3,311 research outputs found

    ๋ถˆํ™•์‹ค์„ฑ์„ ํฌํ•จํ•˜๋Š” ์กฐ๋ฆฝ์ž‘์—…์„ ์œ„ํ•œ ์ปดํ”Œ๋ผ์ด์–ธ์Šค ๊ธฐ๋ฐ˜ ํŽ™์ธํ™€ ์ „๋žต

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    ํ•™์œ„๋…ผ๋ฌธ (๋ฐ•์‚ฌ) -- ์„œ์šธ๋Œ€ํ•™๊ต ๋Œ€ํ•™์› : ์œตํ•ฉ๊ณผํ•™๊ธฐ์ˆ ๋Œ€ํ•™์› ์œตํ•ฉ๊ณผํ•™๋ถ€(์ง€๋Šฅํ˜•์œตํ•ฉ์‹œ์Šคํ…œ์ „๊ณต), 2020. 8. ๋ฐ•์žฌํฅ.The peg-in-hole assembly is a representative robotic task that involves physical contact with the external environment. The strategies generally involve performing the assembly task by estimating the contact state between the peg and the hole. The contact forces and moments, measured using force sensors, are primarily used to estimate the contact state. In this paper, in contrast to past research in the area, which has involved the utilization of such expensive devices as force/torque sensors or remote compliance mechanisms, an inexpensive method is proposed for peg-in-hole assembly without force feedback or passive compliance mechanisms. The method consists of an analysis of the state of contact between the peg and the hole as well as a strategy to overcome the inevitable positional uncertainty of the hole incurred in the recognition process. A control scheme was developed to yield compliant behavior from the robot with physical contact under the condition of hybrid position/force control. Proposed peg-in-hole strategy is based on compliance characteristics and generating the force and moment. The peg is inserted into the hole as it adapts to the external environment. The effectiveness of the proposed method was experimentally verified using a humanoid upper body robot with fifty degrees of freedom and a peg-in-hole apparatus with a small clearance (0.1 mm). Three cases of experiments were conducted; Assembling the peg attached to the arm in the hole fixed in the external environment, grasping a peg with an anthropomorphic hand and assembling it into a fixed hole, and grasping both peg and hole with both hands and assembling each other. In order to assemble the peg-in-hole through the proposed strategy by the humanoid upper body robot, I present a method of gripping an object, estimating the kinematics of the gripped object, and manipulating the gripped object. In addition to the cost aspect, which is the fundamental motivation for the proposed strategy, the experimental results show that