A novel six-legged walking machine tool for in-situ operations
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RESEARCH ARTICLE
Jimu LIU, Yuan TIAN, Feng GAO
A novel six-legged walking machine tool for in-situ operations
© The Author(s) 2020. This article is published with open access at link.springer.com and journal.hep.com.cn
Abstract The manufacture and maintenance of large parts in ships, trains, aircrafts, and so on create an increasing demand for mobile machine tools to perform in-situ operations. However, few mobile robots can accommodate the complex environment of industrial plants while performing machining tasks. This study proposes a novel six-legged walking machine tool consisting of a legged mobile robot and a portable parallel kinematic machine tool. The kinematic model of the entire system is presented, and the workspace of different components, including a leg, the body, and the head, is analyzed. A hierarchical motion planning scheme is proposed to take advantage of the large workspace of the legged mobile platform and the high precision of the parallel machine tool. The repeatability of the head motion, body motion, and walking distance is evaluated through experiments, which is 0.11, 1.0, and 3.4 mm, respectively. Finally, an application scenario is shown in which the walking machine tool steps successfully over a 250 mmhigh obstacle and drills a hole in an aluminum plate. The experiments prove the rationality of the hierarchical motion planning scheme and demonstrate the extensive potential of the walking machine tool for in-situ operations on large parts. Keywords legged robot, parallel mechanism, mobile machine tool, in-situ machining
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Introduction
An increasing demand for manufacturing and maintaining large parts in several industrial fields, such as aeronautics, railroad, shipping, offshore platforms, and power plants, has emerged. Traditionally, large parts are generally Received January 8, 2020; accepted April 23, 2020
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Jimu LIU, Yuan TIAN, Feng GAO ( ) State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China E-mail: [email protected]
machined by large workspace machines [1]. In terms of maintenance and repair, a conventional approach involves disassembling the damaged parts of a system and shipping them to specialized workshops for processing, which is costly, complex, and time consuming. Furthermore, certain situations involve damaged parts that are impossible to disassemble; thus, maintenance relies on human workforce. Therefore, portable or mobile machine tools for performing in-situ post-production tasks for large parts are in demand. Mobile manipulators have been studied for decades. The mobility of a manipulator can be provided by linear guide ways, wheeled or tracked vehicles, or legged robots. One of the most common mobile manipulators is a classical serial robot arm mounted on a wheeled mobile base [2]. MADAR is a dual-arm mobile manipulator with two commercial UR5 arms mounted on an omnidirectional platform. The mobile platform is driven by three specially designed omni-wheels that diff
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