Diagnostics of the drive shaft bearing based on vibrations in the high-frequency range as a part of the vehicle's self-diagnostic system

Currently, one of the trends in the automotive industry is to make vehicles as autonomous as possible. In particular, this concerns the implementation of complex and innovative selfdiagnostic systems for cars. This paper proposes a new diagnostic algorithm that evaluates the performance of the drive shaft bearings of a road vehicle during use. The diagnostic parameter was selected based on vibration measurements and machine learning analysis results. The analyses included the use of more than a dozen time domain features of vibration signal in different frequency ranges. Upper limit values and down limit values of the diagnostic parameter were determined, based on which the vehicle user will receive information about impending wear and total bearing damage. Additionally, statistical verification of the developed model and validation of the results were performed.

Reliability Assessment of Aircraft Commutators

The article describes the method of predicting the reliability and durability of an aircraft commutator, which is a primary source of electric energy in helicopters. Tests were conducted for 10 starter-generators. From this research it follows that the technical condition of brushes and bearings has a significant impact on the reliability of starter-generators. The reliability of starter-generators was determined based on the method consisting of two stages that was adopted: the first stage involved determining the density function of changes in diagnostic parameter depending on the operating time, but the second stage included the assessment of the reliability of bearings of the starter-generator taking into account the real flight profile. The first stage of the adopted method consisted of defining the dynamic model of changing the length of the starter-generator’s brush, which became the probabilistic model. Subsequently, based on differential equations, Fokker–Planck partial differential equation was derived, which describes the process of increasing the brush wear in a probabilistic way. This method enables the prediction of the residual durability of the helicopter’s starter-generator due to the change in a diagnostic parameter which is the wear of brushes during starter-generator operation. The second stage of this method allows determining the durability of starter-generator’s bearings building upon the average helicopter’s flight profile. Owing to the difficulty in measuring the wear of bearings, the relation between the durability of bearings and the temperature of surroundings can be applied by replacing the flight altitude with temperature. The reliability of the helicopter’s starter-generator was determined based on the serial-type reliability structure.

Alteration in 11 Beta-Hydroxysteroid Dehydrogenase Type-2 (HSD11B2) Gene as A Potential Candidate Parameter for Early Detection of Intrauterine Growth Restriction (IUGR) Events

Intrauterine Growth Restriction (IUGR) incidence in Indonesia ranks in the top 10 of the highest in Asia. It is the main perinatal death cause. IUGR also impairs fetal neurodevelopment, which can affect the development of children until later ages. Lack of 11β-hydroxysteroid dehydrogenase type-2 (11β-HSD2) enzyme is influenced by changes in the coding gene, HSD11B2, one of IUGR's causes. The main diagnostic method of IUGR at this time is by using Doppler ultrasound. However, Doppler ultrasound has several limitations as many cases are not detected. Its clinical predictive value in various women is poor, as Doppler ultrasound is not recommended for use in the first trimester, detection of abnormalities in the second trimester seems to be too late for helpful interventions. The study aim is to present an overview concerning HSD11B2 gene alteration in an non-invasive prenatal testing (NIPT) as a possible diagnostic parameter for early detection in IUGR infants. This literature review is based on selected articles and studies taken from the Pubmed, Proquest, and EBSCO databases. A total of 4 studies reported the tendency for DNA methylation and decreased expression of the HSD11B2 gene in IUGR cases. Changes in the HSD11B2 gene have the potential to become a diagnostic parameter in the early detection of infants with IUGR. Further study and investigation of this possibility are needed.Keywords: intrauterine growth restriction, HSD11B2, early detection, diagnostic, non-invasive prenatal testing

Determining an additional diagnostic parameter for improving the accuracy of assessment of the condition of stator windings in an induction motor

This paper has proposed and substantiated the application of an additional diagnostic parameter for assessing the state of stator windings of induction motors during operation. The dependences of the values of phase shifts between phase currents and phase voltages have been obtained. These dependences showed that when an inter-turn short circuit occurs in the stator windings, the phase shifts are the same for all phases of the motor. That has made it possible to obtain the dependence of the change in phase shift on the change in the engine shaft rotation frequency. This study's result has established the dependence of the rates of change of the phase angle on the engine shaft rotation frequency for both one and two damaged phases with varying degrees of damage. When analyzing these dependences, it was found that with an increase in the number of damaged phases of the electric motor, the linear section of the dependences decreases. In addition, with an increase in the degree of phase damage, the angle of inclination of the linear sections of the characteristics decreases. That has made it possible to determine an additional parameter for diagnosing the place and degree of an inter-turn short circuit of the windings in an induction motor with a squirrel-cage rotor. The values of the additional parameter, termed by this paper's authors as a "phase criterion" can be used to assess the condition and degree of damage to the stator winding of induction motors. The values of the phase criteria for various types of damage were: when phase A is damaged by 90 %, ξ=0.634, (deg)2/(rpm)2; when phase A is damaged by 80 %, ξ=0.393, (deg)2/(rpm)2; when phase A is damaged by 80 % and phase B is damaged by 90 %, ξ=0.25, (deg)2/(rpm)2; when phase A is damaged by 80 % and phase B is damaged by 90 %, ξ=0.173, (deg)2/(rpm)2. The results of this research could be used to select an effective method for diagnosing an inter-turn short circuit in the stator winding when building a diagnostic system for induction motors as part of drives of transport equipment

Cyber-Physical Hybrid Processing System Digital Twin

The article proposes a method for obtaining a digital twin of the process of 3D printing by electric arc surfacing using an ensemble of machine learning methods. On the basis of the structural-parametric approach, a set of diagnostic parameters for the signals of current strength, voltage and acoustic emission was determined. Using exploratory analysis, the significance of each diagnostic parameter was assessed. A complex of statistical models has been developed to assess the stability of 3D printing processes using decision trees. Their optimal parameters and efficiency have been determined.

