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Altera_Forum
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17 years ago

Implementation of Digital PID controller in FPGA

I'm trying to implement a PI controller in FPGA using schematic entry method in altera quartus II . I'm using the following equivalent PI controller equation, c(n) = c(n-1)+kp*(e(n)-e(n-1))+Ki...
Altera_Forum's avatar
Altera_Forum
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17 years ago

I'm using a package of extended arithmetic functions for such purposes. Basically I leave it to the compiler to find an appropriate way to realize the intended behaviour. You may want to compare the achieved effectivity with handcoded saturation arithmetic, I'm satisfied with it up to now. 

FUNCTION SUM (X1,X2: SIGNED) RETURN SIGNED IS
  VARIABLE S:SIGNED(X1'length-1 downto 0);
  BEGIN
    S:=X1+X2;
    IF X1>=0 AND X2>=0 AND S<0 THEN
      S:= (others => '1');
      S(S'left):='0';
    ELSIF X1<0 AND X2<0 AND S>=0 THEN
      S(S'left-1 downto 0):= (others => '0');
      S(S'left):='1';
    END IF;		
    RETURN S;
  END;