A new firmware controller for a total optical access single-cylinder engine and test bed for LDV and Schlieren combustion studies

The purpose of the paper is the description of the new electronic control strategy for a total optical access single-cylinder engine designed for LDV and Schlieren combustion studies. The engine is characterized by the presence of valves, ignition and electronically controlled injection, and is driven by a Siemens electric motor controlled by a Simoreg controller. Formerly the control system was realized by a program written in Labview language that, through an ATMIO16E-2 board and an external board mainly acts as an interface between the computer and the various electronic actuators. Few other functions, beside the optical coupling between computer and actuators, were incorporated in the external board, such as dividing by two the encoder's trigger to obtain four- stroke operation, analogue integration of the air flow-rate transducer, and the generation of an analogue signal condensing all actuation commands for post- process control of the experiments. The need, however, to operate other functions also during the engine's working cycle, such as computing airflow rates and consequently injection duration, and DMA activation, in some instances was causing irregular engine operation. This led to the decision to design a new ad hoc firmware controller able to receive the various actuation angles from the computer, operating the different devices comparing the angles with an external synchronous clock, counting the encoder signal from the trigger, naturally divided by two. The reason for this choice, in the presence on the market of real-time controllers by NI, was originally the lack of funds, but in the end the need to obtain a true real-time controller, characterized by delays in the nanoseconds range.