Master Thesis - Hochschule Bonn-Rhein-Sieg

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3. Hard- and software Master Thesis Björn Ostermann page 32 of 126 of the robot. Afterwards it is continually needed to act as a hold to run button, while the robot is remotely controlled by the PC. CAN busses are also used to connect the PLC to the servo controllers and the Safety Controller, which is charged with monitoring the correct execution of the position commands, as well as other safety related features. PC Servocontroller TCP/IP (XML) CAN-Bus (A) Servocontroller Servocontroller CAN-Bus (B) Servocontroller Webserver Servocontroller PLC Servocontroller Safety Controller CAN-Bus Positon encoder signals motor power Control Panel Control Cabinet Figure 17: Control hierarchy from PC to robot – diagram created with the help of F. Som, REIS Robotics Robot If the safety controller detects an error in the execution of a command, it safely and redundantly cuts the power to the robot’s motors, causing the motor’s brakes to activate. Direct communication between the safety controller and the PC is not possible. Thus any errors in the communication of PC and webserver can not be recognized by the safety controller. In a later industrial implementation, the safety controller would have to be included in the process of object avoidance, as described in chapter 7.2.
4. Overall evading concept Master Thesis Björn Ostermann page 33 of 126 4 Overall evading concept In this chapter an overview of the developed concept for evading dynamic objects is presented. The overall task is the acquisition of data from the sensors, the calculation of a collision free path for the robot and its execution. This overview focuses on the interactions of the single components of the workplace and their interfaces. The different subprograms and algorithms themselves therefore are explained only briefly in this chapter. A detailed explanation of the internal mechanics of the single algorithms can be found in chapter 5. At this point, these detailed explanations are not necessary for the understanding of the overall concept, but rather disturbing to the fluency of reading. They are meant for the detailed study of the developed program. 4.1 Tasks hierarchy The task of this project is a safety system. Safety systems need to be able to operate in real time, e.g. their lowest possible response time must be at least as fast as the task demands. Therefore the execution time of the developed program needs to be as fast as possible. It has to be considered that image processing and path planning are tasks that require a relatively large amount of computational effort. Modern PCs are equipped with multicore CPUs that allow parallel processing of different tasks, if those tasks are separated in the executed program in different threads. To use this advantage, the developed PC-program has been divided into four separate tasks, organized in separate kernel threads. In the used PC, a dual core processor was installed. By separation of the program into different threads the operating system has the possibility of allocating the threads to different CPUs, to better balance the computational load. This optimizes the execution time and contributes to the real time ability of the program. The tasks are divided into the following threads: - Graphical User Interface (GUI) (chapter 4.2) - camera control (chapter 4.3) - path planning control (chapter 4.4) - robot control (chapter 4.5) The flow of the data, from the camera’s image acquisition to the robot’s PLC, is depicted in Figure 18.
Page 1 and 2: Master Thesis ”Industrial jointed
Page 3 and 4: Statutory Declaration Master Thesis
Page 5 and 6: Contents Master Thesis Björn Oster
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9. List of Figures Master Thesis Bj
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Master Thesis - Hochschule Bonn-Rhein-Sieg

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