Self-triggered Approach Research Articles

A Self-Triggered Approach for Co-Design of MPC and Computing Resource Allocation

A Self-Triggered Approach for Co-Design of MPC and Computing Resource Allocation

Novel distributed event/self-triggered sliding-mode control: Application to practical fixed-time consensus of second-order multi-agent systems

This paper presents a novel terminal sliding-mode control (SMC) protocol to accomplish the practical fixed-time (PFXT) consensus of second-order multi-agent systems (MASs) through event-triggered scheme (ETS). The main challenge is the digitization of SMC which prevents the controlled system from reaching an ideal sliding phase and the singularity problem in terminal sliding-mode controllers. Firstly, a novel method of PFXT stability is proposed, which guarantees the non-singularity for the controller. Secondly, based on the proposed PFXT control method, a practical non-singular terminal SMC strategy is designed to accomplish the PFXT consensus of MASs through ETS. Besides, a strictly positive minimal triggering interval of each follower is given to exclude the Zeno phenomenon. Different with conventional terminal SMC, maintaining the sliding trajectory constrained on the sliding manifold is not a premise to guarantee the system stability. Then, to eliminate the requirement of continuous monitoring for ETS, the SMC strategy is generalized to the self-triggered approach. At last, a numerical example is presented to validate the developed methods.

Quasi-Bipartite Synchronization of Derivatively Coupled Complex Dynamic Networks: Memory-Based Self-Triggered Approach

Quasi-Bipartite Synchronization of Derivatively Coupled Complex Dynamic Networks: Memory-Based Self-Triggered Approach

Triggered finite‐time consensus of first‐order multi‐agent systems with input saturation

Input saturation, which brings input non-linearity to systems and limits the closed-loop systems' performances severely, is an ubiquitous problem in practice. Here, triggered finite-time consensus problem of disturbed leader-follower multi-agent systems is addressed under input saturation constraint. To overcome the coupling of the non-linearity and finite-time convergence together with input saturation, non-linear triggered control protocol has been proposed, which is confirmed through a two-step stabilization procedure. First, the saturated closed-loop system is designed to be asymptotically stable, under which the systems converge into a desaturated region in finite time. Then in the second step, with the proposed control protocol, the desaturated closed-loop multi-agent systems can achieve practical finite-time consensus. In addition, to get rid of continuous communication in the monitoring of event-triggered condition, a self-triggered approach is further proposed. With rigorous analyses, practical finite-time consensus can be achieved for the overall closed-loop systems and Zeno behavior is also excluded. Simulations are carried out in detail to illustrate the theoretical results in this study.

Resilient self/event-triggered consensus based on ternary control

This paper considers the problem of multi-agent consensus in the presence of adversarial agents. Such adversaries may try to introduce undesired influence on the coordination of the regular agents and to even prevent them from reaching consensus. To our setting, we extend the so-called mean subsequence reduced algorithms with the aim to reduce the use of computation and communication resources of the agents. In particular, by employing self- and event-triggered communication, the frequencies of state updates as well as data transmissions are kept low. Moreover, the control inputs of the agents take the form of ternary signals, allowing them to further reduce the amount of information at each transmission. We will observe that in hostile environments with adversaries, the self-triggered approach can bring certain advantages over the event-triggered counterpart. Moreover, a novel switching scheme is introduced to mix the two protocols to further enhance the performance of the agents.

Robust distributed model predictive consensus of discrete-time multi-agent systems: a self-triggered approach

Robust distributed model predictive consensus of discrete-time multi-agent systems: a self-triggered approach

Self-triggered impulsive control of nonlinear time delay systems: Application to chemotherapeutic dose-regimen design

This paper proposes a self-triggered impulsive control for nonlinear time-delay systems, where the time instant of the next impulsive input is calculated based on the last measurement and the values of the systems’ parameters. Contrary to event-triggered scheme where the actuation is discrete but a continuous monitoring of the system’s states is necessary, in the self-triggered approach, both sampling and actuation are performed at distinct moments of time. Utilizing Lyapunov–Razumikhin method and by upper-bounding the system’s trajectory, the global asymptotic stability of the system’s equilibrium is verified when the rate of change in the Lyapunov function is exponential. In the general case, the global ultimate boundedness of the system’s trajectory is shown where the ultimate bound can be set arbitrarily small. As an application, for the first time, the problem of dose regimen design is formulated in the sampled data framework. Then, based on the obtained theoretical results, the appropriate regimen is suggested. In particular, time-triggered and self-triggered therapy protocols for docetaxel, a phase specific chemotherapeutic drug which is administered intravenously, are proposed. Clinical constraints such as maximum tolerated dose, discontinuous drug administration, and intermittent measurements are met in the proposed therapy protocols. According to in-silico results, both proposed self-triggered and time-triggered dose regimens outperform the traditional weekly fixed dose administration. Finally, the robustness of the proposed schemes to parameter uncertainties is evaluated through an extensive set of simulations.

