How to get the range of a complex Inequality

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Faizah Zahin
Faizah Zahin 2020-2-25
回答： Devineni Aslesha 2020-2-28
I am trying to get the range of values from a complex inequality that I am trying to solve. For example in the following code:
syms kp ki
a5=1;
a4=((2047986680487193847267328*ki - 13715030938073068*kp))/(2047986680487193847267328*kp + 87042659012253300578844672);
a3=(((184889681621683227480892934480434054447104*kp)/625 - 13715030938073068*ki + 17196119675118872248493326935156326400))/(2047986680487193847267328*kp + 87042659012253300578844672);
a2=(((184889681621683227480892934480434054447104*ki)/625 - (22196527874515618602308700203063*kp)/16384))/(2047986680487193847267328*kp + 87042659012253300578844672);
a1=(((18220068596449371851061970182309744452038457569574912*kp)/625 - (22196527874515618602308700203063*ki)/16384 + 846451363799069169891931531128018151619713564672))/(2047986680487193847267328*kp + 87042659012253300578844672);
a0=(18220068596449371851061970182309744452038457569574912*ki)/(1279991675304496154542080000*kp + 54401661882658312861777920000);
b1=(a4*a3-a5*a2)/a4;
b2=(a4*a1-a5*a0)/a4;
b3=(b1*a2-b2*a4)/b1;
b4=(b3*b2-b1*a0)/b3;
S=solve(a4>0,b1>0,b3>0,b4>0,a0>0,[kp,ki])
When I am running this code, it shows that it cannot find an explicit solution. However, when I have put the code inside two for loops and sweeped over a range of values for kp and ki, I get numerous values of them satisfying the inequalities.
But I want to get a more scientific solution instead of sweeping over a random range of values based on trial and error. Can you suggest me any modification that can help me run my code? Thank you in advance.

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回答（1 个）

Devineni Aslesha
Devineni Aslesha 2020-2-28
The range of complex inequality can be obtained by using the following syntax for ‘solve’ function.
S = solve(a0>0, [kp,ki], 'IgnoreAnalyticConstraints', true,'ReturnConditions', true);
For more information, refer the following link.
https://www.mathworks.com/matlabcentral/answers/328751-how-can-i-find-ranges-of-inequalities-using-solve-in-live-script

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