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Rashmi

Simulation in Real-Time

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Hi,

I am new to this forum as well as LabVIEW. So please help me evenif the question I am posting is simple. I am using Labview 7.1. I have developed a 12 ODE solver using RK 4th order and Fixed step of 1ms and simulation time as 10s. I have used Simulation Module and Formula Node for the same. I have done the offline simulation and it works fine. Now I would like to run the simulation in real time without interfacing any hardware. I mean, the step size which I have given as 1ms, I want the operating system to complete all the calculation(12 ODEs) for one iteration within that period and the task should be deterministic. How can I perform this?

Thanks in advance,

Rashmi

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QUOTE (Rashmi @ Aug 22 2008, 05:51 AM)

I am new to this forum as well as LabVIEW. So please help me evenif the question I am posting is simple. I am using Labview 7.1. I have developed a 12 ODE solver using RK 4th order and Fixed step of 1ms and simulation time as 10s. I have used Simulation Module and Formula Node for the same. I have done the offline simulation and it works fine. Now I would like to run the simulation in real time without interfacing any hardware. I mean, the step size which I have given as 1ms, I want the operating system to complete all the calculation(12 ODEs) for one iteration within that period and the task should be deterministic. How can I perform this?

Rashimi,

You can run the LV Simulation code directly on a RT controller if you also have the LabVIEW RT module. The local experts recommend moving to LV 8.6 for this, as the performance of the LV Sim code in RT has improved dramatically in the most recent release.

That being said, moving to LabVIEW RT will give you more determinism but it won't improve the performance (speed) of your code significantly compared to an equivalent processor running Windows (your current offline simulation). So moving from a desktop PC to an RT target will not run your simulation any faster (real-time) unless your RT target has a faster processor on it.

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QUOTE (Rashmi @ Aug 22 2008, 03:51 AM)

Some more information would be helpful.

1 What are you trying to achieve?

2 What PC hardware do you have?

3 Newer versions of LV have much better performance and better multi-core support (I suggest you upgrade).

4 How are you solving the ODE's? mathscript nodes are useful but painfully slow especially in the older versions. Look at the release notes of the various LV versions, they should give you pointers as to what has been optimized or upgraded in each version (there have been a lot of enhancements in terms of performance).

5 Do you HAVE to solve all 12 ODE's together? Can you split out the solving to multiple cores/PC's & put together the results later?

6 Take a look at this http://www.ni.com/niweek/2008/keynote/mike_santori_mike_cerna.htm' target="_blank">Large Telescope Demo from NI-WEEK 08. What you are trying to achieve is quite challenging given the 1ms solution time.

7 Provide some screen shots or code to show your approach so it can be critiqued for better performance.

8 Why do you need the 1ms solution time? Are you controlling something in real-time?

9 Can you simplify the system model to eliminate some of the 12 degrees of freedom to fewer?

Neville.

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