- Email: [email protected]
Novel Integrated Robotic System for Tiny Duct Inspection
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Procedia Manufacturing 17 (2018) 342–349 Procedia Manufacturing 00 (2017) 000–000 www.elsevier.com/locate/procedia
28th International Conference on Flexible Automation and Intelligent Manufacturing 28th International ConferenceJune on Flexible Automation and OH, Intelligent (FAIM2018), 11-14, 2018, Columbus, USA Manufacturing (FAIM2018), June 11-14, 2018, Columbus, OH, USA
Novel Integrated Robotic System for Tiny Duct Inspection
Novel Integrated Robotic System for Tiny Duct Inspection Manufacturing Engineering Society International Conference 2017, MESIC 2017, 28-30 June a a a 2017, Vigo (Pontevedra), Spain Paolo Guardiani , Carlo Canali , Alessandro Pistone , Sergio Leggieria, Claudio
a a a, Carlo Canaliaa, Alessandro Pistonea, Sergio a PaoloGloriani Guardiani Leggieri , Claudio , Nahian Rahman , Ferdinando Cannellaa, Darwin Caldwell a a a a Rahman ,optimization Ferdinando Cannella , Darwin Caldwell CostingGloriani models, Nahian for capacity in Industry 4.0: Trade-off Italian Istitute of Technology (IIT) Genoa, Italy Italian Istitute of Technology (IIT) Genoa, Italy
a
between used capacity and operational efficiency a
A. Santanaa, P. Afonsoa,*, A. Zaninb, R. Wernkeb
Abstract a University of Minho, 4800-058 Guimarães, Portugal Abstract b Unochapecó, 89809-000 Chapecó, SC,toBrazil Every production process, in general, requires a thorough inspection in order meet user specific standard. For example, in the avionicproduction sector, visual inspection and quality control procedures are extremely since the critical partsFor suchexample, as oil ducts of Every process, in general, requires a thorough inspection in orderimportant, to meet user specific standard. in the the gearbox andvisual engine components are often contaminated. Currently, the inspection are carried avionic sector, inspection and quality control procedures are extremely important,procedures since the critical partsout suchbyasworkers oil ductsand of exploiting level of instruments as endoscope or fiberscope. As human operation deficiency the gearboxsome and primary engine components are often such contaminated. Currently, the inspection procedures arecauses carriederrors, out bythe workers and Abstract in the inspection cannot be nullified completely. the goaloroffiberscope. this study As is to designoperation a novel causes automated robotic probe for exploiting some primary level of instruments suchHence, as endoscope human errors, the deficiency reducing the critical levelbeofnullified these visual inspections. Thethe proposed system is suited for checking andprobe cavities, in the inspection cannot completely. Hence, goal of inspection this study is to design a novel automatedducts robotic for Under the concept of "Industry 4.0", production processes will be developed pushed betested increasingly interconnected, with some channels 6 mm in diameter. TheThe robotic probeinspection has been and in a real industrial reducing the critical thinner level ofthan these visual inspections. proposed system istosuited for checking ducts andscenario; cavities, information based onhas a real basis and,thenecessarily, much efficient. In this context, optimization a realsome aircraft gearbox been inspected with proposed probe andmore it successfully identified unwanted residuals suchscenario; as sand, with channels thinner thantime 6 mm in diameter. The robotic probe has been developed and tested in acapacity real industrial goes the traditional aim capacity maximization, contributing also foridentified organization’s profitability and value. swarf, metallic dust andofobstructions. This paperprobe describes the inspection system is developed using a as flexible amachining realbeyond aircraft gearbox has been inspected with the proposed and ithow successfully unwanted residuals such sand, probe andlean its capability to perform and reproducible of complex ducts, bends andisdifferent pathways. Indeed, management continuous improvement approaches capacity optimization instead of machining swarf, metallic dustand andstandard obstructions. This paper inspection describes how the suggest inspection system developed using a flexible probe and its capability to perform standard and reproducible of complex bends and different pathways. maximization. The study of capacity optimization and inspection costing models is anducts, important research topic that deserves © 2018 The Authors. Published by Elsevier contributions from both the practical andB.V. theoretical perspectives. This paper presents and discusses a mathematical © 2018 2018 The Authors. Published by B.V. This is an open accessmanagement article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) © The Authors. Published by Elsevier Elsevier B.V. model for capacity based on differentlicense costing models (ABC and TDABC). A generic model has been This is an open access article under the CC BY-NC-ND (http://creativecommons.org/licenses/by-nc-nd/3.0/) Peer-review under responsibility of the scientific committee of the 28th Flexible Automation Intelligent Manufacturing This is an open access article under CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) developed it was used to analyze capacity and to design towards theand maximization of organization’s Peer-reviewand under responsibility of theidle scientific committee of the strategies 28th Flexible Automation and Intelligent Manufacturing (FAIM2018) Conference. Peer-review under responsibility of the scientific committee of the 28th Flexible Automation and Intelligent Manufacturing (FAIM2018) Conference. value. The trade-off capacity maximization vs operational efficiency is highlighted and it is shown that capacity (FAIM2018) Conference.
optimization might hide operational inefficiency. Keywords: Industry 4.0, Inspection, Quality, Gearbox, Endoscope
© 2017 The Authors. Published by Elsevier B.V. Keywords: Industry 4.0, Inspection, Quality, Gearbox, Endoscope Peer-review under responsibility of the scientific committee of the Manufacturing Engineering Society International Conference 2017.
