Interdyscyplinarność badań naukowych 2018
Praca zbiorowa pod red. J. Szreka
Interdyscyplinarność badań naukowych 2018
Praca zbiorowa pod redakcją Jarosława Szreka
Oficyna Wydawnicza Politechniki Wrocławskiej Wrocław 2018
Redakcja:
Jarosław Szrek
Współpraca:
Aleksander Błachut, Ida Chojnacka, Tomasz Dobosz, Piotr Krysiak, Paweł Maślak, Damian Pietrusiak, Damian Stefanow
Politechnika Wrocławska, Grupa Ko-oper, działająca przy Katedrze Inżynierii Biomedycznej, Mechatroniki i Teorii Mechanizmów
ul. Łukasiewicza 7/9, 50-371 Wrocław
http://ko-oper.pwr.wroc.pl, e-mail: ko-oper@pwr.edu.pl
Recenzenci:
Ida Chojnacka, Łukasz Konat, Piotr Krysiak, Paweł Maślak, Damian Pietrusiak, Jakub Słowiński,
Damian Stefanow, Jarosław Szrek
Wsparcie:
Prorektor ds. Nauczania, prof. dr hab. inż. Andrzej Dziedzic
Projekt okładki:
JS
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i inny bez zgody wydawcy i właścicieli praw autorskich.
© Copyright by Grupa „Ko-oper”, Politechnika Wrocławska, Wrocław 2018
OFICYNA WYDAWNICZA POLITECHNIKI WROCŁAWSKIEJ Wyb. Stanisława Wyspiańskiego 27, 50-370 Wrocław http://www.oficyna.pwr.wroc.pl; e-mail: oficwyd@pwr.wroc.pl
ISBN 978-83-7493-035-2
Spis tre´sci
Spis tre´sci 4
Analysis of the state of stress of the carrying structure of the transport base of the bucket wheel using numerical techniques
- Jakub Andruszko . . . . 6 Design Thinking as a creative approach in conceptual design and testing of electric ma-
chines for construction works
- Jakub Andruszko, Johannes Wilhelm . . . 12 Concept and Prototype of Virtual Reality Input Device for Welding Process Simulation
- Maciej Habiniak, Paweł Krowicki, Bogdan Dybała . . . 16 Design and software development of a stationary 3D scanner with Internet of Things
integration
- Grzegorz Iskierka, Bartosz Poskart, Maciej Habiniak, Paweł Krowicki . . . 22 Dobór geometrii subramy do motocykla elektrycznego z uwzgl˛ednieniem oblicze´n wy-
trzymało´sciowych
- Piotr Konieczny . . . 28 Influence of isothermal heat treatment on the microstructure of the carburized Brinar 500
steel
- Aleksandra Królicka, Dominik Pachnicz . . . 34 A brief history of thermoelastic stress analysis development
- Robert Misiewicz . . . 40 Characteristic of infrared detectors and cameras
- Robert Misiewicz . . . 46 Introduction to thermographic temperature measurements
- Robert Misiewicz . . . 52 Mo˙zliwo´s´c zastosowania złotej spirali w konstrukcji obudowy spiralnej wentylatora pro-
mieniowego
- Piotr Odyjas, Julia Chmielewska . . . 58 Stanowisko do bada´n tribologicznych materiałów polimerowych w ruchu wahadłowym
- Mariusz Opałka . . . 64
The influence of Fe addition on phase transformations in NiTi-based shape memory alloy - W. Orłowski, M. Gnych, I. Gutkowska, M. Hasiak . . . 70 Comparison of two ways of the bone modelling for finite element calculations
- Dominik Pachnicz, Aleksandra Królicka . . . 76 Low cost production of laminating mold with use of 3D printing technology
- Wojciech Pawlak . . . 82 Przystosowanie drukarki 3D do pracy w „Internecie Rzeczy”
- Bartosz Poskart, Grzegorz Iskierka, Maciej Habiniak, Paweł Krowicki . . . 87 Wyznaczanie parametrów materiału ortotropowego
- Michał Sasuła . . . 93 The initial purification of Nucleobindin-2 protein from Gallus gallus domesticus
- Anna Skorupska, Andrzej O˙zyhar, Dominika Bystranowska . . . 99 Wpływ obróbki cieplnej na mikrostruktur˛e i twardo´s´c stali Brinar 400
- Łukasz Szczepa´nski . . . 106 Porównanie dynamiki zmiany pr˛edko´sci obrotowej silnika BLDC sterowanego przez
ró˙zne regulatory
- Wojciech Tarnawski . . . 112 Microstructure and mechanical properties of ni62f e23cr11ti4
- Michał Wawrze´nczyk, Krystian Machaj, Martyna D˛ebowska, Patrycja Turlej, Łu- kasz Poche´c, M. Hasiak . . . 118 Matching loads for strength calculations of portals of spreaders
- J˛edrzej Wi˛eckowski . . . 124 Influences of SUV front-ends on accidents with two-person bicycles
- Johannes Wilhelm, Mariusz Ptak . . . 128 Production, microstructural and physical properties of LaFeSi-based alloys
- Martyna Zemlik, Mariusz Hasiak, Amadeusz Łaszcz . . . 134
Analysis of the state of stress of the carrying structure of the transport base of the bucket wheel using numerical techniques
Jakub Andruszko1
Abstract: The article presents numerical simulation of carrying structure for additional equipment for open-cast mining transport vehicles. In order to correctly assess the assumptions a virtual model of the element was built and numerical calculations were carried out using the Finite Element Method. This approach to determine project guidelines is the best approach for economic reasons, because there is no need to build a large number of prototypes in this case.
