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12 pages, 7207 KiB

Open AccessArticle

Design and Stability Analysis of a Wall-Climbing Robot Using Propulsive Force of Propeller

by Peng Liang, Xueshan Gao, Qingfang Zhang, Rui Gao, Mingkang Li, Yuxin Xu and Wei Zhu

Symmetry 2021, 13(1), 37; https://doi.org/10.3390/sym13010037 - 29 Dec 2020

Cited by 26 | Viewed by 7519

Abstract

This article introduces a wall-climbing robot that uses the reverse thrust of the propeller as the adsorption force. The robot is symmetrically distributed in structure and the adsorption force is symmetrically distributed before and after so that it can adapt to the surface [...] Read more.

This article introduces a wall-climbing robot that uses the reverse thrust of the propeller as the adsorption force. The robot is symmetrically distributed in structure and the adsorption force is symmetrically distributed before and after so that it can adapt to the surface of a variety of different media materials and achieve stable adsorption and movement of a variety of wall surfaces. The robot mainly uses the reverse thrust of the aircraft propeller as the adsorption force to achieve wall adsorption. The robot relies on four wheels to move forward. The forward power mainly comes from the combined action of the propeller reverse thrust component and the front wheel driving force. During the movement of the robot, the steering is realized by the front wheel differential control. In this paper, we design the structure of a dual-propeller dynamic adsorption wall mobile robot, plan the movement process of the robot from the ground to the wall, analyze the stable adsorption conditions of the robot wall, and carry out the robot’s motion performance and adaptability test under different ground/wall environments to verify that the robot is stable and feasible. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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13 pages, 6499 KiB

Open AccessArticle

Axle Temperature Monitoring and Neural Network Prediction Analysis for High-Speed Train under Operation

by Wei Hao and Feng Liu

Symmetry 2020, 12(10), 1662; https://doi.org/10.3390/sym12101662 - 12 Oct 2020

Cited by 8 | Viewed by 3296

Abstract

Predicting the axle temperature states of the high-speed train under operation in advance and evaluating working states of axle bearings is important for improving the safety of train operation and reducing accident risks. The method of monitoring the axle temperature of a train [...] Read more.

Predicting the axle temperature states of the high-speed train under operation in advance and evaluating working states of axle bearings is important for improving the safety of train operation and reducing accident risks. The method of monitoring the axle temperature of a train under operation, combined with the neural network prediction method, was applied. A total of 36 sensors were arranged at key positions such as the axle bearings of the train gearbox and the driving end of the traction motor. The positions of the sensors were symmetrical. Axle temperature measurements over 11 days with more than 38,000 km were obtained. The law of the change of the axle temperature in each section was obtained in different environments. The resultant data from the previous 10 days were used to train the neural network model, and a total of 800 samples were randomly selected from eight typical locations for the prediction of axle temperature over the following 3 min. In addition, the results predicted by the neural network method and the GM (1,1) method were compared. The results show that the predicted temperature of the trained neural network model is in good agreement with the experimental temperature, with higher precision than that of the GM (1,1) method, indicating that the proposed method is sufficiently accurate and can be a reliable tool for predicting axle temperature. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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17 pages, 5788 KiB

Open AccessArticle

On Aluminum Honeycomb Impact Attenuator Designs for Formula Student Competitions

by Phu Ma Quoc, David Krzikalla, Jakub Mesicek, Jana Petru, Jakub Smiraus, Ales Sliva and Zdenek Poruba

Symmetry 2020, 12(10), 1647; https://doi.org/10.3390/sym12101647 - 8 Oct 2020

Cited by 11 | Viewed by 6954

Abstract

The use of impact attenuators (IA) is important for vehicles as they absorb the kinetic energy exerted from the car crashes to protect the drivers from any possible injuries. Under the framework of the Formula Student (FS) competition, we investigate various designs of [...] Read more.

The use of impact attenuators (IA) is important for vehicles as they absorb the kinetic energy exerted from the car crashes to protect the drivers from any possible injuries. Under the framework of the Formula Student (FS) competition, we investigate various designs of IA made of aluminum honeycomb material. Specifically, the crushing behavior of the honeycomb structure is investigated from the theoretical point of view and later verified with numerical simulations. To achieve the desired crushing behavior of the aluminum honeycomb structure, apart from the so-called pre-crushing method, another way to pre-process the aluminum honeycomb is proposed. Modification on the aluminum honeycomb is done in a symmetric manner to ensure the same uniform crushing behavior on the two sides of the mirror plane of the car. Different variations presented in this paper shed a light on future aluminum honeycomb IA designs in the context of FS competitions. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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18 pages, 4213 KiB