1. Introduction 1. Introduction Keywords: Cost Models; ABC; TDABC; Capacity Management; Idle Capacity; Operational Efficiency Aircraft manufacturers, such as Airbus and Boeing, are facing increasing demands for production of commercial Aircraft as Airbus and Boeing, facing of commercial airplanes asmanufacturers, shown by largesuch backlogs of orders. Hence, aare large effortincreasing is ongoingdemands with the for goalproduction of increasing automation airplanes as shownand by large backlogs orders. Hence, a large effort is ongoing with the goal of increasing automation on1.manufacturing assembly linesof [1]. Introduction on manufacturing and assembly lines [1]. 2351-9789 © 2018 Thecapacity Authors. Published by Elsevier information B.V. The cost of idle is a fundamental for companies and their management of extreme importance This is an open access under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) 2351-9789 © 2018 Thearticle Authors. Published by Elsevier B.V. in modern production systems. In general, it is defined as unused capacity or production potential and can be measured Peer-review under responsibility of the scientific committee of the 28th Flexible Automation and Intelligent Manufacturing (FAIM2018) This is an open access article under CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) in several ways: tons of production, available hours of manufacturing, management of (FAIM2018) the idle capacity Conference. under responsibility of the scientific committee of the 28th Flexible Automationetc. Peer-review and The Intelligent Manufacturing * Paulo Afonso. Tel.: +351 253 510 761; fax: +351 253 604 741 Conference. E-mail address: [email protected]
2351-9789 Published by Elsevier B.V. B.V. 2351-9789 ©©2017 2018The TheAuthors. Authors. Published by Elsevier Peer-review underaccess responsibility of the scientific committee oflicense the Manufacturing Engineering Society International Conference 2017. This is an open article under the CC BY-NC-ND (http://creativecommons.org/licenses/by-nc-nd/3.0/) Peer-review under responsibility of the scientific committee of the 28th Flexible Automation and Intelligent Manufacturing (FAIM2018) Conference. 10.1016/j.promfg.2018.10.055
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The possibility of introducing robots and automation into the assembly lines of airplanes is more convenient than an approach based on human workers in order to meet the needs of the market. Aerospace manufacturers are nevertheless bursting at the seams with a backlog of orders. To address that dilemma, they need to automate their factories. The industry is investing heavily in flexible systems that reduce cost, improve quality and boost productivity. In this work, we present a robotic system to be used in the inspection of the oil ducts of gearbox housing. Even if remarkable visual inspection systems have been recently developed, there are inspection tasks that are still far reaching given the complexity of the manufacturing piece and the requested performance. Here we present one of such cases, the inspection of small ducts using endoscopic sensors, a crucial task for specific industrial sectors such as the avionic industry where the quality of the final product must meet very high standards. In particular, we focus on inspection of engine housing produced by avionic industries, which present critical difficulties. Visual inspection is a standard tool for performing quality control, data acquisition, and data analysis. In the manufacturing process, it is a key step in order to guarantee the goodness of the final products before releasing it to the market or to the final customer. Automated optical inspection systems are commonly used, for example, in PCB manufacturing [2] since the use of this technology has been proven to be highly effective in improving the quality standards of such relatively simple process. In other fields, e.g. aerospace components, visual inspection is of the utmost importance since the parts must meet very strict safety standards, therefore an automated system only makes sense if it is able to outperform experienced humans. The construction of many components and parts such as engines, gearboxes and pumps is performed through the die metal casting. This process is essentially characterized by high-pressure injection of molten metal into a mold cavity. The mold cavity is created using hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process. Most die castings are made from non-ferrous metals, specifically zinc, copper, aluminum, magnesium, lead, pewter and tin-based alloys. Depending on the type of metal being cast, a hot or cold chamber machine is used.
Fig. 1 Overview of the whole system
Once an engine block with aluminum and magnesium die castings is obtained it undergoes a series of machining process in order to flatter flanges, create threaded holes and shape the fine details of the object [3]. A critical phase is the inspection of the ducts of lubrication oil, since they must be assured not to contain any type of imperfection. The most common abnormalities that can be found at this point are:
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section reductions; sand residues; metal shavings.
The unwanted particles (metal chips or molding sand as well) often end up settling in areas that are difficult to access by an operator. Because of their size, placement and shape oil ducts are not easily reachable, and the use of an endoscope is the only way for inspecting their interiors. The endoscopes are relatively fragile devices and continuous use takes its toll, often leading to breakdowns and consequent loss of time and need for replacement. Moreover, the inspection procedure is uncomfortable for the human worker because simultaneous tasks of driving the probe and checking the images are required. The stress caused by the number of contemporary activities often leads the operator to skip unintentionally parts of the ducts or failure in noticing the presence of swarf, sand residuals or small defects. This study proposes an approach that tackles these inconveniences by means of a robotic system studied and designed to effectively inspect oil ducts and cavities inside gearbox hulls. The robotic inspection system consists of an arm and a flexible snake-like end effector used as a probe. The probe, equipped with a micro camera, is able to navigate small ducts, and move effortlessly along forks, turns and right angles, even if the path is wrinkled. Once positioned on the duct access point by the arm, the probe is slid inside to perform the inspection procedure. The system can be teleoperated or it can move autonomously during supervised operations. This article focuses on the description of the robotic system and its performance. The system is meant to achieve the following tasks, as described in a related work [4]:
insert an endoscope in the ducts using a robotic arm; create a control system to guide the probe in the duct; recognize anomalies and defects using the probe camera; visually localize the anomalies inside the inspected ducts.
In the following, a discussion about the related works is presented in Section 2. In Section 3 a complete description of the robotic system is given, results, future works and conclusion are then presented in Section 4, 5 and 6. 2. Related work The small diameter of the pathways and the challenging constraints mentioned above restrict the number of approaches that can be used or adapted for this task. Therefore, the search for suitable tools went way beyond standard industrial equipment into medical and surgical tools, given the analogies of the requirements (navigate tight space with precision). A study of the literature looking for suitable mechanisms or micro-robots [5] was performed, and it eventually pointed out a few feasible options to be implemented in the prototype system carried on and few options have been considered to be implemented into the prototype system: flexible robots [6], snake robots [7]. Few categories of suitable devices have been identified and are here briefly discussed. Flexible robots are designed around non-rigid components and actuators are often used in medical and surgical applications [8]. Snake robots are a different type of robots generally employed for conduit and pipe inspection [9]. Such systems are also typically used for microsurgery [10]. Snake-arm robots are devices with hyper-redundant actuation [11] and the high number of degrees of freedom allows the arm to move along a particular path or around an obstacle. This feature is particularly useful for the grasping of objects [12]. Generally, the purpose of these kinds of robots is to operate in spaces that are hard to reach and navigate, require precise movement or imply safety concerns for human workers [7]. In addition to the works mentioned above, many other devices have been developed [13] but they are not suitable for our application mainly for the dimensional constraints, since all these devices are too wide or not sufficiently dexterous.
