symbolic equation solving a a Unknown variable

Question

Thayumanavan 2014-10-12

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/158336-symbolic-equation-solving-a-a-unknown-variable

Te=0.528104000000000;wr=0.955; Pmpu=Te*wr;

Pmactual=Pmpu*5*1000000;

Beta=0.0; gb=121.2; speedact=wr*1500; omegarm=(2*pi*speedact)/(60); wtradsec=omegarm/gb;

c1=0.5176; c2=116; c3=0.4; c4=0; c5=c4; c6=5; c7=21; c8=0.08; c9=0.035; c10=0.0068; syms Vw ; R=40.05; Lamda=(wtradsec*R)/Vw

t1=c2/(Lamda+(c8*Beta)); t2=(c2*c9)/((Beta^3)+1); t3=c3*Beta; t4=c4*(Beta^c5); t5=c6; t6=-c7/(Lamda+(c8*Beta)); t7=(c7*c9)/((Beta^3)+1); t8=c10*Lamda;

cp=(c1*(t1-t2-t3-t4-t5)*exp(t6+t7)) +t8

term=(Pmactual)-(0.5*pi*1.225*(R^2)*cp*Vw*Vw*Vw) symvar(term) Vw=solve(term)

I am getting some answer 49.231911904587234477083430935504 .But is is not correct(anyway i cheked term value is zer0) I tried the exact reverse

With Known Vw

Vw=9.55

Lamda=(wtradsec*R)/Vw t1=c2/(Lamda+(c8*Beta)); t2=(c2*c9)/((Beta^3)+1); t3=c3*Beta; t4=c4*(Beta^c5); t5=c6; t6=-c7/(Lamda+(c8*Beta)); t7=(c7*c9)/((Beta^3)+1); t8=c10*Lamda;

cp=(c1*(t1-t2-t3-t4-t5)*exp(t6+t7)) +t8

term =5415302213717197/2147483648 - Vw^3*((6787202843659081*exp(147/200 - (22624*Vw)/(16999*pi))*((121284032*Vw)/(31873125*pi) - 293091/62500))/2199023255552 + (5884158718107396613869*pi)/(17768107904860160000*Vw)) Pmactual=term+(0.5*pi*1.225*(R^2)*cp*Vw*Vw*Vw) Pmpu=Pmactual/(5*1000000) Te=Pmpu/wr

I am getting same Te as my input.

1.My doubt is why symbolic sove does not gives 9.55 .What mistake i am doing?pls anybody run the code and tell me.

2. While symbol solve MATLAB solves the for Vw for which term is 0 .But in reverse process(ie with Vw known)IF I PRINT TERM it is NON ZER0 why?