Robotics 2010

Without a doubt, robotics has made an incredible progress over the last decades. The vision of developing, designing and creating technical systems that help humans to achieve hard and complex tasks, has intelligently led to an incredible variety of solutions. There are barely technical fields that could exhibit more interdisciplinary interconnections like robotics. This fact is generated by highly complex challenges imposed by robotic systems, especially the requirement on intelligent and autonomous operation. This book tries to give an insight into the evolutionary process that takes place in robotics. It provides articles covering a wide range of this exciting area. The progress of technical challenges and concepts may illuminate the relationship between developments that seem to be completely different at first sight. The robotics remains an exciting scientific and engineering field. The community looks optimistically ahead and also looks forward for the future challenges and new development

Modeling and sliding-mode control of flexible-link robotic structures for vibration suppression

In many applications, the use of slender and light flexible structures has increased due to the requirement of more energetically efficient structures. This kind of structures is easily prone to vibrate due to external forces or due to forces generated in the inner structure during the movement. One objective of this work is to generate models of flexible-link structures: cantilever beam, one flexible-link robot and two flexible-link robot; which include rotational actuators, piezoelectric actuators, and different kinds of sensors (acceleration and deformation). The models are obtained under a classical mechanics approach of Lagrange Euler energy balance; the assumed mode method is used to approximate the flexibility of the elastic components. In the model formulation, new rotation angles are introduced in the distal joints and the joint inertia is separated according to this new kinematic consideration. Some parts of the resulting model involving integral terms are calculated using symbolic programming software; whereas other parts are implemented and calculated dynamically during simulation. The resulting models are programmed in Matlab/Simulink subjected to a novel verification methodology and then validated experimentally in a platform constructed for the implementation. The second objective is to develop, from simplified models of the flexible-link structures, robust controllers for joint tracking and active vibration suppression. Therefore, robust control is used with two basic purposes: to face the model uncertainties due to the discrepancies between the models and real systems and to suppress the vibration of the flexible-link structures. Three control strategies are proposed: Dual loop control approach, decentralized and centralized Lyapunov model-based sliding mode control approach. The values required for the implementation of the controller are obtained from the formulated models. The controllers were implemented in a dSPACE rapid prototyping control card and the experimental results show the effectiveness of the proposed control strategies in terms of joint tracking and vibration suppression.In viele Anwendungen, die Nutzung von schlanken und leichten Strukturen ist wegen Energieanforderungen gestiegen. Solche Strukturen sind anfällig für Schwingung wegen äußere Kräfte oder innere erzeugen Kräfte während der Bewegung. Ein Ziel dieser Arbeit handelt sich um die Erzeugung von verschiedener flexiblen-Glied Strukturen z.B. Kragarm, ein und zwei flexibel-Glied Roboter. Die Strukturen enthalten: rotatotische Aktoren, piezoelektrische Aktoren und verschiedene Sensoren (Beschleunigung und Dehnung). Die Modelle werden im Rahmen klassisches Ansatz von Lagrange Euler Energiebilanz entwickelt; die Angenommene Mode Methode (Assumed Mode Method) wird verwendet, um die Flexibilität der elastischen Komponenten zu approximieren. In der Modellformulierung werden neue Rotationswinkel in die distalen Gelenke eingeführt und die gemeinsame Trägheit gemäß dieser neuen kinematischen Betrachtung getrennt. Einige Elemente des resultierenden Modells integrale Begriffe beinhalten, werden mit symbolischen Programmiersoftware berechnet; während andere Teile umgesetzt und dynamisch aus der Simulation berechnet. Die resultierenden Modelle werden in Matlab/Simulink programmiert, sie werden unter eine neuartige Methodologie verifiziert unterworfen und dann validiert in experimentell in einem Prüfstand. Das zweite Ziel ist von vereinfachten Modellen robuste Controller für die Gelenkablaufverfolgung und aktive Schwingungsunterdrückung zu entwickeln. Daher ist eine robuste Regelung mit zwei grundlegende Zwecke verwendet: die Modellunsicherheiten zu berücksichtigen aufgrund der Unterschiede zwischen den Modellen und realen Systemen und die Schwingung der flexiblen Strukturen zu unterdrücken. Drei Kontrollstrategien werden vorgeschlagen: Dual Regel Ansatz, dezentrale und zentrale Lyapunov modellbasierten Sliding Mode Control Ansätze. Die erforderlichen Werte für die Ausführung der Steuerung sind aus den formulierten Modellen erhalten. Die Regler wurden in einer dSPACE Rapid-Prototyping-Steuerkarte implementiert. Die experimentellen Ergebnisse zeigen die Wirksamkeit der vorgeschlagenen Kontrollstrategien in Bezug auf die Gelenkablaufverfolgung und Schwingungsunterdrückung

Design and Control of an Articulated Robotic Arm Using Visual Inspection for Replacement Activities

Design of robotic systems and their control for inspection and maintenance tasks is highly complex activity involving coordination of various sub-systems. In application like inspections in fusion reactor vessels and deep-mining works, a regular off-line maintenance is necessary in certain locations. Due to the hostile environments inside, robotic systems are to be deployed for such internal observations. In this regard, current work focuses on the methodology for maintenance of the first wall blanket modules in a fusion reactor vessel using a manipulator system. A design is proposed for wall tile inspections in an ideal environment in which vacuum and temperature conditions are not accounted and wall surface curvature is not accounted initially. The entire design has four important modules: (i) mathematical modelling (ii) control system design (iii) machine vision and image processing, (iv) hardware development and testing. A five- axis articulated manipulator equipped with a vision camera in eye-to-hand configuration is designed for performing the pick and place operations of the defected tiles in a systematic manner. Kinematic and dynamics analysis of the system are first carried-out and a scaled prototype is fabricated for testing various operating issues. Forward kinematics of manipulator allows in estimation of robot workspace and in knowing the singular regions during operation, while the inverse kinematics of the manipulator would be needed for real time manipulator control task. Dynamics of manipulator is required for design of model-based controllers. Interactive programs are developed in Matlab for kinematics and dynamics and three-dimensional manipulator assembly configuration is modelled in SolidWorks software. Motion analysis is conducted in ADAMS software in order to compare the results obtained from the classical kinematics. Two types of model-based control schemes (namely Computed Torque Control and Proportional Derivative-Sliding Mode Control approach) with and without external disturbances are implemented to study trajectory tracking performance of the arm with different input trajectories. A disturbance observer model is employed in minimizing the tracking errors during the action of external disturbances such as joint friction and payload. In order to experimentally understand the inspection and replacement activities, a test set-up is developed using vision camera and microcontroller platform to guide the robot joint servos so as to perform defected object replacement activity. Presence of crack and the coordinate of the region are indicated with the use of image-processing operations. Using a high resolution Basler camera mounted at fixed distance from the tile surface, the surface images are acquired and image processing module identifies the crack details using edge detection algorithms. Necessary motion of the end-effector will be provided based on the pose calculations using coordinate transformations. Both visual inspection and joint guidance are combined in a single application and the results are presented with a test case of tile replacement activity. The results are presented sequentially using a test surface with uniform rectangular tiles

Performance limits and robustness issues in the control of flexible link manipulators

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1992.Includes bibliographical references (leaves 179-186).by Carlos Eduardo Padilla Santos.Ph.D