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Real-Time Pacer for Simulink

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Real-Time Pacer for Simulink


Gautam Vallabha


Simulink block for forcing a simulation to run in real (wall clock) time

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The RealTime Pacer block slows down ("paces") simulation time so that it synchronizes with real elapsed time. The degree of slowdown is controllable via a Speedup parameter.

1) The block is implemented using an M S-function, so it works on any supported Simulink platform. It does not support code generation.

2) The block uses the MATLAB PAUSE function to slow down the simulation. The PAUSE command gives up the processor during the pause, so system performance does not degrade.

3) The M-S function illustrates how to use nested functions to simplify the code.

The matching between simulation time and elapsed real time is approximate, with expected differences on the order of 10 to 30 milliseconds. This limitation is due to difficulties of precise timing with a multitasking operating system.


The following FX entries also implement "real time" functionality for Simulink. They are based on C S-functions and therefore support code generation.

* Simulink Real Time Execution (Real-Time Slower) (Filex# 21908)
* Real-Time Blockset 7.1 for Simulink (Filex# 3175)
* RTsync Blockset (Filex# 24975)


This file inspired Maker Faire Mathworks/Competition.

Required Products Simulink
MATLAB release MATLAB 7.7 (R2008b)
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Comments and Ratings (7)
15 Dec 2014 Chethan Pandarinath

Chethan Pandarinath

Thanks, this worked well for me.

26 Nov 2014 Diego


Hi it don't runs in linux

24 Apr 2014 Pramit Biswas

Pramit Biswas

Elapsed real time is what I'm searching for. Very nice implementation. Superb.

Thank you very much for sharing.

12 Jul 2013 Pieter Mosterman

Pieter Mosterman

Great functionality. Does exactly what I was looking for, including scaled real time. Perfect. Thanks so much, Gautam!

10 Jun 2013 Jeff Orchard

Jeff Orchard

Nice. It does exactly what I want, and it was simple to use. Thanks!

23 Mar 2012 Walter


This pacer for Labview works very well for slowing a SIMULINK developed control system to match the timing of a real time device. We are using it to provide control logic to a LabView DAQ system which then controls a hydraulic pump and motor system. To overcome the problem of Microsoft Operating System interrupts, we have added memory to the control system to account for the time losses.

20 Jul 2011 Gustavo


Very nice work!

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