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1 – 10 of over 43000
Article
Publication date: 1 August 2016

Qiuxiang Li

The purpose of this paper is to explore the dynamics and stability of switched supply system considering the influence of the retailer competition and deteriorating items.

Abstract

Purpose

The purpose of this paper is to explore the dynamics and stability of switched supply system considering the influence of the retailer competition and deteriorating items.

Design/methodology/approach

A discrete dynamic switched model is developed to analyze the evolution process of the switched supply chain. The existence and the local stability of the switched supply chain are analyzed using an analytical method and a parameter plot basin.

Findings

The author finds the switched supply chain will exhibit stable, periodic, and divergent behaviors with different parameters due to the system’s switching mechanism and the switched supply chain presents complex dynamics when the stable and unstable subsystem coexist.

Originality/value

The originality and value of the research rests on this paper considering the influence of the retailers’ competition and deteriorating items on the supply chain dynamics under stock-dependent demand. The obtained results provide the decision maker with some guidelines on how to make stable designs for the switched supply chain design according to the parameter values.

Details

Kybernetes, vol. 45 no. 7
Type: Research Article
ISSN: 0368-492X

Keywords

Article
Publication date: 27 March 2009

Zhengrong Xiang and Ronghao Wang

The purpose of this paper is to present the non‐fragile observer design method for nonlinear switched systems with time delay.

Abstract

Purpose

The purpose of this paper is to present the non‐fragile observer design method for nonlinear switched systems with time delay.

Design/methodology/approach

Based on dwell time approach and linear matrix inequalities (LMIs) technology, an exponential stability criterion for the delay switched system with Lipschitz nonlinearity is presented. By using the key technical lemma, the observer design problem can be transferred to the problem of solving a set of LMIs. Moreover, non‐fragile observer is designed by the Schur complement lemma, and the result is also transferred to LMIs, which can be easily realized by MATLAB toolbox.

Findings

Non‐fragile observer design is more effective than the common one and is robust to the observer gain variations.

Originality/value

The proposed non‐fragile observer guarantees the estimated state error dynamics can be exponentially convergent for observer gain perturbations.

Details

International Journal of Intelligent Computing and Cybernetics, vol. 2 no. 1
Type: Research Article
ISSN: 1756-378X

Keywords

Article
Publication date: 25 August 2023

Shuai Yue, Ben Niu, Huanqing Wang, Liang Zhang and Adil M. Ahmad

This paper aims to study the issues of adaptive fuzzy control for a category of switched under-actuated systems with input nonlinearities and external disturbances.

Abstract

Purpose

This paper aims to study the issues of adaptive fuzzy control for a category of switched under-actuated systems with input nonlinearities and external disturbances.

Design/methodology/approach

A control scheme based on sliding mode surface with a hierarchical structure is introduced to enhance the responsiveness and robustness of the studied systems. An equivalent control and switching control rules are co-designed in a hierarchical sliding mode control (HSMC) framework to ensure that the system state reaches a given sliding surface and remains sliding on the surface, finally stabilizing at the equilibrium point. Besides, the input nonlinearities consist of non-symmetric saturation and dead-zone, which are estimated by an unknown bounded function and a known affine function.

Findings

Based on fuzzy logic systems and the hierarchical sliding mode control method, an adaptive fuzzy control method for uncertain switched under-actuated systems is put forward.

Originality/value

The “cause and effect” problems often existing in conventional backstepping designs can be prevented. Furthermore, the presented adaptive laws can eliminate the influence of external disturbances and approximation errors. Besides, in contrast to arbitrary switching strategies, the authors consider a switching rule with average dwell time, which resolves control problems that cannot be resolved with arbitrary switching signals and reduces conservatism.

Details

Robotic Intelligence and Automation, vol. 43 no. 5
Type: Research Article
ISSN: 2754-6969

Keywords

Article
Publication date: 5 January 2010

A. El Aroudi, E. Alarcón, E. Rodríguez and R. Leyva

The purpose of this paper is to characterize the nonlinear dynamical behaviour of a buck‐based power‐switching amplifier controlled by fixed frequency and pulse width modulation…

Abstract

Purpose

The purpose of this paper is to characterize the nonlinear dynamical behaviour of a buck‐based power‐switching amplifier controlled by fixed frequency and pulse width modulation with a proportional‐integral compensator. The system has two forcing frequencies and one natural frequency and therefore it is characterized by three different scales of time. When the frequencies are far one from the other, quasi‐static approximation can be used. However, as the switching and the modulating frequencies become closer, this approximation is not valid and the results based on it lead to erroneous conclusions about the dynamics of the system.

