I believe that it is possible to transfer MATLAB codes to Simulink. When we program in MATLAB, I know that it will execute from top to bottom line by line. On the other hand, Simulink deals with blocks that are connected to each others. There might be feedback signals. There might be subsystems whose outputs are inputs to other blocks and so on...Suppose we have 3 subsystem blocks connected to each other and the last block's output is fed into the first, which block does Simulink start with?
My question might be a foolish one especially after this long of playing with MATLAB and Simulink but I've not come to know the answer for this yet!
This depends on the actual simulation model. Before the simulation starts, Simulink analyzes the model (which blocks are connected in which direction, are there algebraic loops, etc.). The result is the so-called sorted order of the blocks, which is then used to actually execute the blocks' code.
See the documentation for details.
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My problem is that I am running a sweep study with some parameters. I change them in MATLAB and then run a simulation in MATLAB with the sim command. The simulation in SIMULINK contains an external software component from COMSOL with an FEM behind it. In some cases where the configuration is unfavorable (rapid changes in the feedback loop of the controlled system), the FEM tool is not able to converge in finite time, resulting in an error after a few simulation seconds/minutes/hours. The simulation command is inside a try-catch section to avoid that the program is stopped and the next study step starts to process the acquired data.
The problem is that in case the simulation has a convergence problem, the data generated up to this error is not sent to the workspace, but would be valid, and so I cannot find out from the data what was the reason for the convergence problem.
As additional information, I have been using the ToWorkspace block to send the data to my workspace where I do my post processing, and that works fine when the simulation is complete.
If any of you have any ideas on how to solve this problem, maybe you can help me.
Thank you in advance.
I've been modeling different possibilities of obtaining a decision in form of an Enum to compare them, expecting library functions of Simulink performing better than implementing the same functionality calling Matlab functions.
According to this Matlab article interpreted Matlab functions usually perform worse than their library counterparts due to passing through multiple software layers.
For my tests I modeled two systems calculating an output value based on an input signal and ran them for the same number of time steps with a Profiler attached.
The implementation using Matlab function took 16s to execute, while the implementation using library blocks took 566s.
Why does the simulink model using the if-else block run significantly slower? Or is there something wrong with my profiling approach?
I'd be grateful for any insights.
I am struggling with a little project I decided to tackle. I am trying to replicate an example I found on a book using matlab simulink but I have no experience with simulink and control theory (I do understand the principles etc.).
The control block diagram is given but I do not understand some blocks and how to add my input (sine wave block on simulink)?
Here are the details:
Example I wish to reproduce
Schematic of the converter and desired control block diagram
If anyone could give me a little insight or direct me to some examples from which I could build on an understanding would be great!
Thank you in advance.
The portion entitled controller is the closed-loop feedback control for the system. K(s) would typically contain some type of PI control. In a more complicated control system, the structure of K(s) may be a little different, but will usually always contain an integration in order to ensure that the system eventually settles at the desired value.
The input Iref is your current command. In this case you would inject your sinusoid here which would produce a current waveform matching your desired output. If your desired output.
Output m is the modulating waveform produced by the controller. Everything inside the half-bridge converter section is a representation of the converter and everything that it is interfaced to (voltage sources).
The feedforward filter here is also a very important component. Since Vs contains an alternating waveform, the feed forward filter allows the system to respond to changes in Vs without relying on feedback compensation K(s). This helps to decouple current regulation from changes in voltage VD.
To start with the project, you can probably build the half bridge converter as shown. You can inject 400*cos(377t - pi/2) as VD.
For the feedback compensator K(s) you can feed the input into two gains (Ki and Kp) which you will select values for later. At the output of Ki insert an integrator (1/s) then sum the output of Kp and the integrator together.
For the feed-forward filter, you should probably just use a low pass filter with a gain of 1 at DC. The low pass filter prevents noise from entering the system. In this case you are running a simulation, so there will be no noise. However, the filter will eliminate any algebraic loops, which can cause warnings or errors in the simulation.
You can input your control signal at Iref.
Assume that you have a Simulink simulation. You run it twice and consider a plot of a certain signal in time. Is it possible that there are small differences between the two signals?
A possible cause could be a variable-step solver.
Assuming all simulation parameters are the same between runs, if your simulation is complex, and uses custom blocks, such a thing is possible, if there is a bug in the initialization code.
With S-Functions, for example, you can chose if and how to reset internal state between simulation runs. With C code, it is easy enough to forget to reset something altogether, and end up with some uninitialized variable that contains garbage.
Another possibility is that something gets written into the workspace from the simulation, and is fed back into the simulation when it is initialized the next time.
I am trying to run my simulink file which have pid controller connected to s-function block.
When i set three values parameters of pid which are proportional, integral and derivatives it takes too long to run the whole process. Why this is happened?
In the dialog box of my pid diagram, for porportional value, its equal to the value which correspond to the constant amplitude oscillation.
Then for integral, its equal to Kcu/Ti. Ti is the ultimate period(Pu)/2 and
lastly for derivatives, its equal tu Kcu*Td and Td is Pu /8. This is refer to ziegler nichols method. and again my question is why it takes too long to running this file?
MATLAB S-functions are slow because they run in the MATLAB interpreter. Consider implementing it using Simulink blocks or using a "Embedded MATLAB Function" (pre-R2011a) or "MATLAB Function" (R2011a+) block.
Read Guy and Seth's thoughts on Simulation performance.
#Nzbuu is right about the Matlab S-functions.
But I think the problem here could be somewhere else: #Syarina are you saying that the Simulink simulation gets slower after you set the proportional coefficient for the controller? If you simulate the plant alone, in this case the S-function, do you notice a significant difference in the execution speed? If it is really so, I suppose the PID controller makes the ODE system stiff. This means that the different states of the ODE system have really different dynamics - some are very fast, some are very slow. Using an ode-solver that is not suited for stiff equations you will find the simulation much slower (actually you would have luck if it converges at all).
My suggestion is try to change the solver - for example ode15s.