An Optimal Choice of Profile Shift Coefficients for Spur Gears
Fault Diagnosis of Rolling Bearing Based on Shift Invariant Sparse Feature and Optimized Support Vector Machine
Review of Rotor Balancing Methods
Multiscale Modelling and Analysis for Design and Development of a High-Precision Aerostatic Bearing Slideway and Its Digital Twin

Journal Description

Machines

Machines is an international, peer-reviewed, open access journal on machinery and engineering published monthly online by MDPI. The IFToMM is affiliated with Machines and its members receive a discount on the article processing charges.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), Inspec, and many other databases.
Journal Rank: JCR - Q2 (Engineering, Mechanical) / CiteScore - Q1 (Mechanical Engineering)
Rapid Publication: manuscripts are peer-reviewed and a first decision provided to authors approximately 13.1 days after submission; acceptance to publication is undertaken in 3 days (median values for papers published in this journal in the first half of 2021).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.

Impact Factor: 2.428 (2020) ; 5-Year Impact Factor: 2.467 (2020)

Imprint Information Journal Flyer Open Access ISSN: 2075-1702

Latest Articles

Open AccessArticle

Synchronization Control of a Dual-Cylinder Lifting Gantry of Segment Erector in Shield Tunneling Machine under Unbalance Loads

Litong Lyu

Xiao Liang

and

Jingbo Guo

Machines 2021, 9(8), 152; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9080152 (registering DOI) - 02 Aug 2021

Abstract

Segment assembling is one of the principle processes during tunnel construction using shield tunneling machines. The segment erector is a robotic manipulator powered by a hydraulic system to assemble prefabricated concrete segments onto the excavated tunnel surface. Nowadays, automation of the segment erector has become one of the definite developing trends to further improve the efficiency and safety during construction; thus, closed-loop motion control is an essential technology. Within the segment erector, the lifting gantry is driven by dual cylinders to lift heavy segments in the radial direction. Different from the dual-cylinder mechanism used in other machines such as forklifts, the lifting gantry usually works at an inclined angle, leading to unbalanced loads on the two sides. Although strong guide rails are applied to ensure synchronization, the gantry still occasionally suffers from chattering, “pull-and-drag”, or even being stuck in practice. Therefore, precise motion tracking control as well as high-level synchronization of the dual cylinders have become essential for the lifting gantry. In this study, a complete dynamics model of the dual-cylinder lifting gantry is constructed, considering the linear motion as well as the additional rotational motion of the crossbeam, which reveals the essence of poor synchronization. Then, a two-level synchronization control scheme is synthesized. The thrust allocation is designed to coordinate the dual cylinders and keep the rotational angle of the crossbeam within a small range. The motion tracking controller is designed based on the adaptive robust control theory to guarantee the linear motion tracking precision. The theoretical performance is analyzed with corresponding proof. Finally, comparative simulations are conducted and the results show that the proposed scheme achieves high-precision motion tracking performance and simultaneous high-level synchronization of dual cylinders under unbalanced loads. Full article

(This article belongs to the Special Issue Advanced Control of Industrial Electro-Hydraulic Systems)

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Open AccessArticle

Online Nonlinear Error Compensation Circuit Based on Neural Networks

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Machines 2021, 9(8), 151; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9080151 - 31 Jul 2021

Abstract

Nonlinear errors of sensor output signals are common in the field of inertial measurement and can be compensated with statistical models or machine learning models. Machine learning solutions with large computational complexity are generally offline or implemented on additional hardware platforms, which are difficult to meet the high integration requirements of microelectromechanical system inertial sensors. This paper explored the feasibility of an online compensation scheme based on neural networks. In the designed solution, a simplified small-scale network is used for modeling, and the peak-to-peak value and standard deviation of the error after compensation are reduced to 17.00% and 16.95%, respectively. Additionally, a compensation circuit is designed based on the simplified modeling scheme. The results show that the circuit compensation effect is consistent with the results of the algorithm experiment. Under SMIC 180 nm complementary metal-oxide semiconductor (CMOS) technology, the circuit has a maximum operating frequency of 96 MHz and an area of 0.19 mm². When the sampling signal frequency is 800 kHz, the power consumption is only 1.12 mW. This circuit can be used as a component of the measurement and control system on chip (SoC), which meets real-time application scenarios with low power consumption requirements. Full article

(This article belongs to the Section Micro/Nano Electromechanical Systems (MEMS/NEMS))

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Open AccessArticle

Evaluation of the Ability to Accurately Produce Angular Details by 3D Printing of Plastic Parts

