Stanisław Radkowski

A Model-Based Method for Remaining Useful Life Prediction of Machinery

Remaining useful life (RUL) prediction allows for predictive maintenance of machinery, thus reducing costly unscheduled maintenance. Therefore, RUL prediction of machinery appears to be a hot issue attracting more and more attention as well as being of great challenge. This paper proposes a model-based method for predicting RUL of machinery. The method includes two modules, i.e., indicator construction and RUL prediction. In the first module, a new health indicator named weighted minimum quantization error is constructed, which fuses mutual information from multiple features and properly correlates to the degradation processes of machinery. In the second module, model parameters are initialized using the maximum-likelihood estimation algorithm and RUL is predicted using a particle filtering-based algorithm. The proposed method is demonstrated using vibration signals from accelerated degradation tests of rolling element bearings. The prediction result identifies the effectiveness of the proposed method in predicting RUL of machinery.

Impact of Various Factors on Relationships Between Stress and Eigen Magnetic Field in a Steel Specimen

Many materials which could cause a real threat of a catastrophe due to fatigue, exceeding stress limits or plastic strain have magnetic properties that could affect the local magnetic field. Though active magnetic methods of condition monitoring are quite well-known and widely applied however, passive techniques which are based only on the existence of natural magnetic field of the Earth, still require research and improvement. It is obvious that every physical object within the magnetosphere interacts with Earths magnetic field and is subjected to special laws of physics. Such objects can attract or deflect magnetic field lines around their matter. Own magnetic field of an object: H= -grad(w), where w is the magnetic potential, is a function of the gradient of magnetization: w = w(div M). Therefore, the measure of magnetic field of an object depends on an objects magnetization and distribution of its volume in the medium (space). Considering magnetoelastic effects (Villari Effect, magnetostriction), the additional stress causes transformation of the material to magnetic state which reflects the magnetization of an object. The magnetization depends on many factors. Magneto-mechanic phenomena have been known for a long time but as the technology developed, there have emerged new possibilities of acquisition, processing and analysis of these phenomena and of their use in technical diagnosis. Following a simple model analysis, a laboratory experiment was proposed and performed. By controlling plastic and elastic range of the specimens strain, we have investigated the existence of a relation between stress and degree of magnetization, which is strictly connected with deformation and effort. Magnetic anomalies which are generated due to magneto-mechanic effect were collected by the three axial fluxgate magnetometer, which allowed presentation of own magnetic field component, which was least sensitive to the disturbance present in a real world. Experiment included in the paper confirms the existence of a relationship between stress and magnetization degree which additionally depends on the kind of material. In addition the possibility of remote identification of magnetoelastic effects has been contemplated and examined. Finally the paper analyzes the impact of the shape of specimen on the interaction between Earth and eigen magnetic fields during a tension test. Further directions and comments on development of techniques which allow exact stress assessment of technical objects made of ferromagnetic materials have been included.

Chosen properties of a dynamic model of crankshaft assembly with three degrees of freedom

In the work presented herein the dynamic model of the crankshaft assembly with three degrees of freedom has been presented. On the basis of the physical model analysis (with the static mass reduction) the simulation model of the crankshaft assembly using Matlab&Simulink programme, has been designed. On the basis of the derived equations of motion, the authors have analysed the influence of chosen parameters, among others: the moment of flywheel inertia, loading torque, different crankshaft rigidity values, on the operation of the simulation model, whose input parameters reflect the real-life crankshaft assembly employed as the working mechanism in the Stirling engine. As a result of the performed simulations, displacement curves, piston velocity and acceleration values, as well as adequate crankshaft angular displacement, the angular velocity and angular acceleration have been additionally presented. The presented results provide information about the dynamic performance of the simulated real-life object.

The Active Magnetorheological Support as an Element of Damping of Vibrations Transferred from the Ground to Large-Scale Structure Supports

The active support of a large-scale structure, made up of two elements was designed and manufactured. The first of them - piezoelectric actuator, enables the simulations of vibrations transferred from the ground to the structure. In order to minimize vibrations transmitted through the ground to the construction, the second element of the active support - a system based on magnetorheological dampers was used. The active support enables the simulations of vibrations from the ground using a piezoelectric stack controlled in a reverse feedback loop. Control signals of the feedback loop are: the volume of deformation and vibrations in the selected structures node.

Distributed System for Monitoring of the Large Scale Infrastructure Structures Based on Analysis of Changes of its Static and Dynamic Properties

The complexity and diversity of civil engineering structures impose requirements on the monitoring systems, which are difficult to be satisfied. In the paper the concept of the distributed diagnostic system capable of monitoring the technical state of critical elements of large infrastructure objects like steel trusses, supermarket buildings, exposition halls, bridges etc. is discussed. Adaptation of such systems is essential for online assessment of technical state of the infrastructure objects and could limit the possibility of catastrophic disasters with loss of people. As a source of information data from strain gauges, passive magnetic field sensors and acceleration sensors applied to the construction are considered. For the process of selection of sensors and diagnostic methods the mathematical model of the construction and the physical test stand were used.

