Determining age in motors and rotating machinery in general is a serious question. Using the vibration signals collected during motor aging is challenging due to nonlinear and non-stationary nature of these signals. This paper presents a study on applicability of Hurst analysis in motor vibration data collected in an artificial aging process, which at first seems to suggest inapplicability of Hurst Exponents in motor age determinations. Conclusions drawn from the straightforward application of Hurst exponent calculation are used to propose a novel method for Hurst analysis of such signals, named Higuchi-Hurst-Hilbert Vibration Decomposition (H³VD), using Higuchi’s algorithm for Hurst exponent calculation and Feldman’s Hilbert Vibration Decomposition overcoming the shortcomings of the original approach and delivering results that were expected based on previous research on frequency domain features of motor vibration in artificial aging processes. Features of this approach have been presented on both Fractional Gaussian noise model and the real vibration data. Non-accelerated bearing aging vibration data was used to demonstrate practical applicability of this new method.

— Different algorithms for Hurst exponent estimation, namely aggregated variance, absolute moment, Higuchi and Peng method, are applied to eight different vibration signals obtained in induction motor aging process. Signals were obtained with accelerometers during an artificial fluting, thermal and chemical aging process. Applicability of Hurst exponent analysis for motor age detection is discussed based on estimation results. Drop of the exponent value for degraded states with respect to the original state is detected, while no monotonic relationship between subsequent states is found. The anti-persistent nature of vibrations is confirmed

Question of condition monitoring and predictive maintenance is an important one in modern industry. In case of electrical motors, the question of their bearings’ health and remaining useful life of the whole device can be asked. In order to diagnose abnormal states and faults, a wide range of indicators have been used, including stator current, vibration and sound [7]. In this study, we will focus on the properties of vibration signals and ability to do the motor diagnostics based on vibration content. Such approach is widely used in practice [10] with various parameters extracted from the vibration signal. While some authors choose to base their methods of vibration diagnostics on the features of signal in time domain [12], the others use the features in frequency domain [17], which is an attractive area of research and being often considered invariant opposed to amplitude variations in time domain analysis, influenced by the motor type or the sensory equipment employed in the experiment. In case of random vibrations, the classical power spectral density (PSD) is serving just as a foundation for more complex methods of frequency based analysis [16]. Often, in case of motor vibrations, decomposition is applied, for instance the Hilbert Huang Transform or Wavelet Transform, with a possibility of applying frequency analysis to components obtained that way [2], or simply taking time domain characteristics of such components [1]. In this work, we have chosen to work with the whole signal, without any decomposition, avoiding analysis of components’ significance and noise level within each of them. While these works often focus on known bearing faults, showing methods of detecting and identifying them, the practical situation often resembles the one seen in case of artificial motor aging: motor bearings, shaft and windings suffering the unpredicted failures and faults [4, 5]. In that case, it is important to be able to determine what the level of aging the motor is achieved, so the remaining life can be estimated [12]. An important question that arises there is what is the difference between ordinary isolated, controlled bearing faults and those emerging in (artificial) motor aging processes. Hence, this study aims to fill the gap in knowledge about the nature of bearing faults occurring in artificial aging processes of induction motors, as well as to investigate on the frequency spectrum properties of vibration produced in motor aging applicable for determination of motor age. Conclusions are given to support the claim that the aging process is not possible to approximate with a single type of bearing fault, but that characteristics common for certain types of faults appear within the frequency signature of motor vibration in characteristic aging signals. Furthermore, simple statistical measures that are selected for demonstration of emerging patterns in motor aging can readily be used for detection of motor age, without the need for introduction of more complex machine learning and intelligence components. Simplicity of patterns also indicates an existence of a logical theoretical basis for the results obtained. The paper is structured as follows: after an introduction, frequency-based methods and experimental data from motors used in this study are presented in the second part. Third part presents the results Harun SiljAk Abdulhamit SubASi

This paper introduces the novel concept of inverse matching in case of mobile target following, as well as a new algorithm based on merging this concept with elements of fuzzy control. Previously developed hardware and software are combined to produce a functional mobile robot convoy system. Test results of this localization, fuzzy control and inverse matching fusion show the effectiveness as well as practical value of the approach proposed for autonomous robot

A series of computations based on the Fourier spectrum of vibration signals collected in artificial aging processes have been applied in order to tackle trends existing in the signals' sequence. In this study, features extracted from the (Fourier) spectrum of the vibration signal and expressing monotonic changes with respect to the motor age namely mean frequency, low order statistics of the power spectral density and cepstrum are used. Independence of the time domain data allows independent analysis. Results obtained in case of artificial aging are compared with results in case of controlled bearing faults with increasing severity. Clear distinctions are made and conclusions are drawn from the different behavioural patterns. Future research directions are indicated both in practical and theoretical sense.

Purpose – This paper aims to improve the mathematical justification of certain analog signal theory concepts and offer a rigorous framework for it.Design/methodology/approach – The framework relies on functional analysis, namely theory of distributions and the concept of weak limit. Its notation is adjusted to resemble the notation usually used in engineering signal theory. It can be used to prove in a rigorous manner already established results in signal theory, but also to establish new ones.Findings – Examples have shown the lack of rigour caused by using ordinary calculus in proving fundamental signal theoretic results. On that basis, concepts of limit, Fourier transform and derivative are revisited in the spirit of functional analysis. A new useful formula for weak limit computation is proved.Originality/value – Functional analysis is efficiently used in signal theory in a manner approachable by engineers. An original and efficient formula for weak limit computation is presented and proved.

This paper presents an alternative to existing techniques based on Nodal Analysis designed specifically to suit implementation in matrix-oriented programming languages, keeping the simplicity of original Nodal Analysis and bringing improvements to make virtually all circuit topologies solvable through it, dealing with potential singularities, hence the name Singular Nodal Analysis (SNA). Two variants of this novel algorithm are described. Their validity is proven and their applicability is shown through two practical examples.

This paper proposes a self-tuning adaptive controller in order to produce response of a second order block from the typically nonlinear motor. Periodic reset of controller's estimator block is employed as an improvement of the original design. Classical model of DC motor is well-controlled via this improved controller, while for the system containing a motor and thyristor-fired phase-controlled rectifier a new improvement is introduced, the arcsine compensation block. Controller is tested in different simulation conditions and it shows high ability to compensate any effects, produced either by the reference value change or the external error induced by load or thyristor rectifier.

This paper proposes a new algorithm for following a mobile robot target in an outdoor environment. This approach combines a fuzzy tracking control law and an inverse matching based algorithm for finding and following of the moving target. The inverse matching algorithm comprises local maps of a robot environment to identify the target and generate desire path toward it. The localization of the mobile robot is done by the triangulation method based on GPS measurements. In addition, previously developed software system for the mobile robot enables GPS guidance and obstacle avoidance which makes it suitable for creation of mobile convoys. Finally, the experimental verification is performed to confirm the effectiveness and practical value of the proposed approach.

In this paper both hardware and software systems for GPRS communication and GPS navigation are developed. The hardware structure of GPS navigation module was build using Cinterion XT65 platform and appropriate electronic components. The overall navigation system is client-server based that uses GPS and GPRS communications. The GPS communication is used between client (mobile robot) and satellites, while GPRS communication connects server (PC) and client. The algorithm for mobile robot position estimation exploits a triangulation technique. Multiple algorithms (including a fuzzy regulator) for avoiding obstacles are implemented in order to provide safe and precise movement towards the destination point given to robot. The effectiveness and quality of proposed hardware and software structures are verified by experiments.