Open AccessArticle

Influence of Superheated Vapour in Organic Rankine Cycles with Working Fluid R123 Utilizing Low-Temperature Geothermal Resources

by Totok Prasetyo, Mochamad Denny Surindra, Wahyu Caesarendra, Taufik, Adam Glowacz, Muhammad Irfan and Witold Glowacz

Symmetry 2020, 12(9), 1463; https://doi.org/10.3390/sym12091463 - 7 Sep 2020

Cited by 6 | Viewed by 2674

Abstract

An organic Rankine cycle (ORC) system with R123 working fluid has been utilised for generating electricity from low-temperature geothermal resources. The degree of superheated vapour warrants attention to be studied further. This is because the degree of superheated vapour is the last point [...] Read more.

An organic Rankine cycle (ORC) system with R123 working fluid has been utilised for generating electricity from low-temperature geothermal resources. The degree of superheated vapour warrants attention to be studied further. This is because the degree of superheated vapour is the last point to absorb heat energy from geothermal heat sources and influence the amount of expansion power produced by the expander. Therefore, achieving high ORC system efficiency requires a parameter of superheated vapour degree. This paper presents an experimental study on a binary cycle, applying R123 as the working fluid, to investigate the effect of variation in superheated vapour degree on the ORC efficiency. Geothermal heat sources were simulated with conduction oil as an external heat source to provide input heat to the ORC system. The temperature high inlet (TH in) evaporator was designed to remain at 120 °C during the experiment, while mass flow rate was adjusted to make superheated vapour variations, namely set at 278, 280, 282, 284, and 286 K. Furthermore, the effect was observed on heat transfer inlet, pinch, heat transfer coefficient, expander work output, isentropic efficiency, expander shaft power, power generation, thermal efficiency, and ORC efficiency. The experimental results showed that the mass flow rate nearly remained unchanged at different degrees of superheated vapour. The ranges of heat transfer inlet, pinch temperature, and heat transfer coefficient were 25.34–27.89 kJ/kg, 9.35–4.08 °C, 200.62–232.54 W/m²·K, respectively. In conclusion, ORC system efficiency can be triggered by various parameters, including the temperature on the exit side of the evaporator. The superheated vapour of R123 working fluid to higher temperatures has caused a decrease in ORC system efficiency due to the decrease in heat transfer inlets, although theoretically, the work total increased. Further investigation has found that the magnitude of the mass flow rate affects the behaviour of the components of the ORC system. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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13 pages, 5153 KiB

Open AccessFeature PaperArticle

Programming of Industrial Robots Using the Recognition of Geometric Signs in Flexible Welding Process

by Olaf Ciszak, Jakub Juszkiewicz and Marcin Suszyński

Symmetry 2020, 12(9), 1429; https://doi.org/10.3390/sym12091429 - 28 Aug 2020

Cited by 15 | Viewed by 3116

Abstract

The purpose of the article was to build a low-cost system for identifying shapes in order to program industrial robots (on the base of the six-axis “ABB IRB 140” robot) for a welding process in 2D. The whole system consisted of several elements [...] Read more.

The purpose of the article was to build a low-cost system for identifying shapes in order to program industrial robots (on the base of the six-axis “ABB IRB 140” robot) for a welding process in 2D. The whole system consisted of several elements developed in individual stages. The first step was to identify the existing robot control systems, which analysed images from an attached low-cost digital camera. Then, a computer program, which handles communication with the digital camera capturing and processing, was written. In addition, the program’s task was to detect geometric shapes (contours) drawn by humans and to approximate them. This study also presents research on a binarization and contour recognition method for this application. Based on this, the robot is able to weld the same contours on a 2D plane. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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12 pages, 7020 KiB

Open AccessArticle

Recognition of Stator Winding Inter-Turn Fault in Interior-Mount LSPMSM Using Acoustic Signals

by Luqman S. Maraaba, Ssennoga Twaha, Azhar Memon and Zakariya Al-Hamouz

Symmetry 2020, 12(8), 1370; https://doi.org/10.3390/sym12081370 - 17 Aug 2020

Cited by 22 | Viewed by 2413

Abstract

This paper presents a novel stator inter-turn fault diagnosis method for Line Start Permanent Magnet Synchronous Motors (LSPMSMs) using the frequency analysis of acoustic signals resulting from asymmetrical faults. In this method, acoustic data are experimentally collected from a 1 hp interior mount [...] Read more.

