Open AccessArticle
Aeronautical Magnetic Torque Limiter for Passive Protection against Overloads
Machines 2016, 4(3), 17; doi:10.3390/machines4030017 -
Abstract
Actual aerospace and defense technologies present multiple limitations that need to be overcome in order to evolve to less contaminating and more efficient aircraft solutions. Contactless technologies come with essential advantages such as the absence of wear and friction. This work describes [...] Read more.
Actual aerospace and defense technologies present multiple limitations that need to be overcome in order to evolve to less contaminating and more efficient aircraft solutions. Contactless technologies come with essential advantages such as the absence of wear and friction. This work describes the design, prototype, and performance test according to RTCA-DO-160 of an aeronautical magnetic torque limiter. The results show correct continuous transmission operation (2250 rpm and 24 Nm) from −50 °C to +90 °C. Moreover, overload protection has been demonstrated for more than 200 jamming events without damage or required maintenance to the device. Full article
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Open AccessArticle
Self-Sensing Electromagnets for Robotic Tooling Systems: Combining Sensor and Actuator
Machines 2016, 4(3), 16; doi:10.3390/machines4030016 -
Abstract
A low-cost method, which integrates distance sensing functionality into a switched electromagnet by using a hybrid switching mode and current ripple measurements, is proposed. The electromagnet is controlled by a micro-controller via a MOSFET H bridge, utilizing a comparator-based current control. Additionally, [...] Read more.
A low-cost method, which integrates distance sensing functionality into a switched electromagnet by using a hybrid switching mode and current ripple measurements, is proposed. The electromagnet is controlled by a micro-controller via a MOSFET H bridge, utilizing a comparator-based current control. Additionally, a method for calculating the inductance of the electromagnet and approximating the magnetic contact between the electromagnet and its target is also presented. The resulting tool is attached to an industrial robot, and the system performance using this setup is evaluated. Distance sensing in the range of 0 mm to 5.2 mm is demonstrated. It is also shown that the relation between magnetic contact, coil current and calculated inductance can be reduced to a predictive look-up table, enabling the quality of the magnetic contact to be estimated using minimal computational effort. Full article
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Open AccessArticle
Optimization Design and Performance Analysis of a PM Brushless Rotor Claw Pole Motor with FEM
Machines 2016, 4(3), 15; doi:10.3390/machines4030015 -
Abstract
A new type of permanent magnet (PM) brushless claw pole motor (CPM) with soft magnetic composite (SMC) core is designed and analyzed in this paper. The PMs are mounted on the claw pole surface, and the three-phase stator windings are fed by [...] Read more.
A new type of permanent magnet (PM) brushless claw pole motor (CPM) with soft magnetic composite (SMC) core is designed and analyzed in this paper. The PMs are mounted on the claw pole surface, and the three-phase stator windings are fed by variable-frequency three-phase AC currents. The advantages of the proposed CPM are that the slip rings on the rotor are cast off and it can achieve the efficiency improvement and higher power density. The effects of the claw-pole structure parameters, the air-gap length, and the PM thinner parameter of the proposed CPM on the output torque are investigated by using three-dimensional time-stepping finite element method (3D TS-FEM). The optimal rotor structure of the proposed CPM is obtained by using the response surface methodology (RSM) and the particle swarm optimization (PSO) method and the comparison of full-load performances of the proposed CPM with different material cores (SMC and silicon steel) is analyzed. Full article
Open AccessArticle
Open Source Laser Polymer Welding System: Design and Characterization of Linear Low-Density Polyethylene Multilayer Welds
Machines 2016, 4(3), 14; doi:10.3390/machines4030014 -
Abstract
The use of lasers to weld polymer sheets provides a means of highly-adaptive and custom additive manufacturing for a wide array of industrial, medical, and end user/consumer applications. This paper provides an open source design for a laser polymer welding system, which [...] Read more.
