I'm new to Simulink and am working on a project.
The bigger picture is that I want to gather different sensor data, pick out an interval of that, and in my Matlab functions analyze it, a kind of adaption. It feels like I have a fundamental misconception since I thought my Matlab scripts could work directly in Simulink. I have a couple of Matlab function blocks which in Matlab takes vectors as inputs, but when I use a source such as "from workspace" I get the error that it cannot handle more than one value at the same time: Index expression out of bounds. Attempted to access element 2. The valid range is 1-1.
So I wonder if there is any neat way of collecting a given interval of a continuous flow of sensor data (as a beginning, the raw input will just be a vector which will represent sensor data) so that it could be analyzed by some Matlab functions?
Related
I have a Matlab function (created by me) that must be evaluated only at a given rate. I would like to sample the value of a signal, give to this function (discrete values) and then, the calculated output must be hold until the next value is available. Is there a way in simulink to do this? All answers I have found use quantizer + ZOH but in this case I still get "a continuum" (or almost it) of points to be evaluated by thsi function which is really slow. Changing the rate of simulink's solver is also not an option as the result of this function will be given for a continuous time system.
Any help will be highly appreciatted!
Thank you
Assuming by Matlab function you mean a MATLAB Function block, then it sounds as if all you need to do is make the block discrete. Do that by right-clicking on the block, going down to Block Properties and then in the resulting dialog enter your required sample time.
The block will then sample its input and generate an output (which is held between sample times) at each sample time.
I have a MATLAB function block embedded in a Simulink model. In my initFnc callback I set up some vectors which I need to use in my function block inside the simulink model. The vector is 1x10000 and contains setpoints for a robotic arm. The function block simply needs to read the next value at each sample iteration.
So far I've tried using "From Workspace" and "evalin()" but they all throw various errors when building the model (I'm using code generation which doesn't play nice all the time).
What would be a good way to read in that vector in Simulink and feed the cells one by one into my function block? Something like repeating sequence stair but without the repeating part.
I got it to work by reading in the vector into a constant block and feeding that into my embedded function. I then use a persistent iterator which is a 1x1 matrix (ones(1)) and incrementing it every time the value from the vector is read.
I have a relatively basic Simulink block Model in which there is a Gaussian Noise Generator & an Error rate calculator. I want to get data on how changing the "variance" property of the Gaussian noise generator affects the result from the error rate calculator.
The most obvious way to do this is to manually run the simulation, record the results, change the variance of the Gaussian Noise Generator, rerun etc.
However, is there a way of getting the Simulink model to run the model, increase the Gaussian Noise variance by an amount, and rerun automatically for x number of iterations, and then to store the results in a list or array?
I am damn sure there is, but being new to Matlab & Simulink I have no idea of how to go about doing it? Somehow I imagine it would involve setting the "variance" as an input, and collecting the figure from the error rate calculator as an output - but again, I don't really know.
You want to use a for loop, and within the loop use the functions set_param and sim.
Look at the doc for more on how to use those functions.
There are also a couple of examples of using set_param here and using sim here.
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 am trying to find which element(index) of a multidimensional signal is computed at a specific time in a Simulink model. Assume that there is a multidimensional input signal given to an add block together with a constant so Simulink calculates the sum with the constant for each element of the signal and gives the output as multidimensional signal. I want to know which index of the signal is computed at a time so I can do additional computation. How can I do that?
Do you want to do additional computation during simulation or after? In the latter case, you can save the multidimensional signal to the MATLAB Workspace as a "structure with time" variable. Then do your additional computations by finding the index of the time point of interest and the associated multidimensional data point. In the former case, you can probably a MATLAB function block with two inputs: the output of a clock block and the multidimensional signal. Then do your processing in there using MATLAB code.