I would like to use normrnd() on MATLAB Simulink, but every simulation instance provides the same random timeseries of random variables. How can I reset it every time I run the simulink simulation?
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For example, I have a controller consisting of integrator and sine web signal combined in the input. My question may be very naive to you, please help me to understand.
In the picture I have a frequency which is the input of an integrator then two cos and sine block. How to make each Simulink block discrete using ZOH and rate transition block in Simulink.
Two potential solutions
Change the sample time of the sinewave to something that is non-zero. This will make it a discrete signal
Use a Zero Order Hold (as you've mentioned) to convert the signal to discrete, you will need to specify a sample time for this block to perform the conversion. Setting the time to 0.5 will sample the signal every half second for example.
I tried using the 'Spectrum Analyzer' and those signal blocks (sine, pulse generator, triangle generator and sawtooth generator) separately of course, but the spectrum block needs a discrete signal or a non-infinite signal, and there's only a discrete sine block, is there a way to generate the others?
Most input blocks, including those you list, have a Sample Time parameter. Make it a number greater than 0 to specify a discrete sample time. For instance 0.001 would give you a milli-second sample rate.
For the few blocks that don't have this, simply use a Zero-Order Hold on the output of the block, and specify a sample time for the ZOH block.
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.
I'm trying to build a Simulink model containing a "s-function block" simulating a continuous process with a "Matlab Function Block" that use the input and output from s-function.
But I need the input to the "Matlab Function Block" with differents values of the same signal over time. That is, a vector with different sampling times for each input to "Matlab Function Block". This will be needed for testing identification techniques.
How could I do this?
Thank you
Assuming you are using a fixed-step discrete solver, and that you don't have too many values of the same signal to hold, you could use Unit Delay blocks to get the value of the signal at previous time steps. You can then mux all these signals together to form your vector input. Obviously, the practicality of it is limited by how many values of the signals you need to have (and buffer).
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.