1,721,054 research outputs found
Comparison of Under-Actuated and Fully Actuated Serial Robotic Arms: A Case Study
No full textUnder-actuated robots are very interesting in terms of cost and weight since they can result in a state-controllable system with a number of actuators lower than the number of joints. In this paper, a comparison between an under-actuated planar three-degrees-of-freedom (DOF) robot and a comparable fully actuated two-degrees-of-freedom robot is presented, mainly focusing on the performances in terms of trajectories, actuator torques, and vibrations. The under-actuated system is composed of two active rotational joints followed by a passive rotational joint equipped with a torsional spring. The fully actuated robot is inertial equivalent to the under-actuated manipulator: the last link is equal to the sum of the last two links of the under-actuated system. Due to the conditions on the inertia distribution and spring placement, in a simple point-to-point movement the last passive joint starts and ends in a zero-value configuration, so the three DOF robot is equivalent, in terms of initial and final configuration, to the two DOF fully actuated robot, thus they can be compared. Results show how while the fully actuated robot is better in terms of reliable trajectory and actuator torques, the under-actuated robot wins in flexibility and in vibrations at a given configuration
Optimizing Cycle Time of Industrial Robotic Tasks with Multiple Feasible Configurations at the Working Points
Full text linkIndustrial robot applications should be designed to allow the robot to provide the best performance for increasing throughput. In this regard, both trajectory and task order optimization are crucial, since they can heavily impact cycle time. Moreover, it is very common for a robotic application to be kinematically or functionally redundant so that multiple arm configurations may fulfill the same task at the working points. In this context, even if the working cycle is composed of a small number of points, the number of possible sequences can be very high, so that the robot programmer usually cannot evaluate them all to obtain the shortest possible cycle time. One of the most well-known problems used to define the optimal task order is the Travelling Salesman Problem (TSP), but in its original formulation, it does not allow to consider different robot configurations at the same working point. This paper aims at overcoming TSP limitations by adding some mathematical and conceptual constraints to the problem. With such improvements, TSP can be used successfully to optimize the cycle time of industrial robotic tasks where multiple configurations are allowed at the working points. Simulation and experimental results are presented to assess how cost (cycle time) and computational time are influenced by the proposed implementation
Optimization of a Rotary Part Feeder with Circular Blades
No full textPart feeding can be a source of inefficiencies in kitting operations: in common applications, hoppers are used to batch parts, but such hoppers require a double motion for each operation. In previous works, a rotating feeding device has been proven to be more efficient than hoppers, . This rotating device uses blades to compartmentalize parts, and such blades can be optimized to achieve specific design goals. In this paper circular blades are investigated due to their ease of manufacturing, and results show how this shape is suitable for the required design goals
Design and performance of an elbow assisting mechanism
Full text linkAn elbow assisting device is presented as based on a cable-driven parallel mechanism with design solutions that are improvements from a previous original design. The new mechanism, ideal for domestic use, both for therapies and exercises, is characterized by low-cost, portable, easy-to-use features that are evaluated through numerical simulations and experimental tests whose results are reported with discussions
Analytical Movement Optimization of Dual-Arm Planar Robots with Rotating Platform
Full text linkIn the last years some industrial robots have been realized with two robot arms connected to a single rotating platform. Such a redundant structure allows moving the platform to adjust each robot base for optimizing each arm movement. In this paper, a planar model of two 7-axis robots connected to a rotating platform is proposed, and a novel analytical optimization procedure, retrieved from a geometrical analysis, is presented
Design of the Drive Mechanism of a Rotating Feeding Device
Full text linkComponent batching can be a source of time waste in specific industrial applications, such as kitting. Kitting operations are usually performed by hoppers, but other devices can be used to optimize the process. In a previous work, a rotary device has been proved to be more efficient than hoppers; such a device allows the kitting and releasing of the components in a single rotatory movement, while traditional hoppers require at least two movements. In this paper, an improvement of such feeding device is proposed. The movement of the rotary device is driven by a four-bar linkage mechanism which is designed through functional synthesis. Thank to the four-bar linkage mechanism, the alternate motion of the rotary distributor is derived from the constant speed of the motor
Multi-physical Model of a Rainfall Energy Harvester - Sensitivity Analysis
No full textThe kinetic energy of raindrops is a renewable source of energy that can be scavenged by piezoelectric harvesters. Experimental tests have shown that a water layer covering the surface hit by the raindrops strongly enhances the energy transfer from the rain to the harvester. A mathematical model able to explain this phenomenon has been recently developed. This paper focuses on the ability of the model to cope with variations in the characteristics of the raindrop impact. Comparisons with experimental results are made
Lumped Parameters Robot Models to Study Impact Dynamics
Full text linkIn the field of collaborative robotics, safety standards are crucial. Collision prevention, in collaborative scenarios, requires a targeted examination of impact dynamics. This paper addresses collision challenges by introducing simplified lumped parameter models that are not widespread in the robotic field. The proposed method is simpler than traditional methods (Newton-Euler or Lagrange formulations), but maintains accuracy in the prediction of the dynamic quantities relevant to impacts (linear momentum and kinetic energy). The study chiefly deals with 2D robots, including the case of off-center centers of mass (CoM), but some hints about the modeling of 3D robots are given. MATLAB simulations and experimental tests with a robot confirm the validity of the proposed method
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