1,720,969 research outputs found
Progettazione Integrata di Sistemi Robotizzati Modulari per l’aumento di Accuratezza nelle Lavorazioni Meccaniche
No full textLe prestazioni offerte dai moderni sistemi robotizzati permettono di soddisfare i principali requisiti di flessibilità e qualità nell’ambito delle lavorazioni meccaniche. L’utilizzo di tali sistemi è però limitato da problemi legati all’accuratezza dei robot industriali che non consente l’utilizzo degli stessi nel campo delle lavorazioni ad alta precisione, coperto dalle tradizionali macchine a controllo numerico. Ciò restringe l’applicazione di tali sistemi per applicazioni che richiedono ampi campi di variabilità dimensionale e geometrica.
Il presente lavoro di tesi presenta un approccio integrato per lo sviluppo di una cella modulare robotizzata di lavorazione che integra soluzioni tecnologiche allo stato dell’arte, con lo scopo di aumentare l’accuratezza finale sulla parte in lavorazione. La parte iniziale della ricerca ha riguardato l’analisi degli errori attraverso l’esecuzione di vari esperimenti di lavorazione robotizzata. Successivamente è stato sviluppato un approccio progettuale che permette di realizzare una cella modulare attraverso l’integrazione di diverse tecnologie abilitanti che intervengono prima dell’esecuzione del ciclo di lavoro (modalità offline) e in tempo reale (modalità online). La compensazione predittiva offline degli errori del robot è realizzata attraverso il modello cinematico e dinamico del Robot. La compensazione online avviene attraverso un sistema di tracking ottico che permette di misurare la posizione reale del TCP del robot. A questo si aggiunge un sistema di compensazione ad elevata dinamica basato su sensori piezoelettrici. Una successiva campagna sperimentale è stata realizzata al fine di analizzare l’accuratezza dimensionale e geometrica in componenti industriali, prendendo come esempio un componente automotive. Al fine di valutare l’efficacia del metodo proposto, i risultati ottenuti sono stati infine comparati con quelli ottenibili con una componente lavorato con una macchina a controllo numerico standard.Actual industrial robotic systems offer performance to effectively cope with the requirements in manufacturing dealing with flexibility and quality. Especially in machining application, their known limits in accuracy do not allow extending their field of application to high-accuracy machining, actually covered by state-of-the-art CNC machine tools. Consequently, industrial robots are currently limited to applications with low geometrical accuracies and soft materials. This thesis present an integrated approach to develop a robotic modular workcell with enhanced accuracy for machining, through the full integration of different theoretical models, state-of-the-art technological solutions and manufacturing strategies. In order to compensate for robot errors, several experiments under different conditions that represent a typical set of industrial applications and allow a qualified evaluation are performed. Based on this analysis a modular approach to overcome these obstacles, applied both during program generation (offline) and execution (online), is proposed. Predictive offline compensation of machining errors is achieved by means of an innovative programming system, based on kinematic and dynamic robot models. Real-time adaptive machining error compensation is also provided by sensing the real robot positions with an innovative tracking system and corrective feedback to both the robot and an additional high dynamic compensation mechanism on piezo-actuator basis. To evaluate the method effectiveness, an experimental campaign has been designed and realized in order to discuss the dimensional and geometrical quality obtained for an automotive part in comparison with quality and costs offered by a standard 5-axis CNC machine tool
Design of fixture systems in automotive manufacturing and assembly
No full textFixture systems have a great importance in modern manufacturing and assembly because of the high number of scenarios in which they are used. Fixture design is a complex task since the system effectiveness depends both on position and type of locators. Several authors deal with the problem of determine the most suitable design for fixture systems but their investigation is commonly limited to the evaluation of the effects due to the locators’ position. In the present work a design method is proposed to evaluate the fixture systems considering also the locators’ type. Since it is possible to model the fixtures as multi-performance systems, the comparison is performed by introducing appropriate sensitivity indexes. The effectiveness of the design method is proved through the application to an automotive case study
Integration of CAM off-line programming in robot high-accuracy machining
No full textActual industrial robotic systems offer performance to effectively cope with the requirements in manufacturing dealing with flexibility and quality. However, their known limits in accuracy do not allow to extend their field of application to high-accuracy machining, actually covered by state-of-the-art CNC machine tools. The European Project COMET has recently proposed an approach to develop a robotic reconfigurable workcell with enhanced accuracy for machining, through the full integration of different theoretical models, technological solutions and manufacturing strategies. The present paper presents and demonstrates the effectiveness of a demo reconfigurable machining workcell for one of its possible configurations, based on CAM off-line programming. In particular, an experimental campaign has been designed and realized in order to discuss the dimensional and geometrical quality obtained for an aluminium automotive part in comparison with quality and costs offered by a standard 5-axis CNC machine tool. © 2013 IEEE
Evaluation of operator relief for an effective design of HRC workcells
No full textIn recent years, Human Robot Cooperation (HRC)
has found an increasing adoption in manufacturing, especially to
help humans in the execution of manual assembly tasks. An
effective employment of HRC encompasses human relief from
exhausting operations. Therefore, the design of cooperative
solutions should be developed accordingly to ergonomic aspects.
