Drawing inspiration from biology, we describe the way in which visual sensing with a monocular camera can provide a reliable signal for navigation of mobile robots. The work takes inspiration from the classic paper [3] which described a behavioral strategy pursued by diving sea birds based on a visual cue called time-to-contact. A closely related concept of time-to-transit,$\tau$, is defined, and it is shown that steering laws based on monocular camera perceptions of$\tau$can reliably steer a mobile vehicle. The contribution of the paper is two-fold. It provides a simple theory of robust vision-based steering control. It goes on to show how the theory guides the implementation of robust visual navigation using ROS-Gazebo simulations as well as deployment and experiments with a camera-equipped Jackal robot. As will be noted, there is an extensive literature on how animals use optical flow to guide their movements. The novelty of the work below is the introduction of the concepts of Eulerian optical flow and time-to-transit,$\tau$and the demonstration that control laws based on the$\tau$-values associated with an aggregated set of features in the field of view can be used to reliably steer a laboratory robot.

In the years since the launch of the World Wide Web in 1993, there have been profoundly transformative changes to the entire concept of publishing—exceeding all the previous combined technical advances of the centuries following the introduction of movable type in medieval Asia around the year 10001and the subsequent large-scale commercialization of printing several centuries later by J. Gutenberg (circa 1440). Periodicals in print—from daily newspapers to scholarly journals—are now quickly disappearing, never to return, and while no publishing sector has been unaffected, many scholarly journals are almost unrecognizable in comparison with their counterparts of two decades ago. To say that digital delivery of the written word is fundamentally different is a huge understatement. Online publishing permits inclusion of multimedia and interactive content that add new dimensions to what had been available in print-only renderings. As of this writing, the IEEE portfolio of journal titles comprises 59 online only2(31%) and 132 that are published in both print and online. The migration from print to online is more stark than these numbers indicate because of the 132 periodicals that are both print and online, the print runs are now quite small and continue to decline. In short, most readers prefer to have their subscriptions fulfilled by digital renderings only.

This special issue brings together recent research on the efficient use of energy in commercial, residential, and other types of buildings and facilities.

Recent communication, computation, and technology advances coupled with climate change concerns have transformed the near future prospects of electricity transmission, and, more notably, distribution systems and microgrids. Distributed resources (wind and solar generation, combined heat and power) and flexible loads (storage, computing, EV, HVAC) make it imperative to increase investment and improve operational efficiency. Commercial and residential buildings, being the largest energy consumption group among flexible loads in microgrids, have the largest potential and flexibility to provide demand-side management. Recent advances in networked systems and the anticipated breakthroughs of the Internet of Things will enable significant advances in demand-response capabilities of intelligent load networks of power-consuming devices such as HVAC components, water heaters, EV charging stations, and many more. In this paper, a new operating framework, called packetized direct load control (PDLC), is proposed based on the notion of quantization of energy demand. This control protocol is built on top of two communication protocols that carry either complete or binary information regarding the operation status of appliances. We discuss the optimal demand-side operation for both protocols and analytically derive the performance differences between the protocols. We propose an optimal reservation strategy for traditional and renewable energy for the PDLC in both day-ahead and real-time markets. At the end of the paper, we discuss the fundamental tradeoff between achieving controllability and endowing consumer choice and flexibility.

In this paper, research into several aspects of robot-enabled reconnaissance of random fields is reported. The work has two major components: the underlying theory of information acquisition in the exploration of unknown fields and the results of experiments on how humans use sensor-equipped robots to perform a simulated reconnaissance exercise. The theoretical framework reported herein extends work on robotic exploration that has been reported by ourselves and others. Several new figures of merit for evaluating exploration strategies are proposed and compared. Using concepts from differential topology and information theory, we develop the theoretical foundation of search strategies aimed at rapid discovery of topological features (locations of critical points and critical level sets) of a priori unknown differentiable fields. The theory enables study of efficient reconnaissance strategies in which the tradeoff between speed and accuracy can be understood. The proposed approach to rapid discovery of topological features has led in a natural way to the creation of parsimonious reconnaissance routines that do not rely on any prior knowledge of the environment. The design of topology-guided search protocols uses a mathematical framework that quantifies the relationship between what is discovered and what remains to be discovered. The quantification rests on an information theory inspired model whose properties allow us to treat search as a problem in optimal information acquisition. A central theme in this approach is that “conservative” and “aggressive” search strategies can be precisely defined, and search decisions regarding “exploration” versus “exploitation” choices are informed by the rate at which the information metric is changing. The paper goes on to describe a computer game that has been designed to simulate reconnaissance of unknown fields. Players carry out reconnaissance missions by choosing sequences of motion primitives from two families of control laws that enable mobile robots to either ascend/descend in gradient directions of the field or to map contours of constant field value. The strategies that emerge from the choices of motion sequences are classified in terms of the speed with which information is acquired, the fidelity with which the acquired information represents the entire field, and the extent to which all critical level sets have been approximated. The game thus records each player's performance in acquiring information about both the topology and geometry of the unknown fields that have been randomly generated.