This paper presents a novel stator inter-turn fault diagnosis method for Line Start Permanent Magnet Synchronous Motors (LSPMSMs) using the frequency analysis of acoustic signals resulting from asymmetrical faults. In this method, acoustic data are experimentally collected from a 1 hp interior mount LSPMSM for different inter-turn fault cases and motor loading levels, while including the background noise. The signals are collected using a smartphone at a sampling rate of 48,000 samples per second. The signal for each case is analyzed using fast Fourier transform (FFT), which results in the decomposition of the signal into its frequency components. The results indicate that, for both no-load and full-load conditions, 39 components are observed to be affected by the faults, whereby their amplitudes increase with the fault severity. The 40-turns fault shows the highest difference in the component amplitudes compared with the healthy condition acoustic signal. Therefore, this diagnostic method is able to detect the stator inter-turn fault for interior mount LSPMSMs. Moreover, the method is simple and cheap since it uses a readily available sensor. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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22 pages, 4939 KiB

Open AccessArticle

A Digital Twin-Based Approach for the Fault Diagnosis and Health Monitoring of a Complex Satellite System

by Duansen Shangguan, Liping Chen and Jianwan Ding

Symmetry 2020, 12(8), 1307; https://doi.org/10.3390/sym12081307 - 5 Aug 2020

Cited by 54 | Viewed by 8378

Abstract

The ever-increasing functional density and complexity of the satellite systems, the harsh space flight environment, as well as the cost reduction measures that require less operator involvement are increasingly driving the need to develop new approaches for fault diagnosis and health monitoring (FD-HM). [...] Read more.

The ever-increasing functional density and complexity of the satellite systems, the harsh space flight environment, as well as the cost reduction measures that require less operator involvement are increasingly driving the need to develop new approaches for fault diagnosis and health monitoring (FD-HM). The data-driven FD-HM approaches use signal processing or data mining to obtain implicit information for the operating state of the system, which is good at monitoring systems extensively and shallowly and is expected to reduce the workload of the operators. However, these approaches for the FD-HM of the satellite system are driven primarily by the historical data and some static physical data, with little consideration for the simulation data, real-time data, and data fusion between the two, so it is not fully competent for the real-time monitoring and maintenance of the satellite in orbit. To ensure the reliable operation of the complex satellite systems, this paper presents a new physical–virtual convergence approach, digital twin, for FD-HM. Moreover, we present an FD-HM application of the satellite power system to demonstrate the effectiveness of the proposed approach. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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20 pages, 8054 KiB

Open AccessFeature PaperArticle

Specific Problems in Measurement of Coefficient of Friction Using Variable Incidence Tribometer

by Tatiana Kelemenová, Miroslav Dovica, Pavol Božek, Ivana Koláriková, Ondrej Benedik, Ivan Virgala, Erik Prada, Ľubica Miková, Tomáš Kot and Michal Kelemen

Symmetry 2020, 12(8), 1235; https://doi.org/10.3390/sym12081235 - 27 Jul 2020

Cited by 16 | Viewed by 7571

Abstract

The subject of this paper is the solution to specific problems in the measurement of the coefficient of the sliding friction of material pairs using a variable incidence tribometer. The aim of this work was to solve the questions of the measurement of [...] Read more.

The subject of this paper is the solution to specific problems in the measurement of the coefficient of the sliding friction of material pairs using a variable incidence tribometer. The aim of this work was to solve the questions of the measurement of the static coefficient of friction using a variable incidence tribometer from the perspective of metrology. In particular, we intended to research the expression of the credibility of this measurement and the possibility of increasing the credibility of the measurement. Another problem that needs to be solved is the method of carrying out the measurement, which has an impact on its achieved uncertainty. Sliding friction is a phenomenon that depends on many material properties such as contact area roughness, moisture, lubricants, temperature, and relative motion velocity. If environmental conditions are defined, the main input parameter is the relative motion velocity. For this input quantity, friction force becomes a symmetrical problem, and it is only necessary to explore this phenomenon for positive values of velocities. Symmetry in this area simplifies the research of this science topic. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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15 pages, 2651 KiB

Open AccessArticle

A Strategic and Significant Method for the Optimal Placement of Phasor Measurement Unit for Power System Network

by Maveeya Baba, Nursyarizal B. M. Nor, M. Aman.Sheikh, Muhammad Irfan and Mohammad Tahir

Symmetry 2020, 12(7), 1174; https://doi.org/10.3390/sym12071174 - 16 Jul 2020

Cited by 9 | Viewed by 3153

Abstract

Currently the new state of power system relies on a precise monitoring of electrical quantities such as voltage and current phasors. Occasionally, its operation gets disturbed because of the flicking in load and generation which may result in the interruption of power supply [...] Read more.