The present work proposes an approach to support the integration
of ergonomic evaluation of manual operations in the design of
HRC solution, based on modelling and simulation of the human
body along the manufacturing tasks. The proposed modified
model integrates the ergonomic metrics and returns a fatigue level
along the working shift scheduling. A real manual assembly of
biomedical products has been selected to validate the proposed
approach. As a result, the suggested fatigue model provides an
objective ergonomic evaluation of manual operations which
verifies the impact of the HRC solution on the production goals
Offline workpiece calibration method for robotic reconfigurable machining platform
No full textRecent trends in industrial manufacturing impose the adoption of changeable systems, based on reconfigurable and flexible equipment. In this scenario, industrial robotics platforms are central to design highly reconfigurable systems. A Robotic Reconfigurable Machining Platform (RRMP), as defined, is a modular architecture for robotic workcells, designed in order to exploit the flexibility features of robots and extend their field of application to high precision machining. RRMP calibration is a key task, which involves calibration of tools, workpieces and peripherals. However, state-of-the-art calibration methods and tools lead to hardly predictable system downtime, which impacts the reconfiguration phase. A novel method to perform the workpiece calibration is proposed for the reduction of the reconfiguration efforts in RRMPs. The method is addressed through a full integration with a virtual environment for robot simulation and programming. The method is finally applied to an industrial case study and compared to the most widely diffused online approach
Genetic algorithm optimization and robustness analysis for the computer aided design of fixture systems in automotive manufacturing
No full textFixture Systems (FSs) have great importance in machining, welding, assembly, measuring, testing and other manufacturing processes. One of the most critical issue in FS design is the choice of both the type of fixing devices such as clamps, locators, and support points, (configuration), and their arrangement with respect to workpieces (layout). Several authors deal with the problem of determine the most suitable solution for FSs, often investigating their layout without considering the change of the type of locators. A computer aided design method is proposed to compare and evaluate different configurations for a FS, optimizing the locator type and analysing the roboustness of the solution. A multi-objective optimization based on a genetic algorithm is presented and the selection of the most suitable configuration is performed through the definition of robustness indexes. The effectiveness of the design method is demonstrated for an automotive case study
Experimental investigation of sources of error in Robot Machining
No full textThis document is divided into two parts. First a survey is given presenting sources of error in robot machining and outlining their dependencies. Environment dependent, robot dependent and process dependent errors are addressed. The second part analyses the errors according to their source, magnitude and frequency spectrum. Experiments under different conditions represent a typical set of industrial applications and allow a qualified evaluation. This analysis enables the qualified choice of suitable compensation mechanisms in order to reduce the errors in robot machining and to increase machining accuracy
A novel method for sensitivity analysis and characterization in integrated engineering design
No full textPurpose:The present research work aims to analyze and characterize processes in terms of sensitivity of their performances. Robust design techniques, generally adopted for product and process optimization, are not suited for investigating sensitivity. Then a novel approach to such engineering problem needs to be proposed.Method:The developed method integrates and extends to the analysis of manufacturing and technological processes the Performance Sensitivity Distribution (PSD) theory, primarily introduced to provide analytical and geometric description of performance sensitivity for robotic mechanisms.Result:Such novel method, named Specialized PSD, starts from the clarification of the sensitivity analysis problem by defining key parameters, i.e. Design Variables (DVs), Design Parameters (DPs) and Performance Functions (PFs). According to the PSD theory, PF sensitivity is expressed in terms of deviations of DVs and DPs and it is geometrically described by a hyperellipsoid in the n-dimensional space. Sensitivity indexes are then introduced to assess PF variation for different combinations of DVs and DPs deviations. Regression Analysis is adopted to provide the mathematical description of PFs so the PSD theory is finally specialized to be applied in a process sensitivity analysis. Injection molding of a plastic specimen is finally investigated to validate the proposed method.Discussion & Conclusion:This work specialize the PSD theory for manufacturing and technological processes, extending its original field of application thanks to a novel approach to the analytical expression of the PFs. Moreover, when 2 or 3 parameters are considered, sensitivity indexes are graphically represented through tolerance maps of colour, so the method can be easily adopt for integrated design, especially in the early stage of product and process development
A systematic approach to the engineering design of a HRC workcell for bio-medical product assembly
No full textHuman Robot Collaboration (HRC) have proved to be effective if compared to traditional hybrid automation in assembly tasks, especially when human-like sensitivity and high quality are required. However, a rigorous engineering design is mandatory in order to successfully apply HRC to Industry. Academy and Industry are asked to jointly work for exploiting the technical opportunities given by robots and humans. Scientific literature often describes the application of HRC in manufacturing but rarely presents systematic engineering design approaches. The present paper investigates and describes the systematic design of a HRC workcell for assembling bio-medical products. Moreover, productivity and profitability of the developed solution are evaluated and discussed
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