汽车理论课后习题1_3.doc
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解：1）
clear all
f=0.013; G=38800;Ff=G*f; CdA=2.77;u1=0:1:120; Fw=CdA.*u1.^2/21.15;F=Ff+Fw;Ig=[5.56 2.769 1.644 1.000 0.793];k=1:5;
ngk=[600 600 600 600 600];
ngm=[4000 4000 4000 4000 4000];
r=0.367;I0=5.83;eta=0.85;
ugk=0.377*r*ngk(k)./(Ig(k).*I0);
ukm=0.377.*r.*ngm(k)./(Ig(k).*I0);
for k=1:5
u=ugk(k):ukm(k);
n=Ig(k)*I0.*u./r/0.377;
Tq=-19.313+295.27*n/1000-165.44*(n/1000).^2+40.874*(n/1000).^3-3.8445*(n/1000).^4;
Ft=Tq.*Ig(k)*I0*eta/r;
plot(u,Ft,u1,F)
hold on,grid on
end
2）最高车速求解程序：
[n,u]=solve(n=u*0.793*5.83/(0.377*0.367),(-19.313+295.27*(n/1000)-165.44*(n/1000)^2+40.874*(n/1000)^3-3.8445*(n/1000)^4)*0.793*5.83*0.85/0.367-(2.77*u^2/21.15+3880*10*0.013))
n =
3299.9224534468163066899978278864
264.13689338171544956471411061266
3533.8761660967238474546442908623 + 2707.8751259314497120563837339829*i
3533.8761660967238474546442908623 - 2707.8751259314497120563837339829*i
u =
98.757345195946534184690962185964
7.9048701073070256438355939579073
105.75891807712350450878660177051 + 81.039043290184796798403093329529*i
105.75891807712350450878660177051 - 81.039043290184796798403093329529*i
分析：u的后三个解明显不符合题意，所以最高车速是98.757km/h
求最大爬坡度和最大附着系数
I=0.218; Iw1=1.798; Iw2=3.598; L=3.2; m=3880; r=0.367;
eta=0.85;Cd=2.77; f=0.013; i0=5.83; a=1.947; hg=0.9;
g=10;ig=[5.56;2.769;1.644;1.00;0.793];
for i=1:5
th(i)=1+(Iw1+Iw2)/(m*r^2)+(I*i0^2+(ig(i)^2*eta))/(m*r^2);
end
for i=1:5
ual(i,1)=(600*0.377*r)/(ig(i)*i0);
ual(i,2)=(4000*0.377*r)/(ig(i)*i0);
end
ua=ual(1,1):.01:ual(1,2);
[x,y]=size(ua);
for i=1:y
n=ua(i)*ig(1)*i0/(0.377*r);
Tq=-19.313+295.27*(n/1000)-165.44*(n/1000)^2+40.874*(n/1000)^3-3.8445*(n/1000)^4;
Ft(i)=Tq*ig(1)*i0*eta/r;
Fw(i)=Cd*ua(i)^2/21.15;
Fc(i)=Ft(i)-Fw(i)
end
plot(ua,Ft/1000,:,ua,Fc/1000,-,ua,Fw/1000,--)
D=max(Fc)/m/g;
af=asin((D-f*sqrt(1+f^2-D^2))/(1+f^2));
i=tan(af);
q=i;
cf2=q/(a/L+q*hg/L
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