Andrei Marius Mihalache

and

Machines 2021, 9(8), 150; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9080150 - 29 Jul 2021

Abstract

3D printing is a process that has become widely used in recent years, allowing the production of parts with relatively complicated shapes from metallic and non-metallic materials. In some cases, it is challenging to evaluate the ability of 3D printers to make fine details of parts. For such an assessment, the printing of samples showing intersections of surfaces with low angle values was considered. An experimental plan was designed and materialized to highlight the influence of different factors, such as the thickness of the deposited material layer, the printing speed, the cooling and filling conditions of the 3D-printed part, and the thickness of the sample. Samples using areas in the form of isosceles triangles with constant height or bases with the same length, respectively, were used. The mathematical processing of the experimental results allowed the determination of empirical mathematical models of the power-function type. It allowed the detection of both the direction of actions and the intensity of the influence exerted by the input factors. It is concluded that the strongest influence on the printer’s ability to produce fine detail, from the point of view addressed in the paper, is exerted by the vertex angle, whose reduction leads to a decrease in printing accuracy. Full article

(This article belongs to the Special Issue Advances and Trends in Non-conventional, Abrasive and Precision Machining 2021)

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Open AccessArticle

Grasp Point Optimization and Leakage-Compliant Dimensioning of Energy-Efficient Vacuum-Based Gripping Systems

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Machines 2021, 9(8), 149; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9080149 - 29 Jul 2021

Abstract

Vacuum-based handling, used in many applications and industries, offers great flexibility and fast handling processes. However, due to significant energy conversion losses from electrical energy to the useable suction flow, vacuum-based handling is highly energy-inefficient. In preliminary work, we showed that our grasp optimization method offers the potential to save at least 50% of energy by a targeted placement of individual suction cups on the part to be handled. By considering the leakage between gripper and object, this paper aims to extend the grasp optimization method by predicting the effective compressed air consumption depending on object surface roughness, gripper diameter and gripper count. Through balancing of the target pressure difference and the leakage tolerance in combination with the gripper count and gripper diameter, significant reductions of the compressed air, use and therefore the overall energy consumption, can be achieved. With knowledge about the gripper-specific leakage behavior, in the future it will be straightforward for system integrators to minimize the need for oversizing due to process-related uncertainties and therefore to provide application-specific and energy-optimized handling solutions to their customers. Full article

(This article belongs to the Section Automation Systems)

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Open AccessArticle

Reconfigurable Machine Tool Design for Box-Type Part Families

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Machines 2021, 9(8), 148; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9080148 - 29 Jul 2021

Abstract

The reconfigurable manufacturing system (RMS) is a new manufacturing technology and paradigm that resolves the contradictions regarding high efficiency, low cost and flexible production in the mass production of part families. Reconfigurable machine tools (RMTs) are the core components of RMSs. A new approach is proposed for the design of RMTs, which is closely related to the process planning of a given box-type part family. The concepts of the processing unit and the processing segment are presented; they are not only the basic elements of the processing plans of machined parts, but also closely related to the structural design of RMTs. Processing units created by processing features can be combined into various processing segments. All the processing units of one processing segment correspond to the machining operations performed by one RMT. By arranging the processing segments according to the processing sequence, a variety of feasible processing plans for a part can be obtained. Through analysis of the established similarity calculation model for processing plans, the most similar processing plans for the parts in a given part family can be determined and used for the structural design of RMTs. Therefore, the designed RMTs can achieve rapid conversion of processing functions with the least module replacement or adjustment to realize the production of the parts in the part family. Taking the production of a gearbox part family as an example, the validity of the presented method is verified. Full article

(This article belongs to the Special Issue Robotic Machine Tools)

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Open AccessArticle

Target Search Algorithm for AUV Based on Real-Time Perception Maps in Unknown Environment

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Machines 2021, 9(8), 147; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9080147 - 29 Jul 2021

Abstract

For the problem of AUV target searches in unknown underwater environments, a target search algorithm for AUVs based on a real-time perception map is proposed. Real-time perception maps, including target existence probability maps, uncertainty maps, and pheromone maps and their updating rules, are established. Attraction source maps and search status maps based on the environmental information detected by the AUV are established. The maps are used for the AUV to search for corner areas that are unknown to a high degree and areas with low coverage around the current location. At the same time, a release mechanism for attraction and revisiting pheromones is established by combining a neural excitation network algorithm to make the gradient spread in the pheromone grid map. By setting up a search revenue function based on real-time perception maps, an AUV search decision-making method is established. When the AUV finds a suspected target, the AUV approaches the suspected target. The path planning of the AUV is carried out through an improved artificial potential field method. The short-distance confirmation of the target and obstacle avoidance in the search process are realized. The simulation results show that the algorithm has high search efficiency. Additionally, when the target exists in a corner area, the probability of the AUV to quickly search for the target is fast and feasible. Full article

