Question

我正在编写一个关于弹丸摩擦力的代码。我认为我犯了一些错误，但我找不到它。它是一个名为targetangle.m的MATLAB函数，它根据发射速度vs，目标距离d和所需精度e计算武器的最佳目标角度θ。

 function[ theta dif ] = targetangle(vs,d,e)

     % Input the initial condition:

     th = 1:0.1:45;

     for theta=th 

         k = 0.2;

         g = 9.81;

         dt = 0.001;

         the = theta * pi/180.;

         u(1) = vs * cos(the);

         v(1) = vs * sin(the);

         % Launch pad location:

         x(1) = 0.;

         y(1) = 0.;

         for t=1:1:6000;

             u(t+1) = u(t)- dt * (k * sqrt(u(t)^2+v(t)^2) * u(t));

             v(t+1) = v(t)- dt * (k * sqrt(u(t)^2+v(t)^2) * v(t) + g);

             x(t+1) = x(t) + u(t) * dt;

             y(t+1) = y(t) + v(t) * dt;

             % Determination of when the object hits ground:

             if y(t+1) < 0

                 dif = min(abs(x(t+1) - d));

                 plot(x,y)

             end

             if y(t+1) < 0;

                 break

             end

         end

         % Once object hits terminate the computations with a break:

         if y(t+1) < 0; 

             break

         end

     end

     if dif < e

         disp(dif)

     else

         theta = NaN

     end

当你这样输入时：

vs = 100;

d = 12;

e = 1;

[ theta dif ] = targetangle(vs,d,e)

输出应为：

theta =

    4

dif =

    0.0323

但我的代码输出是：

theta =

    NaN


theta =

    NaN


dif =

    3.6718

Answer 1

计算的问题是，在for循环期间不保存最佳结果。所以你的结果是你上一个循环周期的（非常正确的）结果。

对于θ= 45度，你得到theta = NaN，因为你在最后一个if子句中这样说。（顺便说一句：缺少分号是你打印两次的原因）

您需要将最佳结果存储在额外的变量中，例如： Theta_opt，dif_opt等：

function[ theta_opt, dif_opt ] = targetangle(vs,d,e)

 % Input the initial condition:

 th = 1:0.1:45;

 k = 0.2;

 g = 9.81;

 dt = 0.001;

 u = 0:.1:599;

 v = 0:.1:599;

 theta_opt = 1;

 dif_opt = 100;

 for theta=th 

     the = theta * pi/180.;

     u(1) = vs * cos(the);

     v(1) = vs * sin(the);

     % Launch pad location:

     x(1) = 0.;

     y(1) = 0.;

     for t=1:1:6000;

         u(t+1) = u(t)- dt * (k * sqrt(u(t)^2+v(t)^2) * u(t));

         v(t+1) = v(t)- dt * (k * sqrt(u(t)^2+v(t)^2) * v(t) + g);

         x(t+1) = x(t) + u(t) * dt;

         y(t+1) = y(t) + v(t) * dt;

         % Determination of when the object hits ground:

         if y(t+1) < 0

             dif = min(abs(x(t+1) - d));

             if(dif < dif_opt)
                 theta_opt = theta;
                 dif_opt = dif;
                 x_opt = x;
                 y_opt = y;
             end

             break

         end

         % Once object hits terminate the computations with a break:

         if y(t+1) < 0; 

             break

         end

     end

 end

 plot(x_opt, y_opt);

 if dif_opt < e

     disp(dif_opt)

 else

     theta_opt = NaN;

 end

关于轨迹的Matlab代码

1 个答案: