PID / manage_heater

PSD regulator improvement

Firmware/Configuration.h

@@ -131,8 +131,10 @@
   //#define PID_DEBUG // Sends debug data to the serial port.
   //#define PID_OPENLOOP 1 // Puts PID in open loop. M104/M140 sets the output power from 0 to PID_MAX
   //#define SLOW_PWM_HEATERS // PWM with very low frequency (roughly 0.125Hz=8s) and minimum state time of approximately 1s useful for heaters driven by a relay
+// :-O :-O :-O
   #define PID_FUNCTIONAL_RANGE 10 // If the temperature difference between the target temperature and the actual temperature
                                   // is more then PID_FUNCTIONAL_RANGE then the PID will be shut off and the heater will be set to min/max.
+// :-O :-O :-O
   #define PID_INTEGRAL_DRIVE_MAX PID_MAX  //limit for the integral term
   #define K1 0.95 //smoothing factor within the PID
   #define PID_dT ((OVERSAMPLENR * 10.0)/(F_CPU / 64.0 / 256.0)) //sampling period of the temperature routine

Firmware/temperature.cpp

@@ -106,15 +106,15 @@ static volatile bool temp_meas_ready = false;
 
 #ifdef PIDTEMP
   //static cannot be external:
-  static float temp_iState[EXTRUDERS] = { 0 };
-  static float temp_dState[EXTRUDERS] = { 0 };
+  static float iState_sum[EXTRUDERS] = { 0 };
+  static float dState_last[EXTRUDERS] = { 0 };
   static float pTerm[EXTRUDERS];
   static float iTerm[EXTRUDERS];
   static float dTerm[EXTRUDERS];
   //int output;
   static float pid_error[EXTRUDERS];
-  static float temp_iState_min[EXTRUDERS];
-  static float temp_iState_max[EXTRUDERS];
+  static float iState_sum_min[EXTRUDERS];
+  static float iState_sum_max[EXTRUDERS];
   // static float pid_input[EXTRUDERS];
   // static float pid_output[EXTRUDERS];
   static bool pid_reset[EXTRUDERS];
@@ -418,7 +418,7 @@ void updatePID()
 {
 #ifdef PIDTEMP
   for(int e = 0; e < EXTRUDERS; e++) { 
-     temp_iState_max[e] = PID_INTEGRAL_DRIVE_MAX / cs.Ki;  
+     iState_sum_max[e] = PID_INTEGRAL_DRIVE_MAX / cs.Ki;  
   }
 #endif
 #ifdef PIDTEMPBED
@@ -587,6 +587,10 @@ void checkExtruderAutoFans()
 
 #endif // any extruder auto fan pins set
 
+void resetPID(uint8_t extruder)                   // ready for eventually parameters adjusting
+{
+}
+
 void manage_heater()
 {
 #ifdef WATCHDOG
@@ -598,6 +602,7 @@ void manage_heater()
 
   if(temp_meas_ready != true)   //better readability
     return; 
+// more precisely - this condition partially stabilizes time interval for regulation values evaluation (@ ~ 230ms)
 
   updateTemperaturesFromRawValues();
 
@@ -619,38 +624,42 @@ void manage_heater()
     pid_input = current_temperature[e];
 