Currently the new state of power system relies on a precise monitoring of electrical quantities such as voltage and current phasors. Occasionally, its operation gets disturbed because of the flicking in load and generation which may result in the interruption of power supply or may cause catastrophic failure. The advanced technology of phasor measurement unit (PMU) is introduced in the late 1990s to measure the behavior of power system more symmetrically, accurately, and precisely. However, the implementation of this device at every busbar in a grid station is not an easy task because of its expensive installation and manufacturing cost. As a result, an optimum placement of PMU is much needed in this case. Therefore, this paper proposes a new symmetry approach of multiple objectives for the optimum placement of PMU problem (OPPP) in order to minimize the installed number of PMUs and maximize the measurement redundancy of the network. To overcome the drawbacks of traditional techniques in the proposed work a reduction and exclusion of pure transit node technique is used in the placement set. In which only the strategic, significant, and the most desirable buses are selected without considering zero injection buses (ZIBs). The fundamental novelty of the proposed work considers most importantly the reduction technique of ZIBs from the optimum PMU locations, as far as the prior approaches concern almost every algorithm have taken ZIBs as their optimal placement sets. Furthermore, a PMUs channel limits and an alternative symmetry location for the PMUs placement are considered when there is an outage or PMUs failure may occur. The performance of the proposed method is verified on different IEEE-standard such as: IEEE-9, IEEE-14, IEEE-24, IEEE-30, IEEE-57, IEEE-118, and a New England-39 bus system. The success of the proposed work was compared with the existing techniques’ outcomes from the literature. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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14 pages, 3972 KiB

Open AccessArticle

Research on a Sliding Detection Method for an Elevator Traction Wheel Based on Machine Vision

by Jiayan Chen, Limeng Jing, Tao Hong, Hui Liu and Adam Glowacz

Symmetry 2020, 12(7), 1158; https://doi.org/10.3390/sym12071158 - 12 Jul 2020

Cited by 9 | Viewed by 3118

Abstract

To solve the problem that the elevator traction wheel slippage is difficult to detect quantitatively, a slippage detection method is proposed based on machine vision. The slip between the traction wheel and the wire rope will occur during the round-trip operation of the [...] Read more.

To solve the problem that the elevator traction wheel slippage is difficult to detect quantitatively, a slippage detection method is proposed based on machine vision. The slip between the traction wheel and the wire rope will occur during the round-trip operation of the elevator, the displacement distance between the traction wheel and the wire rope in the circumferential direction is obtained through the image signal processing algorithm and related data analysis. First, the ROI (region of interest) of the collected original image is selected to reduce redundant information. Then, a nonlinear geometric transformation is carried out to transform the image into the target image with an equal object distance. Finally, the centroid method is used to obtain the slippage between the traction wheel and the wire rope. The field test results show that the absolute error of the system developed in this paper is 0.74 mm and the relative error is 2%, the extending uncertainty of the slip detection results is (33.8 ± 0.69) mm, the confidence probability is p = 0.95, and the degree of freedom is v = 8, which can meet accuracy requirements of elevator maintenance. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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33 pages, 14184 KiB

Open AccessArticle

Development of a New System for Attaching the Wheels of the Front Axle in the Cross-Country Vehicle

by Ján Dižo, Miroslav Blatnický, Milan Sága, Jozef Harušinec, Juraj Gerlici and Stanisław Legutko

Symmetry 2020, 12(7), 1156; https://doi.org/10.3390/sym12071156 - 11 Jul 2020

Cited by 16 | Viewed by 3705

Abstract

In the introduction of this article the authors deal with a general overview in the area of suspending the wheels of the road vehicles. It is important for creating an original design and this is the core of the operation. The implementation of [...] Read more.

In the introduction of this article the authors deal with a general overview in the area of suspending the wheels of the road vehicles. It is important for creating an original design and this is the core of the operation. The implementation of the design to a real vehicle created a space for modifying this design. The necessity of a modification shows important especially after the MKP analysis of the original design. Currently the Industrial Property Office of the Slovak Republic grants the presented design solution the rights for protection as a utility model. For granting the protection it was not necessary to prove the safety parameters of the design. However, the possibilities of the real utilisation are fully dependent on the safety conditions. Therefore, the research process presented in this article is necessary for building a prototype of this system. As the area is relatively extensive, it was necessary to divide it into several parts. The design and its importance for the industry are presented in the first part. The second part deals with analytical calculations and numerical simulations of the quasi-static loading of the structure. Furthermore, the article considers the kinematic and dynamic area of the vehicle. The authors also deal with the sensitivity analysis of the change of the wheel camber. This simulation is realised by the programme Altair Motionview for the vertical motion of the front axle through the presented design. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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11 pages, 4148 KiB

Open AccessArticle

The Usage of Alternative Materials to Optimize Bus Frame Structure

by Tautvydas Pravilonis, Edgar Sokolovskij, Artūras Kilikevičius, Jonas Matijošius and Kristina Kilikevičienė

Symmetry 2020, 12(6), 1010; https://doi.org/10.3390/sym12061010 - 15 Jun 2020

Cited by 12 | Viewed by 5806

Abstract

The strength and stiffness of the frame is one of the key indicators of vehicle structures. Insufficient stiffness causes vibration and noise, and is also less comfortable for both the passengers and the driver. Symmetry is required between the strength and comfort of [...] Read more.