Design/methodology/approach

A discrete time approach is used to reveal the interesting nonlinear phenomena that the system can exhibit. From numerical simulations using the switched model, it is shown that the system can present period‐doubling bifurcation at the fast scale (switching frequency).

Findings

An exact solution discrete‐time model is derived, able to predict accurately the nonlinear dynamical behaviour of the system.

Originality/value

The discrete time model is obtained without making quasi‐static approximation. The exact switched model is used to validate the discrete‐time model obtained. Finally, the effect of the switching frequency instabilities on the output voltage spectrum has been explored.

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

Article
Publication date: 19 May 2020

Tobias Weiss

The paper aims to clarify the relationship between energy flexibility and building components and technologies. It determines the energy flexibility potential of buildings in…

Abstract

Purpose

The paper aims to clarify the relationship between energy flexibility and building components and technologies. It determines the energy flexibility potential of buildings in relation to their physical characteristics and heat supply systems with respect to external boundary conditions.

Design/methodology/approach

The emphasis of the evaluation is based on the timing and the amount of shiftable and storable thermal loads in buildings under defined indoor thermal comfort conditions. Dynamic building simulation is used to evaluate the potential of selected building characteristics to shift heating loads away from peak demand periods. Insights on the energy flexibility potential of individual technologies are gained by examining the thermal behaviour of single-zone simulation models as different input parameters are varied. For this purpose, parameters such as envelope qualities, construction materials, control systems for heating are modified.

Findings

The paper provides a comprehensive understanding of the influence of the different building parameters and their variations on their energy shifting potential under “laboratory conditions” with steady boundaries. It suggests that the investigated boundary conditions such as outside temperature, infiltration, envelope quality and user behaviour, which influence the heating load of a building, also influence the resulting potential for energy flexibility. The findings show that the combination of a slowly reacting heat transfer system, such as concrete core activation and a readily available storage mass in the room, and a high insulation standard proved to have a high potential to shift heating loads.

Originality/value

In this paper, energy-flexible components were evaluated in a steady-state simulation approach. Outside temperature, solar irradiation and internal loads over the simulation duration were set constant over time to provide laboratory conditions for the potential analysis. On the basis of both duration and performance of the load shifting or storage event, the components were then quantified in a parametric simulation. The determined energy flexibility is directly related to the power of the heating, cooling, hot water and ventilation system, which can be switched on or off. In general, it can be seen that high power (high loads) demand usually can be switched on and off for a short duration, and low power demand usually for a longer duration. The investigated boundary conditions such as outside temperature, infiltration, envelope quality and user behaviour, which influence the load of a building, also influence the resulting potential for energy flexibility. Higher insulation standards, for example, lead to lower loads that can be switched on or off, but increase the duration of the event (flexibility time). So that, in particular, the shiftable load potential is low but results in a long switch-off duration. Furthermore, passive storage potential in buildings like the storage mass inside the room and the type of heat/cooling transfer system can affect the flexibility potential by more than three times. Especially the combination of a high storage mass and a concrete core heat transfer system can significantly increase the flexibility.

Details

Smart and Sustainable Built Environment, vol. 10 no. 4
Type: Research Article
ISSN: 2046-6099

Keywords

Article
Publication date: 25 November 2022

Zhongwen Cao, Liang Zhang, Adil M. Ahmad, Fawaz E. Alsaadi and Madini O. Alassafi

This paper aims to investigate an adaptive prescribed performance control problem for switched pure-feedback non-linear systems with input quantization.

Abstract

Purpose

This paper aims to investigate an adaptive prescribed performance control problem for switched pure-feedback non-linear systems with input quantization.

Design/methodology/approach

By using the semi-bounded continuous condition of non-affine functions, the controllability of the system can be guaranteed. Then, a constraint variable method is introduced to ensure that the tracking error satisfies the prescribed performance requirements. Meanwhile, to avoid the design difficulties caused by the input quantization, a non-linear decomposition method is adopted. Finally, the feasibility of the proposed control scheme is verified by a numerical simulation example.

Findings

Based on neural networks and prescribed performance control method, an adaptive neural control strategy for switched pure-feedback non-linear systems is proposed.

Originality/value

The complex deduction and non-differentiable problems of traditional prescribed performance control methods can be solved by using the proposed error transformation approach. Besides, to obtain more general results, the restrictive differentiability assumption on non-affine functions is removed.

