TR-C-0099 :1994.4.18

ピーター クッカ,大谷淳

Perceptual Kinematics: Vision-based Control of Robot Manipulators

Abstract:Problems involving the control of robot manipulators ("robot arms") typically require knowledge of the relationship between the position and orientation ("pose") of the hand in space and the settings of the joints of the arm. In general, it is easy to determine the pose of the hand given the settings of the joints, but it is difficult to determine how to set the joints to achieve a desired pose of the hand. The former relationship is given by the kinematic map and the latter by the inverse of the kinematic map, but in some cases inversion is not possible, and the inversion computations can be unstable. Approximate computations can relieve some of these problems, but they introduce errors of their own. However, by introducing a sensor (for example, a camera) that can provide data that implicitly captures information about the pose of the hand, it is possible to compensate for these errors. In earlier work [4,9] we presented a new method for manipulator control in which sensory data (specifically, visual data) are incorporated into a perceptual kinematic map (PKM), which expresses the relationship between the settings of the arm joints and quantities measured by the sensor. The method assumes virtually no prior information about the robot's kinematic behavior and therefore avoids the costly and time-consuming calibration required by many existing methods. Instead, it takes advantage of geometric properties of the graph of the PKM, a hypersurface that we call the control surface. In this way, manipulator pose control can be achieved using measurements made on images without the need to explicitly recover the pose itself. This document is divided into two sections. In the first, we review the concepts behind the PKM and PKM-based control (this section also appeared in [4]). In the second, we describe in detail software developed to both simulate a robot manipulator with a PKM controller and to control a real manipulator.