I am using Matlab function in my simulink code where I am using the load command for getting some matrices and variables from the workspace
persistent ProblemParams;
if isempty(ProblemParams)
ProblemParams = load('ProblemParams.mat');
end
This is working well, however there can be problem when I am running multiple simulations at the same time, hence I would like to know what other options do I have to pass an array to this block from MATLAB workspace?
Whether or not the above works, it's not the right way to get data into the block. You should load the variable into the MATLAB Workspace prior to starting the simulation, then pass the variable into the MATLAB Function Block as a Parameter Argument.
Related
I have trained the neural network in matlab script file and saved the trained data into a .mat file. So that after loading the .mat file in Simulink user defined functions, I could use this trained data to test the inputs.
But I get run time error
Call to Matlab function aborted: Error calling Matlab function 'sim'. Press OK to open the debugger.
and in debugger the error is
MATLAB Function Interface Error: Error calling MATLAB function 'sim'. Block Neural Network Function (#108) While executing: none
The code is as
function [tau1p,tau2p] = Nntwork(theta1,theta1d,theta2,theta2d,theta1dd,theta2dd)
coder.extrinsic('load');
coder.extrinsic('sim');
net=load('trainednet.mat');
a=zeros(1,2);
a=sim(net,[theta1;theta1d;theta1dd;theta2;theta2d;theta2dd]);
if some one could help me to resolve this error.
The first thing I'd check is that your variable net is actually a NN object. The syntax that you are using for load loads all variables in the mat file into a structure called net, and you most likely need to use net.net to extract the net variable from the net structure. (Of course if that's the case then you shouldn't call the structure (i.e. the output from load) net as it will be very confusing.
However, I'd suggest the best way to do this is to wrap you code into another function, and call that function from the MATLAB Function Block. i.e.
Make the MATLAB function block something like:
function [tau1p,tau2p] = NntworkWrapper(theta1,theta1d,theta2,theta2d,theta1dd,theta2dd)
coder.extrinsic('Nntwork');
a=zeros(1,2);
a=Nntwork([theta1;theta1d;theta1dd;theta2;theta2d;theta2dd]);
Then have this additional function in a separate m-file:
function a = Nntwork(theta_data)
load('trainednet.mat');
a=sim(net,theta_data);
A set-up like that will enable you to run and test the NN code independently of Simulink, but also call it from Simulink when required.
I'm using a lot of MATLAB for a Control class and something is really bumming me out. They want us to use a lot of Simulink even though I find the visual representation not that helpful and the interface between Simulink and MATLAB scripts hard to figure out in general.
So I have a model and I have added scopes for sinks which can save data directly to the workspace when ran from Simulink. However when I use the command sim in the script to directly use the model according to some parameters (stopTime, solving method, etc.) the results are buried in an object which is poorly documented to say the least so say I have:
simout = sim('lab','StopTime','100','Solver','ode1','FixedStep','2');
Now I have an object in my workspace but to access the data I want I need to go 3, hell 4 layers deep sometimes in the members of simout. My first question is :
Is there a way to access directly or at least know what those members are without using the tedious use of who.
I don't want to compile code to access its documentation! And help is not really helpful for those situations.
Why doesn't the Simulink model save the data when invoked like prescribed in the sink properties. I know that the line of code I mentioned overides some of the simulink block prescriptions (e.g. the solving method used).
How to know how simulink models interact with matlab scripts, granted I am a noob in coding in general, but the documentation doesn't really tell me what are the formal definitions of the model and the way it is used in matlab. I am scared at some points the default settings of 'sim' will overide some settings I set up in an earlier model which would prove to be a nasty buisiness to debug.
TL;DR Is there a quick way to access deeply buried members of an object? For example right now I have to do:
simout = sim('lab','StopTime','100','Solver','ode1','FixedStep','2');
who(simout)
ScopeData = (simout.get('ScopeData'))
signals = (ScopeData.signals)
time = (ScopeData.time)
Can I do something more C-ish of the sort of (Simout->ScopeData).signals?
