A Robotic Method for Creating Radiation Maps using Mercuric Iodide Sensor
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A Robotic Method for Creating Radiation Maps Using Mercuric Iodide Sensor Masao Kume and Pradeep K. Khosla The Robotics Institute, Carnegie Mellon University, Pittsburgh PA 15213
ABSTRACT In this paper we describe the development of a robotic system that uses Mercuric Iodide (HgI2) sensors to create a map of radiation intensity in the environment. The sensors are mounted at the end-effector of a PUMA 560 manipulator. Data from these sensors is used to compute the radiation intensity. A control system is developed that moves the end-effector along constant intensity contours. The experiments use light sources (instead of radiation sources) and demonstrate the efficacy of such a system to create radiation maps.
Introduction In this paper, we describe a system for measuring radiation using Mercuric Iodide detectors attached to a 6 DOF robotic arm. The goal of this system is to find a distribution of radiation intensity in space. An intensity map can, for example, be used for planning robot motions. By properly generating exploratory motions it is also possible to detect and characterize sources of radiation. Mercuric Iodide sensors are especially useful for this because they operate at room temperature. For a description of the characteristics of HgI2 sensors the reader is referred to [4]. The simplest way to achieve our objective is to gather a lot of measurement points by scanning the sensor uniformly in a large space but this is time-consuming and not suitable for understanding the local characteristics of the space. We motivate our work based on recent advances and successful demonstrations of sensor-based robotic systems such as visual servoing systems in the area of active vision [1][2][3]. The attempt to combine motion and perception is reasonable and important not only to increase the amount of spatial information but also to extract it selectively. With this view point we have developed a measurement system to create an iso-intensity contour map by controlling the end-effector.
1. Problems for design of controller We use a PUMA robot system in which a real time position control system is available for ar input of a position displacement with the sampling time interval of 28ms. The radiation sensor, are attached to the robot's end-effector. A block diagram of sensory feed-back system is showr as Fig. 1.We model the process from the robot motion to the change of the radiation intensity b3 describing the process as three sub-processes. The process,Prj, is a model of the kinematic rela. tionship between the robot motion and the potential displacement of the sensor location. Th( second process K shows the intensity derivative in the most descendent direction of the poten
Fig. 1 The sensor module installed to 6 DOF manipulator and the tracking system for a radiation environment Mat. Res. Soc. Symp. Proc. Vol. 302. @1993 Materials Research Society
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tial space. And the third process integrates the change of intensity. The problem in model based controller design is the determination of Prj and K. Since we do
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