Current Issue : January - March Volume : 2013 Issue Number : 1 Articles : 5 Articles
Two different visual servoing controls have been developed to govern a translating parallel manipulator with an eye-in-hand\r\nconfiguration, That is, a position-based and an image-based controller. The robot must be able to reach and grasp a target\r\nrandomly positioned in the workspace; the control must be adaptive to compensate motions of the target in the 3D space. The\r\ntrajectory planning strategy ensures the continuity of the velocity vector for both PBVS and IBVS controls, whereas a replanning\r\nevent is needed. A comparison between the two approaches is given in terms of accuracy, fastness, and stability in relation to the\r\nrobot peculiar characteristics....
The objective is to show that on-board mission replanning for an AUV sensor coverage mission, based on available energy,\r\nenhances mission success. Autonomous underwater vehicles (AUVs) are tasked to increasingly long deployments, consequently\r\nenergy management issues are timely and relevant. Energy shortages can occur if the AUV unexpectedly travels against stronger\r\ncurrents, is not trimmed for the local water salinity has to get back on course, and so forth. An on-board knowledge-based agent,\r\nbased on a genetic algorithm, was designed and validated to replan a near-optimal AUV survey mission. It considers the measured\r\nAUV energy consumption, attitudes, speed over ground, and known response to proposed missions through on-line dynamics and\r\ncontrol predictions. For the case studied, the replanned mission improves the survey area coverage by a factor of 2 for an energy\r\nbudget, that is, a factor of 2 less than planned. The contribution is a novel on-board cognitive capability in the form of an agent\r\nthat monitors the energy and intelligently replans missions based on energy considerations with evolutionary methods....
The geometric parameters of a space robot change with the terrible temperature change in orbit, which will cause the end-effector\r\npose (position and orientation) error of a space robot, and so weakens its operability.With this in consideration, a new geometric\r\nparameter identification method is presented based on a laser-ranger attached to the end-effector. Then, independence of the\r\ngeometric parameters is analyzed, and their identification equations are derived. With the derived identification Jacobian matrix,\r\nthe optimal identification configurations are chosen according to the observability index O3. Subsequently, through simulation\r\nthe geometric parameter identification of a 6-DOF space robot is implemented for these identification configurations, and the\r\nidentified parameters are verified in a set of independent reference configurations. The result shows that in spite of distance\r\nmeasurement alone, pose accuracy of the space robot still has a greater improvement, so the identification method is practical\r\nand valid....
A biologically inspired robot in the form of fish (mackerel) model using rubber (as the biomimetic material) for its hyperredundant\r\njoint is presented in this paper. Computerized simulation of the most critical part of the model (the peduncle) shows\r\nthat the rubber joints will be able to take up the stress that will be created. Furthermore, the frequency-induced softening of the\r\nrubber used was found to be critical if the joints are going to oscillate at frequency above 25 Hz. The robotic fish was able to attain a\r\nspeed of 0.985 m/s while the tail beats at a maximum of 1.7 Hz when tested inside water. Furthermore, a minimum turning radius\r\nof 0.8m (approximately 2 times the fish body length) was achieved....
This paper proposes a kinematic model and an inertial localization system architecture for a riser inspecting robot. The robot\r\nscrolls outside the catenary riser, used for underwater petroleum exploration, and is designed to perform several nondestructive\r\ntests. It can also be used to reconstruct the riser profile. Here, a realistic simulation model of robot kinematics and its environment\r\nis proposed, using different sources of data: oil platform characteristics, riser static configuration, sea currents and waves, vortexinduced\r\nvibrations, and instrumentation model. A dynamic finite element model of the riser generates a nominal riser profile.\r\nWhen the robot kinematic model virtually scrolls the simulated riser profile, a robot kinematic pattern is calculated. This pattern\r\nfeeds error models of a strapdown inertial measurement unit (IMU) and of a depth sensor. A Kalman filter fuses the simulated\r\naccelerometers data with simulated external measurements. Along the riser vertical part, the estimated localization error between\r\nthe simulated nominal and Kalman filter reconstructed robot paths was about 2m. When the robot model approaches the seabed\r\nit assumes a more horizontal trajectory and the localization error increases significantly....
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