Results showing up as NaN

5 次查看（过去 30 天）

Alexandru Bortea 2017-4-19

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/336167-results-showing-up-as-nan

评论： Andrew Newell 2017-4-20

I have been working on a launch control simulation and something happened recently because the matrix z is returning only NaN values now... I do not remember changing anything in the script or the function. I have also attached below the main function used with the code... maybe you spot a mistake there...

global m g I h lR lF r LCREV_MAX LCSPEED_MAX 
LCREV_MAX = 12000;
LCSPEED_MAX = 35;
m = 295;                % mass of vehicle including driver
g = 9.81;               % gravitational acceleration
r = 0.23;               % wheel radius
I = 0.2645;             % tyre moment of inertia
h = 0.28;               % CoG height
lR = 0.765;             % Distance of CoG to rear axle
lF = 0.765;             % Distance of CoG to front axel
z10 = 0;                % initial x position
z20 = 0;                % initial linear velocity
z30 = 0;                % initial angle of rear wheel
z40 = 0;                % intial angular velocity of rear wheel
z0 = [z10 z20 z30 z40]; % initial conditions vector
t0 = 0;                 % intial time
tf = 6;                 % final time 
[t,z] = ode45('LC_eom',(t0:0.1:tf),z0);
x = z(:,1);             % position as first column of z matrix
v = z(:,2);             % linear velocity as second column of z matrix
theta = z(:,3);         % angle as third column of z matrix
omega = z(:,4);         % angular velocity as fourth column of z matrix

8 个评论
显示 6更早的评论隐藏 6更早的评论

Andrew Newell 2017-4-20

编辑：Andrew Newell 2017-4-20

在 MATLAB Online 中打开

One reason you may be using global variables is that ode45 expects a function with two variables. However, that is easily handled using anonymous functions. For example, the function LC_eom needs m, I and r in addition to t and z. However, these are just parameters that (I presume) aren't changing while ode45 is running. You can define

function dz = LC_eom (t,z,m,I,r,)

in LC_eom.m and then, LCS.m, define

fun = @(t,z) LC_eom(t,z,m,I,r);

and use that in ode45:

[t,z] = ode45(fun,(t0:0.1:tf),z0);

Alexandru Bortea 2017-4-20