(This article belongs to the Special Issue Dynamics and Motion Control of Unmanned Aerial/Underwater Vehicles)

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Open AccessArticle

Transformer: A Multifunctional Fast Unmanned Aerial Vehicles–Unmanned Surface Vehicles Coupling System

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Machines 2021, 9(8), 146; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9080146 - 29 Jul 2021

Abstract

With the continuous development of the maritime economy, the maritime unmanned surface vehicles (USVs) and unmanned aerial vehicles (UAVs) have become important parts of the maritime transportation system. Unmanned vehicles play a pivotal role in water safety management, offshore patrol and maritime rescue. Consequently, this article researches and develops an unmanned aerial vehicle–unmanned surface vehicle (UAV-USV) coupling system with multiple functions. The ship body module, the deformation module and the UAV module are designed by using the modular analysis method, then volume of fluid (VOF) technology and STAR-CCM+ software are applied to analyze the ship resistance before and after deformation and optimize it. The results show that the Transformer has high speed before deformation and stable navigation ability after deformation, and it can navigate in high winds and waves. It has a large reconnaissance range and some radar stealth capability, which can fulfill different tasks, such as maritime patrol, military strike and maritime rescue. Full article

Open AccessCommunication

Passive Gravity Balancing with a Self-Regulating Mechanism for Variable Payload

Diego Franchetti

Giovanni Boschetti

and

Basilio Lenzo

Machines 2021, 9(8), 145; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9080145 - 29 Jul 2021

Abstract

Gravity balancing techniques allow for the reduction of energy consumptions in robotic systems. With the appropriate arrangements, often including springs, the overall potential energy of a manipulator can be made configuration-independent, achieving an indifferent equilibrium for any position. On the other hand, such arrangements lose their effectiveness when some of the system parameters change, including the mass. This paper proposes a method to accommodate different payloads for a mechanism with a single degree-of-freedom (DOF). By means of an auxiliary mechanism including a slider, pulleys and a counterweight, the attachment point of a spring is automatically regulated so as to maintain the system in indifferent equilibrium regardless of the position, even when the overall mass of the system varies. Practical implications for the design of the mechanism are also discussed. Simulation results confirm the effectiveness of the proposed approach. Full article

(This article belongs to the Section Machine Design and Theory)

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Open AccessArticle

Mechanical Compound Fault Analysis Method Based on Shift Invariant Dictionary Learning and Improved FastICA Algorithm

Haodong Yuan

Nailong Wu

and

Xinyuan Chen

Machines 2021, 9(8), 144; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9080144 - 29 Jul 2021

Abstract

For mechanical compound fault, it is of great significance to employ the vibration signal of a single-channel compound fault to analyze and realize the separation of multiple fault sources, which is essentially the problem of single-channel blind source separation. Shift invariant K-means singular value decomposition (shift invariant K-SVD) dictionary learning is suitable to extract the periodic and repeated fault features of a rotating machinery fault, hence in this article a single-channel compound fault analysis method is put forward which combines shift invariant K-SVD with improved fast independent component analysis (improved FastICA) algorithm. Firstly, based on single-channel compound fault signal, the shift invariant K-SVD algorithm can be used for learning multiple latent components that can be constructed as a virtual multi-channel signal. Then the improved FastICA algorithm is utilized to realize the separation of multiple fault source signals. With regard to the FastICA algorithm, the third-order convergence Newton iteration method is adopted to improve convergence speed. Moreover, in order to address the problem that FastICA is very sensitive to initialization, a steepest descent method can be applied. The experimental analysis of the compound fault of rolling bearing verifies that the presented method is effective to separate multiple fault source signals and the improved FastICA algorithm can increase convergence rate and overcome the problem of sensitivity to initialization. Full article

(This article belongs to the Section Machines Testing and Maintenance)

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Open AccessArticle

Evaluation of a Thermal Consolidation Process for the Production of Enhanced Technical Fabrics

Georgios Constantinides

Charalabos Doumanidis

and

Vassilis Drakonakis

Machines 2021, 9(8), 143; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9080143 - 28 Jul 2021

