Masaru Takata

Pattern Recognition of a Grasped Object by Unit-Vector Distribution

A pattern recognition method using an artificial hand to identify the pattern of a grasped object and to locate its position relative to the hand coordinates is discussed. In the proposed recognition method, an object is recognized as a pile of two-dimensional slices, namely, a pile of plane closed curves. Each curve (i.e., contour) is described as the distribution pattern of unit-vectors, called the unit-vector distribution (UVD). The proposed recognition method using UVD functions is as follows. 1) Given the a priori information about the contours of objects to be grasped, the UVDs of their contours are calculated and memorized. These are called the original patterns (OPs). 2) Then a sampled UVD is formed from real tactile data and called the data pattern (DP). 3) The DP is compared with the memorized patterns (MPs), which are obtained by blurring the corresponding OP, so as to make it easier to single out the best fitted OP. 4) Finally, the contour is regenerated in the hand coordinate system by using the UVD of the singled out pattern. An experiment using a trial sensor and a model hand has shown the effectiveness of the proposed method in the recognition of several kinds of objects having cylindrical and prismatic contours.

Optimization of weakly coupled subsystems by a two-level method

Abstract A two-level method to find the optimal control of a linear system is presented. We consider that the system is composed of coupled subsystems. And we solve two decoupled first-level problems and one coordinating second-level problem iteratively. When the system can be decoupled into weakly coupled subsystems, the solution fast converges to the optimal.

On the force feedback control of a manipulator with a compliant wrist force sensor

Abstract The force feedback algorithm is presented for the manipulator which consists of a high stiffness position servo system with six-degree of freedom and has a compliant six-component force sensor at its wrist. The obtained algorithm has the following three features. First, this algorithm gives the relation between the position and orientation of the wrist at the present step and that of the wrist to be attained at the next step. Second, an efficient calculation method to obtain each joint movement satisfying this relation is proposed. Third, this algorithm reduces the force feedback control to the position feedback control of each joint in case the force sensor is sufficiently compliant compared with its environment.

On the determination of the optimal feedback gains for multivariable linear systems incorporating integral action

In this paper we present a technique of obtaining the optimal feedback gains for multivariabe linear systems incorporating integral action. Unlike the methods proposed up to now, a performance index in this paper is the practical quadratic one which does not penalize either the integration of output error or the time derivative of control, therefore giving a reasonable solution. The necessary condition for the solution is given by the non-linear simultaneous matrix equations which can be solved by a gradient technique. Also we suggest a minimax solution which minimizes the worst case in order to get practical feedback gains.

Determination of the feedback gains of sampled-data linear systems with integral control using time-weighted quadratic performance indices

Sampled-data feedback control with integral action, minimizing time-weighted quadratic performance indices, is considered for continuous linear systems, The necessary conditions to be satisfied by the feedback gains are developed by using the parameter optimization technique. To remove the dependence of the solution on reference inputs and external disturbances, the performance index based on statistical expectation is considered. The necessary conditions are solved by a gradient technique. Numerical examples are given to illustrate the effect of a time-weighted performance index on the transient responses of the output.

Optimization of linear systems with integral control for time-weighted quadratic performance indices

The necessary conditions to be satisfied by the feedback control constructed by available variables, minimizing time-weighted quadratic performance indices for linear systems incorporating integral action, are developed using the parameter optimization technique. To remove the dependence of the solution on a reference input and an external disturbance, a performance index based on the statistical expectation and a minimax solution are considered. An algorithm based on a gradient technique is given to solve the necessary conditions of the minimax solution. Numerical examples are given to illustrate the effect of a time-weighted performance index on the transient response of the output, and they show that the integral-square-time-square error performance index is acceptable for a reference input.

On sampling period sensitivities of the optimal stationary sampled-data linear regulator

In this paper the stationary sampled-data linear regulator is considered. The third and fourth-order sensitivities, about the zero sampling period, of the cost matrix and the third-order sensitivity of the feedback gain matrix are computed. Also the first and second-order sensitivities, about an arbitrary sampling period, of the cost and feedback gain matrices are computed. Moreover, the relationships between the cost matrix sensitivities and the feedback gain matrix sensitivities are made clear.