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For manufacturing companies, quality management is a key feature for increasing the competitiveness, productivity, profitability, and sustainability of their systems. Quality improvement (QI) methods aim to achieve high-quality parts without reducing performance. The Industry 4.0 framework brought technological developments that cannot be used by traditional QI methods, such as Six Sigma, Lean, Lean Six, the Theory of Constraints, and Total Quality Management, which are widely used in manufacturing companies. The need for higher manufacturing sustainability and market requirements has led to the search for alternative QI methods with superior performance to traditional QI methods such as Zero-Defect Manufacturing (ZDM). The current paper is a position paper with a goal to present the ZDM approach and providing a clear definition about ZDM to align everyone in one common understanding of ZDM. Many researchers and manufactures are skeptical about ZDM, therefore, numerous argumentative questions have been created and answered, to convince them why they should migrate from traditional QI methods to ZDM. The migration to ZDM has already started, to support this statement numerous facts from the literature have been presented. Finally, several directions were identified, demonstrating that there is still plenty of room for research in several domains.

© 2020 Informa UK Limited, trading as Taylor & Francis Group. This paper investigates the weighted coordinated motion of coupled harmonic oscillators over weighted cooperative–competitive interactions. First, the traditional synchronisation and containment control concepts are extended to the weighted synchronisation and weighted containment control for the new cooperative–competitive networks. Then, weighted synchronisation problem and weighted containment tracking motion are respectively solved for the coupled harmonic oscillators. Compared with some existing results, the frequency parameters of coupled harmonic oscillators are unknown in this paper and some novel networked structures are introduced in order to make the harmonic oscillator followers converge to the convex hull spanned by leaders' weighted states. Particularly, if the topologies formed by every leader group and follower group are interactively balanced and every follower is weight-product balanced, or if some leader groups are not interactively balanced but satisfy some conditions, the coupled harmonic oscillators can all realise the weighted containment tracking motion. Simulation results are given to demonstrate the effectiveness of the proposed control schemes.

Lean Thinking has successfully challenged mass production practices, by providing 'leaner' processes and supply chains, i.e. with less waste. Industry 4.0 has become an important strategic approach in the technological change of manufacturing and others. It aims to connect the physical and virtual worlds in industrial production. With such automation associated with Industry 4.0, questions arise about the synergy between this approach and the role of Lean in this ongoing industrial revolution. Therefore, a systematic literature review was carried out in order to identify the role of Lean in this scenario. The review was conducted from 2011 to 2019 timeframe and resulted in a total of 33 papers. This review demonstrated this as an emerging research area with most of the studies published in recent years (2017-2019). A deep analysis was undertaken to understand the Lean effect as a trigger for Industry 4.0. Main findings from a 15 out of the 33 papers revealed elements and facts found in sentences of such papers that act as this trigger. Additionally, a words count indicated that management, processes and people were the most cited words by the 15 papers, reinforcing the role of these key players in the companies' transformation., This work was supported by the Fundaçãoo para a Ciênncia e a Tecnologia.

This paper considers a low-level unit-load warehouse employing single-deep storage lanes and a single-command manual storage and retrieval policy. Analytical travel distance models are developed for class-based and full turnover storage policies under across-aisle, within-aisle and a newly proposed hybrid product placement schemes. Our computational studies show that the analytical models developed in this paper are very accurate as compared to simulation results and a comparative study with a real-world warehouse case. Hybrid storage policies proposed in this paper outperform all other traditional storage policies. The paper also presents insights and simple design rules to warehouse practitioners.

In this paper we provide two significant extensions to the recently developed parameter estimation-based observer design technique for state-affine systems. First, we consider the case when the full state of the system is reconstructed in spite of the presence of unknown, time-varying parameters entering into the system dynamics. Second, we address the problem of reduced order observers with finite convergence time. For the first problem, we propose a simple gradient-based adaptive observer that converges asymptotically under the assumption of generalised persistent excitation. For the reduced order observer we invoke the advanced dynamic regressor extension and mixing parameter estimator technique to show that we can achieve finite convergence time under the weak interval excitation assumption. Simulation results that illustrate the performance of the proposed adaptive observers are given. This include, an unobservable system, an example reported in the literature and the widely popular, and difficult to control, single-ended primary inductor converter.

This paper examines economic growth in 52 African countries for 1961–2016 and seeks to find if there is common growth. As all African countries have their particular features, concerning climate, h...

