| 1. |
- Asbjörnsson, Gauti, 1985, et al.
(författare)
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Application of the Hilbert Transform for Diagnostic and Control in Crushing
- 2020
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Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875. ; 147
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Tidskriftsartikel (refereegranskat)abstract
- The performance of a crusher is an essential element in achieving efficient production of aggregates or metals. The process performance depends on the design and configuration of each process equipment, the configuration of the plant, the design of the control and physical properties of the incoming feed. Crushers, however, do not operate in an ideal condition, and as a result, the crusher’ structure, electrical drive and hydraulic system will experience an uneven load during operation. This paper aims to adapt a Hilbert transform to characterise the pressure variations in actual crushers during operation and to set up potential strategies for quantifying the variation. Two applications are also proposed for how this could be used in operation to compensate for the disturbances from unwanted loading conditions that affect the crusher performance.
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| 2. |
- Erdem, Ilker, 1987, et al.
(författare)
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A novel comparative design procedure for reconfigurable assembly fixtures
- 2017
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Ingår i: CIRP Journal of Manufacturing Science and Technology. - : Elsevier BV. - 1755-5817 .- 1878-0016. ; 19, s. 93-105
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Tidskriftsartikel (refereegranskat)abstract
- While market requirements demand that manufacturing systems increase their responsiveness, assembly fixtures remain limited in corresponding to the same demand. Fixture designers as practitioners are left without guidance to design reconfigurable fixtures. This study proposes a comparative design procedure for reconfigurable assembly fixtures that can adapt to manufacturing system characteristics by using efficiency metrics. In this study, a theoretical analysis based on manufacturing systems is presented to establish efficiency metrics. Later, these metrics are utilized in a design procedure that offers guidance and determines the efficiency of fixtures in conceptual and detailed design stages. Finally, an experimental verification is presented.
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| 3. |
- Erdem, Ilker, 1987, et al.
(författare)
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Automated Flexible Tooling for Wing Box Assembly: Hexapod Development Study
- 2016
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2016-October:October
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Tidskriftsartikel (refereegranskat)abstract
- The ability to adapt to rapidly evolving market demands continues to be the one of the key challenges in the automation of assembly processes in the aerospace industry. To meet this challenge, industry and academia have made efforts to automate flexible fixturing. LOCOMACHS (Low Cost Manufacturing and Assembly of Composite and Hybrid Structures) - a European Union funded project with 31 partners - aims to address various aspects of aero-structure assembly with a special attention directed to the development of a new build philosophy along with relevant enabling technologies. This paper aims to present the results on the developed wing box build philosophy and the integration of automated flexible tooling solutions into the assembly process. The developed solution constitutes the use of synchronized hexapods for the assembly of front spar to upper cover whereas another hexapod was developed to install a rib by using of a force feedback sensor. Both hexapod applications have undergone parametrized mechanical design to provide adaptability to various applications. Furthermore, synchronous control of multiple hexapods has been developed to manipulate and hold the front spar in position and withstand the drilling forces applied by an external automated drilling system during the assembly of cover to spar. Finally, discrete state assembly system utilizing force and torque feedback has been developed to perform the assembly of a rib in order to demonstrate the intelligence capability of hexapods.
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| 4. |
- Erdem, Ilker, 1987, et al.
(författare)
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Development of Affordable Reconfigurable Tooling in Car Manufacturing Cells – A Case Study
- 2015
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Ingår i: 23rd International Conference for Production Research, ICPR 2015, Manila, Philippines, 2-6 August 2015.
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Konferensbidrag (refereegranskat)abstract
- Assembly fixtures are one of the cost driving factors in automotive industry. Previous research have shown that the utilization of affordable reconfigurable tooling (ART) can be a key-enabling technology to reduce the cost and lead times. Inspired by the research results, Volvo Cars Corporation initiated an automated process control project, the aim of which is the automatic inspection and correction of the defects in Body in White (BIW). The project comprises of three stages – the first of which is the in-line measurement of BIW. Then, the results of measurements are transferred to a common database where process evaluation through case-based reasoning suggests corrective actions on the fixture. The last stage involves the development of flexible tooling to meet these changes in a cost and time effective way. Hence, the aim of this paper is to present preliminary results on the development and implementation of ART as flexible tooling.
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| 5. |
- Erdem, Ilker, 1987, et al.
(författare)
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Development of Automated Flexible Tooling as Enabler in Wing Box Assembly
- 2016
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Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 44, s. 233-238
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Konferensbidrag (refereegranskat)abstract
- Flexible tooling has been a focal point of investigation for various industries with an emphasis on cost and time effectiveness. Previous research has shown that when combined with the general requirements of tooling such as rigidness and repeatability, the implementation of flexibility can be a very daunting task. Therefore, LOCOMACHS (Low Cost Manufacturing and Assembly of Composite and Hybrid Structures) project has dedicated a work package for the creation of an automated flexible tooling to meet the demands of future aerospace production. The work package focuses on a creation of a tooling technology that can facilitate the process requirements of an automated wing-assembly by using flexible tooling and intelligence support from a force sensor. Hence, this paper aims to present the framework for automated flexible tooling development and results on a hexapod fixture as a case study.
