精品word 可编辑资料 - - - - - - - - - - - - -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Tq19.313295.27(n)165.44(n)240.874(n)33.8445(n)41000100010001000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nmin=600r/min,最高转速 nmax=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t =0.85滚动阻力系数f=0.013空气阻力系数 迎风面积CDA=2.77m2主减速器传动比i0=5.83飞轮转动惯量If=0.218kg?m2二前轮转动惯量Iw1=1.798kg?m2四后轮转动惯量Iw2=3.598kg?m2变速器传动比ig(数据如下表 )档档档档档四档变速器6.093.091.711.00-五档变速器5.562.7691.6441.000.793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*(n/1000).2+40.874*(n/1000).3-3.8445*(n/1000).4;m=3880;g=9.8;nmin=600;nmax=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;If=0.218;Iw1=1.798;Iw2=3.598;Ft1=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.2/21.15; Fz=Ff+Fw;第 1 页，共 13 页 - - - - - - - - - -精品word 可编辑资料 - - - - - - - - - - - - -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=ginput(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*(n/1000).2+40.874*(n/1000).3-3.8445*(n/1000).4;m=3880;g=9.8;nmin=600;nmax=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;If=0.218;Iw1=1.798;Iw2=3.598;Ft1=Tq*ig(1)*i0*nT/r; ua1=0.377*r*n/ig(1)/i0; Ff=G*f; Fw1=CDA*ua1.2/21.15; Fz1=Ff+Fw1;Fi1=Ft1-Fz1;Zoom on; imax=100*tan(asin(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：第 2 页，共 13 页 - - - - - - - - - -clear n=600:10:4000;精品word 可编辑资料 - - - - - - - - - - - - -Tq=-19.313+295.27*(n/1000)-165.44*(n/1000).2+40.874*(n/1000).3-3.8445*(n/1000).4;m=3880;g=9.8;nmin=600;nmax=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;If=0.218;Iw1=1.798;Iw2=3.598;Ft1=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; Fw1=CDA*ua1.2/21.15; Fw2=CDA*ua2.2/21.15; Fw3=CDA*ua3.2/21.15; Fw4=CDA*ua4.2/21.15; Fw5=CDA*ua5.2/21.15;Ff=G*f; deta1=1+(Iw1+Iw2)/(m*r2)+(If*ig(1)2*i02*nT)/(m*r2); deta2=1+(Iw1+Iw2)/(m*r2)+(If*ig(2)2*i02*nT)/(m*r2); deta3=1+(Iw1+Iw2)/(m*r2)+(If*ig(3)2*i02*nT)/(m*r2); deta4=1+(Iw1+Iw2)/(m*r2)+(If*ig(4)2*i02*nT)/(m*r2); deta5=1+(Iw1+Iw2)/(m*r2)+(If*ig(5)2*i02*nT)/(m*r2); a1=(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(0 99 0 10);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=asin(max(Ft1-Ff-Fw1)/G);C=tan(af)/(a/L+hg*tan(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=第 3 页，共 13 页 - - - - - - - - - -精品word 可编辑资料 - - - - - - - - - - - - -0.4219(4) clear nT=0.85;r=0.367;f=0.013;CDA=2.77;i0=5.83;If=0.218; Iw1=1.798;Iw2=3.598;L=3.2;a=1.947;hg=0.9;m=3880;g=9.8; G=m*g; ig=5.56 2.769 1.644 1.00 0.793; nmin=600;nmax=4000;u1=0.377*r*nmin./ig/i0; u2=0.377*r*nmax./ig/i0; deta=0*ig;for i=1:5deta(i)=1+(Iw1+Iw2)/(m*r2)+(If*(ig(i)2*i02*nT)/(m*r2);end ua=6:0.01:99;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: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/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;elseif ua(i)=