Positioning uncertainty of the control system for the planar motion of a nanopositioning platform

The novel nanopositioning platform (NanoPla) that is in development at the University of Zaragoza has been designed to achieve nanometre resolution in a large working range of 50 mm × 50 mm. The 2D movement is performed by four custom-made Halbach linear motors and a 2D laser system provides positioning feedback, while the moving part of the platform is levitating and unguided. As control hardware, this work proposes the use of a commercial solution, in contrast to other systems, where the control hardware and software were specifically designed for the purpose. In a previous work of this research, the control system of one linear motor implemented in the selected commercial hardware was presented. In this study, the developed control system is extended to the four motors of the nanopositioning platform to generate a 2D planar movement in the whole working range of the nanopositioning platform. In addition, the positioning uncertainty of the control system is assessed. The obtained results satisfy the working requirements of the NanoPla, achieving a positioning uncertainty of ±0.5 µm along the whole working range

Measurement procedure for application of white light scanner in the automotive sector

Advanced optical metrology systems are continuously being developed to cope with the challenges arising from large-scale, high-quality production, especially in the automotive sector. Therefore, these measuring devices are relatively new and they are ruled by very general standards. The main goal of this work is to develop a specific procedure for a white light fringe projection optical measurement equipment from a general measurement system analysis procedure used in the automotive sector (MSA-4 Reference Manual) considering the recent international regulations for the verification of this type of equipments: Technical Recommendation VDI/VDE 2634 and ISO 10360-8: 2013. Only the tests applicable to the equipment used to validate the proposed procedure, a 3D white light structured scanner SIDIO Pro from Nub3d, were analyzed

Positioning Control System for a Large Range 2D Platform with Submicrometre Accuracy for Metrological and Manufacturing Applications

The importance of nanotechnology in the world of Science and Technology has rapidly increased over recent decades, demanding positioning systems capable of providing accurate positioning in large working ranges. In this line of research, a nanopositioning platform, the NanoPla, has been developed at the University of Zaragoza. The NanoPla has a large working range of 50 mm × 50 mm and submicrometre accuracy. The NanoPla actuators are four Halbach linear motors and it implements planar motion. In addition, a 2D plane mirror laser interferometer system works as positioning sensor. One of the targets of the NanoPla is to implement commercial devices when possible. Therefore, a commercial control hardware designed for generic three phase motors has been selected to control and drive the Halbach linear motors.This thesis develops 2D positioning control strategy for large range accurate positioning systems and implements it in the NanoPla. The developed control system coordinates the performance of the four Halbach linear motors and integrates the 2D laser system positioning feedback. In order to improve the positioning accuracy, a self calibration procedure for the characterisation of the geometrical errors of the 2D laser system is proposed. The contributors to the final NanoPla positioning errors are analysed and the final positioning uncertainty (k=2) of the 2D control system is calculated to be ±0.5 µm. The resultant uncertainty is much lower than the NanoPla required positioning accuracy, broadening its applicability scope.<br /

2D positioning control system for the planar motion of a nanopositioning platform

A novel nanopositioning platform (referred as NanoPla) in development has been designed to achieve nanometre resolution in a large working range of 50 mm × 50 mm. Two-dimensional (2D) movement is performed by four custom-made Halbach linear motors, and a 2D laser system provides positioning feedback, while the moving part of the platform is levitating and unguided. For control hardware, this work proposes the use of a commercial generic solution, in contrast to other systems where the control hardware and software are specifically designed for that purpose. In a previous paper based on this research, the control system of one linear motor implemented in selected commercial hardware was presented. In this study, the developed control system is extended to the four motors of the nanopositioning platform to generate 2D planar movement in the whole working range of the nanopositioning platform. In addition, the positioning uncertainty of the control system is assessed. The obtained results satisfy the working requirements of the NanoPla, achieving a positioning uncertainty of ±0.5 µm along the whole working range

Preliminary Modelling and Implementation of the 2D-control for a Nanopositioning Long Range Stage

Different systems are recently developed to obtain effective positioning at nanometer scale with increased working ranges. For this purpose, a two-dimensional nanopositioning platform (NanoPla) has been design and manufactured. To assure the demanding metrological performance the drive and control system is being defined and validated. Based on four home-made linear motors as actuators, this work is focused on the study of the control-loop for 1D- and 2D-cases with the aim of the preliminary modelling and posterior implementation. The different required blocks are presented and an initial controller solution is proposed to achieve the established positioning requests