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3. Design The system, as shown in Fig. 1, consists of three main components: an industrial robot arm, a probe feeder and a flexible robotic probe. An industrial anthropomorphic Abb IRB 1600 [14] drives the probe inside the oil ducts. The probe itself is a snake-like robot and its head is fully synchronized with the axial motion. The robot arm carries the whole mechanism and moves the snake on the entrance of the oil duct to be inspected. The end effector is equipped with a light source, a micro camera and an active steerable head: thanks to its flexible body and the steerable head the probe is able to move inside ducts that can be as narrow as 6mm in diameter, even in presence of multiple curves and bend, as well as forks and t-junctions. Once the end effector is positioned on the oil duct entrance the probe with its camera is pushed inside the oil duct by the feeder. The flexible head of the probe consists of a series of joints driven by three tendons cables. The actuation of the cables allows the head to point in various directions and navigate inside the ducts while pushed by the feeder. Once the inspection is completed, the feeder pulls the probe outside from the duct and the sequence is repeated on another channel of the part. 3.1. Probe Feeder The details about the feeder system shown in Fig. 2. (a) Probe feeder; (b) Probe are given. The feeder is built around a couple of wheels acting on the probe body. The rotation of the wheels pushes or pulls the probe inserting or retracting it from the ducts. The use of stepper motors allows for a fine positioning of the probe with a precision of about 1 mm: another couple of wheels is in contact with the probe and is connected to an encoder that allows a closed loop control of the positioning of the probe.
Active Passive Fig. 2. (a) Probe feeder; (b) Probe
The axial advancement of the probe is actuated through the mechanism indicated in Fig. 2. (a) Probe feeder; (b) Probe. It is possible to observe how the stepper motor indicated with 1 drives the worm 2, which moves the gear 3. The gear 3 is fixed to the roller 4 and the wheel 5 through the c shaft. The coupling between 5 and 6 has transmission ratio of 1:1. Moving the wheel 6 causes the rotation of the roller 7. Subsequently, the two rollers 4,7 counter-rotate with the same speed module, in order to transfer by means of pure friction the tangential velocity to the robotic probe. The components marked as 8 are two passive rollers spun by the probe during its axial movement. Encoder 9 serves the purpose of assessing the movement of the probe by measuring the rotation of the passive rollers. In fact, the normal operating condition is when the tangential speed of the active rollers 4 and 7 coincides with the tangential speed of the passive rollers 8. 3.2. Probe The probe features an active head and a passive flexible body (Fig. 2. (a) Probe feeder; (b) Probe), both with an outer diameter of 5 mm. The body of the snake robot is built out of a steel compression spring. It is flexible so it can passively follow the path of the oil ducts. The length of the flexible body is 1 m and it is terminated by an active system that can orientate the tip of the snake robot in the 3D space.
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The head structure is composed of a series of 6 washers with an external diameter of 5 mm and a length of 2 mm spaced from each other of the same length and fixed to a coil spring. In each washer, there are three holes arranged along the circumference of the washer 120 degrees apart from each other. Wires run along the flexible body of the probe, pass through such holes and are then fixed to the last washer. The control of the bending of the head is obtained by pulling a combination of these wires. As an example Fig. 3 shows the bending of the head along a plane obtained by pulling a single wire. A bending radius of 15 mm is obtained with this setup. Pulling multiple wires in accordance with various combinations allow the head to bend in different directions in the space. This degree of dexterity has been chosen as the most suitable for our needs. The tendon cables are pulled or released through the use of servo motors at the end of the probe (Fig. 1).To avoid undesirable effect due to the elasticity of the tendons, Kevlar fiber wire with a diameter of 0.25 mm has been used. Kevlar fiber was chosen since it features a unique combination of high strength and high Young’s modulus. A brief explanation two-dimensional kinematic model has been inserted below. The head of the probe has been discretized as six elements numbered starting from 0 to 5. The zero element is fixed with the ground. Every element is composed by two part: rigid part (in orange) and flexible part (in black). As shown in Fig. 3 the length of the coil spring has been approximated by the length of the cable for each element. Going further to the model description an incremental model has been formulated taking into account that the angular displacement of 2-D washers is small. Few assumptions for describing the deformation have been made:
as consequences of pulling wires, planar surfaces of the i-flexible part pure rotate around x-axis located in their own center indicated with 𝑂𝑂𝑎𝑎𝑖𝑖 and 𝑂𝑂𝑏𝑏𝑖𝑖 . This assumption is made considering the axial stiffness of the core spring higher than its flexible stiffness; the length of the wire 𝑙𝑙0 − ∆𝑙𝑙𝑖𝑖 and 𝑙𝑙0 + ∆𝑙𝑙𝑖𝑖 in a single i-element is approximated as the length of the core spring in the respective side. As described in Fig. 3, the rotation 𝛼𝛼𝑎𝑎𝑖𝑖 𝑎𝑎𝑎𝑎𝑎𝑎 𝛼𝛼𝑏𝑏𝑖𝑖 of the washer i can be described as:
arccos z
ai arccos z ai z bi-1 bi
bi
z ai
(1)
Fig. 3 Kinematics model of the head
The orientation of the i-element can be defined referred to the previous element as:
i a b arccos z b z b i
i
i
i-1
(2)
Considering s the length of the single rigid part and l the length of the flexible part of the element, it is possible to describe the position of the i-element referred to the OZY coordinate system as:
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i i l cos k 1 ak s cos k 1 zi k 1 k 1 i yi o i l sin k 1 ak s sin k 1 k 1 k 1 o
347
(3)
Due to the assumptions made before and referring to the Fig. 3 the dependences between 𝛼𝛼𝑎𝑎𝑖𝑖 , 𝛼𝛼𝑏𝑏𝑖𝑖 𝑎𝑎𝑎𝑎𝑎𝑎 ∆𝐿𝐿 have been described as: 2L 2L nD nD
arctan a b i
i
(4)
∆𝐿𝐿 is the total negative elongation of the wire, n is the number of elements of the head and D is the diameter where the wires are located. Inserting Eq. (4) inside Eq. (3) and considering i=5 the end effector coordinates have been defined as: 5 5 L L l cos 2k 1 nD s cos 2k nD k 1 k 1 ze 5 5 L L ye l sin 2k 1 s sin 2k nD nD k 1 k 1 e o 5 k k 1 o
(5)
3.3. Vision sensor The tip of the probe is equipped with a light source embedded into the 2.4mm diameter Olympus Iplex TX ultra-thin analog camera [15]. The sensor has a resolution of H768xV576 pixels, with a viewing angle of 80°. The video is acquired and displayed on an external monitor connecting the sensor with an RCA composite video cable that runs inside the probe body. 4. Results 4.1. Operating Scenario Two operational modes are implemented: manual guidance and supervised operation. When operated in manual guidance mode a human operator can remotely drive the probe along the gearbox with the use of a joypad. The system keeps track of the positions reached by the probe, so to have a certifiable log of the performed inspections operations. In supervised mode, the whole procedure is driven by the system and the probe is moved along the ducts through a set of predefined checkpoints. The operator is responsible for checking the status of the duct from the previous checkpoint to the actual checkpoint, before moving to the next sector of the duct. Without any confirmation of the operator, the system does not have the possibility to move on. 4.2. Calibration and Test As a first step, a mockup of an oil duct has been assembled with the use of flexible transparent pipes, as shown in Fig. 4. This setup has been used to test the capability of the system to reach a desired position, the functionality of the probe moving along forks and verifying its bending radius.
