Rewrite from Mathematica to MATLAB

Question

Kseniia Kudriavtceva 2020-11-15

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/648258-rewrite-from-mathematica-to-matlab

评论： Kseniia Kudriavtceva 2020-11-18

在 MATLAB Online 中打开

SO, I have this problem, which I solved for dynamics, but now I should write a code and then generate two plots. (5.38)

I found a solution in Mathematica software, but I can't figure out what am I doing wrong in MATLAB. Here's my code:

% Given
syms theta;
W_A=100;
m_A=W_A/32.2;
W_B=20;
m_B=W_B/32.2;
L=15;
theta_0= deg2rad(70);
% Solve the system of three equations
one = str2sym('W_A*L*(cos(theta)-cos(theta_0))-1/2*m_A*V_A^2-1/2*m_B*V_Bx^2+W_A*L');
two = str2sym('m_B*V_Bx+m_A*(V_Bx+L*theta_1*cos(theta))');
three = str2sym('-V_A^2+(V_Bx+ L*theta_1*cos(theta))^2+(L*theta_1*sin(theta))^2');
[theta_1,V_A,V_Bx] = solve(one,two,three);
% Plot the velocity of the trolley and the speed of the rider as a function of the angle θ of the first half of a full swing
fplot(V_Bx, [-70,70], 'Linewidth',2)
hold on
fplot(V_A, [-70,70], '-.*c')
hold off
% Plot the velocity of the trolley and the speed of the rider as a function of the angle θ of the second half of a full swing
fplot(V_Bx, [-70,70], 'Linewidth',2)
hold on
fplot(V_A, [-70,70], '-.*c')
hold off

Thank you so much in advance!!!

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Ameer Hamza 2020-11-15

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/648258-rewrite-from-mathematica-to-matlab#answer_545018

编辑：Ameer Hamza 2020-11-17

在 MATLAB Online 中打开

Following shows how to write this in MATLAB.

syms theta theta_1 V_A V_Bx;
W_A=100;
m_A=W_A/32.2;
W_B=20;
m_B=W_B/32.2;
L=15;
theta_0= deg2rad(70);
% Solve the system of three equations
one = W_A*L*(cos(theta)-cos(theta_0))-1/2*m_A*V_A^2-1/2*m_B*V_Bx^2+W_A*L;
two = m_B*V_Bx+m_A*(V_Bx+L*theta_1*cos(theta));
three = -V_A^2+(V_Bx+ L*theta_1*cos(theta))^2+(L*theta_1*sin(theta))^2;
[theta_1,V_A,V_Bx] = solve(one,two,three);
% Plot the velocity of the trolley and the speed of the rider as a function of the angle θ of the first half of a full swing
fplot(V_Bx, [-70,70], 'Linewidth',2)
hold on
fplot(V_A, [-70,70], '-.*c')
hold off
% Plot the velocity of the trolley and the speed of the rider as a function of the angle θ of the second half of a full swing
fplot(V_Bx, [-70,70], 'Linewidth',2)
hold on
fplot(V_A, [-70,70], '-.*c')
hold off

The above can take a long time to plot because there are 12 solutions given by solve() functions. To speed up the computation, you can convert the functions to numeric function handle using matlabFunction() and then use fplot().