Characterization of machine tools and measurement system for micromilling

Technological progress has led to increased demand for small components with tiny features, which cannot be achieved through conventional machining. Industrial application of processes based on microcutting is limited by some issues concerning the geometrical scale. The process performance is significantly affected by milling machine, tool holder, tool, workpiece material microstructure, workpiece fixtures, and process parameters. At present, an ultimate micromachining assessment procedure is not available. This study aims to propose and conduct an experiment on a testing procedure for micromilling. The set up to be implemented and the output to be considered are defined and described. Three major stages are identified: estimation of the effective bandwidth of the load cell–tool holder system, the milling machine natural frequency measurement, and micromilling test execution. The entire procedure is performed, and its robustness is demonstrated. Keywords: Micromilling, Machine tool performance test, Tool run-out, Force analysis, Modal analysi

DEEP LEARNING FOR GESTURE RECOGNITION IN GYM TRAINING PERFORMED BY A VISION-BASED AUGMENTED REALITY SMART MIRROR

This paper illustrates the development and the validation of a smart mirror for sport training. The application is based the skeletonization algorithm MediaPipe and runs on an embedded device Nvidia Jetson Nano equipped with two fisheye cameras. The software has been evaluated considering the exercise biceps curl. The elbow angle has been measured by both MediaPipe and the motion capture system BTS (ground truth), and the resulting values have been compared to determine angle uncertainty, residual errors, and intra-subject and inter-subject repeatability. The uncertainty of the joints’ estimation and the quality of the image captured by the cameras reflect on the final uncertainty of the indicator over time, highlighting the areas of improvements for further developments

Validation of Estimators for Weight-Bearing and Shoulder Joint Loads Using Instrumented Crutches

This research paper aimed to validate two methods for measuring loads during walking with instrumented crutches: one method to estimate partial weight-bearing on the lower limbs and another to estimate shoulder joint reactions. Currently, gait laboratories, instrumented with high-end measurement systems, are used to extract kinematic and kinetic data, but such facilities are expensive and not accessible to all patients. The proposed method uses instrumented crutches to measure ground reaction forces and does not require any motion capture devices or force platforms. The load on the lower limbs is estimated by subtracting the forces measured by the crutches from the subject’s total weight. Since the model does not consider inertia contribution in dynamic conditions, the estimation improves with low walking cadence when walking with the two-point contralateral and the three-point partial weight-bearing patterns considered for the validation tests. The shoulder joint reactions are estimated using linear regression, providing accurate values for the forces but less accurate torque estimates. The crutches data are acquired and processed in real-time, allowing for immediate feedback, and the system can be used outdoors in real-world walking conditions. The validation of this method could lead to better monitoring of partial weight-bearing and shoulder joint reactions, which could improve patient outcomes and reduce complications

Computer vision-based mapping of grapevine vigor variability for enhanced fertilization strategies through intelligent pruning estimation

The objective of this study is to develop an affordable and non-invasive method using computer vision to estimate pruning weight in commercial vineyards. The study aims to enable controlled fertilization by leveraging pruning data as an indicator of plant vigor [1]. The methodology entails the analysis of RGB and DEPTH images acquired through an embedded platform (Figure 1) in a vineyard cultivating corvina grapes using the guyot method [2]. Initially, pruning weight was evaluated by processing pictures taken manually with a controlled background. Then, we developed an algorithm to estimate pruned wood weight based on these images. Subsequently, a mobile sensor platform was utilized to automatically capture grapevine images without a controlled background. Collected data will then be used to deploy a convolutional neural network (CNN) for intelligent pruning estimation capable of extracting meaningful data from real-world environments. Additionally, we integrated and validated a visual-odometry sensor (Intel Realsense T265) to map the spatial variability of pruning estimation results