Abstract

Fiber reinforced composites are increasingly used in high value applications. A novel technology (NanoWeld^®) enhancing the structural integrity of the interlayer has demonstrated promising results; however, manufacturing issues related to scalability need to be overcome. The developed technology relies on consolidating thermoplastic nanofiber nonwoven veils onto technical dry fabrics through roll-to-roll ultrasonic welding. The enhanced technical dry fabrics can be further processed as any other technical fabrics for the composites industry. An alternative solution for consolidation is proposed here, based on a thermo-compressive approach to address the scalability issue. A finite element model has been employed to simulate the operating conditions and provide information for optimization of the process. Its results demonstrate that consolidation is achieved rapidly, indicating that the production rate could be accelerated. The quality of enhanced technical dry fabrics produced using the proposed consolidation assembly has been evaluated using scanning electron microscopy as well as mechanical testing of fiber reinforced composites. The mechanical response of such manufactured composites has been compared against benchmark NanoWeld^® composites, demonstrating superior performance. Full article

(This article belongs to the Section Engineering Materials)

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Open AccessArticle

Adaptive Direct Teaching Control with Variable Load of the Lower Limb Rehabilitation Robot (LLR-II)

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Machines 2021, 9(8), 142; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9080142 - 27 Jul 2021

Abstract

Most lower limb rehabilitation robots use fixed training trajectories and lack participation of physiotherapists. In addition, there is a lack of attention on combining direct teaching function with rehabilitation robots, which enables physiotherapists to plan trajectories directly. In this paper, an adaptive direct teaching function with variable load that can be applied to the sitting/lying lower limb rehabilitation robot-II (LLR-II) is proposed. First, the structural design and electrical system of LLR-II are introduced. The dynamic equation of LLR-II considering joint flexibility is derived and analyzed. Then, the impact of joint flexibility on LLR-II is reduced by introducing the intermediate input variables. Based on this, the control law of the dragging teaching stage and the replay stage in the direct teaching function with variable load is designed and the adaptive control strategy eliminates the influence of different patients. In addition, the control law is simulated and verified. Finally, some preliminary experiments of the adaptive direct teaching function with variable load on LLR-II are carried out, and the results showed that the control law has good performance, which lays the foundation for future work. Full article

(This article belongs to the Special Issue Design and Control of Advanced Mechatronics Systems)

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Open AccessArticle

A Novel Automated System for the Handling of Car Seat Wires on Plastic Over-Injection Molding Machines

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Machines 2021, 9(8), 141; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9080141 - 25 Jul 2021

Abstract

The structure of car seats is becoming increasingly complex, with mixing of wire conformation and plastic injection. The plastic over-molding process implies some labor, which can be reduced if novel solutions are applied in this manufacturing area. The handling of the wires used in car seats is the main problem identified in the process, wasting time both in the feeding and in the extraction of the molds used in the wire over-molding process. However, these machines are usually extremely compact and the free space around them is too short. In classic molding injection machines, there are just two half-molds, the female, and the male. In the over-molding process of wires used in car seats, three half-molds are used in order to increase the cycle time. Thus, to solve this problem, the classic robotic solutions are not appliable due to lack of space and elevated cost. This work describes the development of an automated solution able to handle the wires in both the feeding and the extracting phases of the production cycle, avoiding the traditional labor costs associated with this type of machine. Departing from an industrial need, the developed novel solution is described in detail and can be successfully adapted to other situations of low added-value products where it is needed to increase the productivity and competitiveness of the product. The system developed uses mechanical and pneumatic solutions which, combined, can be used to solve the identified problem, occupying a restricted space and requiring a small budget. This solution can be translated into guidelines that will allow the analysis of situations where the same system can be applied. Full article

(This article belongs to the Section Industrial Systems)

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Open AccessArticle

Analysis of the Torque Loss of High-Speed Transmission Mechanism with a Stacked Roller Set

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Machines 2021, 9(8), 140; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9080140 - 22 Jul 2021

