Ján Vittek, Peter Briš, Pavol Makyš and Marek Štulrajter
The purpose of this paper is to discuss the design and verification of a new control algorithm for the drive with permanent magnet synchronous motor (PMSM) and flexible coupling…
Abstract
Purpose
The purpose of this paper is to discuss the design and verification of a new control algorithm for the drive with permanent magnet synchronous motor (PMSM) and flexible coupling based on “Forced dynamics control”. Control laws are derived and tested for the rotor and load angle control and achieve non‐oscillatory position step response with a specified settling time.
Design/methodology/approach
“Forced dynamics control” is a new control technique based on feedback linearization which forces rotor or load position to follow demanded position with prescribed closed‐loop dynamics. The proposed control structure is developed in two steps: first, the feedback linearisation is applied to the rotor speed and then similar technique is used for position control loop.
Findings
The proposed controller is of the cascade structure, comprising an inner speed control loop, respecting vector control principles and outer position control loop designed to control the rotor or load angle, respectively. Estimates of load torques acting on the motor and load side as inputs of control algorithms are produced in observers and used to compensate disturbances offering a certain degree of robustness. Preliminary experiments confirm that proposed system follows the ideal closed‐loop dynamics with moderate accuracy.
Research limitations/implications
The focus is on experimental verification of the position control of flexible PMSM drive with two position sensors and moderate precision, where the oscillations due to hardware setup, achieved sampling frequency and corresponding observers adjustment are limited up to 50 rad s−1.
Practical implications
The designed control structure can substantially improve control performance of industrial plants subjects to torsion oscillations.
Originality/value
Experimental results of a novel control structure for the PMSM drives with torsion oscillations are sufficiently promising and confirmed that the rotor and load angle responses follow the prescribed ones fairly closely.
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In common with many other UK academic libraries using the LIBERTAS library management system, Bristol University Library set out in 1998 to acquire a replacement. This paper…
Abstract
In common with many other UK academic libraries using the LIBERTAS library management system, Bristol University Library set out in 1998 to acquire a replacement. This paper describes the background to the Bristol project to choose a new system, and some of its distinctive features, briefly indicates the outcome (acquisition of Aleph 500 from Ex Libris), and draws some lessons from the experience. It is easy to under. estimate the size of the task involved in installing a modern library management system. Careful thought should be given to an assessment of conversion needs and to the justifcation for retaining existing practices (e.g. use of UKMARC) rather than accepting the international norm. Both staff and users must understand the need for change and be prepared for its consequences. On‐site support from the system supplier is vital and time is of the essence.
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David A. Brenders, Peter Hope and Abraham Ninnan
Presents the findings of a qualitative study of university science, the Student Focus Project, as it relates to the concept of service culture as defined by McCormack, Neil and…
Abstract
Presents the findings of a qualitative study of university science, the Student Focus Project, as it relates to the concept of service culture as defined by McCormack, Neil and Triplett. Assessed 24 focus groups of undergraduate students to find out opinions on positive and negative aspects of student life. Concludes that the approach highlighted reliable themes regarding successes and failure of the university service culture.
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It has often been said that a great part of the strength of Aslib lies in the fact that it brings together those whose experience has been gained in many widely differing fields…
Abstract
It has often been said that a great part of the strength of Aslib lies in the fact that it brings together those whose experience has been gained in many widely differing fields but who have a common interest in the means by which information may be collected and disseminated to the greatest advantage. Lists of its members have, therefore, a more than ordinary value since they present, in miniature, a cross‐section of institutions and individuals who share this special interest.
Alex Lundqvist, Eva Liljeblom, Anders Löflund and Benjamin Maury
The cultural and legal differences between foreign acquirers and African target firms can be substantial. There is also a large variation in cultures and legal systems within…
Abstract
Purpose
The cultural and legal differences between foreign acquirers and African target firms can be substantial. There is also a large variation in cultures and legal systems within Africa. However, there is limited research on merger and acquisition (M&A) performance by foreign firms in Africa. The purpose of this paper is to fill this gap by exploring the “spillover by law” hypothesis (Martynova and Renneboog, 2008) that focuses on the influence of the external environment on the governance and performance of foreign M&As in Africa.
Design/methodology/approach
The data set covers 415 M&A transactions by foreign firms in Africa during the period of 1999–2016. Dynamic data covering the country’s legal, cultural and political environment are collected from the World Bank, the Heritage Foundation and Transparency International.
Findings
The authors find that the legal environment significantly affects the returns of bidders on African firms. For complete acquisitions, bidder returns are significantly higher when the bidder’s country has higher shareholder protection and higher creditor protection compared with the target firm’s country. The results show that the effects are significant when there is a full control change (including a change in the target firm’s nationality) but not in the case of partial control transfers. The results are consistent with the “spillover by law” hypothesis.
Originality/value
The authors contribute to the literature on cross-border M&As by separately studying the valuation effects of full, majority and minority changes in control; by being the first study of the legal spillover effects in Africa; and by being the most extensive study of the legal determinants of the valuations of non-African acquirers of African firms.
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Peter Masefield MA, CEng and FRAeS
AIRCRAFT ENGINEERING'S first half‐century has spanned three‐quarters of the Aviation era since the Wright Brothers first flew on 17th December, 1903. Those 50 active years have…
Abstract
AIRCRAFT ENGINEERING'S first half‐century has spanned three‐quarters of the Aviation era since the Wright Brothers first flew on 17th December, 1903. Those 50 active years have seen a transformation of every aspect of the engineering scene — materials, structures, power‐plants, ancillaries and equipment. Yet still today, the art and the science of aeronautical engineering —and it is certainly both—are advancing as fast as any group in the past, while costs soar.
Education and human capital development are seen by the government of Saudi Arabia as vital to the aim of gaining knowledge economy status. Although financial investment has been…
Abstract
Education and human capital development are seen by the government of Saudi Arabia as vital to the aim of gaining knowledge economy status. Although financial investment has been evident in education and human capital development in Saudi Arabia for many years, knowledge acquisition, production, and diffusion remain problematic. The strategy that underpins the shift to a knowledge economy is based on the assumption drawn from human capital theory that education can transform individual productivity and therefore promote economic development. However, the links between education and economic growth are not as linear as this framing of education suggests, but depend on complex social processes. Within these processes, individual understandings of knowledge and knowledge creation are crucial. The implications of this for Saudi Arabia are discussed with reference to the work of Knorr Cetina (2007) on knowledge cultures and David and Foray (2002) on knowledge communities. A transition to a knowledge economy is more likely to occur when cultural and social conditions enable the development of knowledge cultures and knowledge communities.
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Recently there has been a resurgence in the study of how ideas shape policies. Two perspectives which dominate this literature are what Habermas has called the…
Abstract
Recently there has been a resurgence in the study of how ideas shape policies. Two perspectives which dominate this literature are what Habermas has called the empirical‐analytical tradition and historical‐hermeneutic tradition. These two epistemological positions represent contrasting views. They depict very different pictures of how ideas sway popular values and the policy choices confronted by policymakers. Each also raises important questions about how the processes of knowledge formation and promotion unfold and what actors play a dominant role in furthering these developments.