Search results for "Control system"
showing 10 items of 971 documents
Modeling of Human Posturokinetic Movements by a Linear Feedback System: Relations among Feedback Coefficients
2002
This study describes a method of modeling human trunk and whole body backward bending and suggests a possible neural control strategy. The hypothesis was that the control system can be modeled as a linear feedback system, in which the torque acting at a given joint is a function of the state variables (angular positions and angular velocities). The linear system enabled representation of the feedback system by a gain matrix. The matrix was computed from the kinematics recorded by a movement analysis system and from the joint torques calculated by inverse dynamics. To validate the control model, a comparison was made between the angular kinematics yielded by the model and the experimental d…
Validity, reliability, and sensitivity to motor impairment severity of a multi-touch app designed to assess hand mobility, coordination, and function…
2021
[EN] Background: The assessment of upper-limb motor impairments after stroke is usually performed using clinical scales and tests, which may lack accuracy and specificity and be biased. Although some instruments exist that are capable of evaluating hand functions and grasping during functional tasks, hand mobility and dexterity are generally either not specifically considered during clinical assessments or these examinations lack accuracy. This study aimed to determine the convergent validity, reliability, and sensitivity to impairment severity after a stroke of a dedicated, multi-touch app, named the Hand Assessment Test. Methods: The hand mobility, coordination, and function of 88 individ…
Developing motor planning over ages
2009
International audience; Few studies have explored the development of response selection processes in children in the case of object manipulation. In the current research, we studied the end-state comfort effect, the tendency to ensure a comfortable position at the end rather than at the beginning of simple object manipulation tasks. We used two versions of the unimanual bar transport task. In Experiment 1, only 10-year-olds reached the same level of sensitivity to end-state comfort as adults, and 8-year-olds were less efficient than 6-year-olds. In each age group, children’s sensitivity did not increase during a session: i.e., either clearly showed the sensitivity or showed no sensitivity a…
Diseño de una nueva prueba para medir la función de sensibilidad al contraste con iPad
2015
[EN] Purpose: To introduce a new application (ClinicCSF) to measure Contrast Sensitivity Function (CSF) with tablet devices, and to compare it against the Functional Acuity Contrast Test (FACT). Methods: A total of 42 subjects were arranged in two groups of 21 individuals. Different versions of the ClinicCSF (.v1 and .v2) were used to measure the CSF of each group with the same iPad and the results were compared with those measured with the FACT. The agreements between ClinicCSF and FACT for spatial frequencies of 3, 6, 12 and 18 cycles per degree (cpd) were represented by Bland---Altman plots. Results: Statistically significant differences in CSF of both groups were found due to the change…
The Development of Perceptual Sensitivity to Second-Order Facial Relations in Children
2010
This study investigated children's perceptual ability to process second-order facial relations. In total, 78 children in three age groups (7, 9, and 11 years) and 28 adults were asked to say whether the eyes were the same distance apart in two side-by-side faces. The two faces were similar on all points except the space between the eyes, which was either the same or different, with various degrees of difference. The results showed that the smallest eye spacing children were able to discriminate decreased with age. This ability was sensitive to face orientation (upright or upside-down), and this inversion effect increased with age. It is concluded here that, despite early sensitivity to conf…
Synergy of spatial frequency and orientation bandwidth in texture segregation
2021
Defining target textures by increased bandwidths in spatial frequency and orientation, we observed strong cue combination effects in a combined texture figure detection and discrimination task. Performance for double-cue targets was better than predicted by independent processing of either cue and even better than predicted from linear cue integration. Application of a texture-processing model revealed that the oversummative cue combination effect is captured by calculating a low-level summary statistic (\(\Delta CE_m\)), which describes the differential contrast energy to target and reference textures, from multiple scales and orientations, and integrating this statistic across channels wi…
Effect of Color on Contrast Sensitivity with Two Different Accommodative Stimuli
1993
We studied the influence of color and accommodation on the contrast sensitivity function (CSF). At the same time, we measured the effect of axial chromatic aberration (ACA) on the CSF. The CSF's of two observers were determined using red, green, blue, and white light, at 5- and 0.5-m viewing distances. At 5 m the CSF's were measured with natural vision and also with lenses which compensated the ACA. Results show that the effect of ACA on the CSF is to reduce the sensitivity to blue with respect to the red. The difference in sensitivity between these two colors is between 50 and 150% and varies with the frequency and the subject. When the ACA is compensated the influence of the color on the …
TAKEOFF AND LANDING ROBUST CONTROL SYSTEM FOR A TANDEM CANARD UAV
2005
In spite of modern wide improvements in UAV’s technologies, a few number of such a vehicles is fully autonomous from takeoff to landing . So, either autonomous operation or operation with minimal human intervention is, actually, the primary design goal for the UAV’s researchers. The core of the problem is the design of the landing and takeoff control system. The objective of this paper is to design a control system in which the same state variables are controlled during both the descending/ascending path and the flare, tacking into account the actual ground effect. Robust control techniques are employed with the aim to cope with atmospheric turbulence, measurement noise, parameter variation…
Finite-element design sensitivity analysis for non-linear potential problems
1990
Design sensitivity analysis is performed for the finite-element system arising from the discretization of non-linear potential problems using isoparametric Lagrangian elements. The calculated sensitivity formulae are given in a simple matrix form. Applications to the design of electromagnets and airfoils are given.
Shock control bump design optimization on natural laminar aerofoil
2011
The chapter investigates Shock Control Bumps (SCB) on a Natural Laminar Flow (NLF) aerofoil; RAE 5243 for Active Flow Control (AFC). A SCB approach is used to decelerate supersonic flow on the suction/pressure sides of transonic aerofoil that leads delaying shock occurrence or weakening of shock strength. Such an AFC technique reduces significantly the total drag at transonic speeds. This chapter considers the SCB shape design optimisation at two boundary layer transition positions (0 and 45%) using an Euler software coupled with viscous boundary layer effects and robust Evolutionary Algorithms (EAs). The optimisation method is based on a canonical Evolution Strategy (ES) algorithm and inco…