This paper deals with portfolio selection in terms of fuzzy concept. The objective of this fuzzy portfolio selection is to decide the portfolio selection based on vague aspiration level which decision makers have. The vague aspiration level is expressed by a fuzzy number and maximized by Bellman-Zadeh's maximization principle. In the model logistic membership functions are employed to overcome the several theoretical defects which trapezoidal membership functions result in.
The nature of the Japanese favorite songs becomes to be gradually clear by the recent research works. In the subject of these research works, “Tonality and Tonic (key note)” of the music (T & T) has been attracted a great deal of attention as an important index to determine the character of music. This paper deals with tonal structure recognition method of Japanese favorite songs using information about pitch name and time-duration that appear on musical score (sample data 2, 777 pieces, 274, 737 notes). As a result, the remarkable characters were found. For example, T & T can be recognized with approximately 90 % accuracy by statistical pitch information of the music score. The time-duration dose not play an important role to infer the T & T.
In a previous paper, we proposed a design method, based on the optimal regulator theory for type-1 digital servo systems. The method can cope, with parameter uncertainties and time-continued disturbance to guarantee steady-state robustness of servo systems. However, when this method is applied to actual systems, elements of the weighting matrix have to be repeatedly adjusted in a trial and error fashion, until the given performance-index of the transient process is satisfied. In this paper, we propose, a design algorithm for the weighting matrix, which consists of the following two steps. (1) Express quantitatively the qualitative adjusting-knowledge of the designer by using fuzzy sets and estimate roughly the initial value of the weighting matrix with the fuzzy reasoning method. (2) Compute precisely the optimal elements in the weighting matrix by using the simplex method. By means of these steps, the automation of servo system design is accomplished. Finally, velocity control of a DC motor is taken as an example to show the effectiveness of the method proposed in this paper.
This paper is concerned with robust controller design for hydraulic positioning systems. Generally, hydraulic positioning systems have problems such as large perturbation and input saturation. First, taking account of the large plant perturbation, we give a design method of feedback controllers via an LMI based H∞ loop shaping method, which reflects the current plant dynamics. Second, in order to cope with input saturation, we propose to adopt feedforward controllers which contain velocity limit function. Furthermore, the validity of the proposed design method is shown by experiments.
In recent years, there have been many studies reported concerning control of robots with flexible arms or flexible joints. However, control problems for robots with both flexible arms and flexible joints are rarely addressed. In this paper, we discuss how to model and control one-link robots with a flexible arm and a flexible joint. We show that (1) the flexibility in joints can decrease vibration frequency of flexible arm; (2) a simple PD feedback of motor angle can control satisfatorily the position of robot arm ; (3) PD + strain rate feedback can yield good responses of the arm's positioning and vibration suppression. Simulations are conducted to demonstrate these theoretical results.