Motion Disturbances Research Articles

Proximal femoral derotation osteotomy in children with CP : long term outcome and the role of age at time of surgery

The femoral derotation osteotomy (FDO) is seen as the golden standard treatment in children with cerebral palsy and internal rotated gait. This study provides quantitative evidence in support of the beneficial effect of FDO after long term follow up. Retrospective clinical and kinematic evaluation of 31 CP patients (55 operated limbs) pre-, 1 and 3 years postoperatively after proximal FDO was conducted for a minimal follow-up of 3 years. This group con- sisted of 20 men and 11 women, aged 10.68±3.31 years at the time of surgery. Minimum follow up was 3 years (3.16±0.53 years), with 22 patients (38 operated limbs) having an additional follow up at 5 years (5.02±0.49 years). Age at FU3 and FU5 was 14.06±3.52 years and 15.39±3.08 years respectively. A set of clinical and kinematic parameters were ana- lyzed and showed a significant correction of mean hip rotation and femoral anteversion after FDO. Further plotting of individual data comparing 3 or 5 year postoperative values to 1 year postoperative values showed no further significant changes, indicating sustained correction of internally rotted gait until end of our follow up. Plotting mean hip rotation in stance as well as kinematic knee parameters according to age grouped cohorts could not show age at time of surgery to be a significant factor in recurrence of internally rotated gait or preoperative disturbances of knee motion in the sagittal plane. This study provides quantitative evidence on the beneficial effect of FDO, a surgical technique to improve internally rotated gait in cerebral palsy patients with spastic diplegia. Pre- and postoperative clinical and kinematic para- meters are compared and results are discussed. Minimum follow up was 3 years with a mean follow up of 4.65±0.83 years. The effect of age at time of surgery on recurrence and kinematic parameters were studied.

Motor Speed Control With Convex Optimization-Based Position Estimation in the Current Loop

This article presents a sensorless machine drive scheme, combining the motion model predictive control (MPC) in the speed loop and the position estimation in the current loop. The current-loop-based position estimation algorithm is to estimate the present rotor position with the phase current information of the previous samples. These methods cannot perform perfectly in the low speed when a heavy load suddenly occurs, as the aggressive motion disturbance can impact the convergence of the low-speed position estimation, or even make divergence and estimation failure. This issue is especially terrible for the surface permanent magnet synchronous machines (SPMSMs), as the magnetic saliency is weak at heavy loads. The target of this article is to solve this issue with respect to the servo system, where the machines need to frequently start and stop with heavy loads, and hence the above risk must be considered. The convex optimization is applied in the position estimation, and the optimization cost value is extended to adjust the injection amplitude and the reference trajectory of the MPC control. With this strategy, the sensorless control can operate with a high stability and accuracy. The scheme is validated in an SPMSM test bench.

Single phase based study of Ag-Cu/EO Williamson hybrid nanofluid flow over a stretching surface with shape factor

Hybrid nanofluids is the suspension of two different types of nanoparticles in the base fluid. This enhances the heat transfer capabilities of the ordinary fluids and prove to better heat exponent as compare to the nanofluids. In this research, we investigate the nanofluid for its flow and heat transport features by subjecting it to a slippery surface. The fluid motion disturbance is achieved by with the utilization of non-linear, uniform horizontal porous stretching of the surface with in a Darcy type porous media. The effect of nanoparticle shapes, porous medium, variable thermal conductivity and thermal radiation are also included in this analysis. A numerical method, Keller box is used to find the self-similar solution of equations. Two different types of nanoparticles, Copper(Cu) and Silver(Ag) with non-Newtonian Engine Oil (EO) based fluid have been taken into consideration for our analysis. The valuable finding of this study is that the comparative heat transfer rate of Williamson hybrid nanofluids (Ag − Cu/EO) gradually more increases as compared to conventional nanofluids (Cu − EO). Moreover, Lamina-shaped particles result in the most significant temperature in the boundary layer, while the lowest temperature is observed in spherical-shaped nanoparticles. Finally entropy of the system exaggerates with the incorporation of nanoparticle percentage by volume, thermal radiation, variable thermal conductivity and Williamson variable.