     #ifndef PID_OPENLOOP
-        pid_error[e] = target_temperature[e] - pid_input;
-        if(pid_error[e] > PID_FUNCTIONAL_RANGE) {
-          pid_output = BANG_MAX;
-          pid_reset[e] = true;
-        }
-        else if(pid_error[e] < -PID_FUNCTIONAL_RANGE || target_temperature[e] == 0) {
+        if(target_temperature[e] == 0) {
           pid_output = 0;
           pid_reset[e] = true;
-        }
-        else {
-          if(pid_reset[e] == true) {
-            temp_iState[e] = 0.0;
+        } else {
+          pid_error[e] = target_temperature[e] - pid_input;
+          if(pid_reset[e]) {
+            iState_sum[e] = 0.0;
+            dTerm[e] = 0.0;                       // 'dState_last[e]' initial setting is not necessary (see end of if-statement)
             pid_reset[e] = false;
           }
+#ifndef PonM
           pTerm[e] = cs.Kp * pid_error[e];
-          temp_iState[e] += pid_error[e];
-          temp_iState[e] = constrain(temp_iState[e], temp_iState_min[e], temp_iState_max[e]);
-          iTerm[e] = cs.Ki * temp_iState[e];
-
-          //K1 defined in Configuration.h in the PID settings
+          iState_sum[e] += pid_error[e];
+          iState_sum[e] = constrain(iState_sum[e], iState_sum_min[e], iState_sum_max[e]);
+          iTerm[e] = cs.Ki * iState_sum[e];
+          // K1 defined in Configuration.h in the PID settings
           #define K2 (1.0-K1)
-          dTerm[e] = (cs.Kd * (pid_input - temp_dState[e]))*K2 + (K1 * dTerm[e]);
-          pid_output = pTerm[e] + iTerm[e] - dTerm[e];
+          dTerm[e] = (cs.Kd * (pid_input - dState_last[e]))*K2 + (K1 * dTerm[e]); // e.g. digital filtration of derivative term changes
+          pid_output = pTerm[e] + iTerm[e] - dTerm[e]; // subtraction due to "Derivative on Measurement" method (i.e. derivative of input instead derivative of error is used)
           if (pid_output > PID_MAX) {
-            if (pid_error[e] > 0 )  temp_iState[e] -= pid_error[e]; // conditional un-integration
+            if (pid_error[e] > 0 ) iState_sum[e] -= pid_error[e]; // conditional un-integration
             pid_output=PID_MAX;
-          } else if (pid_output < 0){
-            if (pid_error[e] < 0 )  temp_iState[e] -= pid_error[e]; // conditional un-integration
+          } else if (pid_output < 0) {
+            if (pid_error[e] < 0 ) iState_sum[e] -= pid_error[e]; // conditional un-integration
             pid_output=0;
           }
+#else // PonM ("Proportional on Measurement" method)
+          iState_sum[e] += cs.Ki * pid_error[e];
+          iState_sum[e] -= cs.Kp * (pid_input - dState_last[e]);
+          iState_sum[e] = constrain(iState_sum[e], 0, PID_INTEGRAL_DRIVE_MAX);
+          dTerm[e] = cs.Kd * (pid_input - dState_last[e]);
+          pid_output = iState_sum[e] - dTerm[e];  // subtraction due to "Derivative on Measurement" method (i.e. derivative of input instead derivative of error is used)
+          pid_output = constrain(pid_output, 0, PID_MAX);
+#endif // PonM
         }
-        temp_dState[e] = pid_input;
+        dState_last[e] = pid_input;
     #else 
           pid_output = constrain(target_temperature[e], 0, PID_MAX);
     #endif //PID_OPENLOOP
@@ -667,7 +676,7 @@ void manage_heater()
     SERIAL_ECHO(" iTerm ");
     SERIAL_ECHO(iTerm[e]);
     SERIAL_ECHO(" dTerm ");
-    SERIAL_ECHOLN(dTerm[e]);
+    SERIAL_ECHOLN(-dTerm[e]);
     #endif //PID_DEBUG
   #else /* PID off */
     pid_output = 0;
@@ -677,16 +686,14 @@ void manage_heater()
   #endif
 
     // Check if temperature is within the correct range
-    if(current_temperature[e] < maxttemp[e])
+    if((current_temperature[e] < maxttemp[e]) && (target_temperature[e] != 0))
     {
       soft_pwm[e] = (int)pid_output >> 1;
     }
     else
-	{
+    {
       soft_pwm[e] = 0;
     }
-    if(target_temperature[e]==0)
-      soft_pwm[e] = 0;
 
     #ifdef WATCH_TEMP_PERIOD
     if(watchmillis[e] && millis() - watchmillis[e] > WATCH_TEMP_PERIOD)
@@ -1001,8 +1008,8 @@ void tp_init()
     // populate with the first value 
     maxttemp[e] = maxttemp[0];
 #ifdef PIDTEMP
-    temp_iState_min[e] = 0.0;
-    temp_iState_max[e] = PID_INTEGRAL_DRIVE_MAX / cs.Ki;
+    iState_sum_min[e] = 0.0;
+    iState_sum_max[e] = PID_INTEGRAL_DRIVE_MAX / cs.Ki;
 #endif //PIDTEMP
 #ifdef PIDTEMPBED
     temp_iState_min_bed = 0.0;

Firmware/temperature.h

@@ -87,6 +87,8 @@ extern int current_voltage_raw_bed;
   extern volatile int babystepsTodo[3];
 #endif
 
+void resetPID(uint8_t extruder);
+
 inline void babystepsTodoZadd(int n)
 {
     if (n != 0) {
@@ -137,11 +139,15 @@ FORCE_INLINE float degTargetBed() {
 
 FORCE_INLINE void setTargetHotend(const float &celsius, uint8_t extruder) {  
   target_temperature[extruder] = celsius;
+  resetPID[extruder];
 };
 
 static inline void setTargetHotendSafe(const float &celsius, uint8_t extruder)
 {
-    if (extruder<EXTRUDERS) target_temperature[extruder] = celsius;
+    if (extruder<EXTRUDERS) {
+      target_temperature[extruder] = celsius;
+      resetPID[extruder];
+    }
 }
 
 static inline void setAllTargetHotends(const float &celsius)