And finally, why is the MATLAB suite presented like it was an app for day-traders when it is used a lot by EE people who in general need to know their coding? Why are libraries with headers and good documentation for what you are importing in your code (e.g. boost, string etc.) not used? This last option might be less pretty by hiding the mechanics, but to be able to write code properly I feel like I have to know most of the underlying mechanics of the code.
Invariably when most people start off using MATLAB or Simulink, they hate it. The main reasons I see for this is people are taught MATLAB very poorly which prevents them from understanding the power of MATLAB and when it should be used.
Before I get into describing how the MATLAB workspace, m files and Simulink are all related let's first define what each of those is separately and a few of the things you can do with them.
The MATLAB Workspace
The MATLAB workspace contains all of the variables you have created in MATLAB either explicitly via the command window or implicitly through running a .m file (don't worry I'll come back to these). The simplest method to add a variable to the MATLAB workspace is to directly type into the command window like
>> A = 1
A =
1
which adds the variable A to the workspace and assigns it a value of 1. Even simpler though is to simple type 1 like
>> 1
ans =
1
which adds the variable ans to the workspace with a value of 1. The default workspace variable for any command executed by MATLAB that is not explicitly assigned to a variable is ans.
The workspace browser in MATLAB displays information about all of the variables currently in the workspace. For instance if we were to execute, in the command window,
>> A = 5;
>> B = [6 8];
>> C = [3 6 7; 9 11 12];
>> D = eye(max(size(C)));
the workspace browser would look something like
Some Helpful Workspace Commands
The save and clear commands are helpful commands that work with the MATLAB workspace. save lets you save variables from the workspace to a file whilst clear lets you remove variables from the workspace, thus freeing up memory. clear all will clear every variable from the workspace.
m Files
An m-file (or script file) is a simple text file with a .m file extension. In it you type MATLAB commands which can be executed sequentially by executing just the m-file in the command window. For instance, lets copy our commands from above and paste them into an m-file called mfile_test.m. Now lets add the command C - A to the bottom of the m-file (note do not append a ; after the command). We can execute this m-file from the command window and see the output of all of commands within it executed sequentially
>> mfile_test.m
ans =
-2 1 2
4 6 7
m Files and Functions
m files can also contain functions. For instance we could write a function that calculates the area and circumference of a circle like
function [A, C] = circle(r)
A = pi*r*r;
C = 2*pi*r;
end
and put it in an m-file called circle.m. We could then use this like
>> circle(5)
ans =
78.5398
where ans now holds the area of a circle with a radius of 5 or
>> [A, C] = circle(5)
A =
78.5398
C =
31.4159
where A holds the area of the circle and C the circumference.
Simulink Models
Simulink is a graphical tool that can be used to model various different types of systems as well as modelling dynamic system behaviour. Simulink is closely embedded into the MATLAB ecosystem which adds additional power to it (again I'll come back to this later when describing the similarities).
Simulink models contain blocks which all exhibit different behaviour. There is also the functionality to create your own Simulink blocks should you need. Models in Simulink are made by connecting blocks of different kinds to emulate the system you want to model.
Simulink is quite extensive and I don't recommend learning it on your own. The best way to learn Simulink is invariably as part of a course, Control Systems or Systems Analysis type courses are ideal for this purpose. For that reason I'm not going to dwell on it for much longer here.
How are the MATLAB Workspace, m Files and Simulink all Related?
Well, the MATLAB workspace is available to both m files and Simulink. Variables in the MATLAB workspace can be used in both m files and Simulink.
m files that contain only scripts (and not functions) will write every variable created in them to the MATLAB workspace. m files that contain only functions won't write any of the new variables used in those functions to the MATLAB workspace. The only way a function will alter variables in the MATLAB workspace is by assigning an output value to ans or if you explicitly declare output arguments when calling the function.
