✨ MPC_PTC (#27911)

Marlin/Configuration.h

@@ -735,7 +735,12 @@
   //#define MPC_AUTOTUNE_MENU                         // Add MPC auto-tuning to the "Advanced Settings" menu. (~350 bytes of flash)
 
   #define MPC_MAX 255                                 // (0..255) Current to nozzle while MPC is active.
-  #define MPC_HEATER_POWER { 40.0f }                  // (W) Heat cartridge powers.
+  #define MPC_HEATER_POWER { 40.0f }                  // (W) Nominal heat cartridge powers.
+  //#define MPC_PTC                                   // Hotend power changes with temperature (e.g., PTC heat cartridges).
+  #if ENABLED(MPC_PTC)
+    #define MPC_HEATER_ALPHA { 0.0028f }              // Temperature coefficient of resistance of the heat cartridges.
+    #define MPC_HEATER_REFTEMP { 20 }                 // (°C) Reference temperature for MPC_HEATER_POWER and MPC_HEATER_ALPHA.
+  #endif
 
   #define MPC_INCLUDE_FAN                             // Model the fan speed?
 

Marlin/src/gcode/temp/M306.cpp

@@ -64,9 +64,13 @@ void GcodeSuite::M306() {
         case 2: tuning_type = Temperature::MPCTuningType::FORCE_ASYMPTOTIC; break;
         default: tuning_type = Temperature::MPCTuningType::AUTO; break;
       }
-      LCD_MESSAGE(MSG_MPC_AUTOTUNE);
+      if (TERN0(MPC_PTC, tuning_type == Temperature::MPCTuningType::FORCE_ASYMPTOTIC))
-      thermalManager.MPC_autotune(e, tuning_type);
+        SERIAL_ECHOLNPGM("Aymptotic tuning not avaiable for PTC hotends");
-      ui.reset_status();
+      else {
+        LCD_MESSAGE(MSG_MPC_AUTOTUNE);
+        thermalManager.MPC_autotune(e, tuning_type);
+        ui.reset_status();
+      }
       return;
     }
   #endif
@@ -74,6 +78,10 @@ void GcodeSuite::M306() {
   if (parser.seen("ACFPRH")) {
     MPC_t &mpc = thermalManager.temp_hotend[e].mpc;
     if (parser.seenval('P')) mpc.heater_power = parser.value_float();
+    #if ENABLED(MPC_PTC)
+      if (parser.seenval('L')) mpc.heater_alpha = parser.value_float();
+      if (parser.seenval('Q')) mpc.heater_reftemp = parser.value_float();
+    #endif
     if (parser.seenval('C')) mpc.block_heat_capacity = parser.value_float();
     if (parser.seenval('R')) mpc.sensor_responsiveness = parser.value_float();
     if (parser.seenval('A')) mpc.ambient_xfer_coeff_fan0 = parser.value_float();
@@ -94,16 +102,20 @@ void GcodeSuite::M306_report(const bool forReplay/*=true*/) {
   HOTEND_LOOP() {
     report_echo_start(forReplay);
     MPC_t &mpc = thermalManager.temp_hotend[e].mpc;
-    SERIAL_ECHOPGM("  M306 E", e,
+    SERIAL_ECHOLNPGM("  M306 E", e,
                          " P", p_float_t(mpc.heater_power, 2),
+                         #if ENABLED(MPC_PTC)
+                           " L", p_float_t(mpc.heater_alpha, 4),
+                           " Q", p_float_t(mpc.heater_reftemp, 2),
+                         #endif
                          " C", p_float_t(mpc.block_heat_capacity, 2),
                          " R", p_float_t(mpc.sensor_responsiveness, 4),
-                         " A", p_float_t(mpc.ambient_xfer_coeff_fan0, 4)
+                         " A", p_float_t(mpc.ambient_xfer_coeff_fan0, 4),
+                         #if ENABLED(MPC_INCLUDE_FAN)
+                           " F", p_float_t(mpc.fanCoefficient(), 4),
+                         #endif
+                         " H", p_float_t(mpc.filament_heat_capacity_permm, 4)
     );
-    #if ENABLED(MPC_INCLUDE_FAN)
-      SERIAL_ECHOPGM(" F", p_float_t(mpc.fanCoefficient(), 4));
-    #endif
-    SERIAL_ECHOLNPGM(" H", p_float_t(mpc.filament_heat_capacity_permm, 4));
   }
 }
 

Marlin/src/inc/SanityCheck.h

@@ -1026,6 +1026,7 @@ static_assert(NUM_SERVOS <= NUM_SERVO_PLUGS, "NUM_SERVOS (or some servo index) i
   #undef MPC_AUTOTUNE
   #undef MPC_EDIT_MENU
   #undef MPC_AUTOTUNE_MENU
+  #undef MPC_PTC
 #endif
 
 #if ENABLED(MPC_INCLUDE_FAN)