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Fig. 4 The probe during a test with a mock-up of an oil duct
After a set of test, it has been verified that the system can reach the performance indicated in Table 1. Table 1. List of the typical performance of the system Features Inspectional duct length
90 mm
Minimum duct diameter
6 mm
Minimum duct bending radius
15 mm
Positioning reproducibility
2 mm
To demonstrate the applicability of the device in a real scenario the inspection of ducts has been performed on different models of gearbox housing and a series of duct have been inspected. As an example Table 2 present the list of ducts inspected during a standard inspection cycle on a gearbox housing all the ducts have an inner diameter of 6 mm. Table 2. List of inspected duct on a single gearbox Duct
Length [mm]
Bifurcation
1
60
0
2
80
0
3
500
1
4
650
1
5
150
0
Fig. 5 Different situations can be encountered inside oil ducts: a) d) clean duct b) swarf, c) e) presence of obstructions
Considering a duct, 600 mm long with a single bifurcation, the probe can reach the end of the duct and being retracted. Different situations can be found during the inspection. Fig. 5 shows the most common scenario of clean ducts and obstructed channels. 5. Future Works The ultimate development of this system consists of integrating a subsystem to remove dust and swarf by using up
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space still available on the probe center, implementing a working channel where clamps, cutters or other tools can be placed. Following developments are ongoing and will be described in future works. 6. Conclusion In this paper, a novel robotic system for oil duct inspections has been developed. As a response in increasing demand of automation in avionic sector, the device is suitable to perform the inspection of oil ducts in gearbox housing, engine, components with significant savings in time and in the quality output. Manual guidance and supervised operation can be selected, representing both significant improvements in the inspection procedure currently performed by hand. The system has been tested in a real scenario and the results of the inspection have been presented. References [1] P. Hollienger, "Boeing and Airbus face mammoth task to clear order backlog," Financial Times, 2015. [2] P. M. Vitoriano, T. G. Amaral and O. Pàscoa Dias, "Automatic Optical Inspection for Surface Mounting Devices with IPC-A-610D compliance," in 2011 International Conference on Power Engineering, Energy and Electrical Drives, 2011. [3] T. Trung Do and P. Son Minh, "Pulsed cooling control for improving part warpage in injection molding process," in 2017 International Conference on System Science and Engineering (ICSSE), 2017. [4] S. M. e. al., "Deep Endoscope: Intelligent Duct Inspection for the Avionic Industry," IEEE Transactions on Industrial Informatics, vol. PP, no. 99, pp. 1-1. [5] B. J. Nelson, I. K. Kaliakatsos and J. J. Abbott, Microrobots for Minimally Invasive Medicine, vol. Annual Review of Biomedical Engineering, 2010. [6] D.-G. Choi, B.-J. Yi and W.-K. Kim, "Design of a spring backbone micro endoscope," in IEEE/RSJ International Conference on Intelligent Robots and Systems, 2007. [7] N. Simaan, "Snake-Like Units Using Flexible Backbones and Actuation Redundancy for Enhanced Miniaturization," in Proceedings of the 2005 IEEE International Conference on Robotics and Automation, 2005. [8] J. Ortiz, L. S. Mattos and D. G. Caldwell, "Smart Devices in Robot-Assisted Laser Microsurgery: Towards Ubiquitous Tele-Cooperation," in 2012 IEEE International Conference on Robotics and Biomimetics, ROBIO, 2012. [9] T. Kishi, M. Ikeuchi and T. Nakamura, "Development of a peristaltic crawling inspection robot for 1-inch gas pipes with continuous elbows," in 2013 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2013. [10] R. E. Goldman, A. Bajo and N. Simaan, "Compliant Motion Control for Multisegment Continuum Robots With Actuation Force Sensing," IEEE Transactions on Robotics, vol. 30, no. 4, pp. 890-902, 2014. [11] "Snake-arm Robots.," [Online]. Available: http://www.ocrobotics.com/technology-/snakearm-robots/. [12] R. S. Penning and M. R. Zinn, "A combined modal-joint space control approach for continuum manipulators," Advanced Robotics, vol. 28, no. 16, pp. 1091-1108, 2014. [13] N. Simaan, R. Taylor and P. Flint, "High Dexterity Snake-Like Robotic Slaves for Minimally Invasive Telesurgery of the Upper Airway," in Medical Image Computing and Computer-Assisted Intervention -MICCAI 2004: 7th International Conference, Saint-Malo, France, 2004. [14] ABB, "ABB," [Online]. Available: http://new.abb.com/products/robotics/industrial-robots/irb-1600. [Accessed 18 01 2018]. [15] Olympus Solutions Americas Corp, [Online]. Available: https://www.olympus-ims.com/en/rvi-products/iplextx/. [Accessed 18 01 2018].