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| 6. |
- Erdem, Ilker, 1987
(författare)
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EFFICIENCY OF FLEXIBLE FIXTURES: DESIGN AND CONTROL
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The manufacturing industries have been using flexible production technologies to meet the demand for customisation. As a part of production, fixtures have remained limited to dedicated technologies, even though numerous flexible fixtures have been studied and proposed by both academia and industry. The integration of flexible fixtures has shown that such efforts did not yield the anticipated performance and resulted in inefficiencies of cost and time. The fundamental formulation of this thesis addresses this issue and aims to increase the efficiency of flexible fixtures. To realise this aim, the research in this thesis poses three research questions. The first research question investigates the efficiency description of flexible fixtures in terms of the criteria. Relative to this, the second research question investigates the use of efficiency metrics to integrate efficiency criteria into a design procedure. Once the efficiency and design aspects have been established, the third research question investigates the active control of flexible fixtures to increase their efficiency. The results of this thesis derive from the outcome of seven studies investigating the automotive and aerospace industries. The results that answer the first research question use five criteria to establish the efficiency of flexible fixtures. These are: fundamental, flexibility, cost, time and quality. By incorporating design characteristics in respect of production system paradigms, each criterion is elaborated upon using relevant sub-criteria and metrics. Moreover, a comparative design procedure is presented for the second research question and comprising four stages (including mechanical, control and software aspects). Initially, the design procedure proposes conceptual design and verification stages to determine the most promising flexible fixture for a target production system. By executing detailed design and verification, the design procedure enables a fixture designer to finalise the flexible fixture and determine its efficiency. Furthermore, a novel parallel kinematics machine is presented to demonstrate the applicability of the design procedure’s analytical steps and illustrate how appropriate kinematic structures can facilitate the efficiency-orientated design of flexible fixtures. Based on the correlation established by the controller software’s design procedure, the active control of flexible fixtures directly affects the quality criterion of flexible fixture efficiency. This provides the answer to the third research question, on general control strategies for active control of flexible fixtures. The introduction of a system model and manipulator dynamics proposes force and position control strategies. It is shown that any flexible fixture using a kinematic class can be controlled, to regulate the force and position of a workpiece and ensure that process nominals are preserved. Moreover, using both direct and indirect force control strategies, a flexible fixture’s role in active control can be expanded into a system of actively controlled fixtures that are useful in various processes. Finally, a position controller is presented which has the capacity to regulate both periodic and non-periodic signals. This controller uses an additional feedforward scheme (based on the Hilbert transform) in parallel with a feedback mechanism. Thus, the position controller enables flexible fixtures to regulate the position of a workpiece in respect of any kind of disturbance.
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| 7. |
- Erdem, Ilker, 1987, et al.
(författare)
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Feedforward control for oscillatory signal tracking using Hilbert transform
- 2019
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Ingår i: European Journal of Control. - : Elsevier BV. - 0947-3580. ; 50, s. 41-50
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents feedforward control for oscillatory signal tracking using Hilbert transform. The proposed controller utilizes Hilbert transform and analysis techniques to determine the signal's amplitude, frequency, and phase. By using the frequency response of the linear time-invariant process model, an amplified and phase-shifted feedforward signal is reconstructed. The proposed controller also analyzes the system response to determine the differences from the model to modify the feedforward signal. Simulation experiments with multicomponent stationary, amplitude-, and frequency-modulated signals are also conducted. The results show that using an amplified and phase-shifted signal determined by Hilbert analysis can enable an effective tracking performance.
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| 8. |
- Erdem, Ilker, 1987
(författare)
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FLEXIBLE FIXTURES - A TREATISE ON FIXTURE DESIGN AND EFFICIENCY
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Even though a variety of efforts have been made in the area of flexible fixtures, the manufacturing industry still relies on dedicated fixtures with minor modular features. The main underlying reason, as these attempts have shown, is that the application of flexible fixtures has failed to yield the expected results, with the implemented technologies often leading to increased manufacturing costs when compared to dedicated fixtures. As this has a negative impact on industry’s return on investment, a grey and largely uncharted area has arisen around the efficiency of flexible fixtures. The research that forms the basis of this thesis is intended to explore, describe and increase the efficiency of flexible fixtures in manufacturing industry. In order to fulfil this aim, two research questions have been asked. The first question focuses on exploring and description of the efficiency, while the second question focuses on how methodically the concept of efficiency can be used in fixture design.The results presented in this thesis are based on four experimental studies carried out in the automotive and aerospace industries covering different aspects of modular and reconfigurable fixtures with manual, automated and active features. Based on these experimental studies, seven criteria regarding the efficiency of flexible fixtures have been identified. These criteria relate to physical flexibility, quality, interactivity, cost, time, modularity and maintenance. Furthermore, the thesis provides the expected states of criteria along with relevant metrics. Subsequently, a design procedure using these metrics is presented based on the characteristics of a manufacturing system, in order to identify the most efficient fixturing solution. Finally, the efficiency of flexible fixtures is found to be correlated to the individual and unique needs of a manufacturing system. Consequently, the ability of a fixture designer to understand and adapt to those needs is the key to increased efficiency; thus, the applicability of flexible fixtures.
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| 9. |
- Erdem, Ilker, 1987, et al.
(författare)
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Workpiece force and position control for active and flexible fixtures in assembly
- 2021
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Ingår i: International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media LLC. - 0268-3768 .- 1433-3015. ; 112:1-2, s. 333-346
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Tidskriftsartikel (refereegranskat)abstract
- With strengthening focus on digitalization and flexibility, active and flexible fixtures can provide the right tools for manufacturing systems. However, fixturing solutions are often too individualized for processes and need a universal approach. Firstly, a system formulation of multiple workpieces interacting with each other is presented. Secondly, strategies for direct and indirect force control along with their characteristics have been developed. The stability of assembly of force-controlled components has been analyzed, and certain key characteristics have been presented. The position control under different signal types, including oscillatory, have been discussed. Finally, a set of experiments have been conducted for performance evaluation.
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