Implement separate I gain multiplier for negative error and adjust PID values

Author: AxxAxx

AxxSolder_firmware/Core/Inc/pid.h

@@ -60,6 +60,8 @@ typedef struct{
 
 	double			IminError;
 
+	double			NegativeErrorIgainMultiplier;
+
 }PID_TypeDef;
 
 /* Init */
@@ -85,6 +87,9 @@ void PID_SetILimits(PID_TypeDef *uPID, double Min, double Max);
 /* Minimum error where I is added */
 void PID_SetIminError(PID_TypeDef *uPID, double IminError);
 
+/* Set the I gain multiplier for negative error*/
+void PID_SetNegativeErrorIgainMult(PID_TypeDef *uPID, double NegativeErrorIgainMultiplier);
+
 /* PID Tunings */
 void PID_SetTunings(PID_TypeDef *uPID, double Kp, double Ki, double Kd);
 

AxxSolder_firmware/Core/Src/main.c

@@ -57,9 +57,9 @@ uint8_t fw_version_patch =  1;
 #define MAX_I_NT115 	150
 
 #define KP_T210 		5
-#define KI_T210 		5.5//5
+#define KI_T210 		3//5
 #define KD_T210 		0.25
-#define MAX_I_T210 		125//250
+#define MAX_I_T210 		300//250
 
 #define KP_T245 		8
 #define KI_T245 		5
@@ -137,7 +137,8 @@ uint8_t custom_temperature_on = 0;
 /* PID parameters */
 #define PID_MAX_OUTPUT 500
 #define PID_UPDATE_INTERVAL 25
-#define PID_add_I_min_error 999//50
+#define PID_ADD_I_MIN_ERROR 75
+#define PID_NEGATIVE_ERROR_I_GAIN_MULTIPLIER 5
 
 /* Buffer for UART print */
 char UART_buffer[40];
@@ -1427,7 +1428,8 @@ int main(void)
 	PID_SetSampleTime(&TPID, PID_UPDATE_INTERVAL, 0); 		//Set PID sample time to "PID_UPDATE_INTERVAL" to make sure PID is calculated every time it is called
 	PID_SetOutputLimits(&TPID, 0, PID_MAX_OUTPUT); 			// Set max and min output limit
 	PID_SetILimits(&TPID, 0, 0);         					// Set max and min I limit
-	PID_SetIminError(&TPID,PID_add_I_min_error);
+	PID_SetIminError(&TPID,PID_ADD_I_MIN_ERROR);
+	PID_SetNegativeErrorIgainMult(&TPID, PID_NEGATIVE_ERROR_I_GAIN_MULTIPLIER);
 
 	/* Init and fill filter structures with initial values */
 	for (int i = 0; i<200;i++){

AxxSolder_firmware/Core/Src/pid.c

@@ -80,13 +80,15 @@ uint8_t PID_Compute(PID_TypeDef *uPID){
 		output += uPID->DispKd_part;
 
 		/* Conditional integration as anti-windup (clamping) */
-		if(check_clamping(output + uPID->Ki * error  * timeChange_in_seconds, uPID->OutMin, uPID->OutMax) && (error*(output + uPID->OutputSum) > 0)){
-		//if((error > proportional_band_max) || (error < proportional_band_min)){
+		if(check_clamping(output + 5*uPID->Ki * error  * timeChange_in_seconds, uPID->OutMin, uPID->OutMax) && (error*(output + uPID->OutputSum) > 0)){
 			uPID->OutputSum     += 0;
 		}
-		else{
+		else if(error > 0){
 			uPID->OutputSum     += (uPID->Ki * error * timeChange_in_seconds);
 		}
+		else{
+			uPID->OutputSum     += 5*(uPID->Ki * error * timeChange_in_seconds);
+		}
 
 		/* Clamp Integral part */
 		uPID->OutputSum = double_clamp(uPID->OutputSum, uPID->IMin, uPID->IMax);
@@ -97,13 +99,11 @@ uint8_t PID_Compute(PID_TypeDef *uPID){
 		}
 
 		/* only add I part if error is smaller than IminError and scale it from IminError to 0 */
-		if(error < fabs(uPID->IminError)){
-			uPID->DispKi_part = (uPID->IminError - fabs(error))/uPID->IminError * uPID->OutputSum;
-		}
-		else{
-			uPID->DispKi_part = 0;
+		if(error > fabs(uPID->IminError)){
+			uPID->OutputSum = 0;
 		}
 
+		uPID->DispKi_part = uPID->OutputSum;
 		/* Final summation */
 		output += uPID->DispKi_part;
 
@@ -176,6 +176,14 @@ void PID_SetIminError(PID_TypeDef *uPID, double IminError){	/* Check value */
 	uPID->IminError = IminError;
 }
 
+/* Set the I gain multiplier for negative error*/
+void PID_SetNegativeErrorIgainMult(PID_TypeDef *uPID, double NegativeErrorIgainMultiplier){
+	if (NegativeErrorIgainMultiplier < 0){
+		return;
+	}
+
+	uPID->NegativeErrorIgainMultiplier = NegativeErrorIgainMultiplier;
+}
 
 /* PID Tunings */
 void PID_SetTunings(PID_TypeDef *uPID, double Kp, double Ki, double Kd){