Platform Tilt Research Articles

Analysis of anticipatory and compensatory postural adjustment in women of different age groups using surface electromyography.

Postural balance is crucial for daily activities, relying on the coordination of sensory systems. Balance impairment, common in the elderly, is a leading cause of mortality in this population. To analyze balance, methods like postural adjustment analysis using electromyography (EMG) have been developed. With age, women tend to experience reduced mobility and greater muscle loss compared to men. However, few studies have focused on postural adjustments in women of different ages using EMG of the lower limbs during laterolateral and anteroposterior movements. This gap could reveal a decrease in muscle activation time with aging, as activation time is vital for postural adjustments. This study aimed to analyze muscle activation times in women of different ages during postural adjustments. Thirty women were divided into two groups: young and older women. A controlled biaxial force platform was used for static and dynamic balance tests while recording lower limb muscle activity using EMG. Data analysis focused on identifying muscle activation points and analyzing postural adjustment times. Results showed significant differences in muscle activation times between the two groups across various muscles and platform tilt conditions. Younger women had longer muscle activation times than older women, particularly during laterolateral platform inclinations. In anteroposterior movements, older women exhibited longer activation times compared to their laterolateral performance, with fewer differences between the groups. Overall, older women had shorter muscle activation times than younger women, suggesting a potential indicator of imbalance and increased fall risk.

Experimental Study of a Puncture Warning System for a Jack-Up Offshore Platform

Abstract During the operation of jack-up offshore platforms, the complex and variable seabed geological conditions involved can lead to serious accidents, such as pile leg punctures and platform tilt. The aim of this study is to introduce an early warning method for punctures that ensures the operational safety of these platforms. To accomplish this, a real-time monitoring and controlling system is designed using a programmable logic controller that shares data from sensors measuring displacement, tilt, and pressure. In addition, an experimental device is constructed to simulate a jack-up offshore platform in order to assess the safety response of the control system. The working state of the platform under different working conditions (puncture of one independent pile, same side or diagonal piles, and three-pile linkage) is evaluated by analysing the structural motion response, including platform tilt and foundation pressure. The findings reveal that the system developed in this study accurately detects the tilt condition of the offshore platform, and can ensure the operational safety of jack-up offshore platforms.

Drainage evolution in porous carbonate terrain in semi-arid environments: The role of tectonics and climatic change – The case study of the Boukadir carbonate platform, Algeria

Porous carbonate terrains are widespread around the Mediterranean area and form non classical karstic landscapes. The related diffuse infiltration is expected to impede karstification and the establishment of dense drainage networks. In such terrain, the effect of tectonics and climate on drainage development and evolution remains poorly understood. To address this issue, we focus on a semi-arid area with a tuffaceous Messinian carbonate platform characterized by a well-established dendritic network in an active tectonic context. The platform is situated in the Chélif Basin in Algeria, affected by transpressive deformation in relation to the Africa-Eurasia collision. We combine geomorphological observations with drainage morphometric analyses using satellite images and DEM. The drainage network analysis reveals varying tectonic deformation and morphological anomalies resulting from instability in the drainage systems, expressed through (1) variable platform tilt and (2) the presence of knickpoints and convexities in river profiles. These anomalies are particularly pronounced in the west, where knickpoints are more numerous, and incisions deeper. We relate the origin of the tilt to the differential marl compaction and remobilization, and in the area with the highest tilt a recent propagation of the Boukadir thrust underneath the platform might also play a role. Finally, we propose a general model of drainage evolution which highlights the importance of weathering in the Maghreb area transforming the porous media in an indurated carbonate or calcrete.

Influence of platform motion on the energy production of a floating wind farm

This study investigates the dynamics of energy production in floating wind farms. Unlike their bottom-fixed counterparts, floating wind turbines experience large-amplitude, low-frequency movements affecting the rotor response and the wake development. We employed the multi-physics simulator FAST.Farm to study a seven-turbine wind farm, comparing conventional monopile foundations with semi-submersibles. Results show that, under undisturbed wind conditions, floating turbines exhibit a lower power-conversion efficiency due to platform tilt and the use of a thrust clipping controller. Conversely, waked turbines in a floating configuration have a higher power output than with a bottom-fixed foundation. This is attributed to the higher wind speed in their wake which is due to the lower thrust set point of the floating controller, the vertical deflection of the wake and the dynamic conditions at rotor created by motion.

