This paper reports a linear-type steering mechanism, an image guidance system, and a steering control method in linear-type automated guided vehicles using linear induction motors. To improve the steering characteristics of four-wheel linear-type automated guided vehicles, we propose linear-type traveling, and steering mechanisms made up of on-the-vehicle two linear induction motors. They generate a thrust between the motors and reaction plates layed on the floor of the vehicle's guide track. A guiding tape affixed on the reaction plate is accurately and quickly recognized by an image guidance system that uses the signals from an image sensor to control a linear-type steering mechanism. In traveling experiments, a prototype automated guided vehicle was verified to travel smoothly on a straight track at 240 m/min with as little as ±12 mm amplitude deviation which is less than the guiding tape 50 mm width.
In this paper, a new stability criterion for nonlinear feedback systems which include a nonlinearity consisting of the main term and the deviation term is presented. The main term is assumed to be time-invariant and to depend only upon the output of the linear part. The deviation term is allowed to be time-varying and to depend on all state variables. The criterion converges to the Popov criterion when the deviation term approaches 0. It generally gives a sharper result than the circle criterion. The result is especially useful to analyze stability of feedback systems, such as fuzzy control systems, which contain “slightly time-varying and/or multivariable” nonlinearities.
Parametric absolute stability is considered for nonlinear feedback control systems consisting of a linear plant with uncertain parameters, a linear controller with tuning parameters, and a sectorial bounded nonlinearity. The stability concept originally defined for Lur'e systems, provides a mathematical framework for solving the joint problem of feasibility and stability of equilibrium states. The central issue of this problem is the change of the equilibrium state caused by the variations of reference inputs and parameters, which may affect stability. In this paper, the plant and controller are supposed to be stable or to possess one pole at the origin. Popov-type sufficient conditions are presented for parametric absolute stability.
The coronary arterial 3-D reconstruction is playing an important role in grasping their structures of anatomy and providing quantitative information such as flow or stenosis measurements. This paper describes a new method to reconstruct 3-D coronary arterial branches from 2 plane X-ray angiograms. The key point of the method is estimating the 3-D coordinates necessary for reconstruction through the information extracted from the original angiograms and easily notable parameters ; the geometric parameters of the X-ray system and the mutual position between the patient and the X-ray system. It is not necessary to take images of a phantom as the standard for the measurement of the shape and the position. Thus this method gives easy 3-D reconstruction process in clinical medicine. Some 3-D results applied to the actual angiograms are shown. Moreover for easy understanding of the structure, 3-D image fusion is introducted; 3-D left ventricle with the aorta reconstructed through the usual left ventriculograms and 3-D coronary artery reconstructed through the coronary angiograms.