In order to improve efficiency of high-performance drilling processes while preserving tool life, the current study focuses on the design and implementation of an optimal fuzzy-control system for drilling force. The main topic of this study is the design and implementation of a networked fuzzy controller. The control algorithm is connected to the process through a multipoint interface (MPI) bus, a proprietary programming and communication interface for peer-to-peer networking that resembles the PROFIBUS protocol. The output (i.e., feed-rate) signal is transmitted through the MPI; therefore, network-induced delay is unavoidable. The optimal tuning of the fuzzy controller using a maximum known delay is based on the integral time absolute error (ITAE) criterion. In this study, a step in the force reference signal is considered a disturbance, and the goal is to assess how well the system follows set-point changes using the ITAE criterion. The main advantage of the approach presented herein is the design of an optimal fuzzy controller using a known maximum allowable delay to deal with uncertainties and nonlinearities in the drilling process and delays in the network-based application. In order to suppress the cutting-force increase, the feed rate is decreased gradually as the drilling depth increases, and the cutting force is quite well regulated at the given setpoint. The good transient response is verified by improvements in the integral time absolute error (11.77), integral time square error (2.912) and integral of absolute error (12.81) performance indices. Moreover, the experimental results without oscillations and overshoot corroborate that increases and fluctuations in force drilling can be suppressed despite an increase in drilling depth. Thus, the drilling process can be stabilized and the risk of drill failure can be greatly reduced through a fuzzy-control system.

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