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fboss:fan_service: correct fan_service position PID algorithm #560

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fboss:fan_service: correct fan_service position PID algorithm #560

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10 changes: 4 additions & 6 deletions fboss/platform/fan_service/PidLogic.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@
namespace facebook::fboss::platform::fan_service {

int16_t PidLogic::calculatePwm(float measurement) {
float newPwm, pwmDelta{0};
float newPwm;
float minVal = *pidSetting_.setPoint() - *pidSetting_.negHysteresis();
float maxVal = *pidSetting_.setPoint() + *pidSetting_.posHysteresis();
std::optional<float> error{};
Expand All @@ -21,9 +21,8 @@ int16_t PidLogic::calculatePwm(float measurement) {
if (error.has_value()) {
integral_ = integral_ + *error * dT_;
auto derivative = (*error - lastError_) / dT_;
pwmDelta = (*pidSetting_.kp() * error.value()) +
newPwm = (*pidSetting_.kp() * error.value()) +
(*pidSetting_.ki() * integral_) + (*pidSetting_.kd() * derivative);
newPwm = lastPwm_ + pwmDelta;
} else {
newPwm = lastPwm_;
}
Expand All @@ -39,17 +38,16 @@ int16_t PidLogic::calculatePwm(float measurement) {
// increasing pwm when measurement is higher than setPoint. To avoid this,
// we reset integral_ when measurement is lower than setPoint.
if (measurement <= maxVal) {
integral_ = pwmDelta / *pidSetting_.ki();
integral_ = newPwm / *pidSetting_.ki();
}

XLOG(DBG2) << fmt::format(
"Measurement: {}, Error: {}, Last PWM: {}, integral_: {}, "
"PWM Delta: {}, New PWM: {}",
"New PWM: {}",
measurement,
error.value_or(0),
lastPwm_,
integral_,
pwmDelta,
newPwm);

lastPwm_ = newPwm;
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