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/*
* PIDThread.cpp
*
* Created on: 29 May 2020
* Author: Ralim
*/
#include "BSP.h"
#include "FreeRTOS.h"
#include "Settings.h"
#include "TipThermoModel.h"
#include "cmsis_os.h"
#include "history.hpp"
#include "main.hpp"
#include "power.hpp"
#include "task.h"
static TickType_t powerPulseWaitUnit = 25 * TICKS_100MS; // 2.5 s
static TickType_t powerPulseDurationUnit = (5 * TICKS_100MS) / 2; // 250 ms
TaskHandle_t pidTaskNotification = NULL;
volatile TemperatureType_t currentTempTargetDegC = 0; // Current temperature target in C
int32_t powerSupplyWattageLimit = 0;
bool heaterThermalRunaway = false;
static int32_t getPIDResultX10Watts(TemperatureType_t tError);
static void detectThermalRunaway(const TemperatureType_t currentTipTempInC, const TemperatureType_t tError);
static void setOutputx10WattsViaFilters(int32_t x10Watts);
static int32_t getX10WattageLimits();
/* StartPIDTask function */
void startPIDTask(void const *argument __unused) {
/*
* We take the current tip temperature & evaluate the next step for the tip
* control PWM.
*/
setTipX10Watts(0); // disable the output at startup
currentTempTargetDegC = 0; // Force start with no output (off). If in sleep / soldering this will
// be over-ridden rapidly
pidTaskNotification = xTaskGetCurrentTaskHandle();
TemperatureType_t PIDTempTarget = 0;
// Pre-seed the adc filters
for (int i = 0; i < 32; i++) {
ulTaskNotifyTake(pdTRUE, 5);
TipThermoModel::getTipInC(true);
getInputVoltageX10(getSettingValue(SettingsOptions::VoltageDiv), 1);
}
while (preStartChecks() == 0) {
resetWatchdog();
ulTaskNotifyTake(pdTRUE, 2000);
}
int32_t x10WattsOut = 0;
for (;;) {
x10WattsOut = 0;
// This is a call to block this thread until the ADC does its samples
if (ulTaskNotifyTake(pdTRUE, TICKS_SECOND * 2)) {
// Do the reading here to keep the temp calculations churning along
TemperatureType_t currentTipTempInC = TipThermoModel::getTipInC(true);
PIDTempTarget = currentTempTargetDegC;
if (PIDTempTarget > 0) {
// Cap the max set point to 450C
if (PIDTempTarget > 450) {
// Maximum allowed output
PIDTempTarget = 450;
}
// Safety check that not aiming higher than current tip can measure
if (PIDTempTarget > TipThermoModel::getTipMaxInC()) {
PIDTempTarget = TipThermoModel::getTipMaxInC();
}
TemperatureType_t tError = PIDTempTarget - currentTipTempInC;
detectThermalRunaway(currentTipTempInC, tError);
x10WattsOut = getPIDResultX10Watts(tError);
} else {
detectThermalRunaway(currentTipTempInC, 0);
}
setOutputx10WattsViaFilters(x10WattsOut);
} else {
// ADC interrupt timeout
setTipPWM(0, false);
}
#ifdef DEBUG_UART_OUTPUT
log_system_state(x10WattsOut);
#endif
}
}
template <class T = TemperatureType_t> struct Integrator {
T sum;
T update(const T val, const int32_t inertia, const int32_t gain, const int32_t rate, const int32_t limit) {
// Decay the old value. This is a simplified formula that still works with decent results
// Ideally we would have used an exponential decay but the computational effort required
// by exp function is just not justified here in respect to the outcome
sum = (sum * (100 - (inertia / rate))) / 100;
// Add the new value x integration interval ( 1 / rate)
sum += (gain * val) / rate;
// constrain the output between +- our max power output, this limits windup when doing the inital heatup or when solding something large
if (sum > limit) {
sum = limit;
} else if (sum < -limit) {
sum = -limit;
}
return sum;
}
void set(T const val) { sum = val; }
T get(bool positiveOnly = true) const { return (positiveOnly) ? ((sum > 0) ? sum : 0) : sum; }
};
int32_t getPIDResultX10Watts(TemperatureType_t setpointDelta) {
static TickType_t lastCall = 0;
static Integrator<TemperatureType_t> powerStore = {0};
const TickType_t rate = TICKS_SECOND / (xTaskGetTickCount() - lastCall);
lastCall = xTaskGetTickCount();
// Sandman note:
// PID Challenge - we have a small thermal mass that we to want heat up as fast as possible but we don't
// want to overshot excessively (if at all) the set point temperature. In the same time we have 'imprecise'
// instant temperature measurements. The nature of temperature reading imprecision is not necessarily
// related to the sensor (thermocouple) or DAQ system, that otherwise are fairly decent. The real issue is
// the thermal inertia. We basically read the temperature in the window between two heating sessions when
// the output is off. However, the heater temperature does not dissipate instantly into the tip mass so
// at any moment right after heating, the thermocouple would sense a temperature significantly higher than
// moments later. We could use longer delays but that would slow the PID loop and that would lead to other
// negative side effects. As a result, we can only rely on the I term but with a twist. Instead of a simple
// integrator we are going to use a self decaying integrator that acts more like a dual I term / P term
// rather than a plain I term. Depending on the circumstances, like when the delta temperature is large,
// it acts more like a P term whereas on closing to set point it acts increasingly closer to a plain I term.