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Procedia Manufacturing 17 (2018) 342–349 Procedia Manufacturing 00 (2017) 000–000 www.elsevier.com/locate/procedia
28th International Conference on Flexible Automation and Intelligent Manufacturing 28th International ConferenceJune on Flexible Automation and OH, Intelligent (FAIM2018), 11-14, 2018, Columbus, USA Manufacturing (FAIM2018), June 11-14, 2018, Columbus, OH, USA
Novel Integrated Robotic System for Tiny Duct Inspection
Novel Integrated Robotic System for Tiny Duct Inspection Manufacturing Engineering Society International Conference 2017, MESIC 2017, 28-30 June a a a 2017, Vigo (Pontevedra), Spain Paolo Guardiani , Carlo Canali , Alessandro Pistone , Sergio Leggieria, Claudio
a a a, Carlo Canaliaa, Alessandro Pistonea, Sergio a PaoloGloriani Guardiani Leggieri , Claudio , Nahian Rahman , Ferdinando Cannellaa, Darwin Caldwell a a a a Rahman ,optimization Ferdinando Cannella , Darwin Caldwell CostingGloriani models, Nahian for capacity in Industry 4.0: Trade-off Italian Istitute of Technology (IIT) Genoa, Italy Italian Istitute of Technology (IIT) Genoa, Italy
a
between used capacity and operational efficiency a
A. Santanaa, P. Afonsoa,*, A. Zaninb, R. Wernkeb
Abstract a University of Minho, 4800-058 Guimarães, Portugal Abstract b Unochapecó, 89809-000 Chapecó, SC,toBrazil Every production process, in general, requires a thorough inspection in order meet user specific standard. For example, in the avionicproduction sector, visual inspection and quality control procedures are extremely since the critical partsFor suchexample, as oil ducts of Every process, in general, requires a thorough inspection in orderimportant, to meet user specific standard. in the the gearbox andvisual engine components are often contaminated. Currently, the inspection are carried avionic sector, inspection and quality control procedures are extremely important,procedures since the critical partsout suchbyasworkers oil ductsand of exploiting level of instruments as endoscope or fiberscope. As human operation deficiency the gearboxsome and primary engine components are often such contaminated. Currently, the inspection procedures arecauses carriederrors, out bythe workers and Abstract in the inspection cannot be nullified completely. the goaloroffiberscope. this study As is to designoperation a novel causes automated robotic probe for exploiting some primary level of instruments suchHence, as endoscope human errors, the deficiency reducing the critical levelbeofnullified these visual inspections. Thethe proposed system is suited for checking andprobe cavities, in the inspection cannot completely. Hence, goal of inspection this study is to design a novel automatedducts robotic for Under the concept of "Industry 4.0", production processes will be developed pushed betested increasingly interconnected, with some channels 6 mm in diameter. TheThe robotic probeinspection has been and in a real industrial reducing the critical thinner level ofthan these visual inspections. proposed system istosuited for checking ducts andscenario; cavities, information based onhas a real basis and,thenecessarily, much efficient. In this context, optimization a realsome aircraft gearbox been inspected with proposed probe andmore it successfully identified unwanted residuals suchscenario; as sand, with channels thinner thantime 6 mm in diameter. The robotic probe has been developed and tested in acapacity real industrial goes the traditional aim capacity maximization, contributing also foridentified organization’s profitability and value. swarf, metallic dust andofobstructions. This paperprobe describes the inspection system is developed using a as flexible amachining realbeyond aircraft gearbox has been inspected with the proposed and ithow successfully unwanted residuals such sand, probe andlean its capability to perform and reproducible of complex ducts, bends andisdifferent pathways. Indeed, management continuous improvement approaches capacity optimization instead of machining swarf, metallic dustand andstandard obstructions. This paper inspection describes how the suggest inspection system developed using a flexible probe and its capability to perform standard and reproducible of complex bends and different pathways. maximization. The study of capacity optimization and inspection costing models is anducts, important research topic that deserves © 2018 The Authors. Published by Elsevier contributions from both the practical andB.V. theoretical perspectives. This paper presents and discusses a mathematical © 2018 2018 The Authors. Published by B.V. This is an open accessmanagement article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) © The Authors. Published by Elsevier Elsevier B.V. model for capacity based on differentlicense costing models (ABC and TDABC). A generic model has been This is an open access article under the CC BY-NC-ND (http://creativecommons.org/licenses/by-nc-nd/3.0/) Peer-review under responsibility of the scientific committee of the 28th Flexible Automation Intelligent Manufacturing This is an open access article under CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) developed it was used to analyze capacity and to design towards theand maximization of organization’s Peer-reviewand under responsibility of theidle scientific committee of the strategies 28th Flexible Automation and Intelligent Manufacturing (FAIM2018) Conference. Peer-review under responsibility of the scientific committee of the 28th Flexible Automation and Intelligent Manufacturing (FAIM2018) Conference. value. The trade-off capacity maximization vs operational efficiency is highlighted and it is shown that capacity (FAIM2018) Conference.
optimization might hide operational inefficiency. Keywords: Industry 4.0, Inspection, Quality, Gearbox, Endoscope
© 2017 The Authors. Published by Elsevier B.V. Keywords: Industry 4.0, Inspection, Quality, Gearbox, Endoscope Peer-review under responsibility of the scientific committee of the Manufacturing Engineering Society International Conference 2017.