Abstract

Two-dimensional pumps have broad application prospects in aerospace. However, the performance of the pump is degraded because of the clearance problem of the current 2D transmission mechanism. In order to eliminate the clearance between the cam rail and the rollers, a high-speed transmission mechanism with a stacked roller set is proposed. The stacked roller set is compressed by the load pressure. The axial inertia force is balanced when the transmission mechanism works at high speed, via the equal acceleration and reverse movement of two cam rail sets. Thus, the transmission mechanism meets the high-speed demand. In this paper, the mathematical model of the transmission mechanism is established based on the enveloping surface theory and the differential geometry principle. Afterwards, numerical analysis of the mathematical model is performed based on MATLAB, combined with the experiment, to study the influence of load pressure and rotational speed on the torque loss. Then, the torque characteristics of the transmission mechanism is obtained. According to a test, the deviation between theoretical data and experimental data is 11.9%; therefore, the mathematical model can predict the torque of the transmission mechanism effectively. It is concluded that the torque loss of the transmission mechanism increases linearly with the load pressure, and the rotational speed has a slight effect on the torque loss. Full article

(This article belongs to the Section Machine Design and Theory)

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Open AccessArticle

A Novel Method for Harmonic Current Injection with Sensor Supported Adaptation on Permanent Magnet Synchronous Machines

Matthias Vollat

Dominik Krahe

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Frank Gauterin

Machines 2021, 9(8), 139; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9080139 - 22 Jul 2021

Abstract

To reduce torque oscillations in electric motors, harmonic current injection (HCI) has been used in industry for some time. For this purpose, higher harmonic currents calculated in advance are injected into the machine. Since the general conditions for the machine can change during its life cycle, this article presents a method that makes it possible to change the parameters of HCI during operation. For this purpose, sensor signals are used to detect the reaction of the electric motor to small variations of the HCI parameters. The knowledge gained in this way is used to make further suitable variations. FEM simulations were used to verify the effectiveness of the approach. The results show that the algorithm can independently optimize the HCI parameters during runtime and reduces the amplitude of the 6th harmonic in the torque by 87% for a permanent magnet synchronous machine. Full article

(This article belongs to the Section Machine Design and Theory)

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Open AccessArticle

A Low-Cost System for Remote Access and Control of Automation Equipment

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Machines 2021, 9(7), 138; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9070138 - 20 Jul 2021

Abstract

The shift towards remote access and control of equipment has become more prominent, especially due to COVID-19 lockdowns. Access to physical/real equipment for practical learning remains important for engineering studies. Thus, this paper presents an approach for remotely accessing and controlling automation equipment for engineering practical activities. Specifically, it addresses the issue of accessing and controlling machines for programmable logic controller (PLC) programming tasks. The combination of a scheduler, remote desktop access, graphical user interface, and a micro-controller allows students to work remotely on practical equipment. The lab computer can be accessed via a remote computer to select one of multiple equipment for practical activities. A prototype system was constructed as proof of concept. The prototype system functions as required. Full article

(This article belongs to the Special Issue Intelligent Machines and Control Systems)

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Open AccessArticle

Coil Number Impact on Performance of 4-Phase Low Speed Toothed Doubly Salient Permanent Magnet Motors

Cherif Guerroudj

Jean-Frederic Charpentier

Rachid Saou

Yannis L. Karnavas

Nicolas Bracikowski

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Mohammed El-Hadi Zaïm

Machines 2021, 9(7), 137; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9070137 - 16 Jul 2021

Abstract

The low speed toothed doubly salient permanent-magnet (TDSPM) machine is an interesting candidate motor for electric ship applications because, of its high torque output, maintenance-free operation and flexible working modes, which gives the opportunity to increase system’s reliability, and decrease the system size, weight and noise which are key features for naval applications. However, particularly in the 3-phase configuration, the stator and rotor saliency of these machines leads to a high level of torque ripple. To overcome these drawbacks, the use of polyphase machines (with a number of phases greater than three) can be a relevant solution. In this paper, an optimal design of two kind of novel 4-phase motors is performed in order to fulfil the specifications of a high power naval ship propulsion. The designs aim to maximize the torque to mass ratio. The motors’ performances are directly linked to their structural parameters, so, the impact of the coil number in terms of mean torque, torque ripple, energy ratio values, and efficiency is also presented and analysed. The design of these two electromagnetic structures, as well as the determination of their electromagnetic performances, are carried out using a particle swarm optimization algorithm (PSO) with taking into account thermal constraint. The performance of the proposed machine in terms of mean torque, torque ripple, energy ratio, and efficiency values is presented and analysed. The results obtained reveal that the TDSPM machines with four poles/phase are good candidates to meet the requirements of high power direct-drive ship propulsion system. Full article

(This article belongs to the Special Issue Synchronous Reluctance Motor-Drive Advancements)

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Open AccessArticle

Blaise Pascal’s Mechanical Calculator: Geometric Modelling and Virtual Reconstruction

