Networked control systems are spatially distributed systems in which the communication between sensors, actuators, and controllers occurs through a shared band-limited digital communication network. Several advantages of the network architectures include reduced system wiring, plug and play devices, increased system agility, and ease of system diagnosis and maintenance. Consequently, networked control is the current trend for industrial automation and has ever-increasing applications in a wide range of areas, such as smart grids, manufacturing systems, process control, automobiles, automated highway systems, and unmanned aerial vehicles. The modelling, analysis, and control of networked control systems have received considerable attention in the last two decades. The &#x2018 control over networks &#x2019 is one of the key research directions for networked control systems. This paper aims at presenting a survey of trends and techniques in networked control systems from the perspective of &#x2018 control over networks &#x2019 , providing a snapshot of five control issues: sampled-data control, quantization control, networked control, event-triggered control, and security control. Some challenging issues are suggested to direct the future research.

Networked control systems: a survey of trends and techniques

Probabilistic‐constrained filtering for a class of nonlinear systems with improved static event‐triggered communication

In this note, the event-triggered adaptive control for a class of uncertain nonlinear systems is considered. Unlike the traditional adaptive event-triggered control, the controller and parameter estimator are event-triggered simultaneously. Asymptotical convergence of stabilization error is guaranteed. To solve this problem, we design a set of event-triggering conditions, which is updated for each triggering. At the same time, the input-to-state stable assumption is not needed. It is shown that the proposed control schemes guarantee that all the closed-loop signals are globally bounded and the stabilization error converges to the origin asymptotically. Simulation results illustrate the effectiveness of our scheme.

Adaptive Event-Triggered Control of Nonlinear Systems With Controller and Parameter Estimator Triggering

Input-to-state stability of integral-based event-triggered control for linear plants

In event-triggered control (ETC) systems, the measured state or output of the plant is sent to the controller at so-called event times . In many ETC systems, these event times are generated based on a static function of the current state or output measurement of the system and its sampled-and-held version that is available to the controller. Hence, the event-generator does not include any dynamics of its own. In contrast, dynamic event-generators trigger events based on additional dynamic variables, whose dynamics depend on the state or output of the system. In this paper, we propose new static and dynamic continuous event-generators (which require continuous measuring of the plant output) and periodic event-generators (which only require periodic sampling of the plant output) for linear control systems with communication delays. All event-generators we propose lead to closed-loop systems which are globally exponentially stable with a guaranteed decay rate, $\mathcal L_2$ -stable with a guaranteed $\mathcal L_2$ -gain, and have a guaranteed positive minimum inter-event time. By using new Riccati-based analysis tools tailored to linear systems, the conservatism in our decay rate and $\mathcal L_2$ -gain estimates is small. The dynamic event-generators even further reduce this conservatism, and as a result typically generate significantly fewer events than their static counterparts, while guaranteeing the same control performance. The benefits of these new event-generators are demonstrated via two numerical examples.

Riccati-Based Design of Event-Triggered Controllers for Linear Systems With Delays

In this study, an integral-based event-driven mechanism is proposed for a general class of non-linear systems. The proposed scheme is less conservative than earlier work on the subject and achieves asymptotic stability without forcing the derivative of the Lyapunov function to be negative between samples. A rigorous proof is given, showing that the proposed triggering condition is more effective than the corresponding traditional approaches. Simulation results are provided to illustrate the effectiveness of the proposed solution.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-cta.2014.1322

Integral-based event-triggered control scheme for a general class of non-linear systems

This paper studies performance preserving event design in nonlinear event-based control systems based on a local L2-type performance criterion. Considering a finite gain local L2-stable disturbance driven continuous-time system, we propose a triggering mechanism so that the resulting sampled-data system preserves similar disturbance attenuation local L2-gain property. The results are applicable to nonlinear systems with exogenous disturbances bounded by some Lipschitz-continuous function of state. It is shown that an exponentially decaying function of time, combined with the proposed triggering condition, extends the inter-event periods. Compared to the existing works, this paper analytically estimates the increase in intersampling periods at least for an arbitrary period of time. We also propose a so-called discrete triggering condition to quantitatively find the improvement in inter-event times at least for an arbitrary number of triggering iterations. Illustrative examples support the analytically derived results.

On the Local Input-Output Stability of Event-Triggered Control Systems

In this paper, a new integral-based triggering scheme is introduced for LTI systems. The main feature of the novel triggering condition is that it does not require the derivative of Lyapunov function to be negative at the all time instants and so, it is less conservative than the corresponding available conditions in the literature. Morever, a well-proved comparison with traditional triggering condition and simulation results for a satellite system are given to show the effectiveness of the proposed system.

A novel integral-based event triggering control for linear time-invariant systems

The majority of event-triggered control (ETC) literature concentrates on designing triggering rule while assuming control input to emulate an analog design. In this article, however, both state and output feedback laws are jointly synthesized with the triggering law for nonlinear Lipschitz systems. In the proposed method, the dominant eigenvalues of the linear stability matrices are assigned according to desired performance and triggering specifications. The results serve as a local framework for stability of general nonlinear ETC systems. The efficiency of design is validated through compelling examples.

On the Event-Triggered Controller Design

In an event-based scenario, a system decides when to update the actuators based on a real-time triggering condition (TC) on the measured signals. This condition can be defined in various forms and varies depending on the system properties and design problem. This paper proposes a framework to design the TC while keeping $\mathcal {L}_p$ performance within desired limits. Our general framework captures several existing state-based triggering rules as a special case, and it can achieve the performance objectives while reducing transmissions. Indeed, this general structure is shown to enlarge the minimum interevent time by a specified amount, for a desired period of time. Numerical examples suggest that the proposed mechanism effectively enlarges the average sampling time.

Mohsen Ghodrat

Papers

Integral-based event-triggered control scheme for a general class of non-linear systems

On the Local Input-Output Stability of Event-Triggered Control Systems

A novel integral-based event triggering control for linear time-invariant systems

On the Event-Triggered Controller Design

Event-Triggered Design With Guaranteed Minimum Interevent Times and $\mathcal {L}_p$ Performance