Search results for "observer"

Comparative evaluation of three semi-quantitative radiographic grading techniques for knee osteoarthritis in terms of validity and reproducibility in…

2008

OBJECTIVE: The objective of this work was to compare the measurement properties of three categorical X-ray scoring methods of knee osteoarthritis (OA), both on semiflexed and extended views. METHODS: In data obtained from trials and cohorts, X-rays were graded using Kellgren and Lawrence (KL), the OA Research Society International (OARSI) joint space narrowing score, and measurement of joint space width (JSW). JSW was analyzed as a categorical variable. Construct validity was assessed through logistic regression between X-ray stages and Western Ontario and McMaster Universities OA Index. Inter-observer reliability was assessed in 50 subjects for extended views by weighted kappa. Intra-obser…

On temporal deixis and cognitive models in early Indo-European

2013

Crosslinguistic evidence suggest that there are two different (often coexistent) basic cognitive models for time, on the basis of which the world’s languages express time in terms of conceptual metaphor from the source spatial domain to the target temporal domain: i) the Time-based (Time-Reference-Point) model, in which time is conceptualized in terms of sequentially arrayed objects moving in space, so that a temporal event is relative to another earlier or later temporal event; ii) the Ego-based (Ego-Reference-Point) model, which is considered to have a more complex structure in which times are conceptualized as objects relative to a canonical deictic observer (Ego) located at the hic et n…

Sensorimotor Coarticulation in the Execution and Recognition of Intentional Actions

2017

Humans excel at recognizing (or inferring) another's distal intentions, and recent experiments suggest that this may be possible using only subtle kinematic cues elicited during early phases of movement. Still, the cognitive and computational mechanisms underlying the recognition of intentional (sequential) actions are incompletely known and it is unclear whether kinematic cues alone are sufficient for this task, or if it instead requires additional mechanisms (e.g., prior information) that may be more difficult to fully characterize in empirical studies. Here we present a computationally-guided analysis of the execution and recognition of intentional actions that is rooted in theories of m…

Trajectory robust control of autonomous quadcopters based on model decoupling and disturbance estimation

2021

In this article, a systematic procedure is given for determining a robust motion control law for autonomous quadcopters, starting from an input–output linearizable model. In particular, the suggested technique can be considered as a robust feedback linearization (FL), where the nonlinear state-feedback terms, which contain the aerodynamic forces and moments and other unknown disturbances, are estimated online by means of extended state observers. Therefore, the control system is made robust against unmodelled dynamics and endogenous as well as exogenous disturbances. The desired closed-loop dynamics is obtained by means of pole assignment. To have a feasible control action, that is, the fo…

ROS/Gazebo-Based Simulation of Quadcopter Aircrafts

2018

The main purpose of this work is to present a tutorial description on how to design and develop an observer, which is capable of estimating the position and the orientation of a drone commanded by a controller, whose shape and structure are unknown. Starting from Newton's and Euler's laws, a mathematical model describing the dynamics of a quadcopter has first been obtained. By linearizing this model it is possible to implement a Luenberger observer and validate it with simulations in a Linux environment, thanks to the use of the Ardupilot controller and the Gazebo simulator. Finally, starting from the results obtained from the simulation, it is possible to evaluate the error made in the est…

Wind gust estimation for precise quasi-hovering control of quadrotor aircraft

2021

Abstract This paper focuses on the control of quadrotor vehicles without wind sensors that are required to accurately track low-speed trajectories in the presence of moderate yet unknown wind gusts. By modeling the wind disturbance as exogenous inputs, and assuming that compensation of its effects can be achieved through quasi-static vehicle motions, this paper proposes an innovative estimation and control scheme comprising a linear dynamic filter for the estimation of such unknown inputs and requiring only position and attitude information. The filter is built upon results from Unknown Input Observer theory and allows estimation of wind and vehicle state without measurement of the wind its…

The role of the reporting framework MIATA within current efforts to advance immune monitoring

2014

Pre-training inter-rater reliability of clinical instruments in an international psychosis research project.

2021

International audience

Responsiveness to change and reliability of measurement of radiographic joint space width in osteoarthritis of the knee: a systematic review

2011

Import JabRef | WosArea Orthopedics; Rheumatology; International audience; Objective: The goal of this systematic review was to report the responsiveness to change and reliability of conventional radiographic joint space width (JSW) measurement. Method: We searched the PubMed and Embase databases using the following search criteria: [osteoarthritis (OA) (MeSH)] AND (knee) AND (X-ray OR radiography OR diagnostic imaging OR radiology OR disease progression) AND (joint space OR JSW or disease progression). We assessed responsiveness by calculating the standardized response mean (SRM). We assessed reliability using intra- and inter-reader intra-class correlation (ICC) and coefficient of variati…

Robust Control of Nonlinear Systems: An Unknown Input Observer Based Approach

2023

Questa tesi propone un controllore robusto per sistemi non lineari tramite l'utilizzo di un osservatore ad ingressi sconosciuti. Attraverso un'opportuna riformulazione dinamica del modello, un generico sistema non lineare viene descritto come la somma di due funzioni, la prima lineare e nota e la seconda altamente non lineare e sconosciuta, derivante dalla conoscenza imperfetta del modello dinamico, dei parametri, o di eventuali disturbi esogeni agenti sul sistema etc., modellabili come perturbazioni (disturbi) della funzione lineare. Questa semplificazione consente una vantaggiosa descrizione dinamica del sistema in forma matriciale. Le informazioni necessarie sono stimate attraverso l'uti…