第一大题确定一辆轻型货车的动力性能
1、绘制发动机的使用外特性曲线
n=600:1:4000
N=n/1000
T=-19.313+295.27*n/1000-165.44*N.*N+40.874*N.*N.*N-3.8445*N.*N.*N.*N
Pe=T.*n/9550 %发动机的净功率
figure(1)
plot(n,T)
xlabel('转速n')
ylabel('转矩T')
figure(2)
plot(n,Pe)
xlabel('转速n')
ylabel('功率Pe')
180170160150转矩T1401301201101005001000150020002500转速n300035004000
706050功率Pe4030201005001000150020002500转速n300035004000
2、绘制驱动力---行驶阻力平衡图
i0=6.17; %减速器的传动比
ig(1)=6.09 % 一档的传动比
ig(2)=3.09
ig(3)=1.71
ig(4)=1.00
nT=0.85
r=0.367
f=0.013
m1=3880
m2=9590
CdA=2.77
Ff1=m1*9.8*f
Ff2=m2*9.8*f
ft1=T*ig(1)*i0*nT/r %一档所产生的驱动力
ft2=T*ig(2)*i0*nT/r
ft3=T*ig(3)*i0*nT/r
ft4=T*ig(4)*i0*nT/r
Ft=[ft1;ft2;ft3;ft4]';
ua1=0.377*r*n/(ig(1)*i0) %一档的速度
ua2=0.377*r*n/(ig(2)*i0)
ua3=0.377*r*n/(ig(3)*i0)
ua4=0.377*r*n/(ig(4)*i0)
ua=[ua1;ua2;ua3;ua4]';
fw1=CdA*ua1.^2/21.15+Ff1 %一档的行驶阻力
fw2=CdA*ua2.^2/21.15+Ff1
fw3=CdA*ua3.^2/21.15+Ff1
fw4=CdA*ua4.^2/21.15+Ff1
Fz1=[fw1;fw2;fw3;fw4]';
figure(3)
plot(ua,Ft) %绘制各档的驱动力曲线
hold on
plot(ua,Fz1) %绘制行驶阻力曲线
hold on
plot(ua4,Ff2) %绘制滚动阻力曲线
xlabel('ua/(km.h)')
ylabel('F/N')
title('汽车驱动力-行驶阻力平衡图')
text(20,12000,'Ft1');
text(30,6000,'Ft2');
text(40,4000,'Ft3');
text(80,3000,'Ft4');
text(90,2200,'（空载）Ff+fw');
text(105,1450,'满载Ff')
汽车驱动力-行驶阻力平衡图16000140001200010000F/NFt180006000400020000（空载）Ff+Fw01020304050ua/(km.h)60708090Ft2Ft3Ft4
一档的驱动力很大，可用于爬坡且坡度较大；二档用于直接原地起步加速
3、绘制动力特性图
D=(Ft-Fw)/(m1*9.8) %求动力因数
f1=0.0076+0.000056*ua %一定车速条件下的滚动阻力
figure(4)
plot(ua,D)
hold on
plot(ua,f1)
text(20,0.3,'I')
text(20,0.154,'II')
text(40,0.1,'III')
text(80,0.05,'IV')
text(110,0.025,'f')
title('汽车动力特性图')
xlabel('ua/(km.h)')
ylabel('D')
汽车动力特性图0.450.40.350.30.25ID0.20.150.10.050IIIIIIV01020304050ua/(km.h)60708090
If=0.218
Iw1=1.798
Iw2=3.598
die1=1+(Iw1+Iw2)/(m1*r^2)+(If*i0^2*nT*ig(1).^2)/(m1*r^2);%一档的旋转质量换算系数
die2=1+(Iw1+Iw2)/(m1*r^2)+(If*i0^2*nT*ig(2).^2)/(m1*r^2);
die3=1+(Iw1+Iw2)/(m1*r^2)+(If*i0^2*nT*ig(3).^2)/(m1*r^2);
die4=1+(Iw1+Iw2)/(m1*r^2)+(If*i0^2*nT*ig(4).^2)/(m1*r^2);
die=[die1;die2;die3;die4]';
a1=9.8*D(:,1)/die1-9.8*f/die1; %求一档的加速度
a2=9.8*D(:,2)/die2-9.8*f/die2;
a3=9.8*D(:,3)/die3-9.8*f/die3;
a4=9.8*D(:,4)/die4-9.8*f/die4;
aI=1./a1 %求一档的加速度倒数
aII=1./a2
aIII=1./a3
aIV=1./a4
aa=[aI,aII,aIII,aIV]';
figure(5) %绘制各档的加速度倒数曲线
plot(ua1,aI)
hold on
