Kailong Zhang

State-Driven Priority Scheduling Mechanisms for Driverless Vehicles Approaching Intersections

Scheduling driverless vehicles with different priorities to pass through intersections efficiently and safely has been becoming an important passing-through intersection (PTI) problem in the field of novel intelligent traffic systems (ITS), which is increasingly becoming cyber-physical-fused and social-service-oriented. Considering new emerging features with possible priorities, a novel centralized priority scheduling mechanism is mainly explored in this paper. First, related pivotal aspects of environment and driverless vehicles are modeled by fusing their physical and kinematic characters. Based on these models, PTI-related motions are further abstracted as several reservation-oriented standard states and actions. Then, an event-triggered and state-driven autonomous control procedure is designed. By mapping vehicular relations in spatiotemporal domain into time-distance windows, a universal passing-through principle, rules, and priority-based scheduling mechanisms are proposed and described in detail. Finally, a priority scheduling algorithm sPriorFIFO is proposed and designed. These models and mechanisms are then implemented within an algorithm simulator, through which scheduling performances are verified and evaluated.

Analysis and Modeled Design of One State-Driven Autonomous Passing-Through Algorithm for Driverless Vehicles at Intersections

Autonomous passing-through intersections has been becoming one important research problem in the domain of intelligent traffic, especially with the real emerging of driverless vehicles. After analyzing this problem and related work, some pivotal aspects, including the lane, path, critical section and vehicle, are modeled with considering relations among their physical and kinetic characters. Then, we abstract some basic actions of this passing procedure, and propose a universal state-based action model. With this model, the procedure will be equal to the switching between these actions and their states. Further, we propose a new centralized scheduling algorithm that is reservation-oriented, and can guarantee the higher request to be responded preferentially. Finally, this algorithm is simulated and the results show that it can promote the traffic efficiency, especially for vehicles with high priority.

A Software Fault-Tolerant Method Based on Exception Handling in RT/E System

Due to the strict requirements of reliabilities in safety-critical domains, this paper researches and proposes an embedded adaptive real-time software fault-tolerant method based on hierarchical and multi-strategy structure. This paper mainly researches on the key issues and appropriate solutions of checkpoints rollback recovery and adaptive task migration. Based on this fault-tolerant method, this paper gives the algorithms of fault monitoring period, checkpoints number and a constraint condition of setting checkpoints. The test result shows that the method improves embedded software reliability effectively under the premise of no additional redundant hardware resources and ensuring the system real-time requirements.

Adaptive resource management architecture for distributed real-time embedded systems

Avionic distributed real-time embedded (DRE) systems execute in open environments where operational conditions, input workload, and resource availability cannot be characterized accurately a prior. We present adaptive resource management architecture for these systems to achieve end-to-end QoS. The architecture contains two loops and adopts bottom-up philosophy to deal with workload/resource variations. The inner loop is established based on feedback control theory, and handles mild variations; while the outer one includes subtask allocation and migration algorithms, to cope with drastic variations.

Service-Oriented Cooperation Models and Mechanisms for Heterogeneous Driverless Vehicles at Continuous Static Critical Sections

As driverless vehicles are increasingly becoming possible, so does the use of such vehicles as intelligent carriers in different domains. Intelligent transportation systems (ITSs) show increasingly heterogeneous, cyber-physical, cooperative, and service-oriented features and are beginning to be merged with the emerging cyber-physical-social systems. Given this new trend, how to make these intelligent vehicles cooperate more safely and efficiently with one another according to novel constraints, such as mission type and quality-of-service (QoS), has become a vital aspect of cooperative ITS (C-ITS). With these emerging characteristics, the classical passing-through-intersection problem has gained new connotations, worth further exploring. After analyzing the essences of this new problem, service-oriented cooperation models and mechanisms for whole autonomous vehicles approaching intersections are investigated in this paper. First, related traffic objects and possible vehicular behaviors are abstracted and modeled with the cyber-physical cooperative features and QoS constraints. A new reservation-based scheduling procedure is then conducted by employing the concepts of vehicle-to-infrastructure communication, and typical vehicular passing-through behaviors and several spatial-temporal constraints are designed to coordinate vehicles passing through an intersection divided as a series of continuous static critical sections. Given these considerations, a priority-based centralized scheduling algorithm, named csPriorFIFO, which adopts a novel priority inheritance mechanism to promote the traffic QoS of emergent vehicles, is proposed. Finally, all these designs are implemented in a traffic simulator named QoS-CITS, and the functions and the performance of these studied methods are verified and compared.

