voltage compensated vvt #209

firmware/CHANGELOG.md

@@ -31,6 +31,7 @@ Release template (copy/paste this for new release):
 ### Added
  - Log per-cylinder true ignition timing (includes trim, knock retard, etc) #76
  - Add mode for CLT/IAT sensors that are installed "high side" instead of typical "low side" #116
+ - Automatic supply voltage compensation for VVT solenoids, giving more stable control as battery voltage changes #209
 
 ### Fixed
  - Improved bench test resolution (more usable for testing injectors, dwell, etc)

firmware/controllers/actuators/vvt.cpp

@@ -106,13 +106,22 @@ void VvtController::setOutput(expected<percent_t> outputValue) {
 			&& engine->rpmCalculator.getSecondsSinceEngineStart(getTimeNowNt()) > engineConfiguration->vvtActivationDelayMs / MS_PER_SECOND
 			 ;
 
-	vvtOutput = outputValue.value_or(0);
-
 	if (outputValue && enabled) {
-		m_pwm->setSimplePwmDutyCycle(PERCENT_TO_DUTY(outputValue.Value));
+		float vvtPct = outputValue.Value;
+
+		// Compensate for battery voltage so that the % output is actually % solenoid current normalized
+		// to a 14v supply (boost duty when battery is low, etc)
+		float voltageRatio = 14 / Sensor::get(SensorType::BatteryVoltage).value_or(14);
+		vvtPct *= voltageRatio;
+
+		vvtOutput = vvtPct;
+
+		m_pwm->setSimplePwmDutyCycle(PERCENT_TO_DUTY(vvtPct));
 	} else {
 		m_pwm->setSimplePwmDutyCycle(0);
 
+		vvtOutput = 0;
+
 		// we need to avoid accumulating iTerm while engine is not running
 		m_pid.reset();
 	}