Vision-based initial point alignment control for the wheel hubs in the robotic polishing system
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ORIGINAL ARTICLE
Vision-based initial point alignment control for the wheel hubs in the robotic polishing system Zaojun Fang1 · Junjie Li1 · Chi Zhang1 · Guilin Yang1 Received: 30 June 2020 / Accepted: 20 September 2020 / Published online: 14 October 2020 © Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract In the robotic polishing system for the wheel hubs, initial point alignment is a very important procedure before the robot starts to polish. Since the surface shapes of the wheel hubs are complex, traditional contact sensors are not suitable for the initial point alignment. Therefore, this paper presents a vision-based initial point alignment control method due to the merits of non-contact and high precision of the vision sensor. The main procedures of the new proposed initial point alignment methods are as follows. Firstly, the center point of the wheel hub is computed based on the growth of sampled points (GSP) method. Secondly, the center lines of the spokes of the wheel hub are extracted based on the edges of the spokes. Based on the center point and the center lines of the spokes, the needed rotation angle of the wheel hub denoting the current and target initial points can be computed. Thirdly, an alignment controller is designed to align the current initial point with the target one. Finally, experiments are well conducted to demonstrate the effectiveness of the proposed initial point alignment control method for the wheel hubs. Keywords Vision · Robotic polishing system · Alignment control · Wheel hub · Initial point
1 Introduction Wheel hubs are the important parts of the motor vehicles, which have critical impacts on the safety, comfort, and appearance of the motor vehicles [1]. Generally, the manufacturing of the wheel hub consists of five main processes, i.e., smelting, casting with low pressure, heat treatment, polishing, electroplating, or coating [2, 3]. Among the five processes, polishing is the most important factor affecting the final quality and appearance of the wheel hub. However, at present, polishing is almost accomplished manually. The polishing efficiency is low, and the consistency of polishing quality cannot be guaranteed. Moreover, the poor polishing environment is harmful to the workers. To solve the problem, robotic polishing system for the wheel hubs needs to be designed.
Zaojun Fang
[email protected] 1
Zhejiang Key Laboratory of Robotics and Intelligent Manufacturing Equipment Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, People’s Republic of China
Compared with the manual polishing, the robotic polishing system has several obvious advantages such as high polishing efficiency, high polishing precision, and good flexibility. Several robotic polishing systems have been designed. Tian [4] designed a robotic polishing system for curved surfaces, in which an industrial robot with six degrees of freedom (DOFs) and a six-dimensional force/torque sensor was used. Wang [5] developed a selfdetermi
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