MATLAB: Differentiation of vol for theta

diff()

Can you show me what is the answer?What is the answer?

dvol/dtheta?

clear();
r = 8;            % compression ratio
s = 100;          % stroke (mm)
b=s;              % bore=stoke
len= 150;         % connecting rod length (mm)
Vd= b^2*s*pi/4;   % displacement volume
Vc=Vd/(r-1);      % clearence volume
a=s/2;            % radius of crank shaft
theta=-180:1:180; % crankangle theta vector
y =len+a-((len^2-a^2*sind(theta).^2).^(1/2) +a*cosd(theta)); %  .^2).^  
vol= Vc+y*b^2*pi/4;  % exact volume

Best Answer

Use gradient to differentiate vol with respect to theta numerically

dvol_dtheta = gradient(vol, theta);

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MATLAB: Data must be numeric, datetime, duration or an array convertible to double.

See the difference between following code and your code

% this program computes and plots the exact cylinder volume
clear();
r = 8; % compression ratio
s = 100;   % stroke (mm)
b=s;         %bore=stoke
len= 150; %connecting rod length (mm)
Vd= b^2*s*pi/4;     %displacement volume
Vc=Vd/(r-1);       %clearence volume
a=s/2;            % radius of crank shaft
theta=-180:1:180; %crankangle theta vector
y =len+a-((len^2-a^2*sind(theta).^2).^(1/2) +a*cosd(theta)); %  .^2).^  nokta istiyor  exact 
vol= Vc+y*b^2*pi/4;  % exact volume
% syms theta % no need for symbolic variable
dvdtheta=vol;
diff(dvdtheta) %dv /dtheta 
%plot results
figure;
plot(theta,gradient(dvdtheta),'--','linewidth',2); % use gradient function
xlabel('Crank Angle (deg)','fontsize', 18);
ylabel('dv/dtheta mm3','fontsize', 18);
% axis ([-200 200 -1000000 1000000])
legend( 'dv/dtheta','Location', 'North');

MATLAB: How to wrote theta as a matlab code

syms theta
2*sin(theta)

Then by substituting theta with any numeric variable, you can calculate 2*sin(theta)

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MATLAB: Data must be numeric, datetime, duration or an array convertible to double.

MATLAB: How to wrote theta as a matlab code

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