E-commerce companies often use manual order-picking systems in their warehouses since these systems can provide the required flexibility and scalability. Manual systems have been widely studied, but the operating policies may require significant changes for e-commerce settings. First, to maintain consumers' loyalty, it is important to maintain delivery reliability even on the busiest days. When the number of order pickers in an area increases, however, more delays due to interactions may occur. For example, travel speed may need to be lowered when order pickers pass each other in narrow aisles. Second, many products sold through e-commerce are returned by consumers. Before these returned products can be sold again, they must be reintegrated in the stock. This paper presents hybrid genetic algorithms to determine routes for simultaneous pickup of products in response to consumers' orders and delivery of returned products to storage locations. Furthermore, interactions between the order pickers are considered in the routing decisions. The developed algorithms use specific warehouse problem characteristics. We identify the mix of pickups and deliveries to realise the highest savings in practice. It is shown that order-picker interactions can be a significant cause for delay and should be accounted for in the routing.

New frequency-domain 2-stability criteria are derived for nonlinear discrete-time MIMO systems, having a linear time-invariant block with the transfer function (z), in negative feedback with an aperiodic matrix gain A(k), k = 0, 1, 2,..., and a linear combination of a vector of certain classes of (generalised) first-and-third-quadrant non-monotone nonlinearities.(center dot), having arguments with constant and time-varying delays, but without restrictions on their slopes. The framework does not employ Lyapunov-Krasovskii functionals involving linear matrix inequalities (LMIs) or their equivalent. The new stability criteria seem to be the most general for nonlinear and time variying time-delay systems, and have the following structure: (1) positive definiteness of the real part (as evaluated on | z| = 1) of the product of (z) and an algebraic sum of general causal and anticausal matrix multiplier functions of z. (2) An upper bound on the L1-norm of the inverse Fourier transform of the multiplier function, the L1-norm being weighted by certain novel, quantitative characteristic parameters (CPs) of the nonlinearities.(center dot) without the asumptions of monotonicity, slope restrictions and the like. And (3) constraints on certain global averages of the generalised eigenvalues of (A(k + 1), A(k)), k = 1, 2,..., that are expressed in terms of (i) CPs of the nonlinearities, (ii) their coefficients, and, in general, (iii) time-delays in their arguments, a trade-off among all the three being possible. These global averages imply a restriction on the rate of variation of A(k) in a new sense. The literature results turn out to be special cases of the results of the present paper. Examples illustrate the stability theorems.

Spare parts management is a function of maintenance management that aims to support maintenance activities, giving real-time information on the available quantities of each spare part and adopting the inventory policies that ensure their availability when required, minimizing costs. The classification of spare parts is crucial to control the vast number of parts that have different characteristics and specificities. Spare parts management involves mainly two areas, maintenance and logistics. Therefore, the integration of both input information is recommended to make decisions. This paper presents a multi-criteria classification methodology combining maintenance and logistics perspectives that intends to differentiate and group spare parts to, subsequently, define the most appropriate stock management policy for each group. The methodology was developed based on a case study carried out in a multinational manufacturing company and is intended to be included in its computerized maintenance management system to support decision-making., This work was supported by European Structural and Investment Funds in the FEDER component, through the Operational Competitiveness and Internationalization Programme (COMPETE 2020) [Project no 002814; Funding Reference: POCI-01-0247-FEDER-002814].

This paper proposes a proportional derivative (PD)-like controller applied to the delayed bilateral teleoperation of wheeled robots with force feedback in face of asymmetric and varying-time delays. In contrast to bilateral teleoperation of manipulator robots, in these systems, there is a mismatch between the models of the master and slave (mobile robot), problem that is approached in this work, where the system stability is analysed. From this study, it is possible to infer the control parameters, depending on the time delay, necessary to assure stability. Finally, the performance of the delayed teleoperation system is evaluated through tests where a human operator drives a 3D simulator as well as a mobile robot for pushing objects. Fil: Slawiñski, Emanuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Automática. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Automática; Argentina Fil: Mut, Vicente Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Automática. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Automática; Argentina Fil: Santiago, Diego Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Automática. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Automática; Argentina

This paper investigates the robust stability problem for dynamical neural networks in the presence of time delays and norm-bounded parameter uncertainties with respect to the class of non-decreasing, non-linear activation functions. By employing the Lyapunov stability and homeomorphism mapping theorems together, a new delay-independent sufficient condition is obtained for the existence, uniqueness and global asymptotic stability of the equilibrium point for the delayed uncertain neural networks. The condition obtained for robust stability establishes a matrix-norm relationship between the network parameters of the neural system, which can be easily verified by using properties of the class of the positive definite matrices. Some constructive numerical examples are presented to show the applicability of the obtained result and its advantages over the previously published corresponding literature results. Publisher's Version

This paper proposes a set of distributed real-time optimisation schemes for the steady-state optimisation of parametrically and structurally uncertain systems that are composed of multiple interconnected subsystems. These schemes are derived in the framework of modifier adaptation and use uncertain system models of varying complexity. Consequently, each distributed modifier-adaptation scheme imposes different requirements on the available plant measurements, the communication network, and the control architecture. We prove that every scheme can converge to the plant optimum despite model uncertainty and compare the main features of each approach. Finally, we illustrate our findings via a numerical example.