Is there anything special about the accelerometer signal? Or is random, random? If so, just look in the Sources library: White Noise, Random Number, Signal Generator can all give you a random signal, for various definitions of random.

If by "random", you don't mean mathematically random and instead mean an arbitrary human movement acceleration signal, then there might be a bit more work to do. In that case, the Band-Limited White Noise might still do the trick, or you might even plug the Random Number into an Integrator or two to get a smoothed random signal.

If even that is too unrealistic, perhaps a number of Signal Generators set to sine function into a Sum block might do the trick?

Anything there close to the mark?

Dear "LiteYear",

Thank you very much for the reply! And my "random" means an arbitary human movement acceleration signal (x, y, z axes).
My project is to develop a software system which detect elderly fall and distinguish normal activities (walking, stand up, sit down, fall).

I need to implement by simulation: Get activity acceleration signals in xyz axes and use those signals in the fall detection algorithm. As there is no hardware included, I guess I need to generate my own random acceleration signal.
According to your suggested ways, I guess I will try to get 3 siganl generators (sine wave function) and sum them together to create my acceleration signal.
Regarding Band-Limited White Noise, I will look into it too!

I don't know whether I ask too much, regarding human movement model (walking, standing up, sitting down, falling), any idea how can I get the equations of the model? Any references that can reconmmend to me?

Thanks!