576 research outputs found

    Design, Fabrication, and Testing of a Capsule With Hybrid Locomotion for Gastrointestinal Tract Exploration

    Get PDF
    Abstract—This paper describes a novel solution for the active lo-comotion of a miniaturized endoscopic capsule in the gastrointesti-nal (GI) tract. The authors present the design, development, and testing of a wireless endocapsule with hybrid locomotion, where hybrid locomotion is defined as the combination between internal actuation mechanisms and external magnetic dragging. The cap-sule incorporates an internal actuating legged mechanism, which modifies the capsule profile, and small permanent magnets, which interact with an external magnetic field, thus imparting a dragging motion to the device. The legged mechanism is actuated whenever the capsule gets lodged in collapsed areas of the GI tract. This allows modification of the capsule profile and enables magnetic dragging to become feasible and effective once again. A key com-ponent of the endoscopic pill is the internal mechanism, endowed with a miniaturized brushless motor and featuring compact design, and adequate mechanical performance. The internal mechanism is able to generate a substantial force, which allows the legs to open against the intestinal tissue that has collapsed around the capsule body. An accurate simulation of the performance of the minia-turized motor under magnetic fields was carried out in order to define the best configuration of the internal permanent magnets (which are located very close to the motor) and the best tradeoff operating distance for the external magnet, which is responsible for magnetically dragging the capsule. Finally, a hybrid capsule was developed generating 3.8 N at the tip of the legged mechanism and a magnetic link force up to 135 mN. The hybrid capsule and its wireless control were extensively tested in vitro, ex vivo, and in vivo, thus confirming fulfilment of the design specifications and demon-strating a good ability to manage collapsed areas of the intestinal tract. Index Terms—Capsule endoscopy, endoscopic capsule, magnetic locomotion, robotic surgery. I

    Flux switching machine design for high-speed geared drives

    Get PDF
    Electrical machines capable of high-speed operation are key technology used in many modern applications, such as gas turbine electrical systems, high-speed fly-wheels, turbochargers, and computer numerical control (CNC) machines. The use of geared high-speed machines to replace low-speed high torque drives has not been adequately researched to-date. The rationale of this thesis is to investigate a candidate high speed machine, namely flux switching machines to be used together with new types of core material with mechanical gearing to deliver high-torque and low speeds. Modern developments in advanced material technology have produced new magnetic materials capable of dealing with high resulting in very low losses in high speed machines. However, such metals typically have low mechanical strength, and they are found to be brittle. In order to manufacture electromechanical device with such new materials, it has to be reinforced with a mechanically strong structure. The use of multiple types of magnetic materials referred as a MMLC has been proposed in this thesis for high-speed machine design. In this research, a generic method using magnetic equivalent circuit to model flux switching machines (FSMs) is investigated. Moreover modeling, based on machine dimensions for multiphase FSMs having any pole and slot number has been introduced. The air-gap permeance modeling to simplify the magnetic circuit calculation of FSMs was also investigated in this thesis. It is shown that the permeability of magnetic material can be adjusted with the use of MMLC material. Using this feature, the FSM mathematical model is used to show the impact on electromagnetic performance using MMLCs and is shown to be beneficial. In order the evaluate the weight benefits of using geared high speed FSMs, the planetary gear systems are studies and their design constraints have been identified. An abstract form of weight estimation for given torque and speed requirements has been developed and validated using commercially available planetary gear specifications. FSMs together with gear boxes have been considered and it is shown that significant weight savings can be achieved at higher diameter and at high speeds

    Design And Performance Evaluation Of An Integrated Miniature Single Stage Centrifugal Compressor And Permanent Magnet Synchronous Motor

    Get PDF
    An attempt has been made in this present work to design, fabricate and performance evaluate an integrated single stage centrifugal compressor and permanent magnet synchronous motor which is a key component of the reverse brayton cycle cryocooler. An off the shelf compressor – the driven and electric motor – the driver was not available commercially to suffice the requirements of the reverse brayton cryocooler. The integrated compressor-motor system was designed and tested with air as the working fluid at mass flow rate of 7.3 grams per sec, with a compression ratio of 1.58 and driven by a 2 KW permanent magnet synchronous motor at a design speed of 108,000 rpm. A permanent magnet synchronous motor rotor was designed to operate to operate over 200,000 rpm at 77 Kelvin temperature. It involved iterative processes involving structural, thermal and rotordynamic analysis of the rotor. Selection of high speed ceramic ball bearings, their mounting, fit and pre-load played prominent role. Attempts were made to resolve misalignment issues for the compressor – motor system, which had severe impact on the rotordynamic performance of the system and therefore losses at high speeds [15], [16]. A custom designed flexible coupler was designed and fabricated to run the compressor – motor system. An integrated compressor – motor system was an innovative design to resolve considerably several factors which hinder a high operational speed. Elimination of the coupler, reduction of number of bearings in the system and usage of fewer components on the rotor to increase the stiffness were distinct features of the integrated system. Several custom designed test-rigs were built which involved precision translation stages and angle brackets. Motor control software, an emulator, a DSP and a custom designed motor controller was assembled to run the motor. A cooling system was specially designed to cool the stator – rotor system. A pre-loading structure was fabricated to adequately pre-load the bearings. Flow measurement instruments such as mass flow meter, pressure transducers and thermocouples were used at several locations on the test rig to monitor the flow. An adjustable inlet guide vane was designed to control the tip clearance of the impeller

