Search results

1 – 10 of over 42000
To view the access options for this content please click here
Article
Publication date: 7 May 2019

Hanseung Woo and Kyoungchul Kong

Actuators for human-interactive robot systems require transparency and guaranteed safety. An actuation system is called transparent when it is able to generate an…

Abstract

Purpose

Actuators for human-interactive robot systems require transparency and guaranteed safety. An actuation system is called transparent when it is able to generate an actuation force as desired without any actuator dynamics. The requirements for the transparent actuation include high precision and large frequency bandwidth in actuation force generation, zero mechanical impedance and so on. In this paper, a compact rotary series elastic actuator (cRSEA) is designed considering the actuation transparency and the mechanical safety.

Design/methodology/approach

The mechanical parameters of a cRSEA are optimally selected for the controllability, the input and output torque transmissibility and the mechanical impedance by simulation study. A mechanical clutch that automatically disengages the transmission is devised such that the human is mechanically protected from an excessive actuation torque due to any possible controller malfunction or any external impact from a collision. The proposed cRSEA with a mechanical clutch is applied to develop a wearable robot for incomplete paraplegic patients. To verify torque tracking performance and disengagement of the mechanical clutch, experiments were conducted.

Findings

As the effects of the gear ratio, N1, on the four control performance indexes are conflicting, it should be carefully selected such that the controllability and the output torque transmissibility are maximized, while the disturbance torque transmissibility and the mechanical impedance are minimized. When the four control performance indexes were equally weighted, N1 was selected as 30. Experimental results showed that the designed cRSEA provided good control performances and the mechanical clutch worked properly.

Originality/value

It is important to design the actuator so as to maximize the control performance in accordance with its purpose. This paper presents the design guidelines for the SEA by introducing four control performance indexes and analyzing how the performance indexes vary according to the change of design parameter. From the viewpoint of practicality, a mechanical clutch design method that prevents excessive torque from being transmitted to the wearer and an analysis to solve the locking phenomenon when using a worm gear are presented, and a design method of SEA satisfying both control performance and practicality is presented.

Details

Industrial Robot: the international journal of robotics research and application, vol. 46 no. 2
Type: Research Article
ISSN: 0143-991X

Keywords

To view the access options for this content please click here
Article
Publication date: 19 February 2021

Furkan Ulu, Ravi Pratap Singh Tomar and Ram Mohan

PolyJet technology allows printing complex multi-material composite configurations using Voxel digital designs' capability, thus allowing rapid prototyping of 3D printed…

Abstract

Purpose

PolyJet technology allows printing complex multi-material composite configurations using Voxel digital designs' capability, thus allowing rapid prototyping of 3D printed structural parts. This paper aims to investigate the processing and mechanical characteristics of composite material configurations formed from soft and hard materials with different distributions and sizes via voxel digital print design.

Design/methodology/approach

Voxels are extruded representations of pixels and represent different material information similar to each pixel representing colors in digital images. Each geometric region of a digitally designed part represented by a voxel can be printed with a different material. Multi-material composite part configurations were formed and rapidly prototyped using a PolyJet printer Stratasys J750. A design of experiments composite part configuration of a soft material (Tango Plus) within a hard material matrix (Vero Black) was studied. Composite structures with different hard and soft material distributions, but at the same volume fractions of hard and soft materials, were rapidly prototyped via PolyJet printing through developed Voxel digital printing designs. The tensile behavior of these formed composite material configurations was studied.

Findings

Processing and mechanical behavior characteristics depend on materials in different regions and their distributions. Tensile characterization obtained the fracture energy, tensile strength, modulus and failure strength of different hard-soft composite systems. Mechanical properties and behavior of all different composite material systems are compared.

Practical implications

Tensile characteristics correlate to digital voxel designs that play a critical role in additive manufacturing, in addition to the formed material composition and distributions.

Originality/value

Results clearly indicate that multi-material composite systems with various tensile mechanical properties could be created using voxel printing by engineering the design of material distributions, and sizes. The important parameters such as inclusion size and distribution can easily be controlled within all slices via voxel digital designs in PolyJet printing. Therefore, engineers and designers can manipulate entire morphology and material at each voxel level, and different prototype morphologies can be created with the same voxel digital design. In addition, difficulties from AM process with voxel printing for such material designs is addressed, and effective digital solutions were used for successful prototypes. Some of these difficulties are extra support material or printing the part with different dimension than it designed to achieve the final part dimension fidelity. Present work addressed and resolved such issued and provided cyber based software solutions using CAD and voxel discretization. All these increase broad adaptability of PolyJet AM in industry for prototyping and end-use.