The use of lasers to weld polymer sheets provides a means of highly-adaptive and custom additive manufacturing for a wide array of industrial, medical, and end user/consumer applications. This paper provides an open source design for a laser polymer welding system, which can be fabricated with low-cost fused filament fabrication and off-the-shelf mechanical and electrical parts. The system is controlled with free and open source software and firmware. The operation of the machine is validated and the performance of the system is quantified for the mechanical properties (peak load) and weld width of linear low density polyethylene (LLDPE) lap welds manufactured with the system as a function of linear energy density. The results provide incident laser power and machine parameters that enable both dual (two layers) and multilayer (three layers while welding only two sheets) polymer welded systems. The application of these parameter sets provides users of the open source laser polymer welder with the fundamental requirements to produce mechanically stable LLDPE multi-layer welded products, such as heat exchangers. Full article
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Open AccessArticle
Software Architecture and Framework for Programmable Logic Controllers: A Case Study and Suggestions for Research
Machines 2016, 4(2), 13; doi:10.3390/machines4020013 -
Abstract
Programmable Logic Controllers (PLCs) are widely used for control and automation of machines and processes, so the quality of PLC software has a direct impact on production efficiency. This paper describes a PLC program for a food production line that was completely [...] Read more.
Programmable Logic Controllers (PLCs) are widely used for control and automation of machines and processes, so the quality of PLC software has a direct impact on production efficiency. This paper describes a PLC program for a food production line that was completely rewritten using a different software architecture and framework. The PLC hardware and the production line equipment were not changed, so this project provides an opportunity to quantify the impact of different PLC software architecture on production efficiency. The average number of cases of products produced per production hour during the first ten months with the new program was 6.1% higher than the average during the previous ten months with the old program. PLC software, unlike most other software, is often used by the end-user for troubleshooting. In this case, a relatively simple architecture and framework that favors the end-user significantly improved production efficiency over a more sophisticated architecture and framework that favors the software developer. Suggestions for further research on software architecture and framework are given. Full article
Open AccessArticle
Z-Damper: A New Paradigm for Attenuation of Vibrations
Machines 2016, 4(2), 12; doi:10.3390/machines4020012 -
Abstract
Magnetic linear gear provides a new and unique opportunity for coupling mechanical impedances and optimizing vibration damping. In the present paper a new magneto-mechanical vibration damper (the so-called Z-damper) is described. Its expected theoretical dynamic behavior shows a particularly high damping capability, [...] Read more.
Magnetic linear gear provides a new and unique opportunity for coupling mechanical impedances and optimizing vibration damping. In the present paper a new magneto-mechanical vibration damper (the so-called Z-damper) is described. Its expected theoretical dynamic behavior shows a particularly high damping capability, a low frequency, as well as an optimal behavior for high frequencies. Full article
Open AccessArticle
Performance Evaluation of a Prototyped Breadfruit Seed Dehulling Machine
Machines 2016, 4(2), 11; doi:10.3390/machines4020011 -
Abstract
The drudgery involved in dehulling breadfruit seed by traditional methods has been highlighted as one of the major problems hindering the realization of the full potential of breadfruit as a field to food material. This paper describes a development in an African [...] Read more.
The drudgery involved in dehulling breadfruit seed by traditional methods has been highlighted as one of the major problems hindering the realization of the full potential of breadfruit as a field to food material. This paper describes a development in an African breadfruit seed dehulling machine with increased throughput of about 70% above reported machines. The machine consists of a 20 mm diameter shaft, carrying a spiral wound around its circumference (feeder). The feeder provides the required rotational motion and turns a circular disk that rotates against a fixed disk. The two disks can be adjusted to maintain a pre-determined gap for dehulling. An inbuilt drying unit reduces the moisture content of the breadfruit for easy separation of the cotyledon from the endosperm immediately after the dehulling process. The sifting unit that separates the shell from the seed is achieved in this design with an electric fan. The machine is design to run at a speed of 250 rpm with an electric motor as the prime mover. The dehulling efficiency up to 86% and breakage of less than 1.3% was obtained at a clearance setting of 12.4 mm between disks. A sifting efficiency of 100% was achieved. Based on the design diameter and clearance between the dehulling disks, the machine throughput was 216 kg/h with an electric power requirement of 1.207 kW. Full article
Open AccessArticle
A Novel Modelling Approach for Condensing Boilers Based on Hybrid Dynamical Systems
Machines 2016, 4(2), 10; doi:10.3390/machines4020010 -
Abstract
Condensing boilers use waste heat from flue gases to pre-heat cold water entering the boiler. Flue gases are condensed into liquid form, thus recovering their latent heat of vaporization, which results in as much as 10%–12% increase in efficiency. Modeling these heat [...] Read more.
