effectively reduces the 3-d level surface from a 2 dimensional manifold floaing in the 3-d space you describe, into a 1-d curvilinear path in that space. And you have 4 such "constraints", then there is no level surface to be found. So please explain clearly what your problem is. What do those constraints mean? Are they inequalities?

Misi 2022-12-14

actually this is an optimizatio problem. I want to draw objective function for disserent values and g1, g2, g3 and g4 are inequality constraints. Design vaiables are Rd, Rb and bd that are in LB and UB bounds.

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