Cyberphysical systems (CPSs) are new class of engineered systems that offer close interaction between cyber and physical components. The field of CPS has been identified as a key area of research, and CPSs are expected to play a major role in the design and development of future systems. In this paper, we survey recent advancements made in the development and applications of CPSs. We classify the existing research work based on their characteristics and identify the future challenges. We also discuss the examples of prototypes of CPSs. The aim of this survey is to enable researchers and system designers to get insights into the working and applications of CPSs and motivate them to propose novel solutions for making wide-scale adoption of CPS a tangible reality.

Design Techniques and Applications of Cyberphysical Systems: A Survey

The Art of Multiprocessor Programming

Quadrotor helicopters have become increasingly important in recent years as platforms for both research and commercial unmanned aerial vehicle applications. This paper extends previous work on several important aerodynamic effects impacting quadrotor flight in regimes beyond nominal hover conditions. The implications of these effects on quadrotor performance are investigated and control techniques are presented that compensate for them accordingly. The analysis and control systems are validated on the Stanford Testbed of Autonomous Rotorcraft for Multi-Agent Control quadrotor helicopter testbed by performing the quadrotor equivalent of the stall turn aerobatic maneuver. Flight results demonstrate the accuracy of the aerodynamic models and improved control performance with the proposed control schemes.

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Aerodynamics and control of autonomous quadrotor helicopters in aggressive maneuvering

Many network applications, eg, industrial control, demand ultra-low latency (ULL) However, traditional packet networks can only reduce the end-to-end latencies to the order of tens of milliseconds The IEEE 8021 time sensitive networking (TSN) standard and related research studies have sought to provide link layer support for ULL networking, while the emerging IETF deterministic networking (DetNet) standards seek to provide the complementary network layer ULL support This paper provides an up-to-date comprehensive survey of the IEEE TSN and IETF DetNet standards and the related research studies The survey of these standards and research studies is organized according to the main categories of flow concept, flow synchronization, flow management, flow control, and flow integrity ULL networking mechanisms play a critical role in the emerging fifth generation (5G) network access chain from wireless devices via access, backhaul, and core networks We survey the studies that specifically target the support of ULL in 5G networks, with the main categories of fronthaul, backhaul, and network management Throughout, we identify the pitfalls and limitations of the existing standards and research studies This survey can thus serve as a basis for the development of standards enhancements and future ULL research studies that address the identified pitfalls and limitations

Ultra-Low Latency (ULL) Networks: The IEEE TSN and IETF DetNet Standards and Related 5G ULL Research

http://ai.stanford.edu/~gabeh/papers/cepStarmac.pdf

Precision flight control for a multi-vehicle quadrotor helicopter testbed

The enhancements being developed by the Time-Sensitive Networking Task Group as part of IEEE 802.1 emerge as the future of real-time communication over Ethernet networks for automotive and industrial application domains. In particular IEEE 802.1Qbv is key to enabling timeliness guarantees via so-called time-aware shapers. In this paper, we address the computation of fully deterministic schedules for 802.1Qbv-compliant multi-hop switched networks. We identify and analyze key functional parameters affecting the deterministic behaviour of real-time communication under 802.1Qbv and, based on a generalized configuration of these parameters, derive the required constraints for computing offline schedules guaranteeing low and bounded jitter and deterministic end-to-end latency for critical communication flows. Furthermore, we discuss several optimization directions and concrete configurations exposing trade-offs against the required computation time. We also show the performance of our approach via synthetic network workloads on top of different network configurations.

Scheduling Real-Time Communication in IEEE 802.1Qbv Time Sensitive Networks

Ethernet-based time-triggered networks (e.g. TTEthernet) enable the cost-effective integration of safety-critical and real-time distributed applications in domains where determinism is a key requirement, like the aerospace, automotive, and industrial domains. Time-Triggered communication typically follows an offline and statically configured schedule (the synthesis of which is an NP-complete problem) guaranteeing contention-free frame transmissions. Extending the end-to-end determinism towards the application layers requires that software tasks running on end nodes are scheduled in tight relation to the underlying time-triggered network schedule. In this paper we discuss the simultaneous co-generation of static network and task schedules for distributed systems consisting of preemptive time-triggered tasks which communicate over switched multi-speed time-triggered networks. We formulate the schedule problem using first-order logical constraints and present alternative methods to find a solution, with or without optimization objectives, based on satisfiability modulo theories (SMT) and mixed integer programming (MIP) solvers, respectively. Furthermore, we present an incremental scheduling approach, based on the demand bound test for asynchronous tasks, which significantly improves the scalability of the scheduling problem. We demonstrate the performance of the approach with an extensive evaluation of industrial-sized synthetic configurations using alternative state-of-the-art SMT and MIP solvers and show that, even when using optimization, most of the problems are solved within reasonable time using the incremental method.

