Abstract
A project was described that combined three sensor technologies to provide three different levels of protection to workers within the work zone of an industrial robot. The responses initiated by sensors in the three zones of hazard potential, as defined by the National Bureau of Standards, were: for level-I, a light curtain to detect intrusion by a solid object, with activation of a flashing light and reduction of the robot speed by 30 percent; for level-II, pressure mats to sensitize the floor of a hazardous area, to activate a light and beeper and reduce the robot speed by 60 percent; for level-III, an ultrasonic sensor traveling on the robot's arm, to activate a loud horn and halt the robot manipulator on sensing intrusion. Details of the hardware and software design, the rationales for choosing the three sensors, and a summary of the interfacing and implementation considerations were presented. The authors conclude that performance evaluations of the three sensors should be application specific and performed in an industrial environment. They also conclude that sensors should be developed not only for the robot, but for the whole robotic workstation, and that a hazard analysis of the workstation should be performed and the safeguarding system designed to correspond to the level of hazard found.