The preferred growth direction of cathodic arc physical vapor deposition-produced TiN coatings changes from (1 1 1) to (2 2 0) with high voltage pulsed bias application in the presence of Ar gas. In this study, tribological properties of these coatings were investigated via reciprocating wear tests against an inert counterbody for observing the role of orientation on tribological properties. Friction coefficients and wear of (2 2 0) oriented coatings were observed to be significantly lower compared to (1 1 1) oriented coatings. Micro-Raman investigations of the wear debris formed during tribotest revealed clear differences between (1 1 1) and (2 2 0) oriented films. Wear debris obtained from (2 2 0) oriented coatings consisted of nc TiO2 phases (anatase and rutile) whereas (1 1 1) oriented coatings produced amorphous Ti oxides. This behavior is attributed to the orientation dependent oxidation kinetics of the coatings as verified with isothermal oxidation tests. A mechanism for improved tribological behavior is proposed based on the obtained results.
This paper presents the design and implementation of a fuzzy logic controller using Very High Speed Integrated Circuit Hardware Description Language (VHDL) on a field programmable gate array (FPGA). First, a Sugeno-type fuzzy logic controller with five triangular and trapezoidal membership functions for two inputs and with nine singleton membership functions for one output is examined. The proposed structure is tested with second- and third-order system model using FPGA-in-the-loop simulation via a MATLAB/Simulink environment. Then, for different kinds of fuzzy logic controllers, a new look-up table (LUT) and interpolation-based controller implementation is proposed to eliminate the computational complexity of the primarily designed structure. As a case study, a magnetic levitation system is controlled with an adaptive neuro-fuzzy inference system (ANFIS) trained fuzzy logic controller, then it is simulated and implemented using a LUT-based controller. Finally, we provide a comparison of results.
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