Key words: design, supporting systems, tracked transporter, open-cast mining, numerical simulation, FEM
1. Introduction
The transport of oversized parts of mining machines is a very important aspect in terms of economic issues. Unplanned interruption in the extraction of mining material or prolong planned machine downtime due to delays in delivering the necessary equipment cause huge economic losses for the mine company. Supply of new or after repairing parts can be done with the help of specialized machines. Until now, specialized TUR tracked transporters have been used to transport e.g. oversized stations. Thanks to these machines time-consuming transport can be avoided.
The article presents the analysis of the state of stress of the carrying structure of the transport base for tracked transporter - TUR. Determining the sufficient strength of the structure gives the answer about the possibility of applying a new construction supporting transport of the bucket wheel, which will enable its quick delivery instead of place of stationing the machine, e.g. when it will be need to replace it after a breakdown [1].
Fig. 1. An example of TUR's tracked transporter made by FUGO Sp. z o. o. [8]
1 Faculty of Mechanical Engineering, Department of Machine Design and Research, Wroclaw University of Science and Technology, Lukasiewicza St. 7/9 50-371, Wroclaw, jakub.andruszko@pwr.edu.pl
2. 3D geometric model
On the basis of technical documentation of the original version of the carrying structure of the transport base of the bucket wheel for the TUR machine, a 3D geometric model was prepared. The use of the shell model eliminates the number of finite elements used in the discrete model [3]. The location of the bucket wheel on the machine and the 3D geometric model of the carrying structure of the designed element are shown in Fig. 2.
Fig. 2. Location of the bucket wheel on the TUR machine and the 3D geometric model of the transport base
Thanks to the previously built 3D geometric model of the transport base for the bucket wheel, a discreet model was built by applying a mesh with an average element size of 15 mm.
The discrete model has 95 844 higher-order elements and it consist of 290 029 nodes.
The following types of elements with their numbers were used [3, 4, 5]:
THIN SHELL: 95 844,
CONNECTION ELEMENT: 1534 or 2617 – depending on the type of analysis. Greater number when lateral force is used.
Discretized model whose colors reflect individual sheet thicknesses are shown in Fig. 3.
Fig. 3. Discreet model of the transport base of the bucket wheel with the distinction of sheet thickness - isometric view
3. Numerical model
The material to be used is S235J2 steel. Material properties of the above-mentioned steel, depending on the thickness of the sheet, are shown in Table 1.
Transport base
Tab. 1. Material properties of S235J2
Material Type
Re0.2
[MPa] Rm
[MPa]
g<16 16<g<40
S235J2 Non-alloy structural steel 235 225 360÷510 According to [6], the safety factor of 1.5 was assumed. In connection with the accepted steel S235J2, the allowable stresses for individual sheet thicknesses will be:
σdop(g<16)= Rxe0,2
b = 2351,5 = 157 MPa (1)
σdop(16<g<40)= Rxe0,2
b = 2251,5 = 150 MPa (2)
The boundary conditions for particular load cases were determined in accordance with the principle of accepting the worst possible load situation. The lateral force is determined on the basis of [7]
with a slope ratio of 1:10. Values of assumed loads are presented in Tab. 2.
Tab. 2. Load cases
Load case
The mass of the bucket wheel and sliding ele- ments - E
The horizontal compon- ent of gravity force of the bucket wheel resulting from the inclination of the machine - Eh
Vertical component of the gravity force of the bucket wheel resulting from the inclination of the machine - Ev
Value [kN] 880 88 871.2
Load cases and the method of supporting the transport base are shown in Fig. 4.
Fig. 4. The boundary conditions for each case Ux = 0
Ux = 0 Uy = 0 Eh
Ev
Eh Ev
Ux = 0
Ux = 0 Uy = 0
Ux = 0
Ux = 0
Uy = 0 Eh
Ev
Ux = 0
Ux = 0
Uy = 0 Eh
Ev
Ux = 0 Ux = 0
Uy = 0 Eh
Ev
4. Strength calculations using Finite Element Method
As a result of the analysis of the results, 14 areas were selected in which high stress values were found for the transport base of the bucket wheel. Their locations are shown in Fig. 5.
Fig. 5. Location and designation of overstress areas
The above-mentioned stress values are summarized in Tab. 3, where areas close to admissible values were marked in green, values exceeding the admissible values were highlighted in yellow and values significantly exceeding them in red.
Tab. 3. Stress values in predefined areas
Case
Value of stresses [MPa]
Number of area on the structure
1 2 3 4 5 6 7 8 9 10 11 12 13 14
1 169 156 193 98 155 135 182 156 169 121 155 84 6 6 2 171 159 183 58 102 81 182 160 174 184 211 135 8 8 3 143 158 208 114 211 165 206 158 147 89 102 66 6 6 4 112 118 137 81 155 129 247 204 203 142 155 96 7 201 5 214 205 248 106 157 132 135 118 121 130 156 106 198 7 Carried out calculations showed that the decisive cases causing a significant effort in the transport base of the bucket wheel are situations when the machine is in the lateral inclination. Table 4 presents stresses distribution according to the H-M-H theory for cases when they exceed the acceptable values [2]. For the two worst cases, buckling analysis was carried out, and the buckling coefficients were determined:
case 4 – buckling coefficient = 22.8
case 5 – buckling coefficient = 22.7
These coefficients indicate how much the applied load must be increased, so that the structure will lose its stability. The first buckling mode for individual cases are also shown in Tab. 4.