Marlin/src/module/settings.cpp

@@ -3710,6 +3710,10 @@ void MarlinSettings::reset() {
   #if ENABLED(MPCTEMP)
 
     constexpr float _mpc_heater_power[] = MPC_HEATER_POWER;
+    #if ENABLED(MPC_PTC)
+      constexpr float _mpc_heater_alpha[] = MPC_HEATER_ALPHA;
+      constexpr float _mpc_heater_reftemp[] = MPC_HEATER_REFTEMP;
+    #endif
     constexpr float _mpc_block_heat_capacity[] = MPC_BLOCK_HEAT_CAPACITY;
     constexpr float _mpc_sensor_responsiveness[] = MPC_SENSOR_RESPONSIVENESS;
     constexpr float _mpc_ambient_xfer_coeff[] = MPC_AMBIENT_XFER_COEFF;
@@ -3719,6 +3723,10 @@ void MarlinSettings::reset() {
     constexpr float _filament_heat_capacity_permm[] = FILAMENT_HEAT_CAPACITY_PERMM;
 
     static_assert(COUNT(_mpc_heater_power) == HOTENDS, "MPC_HEATER_POWER must have HOTENDS items.");
+    #if ENABLED(MPC_PTC)
+      static_assert(COUNT(_mpc_heater_alpha) == HOTENDS, "MPC_HEATER_ALPHA must have HOTENDS items.");
+      static_assert(COUNT(_mpc_heater_reftemp) == HOTENDS, "MPC_HEATER_REFTEMP must have HOTENDS items.");
+    #endif
     static_assert(COUNT(_mpc_block_heat_capacity) == HOTENDS, "MPC_BLOCK_HEAT_CAPACITY must have HOTENDS items.");
     static_assert(COUNT(_mpc_sensor_responsiveness) == HOTENDS, "MPC_SENSOR_RESPONSIVENESS must have HOTENDS items.");
     static_assert(COUNT(_mpc_ambient_xfer_coeff) == HOTENDS, "MPC_AMBIENT_XFER_COEFF must have HOTENDS items.");
@@ -3730,6 +3738,10 @@ void MarlinSettings::reset() {
     HOTEND_LOOP() {
       MPC_t &mpc = thermalManager.temp_hotend[e].mpc;
       mpc.heater_power = _mpc_heater_power[e];
+      #if ENABLED(MPC_PTC)
+        mpc.heater_alpha = _mpc_heater_alpha[e];
+        mpc.heater_reftemp = _mpc_heater_reftemp[e];
+      #endif
       mpc.block_heat_capacity = _mpc_block_heat_capacity[e];
       mpc.sensor_responsiveness = _mpc_sensor_responsiveness[e];
       mpc.ambient_xfer_coeff_fan0 = _mpc_ambient_xfer_coeff[e];

Marlin/src/module/temperature.cpp

@@ -1864,7 +1864,8 @@ void Temperature::mintemp_error(const heater_id_t heater_id OPTARG(ERR_INCLUDE_T
       }
 
       // Update the modeled temperatures
-      float blocktempdelta = hotend.soft_pwm_amount * mpc.heater_power * (MPC_dT / 127) / mpc.block_heat_capacity;
+      const float _heater_power = DIV_TERN(MPC_PTC, mpc.heater_power, 1.0f + mpc.heater_alpha * (hotend.modeled_block_temp - mpc.heater_reftemp));
+      float blocktempdelta = hotend.soft_pwm_amount * _heater_power * (MPC_dT / 127) / mpc.block_heat_capacity;
       blocktempdelta += (hotend.modeled_ambient_temp - hotend.modeled_block_temp) * ambient_xfer_coeff * MPC_dT / mpc.block_heat_capacity;
       hotend.modeled_block_temp += blocktempdelta;
 
@@ -1888,7 +1889,7 @@ void Temperature::mintemp_error(const heater_id_t heater_id OPTARG(ERR_INCLUDE_T
         power -= (hotend.modeled_ambient_temp - hotend.modeled_block_temp) * ambient_xfer_coeff;
       }
 
-      float pid_output = power * 254.0f / mpc.heater_power + 1.0f;        // Ensure correct quantization into a range of 0 to 127
+      float pid_output = power * 254.0f / _heater_power + 1.0f;        // Ensure correct quantization into a range of 0 to 127
       LIMIT(pid_output, 0, MPC_MAX);
 
       /* <-- add a slash to enable

Marlin/src/module/temperature.h

@@ -386,6 +386,10 @@ typedef struct { float p, i, d, c, f; } raw_pidcf_t;
     static bool e_paused;               // Pause E filament permm tracking
     static int32_t e_position;          // For E tracking
     float heater_power;                 // M306 P
+    #if ENABLED(MPC_PTC)
+      float heater_alpha;               // M306 L
+      float heater_reftemp;             // M306 Q
+    #endif
     float block_heat_capacity;          // M306 C
     float sensor_responsiveness;        // M306 R
     float ambient_xfer_coeff_fan0;      // M306 A