José Ignacio Rojas-Sola

Gloria del Río-Cidoncha

Arturo Fernández-de la Puente Sarriá

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Verónica Galiano-Delgado

Machines 2021, 9(7), 136; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9070136 - 16 Jul 2021

Abstract

This article shows the three-dimensional (3D) modelling and virtual reconstruction of the first mechanical calculating machine used for accounting purposes designed by Blaise Pascal in 1642. To obtain the 3D CAD (computer-aided design) model and the geometric documentation of said invention, CATIA V5 R20 software has been used. The starting materials for this research, mainly the plans of this arithmetic machine, are collected in the volumes Oeuvres de Blaise Pascal published in 1779. Sketches of said machine are found therein that lack scale, are not dimensioned and certain details are absent; that is, they were not drawn with precision in terms of their measurements and proportions, but they do provide qualitative information on the shape and mechanism of the machine. Thanks to the three-dimensional modelling carried out; it has been possible to explain in detail both its operation and the final assembly of the invention, made from the assemblies of its different subsets. In this way, the reader of the manuscript is brought closer to the perfect understanding of the workings of a machine that constituted a major milestone in the technological development of the time. Full article

(This article belongs to the Special Issue Machines throughout History for Technological Development: Analysis from Engineering Graphics)

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Open AccessArticle

Development and Application of Fuzzy Proportional-Integral Control Scheme in Pitch Angle Compensation Loop for Wind Turbines

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Machines 2021, 9(7), 135; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9070135 - 16 Jul 2021

Abstract

Wind energy is regarded as one of the oldest energy sources and has played a significant role. As the nature of wind changes continuously, the generated power varies accordingly. Generation of the pitch angle of a wind turbine’s blades is controlled to prevent damage during high wind speed. This paper presents the development and application of a fuzzy proportional integral control scheme combined with traditional proportional control in the dynamic behavior of pitch angle-regulated wind turbine blades. The combined control regulates rotor speed and output power, allowing control of the power while maintaining the desired rotor speed and avoiding equipment overloads. The studied model is a large-scale wind farm of 120 MW in the Gulf El-Zayt region, Red Sea, Egypt. The control system validity is substantiated by studying different cases of wind speed function: ramp, step, random, and extreme wind speed. The results are compared with the traditional combined control. The model is simulated using MATLAB/SIMULINK software. The simulation results proved the effectiveness of fuzzy tuned PI against traditional PI control. Full article

(This article belongs to the Section Turbomachinery)

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Open AccessArticle

PFC-Based Control of Friction-Induced Instabilities in Drive Systems

Ievgen Golovin

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Stefan Palis

Machines 2021, 9(7), 134; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9070134 - 16 Jul 2021

Abstract

This paper is concerned with control-based damping of friction-induced self-excited oscillations that appear in electromechanical systems with an elastic shaft. This approach does not demand additional oscillations measurements or an observer design. The control system provides the angular velocity and damping control via [...] Read more.

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-tracking feedback control. The PFC is designed to stabilize the zero dynamics of an augmented system and renders it almost strict positive real (ASPR). The proposed control approach is tested in simulations. Full article

(This article belongs to the Special Issue Advances in Electric Machines and Associated Drives for More Electric Transportation (Aircraft, Automotive, Rail and Marine))

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Open AccessArticle

VIAM-USV2000: An Unmanned Surface Vessel with Novel Autonomous Capabilities in Confined Riverine Environments

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Machines 2021, 9(7), 133; https://0-doi-org.brum.beds.ac.uk/10.3390/machines9070133 - 15 Jul 2021

Abstract

Unmanned Surface Vessels (USVs) have witnessed an increasing growth in demand for development due to their compactness, mobility and maneuverability, which make them well-suited for environmental monitoring on narrow water in Vietnam in particular and in general at several similar tropical regions. However, current surface vessels are limited to operation on open water only. In this paper, we design a USV, namely, VIAM-USV2000, equipped with advanced autonomous capabilities to satisfactorily carry out missions in confined riverine environments. More specifically, our prototype is designed to follow a smooth B-Spline path that is self-planned to meet the limiting curvature and avoid static obstacles. Moreover, the vessel is capable of avoiding dynamic obstacles by an advanced Set-based Guidance mechanism. Simulated and experimental results at a local lake prove the effectiveness of the proposed capabilities, thereby paving the way for the extensive deployment of USVs in many real-world applications. Full article

(This article belongs to the Special Issue Dynamics and Motion Control of Unmanned Aerial/Underwater Vehicles)

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