5
7 6 8
9 10
11 12
13 1
14 2 3
4
Tab. 4. Stress values according to H-M-H theory and buckling modes
Case 4 – maximum stress – 247 MPa Case 5 – maximum stress – 248 MPa
Case 4 – first buckling mode - 22.8 Case 5 – first buckling mode - 22.7
A definite exceeding of the permissible stress values, in the case of lateral inclination of the machine, for two types of base mounting on the machine was found in the following areas:
case 4: area 7 (Fig. 5):
max = 247 MPa > dop = 157 MPa
case 5: area 3 (Fig. 5):
max = 248 MPa > dop = 157 MPa
In other cases, the permissible stresses were also exceeded in the following cases and areas:
case 1: area 3 (Fig. 5):
max = 193 MPa > dop = 157 MPa
case 2: area 11 (Fig. 5):
max = 211 MPa > dop = 157 MPa
case 3: area 3, 5 and 7 (Fig. 5):
area 3: max = 208 MPa > dop = 157 MPa area 5: max = 211 MPa > dop = 157 MPa area 7: max = 206 MPa > dop = 157 MPa
3. Summary
The main purpose of this article was to check the state of stress of the construction of the transport base of the new bucket wheel of the SchRs4600 excavator adapted to the tracked transporter - TUR. The basic and the worst possible load cases were identified. Based on the obtained results from numerical calculation, the locations of the highest concentration of stresses were identified.
In the current design of the transport base for the bucket wheel, in the case of inclination analysis, it was found that the value of yield stress of the material was exceeded by 13 MPa.
The calculations showed that the decisive load cases are lateral inclinations.
Conducting the analysis using Finite Element Method allows us to reduce the number of prototypes of the designed structure and to define guidelines for changes in the most devoted areas. As a result of the analysis, it was found to optimize the structure.
Literatura
[1] J. Czmochowski, P. Maślak, P. Działak, G. Przybyłek, M. Stańco: Assessment methodology of a technical condition of the bucket chain excavator structure. Materials Today: Proceedings, 2017, Vol.4(5), pp.5785-5790. ISSN: 2214-7853; DOI: 10.1016/j.matpr.2017.06.046.
[2] E. Rusiński, J. Czmochowski, A. Iluk, M. Kowalczyk: An analysis of the causes of a BWE counterweight boom support fracture. Engineering Failure Analysis, 2010, Vol.17(1), pp.179- 191. ISSN: 1350-6307 ; DOI: 10.1016/j.engfailanal.2009.06.001
[3] E. Rusiński: Metoda elementów skończonych. System COSMOS/M. Wydawnictwo Komuni- kacji i Łączności, Warszawa 1994
[4] E. Rusiński, J. Czmochowski, T. Smolnicki: Zaawansowana metoda elementów skończonych w ustrojach nośnych maszyn. Oficyna Wydawnicza Politechniki Wrocławskiej, Wrocław 2000 [5] O. C. Zienkiewicz, R. L. Taylor: The finite element method. Vol. 1, Vol. 2. McGraw-Hill Bool
Company, London 1991
[6] Niezgodziński T.: Wytrzymałość materiałów. Wyd. 16, Warszawa: PWN, 2010. ISBN 978-83- 01-15966- 5.
[7] PN-G 47000-2: 2011 „Górnictwo odkrywkowe – Koparki wielonaczyniowe i zwałowarki. Część
2. Podstawy obliczeniowe”
[8] www.fugo.com.pl
ANALIZA STANU WYTĘŻENIA KONSTRUKCJI NOŚNEJ PODSTAWY TRANSPORTOWEJ KOŁA CZERPAKOWEGO Z WYKORZYSTANIEM TECHNIK NUMERYCZNYCH
W artykule przedstawiono analizę wytężenia konstrukcji nośnej podstawy transportowej koła czerpakowego dla transportera gąsienicowego. Aby poprawnie ocenić przyjęte założenia zbudowano wirtualny model ustroju, a z wykorzystaniem Metody Elementów Skończonych przeprowadzono badania numeryczne. Takie podejście do określania stanu wytężenia ustrojów nośnych jest podejściem ze względów ekonomicznych zdecydowanie najlepszym, ponieważ nie występuje w tym przypadku konieczność budowy dużej ilości prototypów. Opisane zostały wszystkie etapy przygotowania modelu obliczeniowego – od samego wirtualnego modelu 3D do ostatecznego modelu gotowego do obliczeń. Przeprowadzono szereg obliczeń wytrzymałościowych z wykorzystaniem Metody Elementów Skończonych przy określeniu odpowiednich warunków brzegowych modelu oraz oceniono poprawność założeń projektowych przyjętych przez konstruktorów.
Design Thinking as a creative approach in conceptual design and testing of electric machines for construction works
Jakub Andruszko1, Johannes Wilhelm2
Abstract: The article presents the implementation of Design Thinking method in conceptual design and testing of electric machines for construction works. The creative approach to design allows the designer to be outside the box. Although the design is always dependent on the client's personal taste, but the method of design thinking provides a set of values that can move innovation forvard. These values are primarily creativity, thinking outside the box, the work of interdisciplinary teams and focusing on a common goal.
Key words: design, design thinking, conceptual design, creative design, demolition machine, testing
1. Design Thinking
Design Thinking is a method of creating products and services with high innovation, based on a deep understanding of the potential user's needs and problems. This approach allows to a systematic approach to the process of creating innovation [3].
A very important, first step in the process of creating innovative solutions, based on the Design Thinking method, it is to create an interdisciplinary team composed of specialists from various fields who can look at solving the problem from a different perspective. The team implements step-by-step, previously established stages of the procedure in the Design Thinking method. These stages are shown in Fig. 1.
Fig. 1. Design Thinking Process [5]
This process does not have to be linear, which means that when performing specific tasks, in case of a wrongly defined and evaluated previous task, we can return to the previous stage or jump to the very beginning of the process.
1 Faculty of Mechanical Engineering, Department of Machine Design and Research, Wroclaw University of Science and Technology, Lukasiewicza St. 7/9 50-371, Wroclaw, jakub.andruszko@pwr.edu.pl
2 Faculty of Mechanical Engineering, Department of Machine Design and Research, Wroclaw University of Science and Technology, Lukasiewicza St. 7/9 50-371, Wroclaw, johannes.wilhelm@pwr.edu.pl
These steps are [3, 6]:
EMPATHIZE: The approach to innovation starts with empathy. Defining user’s needs.