Diagnostic Efficacy of Pelvic Ultrasound in Central Precocious Puberty in Girls: a Retrospective Cohort Study

Background: Differentiating central precocious puberty (CPP) patients from normal cases and CPP-like patients “isolated premature thelarche (IPA) and isolated premature thelarche (IPT)” is important for beginning of treatment. Although the GnRH stimulation test is considered the gold standard for diagnosis of CPP, Because of its wide limitations, our study targets to evaluate pelvic sonography parameters as a contributory tool for CPP diagnosis.Methods: We consecutively enrolled 183 cases (93 CPP, 16 IPT, 12 IPA and 62 of age-matched normal controls) in our study over four years. All cases are classified by clinical and laboratory findings and are followed up for at least 2 years. Pelvic sonography parameters included uterine fundus, body and cervix anteroposterior diameter, fundus/cervix ratio, uterine length and transverse diameter, uterine volume, endometrial thickness, ovarian volumes and diameter of the largest follicle are evaluated in all classified groups. One-way ANOVA, post hoc and receiver operating characteristic (ROC) analysis was used to compare the study groups.Results: Our study found that all sonography parameters differ significantly between CPP and normal control cases, also a significant difference is found between CPP compared to IPT or IPA cases in all parameters except in cervix anteroposterior diameter, ovarian volumes and diameter of the largest follicle. In order of best parameters for differentiating CPP compared to study groups, uterine volume (a cut-off of 1.40 ml had a sensitivity of 75.27% and a specificity of 75.56%), transverse diameter (a cut-off of 13.5 mm had a sensitivity of 72.04% and a specificity of 71.11%) and F/C ratio (a cut-off of 0.98 had a sensitivity of 78.49% and a specificity of 70%) was selected. Our study also classified sonography parameters as in equal diagnostic value to uterine volume (as the best diagnostic parameter with area under the curve of 0.826) and not equal diagnostic value to uterine volume.Conclusions: Pelvic Sonography parameters may improve the diagnosis of CPP patients and can have a contributory role in distinguishing treatment needed patients from other patients. The best diagnostic parameter and its cut-off value could change according to different ethnicities and studies.

Assessment of the usability of the EUSAMA and the phase angle method in examining the condition of shock absorbers installed in a vehicle

The article is a continuation of the author's earlier considerations concerning the methods of testing shock absorbers installed in the vehicle. The work concerns the analysis of the usability of two methods: the EUSAMA method and the phase angle method. The first one examines the minimum ratio of the force in contact between the wheel and the vibration-inducing plate (on which the wheel of the tested suspension rests) and the static value of this force. The second one uses the minimum of the phase shift angle between the excitation (vertical movement of the said plate) and the force in contact between the tire and this plate for diagnosis. Two linear quarter-car models and their description in the frequency domain were used to evaluate two analyzed methods. For both evaluated methods, the monotonicity of the dependence of the diagnostic parameter on the diagnosed one (damping in suspension) is visible; in the case of the phase angle method it is close to linear. The correction of the results related to the inertia of the vibration-inducing plate was considered. The calculations were made for two typical data sets: for the front and rear suspension of a middle-class passenger car. They allow a general qualitative and (to a limited extent) quantitative assessment of the usefulness of the analyzed methods. For the EUSAMA method, the test result has a noticeable effect of the inertia of the vibration-inducing plate. This confirms the legitimacy of correcting the force measured in the diagnostic stand. Values without correction are more optimistic. For cars with a low weight or a lightly loaded road axle (especially the rear axle) of heavier vehicles, low values of the diagnostic parameter are obtained, suggesting a bad condition of the shock absorbers, which is not confirmed by their examination in the state removed from the vehicle. In the second assessed method, there are clear differences between the values of the phase angle obtained based on testing the force in the wheel-plate contact and those obtained for the analysis of the force measured in the test stand. Therefore, the correction for the value of the station plate inertia force is significant. Values without correction are more pessimistic, although it is not justified in the condition of the tested vehicle. The works cited in the article describe several practical drawbacks of the phase angle assessment method. The author points to the importance of further research, much more laborious, with the use of nonlinear models and the necessary experimental verification of the obtained simulation results.

Curve Fitting for Mechanical and Tribological Problems

This chapter devoted to matching the data with mathematical expressions. Here the functions using fitting by polynomial and non-polynomial expressions is represented by examples from the mechanics and tribology (M&T) fields. The Basic Fitting tool and examples of its use are described. Single and multivariate fitting through optimization are discussed. Application examples are demonstrate the curve fitting for the following data: fuel efficiency-velocity, yield strength-grain diameter, friction coefficient-time, and machine diagnostic parameter.