Search results for "motor"
showing 10 items of 3137 documents
A model for torque losses in variable displacement axial piston motors
2018
This paper includes a comparison of earlier presented models for torque losses in hydraulic motors and several proposed models that all rely on data typically available for a system engineer. The new models and the old ones are compared. The new models are all based on a model developed by Jeong 2007 with an expansion that include variable displacement. All of the new models yield very good accuracy down to approximately 50% of maximum displacement and down to approximately 15% of maximum speed. In these operational ranges the deviation in torque is less than 1%. The main purpose of the new models is to facilitate simulations of hydraulically actuated winches with a balance between accuracy…
Heat Pump Induction Motor Faults Caused by Soft Starter Topology — Case Study
2021
This paper presents a case study of electrical machine faults, emerging in heat pump systems. In Nordic countries, heat pumps have been gaining popularity during the past years and have become one of the leading ways of heating in households and smaller public buildings. Although not a very complicated setup, the devices used are still prone to unexpected failures, especially if wrongly chosen, installed or maintained. The paper presents a study conducted on five real-life cases with very similar outcomes and failure modes. The setup of the systems is explained, faults are listed and presented, causes of the faults including modeling and measurement data are provided. The suggestions are gi…
La rétropulsion du sujet âgé: mise au point sur un symptôme grave et proposition d'une échelle pour une évaluation quantifiée
2007
Resume Propos Bien qu'il n'existe a l'heure actuelle aucune donnee epidemiologique sur la retropulsion, ce trouble postural semble relativement frequent chez le sujet âge fragile. Actualites et points forts La retropulsion se caracterise par un dejettement posterieur du tronc en position assise, une insuffisance d'avancee du tronc dont la projection du tronc au sol est situee en arriere de la base de sustentation lors du passage assis–debout et une tendance a la chute en arriere en position debout. Plusieurs situations pathologiques aussi bien somatiques (lesions cerebrales degeneratives, ischemiques, traumatiques), que psychosomatiques (syndrome de desadaptation psychomotrice, alitement pr…
Cognitive network hyperactivation and motor cortex decline correlate with ALS prognosis.
2021
We aimed to quantitatively characterize progressive brain network disruption in Amyotrophic Lateral Sclerosis (ALS) during cognition using the mismatch negativity (MMN), an electrophysiological index of attention switching. We measured the MMN using 128-channel EEG longitudinally (2-5 timepoints) in 60 ALS patients and cross-sectionally in 62 healthy controls. Using dipole fitting and linearly constrained minimum variance beamforming we investigated cortical source activity changes over time. In ALS, the inferior frontal gyri (IFG) show significantly lower baseline activity compared to controls. The right IFG and both superior temporal gyri (STG) become progressively hyperactive longitudina…
Intracortical facilitation within the migraine motor cortex depends on the stimulation intensity. A paired-pulse TMS study
2018
Abstract Introduction Connectivity within the primary motor cortex can be measured using the paired-pulse transcranial magnetic stimulation (TMS) paradigm. This evaluates the effect of a first conditioning stimulus on the motor evoked potential (MEP) elicited by a second test stimulus when different interstimulus intervals are used. Aim of the present study was to provide, in patients suffering from migraine without aura (MwoA), additional information on intracortical facilitation (ICF), short intracortical inhibition (SICI), and long intracortical inhibition (LICI), using different intensities of the test stimulus (TS). Methods We enrolled 24 patients with episodic MwoA and 24 age- and sex…
Differential contributions of the two human cerebral hemispheres to action timing
2019
Rhythmic actions benefit from synchronization with external events. Auditory-paced finger tapping studies indicate the two cerebral hemispheres preferentially control different rhythms. It is unclear whether left-lateralized processing of faster rhythms and right-lateralized processing of slower rhythms bases upon hemispheric timing differences that arise in the motor or sensory system or whether asymmetry results from lateralized sensorimotor interactions. We measured fMRI and MEG during symmetric finger tapping, in which fast tapping was defined as auditory-motor synchronization at 2.5 Hz. Slow tapping corresponded to tapping to every fourth auditory beat (0.625 Hz). We demonstrate that t…
Right inferior frontal gyrus implements motor inhibitory control via beta-band oscillations in humans
2021
Motor inhibitory control implemented as response inhibition is an essential cognitive function required to dynamically adapt to rapidly changing environments. Despite over a decade of research on the neural mechanisms of response inhibition, it remains unclear, how exactly response inhibition is initiated and implemented. Using a multimodal MEG/fMRI approach in 59 subjects, our results reliably reveal that response inhibition is initiated by the right inferior frontal gyrus (rIFG) as a form of attention-independent top-down control that involves the modulation of beta-band activity. Furthermore, stopping performance was predicted by beta-band power, and beta-band connectivity was directed f…
Long-term physical activity modulates brain processing of somatosensory stimuli: Evidence from young male twins.
2016
Leisure-time physical activity is a key contributor to physical and mental health. Yet the role of physical activity in modulating cortical function is poorly known. We investigated whether precognitive sensory brain functions are associated with the level of physical activity. Physical activity history (3-yr-LTMET), physiological measures and somatosensory mismatch response (sMMR) in EEG were recorded in 32 young healthy twins. In all participants, 3-yr-LTMET correlated negatively with body fat%, r = −0.77 and positively with VO2max, r = 0.82. The fat% and VO2max differed between 15 physically active and 17 inactive participants. Trend toward larger sMMR was seen in inactive compared to ac…
New insights in the neurological phenotype of aceruloplasminemia in Caucasian patients
2017
Abstract Introduction The diagnosis aceruloplasminemia is usually made in patients with advanced neurological manifestations of the disease. In these patients prognosis is poor, disabilities are severe and patients often die young. The aim of our study was to facilitate recognition of aceruloplasminemia at a disease stage at which treatment can positively influence outcome. Currently, the neurological phenotype of aceruloplasminemia has been mainly described in Japanese patients. This ‘classical’ phenotype consists of cerebellar ataxia, hyperkinetic movement disorders and cognitive decline. In this study we describe the spectrum of neurological disease in Caucasian patients. Methods Data on…
Having your cake and eating it: Faster responses with reduced muscular activation while learning a temporal interval
2019
International audience; We examined how motor responses to a stimulus evolve as individuals learn to predict when a stimulus will appear, by comparing responses to a regular versus irregular stimulus train. The study was conducted with two groups of adults — one responded to the regular appearance of a visual stimulus every 3 s (R group) and the second responded to the irregular presentation of the same stimulus (IR group) at intervals varying between 2 and 4 s. Participants responded to the appearance of the stimulus by bending over to press a button that was slightly out of reach. This whole body reach requires muscular activation at the ankles. Over the course of 50 consecutive responses…