    Automated Design Optimization of Synchronous Machines: Development and Application of a Generic Fitness Evaluation Framework

    Get PDF
    A rotating synchronous electric machine design can be described to its entirety by a combination of 17 to 24 discrete and continuous parameters pertaining the geometry, material selection, and electrical loading. Determining the performance attributes of a design often involves numerical solutions to thermal and magnetic equations. Stochastic optimization methods have proven effective for solving specific design problems in literature. A major challenge to design automation, however, is whether the design tool is versatile enough to solve design problems with different types of objectives and requirements. This work proposes a black-box approach in an attempt to encompass a wide variety of synchronous machine design problems. This approach attempts to enlist all possible attributes of interest (AoIs) to the end-user so that the design optimization problem can be framed by combination of such attributes only. The number of ways the end-user can input requirements is now defined and limited. Design problems are classified based on which of the AoI’s are constraints, objectives or design parameters. It is observed that regardless of the optimization problem definition, the evaluation of any design is based on a common set of physical and analytical models and empirical data. Problem definitions are derived based on black-box approach and efficient fitness evaluation algorithms are tailored to meet requirements of each problem definition. The proposed framework is implemented in Matlab/C++ environment encompassing different aspects of motor design. The framework is employed for designing synchronous machines for three applications where designs based on conventional motor construction did not meet all design requirements. The first design problem is to develop a novel bar-conductor tooth-wound stator technology for 1.2 kW in-wheel direct drive motor for an electric/hybrid-electric two wheeler (including practical implementation). The second design problem deals with a novel outer-rotor buried ferrite magnet geometry for a 1.2 kW in-wheel geared motor drive used in an electric/hybrid-electric two wheeler (including practical implementation). The third application involves design of an ultra-cost-effective and ultra-light-weight 1 kW aluminum conductor motor. Thus, the efficacy of automated design is demonstrated by harnessing the framework and algorithms for exploring new technologies applicable for three distinct design problems originated from practical applications

    Design and Development of a Planetary Gearbox for Electromechanical Actuator Test Bench through Additive Manufacturing

    Get PDF
    The development and validation of prognostic algorithms and digital twins for Electromechanical Actuators (EMAs) requires datasets of operating parameters that are not commonly available. In this context, we are assembling a test bench able to simulate different operating scenarios and environmental conditions for an EMA in order to collect the operating parameters of the actuator both in nominal conditions and under the effect of incipient progressive faults. This paper presents the design and manufacturing of a planetary gearbox for the EMA test bench. Mechanical components were conceived making extensive use of Fused Deposition Modelling (FDM) additive manufacturing and off-the-shelf hardware in order to limit the costs and time involved in prototyping. Given the poor mechanical properties of the materials commonly employed for FDM, the gears were not sized for the maximum torque of the electric motor, and a secondary torque path was placed in parallel of the planetary gearbox to load the motor through a disc brake. The architecture of the gearbox allowed a high gear ratio within a small form factor, and a bearingless construction with a very low number of moving parts

    Comparative Analysis of Bearings for Micro-GT: An Innovative Arrangement

    Get PDF
    Microgas turbines are a widespread technology in cogenerative and propulsion applications. Bearings are a key factor in their design and development. The aim of the present research work is the development of the support system for a typical microturbine intended for power generation. To this goal, the present chapter defines the typical requirements of the machine and, afterward, describes the different technologies available to develop the support system of a reliable microturbine. Conventional (rolling element and oil-film) supports and cutting-edge (magnetic, aerodynamic, and aerostatic) bearings are reviewed. Particularly, their suitability to the operating conditions is compared by means of a literature review and elaboration of the relevant data. By analyzing all this information, a new concept for the design of a micro-GT support system is devised. Instead of using a single type of bearing as usual, the new system includes different types in order to take advantage of the best characteristics of each one and, simultaneously, to minimize the effects of the relevant flaws. The innovative support system requires a suitable bearing arrangement, which is compared with the conventional ones. The conceptual design of the innovation is completed by a discussion of its advantages, drawbacks, and prospective improvements

    Design of Machines and Structures 12.

    Get PDF

    Design of silent, miniature, high torque actuators

    Get PDF
    Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999.Includes bibliographical references (p. 132-139).by John HEnry Heyer, III.S.M

    Effect of granulometry and oxygen content on SMC magnetic properties

    Get PDF
    The interest around the adoption of Soft Magnetic Composite materials (SMC) in the realization of electric machines, or parts of electric machines, is continuously increasing. The main reason lies on the opportunity to realize magnetic circuits following a 3D design procedure, which is not allowed with the adoption of the traditional lamination sheets. This is not the only reason, as a lot of research is being carried out on the losses distribution in the magnetic material, particularly as function of the frequency. In this paper different iron powders have been analyzed to investigate the impact of the granulometry on the SMC performance; in particular the grain size and the oxygen content have been considered variable parameters. The materials, prepared, compacted and tested in our laboratories, have been characterized to obtain the magnetic characteristic and information about the iron losses
    • …
    corecore