Contact Stability and Contact Safety of a Magnetic Resonance Imaging-Guided Robotic Catheter Under Heart Surface Motion.

Contact force quality is one of the most critical factors for safe and effective lesion formation during catheter based atrial fibrillation ablation procedures. In this paper, the contact stability and contact safety of a novel magnetic resonance imaging (MRI)-actuated robotic cardiac ablation catheter subject to surface motion disturbances are studied. First, a quasi-static contact force optimization algorithm, which calculates the actuation needed to achieve a desired contact force at an instantaneous tissue surface configuration is introduced. This algorithm is then generalized using a least-squares formulation to optimize the contact stability and safety over a prediction horizon for a given estimated heart motion trajectory. Four contact force control schemes are proposed based on these algorithms. The first proposed force control scheme employs instantaneous heart position feedback. The second control scheme applies a constant actuation level using a quasi-periodic heart motion prediction. The third and the last contact force control schemes employ a generalized adaptive filter-based heart motion prediction, where the former uses the predicted instantaneous position feedback, and the latter is a receding horizon controller. The performance of the proposed control schemes is compared and evaluated in a simulation environment.

Oral Atenolol Therapy in the Treatment of Infantile Hemangioma: A Prospective Study

Background: Infantile haemangiomas (IH) are the most common tumors ofinfancy with an incidence of >2% of infants in general, and of 10% of Caucasian children, in particular.
 Objective: The aim of this study was to assess the efficacy and safety of atenolol in the treatment of proliferating IHs.
 Methods: This prospective study was conducted among 120 patients’ up to 30 months of age, clinically diagnosed with IH’s in surgical outpatient department (SOPD) of the Dhaka Shishu Hospital from July 2013 to March 2018. Atenolol was started initially 0.5mg/kg. Then doses were titrated according to clinical response (0.5- 3mg/kg/day OD). Parents were instructed to interrupt the administration of the drug if the child had a serious cough with dysponea or gastroenteritis with vomiting or diarrhoea. Patients’ were advised to come for follow up visit and in each follow up blood pressure, percentage of regression (of size), color change, complications were recorded. The change in the appearance of IH was evaluated on a visual analogue scale (VAS). Regression in the size and color clearance of IHs were evaluated according to 0%-to-100% scale.
 Results: Majority of the babies were from 1-10 months age group. Most of the infants were term babies and majority of the infants were girls. Majority of the IHs were located in head and neck regions. Majority of the mothers had multiple gestation pregnancy and few had family history of IH. Excellent, good and fair colour regression was found in 74.17%, 22.50% and 3.33% participants respectively. Excellent, good and fair size regression was found in 57.50%, 38.33% and 4.17% participants respectively. Adverse effects of drug like loose motion (7.50%) and sleep disturbance (3.33%) were found among the participants.
 DS (Child) H J 2018; 34(1) : 26-29

Motion-Robust Multimodal Heart Rate Estimation Using BCG Fused Remote-PPG With Deep Facial ROI Tracker and Pose Constrained Kalman Filter

The heart rate (HR) signal is so weak in remote photoplethysmography (rPPG) and ballistocardiogram (BCG) that HR estimation is very sensitive to face and body motion disturbance caused by spontaneous head and body movements as well as facial expressions of subjects in conversation. This article proposed a novel multimodal quasi-contactless HR sensor to ensure the robustness and accuracy of HR estimation under extreme facial poses, large-motion disturbances, and multiple faces in a video for computer-aided police interrogation. Specifically, we propose a novel landmark-based approach for a deep facial region of interest (ROI) tracker and face pose constrained Kalman filter to continuously and robustly track target facial ROIs for estimating HR from face and head motion disturbances in rPPG. This motion-disturbed rPPG signal is further fused with a minimally disturbed BCG signal by the face and head movements via a bank of notch filters with a recursive weighting scheme to obtain the dominant HR frequency for final accurate HR estimation. To facilitate reproducible HR estimation research, we synchronously acquire and publicly share a multimodal data set that contains 20 sets of ECG and BCG signals as well as uncompressed, rPPG-dedicated videos from ten subjects in a stable state and large-motion state (MS) without and with large face and body movements in a sitting position. We demonstrate through experimental comparisons that the proposed multimodal HR sensor is more robust and accurate than the state-of-the-art single-modal HR sensor solely with rPPG- or BCG-based methods. The mean absolute error (MAE) of HR estimation is 7.13 BPM lower than the BCG algorithm and 3.12 BPM lower than the model-based plane-orthogonal-to-skin (POS) algorithm in the MS.

