Understanding a Rapidly Reconfigurable Robotic Workcell

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Submitted to Journal of Japan Society of Precision Engineering

Realization of A Rapidly Reconfigurable Robotic Workcell
I-Ming Chen School of Mechanical and Production Engineering Nanyang Technological University Nanyang Ave, Singapore 639798 ABSTRACT This article describes the development of a component technology based robot workcell that can be rapidly configured to perform a specific manufacturing task. The workcell is conceived with standard and inter-operable components including actuator modules, rigid link connectors and tools that can be assembled into robots with arbitrary geometry and degrees of freedom. The reconfigurable "plug-and-play" robot modeling algorithms are developed based on the Local Product-Of-Exponentials formulation. These algorithms are the basis for the control and simulation of reconfigurable robots. The concept of robot configuration optimization is introduced to establish optimal and effective use of the rapidly reconfigurable robots. Control and communications of the workcell components are facilitated by a workcell-wide TCP/IP network and device level CAN-bus networks. An object-oriented simulation and visualization software for the reconfigurable robot is developed based on Windows NT. A prototype of the robot workcell configured to perform light machining task is constructed and demonstrated.

1. INTRODUCTION An automated manufacturing system usually consists of a collection of material processing and handling devices such as CNC machines, robots, part feeders, conveyors, and sensors. These devices are traditionally designed and commissioned with the intent that they will be operated with few significant changes so long as the specific product is being manufactured. Certain flexibility has been given to those devices through programmable controllers. However, it is time-consuming and not cost effective to reconfigure them for other products. In the rapidchanging and highly competitive global economy environment, such drawbacks reduce the attractiveness of automation systems for manufactures that are involved in high-mix, low-volume production. For manufacturers adopting the fixed automation systems, not being able to respond quickly to market changes will place them at a disadvantage. 1

Submitted to Journal of Japan Society of Precision Engineering

The Nanyang Technological University and Gintic Institute of Manufacturing Technology are currently involved in a project to improve agility and flexibility in automation systems by developing a “rapidly reconfigurable” robotic workcell. The key to the concept of reconfigurability lies in the "plug-and-play" component-based technology (Figure 1). Ultimately, workcells will be made of standard interchangeable modular components, such as actuators, rigid links, end-of-arm tooling, and sensors. These components can be rapidly assembled and configured to form robots with various geometry and degrees of freedom (DOF). The robots, together with other peripheral devices, will form a complete robotic workcell to execute a specific manufacturing task or process. The corresponding intelligent control and simulation software components are then reconfigured according to the change of the workcell configuration. Therefore, hardware and software components become reusable, and maintenance and upgrade of the system become very easy. Most important of all, converting one manufacturing line from one product to another can be very fast and easy in order to keep up with the rapid changing marketplace. In this article, the development of such a component-based reconfigurable robotic workcell is introduced. The development of the workcell consists of five major aspects: 1) Robot/workcell hardware component design - standard active and passive modules for reconfigurability and inter-operability 2) Reconfigurable and “plug-and-play” kinematics and dynamics modeling - to ensure uniform control and operation of robots with different geometry and DOFs 3)...
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