Microgravity Decoupling in Torsion Pendulum for Enhanced Micro-Newton Thrust Measurement

To enhance the accuracy of micro-Newton thrust measurements via a torsion pendulum, addressing microgravity coupling effects caused by platform tilt and pendulum mass eccentricity is crucial. This study focuses on analyzing and minimizing these effects by alleviating reference surface tilt and calibrating the center of mass during thrust measurements. The study introduced analysis techniques and compensation measures. It first examined the impact of reference tilt and center of mass eccentricity on the stiffness and compliance of the torsion pendulum by reconstructing its dynamic model. Simscape Multibody was initially employed for numerical analysis to assess the dynamic coupling effects of the tilted pendulum. The results showed the influence of reference tilt on the stiffness and compliance of the torsion pendulum through simulation. An inverted pendulum was developed to amplify the platform’s tilt angle for microgravity drag-free control. Center of mass calibration can identify the gravity coupling caused by the center of mass position. Based on the displacement signal from the capacitive sensor located at the end of the inverted pendulum, which represents the platform’s tilt angle, the pendulum’s vibration at 0.1 mHz was reduced from 5.7 μm/Hz1/2 to 0.28 μm/Hz1/2 by adjusting the voltage of piezoelectric actuator. Finally, a new two-stage torsion pendulum structure was proposed to decouple the tilt coupling buried in both pitch and roll angle. The study utilized theoretical models, numerical analysis, and experimental testing to validate the analysis methods and compensation measures for microgravity coupling effects in torsion pendulums. This led to a reduction in low-frequency noise caused by ground vibrations and thermal strains, ultimately improving the micro-Newton thrust measurement accuracy of the torsion pendulum through the platform’s drag-free control.

The Effect of Roll Circular Vection on Roll Tilt Postural Responses and Roll Subjective Postural Horizontal of Healthy Normal Subjects.

Background: Falls and related injuries are critical issues in several disease states, as well as aging, especially when interactions between vestibular and visual sensory inputs are involved. Slow support surface tilt (0.6 deg/s) followed by subjective postural horizontal (SPH) assessments have been proposed as a viable method for assessing otolith contributions to balance control. Previous assessments of perceived body alignment to vertical, including subjective visual vertical, have suggested that visual inputs are weighted more when vestibular information is near the threshold and less reliable during slow body tilt. To date, no studies have examined the influence of visual stimuli on slow roll-tilt postural responses and the SPH. Therefore, this study investigated how dynamic visual cues, in the form of circular vection (CV), influence postural responses and the perception of the horizontal during and after support surface tilt. Methods: Ten healthy young adults (6 female, mean age 23) wore a head-mounted display while standing on a tilting platform. Participants were asked to remain upright for 30 s, during which (1) the visual scene rotated, inducing roll CV clockwise (CW) or counter-clockwise (CCW) at 60°/s; (2) the platform only (PO) rotated in roll to test SPH (0.6°/s, 2°, CW or CCW); (3) a combination of both; or (4) neither occurred. During SPH trials, participants used a hand-held device to reset the position of the platform to 0.8°/s to their perceived SPH. The angular motion of body segments was measured using pairs of light-emitting diodes mounted on the head, trunk and pelvis. Segment motion, prior to platform motion, was compared to that at peak body motion induced by platform motion and when SPH had been set. Results: When the support surface was tilted 2°, peak upper body tilt significantly increased for congruent CV and platform tilt and decreased at the pelvis for incongruent CV when compared to PO, leading to significant differences across body segments for congruent and incongruent conditions (p ≤ 0.008). During PO, participants' mean SPH deviated from horizontal by 0.2°. The pelvis deviated 0.2°, the trunk 0.3°, and the head 0.5° in the direction of initial platform rotation. When platform tilt and CV directions were congruent or incongruent, only head tilt at SPH reset under congruent conditions was significantly different from the PO condition (1.7° vs. 0.5°). Conclusions: Roll CV has a significant effect on phasic body responses and a less significant effect on tonic body responses to lateral tilt. The SPH of the support surface was not altered by CV. Responses during tilt demonstrated enhanced reactions for congruent and reduced reactions for incongruent CV, both different from responses to CV alone. Tonic body displacements associated with SPH were changed less than those during tilt and were only slightly larger than displacements for CV alone. This study supports the hypothesis of weighted multisensory integration during dynamic postural tasks being highly dependent on the direction of visual cues during tilt and less dependent on tonic SPH offsets. These techniques could be used to examine vestibular and visual interactions within clinical populations, particularly those with visual vertigo and dizziness.