Свободное вращение простых молекул и характеристические температуры в стеклообразных полимерах

Purely rotational spectra of CO and HCl molecules added as a probe to polypropylene (PP) and polyvinyl chloride (PVC) were obtained and analyzed. It is shown that the shape of the bands of these spectra, which reflects the degree of disturbance of the rotational motion, is strongly influenced by the local dynamics of the polymer matrix. From the change in the integrated intensity of absorption with the temperature were found temperatures of the transition from free rotation of CO and HCl molecules to their libration, as well as the temperatures of the onset of defrosting of the conformational mobility of the chains of PP and PVC macromolecules.

Optimal Control Problems in Drone Operations for Disaster Search and Rescue

This article concerns some optimal control problems arising in the operation of drone systems to support search and rescue operations in the aftermath of disasters, such as earthquakes, floods, tsunamis, extremal weather events, among others. More precisely, we focus on issues arising in multiple drone systems to support communications and situational awareness for the planning and execution of agile and effective search and rescue operation in diverse disaster scenarios. This is of utmost importance to mitigate the impact of the destruction and, in particular, the loss of life. After describing two key operation scenarios, we point out challenges arising in communications and control, and outline a systems design framework leading to the formulation of the several optimal motion control problems that, typically, feature state constraints. Then, a Pontryagin maximum principle in the Gamkrelidze form is presented. Under certain regularity assumptions, its measure multiplier is continuous, and, thus, amenable to the formulation of effective computational algorithms based on indirect methods. Feedback control strategies to compensate for motion disturbances, on the one hand, and the optimization over multiple concatenated modes of operation - often entailing the need of different dynamic models -, on the other hand, are obtained by embedding the procedure to solve the optimal control problem in a receding horizon framework of the model predictive control type.

A Computational Study on Lateral Flight Stability of the Cranefly in Hover

The dynamic flight stability of hovering insects includes the longitudinal and lateral motion. Research results have shown that for the majority of hovering insects the same longitudinal natural modes are identified and the hovering flight in longitudinal is unstable. However, in lateral, the modal structure for hovering insects could be different and the stability property of lateral disturbance motion is not as robust as that of longitudinal motion. The cranefly possesses larger aspect ratio and lower Reynolds number, and such differences in morphology and kinematics may make the lateral dynamic stability different. In this paper, the lateral flight stability of the cranefly in hover is investigated by numerical simulation. Firstly, the stability derivatives are acquired by solving the incompressible Navier–Stokes equations. Subsequently, the dynamic stability characteristics are checked by analyzing the eigenvalues and eigenvectors of the linearized system. Computational results indicate that the lateral dynamic modal structure of cranefly is different from most other insects, consisting of three natural modes, and the weakly oscillatory mode illustrates the hovering lateral flight is nearly neutral. This neutral stability is mainly caused by the negative derivative of roll-moment vs. sideslip-velocity, which can be attributed to the weaker ‘changing-LEV-axial-velocity’ effect. These results suggest that insects in nature may exhibit different dynamic stabilities with different morphological and kinematic parameters, which should be considered in the designs of flapping wing air vehicles.

Disturbed transatmospheric motion of the first stage of an aerospace system

The paper deals with disturbed transatmospheric motion of the first stage of an aerospace system. Deviations of atmospheric density and deviations of aerodynamic force coefficients from reference values are taken as disturbances. Optimal angle-of-attack schedules for the first stage are specified. Comparative analysis of optimal control programs for disturbed and undisturbed motion is carried out.

