Cable robots or wire driven robots possess many advantages that makes them very well suited to be used as haptic interfaces. They exhibit very low inertia and very low friction because of their very light mechanical structure. The use of cables, however, leads to an under-constrained system which shows complex properties.The main drawback is the difficulty to estimate the useful workspace, and the maximum tension in the cables, as the relation between the maximum force at the tip of the interface and the maximum tension in the cables can not be easily established. In this paper we present a method to calculate these tensions in a given workspace and to estimate what we have called "the tension capable workspace" for a 3 cables 2 d.o.f (degree of freedom) planar haptic interface and for a 4 cables 2 d.o.f. one.
Reactor pressure vessel nozzle inner radius (NIR) areas are identified as a specific target for ultrasound examination (UT) by many regulatory codes. This region represents a particularly challenging geometry to examine. Typically the examination is performed from inside the vessel with at least the upper internals removed. Normally the inspection is on the critical path so minimizing the schedule and vessel occupation time is important to the utilities outage planning and ultimate financial performance. Although some inspection vendors have traditional qualifications for this NIR examination under various codes, this paper addresses several advanced techniques have been developed to minimize the critical path inspection time. Technology advancements include: • Stereo-vision with laser reference for precise VT sizing of any observed indication • A Small 5 degree-of-freedom arm to precisely track a transducer set along the inner-radius surface for immersion ultrasonic examination • A simple nozzle-only tool with a passive mechanism to track the nozzle inner-radius surface for contact ultrasonic examination • Advanced software (3-D iMaV) coupled with a 5-axis robot to analyze and control transducer placements and coverage from the nozzle and shell outside (OD) The net result is a more efficient examination with shorter schedules and lower overall outage costs.
Force platforms are the basic equipment to measure ground reaction forces and moments in biomechanical studies. So, accurate in situ calibration of force platforms is critical for ensuring the accuracy and precision of the results of experimental studies. Although there are different avaliable approaches for in situ calibration, most of the existing methods do not use realistic and repeteable force patterns to calibrate platforms. In this paper, a new technique based on the use of a 3PRS parallel robot for applying a predefined dynamical load is proposed, where force patterns can be reproduced in a similar way as the used during actual experimental measures. This robot can be programmed to apply force patterns simulating the conditions of human gait, running or jumping. Calibration is performed by comparing the forces measured by the platform and the ones measured by a calibrated load cell. A new algorithm was developed for correcting the sensitivity coefficients, including an estimation of errors in the orientation of the load cell. This method has been validated by means of an specific experiment.
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