Simulink error: Unable to determine a fixed step size based on the sample times in the model

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I get the following error while running my SIMULINK model (closed-loop control feedback):
'Unable to determine a fixed step size based on the sample times in the model 'normal_force_input', because the model does not have any discrete sample times. Picking a fixed step size of (12.0) based on simulation start and stop times...
In Solver pane, here are the settings:
Start time: 0.0 Stop time: 10.0
Type: Fixed-step Solver: ODE3 (Boga...)
Fixed step size(fundamental sample time): auto
periodic sample time constraint: unconstrained
Tasking mode ...: auto
Automatically handle ....: unchecked
Higher priority: unchecked
What am I missing? Please help. Thank you.

Accepted Answer

Maximilian on 3 Jul 2014
I believe that this issue is caused by having the "auto" setting for your fixed step size. When using auto, the solver looks for all the discrete sample times in the model and picks a step size that is a common denominator to all the sample times. Without any discrete sample times the solver doesn't know what to look for. Try to specify your own step size and see if it runs.

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