the proposed strategy has advantages such as fast assembly time and high success rate, but has the disadvantage of unpredictable elapsed time. The reason for having a high variance value for the success time is that the spiral trajectory, which is most commonly used, is used. In this study, I analyze the efficiency of spiral force trajectory and propose an improved force trajectory. The proposed force trajectory reduces the distribution of elapsed time by eliminating the uncertainty in the time required to find a hole. The efficiency of the force trajectory is analyzed numerically, verified through repeated simulations, and verified by the actual experiment with humanoid upper body robot developed by Korea institute of industrial technology.ํŽ™์ธํ™€ ์กฐ๋ฆฝ์€ ๋กœ๋ด‡์˜ ์ ‘์ด‰ ์ž‘์—…์„ ๋Œ€ํ‘œํ•˜๋Š” ์ž‘์—…์œผ๋กœ, ํŽ™์ธํ™€ ์กฐ๋ฆฝ ์ „๋žต์„ ์—ฐ๊ตฌํ•จ์œผ๋กœ์จ ์‚ฐ์—… ์ƒ์‚ฐ ๋ถ„์•ผ์˜ ์กฐ๋ฆฝ์ž‘์—…์— ์ ์šฉํ•  ์ˆ˜ ์žˆ๋‹ค. ํŽ™์ธํ™€ ์กฐ๋ฆฝ์ž‘์—…์€ ์ผ๋ฐ˜์ ์œผ๋กœ ํŽ™๊ณผ ํ™€ ๊ฐ„์˜ ์ ‘์ด‰์ƒํƒœ๋ฅผ ์ถ”์ •ํ•จ์œผ๋กœ์จ ์ด๋ฃจ์–ด์ง„๋‹ค. ์ ‘์ด‰์ƒํƒœ๋ฅผ ์ถ”์ •ํ•˜๊ธฐ ์œ„ํ•ด ๊ฐ€์žฅ ๋„๋ฆฌ ์“ฐ์ด๋Š” ๋ฐฉ๋ฒ•์€ ํž˜ ์„ผ์„œ๋ฅผ ์‚ฌ์šฉํ•˜๋Š” ๊ฒƒ์ธ๋ฐ, ์ ‘์ด‰ ํž˜๊ณผ ๋ชจ๋ฉ˜ํŠธ๋ฅผ ์ธก์ •ํ•˜์—ฌ ์ ‘์ด‰์ƒํƒœ๋ฅผ ์ถ”์ •ํ•˜๋Š” ๋ฐฉ์‹์ด๋‹ค. ๋งŒ์•ฝ ์ด๋Ÿฌํ•œ ์„ผ์„œ๋ฅผ ์‚ฌ์šฉํ•˜์ง€ ์•Š์„ ์ˆ˜ ์žˆ๋‹ค๋ฉด, ํ•˜๋“œ์›จ์–ด ๋น„์šฉ๊ณผ ์†Œํ”„ํŠธ์›จ์–ด ์—ฐ์‚ฐ๋Ÿ‰ ๊ฐ์†Œ ๋“ฑ์˜ ์žฅ์ ์ด ์žˆ์Œ์€ ์ž๋ช…ํ•˜๋‹ค. ๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ํž˜ ์„ผ์„œ ํ˜น์€ ์ˆ˜๋™ ์ปดํ”Œ๋ผ์ด์–ธ์Šค ์žฅ์น˜๋ฅผ ์‚ฌ์šฉํ•˜์ง€ ์•Š๋Š” ํŽ™์ธํ™€ ์ „๋žต์„ ์ œ์•ˆํ•œ๋‹ค. ํ™€์— ๋Œ€ํ•œ ์ธ์‹ ์˜ค์ฐจ ํ˜น์€ ๋กœ๋ด‡์˜ ์ œ์–ด ์˜ค์ฐจ๋ฅผ ๊ทน๋ณตํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๋จผ์ € ํŽ™๊ณผ ํ™€์˜ ์ ‘์ด‰ ๊ฐ€๋Šฅ ์ƒํƒœ๋ฅผ ๋ถ„์„ํ•˜๊ณ  ๋กœ๋ด‡์˜ ์ปดํ”Œ๋ผ์ด์–ธ์Šค ๋ชจ์…˜์„ ์œ„ํ•œ ์ œ์–ด ํ”„๋ ˆ์ž„์›Œํฌ๋ฅผ ๋””์ž์ธํ•œ๋‹ค. ์ „๋žต์€ ์ปดํ”Œ๋ผ์ด์–ธ์Šค ํŠน์ง•์— ๊ธฐ๋ฐ˜ํ•˜๋ฉฐ ํŽ™์— ํž˜๊ณผ ๋ชจ๋ฉ˜ํŠธ๋ฅผ ์ƒ์„ฑ์‹œํ‚ด์œผ๋กœ์จ ์กฐ๋ฆฝ์ž‘์—…์„ ์ˆ˜ํ–‰ํ•œ๋‹ค. ํŽ™์€ ์™ธ๋ถ€ํ™˜๊ฒฝ์— ์ˆœ์‘ํ•จ์œผ๋กœ์จ ํ™€์— ์‚ฝ์ž…๋œ๋‹ค. ์ œ์•ˆํ•œ ์ „๋žต์€ ๋‚ฎ์€ ๊ณต์ฐจ๋ฅผ ๊ฐ–๋Š” ํŽ™์ธํ™€ ์‹คํ—˜์„ ํ†ตํ•ด์„œ ๊ทธ ์œ ํšจ์„ฑ์ด ๊ฒ€์ฆ๋œ๋‹ค. ํŽ™๊ณผ ํ™€์„ ๋กœ๋ด‡ํŒ”๊ณผ ์™ธ๋ถ€ํ™˜๊ฒฝ์— ๊ฐ๊ฐ ๊ณ ์ •๋œ ํ™˜๊ฒฝ์—์„œ์˜ ์‹คํ—˜, ์ธ๊ฐ„ํ˜• ๋กœ๋ด‡ํ•ธ๋“œ๋ฅผ ์ด์šฉํ•˜์—ฌ ํŽ™์„ ์žก์•„์„œ ๊ณ ์ •๋œ ํ™€์— ์‚ฝ์ž…ํ•˜๋Š” ์‹คํ—˜, ๊ทธ๋ฆฌ๊ณ  ํ…Œ์ด๋ธ”์— ๋†“์ธ ํŽ™๊ณผ ํ™€์„ ๊ฐ๊ฐ ๋กœ๋ด‡ํ•ธ๋“œ๋กœ ํŒŒ์ง€ํ•˜์—ฌ ์กฐ๋ฆฝํ•˜๋Š” ์ด ์„ธ ๊ฐ€์ง€์˜ ์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ํ•ธ๋“œ๋กœ ํŽ™์„ ํŒŒ์ง€ํ•˜๊ณ  ์กฐ์ž‘ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ, ํŒŒ์ง€ ๋ฐฉ๋ฒ•๊ณผ ํ•ธ๋“œ๋ฅผ ์ด์šฉํ•œ ๋ฌผ์ฒด ์กฐ์ž‘ ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ ๊ฐ„๋žตํžˆ ์†Œ๊ฐœํ•˜์˜€๋‹ค. ์ œ์•ˆํ•œ ์ „๋žต์˜ ์„ฑ๋Šฅ์„ ์‹คํ—˜์ ์œผ๋กœ ๋ถ„์„ํ•œ ๊ฒฐ๊ณผ, ๋†’์€ ์กฐ๋ฆฝ ์„ฑ๊ณต๋ฅ ์„ ๊ฐ–๋Š” ๋Œ€์‹  ์กฐ๋ฆฝ์‹œ๊ฐ„์ด ์˜ˆ์ธกํ•  ์ˆ˜ ์—†๋Š” ๋‹จ์ ์ด ๋‚˜ํƒ€๋‚˜ ์ด๋ฅผ ๋ณด์™„ํ•˜๊ธฐ ์œ„ํ•ด์„œ ๋ Œ์น˜ ๊ถค์  ๋˜ํ•œ ์ œ์•ˆํ•˜์˜€๋‹ค. ๋จผ์ € ๊ฐ€์žฅ ์ผ๋ฐ˜์ ์œผ๋กœ ์‚ฌ์šฉ๋˜๋Š” ๋‚˜์„  ํž˜ ๊ถค์ ์„ ์ด์šฉํ–ˆ์„ ๋•Œ ์กฐ๋ฆฝ ์„ฑ๊ณต์‹œ๊ฐ„์˜ ๋ถ„์‚ฐ์ด ํฐ ์ด์œ ๋ฅผ ํ™•๋ฅ ๊ฐœ๋…์„ ์ด์šฉํ•ด ๋ถ„์„ํ•˜๊ณ , ์ด๋ฅผ ๋ณด์™„ํ•˜๊ธฐ ์œ„ํ•œ ๋ถ€๋ถ„์  ๋‚˜์„  ํž˜ ๊ถค์ ์„ ์ œ์•ˆํ•œ๋‹ค. ์ œ์•ˆํ•œ ํž˜ ๊ถค์ ์ด ๋‚˜์„  ํž˜ ๊ถค์ ์— ๋น„ํ•ด ๊ฐ–๋Š” ์„ฑ๋Šฅ์˜ ์šฐ์ˆ˜์„ฑ์„ ์ฆ๋ช…ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์ˆ˜์น˜์  ๋ถ„์„, ๋ฐ˜๋ณต์  ์‹œ๋ฎฌ๋ ˆ์ด์…˜, ๊ทธ๋ฆฌ๊ณ  ๋กœ๋ด‡์„ ์ด์šฉํ•œ ์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค.1 INTRODUCTION 1 1.1 Motivation: Peg-in-Hole Assembly 1 1.2 Contributions of Thesis 2 1.3 Overview of Thesis 3 2 COMPLIANCE BASED STRATEGY 5 2.1 Background & Related Works 5 2.2 Analysis of Peg-in-Hole Procedure 6 2.2.1 Contact Analysis 7 2.2.2 Basic Idea 9 2.3 Peg-in-Hole Strategy 12 2.3.1 Unit Motions 12 2.3.2 State of Strategy 13 2.3.3 Conditions for State Transition 15 2.4 Control Frameworks 18 2.4.1 Control for Compliant Behavior 18 2.4.2 Friction Compensate 20 2.4.3 Control Input for the Strategy 25 2.5 Experiment 29 2.5.1 Experiment Environment 29 2.5.2 Fixed Peg and Fixed Hole 31 2.5.2.1 Experiment Results 31 2.5.2.2 Analysis of Force and Control Gain 36 2.5.3 Peg-in-Hole with Multi Finger Hand 41 2.5.3.1 Object Grasping 42 2.5.3.2 Object In-Hand Manipulation 44 2.5.3.3 Experiment Results 49 2.5.4 With Upper Body Robot 50 2.5.4.1 Peg-in-Hole Procedure 52 2.5.4.2 Kinematics of Grasped Object 54 2.5.4.3 Control Frameworks 54 2.5.4.4 Experiment Results 56 2.6 Discussion 59 2.6.1 Peg-in-Hole Transition 59 2.6.2 Influential Issues 59 3 WRENCH TRAJECTORY 63 3.1 Problem Statement 64 3.1.1 Hole Search Process 64 3.1.2 Spiral Force Trajectory Analysis 66 3.2 Partial Spiral Force Trajectory 70 3.2.1 Force Trajectory with Tilted Posture 70 3.2.2 Probability to Three-point Contact 76 3.3 SIMULATION & EXPERIMENT 78 3.3.1 Simulation 78 3.3.2 Experiment 83 4 CONCLUSIONS 90 Abstract (In Korean) 102Docto

