Design of reduced-order observer-based output feedback stabilizing controllers is considered for nonlinear sampled-data strict-feedback systems. First reduced-order observers are derived for the Euler model of the sampled-data strict-feedback systems. Then reduced-order observer-based output feedback semiglobal practical input-to-state stabilizing controllers are given for nonlinear sampled-data strict-feedback systems with sampled observation noise. A numerical example is given to illustrate the proposed design of output feedback controllers.
A protein stabilization system is a type of post-transcriptional processing that ubiquitously exists in various types of cells, and it plays a major role in stabilizing the three-dimensional conformation of a translated protein. It comprises a series of activation-deactivation reactions coupled with nucleocytoplasmic shuttling, and it is described by a four-dimensional nonlinear ordinary differential equation based on chemical kinetics. This study shows that this system can variously function as two types of integral controllers, low-pass filter, and integrator depending on the combination of the statuses of cytoplasmic and nucleus enzymes that mediate its reaction rates. This indicates that the system is multifunctional, where these statuses are controlled by the peripheral system around the stabilization system. In particular, because realizing an integral controller for regulating the concentration of a particular molecule to a desired level in biochemical reactions is theoretically and technically important in molecular robotics, the author demonstrates some numerical simulation results regarding integral control.
For binaural reproduction, in general, head-related transfer functions (HRTFs) are modeled as finite impulse response (FIR) models requiring a lot of parameters. The purpose of this study is to reduce the computational load of binaural processing through low-order modeling of the HRTFs. In this paper, an asymptotic method is used to identify the HRTFs in order to reduce the model orders. Experiments proved that the proposed method enables the HRTFs to be approximated with low-order models.
Train driver's attentive behavior can be considered to reflect differences in his/her level of expertise. In this paper, the authors investigate train drivers' eye-gaze movements to identify characteristic attentive patterns that can distinguish different levels of driver expertise. Eye-gaze data were collected from measurement experiments in which six active train drivers participated. Classified into experienced and younger drivers groups, the data sets are analyzed using “sequence alignment”, which helps us to extract partial temporal sequences of areas of interest that are common in each group of drivers. Resultant sequences are compared with each other to find features that could distinguish the groups in their visual behavior.
A locally semiconcave control Lyapunov function exists for every globally asymptotically controllable system; however for nonholonomic systems, the issue of a locally semiconcave generalized homogeneous control Lyapunov function is not investigated. In this paper, the authors propose a locally semiconcave generalized homogeneous control Lyapunov function for Brockett integrator as a canonical form of nonholonomic systems. Moreover, the authors propose an exponentially stabilizing controller for a two-wheeled mobile robot with the function. The effectiveness of the proposed method are confirmed by computer simulation and an experiment, and advantages over previously proposed controllers are confirmed by experiments.
This paper investigates the vortex-induced vibration of a circular cylinder supported by flexible cantilever beams under a uniform air flow. To improve the vortex-induced vibration model, the chaotic phenomena of the vortex are modeled as a random component of the fluid force. Next, the vibration properties of a cylinder supported by a pair of elastic cantilever beams are investigated in wind-tunnel experiments over a wide range of flow speeds. The hysteresis property of the vortex-induced vibration is experimentally investigated under two conditions; the “increase-direction” condition, in which the flow speed is increased, and the “decrease-direction” condition, in which the flow speed is decreased. The time-historical responses of the vortex-induced vibration are measured and subjected to time-frequency analysis revealing the characteristics of the nonlinear coupled vibrations between the fluid and structure. The wake oscillator models with acceleration coupling and random components are evaluated in numerical simulations. The proposed models with random components more closely reproduce the experimental results than the ordinal model.
Practical application of a human monitoring system draws increasing attention with the high developments of information & communication technology and robot technology. Utilizing these technologies, a kindergarten support system for children, parents, and childminders using the activity recognition (AR) has been studied in author's previous studies. In this paper, several wake/sleep identification algorithms for infants as an additional AR were verified by using orthodox algorithms that were used for adults. Investigating combinations of sensor position to infant's body (arm or leg), sampling frequency (5Hz to 50Hz), threshold for acceleration detection (0.1m/s2 to 0.9m/s2), and types of wake/sleep detection algorithms (count-scaled, Cole, Sadeh, and zero-threshold algorithms), it was confirmed that the count-scaled algorithm could obtain highest identification accuracy as high as 89.0% under adequate measurement condition.