DEVELOPMENT OF A MEASUREMENT SYSTEM FOR THE EVALUATION OF KINEMATICS AND IMPACT FORCES IN HISTORICAL FENCING COMBAT

This study aims at evaluating the impact forces acting on the blades of swords during a combat. Such forces will be used as input for numerical simulations to estimate the sword durability. Some replicas of the 17th century swords were instrumented with strain gauges and inertial sensors were placed on athletes’ joints to reconstruct arm kinematic. The forces along the two relevant axes are calculated by linear regression of two Wheatstone bridges and results were consistent with previsions. The calibration showed small uncertainty (max 11 N) with the transverse sensitivity being directly included in calibration parameters. In addition, the system was fully synchronized between all its parts and the bandwidth seems sufficient to calculate the impacts

A novel optical apparatus for the study of rolling contact wear/fatigue based on a high-speed camera and multiple-source laser illumination

Rolling contact wear/fatigue tests on wheel/rail specimens are important to produce wheels and rails of new materials for improved lifetime and performance, which are able to operate in harsh environments and at high rolling speeds. This paper presents a novel non-invasive, all-optical system, based on a high-speed video camera and multiple laser illumination sources, which is able to continuously monitor the dynamics of the specimens used to test wheel and rail materials, in a laboratory test bench. 3D macro-topography and angular position of the specimen are simultaneously performed, together with the acquisition of surface micro-topography, at speeds up to 500 rpm, making use of a fast camera and image processing algorithms. Synthetic indexes for surface micro-topography classification are defined, the 3D macro-topography is measured with a standard uncertainty down to 0.019 mm, and the angular position is measured on a purposely developed analog encoder with a standard uncertainty of 2.9°. The very small camera exposure time enables to obtain blur-free images with excellent definition. The system will be described with the aid of end-cycle specimens, as well as of in-test specimens

Deep learning-based hand gesture recognition for collaborative robots

This paper is a first step towards a smart hand gesture recognition set up for Collaborative Robots using a Faster R-CNN Object Detector to find the accurate position of the hands in RGB images. In this work, a gesture is defined as a combination of two hands, where one is an anchor and the other codes the command for the robot. Other spatial requirements are used to improve the performances of the model and filter out the incorrect predictions made by the detector. As a first step, we used only four gestures

Biomechanics in crutch assisted walking

Crutch-assisted walking is very common among patients with a temporary or permanent impairment affecting lower limb biomechanics. Correct crutches’ handling is the way to avoid undesired side effects in lower limbs recovery or, in chronic users, upper limbs joints diseases. Active exoskeletons for spinal cord injured patients are commonly crutch assisted. In such cases, in which upper limbs must be preserved, specific training in crutch use is mandatory. A walking test setup was prepared to monitor healthy volunteers during crunch use as a first step. Measurements were performed by using both a motion capture system and instrumented crutches measuring load distribution. In this paper, we present preliminary tests results based on different subjects - having a variety of anthropometrical characteristics - during walking with parallel or alternate crutches, the so-called three and two-points strategies. Tests results present inter and intra subject variabilities and, as a first goal, influencing factors affecting crutch loads have been identified. In the future we aim to address crutch use errors that could lead to delayed recovery or upper limbs suffering in patients, giving valuable information to physicians and therapists to improve user’s training

a study of wear and rolling contact fatigue on a wheel steel in alternated dry wet contact aided by innovative measurement systems

Abstract Wear and rolling contact fatigue are competing phenomena in railway wheels, as wear tends to shorten or remove surface cracks nucleated by ratcheting. The presence of water at the contact interface can enhance crack propagation leading to fatigue failure. This topic was studied taking advantage of innovative measurement systems developed for assessing the damage in bi-disc rolling contact tests, including a vision system for the acquisition and elaboration of surface images and a machine-learning technique for vibration measurement and analysis. Tests of different total duration with alternated dry and wet contact phases were carried out. The analysis of the collected measurements allowed identifying when crack propagation begins to prevail on wear: this occurred well earlier than the visible emergence of fatigue damage. If short dry and wet contact sessions are alternated, the onset of fluid driven crack propagation is delayed, because initially the dry sessions are not long enough to allow surface cracks to form by ratcheting, and in the subsequent wet session ratcheting is suspended due to low friction. If the alternated dry-wet contact sessions are longer, the onset of fluid driven crack propagation is accelerated, as in the dry sessions ratcheting proceeds more forming longer surface cracks, which are able to propagate in the subsequent wet phase