    Best practice report โ€“ mooring of floating marine renewable energy devices

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    MERiFIC is an EU project linking Cornwall and Finistรจre through the ERDF INTERREG IVa France (Manche) England programme. The project seeks to advance the adoption of marine energy in Cornwall and Finistรจre, with particular focus on the island communities of the Parc naturel marin dโ€™Iroise and the Isles of Scilly. Project partners include Cornwall Council, University of Exeter, University of Plymouth and Cornwall Marine Network from the UK, and Conseil gรฉnรฉral du Finistรจre, Pรดle Mer Bretagne, Technรดpole Brest Iroise, IFREMER and Bretagne Dรฉveloppement Innovation from France.This report is a deliverable of MERiFIC Work Package 3: โ€˜Dynamic Behaviour of Marine Energy Devicesโ€™ involving the collaboration of IFREMER (Institut franรงais de recherche pour l'exploitation de la mer) in France and the University of Exeter in the United Kingdom. It is anticipated that the International Electrotechnical Commissionโ€™s guidelines Marine energy - Wave, tidal and other water current converters - Part 10: The assessment of mooring system for marine energy converters (MECs) will be published by the end of 2013. Although there are several guidance documents in the literature regarding the mooring of marine renewable energy (MRE) devices, the IEC document is one of the first to be produced on this subject, with guidance also available in documents produced by Det Norske Veritas. This document is intended to provide a concise introduction to mooring systems for MRE devices with reference given to guidelines and standards which may be applicable to the design of moorings for marine renewable energy (MRE) devices. The document begins by setting the scene to give background on the fundamental differences between conventional offshore equipment and MRE devices. In Section 2 design considerations are introduced, including cost, geometry and the importance of conducting risk analysis. Section 3 then gives an overview of moored system numerical modelling. Key findings of the report are then summarised in Section 4.MERiFIC was selected under the European Cross-Border Cooperation Programme INTERREG IV A France (Channel) โ€“ England, co-funded by the ERDF

