Robust Fastener Detection Based on Force and Vision Algorithms in Robotic (Un)Screwing Applications.

This article addresses how to tackle one of the most demanding tasks in manufacturing and industrial maintenance sectors: using robots with a novel and robust solution to detect the fastener and its rotation in (un)screwing tasks over parallel surfaces with respect to the tool. To this end, the vision system is based on an industrial camera with a dynamic exposure time, a tunable liquid crystal lens (TLCL), and active near-infrared reflectance (NIR) illumination. Its camera parameters, combined with a fixed value of working distance (WD) and variable or constant field of view (FOV), make it possible to work with a variety of fastener sizes under several lighting conditions. This development also uses a collaborative robot with an embedded force sensor to verify the success of the fastener localization in a real test. Robust algorithms based on segmentation neural networks (SNN) and vision were developed to find the center and rotation of the hexagon fastener in a flawless condition and worn, scratched, and rusty conditions. SNNs were tested using a graphics processing unit (GPU), central processing unit (CPU), and edge devices, such as Jetson Javier Nx (JJNX), Intel Neural Compute Stick 2 (INCS2), and M.2 Accelerator with Dual Edge TPU (DETPU), with optimization parameters, such as the unsigned integer (UINT) and float (FP), to understand their performance. A virtual program logic controller (PLC) was mounted on a personal computer (PC) as the main control to process the images and save the data. Moreover, a mathematical analysis based on the international standard organization (ISO) and patents of the manual socket wrench was performed to determine the maximum error allowed. In addition, the work was substantiated using exhaustive evaluation tests, validating the tolerance errors, robotic forces for successfully completed tasks, and algorithms implemented. As a result of this work, the translation tolerances increase with higher sizes of fasteners from 0.75 for M6 to 2.50 for M24; however, the rotation decreases with the size from 5.5° for M6 to 3.5° for M24. The proposed methodology is a robust solution to tackle outliers contours and fake vertices produced by distorted masks present in non-constant illumination; it can reach an average accuracy to detect the vertices of 99.86% and the center of 100%, also, the time consumed by the SNN and the proposed algorithms is 73.91 ms on an Intel Core I9 CPU. This work is an interesting contribution to industrial robotics and improves current applications.

Validation of a Hybrid Exoskeleton for Upper Limb Rehabilitation. A Preliminary Study.

Recovery of therapeutic or functional ambulatory capacity in patients with rotator cuff injury is a primary goal of rehabilitation. Wearable powered exoskeletons allow patients to perform repetitive practice with large movements to maximize recovery, even immediately after the acute event. The aim of this paper is to describe the usability, acceptability and acceptance of a hybrid exoskeleton for upper-limb passive rehabilitation using the System Usability Scale (SUS) questionnaire. This equipment, called ExoFlex, is defined as a hybrid exoskeleton since it is made up of rigid and soft components. The exoskeleton mechanical description is presented along with its control system and the way motion is structured in rehabilitation sessions. Seven patients (six women and one man) have participated in the evaluation of this equipment, which are in the range of 50 to 79 years old. Preliminary evidence of the acceptance and usability by both patients and clinicians are very promising, obtaining an average score of 80.71 in the SUS test, as well as good results in a questionnaire that evaluates the clinicians' perceived usability of ExoFlex.

Efficient Upper Limb Position Estimation Based on Angular Displacement Sensors for Wearable Devices.

Motion tracking techniques have been extensively studied in recent years. However, capturing movements of the upper limbs is a challenging task. This document presents the estimation of arm orientation and elbow and wrist position using wearable flexible sensors (WFSs). A study was developed to obtain the highest range of motion (ROM) of the shoulder with as few sensors as possible, and a method for estimating arm length and a calibration procedure was proposed. Performance was verified by comparing measurement of the shoulder joint angles obtained from commercial two-axis soft angular displacement sensors (sADS) from Bend Labs and from the ground truth system (GTS) OptiTrack. The global root-mean-square error (RMSE) for the shoulder angle is 2.93 degrees and 37.5 mm for the position estimation of the wrist in cyclical movements; this measure of RMSE was improved to 13.6 mm by implementing a gesture classifier.

Application of HFCT and UHF sensors in on-line partial discharge measurements for insulation diagnosis of high voltage equipment.

Partial discharge (PD) measurements provide valuable information for assessing the condition of high voltage (HV) insulation systems, contributing to their quality assurance. Different PD measuring techniques have been developed in the last years specially designed to perform on-line measurements. Non-conventional PD methods operating in high frequency bands are usually used when this type of tests are carried out. In PD measurements the signal acquisition, the subsequent signal processing and the capability to obtain an accurate diagnosis are conditioned by the selection of a suitable detection technique and by the implementation of effective signal processing tools. This paper proposes an optimized electromagnetic detection method based on the combined use of wideband PD sensors for measurements performed in the HF and UHF frequency ranges, together with the implementation of powerful processing tools. The effectiveness of the measuring techniques proposed is demonstrated through an example, where several PD sources are measured simultaneously in a HV installation consisting of a cable system connected by a plug-in terminal to a gas insulated substation (GIS) compartment.