plot(ua2,aII)
hold on
plot(ua3,aIII)
hold on
plot(ua4,aIV)
axis([5 99 0.01 10])
加速度倒数曲线1098761/a5432aIII1aI10aII2030405060ua/(km.h)708090aIV
由图可知，加速度倒数没有交点，则可以在每档达到最大车速时换挡
nT=0.85;r=0.367;f=0.013;CDA=2.77;i0=6.17;If=0.218;
Iw1=1.798;Iw2=3.598;L=3.950;a=2.000;hg=0.9;m=3880;g=9.8;
G=m*g; ig=[6.09 3.09 1.71 1.00 ];
nmin=600;nmax=4000;
u1=0.377*r*nmin./ig/i0;
u2=0.377*r*nmax./ig/i0;
deta=0*ig;
for i=1:4
deta(i)=1+(Iw1+Iw2)/(m*r^2)+(If*(ig(i))^2*i0^2*nT)/(m*r^2);
end
ua=[0:0.01:99];N=length(ua);n=0;Tq=0;Ft=0;inv_a=0*ua;delta=0*ua;
Ff=G*f;
Fw=CDA*ua.^2/21.15;
for i=1:N
k=i;
if ua(i)<=u2(2)
n=ua(i)*(ig(2)*i0/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(2)*i0*nT/r;
inv_a(i)=(deta(2)*m)/(Ft-Ff-Fw(i));
delta(i)=0.01*inv_a(i)/3.6;
elseif ua(i)<=u2(3)
n=ua(i)*(ig(3)*i0/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(3)*i0*nT/r;
inv_a(i)=(deta(3)*m)/(Ft-Ff-Fw(i));
delta(i)=0.01*inv_a(i)/3.6;
else ua(i)<=u2(4)
n=ua(i)*(ig(4)*i0/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(4)*i0*nT/r;
inv_a(i)=(deta(4)*m)/(Ft-Ff-Fw(i));
delta(i)=0.01*inv_a(i)/3.6;
end
a=delta(1:k);
t(i)=sum(a);
end
plot(t,ua,'b','LineWidth',2);
axis([0 100 0 100]);
title('四档汽车二档原地起步换挡加速时间曲线');
xlabel('时间t（s）');
ylabel('速度ua（km/h）');
四档汽车二档原地起步换挡加速时间曲线100908070速度ua（km/h）60504030201000102030405060时间t（s）708090100
第二大题
n=600:1:4000
N=n/1000
T=-19.313+295.27*n/1000-165.44*N.*N+40.874*N.*N.*N-3.8445*N.*N.*N.*N
Pe=T.*n/9550
figure(1)
plot(n,T)
text(1000,120,'转矩T')
hold on
plot(n,Pe)
text(2000,20,'发动机净功率Pe')
i0=6.17;
ig(1)=6.09
ig(2)=3.09
ig(3)=1.71
ig(4)=1.00
180160140120转矩T10080604020发动机净功率Pe05001000150020002500300035004000
nT=0.85
r=0.367
f=0.013
m1=3880
m2=9590
CdA=2.77
ua1=0.377*r*n/(ig(1)*i0)
ua2=0.377*r*n/(ig(2)*i0)
ua3=0.377*r*n/(ig(3)*i0)
ua4=0.377*r*n/(ig(4)*i0);
ua=10:1:100
Pf=m1*9.8*f.*ua/(3600)
Pw=CdA*ua.^3/(76140)
figure(2)
plot(ua1,Pe)
hold on
plot(ua2,Pe)
hold on
plot(ua3,Pe)
hold on
plot(ua4,Pe)
hold on
plot(ua,(Pf+Pw)/nT)
7060504030201000102030405060708090100
评价：一二三档的后备功率都比较大，可在一定坡度的道路上直接启动加速；
在最高档达到最高车速时，
n0=[815 1207 1614 2012 2603 3006 3403 3884]
B00=[1326.8 1354.7 1284.4 1122.9 1141.0 1051.2 1233.9 1129.7]
B10=[-416.46 -303.98 -189.75 -121.59 -98.893 -73.714 -84.478 -45.291]