DEFINE: Synthesizing the information collected during the empathy phase and on its basis the proper definition of the problem.
IDEATE: Generating as many ideas of solutions for a defined problem as possible. The basic tool is brainstorming.
PROTOTYPE: Building simple prototypes based on previously generated ideas, to outline the functionality of a potential solution.
TEST: Selection of the best prototype solution and its testing in the user's environment. Define the parameters that must be achieve.
2. Conceptual design and prototyping of the hybrid demolition machine
Thanks to an interdisciplinary team consisting of scientists from the Wrocław University of Science and Technology and the Academy of Fine Arts in Wrocław and Advanced Robotic Engineering company from the demolition industry, the approach to the Design Thinking method was initiated.
According to the requirements of this method, a complete process of designing a hybrid demolition machine was carried out. In the first stage, the client's requirements at the technical and functional level were precisely defined. In the process of empathizing, a good understanding of the needs resulting from the development of our own machine, better in terms of strength than the machines of competing companies, allowed for the creation of accurate output data. In addition to the purpose defined by the user himself to increase the strength of the robot's carrying structure, it was possible to identify hidden needs i.e. improve the machine transport process to the workplace and increase the efficiency of the demolishing proces. After several brainstorms, the concept of a new machine was developed using improvements resulting from hidden targets. Thanks to the optimal understanding of the hidden needs in the new concept of the demolition machine, a hybrid driving system consisting of two electric motors is used, one of which is powered from the mains and the other from a battery system located on the machine. The use of a second engine coupled with batteries makes it possible to transport the machine to the workplace without connecting the robot to the mains.
Thanks to the use of the above-mentioned amendments, it was proposed to build a prototype of the new machine. In connection with the assumptions of the Design Thinking method that prototypes should be as simple as possible and not take a large financial outlay to make it, it was decided to use Computer Aided Engineering methods. After verifying the correctness of the model's execution, the actual prototype of the machine was made. The 3D virtual model and prototype of new machine are shown in Figure 2.
Fig. 2. From concept to prototype
3. Testing
In order to determine the correctness of the adopted design assumptions many verification methods can be used. The method proposed by the authors is a numerical and experimental approach [1, 2]. The authors decided to verify the adopted assumptions with the use of experimental research using strain gauges and in the next step an analysis using Finite Elements Method allowing to determine the critical points of the robot's load-bearing structure [4]. In order to verify numerical models, an appropriate measurement system should be built and verification cases should be determined first, which will be used to verify the correctness of the numerical model. One example of the load to verify the numarical model is shown in Fig. 3.
Fig. 3. Numerical-experimental approach to testing
A further process is to take measurements during machine operation and to adjust the numerical model accordingly in order to obtain the most accurate values of stresses in places where strain gauges are mounted on the real object. The experimental tests should be carried out in the working environment of the machine with pre-determined work cases. Correct selection of measuring cases is a key stage for later determination of the effort of the carrying structure and assessment of the correctness of the assumptions. The working conditions of such a demolition robot are very specific and heavy. By determining the maximum stress values in the structure, the potential machine operator can be fully aware of which positions during machine operation can be sensitive and can later lead to destruction of the structure.
4. Remarks
Although the project is usually subject to the personal taste of the user, the method of design thinking provides a set of large numbers of data that can move innovation forward. Going beyond the box allows you to define the needs not only of those that the potential user thinks about, but also those that remain hidden, and after disclosure become key elements in the process of creating something new
Conducting the design process using an interdisciplinary team, design thinking and experimental and numerical techniques to determine the correctness of input data to the process allows you to develop a certain scheme, which is a new approach to the design of such machines.
The process specified by the authors can be represented by the diagram shown in Fig. 4.
Compared with results from strain gauge
Fig. 4. The process developed by the authors
Acknowledgements
The project was carried with the support of the National Centre for Research and Development in Poland under the “Szybka Ścieżka” program no POIR.01.01.01-00-0582/15-00, in cooperation with Advanced Robotic Engineering Ltd. company.
Literatura
[1] Derlukiewicz, D., Ptak, M., Wilhelm, J., Jakubowski, K. The numerical-experimental studies of demolition machine operator work. Springer, 2017, 129-138.
[2] Karliński, J., Rusiński, E., Lewandowski, T. New generation automated drilling machine for tunneling and underground mining work. Automation in Construction, 2008, vol. 17, 224- 231.
[3] Nigel Cross, Design Thinking: Understanding How Designers Think and Work, Bloomsbury Academic, 2011.
[4] Rusiński, E., Czmochowski, J., Smolnicki, T. Zaawansowana metoda elementów skończonych w konstrukcjach nośnych. Oficyna Wydaw. PWroc., 2000.
[5] Thomas Lockwood, Design Thinking: integrating innovation, customer experience, and brand value, Allworth Press 2010.
[6] Web-site: http://dschool.stanford.edu, dSchool, Institue of Design at Stanford, CA, USA 2014.
DESIGN THINKING JAKO KREATYWNE PODEŚCIE DO PROJEKTOWANIA KONCEPCYJNEGO ORAZ TESTOWANIA ELEKTRYCZNEJ MASZYNY DO PRAC
BUDOWLANYCH
W artykule przedstawiono proces projektowania elektrycznej maszyny do prac budowlanych z wykorzystaniem kreatywnych metod bazując na metodzie Design Thinking. Autorzy przedstawili podejście do projektowania takich maszyn w zupełnie nowym świetle. Myślenie poza schematami oraz odpowiednio dobrany interdyscyplinarny zespół jest w stanie wygenerować odpowiednio dużą liczbę nowych rozwiązań z zachowaniem postawionych przez potencjalnego użytkownika celów.
