Code about paper airplane simulation cannot be run

Question

Lau Pei Shan 2019-12-20

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/497512-code-about-paper-airplane-simulation-cannot-be-run

评论： Lau Pei Shan 2019-12-24

I am not that proficient in programming. The error occured on the line "function sdot = PaperHoriz(t,s)", and I am not sure how to solve this error. The name of this M file is "PaperHoriz.m".

%paper airplane simulation
global CL CD S m g rho
S = 0.017;
m = 0.003;
g = 9.81;
rho = 1.225;
CD = 0.04; %lift and drag coeff simply given
CL = 0.22; %for this flight regime
gamma0 = -atan(CD/CL); %-ve sign because decent angle
v0 = sqrt(2*m*g/(rho*S*sqrt(CL^2+CD^2))); %initial velocity for min descent angle
 
%various initial flight condition
H = 2;
R = 0;
t0 = 0;
tf = 6;
tspan = [t0 tf];
 
%a) trimmed flight case
%initial angle is min angle of descent
s0 = [H;R;v0;gamma0]; %state vector's initial state
[ta, sa] = ode23('PaperHoriz',tspan,s0);
 
%b) same initial velocity but release at horizontal angle
gamma0 = 0;
s0 = [H;R;v0;gamma0];
[tb, sb] = ode23('PaperHoriz',tspan,s0);
 
%c) release at horizontal angle, double min-descent speed
newv0 = 2*v0;
s0 = [H;R;newv0;gamma0];
[tc, sc] = ode45('PaperHoriz',tspan,s0);
 
%d) release at horizontal angle, triple min-descent speed
newv0 = 3*v0;
s0 = [H;R;newv0;gamma0];
[td, sd] = ode45('PaperHoriz',tspan,s0);
 
%plot all the results
plot(sa(:,2),sa(:,1),sb(:,2),sb(:,1),sc(:,2),sc(:,1),sd(:,2),sd(:,1))
grid on;
ylim([0 5]);
xlim([-0.5 18]);
 
%invoked file with dynamics in it called PaperHoriz.m
function sdot = PaperHoriz(t,s) %error occured in this line
global CL CD S m g rho
v = s(3);
gamma = s(4);
q = rho/2*v^2;
 
%state vector = [H;R;v;gamma]
sdot = [v*sin(gamma);v*cos(gamma);1/m*(-q*S*CD-m*g*sin(gamma));1/(m*v)*(q*S*CL-m*g*cos(gamma))];
end

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Steven Lord 2019-12-20

What is the full and exact text of the error message you receive (all the text displayed in red and/or orange, exactly as it's displayed in the Command Window)?

Which release of MATLAB are you using?

Lau Pei Shan 2019-12-21

I am using R2019a version of matlab and this is the error I received.

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Answer 1

Walter Roberson 2019-12-21

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/497512-code-about-paper-airplane-simulation-cannot-be-run#answer_407302

The name of this M file is "PaperHoriz.m".

Name the file something else, like PaperHorizDriver.m .

When you have a script that defines a function, the script name cannot be the same as the name of the function you are defining.

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Lau Pei Shan 2019-12-24

在 MATLAB Online 中打开

I have corrected the error and finally there are no more error pop out, but here comes another problem, a graph supposed to be plotted out but it did not after I run the programme. Here is the latest coding.

%paper airplane simulation
global CL CD S m g rho
S = 0.017;
m = 0.003;
g = 9.81;
rho = 1.225;
CD = 0.04; %lift and drag coeff simply given
CL = 0.22; %for this flight regime
gamma0 = -atan(CD/CL); %-ve sign because decent angle
v0 = sqrt(2*m*g/(rho*S*sqrt(CL^2+CD^2))); %initial velocity for min descent angle
 
%various initial flight condition
H = 2;
R = 0;
t0 = 0;
tf = 6;
tspan = [t0 tf];
 
%a) trimmed flight case
%initial angle is min angle of descent
s0 = [H;R;v0;gamma0]; %state vector's initial state
[ta, sa] = ode23(@PaperHoriz,tspan,s0);
 
%b) same initial velocity but release at horizontal angle
gamma0 = 0;
s0 = [H;R;v0;gamma0];
[tb, sb] = ode23(@PaperHoriz,tspan,s0);
 
%c) release at horizontal angle, double min-descent speed
newv0 = 2*v0;
s0 = [H;R;newv0;gamma0];
[tc, sc] = ode45(@PaperHoriz,tspan,s0);
 
%d) release at horizontal angle, triple min-descent speed
newv0 = 3*v0;
s0 = [H;R;newv0;gamma0];
[td, sd] = ode45(@PaperHoriz,tspan,s0);
 
%plot all the results
plot(sa(:,2),sa(:,1),sb(:,2),sb(:,1),sc(:,2),sc(:,1),sd(:,2),sd(:,1))
grid on;
ylim([0 5]);
xlim([-0.5 18]);
 
%invoked file with dynamics in it called PaperHoriz.m
function sdot = PaperHoriz(s)
global CL CD S m g rho
v = s(3);
gamma = s(4);
q = rho/2*v^2;
 
%state vector = [H;R;v;gamma]
sdot = [v*sin(gamma);v*cos(gamma);1/m*(-q*S*CD-m*g*sin(gamma));1/(m*v)*(q*S*CL-m*g*cos(gamma))];
end

Walter Roberson 2019-12-24

在 MATLAB Online 中打开

Change

function sdot = PaperHoriz(s)

to

function sdot = PaperHoriz(~,s)

Lau Pei Shan 2019-12-24

My programme worked well finally. I am very thankful and appreciated with your guidances. Thank you so much!

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