Condensing boilers use waste heat from flue gases to pre-heat cold water entering the boiler. Flue gases are condensed into liquid form, thus recovering their latent heat of vaporization, which results in as much as 10%–12% increase in efficiency. Modeling these heat transfer phenomena is crucial to control this equipment. Despite the many approaches to the condensing boiler modeling, the following shortcomings are still not addressed: thermal dynamics are oversimplified with a nonlinear efficiency curve (which is calculated at steady-state); the dry/wet heat exchange is modeled in a fixed proportion. In this work we cover these shortcomings by developing a novel hybrid dynamic model which avoids the static nonlinear efficiency curve and accounts for a time-varying proportion of dry/wet heat exchange. The procedure for deriving the model is described and the efficiency of the resulting condensing boiler is shown. Full article
Open AccessArticle
One-Dimensional Haptic Rendering Using Audio Speaker with Displacement Determined by Inductance
Machines 2016, 4(1), 9; doi:10.3390/machines4010009 -
Abstract
We report overall design considerations and preliminary results for a new haptic rendering device based on an audio loudspeaker. Our application models tissue properties during microsurgery. For example, the device could respond to the tip of a tool by simulating a particular [...] Read more.
We report overall design considerations and preliminary results for a new haptic rendering device based on an audio loudspeaker. Our application models tissue properties during microsurgery. For example, the device could respond to the tip of a tool by simulating a particular tissue, displaying a desired compressibility and viscosity, giving way as the tissue is disrupted, or exhibiting independent motion, such as that caused by pulsations in blood pressure. Although limited to one degree of freedom and with a relatively small range of displacement compared to other available haptic rendering devices, our design exhibits high bandwidth, low friction, low hysteresis, and low mass. These features are consistent with modeling interactions with delicate tissues during microsurgery. In addition, our haptic rendering device is designed to be simple and inexpensive to manufacture, in part through an innovative method of measuring displacement by existing variations in the speaker’s inductance as the voice coil moves over the permanent magnet. Low latency and jitter are achieved by running the real-time simulation models on a dedicated microprocessor, while maintaining bidirectional communication with a standard laptop computer for user controls and data logging. Full article
Open AccessArticle
Design and Analysis of a Haptic Device Design for Large and Fast Movements
Machines 2016, 4(1), 8; doi:10.3390/machines4010008 -
Abstract
Haptic devices tend to be kept small as it is easier to achieve a large change of stiffness with a low associated apparent mass. If large movements are required there is a usually a reduction in the quality of the haptic sensations [...] Read more.
Haptic devices tend to be kept small as it is easier to achieve a large change of stiffness with a low associated apparent mass. If large movements are required there is a usually a reduction in the quality of the haptic sensations which can be displayed. The typical measure of haptic device performance is impedance-width (z-width) but this does not account for actuator saturation, usable workspace or the ability to do rapid movements. This paper presents the analysis and evaluation of a haptic device design, utilizing a variant of redundant kinematics, sometimes referred to as a macro-micro configuration, intended to allow large and fast movements without loss of impedance-width. A brief mathematical analysis of the design constraints is given and a prototype system is described where the effects of different elements of the control scheme can be examined to better understand the potential benefits and trade-offs in the design. Finally, the performance of the system is evaluated using a Fitts’ Law test and found to compare favourably with similar evaluations of smaller workspace devices. Full article
Open AccessArticle
Algorithms for Optimal Model Distributions in Adaptive Switching Control Schemes
Machines 2016, 4(1), 7; doi:10.3390/machines4010007 -
Abstract
Several multiple model adaptive control architectures have been proposed in the literature. Despite many advances in theory, the crucial question of how to synthesize the pairs model/controller in a structurally optimal way is to a large extent not addressed. In particular, it [...] Read more.
