4,974 research outputs found

    To develop an efficient variable speed compressor motor system

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    This research presents a proposed new method of improving the energy efficiency of a Variable Speed Drive (VSD) for induction motors. The principles of VSD are reviewed with emphasis on the efficiency and power losses associated with the operation of the variable speed compressor motor drive, particularly at low speed operation.The efficiency of induction motor when operated at rated speed and load torque is high. However at low load operation, application of the induction motor at rated flux will cause the iron losses to increase excessively, hence its efficiency will reduce dramatically. To improve this efficiency, it is essential to obtain the flux level that minimizes the total motor losses. This technique is known as an efficiency or energy optimization control method. In practice, typical of the compressor load does not require high dynamic response, therefore improvement of the efficiency optimization control that is proposed in this research is based on scalar control model.In this research, development of a new neural network controller for efficiency optimization control is proposed. The controller is designed to generate both voltage and frequency reference signals imultaneously. To achieve a robust controller from variation of motor parameters, a real-time or on-line learning algorithm based on a second order optimization Levenberg-Marquardt is employed. The simulation of the proposed controller for variable speed compressor is presented. The results obtained clearly show that the efficiency at low speed is significant increased. Besides that the speed of the motor can be maintained. Furthermore, the controller is also robust to the motor parameters variation. The simulation results are also verified by experiment

    A lightweight, high strength dexterous manipulator for commercial applications

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    The concept, design, and features are described of a lightweight, high strength, modular robot manipulator being developed for space and commercial applications. The manipulator has seven fully active degrees of freedom and is fully operational in 1 G. Each of the seven joints incorporates a unique drivetrain design which provides zero backlash operation, is insensitive to wear, and is single fault tolerant to motor or servo amplifier failure. Feedback sensors provide position, velocity, torque, and motor winding temperature information at each joint. This sensing system is also designed to be single fault tolerant. The manipulator consists of five modules (not including gripper). These modules join via simple quick-disconnect couplings and self-mating connectors which allow rapid assembly and/or disassembly for reconfiguration, transport, or servicing. The manipulator is a completely enclosed assembly, with no exposed components or wires. Although the initial prototype will not be space qualified, the design is well suited to meeting space requirements. The control system provides dexterous motion by controlling the endpoint location and arm pose simultaneously. Potential applications are discussed

    Wheel Design and Tension Analysis for the Tethered Axel Rover on Extreme Terrain

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    As the Mars Exploration rovers have reaffirmed, some of the most interesting sites for scientists to explore on planetary surfaces lie in terrains that are currently inaccessible to state-of-the art rovers. We have been developing the Axel rover as a robotic platform to access steep and challenging terrain. We will summarize the recent mechanical upgrades since we introduced the tethered Axel concept last year

    A holistic integrated dynamic design and modelling approach applied to the development of ultraprecision micro-milling machines

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    Ultraprecision machines with small footprints or micro-machines are highly desirable for micro-manufacturing high-precision micro-mechanical components. However, the development of the machines is still at the nascent stage by working on an individual machine basis and hence lacks generic scientific approach and design guidelines. Using computer models to predict the dynamic performance of ultraprecision machine tools can help manufacturers substantially reduce the lead time and cost of developing new machines. Furthermore, the machine dynamic performance depends not only upon the mechanical structure and components but also the control system and electronic drives. This paper proposed a holistic integrated dynamic design and modelling approach, which supports analysis and optimization of the overall machine dynamic performance at the early design stage. Based on the proposed approach the modelling and simulation process on a novel 5-axis bench-top ultraprecision micro-milling machine tool – UltraMill – is presented. The modelling and simulation cover the dynamics of the machine structure, moving components, control system and the machining process, and are used to predict the overall machine performance of two typical configurations. Preliminary machining trials have been carried out and provided the evidence of the approach being helpful to assure the machine performing right at the first setup

    An Ontology-Based Expert System for the Systematic Design of Humanoid Robots

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    Die Entwicklung humanoider Roboter ist eine zeitaufwendige, komplexe und herausfordernde Aufgabe. Daher stellt diese Thesis einen neuen, systematischen Ansatz vor, der es erlaubt, Expertenwissen zum Entwurf humanoider Roboter zu konservieren, um damit zukünftige Entwicklungen zu unterstützen. Der Ansatz kann in drei aufeinanderfolgende Schritte unterteilt werden. Im ersten Schritt wird Wissen zum Entwurf humanoider Roboter durch die Entwicklung von Roboterkomponenten und die Analyse verwandter Arbeiten gewonnen. Dieses Wissen wird im zweiten Schritt formalisiert und in Form einer ontologischen Wissensbasis gespeichert. Im letzten Schritt wird diese Wissensbasis von einem Expertensystem verwendet, um Lösungsvorschläge zum Entwurf von Roboterkomponenten auf Grundlage von Benutzeranforderungen zu generieren. Der Ansatz wird anhand von Fallstudien zu Komponenten des humanoiden Roboters ARMAR-6 evaluiert: Sensor-Aktor-Controller-Einheiten für Robotergelenke und Roboterhände

    Advances in the Field of Electrical Machines and Drives

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    Electrical machines and drives dominate our everyday lives. This is due to their numerous applications in industry, power production, home appliances, and transportation systems such as electric and hybrid electric vehicles, ships, and aircrafts. Their development follows rapid advances in science, engineering, and technology. Researchers around the world are extensively investigating electrical machines and drives because of their reliability, efficiency, performance, and fault-tolerant structure. In particular, there is a focus on the importance of utilizing these new trends in technology for energy saving and reducing greenhouse gas emissions. This Special Issue will provide the platform for researchers to present their recent work on advances in the field of electrical machines and drives, including special machines and their applications; new materials, including the insulation of electrical machines; new trends in diagnostics and condition monitoring; power electronics, control schemes, and algorithms for electrical drives; new topologies; and innovative applications