    Learning Task Constraints from Demonstration for Hybrid Force/Position Control

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    We present a novel method for learning hybrid force/position control from demonstration. We learn a dynamic constraint frame aligned to the direction of desired force using Cartesian Dynamic Movement Primitives. In contrast to approaches that utilize a fixed constraint frame, our approach easily accommodates tasks with rapidly changing task constraints over time. We activate only one degree of freedom for force control at any given time, ensuring motion is always possible orthogonal to the direction of desired force. Since we utilize demonstrated forces to learn the constraint frame, we are able to compensate for forces not detected by methods that learn only from the demonstrated kinematic motion, such as frictional forces between the end-effector and the contact surface. We additionally propose novel extensions to the Dynamic Movement Primitive (DMP) framework that encourage robust transition from free-space motion to in-contact motion in spite of environment uncertainty. We incorporate force feedback and a dynamically shifting goal to reduce forces applied to the environment and retain stable contact while enabling force control. Our methods exhibit low impact forces on contact and low steady-state tracking error.Comment: Under revie

    Improvisation of deepwater weight distributed steel catenary riser

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    Master's thesis in Offshore technology : subsea technologyNowadays, oil and gas sources are found in deeper water depths and in more hostile environments. This results in the need for more advance technologies. Riser system is a key element in providing safety. Riser failure results in spillage or pollution and could endanger lives. Hence, it is important to establish a high degree of reliability for riser design. Steel catenary risers (SCRs) have been a preferred riser solution for deep-water field developments due to its simple engineering concept, cost effective, flexibility in using different host platform and flexibility in geographical and environmental conditions. Flexible riser, on the other hand, is limited by technical and economical reasons when it comes to deep water field. Larger diameter is required in deep water to increase collapse resistance due to high hydrostatic pressure. Consequently, increase in cost and limit the option of host platform. Alternatively, Hybrid riser is a robust design for deepwater and harsh environments. It is insensitive to motion induced fatigue. However, hybrid riser is considered to be an expensive solution because it comprises a number of complex components (buoyancy can, riser bundle, flex joint, etc). A number of SCRs have been installed worldwide over the past years and more to come in the future oil and gas explorations. However, there is no SCR that has been installed in deepwater with harsh environments to date. It is mainly because SCRs in harsh environments experience a great challenge due to large motions from host platform such as semi-submersibles and FPSOs. Therefore, significant design effort is required to prove that the SCRs could safely withstand environmental loads in harsh environments and the effects of deep water. The study investigates the feasibility of 10 inch production SCR for Offshore Norway in a 1000m water depth with SCR attached to a semi-submersible vessel. Conventional SCR was analyzed and found difficulty in meeting strength design criteria at the touch down point (TDP) and at the riser hang off location. From previous industry work, the weight variation along the riser length has demonstrated a remarkable improvement to SCR response, particularly at TDP. This study concentrates on fundamental aspects related to improvement from conventional SCR to weight distributed SCR. A number of insightful sensitivity analyses were performed in order to understand the correlation between the peak response and some fundamental parameters such as displacement, velocity and acceleration. Feasibility enhancement of present weight distributed SCR concept was also studied to provide more applicable SCR configuration solution. The study addresses global design considerations including analysis of strength and fatigue. Deepwater SCR Installation scheme was also discussed. The study concludes that there is significant improvement in SCR response from conventional SCR to weight distributed SCR concept. It also proves that even though the design of SCR in harsh environments and deep water is technically challenging, innovative solutions can be developed

    The design concept of the 6-degree-of-freedom hydraulic shaker at ESTEC

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    The European Space Agency (ESA) has decided to extend its test facilities at the European Space and Technology Center (ESTEC) at Noordwijk, The Netherlands, by implementing a 6-degree-of-freedom hydraulic shaker. This shaker will permit vibration testing of large payloads in the frequency range from 0.1 Hz to 100 Hz. Conventional single axis sine and random vibration modes can be applied without the need for a configuration change of the test set-up for vertical and lateral excitations. Transients occurring during launch and/or landing of space vehicles can be accurately simulated in 6-degrees-of-freedom. The performance requirements of the shaker are outlined and the results of the various trade-offs, which are investigated during the initial phase of the design and engineering program are provided. Finally, the resulting baseline concept and the anticipated implementation plan of the new test facility are presented

