Why is my Graph not plotting properly?

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Kathryn Warner
Kathryn Warner 2019-4-22
回答： Star Strider 2019-4-22
Below is code for calculating the velocity, acceleration and angular acceleration of a slider crank. Although I got the loop to work correctly for the calculations, I cannot get it to graph properly. Currently it is only plotting a single point. I know this is something to do with my stucture of the fuctions, I just do not know how to fix it.
I need to plot 4 figures. Figure 1 must plot Vbx, Vby and Vpx vs theta on a single figure. Figure 2 must plot Abx, Aby, Apx vs theta on a single figure. Figure 3 should plot Pomega vs theta and figure 4 must plot Palpha vs theta each on their own figure. Any thing helps, thank you.
clear
clc
close all
%%%%%% Defining Variables of Givens %%%%%%
theta = 0; % Rotational arm angle %
while(theta <= 360) % Beinging theta loop for 0 to 360 %
phi = asind(0.03/sind(theta)); % slider arm angle %
r = [0.06*cosd(theta), 0.06*sind(theta), 0]; % Rotational arm vector (m) %
ry = [0, 0.06*sind(theta), 0]; % Rotational arm vector in y direction (m) %
rx = [0.06*cosd(theta), 0, 0]; % Rotational arm vector in x direction (m) %
rxs = 0.06*cosd(theta);
rs = 0.06; % Rotational arm length scalar (m) %
d = [0.18*cosd(phi), -0.18*sind(phi), 0]; % Sliding arm length (m) %
dy = [0, -0.18*sind(phi), 0]; % Sliding arm length in y direction (m) %
dys = -0.18*sind(phi); % Sliding arm length in y direction (m) %
dx = [0.18*cosd(phi),0, 0]; % Sliding arm length (m) %
dxs = 0.18*cosd(phi); % Sliding arm length (m) %
ds = 0.18; % Sliding arm length scalar (m) %
Bomega = [0,0,250]; % Omega AB (Rad/s) %
Bomegas = 250; % Omega AB scalar %
%%%%%% Solved for Variables %%%%%%
Vbys = Bomegas*0.06*cosd(theta); % Velocity of B in the y direction scalar %
Pomegas = -Vbys/0.18; % Omega BP scalar(rad/s) %
Pomega = [0,0,Pomegas]; % Omega BP (rad/s) %
%%%%%% Equations for Velcocity at B %%%%%%
Vb = cross(Bomega, r); % Velocity of point B (m/s) %
Vby = cross(Bomega,rx); % Velocity of B in the y direction %
Vbx = cross(Bomega,ry);
Vbys = Bomegas*0.06*cosd(theta); % Velocity of B in the y direction scalar %
Vbxs = Bomegas*0.06*sind(theta) % Velocity of B in the x direction scalar %
%%%%%% Equations for Acceleration at B %%%%%%
Ab = -(Bomegas^2)*r; % Acceleration of point B (m/s^2) %
Abx = -(Bomegas^2)*rx; % Acceleration of point B in the x direction (m/s^2) %
Abxs = -(Bomegas^2)*rxs; % Scalar acceleration of point B in the x direction (m/s^2) %
Aby = -(Bomegas^2)*ry; % Acceleration of point B in the y direction (m/s^2) %
%%%%%% Equations for point P %%%%%%
Vp = Vb+cross(Pomega, d); % Velocity of point P %
Vpx = Vbx+cross(Pomega, dy); % Velocity of point P as a vector in the x direction %
Vps = -(Vbxs+Pomegas*dys); % Velocity of point P %
Palphas = (Abxs + (Pomegas^2)*(0.18*sind(phi)))/(0.18*cosd(phi)); % Alpha at point P scalar %
Palpha = [0,0,Palphas]; % Vector Alpha at point P %
Ap = Ab + cross(Palpha, dx) - Pomegas^2*(dx); % Acceleration at point P %
theta = theta + 10 % Looping Theta %
end; % end looping %
figure, plot(theta,Vbxs, '*')
xlim([0, 360])
ylim([-16,16])

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回答（1 个）

Star Strider
Star Strider 2019-4-22
Add a counter.
At the beginning of your while loop:
k1 = 0;
theta = 0; % Rotational arm angle %
while(theta <= 360) % Beinging theta loop for 0 to 360 %
k1 = k1 + 1;
. . .
and subscript the ‘Vbxs’ values to record them:
Vbxs(k1) = Bomegas*0.06*sind(theta) % Velocity of B in the x direction scalar %
then at the end, create a vector ‘thetav’ to record the ‘theta’ values:
. . .
theta = theta + 10 % Looping Theta %
thetav(k1) = theta;
end; % end looping %
and the plot call is then:
figure
plot(thetav,Vbxs, '*')
xlim([0, 360])
ylim([-16,16])

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