The strength and stiffness of the frame is one of the key indicators of vehicle structures. Insufficient stiffness causes vibration and noise, and is also less comfortable for both the passengers and the driver. Symmetry is required between the strength and comfort of the structural frame, which depends on vibration and noise. This article analyses the frame of the structure of a medium-sized passenger bus and its dynamic properties, when replacing materials of structural elements which do not affect the symmetry of the structure. The conducted theoretical and experimental modal analysis of the bus, allows for evaluating dynamic parameters and validating the theoretical model based on the experimental results. The optimization of the medium-sized passenger bus frame—by replacing the material of the ancillary frame elements with fiberglass—reveals that its dynamic characteristics change by up to 20%, comparing the values of the first three resonant frequencies with those of the steel structure. The obtained results show that replacing the material of ancillary frame elements with fiberglass, while maintaining the symmetrical arrangement of the elements in the structure, does not change the safety characteristics of the structure, reducing the mass of the frame by 11%, and shifting the coordinate of the centre of gravity vertically downwards, which is very important for stability, comfort and fuel consumption. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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25 pages, 17015 KiB

Open AccessArticle

Investigation of Snake Robot Locomotion Possibilities in a Pipe

by Ivan Virgala, Michal Kelemen, Pavol Božek, Zdenko Bobovský, Martin Hagara, Erik Prada, Petr Oščádal and Martin Varga

Symmetry 2020, 12(6), 939; https://doi.org/10.3390/sym12060939 - 3 Jun 2020

Cited by 31 | Viewed by 4038

Abstract

This paper analyzed the locomotion of a snake robot in narrow spaces such as a pipe or channel. We developed a unique experimental snake robot with one revolute and one linear joint on each module, with the ability to perform planar motion. The [...] Read more.

This paper analyzed the locomotion of a snake robot in narrow spaces such as a pipe or channel. We developed a unique experimental snake robot with one revolute and one linear joint on each module, with the ability to perform planar motion. The designed locomotion pattern was simulated in MATLAB R2015b and subsequently verified by the experimental snake robot. The locomotion of the developed snake robot was also experimentally analyzed on dry and viscous surfaces. The paper further describes the investigation of locomotion stability by three symmetrical curves used to anchor static modules between the walls of the pipe. The stability was experimentally analyzed by digital image correlation using a Q-450 Dantec Dynamics high-speed correlation system. The paper presents some input symmetrical elements of locomotion and describes their influence on the results of locomotion. The results of simulations and experiments show possibilities of snake robot locomotion in a pipe. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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14 pages, 5917 KiB

Open AccessArticle

Design Procedure of a Topologically Optimized Scooter Frame Part

by Lukas Jancar, Marek Pagac, Jakub Mesicek and Petr Stefek

Symmetry 2020, 12(5), 755; https://doi.org/10.3390/sym12050755 - 6 May 2020

Cited by 15 | Viewed by 4719

Abstract

This article describes the design procedure of a topologically optimized scooter frame part. It is the rear heel of the frame, one of the four main parts of a scooter made with stainless steel 3D printing. The first part of the article deals [...] Read more.

This article describes the design procedure of a topologically optimized scooter frame part. It is the rear heel of the frame, one of the four main parts of a scooter made with stainless steel 3D printing. The first part of the article deals with the design area definition and the determination of load cases for topology calculation. The second part describes the process of the topology optimization itself and the creation of the volume body based on the calculation results. Finally, the final control using an FEM (Finite Element Method) analysis and optimization of created Computer-Aided Design (CAD) data is shown. Part of the article is also a review of partial iterations and resulting versions of the designed part. Symmetry was used to define boundary conditions, which led to computing time savings, as well as during the CAD model creation, where non-parametric surfaces were mirrored to shorten the design time. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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21 pages, 12441 KiB

Open AccessArticle

The Influence of Different Loads on the Footbridge Dynamic Parameters

by Artūras Kilikevičius, Darius Bačinskas, Jaroslaw Selech, Jonas Matijošius, Kristina Kilikevičienė, Darius Vainorius, Dariusz Ulbrich and Dawid Romek

Symmetry 2020, 12(4), 657; https://doi.org/10.3390/sym12040657 - 22 Apr 2020

Cited by 15 | Viewed by 3747

Abstract

Bringing together the experience and knowledge of engineers allowed building modern footbridges as very slender structures. This in turn has led to structural vibration problems, which is a direct consequence of slender structures. In some footbridges, this problem occurs when natural construction frequencies [...] Read more.