B20=[72.379 36.657 14.524 7.0035 4.4763 2.8593 2.9788 0.71113]
B30=[-5.8629 -2.0533 -0.51184 -0.18517 -0.091077 -0.05138 -0.047449 -0.00075215]
B40=[0.17768 0.043072 0.0068164 0.0018555 0.00068906 0.00035032
0.00028230 -0.000038568]
B0=spline(n0,B00,n)
B1=spline(n0,B10,n)
B2=spline(n0,B20,n)
B3=spline(n0,B30,n)
B4=spline(n0,B40,n)
Pf3=m1*9.8*f.*ua3/(3600)
Pw3=CdA*ua3.^3/(76140)
Pf4=m1*9.8*f.*ua4/(3600)
Pw4=CdA*ua4.^3/(76140)
Ff1=m1*9.8*f
fz3=CdA*ua3.^2/21.15+Ff1
fz4=CdA*ua4.^2/21.15+Ff1
%Pe3=fz3.*ua3./(3600*nT);
%Pe4=fz4.*ua4./(3600*nT);
Pe3=(Pf3+Pw3)/nT
Pe4=(Pf4+Pw4)/nT
b3=B0+B1.*Pe3+B2.*Pe3.^2+B3.*Pe3.^3+B4.*Pe3.^4
b4=B0+B1.*Pe4+B2.*Pe4.^2+B3.*Pe4.^3+B4.*Pe4.^4
Qs4=Pe4.*b4./(1.02*ua4*7.10*9.8)
Qs3=Pe3.*b3./(1.02*ua3*7.10*9.8)
figure(3)
plot(ua4,Qs4)
hold on
plot(ua3,Qs3)
2.82.62.42.221.81.61.40102030405060708090
n=600:1:4000
N=n/1000
T=-19.313+295.27*n/1000-165.44*N.*N+40.874*N.*N.*N-3.8445*N.*N.*N.*N
Pe=T.*n/9550
i0=6.17;
ig(1)=6.09
ig(2)=3.09
ig(3)=1.71
ig(4)=1.00
nT=0.85
r=0.367
f=0.013
m1=3880
m2=9590
CdA=2.77
ua1=0.377*r*n/(ig(1)*i0)
ua2=0.377*r*n/(ig(2)*i0)
ua3=0.377*r*n/(ig(3)*i0)
ua4=0.377*r*n/(ig(4)*i0);
n0=[815 1207 1614 2012 2603 3006 3403 3884]
B00=[1326.8 1354.7 1284.4 1122.9 1141.0 1051.2 1233.9 1129.7]
B10=[-416.46 -303.98 -189.75 -121.59 -98.893 -73.714 -84.478 -45.291]
B20=[72.379 36.657 14.524 7.0035 4.4763 2.8593 2.9788 0.71113]
B30=[-5.8629 -2.0533 -0.51184 -0.18517 -0.091077 -0.05138 -0.047449 -0.00075215]
B40=[0.17768 0.043072 0.0068164 0.0018555 0.00068906 0.00028230 -0.000038568]
B0=spline(n0,B00,n)
B1=spline(n0,B10,n)
B2=spline(n0,B20,n)
B3=spline(n0,B30,n)
B4=spline(n0,B40,n)
Pf3=m1*9.8*f.*ua3/(3600) %三档的滚动阻力功率
Pw3=CdA*ua3.^3/(76140) %三档的的空气阻力功率
Pf4=m1*9.8*f.*ua4/(3600)
Pw4=CdA*ua4.^3/(76140)
0.00035032 Ff1=m1*9.8*f
Pe3=(Pf3+Pw3)/nT %三档的发动机净功率
Pe4=(Pf4+Pw4)/nT %四档的发动机净功率
b3=B0+B1.*Pe3+B2.*Pe3.^2+B3.*Pe3.^3+B4.*Pe3.^4
b4=B0+B1.*Pe4+B2.*Pe4.^2+B3.*Pe4.^3+B4.*Pe4.^4
Qs4=Pe4.*b4./(1.02*ua4*7.10) %四档的百公里油耗
Qs3=Pe3.*b3./(1.02*ua3*7.10) %三档的百公里油耗
ua=[25 40 50]
ss=[50 250 250]
fz=CdA*ua.^2/21.15+Ff1 %匀速条件下的阻力
Pee=fz.*ua/(3600*nT);
b=spline(b4,Pe4,Pee) %匀速条件下的燃油消耗率
Qsy=Pee.*b./(1.02*ua*7.10)
a=[0.2 0.2 -0.36]
dt1=1/(3.6*0.2)
dt2=1/(3.6*0.2)
dt3=1/(3.6*(0.36))
ua11=25:1:40