1. Introduction 1. Introduction Keywords: Cost Models; ABC; TDABC; Capacity Management; Idle Capacity; Operational Efficiency Aircraft manufacturers, such as Airbus and Boeing, are facing increasing demands for production of commercial Aircraft as Airbus and Boeing, facing of commercial airplanes asmanufacturers, shown by largesuch backlogs of orders. Hence, aare large effortincreasing is ongoingdemands with the for goalproduction of increasing automation airplanes as shownand by large backlogs orders. Hence, a large effort is ongoing with the goal of increasing automation on1.manufacturing assembly linesof [1]. Introduction on manufacturing and assembly lines [1]. 2351-9789 © 2018 Thecapacity Authors. Published by Elsevier information B.V. The cost of idle is a fundamental for companies and their management of extreme importance This is an open access under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) 2351-9789 © 2018 Thearticle Authors. Published by Elsevier B.V. in modern production systems. In general, it is defined as unused capacity or production potential and can be measured Peer-review under responsibility of the scientific committee of the 28th Flexible Automation and Intelligent Manufacturing (FAIM2018) This is an open access article under CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) in several ways: tons of production, available hours of manufacturing, management of (FAIM2018) the idle capacity Conference. under responsibility of the scientific committee of the 28th Flexible Automationetc. Peer-review and The Intelligent Manufacturing * Paulo Afonso. Tel.: +351 253 510 761; fax: +351 253 604 741 Conference. E-mail address: [email protected]
2351-9789 Published by Elsevier B.V. B.V. 2351-9789 ©©2017 2018The TheAuthors. Authors. Published by Elsevier Peer-review underaccess responsibility of the scientific committee oflicense the Manufacturing Engineering Society International Conference 2017. This is an open article under the CC BY-NC-ND (http://creativecommons.org/licenses/by-nc-nd/3.0/) Peer-review under responsibility of the scientific committee of the 28th Flexible Automation and Intelligent Manufacturing (FAIM2018) Conference. 10.1016/j.promfg.2018.10.055
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The possibility of introducing robots and automation into the assembly lines of airplanes is more convenient than an approach based on human workers in order to meet the needs of the market. Aerospace manufacturers are nevertheless bursting at the seams with a backlog of orders. To address that dilemma, they need to automate their factories. The industry is investing heavily in flexible systems that reduce cost, improve quality and boost productivity. In this work, we present a robotic system to be used in the inspection of the oil ducts of gearbox housing. Even if remarkable visual inspection systems have been recently developed, there are inspection tasks that are still far reaching given the complexity of the manufacturing piece and the requested performance. Here we present one of such cases, the inspection of small ducts using endoscopic sensors, a crucial task for specific industrial sectors such as the avionic industry where the quality of the final product must meet very high standards. In particular, we focus on inspection of engine housing produced by avionic industries, which present critical difficulties. Visual inspection is a standard tool for performing quality control, data acquisition, and data analysis. In the manufacturing process, it is a key step in order to guarantee the goodness of the final products before releasing it to the market or to the final customer. Automated optical inspection systems are commonly used, for example, in PCB manufacturing [2] since the use of this technology has been proven to be highly effective in improving the quality standards of such relatively simple process. In other fields, e.g. aerospace components, visual inspection is of the utmost importance since the parts must meet very strict safety standards, therefore an automated system only makes sense if it is able to outperform experienced humans. The construction of many components and parts such as engines, gearboxes and pumps is performed through the die metal casting. This process is essentially characterized by high-pressure injection of molten metal into a mold cavity. The mold cavity is created using hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process. Most die castings are made from non-ferrous metals, specifically zinc, copper, aluminum, magnesium, lead, pewter and tin-based alloys. Depending on the type of metal being cast, a hot or cold chamber machine is used.
Fig. 1 Overview of the whole system
Once an engine block with aluminum and magnesium die castings is obtained it undergoes a series of machining process in order to flatter flanges, create threaded holes and shape the fine details of the object [3]. A critical phase is the inspection of the ducts of lubrication oil, since they must be assured not to contain any type of imperfection. The most common abnormalities that can be found at this point are:
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section reductions; sand residues; metal shavings.
The unwanted particles (metal chips or molding sand as well) often end up settling in areas that are difficult to access by an operator. Because of their size, placement and shape oil ducts are not easily reachable, and the use of an endoscope is the only way for inspecting their interiors. The endoscopes are relatively fragile devices and continuous use takes its toll, often leading to breakdowns and consequent loss of time and need for replacement. Moreover, the inspection procedure is uncomfortable for the human worker because simultaneous tasks of driving the probe and checking the images are required. The stress caused by the number of contemporary activities often leads the operator to skip unintentionally parts of the ducts or failure in noticing the presence of swarf, sand residuals or small defects. This study proposes an approach that tackles these inconveniences by means of a robotic system studied and designed to effectively inspect oil ducts and cavities inside gearbox hulls. The robotic inspection system consists of an arm and a flexible snake-like end effector used as a probe. The probe, equipped with a micro camera, is able to navigate small ducts, and move effortlessly along forks, turns and right angles, even if the path is wrinkled. Once positioned on the duct access point by the arm, the probe is slid inside to perform the inspection procedure. The system can be teleoperated or it can move autonomously during supervised operations. This article focuses on the description of the robotic system and its performance. The system is meant to achieve the following tasks, as described in a related work [4]:
insert an endoscope in the ducts using a robotic arm; create a control system to guide the probe in the duct; recognize anomalies and defects using the probe camera; visually localize the anomalies inside the inspected ducts.
In the following, a discussion about the related works is presented in Section 2. In Section 3 a complete description of the robotic system is given, results, future works and conclusion are then presented in Section 4, 5 and 6. 2. Related work The small diameter of the pathways and the challenging constraints mentioned above restrict the number of approaches that can be used or adapted for this task. Therefore, the search for suitable tools went way beyond standard industrial equipment into medical and surgical tools, given the analogies of the requirements (navigate tight space with precision). A study of the literature looking for suitable mechanisms or micro-robots [5] was performed, and it eventually pointed out a few feasible options to be implemented in the prototype system carried on and few options have been considered to be implemented into the prototype system: flexible robots [6], snake robots [7]. Few categories of suitable devices have been identified and are here briefly discussed. Flexible robots are designed around non-rigid components and actuators are often used in medical and surgical applications [8]. Snake robots are a different type of robots generally employed for conduit and pipe inspection [9]. Such systems are also typically used for microsurgery [10]. Snake-arm robots are devices with hyper-redundant actuation [11] and the high number of degrees of freedom allows the arm to move along a particular path or around an obstacle. This feature is particularly useful for the grasping of objects [12]. Generally, the purpose of these kinds of robots is to operate in spaces that are hard to reach and navigate, require precise movement or imply safety concerns for human workers [7]. In addition to the works mentioned above, many other devices have been developed [13] but they are not suitable for our application mainly for the dimensional constraints, since all these devices are too wide or not sufficiently dexterous.
