The deployment and coordination of mobile sensor networks for coverage control applications can present several practical challenges, including how to efficiently share limited communication resources and how to reduce the use of localization devices (e.g., radars and lidars). One potential solution to these challenges is to reduce the frequency at which agents communicate or sample each other's position. In this article, we present a distributed asynchronous self-triggered control policy for centroidal Voronoi coverage control that is shown to decrease the sampling or communication instants among agents without degrading the performance of the mobile sensor network. Each agent independently decides when to sample the position of nearby agents and uses outdated information of its neighbors until new information is required. We prove that the locational cost function describing the distribution of agents monotonically decreases everywhere outside of a bounded neighborhood around the group's optimal configuration and that the agents asymptotically converge to their Voronoi centroids if the data-sampled centroid errors approach zero. In addition, we show that the sampling intervals are always positive and lower bounded and, as illustrated by simulations and experiments, they tend to stabilize at a large value as the mobile sensor network comes to a steady state. Simulations and experiments with ground vehicles validate the control strategy and show that the proposed policy can achieve similar level of performance as a continuous or fast periodic implementation.

A major challenge in networked control systems is to reduce the use of shared communication and control resources without compromising the performance of the closed-loop system. Motivated by this challenge, this paper presents an observer-based controller with irregular sampling that reduces the control attention and guarantees closed-loop stability and global ultimate boundedness of the plant's state vector regardless of bounded input and output disturbances. The feedback control design is based on self-triggered control, whereas the observer is based on the block-form state-space representation of the plant. It is shown via analysis and simulation that the overall control law decreases the number of samples without loosing observability and closed-loop stability, reducing the utilization of communication resources.

This paper presents a networked cyber-physical system (CPS) testbed used in an undergraduate course project-based learning activity. The low-cost, portable testbed can be used in wide-ranging activities to include exploration of modeling and simulation, controls, communications, networks, embedded systems, and cyber security. The activity presented focuses on a subset of this list, providing students with an opportunity to demonstrate understanding of course lecture material while working in a small team.

The implementation of collision detection mechanisms on-board of unmanned vehicles typically relies on digital platforms and shared communication networks. The discrete nature of these technologies does not only limit the frequency at which nearby obstacles and other vehicles are detected, but it also raises the demand for a better allocation of the vehicle's computational and communication resources. For instance, it is natural and convenient to adapt the frequency at which other vehicles are observed based on their distance and collision risk, a notion that relates to topics in minimum attention control and self-triggered control. In this paper, we report on a cooperative, decentralized self-triggered avoidance control law for an arbitrary large group of unmanned vehicles that reduces the attention and sampling frequency of other vehicles' position. The proposed control strategy guarantees the safe coordination of all vehicles at all times while reducing the sampling frequency of other vehicles' position based on their last available sample. We show that the sampling intervals are positive and lower bounded, which is critical for digital implementation. A simulation example is used to illustrate the performance of the avoidance control strategy.

Passivity-based bilateral teleoperation control systems can offer robust stability against arbitrarily large communication delays at the expense of poor transparency. In fact, most passive control frameworks are designed for a particular task and do not adjust transparency when transitioning between different environments. This paper presents a bilateral control strategy that passively compensates transparency when transitioning between free motion and hard contact motion scenarios. The proposed control framework exploits the effect that the wave impedance (a design parameter of the passivity-based scattering transformation) has on transparency without compromising closed-loop stability regardless of time-varying communication delays. To adjust transparency, the control scheme smoothly switches the wave impedance between a low value, ideal for free motion, and a sufficiently large value, suited for hard contact scenarios. We show, by rigorous mathematical treatment and simulations, that the proposed control strategy can effectively adjust the transparency of the system without compromising stability.

Among the still existing issues in bilateral teleoperation, there is the inability by force-feedback control schemes to guarantee delay-independent stability and achieve both position coordination and force reflection independently of the remote environmental dynamics. Particularly, most bilateral control frameworks fail to address position coordination when interacting with rigid environments. In this paper we present a novel control strategy that aims to passively compensate for position errors that arise during contact tasks and, in general, achieve stability and transparency when alternating between unobstructed (free) and obstructed (contact) environments. The proposed control framework exploits the wave impedance independent passivity property of the scattering transformation to guarantee stability and transparency by gradually switching between a low wave impedance, ideal for free motion, and a sufficiently large impedance, suitable for contact tasks. The validity of the control framework is verified through simulations and experiments on a pair of nonlinear robots.

A detailed experimental comparison study of several published algorithms for motion and force control of bilateral teleoperators, with emphasis on Internet-based teleoperation, is presented. The study investigates the effects of data losses, communication delays, and environmental constraints on a teleoperation system for different control techniques, which are based on wave variables, Smith predictors, and recent algorithms on synchronization. The controllers are compared on stability, transparency, and complexity using two identical nonlinear robots coupled via a stochastic network model that allowed transmission round-trip delays and data-loss rates to range from 8 to 1088 ms and 0% to 50%, respectively. A total of 18 subjects, which were distributed among 26 experiments with the aims of regulating the effects of the operators learning process and dynamic properties, participated in this study. Overall, the comparison study reports a deteriorating effect in the performance (i.e., larger position errors and lower fidelity of contact information) from delays and data losses. Yet, the effect of data losses is less critical when compared with time delays. In addition, the preference for a particular control framework is shown to strongly depend on the operational conditions of the system, such as the characteristics of the coupling channel, the specifics of the remote task, and the computational capabilities of the manipulators.