The target of this study is to develop the simultaneous optimization method for trajectory and sequence in the airspace near airports (terminal area). Traditionally, the arrival sequence optimization is well studied. However, now it is required that the trajectory is also optimized for the future free flight. In the previous study, the receding horizon guidance (RHG) is developed, and the RHG is able to optimize the trajectory and the sequence. However, this optimization method is able to deal with only two aircraft. In this study, the simultaneous optimization method for trajectory and sequence that is applicable for multiple aircraft by introducing the mixed integer linear programming (MILP) and the continuous method is introduced. The simultaneous optimization method for trajectory and sequence is combined with the RHG. To demonstrate the performance of the RHG with the simultaneous optimization method for trajectory and sequence, the simulation is performed. In this simulation, it is confirmed that the new guidance law is able to optimize the trajectory and the sequence simultaneously and has robustness for uncertainty for time in the terminal area.
AD/DA conversion has become a core technology in digital signal processing. Signal compression is one of the important components for AD/DA conversion systems. Delta-sigma modulator (DSM) is well known as an effective method for encoding analog signals into digital signals. Traditional data conversion systems are composed of the post-filter and the DSM. It is required to satisfy small quantization noise and small signal distortion characteristics by appropriate design of the filter and DSM. In this study, the authors propose a new design method of data conversion system that includes pre-filter in addition to the traditional data conversion system. To design easier, an evaluation framework of the data conversion system is proposed. Then, a design algorithm based on the evaluation framework is proposed by using particle swarm optimization algorithm. Post and pre-filters are designed so as to minimize the effect of the noise and the signal distortion due to quantization. In this paper, the authors verify the AD/DA systems with post and pre-filters by using the voice signal compression system. The effectiveness of the proposed design method is illustrated by the numerical simulations.
Recently, a number of safety assistance systems for automobiles have been proposed. Most systems, such as adaptive cruise control systems (ACC), attempt to assist in improving driving safety for individual drivers. The authors' study focuses on a new type of safety assistance system, by which drivers are able to mutually assist each other based on a “Mutual Assistance” paradigm. The authors' previous study examined the effectiveness of the mutual assistance system from both the recipient and assister side with a driving simulator. In this paper, the effectiveness of a mutual assistance system is examined with a more detailed analysis. The results of experiments from the assistance recipient side indicate that early warning from a mutual assistance system statistically decreases the risks of collision by increasing the margin of collision avoidance. The results from the assister side indicate that a mutual assistance system brings positive attitude changes and enhances self-efficacy, particularly by including some voluntary actions. From the results of experiments the authors' proposed system is expected to contribute to a much safer driving environment by reducing the target level of risk.
This paper presents a technique to approximate heat diffusion on Riemannian manifolds. Specifically, the authors provide a framework to approximate the solution to the heat equation by using the idea of random walks of heat particles, governed by a continuous-time Markov chain, where the transition rates of the Markov chain are characterized by the metric of a given grid with non-uniformly placed nodes imposed on a manifold. The emphasis lies on the fact that nodes do not need to be distributed equidistant from each other, since such a regular grid is not effective on many manifolds. Some segments of the manifold may have a high curvature and require many nodes while other segments of the same manifold have zero curvature and require less nodes. The authors show how to characterize the Markov chain for a given grid in order to build a framework for numerical approximation of the solution to the heat equation on Riemannian manifolds. When viewing a grid as a graph, the infinitesimal generator of a random walk on a graph is also known as the graph Laplacian or discrete Laplace operator. Hence the authors effectively show how to choose the weights of the graph Laplacian such that the continuous Laplace-Beltrami operator which is used on Riemannian manifolds is approximated. Furthermore, we discuss advantages of this technique and provide examples and simulations of our results.
This paper is concerned with stochastic bounded stability for a general class of nonlinear stochastic systems. The bounded stability concept considered here is such that for a given bounded region and realization probability, sample paths remain bounded in the assigned region with the assigned probability. The authors provide a sufficient condition for the proposed bounded stability to be satisfied based on a Lyapunov-like function. The proposed result is applicable to a system with non-vanishing noise at a target point, which the conventional stochastic stability concepts do not deal with.