Metoda Design Thinkig pozwoliła na określenie niezdefiniowanych potrzeb użytkownika, przez co maszyna stała się jeszcze bardziej unikatowa, z rozwiązaniami, które nie są dostępne w maszynach konkurencyjnych. Połączenie kreatywnych metod projektowania oraz numeryczno-doświadczalnych metod weryfikacji założeń konstrukcyjnych pozwala na stworzenie schematu nowego podejścia do konstruowania tego. typu maszyn.
Concept and Prototype of Virtual Reality Input Device for Welding Process Simulation
Maciej Habiniak1, Paweł Krowicki1, Bogdan Dybała1
Abstract: Last years show significant growth in the use of virtual reality technologies, mostly immersive virtual environments consisting of sophisticated software and hardware.
It is also easier to find effective, user friendly, easily programmable and even conditionally free software, such as Unreal Engine or Unity. More problematic may be the selection of input devices, especially if they should provide positioning or force feedback. The cost of such input tools may reach thousands of Euros. Therefore the authors of this paper decided to build and test their own relatively cheap, pointing-haptic device. A simulator of welding processes was taken as an example of use. Visualization process for the newly developed tool was realized with the Unreal Engine. Important tasks to be performed by the device were tracking of the position of the electrode tip and force feedback during simulation of a welding process. These data after appropriate processing provide information about the performance of the welding process. Development of the input device was based on Atmel AVR microcontroller with additional accelerometer, gyroscope, force feedback module and LEDs. Orientation and acceleration data were preliminary calculated by specially developed algorithm and transmitted directly to the visualization software. LEDs were applied as markers for a video tracking system. Combination of data derived from the video tracking system and the sensors connected to the AVR microcontroller results in a transformation matrix fully describing orientation and position of the welding tool.
Validation of the newly created tool was carried out and compared with a professional haptic device – Geomagic Touch. In conclusion, the results confirmed the success of constructing an accurate and cost effective input device what was the goal of this work.
Keywords: Haptic device, virtual reality, welding, process simulation, microcontroller
1. Introduction
Despite constant progress in industrial robotics often the only possible solution for welding is manual work. It is especially noticeable for small series products and large-size elements or if it is necessary to weld a construction at its destined place. Welding is commonly known as one of harder professions. Conditions at welding workplaces such as high temperature, presence of gases and strong light source are dangerous for health, specifically for beginners or learners which haven’t been prepared for unassisted work. Additionally welding is a costly process because of prices of welding torches, swatches, electrodes and utilities like electrical energy or inert gas. Based on those arguments the authors of this article developed an interest in developing a welding simulation system. The goal was an application which would allow users to learn and practice welding technique at home or in a learning centre. The main advantage will be noticeable in early stages of learning through minimization of costs and maximization of safety.
The initial goal was to implement a system to control the virtual welding grip by user’s real moves. The case was termed an input methodology which allows to training sequences of moves similar to those in a real welding process. Finally, two input tools were tested: the first was a commercial haptic device from Geomagic, the second – a newly developed device based on an AVR microcontroller. Both of them are described in this article.
1 Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, email:
maciej.habiniak@pwr.edu.pl
2. Device Development
The input device development was subdivided into two main parts dependent on the character of a measured value. First was the module based on Atmel AVR microcontroller which controls measurements of the direction. A second element was needed to recognize relative locations of the controller and was implemented in the Unreal Engine’s algorithm.
The rotation tracking element uses a programmable microcontroller and a 3-axis gyroscope with an accelerometer sensor module MPU-6050. The C-code program for the Atmel AVR includes the libraries: Wire.h, MPU6050.h and KalmanFilter.h. Wire.h has been provided to use communication between the microprocessor and the sensor module by a single computer bus I2C. MPU6050.h is the dedicated library for a module with the same name. KalmanFilter.h is used for filtration gyroscope and accelerometer measured values.
The Kalman filter is also known as Linear Quadratic Estimation (LQE), which for example is exploited in engineering or economics. The main effect of the filter is to provide estimates of unknown variables, calculated from measurements observed over time and containing noises and sampling errors [2]. Afterward parameters were configured such as the maximal over time. Then the I2C bus and UART serial were initialized. Communication between the microprocessor and the computer simulation is established in the programme and the transfer of actual rotation vectors from the MPU-6050 module. In the next step the program’s main loop runs in every work cycle. The algorithm starts with actual values measured by gyroscope and accelerometer. Then the values are passed to the Kalman filter to obtain the unknown variables. Next the values are normalized to larger than zero and sent to simulation by UART serial. The last stage is a delay function, because it is necessary to determinate a constant pause between measurements.
There were trials with the program to run without the Kalman filter, with actual or averaged values from the gyroscope and the accelerometer for each axis. But the digital gyroscope and the accelerometer are not very accurate sensors. The disadvantage of the gyroscope is its vulnerability to leeway. It shows as an increase in the value of yaw even during stillness. The reason of gyroscope’s leeway is the influence of the gravitational field. The observational error increases in time, because deviation is constant and modified result based on integral of discrete variable is dependent on previous results. Therefore inaccurate values were produced in low frequencies. On the other hand, accelerometers give correct results in low frequencies and results are perturbed with high frequencies. In effect, low-pass and high-pass filters are used for both signals.
The main guidelines for position tracking element is to describe the position as a vector using Cartesian coordinate system in three directions. Position tracking is based on a visual system.
The main tools which are used are a web camera and the OpenCV library. OpenCV is an open source collection of functions supporting image modifications necessary to localize input devices.
The library has a C++ interface and Windows support so it may cooperate with the Unreal Engine.
