センサレス切削力推定における誤差因子の影響

抄録

Error factors in sensorless cutting force estimation under ball-screw-driven stage were discussed. In addition, their influence on estimation accuracy was experimentally evaluated through several end milling tests. Because rigid body-based formulation is difficult in ball-screw-driven stage, estimation principle of cutting force needs to be formulated considering interaction between rotation and translation to enhance estimation accuracy of the cutting force. Simulation results revealed that phase lag element between current and position/angle response was non-negligible in higher frequencies as well as measurement error of acceleration due to numerical differential. Therefore, both phase lag compensation and high-resolution encoders are necessary. Fluctuations of disturbance force and acceleration synchronizing rotation of servomotor were classified in terms of their period: comparatively low-frequency fluctuations ranging from submillimeter to millimeter resulting from mechanical elements; high-frequency fluctuations with period of several micrometers resulting from interpolation error of encoder signal. The former can be eliminated more effectively than the latter, because preliminary identification is possible based on position dependency and repeatability. On the other hand, the latter needs to be eliminated by signal processing, because preliminary identification including phase is difficult. The result of milling tests revealed that it was possible to enhance estimation accuracy of the cutting force by constructing estimation system considering the above error factors.