TREBALL FI DE GRAU Grau en Enginyeria Mecànica MECHANICAL DESIGN OF A PHOTOGRAMMETRY IMAGING PLATFORM FOR PROTOTYPE MESHING Volume I (of III) Report Author: Carlos Gómez Gaibar Director: Pedro Ortiz Morón Call: June 2017 Mechanical design and manufacturing of a photogrammetry imaging platform for prototype meshing TABLE OF CONTENTS 1. OBJECTIVE, BACKGROUND AND MOTIVATION .......................................................................................... 1 2. PHOTOGRAPHY AND PHOTOGRAMMETRY: A BRIEF DESCRIPTION .......................................................... 2 2.1. Photography ....................................................................................................................................... 2 2.2. Photogrammetry ................................................................................................................................ 2 3. WORKING PRINCIPLES AND APPLICATIONS OF PHOTOGRAMMETRY ....................................................... 4 4. PATH TOWARDS THE CHOICE OF A SPECIFIC APPROACH .......................................................................... 6 4.1. Laser reconstruction and Surface from Motion (SFM) ....................................................................... 6 4.1.1. The use of laser in 3-D reconstruction operations ..................................................................... 6 4.1.2. Direct, realistic results ................................................................................................................ 6 4.2. Turntable vs orbiting camera ............................................................................................................. 6 4.2.1. Shadow casting issues ................................................................................................................ 7 4.2.2. Need for a static scene ............................................................................................................... 7 5. PROBLEM SOLVING AND IMPLEMENTED SOLUTIONS ............................................................................... 9 5.1. Design restrictions and guidelines ...................................................................................................... 9 6. COMMERCIAL ELECTRONICS ....................................................................................................................11 6.1. ACER emachines EM355 Netbook ....................................................................................................11 6.2. Raspberry Pi Model B .......................................................................................................................11 6.3. Logitech QuickCam Pro 9000 webcam .............................................................................................12 6.4. Stepper motor ..................................................................................................................................14 6.5. ULN2803 Stepper controller .............................................................................................................16 6.6. Raspberry Pi GPIO cobbler breakout board .....................................................................................17 6.7. Wiring diagram .................................................................................................................................20 7. INTRODUCTION TO STEPPER MOTORS ....................................................................................................21 I Report 7.1. Stepper motors .................................................................................................................................21 7.2. Advantages of stepper motors .........................................................................................................21 7.3. Limitations of stepper motors ..........................................................................................................22 7.4. Step Count ........................................................................................................................................23 7.5. Gearing .............................................................................................................................................23 7.6. Coils and Phases ...............................................................................................................................24 7.7. 5-Wire motor ....................................................................................................................................25 7.8. 6-Wire Motor ....................................................................................................................................25 7.9. 8-Wire Motor ....................................................................................................................................26 8. COMMERCIAL MATERIALS .......................................................................................................................27 8.1. Vertical support (617CV00) and horizontal beam (617CH00) ..........................................................27 8.1.1. T-nuts for slotted 20x20 square aluminum extrusion profile ..................................................27 8.1.2. Aluminum L-plates (617CU00)..................................................................................................28 8.2. Mechanical union elements .............................................................................................................29 8.3. Low friction idle shaft subjection (617CR00)....................................................................................30 8.3.1. Considerations regarding low friction solutions ......................................................................30 8.3.2. Load absorption and spacing ....................................................................................................31 8.4. Timing pulleys (617CP00) .................................................................................................................33 8.5. Timing belt (617CP0A/B/X) ...............................................................................................................34 8.5.1. Option 1: Open-ended timing belt (617CP0X)..........................................................................35 8.5.2. Option 2: Closed loop timing belts (617CP0A/B) .....................................................................36 9. MANUFACTURED PARTS ..........................................................................................................................38 9.1. Bearing support (617MH01) .............................................................................................................38 9.2. Stepper support (617MH00) ............................................................................................................39 9.3. Idle shaft (617MR00) ........................................................................................................................41 9.4. Base clamp (617MV00) .....................................................................................................................42 II Mechanical design and manufacturing of a photogrammetry imaging platform for prototype meshing 9.5. Base (617MB00) ...............................................................................................................................43 9.6. Webcam support (617MR02) and Fixing cap (617MR03) ................................................................43 9.7. Rotating beam (617MR01) ...............................................................................................................44 9.8. Safety jail (617MS00) ........................................................................................................................45 10. WEBCAM DETECTION, SOFTWARE NEEDED AND SETUP ........................................................................47 10.1. Logitech QuickCam Pro 9000 compatibility with Raspberry Pi ....................................................47 10.2. List and description of software packages to install ....................................................................47 11. STEPPER MOTION CONTROL VIA USER-FRIENDLY, EDITABLE CODE .......................................................50 11.1. Control interface designs ..............................................................................................................50 11.2. Python modules ............................................................................................................................51 11.2.1. Tkinter and PyGTK ....................................................................................................................51 11.2.2. RPi.GPIO module import ..........................................................................................................51 11.3. System software calls from Python ..............................................................................................52 12. NETWORK AND INTERFACE SETUP ..........................................................................................................53 12.1. Controlling the Raspberry Pi through a tactile display .................................................................53 12.2. Connecting the Raspberry Pi directly to a computer ...................................................................53 12.2.1. Establishing a static IP for the Raspberry Pi .............................................................................54