A CO2 and H2O Gas Analyzer with Reduced Error due to Platform Motion

Abstract One long-standing technical problem affecting the accuracy of eddy correlation air–sea CO2 flux estimates has been motion contamination of the CO2 mixing-ratio measurement. This sensor-related problem is well known but its source remains unresolved. This report details an attempt to identify and reduce motion-induced error and to improve the infrared gas analyzer (IRGA) design. The key finding is that a large fraction of the motion sensitivity is associated with the detection approach common to most closed- and open-path IRGA employed today for CO2 and H2O measurements. A new prototype sensor was developed to both investigate and remedy the issue. Results in laboratory and deep-water tank tests show marked improvement. The prototype shows a factor of 4–10 reduction in CO2 error under typical at-sea buoy pitch and roll tilts in comparison with an off-the-shelf IRGA system. A similar noise reduction factor of 2–8 is observed in water vapor measurements. The range of platform tilt motion testing also helps to document motion-induced error characteristics of standard analyzers. Study implications are discussed including findings relevant to past field measurements and the promise for improved future flux measurements using similarly modified IRGA on moving ocean observing and aircraft platforms.

Rectified transport of a single vibration-driven vehicle in the asymmetric channel

The rectification transport of a single vibration-driven self-propelled vehicle in a two-dimensional left–right asymmetric channel was experimentally investigated. The rectification efficiency of the vehicle moving from the center to the exit was statistically obtained for the range of channel widths, inter-channel asymmetry degrees, and platform tilt angles. The trajectory of its movement was also analyzed. It was found that the structure of the channel provides the main influence. Different channel shapes lead to different ranges of unfavorable widths, and transport efficiency decreases when the asymmetry diminishes — the two channels converge. The addition of external gravity does not counteract the structural limitations, but only affects the probability of departure.

Vibrating Tilt Platform Enhancing Immersive Experience in VR

One of the disadvantages of virtual reality systems of the past was the fact that they had visual-only interfaces. However, with the development of haptic technology, peripheral solutions to enhance the VR experience are gaining momentum, and many haptic systems are being developed for deepening VR immersion. This paper deals with the concept of a vibrating tilt platform allowing the change of three angles of inclination to thus reinforce the VR experience. The proposed system is flexible and adaptable to different sports, health, and education applications. In this paper, we present the mechanical and mechatronics aspects of the platform and usability testing results based on an immersive geological experience application. The first tests were studied in terms of the cyber sickness, perceived realism, and anxiety through both subjective (questionnaires) and objective (electroencephalogram) measurements. The results indicate that our platform increased anxiety levels and was perceived as realistic. Adding vibrations and tilting had a considerable impact on the immersion level and brain activity.