A Zeno-Free Self-Triggered Approach to Practical Fixed-Time Consensus Tracking With Input Delay

This article considers the practical fixed-time self-triggered consensus tracking problem of delayed multiagent networks (MANs) subject to external disturbances under undirected topology and directed topology. The fixed-time consensus implies that the consensus is reached in a finite time and the convergence time is independent of initial conditions under the nonlinear consensus protocols. A self-triggered control (STC) strategy is developed based on the event-triggered control (ETC) strategy. For the ETC strategy, the nonlinear controllers and the measurement errors are designed based on the hyperbolic tangent function to avoid a nondifferential problem and Zeno behavior. To avoid continuous monitoring, the STC strategy is presented. Furthermore, the minimal interevent interval is strictly positive, which implies that no Zeno behavior occurs in the STC strategy. Finally, a numerical example is presented to verify the availability of the algorithms.

Stochastic stability analysis for Vehicular Networked Systems with State-dependent bursty fading channels: A self-triggered approach

Vehicular Networked Systems (VNS) are mobile ad hoc networks where vehicles exchange information over wireless communication networks to ensure safe and efficient operation. It is, however, challenging to ensure system safety and efficiency as the wireless channels in VNS are often subject to state-dependent deep fades where the data rate suffers a severe drop and changes as a function of vehicle states. Such couplings between vehicle states and channel states in VNS thereby invalidate the use of separation principle to design event-based control strategies. By adopting a state-dependent fading channel model, this paper presents a novel self-triggered scheme under which the VNS ensures efficient use of communication bandwidth while preserving stochastic stability. Under the proposed self-triggered scheme, this paper presents a novel source coding scheme that tracks vehicle’s states with performance guarantee in the presence of state-dependent fading channels. The efficacy and advantages of the proposed scheme over other event-based strategies are verified by a leader–follower example.

Model-Based Network Scheduling and Control for Systems over the IEEE 802.15.4 Network

The scheduling and control of a class of wireless networked control system is investigated, whose control loop is closed via a shared IEEE 802.15.4 wireless network. By using a gain scheduler within the packet-based control framework and fitting the delay-dependent gains into a time-delay system model, a less conservative self-triggered approach is proposed to determine the sampling update, which consequently enables the design of two network scheduling algorithms to reduce the communication usage. Numerical and TrueTime based examples illustrate the effectiveness of the proposed approach in the sense that it reduces greatly the communication usage while maintaining satisfactory control performance.

Distributed min–max MPC for dynamically coupled nonlinear systems: A self-triggered approach

This paper considers the formation stabilization problem of dynamically coupled nonlinear systems with parametric uncertainties and additive disturbances. We develop a distributed min–max model predictive control (MPC) framework, in which each subsystem adopts the local optimal control action by solving the constrained optimization problem. As a main contribution of this paper, a self-triggered strategy is presented within the proposed framework for resource-constrained coupled systems. By implementing the distributed self-triggered scheduler, the communication burden is significantly alleviated while ensuring comparable control performance. In addition, for each subsystem the latest information is transmitted to its neighbors asynchronously at the local triggering time instants. Moreover, the resulting distributed self-triggered min–max MPC framework ensures the constraints satisfaction and the closed-loop stability. Finally, the numerical experiments are performed to verify the theoretical results.

Distributed control plane for safe cooperative vehicular cyber physical systems

Cooperative vehicular cyber physical systems build a group of entities that can accomplish a cooperative task using the distributed control approaches. To this end, such a cooperative task can be coordinated and managed by a distributed control plane that will be able to encapsulate all the required functionality in a layered architecture providing the required interoperability. Here, the authors propose such a distributed control plane that consists of the cooperative awareness layer, the communication layer and the distributed control layer. Wireless communications play an important role for the mobility provision, taking into account different constraints in order to provide high reliability and low latency. A simulation environment is considered with a leader–follower control format, where the reliability is evaluated. Further, a distributed safety monitoring approach is devised, given a control diagram and mapping of the events to the different components. The event monitoring relies on the self-triggered approach, where a use case is evaluated to highlight the impact of the input and output delays to the model predictive control component of the overall distributed control diagram including the calculation of the number of triggered events.

Event- and self-triggered consensus for double-integrator networks with relative state measurements

ABSTRACTThis paper addresses the consensus problem of double-integrator networks via event- and self-triggered control approaches. In the proposed control protocol, only relative state information is utilised to synchronise all agents. First, an event-triggering algorithm with periodic event detection is designed to determine the event times of each agent. Then, a self-triggered control algorithm is provided to further reduce resource consumption. Two numerical simulations are conducted to illustrate the effectiveness of the results.

