99 research outputs found

    Calibration of Gantry-Tau Robot and Prototyping of Extruder for 3D Printing

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    This master thesis is about improving the accuracy of a Gantry-Tau robot by identifying the key parameters in the kinematics of the robot. This is done using a vision system and then estimating the parameters by minimizing the closure equation of the kinematics. The robot with improved control is then used for additive manufacturing. Furthermore, a prototype for a large plastic printer head is presented

    Error Modeling and Accuracy of Parallel Industrial Robots

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    Stiffness modeling of robotic manipulator with gravity compensator

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    The paper focuses on the stiffness modeling of robotic manipulators with gravity compensators. The main attention is paid to the development of the stiffness model of a spring-based compensator located between sequential links of a serial structure. The derived model allows us to describe the compensator as an equivalent non-linear virtual spring integrated in the corresponding actuated joint. The obtained results have been efficiently applied to the stiffness modeling of a heavy industrial robot of the Kuka family

    Modeling and Balancing of Spherical Pendulum using a Parallel Kinematic Manipulator

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    The balancing act of an inverted pendulum with a robotic manipulator is a classical benchmark for testing modern control strategies in conjunction with fast sensor-guided movements. From the control design perspective, it presents a challenging and difficult problem as the system is open-loop unstable and includes nonlinear effects in the actuators, such as friction, backlash, and elasticity. In addition, the necessity of a sensor system that can measure the inclination angles of the pendulum contributes to the complexity of the balancing problem. The pendulum is projected onto the xz and yz planes of the inertial coordinate system. These projections are controlled by a state-space controller. A specially developed sensor system allows the contactless measurement of the inclination angles of the pendulum. This system consists of a small magnet, placed at the bottom of the pendulum and Hall-effect sensors placed below the end effector

    Position Accuracy with Dual Motor Control for a Gantry-Tau Robot

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    Very high accuracy and a very high repeatability, both in the range of a few microns, is very hard to achieve with today's common serial robots. An approach utilizing the Gantry-Tau principle is used in my theses together with a dual motor control to eliminate the troublesome backlash rising from the mechanical limitations. Both hardware and software will be regarded and with an antagonistic control structure I will show that the accuracy of a few micron really can be achieved. To evaluate the regulators parameter and test the control strategies a command prompt was made for the serial communication and a graphical interface was also made for the Ethernet communication

    Control of a Gantry-Tau Structure

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    Todays, industrial robots don't correspond to the needs of the Small and Medium sized Enterprises (SME). Indeed, industrial robots are in many cases too hard to program or too expensive to be used by this kind of enterprises. In order to respond to this need, a European project was created, regrouping five major European robot manufacturers and five leading research institute and universities, named SMErobot. Its main task consists of exploiting the potentials of industrial robots, because they constitute the most flexible existing automation technology. This project set to create a radically new type of robot system, a whole family of SME-suitable robots. A new structure of parallel robots was hence designed to respond to these needs, named a Gantry-Tau structure. A prototype of this parallel kinematic structure was created in the Lund Robotics Laboratory, to test its characteristics and the different control methods that can be applied to it. Moreover, it can be use as a demonstration tool. The thesis project concerns the velocity and position control of the small-scale linear actuators which are used for a prototype of the Gantry-Tau robot

    Kinematic calibration of Orthoglide-type mechanisms from observation of parallel leg motions

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    The paper proposes a new calibration method for parallel manipulators that allows efficient identification of the joint offsets using observations of the manipulator leg parallelism with respect to the base surface. The method employs a simple and low-cost measuring system, which evaluates deviation of the leg location during motions that are assumed to preserve the leg parallelism for the nominal values of the manipulator parameters. Using the measured deviations, the developed algorithm estimates the joint offsets that are treated as the most essential parameters to be identified. The validity of the proposed calibration method and efficiency of the developed numerical algorithms are confirmed by experimental results. The sensitivity of the measurement methods and the calibration accuracy are also studied

    Activity Report: Automatic Control 2012

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    CAD-based approach for identification of elasto-static parameters of robotic manipulators

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    The paper presents an approach for the identification of elasto-static parameters of a robotic manipulator using the virtual experiments in a CAD environment. It is based on the numerical processing of the data extracted from the finite element analysis results, which are obtained for isolated manipulator links. This approach allows to obtain the desired stiffness matrices taking into account the complex shape of the links, couplings between rotational/translational deflections and particularities of the joints connecting adjacent links. These matrices are integral parts of the manipulator lumped stiffness model that are widely used in robotics due to its high computational efficiency. To improve the identification accuracy, recommendations for optimal settings of the virtual experiments are given, as well as relevant statistical processing techniques are proposed. Efficiency of the developed approach is confirmed by a simulation study that shows that the accuracy in evaluating the stiffness matrix elements is about 0.1%.Comment: arXiv admin note: substantial text overlap with arXiv:0909.146

    Design of a Cable-Driven Manipulator for Large-Scale Additive Manufacturing

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    Additive manufacturing of concrete is a growing field of research, yet current motion platforms do not offer viable routes towards large scale deployable systems. This thesis presents the design and analysis of a novel cable-driven robot for use in large scale additive manufacturing. The system developed, termed SkyBAAM, is designed to be easily deployable to a construction site for on-site additive manufacturing of buildings and other large structures. The design philosophy behind this system is presented. Analysis of this system first explores the kinematics, and stiffness as a function of cable tension. Analysis of the workspace and singularities is also performed, and scaling laws for the system are examined. A prototype system that was built at ORNL is presented, and data from this system shows is suitability for large-scale printing. In order to scale this out to full-size deployment there are, however, challenges associated with scaling and workspace shape that are identified as targets for future research. However, the success of this system demonstrates the feasibility of cable-driven robots for large, deployable additive manufacturing systems
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