To view the access options for this content please click here
Article
Publication date: 5 January 2010

Mario Pacas, Sebastian Villwock, Piotr Szczupak and Henning Zoubek

The purpose of this paper is to summarize several identification methods for the automatic commissioning of electrical drives that are presented in different earlier…

Abstract

Purpose

The purpose of this paper is to summarize several identification methods for the automatic commissioning of electrical drives that are presented in different earlier papers of the same authors. This paper is intended as a contribution to the development of expert systems, taking into account parametric models of the mechanical and electrical subsystem as well as the corresponding parameter fitting.

Design/methodology/approach

Some system parameters, which are mandatory for the commissioning of electrical and mechanical systems are often not known. For their identification, a method based on the frequency response calculation utilizing the Welch method is now presented. The main focus of the work is directed to the measurement of the frequency response by exciting the system with pseudo‐random binary signals and to the subsequent procedure for the calculation of the corresponding parameter by utilizing the Levenberg‐Marquardt algorithm.

Findings

The presented identification procedure leads to outstanding results during the commissioning of the system as well as under normal operation conditions. The identification of the parameter of the mechanical and electrical systems is therefore possible during the commissioning of the drive as well as in running machines. Further, some restrictions regarding the measurement facilities are presented.

Originality/value

The presented identification procedure can be applied in a variety of conditions and can be applied for diagnostic tasks. New measurement and considerations regarding the restrictions of the applied method also under normal operation of the systems underline this fact.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 29 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

To view the access options for this content please click here
Article
Publication date: 2 October 2018

Mohammad A. Hassanain, Mohammad Aljuhani, Muizz O. Sanni-Anibire and Abdullatif Abdallah

The purpose of this paper is to develop and assess interdisciplinary design checklists for mechanical, electrical and plumbing (MEP) systems’ coordination, for building…

Abstract

Purpose

The purpose of this paper is to develop and assess interdisciplinary design checklists for mechanical, electrical and plumbing (MEP) systems’ coordination, for building projects, in Saudi Arabia.

Design/methodology/approach

Relevant documents were acquired including: heating, ventilation and air conditioning schedules; ductwork and chilled water pipes layout; and technical queries, among others, from residential and school projects. Next, factors influencing MEP systems’ coordination were extracted, and verified to ensure clarity and validity. They were formulated into design checklist items for MEP systems. Finally, the checklist items were assessed through a questionnaire based on a five-point Likert scale of importance. Respondents were comprised of mechanical, architectural, construction, electrical engineers, design coordinators and quality assurance managers. Data were then analyzed using the relative importance index.

Findings

This study presents 63 design checklist items. The items for each discipline were grouped under four categories, highlighting specific considerations. The findings revealed that careful consideration and communication between the mechanical, structural and architectural design teams was paramount in achieving proper mechanical coordination. Furthermore, it was found that constant communication between the electrical and the other design teams was necessary, to avoid electrical design conflicts. Finally, fire safety consideration was found to be most important in plumbing systems’ coordination.

Originality/value

The checklists for facilitating the MEP coordination process in building projects aim at minimizing waste in resources and enhancing the overall quality and productivity. In the absence of existing checklists, this paper provides a practical benefit to design professionals to alert them to devote more effort to the dominant category of checklist items.

Details

Built Environment Project and Asset Management, vol. 9 no. 1
Type: Research Article
ISSN: 2044-124X

Keywords

To view the access options for this content please click here
Article
Publication date: 17 October 2018

Xiaokai Mu, Qingchao Sun, Wei Sun, Yunlong Wang, Chuanhua Wang and Xiaobang Wang

The traditional precision design only takes the influence of geometric tolerance of the parts and does not involve the load deformation in the assembly process. This paper…

Abstract

Purpose

The traditional precision design only takes the influence of geometric tolerance of the parts and does not involve the load deformation in the assembly process. This paper aims to analyze the influence mechanism of flexible parts deformation on the geometric precision, and then to ensure the reliability and stability of the mechanical system.

Design/methodology/approach

Firstly, this paper adopts the N-GPS to analyze the influence mechanism of flexible parts deformation on the geometric precision and constructs a coupling 3D tolerance mathematical model of the geometric tolerance and the load deformation deviation based on the SDT theory, homogeneous coordinate transformation theory and surface authentication idea. Secondly, the least square method is used to fit the deformation surface of the mating surface under load so as to complete the conversion from the non-ideal element to the ideal element.

