1.3确定一轻型货车的动力性能（货车可装用4挡或5挡变速器，任选其中的一种进行整车性能计算）：1）绘制汽车驱动力与行驶阻力平衡图。

2）求汽车最高车速，最大爬坡度及克服该坡度时相应的附着率。

3）绘制汽车行驶加速度倒数曲线，用图解积分法求汽车用2档起步加速行驶至70km/h的车速一时间曲线，或者用计算机求汽车用2档起步加速行驶至70km/h的加速时间。

轻型货车的有关数据：汽油发动机使用外特性的Tq-n曲线的拟合公式为一19.313 295.27（金）一165・44（金）2 4°.874侖）3一3・8445式中，Tq为发动机转矩（N?m）;n为发动机转速（r/min ）。

发动机的最低转速n min=600r/min,最咼转速r max=4000r/min。

装载质量2000kg整车整备质量1800kg总质量3880kg车轮半径0.367m传动系机械效率n=0.85滚动阻力系数f=0.013空气阻力系数X迎风面积C D A=2.77m2主减速器传动比i0=5.83飞轮转动惯量 2|f=0.218kg?m一前轮转动惯量I w1=1.798kg?m四后轮转动惯量I w2=3.598kg?m变速器传动比ig（数据如下表）轴距L=3.2m质心至前轴距离（满载）a=1.974m 质心高（满载）hg=0.9m解：Matlab程序：(1)求汽车驱动力与行驶阻力平衡图和汽车最高车速程序：n=[600:10:4000];Tq=-19.313+295.27*( n/1000)-165.44*(门/1000)八2+40.874*(门/1000)八3- 3.8445*( n/1000).A4;m=3880;g=9.8; nmi n=600; nm ax=4000;G=m*g;ig=[5.56 2.769 1.644 1.00 0.793];nT=0.85;r=0.367;f=0.013;CDA=2.77;i0=5.83; L=3.2;a=1.947;hg=0.9;lf=0.218;lw1= 1.798;lw2=3.598;Ft仁Tq*ig(1)*i0* nT/r;Ft2=Tq*ig(2)*i0* nT/r;Ft3=Tq*ig(3)*i0* nT/r;Ft4=Tq*ig(4)*i0* nT/r;Ft5=Tq*ig(5)*i0* nT/r;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;ua5=0.377*r* n/ig(5)/i0;ua=[0:5:120];Ff=G*f;Fw=CDA*ua.A2/21.15;Fz=Ff+Fw;plot(ua1,Ft1,ua2,Ft2,ua3,Ft3,ua4,Ft4,ua5,Ft5,ua,Fz);title('驱动力-行驶阻力平衡图');xlabel('ua(km/s)');ylabel('Ft(N)');gtext('Ft1'),gtext('Ft2'),gtext('Ft3'),gtext('Ft4'),gtext('Ft5'),gtext('Ff+Fw'); zoom on; [x,y]=gi nput(1);zoom off;disp(汽车最高车速=');disp(x);disp('km/h');汽车最高车速=99.3006km/h(2)求汽车最大爬坡度程序：n=[600:10:4000];Tq=-19.313+295.27*( n/1000)-165.44*(门/1000)八2+40.874*(门/1000)八3- 3.8445*( n/1000).A4;m=3880;g=9.8; nmi n=600; nm ax=4000;G=m*g;ig=[5.56 2.769 1.644 1.00 0.793];nT=0.85;r=0.367;f=0.013;CDA=2.77;i0=5.83;L=3.2;a=1.947;hg=0.9;lf=0.218;lw1= 1.798;lw2=3.598;Ft仁Tq*ig(1)*i0* nT/r;ua1=0.377*r* n/ig(1)/i0;Ff=G*f;Fw仁CDA*ua"2/21.15;Fz仁Ff+Fw1;Fi1= Ft1-Fz1;Zoom on;imax=100*ta n(asi n(max(Fi1/G)));disp(汽车最大爬坡度=');disp(imax);disp('%');汽车最大爬坡度=35.2197%(3)求最大爬坡度相应的附着率和求汽车行驶加速度倒数曲线程序：clearn=[600:10:4000];Tq=-19.313+295.27*( n/1000)-165.44*(门/1000)八2+40.874*(门/1000)八3-3.8445*( n/1000).A4;m=3880;g=9.8; nmi n=600; nm ax=4000;G=m*g;ig=[5.56 2.769 1.644 1.00 0.793];nT=0.85;r=0.367;f=0.013;CDA=2.77;i0=5.83;L=3.2;a=1.947;hg=0.9;lf=0.218;lw1= 