Abstract: The dynamic error is the main factor that influences crankshaft noncircular grinding accuracy, real-time dynamic error compensation can correct various errors of non-circular grinding process, and ensure the machining accuracy of work piece after supplementary machining. Through analyzing the reasons of dynamic errors in the crankshaft non-circular grinding process, the servo lag errors of CNC system in the non-circular grinding are analyzed quantitatively, and simulation computation of the motion model based on constant line speed is carried out. The computation results show that the servo lag errors seriously affect the machining accuracy, and the adjustment of CNC system can only reduce, but cannot eliminate, the servolag errors. To deal with the dynamic error, a new compensation way is presented to forecast the errors by using RBF-NN based on online measuring system. Through offline measurement test, the errors of crank shaft noncircular grinding are compensated by adoptjng the RBF network.

Key words: Crankshaft, Dynamic error, Error compensating, Noncircular grinding, RBF, flexible coupling, frequency response function, receptance coupling substructure analysis, shafts, Timoshenko beam