Findings

This paper takes the horizontal machining center as a case to obtain the deformation information of the mating surface under the self-weight load. The results show that the deformation deviation of the parts has the trend of transmission and accumulation under the load. The terminal deformation cumulative amount of the system is up to –0.0249 mm, which indicated that the influence of parts deformation on the mechanical system precision cannot be ignored.

Originality/value

This paper establishes a comprehensive 3D tolerance mathematical model, which comprehensively considers the effect of the dimensional tolerance, geometric tolerance and load deformation deviation. By this way, the assembly precision of mechanical system can be accurately predicted.

Details

Engineering Computations, vol. 35 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

To view the access options for this content please click here
Article
Publication date: 3 January 2017

Peyman Rafiee, Golta Khatibi and Michael Zehetbauer

The purpose of this paper is to provide an overview of the major reliability issues of microelectromechanical systems (MEMS) under mechanical and environmental loading…

Abstract

Purpose

The purpose of this paper is to provide an overview of the major reliability issues of microelectromechanical systems (MEMS) under mechanical and environmental loading conditions. Furthermore, a comprehensive study on the nonlinear behavior of silicon MEMS devices is presented and different aspects of this phenomenon are discussed.

Design/methodology/approach

Regarding the reliability investigations, the most important failure aspects affecting the proper operation of the MEMS components with focus on those caused by environmental and mechanical loads are reviewed. These studies include failures due to fatigue loads, mechanical vibration, mechanical shock, humidity, temperature and particulate contamination. In addition, the influence of squeeze film air damping on the dynamic response of MEMS devices is briefly discussed. A further subject of this paper is discussion of studies on the nonlinearity of silicon MEMS. For this purpose, after a description of the basic principles of nonlinearity, the consequences of nonlinear phenomena such as frequency shift, hysteresis and harmonic generation and their effects on the device performance are reviewed. Special attention is paid to the mode coupling effect between the resonant modes as a result of energy transfer because of the nonlinearity of silicon. For a better understanding of these effects, the nonlinear behavior of silicon is demonstrated by using the example of Si cantilever beams.

Findings

It is shown that environmental and mechanical loads can influence on proper operation of the MEMS components and lead to early fracture. In addition, it is demonstrated that nonlinearity modifies dynamic response and leads to new phenomena such as frequency shift and mode coupling. Finally, some ideas are given as possible future areas of research works.

Originality/value

This is a review paper and aimed to review the latest manuscripts published in the field of reliability and nonlinearity of the MEMS structures.

Details

Microelectronics International, vol. 34 no. 1
Type: Research Article
ISSN: 1356-5362

Keywords

To view the access options for this content please click here
Article
Publication date: 22 April 2020

Huahan Liu, Qiang Dong and Wei Jiang

The purpose of this paper is to present a new methodology, used for dynamic reliability analysis of a gear transmission system (GTS) of wind turbine (WT), which could be…

Abstract

Purpose

The purpose of this paper is to present a new methodology, used for dynamic reliability analysis of a gear transmission system (GTS) of wind turbine (WT), which could be used for assembly decision-making of the parts with errors to improve the GTS’s performance.

Design/methodology/approach

This paper involves the dynamic and dynamic reliability analysis of a GTS. The history curves of dynamic responses of the parts are obtained with the developed gear-bearing coupling dynamic model considering the random errors, failure dependency and random load. Then, the surrogate models of the mean and standard deviation of responses are presented by statistics, rain flow counting method and corrected-partial least squares regression response surface method. Further, a novel dynamic reliability model based on the maximum extreme theory, a theory of sequential statistics, equivalent principles and the inverse transform theory of random variable sampling, is developed to overcome the limitations of traditional methods.

Findings

The dynamic reliability of GTS considering the different impact factors are evaluated. The proposed reliability methodology not only overcomes the limitations associated with traditional approaches but also provides good guidance to assembly the parts in a GTS to its best performance.

Originality/value

Instead of constant errors, this paper considers the randomness of the impact factors to develop the dynamic reliability model. Further, instead of the limitation of the normal distribution of the random parameters in the traditional method, the proposed methodology can deal with the problems with non-normal distribution parameters, which is more suitable for the real engineering problems.