Details

Assembly Automation, vol. 42 no. 6
Type: Research Article
ISSN: 0144-5154

Keywords

Article
Publication date: 1 December 1975

G.H. Garbett and AMRAeS

Smiths Industries is to supply the head‐up display system for the Sea Harrier. The company will design, develop and make the electronic head‐up display and weapon aiming computer…

Abstract

Smiths Industries is to supply the head‐up display system for the Sea Harrier. The company will design, develop and make the electronic head‐up display and weapon aiming computer system for the latest version of the HS Harrier which will operate from Royal Navy ships.

Details

Aircraft Engineering and Aerospace Technology, vol. 47 no. 12
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 1 April 1988

Leslie B. Southwick

The University of Michigan has installed one of the largest private communications switches in the world. The switch and supporting network are designed to meet the voice, data…

101

Abstract

The University of Michigan has installed one of the largest private communications switches in the world. The switch and supporting network are designed to meet the voice, data service, security, and video transmission requirements of the university into the next century. The processes of defining needs, selecting a vendor, and implementing the system are discussed.

Details

Library Hi Tech, vol. 6 no. 4
Type: Research Article
ISSN: 0737-8831

Article
Publication date: 7 November 2019

Megha G. Krishnan, Abhilash T. Vijayan and Ashok Sankar

This paper aims to improve the performance of a two-camera robotic feedback system designed for automatic pick and place application by modifying its velocity profile during…

Abstract

Purpose

This paper aims to improve the performance of a two-camera robotic feedback system designed for automatic pick and place application by modifying its velocity profile during switching of control.

Design/methodology/approach

Cooperation of global and local vision sensors ensures visibility of the target for a two-camera robotic system. The master camera, monitoring the workspace, guides the robot such that image-based visual servoing (IBVS) by the eye-in-hand camera transcends its inherent shortcomings. A hybrid control law steers the robot until the system switches to IBVS in a region proven for its asymptotic stability and convergence through a qualitative overview of the scheme. Complementary gain factors can ensure a smooth transition in velocity during switching considering the versatility and range of the workspace.

Findings

The proposed strategy is verified through simulation studies and implemented on a 6-DOF industrial robot ABB IRB 1200 to validate the practicality of adaptive gain approach while switching in a hybrid visual feedback system. This approach can be extended to any control problem with uneven switching surfaces or coarse/fine controllers which are subjected to discrete time events.

Practical implications

In complex workspace where robots operate in parallel with other robots/humans and share workspaces, the supervisory control scheme ensures convergence. This study proves that hybrid control laws are more effective than conventional approaches in unstructured environments and visibility constraints can be overcome by the integration of multiple vision sensors.

Originality/value

The supervisory control is designed to combine the visual feedback data from eye-in-hand and eye-to-hand sensors. A gain adaptive approach smoothens the velocity characteristics of the end-effector while switching the control from master camera to the end-effector camera.

Details

Industrial Robot: the international journal of robotics research and application, vol. 47 no. 1
Type: Research Article
ISSN: 0143-991X

Keywords

Article
Publication date: 1 December 2000

Katsuhiko Takahashi and Nobuto Nakamura

As a just‐in‐time (JIT) ordering system for multi‐stage production inventory systems, both the kanban system and its alternative, the concurrent ordering system, have been…

2464

Abstract

As a just‐in‐time (JIT) ordering system for multi‐stage production inventory systems, both the kanban system and its alternative, the concurrent ordering system, have been proposed. For both JIT ordering systems, the reactive JIT ordering systems that adjust the buffer size responding to unstable changes in demand were proposed. In addition to the adjustment of buffer size, switching ordering systems between the kanban system and the concurrent ordering system is proposed in order to realize agile control in JIT ordering systems. In the proposed system, the time series data of demand is monitored, and switching the order release systems and adjusting the buffer size are considered when an unstable change in demand is detected with the exponentially weighted moving average charts. The effectiveness of the proposed system is analyzed using simulation experiments under unstable conditions. From these simulation experiments, it is clear that the proposed system can react to unstable changes in demand and satisfy the required level for the mean waiting time of demand. Also, to attain the required level, the proposed system must possess much less work‐in‐process inventories than the previous systems which adjust only the buffer size and do not switch ordering systems.

Details

International Journal of Agile Management Systems, vol. 2 no. 3
Type: Research Article
ISSN: 1465-4652

Keywords

1 – 10 of over 43000