The authors of this paper have found that putting an obstacle in front of an exit in a congested situation increases the pedestrian outflow, which is the number of pedestrians going through an exit with a unit width in a unit time, from their experiments. In this paper, the effects of conflicts and turning, which affect the pedestrian outflow significantly, are introduced by the frictional and turning functions to analyze the effect of an obstacle. They clearly explain the mechanism of the effect of an obstacle, i.e., it blocks a pedestrian moving to the exit and decreases the average number of pedestrians involved in the conflict. The authors have also studied when an obstacle contributes to ease the congestion most effectively. The results of their simulation indicate that its maximum efficacy is achieved at the point where the cluster of pedestrians is started to form. The mean traveling time of pedestrians becomes a quarter if an obstacle is set up since it prevents the formation of the cluster against increase of the inflow by reducing the impact of conflicts.
The authors of this paper have been studying a real-time speech-to-caption system using speech recognition technology with a “repeat-speaking” method. In this system, they used a “repeat-speaker” who listens to a lecturer's voice and then speaks back the lecturer's speech utterances into a speech recognition computer. The througoing system showed that the accuracy of the captions is about 97% in Japanese-Japanese conversion and the conversion time from voices to captions is about 4 seconds in English-English conversion in some international conferences. Of course it required a lot of costs to achieve these high performances. In human communications, speech understanding depends not only on verbal information but also on non-verbal information such as speaker's gestures, and face and mouth movements. So the authors found the idea to display information of captions and speaker's face movement images with a suitable way to achieve a higher comprehension after storing information once into a computer briefly. In this paper, we investigate the relationship of the display sequence and display timing between captions that have speech recognition errors and the speaker's face movement images. The results show that the sequence “to display the caption before the speaker's face image” improves the comprehension of the captions. The sequence “to display both simultaneously” shows an improvement only a few percent higher than the question sentence, and the sequence “to display the speaker's face image before the caption” shows almost no change. In addition, the sequence “to display the caption 1 second before the speaker's face shows the most significant improvement of all the conditions.
We consider a new class of dynamical systems whose state is represented by a Hermitian matrix motivated by treating quantum control problems. We develop theory and techniques of differential geometric analysis for dynamical systems in that class, where a Lie product of matrix functions is introduced and plays an important role. We provide a simple and coordinate-free calculation method for the Lie product of matrix functions which enables efficient differential geometric analysis. The result of this paper will be used in a follow-up paper on analysis of local state transition of controlled quantum systems under continuous quantum measurement with imperfect detector efficiency.
In this paper, we analyze local state transition of controlled quantum systems under continuous quantum measurement, which is described by a matrix-valued nonlinear stochastic differential equation. To this end, we utilize the method of differential geometric analysis for systems with matrix-valued states developed in the first part of this series. The method provides us a direct and efficient way of analysis with a clear perspective. We study local state transition of the controlled quantum systems with imperfect detector efficiency which has not been studied enough in previous works. The controlled quantum system with perfect detector efficiency is also investigated as a special case. Sufficient conditions for the measurement operator and the control Hamiltonian are derived, under which the local state transition is quite limited. We also show that the conditions are satisfied in many typical situations. The results reveal fundamental nature of the controlled quantum systems under continuous quantum measurement.
This paper considers local stability analysis of nonlinear systems with deriving a positively invariant set based on the Rantzer's stability theory by using density functions. We define a notion of locally defined density functions around an equilibrium that give monotonously increasing positive measures near the equilibrium of a nonlinear system. Under certain assumptions, it is shown that some level set of a locally defined density function is a positively invariant set where almost all of the system trajectories converge to the equilibrium. We also mention an SOS (sum-of-squares) formulation for synthesis of a nonlinear gain via locally defined density functions.
This work is intended to develop a software-defined Global Positioning System (GPS) receiver specifically designed to process reflected GPS signals off the ground or the ocean surface for the purpose of remote sensing. A set of airborne campaign was conducted to evaluate the performance of the prototype GPS reflectometry receiver. The reflected signal was tracked in an open-loop manner using the so called delay mapping receiver. The result shows that the prototype receiver is capable of providing altimetric measurements with a better precision than a few meters.