Combined task- and network-level scheduling for distributed time-triggered systems

In this study the authors are interested in safety-critical real-time applications implemented on distributed architectures supporting the time-sensitive networking (TSN) standard. The on-going standardisation of TSN is an IEEE effort to bring deterministic real-time capabilities into the IEEE 802.1 Ethernet standard supporting safety-critical systems and guaranteed quality-of-service. TSN will support time-triggered (TT) communication based on schedule tables, audio-video-bridging (AVB) flows with bounded end-to-end latency as well as best-effort messages. The authors first present a survey of research related to the optimisation of distributed cyber-physical systems using real-time Ethernet for communication. Then, the authors formulate two novel optimisation problems related to the scheduling and routing of TT and AVB traffic in TSN. Thus, the authors consider that they know the topology of the network as well as the set of TT and AVB flows. The authors are interested to determine the routing of both TT and AVB flows as well as the scheduling of the TT flows such that all frames are schedulable and the AVB worst-case end-to-end delay is minimised. The authors have proposed an integer linear programming formulation for the scheduling problem and a greedy randomised adaptive search procedure-based heuristic for the routing problem. The proposed approaches have been evaluated using several test cases.

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Design optimisation of cyber-physical distributed systems using IEEE time-sensitive networks

Time Sensitive Networks (TSN) emerge as the set of sub-standards incorporating real-time support as an extension of standard Ethernet. In particular, IEEE 802.1Qbv defines a time-triggered communication paradigm with the addition of a time-aware shaper governing the selection of frames at the egress queues according to a predefined schedule, encoded in so-called Gate Control Lists (GCL). Nonetheless, the design of compositional systems with real-time demands requires a proper configuration of these mechanisms to truly achieve the temporal isolation of communication streams with end-to-end timeliness guarantees. In this paper we address how the synthesis of communication schedules for GCLs defined in IEEE 802.1Qbv can be formalized as a system of constraints expressed via first-order theory of arrays (T_A). We formulate the necessary constraints showing the suitability of the theory of arrays and discuss optimization opportunities arising from the underlying scheduling problem. Our evaluation using general-purpose SMT/OMT solvers proves the validity of the approach, scaling well for small-to medium-networks, and exposing trade-offs for the time needed to synthesize a schedule. Furthermore, we conduct a comparison against previous work and conclude the appropriateness of the method as the basis for future TSN scheduling tools.

IEEE 802.1Qbv Gate Control List Synthesis Using Array Theory Encoding

Distributed safety-critical applications in industrial automation, aerospace, and automotive, require worst-case end-to-end latency analysis for critical communication flows in order to prove their correct behavior in the temporal domain. With the advent of time sensitive networks (TSNs), distributed applications can be built on top of standard Ethernet technologies without sacrificing real-time characteristics. The time-based transmission selection and clock synchronization mechanism defined in the TSN enable the real-time transmission of frames based on a global schedule configured through so-called gate control lists (GCLs). This paper has an enhancement of allowing a mixture of the priority-based scheduling and time-triggered, which expand the solution space for the GCLs. Then, it is necessary to analyze the latency bounds for the critical traffic in the TSN network. In this paper, we start from the assumption that the GCLs, i.e., the communication schedules, and the traffic class (priority) assignment for critical flows are given for each output port and derive, using network calculus, an analysis of the worst-case delays that individual critical flows can experience along the hops from sender to receiver(s). Our method can be employed for the analysis of the TSNs where the GCLs have been created in advance, as well as for driving the GCL synthesis that explores a larger solution space than previous methods, which required a complete isolation of transmission events from different traffic classes. We validate our model and analysis by performing experiments on both synthetic and real-world use-cases, showing the scalability of our implementation as well as the impact of certain GCL properties (gate overlapping and traffic class assignments) on the worst-case latency of critical communication flows.

Silviu S. Craciunas

Papers

Scheduling Real-Time Communication in IEEE 802.1Qbv Time Sensitive Networks

Combined task- and network-level scheduling for distributed time-triggered systems

Design optimisation of cyber-physical distributed systems using IEEE time-sensitive networks

IEEE 802.1Qbv Gate Control List Synthesis Using Array Theory Encoding

Worst-Case Latency Analysis for IEEE 802.1Qbv Time Sensitive Networks Using Network Calculus