Density-Aware Rate Adaptation for Vehicle Safety Communications in the Highway Environment

In this letter, we propose a density-aware rate adaptation (DARA) protocol to ensure reliable vehicle safety communication in a highway broadcast environment. DARA significantly improves system reliability by addressing the challenges of estimating channel conditions caused by various dynamics due to factors, including channel fading, interference, and varying traffic density. One salient advantage of DARA is that it can estimate the average packet loss rate for each sender locally without the use of any control frames (such as ACK and RTS/CTS). DARA can also distinguish the interference losses from the fading losses based on an empirical model. It adjusts the bit rate only in response to the packet loss due to channel fading and the change of the traffic density. Simulation results demonstrate that DARA can provide reliability guarantees for vehicle safety communication.

Agent Based Adaptive Cooperative Models and Mechanisms of Multiple Autonomous Cyber-Physical Systems

Networked cooperation is one primarily problem for autonomous Cyber-Physical Systems(CPS) that feature cyber-physical fusion, and smart behavior. After analyzing current contributions, a three-level task model, with which missions can be recognized and mapped to tasks, is studied firstly in this paper. And then, based on a designed uniform model of the surroundings, external missions and internal computational resources, two hybrid models, which are autonomously cooperative and real-time reactive by taking advantages of agent and adaptive control, are illuminated respectively. Further, a hierarchal cooperation mechanism of CPS fleet is put forward. With this mechanism, the dynamic topologies of a fleet will be more flexible and dependable, and by adopting an intelligent algorithm, all tasks mapped from a mission can be autonomously assigned to suitable members under decentralized consultation or centralized allocation mode. In this paper, an optimized genetic algorithm is employed to illustrate the process of proposed mechanisms.

A New Universal-Environment Adaptive Multi-processor Scheduler for Autonomous Cyber-Physical System

Robot, spaceship and other applications that can be called autonomous Cyber-Physical Systems (CPS) are all smart embedded systems, which usually run in open environment by themselves with inhered intelligent capabilities. Besides the application intelligence, the researches of adaptive platform for such systems have also become topics recently. Based on the analysis of current work, a new environment adaptive scheduler (α-S) for multiprocessor platform of a cyber-physical system is proposed in this article. And then, its related structures, models, and reasoning methods are studied deeply. Different from the existing ones, α-S can schedule all tasks according to the environment change by two layered functions. The upper one uses not only the properties of a task but also the state of environment and system resources as input variables, which is defined as Universal Environment (UE), and then calculates the Quality of Scheduling of all tasks with a customized fuzzy logic. The lower one allocates these tasks onto processors automatically under the dynamic performance evaluation of computing resources, such as load and success rate of each processor. Further, some allocation policies are studied and defined to make α-S be more flexible to adapt different requirements. Finally, studied methods are simulated and then experimented on an obstacle-avoiding robot system.

An Adaptive Performance Management Method for Failure Detection

Failure detection is an essential part to build high dependable distributed real-time embedded systems. However, the performance degradation of production work due to the execution of failure detection cannot be omitted. We present an adaptive performance management method for failure detection based on feedback control theory. This method is autonomous and thus allows the system to self-manage the CPU resources allocated for failure detection, with only the high-level policy input. Therefore, it limits the performance impact due to the execution of failure detection, even in the dynamic environment.

A Flexible Multi-Channel Coordination MAC Protocol for Vehicular Ad Hoc Networks

The IEEE 802.11p/1609.4 standard supports both safety applications and non-safety services for vehicular ad hoc networks (VANETs) via multi-channel operations. In this letter, we establish an analytical model to calculate the optimal bandwidth resource allocation and propose a flexible multi-channel coordination MAC (FMC-MAC) protocol for VANETs. The FMC-MAC protocol allows safety messages broadcasted on service channel and non-safety data transmitted on control channel in a flexible way. It does not only guarantee the reliability of safety applications, but also improve the throughput of non-safety services. The simulation results validate the analytical model and the proposed FMC-MAC protocol.