Rate Transition Data Control

I'm implementing an Extended Kalman Filter on SIMULINK for sensor fusion. I have Accelerometer, Gyroscope, GPS and a magnetometer. Accelerometer and Gyroscope are giving data at a high rate i.e., at 10 msec whereas GPS and magnetometer are giving outputs at 100 msec.

To handle this sampling rate, I have used rate transition blocks as shown in figure below.

I was expecting that in the EKF block, GPS data would be empty for the time steps that come in between 100 msec, but I see that it is holding the value at the previous time step of 100 msec. How can I handle this? I want GPS/Magnetometer output at 100, 200, 300, ... and so on and they should be empty at 110, 120, 130 etc

Answer 1

[Joel Van Sickel]

Simulink signals don't support an 'empty' value. They will simply stay at whatever value they were at previously. This is the same behavior you would see in a variable if you updated it at a slower rate than a different variable by writing code by hand. If you want, you can set their values to 0 for other moments, but that would require you to leave them at a faster rate and require much more logic to write a value of 0 anytime you aren't at an interval of 100 msec. This is the concept of a zero order hold and it does not prevent you from using a kalman filter.