After wrong passive target objects were established an active light source like a light emitting diode which colour will be independent from the environment light. At first there was a problem of diffuse light. To survey the negative effects a physical filter was installed on the camera lens. A piece of polyethylene terephthalate (PETE) was used as a filter. The filter passes from red visible light to infrared and the camera has an embedded infrared filter – finally recorded are only red light sources and the tracking system is based on colour detection. Using OpenCV library functions is realized with a 4-step algorithm:
1. Get camera frame 2. Edit to symmetry image
3. Convert RGB into HSV colour model
4. Thresholding to get LED area on a binary mask
In the last stage a method to determine point’s localization on an image and calculate distance between white fields was developed. The location on the image is determined as X and Z location, and distance is bound with the Y coordinate which is perpendicular to the camera plane.
3. Commercial Device Geomagic Touch
During development of the welding simulation a commercial device Goemagic Touch was used (see figure 1). It is a simple manipulator with six degrees of freedom. Touch is one of the smallest devices in offer because of the workspace is contained in a box with dimensions 160x120x70 mm. The producer declares that in this space it is possible to perform effortless hand motion and little arm movement. The main parameter of a haptic device is the force feedback strength and the amount of directions of force. Geomagic Touch generates force at 3.3 N for each 3 axes and does not generate any torque. Using a dedicated library implemented was communication with the device based on serial communication. There are functions in the library to read angles in every joint, from which the actual position of the effector, as manipulated by user [1], [7], may be calculated.
Fig 1. Geomagic Touch haptic device
4. Simulator
The welding simulation was created in Unreal Engine, a graphical engine developed by Epic Games. Unreal Engine now is available in version 4. The biggest benefits of the Unreal Engine are its capabilities and the possibility to append own functionality based on C++ code. Unreal Engine cooperates with a popular programing environment – the Visual Studio from Microsoft.
Additionally the current version of the engine is free for non-commercial use. For commercial applications the royalty fees are equal to 5% of gross revenue after the first $3 000 per 3 months.
All virtual geometrical objects used in the simulation were developed in Autodesk 3DSMax Studio and transferred in the FBX format. In effect, a virtual space contains basic accessories: welding table, weld sample and electrode holder.
Communication and data reading from the commercial input device were implemented in Unreal Engine. The distributor of Geomagic Touch provides a developer’s library for communication with the device. The most time-consuming problem was to add libraries for the Unreal Engine. It was necessary to put the files in correct folders and switch the C++ code to additional sources.
Finally, a virtual room was created, in which the welding accessories were positioned: a specialist desk, welding swatch and movable grip. Figure 2 shows the virtual environment. The screenshot was taken after a welding process, so the weld is visible. On the right hand side of the screen the top of the sample is shown with a green line which is the recorded trajectory of the end point of the electrode. The line was recorded only during active electrical arc and results from five streams of values: 3 values of location and 2 of rotation.
The additional advantage in the simulator is the possibility to hold past information about the effector’s location. It is therefore possible to establish a simple grade of the welding based on welding linear energy, dependent on voltage, current, welding method, welding velocity and length of the arc. From those information a value of ratio between height and width of weld cross may be calculated which can be a first step of visual assessment [3-6].
Fig. 2. Virtual space and recorded trajectory shown on a metal sample
4. Conclusion
The work described in the paper shows a dependency between the total cost of devices and the quality of measured results. The cost of the developed device is about 15 times lower the price if Geomagic Touch. The charts in figure 3 provide time series in static tests which consisted of 20- second recordings of values of the effector location and rotation when positioned motionless on the table. There are random oscillations for the developed device while for Geomagic Touch a change in rotation in one axis occurs 4 times with a minor value of 1°. It is up to the software to deal with this – a solution was presented in the paper.
Fig. 3. Recorded time series for rotation and location: a and c – Geomagic Touch, b and d – developed device
References
[1] Geomagic. Geomagic Touch Specifications, January 2014
[2] Welch G., Bishop G., 2006, An Introduction to the Kalman Filter, Departament of Computer Science, University of North, Carolina at Chapel Hill
[3] Wang, Q, L, 1991, Real-time full-penetration control with arc sensor in the TIG welding of Al alloy, Proceedings of the International Conference on Joining/Welding 2000, IIW, the netherlands [4] Bęczkowski R., Gucwa M., 2011, Statystyczna ocena wpływu parametrów napawania SSA na geometrię napoin, Przegląd Spawalnictwa 10/2011
[5] Dobaj E.: Maszyny i urządzenia spawalnicze.
WNT, Warszawa, 1998.
[6] Szefner Zbigniew, 2007, Koncepcje sterowania współczesnych systemów spawalniczych, Przegląd Spawalnictwa 2-3/2007
[7] Urządzenia haptyczne [Internet]. Geomagic Touch, Freeform, Sculpt.