Details

Engineering Computations, vol. 37 no. 8
Type: Research Article
ISSN: 0264-4401

Keywords

To view the access options for this content please click here
Article
Publication date: 1 June 2000

P.Di Barba

Introduces the fourth and final chapter of the ISEF 1999 Proceedings by stating electric and magnetic fields are influenced, in a reciprocal way, by thermal and mechanical

Abstract

Introduces the fourth and final chapter of the ISEF 1999 Proceedings by stating electric and magnetic fields are influenced, in a reciprocal way, by thermal and mechanical fields. Looks at the coupling of fields in a device or a system as a prescribed effect. Points out that there are 12 contributions included ‐ covering magnetic levitation or induction heating, superconducting devices and possible effects to the human body due to electric impressed fields.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 19 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

To view the access options for this content please click here
Article
Publication date: 17 July 2009

Emmanuel Blanchard, Adrian Sandu and Corina Sandu

The purpose of this paper is to propose a new computational approach for parameter estimation in the Bayesian framework. A posteriori probability density functions are…

Abstract

Purpose

The purpose of this paper is to propose a new computational approach for parameter estimation in the Bayesian framework. A posteriori probability density functions are obtained using the polynomial chaos theory for propagating uncertainties through system dynamics. The new method has the advantage of being able to deal with large parametric uncertainties, non‐Gaussian probability densities and nonlinear dynamics.

Design/methodology/approach

The maximum likelihood estimates are obtained by minimizing a cost function derived from the Bayesian theorem. Direct stochastic collocation is used as a less computationally expensive alternative to the traditional Galerkin approach to propagate the uncertainties through the system in the polynomial chaos framework.

Findings

The new approach is explained and is applied to very simple mechanical systems in order to illustrate how the Bayesian cost function can be affected by the noise level in the measurements, by undersampling, non‐identifiablily of the system, non‐observability and by excitation signals that are not rich enough. When the system is non‐identifiable and an a priori knowledge of the parameter uncertainties is available, regularization techniques can still yield most likely values among the possible combinations of uncertain parameters resulting in the same time responses than the ones observed.

Originality/value

The polynomial chaos method has been shown to be considerably more efficient than Monte Carlo in the simulation of systems with a small number of uncertain parameters. This is believed to be the first time the polynomial chaos theory has been applied to Bayesian estimation.

Details

Engineering Computations, vol. 26 no. 5
Type: Research Article
ISSN: 0264-4401

Keywords

To view the access options for this content please click here
Article
Publication date: 9 March 2015

Anake Pomprapa, Danita Muanghong, Marcus Köny, Steffen Leonhardt, Philipp Pickerodt, Onno Tjarks, David Schwaiberger and Burkhard Lachmann

The purpose of this paper is to develop an automatic control system for mechanical ventilation therapy based on the open lung concept (OLC) using artificial intelligence…

Abstract

Purpose

The purpose of this paper is to develop an automatic control system for mechanical ventilation therapy based on the open lung concept (OLC) using artificial intelligence. In addition, mean arterial blood pressure (MAP) is stabilized by means of a decoupling controller with automated noradrenaline (NA) dosage to ensure adequate systemic perfusion during ventilation therapy for patients with acute respiratory distress syndrome (ARDS).

Design/methodology/approach

The aim is to develop an automatic control system for mechanical ventilation therapy based on the OLC using artificial intelligence. In addition, MAP is stabilized by means of a decoupling controller with automated NA dosage to ensure adequate systemic perfusion during ventilation therapy for patients with ARDS.

Findings

This innovative closed-loop mechanical ventilation system leads to a significant improvement in oxygenation, regulates end-tidal carbon dioxide for appropriate gas exchange and stabilizes MAP to guarantee proper systemic perfusion during the ventilation therapy.

Research limitations/implications

Currently, this automatic ventilation system based on the OLC can only be applied in animal trials; for clinical use, such a system generally requires a mechanical ventilator and sensors with medical approval for humans.

Practical implications

For implementation of a closed-loop ventilation system, reliable signals from the sensors are a prerequisite for successful application.

Originality/value

The experiment with porcine dynamics demonstrates the feasibility and usefulness of this automatic closed-loop ventilation therapy, with hemodynamic control for severe ARDS. Moreover, this pilot study validated a new algorithm for implementation of the OLC, whereby all control objectives are fulfilled during the ventilation therapy with adequate hemodynamic control of patients with ARDS.

Details

International Journal of Intelligent Computing and Cybernetics, vol. 8 no. 1
Type: Research Article
ISSN: 1756-378X

Keywords

1 – 10 of over 42000