Use of Condition Monitoring in the Proactive Maintenance Strategy

The objectives of the presented paper are to better understand the mechanism of failure development in the dynamic mechanical systems. It is important to consider carefully the present changes in technical conditions of elements of the system when planning the requirements to a proactive risk management’s strategy. While a dynamical system traditionally is modeled by structural decomposition, in the paper the dynamic behavior of system is modeled by decomposition of the behavior flow into events and errors accompanying occurrence of failure. From this point of view the nonlinear model of failure occurrence is analyzed to realizing long term benefits of a proactive maintenance strategy. The models describe the effect on the evolution at the process variables for each hypothesized fault failure. In the paper it is also analyzed the impact of nonlinearity of the sub-section on the behavior of the whole system.

ENERGY SCAVENGING IN A VEHICLE'S EXHAUST SYSTEM

Present- day development of power transmission systems, especially the ones based on combustion engines, is trying to cope with the issue of improving the energy efficiency of energy processing systems. One of the directions is to use the techniques of thermal energy recovery from an engine’s exhaust system. Vast part of the energy produced while burning the air- fuel mixture is lost in the cooling and exhaust systems. Research in this area was conducted by numerous teams, both abroad and in Poland, while focusing on use of Peltirea cells. The results of their research demonstrated small efficiency of these cells. In this paper, the authors have focused on modifications of the exhaust system in order to improve heat exchange between the exhaust system’s elements and TEG. The research was conducted while using the ECOTEC 1.8 litre engine from Opel, the X18XE model. The engine was installed in a testbed, in the mechatronic lab at the Faculty of Automotive and Construction Machinery Engineering (SIMR) of Warsaw University of Technology. Spartan HE923 radiators were installed on the cold end of the module. The paper presents the results of the research related to interworking of TEG’s with the exhaust system’s heat-generating elements of various shapes. The paper reviews the energy efficiency of TEG depending on diverse parameters of gas flow. A parallel system has been assumed (controlled stream and pressure of the flowing exhaust gases without any interference as regards the speed of the of combustion engine). The factor-related experiment accounts for the influence that the pressure and temperature difference, depending on the volume and discharge of exhaust fumes, have on the efficiency of TEG for the same temperature. The results of the experiment are presented in the last section of the article.

Analysis of Vibration of Rotors in Unmanned Aircraft

In the paper, solution of the problem of vibrations which appears during the maneuvers of quadrocopters is presented. Those special kinds of vibration aren’t related to mounting or manufacturing faults. In this kinds of flying machines the main sources of vibration comes from motors and/or propellers unbalance. The paper shows analytical description of the source of this problem. Mathematical description of rotor which was subjected of additional rotation had been modeled in MATLAB/Simulink environment. It was shown, that correct set of parameters lead to total elimination of this kind of vibration.

Analysis of Possibility of Use Peltier Modules in Task of Energy Scavenging

Actually in motor industry, specialty in car market is tender to maximum utilization of energy included in fuel air mixture, which most of part of burning process is lost. In todays times Peltier module are generally available, which is mainly used in coolers for keeping of low temperature. They make use of Peltier phenomenon, relying on power module from electric net for manufactured low temperature on cold side that module. Module producers usually available voltages characteristics thats working modules.In realize research use that same modules but for recuperate electrical energy from temperature. Research target was in temperature equivalent on cold side and warm side check value of manufactured voltage from these modules. Utilized of Seebeck phenomenon depends on heat of warm side with simultaneously cool module cold side which manufacture electricity.In effect realize research findings series of results for which equivalent characteristics describing those module capacities. The first influence from realize research is fact that characteristics isnt identical with characteristics for that same modules manufactured low temperature.

Diagnostic Model of Hysteresis for Condition Monitoring of Large Construction Structures

The conception of diagnostics, based on passive magnetic field measurements is being presented. It was shown that the transformation of the signal to the appropriate form of hysteresis, creates new potential for identifying changes in signal parameters that correspond to specific physical phenomena. Model supported analysis of changes in the magnetic field, made it possible to obtain diagnostic parameters characterizing magnetomechanical hysteresis, which can be used in determining the state of the material strain on the object structure subjected to variable loads. Suitable model of hysteresis was elaborated and conditions in which it could be applied were stated. Obtained by authors diagnostic parameter confirm the validity of the hysteresis model used for this case. The chapter concludes that state of polarization of the magnetic structure (the distribution of magnetization) is carrier of diagnostic information about the level of effort and the progressive degradation of the material structure. It is possible to obtain the diagnostic information through a remote, non-contact measurement of magnetic field near the test structure.