In this paper, a hybrid adaptive control algorithm that controls feedrate to regulate spindle current and detects tool wear is proposed. For this purpose, variation of steady state spindle current, time constant, and time delay were examined through experiments based on step end milling under various cutting conditions. The developed hybrid adaptive control algorithm is composed of adjustable proportional feedback control (adjustable P control), fine control, entry feedrate control, and tool wear detection algorithm. Adjustable P control carries out large scale control, fine control carries out detailed control, entry feedrate control reduces the peak current produced when a tool makes contact with a workpiece, and tool wear detection algorithm perceives tool wear and breakage qualitatively. The adjustable P control algorithm was verified through comparisons between calculated P gains and experimentally obtained P gains. The hybrid adaptive control algorithm was applied to various cutting conditions and it showed global stability as well as excellent applicability behavior.

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