《汽车理论》第三章作业

一款汽车参数如下，做出主减速器传动比在不同值时燃油经济性-加速时间曲线

|--------------------------------|-----------------|-----------------|------------------|------------------|
| f = 0.013; | CdA = 2.77; | If = 0.218; | nt = 0.85; | Iw1 = 1.798; |
| m = 3880; | g = 9.8; | r = 0.367; | Iw2 = 3.598; | L = 3.2; |
| ig = $6.09 3.09 1.71 1$ ; | hg = 0.9; | a = 1.947; | | |

做出图如下所示：

|--------------|-------------|-------------|-------------|-------------|
| 各i0值对应的加速时间 |||||
| 295.0426 | 75.6065 | 66.6574 | 50.7327 | 45.8679 |

从曲线图可以看出，i0值越大，汽车加速性能越好，但燃油经济性越差

代码如下所示

Matlab 复制代码

m = 3880;
g = 9.8;
r = 0.367;
nt = 0.85;
f = 0.013;
CdA = 2.77;
If = 0.218;
Iw1 = 1.798;
Iw2 = 3.598;
ig = [6.09 3.09 1.71 1];
L = 3.2;
a = 1.947;
hg = 0.9;
i0 = [5.17 5.43 5.83 6.17 6.33];
Pe = 60;
B = 0.00028230*Pe^4 - 0.047449*Pe^3 + 2.9788*Pe^2 - 84.478*Pe + 1233.9;

for s = 1:5 % 设各个i0值对应的速度在该情况下为ua0
    ua0(s) = 0.377*r*3403/(ig(4)*i0(s));
    Qs(s) = Pe*B/(1.02*ua0(s)*7.0); % 求出各i0值的等速百公里油耗
end

for i = 1:69
    n(i) = (i + 11)*50;
    Tq(i) = -19.313 + 295.27*(n(i)/1000) - 165.44*(n(i)/1000).^2 + 40.874*(n(i)/1000).^3 - 3.8445*(n(i)/1000).^4;
end



for s = 1:5
    for j = 1:4
        for i = 1:69
            deta(j) = 1 + (Iw1 + Iw2)/(m*r^2) + If*ig(j)^2*i0(s)^2*nt/(m*r^2);
            ua(i,j) = 0.377*r*n(i)/(ig(j)*i0(s));
            Ft(i,j) = Tq(i)*ig(j)*i0(s)*nt/r;
            Fw(i,j) = CdA*ua(i,j)^2/21.15;
            a(i,j) = (Ft(i,j) - Fw(i,j) - m*g*f)/(deta(j)*m);
            b(i,j) = 1/a(i,j); % b(i,j)为加速度倒数函数
        end
    end

    k = -1;
    i = 1;
    while(k < 0)
        k = ua(i,2) - ua(69,1);
        i = i + 1;
    end
    w = i - 1; % w为从1挡换至2挡时的转速的自变量

    k = -1;
    i = 1;
    while (k < 0)
        k = ua(i,3) - ua(69,2);
        i = i + 1;
    end
    x = i - 1; % x为换至3挡时的转速的自变量

    k = -1;
    i = 1;
    while (k < 0)
        k = ua(i,4) - ua(69,3);
        i = i + 1;
    end
    y = i - 1; % y为换至4挡时的转速的自变量

    t(s) = ua(1,1)*b(1,1); % 1挡600r/min 前的加速时间
    % 1挡加速时间
    for i1 = 2:69
        t1(i1) = 0.5*(ua(i1,1) - ua(i1-1,1))*(b(i1,1) + b(i1-1,1));
        t(s) = t(s) + t1(i1);
    end
    t(s) = t(s) + (ua(w,2) - ua(69,1))*b(w,2);

    for i2 = w:69
        % 2 挡加速时间
        t2(i2) = 0.5*(ua(i2,2) - ua(i2-1,2))*(b(i2,2) + b(i2-1,2));
        t(s) = t(s) + t2(i2);
    end
    t(s) = t(s) + (ua(x,3) - ua(69,2))*b(x,3);

    for i3 = x:69
        % 3挡加速时间
        t3(i3) = 0.5*(ua(i3,3) - ua(i3-1,3))*(b(i3,3) + b(i3-1,3));
        t(s) = t(s) + t3(i3);
    end
    t(s) = t(s) + (ua(y,4) - ua(69,3))*b(y,4);

    % 4挡加速至最高速时间
    for i4 = y:69
        t4(i4) = 0.5*(ua(i4,4) - ua(i4-1,4))*(b(i4,4) + b(i4-1,4));
        t(s) = t(s) + t4(i4);
    end
    t(s) = t(s)/3.6; % 把时间单位从(km·s^2)/(m·h)转为s
end

% 输出各i0值对应的加速时间
disp('各i0值对应的加速时间');
disp(t);

% 绘制燃油经济性 - 加速时间曲线
plot(Qs, t, 'o');
title('燃油经济性一加速时间曲线');
xlabel('Qs(L)');
ylabel('t(s)');

% 从曲线图可以看出，i0值越大，汽车加速性能越好，但燃油经济性越差。