We consider a high-pressure steam condenser, which is a constrained system with various saturation characteristics and physical constraints on the input and output signals. If these constraints are not properly accounted for, then a rapid change of disturbance may lead to constraint violations and, as a result, cause control performance deterioration or mess up stable operations of the system. It is thus desired to avoid the constraint violations due to such a change of disturbance. This paper presents a method for reducing the risk of the constraint violations by using an additional mechanism called a reference governor, which modifies a reference signal and inputs the resulting signal to the closed-loop system designed a priori. Simulation and experimental results show that the present simple reference governor algorithm is quite effective in control of the high-pressure steam condenser.
Collaborative filtering is a technique for reducing information overload, and personalized recommendation is performed by predicting missing values in a data matrix. Linear fuzzy clustering is a technique for local principal component analysis and can be used for constructing local prediction models considering data substructures. This paper proposes a new algorithm for constructing local linear models that performs a simultaneous application of fuzzy clustering and principal component analysis based on sequential subspace learning. In numerical experiments, the diagnostic power of the filtering system is shown to be improved by predicting missing values using the proposed local linear models.
The criteria that explain the hand reaching movements of the human, based on the framework of the optimization problem, have a possibility of being applied to the other complex movements. In this paper, we attempt to explain a basic gymnastic maneuver on the horizontal bar, referred to as the kip motion, as a difficult goal-directed movement under a nonholonomic constraint. First, we show the results of the motion measurement of the kip motion performed by expert gymnasts, where the motions of each subject are very similar among the trials. Second, we construct a model of the gymnast performing the kip motion as a rigid 3-link with an unactuated joint at the hand and actuated joints at the shoulder and the hip, where the angle profiles of the actuated joints are approximated by fifth spline functions. Moreover, it is confirmed that the model's motion is approximately consistent with the measured motion. Third, by using the above model, the kip motion connecting the initial, via-, and final posture is generated with the minimum torque change criterion, which is known to explain the hand reaching movements. The results of the numerical analysis show that various kip motions are generated depending on imposed via-postures, and a very similar motion to the measured data is generated when an appropriate via-posture is imposed for each subject. The results suggest that the motion generation of the kip movements and the hand reaching movements could be understood by using a common criterion.
In stability analysis of linear time-delay systems, Lyapunov-Krasovskii functional approach often requires model transformations of the systems in order to obtain delay-dependent stability criteria. Some model transformations, however, give rise to conservativeness of the stability analysis. The source of the conservativeness attributes to additional dynamics brought about by the transformations. In this paper, we investigate stability of the additional dynamics by using Lambert W function. The function yields precise analysis of the additional dynamics and easily-checkable stability criteria due to commercially available software, which implements the function. These features are illustrated by numerical examples.
In this paper, a master-slave robot system involving haptic feedback and teleoperation for rehabilitation is presented. A teleoperation mechanism capable of force feedback by means of brake is proposed. The stability of the teleoperation system with haptic feedback via a time-delay communication environment is mathematically proved. Moreover, in order to reduce the packet transfer rate for data transmission, a deadband control approach is used. A new data reconstruction algorithm is proposed to improve the system's performance while maintaining the system's stability. This system allows passive assisted movement utilizing teleoperation for the rehabilitation of upper limb function.