Dostępne na: http://www.geomagictouch.com/index.php/urzadzenia/
KONCEPCJA I PROTOTYP URZĄDZENIA WEJŚCIOWEGO NA POTRZEBY SYMULATORA SPAWALNICZEGO
Pomimo nieustannego rozwoju oraz wprowadzania robotyzacji w wiele dziedzin produkcji spawanie ręcznie często pozostaje głównym rozwiązaniem. Przykładem takich są sytuacje serii jednostkowych i wielkogabarytowych lub konieczność wykonania spoin na miejscu budowy konstrukcji spawanej. Niestety ta technika spajania często niesie pewne zagrożenia dla operatora w postaci wysokich temperaturę, unoszenia się szkodliwych gazów czy silnie promieniującego światła. Autorzy artykułu w odpowiedzi na dostrzeżony problem postanowili zaprojektować symulator spawania ręcznego. Jednym z założeń początkowych była możliwość sterowania wirtualnym uchwytem spawalniczym poprzez ruchy użytkownika. W tym celu zaproponowano rozwiązanie dualne problemu, zastosowano dwa narzędzia wejściowe. Pierwsze z nich to dostępny komercyjnie manipulator haptyczny Geomagic Touch. Jest to 6-osiowe urządzenie pozwalające na swobodne ruchy dłoni oraz generujące sprzężenie zwrotne siłowe do 3N. Drugim urządzeniem jest autorski układ opierający się na mikrokontrolerze AVR oraz systemie wizyjnym. Mikrokontroler odpowiada za pracę cyfrowego układu MPU6050, który z wykorzystaniem filtracji Kalmana pozwala na określenie aktualnej rotacji urządzenia. System wizyjny śledzi dwie diody zamontowane na urządzeniu. Na podstawie filtracji z obrazu są odseparowywane elementy nie będące źródłem światła, następnie obraz jest sprowadzany do mapy bitowej, na podstawie której algorytm określa pozycję obu diod. Z zależności dwóch odczytów wyliczana jest odległość urządzenia od kamery, względna wysokość oraz przesunięcie na boki. Ostateczną stabilność oraz porównanie obu urządzeń zaprezentowano na wykresach.
Design and software development of a stationary 3D scanner with Internet of Things integration
Grzegorz Iskierka1, Bartosz Poskart1, Maciej Habiniak1, Paweł Krowicki1
Abstract: The paper describes design and software development of a stationary 3D scanner with Internet of Things integration. It also explains the possibilities and limitations of the developed scanner and touches on its construction, calibration process, and validation of scanned geometry results in comparison with other commercially available scanners.
Keywords: 3D scanning, laser triangulation, Internet of Things
1. Introduction
Considering recent movements in the field of reverse engineering, tackling problems like digitalisation of physical 3D objects, many spatial scanning methods have been developed. Reverse engineering in such a form have, and may further benefit both the industrial and academic sectors, aiding various design methodologies such as rapid prototyping or design thinking.
Certain scanning methods became more apparent when it comes to implementation, considering the stationary character of the designed machine. Through the analysis of advantages and disadvantages of available scanning technologies, the most suitable for the application has been chosen – laser triangulation. Additionally, the platform has been designed with possible improvements in mind, and in such a way to allow for development of various scanning methods such as different variants of structured light projection or recently popularised photogrammetry.
Implemented scanning technology, though not presenting the most accurate results, with its relatively short scanning time, it may be extremely useful for simple visualisation purposes, allowing the user to view scanned models in native scale through Augmented Reality applications or in virtual environments.
To create natural conditions for communities to form and thrive, Internet of Things connection has been implemented into the device to allow for cloud storage, as well as provide a platform for easy exchange of scanned models.
2. Scanning method
There are two major types of 3D scanners – handheld and stationary. While both have their advantages, this article will focus on the stationary scanner, since the device is designed to have its own computing unit, without the need to connect it to an external PC. With stationary scanners, few different scanning methods can be recognised, such as structured light 3D scanning or recently popularised photogrammetry [1,2]. While photogrammetry may be a natural next step in the evolution of the designed scanner, a structured light 3D scanning method, based on a line laser and a camera, has been chosen for implementation.
1 Wrocław University of Science and Technology, Łukasiewicza 5 50-371 Wrocław, greg.iskierka@gmail.com, tel.: 781 233 348
In order to capture an objects shape, a laser line is being projected onto its side surface.
Since the laser is set at an angle relative to the camera, the projected straight line appears distorted in the registered image. The scanned object is set on a turntable, which allows for its rotation to capture several of its profiles, which can then be used to reconstruct the object as a 3D model.
Computation of registered data is done with the use of simple triangulation algorithms based on set laser-camera (LC) and camera-object (OC) distances, presented on the figure below (Figure 1).
Figure 1 Triangulation method schematic
3. Design and hardware
The designed scanner is meant to be compact and work completely independently of external computers. For this reason, a small computing unit had to be selected for implementation.
From many commercially available micro-computers, the choice had been narrowed down to two options – Raspberry Pi (Figure 2a) or NVIDIA Jetson TX1 (Figure 2b).
a) b)
Figure 2 Micro-computers: Raspberry Pi 3 Model B (a) [5], NVIDIA Jetson TX1 (b) [6]
Ultimately, though NVIDIA Jetson TX1 provides more processing power, Raspberry Pi has been chosen, mainly due to its lower cost and higher accessibility. Additional elements, essential for the chosen scanning method, such as a line laser (Figure 3a) and a digital camera (Figure 3b) have been selected.
a) b)
Figure 3 Additional necessary components: line laser (a), Logitech c510 digital camera (b) [7]
The rotary turntable has been designed with the use of Igus Robolink D standard robot joint (Figure 4) to allow scanning of heavier objects and more precise angle of rotation control. Although the used robot joint is not necessary, it may yield better scanning results and allow for further development due to additional precision.
Figure 4 Igus Robolink D standard robot joint [8]
In order to ensure similar lighting conditions, all of the aforementioned components have been enclosed in a darkened chamber (Figure 5), in a configuration previously presented in Figure 1, with an additional line laser on the opposite side of the camera for eventual further improvements. The chamber has also been equipped with LED lighting for maintenance purposes.
Figure 5 Lit scanning chamber
4. Software
Scanning software has been developed in Python, with the use of OpenCV [3, 4] library for image acquisition and processing, as well as Numpy library for further calculations. To fully automate the scanning process, image processing, profile’s rotation transformation and writing an STL file algorithms have been devised and will be further explained. The core scanning algorithm is presented on Figure 6, where green boxes show the aforementioned algorithms.