ua22=40:1:50
ua33=50:-1:25
b11=spline(ua4,b4,ua11) b22=spline(ua4,b4,ua22)b33=spline(ua4,b4,ua33)If=0.218
Iw1=1.798
Iw2=3.598
%在加速条件下的各个速度节点的燃油消耗率
die4=1+(Iw1+Iw2)/(m1*r^2)+(If*i0^2*nT*ig(4).^2)/(m1*r^2);
Pej1=(m1*9.8*f.*ua11/(3600)+CdA.*ua11.^3/(76140)+(die4*m1.*ua11/3600)*0.2)/nT %在三个加速条件下的各个速度节点
Pej2=(m1*9.8*f.*ua22/(3600)+CdA.*ua22.^3/(76140)+(die4*m1.*ua22/3600)*0.2)/nT %的发动机净功率
Pej3=(m1*9.8*f.*ua33/(3600)+CdA.*ua33.^3/(76140)+(die4*m1.*ua33/3600)*0.2)/nT %
Qstj1=Pej1.*b11/(367.1*7.10) %在三中加速条件下的，各自的单位时间的燃油消耗量
Qstj2=Pej2.*b22/(367.1*7.10)
Qstj3=Pej3.*b33/(367.1*7.10)
i11=size(Qstj1)
i22=size(Qstj2)
i33=size(Qstj3)
i1=i11(2)
i2=i22(2)
i3=i33(2)
Qt1=Qstj1(2:i1-1)
Qt2=Qstj2(2:i2-1)
Qt3=Qstj3(2:i3-1)
q1=((Qstj1(1)+Qstj1(i1))*dt1./2+sum(Qt1)*dt1)/10
q2=((Qstj2(1)+Qstj2(i2))*dt2./2+sum(Qt2)*dt2)/10
q3=((Qstj3(1)+Qstj3(i3))*dt3./2+sum(Qt3)*dt3)/10
Qall=(q1+q2+q3+Qsy(:,1)+Qsy(:,2)+Qsy(:,3))*100/1075
q1 =5.8526
q2 =4.9810 q3 =6.0186 Qall =2.7916
第三大题
(1)
m0=4880; %空载质量m/kg
hg0=0.845; %空载质心高
L0=3.95; %空载轴距
a0=2.100; m=9290; hg=1.170; L=3.95; a=2.950; B=0.38; g=9.8;
G=m*g;
b=L-a;
G0=m0*g;
%空载质心至前轴距离
%满载质量m/kg
%满载质心高
%满载轴距
%满载质心至前轴距离B%B为制动力分配系数
b0=L0-a0;
Fu1 =0:1000:100000;
Fu2=1/2*(G/hg*(b^2+4*hg*L/G*Fu1).^0.5-(G*b/hg+2*Fu1));
Fu02=1/2*(G0/hg0*(b0^2+4*hg0*L0/G0*Fu1).^0.5-(G0*b0/hg0+2*Fu1));
F2=(1-B)*Fu1/B;
plot(Fu1,Fu2) %绘制满载时的I曲线
hold on
plot(Fu1,Fu02) %绘制空载时的I曲线
hold on
plot(Fu1,F2); %%绘制beta曲线
title('beta线和I曲线')
text(30000,50000,'beta曲线')
text(25000,10000,'空载时I曲线')
text(25000,30000,'满载时I曲线')
xlabel('Fu1')
ylabel('Fu2')
figure(2)
fe=[0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9];
for i=1:10
Fxb1fk=0:100:120000;Fxb1rk=0:100:120000;
Fxb2fk=(L0-fe(i)*hg0)/(fe(i)*hg0).*Fxb1fk-G0*b0/hg0;
Fxb2rk=(-1*fe(i)*hg0)/(L0+fe(i)*hg0).*Fxb1rk+fe(i)*G0*a0/(L0+fe(i)*hg0);
plot(Fxb1fk,Fxb2fk)
hold on
plot(Fxb1rk,Fxb2rk,'r')
hold on
end
xlabel('Fxb1')
ylabel('Fxb2')
axis([0 120000 0 40000])
title('空载时的f、r线组图')
figure(3)
for i=1:10
Fxb1fk=0:100:220000;Fxb1rk=0:100:220000;
Fxb2fk=(L-fe(i)*hg)/(fe(i)*hg).*Fxb1fk-G*b/hg;
Fxb2rk=(-1*fe(i)*hg)/(L+fe(i)*hg).*Fxb1rk+fe(i)*G*a/(L+fe(i)*hg);
plot(Fxb1fk,Fxb2fk)
hold on
plot(Fxb1rk,Fxb2rk,'r')
hold on
end
xlabel('Fxb1')
ylabel('Fxb2')
axis([0 220000 0 80000])