Analysis of Platform Leveling Systems for Tracked Feller-Buncher Machines

The study was devoted to the analysis of feller buncher platform leveling systems. The widespread use of these systems in the design of modern feller-buncher machines makes the study relevant to assess operational efficiency. The analysis was conducted in five stages using analytical and stochastic mathematical modeling methods. In the first stage, the existing layouts of alignment systems were analyzed from the position of force on the hydraulic cylinder rods of the platform tilt drive. The three-cylinder layout scheme, where the force on the hydraulic cylinder rod was 50…60% less than that on the two-cylinder layout, appeared to be the most expedient. In the second stage, a mathematical model for determining changes in the position of the center of mass of the feller-buncher depending on the inclination angle of the platform was derived. In the third stage, a mathematical model was derived for determining the limiting angle of slope of the terrain when the feller buncher moved up the slope. For this purpose, two calculation schemes were considered when the machine moved up the slope without and with a tilted platform. Zero support reaction on the front roller was taken as the stability criterion. In the fourth stage, a mathematical model for determining the limiting angle of slope of the terrain during the roll of the feller-buncher machine was obtained. In the fifth stage, the efficiency of the application of leveling systems was evaluated. A graph of the dependence of changes in the terrain slope angle on the platform slope angle was plotted, and a regression dependence for an approximate estimate was obtained. A regression analysis was also carried out, and dependencies were obtained to determine the weight of a feller-buncher with a leveling system and the added pressure on the ground caused by the increase in the weight of the base machine. The analysis of platform leveling systems showed the effectiveness of their application in the designs of feller-buncher machines, as it allows the machines to work on slopes with an inclination of 50…60% more than without them.

Heliotracking Device using Liquid Crystalline Elastomer Actuators

AbstractMany living organisms in nature respond to light stimulus and track the light source. Inspired by this, and to maximize the light‐harvesting ability of solar cells, here, a spontaneous helio‐tracking device based on the differential light‐induced actuation of liquid crystalline elastomers (LCEs) is demonstrated. The synthesis of the actuator material involves a robust thiol “click” polymerization, while the addition of indocyanine green (ICG) dye imparts the sensitivity to broad‐spectrum and near‐infrared light. Highly reproducible thermal and photo‐induced linear actuation is demonstrated. The device is based on a freely pivoting payload platform held in place by several linear LCE actuators around the 360° circumference. The side of the device, which is exposed to light, has the actuators contracting and tilting the platform toward the light source. As the light source (e.g., the Sun) is moving around the device, the platform tilt followed, always exposing the payload face to the light; in the dark, the device recovers its neutral position.

Modelling and Motion Control of BLDC motor for Pan tilt Platform

The usage of Brush-Less Direct Current (BLDC) motor has been increased in the industry especially in the field of Aerospace and electric bikes. The requirements for motion control were generated from the human eye features. The settling time and % overshoot were the desired features and design parameters. Based on desired features, values of  and ωn were found. The root-locus technique was applied to the uncompensated and compensated system, the results were not satisfactory. The % overshoot was very high, and the steady-state error was also very high. The state feedback controller was applied to the system. The % overshoot was controlled successfully but the steady-state error was still very high. To reduce the steady-state error to zero the integral control was applied. The comparison of results is presented in tabular form in the last section.

The role of enhanced plantar-surface sensory feedback on lower limb EMG during planned gait termination

Purpose/aim of the study: Generation of smooth movement relies on the central nervous system (CNS) having information from the visual, vestibular and somatosensory systems to effectively execute motor behaviour. Recently, cutaneous afferent inputs have been linked to lower leg motorneuron pools, resulting in a growing interest of adding texture to the plantar foot sole interface as a novel method to facilitate cutaneous feedback. The aim of this study was to characterize the changes in magnitude and temporal organization of muscle activity, and to investigate motor output changes from enhanced tactile feedback during perturbed gait termination. Materials and methods: Thirty young adults experienced an unpredictable platform perturbation when completing planned gait termination. The study manipulated two experimental variables: 1) direction of platform tilt (anterior, posterior, medial, lateral), and 2) foot sensory facilitation (non-facilitated, facilitated). Upper and lower leg EMG onset, cessation time and integrated EMG (iEMG) were measured in addition to common gait parameters (walking velocity, step length, step width). Results: Gait termination over a textured surface resulted in significantly earlier upper leg EMG onset times and modified iEMG of rectus femoris, vastus medialis and biceps femoris muscles. Conclusions: Results of this study suggest that the addition of cutaneous feedback under the plantar-surface of the foot increases the ability to generate an earlier muscle response, consequently improving response ability to an unexpected perturbation. Secondly, enhanced tactile feedback appears to inform the CNS of the magnitude of the threat to the balance control system, providing additional insight into how the CNS uses enhanced tactile feedback during a gait termination task.

