Im using a Simulink model in a loop, by changing a parameter.
for i = 1:length(c_slip_sweep);
...
c_slip=c_slip_sweep(i)
tic; [tt2{i},xx2{i},yy2{i}]=sim(model,stop_time); toc
...
end
As the model spend much time to perform (100s), I'm trying to optimize it.
I've only find the "Rapid Accelerator" simulation mode reducing to 70s. But I don't know if there is a better way. Can I compile the model once, and re-use it in the loop ? Or can I give a vector instead a parameter (whithout Parallel Computing Toolbox) ?
Related
I'm new to Matlab/Simulink but have a requirement to interface with a Simulink model from a piece of software.
At the moment I have created a simple Simulink function 'Inc' which has 1 input to an addition block with a constant 1 and an output. I have used To/From Workspace blocks and can run the simulation over a fixed time using a time/value vector input, such as simin = [0,0;5,0;5,1;10,1].
What I would like to do is run my model continuously? Reading Workspace values in real-time rather than a pre-defined time based vector?
I can't see how to set this up? Can Matlab/Simulink do this?
To summarise, I would like simin and simout to be single values i.e. simin = 1, then with the model running continuously(infinitely) at the next fixed step simout would update to simout = 2. simin changes would be made at the Workspace at varying intervals.
The short answer is you can't (easily) do that, that's not how Simulink works. The MATLAB workspace is read/accessed at the beginning of the simulation and passed to the Simulink engine, and even if the values in the workspace change before the simulation is finished, this is not taken into account by the Simulink model running.
There are ways to work around this, but if you are a novice to MATLAB & Simulink, be aware that these are fairly advanced techniques, and I would advise to familiarise yourself with Simulink first.
Have a look at these similar questions for suggestions of how to do what you want:
Stream data form MATLAB to Simulink
Problem of variable updating in workspace
How Do I Change a Block Parameter Based on the Output of Another Block?
Tuning block parameters at every time step in a simulation
Simulink Signal Viewing using Event Listeners and a MATLAB UI
Obviously, you need to change the simulation end time to Inf or some large number.
Hopefully, I will be able to explain my question well.
I am working on Nonlinear model predictive control implementation.
I have got 3 files:
1). a simulink slx file which is basically a nonlinear pendulum model.
2). A function file, to get the cost function from the simulink model.
3). MPC code.
code snippet of cost function
**simOut=sim('NonlinearPendulum','StopTime', num2str(Np*Ts));**
%Linearly interpolates X to obtain sampled output states at time instants.
T=simOut.get('Tsim');
X=simOut.get('xsim');
xt=interp1(T,X,linspace(0,Np*Ts,Np+1))';
U=U(1:Nu);
%Quadratic cost function
R=0.01;
J=sum(sum((xt-repmat(r,[1 Np+1])).*(xt-repmat(r,[1 Np+1]))))+R*(U-ur)*...
(U-ur)';
Now I take this cost function and optimize it using fmincon to generate a sequence of inputs to be applied to the model, using my MPC code.
A code snippet of my MPC code.
%Constraints -1<=u(t)<=1;
Acons=[eye(Nu,Nu);-eye(Nu,Nu)];
Bcons=[ones(Nu,1);ones(Nu,1)];
options = optimoptions(#fmincon,'Algorithm','active-set','MaxIter',100);
warning off
for a1=1:nf
X=[]; %Prediction output
T=[]; %Prediction time
Xsam=[];
Tsam=[];
%Nonlinear MPC controller
Ubreak=linspace(0,(Np-1)*Ts,Np); %Break points for 1D lookup, used to avoid
% several calls/compilations of simulink model in fmincon.
**J=#(v) pendulumCostFunction(v,x0,ur,r(:,a1),Np,Nu,Ts);**
U=fmincon(J,U0,Acons,Bcons,[],[],[],[],[],options);
%U=fmincon(J,U0,Acons,Bcons);
U0=U;
UUsam=[UUsam;U(1)];%Apply only the first selected input
%Apply the selected input to plant.
Ubreak=[0 Ts]; %Break points for 1D lookup
U=[UUsam(end) UUsam(end)];
**simOut=sim('NonlinearPendulum','StopTime', num2str(Ts));**
In both the codes, I have marked the times we call our simulink model. Now, issue is that to run this whole simulation for just 5 seconds it takes around 7-8 minutes on my windows machine, MATLAB R2014B.
Is there a way to optimize this? As, I am planning to extend this algorithm to 9th order system unlike 2nd order pendulum model.
If, anyone has suggestion on using simulink coder to generate C code:
I have tried that, and the problem I face is that I don't know what to do with the several files generated. Please be as detailed as possible.
From the code snippets, it appears that you are solving a linear time invariant model with a quadratic objective. Here is some MATLAB (and Python) code for an overhead crane pendulum and inverted pendulum, both with state space linear models and quadratic objectives.
One of the ways to make it run faster is to avoid a Simulink interface and a shooting method for solving the MPC. A simultaneous method with orthogonal collocation on finite elements is faster and also enables higher index DAE model forms if you'd like to use a nonlinear model.
I'm doing simulation in Matlab where some data from the simulation are obtained by executing another software. The idea is when the calculation time is beyond a limit the data from the simulation will not be accepted. How to set a maximum calculation time to automatically stop this unnecessary calculation? I don't use Simulink at the moment.
Thanks in advance!
You can try investigating the use of tic, toc commands if you are doing loop-styled calculations. e.g. at the very start of the calculation:
tic;
just before end of each loop:
if (toc>60) %//However many seconds you want
break;
end
This might not be useful if you don't have loop-style calculations you have direct access to.
I want to model a for loop system in Simulink, how I can model the following MATLAB syntax into Simulink model?
N=3;
for i=0:1:N
sum(i+1)=factorial(i)/factorial(N);
end
I have tried for loop sub systems in Simulink and also Sum block for iteration loop but doesn't help me. factorial function can be calculated with FCN function.
Suggest me the ways to resolve this model with step time.
If you have the code already in matlab use a embedded matlab function to implement it i your simulink model. This is in general quite efficient since it will be compiled (compared to interpreted matlab function blocks)
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.