Search results

The purpose of this paper is to present the development and validation of a methodology which allows modeling and solving the inverse and direct dynamic problem in real time in robot manipulators.

The robot dynamic equation is based on the Gibbs‐Appell equation of motion, yielding a well‐structured set of equations that can be computed in real time. This paper deals with the implementation and calculation of the inverse and direct dynamic problem in robots, with an application to the real‐time control of a PUMA 560 industrial robot provided with an open control architecture based on an industrial personal computer.

The experimental results show the validity of the dynamic model and that the proposed resolution method for the dynamic problem in real time is suitable for control purposes.

The accuracy of the applied friction model determines the accuracy of the identified overall model and consequently of the control. This is especially obvious in the case of the PUMA 560 robot, in which the presence of friction is remarkable in some of their joints. Hence, future work should focus on identifying a more precise friction model. The robot model could also be extended by incorporating rotor dynamics and could be applied for different robot configurations as parallel robots.

Gibbs‐Appell equations are used in order to develop the robotic manipulator dynamic model, instead of more usual dynamics formulations, due to several advantages that these exhibit. The obtained non‐physical identified parameters are adapted in order to enable their use in a control algorithm.

Prevailing information asymmetry in business processes alters the market dynamics. Quality uncertainty ensues from this phenomenon. Philosophy of information economics is implemented to correlate total quality management (TQM) practices in industry with quality perceived by customers. Quality perception, a newly coined term, is discussed at length, along with causal factors. This paper aims to provide a system dynamics framework for quality perception and to investigate the role of the changing level of market‐side enablers on quality perception.

System dynamics is used for modeling and analysis. To realize the impact of information asymmetry on quality perception, simulation runs are carried out for an Indian case.

Enablers, such as advertising, word‐of‐mouth, rebate, warranty and guarantee, mitigate the effect of information asymmetry on quality perception, and commensurately translate TQM to market value.

The study of some aspects of information asymmetry and quality perception is attempted. Further study is required to understand repercussions of information asymmetry on the complete supply chain processes.

The model has a practical relevance to implement quality perception enhancement by deciding upon the policy mix.

With quality perception defined and modeled, the paper attempts market orientation to quality paradigm.

The paper aims to study market dynamics in the backdrop of information symmetry and quality perception. The position of high quality products (HQPs) in the market is a focus of this analysis. Also, an attempt is made to unfold the prevailing parametric relationships in the market of developed and developing nations.

Related literature is reviewed and investigation is attempted into market dynamics. System dynamics is used for preliminary modelling and analysis. Simulation runs are carried out to assess the impact of company reputation and advertising on market parameters.

Behaviours of market parameters are unraveled. From using correlation analysis and analytic hierarchy approach, the policy measures to improve the HQP position in the market are revealed.

The study of some aspects of market dynamics is attempted. Further, study and modelling are required to completely understand the market behaviour.

The model has a practical relevance to implement quality perception enhancement by deciding on the policy mix.

This is a start for systems analysis of the market, which may offer a long‐term foundation to market dynamics.

High-tech start-up creation is associated with complex challenges originating from quick transformations in technologies and markets. To raise start-up survival and success chances, founders need to ensure a rapid conversion of a venture idea into a working business. This paper aims to explore how identity-related characteristics of founders influence the speed of the start-up creation process.

For this study, a longitudinal multiple-case-study design was selected to identify a vivid flow of decisions and actions taken by high-tech start-ups for analysis in depth. Over 20 months, a series of interviews were organized with founders of six start-ups located in the same business incubator in Russia. Also, a set of additional data sources was engaged, including publicly available data and internal documents provided by businesses.

The findings reveal contrasting dynamics of start-up creation processes among founders with differing role identities. Identity fit and identity misfit are suggested to be serious pull and push factors in the process of organizational becoming through the impact they have on the situational regulatory focus of founders.

The current research contributes to the entrepreneurship stream of research by extending the knowledge of how cognition affects the process of new venture creation.

The paper explores the role of narcissism on entrepreneurs' decisions in terms of organizational choices, discussing gender differences. The aim relies in the influence that entrepreneurs' personality, capabilities and cognitive orientation have in the creation and management of start-ups.

Analyzing an Italian sample of 207 entrepreneurs and using Analysis of variance (ANOVA) and generalized linear model methods, the hypotheses were tested to understand whether and how narcissism affects Research and development (R&D) expenditure, patent ownership and the presence of a specialized team in organizations led by women and men entrepreneurs.

Differences in the management and organizational choices of narcissistic women entrepreneurs compared to their men counterparts emerged. First, results show that women entrepreneurs are less narcissistic than men. Second, gender is shown to moderate the effect of narcissism on the choice of having a qualified team in a start-up. Third, narcissistic women entrepreneurs were found to engage less in risk-taking activities, such as R&D expenditure, and to patent their ideas more than their male counterparts.

The study expands the existing literature by applying a gendered lens to entrepreneurs' narcissism to investigate whether they behave and manage their start-ups differently.

The purpose of this study a fast procedure for the structural analysis of gas turbine blades in aircraft engines. In this connection, investigations on the behavior of gas turbine blades concentrate on the analysis and evaluation of starting dynamics and fatigue strength. Besides, the influence of structural mistuning on the vibration characteristics of the single blade is analyzed and discussed.

