How to do vector loop equation?

Question

Mhadi Alessa 2019-10-14

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/485272-how-to-do-vector-loop-equation

编辑： Karim 2022-10-26

'input';
for R1=8 
R2=5; 
R3=7; 
R4=6;
end 
for angle_2=25 
    omega_2=24; 
    alpha_2=-4;
end
'syms, angle_3, angle_4';
[angle_3]='solve(R2*cos(angle2)+R3*cos(angle3)-R4*cos(angle4)-R1=0';
[angle_4] = 'solve(R2*sin(angle2)+R3*sin(angle3)-R4*sin(angle4)=0';
[omega_3] = 'solve(-R2*(omega2)*sin(angle2)-R3*(omega3)*sin(angle3)+R4*(omega4)*sin(angle4)=0';
[omega_4]= 'solve(R2*(omega2)*cos(angle2)+R3*(omega3)*cos(angle3)-R4*(omega4)*cos(angle4)=0';
[alpha_3] = 'solve(-R2*(alpha2*sin(angle2)+(omega2)^2*cos(angle2))-R3*(alpha3*sin(angle3)+(omega3)^2*cos(angle3))+R4*(alpha4*sin(angle4)+(omega4)^2*cos(angle4))=0';
[alpha_4] = 'solve(R2*(alpha2*cos(angle2)-(omega2)^2*sin(angle2))+R3*(alpha3*cos(angle3)-(omega3)^2*sin(angle3))-R4*(alpha4*cos(angle4)-(omega4)^2*sin(angle4))=0';
angle_R3=angle3;
angle_R4=angle4;
R3_angular_velocity=omega_3;
R4_angular_velocity=omega_4;
R3_angular_acceleation=alpha_3;
R4_angular_acceleation=alpha_4;

4 个评论
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Zubair Ghafoor 2022-10-26

Hi you haven't initialized the Angle3 can you please first give the value of this, then your code is going to work.

Jan 2022-10-26

在 MATLAB Online 中打开

@Mhadi Alessa: The code looks very strange:

'input';  % Why? Do you just want to display a message? Then:
disp('input')
for R1=8 % What is the purpose to run a loop over one element?
% easier without FOR:
R1 = 8;
R2=5; 
R3=7; 
R4=6;
%for angle_2=25  see above
angle_2=25;
omega_2=24; 
alpha_2=-4;
% end
% See above: 'syms, angle_3, angle_4';
% Why do you use square brackets here?
  [angle_3]='solve(R2*cos(angle2)+R3*cos(angle3)-R4*cos(angle4)-R1=0';
% ^       ^ ?
% Setting angle_3 to a char vector looks strange also.
% Do you mean:
angle_3 =  solve('R2*cos(angle2)+R3*cos(angle3)-R4*cos(angle4)-R1 = 0');

Currently the complete code does neither look like meaningful Matlab code nor does it compute anything.

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Answer 1

Karim 2022-10-26

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/485272-how-to-do-vector-loop-equation#answer_1084118

编辑：Karim 2022-10-26

在 MATLAB Online 中打开

The syntax for the solve function works a bit different, see below for a demonstration.

Notice that if you have a set of two equations with two unkowns, you can pass both of them directly into the solve function.

R1 = 8;
R2 = 5; 
R3 = 7; 
R4 = 6;
angle_2 = 25;
omega_2 = 24; 
alpha_2 = -4;
syms angle_3 angle_4 omega_3 omega_4 alpha_3 alpha_4
% set up equations
Angle_eqs = [R2*cos(angle_2)+R3*cos(angle_3)-R4*cos(angle_4)-R1 == 0;
             R2*sin(angle_2)+R3*sin(angle_3)-R4*sin(angle_4)    == 0];
Omega_eqs = [-R2*(omega_2)*sin(angle_2)-R3*(omega_3)*sin(angle_3)+R4*(omega_4)*sin(angle_4) == 0;
              R2*(omega_2)*cos(angle_2)+R3*(omega_3)*cos(angle_3)-R4*(omega_4)*cos(angle_4) == 0];
Alpha_Eqs = [-R2*(angle_2*sin(angle_2)+(omega_2)^2*cos(angle_2))-R3*(alpha_3*sin(angle_3)+(omega_3)^2*cos(angle_3))+R4*(alpha_4*sin(angle_4)+(omega_4)^2*cos(angle_4)) == 0;
              R2*(angle_2*cos(angle_2)-(omega_2)^2*sin(angle_2))+R3*(alpha_3*cos(angle_3)-(omega_3)^2*sin(angle_3))-R4*(alpha_4*cos(angle_4)-(omega_4)^2*sin(angle_4)) == 0];
% solve the equations
Angle = solve(Angle_eqs,[angle_3 angle_4]);
angle_3 = eval(Angle.angle_3); 
angle_4 = eval(Angle.angle_4); 
% this provides two possible solutions. Below i simply pick the first slution,
% However you need to check if this is the one you want
angle_3 = angle_3(1);
angle_4 = angle_4(1);
Omega = solve(Omega_eqs,[omega_3 omega_4]);
omega_3 = eval(Omega.omega_3);
omega_4 = eval(Omega.omega_4);
Alpha = solve(Alpha_Eqs,[alpha_3 alpha_4]);
alpha_3 = eval(Alpha.alpha_3);
alpha_4 = eval(Alpha.alpha_4);
% print results to the display
fprintf("Angle 3 = %.3f\nAngle 4 = %.3f\n",angle_3,angle_4)
Angle 3 = -0.809
Angle 4 = -1.268
fprintf("Omega 3 = %.3f\nOmega 4 = %.3f\n",omega_3,omega_4)
Omega 3 = -35.070
Omega 4 = -28.245
fprintf("Alpha 3 = %.3f\nAlpha 4 = %.3f\n",alpha_3,alpha_4)
Alpha 3 = -1372.136
Alpha 4 = -2497.489