1,721,009 research outputs found
Handcycling Assessment Through a Bench Simulator: Preliminary Analysis of IMUs Positioning on an Artificial Upper Limb Mechanism (AULM)
No full textStudy of neural-kinematics architectures for model-less calibration of industrial robots
No full textModeless industrial robot calibration plays an impor-tant role in the increasing employment of robots in industry. This approach allows to develop a proce-dure able to compensate the pose errors without complex parametric model. The paper presents a study aimed at comparing neural-kinematic (N-K) architectures for a modeless non-parametric robotic cali-bration. A multilayer perceptron feed-forward neural network, trained in a supervised manner with the back-propagation learning technique, is coupled in different modes with the ideal kinematic model of the robot. A comparative performance analysis of different neural-kinematic architectures was executed on a two degrees of freedom SCARA manipulator, for di-rect and inverse kinematics. Afterward the optimal schemes have been identified and further tested on a three degrees of freedom full SCARA robot and on a Stewart platform. The analysis on simulated data shows that the accuracy of the robot pose can be im-proved by an order of magnitude after compensation
Real-time trajectory scaling for robot manipulators
Full text linkRecent developments in industrial robotics use real-time trajectory modification to improve throughput and safety in automatic processes. Online trajectory scaling is often used to this purpose. In this paper, we propose a feedback trajectory scaling approach that is able to recover from the delay introduced by the speed modulation and improves the path-following performance thanks to an additional inner control loop. Simulation and experimental results on an industrial 6-degree-of-freedom robot show the effectiveness of the proposed approach compared to standard algorithms
Performance Indices for the Evaluation of Microgrippers Precision in Grasping and Releasing Phases
No full textIn manipulating and assembly tasks, the gripper plays a fundamental role. Tasks at the microscale are particularly challenging due to the possible effect of unwanted stiction. Many different grasping tools (generally called microgrippers) have been developed and are described in literature. The differences rely on size, shape, exchanged forces with the manipulated parts and working principle depending on the application field. Despite the large number of research and industrial cases, each author has developed different and not comparable procedures and indices to assess the device grasping and releasing performance. Therefore, the paper proposes a formalization of methods and indices for the evaluation of the performance of a generic contact microgripper in terms of precision in grasping and releasing and successful rate. This review could be helpful to support the design or the choice of the most suitable gripper according to the properties of the components to be manipulated, the task requirements and the system constraints (i.e., according to the application requirements). The validity of the proposed methodologies and indices is confirmed by theory and experimental data analysis
Kinematics Analysis of a Class of Spherical PKMs by Projective Angles
Full text linkThis paper presents the kinematics analysis of a class of spherical PKMs Parallel Kinematics Machines exploiting a novel approach. The analysis takes advantage of the properties of the projective angles, which are a set of angular conventions of which their properties have only recently been presented. Direct, inverse kinematics and singular configurations are discussed. The analysis, which results in the solution of easy equations, is developed at position, velocity and acceleration level
Evaluation and modeling of the friction in robotic joints considering thermal effects
No full textThe paper presents a second-order friction model for the joints of industrial robot manipulators that takes into account temperature effects. A solution based on a polynomial description of the friction is proposed. The theoretical analysis and the experimental measurements have shown that friction decreases with increasing temperature, which in turn depends on the working cycle of the manipulator. The mathematical model here proposed allows to foresee the friction variation during extensive working cycles and it does not require the use of a transducer for the measurement of the joint internal temperature; therefore it is well suitable for low-cost industrial applications, to improve the control performance or to predict the energy consumption. Experimental tests performed on a commercial six degrees-of-freedom (6 DOF) manipulator show that the model is effective in estimating the joint temperature and the friction torque during the robot operations
A practical algorithm for smooth interpolation between different angular positions
No full textThis paper proposes a new methodology for the interpolation of a given set of 3D rotation poses that have to be reached in successive times by preserving continuity in orientation, angular velocity and angular acceleration. The discussed algorithm ensures the generation of smooth angular trajectories without singularities. The distinctive features of the proposed approach are the straightforward formulation, the reduced computational burden and the lack of iterative procedures. The presented methodology has applications in the generation of spatial motion of mechanical systems (e.g. robotics, flying devices) or in 3D computer graphics. After a theoretical introduction, the proposed algorithm is compared with other methods available in literature and some possible applications are presented
A patient with a 12-year history characterized by four non-AIDS-related malignancies, occurring before and after the disclosure of HIV infection
No full textA patient with a 12-year history characterized by four non-AIDS-related malignancies, occurring before and after the disclosure of HIV infectio
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