Holonic planning and scheduling for a robotic assembly testbed

Abstract

A holonic manufacturing system (HMS) is a manufacturing system where key elements, such as machines, products, parts, etc., have autonomous and cooperative properties. These elements are called "holons," a word coined by combining "holos" (the whole) and "on" (a particle) following Koestler. In an HMS, each holon's activities are determined through cooperation with other holons, as opposed to being determined by a centralized mechanism. An HMS could therefore enjoy high agility, which is an important characteristic for future manufacturing systems. Effective cooperation of holons for overall system performance, however, is mostly on open issue. In this paper, the holonic concept is applied to a simple robotic assembly testbed, and cooperation mechanisms among holons for planning and scheduling are established, respectively, based on an adaptive consistency algorithm and the Lagrangian relaxation technique. It turns out that Lagrangian relaxation provides a theoretical foundation for the cooperation of scheduling activities among holons. The system has been implemented in an object-oriented framework, and evaluated based on the computation times for generating assembly plans and schedules and the quality of schedules under different circumstances. Preliminary testing showed that the system can generate assembly plans and high quality schedules, and respond to dynamic changes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>