Syntax error Please help.

The expression:

u(5)*sin(u(1))*sec(u(2)) + u(6)*cos(u(1))*sec(u(2))

has a syntax error.

What is error, anybody guide me please.

[Walter Roberson]

That expression is fine in itself. There might be problems with the surrounding code.

What is the error message you are getting?

[Muhammad Azeem]

The expression: u(5)*sin(u(1))*sec(u(2)) + u(6)*cos(u(1))*sec(u(2))

in 'File_Name'

has a syntax error

[Walter Roberson]

Is this in the context of a Simulink Function Block (also known as a Math Block) ?

[Muhammad Azeem]

Yes

[madhan ravi]

Show the model.

[Muhammad Azeem]

Can I share via email?

[Muhammad Azeem]

This model.

[Walter Roberson]

Is it possibly an Interpreted MATLAB Function block? https://www.mathworks.com/help/simulink/slref/interpretedmatlabfunction.html

It is worth experimenting to see if removing the spaces helps.

[Walter Roberson]

R2019b does not find any error in that .mdl that you attached.

However,

Found algebraic loop containing:

Spacecraft_control_Magnetic/B_dot3

Spacecraft_control_Magnetic/Derivative2 (algebraic variable)

Spacecraft_control_Magnetic/B_dot2

Spacecraft_control_Magnetic/Derivative1 (algebraic variable)

Spacecraft_control_Magnetic/B_dot1

Spacecraft_control_Magnetic/Derivative (algebraic variable)

Spacecraft_control_Magnetic/B3 (algebraic variable)

Spacecraft_control_Magnetic/B2 (algebraic variable)

Spacecraft_control_Magnetic/uz (algebraic variable)

Spacecraft_control_Magnetic/ux (algebraic variable)

Spacecraft_control_Magnetic/B1 (algebraic variable)

This warning is correct: you feed the output of those variables right back as inputs, without there being any time delays. In order for that to be mathematically possible, the outputs would have to be steady-state, and working that out requires algebraic equations.

You should probably have some kind of delay. See https://blogs.mathworks.com/simulink/2015/07/18/why-you-should-never-break-an-algebraic-loop-with-with-a-memory-block/