Sensing Strategies to Monitor the Motion of a Full Variable Valve Train in Combustion Engines

This paper deals with all required parts to set up the full variable valve train (FVVT) system to be used in intake and exhaust valves of combustion engines from the electrical/electronic point of view. This includes the displacement and pressure sensors that are needed to conduct research on the fully variable valve train while in operation and the electronic auxiliaries such as the amplifier for the piezo actuator, the dSPACE control system and the used function generator. In particular, the use of displacement transducers for all relevant pistons and stems is crucial for the FVVT system control. As only the piezo actuator is equipped with a displacement sensor, the remaining sensors still need to be chosen. Within the previous FVVT system two different displacement sensors have been used on the engine valve stem. Three displacement sensors and one pressure sensor are implemented into the mechanical core of the system (consisting of lever transmission, control unit, servo valve and engine valve body), which is driven by the piezo actuator and supplied with hydraulic pressure by a pump, that requires a 230 V power supply and a tank, which the hydraulic fluid can return to. While the pressure sensor monitors the hydraulic pressure within the lever transmission, displacement sensors need to be chosen to monitor the motion of the 

1. control piston in the control unit 
2. servo piston within the servo valve
3. engine valves. 

Measured results are presented.