Multisensory Interactions in Head and Body Centered Perception of Verticality.

Percepts of verticality are thought to be constructed as a weighted average of multisensory inputs, but the observed weights differ considerably between studies. In the present study, we evaluate whether this can be explained by differences in how visual, somatosensory and proprioceptive cues contribute to representations of the Head In Space (HIS) and Body In Space (BIS). Participants (10) were standing on a force plate on top of a motion platform while wearing a visualization device that allowed us to artificially tilt their visual surroundings. They were presented with (in)congruent combinations of visual, platform, and head tilt, and performed Rod & Frame Test (RFT) and Subjective Postural Vertical (SPV) tasks. We also recorded postural responses to evaluate the relation between perception and balance. The perception data shows that body tilt, head tilt, and visual tilt affect the HIS and BIS in both experimental tasks. For the RFT task, visual tilt induced considerable biases (≈ 10° for 36° visual tilt) in the direction of the vertical expressed in the visual scene; for the SPV task, participants also adjusted platform tilt to correct for illusory body tilt induced by the visual stimuli, but effects were much smaller (≈ 0.25°). Likewise, postural data from the SPV task indicate participants slightly shifted their weight to counteract visual tilt (0.3° for 36° visual tilt). The data reveal a striking dissociation of visual effects between the two tasks. We find that the data can be explained well using a model where percepts of the HIS and BIS are constructed from direct signals from head and body sensors, respectively, and indirect signals based on body and head signals but corrected for perceived neck tilt. These findings show that perception of the HIS and BIS derive from the same sensory signals, but see profoundly different weighting factors. We conclude that observations of different weightings between studies likely result from querying of distinct latent constructs referenced to the body or head in space.

Analysis on influence of static calibration on the axle-group weigh-in-motion system accuracy

The axle-group weigh-in-motion system has two functions: static weighing and dynamic weighing. According to the weighing model, the accuracy of dynamic weighing is affected by the static performance. This paper analyses the size of various factors affecting the static performance, such as sensor tilt installation, platform deformation, platform tilt installation, and these errors will lead to sensor swing, bearing head tilt, gravity line of action and sensor axis direction is not consistent, thus affecting the static weighing accuracy. However static calibration is the best way to reduce or even eliminate the above errors. The dynamic truck scale of different manufacturers with or without static calibration is used in the test process. The results show that the dynamic performance index can meet the requirements only after the static calibration is used.

Liquid marble particle wetting separation

Liquid marbles to separate wetting (silver nanowires) from non-wetting (graphite and talcum) particles is described here. Two types of liquid marbles are formed by coating the dry mixture test material on pendant or sessile drops. The silver nanowire particles are separated from the graphite or talcum shell by entering into the liquid core of the marbles. The liquid core is extracted into capillary tubes where the presence of silver nanoparticles was confirmed by a blue to colourless change arising from silver-mediated catalytic reduction of methylene blue and sodium borohydride solution. The use of an inclined rotating surface to coat the pendant drop was found to create liquid marbles in a more controllable manner. A platform tilt angle of 15o followed by rotation was found to provide more uniform albeit only partially coating the bottom of the pendant drop.

Singularity Analysis of 3 DOF Parallel Manipulators for Angular Drilling in Medical Applications

This paper focuses on two 3 – PRS (Prismatic – Revolute – Spherical) parallel manipulators (PMs) carried out by considering three type of singularities. For the study, pin joint forces and torques, linear displacement of nut and mobile platform (MP) tilt of TRIPOD and TRI-GLIDE PMs are taken as important parameters. The singularity positions of the parallel manipulators are simulated in ADAMS environment. The geometrical parameters of the parallel manipulators are considered in logical approach. Based on the results, the concluding remarks are summarized at the end to design the 3 - PRS parallel manipulators with better singular positions for angular drilling in medical applications.

