added slew rate filter

Rate Limiter Slew Rate Filter.txt

@@ -0,0 +1,37 @@
+#Limits how fast the signal can change per scan cycle — useful for preventing actuator shock.
+
+FUNCTION_BLOCK FB_RateLimiter
+VAR_INPUT
+    xEnable      : BOOL;
+    rInput       : REAL;
+    rMaxRiseRate : REAL := 10.0;   // Max units per second rising
+    rMaxFallRate : REAL := 10.0;   // Max units per second falling
+    rCycleTimeS  : REAL := 0.1;    // OB cycle time in seconds
+END_VAR
+VAR_OUTPUT
+    rOutput : REAL;
+END_VAR
+VAR
+    xFirst : BOOL := TRUE;
+    rMaxStep : REAL;
+    rMinStep : REAL;
+    rDelta   : REAL;
+END_VAR
+
+IF NOT xEnable THEN
+    xFirst  := TRUE;
+    rOutput := rInput;
+    RETURN;
+END_IF;
+
+IF xFirst THEN
+    rOutput := rInput;
+    xFirst  := FALSE;
+    RETURN;
+END_IF;
+
+rMaxStep :=  rMaxRiseRate * rCycleTimeS;
+rMinStep := -rMaxFallRate * rCycleTimeS;
+rDelta   := rInput - rOutput;
+rDelta   := MAX(MIN(rDelta, rMaxStep), rMinStep);
+rOutput  := rOutput + rDelta;