A formal notion of gesturing defined as the modulation of relative separation between mobile robots has been explored in. We extend this work by developing a peer-to-peer communication channel and an associated distributed communication protocol based exclusively on the modulation of relative motion and its observation. Protocols that enable two unicycle vehicles modulating their relative separation in the plane to effectively exchange information, as well as nonlinear control laws that enable these protocols are presented. Only local information is assumed for the control action. We illustrate the contextual nature of such signaling by showing applications to secure communication as well as robot formation motion. Simulations are presented to validate the work.

A current survey of the emerging field of networked control systems is provided. The aim is to introduce the fundamental issues involved in designing successful networked control systems, to provide a snapshot assessment of the current state of research in the field, to suggest useful future research directions, and to provide a broad perspective on recent fundamental results. Reflecting the goals of the Special Issue itself, this paper surveys relevant work from the areas of systems and control, signal processing, detection and estimation, data fusion, and distributed systems. We discuss appropriate network architectures, topics such as coding for robustly stable control in the presence of time-varying channel capacity, channels with fixed versus adaptively variable data width, issues in data rate problems in nonlinear feedback problems, and problems in routing for stability and performance. In surveying current research on networked control systems, we find that recent theoretical advances and target applications are intimately intertwined. The common goal of papers in the Special Issue which follows is to describe key aspects of this relationship. We also aim to provide a bridge between networked control systems and closely related contemporary work dealing with sensor networks and wireless communication protocols

The author studies robot manipulators which simultaneously exhibit features of joint elasticity and kinematic redundancy. More specifically, he discusses manipulators in which there are more controlled (joint space) degrees of freedom than task space degrees of freedom and in which at least one of these controlled joints is connected to an adjacent link through an elastic coupling. It is shown that there is a wide class of examples for which it is impossible to find joint space motions which track a given end effector trajectory and do not at the same time excite elastic dynamics. For this class of geometries, the most that can in general be achieved is motion without storage of elastic energy in the joints. For certain congenial manipulator geometries, it is shown that under certain assumptions it is possible to plan such motions. It is shown how trajectories interpolating prescribed endpoints in the work space may be planned using fifth-order splines. The problem of exactly tracking end effector trajectories with minimum average elastic energy storage is discussed.>

Necessary conditions for pathwise optimal resolution of redundancy in robot manipulation kinematics are given in terms of boundary value problems. The true optimal solution must be selected from a family of mutually nonhomotopic locally optimal solutions. By means of careful singular perturbation analysis, it is shown that homotopy continuation may be used to simplify the calculation of optimal trajectories. >

Path planning techniques for kinematically redundant manipulators are developed which involve the optimization of integral cost criteria. For a variety of such criteria, the necessary condition consists of n+l first-order differential equations, where n is the number of manipulator degrees of freedom and l is the degree of the redundancy. This necessary condition is essentially equivalent to the system of 2n equations announced by Y. Nakamura, H. Hanafusa (Int. J. Robotics Res., vol.6, no.1, pp.32-42, 1987). Refinements to these basic necessary conditions involve various boundary conditions. Numerical examples highlight the advantages of optimally resolving kinematic redundancy according to an integral cost criterion (compared with the more common approach of optimizing an instantaneous criterion). It is seen, however, that care must be taken regarding trajectories which meet the necessary conditions yet fail to be optimal. It is concluded that any sufficiency conditions for such optimization will involve explicit consideration of the topology of liftings of workspace paths.>

Recently a number of measures of mechanism dexterity have been proposed in the robotics literature. These are defined as functions of the configuration, and are primarily promoted as criteria which should be optimized in the planning of robot motions. In this paper, a coordinate-free version of the manipulatability index is presented. This permits the index to be evaluated in a meaningful way for a (kinematically redundant) mechanism operating under imposed functional constraints on the joint variables. Such an intrinsic quantity is useful for deciding which of several possible constraints yields the best performance of a given mechanism, and conversely, it may be employed as a constraint oriented figure-of-merit in the design of kinematically redundant manipulators. It also provides a new computational tool for finding the singularitites inherent in most approaches to redundancy resolution by means of functional constraints.

While obstacles in a robot workspace can effectively reduce the number of degrees of freedom, there need not be a corresponding loss of functionality for kinematically redundant mechanisms. In this paper, disk-like obstacles for a planar three-bar mechanism are classified. The extended Jacobian technique is used to implement an obstacle avoidance technique based on optimizing a distance criterion. The feasibility of applying multiple constraints or optimality criteria for resolving redundancy is investigated.

In the growing literature on redundant manipulator control, a number of techniques have been proposed for solving the inverse kinemetics problem. Some of these techniques are surveyed with a discussion of strengths and weaknesses of each. A new approach, called the extended Jacobian technique, is also presented. It is argued that because this technique may be expected to lift closed end effector paths to closed joint angle paths, it provides a promising approach for the control of kinematically redundant industrial manipulators. It is further shown that this technique may be implemented as a suitably parameterized generalized inverse method.