Several multiple model adaptive control architectures have been proposed in the literature. Despite many advances in theory, the crucial question of how to synthesize the pairs model/controller in a structurally optimal way is to a large extent not addressed. In particular, it is not clear how to place the pairs model/controller is such a way that the properties of the switching algorithm (e.g., number of switches, learning transient, final performance) are optimal with respect to some criteria. In this work, we focus on the so-called multi-model unfalsified adaptive supervisory switching control (MUASSC) scheme; we define a suitable structural optimality criterion and develop algorithms for synthesizing the pairs model/controller in such a way that they are optimal with respect to the structural optimality criterion we defined. The peculiarity of the proposed optimality criterion and algorithms is that the optimization is carried out so as to optimize the entire behavior of the adaptive algorithm, i.e., both the learning transient and the steady-state response. A comparison is made with respect to the model distribution of the robust multiple model adaptive control (RMMAC), where the optimization considers only the steady-state ideal response and neglects any learning transient. Full article
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Open AccessArticle
Bidirectional Haptic Communication: Application to the Teaching and Improvement of Handwriting Capabilities
Machines 2016, 4(1), 6; doi:10.3390/machines4010006 -
Abstract
The objective of this work is to study the relevance of haptic feedback in remote communication between people. The application is handwriting. A haptic device designed to help people to improve their writing skills is presented. Two experimental sessions are then proposed [...] Read more.
The objective of this work is to study the relevance of haptic feedback in remote communication between people. The application is handwriting. A haptic device designed to help people to improve their writing skills is presented. Two experimental sessions are then proposed to a group of people. In the first test, two subjects communicate through a bilateral system by means of a haptic feedback to accomplish the task. Secondly, a blank test is performed. The results of the two tests are compared and analyzed in order to evaluate the importance of the haptic feedback in the context of collaboration between two people. Full article
Open AccessArticle
Joint Mechanism That Mimics Elastic Characteristics in Human Running
Machines 2016, 4(1), 5; doi:10.3390/machines4010005 -
Abstract
Analysis of human running has revealed that the motion of the human leg can be modeled by a compression spring because the joints of the leg behave like a torsion spring in the stance phase. In this paper, we describe the development [...] Read more.
Analysis of human running has revealed that the motion of the human leg can be modeled by a compression spring because the joints of the leg behave like a torsion spring in the stance phase. In this paper, we describe the development of a joint mechanism that mimics the elastic characteristics of the joints of the stance leg. The knee was equipped with a mechanism comprising two laminated leaf springs made of carbon fiber-reinforced plastic for adjusting the joint stiffness and a worm gear in order to achieve active movement. Using this mechanism, we were able to achieve joint stiffness mimicking that of a human knee joint that can be adjusted by varying the effective length of one of the laminated leaf springs. The equation proposed for calculating the joint stiffness considers the difference between the position of the fixed point of the leaf spring and the position of the rotational center of the joint. We evaluated the performance of the laminated leaf spring and the effectiveness of the proposed equation for joint stiffness. We were able to make a bipedal robot run with one leg using pelvic oscillation for storing energy produced by the resonance related to leg elasticity. Full article
Open AccessArticle
Dynamic Contact between a Wire Rope and a Pulley Using Absolute Nodal Coordinate Formulation
Machines 2016, 4(1), 4; doi:10.3390/machines4010004 -
Abstract
Wire rope and pulley devices are used in various machines. To use these machines more safely, it is necessary to analyze the behavior of the contact between them. In this study, we represent a wire rope by a numerical model of a [...] Read more.
Wire rope and pulley devices are used in various machines. To use these machines more safely, it is necessary to analyze the behavior of the contact between them. In this study, we represent a wire rope by a numerical model of a flexible body. This flexible body is expressed in the absolute nodal coordinate formulation (ANCF), and the model includes the normal contact force and the frictional force between the wire rope and the pulley. The normal contact force is expressed by spring-damper elements, and the frictional force is expressed by the Quinn method. The advantage of the Quinn method is that it reduces the numerical problems associated with the discontinuities in Coulomb friction at zero velocity. By using the numerical model, simulations are performed, and the validity of this model is shown by comparing its results with those of an experiment. Through numerical simulations, we confirm the proposed model for the contact between the wire rope and the pulley. We confirmed that the behavior of the wire rope changes when both the bending elastic modulus of the wire rope and the mass added to each end of the wire rope are changed. Full article
Open AccessArticle
High-Efficiency Solar-Powered 3-D Printers for Sustainable Development
Machines 2016, 4(1), 3; doi:10.3390/machines4010003 -
Abstract
The release of the open source 3-D printer known as the RepRap (a self-Replicating Rapid prototyper) resulted in the potential for distributed manufacturing of products for significantly lower costs than conventional manufacturing. This development, coupled with open source-appropriate technology [...] Read more.
