Showing papers by "Roberto Passerone published in 2018"

Contracts for System Design

Abstract: Recently, contract-based design has been proposed as an “orthogonal” approach that complements system design methodologies proposed so far to cope with the complexity of system design. Contract-based design provides a rigorous scaffolding for verification, analysis, abstraction/refinement, and even synthesis. A number of results have been obtained in this domain but a unified treatment of the topic that can help put contract-based design in perspective was missing. This monograph intends to provide such a treatment where contracts are precisely defined and characterized so that they can be used in design methodologies with no ambiguity. In particular, this monograph identifies the essence of complex system design using contracts through a mathematical “meta-theory”, where all the properties of the methodology are derived from a very abstract and generic notion of contract. We show that the meta-theory provides deep and illuminating links with existing contract and interface theories, as well as guidelines for designing new theories. Our study encompasses contracts for both software and systems, with emphasis on the latter. We illustrate the use of contracts with two examples: requirement engineering for a parking garage management, and the development of contracts for timing and scheduling in the context of the AUTOSAR methodology in use in the automotive sector.

Design and Characterization of a Low-Cost FPGA-Based TDC

Abstract: We present a field-programmable gate array (FPGA) implementation of a time-to-digital converter (TDC) based on a low-cost, low-area Spartan 6 device. The converter is based on a tapped delay line model. Several implementation details are discussed with a particular focus on critical blocks such as the input stage and thermometer-to-binary decoding techniques. We implemented a tap filtering technique to improve the differential nonlinearity (DNL) of the single delay line while keeping a good LSB value of 25.57 ps with a single-shot precision (SSP) between $0.69\div 1.46$ LSB. Measured DNL and integral nonlinearity (INL) lie in the range between $-0.90\div 1.23$ and $-0.43\div 2.96$ LSB, respectively. Measured DNL and INL lie in the range between $-0.90\div 1.23$ and $-0.43\div 2.96$ LSB, respectively. We then implemented an interpolating TDC to overcome the limitations of a single delay line in terms of linearity and measurement range. The interpolating TDC uses the sliding scale technique, where the time interval to be measured is asynchronous with respect to the FPGA clock, achieving DNL and INL in the range $-0.072\div 0.070$ and $-0.755\div 0.872$ LSB. SSP is in the $1.096\div 2.815$ range. Moreover, we present a novel comparison between the DNLs obtained with two different methods: statistical code density test and using a finely controlled delay source. Finally, we present the results of a Monte Carlo simulation used to investigate the effects of nonlinear propagation of the signal through the delay line.

Dependability Assessment of SOA-Based CPS With Contracts and Model-Based Fault Injection

Abstract: Engineering complex distributed systems is challenging. Recent solutions for the development of cyber-physical systems (CPS) in industry tend to rely on architectural designs based on service orientation, where the constituent components are deployed according to their service behavior and are to be understood as loosely coupled and mostly independent. In this paper, we develop a workflow that combines contract-based and CPS model-based specifications with service orientation, and analyze the resulting model using fault injection to assess the dependability of the systems. Compositionality principles based on the contract specification help us to make the analysis practical. The presented techniques are evaluated on two case studies.

A battery-free non-intrusive power meter for low-cost energy monitoring

Abstract: As highlighted by the Intergovernmental Panel for Climate Change (IPCC), providing clean, reliable and affordable energy for people everywhere will require the reduction of gas emission in the energy domain by 90%, compared to 2010 emissions, between the years 2040 and 2070. In addition, to a change in choices, preferences and behavior of individuals and households in energy demand and consumption, to achieve a successful transition to a more sustainable energy system, the adoption of new metering solutions to foster a wide range of sustainable actions by diverse people across the globe will be required. In this paper, we discuss the development of an ultra-low-power energy meter exploiting a single current transformer (CT) sensor for harvesting energy from the same load under monitoring. Starting from the hypothesis that the node activation rate increases monotonically with the primary load draw, and assuming that the node consumes fixed energy quanta during each activation, it is possible to infer the load power from the interval between activations. With this approach, we can provide a device that lowers maintenance cost related to installation and battery replacement; does not need to deal with high main voltage; and does not introduce any additional energy consumption overhead as it draws zero-power under zero-load condition. Energy budget is guaranteed also thanks to the use of a LoRa radio for data transmission.

Optimal landmark placement for indoor positioning using context information and multi-sensor data

Abstract: The most effective solutions for indoor positioning of mobile agents typically rely on multi-sensor data fusion. In particular, good trade-offs in terms of accuracy, scalability and availability can be achieved by combining dead reckoning techniques (e.g. based on odometry) and measurements of distance and attitude with respect to suitable landmarks with a known position and/or orientation within a given reference frame. A crucial problem of this kind of techniques is landmark deployment, which should keep into account not only the limited detection range of the adopted sensors and the non-null probability of missing a landmark, even if it actually lies within the sensor detection area (SDA). This paper focuses on minimum landmark placement taking into account possible environment contextual information. This solution relies on a greedy placement algorithm that optimally solves the problem while keeping positioning uncertainty below a given limit. The correctness of the proposed approach is verified through multiple simulations in the context of the EU project ACANTO, which requires to localise one or more smart robotic walkers in large, public and potentially crowded environments such as shopping malls or airports.

A Low-Power Vision System With Adaptive Background Subtraction and Image Segmentation for Unusual Event Detection

Abstract: This paper presents a smart ultra-low power vision system targeted to video surveillance applications. The sensor embeds a low-level image processing technique that autonomously detects unusual events occurring in the scene, relying on adaptive background subtraction. The resulting binary image is then directly segmented by an FPGA, which triggers the higher layer of processing, transferring only aggregate feature information. The on-board processing relieves the rest of the vision system from expensive computation. The $104\times 104$ pixels vision chip consumes $80~\mu \text{W}$ at 30 frames/s, while segmentation dramatically cuts down the amount of data to be transferred, resulting in an extremely low-power system suitable for embedded applications.

Sharpening the Scythe of Technological Change: Socio-Technical Challenges of Autonomous and Adaptive Cyber-Physical Systems

Abstract: Autonomous and Adaptative Cyber-Physical Systems (ACPS) represent a new knowledge frontier of converging “nano-bio-info-cogno” technologies and applications. ACPS have the ability to integrate new ‘mutagenic’ technologies, i.e., technologies able to cause mutations in the society. Emerging approaches, such as artificial intelligence techniques and deep learning, enable exponential speedups for supporting increasingly higher levels of autonomy and self-adaptation. In spite of this disruptive landscape, however, deployment and broader adoption of ACPS in safety-critical scenarios remains challenging. In this paper, we address some challenges that are stretching the limits of ACPS safety engineering, including tightly related aspects such as ethics and resilience. We argue that a paradigm change is needed that includes the entire socio-technical aspects, including trustworthiness, responsibility, liability, as well as the ACPS ability to learn from past events, anticipate long-term threads and recover from unexpected behaviors.

Optimized selection of wireless network topologies and components via efficient pruning of feasible paths

Abstract: We address the design space exploration of wireless networks to jointly select topology and component sizing. We formulate the exploration problem as an optimized mapping problem, where network elements are associated with components from pre-defined libraries to minimize a cost function under correctness guarantees. We express a rich set of system requirements as mixed integer linear constraints over path variables, denoting the presence or absence of paths between network nodes, and propose an algorithm for efficient, compact encoding of feasible paths that can reduce by orders of magnitude the complexity of the optimization problem. We incorporate our methods in a system-level design space exploration toolbox and evaluate their effectiveness on design examples from data collection and localization networks.