The scanning process starts by loading threshold settings, previously set with a separately developed piece of software, which allows for correct thresholding, and in return, correct recognition of the projected line. Afterwards, the software proceeds into the main scanning loop consisting of consecutive image processing operations as well as rotation transformation of gathered data, in order to create a spatial point cloud correlating with the scanned objects orientation. After a full revolution of the scanned object, software uses the calculated coordinates of gathered points to create a meshed 3D model, later saved in an ASCII STL file format.
a) b)
c)
d)
Figure 6 Core scanning algorithm (a), image processing algorithm (b), profile’s rotation transformation algorithm (c), writing an STL file algorithm (d)
5. Initial calibration
Due to differences between various cameras, it is imperative to perform calibration, to compensate for the curvature of cameras lens distorting the image. To do that, previously mentioned OpenCV library is utilised, using a predefined checkerboard pattern to determine compensation values. The calibration process is conducted according to the instructions contained in the OpenCV documentation [9]. Exemplary images captured during the calibration process are presented on the figure below (Figure 7).
Figure 7 Exemplary calibration images
For best results several calibration images should be captured (around 15 to 20) for further analysis. Afterwards, the distortion correction matrices are computed and saved for later use during the scanning process.
6. Internet of Things integration
Internet of Things has become very prominent in the industry, with countless new devices being connected to the Internet each year. With internet connectivity come additional functionalities and features, aiding the user in various ways. Thanks to Raspberry Pi’s built-in Wi-Fi module and a set-up global server, the device is capable of 3D models cloud storage.
To allow quick connection and good responsiveness, a REST (Representational State Transfer) server has been set up using PythonAnywhere service, which allows running a Python script globally to communicate through standardised HTTP request protocols utilising Flask API.
The PythonAnywhere account includes additional disk space on the server (500 MB for free users), which for this application serves as a storage space for uploaded 3D models. The files are simply contained on the server’s hard drive, and can be easily accessed with previously programmed URL (Uniform Resource Locator). The URL can be accessed from multiple sources through GET requests. This means that the file can be downloaded programmatically, directly through any web browser or other specialised software (e.g. Postman [10]).
Figure 8 Stored models information returned in a JSON (JavaScript Object Notation) format
The list of models presented in Figure 8 organises the files for external applications to interpret or to be accessed through a web browser. The most important position in the list is a
“link_STL” key, which provides a link to direct download of a selected 3D model.
8. Comparison with commercially available scanners
As stated before, the developed scanner in its current form does not provide good quality scans due to the scanning technique used and the developed algorithms. Although it can be built cheaply and provides a good platform for further improvements, the quality presented in Figure 9 can by no means compete with the commercially available scanners in such state.
a) b)
Figure 9 Comparison between models: side by side (Sense V2 – left, developed scanner – right) (a), overlapped (b)
Comparison between the two models presented above is shown in the table below (Table 1).
Table 1 Comparison between Sense V2 and the developed scanner Sense V2 Developed scanner
Vertices count 1142 8946
Faces count 2354 18324
Model volume [cm3] 100 50
7. Capabilities and limitations
Current iteration of the developed scanner is best suited for objects of simple geometry, mostly because of the limitations of the scanning method used and the developed algorithms. Since the method used is structured light-based, it is important to notice that best results can be achieved for white or bright-coloured objects with less-reflective surfaces. Worst results were observed for highly reflective, black, or dark-coloured objects.
Considering the meshing method used in the scanning software, it can be concluded that under current implementation it is impossible to produce through holes. Additionally, due to camera’s position and orientation, it is impossible to register any concave structures on the top or bottom part of scanned objects.
The produced scanner is by no means a precise measuring tool, but besides its limitations, it can be a useful visualisation or reconstruction tool for rapid prototyping or quick testing purposes.
References
1. Thomas Luhmann, Stuart Robson, Stephen Kyle, Jan Boehm, “Close-Range Photogrammetry and 3D Imaging”, de Gruyter, 2013
2. Atkinson, KB, “Close range photogrammetry and machine vision”, Dunbeath: Whittles Publ., 1996.
3. Gary Bradski, Adrian Kaehler, “Learning OpenCV: Computer Vision with the OpenCV Library”, O'Reilly Media, Inc., 2008
4. Kari Pulli, Anatoly Baksheev, Kirill Kornyakov, Victor Eruhimov, “Realtime Computer Vision with OpenCV”, ACM Queue magazine, Volume 10 Issue 4, April 2012, ACM New York
5. www.raspberrypi.org
6. www.nvidia.pl/object/jetson-tx1-module-pl.html 7. www.logitech.com
8. www.igus.eu
9. https://docs.opencv.org/3.0-beta/doc/py_tutorials/py_calib3d/py_calibration/
py_calibration.html#calibration 10. www.getpostman.com
PROJEKT I OPROGRAMOWANIE STACJONARNEGO SKANERA 3D PRZYSTOSOWANEGO DO DZIAŁANIA W INTERNECIE RZECZY
Coraz częściej dąży się do dygitalizacji danych. Wraz z rozwojem technologii skanowania przestrzennego możliwe jest również tworzenie cyfrowych kopii rzeczywistych przedmiotów przestrzennych. W artykule przedstawiono opracowanie skanera przestrzennego opartego na technologii triangulacji laserowej, wykorzystującej system wizyjny do przetwarzania obrazu.
Dodatkowo, przedstawiono cel, sposób oraz korzyści wynikające z przystosowania takiego skanera do pracy w Internecie Rzeczy. W pracy przedstawiono zarówno możliwości, jak i limitacje opracowanego skanera.
Zastosowana technologia skanowania pomimo swojej małej dokładności mogłaby okazać się przydatna w celach szybkiej wizualizacji, np. przy użyciu technologii wirtualnej lub rozszerzonej rzeczywistości, czy też szybkiego prototypowania zgodnie z metodologiami rapid prototyping lub design thinking.
