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Nowadays brushless DC motors (BLDCMs) are becoming indispensable components as the electrification revolution in the mobility industry is happening. Electric kick scooters, so-called e-scooters, are among these micro-mobility vehicles which are powered by these motors. Due to the uncertain and nonlinear features, the controller performance developed for these motors degrades. For these reasons, a chattering-reduced cascaded Sliding Mode Control (SMC) scheme to effectively track reference motor speed in the outer loop by eliminating torque ripples in the inner loop current control was designed. Field-oriented Control (FOC) methodology was used to implement the SMC in the BLDCM. An exponential reaching law algorithm was proposed for sliding surfaces of the inner and outer loop controllers. The suitability and performance of electric scooter-hub motors were analyzed in terms of traction control. A cascaded speed and torque controller produced significantly favorable results representing minimized torque and current ripples, and operation over a wide speed range.

Nowadays brushless DC motors (BLDCMs) are becoming indispensable components as the electrification revolution in the mobility industry is happening. Electric kick scooters, so-called e-scooters, are among these micro-mobility vehicles which are powered by these motors. Due to the uncertain and nonlinear features, the controller performance developed for these motors degrades. For these reasons, a chattering-reduced cascaded Sliding Mode Control (SMC) scheme to effectively track reference motor speed in the outer loop by eliminating torque ripples in the inner loop current control was designed. Field-oriented Control (FOC) methodology was used to implement the SMC in the BLDCM. An exponential reaching law algorithm was proposed for sliding surfaces of the inner and outer loop controllers. The suitability and performance of electric scooter-hub motors were analyzed in terms of traction control. A cascaded speed and torque controller produced significantly favorable results representing minimized torque and current ripples, and operation over a wide speed range.

Sound radiation from thin metal plates has consistently been recognized as a severe noise problem. One of the most popular approaches to suppressing this noise is applying viscoelastic layers, also called free layer damping (FLD), on the plate surface, which can damp the structural motion and minimize the radiated sound. The thickness of the FLD is an important parameter. It needs to be optimized for the target acoustic limits through numerical simulations, as the total mass and the costs may rise unnecessarily. This paper investigates the sound radiation from thin metals of particular sizes with different thickness values of FLD. A unique test setup was established to measure vibration and sound for three different sized plates, with each one having three different FLD thicknesses, namely, 0.5 mm, 0.75 mm, and 1 mm. In parallel, vibro-acoustic analyses were performed for the same configurations using the finite element method. The damping of the FLD was defined using the Rayleigh damping model, of which coefficients were obtained through a prediction formula developed earlier by the authors. After validating the model with the test, the effect of FLD on the extended acoustic parameters (radiated sound power, directivity) was also analyzed.

Train safety and operational efficiency can be improved by investigating the dynamics of the train under varying conditions. Longitudinal train dynamics (LTD) simulations performed for such purposes, usually by utilising a nonlinear time-domain model. This paper covers two modes of LTD results corresponding to the time domain and frequency domain analysis. Time-domain solutions are essential to evaluate the full response used for parameter optimisation and controller design studies while frequency domain solutions can provide significant but straightforward clues regarding system dynamics. An advanced draft gear model, which works under a four-stage process is constructed considering all structural components, geometric relationships, friction modelling and dynamic characteristics such as hysteresis, stiffening, state transition, locked unloading, softening. Then, this model is parametrically reduced and implemented into an LTD simulation. The simulation in the time domain is conducted assuming a locomotive connected with a nine wagon via “ode3” fixed-step solver. The transfer function among the first wagon acceleration (output) and the locomotive force (input) estimated through system identification methodology. Then, the identification results interpreted by investigating step-response characteristic and best response giving parameter set is selected. Next, the modal and spectral analysis performed to reveal the behaviour of the in-train forces and the effects of vibration. This paper discusses a reliable methodology for the longitudinal dynamic analysis of the multi-bodied train in time and frequency domain and clarifies in-train vibration behaviour under the existence of sophisticated draft gear.

The use of big data to statistically evaluate system performance with the help of Machine Learning (ML) tools is a very popular method. Classic experimental methods of system performance can be impractical when needing to test a variety of input parameters within a range of specific limits and can take enormous time and effort. Mathematical models which numerically mimic the physical system dynamics can be deployed for the same aim. In this study, a system modeling based data analysis approach has been implemented to gather the data to understand the input-output relationship of an e-scooter and rider system in terms of its stability dynamics while driving over a curb of a specific height. Based on the test conditions specified in the German e-KFV standard, a virtual driving test has been created which consists of a kinematic e-scooter model with its rider and a test track. In the range of input parameter space, over 20,000 numbers of different cases have been solved and the results are recorded. The interaction between the rider and the vehicle is achieved through elastic connections which enable not only the recording of loading data on the arms and legs, but also allows the simulation to reflect the real-time effects of the rider scooter interaction. Through statistical analysis and using ML techniques, the influence of each parameter (tire size, speed, rider mass, etc.) on the objective outputs (loading on arms, ability to ascend the curb, etc.) regarding the stability and safety while driving over the curb have been reported and shared for further analysis by the e-scooter community.

