Commensurate and Non-Commensurate Fractional-Order Discrete Models of an Electric Individual-Wheel Drive on an Autonomous Platform.

This paper presents integer and linear time-invariant fractional order (FO) models of a closed-loop electric individual-wheel drive implemented on an autonomous platform. Two discrete-time FO models are tested: non-commensurate and commensurate. A classical model described by the second-order linear difference equation is used as the reference. According to the sum of the squared error criterion (SSE), we compare a two-parameter integer order model with four-parameter non-commensurate and three-parameter commensurate FO descriptions. The computer simulation results are compared with the measured velocity of a real autonomous platform powered by a closed-loop electric individual-wheel drive.

Optimal Digital Implementation of Fractional-Order Models in a Microcontroller.

The growing number of operations in implementations of the non-local fractional differentiation operator is cumbersome for real applications with strict performance and memory storage requirements. This demands use of one of the available approximation methods. In this paper, the analysis of the classic integer- (IO) and fractional-order (FO) models of the brushless DC (BLDC) micromotor mounted on a steel rotating arms, and next, the discretization and efficient implementation of the models in a microcontroller (MCU) is performed. Two different methods for the FO model are examined, including the approximation of the fractional-order operator s ν ( ν ∈ R ) using the Oustaloup Recursive filter and the numerical evaluation of the fractional differintegral operator based on the Grünwald-Letnikov definition and Short Memory Principle. The models are verified against the results of several experiments conducted on an ARM Cortex-M7-based STM32F746ZG unit. Additionally, some software optimization techniques for the Cortex-M microcontroller family are discussed. The described steps are universal and can also be easily adapted to any other microcontroller. The values for integral absolute error (IAE) and integral square error (ISE) performance indices, calculated on the basis of simulations performed in MATLAB, are used to evaluate accuracy.

Effect of zirconia surface treatment on its wettability by liquid ceramics.

STATEMENT OF PROBLEM: The wettability of the framework by liquid ceramics is important in ensuring a suitable bond between veneering ceramics and zirconia. PURPOSE: The purpose of this in vitro study was to examine the dependence of the wetting angle on temperature to determine the transition temperature from nonwettable to wettable states and to calculate the values of the relative wetting forces of the milled surfaces. MATERIAL AND METHODS: Fifty zirconia cylinders were divided into 5 groups (n=10) and subjected to the following treatments: milling, grinding, polishing, and airborne-particle abrasion with Al2O3 or SiC. After treatment, the specimens were rinsed, dried, and examined with respect to their wettability by liquid ceramics by using the automated Thermo-Wet test bench. The results were statistically analyzed by an ANOVA (α=.05). RESULTS: The most rapid wettability was obtained through airborne-particle abrasion with Al2O3 at 930 °C. Additionally, the highest relative bond strength (with respect to the machined surface) was obtained with Al2O3 abrasion. CONCLUSIONS: Because of variations in the wettability of the zirconia surface after different treatment methods, the firing temperature of the ceramic should also vary depending on the type of surface treatment applied. Thus, it is determined individually according to the chosen method.