How do I get a real time clock in simulations using Simulink?

Solution:

It is possible to slow down a simulation to a rate close to real-time using hand written code.

The attached model illustrates how it is possible to slow down a simulation using the MATLAB Function block. In this example, the MATLAB function goes into a "busy wait" loop which kills time to slow down the simulation until the system clock catches up to the Simulink clock.

An example of a C MEX S-function used to slow down a model close to real-time can be found on the MATLAB Central File Exchange at the following address:

http://www.mathworks.com/matlabcentral/fileexchange/21908-simulink%C2%AE-real-time-execution

Note that the two above examples allow the system to run approximately in real-time, but not exactly. It should only be used to reduce the speed of a Simulink model so that a user can interact with it and observe the results in real-time.

For applications like Rapid Prototyping and HIL Simulation where accurate hard real-time is required, you should consider using xPC Target or Real-Time Windows Target:

http://www.mathworks.com/products/xpctarget/

http://www.mathworks.com/products/rtwt/