Bringing together the experience and knowledge of engineers allowed building modern footbridges as very slender structures. This in turn has led to structural vibration problems, which is a direct consequence of slender structures. In some footbridges, this problem occurs when natural construction frequencies are close to excitation frequencies. This requires a design methodology, which would ensure user safety and convenience of use of the footbridge in operation. Considering the aforementioned dynamic response, the analysis of the finite element model of a footbridge was conducted focusing on critical acceleration and deformation meanings. The model was based on the footbridge prototype located in Vilnius, Lithuania. Two different loading methods were developed to investigate the dynamic effects caused by people crossing a footbridge. The comparison of experimental and finite element model (FEM) results revealed that the footbridge in operation is within the limit values of comfort requirements in terms of its vibrations. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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18 pages, 8100 KiB

Open AccessArticle

Pattern Recognition of Single-Channel sEMG Signal Using PCA and ANN Method to Classify Nine Hand Movements

by Moh Arozi, Wahyu Caesarendra, Mochammad Ariyanto, M. Munadi, Joga D. Setiawan and Adam Glowacz

Symmetry 2020, 12(4), 541; https://doi.org/10.3390/sym12040541 - 3 Apr 2020

Cited by 49 | Viewed by 4533

Abstract

A number of researchers prefer using multi-channel surface electromyography (sEMG) pattern recognition in hand gesture recognition to increase classification accuracy. Using this method can lead to computational complexity. Hand gesture classification by employing single channel sEMG signal acquisition is quite challenging, especially for [...] Read more.

A number of researchers prefer using multi-channel surface electromyography (sEMG) pattern recognition in hand gesture recognition to increase classification accuracy. Using this method can lead to computational complexity. Hand gesture classification by employing single channel sEMG signal acquisition is quite challenging, especially for low-rate sampling frequency. In this paper, a study on the pattern recognition method for sEMG signals of nine finger movements is presented. Common surface single channel electromyography (sEMG) was used to measure five different subjects with no neurological or muscular disorder by having nine hand movements. This research had several sequential processes (i.e., feature extraction, feature reduction, and feature classification). Sixteen time-domain features were employed for feature extraction. The features were then reduced using principal component analysis (PCA) into two and three-dimensional feature space. The artificial neural network (ANN) classifier was tested on two different feature sets: (1) using all principal components obtained from PCA (PC1–PC3) and (2) using selected principal components (PC2 and PC3). The third best principal components were then used for classification using ANN. The average accuracy using all subject signals was 86.7% to discriminate the nine finger movements. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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13 pages, 874 KiB

Open AccessArticle

Analyzing the Energy Efficiency of Fan Systems by Using the Dimensional Analysis (DA) Method

by Gencho Popov, Kliment Klimentov, Boris Kostov and Reneta Dimitrova

Symmetry 2020, 12(4), 537; https://doi.org/10.3390/sym12040537 - 3 Apr 2020

Cited by 6 | Viewed by 2402

Abstract

This work represents a method for investigating the energy efficiency of fan systems used to transport fluids. Applying the methods of dimensional analysis (DA) enables establishing five dimensionless complexes (

π

criteria), including some basic parameters having impacts on the consumed energy used [...] Read more.

This work represents a method for investigating the energy efficiency of fan systems used to transport fluids. Applying the methods of dimensional analysis (DA) enables establishing five dimensionless complexes (

π

criteria), including some basic parameters having impacts on the consumed energy used for the transportation of a unit quantity of air. The proposed criterion

π_{1}

includes the specific energy consumption

e_{v}

(specific fan power SFP), and is used for the quantitative evaluation of the energy effectiveness of the fluid transportation. This criterion also includes the main geometric size of the pipe system (network) and the gas properties. The criterion

π_{3}

indicates the impact of the applied method of flow rate regulation on the effective energy use of fan systems. This criterion includes parameters characterizing the selected method of flow rate regulation: speed (

n

) for using the frequency method and the referred length (

L_{T P}

) of the pipe system for using the throttle method. The established (proposed) dimensionless parameters are used to study a concrete fan system. The obtained results concerning the evaluation of the impact of the two most used methods of flow rate regulation (frequency and throttle), as well as the density variation as a result of the temperature change, on the effective energy use are graphically presented:

