Search results for "Inertia"
showing 10 items of 263 documents
Finite-Time Control for Attitude Tracking Maneuver of Rigid Satellite
2014
Published version of an article in the journal: Abstract and Applied Analysis. Also available from the publisher at: http://dx.doi.org/10.1155/2014/302982 Open Access The problem of finite-time control for attitude tracking maneuver of a rigid spacecraft is investigated. External disturbance, unknown inertia parameters are addressed. As stepping stone, a sliding mode controller is designed. It requires the upper bound of the lumped uncertainty including disturbance and inertia matrix. However, this upper bound may not be easily obtained. Therefore, an adaptive sliding mode control law is then proposed to release that drawback. Adaptive technique is applied to estimate that bound. It is prov…
A hybrid observer for localization of mobile vehicles with asynchronous measurements
2019
The aim of this paper is the design of a hybrid nonlinear observer for mobile vehicles. The main problem is that position and velocity measurements are provided with a very low frequency, and the time between two consecutive measurements could be not constant, but it could vary randomly within a certain interval of time. For this reason the proposed observer has been contextualized in the hybrid systems framework. The convergence analysis of the estimation error has been carried out, and the sensitivity analysis has been performed in order to evaluate the bound of the estimation error when the measurements are biased and/or noisy. Simulation and experimental results, carried out on a mobile…
Thermal inertia mapping from NOAA-AVHRR data
1998
Abstract This paper presents a method to retrieve thermal inertia from NOAA-AVHRR data. The method, based on Xue and Cracknell's model (1992), involves using the phase angle information of the diurnal surface temperature change. The method needs three different NOAA overpasses of the same area throughout a single diurnal cycle. To apply this method we present a methodology that takes into account satellite calibrations, viewing geometry and correction of atmospheric effects. The advantage is that it does not need other data than the ones supplied by the satellite. Finally, we present the preliminary results obtained using the proposed method and the methodology for AVHRR data over the Iberi…
A new airborne tandem platform for collocated measurements of microphysical cloud and radiation properties
2009
Abstract. A new airborne tandem measurement platform for cloud-radiation interaction studies is introduced in this paper. It consists of a Learjet 35A research aircraft and the AIRcraft TOwed Sensor Shuttle (AIRTOSS), which is an instrumented drag-body towed by the Learjet. Currently, the AIRTOSS is instrumented with a Cloud Imaging Probe (CIP) for measuring cloud microphysical properties and an Inertial Navigation System (INS) for measurements of flight attitudes. The cable dragging AIRTOSS can be as long as four kilometres. Thus, truly collocated measurements in two altitudes above, in, and below clouds can be obtained. Results from first test flights with Learjet and AIRTOSS are reported…
Analysis of a Fast Reserve Unit Behaviour with Additional Modular Synthetic Inertia Control
2021
The paper presents the results of a theoretical study on the behaviour of a battery storage system operated as a Fast Reserve Unit and equipped with additional synthetic inertia control. The Fast Reserve Unit is assumed connected to the transmission system of Sicily, operated as an isolated grid in order to show more clearly the effect of the Fast Reserve Unit intervention during a power imbalance. The unit is controlled also to provide synthetic inertia with a conventional control scheme and with a new scheme proposed by the authors and named “Modular Synthetic Inertia”. The latter has been conceived for offering a modular response as a function of the Rate of Change of Frequency, to avoid…
Bicausative matrices to measure structural change: Are they a good tool?
1999
The causative-matrix method to analyze temporal change assumes that a matrix transforms one Markovian transition matrix into another by a left multiplication of the first matrix; the method is demand-driven when applied to input-output economics. An extension is presented without assuming the demand-driven or supply-driven hypothesis. Starting from two flow matrices X and Y, two diagonal matrices are searched, one premultiplying and the second postmultiplying X, to obtain a result the closer as possible to Y by least squares. The paper proves that the method is deceptive because the diagonal matrices are unidentified and the interpretation of results is unclear. Keywords : Input-Output ; Ch…
The gait is less stable in children with cerebral palsy in normal and dual-task gait compared to typically developed peers
2021
There is limited evidence about gait stability and its alteration by concurrent motor and cognitive tasks in children with cerebral palsy (CP). We examined gait stability and how it is altered by constrained cognitive or motor task in CP and their typically developed (TD) controls. Gait kinematics were recorded using inertial-measurement units (IMU) from 18 patients with hemiplegia (13.5 +/- 2.4 years), 12 with diplegia (13.0 +/- 2.1 years), and 31 TD controls (13.5 +/- 2.2 years) during unconstrained gait, and motor (carrying a tray) and cognitive (word naming) task constrained gait at preferred speed (similar to 400 steps/task). Step duration, its standard deviation and refined-compound-m…
P 042 - Gait complexity quantified using inertial measurement units in children with cerebral palsy
2018
Abstract Children with cerebral palsy (CP) have gait impairments, and their gait is affected by concurrent tasks. We used inertial measurement units (IMU) to quantify CP-related gait complexity alterations, and identify effects of dual tasks on gait variability from 12 children with CP and 23 typically developed (TD) controls. The data were collected for normal and dual-tasks (motor; carrying a tray, cognitive; word naming) during walking. Step duration and adjusted multiscale entropy (MSE) index were computed. In overall, children with CP had shorter step duration and greater gait complexity than TD. Gait complexity was higher in vertical direction during the cognitive than normal and moto…
Theoretical study on travelling web dynamics and instability under non-homogeneous tension
2013
Problems of dynamics and stability of a moving web, travelling between two rollers at a constant velocity, are studied using analytical approaches. Transverse vibrations of the web are described by a partial differential equation that includes the centrifugal force, in-plane tension, elastic reaction and nonstationary inertial terms. The model of a thin elastic plate subjected to bending and non-homogeneous tension is used to describe the bending moment and the distribution of membrane forces. The stability of the plate is investigated with the help of studies of small out-of-plane vibrations. The influence of linearly distributed in-plane tension on the characteristics of the web vibration…
A Trajectory-Driven 3D Channel Model for Human Activity Recognition
2021
This paper concerns the design, analysis, and simulation of a 3D non-stationary channel model fed with inertial measurement unit (IMU) data. The work in this paper provides a framework for simulating the micro-Doppler signatures of indoor channels for human activity recognition by using radiofrequency-based sensing technologies. The major human body segments, such as wrists, ankles, torso, and head, are modelled as a cluster of moving point scatterers. We provide expressions for the time variant (TV) speed and TV angles of motion based on 3D trajectories of the moving person. Moreover, we present mathematical expressions for the TV Doppler shifts and TV path gains associated with each movin…