Analysis of different camera calibration methods on a camera-projector measuring system

The accuracy of metrology equipment formed by a camera-projector pair depends directly on the calibration procedure used. This kind of equipment allows to perform the calibration by two different approaches: as a whole system or separately. The most common approach is the second one: conventional calibration. Studies show that the uncertainty of the camera parameters from its calibration propagates to the projector parameters. The objective of this study is to have a clear comprehension of the relationships between the camera and projector parameters and of how uncertainty is propagated. This will be done by using a camera previously calibrated by Tsai, Zhang or Direct Linear Calibration (DLC) methods, followed by the calibration of the projector using DLC

The use of a Laser Tracker and a Self-centring Probe for Rotary Axis Verification

This paper presents a small collection of tests related with the analysis of a rotary axis according to ISO 230-7 but introducing two alternative equipments briefly explaining each method. The disadvantages of the methods in which the movement of a rotary axis engages the translational axes of a Machine Tool are expressed, which leads to the proposed study. The errors of a rotary axis are described as established in standards and the measurement procedures carried out in the tests for verification of a rotary indexing table, based on the use of a self-centring probe and a laser tracker, are explained. Also, the necessary elements setup for measurement are described. Then, the followed calculation process of the measured errors is explained in detail. Finally, the results of the most significant errors obtained from the test measurements are presented

Mejora de la calidad superficial en fabricación aditiva "FDM" mediante el uso de trayectorias no planas generadas a través de diseño algorítmico

El modelado por deposición fundida (FDM), es un proceso de fabricación aditiva con un gran potencial de aplicación en un amplio rango de sectores. Mediante la disposición sucesiva de capas se obtienen prototipos y partes funcionales con una gran complejidad geométrica. Sin embargo, inherente a la técnica, la deposición del material capa a capa produce escalonamientos que llevan consigo una baja calidad superficial, acentuándose este hecho cuando hablamos de superficies con pequeña inclinación. Para solucionar este problema, la impresión no-plana surge como un sustituto adecuado a la impresión plana tradicional. En este trabajo, se realizará un acercamiento al método, incluyendo teoría y experimentación. A través de un novedoso procedimiento de diseño asistido por algoritmos obtendremos las trayectorias que seguirá la boquilla durante la impresión. En esta técnica no-plana, la geometría de la boquilla puede ocasionar colisiones y deformaciones sobre el material ya depositado, de tal forma, se estudiará un experimental tipo de boquilla de reciente introducción en el mercado. Por último, obtenidas mediante impresión varias geometrías, someteremos a éstas a un análisis de rugosidad superficial con el fin de comprobar la eficacia del método no-planar frente al tradicional, en cuanto a acabado superficial se refiere.<br /

Design optimization for the measurement accuracy improvement of a large range nanopositioning stage

Both an accurate machine design and an adequate metrology loop definition are critical factors when precision positioning represents a key issue for the final system performance. This article discusses the error budget methodology as an advantageous technique to improve the measurement accuracy of a 2D-long range stage during its design phase. The nanopositioning platform NanoPla is here presented. Its specifications, e.g., XY-travel range of 50 mm ˆ 50 mm and sub-micrometric accuracy; and some novel designed solutions, e.g., a three-layer and two-stage architecture are described. Once defined the prototype, an error analysis is performed to propose improvement design features. Then, the metrology loop of the system is mathematically modelled to define the propagation of the different sources. Several simplifications and design hypothesis are justified and validated, including the assumption of rigid body behavior, which is demonstrated after a finite element analysis verification. The different error sources and their estimated contributions are enumerated in order to conclude with the final error values obtained from the error budget. The measurement deviations obtained demonstrate the important influence of the working environmental conditions, the flatness error of the plane mirror reflectors and the accurate manufacture and assembly of the components forming the metrological loop. Thus, a temperature control of ¿0.1 ¿C results in an acceptable maximum positioning error for the developed NanoPla stage, i.e., 41 nm, 36 nm and 48 nm in X-, Y- and Z-axis, respectively