π_{1} = f (π_{3})

. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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16 pages, 3470 KiB

Open AccessArticle

Schematic Diagrams Design of Displacement Suppression Mechanism with One Degree-of-Freedom in a Rope-Guided Hoisting System

by Lu Yan, Guohua Cao, Naige Wang and Weihong Peng

Symmetry 2020, 12(3), 474; https://doi.org/10.3390/sym12030474 - 18 Mar 2020

Cited by 2 | Viewed by 3468

Abstract

Since it is difficult for lateral stiffness of rope-guided rails to meet industry criteria in deep construction shaft, schematic diagrams of displacement suppression mechanisms (DSMs) are designed with a systematic approach demonstrated to reduce the lateral displacement of rope-guided rails in this paper. [...] Read more.

Since it is difficult for lateral stiffness of rope-guided rails to meet industry criteria in deep construction shaft, schematic diagrams of displacement suppression mechanisms (DSMs) are designed with a systematic approach demonstrated to reduce the lateral displacement of rope-guided rails in this paper. DSMs are simplified as planar four-bar and six-bar topological graphs based on topological theory. Each corresponding mechanical chain of these four-bar and six-bar mechanisms is divided into a rack, mechanical parts, prismatic, and revolute joints. An extended adjacency matrix is defined to represent the rack position, specific types of kinematic joints, and adjacency relationships between kinematic parts. Then, a symmetric vertex identification method is proposed with regard to planar 1-DOF (one degree of freedom) four-bar and six-bar topological graphs to get the sequences of prismatic joints for kinematic chains of DSMs. Finally, the alternative schematic diagrams of DSMs are obtained. The results show four-bar mechanisms with simple structure; few kinematical parts but less resident force are suitable for a mine shaft with small space and small swing. Six-bar mechanisms with two prismatic joints and three mechanical rack degree are applicable for wide shaft space in deep shaft, due to their stable structure and double resistant force. This development is helpful for DSM dimension synthesis design in future. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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15 pages, 6223 KiB

Open AccessFeature PaperArticle

A Novel Method of Laser Coating Process on Worn-Out Cutter Rings of Tunnel Boring Machine for Eco-Friendly Reuse

by Anil Kumar Agrawal, Somnath Chattopadhyaya, V. M. S. R. Murthy, Stanisław Legutko and Grzegorz Krolczyk

Symmetry 2020, 12(3), 471; https://doi.org/10.3390/sym12030471 - 17 Mar 2020

Cited by 20 | Viewed by 3514

Abstract

Cutter rings form an integral part of tunnel boring machines (TBM). These cutters are deployed in various hard rock tunneling projects. The life of the cutter rings governs the economics of tunneling significantly. This paper presents a novel methodology to enhance hardness and [...] Read more.

Cutter rings form an integral part of tunnel boring machines (TBM). These cutters are deployed in various hard rock tunneling projects. The life of the cutter rings governs the economics of tunneling significantly. This paper presents a novel methodology to enhance hardness and wear resistance of used worn out disc cutters in TBM for eco-friendly reuse. Disc cutters are mainly made of H13 tool steel. To improve the hardness and wear resistance, a layer of tungsten carbide is coated on the used cutter rings. Considering the long operating hours of TBM, cutter rings get worn out due to severe interaction with the hard rock both in compression and rolling mode. Replacement of the cutter-ring is costly, and quite a time consuming and cumbersome job. Refurbishment is always a better option and laser cladding is a novel technique for enhanced life of cutters. It increases the hardness and wear resistance of the cutters to a considerable extent. Cladding is carried out with the help of a laser beam. In this method, a layer of nanoparticles of tungsten carbide powder is deposited on the worn-out surface of the cutters. For carrying out the investigation, different coating parameters are selected based on the central composite design (CCD). With different capacities of laser, a total of 13 samples were prepared at various scanning speeds varying between 200 to 300 mm/min and a level of laser power varying between 100 to 200 W. The coating is critically inspected by various means such as an optical microscope, FESEM, and EDS. Hardness testing was accomplished by Vicker’s hardness testing machine. Wear testing was carried out with the aid of pin on disc setup. The results shows an asymmetrical behavior between the yield parameters (hardness and wear rate) and process parameters (scanning speed and laser power). The hardness values increased from 16% to 95%. A correlation test was conducted between the hardness and wear rate. The results depict a clear negative correlation between them, indicating the advantage of laser coating for reducing cutter ring wear in TBM. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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12 pages, 2315 KiB

Open AccessArticle

Symmetric Performance Analysis for Mechanical Properties of Sustainable Asphalt Materials under Varying Temperature Conditions: An Application of DT and NDT Digital Techniques

by Muhammad Kashif Anwar, Syyed Adnan Raheel Shah, Abdullah Naveed Sadiq, Muhammad Usman Siddiq, Hassam Ahmad, Saqib Nawaz, Asif Javead, Muhammad Hasnain Saeed and Ahsan Rehman Khan

Symmetry 2020, 12(3), 433; https://doi.org/10.3390/sym12030433 - 8 Mar 2020

Cited by 6 | Viewed by 3333

Abstract

During the development of symmetric asphalt concrete material samples, aggregates play a vital role in the performance of its production. Shape characteristics and aggregates geology are two major factors influencing strength parameters of the asphalt concrete mix. In this study, two different geological [...] Read more.