In this paper, an optimal driving control system based on model predictive control (MPC) is developed for the purpose of processing more surrounding information which is essential for improving the current intelligent driving assistance and further dealing with traffic issues caused by automobiles. The proposed system provides a method of calculating a desirable driving path based on surrounding traffic environments. The performance of this system is evaluated through simulations which are carried out with introduction of surrounding information such as traffic jams, traffic signal changes, and fuel consumption. Simulation results reveal that the proposed system as a driving assist system has a potential of finding optimal driving paths for drivers.
The paper presents a sum of squares (SOS) based backstepping control design method for a three wheels omni-directional mobile robot. The characteristic of the strict-feedback system associated with mobile robots is considered to construct the backstepping controller. To account for the saturation problem in the mobile robot, the SOS conditions are developed based on the backstepping controller framework to achieve stability and enlarge the guaranteed region of convergence. Computer simulations for mobile robots demonstrate the effectiveness of the proposed SOS-based backstepping controller design method.
This paper describes a design method of an I-PD (integral preceded by proportional-derivative) controller for a single-input-single-output plant. The proposed method, which is relatively simple compared with the conventional methods, consists of two stages: First, a second-order model is determined by applying the balanced truncation to the closed-loop system for a given higher-order plant, and then, an output and error signal feedback controller based on integral-type optimal servomechanism is designed for the second-order model. The resultant controller gives as sufficient stability margins and good control performance as an observer-based state feedback controller. Design examples are presented to demonstrate the effectiveness and usefulness of the proposed method.
This paper is concerned with the sensitivity reduction (SR) and complementary sensitivity reduction (CSR) problems of sampled-data systems. We begin our study by showing that, given a sampled-data system Σ, the H∞ norms of the sensitivity and complementary sensitivity of Σ can be expressed as those for an equivalent discrete-time system Σ called the doubly sensitivity-preserving discretized system. We also consider the conventional ‘hold equivalent’ discretized system Σd, which has generally been believed, due to the ignoring of the intersample behavior, to be irrelevant to the SR/CSR problems of Σ (and thus Σ). We then establish that there in fact exists an important relation between the seemingly completely irrelevant discrete-time systems Σ and Σd. More precisely, we show through the coprime factorization approach about Σ and Σd that the CSR problem of Σ (and thus Σ) is equivalent to a weighted CSR problem of Σd and that the SR problem of Σ is equivalent to a weighted mixed sensitivity reduction problem of Σd. In particular, we show that the frequency-dependent weights that arise in this interplay between Σ and Σd can be described with an important function called the aliasing factor ψ, and further clarify an important analytic property of ψ. We then demonstrate that this property of ψ can be used to prove some relation between the best achievable performance in the SR (respectively, CSR) problem of Σ (and thus Σ) and that of Σd. An interesting property between the SR problem and CSR problem of Σ is also provided.
Many of practical design specifications are provided by finite frequency properties described by inequalities over restricted finite frequency intervals. A quadratic differential form (QDF) is a useful algebraic tool to characterize energy and power functions when we consider dissipation theory based on the behavioral approach. In this paper, we investigate time domain characterizations of the finite frequency domain inequalities (FFDIs) using QDFs. QDFs allow us to derive a clear characterization of the FFDIs using some inequality in terms of them as a main result. This characterization leads to a physical interpretation in terms of the dissipation inequality with the compensating rate which guarantees dissipativity of a behavior with some rate constraints. Such an interpretation has not been clarified by the previous studies of finite frequency properties. The aforementioned characterization yields an LMI condition whose solvability is equivalent to the FFDIs. This can be regarded as the finite frequency KYP lemma in the behavioral framework.
This paper examines a satellite images processing system with a mechanism for detecting the inundated areas and supporting to flood monitoring and warning. The interoperable handling system is established in order to freely access the inundated areas with no defensive barrier by the software operability limitations. The ultimate goal of this effort is to bring awareness of the potentially catastrophic occurrence that can be pre-detected and prevented altogether. The development of the algorithm to extract the inundated areas and convey urgent messages during the time of crisis is performed on a user-friendly web based interface. A careful examination of various locations on LANDSAT images yields promising results. Although the size of images is limited by the available bandwidth of the web based application, processing at 4000*4000*3 bands per image takes approximately 3 minutes. This is a significant improvement over currently available methods for inundated detection systems. Additional benefits include software operation cost saving, and reduction of operational expenses and time. Furthermore, it does not require technical expertise to predict the rise of flood disasters.