Simulink and the MATLAB workspace have a very similar relationship to m files and the MATLAB workspace. Any variable in the MATLAB workspace is available for use in Simulink (in any part, including configuration). For instance in the below configuration I use the MATLAB workspace variables start_time, stop_time and step_time to set up the parameters of model. Typically I would define these in an m-file before I run my Simulink model with sim(). This is how we can relate all 3 together.
Simulink can write variables to the MATLAB workspace by adding output arguments to the sim() command. However, as you've found this can be quite nasty to navigate and extract what you really want! A better approach would be to use the Data Import/Export options in Simulink coupled with a To Workspace block to grab the outputs that you are concerned with so that you can ignore everything else.
Below I have a screenshot of the Simulink Data Import/Export pane. You can see there are options in here for us to send variables to the MATLAB workspace. Typically, the most common you would need is tout which will be a range given by start_time:step_time:stop_time from the earlier configuration pane. Other areas that would be of primary interest in this screen would be xInitial and xout which are used in Root Locus analysis.
However, all that aside one of the best blocks in Simulink is the To Workspace block. This block can be used to store variables directly in the MATLAB workspace and is one of the keys to being able to link MATLAB and Simulink. You get the power of Simulink but the computational and plotting abilities of MATLAB. I've included a screenshot of it below as well as a typical configuration I would use. The default Save Format for this block is Timeseries, however, I recommend changing this to Array as it will make your life much easier.
OK, where was I? I feel like I'm giving a lecture instead of writing an answer!
A Practical Explanation
Simulink Model
So now let's put everything we've learned into practice with a simple example. First we are going to create a simple Simulink model like this
Now we'll set up our configuration for this, as before for the Solver section
We'll also untick Limit data points to last: in the Data Import/Export section
And, that's it. Our simple Simulink model has been created and setup. For the purposes of this answer, I'm saving mine as stackoverflow_model.slx.
MATLAB Script
Now we'll create simple MATLAB script (m-file) called stackoverflow_script.m that will set up the necessary variables for our Simulink model by adding them to the MATLAB workspace. We'll then call our Simulink model and check what new variables it added to the workspace. And, finally we'll generate a simple plot to show the benefits of this approach.
So here is the MATLAB script
% Script developed to describe the relationship between the MATLAB
% workspace, m-files and Simulink
close all
clear all
% Initialise variables
start_time = 0;
stop_time = 10;
step_time = (stop_time - start_time) / 1000; % Creates 1000 + 1 points
% Choose k
k = 60;
% Execute Simulink model
sim('stackoverflow_model');
whos % To display variables returned from Simulink
% Plot results
figure;
plot(tout, yout, 'r');
title('Sample Plot');
xlabel('Time (s)');
ylabel('Output');
Putting it All Together
Now we execute this script in the command window with stackoverflow_script and sit back and marvel at the POWER of MATLAB and Simulink combined.
>> stackoverflow_script
Name Size Bytes Class Attributes
k 1x1 8 double
start_time 1x1 8 double
step_time 1x1 8 double
stop_time 1x1 8 double
tout 1001x1 8008 double
yout 1001x1 8008 double
We can see from the output above that all of the variables Simulink needs (k, start_time, step_time and stop_time) are all in the MATLAB workspace. We can also see that Simulink adds 2 new variables to the MATLAB workspace tout and yout which are simple 1001x1 vectors of doubles. No nasty structs to navigate.
And finally, this produces a nice plot
And so that concludes our whistle stop tour through MATLAB, m files and Simulink! I hope you've enjoyed it as much as I did writing it!
P.S. I haven't checked this for spelling or grammar mistakes so edits are very much welcome ;)
General
Well to put it short workspace is the variable-environement you are working in. If you run a script, your workspace is 'base', which is the same the console uses. So Matlab does have different environements, one is a kind of included environement known as path, the other one is for variables, known as workspace.
Simulink uses a different one, which prevents shadowing variable names I guess.
To check check members in the current workspace use who
To write members to another workspace use assignin
To run something in a specified workspace use evalin
Your Questions
1.
