This paper presents a short-range communication system using airborne ultrasonic wave. This system is well suited to transmit environmental information in small area. In this paper, we also consider to apply the system to a sign-post system for visually handicapped persons. The sign-post system plays an important role in supporting the visually handicapped who walk without a supporter.
This paper proposes a new thickness control method for the rolling mill using the robust PI controller with Smith predictor and adaptive modification. In the rolling process, Several kind of AGC (Automatic Gage Control) were proposed. However, there remain problems that are an absence of robust stability and the difficulty of tuning and maintenance for the parameter change. The proposed method compensates the time delay by Smith method and stabilizes robustly the Smith predictor having vulnerability for the parameter change. And the adjustment and the maintenance of the contoroller become easy, because the PI controller is used as the main regulator. Moreover, Adaptive modification for the accelerating rolling speed enable the excellent thickness property every part of the strip. The results of numerical experiment show the usefulness of the proposed controller.
This paper proposes an analytical criterion for stability boundaries of non-autonomous systems. The criterion can analytically enlarge the conservative stability limits obtained by the classical Lyapunov's direct method almost up to the exact stability boundaries even for non-autonomous systems. It is based on the Melnikov's method which estimates homoclinic intersections in the dynamical systems theory. The definition of the criterion has strong advantages in its easy and quick estimation of the stability, compared with the numerical integration of the non-autonomous systems. The effectiveness is confirmed in its application to an electric power system with dc transmission under periodic swing.
This paper considers a stabilization problem for a communication system where a controller and a plant are linked with a network bus. The network bus usually has a capacity constraint so that it is impossible to transmit or receive all data at the same time which we need to control the plant. In this paper, we assume a periodic constraint of the data transmission. To solve such a stabilization problem with the periodic constraint, we adopt a periodic observer-based controller. Furthermore, we derive stabilizability and detectability conditions for the system and develop the design method of the periodic controller gain.
In the conventional neural associative memories, auto-correlation (Hebbian) learning has often been used. This paper proposes an associative memory model consisting of visible units and hidden units. The connections among the visible units are determined by auto-correlation learning, and the connections between the visible units and hidden units are determined by the error back-propagation learning. These two kinds of learning constitiute a hybrid unsupervised learning. Experiments show that our associative memory based on the hybrid learning has larger basins of attraction and less spurious memories than the existing models.
Since the training of support vector machines needs to solve the dual problem with the number of variables equal to the number of training data, the training becomes slow when the number of training data is large. To speed up training the Sequential Minimal Optimization (SMO) technique has been proposed, in which two data are optimized simultaneously. In this paper, we propose to extend SMO so that more than two data are optimized simultaneously. Namely, we select a working set including variables, solve the equality constraint for one variable included in the working set, and substitute it into the objective function. Then we solve the subproblem related to the working set by calculating the inverse of the Hessian matrix. We evaluate our method for the five benchmark data sets and show the speed-up of training over SMO.
We investigate a method of attitude control with two wheels when a spacecraft has initial angular momentum. If we assume the wheels as attitude control actuators, the spacecraft body generally rotates since the whole angular momentum of the spacecraft is conserved in the inertial system. Assuming the motion of the spacecraft body as pure spin motion around a certain axis, we consider the problem of directing the axis of rotation to the desired direction in the inertial system. The attitude control law proposed here has a very simple form and can achieve the desired motion with the wheels by devising the attitude variables and the direction of the inertial system. Finally, we confirm the effectiveness of this attitude control law by numerical simulations.