Combustion Supervision by Evaluating the Crankshaft Speed and Acceleration 2000-01-0558

Modern Diesel injection systems have to serve different demands. Beside the improvement of the injection timing and assignment special concentration is focused on increasing injection pressure to improve combustion and lower exhaust gas emissions. With the higher complexity of these systems and the high burden on the pump components especially in the high pressure part of the injection pumps, the wish for supervision of delicate components occurs. Therefore suitable and efficient supervision methods have to be developed to early detect initiating faults.

Because of the correlation between combustion and injection, one way to detect faults in the injection system is to supervise the combustion in the individual cylinders. This can be done by evaluating the crankshaft speed at the flywheel. Speed is directly related to combustion by the indicated pressure and the indicated torque respectively, the crankshaft drive and the resulting torque at the crankshaft. The faults be considered, lead to constant offsets in the injection mass of individual cylinders. Such faults result for example from production tolerances in the injectors or maturation effects like coking. Varying fuel mass leads to different torque contributions of the individual cylinders at the crankshaft. This can be recognized in the relative change of kinetic energy between successive cylinders due to the different displaced combustion energy. The variation of the mean angular acceleration is a measure for this. CASMA filtering, [4], is proposed to measure the mean angular acceleration. The filter algorithm was shown before to be easily implemented in hardware and to meet all performance requirements for on-board implementation. Finally it is shown that the filter output can be used to realize a homokinetic control.