Communication schemes for centralized and decentralized event-triggered control systems

No abstract

Ventroposterior medialis parvocellularis (VPMpc) of thalamus, the thalamic relay nucleus for gustatory sensation, receives primary input from parabrachial nucleus, and projects to insular cortex. To reveal unique properties of gustatory thalamus in comparison to archetypical sensory relay nuclei, this study examines the morphology of synaptic circuitry in VPMpc, focusing on parabrachiothalamic driver input and corticothalamic feedback. Anterogradely visualized parabrachiothalamic fibers in VPMpc bear large swellings. At electron microscope resolution, parabrachiothalamic axons are myelinated and make large boutons, forming multiple asymmetric, adherent and perforated synapses onto large caliber dendrites and dendrite initial segments. Labeled boutons contain dense-core vesicles, and they resemble a population of calcitonin gene-related peptide containing terminals within VPMpc. As typical of primary inputs to other thalamic nuclei, parabrachiothalamic terminals are over 5 times larger than other inputs, while constituting only 2% of all synapses. Glomeruli and triadic arrangements, characteristic features of other sensory thalamic nuclei, are not encountered. As revealed by anterograde tracer injections into insular cortex, corticothalamic projections in VPMpc form a dense network of fine fibers bearing small boutons. Corticothalamic terminals within VPMpc were also observed to synapse on cells that were retrogradely filled from the same injections. The results constitute an initial survey in describing unique anatomical properties of rodent gustatory thalamus.

Asynchronous decentralized event-triggered control (ADETC) [6] is an implementation of controllers characterized by decentralized event generation, asynchronous sampling updates, and dynamic quantization. Combining those elements in ADETC results in a parsimonious transmission of information which makes it suitable for wireless networked implementations. We extend the previous work on ADETC by introducing periodic sampling, denoting our proposal asynchronous decentralized periodic event-triggered control (ADPETC), and study the stability and L2-gain of ADPETC for implementations affected by disturbances. In ADPETC, at each sampling time, quantized measurements from those sensors that triggered a local event are transmitted to a dynamic controller that computes control actions; the quantized control actions are then transmitted to the corresponding actuators only if certain events are also triggered for the corresponding actuator. The developed theory is demonstrated and illustrated via a numerical example.

Periodic event-triggered control (PETC) [13] is a version of event-triggered control (ETC) that only requires to measure the plant output periodically instead of continuously. In this work, we present a construction of timing models for these PETC implementations to capture the dynamics of the traffic they generate. In the construction, we employ a two-step approach. We first partition the state space into a finite number of regions. Then in each region, the event-triggering behavior is analyzed with the help of LMIs. The state transitions among different regions result from computing the reachable state set starting from each region within the computed event time intervals.

No abstract

Wide Area Cyber-Physical Systems (WA-CPSs) are a class of control systems that integrate low-powered sensors, heterogeneous actuators, and computer controllers into large infrastructure that span multi-kilometre distances. Current wireless communication technologies are incapable of meeting the communication requirements of range and bounded delays needed for the control of WA-CPSs. To solve this problem, we use a Control Communication Co-design approach for WA-CPSs, that we refer to as the C 3 approach, to design a novel Low-Power Wide Area (LPWA) MAC protocol called Ctrl-MAC and its associated event-triggered controller that can guarantee the closed-loop stability of a WA-CPS. This is the first article to show that LPWA wireless communication technologies can support the control of WA-CPSs. LPWA technologies are designed to support one-way communication for monitoring and are not appropriate for control. We present this work using an example of a water distribution network application, which we evaluate both through a co-simulator (modeling both physical and cyber subsystems) and testbed deployments. Our evaluation demonstrates full control stability, with up to 50% better packet delivery ratios and 80% less average end-to-end delays when compared to a state-of-the-art LPWA technology. We also evaluate our scheme against an idealised, wired, centralised, control architecture, and show that the controller maintains stability and the overshoots remain within bounds.

Decentralized periodic event-triggered control (DPETC) strategies are an attractive solution for wireless cyberphysical systems where resources such as network bandwidth and sensor power are scarce. This is because these strategies have the advantage of preventing unnecessary data transmissions and therefore reduce bandwidth and energy requirements, however the sensor sampling regime remains synchronous. Typically the action of sampling leads almost immediately to a transmission on an event being detected. If the sampling is synchronous, multiple transmission requests may be raised at the same time which further leads to bursty traffic patterns. Bursty traffic patterns are critical to the DPETC systems performance as the probability of collisions and the amount of requested bandwidth resources become high ultimately causing delays. In this paper, we propose an asynchronous sampling scheme for DPETC. The scheme ensures that at each sampling time, no more than one transmission request can be generated which prevents the occurrence of network traffic collision. At the same time, for the DPETC system with asynchronous sampling a pre-designed global exponential stability and L2gain performance can still be guaranteed. We illustrate the effectiveness of the approach through a numerical example.