Identification of acceleration deceleration profile of feed drive systems in CNC machines

Abstract

In process planning, trajectory planning has generally disregarded the limitations of the feed drive systems in terms of acceleration, jerk, and motion blending. It results in poor prediction of the feed rate mainly in the transient phases and affects, consequently, the machining integrity and safety. Therefore, identifying and integrating the feed drive system limitations with the trajectory planning of the tool path are crucial in order to achieve the desired feed rate at the appropriate tool position. In this paper, a methodology based on time series modeling is proposed to identify the acceleration/deceleration (Acc/Dec) profile of a feed drive system. This profile provides the relationship between the actual feed rate, assumed proportional to the tachometer signal, and the commanded feed rate specified in the G-Code file. A particular shape of the input has been addressed to allow the application of the time series modeling. The different characteristics of this input are carefully considered to avoid both nonlinear response due to saturation and excitation of the high frequency components of the feed drive. The resulting model is transformed into a Finite Impulse Response (FIR) filter and applied as an (Acc/Dec) processor to determine the actual feed rate from the commanded feed rate. The good agreement between the model output and the experimental results demonstrates the effectiveness of the proposed identification method. It is demonstrated that integrating these limitations with the trajectory planing results in a feasible trajectory.