Who lists all the variables in the current workspace you don't need it for the thing you wanna do.
The whole simulink documentation isn't that good...
2.
It does...
3.
If you run a script and define variables they are defined in the base workspace. When you specify a variable in simulink by just entering its name (for example a), it does load it from the base workspace (hence this way arround no problems).
The other way arround is to either use the given export blocks, or specify export values in your own blocks by either using global or assignin.
4.
If you open the scope block and hit the options-buttion (the little gear), you can select an export option. You can aswell specify the type you wan't to use. You seem to use the struct with time option, which is the one with the most lvls, I'd suggest to use the array-type if your problem is just the fact that it is a struct.
You can also just use the Outputblock to specify the export type and name.
So I'd go with:
sim('modelname');
signals=ScopeData.signals;
time=ScopeData.time;
Or when specified as an array:
sim('modelname');
signals=ScopeData(:,2);
time=ScopeData(:,1);
In the example above I don't specify the way the model is run, however you can also specify it as you posted.
In simulink I have a function block. Basically it contains
function y=fcn(u)
if u==1
a=[0,...,1];
b=[1,...,2];
end
y=[a',b'];
%y=struct('time',a,'value',b); %Second option
I want to use these arrays as a signal. As you see I have tried two options, making an output as an array and as a structure, non of them work for me.
In short, I'd like to be able to connect a scope to the output of the function and see the signal generated by (a,b). The reason I want to do it from a Simulink block is that I can just switch between many options of signals without having to build again the model. More over, I'd prefer that if the simulation time is bigger than whatever is specified in a then the signal keeps the last value of b.
p.s. I have tried this using a From Workspace block and it works fine.
I am building a reduced order observer in MATLAB. The matrices are calculated using functions/script files outside matlab and simulink function blocks are using these functions to calculate values.
The problem is that some commands like 'acker', 'place' etc which used to work on command window/function/script files are not working in simulink function block and showing errors.
I tried using simin block to take these matrices from workspace but it is also showing errors which I can't understand.
Thanks for your help.
If I get your question correctly then, from User defined functions, you could add a Matlab function block with the following code:
function fcn(in)
%#codegen
coder.extrinsic('acker', 'place')
# Now you can use acker, place so add more code.
I have observed a strange behavior in running the same code in a Matlab function and in the command window. It's already described in How does scoping in Matlab work? , but I don't understand how I could solve my specific problem.
The code is the following:
exporteddata.m %File created by an external program
%to export data in Matlab format
surface = struct('vertices', [...]) ;
%I can't specify in the external program
%the name of the variable, it's always "surface"
My actual code is:
myfunction.m
function output = myfunction(input)
load(input);
n = size(surface.vertices);
....
When running
myfunction('exporteddata.m');
I get the following error:
??? No appropriate method, property, or field vertices for class hg.surface.
When running the same instructions from the command window or in debug mode, the code works well.
How can I specify in the function that I need the variable surface present in the workspace, not the Matlab function?
First of all, I must point out that surface is a built-in function in MATLAB, so overloading it is just... bad. Bad, bad, BAD!
Having said that, the MATLAB interpreter does a pretty good job at resolving variable names and usually tells them apart from function names correctly. So where's your problem, you ask?
I believe that you're using the wrong function: load is a function that loads data from MAT files into the workspace. It is not fit for m-files. By not executing "exportedata.m" properly, surface has never been created as a variable, so MATLAB identifies it as a function name. If you want to execute "exportedata.m", just type:
exportedata
and if you want to run the file with the filename stored in input, you can use run:
run(input)
By executing run(input) from within myfunction, surface should be created in myfunction's local scope, and it should work.
EDIT:
I've just tested it, and the interpreter still gets confused. so the issue of the variable name resolution remains. Here's a workaround:
function output = myfunction(input)
surface = 0; %// <-- Pay attention to this line
run(input);
n = size(surface.vertices);
Predefining surface allows the interpreter to identify it as a variable throughout your entire function. I've tried it and it works.