Robots have been used to transfer part material in stamping operations for many years, but what safety issues should be addressed and techniques applied when humans need to share space in the robotic work cell? Balluff, Inc., Florence, KY, a manufacturer of sensors, precision mechanical limit switches and linear position transducers, has some advice. U.S. robot safety standard ANSI/RIA R15.06-1999, according to Balluff officials, provides guidelines for the safe interlocking of robot position to the presence of a human operator through a process known as Dynamic Envelope Restriction. Section 10.2.3 of the standard permits the use of dynamic limiting devices (DLDs) to reliably monitor the position of the robot and allow it to continue working while it is safely out of the area occupied by the operator. The use of DLDs, also known as zone limits, can significantly increase the hourly productivity of a robot without compromising the safety of personnel working with the robot. The challenge for robot integrators and control system designers: devise a way to economically and reliably implement zone limits while meeting strict ANSI/RIA requirements for control reliability under section 4.5.4.
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