Kernel Design and Distributed, Self-Triggered Control for Coordination of Autonomous Multi-Agent Configurations

SUMMARYAutonomous multi-agent systems show promise in countless applications, but can be hindered in environments where inter-agent communication is limited. In such cases, this paper considers a scenario where agents communicate intermittently through a cloud server. We derive a graph transformation mapping the kernel of a graph's Laplacian to a desired configuration vector while retaining graph topology characteristics. The transformation facilitates derivation of a self-triggered controller driving agents to prescribed configurations while regulating instances of inter-agent communication. Experimental validation of the theoretical results shows the self-triggered approach drives agents to a desired configuration using fewer control updates than traditional periodic implementations.

Digital implementation of a self-triggered control approach for a mechatronic platform: experimental results

This paper addresses the design and presents the experimental results of an aperiodic remote-controlled mechatronic plant using a MiniDK2 electronic development board. We compare the classic periodic control solution with our self-triggered approach. The triggering mechanism consists of evaluating if the measurement error exceeds a predefined value. This measurement error is defined as the difference between the output signal of a model with and without a sample-and-hold that is activated only at the triggering instants. The minimum inter-execution time is the reference period and the maximum time is set by the designer, guaranteeing the stability of the closed loop system. At each new triggering instant, the remote controller receives a new measurement of the system and sends the actuation signal to the mechatronic plant.

Collision-Aware Communication for Intersection Management of Automated Vehicles

Intersection management of automated vehicles relies on wireless communication, whereby communication resources should be allocated to vehicles while maintaining safety. We present a collision-aware resource allocation (CARA) strategy for coordination of automated and connected vehicles by a centralized intersection manager. The proposed strategy is based on a self-triggered approach and proactively reduces the risk of channel congestion by only assigning communication resources to vehicles that are in critical configurations, i.e., when there is a risk for a future collision. Compared with collision-agnostic communication strategies, typically considered for automated intersection management, the CARA strategy aims to bridge the gap between control, sensing, and communication. It is shown to significantly reduce the required amount of communication (albeit with a slight increase in the control cost), without compromising safety. Furthermore, control cost can be reduced by allowing more frequent communication, which we demonstrate through a trade-off analysis between control performance and communication load. Hence, CARA can operate in communication-limited scenarios, but also be modified for scenarios where the control cost is of primary interest.

Event-based consensus of second-order multi-agent systems with discrete time

Event-based control has received considerable attention due to its irreplaceable advantage in resource-limited systems. In this paper, event-based consensus of second-order discrete-time multi-agent systems is investigated. The event-based controller is designed for each agent, which is based on the state measurement error among neighborhood agents at its own triggering time instants. Some sufficient conditions are obtained for achieving consensus. To avoid observing the current states of its neighbor agents as well as its own state at every discrete-time, a self-triggered approach is presented to determine the triggering time sequence. Furthermore, certain conditions are given to avoid controller update at every discrete time. Finally, a simulation example is given to illustrate the efficiency of the proposed control strategy.

Adaptive self-triggered control of a remotely operated P3-DX robot: Simulation and experimentation

In this paper the problem of remotely operating an autonomous robot through a wireless communication channel is considered. The main goal is to achieve a satisfactory tracking performance while reducing network usage. To attain this objective, a self-triggered strategy that adjusts the triggering condition to the observed tracking error is implemented. After the theoretical justification, simulation results of a P3-DX mobile robot remotely controlled using TrueTime are presented. Also, the same adaptive self-triggered approach has been tested on a real robot. The experiments reinforce the relevant reduction on the generated network traffic compared to a periodic implementation and to a non-adaptive self-triggered approach, while the tracking performance is barely degraded.

Experimental evaluation of slack management in real-time control systems: Coordinated vs. self-triggered approach

Effective slack management, i.e., management of unused computing resources, for real-time control tasks mandates to redistribute the available resources between controllers as a function of the state of the controlled plants. Slack can be allocated to control tasks to alter their rate of progress via e.g., the controllers’ period, in order to adapt their behavior to changes in the computing platform and in the environment. This paper presents an experimental evaluation of two representative slack redistribution policies for multitasking real-time control systems: “coordinated” vs. “self-triggered”. In the coordinated policy a resource manager is responsible for modifying each control task progress. Alternatively, in the self-triggered policy, each control task decides its progress. The demands that each policy poses to the computing platform are analyzed and different operating system architectures providing flexibility and adaptivity are discussed. A proof-of-concept implementation including the real-time control of three double integrator plants in the form of electronic circuits is presented, and a complete performance analysis is reported.