How do I solve/avoid this error?

Hello.I am Brandon.

I am building a model of a quadrotor in Simulink for my research.As I proceed to perform the simulation, I obtain the error message below:

"Error using main_quadrotor (line 21) Cannot solve algebraic loop involving 'Quadrotor_numerical/Derivative4' because it consists of blocks that cannot be assigned algebraic variables, such as blocks with discrete-valued outputs, blocks with non-double or complex outputs, Stateflow blocks, or nonvirtual subsystems. Consider breaking the algebraic loop. For example, add a delay or a memory block to the loop."

Is there any way for me to avoid this error at all?As adding memory block in the model always cause me numerical problem like singularity and so on.

Please do guide me on this and thanks.

Answer 1

[MUHAMMED FASIL]

Add "unit delay" blocks in front of the "errored" blocks

[Kah Wei]

Thanks for answer.I tried your suggestion and I am facing singularity issues.I exhausted all the available solvers and change the step size but still cant complete the simulation.

Answer 2

[Walter Roberson]

http://blogs.mathworks.com/seth/2015/07/18/why-you-should-never-break-an-algebraic-loop-with-with-a-memory-block/