The release of the open source 3-D printer known as the RepRap (a self-Replicating Rapid prototyper) resulted in the potential for distributed manufacturing of products for significantly lower costs than conventional manufacturing. This development, coupled with open source-appropriate technology (OSAT), has enabled the opportunity for 3-D printers to be used for sustainable development. In this context, OSAT provides the opportunity to modify and improve the physical designs of their printers and desired digitally-shared objects. However, these 3-D printers require electricity while more than a billion people still lack electricity. To enable the utilization of RepRaps in off-grid communities, solar photovoltaic (PV)-powered mobile systems have been developed, but recent improvements in novel delta-style 3-D printer designs allows for reduced costs and improved performance. This study builds on these innovations to develop and experimentally validate a mobile solar-PV-powered delta 3-D printer system. It is designed to run the RepRap 3-D printer regardless of solar flux. The electrical system design is tested outdoors for operating conditions: (1) PV charging battery and running 3-D printer; (2) printing under low insolation; (3) battery powering the 3-D printer alone; (4) PV charging the battery only; and (5) battery fully charged with PV-powered 3-D printing. The results show the system performed as required under all conditions providing feasibility for adoption in off-grid rural communities. 3-D printers powered by affordable mobile PV solar systems have a great potential to reduce poverty through employment creation, as well as ensuring a constant supply of scarce products for isolated communities. Full article
Open AccessFeature PaperArticle
Concentrated Windings in Compact Permanent Magnet Synchronous Generators: Managing Efficiency
Machines 2016, 4(1), 2; doi:10.3390/machines4010002 -
Abstract
In electric power generation, customers want generators with high efficiency. Nowadays, modern turbo-generators have efficiencies greater than 98%. Although this amount should not be obtained for all kind of machines, efficiency will remain one of the main parameters for customer choice. Efficiency [...] Read more.
In electric power generation, customers want generators with high efficiency. Nowadays, modern turbo-generators have efficiencies greater than 98%. Although this amount should not be obtained for all kind of machines, efficiency will remain one of the main parameters for customer choice. Efficiency is also linked to the life of the machine: the higher the efficiency is, the longer the machine’s lifetime. During the past decade, new forms of energy production have appeared and generators have been developed to fit well into this market. For example, wind generators evolved towards permanent magnet generators having high polarity and running at low speed. Nevertheless, their structure is not fixed. An industrial company has built a prototype of such a generator which uses fractional-slot concentrated-windings (FSCW). This kind of winding is not the structure used by default in such electrical machines. Another field of interest is in autonomous generators which can be used on boats. Even if everyone has in mind large merchant ships, we must not forget smaller ships, such as fishing boats and short-range cruise ships, which spend the most of their time near the coast. This kind of ship does nothave large areas for installing the electric generation or the electric propulsion. It is the reason why, in this article, we focus on the efficiency of machines using fractional-slot concentrated-windings. In many publications which compare performances between distributed and concentrated windings, the result is almost the same. The efficiency of FSCW is not as high as the efficiency associated to the machines which are using distributed windings. Design methods have to be redrawn to integrate, as soon as possible, the loss mitigation in order to provide the best efficiency in power conversion. The following discussion, step by step, introduces the loss mitigation in every part of a machine using FSCW. To close the discussion, a design is produced and it appears that efficiency can be enhanced with suitable design methods. Full article
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Open AccessArticle
A Novel Design for Adjustable Stiffness Artificial Tendon for the Ankle Joint of a Bipedal Robot: Modeling & Simulation
Machines 2016, 4(1), 1; doi:10.3390/machines4010001 -
Abstract
Bipedal humanoid robots are expected to play a major role in the future. Performing bipedal locomotion requires high energy due to the high torque that needs to be provided by its legs’ joints. Taking the WABIAN-2R as an example, it uses harmonic [...] Read more.
