How do I generate following signal in simulink:
t=(0:1000)/1000*10*pi;
I want to build the model of the following matlab code:
t=(0:1000)/1000*10*pi;
x = (t).*sin(t);
y = (t).*cos(t);
z = t;
This is fairly basic stuff. Have you gone through any Simulink tutorial, introduction videos/webinars or even the getting started guide of the documentation?
Here are a few suggestions to help you answer your question:
Set the stop time of your model to 1000s and use a fixed-step solver with a step time of 1s.
Use a Clock block with a decimation of 1. That's your 0:1000 vector.
Feed the output of your Clock block to a Gain block, with the gain set to 1/(10000*pi). That's your t vector.
Feed your t signal to two Trigonometric Function blocks, one set to sin and one set to cos. That will generate two signals, sin(t) and cos(t).
Now multiply your t signal with your sin(t) signal using a Product block, to generate your x signal (t*sin(t)).
Do the same thing with t and cos(t) to generate your y signal. z is already done since it's equal to t.
EDIT following comments
The answer to your comment is really basic Simulink stuff. You should learn how to use Simulink before trying to do advance stuff like VR in Simulink. It's a bit like trying to run before you can walk.
Here are a few resources that may be useful:
Simulink Videos and Examples
Simulink Webinars
Simulink tutorial
Getting Started with Simulink in the Simulink Documentation
I don't know much about VRML, but be aware that the coordinate system in VRML is different from that in MATLAB/Simulink (see http://www.mathworks.co.uk/help/sl3d/vrml.html). You should also have a look at Virtual World Connection to a Model in the Simulink 3D Animation documentation.
Related
I build an equivalent circuit in Simulink and it works. Now I want to get the nquvist plot of this equivalent circuit. Does anyone have an idea how to achieve this. Till now I only get the Impedance versus the frequency. I attached the equivalent circuit:
Thanks a lot
When using blocks from "Simscape Power Systems Specialized Technology" use voltage/current measurement blocks (depending on the numerator/denumerator of the transfer function). The outputs of these blocks are Simulink signals. Once you have the signals, you can use the "Simulink Control Design" toolbox to display a Nyquist plot directly. See following link for an example (although for Bode plot, but it is straight forward to apply the procedure to Nyquist plots).
I'm trying to generate a sine wave without using any standard blocks available in Simulink. Right now I'm using constants for phase angle and frequency but eventually I want to vary this and hence not using the standard blocks. Here is the Simulink model
Here is the scope output
The output is not a sinusoidal wave. What am I screwing up here?
I'm using a fixed step auto solver.
As I'm currently not in the possession of Matlab/Simulink so I can't construct a working example. But I think the best solution for your problem is using a Simulink function block. In this block you can define a Matlab function of your own design and it will allow you to generate any signal you want.
Mathworks example
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 believe I am doing something fundamentally wrong when trying to import and test a transfer function in Simulink which was created within the System Identification Toolbox (SIT).
To give a simple example of what I am doing.
I have an input which is an offset sinusoidal wave from 12 seconds to 25 seconds with an amplitude of 1 and a frequency of 1.5rad/s which gives a measured output.
I have used SIT to create a simple 2 pole 1 zero transfer function which gives the following agreement:
I have then tried to import this transfer function into Simulink for investigation in the following configuration which has a sinusoidal input of frequency 1.5rad/s and a starting t=12. The LTI system block refers to the transfer function variable within the workspace:
When I run this simulation for 13 seconds the input to the block is as expected but the post transfer function signal shows little agreement with what would be expected and is an order of magnitude out.
pre:
post:
Could someone give any insight into where I am going wrong and why the output from the tf in simulink shows little resemblance to the model output displayed in the SIT. I have a basic grasp of control theory but I am struggling to make sense of this.
This could be due to different initial conditions used in SimuLink and the SI Toolbox, the latter should estimate initial conditions with the model, while Simulink does nothing special with initial conditions unless you specify them yourself.
To me it seems that your original signals are in periodic regime, since your output looks almost like a sine wave as well. In periodic regime, initial conditions have little effect. You can verify my assumption by simulating your model for a longer amount of time: if at the end, your signal reaches the right amplitude and phase lag as in your data, you will know that the initial conditions were wrong.
In any case, you can get the estimated initial state from the toolbox, I think using the InitialState property of the resulting object.
Another thing that might go wrong, is the time discretization that you use in Simulink in case you estimated a continuous time model (one in the Laplace variable s, not in z or q).
edit: In that case I would recommend you check what Simulink uses to discretize your CT model, by using c2d in MATLAB and a setup like the one below in Simulink. In MATLAB you can also "simulate" the response to a CT model using lsim, where you have to specify a discretization method.
This set-up allows you to load in a CT model and a discretized variant (in this case a state-space representation). By comparing the signals, you can see whether the discretization method you use is the same one that SimuLink uses (this depends on the integration method you set in the settings).
I'm trying to create a Matlab simulink model of the following equation:
I am very new to simulink and need some help getting started.
Ok, this is very easy to do.
set the equation so the result is the highest derivative. in you case d^3y/dt^3
There you have. nothing more to do.
How to follow from here you may ask:
you got x, and you can derive it, or apply any equation you want to it. The only doubt may come is: where the hell should i get y from?
Easy! you have the equation, integrate the result once and use that value for 4*(dydy/dt^2)^2 , integrate it again and use it for the last item and integrate it again and use it to multiply x. That's the advantage of simulink. You can close a loop using the "result" in the equation to calculate the "result" (this is no 100% true, as you use the value of 1 step before in each integration, but it works).
This is the power of simulink, still I strongly recommend you to read a bit about it, so you can understand why to use simulink, but I think playing with it is necessary to learn so: go!
In general when setting up equations in Simulink you should set up a number of integrator blocks to get all your states. When that is done you can sum the different factors together.
Unfortunately I can not post the model I made for the equaltion because of my low reputation points (new here).
dddy ddy dy y
+ --------> 1/s ------> 1/s -----> 1/s ----->