On Nov 11, 11:58 am, email@example.com wrote:
I did use Scilab a bit. I tried using Scilab to solve a significant
motion profile generator problem. I found that Scilab's debugging
didn't work very well. HMI programming is awkward. I went back to C
and C++. I haven't used the Scicos part which is what you really
should be asking about since it directly competes with SimApp.
On Tue, 11 Nov 2008 17:55:30 -0800, pnachtwey wrote:
OTOH, I use Scilab all the time.
I stopped using Simulink the second time I had a big simulation break
thanks to a MatLab upgrade, so I'm out of the habit now with Scilab.
The debugging has gotten miles better in recent versions, although the
move to 5.0.x was huge (they migrated from Tcl to Java) and they're still
shaking the bugs out.
I didn't notice the migration to Java. I will look into it. That may
restart my interest.
Right now I am writing a hydraulic servo simulator in java. I had
considered doing it in Scilab but switched to Java when my previous
project didn't work too well.
Is simapp or Scilab widely used in control engineering? As far as I
know, in China, we mostly use Matlab and Simuboth in both industry and
academics. Scilab is used in some embedded systems to run some
On Wed, 12 Nov 2008 21:48:13 -0800, workaholic wrote:
I can get Matlab with all the toolboxes and extra bits I need to do
control engineering with about the same amount of money as I could spend
to get a nice, reliable, late model used small car. Then the next year I
can get it all upgraded for the price of a major repair to the car.
I can get Scilab for the price of a download, it does nearly everything
that Matlab does plus plenty that Matlab doesn't, and upgrades cost
Since I don't have a big corporation with more dollars than sense backing
me, guess which one I use.
How much does a Matlab seat with all the control systems trimmings cost
Control systems and communications consulting
But I think it is nearly impossible for one with no practical numeric
computation knowledge and adetp programming skills to directly do
simulation in C/C++, even with a numeric library... What will you do
if you have to solve a stiff ODE problem?
There should be a price for ignorance. Pay to have it done, buy
Matlab, or invest in yourself and learn what you need. I chose the
latter. I had calculus and differential equations is college and a
few terms of numerical analysis. That is all I needed. The rest is
learned from the school of hard knocks.
Write a RK4 program is easy. Solving a system of first order linear
and non-linear equations is easy. One should be able to do a simple
RK4 in 15 minutes in C.
Reduce the sample intervals. The stiff equations are not as big a
problem as what to do when a limit is hit. For instance an actuator
hits the end of the cylinder or the pressure go to 0 and can't go
lower. The limits are usually reached in the time between two
samples. Then I divide the sample time into the time before and after
the limit was hit. A more brainless approach is to divide the current
sample time in to smaller equal sample times. RK4 is easy to restart
after the leaving the limit.
There are much fancier methods than RK4 but RK4 is easy to make work
well enough and efficiency is not a problem unless you are trying to
do real time simulations.
What is funny is that I saw a page
that had some useful information that I could have used a few years
ago. It would have helped. I learned on my own and can now easily
determine when systems are unstable. It is a problem for us because
we have a real time simulator built into our motion controller so
engineers can test at their desk. We must limit the damping factor
and natural frequency the customer can simulate so our simulator
doesn't go unstable. This limit is rather high so it doesn't affect
any practical applications. We don't have the extra time to play
games with reducing the sample intervals.
Well, I have to admit that nowadays majority of engineers who cannot
write numeric programs on their own, or if they have to, it requires a
lot of time because they have never really tried it out when taking
numeric analysis courses in universities, someone still cannot do
that, though with a M.Eng degree. I don't know how many people like
you are there in U.S.
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