Evaluation of Model-based Control of Reaction Forces at the Supports of Large-size Crankshafts

A support control automation system employing force sensors to a large-size crankshaft main journals' flexible support-system was studied. The current system was intended to evaluate the geometric condition of crankshafts in internal combustion diesel engines. The support reaction forces were changed to minimize the crankshaft elastic deflection as a function of the crank angle. The aim of this research was to verify the hypothesis that the mentioned change can be expressed by a monoharmonic model regardless of a crankshaft structure. The authors' investigations have confirmed this hypothesis. It was also shown that an algorithmic approach improved the mathematical model mapping with the reaction forces due to faster and more accurate calculations of a phase shift angle. The verification of the model for crankshafts with different structural designs made it possible to assess how well the model fits the coefficients of determination that were calculated with the finite element analysis (FEA). For the crankshafts analyzed, the coefficients of determination R² were greater than 0.9997, while the maximum relative percentage errors δ_max were up to 1.0228%. These values can be considered highly satisfactory for the assessment of the conducted study.