Kalman Filter - Activating or Enabling a matlab function block in simulink

Hello,

I have data of 3 signals in matlab workspace and each signal was recorded with different sampling rate. I want to use these signals in simulink however i am not sure what is the best way to do that for my case.

I have build a kalman filter in simulink that was tested using simulated data. Now I have real data which means the setup is slightly different. I want to trigger a matlab function block to be used only when data is available.

Any ideas how to do that?

Thank you.

Answer 1

[Adarsh]

Hi @Hussein,

Given your situation where the 3 input signals are of different sample rates, “Rate Transition” block or a “Zero-Order Hold” block can be used to ensure the simulation runs properly in a Multi-Rate system. Usage of “Rate Transition” block is best when the sample times of the input signals are multiples of each other.

If not, the next best option would be to use the “Zero-Order Hold” block. The “Zero-Order Hold” block holds its input for the sample period you specify. If the input is a vector, the block holds all elements of the vector for the same sample period. Using these blocks the signals with different sample rates can be handled.

Similarly, to create a trigger for a MATLAB function, you can either condition the trigger in the MATLAB function itself or use a “Enabled/Triggered Subsystem”.

For creating the trigger you can use a “Unit Delay” block and a “Relational Operator (~=)” block to check whether there is a change in the signal values and send the result through a switch or to the conditional input to the “Enabled/Triggered Subsystem”, by which we can set the condition to activate the subsystem only when the conditional input is satisfied.

Alternatively, you can check the change in data at previous and current time step in the MATLAB function itself and give the output accordingly.

Here is a sample code on how this validation can be done in the MATLAB function itself,

function [output, isNewData] = processData(inputSignal)

% Define a persistent variable to store the previous signal value

persistent prevData;

% Initialize the persistent variable on the first run

if isempty(prevData)

prevData = inputSignal; % Initialize with the first input

end

% Initialize output

output = prevData;

isNewData = false;

% Check if the current signal is different from the previous one

if inputSignal ~= prevData

% New data is available

isNewData = true;

% Update the output

output = inputSignal;

% Update the persistent variable

prevData = inputSignal;

end

end

For more information on “Zero-Order Hold”, “Rate Transition” blocks or “Enabled/Triggered Subsystems” you can refer the following documentation links:

1. “Zero-Order Hold” - https://www.mathworks.com/help/simulink/slref/zeroorderhold.html
2. “Rate Transition” - https://www.mathworks.com/help/simulink/slref/ratetransition.html
3. “Enabled Subsystem” - https://www.mathworks.com/help/simulink/slref/enabledsubsystem.html
4. “Triggered Subsystem” - https://www.mathworks.com/help/simulink/slref/triggeredsubsystem.html

Hope this helps!