81 lines
2.0 KiB
VHDL
81 lines
2.0 KiB
VHDL
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-- Test crude algorithm for a simple motor controller.
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library ieee;
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use ieee.std_logic_1164.all;
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entity mc is
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-- Control values that may be overrriden by the "sim_args" option
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-- in a netlist's .model line. Intgers are used as GHDL does not
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-- support overriding Real values.
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generic (
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Target : Integer := 4000; -- notional RPM
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Dead_Band : Integer := 200;
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Full_Band : Integer := 600
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);
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port (
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Zero : in std_logic;
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Tach : in std_logic;
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Trigger : out std_logic
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);
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end mc;
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architecture mc_arch of mc is
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shared variable Speed : Real := 0.0;
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begin
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Tachometer : process (Tach) is
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variable Time : Real := 0.0;
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variable Last_pulse : Real := 0.0;
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begin
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if rising_edge(Tach) or falling_edge(Tach) then
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Time := real(now / 1 ns) * 1.0e-9;
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Speed := 30.0 / (Time - Last_pulse);
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Last_pulse := Time;
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end if;
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end process Tachometer;
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Controller : process (Zero) is
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variable Skip : Integer := 0;
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variable Count : Integer := 0;
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variable Even : Boolean := True;
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variable Was_even : Boolean := True;
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variable Error : Integer;
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begin
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-- Trigger triac on zero crossings, preventing DC current.
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if rising_edge(Zero) then
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Even := not Even;
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if (Count >= Skip) and (Even /= Was_even) then
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Trigger <= '1';
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Was_even := Even;
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if Count > Skip then
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Count := 0;
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else
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Count := -1;
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end if;
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else
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Trigger <= '0';
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end if;
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Count := Count + 1;
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-- A very crude feedback mechanism.
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Error := integer(Speed) - Target;
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if Error > Full_Band then
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-- No drive
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Skip := 1;
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Count := 0;
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elsif Error < -Full_Band then
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-- Full Drive
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Skip := 0;
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elsif Error > Dead_Band then
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Skip := Skip + 1;
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elsif Error < -Dead_Band then
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if Skip > 0 then
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Skip := Skip - 1;
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end if;
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end if;
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end if;
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end process Controller;
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end mc_arch;
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