Syntax error in simulink

Getting syntax error in Simulink for this expression

m*(u(1)-l*u(3)*u(3)*sin(u(2))+l*u(4)*cos(u(2)))

The equation seems correct. Can anyone explain it?

[Walter Roberson]

We will need more context and the complete error message.

For example that expression would not be valid in a MATLAB Function block because MATLAB Function block need a "function" header.

[Quamar Niyaz]

I tried to put in fcn block parameters window by double clicking the fcn block. I have four function blocks in my model. The expressions in few of them are working, however in few of them, they are not working. For example: (1/M)*(u(1)-u(2)-b*u(3)) worked perfectly.

[Image Analyst]

I think you overlooked where he said "We will need ... the complete error message." That means ALL the red text from the command window.

[Walter Roberson]

When I copy and paste your code into a Fcn block or Interpreted Fcn block in R2016a, I am not told of any error.

[Quamar Niyaz]

I am trying to implement this example http://ctms.engin.umich.edu/CTMS/index.php?example=InvertedPendulum&section=SimulinkModeling. I have followed the procedure as specified in it, but getting the errors in the third function block which is as follows:

The expression: m*(u(1)-l*((u(3))^2)*sin(u(2))+l*u(4)*cos(u(2)))
in 'Sim_Exp7/Subsystem/Subsystem/N' has a syntax error

I have also attached my mdl and error files. My Matlab version is R2015b.

[Shoanaliy Arul]

I am also getting the simular error.

Mine says:

The expression: m*(u(1) - l*u(3)*u(3)*sin(u(2)) + l*u(4)*cos(u(2))) in 'Pend_Model/Subsystem/N' has a syntax error

Answer 1

[Mark McBroom]

The following variables need to be defined in the MATLAB workspace:

I, g, b, m, l, M

thetadot is missing a paren. It hsould be:

1/I*(-u(1)*cos(u(3)) - u(2)*sin(u(3)))

[Mark McBroom]

Note. I debugged this by cutting and pasting each of the equations into the MATLAB workspace. This gives more detailed info on undefined variables and syntax errors.