During the development of symmetric asphalt concrete material samples, aggregates play a vital role in the performance of its production. Shape characteristics and aggregates geology are two major factors influencing strength parameters of the asphalt concrete mix. In this study, two different geological sources of aggregates with different shape characterizations have been utilized for the development of the asphalt concrete mix. In addition to that, the stability analysis has been performed under different temperature conditions ranging between 25 and 60 °C. By the application of the destructive technique (DT) and non-destructive technique (NDT), the performance of the asphalt concrete mix has been analyzed and compared based on the geology of aggregates under various temperatures. Furthermore, a statistical model has been developed to analyze the stability and performance of the developed asphalt concrete mix with reference to regional climatic conditions. This study will help in the development of symmetric formation of sustainable asphalt materials. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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7 pages, 1698 KiB

Open AccessFeature PaperArticle

Differential Entropy Analysis of the Acoustic Characteristics of a Biomimetic Dynamic Sonar Emitter

by Luhui Yang and Rolf Müller

Symmetry 2020, 12(3), 391; https://doi.org/10.3390/sym12030391 - 3 Mar 2020

Cited by 2 | Viewed by 2027

Abstract

Active noseleaf deformations during pulse emission observed in hipposiderid and rhinolophid bats have been shown to add a time dimension to the bats’ acoustic emission characteristics beyond the established dependencies on frequency and direction. In this study, a dense three-dimensional acoustic characteristics were [...] Read more.

Active noseleaf deformations during pulse emission observed in hipposiderid and rhinolophid bats have been shown to add a time dimension to the bats’ acoustic emission characteristics beyond the established dependencies on frequency and direction. In this study, a dense three-dimensional acoustic characteristics were obtained by the time series of smoothed signal amplitudes at different directions and frequencies collected by a biomimetic dynamic sonar emitter. These data have been analyzed using differential entropy which was used as a measure to compare the encoding capacity for sensory information between the three different dimensions. The capacity for sensory information encoding measured in this way along time dimension was found to be similar to that along the frequency dimension. But both of them provided less information than provided by the direction dimension. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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13 pages, 2582 KiB

Open AccessBrief Report

Remaining Useful Life Prediction of an IGBT Module in Electric Vehicles Statistical Analysis

by Huawei Wu, Congjin Ye, Yuanjin Zhang, Jingquan Nie, Yong Kuang and Zhixiong Li

Symmetry 2020, 12(8), 1325; https://doi.org/10.3390/sym12081325 - 8 Aug 2020

Cited by 9 | Viewed by 4501

Abstract

The whole life cycle of an insulated gate bipolar transistor (IGBT) is a kind of asymmetry process, while the whole life cycles of a set of IGBTs can be regarded as a symmetry process. Modelling these symmetry characteristics of the IGBT life cycles [...] Read more.

The whole life cycle of an insulated gate bipolar transistor (IGBT) is a kind of asymmetry process, while the whole life cycles of a set of IGBTs can be regarded as a symmetry process. Modelling these symmetry characteristics of the IGBT life cycles enables the improvement of the remaining useful life (RUL) prediction performance. For this purpose, based on the key failure mechanism of IGBT in electric vehicles, a new method for estimating the RUL of an IGBT module is proposed based on the two-stress acceleration synthesis environment of junction temperature and vibration. The maximum likelihood estimation (MLE) was employed to estimate the logarithmic standard deviation and covariance matrix. The Shapiro–Wilk (S–W) test was performed to investigate the satisfaction degree of the RUL of the IGBT module to the lognormal distribution. The accelerated life test datasets of the IGBT module were analyzed using the Weibull++ software. The analysis results demonstrate that the IGBT lifetime is confirmed to lognormal distribution, and the accelerated model accords with the generalized Eyring acceleration model. The proposed method can estimate IGBT RUL in a short time, which provides a certain technical reference for the reliability analysis of the IGBT module. Full article

(This article belongs to the Special Issue Symmetry in Mechanical Engineering Ⅱ)

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