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26 CHAPTER 4. METHOD • Components are the building blocks of each system. They send data via ports to other components. • TF Data is the data that contains the information on how to perform the transformations between the frames. One data element always contains the transformation between two tf frames. • Joint Data is for example the angle of a revolute joint or the position in case of a prismatic joint. Out of this and some additional data it is possible to determine the TF Data. For more information on joints and how this conversion works, see Section 3.1. • Normal Data is all other data that components exchange. In relation to transformations this is mostly sensor data. • Ports are the connection points between components and used to exchange data. They can be used in synchronous (request/reply) and asynchronous (publish/subscribe) manner. Component robot base TF Data Joint Data Normal Data synchronous communication asynchronous communication Comment some text in the comment Figure 4.7: The elements to represent different systems. The graphical expressions of these elements can be found in Figure 4.7. In this figure also an additional element named Comment is introduced. This element does not describe any element of the system, but it allows to add some additional information to a specific element. Out of these elements it is possible to construct any kind of system. This is done by connecting the ports of different components. Over these links messages containing the specific data are exchanged. A list of how the elements can be combined to form a system and what the corresponding expression means is presented in Figure 4.8. As it can be seen from this figure, it is possible to get data from a component in different ways. Components can convert Joint Data to TF Data with some conversion rules described in the component itself or loaded from a file. Further it is possible to build chains of components, where each component can add the message it has received from another component to the outgoing message.
4.3. ABSTRACT SYSTEM DESCRIPTION 27 comp_1 Component that controls one or more joints. comp_1 Component that generates normal data. This component for example can control a sensor. comp_1 comp_2 Joint Data is send from one component to another component over an asynchronous channel. comp_1 comp_2 TF Data is converted from Joint Data and a convertion rule in comp_1. Then it is send to another component over an asynchronous channel. comp_1 comp_2 comp_2 requests TF Data from comp_1 over a synchronous channel. comp_1 comp_2 comp_1 sends TF Data to comp_2. This component then adds the TF Data to its own data and sends it to comp_3. comp_3 Figure 4.8: How the different elements can be combined to form a system. The shown elements provide a method to describe a component-based system on an abstract level. However like introduced in Section 1.2 there also exists a tree representation of the coordinate frames on the robot. This tf tree shows how the frames are connected in a parent/child relationship. To link these two representations corresponding names can be assigned to tf frames and TF Data. How this looks like is shown in Figure 4.9. The names can either be written into the TF Data element or next to it. This labeling allows to see which TF Data contains the information for which tf frame. Further the components providing the data for a tf frame can be determined.
Page 1: Managing Coordinate Frame Transform
Page 5: Abstract Autonomous mobile robots i
Page 9 and 10: Contents 1 Introduction 1 1.1 Intro
Page 11 and 12: Chapter 1 Introduction 1.1 Introduc
Page 13 and 14: 1.2. OVERVIEW OF THE TRANSFORMATION
Page 15 and 16: Chapter 2 Related Work This chapter
Page 17 and 18: 2.2. COMPONENT-BASED ROBOTIC MIDDLE
Page 19 and 20: Chapter 3 Fundamentals In this chap
Page 21 and 22: 3.2. TRANSFORMATIONS 11 This transl
Page 23 and 24: 3.2. TRANSFORMATIONS 13 the popular
Page 25 and 26: 3.3. TIME SYNCHRONIZATION 15 3.3 Ti
Page 27 and 28: 3.3. TIME SYNCHRONIZATION 17 Master
Page 29 and 30: Chapter 4 Method At the beginning o
Page 31 and 32: 4.1. USE CASES 21 (a) Tilting plana
Page 33 and 34: 4.2. ANALYSIS OF REQUIREMENTS 23 To
Page 35: 4.3. ABSTRACT SYSTEM DESCRIPTION 25
Page 39 and 40: 4.4. QUALITY OF TRANSFORMATIONS 29
Page 45 and 46: 4.5. CLIENT/SERVER SEPARATION 35 va
Page 47 and 48: 4.5. CLIENT/SERVER SEPARATION 37 Da
Page 49 and 50: 4.6. CONSTRUCTING TF SYSTEMS 39 val
Page 51 and 52: 4.6. CONSTRUCTING TF SYSTEMS 41 bas
Page 53 and 54: 4.6. CONSTRUCTING TF SYSTEMS 43 1.8
Page 55 and 56: 4.6. CONSTRUCTING TF SYSTEMS 45 •
Page 57 and 58: tilt_frame sensor_frame 4.6. CONSTR
Page 59 and 60: Chapter 5 Results To better examine
Page 61 and 62: 5.1. SIMULATION 51 • the torso_fr
Page 63 and 64: 5.2. DISCUSSION OF THE RESULTS 53 l
Page 65 and 66: Chapter 6 Summary and Future Work 6
Page 67 and 68: List of Figures 1.1 Three state-of-
Page 69 and 70: List of Tables 3.1 Comparison of ma
Page 71 and 72: Bibliography [1] N. Ando et al. “

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