Transformational supervisor synthesis for evolving systems

Supervisory controller synthesis is a means to compute correct-by-construction controllers for discrete event systems. As these systems and their requirements evolve over time, an updated supervisor needs to be computed each time an adaptation takes place. We consider the case that a supervisor has been synthesized for a given model, after which this model is (slightly) adapted. We investigate how we can make use of the previous synthesis result, in order to more efficiently compute the supervisor for the adapted model. We introduce model deltas as a means to describe the difference between pairs of models. Using the model deltas, a notion of atomic adaptations is introduced. For these atomic adaptations, algorithms are provided to compute the supervisor for the adapted model in a transformational manner from the previous synthesis result, rather than performing a completely new synthesis. These atomic adaptations can be iterated over, to transformationally compute a supervisor for model deltas that contain a number of atomic adaptations. To improve efficiency, it is shown how atomic adaptations can be grouped together based on their required computations and be processed at the same time. A running example is used to support the explanations on the functioning of the algorithms. The efficiency of the method is evaluated by means of both an academic and an industrial use case.</p

Correction to:Transformational supervisor synthesis for evolving systems

The paper mentioned in the title used an incorrect implementation of the algorithms to produce the experimental results. The mistake significantly impacts the computational efficiency of the algorithms, on which they are evaluated. In this correction we explain the mistake, present the new results, and update our conclusions based on the new results.</p

Conversion of LSAT behavioral specifications to automata

The Logistics Specification and Analysis Tool (LSAT) is a model-based engineering tool used for manufacturing system design and analysis. Using a domain specific language, a system can be specified in LSAT. In this paper, a conversion method is presented to obtain the system behavior of an LSAT specification in automata structure.Comment: 10 pages, 6 figure

Chemical distribution in Belgium from 2007 to 2010:an empirical study

Chemical distribution is described from a product lifecycle perspective. The impact of the economic decline in 2009 on Belgian chemical distribution is given in figures. In 2010 the sector recovered sharply. Although the individual companies performed very differently, overall, 2010 was even better than 2008. Increasingly complex legislation on chemical products has initiated a consolidation trend in the sector which in turn has brought on trends in outsourcing and inventory management.<br

Efficiently enforcing mutual state exclusion requirements in symbolic supervisor synthesis

Given a model of an uncontrolled system and a requirement specification, a supervisory controller can be synthesized so that the system under control adheres to the requirements. There are several ways in which informal behavioral safety requirements can be formalized, one of which is using mutual state exclusion requirements. In current implementations of the supervisor synthesis algorithm, synthesis may be inefficient when mutual state exclusion requirements are used. We propose a method to efficiently enforce these requirements in supervisor synthesis. We consider symbolic supervisor synthesis, where Binary Decision Diagrams are used to represent the system. The efficiency of the proposed method is evaluated by means of an industrial and academic case study

Beyond 110 GHz uni-traveling carrier photodiodes on an InP-membrane-on-silicon platform

In this work we have demonstrated a waveguide integrated uni-traveling carrier photodiode on an InP-membrane-on-silicon platform with 3 dB bandwidth beyond 110 GHz. With design optimization and an improved process, devices as small as 3 ×2;μm2 are successfully realized. An electrical equivalent circuit model based on measured S-parameters revealed ultra-small series resistance and junction capacitance as low as 6.5 Ω and 4.4 fF, respectively, in the diodes. The model also provided insight in the photocurrent dependent characteristics in the bandwidth and resonsivity of the devices. Finally, data transmission measurements are demonstrated, showcasing the high speed telecommunication abilities of the UTC-PD.</p

Assessing and facilitating warehouse safety

Purpose – The purpose of this paper is to investigate how warehouse safety can be assessed and facilitated. Methodology – Through a literature study, we build a theoretical framework to provide insights in how safety in Logistics Service Providers (LSPs) can be assessed and facilitated. We perform a case study at a large Dutch LSP using interviews and questionnaires to determine the relevance of the sub-dimensions to assess warehouse safety. Findings – Using literature, we identify people, procedures and technology related sub-dimensions of safety culture and safety behavior and factors that may affect how safety culture translates to safety behavior. Using a case study our findings indicate which sub-dimensions and influencing factors LSP employees find important and why. We found differences in the importance assigned to safety, which may point to the existence of sub-cultures across warehouses. Research limitations/implications – This paper contributes to the limited existing warehouse safety literature in which the factors that influence safety are not well explored. Although the case study investigates one LSP and as such does not generalize across LSPs, it provides valuable insights in important aspects of safety and how they can be influenced. Practical implications – This paper offers safety managers insights in how to assess and facilitate safety within their warehouses. Originality – Although warehouse safety is important, there is scarce academic research that explores this issue