I have been developing a Xcos simulation where I have a disturbance observer in discrete domain. My intention was to implement the observer itself as a Scilab function invoked in periodic manner from the scifunc_block_m block i.e. the block has an event port connected to the clock source. May I ask you for an advice how to properly handle the observer state. In other words I need to have some variables which values are persistent between the individual clock events.
I have noticed that the scifunc_block_m has some discrete state in the configuration dialog. Is it intended for such usage? If so, how can I access to the state in the function code? Thanks in advance for your answer.
I have decided to implement much more simple discrete system at the beginnig. I have attempted to implement the discrete first order low pass filter. So I have just defined the below given function in a separate .sci file
function [xnew, y1]=Digital_low_pass_filter(flag, x, u1, rpar, ipar)
disp("ARGS: " + string(argn(2)));
disp("FLAG: " + string(flag));
select flag
case 1 then
// system output update (occurs in every time step of the simulation)
disp("Flag value: 1");
y1 = x;
xnew = x;
case 2 then
// system dicrete state update (occurs only at discrete event)
disp("Flag value: 2");
T = rpar(1);
tau = rpar(2);
a = T/(T + tau);
b = 1 - a;
xnew = a*u1 + b*x;
y1 = [];
case 3 then
// continuous state update
y1 = [];
xnew = x;
case 4 then
// init
disp("Flag value: 4");
xnew = 0;
y1 = [];
case 5 then
// end of simulation
disp("Flag value: 5");
y1 = [];
xnew = x;
case 6 then
// derivative computation
disp("Flag value: 6");
y1 = [];
xnew = x;
case 9 then
// zero-crossing
disp("Flag value: 9");
y1 = [];
xnew = x;
else
// default
disp("Unexpected flag value.");
y1 = [];
xnew = x;
end
endfunction
Unfortunately the simulation crashes. The diagnostic printing in the Console window occurs: “ARGS: 5“ and a warning occurs at the scifunc_block_m right down corner. Namely there is “Wrong number of input arguments.Expected 3.“ written.
May I ask you for an advice how to implement this simple discrete system via the scifunc_block_m?
I think you are mixing up scifunc_block_m and generic_block3 (I recognize that generic_block3 is not sufficiently documented and misses examples). Maybe @davidcl can confirm ?
Hello, thank you for your reaction. I have placed the scifunc_block_m block from the User defined functions category into my simulation. Why do you think I have used the generic_block3?
has the argument list of functions used by the generic_block3 block. Inside a scifunc_block_m, if you call your function, there is no mecanism that would give you values to flag, x, u1, rpar, ipar (unless you pass actual arguments by defining them explicitely).
Thank you very much for your reaction. Does it mean that I have to remove the flag parameter from the function header? If so what is the correct approach for control of the scifunc_block_m i.e. what is the mechanism how the solver interacts with the scifunc_block_m?
