Adaptive chatter mitigation control for machining processes with input saturations

Abstract

Chatter is an unstable nonlinear dynamical phenomenon often encountered in machining operations because of the self-excitation mechanism, which may lead to overcut or rapid tool wear, and hence, greatly influence the surface quality and productivity in milling operations. Recent years have witnessed an increasing industrial demand of high quality and high efficiency machining. This paper hereby develops a constrained active adaptive control method to mitigate the chatter dynamics with input saturations. To guarantee the feasibility of the proposed approach, moderate stable conditions of the closed-loop system are afterwards derived by using the LaSalle-Yoshizawa theorem as well. Finally, numerical simulations are conducted to show the substantially enlarged stable region in the Lobe Diagram. Thus, the method can be expected to improve the efficiency of milling processes. ADAPTIVE CHATTER MITIGATION CONTROL 3089 have been devoted to adjust the process parameters such as spindle speed, feed per tooth, pitch angle, and helix angle, which guarantee the system to work in the stable region of the SLD . Meanwhile, some scholars [8][9][10][11][12][13] used sinusoid or triangular spindle speed to disturb the regenerative effect to avoid the unstable region. Still, some other researchers sought assistance from specified actuators like dampers [14] and vibration absorbers [15] to dissipate the chatter energy. These lowcost passive control methods do not require any external power source. However, the practically improvement on damping is rather limited, as the domain of stable operation points toward those of higher productivity can not be enlarged. Consequently, the productivity of passive control-based milling systems is still limited.By comparison, the active control is a more promising one, which installs suitable sensors and actuators (like electrostrictive actuators [16], piezoelectric motors [17], or active magnetic bearing [18]) onto spindles or tool holders to generate desired chatter suppression forces. As representative works, Dohner et al. [19] applied active damping on a milling spindle equipped with two orthogonal pairs of electrostrictive stack. By this means, he developed a linear-quadratic-Gaussian control law to achieve a good balance between performance and robustness. Zhang and Sims [20] improved the workpiece flexibilities by mounting piezoelectric actuators and sensors to thin-walled workpieces, and the stability of high-speed milling machining processes was ensured. Chen and Knospe [2,21] designed -synthesis robust control approaches for speed-independent, speed-specified and speedinterval control, respectively. In 2014, Chen et al. [22] proposed an adaptive control scheme to compensate the regenerative effect especially for high-speed machining cases. Analogously, van. Dijk et al. [4] presented a fixed-structure robust stabilization control method, which transform a nonsmooth constrained optimization problem to an unconstrained non-smooth one. In 2014, Monnin et al. [23,24] developed optimal contro...

Prediction, detection, and suppression of regenerative chatter in milling

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