Abstract
Autonomous industrial mobile manipulator (AIMM), which is composed of a mobile platform and a robot arm of six degrees of freedom (DoFs), can move autonomously and perform dexterous tasks independently in the industrial environment. A novel on-line calibration system for AIMM in real manufacturing workshop is proposed in this paper. Compared to calibration scenarios of fixed-base robot, we focus on the large-space autonomous calibration for AIMM. To cope with the issue of high precision calibration in large space, we propose a multi-level guided-based measurement strategy, which includes the low-cost vision positioning and guidance system, and the high-precision distributed base station (BS) measurement system. The corresponding experiment proves that the total uncertainty of measurement system is less than 0.1 mm. Based on the measured data of end-effector installed at the end of robot arm, the AIMM can perform on-line calibration tasks anywhere automatically without taking into account the expensive devices for the high-precision location of mobile platform and the downtime for the robotic off-line calibration. The mean positioning error of AIMM after calibration reduces 93% based on the calibration experiment.
Highlights
Manufacturing problem of the large components, such as aircraft skins, space capsules, and carriage bodies of highspeed train, has become growing hot topic for related industry corporations or organizations [1]–[3]
Due to the overall machining accuracy of large component is important in the manufacturing process, we are more concerned with the on-site absolute positioning accuracy of end-effector of the Autonomous industrial mobile manipulator (AIMM)
Before the AIMM enters the work space, external pose measurement equipment is used to calibrate the robot arm in off-line mode, the pose of end-effector need to be determined in real-time when the AIMM is moving/operating in the work space
Summary
Manufacturing problem of the large components, such as aircraft skins, space capsules, and carriage bodies of highspeed train, has become growing hot topic for related industry corporations or organizations [1]–[3]. If a global or distributed positioning device is used to locate the mobile platform, the positioning error of mobile platform is transmitted to the base coordinate system of the robot arm [6], [7], and to the end effector, making it difficult to achieve high-precision machining of the end effector. Compared with the existing ‘‘real-time positioning + offline calibration’’ solution, the proposed solution abandons the strategy of using global or distributed measurement sensors to locate the robot, but directly adopts the on-site automatic calibration to achieve the same accuracy as the calibrated fixed mechanical arm in a large work space. Experiments prove the high precision of measuring network and feasibility of the total calibration system with real geometrical parameters
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