Model Analysis and Modified Control Method of Ship-Mounted Stewart Platforms for Wave Compensation

Offshore installations e.g. marine transportation, oil platforms, etc. are strongly depended on sea conditions. To increase workable time of carrying out these operations, a Stewart platform is installed on a ship to serve as a motion compensation base and equipment on the base can have the same precision with those on the land-fixed base. Since movements of the Stewart platform are influenced by persistent ship motions, they present more complicated dynamical characteristics which make the control issue much more challenges. In the existing results, the established model does not consider the ship motion disturbances or is a linearized model, besides, the actuator velocity is also needed. In this paper, a modified control method is proposed for the ship-mounted Stewart platform. Specifically, the dynamics model considering ship motion disturbances is established and the influence of ship motions on the Stewart platform is analyzed. Through the model analysis, a modified motion controller is proposed with utilizing a multiple degrees of freedom velocity feedforward compensator. Finally, simulations are included to illustrate the effectiveness of the modified control method by contrast.

Construction of Natural Loofah/Poly(vinylidene fluoride) Core-Shell Electrospun Nanofibers via a Controllable Janus Nozzle for Switchable Oil-Water Separation.

Developing microstructure and multifunctional membranes toward switchable oil-water separation has been highly desired in oily wastewater treatment. Herein, a controllable Janus nozzle was employed to innovatively electrospin natural loofah/poly(vinylidene fluoride) (PVDF) nanofibers with a core-shell structure for gravity-driven water purification. By adjusting flow rates of the PVDF component, a core-shell structure of the composite fibers was obtained caused by the lower viscosity and surface tension of PVDF. In addition, a steady laminar motion of fluids was constructed based on the Reynolds number of flow fields being less than 2300. In order to investigate the formation mechanism of the microstructure, a series of Janus nozzles with different lengths were controlled to study the blending of the two immiscible components. The gravity difference between the two components might cause disturbance of the jet motion, and the PVDF component unidirectionally encapsulated the loofah to form the shell layer. Most importantly, the dry loofah/PVDF membranes could separate oil from an oil-water mixture, while the water-wetted membrane exhibited switchable separation that could separate water from the mixtures because of the hydroxyl groups of the hydrophilic loofah hydrogen-bonding with water molecules and forming a hydration layer. The composite fibers can be applied in water remediation in practice, and the method to produce core-shell structures seems attractive for technological applications involving macroscopic core-shell nano- or microfibers.

Short-Term Forecast of the Earth’s Pole Motion, Taking Into Account Lunar Disturbances

On the basis of a numerical-analytical approach, the disturbed motion of the Earth’s pole is investigated. The existence of various modes of the oscillatory process is shown that affect the accuracy of predicting its position. Perturbations are found that lead to a change in the average speed of the Earth’s pole and to a change in its oscillatory mode. A method is proposed for constructing a modification of a low-parameter two-frequency model, which makes it possible to improve the accuracy of forecasting the movement of the Earth’s pole for short time intervals.

Finite-time observer-based control for Markovian jump systems with time-varying generally uncertain transition rates

This paper addresses the finite-time observer-based control for Markovian jump systems with time-varying generally uncertain transition rates. In order to estimate the states, a suitable observer is designed, in which both external disturbance and Brownian motion exist. In order to solve the complex time-varying transition rates, a quantization mechanism is raised to prove the closed-loop system and the observer error system be stable. Sufficient conditions of the existences of both the observer and the observer-based controller are derived in terms of linear matrix inequalities. Eventually, two practical examples are given to testify the correctness of the results.

Auditory Feedback Effectiveness for Enabling Safe Sclera Force in Robot-Assisted Vitreoretinal Surgery: a Multi-User Study.

Robot-assisted retinal surgery has become increasingly prevalent in recent years in part due to the potential for robots to help surgeons improve the safety of an immensely delicate and difficult set of tasks. The integration of robots into retinal surgery has resulted in diminished surgeon perception of tool-to-tissue interaction forces due to robot's stiffness. The tactile perception of these interaction forces (sclera force) has long been a crucial source of feedback for surgeons who rely on them to guide surgical maneuvers and to prevent damaging forces from being applied to the eye. This problem is exacerbated when there are unfavorable sclera forces originating from patient movements (dynamic eyeball manipulation) during surgery which may cause the sclera forces to increase even drastically. In this study we aim at evaluating the efficacy of providing warning auditory feedback based on the level of sclera force measured by force sensing instruments. The intent is to enhance safety during dynamic eye manipulations in robot-assisted retinal surgery. The disturbances caused by lateral movement of patient's head are simulated using a piezo-actuated linear stage. The Johns Hopkins Steady-Hand Eye Robot (SHER), is then used in a multi-user experiment. Twelve participants are asked to perform a mock retinal surgery by following painted vessels inside an eye phantom using a force sensing instrument while auditory feedback is provided. The results indicate that the users are able to handle the eye motion disturbances while maintaining the sclera forces within safe boundaries when audio feedback is provided.

