An iterative identification method for a multivariable linear system with outliers in the observations is proposed by applying the EM (Expectation-Maximization) algorithm. The outliers are detected by a likelihood ratio test using residuals computed from the smoothed state estimates obtained in the previous iterations, while the parameter estimation is performed by treating outliers as missing data. As an example, we identify a simple COD model based on the real data of three points of the lower reaches of the Lake Biwa. We show that the accuracy of the model is greatly improved by introducing the probability pj specifying the observation outliers. We also show that the algorithm can be applied when many data are missing.
A method of hierarchical multiple model adaptive estimation and control is proposed for discrete-time distributed systems with unknown parameters, in which the decentralized structure consists of a central station and of two local stations which do not communicate between each other. It is assumed that the global and local hypotheses on the unknown parameters are introduced to the decentralized multiple model structure. This modeling provides a flexible design algorithm for passively adaptive control problems in steady-state. Instead of utilizing the local a posteriori probabilities, the probability density functions of the innovation processes for the local Kalman filters are adopted to simply reconstruct the global a posteriori probability in the central station. The effectiveness of the present method is illustrated through a numerical simulation of the FDI (failure detection and idetification) system for a hydrofoil boat.
Accurate antenna pointing control is one of the key technologies in developing a multibeam communications satellite. This paper describes evaluations of the coupling of an antenna pointing control system consisting of a satellite attitude control loop and an antenna drive control loop. The evaluation of coupling between two loops is a significant problem in satisfying accuracy requirements of the system with large antennas and flexible solar paddles. First, the coupling factor was formulated from the dynamics of the 3-axis stabilized satellite with antennas and solar paddles. Second, values of the coupling factors of a 2-ton class satellite were calculated for two antenna drive methods. The results confirm that the coupling factor mainly depends on the paddle structural characteristics, moments of inertia of antenna reflectors and the ratio of the beam angle to the antenna drive angle.
This paper is concerned with a coordinative manipulation problem by multiple robot manipulators in the three dimensional-space. First, taking account of not only the dynamics of manipulators but also the dynamics of object motion, we derive a basic equation of a coordinative manipulation system by three manipulators in the three dimensional space, which is a suitable form for designing a position control system. Second, based on this equation, a positioning servo system is designed which achieves the desired command response and has some robustness to cope with the modeling error. Also, a potential is introduced to achieve a firm grasp. Finally, a simulation result is given to show the validity of our method.