1.798;Iw2=3.598;Ft仁Tq*ig(1)*i0* nT/r;Ft2=Tq*ig(2)*i0* nT/r;Ft3=Tq*ig(3)*i0* nT/r;Ft4=Tq*ig(4)*i0* nT/r;Ft5=Tq*ig(5)*iO* nT/r;ua1=0.377*r* n/ig(1)/iO;ua2=0.377*r* n/ig(2)/iO;ua3=0.377*r* n/ig(3)/iO;ua4=0.377*r* n/ig(4)/i0;ua5=0.377*r* n/ig(5)/i0;Fw1=CDA*ua1.A2/21.15;Fw2=CDA*ua2.A2/21.15;Fw3=CDA*ua3.A2/21.15;Fw4=CDA*ua4.A2/21.15;Fw5=CDA*ua5.A2/21.15;Ff=G*f;deta1=1+(lw1+lw2)/(m*rA2)+(lf*ig⑴八2*心八2* nT)/(m*「A2); deta2=1+(lw1+lw2)/(m*rA2)+(lf*ig (2)八2诃2* nT)/(m*「A2); deta3=1+(lw1+lw2)/(m*rA2)+(lf*ig(3)A2*i0A2* nT)/(m*「A2);deta4=1+(lw1+lw2)/(m*rA2)+(lf*ig ⑷八2*心八2* nT)/(m*「A2);deta5=1+(lw1+lw2)/(m*rA2)+(lf*ig(5)A2*i0A2* nT)/(m*「A2);a仁(Ft1-Ff-Fw1)/(deta1*m);ad1=1./a1;a2=(Ft2-Ff-Fw2)/(deta2*m);ad2=1./a2;a3=(Ft3-Ff-Fw3)/(deta3*m);ad3=1./a3;a4=(Ft4-Ff-Fw4)/(deta4*m);ad4=1./a4;a5=(Ft5-Ff-Fw5)/(deta5*m);ad5=1./a5;Plot(ua1,ad1,ua2,ad2,ua3,ad3,ua4,ad4,ua5,ad5);axis([O 99 010]);title('汽车的加速度倒数曲线');xlabel('ua(km/h)');ylabel('1/a');gtext('1/a1');gtext('1/a2');gtext('1/a3');gtext('1/a4');gtext('1/a5'); a=max(a1);af=asi n(max(Ft1-Ff-Fw1)/G);C=ta n(af)/(a/ L+hg*ta n(af)/L);disp(假设后轮驱动，最大爬坡度相应的附着率=');disp(C);假设后轮驱动，最大爬坡度相应的附着率=0.4219(4) >>clear nT=0.85;r=0.367;f=0.013;CDA=2.77;i0=5.83;lf=0.218;Iw1= 1.798;lw2=3.598;L=3.2;a=1.947;hg=0.9;m=3880;g=9.8;G=m*g; ig=[5.56 2.7691.6441.00 0.793];nmin=600;nm ax=4000;u1=0.377*r* nmin ./ig/i0;u2=0.377*r* nm ax./ig/i0;deta=0*ig;for i=1:5deta(i)=1+(Iw1+Iw2)/(m*r A2)+(If*(ig(i))A2*i0A2* nT)/(m*r A2);endua=[6:0.01:99];N=le ngth(ua); n=0;Tq=0;Ft=0;i nv_a=0*ua;delta=0*ua;Ff=G*f;Fw=CDA*ua.A2/21.15;for i=1:Nk=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/1000F2+40.874*( n/1000F3- 3.8445*( n/1000)A4;Ft=Tq*ig(2)*i0* nT/r;in v_a(i)=(deta(2)*m)/(Ft-Ff-Fw(i));delta(i)=0.01*i nv_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/1000F2+40.874*( n/1000F3- 3.8445*( n/1000)A4;Ft=Tq*ig(3)*i0* nT/r;in v_a(i)=(deta(3)*m)/(Ft-Ff-Fw(i));delta(i)=0.01*i nv_a(i)/3.6;elseif ua(i)<=u2 (4)n=ua(i)*(ig ⑷ *i0/r)/0.377;Tq=-19.313+295.27*( n/1000)-165.44*( n/1000F2+40.874*( n/1000F3- 3.8445*( n/1000)A4;Ft=Tq*ig(4)*i0* nT/r;in v_a(i)=(deta(4)*m)/(Ft-Ff-Fw(i));delta(i)=0.01*i nv_a(i)/3.6;elsen=ua(i)*(ig (5)*i0/r)/0.377;Tq=-19.313+295.27*( n/1000)-165.44*( n/1000F2+40.874*( n/1000F3- 3.8445*( n/1000)A4;Ft=Tq*ig(5)*i0* nT/r;in v_a(i)=(deta(5)*m)/(Ft-Ff-Fw(i));delta(i)=0.01*i nv_a(i)/3.6;enda=delta(1:k);t(i)=sum(a);end plot(t,ua);axis([O 80 0100]);title('汽车2档原地起步换挡加速时间曲线');xlabel('时间t (s)');ylabel('速度ua( km/h)');>> gin putans=25.8223 70.073725.7467 70.0737所以汽车2档原地起步换挡加速行驶至70km/h的加速时间约为25.8s2.7已知货车装用汽油发动机的负荷特性与万有特性。