Polynomial mechanics and optimal control

We describe a new algorithm for trajectory optimization of mechanical systems. Our method combines pseudo-spectral methods for function approximation with variational discretization schemes that exactly preserve conserved mechanical quantities such as momentum. We thus obtain a global discretization of the Lagrange-d'Alembert variational principle using pseudo-spectral methods. Our proposed scheme inherits the numerical convergence characteristics of spectral methods, yet preserves momentum-conservation and symplecticity after discretization. We compare this algorithm against two other established methods for two examples of underactuated mechanical systems; minimum-effort swing-up of a two-link and a three-link acrobot.Comment: Final version to EC

Optimal strategies for throwing accurately

Accuracy of throwing in games and sports is governed by how errors at projectile release are propagated by flight dynamics. To address the question of what governs the choice of throwing strategy, we use a simple model of throwing with an arm modelled as a hinged bar of fixed length that can release a projectile at any angle and angular velocity. We show that the amplification of deviations in launch parameters from a one parameter family of solution curves is quantified by the largest singular value of an appropriate Jacobian. This allows us to predict a preferred throwing style in terms of this singular value, which itself depends on target location and the target shape. Our analysis also allows us to characterize the trade-off between speed and accuracy despite not including any effects of signal-dependent noise. Using nonlinear calculations for propagating finite input-noise, we find that an underarm throw to a target leads to an undershoot, but an overarm throw does not. Finally, we consider the limit of the arm-length vanishing, i.e. shooting a projectile, and find that the most accurate shooting angle bifurcates as the ratio of the relative noisiness of the initial conditions crosses a threshold.Comment: 18 pages, 8 figure

Spatially distributed force measurement for small terrestrial animals

The 11th International Symposium on Adaptive Motion of Animals and Machines. Kobe University, Japan. 2023-06-06/09. Adaptive Motion of Animals and Machines Organizing Committee.Poster Session P7

Comparison of health related quality of life of primary school deaf children with and without motor impairment

<p>Abstract</p> <p>Objective</p> <p>To compare the health-related quality of life (HRQOL) of primary school-age deaf children with or without motor impairment to that of typically developing peers.</p> <p>Methods</p> <p>This study was a prospective, cross sectional study. With age-matched controls, 100 children were analyzed in each of the following three categories: normal hearing, hearing impaired without motor impairment, and hearing impairment with motor impairment. The Paediatric Quality of Life Inventory (PedsQL™) version 4.0 was used to assess the HRQOL.</p> <p>Results</p> <p>Hearing impairment along with motor impairment in children is associated with significantly increased proportions of suboptimal levels of function and significantly lower HRQOL. Children with hearing impairment and no motor impairment had significantly lower scores in the emotional health and school function domains of the PedsQL than children with normal hearing, but there was no significant difference in the physical and social health domain scores. Children with hearing impairment and motor impairment showed significantly lower scores in all domains of the PedsQL compared to children with normal hearing. Scores in all four domains of the PedsQL differed between children with hearing impairment and no motor impairment and children with hearing impairment and motor impairment.</p> <p>Conclusion</p> <p>These findings indicate that children with hearing impairment, both with and without motor impairment, have a diminished health-related quality of life.</p

Motor Development and Postural Control Evaluation of Children With Sensorineural Hearing Loss: A Review of Three Inexpensive Assessment Tools-Pbs, Tgmd-2, And P-Ctsib

ObjectiveSensorineural hearing loss is believed to be the result of a physiologic malfunction in the inner ear or acoustic nerve. Depending on the rapidity of progression and severity, sensorineural hearing loss can be endlessly annoying, frightening and can constitute a permanent after effect. Moreover, there is no surgical procedure that can reverse or lessen the severity of a sensorineural hearing loss.Furthermore, children with sensorineural hearing loss present with additional disabilities in 30 to 40% of the cases. Children with profound sensorineural hearing loss may exhibit abnormalities of vestibular structures, which may lead to impairment of postural control, locomotion and gait. The development of gross motor functions such as head control, sitting and walking are likely to be delayed in these children. Evaluation of motor skills and balance are the coreof the pediatrician and physical therapist's expertise and practice. Knowledge of the reliable, valid and inexpensive assessment tools for measuring motor skills and balance are necessary to gauge the progression of the disease and the impact of treatment. In this review, we aim to summarize inexpensive tools such as TGMD-2, PBS, and P-CTSIB

An overview of motor skill performance and balance in hearing impaired children

Childhood hearing impairment is a common chronic condition that may have a major impact on acquisition of speech, social and physical development. Numerous literature states that injury to the vestibular organs may result in accompanying balance and motor development disorders. But still postural control and motor assessments are not a routine procedure in hearing impaired children. Hence, we aim to provide an overview on motor skill performance and balance in hearing impaired children