High Angular Velocity Research Articles

Spacecraft Nonlinear Attitude Dynamics Control with Adaptive Neuro-Fuzzy Inference System

Spacecraft undergoes several operation modes during its lifetime such as de-tumbling mode, attitude acquisition mode, stand-by mode, and high accuracy mode. Some of these modes are characterized by high nonlinearity while some are characterized by linearity. Thus, a high performance nonlinear discrete controller (HPNDC) is utilized. The controller behaves like a nonlinear attitude control algorithm when dealing with maneuvers with large spacecraft attitude angles, and behaves like a linear PD controller for maneuvers with small angles. The gains of the controller are calculated to account for the discretization process. Controller stability is proven using Lyapunov second method. The controller can effectively deal with the attitude dynamics and kinematics represented by a six degrees of freedom system. In order to avoid singularities in the attitude representation, the rotation is expressed by a quaternion. A quaternion error vector is utilized to express the difference between the spacecraft direction and the target direction. An adaptive neuro-fuzzy inference system (ANFIS) controller is developed in order to mimic the performance of HPNDC. The Fuzzy Inference System is Sugeno-type. In order to model the training data set, a combination of back-propagation gradient descent methods and the least-squares algorithms is used. A weighted average defuzzification is used to obtain the output. Training ratio is 0.85, and the rest of training data is utilized to test the training data overfitting. Disturbance torques acting on the spacecraft are mainly due to gravity gradient torques which are considered as the dominant effects for low earth orbit spacecraft. The high initial angular velocities and attitude angles are nullified by the ANFIS controller. The proposed algorithm can bring the spacecraft from the de-tumbling mode to the high accuracy mode within two orbits.

Relationship Between Lower Extremity Strength Asymmetry And Jump And Sprint Performance

The relationship between inter-limb strength asymmetry and athletic performance is not clearly well-known. Different results in the literature makes it difficult to form a common consensus on this issue. The aim of this study was to investigate the relationship between inter-lower limb strength asymmetry (ILLSA) values and jump and sprint performances. Forty-eight individuals (21.5±2.8 years, 1.74±0.1 m, 67.3±9.7 kg) voluntarily participated in this study. All participants participated in squat (SJ), countermovement jump (CMJ), 40m sprint run tests and right and left isokinetic concentric knee flexion and extension strength (IS) test at low (60°.s -1 ) and high (300°.s -1 ) angular velocities. The symmetry angle formula was used in order to determine the isokinetic knee strength asymmetry values between inter-lower limb. According to the results it was revealed that there was no relation (p>0.05) between ILSSA at low and high angular velocities and squat jump (r = -0.106 0.200), countermovement jump (r = -0.11 0.087) and 40m sprint (r = 0.012 0.810) performance. In conclusion, there is no negative or positive relationship between inter limb isokinetic knee strength symmetry angle and jump and sprint performances in physically active individuals.

Skater's Cramp: A Possible Task-Specific Dystonia in Dutch Ice Skaters.

ABSTRACTBackgroundSkater's cramp is an involuntary lower leg movement in skilled speed skaters. We aim to evaluate whether skater's cramp is compatible with task‐specific dystonia.MethodsA case‐control study tested 5 speed skaters exhibiting symptoms of skater's cramp and 5 controls. Affected skaters completed a standardized questionnaire and neurological examination. Video analyses included skating normally, intensely, and with extra mass around the skater's ankles. An Inertial Motion Capturing (IMC) device mounted on both skates provided angular velocity data for both feet.ResultsMedian time of onset of skater's cramp occurred after 12 (range 3–22) years of speed skating. Skater's cramp appeared as task specific; its onset was sudden and correlated to stress and aberrant proprioception. Symptoms presented acutely and consistently during skating, unilaterally in 4 and bilaterally in 1 skater. Visually, skater's cramp was an active, patterned, and person‐specific jerking of a skater's foot, either exo‐ or endorotationally. It presented asymmetrically, repeating persistently as the foot neared the end of the swing phase. The skater's affected leg had a longer swing phase (median, 1.37 [interquartile range {IQR}, 0.35]/1.18 [IQR, 0.24] seconds; P < 0.01), a shorter glide phase (median, 1.09 [IQR, 0.25]/1.26 (IQR, 0.29) seconds; P < 0.01), and higher angular velocity during the jerking motion. Symptoms remained constant irrespective of speed or extra mass around the ankle (P > 0.05). No significant differences between legs were detected in the control group.ConclusionsObserved clinical, visual, and kinematic data could be an early and tentative indication of task‐specific dystonia.