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3. Design The system, as shown in Fig. 1, consists of three main components: an industrial robot arm, a probe feeder and a flexible robotic probe. An industrial anthropomorphic Abb IRB 1600 [14] drives the probe inside the oil ducts. The probe itself is a snake-like robot and its head is fully synchronized with the axial motion. The robot arm carries the whole mechanism and moves the snake on the entrance of the oil duct to be inspected. The end effector is equipped with a light source, a micro camera and an active steerable head: thanks to its flexible body and the steerable head the probe is able to move inside ducts that can be as narrow as 6mm in diameter, even in presence of multiple curves and bend, as well as forks and t-junctions. Once the end effector is positioned on the oil duct entrance the probe with its camera is pushed inside the oil duct by the feeder. The flexible head of the probe consists of a series of joints driven by three tendons cables. The actuation of the cables allows the head to point in various directions and navigate inside the ducts while pushed by the feeder. Once the inspection is completed, the feeder pulls the probe outside from the duct and the sequence is repeated on another channel of the part. 3.1. Probe Feeder The details about the feeder system shown in Fig. 2. (a) Probe feeder; (b) Probe are given. The feeder is built around a couple of wheels acting on the probe body. The rotation of the wheels pushes or pulls the probe inserting or retracting it from the ducts. The use of stepper motors allows for a fine positioning of the probe with a precision of about 1 mm: another couple of wheels is in contact with the probe and is connected to an encoder that allows a closed loop control of the positioning of the probe.
Active Passive Fig. 2. (a) Probe feeder; (b) Probe
The axial advancement of the probe is actuated through the mechanism indicated in Fig. 2. (a) Probe feeder; (b) Probe. It is possible to observe how the stepper motor indicated with 1 drives the worm 2, which moves the gear 3. The gear 3 is fixed to the roller 4 and the wheel 5 through the c shaft. The coupling between 5 and 6 has transmission ratio of 1:1. Moving the wheel 6 causes the rotation of the roller 7. Subsequently, the two rollers 4,7 counter-rotate with the same speed module, in order to transfer by means of pure friction the tangential velocity to the robotic probe. The components marked as 8 are two passive rollers spun by the probe during its axial movement. Encoder 9 serves the purpose of assessing the movement of the probe by measuring the rotation of the passive rollers. In fact, the normal operating condition is when the tangential speed of the active rollers 4 and 7 coincides with the tangential speed of the passive rollers 8. 3.2. Probe The probe features an active head and a passive flexible body (Fig. 2. (a) Probe feeder; (b) Probe), both with an outer diameter of 5 mm. The body of the snake robot is built out of a steel compression spring. It is flexible so it can passively follow the path of the oil ducts. The length of the flexible body is 1 m and it is terminated by an active system that can orientate the tip of the snake robot in the 3D space.
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The head structure is composed of a series of 6 washers with an external diameter of 5 mm and a length of 2 mm spaced from each other of the same length and fixed to a coil spring. In each washer, there are three holes arranged along the circumference of the washer 120 degrees apart from each other. Wires run along the flexible body of the probe, pass through such holes and are then fixed to the last washer. The control of the bending of the head is obtained by pulling a combination of these wires. As an example Fig. 3 shows the bending of the head along a plane obtained by pulling a single wire. A bending radius of 15 mm is obtained with this setup. Pulling multiple wires in accordance with various combinations allow the head to bend in different directions in the space. This degree of dexterity has been chosen as the most suitable for our needs. The tendon cables are pulled or released through the use of servo motors at the end of the probe (Fig. 1).To avoid undesirable effect due to the elasticity of the tendons, Kevlar fiber wire with a diameter of 0.25 mm has been used. Kevlar fiber was chosen since it features a unique combination of high strength and high Young’s modulus. A brief explanation two-dimensional kinematic model has been inserted below. The head of the probe has been discretized as six elements numbered starting from 0 to 5. The zero element is fixed with the ground. Every element is composed by two part: rigid part (in orange) and flexible part (in black). As shown in Fig. 3 the length of the coil spring has been approximated by the length of the cable for each element. Going further to the model description an incremental model has been formulated taking into account that the angular displacement of 2-D washers is small. Few assumptions for describing the deformation have been made:
as consequences of pulling wires, planar surfaces of the i-flexible part pure rotate around x-axis located in their own center indicated with 𝑂𝑂𝑎𝑎𝑖𝑖 and 𝑂𝑂𝑏𝑏𝑖𝑖 . This assumption is made considering the axial stiffness of the core spring higher than its flexible stiffness; the length of the wire 𝑙𝑙0 − ∆𝑙𝑙𝑖𝑖 and 𝑙𝑙0 + ∆𝑙𝑙𝑖𝑖 in a single i-element is approximated as the length of the core spring in the respective side. As described in Fig. 3, the rotation 𝛼𝛼𝑎𝑎𝑖𝑖 𝑎𝑎𝑎𝑎𝑎𝑎 𝛼𝛼𝑏𝑏𝑖𝑖 of the washer i can be described as:
arccos z
ai arccos z ai z bi-1 bi
bi
z ai
(1)
Fig. 3 Kinematics model of the head
The orientation of the i-element can be defined referred to the previous element as:
i a b arccos z b z b i
i
i
i-1
(2)
Considering s the length of the single rigid part and l the length of the flexible part of the element, it is possible to describe the position of the i-element referred to the OZY coordinate system as:
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i i l cos k 1 ak s cos k 1 zi k 1 k 1 i yi o i l sin k 1 ak s sin k 1 k 1 k 1 o
347
(3)
Due to the assumptions made before and referring to the Fig. 3 the dependences between 𝛼𝛼𝑎𝑎𝑖𝑖 , 𝛼𝛼𝑏𝑏𝑖𝑖 𝑎𝑎𝑎𝑎𝑎𝑎 ∆𝐿𝐿 have been described as: 2L 2L nD nD
arctan a b i
i
(4)
∆𝐿𝐿 is the total negative elongation of the wire, n is the number of elements of the head and D is the diameter where the wires are located. Inserting Eq. (4) inside Eq. (3) and considering i=5 the end effector coordinates have been defined as: 5 5 L L l cos 2k 1 nD s cos 2k nD k 1 k 1 ze 5 5 L L ye l sin 2k 1 s sin 2k nD nD k 1 k 1 e o 5 k k 1 o
(5)
3.3. Vision sensor The tip of the probe is equipped with a light source embedded into the 2.4mm diameter Olympus Iplex TX ultra-thin analog camera [15]. The sensor has a resolution of H768xV576 pixels, with a viewing angle of 80°. The video is acquired and displayed on an external monitor connecting the sensor with an RCA composite video cable that runs inside the probe body. 4. Results 4.1. Operating Scenario Two operational modes are implemented: manual guidance and supervised operation. When operated in manual guidance mode a human operator can remotely drive the probe along the gearbox with the use of a joypad. The system keeps track of the positions reached by the probe, so to have a certifiable log of the performed inspections operations. In supervised mode, the whole procedure is driven by the system and the probe is moved along the ducts through a set of predefined checkpoints. The operator is responsible for checking the status of the duct from the previous checkpoint to the actual checkpoint, before moving to the next sector of the duct. Without any confirmation of the operator, the system does not have the possibility to move on. 4.2. Calibration and Test As a first step, a mockup of an oil duct has been assembled with the use of flexible transparent pipes, as shown in Fig. 4. This setup has been used to test the capability of the system to reach a desired position, the functionality of the probe moving along forks and verifying its bending radius.