    Teleoperation in the Presence of Communication Delays

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    Modern industrial processes, public service needs, and research interests have established a clear need to perform work remotely [12][4]. Teleoperators were developed with the advent of nuclear industry in the mid 1940\u27s and have been since used extensively to perform work in hazardous environments (nuclear, chemical), undersea (resource exploration, waste management, pollution monitoring), and in the outer space (sample acquisition, satellite deployment/repair). Sophisticated systems have been designed and built to meet these needs, providing the human operator with high bandwidth and high fidelity visual and kinesthetic feedback information about the task in progress [22] [32] [16] [6]

    Force Controlled Assembly of Flexible Aircraft Structure

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    The use of industrial robots in the aircraft industry has been hampered by a combination of poor accuracy of the robots and poor calibration of the workcell, and also manufacturing variability in composite parts. A way to handle these difficulties is using force control. An experimental case where a semi-compliant rib is aligned to multiple surfaces is used as an example to show this. The constraint-based task specification framework is used for the modelling and control, and the search and alignment sequence required for the assembly is modeled with a state machine. An implementation on an industrial robot system is presented and experimental data is evaluated. The described approach is easy to apply to other fields and more complicated assembly operations as well

    Momentum Control with Hierarchical Inverse Dynamics on a Torque-Controlled Humanoid

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    Hierarchical inverse dynamics based on cascades of quadratic programs have been proposed for the control of legged robots. They have important benefits but to the best of our knowledge have never been implemented on a torque controlled humanoid where model inaccuracies, sensor noise and real-time computation requirements can be problematic. Using a reformulation of existing algorithms, we propose a simplification of the problem that allows to achieve real-time control. Momentum-based control is integrated in the task hierarchy and a LQR design approach is used to compute the desired associated closed-loop behavior and improve performance. Extensive experiments on various balancing and tracking tasks show very robust performance in the face of unknown disturbances, even when the humanoid is standing on one foot. Our results demonstrate that hierarchical inverse dynamics together with momentum control can be efficiently used for feedback control under real robot conditions.Comment: 21 pages, 11 figures, 4 tables in Autonomous Robots (2015

    Tribological and mechanical properties of compliant bearings for total joint replacements.

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    The tribology of a wide range of designs of compliant layer acetabular cups has been evaluated using a simulator. The simulator applied a dynamic load of 2 kN and a sinusoidal motion of ยฑ25 , and measured the frictional resistance directly. In general the friction developed in these joints was extremely low, with friction factors typically below 0.01. When the experimental results were compared with theoretical estimates of friction a poor correlation was found. Further analysis suggested that the design of compliant layer acetabular cups was insensitive to many of the parameters suggested by theory. In particular, the radial clearance and femoral head size were not found to be critical. In addition, methods were proposed and their effectiveness demonstrated to measure friction at the on-set of motion (start-up friction), and the steady state friction in realistic compliant layer knees. The adhesion between compliant layers and a rigid backing have been investigated, with the aim of developing a good bond between them. The peel test was used to demonstrate an excellent diffusion bond between a low modulus medical grade polyurethane, and a similar high modulus grade of polyurethane. The processing conditions used to manufacture the test piece were optimised to maximise the bond strength. The bond was found to be stable after immersion in Ringers solution at 37 C for 52 weeks, and after acetabular cups were subjected to 14 million 4 kN loading cycles. A six station knee wear simulator was designed and commissioned. The simulator applied a dynamic load and an anterior-posterior translation individually to each station, as well as a flexion-extension motion common to all six stations. The simulator was computer controlled entirely using servo hydraulics. Wear rates were obtained from tests lasting up to 8 million cycles conducted on UHMWPE joints
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