// So in a sense, we have a bit of both.
// So there we go...
// P = (Thermal Mass) x (Delta Temperature ) / 1sec, where thermal mass is in X10 J / °C and
// delta temperature is in °C. The result is the power in X10 W needed to raise (or decrease!) the
// tip temperature with (Delta Temperature ) °C in 1 second.
// Note on powerStore. On update, if the value is provided in X10 (W) units then inertia shall be provided
// in X10 (J / °C) units as well.
return powerStore.update(((TemperatureType_t)getTipThermalMass()) * setpointDelta, // the required power
getTipInertia(), // Inertia, smaller numbers increase dominance of the previous value
2, // gain
rate, // PID cycle frequency
getX10WattageLimits());
}
void detectThermalRunaway(const TemperatureType_t currentTipTempInC, const TemperatureType_t tError) {
static TemperatureType_t tipTempCRunawayTemp = 0;
static TickType_t runawaylastChangeTime = 0;
// Check for thermal runaway, where it has been x seconds with negligible (y) temp rise
// While trying to actively heat
// If we are more than 20C below the setpoint
if ((tError > THERMAL_RUNAWAY_TEMP_C)) {
// If we have heated up by more than 20C since last sample point, snapshot time and tip temp
TemperatureType_t delta = currentTipTempInC - tipTempCRunawayTemp;
if (delta > THERMAL_RUNAWAY_TEMP_C) {
// We have heated up more than the threshold, reset the timer
tipTempCRunawayTemp = currentTipTempInC;
runawaylastChangeTime = xTaskGetTickCount();
} else {
if ((xTaskGetTickCount() - runawaylastChangeTime) > (THERMAL_RUNAWAY_TIME_SEC * TICKS_SECOND)) {
// It has taken too long to rise
heaterThermalRunaway = true;
}
}
} else {
tipTempCRunawayTemp = currentTipTempInC;
runawaylastChangeTime = xTaskGetTickCount();
}
}
int32_t getX10WattageLimits() {
int32_t limit = availableW10(0);
if (getSettingValue(SettingsOptions::PowerLimit) && limit > (getSettingValue(SettingsOptions::PowerLimit) * 10)) {
limit = getSettingValue(SettingsOptions::PowerLimit) * 10;
}
if (powerSupplyWattageLimit && limit > powerSupplyWattageLimit * 10) {
limit = powerSupplyWattageLimit * 10;
}
return limit;
}
void setOutputx10WattsViaFilters(int32_t x10WattsOut) {
static TickType_t lastPowerPulseStart = 0;
static TickType_t lastPowerPulseEnd = 0;
#ifdef SLEW_LIMIT
static int32_t x10WattsOutLast = 0;
#endif
// If the user turns on the option of using an occasional pulse to keep the power bank on
if (getSettingValue(SettingsOptions::KeepAwakePulse)) {
const TickType_t powerPulseWait = powerPulseWaitUnit * getSettingValue(SettingsOptions::KeepAwakePulseWait);
if (xTaskGetTickCount() - lastPowerPulseStart > powerPulseWait) {
const TickType_t powerPulseDuration = powerPulseDurationUnit * getSettingValue(SettingsOptions::KeepAwakePulseDuration);
lastPowerPulseStart = xTaskGetTickCount();
lastPowerPulseEnd = lastPowerPulseStart + powerPulseDuration;
}
// If current PID is less than the pulse level, check if we want to constrain to the pulse as the floor
if (x10WattsOut < getSettingValue(SettingsOptions::KeepAwakePulse) && xTaskGetTickCount() < lastPowerPulseEnd) {
x10WattsOut = getSettingValue(SettingsOptions::KeepAwakePulse);
}
}
// Secondary safety check to forcefully disable header when within ADC noise of top of ADC
if (getTipRawTemp(0) > (0x7FFF - 32)) {
x10WattsOut = 0;
}
if (heaterThermalRunaway) {
x10WattsOut = 0;
}
#ifdef SLEW_LIMIT
if (x10WattsOut - x10WattsOutLast > SLEW_LIMIT) {
x10WattsOut = x10WattsOutLast + SLEW_LIMIT;
}
if (x10WattsOut < 0) {
x10WattsOut = 0;
}
x10WattsOutLast = x10WattsOut;
#endif
setTipX10Watts(x10WattsOut);
resetWatchdog();
}
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