Search results for "nema"
showing 10 items of 1972 documents
Off-line path correction of robotic face milling using static tool force and robot stiffness
2015
In this paper the developed method for off-line compensation of tool deflections when milling aluminum with an industrial robot is presented. The efficiency of this approach is verified with high precision measurements of deflections using a laser tracker. The compensation method includes both the static milling process model which can predict the mean value components of the tool forces and a new combined local/global approach for estimating the combined stiffnesses of joints. With a process model such as the one presented in this paper and estimates of the robot's joint stiffness values, the tool path can be adjusted to counteract deflections of the tool during milling operations. The mod…
Development of 3D Anti-Swing Control for Hydraulic Knuckle Boom Crane
2021
In this paper, 3D anti-swing control for a hydraulic loader crane is presented. The difference between hydraulic and electric cranes are discussed to show the challenges associated with hydraulic actuation. The hanging load dynamics and relevant kinematics of the crane are derived to model the system and create the 3D anti-swing controller. The anti-swing controller generates a set of tool point velocities which are added to the electro-hydraulic motion controller via feedforward. A dynamic simulation model of the crane is made, and the control system is evaluated in simulations with a path controller in actuator space. Simulation results show significant reduction in the load swing angles …
The mechanics of continuous chip formation in oblique cutting with single-edged tool — Part I. Theory
1990
Abstract The paper presents a new point of view on oblique cutting mechanics when cutting with a single-edged tool. This is based on the main assumption that plastic flow of material during chip forming occurs in the set of planes normal to the cutting edge. As a consequence of the transformation of various orthocartesian systems some new generalized relationships for kinematics of oblique cutting operation and plastic deformation in the shear zone are derived.
Reconstruction and simulation of the vehicle to road safety barrier oblique collision based on the Levenberg–Marquardt algorithm
2012
Vehicle crash modeling and reconstruction is an important field for research since the safety statistics from many countries show that the fatality rate of passenger vehicle occupants involved in road accidents is high. In particular, side impact are considered to be a serious problem. For this reason, in this paper, there is presented a methodology to reconstruct a given vehicle to road safety barrier oblique collision. An easy to analyze, viscoelastic model is established to represent a vehicle crash event. The reasonable modeling simplifications are assumed (namely: the vehicle is rigid and deformation of the safety barrier is negligible) which let the computational efficiency of the pro…
Finite element analysis of two total knee joint prostheses
2012
Aim of this work is to compare two different total knee prostheses that differ mainly in the shape of the polyethylene (PE) component inserted between the femoral and tibial plates. The best solution between them has been originally reshaped in order to reduce stress peaks. The study procedure has been divided into the following steps. First step is the digitalisation of the shape of the prostheses by means of a 3D laser scanner. The morphology of two prototypes of the prostheses has been acquired by elaborating multiple Moire fringe patterns projected on their surfaces. Second step consisted on the manipulation of these data in a CAD module, that is the interpolation of raw data into NURBS…
A pedagogical flight simulator for longitudinal airplane flight
2009
This article presents a bi-dimensional model of flight and describes the implementation of a flight simulator able to describe the different phases of longitudinal flight of a real airplane. After identifying the relevant physical variables, the equations of motion are written and solved using a numerical integration method. Using computer simulations, flight paths and time evolution of the kinematics variables are analyzed for a complete flight of a light commercial airplane. The simulations take into account and reproduce the basic actions of a pilot to control the flight. The main maneuvers involved in pilotage are also predicted and explained in terms of model parameter variations induc…
Emergent behaviors and scalability for multi-agent reinforcement learning-based pedestrian models
2017
This paper analyzes the emergent behaviors of pedestrian groups that learn through the multiagent reinforcement learning model developed in our group. Five scenarios studied in the pedestrian model literature, and with different levels of complexity, were simulated in order to analyze the robustness and the scalability of the model. Firstly, a reduced group of agents must learn by interaction with the environment in each scenario. In this phase, each agent learns its own kinematic controller, that will drive it at a simulation time. Secondly, the number of simulated agents is increased, in each scenario where agents have previously learnt, to test the appearance of emergent macroscopic beha…
Entomopatogēno nematožu Steinernema feltiae (Filipiev 1934) sastopamības novērtējuma aprobācija pēc Galleria mellonella metodes, to populācijas izmai…
2020
Darbā kalibrēta vienkārša, kvantitatīva metode entomopatogēno nematožu Steinernema feltiae (Filipiev, 1934) sastopamības novērtēšanai izmantojot Galleria mellonella (Linnaeus, 1758) kāpurus kā ēsmu. G. mellonella ēsmas tests tika kalibrēts divu dažāda vecuma sterilizētas kokosa šķiedras substrātā, kur tika konstatēta būtiska korelācija starp S. feltiae indivīdu blīvumu un G. mellonella mirstību 48h laikā gan svaigā (p<0.01, r=0.86, n=25), gan trīs gadus lietotajā (p<0.01, r=0.85, n=25) substrātā. Piecu nedēļu laikā dažāda vecuma rožu stādījumos ievāktos paraugos reģistrētas atšķirības pētījumā iesaistīto taksonu sastāvā, konstatēta S. feltiae telpiskās izplatības heterogenitāte, ilgstoša sa…
Pioneer trees of Betula pendula at a red gypsum landfill harbour specific structure and composition of root-associated microbial communities.
2020
The study of root-associated microbial communities is important to understand the natural processes involved in plant recolonisation at degraded areas. Root associated bacterial and fungal communities of woody species colonising a red gypsum landfill (a metal-enriched environment) were characterised through metabarcoding. Among trees naturally growing on the landfill, Betula pendula is the only tree species in the centre of the area, whereas companion tree species such as Populus nigra, P. tremula and Salix purpurea were present on the edges. The bacterial community was dominated by Proteobacteria (38%), Actinobacteria (35%) and Bacteroidetes (20%) and the most abundant bacterial OTU belong…
Apocalisse e normalità. Epidemia e inconscio visuale
2020
Il saggio esamina con gli strumenti del cinema l'emergenza sanitaria, Covid-19