It's my first time using simulink and I just need it for a quick thing as part of a larger assignment.
I need to add a zero as part of controller for a feedback control system.
s+5
I'm trying to use the transfer function block but I can't enter just a numerator without a denominator. I tried the zero-pole block but it's giving errors too without poles. Is there just a zero block that I can use.
Here's the error
A time domain realization of the given zero-pole block 'untitled/Zero-Pole' failed. Check values of 'Zeros', 'Poles' and 'Gain' parameters.
Zeros: [5]
Poles: [0]
You can not use simulink to implement just a zero;numerator and denominator must have the same degree, if this condition is not realizable the system is non-causal
Related
Im trying to do some calculations in a Matlab (R2015b) Simulink function block. I use a signal that gives discrete values in 1-minute intervals.
What i want to do is store the signal values of 1 day (1440 values), convert them into a vector and input it in my Matlab function for calculation (getting time between first and last value > x). All while the simulation is running.
Unit delay, and Transport delay blocks wont work because i need all the stored values at once.
Any ideas on this are much appreciated!
Thanks!
You need to add a "To Workspace" block to your simulink diagram. Setting the options as you wish will allow you to save all the outputs in a single vector. You can select the variable's name, and the default is "simout".
Then, after running the diagram, you have the variable you want in the workspace (as if you had typed it in the console). So next, you can call your function with the argument.
I'm trying to model the respective processes of an internal combustion engine. My current modelling approach is to have different sub functions which model the different processes.
Within each sub function is a Level 2 S-Function which solves the ODEs to give the in cylinder state (pressure, temperature, etc).
The problem that I'm having is that each sub function is enabled depending on the current crank angle which is computed from the current timestep in Simulink. The first process works fine as I manually set the initial values, but then I can't pass the latest in-cylinder state (the output from the first sub function) to the second sub function to use as the initial conditions (it insists on using the initial values I set at the beginning of the simulation).
Is there any way round this? Currently I'm going along a path of global data stores, but haven't had any joy so far.
There are a lot of different ways to solve this problem.
I'll show some of them as examples.
You can create additive output with Unit dalay block like this:
So you can get value of your crank angle from previous timestep and USE IT in formula for solving you equations.
Also you can use some code like this:
if (t == 0)
% equations with your initial values
sred = 0;
else
% equations with other values
y = uOld + myCoeef;
end
Another idea: sometimes I use persistent variables in Matlab function to save values of some variable from previous step. But I think it makes calculation slower.
One more idea - if you have Stateflow you can create chart with two states: first for initial moment with your coefficient and second to solve new equations.
If I understood you in wrong way you can show your code and we'll offer some new ideas!
P.S. Example of my using of S-Function:
My S-Function needs 2 values: Q is calculated in simulink at every step, ro is initial I took from big matrix I loaded from workspace in table and took necessary value depending of time.
So there is no any initial values in S-Function - all needed values I transmit into it from simulink!
I need to implement a if/else in simulink to find out if a input is a scalar value or a matrix. Please see, the diagram below :
Given:
Block(1) - is a input that can be a scalar "1" or a matrix "[[0 15];[5 10]]"
Block(2) - must return the signal dimension of the input. Ex: 1 for scalar and >1 for a matrix
The requirements are:
Everything must work interpreted or compiled (Simulink coder)
The final output of blocks (4) and (5) are scalars
I have average understanding of CMexSFunctions. So if I need to implement one to solve the problem it is ok
So far, I have had the following problems:
I don't at all if what I am planning to do is feasible
I don't know how to implement Block(2) to work on compiled mode
Even though there is a if/else, simulink performs a pre-check before running to verify if all signal dimensions are ok. During this check, it gives a error saying ex: that Block(5) has a input of matrix
Any Clues?
Block(2) is the easiest part which can be implemented using the "Probe" block in Simulink library. Your Input at port 1 must be variable sized signal since you are expecting a scalar or matrix.
I assume you are feeding Input(1) to blocks 4 and 5. At model compile time Simulink does not know which one of these blocks are going to run based on the input size. So Simulink needs to assume both blocks may get scalar or matrix. You need to make blocks 4 and 5 not throw error for both scalar and matrix even though they will be used only for one type at run-time.
If you are not able to do this, for the scalar case a simple work around is to place a Selector before block 5 that selects the first sample always. This will let Simulink know that the input to block 5 is always a scalar.
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'm trying to parameterize one of my Simulink models, so that I will have a gain in the model whose value is equal to an element of a MATLAB workspace vector indexed by the model parameter. That is, I want to define a model argument WheelIndex and have a gain inside the model with a value AxelLoads(WheelIndex).
When I do it exactly as I've described above, I get "vector indices must be real and positive integers" error. When I change the model argument to AxelLoad(To be used directly in the gain component) and assign its value to be AxelLoads(1)(for the first wheel) I get:
Error in 'Overview/Wheel1'. Parameter '18000.0, 15000.0, 17000.0,
21000.0' setting: "18000.0, 15000.0, 17000.0, 21000.0" cannot be evaluated.
I've also tried importing the vector as a constant block into the model, and use a selector block parameterized by the WheelIndex argument to direct the right element to a multiplication block (thereby making an ugly gain block), but then Simulink complains that I'm trying to use a model argument to define an "un-tunable value".
I just want to somehow define the parameters in the MATLAB workspace to be used in each model instance, so that I can, say, calculate the total weight by adding the loads on each wheel. Simulink seems to block all workarounds I've been trying.
Thanks
Could you use a lookup table to obtain AxelLoads vs. WheelIndex?
The easiest way is if I just came over? :P
Perhaps this explaination of tunable parameters helps a little?