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Fig. 4 The probe during a test with a mock-up of an oil duct
After a set of test, it has been verified that the system can reach the performance indicated in Table 1. Table 1. List of the typical performance of the system Features Inspectional duct length
90 mm
Minimum duct diameter
6 mm
Minimum duct bending radius
15 mm
Positioning reproducibility
2 mm
To demonstrate the applicability of the device in a real scenario the inspection of ducts has been performed on different models of gearbox housing and a series of duct have been inspected. As an example Table 2 present the list of ducts inspected during a standard inspection cycle on a gearbox housing all the ducts have an inner diameter of 6 mm. Table 2. List of inspected duct on a single gearbox Duct
Length [mm]
Bifurcation
1
60
0
2
80
0
3
500
1
4
650
1
5
150
0
Fig. 5 Different situations can be encountered inside oil ducts: a) d) clean duct b) swarf, c) e) presence of obstructions
Considering a duct, 600 mm long with a single bifurcation, the probe can reach the end of the duct and being retracted. Different situations can be found during the inspection. Fig. 5 shows the most common scenario of clean ducts and obstructed channels. 5. Future Works The ultimate development of this system consists of integrating a subsystem to remove dust and swarf by using up
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space still available on the probe center, implementing a working channel where clamps, cutters or other tools can be placed. Following developments are ongoing and will be described in future works. 6. Conclusion In this paper, a novel robotic system for oil duct inspections has been developed. As a response in increasing demand of automation in avionic sector, the device is suitable to perform the inspection of oil ducts in gearbox housing, engine, components with significant savings in time and in the quality output. Manual guidance and supervised operation can be selected, representing both significant improvements in the inspection procedure currently performed by hand. The system has been tested in a real scenario and the results of the inspection have been presented. References [1] P. Hollienger, "Boeing and Airbus face mammoth task to clear order backlog," Financial Times, 2015. [2] P. M. Vitoriano, T. G. Amaral and O. Pàscoa Dias, "Automatic Optical Inspection for Surface Mounting Devices with IPC-A-610D compliance," in 2011 International Conference on Power Engineering, Energy and Electrical Drives, 2011. [3] T. Trung Do and P. Son Minh, "Pulsed cooling control for improving part warpage in injection molding process," in 2017 International Conference on System Science and Engineering (ICSSE), 2017. [4] S. M. e. al., "Deep Endoscope: Intelligent Duct Inspection for the Avionic Industry," IEEE Transactions on Industrial Informatics, vol. PP, no. 99, pp. 1-1. [5] B. J. Nelson, I. K. Kaliakatsos and J. J. Abbott, Microrobots for Minimally Invasive Medicine, vol. Annual Review of Biomedical Engineering, 2010. [6] D.-G. Choi, B.-J. Yi and W.-K. Kim, "Design of a spring backbone micro endoscope," in IEEE/RSJ International Conference on Intelligent Robots and Systems, 2007. [7] N. Simaan, "Snake-Like Units Using Flexible Backbones and Actuation Redundancy for Enhanced Miniaturization," in Proceedings of the 2005 IEEE International Conference on Robotics and Automation, 2005. [8] J. Ortiz, L. S. Mattos and D. G. Caldwell, "Smart Devices in Robot-Assisted Laser Microsurgery: Towards Ubiquitous Tele-Cooperation," in 2012 IEEE International Conference on Robotics and Biomimetics, ROBIO, 2012. [9] T. Kishi, M. Ikeuchi and T. Nakamura, "Development of a peristaltic crawling inspection robot for 1-inch gas pipes with continuous elbows," in 2013 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2013. [10] R. E. Goldman, A. Bajo and N. Simaan, "Compliant Motion Control for Multisegment Continuum Robots With Actuation Force Sensing," IEEE Transactions on Robotics, vol. 30, no. 4, pp. 890-902, 2014. [11] "Snake-arm Robots.," [Online]. Available: http://www.ocrobotics.com/technology-/snakearm-robots/. [12] R. S. Penning and M. R. Zinn, "A combined modal-joint space control approach for continuum manipulators," Advanced Robotics, vol. 28, no. 16, pp. 1091-1108, 2014. [13] N. Simaan, R. Taylor and P. Flint, "High Dexterity Snake-Like Robotic Slaves for Minimally Invasive Telesurgery of the Upper Airway," in Medical Image Computing and Computer-Assisted Intervention -MICCAI 2004: 7th International Conference, Saint-Malo, France, 2004. [14] ABB, "ABB," [Online]. Available: http://new.abb.com/products/robotics/industrial-robots/irb-1600. [Accessed 18 01 2018]. [15] Olympus Solutions Americas Corp, [Online]. Available: https://www.olympus-ims.com/en/rvi-products/iplextx/. [Accessed 18 01 2018].