СИНЕРГЕТИЧЕСКИЙ СИНТЕЗ НАБЛЮДАТЕЛЯ ВОЗМУЩЕНИЙ ДЛЯ СИСТЕМЫ УПРАВЛЕНИЯ «ЛЕТАЮЩЕЙ ПЛАТФОРМОЙ»

The work is devoted to the synergetic synthesis of the harmonic disturbance asymptotic observerfor the aircraft hierarchical control system. The paper contains the general description of “flying platform”type vertical take-off & landing aircraft & an asymptotic observer of external disturbing influences(for example, wind) that have a harmonic dynamics & cause periodic changes in flight height, aswell as in pitch & roll angles. An asymptotic observer must ensure the asymptotic stability of a reservedsystem, the implementation of technological invariants, the estimation of unobservable external influencesfrom the current values of the observed state-space variables, & the absorption of harmonic winddisturbances. The article also presents an extended mathematical model of the “flying platform” in thevertical movement mode under external harmonic disturbing influences, including a mathematical descriptionof the disturbance dynamics, & the upper hierarchy level control algorithms based on thegiven technological invariants are synthesized. In addition, the equations of the disturbing influencesasymptotic observer are calculated, which supplement the mathematical model of the “flying platform”under disturbed motion, & the equations for asymptotic estimates of unobserved variables are calculated,which are further included in the upper hierarchy level control laws. The possibility of the disturbanceobserver synthesis was verified using the observability criterion. Finally, the results of computersimulation of the upper & the lower hierarchy levels’ nonlinear dynamics under disturbed motion withsuppression of external disturbances by an asymptotic observer are shown, as well as the results ofcomputer simulation of the vehicle’s nonlinear dynamics under disturbed motion without an asymptoticobserver to allow a visual assessment of the observer’s performance by comparison. The relevance ofthe work consists in the necessity of “flying platform” type vertical take-off & landing aircraft creationto increase the effectiveness of people rescue operations in those disaster areas where helicopters &other modern means don’t cope with a task. The scientific novelty of the work consists in synergeticapproach application to the design of the vehicle’s spatial position system equipped with an asymptoticobserver to suppress disturbing influences.

The Poor Validity of Asymmetric Laryngoscopic Findings in Predicting Laterality in Vocal Fold Paresis

To determine the laryngoscopic findings most predictive of laterality in vocal fold paresis in patients with known RLN and/or SLN paresis by laryngeal electromyography (LEMG). Blinded, prospective video perceptual analysis study. Patients with vocal fold paresis diagnosed by LEMG at a tertiary care hospital from 2017 to 2019 were identified. Two fellowship-trained laryngologists blinded to clinical history and LEMG results reviewed laryngostroboscopic examinations and assessed for evidence of paresis using defined criteria. Inclusion criteria were adults with laryngeal asymmetry and evidence of decreased recruitment on LEMG. Exclusion criteria were children, presence of laryngeal lesions, myasthenia gravis, vocal fold paralysis, and normal laryngeal symmetry. We identified 95 patients who were diagnosed with vocal fold paresis with LEMG who met inclusion and exclusion criteria (mean age 43.8 ± 20.4 years (18-88), 38.9% male). When comparing the laterality of the observed laryngoscopic finding with LEMG, we found that in patients who had severe true vocal fold (TVF) range of motion disturbance, the laterality of the finding matched the LEMG distribution of paresis in 12 out of 13 (92.3%) patients (P=0.002). No other laryngoscopic findings reliably predicted laterality including corniculate and cuneiform cartilage asymmetry, pyriform sinus dilation, abnormal TVF show, petiole deviation, abnormal ventricular show, increased supraglottic area, and FVF hyperfunction of the opposite side. With the exception of severe TVF range of motion disturbance, there seems to be poor validity of laryngoscopic findings in predicting the affected side in vocal fold paresis. We recommend neurophysiologic testing to confirm the clinical diagnosis of vocal fold paresis.

