DYNAMIC CUTTING PROCESS IDENTIFICATION BY DYNAMIC DATA SYSTEM (DDS) MODELS.

摘要

Anticipating the stochastic nature of the cutting process and the double modulation principle, Dynamic Data System methodology was employed for the dynamic cutting process identification model. Modified Autoregressive Moving Average Vector (MARMAV) modelling approach was chosen for the determination of the dynamic cutting process model. Transfer function of the dynamic cutting processes in the form of the dynamic cutting force coefficients (DCFC) were obtained from the MARMAV models.;The first method considers the cutting process with two inputs, inner and outer modulations, one output, dynamic force component. Consequently, this process has to be handled as a three variable system in relation to the MARMAV modeling approach which leads to the inner and outer modulation dynamics identification. On the other hand, the second method sees the cutting process as a one-input one-output process consisting of the inner modulation and dynamic force component. Accordingly, the MARMAV model uses the bivariate concept for model fitting which gives inner modulation dynamics only. In the latter case, the outer modulation dynamics effect on the cutting process is determined by analyzing the disturbance noise dynamics under the same assumptions.;The identification of the cutting process dynamics was carried out using the actual data collected from an orthogonal turning process of a tubular workpiece under bandlimited white noise excitation. Besides, experimental and analytical works for the two existing typical methods, the shear plane method and the double modulation method, has been carried to determine the dynamic cutting force coefficients.;For comparison purposes, DCFC's in frequency domain were determined by the proposed two methods, as well as by the other two classical methods. It has been shown that the proposed methods are capable of representing the cutting process dynamics with good accuracy.;For the determination of the dynamic cutting force coefficients, two different methods, were proposed according to the input conditions of the cutting process.;Further extension of the proposed method to the non-orthogonal cutting process for which the theoretical work has been given, assures that the proposed method will offer a basis for practical solutions of the general three-dimensional cutting dynamics problem.