A method for dramatically improving positioning accuracy of an indoor messaging system (IMES), whose accuracy is normally 10-20 m, was developed. This method uses Doppler shifts (produced by moving a receiver antenna) and three-dimensional attitude of the receiver to determine the receiver's position. Since trilateration is not used, positioning is possible even if the number of visible IMES transmitters is only one. A rotation-type Doppler-measurement system applying this method was developed. To evaluate the system, two experiments were conducted: in one, the rotation radius of a movable receiver antenna was varied; in the other, the position where positioning is conducted was varied. The experimental results show that the method can achieve centimeter-to decimeter-level positioning accuracy. As for design reference for setting up an IMES, the initial value of the non-linear least squares that converges to a proper solution was determined, and the influence of magnetic-declination error for the proposed positioning method was analyzed.
Accurate air-fuel ratio control is one of the subjects of low-emission technologies for gasoline engines, and can maximize the conversion efficiency of a three-way catalyst by controlling the air-fuel ratio of combustion gas to an optimal target value. The engine equipped with a continuously variable lift and phase mechanism has been introduced to improve fuel consumption. However, it indicates large part-to-part variation and aging effect in regard to the suction air amount in each combustion chamber, and the control accuracy of the air-fuel ratio of the engine is significantly lower than that of conventional gasoline engines. Conventional control methods using feedback algorithms do not realize sufficient control accuracy of air-fuel ratio control under transient phase. Therefore, a control system composed of an adaptive feedforward algorithm as well as a feedback algorithm was newly designed and applied to the engine.
This paper investigates a vision-based 3D rigid-body motion estimation problem. In one of our previous works, the authors addressed the problem using no prior information on the target motion. On the other hand, this paper presents another approach assuming some target motion patterns. The authors first consider a constant velocity model, which is a typical choice of motion patterns, and present a novel motion observer integrating the motion model. It is then proved based on passivity that the presented observer leads both of the estimates of the target object pose and body velocity to their actual values. Moreover, the result is extended to a more general motion pattern. Finally, the effectiveness of the presented estimation mechanism is demonstrated through experiments.
This paper presents a design method for a pre-filter for relocating sampling zeros based on the Taylor expansion, which was recently found to be reduced to a simple formula for a relative degree of 2. The method is successfully applied to sampled-data systems of a DC motor, which usually has a sampling zero near -1 that makes it difficult to apply feedforward control based on pole-zero cancellation. The authors experimentally demonstrate that the discrete-time model following controller works well and is free from oscillations or ringing for sampled-data systems of a DC motor when the proposed zero-relocation filter is implemented as an analog circuit for an operational amplifier connected to a power amplifier. The authors also experimentally demonstrate that an analog filter can be replaced by a fast digital filter.
Exploring an intranet or internet database enables us to discover useful knowledge. In this process, a search engine plays a pivotal role. To this end, various search engines have been proposed to heighten information accuracy by exploiting key content relations in semantic web resources. But a general-purpose search engine always includes useless or irrelevant web pages in the search results. The next generation of web architecture, known as Semantic Web, can build a layered architecture to possibly mitigate this deficiency by decreasing the noisy data in a searched result. The objective of this paper is to propose a Probabilistic Latent Semantic Indexing (PLSI) method used in semantic web search engines. The method can better return appropriate information for user queries; in particular, a novel ranking strategy is provided to measure the relevance score of an annotated set of web results by considering user queries, data annotation, and the underlying ontology.
In this paper, operator-based robust nonlinear tracking control for a manipulator with human multi-joint arm-like viscoelastic properties is considered by using the robust right coprime factorization approach and a forward compensation operator. First, an operator controller based on real measured data from human multi-joint arm viscoelasticity is designed to obtain a desired motion mechanism, the forward compensation operator is presented to compensate the term related to the effect of the central nervous system (CNS), and a nonlinear feedback control scheme is proposed to eliminate effect of the uncertain plant. Second, the robust stability of the present control system is discussed, and the performance of output tracking is realized. Finally, the effectiveness of the proposed method is confirmed by the simulation results based on experimental data.
This paper deals the leader-following formation navigation (LFFN), which is one of the most important issues in formation control. In this formation, one leader is controlled by a human operator, while multiple followers pass along the leader's trajectory in the same motion as the leader. The followers move along the leader's path behind the leader after some intervals. Thus, around the initial time, the followers cannot determine routes to track because there is no leader's path before the initial time. Moreover, if the followers try to mimic the motion of the leader completely, they have to stop at the initial position of the leader. This paper discusses how the followers should move around the initial time in order to start up naturally and to achieve the LFFN afterwards. Comparing to the authors' previous method, these desired followers' velocities can be designed online, and an experiment with three mobile robots demonstrates the effectiveness of the presented method.
This paper proposes a fault-tolerant control (FTC) scheme for polytopic linear parameter varying (LPV) systems. First, a fault compensator is proposed. Its structure is simple, but it is effective against actuator faults. Then, in order to show its basic idea, the authors consider a state feedback FTC scheme based on the fault compensator. Next, the FTC algorithm is extended to an output feedback FTC scheme. The FTC scheme for LPV systems involves a fault compensator based on the estimated fault and an observer based on linear matrix inequality (LMI). The proposed FTC method is applicable to a variety of systems and guarantees bounded states of the system in the event of actuator faults. Numerical examples are given to demonstrate its effectiveness.