Add rate-limmiter-md

rate-limmiter-md

@@ -0,0 +1,73 @@
+FUNCTION "FC_RateLimiter" : Void
+{ S7_Optimized_Access := 'TRUE' }
+VERSION : 0.1
+   VAR_INPUT 
+      analog_input : Real;           // Raw input signal (setpoint or feedback)
+      pos_slew_rate : Real := 10.0;  // Max allowed increase per PLC scan (engineering units)
+      neg_slew_rate : Real := 10.0;  // Max allowed decrease per PLC scan (engineering units)
+      enable : Bool := TRUE;         // Enable rate limiting
+      reset : Bool := FALSE;         // Reset: output snaps to input immediately
+   END_VAR
+
+   VAR_OUTPUT 
+      rate_limited_output : Real;    // Slew-rate limited output
+   END_VAR
+
+   VAR 
+      prev_output : Real;            // Previous output value (retains between scans)
+      initialized : Bool := FALSE;   // First-run initialization flag
+   END_VAR
+
+   VAR_TEMP 
+      delta : Real;                  // Calculated change from previous output
+      max_rise : Real;               // Clamped positive limit for this cycle
+      max_fall : Real;               // Clamped negative limit for this cycle
+   END_VAR
+
+BEGIN
+	// Handle reset: snap output to input immediately
+	IF #reset THEN
+		#rate_limited_output := #analog_input;
+		#prev_output := #analog_input;
+		#initialized := TRUE;
+		RETURN;
+	END_IF;
+	
+	// Bypass if disabled: pass-through mode
+	IF NOT #enable THEN
+		#rate_limited_output := #analog_input;
+		#prev_output := #analog_input;
+		RETURN;
+	END_IF;
+	
+	// Initialize on first run to avoid startup transient
+	IF NOT #initialized THEN
+		#rate_limited_output := #analog_input;
+		#prev_output := #analog_input;
+		#initialized := TRUE;
+		RETURN;
+	END_IF;
+	
+	// Ensure slew rates are non-negative
+	#max_rise := ABS(#pos_slew_rate);
+	#max_fall := ABS(#neg_slew_rate);
+	
+	// Calculate desired change
+	#delta := #analog_input - #prev_output;
+	
+	// Apply asymmetric slew limiting
+	IF #delta > #max_rise THEN
+		// Rising too fast: limit to max rise
+		#rate_limited_output := #prev_output + #max_rise;
+	ELSIF #delta < -#max_fall THEN
+		// Falling too fast: limit to max fall
+		#rate_limited_output := #prev_output - #max_fall;
+	ELSE
+		// Within allowed slew range: pass through
+		#rate_limited_output := #analog_input;
+	END_IF;
+	
+	// Store for next scan
+	#prev_output := #rate_limited_output;
+	
+END_FUNCTION