Purpose

The purpose of this paper is to propose a novel measurement technique and a modelless calibration method for improving the positioning accuracy of a three-axis parallel kinematic machine (PKM). The aim is to present a low-cost calibration alternative, for small and medium-sized enterprises, as well as educational and research teams, with no expensive measuring devices at their disposal.

Design/methodology/approach

Using a chessboard pattern on a ground-truth plane, a digital indicator, a two-dimensional eye-in-hand camera and a laser pointer, positioning errors are explored in the machine workspace. With the help of these measurements, interpolation functions are set up per direction, resulting in an interpolation vector function to compensate the volumetric errors in the workspace.

Findings

Based on the proof-of-concept system for the linear-delta PKM, it is shown that using the proposed measurement technique and modelless calibration method, positioning accuracy is significantly improved using simple setups.

Originality/value

In the proposed method, a combination of low-cost devices is applied to improve the three-dimensional positioning accuracy of a PKM. By using the presented tools, the parametric kinematic model is not required; furthermore, the calibration setup is simple, there is no need for hand–eye calibration and special fixturing in the machine workspace.

中文翻译：

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一种用于 3 轴平行运动机器无模型校准的新型低成本技术

目的

本文的目的是提出一种新的测量技术和无模型校准方法，以提高三轴平行运动机 (PKM) 的定位精度。目的是为中小型企业以及教育和研究团队提供一种低成本的校准替代方案，无需昂贵的测量设备。

设计/方法/方法

使用真实平面上的棋盘图案、数字指示器、二维手眼相机和激光指示器，在机器工作区中探索定位误差。在这些测量的帮助下，每个方向都设置了插值函数，从而产生了一个插值向量函数来补偿工作空间中的体积误差。

发现

基于线性增量 PKM 的概念验证系统，表明使用所提出的测量技术和无模型校准方法，使用简单的设置显着提高了定位精度。

原创性/价值

在所提出的方法中，应用低成本设备的组合来提高 PKM 的三维定位精度。通过使用所提供的工具，不需要参数化运动学模型；此外，校准设置简单，无需在机器工作区进行手眼校准和特殊夹具。