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8 CHAPTER 2. RELATED WORK the transformation parameters. As a result the transformed data is returned. The implemented utility component for the iSpace is tailored for the use in the iSpace and thus can not be reused in other applications. This proprietary solution shows the need for a general solution by the framework. 2.2.4 SMARTSOFT SMARTSOFT was first described in [27] and later in more detail in [28]. It is a component-based framework with seven Communication Patterns that enable easy communication between components. Each pattern defines the communication mode, provides predefined access methods and hides all communication and synchronization issues. Communication Objects define the data which is exchanged between components and the combination of a Communication Pattern and a Communication Object build a Service that the component offers. Further each component defines a state automaton which represents the life-cycle of the component. It also allows to switch the component from external into a different state, for example activate/deactivate a camera. SMARTSOFT does not come with a special library for coordinate transformations, but the available Communication Objects on SourceForge 1 have special access methods which allow to transform the data to basic coordinate frames like base frame or world frame. Thus a basic support is given but if special transformations are needed the developer has to do them by himself. The way transformations are supported in SMARTSOFT makes it really easy for the developer to use them if he is only interested in basic transformations. However the embedding of TF Data into other messages like a laser scan message introduces problems which does not occur if the data is separated. For example the implementation of Communication Objects gets more difficult, because all the logic has to be added to the Communication Object. Further also the components get more complex. For example a component for a laser ranger, which normally just publishes the laser data, now also have to put the TF Data into the laser scan message. This TF Data must be acquired from another component. Thus additional ports and connections to other components have to be added which increases the overall system complexity. SMARTSOFT has inspired this work by the clear separation of components by Communication Objects. Further together with ROS it showed the need of an abstract method to describe different systems, to allow a comparison of them. 1 http://smart-robotics.sourceforge.net
Chapter 3 Fundamentals In this chapter fundamentals, which help to understand the content of the further chapters, are presented. After looking at the different types of joints, the term Transformation is introduced which is a key element of the his work. Later the problem of Time Synchronization and how clocks can be synchronized are described. This is interesting, because time plays an important role in concurrent and distributed systems. 3.1 Different Types of Joints A robot is built out of joints and links whereas the links are connected through joints. To describe a robot the Unified Robot Description Format (URDF) [32] can be used. It allows to describe the robot with all its kinematics and dynamics in a XML format. A lot of robots like the PR2, the Care-O-bot or the Nao are modeled in URDF. For this thesis the different joint types which are supported by URDF are interesting, because they have proven to allow a description of arbitrary robot setups. If the URDF description should be used for building the tf tree of a robot, a mapping of joint values to coordinate frames must be performed. Figure 3.1 shows two links which are connected by Joint axis in joint frame Child frame = Joint frame Joint Child Joint origin Parent Parent frame Figure 3.1: Relationship between frames and joints. 9
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: 2.2. COMPONENT-BASED ROBOTIC MIDDLE
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 and 36: 4.3. ABSTRACT SYSTEM DESCRIPTION 25
Page 37 and 38: 4.3. ABSTRACT SYSTEM DESCRIPTION 27
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-
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List of Tables 3.1 Comparison of ma
Page 71 and 72:
Bibliography [1] N. Ando et al. “
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