The aim of this study is to develop solutions for the propagation of spinning sound waves in air-filled circular ducts containing water droplets (regarded as an aerosol). There exist several theoretical approaches in literature for treatment of basic (mostly 1-D) aerosol problems with certain limitations, but these approaches are mostly suitable for plane waves. A numerical methodology based on the linearized Euler equations in frequency domain has been developed to account for spatial effects both in azimuthal and radial directions. The interactions between the fluid and particle phases are considered through momentum. The paper also presents an analytical solution with which the numerical solutions are compared. Example solutions for plane and spinning modes are presented with emphasis on the effects of aerosol parameters on propagation characteristics as well as geometric cut-off frequencies.

Today repeated GPS measurements are still in use, because we cannot always employ GPS permanent stations due to a variety of limitations. One area of study that uses velocities/deformation rates from repeated GPS measurements is the monitoring of crustal motion. This paper discusses the quality of the velocities derived using repeated GPS measurements for the aim of monitoring crustal motion. From a global network of International GNSS Service (IGS) stations, we processed GPS measurements repeated monthly and annually spanning nearly 15 years and estimated GPS velocities for GPS baseline components latitude, longitude and ellipsoidal height. We used web-based GIPSY for the processing. Assuming true deformation rates can only be determined from the solutions of 24 h observation sessions, we evaluated the accuracy of the deformation rates from 8 and 12 h sessions. We used statistical hypothesis testing to assess the velocities derived from short observation sessions. In addition, as an alternative control method we checked the accuracy of GPS solutions from short observation sessions against those of 24 h sessions referring to statistical criteria that measure the accuracy of regression models. Results indicate that the velocities of the vertical component are completely affected when repeated GPS measurements are used. The results also reveal that only about 30% of the 8 h solutions and about 40% of 12 h solutions for the horizontal coordinates are acceptable for velocity estimation. The situation is much worse for the vertical component in which none of the solutions from campaign measurements are acceptable for obtaining reliable deformation rates.

In order to make effective works with the mobile robot and maximize its working performance, it is necessary to estimate and track the current pose of the mobile robot. In this paper, under the assumption that the initial pose, kinematics and environmental model of a mobile robot are known, the localization and tracking of the mobile robot's position and orientation have been carried out. The odometry model with the problem of accumulation of unlimited errors is used for tracking the pose, and sensor fusion algorithms are applied to solve this problem. By using the odometry and laser range finder model, the Extended Kalman Filter (EKF), Unscented Kalman Filter (UKF), Unscented Information Filter (UIF), Extended Information Filter (EIF) algorithms were tested on a graphical user interface (GUI) based on occupancy grid maps as an environment model, respectively. In this context, the pose tracking and estimation performances of the non-linear model based estimators are compared to each other. Since occupancy grid maps are utilized, only the laser range finder measurement uncertainty should be considered unlike feature based maps. In this way, the computational complexity can be reduced. When the simulation results are evaluated, it is determined that the Extended Information Filter algorithm has expressed more stable performance in terms of the mobile robot pose estimation.

Application of damping coatings on metal sheets is a commonly used method to suppress the undesirable vibration and noise levels in various industries. As numerical simulations have a vital role while designing a high-quality product with fewer costs, an accurate and practical way of modelling such type of structures is necessary. It was aimed to develop a methodology that helps to define damping parameters of such viscoelastic coating layers through Rayleigh damping coefficients. Machine learning tools were considered to find a prediction formula which yields Rayleigh coefficients based on thicknesses. For this purpose, several tests were conducted with different coating thicknesses on steel plates. In parallel, a great number of simulations were performed not only to make comparisons with the reference values from tests but also to feed the learning algorithms with the data sets. The results were compared including the ones from the Oberst equation. The results from the machine learning showed significantly better matching performance with the tests, as there seems to be a limitation problem for Oberst accuracy.

In this paper sound propagation through an air-filled circular duct containing water droplets has been studied by solving numerically one-dimensional linearized Euler equations in frequency domain. Interactions between the liquid and gas phases were accounted for by proper source terms. Waves were introduced into the domain via Perfectly Matched Layers (PML) equations applied in finite regions adjacent to the truncated ends of the duct. Absorption and dispersion results due to energy transfer from air to the water droplets were obtained as a function of average droplet diameter and droplet concentration as well as finite mass loading. Results agree well with those available in the literature.