A basic computation cycle is generated from a flight profile to describe the operating history of the gas turbine blade properly. Within an approximation approach for high-frequency vibrations, maximum vibration amplitudes are computed by superposition of stationary frequency responses by means of weighting functions. In addition, a two-way coupling approach determines the influence of structural mistuning on the vibration of a single blade. Fatigue strength of gas turbine blades is analyzed with a semi-analytical approach. The progressive damage analysis is based on MINER’s damage accumulation assuming a quasi-stable behavior of the structure.

The application to a gas turbine blade shows the computational capabilities of the approach presented. Structural characteristics are obtained by robust and stable computations using a detailed finite element model considering different load conditions. A high quality of results is realized while reducing the numerical costs significantly.

The method used for analyzing the starting dynamics is based on the assumption of a quasi-static state. For structures with a sufficiently high stiffness, such as the gas turbine blades in the present work, this procedure is justified. The fatigue damage approach relies on the existence of a quasi-stable cyclic stress condition, which in general occurs for isotropic materials, as is the case for gas turbine blades.

Owing to the use of efficient analysis methods, a fast evaluation of the gas turbine blade within a stochastic analysis is feasible.

The fast numerical methods and the use of the full finite element model enable performing a structural analysis of any blade structure with a high quality of results.

This study aims to investigate the cross-sectional reshaping in transitioning/starting rectangular jets of aspect ratio 2 under various inlet perturbation conditions at the Reynolds number of Re = UD_h/v = 17,750.

Large eddy simulation results compared with the phase-locked particle image velocimetry data exhibit the cross-sectional jet deformations from rectangular to rounder shapes. Inflow velocity oscillations are introduced at the fundamental frequency associated with the Kelvin–Helmholtz instability characterized by the spectral analysis of the hotwire data and the linear stability predictions.

The initially rectangular cross-section of the jet reshapes into the rounder geometries with increased downstream distance while the edges of the jet become distorted due to the shear layer instability more significantly observed near the high curvature corners. The different expansion rates in the longer and shorter edges of the jet and the consequent cross-sectional reshaping are found to be sensitive to small levels of random inlet perturbations. In addition, introducing controlled sinusoidal oscillations results in the formation of more organized trailing shear layer where the stronger vortex rings go through the curvature-induced deformations.

Spatio-temporal study of vortex dynamics in transitioning rectangular jets reveals important information about the effect of the controlled jet forcing on local entrainment. Dynamics of the leading vortex dominates the entrainment in transitioning jets which are commonly used in practical applications. Near-field entrainment is also promoted proportional to the amplitude of the controlled inlet oscillations within the trailing vortex rings.

This paper aims to provide a theoretical conception that establishes growth rate dynamics for co-operatives and studies Moroccan co-operatives’ start-ups and closures, by analyzing the co-operatives’ growth rate speed of adjustment (SOA).

This paper documents the basic patterns of entry and exit flow for agricultural, artisanal, housing and fishery co-operatives; highlights, with econometric tests, whether co-operatives’ growth rate is mean reverting or a unit root random walk; and estimates the growth rate adjustment speed, using a quadratic interval reverting model to capture both the upward and downward speeds of adjustment.

The empirical results indicate that co-operatives’ growth rate is significantly mean reverting for all sectors. Also, it concludes that the upward and downward adjustment speeds are significantly different within and between sectors, with negative indicator for artisanal co-operatives. The paper discusses these results, which are of interest to academics and policymakers.

The study does not investigate the causes of the growth rate SOA. Further, in-depth work with the results of this study would help scholars and policymakers to get close to the accurate research questions that characterize the mean reverting and affects the adjustment processes for Moroccan co-operatives.

The suggested model – with upward and downward adjustment speeds– could be valuable for policymakers’ strategies on co-operatives’ emergence.

The paper moves policymakers closer to social work and socio-economic trends to explain the empirical regularities of co-operatives’ dynamics. The model could be of value to avoid a volatile rate of entries and exits, to ensure continuity, to avoid fast failure of co-operative memberships and then to achieve the social inclusion.

The paper provides empirical evidence and results for co-operatives’ start-ups and closures adjustment speed and determines the conditions in which government policy must be clarified and specified. To the best of the authors’ knowledge, this paper is the first empirical analysis for the co-operatives’ SOA over entry and exit dynamics.

The purpose of the paper is to find a speed control structure with two degrees of freedom robust against drive parameters variations. Application of structure model following control (MFC) and fuzzy technique in the controller of PI type creates proper non‐linear characteristics, which ensures controller robustness.

The use of proper structure with two degrees of freedom and non‐linear characteristic introduced by fuzzy technique ensures the robustness of the speed control system. The paper proposes a novel approach to MFC synthesis to be performed in two stages. The first stage consists in the set value of P type controller of model and the process controller simultaneously should be designing by fuzzy technique. At the second stage of the synthesis consist in tuning parameters of process fuzzy controller by the swarm of particles method (particle swarm optimization) on the basis of a defined quality index formulated in the paper. The synthesis is performed using simulation techniques and subsequently the behavior of a laboratory speed control system is validated in the experimental setup. The control algorithms of the system are performed by a microprocessor floating point DSP control system.

Use of proper structure with two degrees of freedom of the non‐linear fuzzy controller guarantees expected robustness and improves the dynamics of speed control significantly.

The proposed structure of MFC was tested on a single machine under well‐defined conditions. Further investigations are required before any industrial applications.

The proposed controller synthesis and its results may be very helpful in robotic system where changing of system parameters is characteristic for many industrial robots and manipulators.

The paper proposes an original method of synthesis of robust system with two degrees of freedom system validated by simulation and experimental investigations.