This paper presents analysis and synthesis of interconnected systems where the interconnected system of interest consists of discrete-time positive subsystems and an interconnection matrix. The paper gives sufficient conditions for the discrete-time single-input single-output (SISO) subsystems and the interconnection matrix so that the interconnected system has the property of persistence. The fundamental differences for the persistence between the conditions of the discrete-time setting and those of a continuous-time setting are also discussed. The obtained analysis result can apply to formation control for multi-agent systems, which is a synthesis part of the paper. Numerical examples including formation control of mobile robots are shown to illustrate the proposed formation control design method.
This paper studies an optimal inputs elimination problem in large-scale network systems. We first solve an H2 optimization problem of the difference between the transfer functions of the original system and the system after the input variables elimination. It is shown that the problem can be rigorously solved by calculating the gradient and Hessian of this objective function. The solution means that, when the input variables to be eliminated were fixed, the H2 optimal inputs elimination is achieved by simply eliminating input variables without changing the driver nodes, which are state variables that are directly affected by an input signal. We next solve a finite combinatorial optimization problem to decide input variables to be eliminated. The objective function is defined by using the solution to the H2 optimization problem. It is shown that a greedy algorithm gives the global optimal solution to the finite combinatorial problem within a practical time. The algorithm can be understood that we eliminate input variables in ascending order of the average controllability centralities which assign relative importances to each node within a network. Finally, we demonstrate how to use the results in this paper by a simple example.
This paper focuses on how to reduce the cognitive loads of air traffic controllers while solving the airport landing problem (ALP), which is the optimization of both aircraft landing routes and sequences. A method is proposed for adaptively changing landing sequences by optimization according to routes partially fixed by the controllers as a factor of human intervention. Intensive simulations conducted at Haneda Airport have revealed that the method (1) can maintain the same level of results without needing to fix some of the routes (i.e., the same total distance of all aircraft from their starting positions to the same destination airport) and (2) has much potential for reducing the cognitive loads of controllers by fixing some routes to reduce the number of aircraft that need to be monitored continuously.
Design methods of inverse optimal adaptive H∞ consensus control of multi-agent systems denoted by the first-order and the second-order regression models on directed network graphs are presented in this paper. The proposed control schemes are derived as solutions of certain H∞ control problems, where estimation errors of tuning parameters are regarded as external disturbances to the process. It is shown that the resulting control systems are robust to uncertain system parameters and that the desirable consensus tracking is achieved approximately via adaptation schemes and design parameters.
In this research, we aim to visualize activities in a local community for achieving resident-centered community design utilizing information and communication technology (ICT). For that purpose, we introduced a new core concept of “media spots” not only as places where residents could communicate with one another more frequently than in the other areas but also as a prospective platform to mediate relationality between people, “Mono” as tangible and physically perceived things, and “Koto” as intangible and cognitively conceived things. That is, “media spots” should have the potential to proactively promote resident-motivated communications and activities in local community. We have proposed, in this paper, a visualization method for media spots estimation from residents' location information that uses DBSCAN (density-based spatial clustering of applications with noise) for cleaning enormous amount of raw location information data. The present results suggested that representative points extracted by using DBSCAN could visualize activities in a local community more effectively, and estimate media spots more accurately, than the previously used method.
When using a wearable robot, the interaction force applied at the point of contact may cause skin injuries. Therefore, validating the safety of wearable robots becomes important for their practical application. One method for evaluating contact safety at the fixation area of a wearable robot is to reproduce the relative motion and interaction force that occur at the area on a dummy. However, humans have various shapes, and evaluation of various human skin shapes is required. This study aims to develop a three-dimensional skin-shape reproduction mechanism with which to validate the safety of wearable robots. To that end, we have developed a simulation consisting of a cable-reinforced membrane that estimates surface deformation to examine different dummy shapes. Comparisons between device and simulation shapes validated the process of reproducing human skin and the range of deformation and elasticity of the dummy.