title('满载时的f、r线组图')
1816141210x 104beta线和I曲线Fu286beta曲线4满载时I曲线2空载时I曲线0-2012345Fu1678910x 104
43.532.5x 104空载时的f、r线组图Fxb221.510.500246Fxb181012x 104
8765Fxb2x 104满载时的f、r线组图4321000.20.40.60.811.2Fxb11.41.61.822.2x 105
(2)-(3)
m0=4880; %空载质量m/kg
hg0=0.845; %空载质心高
L0=3.95; %空载轴距
a0=2.100; %空载质心至前轴距离
m=9290; hg=1.170; L=3.95; a=2.950; B=0.38; g=9.8;
G=m*g;
b=L-a;
G0=m0*g;
b0=L0-a0;
%满载质量m/kg
%满载质心高
%满载轴距
%满载质心至前轴距离B%B为制动力分配系数
z=0:0.1:1; %制动强度
fef=B*z*L./(b+z*hg);
fef0=B*z*L0./(b0+z*hg0);
fer=(1-B)*z*L./(a-z*hg);
fer0=(1-B)*z*L0./(a0-z*hg0);
figure(1)
plot(z,fef,z,fef0,z,fer,z,fer0,z,z)
text(0.8,1.5,'空车后轮')
text(0.8,1.2,'满载后轮')
text(0.7,0.6,'满载前轮')
text(0.8,0.4,'空车前轮')
figure(2)
Ef=z./fef*100
Ef0=z./fef0*100
Er=z./fer*100
Er0=z./fer0*100
plot(fef,Ef,fer,Er)
hold on
plot(fef0,Ef0,fer0,Er0)
axis([0 1 0 100])
text(0.3,90,'Ef')
text(0.8,90,'Er满载')
text(0.3,70,'Er空载')
21.81.6空车后轮1.41.210.80.60.40.2000.10.20.30.40.50.60.70.80.91满载前轮空车前轮满载后轮
100908070605040302010000.10.20.30.40.50.60.70.80.91Er空载EfEr满载
m0=4880;hg=0.845;l=3.950;a=2.100;b=1.850;beita=0.38;g=9.8;G0=m0*g;
m=9290;Hg=1.170;L=3.950;A=2.950;B=1.050;beita=0.38;g=9.8;G=m*g;
t1=0.02;t2=0.02;ua0=30;fai=0.80;
z=0:0.01:1.0;
faifk=beita*z*l./(b+z*hg);
faifm=beita*z*L./(B+z*Hg);
fairk=(1-beita)*z*l./(a-z*hg);
fairm=(1-beita)*z*L./(A-z*Hg);
Efk=z./faifk*100;
Efm=z./faifm*100;
Erk=z./fairk*100;
Erm=z./fairm*100;
ak1=Erk(81)*g*fai/100;
am1=Erm(81)*g*fai/100;
Sk1=(t1+t2/2)*ua0/3.6+ua0^2/(25.92*ak1);
Sm1=(t1+t2/2)*ua0/3.6+ua0^2/(25.92*am1);
disp('空载时，汽车制动距离Sk1=');
disp(Sk1);
disp('满载时，汽车制动距离Sm1=');
disp(Sm1);
ak2=fai*g*a/(l+fai*hg);
am2=fai*g*A/(L+fai*Hg);
ak3=fai*g*b/(l-fai*hg);
am3=fai*g*B/(L-fai*Hg);
Sk2=(t1+t2/2)*ua0/3.6+ua0^2/(25.92*ak2);
Sm2=(t1+t2/2)*ua0/3.6+ua0^2/(25.92*am2);
Sk3=(t1+t2/2)*ua0/3.6+ua0^2/(25.92*ak3);
Sm3=(t1+t2/2)*ua0/3.6+ua0^2/(25.92*am3);
disp('空载时，前制动器损坏，汽车制动距离Sk2=');
disp(Sk2);
disp('满载时，前制动器损坏，汽车制动距离Sm2=');
disp(Sm2);
disp('空载时，后制动器损坏，汽车制动距离Sk3=');
disp(Sk3);
disp('满载时，后制动器损坏，汽车制动距离Sm3=');
disp(Sm3);
空载时，汽车制动距离Sk1=7.8668
满载时，汽车制动距离Sm1=5.6354
空载时，前制动器损坏，汽车制动距离Sk2=10.0061
满载时，前制动器损坏，汽车制动距离Sm2=7.5854
空载时，后制动器损坏，汽车制动距离Sk3=8.0879
满载时，后制动器损坏，汽车制动距离Sm3=12.9629
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