Extended Order High Gain Observer Based Stabilization of 2 DOF Pan Tilt Platform for Aerial Imaging System

Aerial imaging systems are mounted on two axis serial robotic manipulators with high powered pan and tilt actuations, known as a Gimbal. The angular displacement of the gimbal is measured through very high precision sensors, typically shaft encoders with high PPR specifications. The purpose of the gimbal is to keep the orientation of the payload towards the target irrespective of the displacement of the UAV (unmanned aerial vehicle) and any other vibrations/disturbances that might be introduced into the system. Because of 2-DOF (degrees of freedom) dynamical model of the gimbal, frictional force, noise, cable restraint, disturbances from the external environment along with the motions of the vehicle’s body (as a result of manoeuvring or vibration), the spotting and tracking accuracy of the gimbal platform system may significantly degrade. The nature of these redundant disturbances is mostly of nonlinear nature and their modelling is a difficult task as they keep on changing. In order to cancel out these redundant disturbances and uncertainties, extended order high gain observer (EHGO) based feedback linearization control is used and extensive simulations are performed to show the comparison of tracking control without EHGO and after augmenting EHGO.

H-reflex modulation preceding changes in soleus EMG activity during balance perturbation.

When balance is compromised, postural strategies are induced to quickly recover from the perturbation. However, neuronal mechanisms underlying these strategies are not fully understood. Here, we assessed the amplitude of the soleus (SOL) H-reflex during forward and backward tilts of the support surface during standing (n = 15 healthy participants). Electrical stimulation of the tibial nerve was applied randomly before platform tilt (control) and 0, 25, 50, 75, 100 or 200ms after tilt onset. During backward tilt, a significant decrease in H-reflex amplitude was observed at 75, 100 and 200ms. The onset of the decreased H-reflex amplitude significantly preceded the onset of the SOL EMG decrease (latency: 144 ± 16ms). During forward tilt, the amplitude of the H-reflex increased at 100 and 200ms after tilt onset. The onset of H-reflex increase did not occur significantly earlier than the onset of the SOL EMG increase (127 ± 5ms). An important inter-subject variability was observed for the onset of H-reflex modulation with respect to EMG response for each direction of tilt, but this variability could not be explained by the subject's height. Taken together, the results establish the time course of change in SOL H-reflex excitability and its relation to the increase and decrease in SOL EMG activity during forward and backward tilts. The data presented here also suggest that balance mechanisms may differ between forward and backward tilts.

The effects of toe-out and toe-in postures on static & dynamic balance, risk of fall and TUG score in healthy adults

BackgroundToe-in and toe-out foot positions have not yet been tested for dynamic balance and risk of fall. The aim of this study was to investigate the effects of these two modifications on static and dynamic postural stability and risk of fall through instrumental (Biodex Balance System®) and functional (timed up and go-TUG test) tools. MethodologyTwenty healthy adults (8 males, 12 females, age: 29±4.10years, BMI: 21.56±2.36kg/m2) participated in this study. Static and dynamic (levels 8 and 2) balance with single stance and double stance and dynamic (level 8 and levels 6–2) for risk of fall with double stance were tested with the Biodex Balance System with three self-selected feet positions: straight (13.8°), toe-out (35.6°) and toe-in (−11.9°) for each test condition. Additionally, TUG test was performed with toe-out and toe-in gait. ResultsThe results of repeated measures ANOVA showed significant differences (p<0.05) between straight and modified toe angles in balance at dynamic level 2 with both double and single stance conditions. Significant differences (p<0.001) were also found in TUG scores for the test conditions. ConclusionToe-in and toe-out gait modifications have significant effects on balance at higher levels of platform tilt and functional balance. Further investigations with knee osteoarthritis patients and electromyography may provide insight in balancing strategies adopted by the body in toe-out and toe-in gait.