Bipedal humanoid robots are expected to play a major role in the future. Performing bipedal locomotion requires high energy due to the high torque that needs to be provided by its legs’ joints. Taking the WABIAN-2R as an example, it uses harmonic gears in its joint to increase the torque. However, using such a mechanism increases the weight of the legs and therefore increases energy consumption. Therefore, the idea of developing a mechanism with adjustable stiffness to be connected to the leg joint is introduced here. The proposed mechanism would have the ability to provide passive and active motion. The mechanism would be attached to the ankle pitch joint as an artificial tendon. Using computer simulations, the dynamical performance of the mechanism is analytically evaluated. Full article
Open AccessArticle
Trends and Potential of the Market for Combine Harvesters in Germany
Machines 2015, 3(4), 364-378; doi:10.3390/machines3040364 -
Abstract
Combine harvesters used today can achieve throughput rates of over 70 tons of grain per hour; however, their technical performance potential is currently not being exhausted by any means. The global market for combine harvesters, its stocks and recent production is described. [...] Read more.
Combine harvesters used today can achieve throughput rates of over 70 tons of grain per hour; however, their technical performance potential is currently not being exhausted by any means. The global market for combine harvesters, its stocks and recent production is described. According to farm size distribution and regional field sizes, Germany was divided into three combine-harvesting regions. The simulation results show that in Germany about 45,000 units of combine harvesters in three performance categories are necessary. However, the calculations also show that future domestic sales of combine harvesters will depend greatly on the service life of the units currently in use. Full article
Open AccessArticle
Double Lighting Machine Vision System to Monitor Harvested Paddy Grain Quality during Head-Feeding Combine Harvester Operation
Machines 2015, 3(4), 352-363; doi:10.3390/machines3040352 -
Abstract
A machine vision system to evaluate harvested paddy grain quality during harvesting using double lighting was developed. The prototype consisted of a low-cost web camera and two lighting systems: a ring white LED for front lighting, and a flat dome white LED [...] Read more.
A machine vision system to evaluate harvested paddy grain quality during harvesting using double lighting was developed. The prototype consisted of a low-cost web camera and two lighting systems: a ring white LED for front lighting, and a flat dome white LED light for backlighting. Both lighting systems were arranged in a coaxial axis, making the system simple, compact and easy to handle. The aim of the system is to analyse the captured images and determine the amount of unwanted materials (rachis branch, grass and leaves, and stems) and damaged grain (brown and crack rice) present in the paddy as it is being harvested. In this paper, we introduce the first step in the development of the system: the design and selection of components to optimize the performance of the system to monitor harvested paddy grain quality. The idea would be to mount the system on top of the inlet channel of the grain tank of a combine harvester to provide real-time assessment of harvesting operational parameters. Full article
Open AccessArticle
Integrated Voltage—Current Monitoring and Control of Gas Metal Arc Weld Magnetic Ball-Jointed Open Source 3-D Printer
Machines 2015, 3(4), 339-351; doi:10.3390/machines3040339 -
Abstract
To provide process optimization of metal fabricating self-replicating rapid prototyper (RepRap) 3-D printers requires a low-cost sensor and data logger system to measure current (I) and voltage (V) of the gas metal arc welders (GMAW). This paper builds on previous open-source hardware [...] Read more.
To provide process optimization of metal fabricating self-replicating rapid prototyper (RepRap) 3-D printers requires a low-cost sensor and data logger system to measure current (I) and voltage (V) of the gas metal arc welders (GMAW). This paper builds on previous open-source hardware development to provide a real-time measurement of welder I-V where the measuring circuit is connected to two analog inputs of the Arduino that is used to control the 3-D printer itself. Franklin firmware accessed through a web interface that is used to control the printer allows storing the measured values and downloading those stored readings to the user’s computer. To test this custom current and voltage monitoring device this study reports on its use on an upgraded all metal RepRap during the printing of aluminum alloy (ER1100, ER4043, ER4943, ER4047, and ER5356). The voltage and current data were analyzed on a per alloy basis and also layer-by-layer in order to evaluate the device’s efficacy as a monitoring device for 3-D printing and the results of the integrated design are discussed. Full article
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