Toshio Ogiso

Partitioned neural network architecture for inverse kinematic calculation of a 6 DOF robot manipulator

A parallel neural network architecture called a partitioned network is proposed for applications which demand high learning accuracy. The partitioned neural network is composed of a preprocessing layer and partition modules containing dedicated neurons. The learning equations used are those of the backpropagation algorithm. The network has been applied to learning of the inverse kinematic solution of a six-degree-of-freedom robot manipulator. After training, the partitioned network was able to predict robot joint angles not included in the training data set with average errors of 0.9 degrees , 3.6 degrees , 2.1 degrees , 6.9 degrees , 6.5 degrees , and 8.5 degrees for the first, second, third, fourth, fifth, and sixth joints, respectively.<<ETX>>

Calibration analysis of a direct drive robot

A software-based calibration method is developed to decrease the positioning errors of a SCARA assembly robot caused by static deflection of the robot arm under force and moment load. A robot stiffness model is constructed and used to calculate differential joint angle corrections which are then applied to the inverse kinematic solution of the ideal robot model to compensate for the static deflection errors. Least squares polynomial approximation and a neural network are used for storing the joint correction values and for interpolation. A computer simulation of the calibration method demonstrated a decrease in the average positioning error from 0.43 mm to 0.03 mm and in the range of error from +or-0.35 mm to +or-0.10 mm in the calibrated area.<<ETX>>

Optimal design method for dynamic vibration absorbers installed in multijoint mechanisms

In order to achieve fast robotic movement, a control system with a fast response time achieved by using a velocity control unit with high proportional control gain is needed. However, low-frequency mechanical resonance is a limitation. Installation of dynamic vibration absorbers is an effective method for decreasing the resonance peak and increasing the proportional gain. This paper proposes an optimal design method for dynamic vibration absorbers installed in multijoint mechanisms. The absorbers are driven by several motors and have dynamic coupling axes. Results of an experiment using a mechanisms with and without absorbers, are described and the validity of the proposed design method is confirmed.<<ETX>>