    Mechatronics Design Process with Energy Optimization for Industrial Machines

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    The need for designing industrial machines with higher energy efficiency, reliability, flexibility, and accuracy has increased to satisfy market demand for higher productivity at reduced costs in a sustainable manner. As machines become more complex, model-based design is essential to overcome the challenges in mechatronic system design. However, a well-designed mechanical system with a well-designed and tuned control system are not sufficient for machines to operate at high-performance conditions; this also heavily depends on trajectory planning and the appropriate selection of the motors controlling the axes of the machine. In this work, a model-based design approach to properly select motors for single-axes or multi-axes coordinated systems was proposed. Additionally, a trajectory planning approach was also proposed to improve performance of industrial machines. The proposed motor selection process and trajectory planning approach were demonstrated via modeling, simulation, and experimental validation for three systems: two-inertia system, planar robot, and self-balancing transporter. Over 25% of the electric energy delivered in the U.S. in 2013 was used in the industrial sector according to the U.S. Energy Information Administration, with an estimated efficiency of 80% according to the Lawrence Livermore National Laboratory. This entails major responsibility by the industry to utilize energy efficiently and promote sustainable energy usage. To help improve the energy efficiency in the industrial sector, a novel method to optimize the energy of single-axis and multi-axis coordinated systems of industrial machines was developed. Based on trajectory boundaries and the kinetic model of the mechanism and motors, this proposed energy optimization method performs iterations to recalculate the shape of the motion profile for each motor of the system being optimized until it converges to a motion profile with optimal energy cost and within these boundaries. This method was validated by comparing the energy consumption of those three systems while commanded by the optimized motion profile and then by motion profiles typically used in industrial applications. The energy saved was between 5% and 10%. The implementation cost of this method in industrial systems resides in machine-code changes; no physical changes are needed

    Cycloidal Rotor Systems

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    Improved transistor-controlled and commutated brushless DC motors for electric vehicle propulsion

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    The development, design, construction, and testing processes of two electronically (transistor) controlled and commutated permanent magnet brushless dc machine systems, for propulsion of electric vehicles are detailed. One machine system was designed and constructed using samarium cobalt for permanent magnets, which supply the rotor (field) excitation. Meanwhile, the other machine system was designed and constructed with strontium ferrite permanent magnets as the source of rotor (field) excitation. These machine systems were designed for continuous rated power output of 15 hp (11.2 kw), and a peak one minute rated power output of 35 hp (26.1 kw). Both power ratings are for a rated voltage of 115 volts dc, assuming a voltage drop in the source (battery) of about 5 volts. That is, an internal source voltage of 120 volts dc. Machine-power conditioner system computer-aided simulations were used extensively in the design process. These simulations relied heavily on the magnetic field analysis in these machines using the method of finite elements, as well as methods of modeling of the machine power conditioner system dynamic interaction. These simulation processes are detailed. Testing revealed that typical machine system efficiencies at 15 hp (11.2 kw) were about 88% and 84% for the samarium cobalt and strontium ferrite based machine systems, respectively. Both systems met the peak one minute rating of 35 hp

    Design of high-power ultra-high-speed permanent magnet machine

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    The demand for ultra-high-speed machines (UHSM) is rapidly growing in high-tech industries due to their attractive features. A-mechanically-based-antenna (AMEBA) system is another emerging application of UHSM. It enables portable wireless communication in the radio frequency (RF)-denied environment, which was not possible until recently. The AMEBA system requires a high-power (HP) UHSM for its effective communication performance. However, at the expected rotational speed range of 0.5 to 1 million rpm, the power level of UHSM is limited, and no research effort has succeeded to improve the power level of UHSM. The design of HP-UHSM is highly iterative, and it presents several critical challenges, unlike low-power UHSM, such as critical-bending-resonance (CBR), strong mutual influence among Multiphysics performances, exponential air-friction loss, and material limitation. When the magnetic loading of the UHSM rotor is increased to improve the power level, the rotor experiences serious mechanical vibration due to the excessive centrifugal forces and CBR. This vibration limits the operation of HP-UHSM and leads to structural breakdown. Furthermore, the design process becomes more critical when it considers the multidisciplinary design constraints and application requirements. This dissertation proposed a new Multiphysics design method to develop HP-UHSM for critical applications. First, the critical design constraints which prevent increasing the output power of UHSM are investigated. Then, a Multiphysics optimization model is developed by coupling several multidisciplinary analysis modules. This proposed optimization model enables (i) defining multidisciplinary design constraints, (ii) consideration of Multiphysics mutual influence, and (iii) a trade-off analysis between the efficiency and design-safety-margin. The proposed design model adopts the multiphase winding system to effectively increase the electrical loading in the slotless stator. Finally, a 2000 W 500,000 rpm HP-UHSM is optimized for an AMEBA system using the proposed design method. The optimized 2 kW 500,000 rpm machine prototype and its dynamo setup are built in the laboratory. Extensive finite element simulations and experimental testing results are presented to validate the effectiveness of the proposed design method. The results show that the proposed HP-USHM has 94.5% efficiency, 47 kW/L power density, 30% global design safety margin at the maximum speed and no CBR frequency below 11 kHz
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