Patient-reported outcomes of joint-preserving surgery for moderate hallux rigidus: a 1-year follow-up of 296 patients from Swefoot

Background and purpose — Hallux rigidus (HR) may cause decreased range of motion, joint pain, and gait disturbances. There is a lack of evidence regarding the outcome of different surgical procedures for moderate HR. We report patient-reported outcomes after joint-preserving surgical procedures for moderate HR. Patients and methods — We included 296 patients registered in Swefoot (Swedish national registry of foot and ankle surgery) who underwent primary surgery for moderate HR 2014 through 2018. We extracted information on anthropometrics, grading of HR, chosen surgical procedure, and patient-reported data including the PROMs SEFAS (summary score 0–48) and EQ-5D-3L (index 0–1) preoperatively and 1 year postoperatively. Results — 115 patients underwent metatarsal decompression (i.e., Youngswick) osteotomy (YOT) and 181 underwent cheilectomy. The mean improvement in SEFAS score 1 year after surgery was 12 points (95% CI 10 − 13) for YOT and 10 points (CI 9 − 12) for cheilectomy. Also, EQ-5D improved in both groups. Patients who underwent YOT were more satisfied with the procedure (84% vs. 70% for cheilectomy, p = 0.02). Interpretation — Surgically treated patients with moderate HR improved after both YOT and cheilectomy, according to patient-reported data from Swefoot. Patients who underwent a YOT were more satisfied with their procedure. One possible explanation may be that more patients in the YOT group had a concomitant hallux valgus; however, we have no information on this.

State and disturbance estimation for test masses of drag-free satellites based on self-recurrent wavelet neural network

In recent years, the drag-free satellites have been widely used for some fundamental physical experiments, such as checking short-range effects of general relativity, geopotential determination and the exploration of static ocean current. And the space-borne detector of gravitational waves is one of the important applications for drag-free satellites in the future. In this study, the estimation of relative motion state and disturbance for test masses of drag-free satellite after release are researched. Firstly, the relative motion model between the test masses is established based on corresponding reference frames. Secondly, a self-recurrent wavelet neural network estimator is designed to estimate the pure gravitational relative motion state and disturbance for the test masses, and the sliding mode controller is used to transfer the relative motion state to the ideal state. Finally, the proposed estimation methods are verified by the simulation results.

Development of a new form of equations of disturbed motion of a satellite in nearly circular orbits

The use of simple physical reasoning instead of the method of varying constants has made it possible to elaborate a short scheme of deriving equations of disturbed motion of a satellite in nearly circular orbits. The use of a circular Keplerian orbit as a reference orbit has ensured the nondegeneracy of equations and their simple relation with time. All this taken together has made it possible to propose a form of equations convenient for carrying out numerical and analytical studies with its variables having a simple physical meaning. A relationship between the introduced variables and the Keplerian elements of the orbits was described for undisturbed motion. It was shown that the variables describing the deviation of the orbit radius from the radius of the reference orbit are proportional to eccentricity and deviation of the focal parameter is proportional to the square of the eccentricity. Relationships were constructed that describe the connection between the introduced variables and the Cartesian coordinates of position and velocity in the inertial coordinate system as well as arguments for choosing the radius of the reference orbit. From the condition of equality of energies of motion along circular reference orbit and in elliptical Keplerian orbit, it is expedient to take the radius of the reference orbit equal to the semi-major axis of the Keplerian ellipse. Approaches to the possible development of the proposed equations were presented. They make it possible to describe changes in the argument of the orbit perigee. The proposed change of variables makes it possible to avoid degeneracy of equations at very small eccentricities when studying the change in the orbit perigee. The advantages of using the proposed equations for numerical and analytical studies of satellite motion in nearly circular orbits were shown on concrete calculation examples. It was shown that the results of numerical integration in the proposed variables give almost five orders of magnitude less error than the results of the integration of equations in Cartesian coordinates