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Machines, Volume 2, Issue 2 (June 2014), Pages 99-157

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Research

Open AccessArticle Fuzzy Pattern Classification Based Detection of Faulty Electronic Fuel Control (EFC) Valves Used in Diesel Engines
Machines 2014, 2(2), 99-119; doi:10.3390/machines2020099
Received: 19 January 2014 / Revised: 30 March 2014 / Accepted: 15 April 2014 / Published: 7 May 2014
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Abstract
In this paper, we develop mathematical models of a rotary Electronic Fuel Control (EFC) valve used in a Diesel engine based on dynamic performance test data and system identification methodology in order to detect the faulty EFC valves. The model takes into account
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In this paper, we develop mathematical models of a rotary Electronic Fuel Control (EFC) valve used in a Diesel engine based on dynamic performance test data and system identification methodology in order to detect the faulty EFC valves. The model takes into account the dynamics of the electrical and mechanical portions of the EFC valves. A recursive least squares (RLS) type system identification methodology has been utilized to determine the transfer functions of the different types of EFC valves that were investigated in this study. Both in frequency domain and time domain methods have been utilized for this purpose. Based on the characteristic patterns exhibited by the EFC valves, a fuzzy logic based pattern classification method was utilized to evaluate the residuals and identify faulty EFC valves from good ones. The developed methodology has been shown to provide robust diagnostics for a wide range of EFC valves. Full article
(This article belongs to the Special Issue Advances in Control Engineering)
Open AccessArticle A Complete Design of a Rare Earth Metal-Free Permanent Magnet Generator
Machines 2014, 2(2), 120-133; doi:10.3390/machines2020120
Received: 25 February 2014 / Revised: 2 April 2014 / Accepted: 13 May 2014 / Published: 16 May 2014
Cited by 3 | PDF Full-text (1031 KB) | HTML Full-text | XML Full-text
Abstract
The price of rare-earth metals used in neodymium-iron-boron (NdFeB) permanent magnets (PMs) has fluctuated greatly recently. Replacing the NdFeB PMs with more abundant ferrite PMs will avoid the cost insecurity and insecurity of supply. Ferrite PMs have lower performance than NdFeB PMs and
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The price of rare-earth metals used in neodymium-iron-boron (NdFeB) permanent magnets (PMs) has fluctuated greatly recently. Replacing the NdFeB PMs with more abundant ferrite PMs will avoid the cost insecurity and insecurity of supply. Ferrite PMs have lower performance than NdFeB PMs and for similar performance more PM material has to be used, requiring more support structure. Flux concentration is also necessary, for example, by a spoke-type rotor. In this paper the rotor of a 12 kW NdFeB PM generator was redesigned to use ferrite PMs, reusing the existing stator and experimental setup. Finite element simulations were used to calculate both electromagnetic and mechanical properties of the design. Focus was on mechanical design and feasibility of construction. The result was a design of a ferrite PM rotor to be used with the old stator with some small changes to the generator support structure. The new generator has the same output power at a slightly lower voltage level. It was concluded that it is possible to use the same stator with either a NdFeB PM rotor or a ferrite PM rotor. A ferrite PM generator might require a larger diameter than a NdFeB generator to generate the same voltage. Full article
(This article belongs to the Special Issue Advances in Machinery for Renewable Power Generation)
Open AccessArticle Control of Adjustable Compliant Actuators
Machines 2014, 2(2), 134-157; doi:10.3390/machines2020134
Received: 28 February 2014 / Revised: 6 May 2014 / Accepted: 15 May 2014 / Published: 20 May 2014
Cited by 2 | PDF Full-text (2233 KB) | HTML Full-text | XML Full-text
Abstract
Adjustable compliance or variable stiffness actuators comprise an additional element to elastically decouple the actuator from the load and are increasingly applied to human-centered robotic systems. The advantages of such actuators are of paramount importance in rehabilitation robotics, where requirements demand safe interaction
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Adjustable compliance or variable stiffness actuators comprise an additional element to elastically decouple the actuator from the load and are increasingly applied to human-centered robotic systems. The advantages of such actuators are of paramount importance in rehabilitation robotics, where requirements demand safe interaction between the therapy system and the patient. Compliant actuator systems enable the minimization of large contact forces arising, for example, from muscular spasticity and have the ability to periodically store and release energy in cyclic movements. In order to overcome the loss of bandwidth introduced by the elastic element and to guarantee a higher range in force/torque generation, new actuator designs consider variable or nonlinear stiffness elements, respectively. These components cannot only be adapted to the walking speed or the patient condition, but also entail additional challenges for feedback control. This paper introduces a novel design method for an impedance-based controller that fulfills the control objectives and compares the performance and robustness to a classical cascaded control approach. The new procedure is developed using a non-standard positive-real Η2 controller design and is applied to a loop-shaping approach. Robust norm optimal controllers are designed with regard to the passivity of the actuator load-impedance transfer function and the servo control problem. Classical cascaded and positive-real Η2 controller designs are validated and compared in simulations and in a test bench using a passive elastic element of varying stiffness. Full article
(This article belongs to the Special Issue Advances in Control Engineering)

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