Robust adaptive relative position and attitude integrated control for approaching uncontrolled tumbling spacecraft

The six-degree-of-freedom coupling control of the relative orbit and relative attitude of a chaser approaching an uncontrolled tumbling target is studied in this paper. The chaser must reach an aimed position in the body coordinate system of the uncontrolled tumbling target spacecraft, and at the same time the attitude of the chaser should be synchronized with the attitude of the target. First, the integrated model of relative position and attitude is established based on the T–H equations and the error quaternion. Then, considering the safety of the approaching process, the nominal trajectory of the chaser is designed. Finally, a robust adaptive relative position and relative attitude controller is designed. An adaptive tuning method is used to deal with external disturbances and system uncertainties, and the upper bounds need not be known in advance. Simulation results show that the proposed method can track the aimed position of the uncontrolled tumbling target and complete the attitude synchronization, and the controller is still effective even for the target tumbling at a high angular velocity. Compared with the existing researches, the duration to complete position tracking and attitude synchronization is greatly reduced, the required maximum force and torque are smaller, and the dynamic response performance of the system is improved.

A digital interface integration circuit design for high precision quartz-gyro

A design of digital application specific integrated circuit (ASIC) of quartz-gyro is proposed in this paper. The digital drive circuit with fast-start oscillation and digital detection circuit with low noise are adopted to implement the digital output of the main circuit node and high precision angular velocity detection. The interface circuit is fabricated in a standard 0.35 [Formula: see text]m CMOS technology and test result shows the angular random walk and zero stability are [Formula: see text]/[Formula: see text] and [Formula: see text]/h ([Formula: see text]), respectively. The bias-instability is [Formula: see text]/h (Allen). The nonlinearity is limited to 0.035% and the zero temperature drift is [Formula: see text]/h from [Formula: see text] to [Formula: see text]. The chip exhibits great superiority on the aspects of high precision angular velocity digital detection and temperature characteristics of overall system.

Method of improving synchronisation of motion accuracy of rotary axis and linear axes under a constant feed-speed vector of end-milling point

ABSTRACTA five-axis machining centre is noted for its synchronous control capability that makes it feasible to create complicated three-dimensional surfaces such as propellers and hypoid gears quickly. As stated in this research, it is necessary to improve not only the accuracy of the machined shape but also the roughness of the machined surface of free-form surfaces. Therefore, in this study, it is aimed at maintaining the feed-speed vector at the milling point by through controlling two linear axes and a rotary axis to improve the machined surface quality. In addition, a method was suggested for reducing the shape error of machined workpieces by considering the differences in the servo characteristics of the three axes. The shape error was greatly decreased by applying the proposed method of using parameters (referred to as the precedent FF coefficient in this paper) determined by calculation instead of by trial and error. Moreover, to decrease the shape error, even in machining complex shapes that exhibit high angular velocity, the motor load, which is a key factor in the shape error, served as the focus, and a block diagram that considers the motor load was developed. The shape error can be evaluated via the simulation.

Influence of various setting angles on vibration behavior of rotating graphene sheet: continuum modeling and molecular dynamics simulation.

The Eringen's nonlocal elasticity theory is employed to examine the free vibration of a rotating cantilever single-layer graphene sheet (SLGS) under low and high temperature conditions. The governing equations of motion and the related boundary conditions are obtained through Hamilton's principle based on the first-order shear deformation theory (FSDT) of nanoplates. The generalized differential quadrature method (GDQM) is utilized to solve the nondimensional equations of motion. The molecular dynamics (MD) simulation is conducted, and fundamental frequencies of the rotating cantilever square SLGS are computed using the fast Fourier transform (FFT). The comparison of MD and GDQM results leads to finding the appropriate value of the nonlocal parameter for the first time. As an interesting result, this value of the nonlocal parameter is independent of the angular velocity. Results indicate that increases in various parameters, such as the angular velocity, hub radius, nonlocal parameter, and temperature changes in low temperature conditions, leads the first and the second frequencies to increase. In addition, it can be seen that the influence of the hub radius or nonlocal parameters on frequencies cannot be ignored in high angular velocities. Moreover, it is not possible to neglect the angular velocity or nonlocal parameter in high hub radius. The results show that the influence of parameters such as setting angle or nonlocal parameter on the first and the second frequencies increases when some parameters increase, such as the angular velocity, hub radius or temperature change. Graphical abstract (a) A schematic of a rotating cantilever nanoplate. (b) A schematic of cantilever armchair SLGS simulated by MD.

The impact of cavitation-activated water on combustion dynamics and environmental characteristics of coal-water slurry fuel

Among the new coal technologies the burning of low-grade coal in the form of coal-water slurry fuel (CWSF) is of a great interest. The basis of CWSF is a highly concentrated coal-water slurry consisting of finely ground coal, water or other liquid and plasticizing agents. The development of CWSF technology is highly relevant for solving global problems of resource conservation and ecology. The study is dedicated to CWSF properties with respect to Kansk-Achinsk coal and water. This paper presents the results of the influence of CWSF’s preliminary cavitation water treatment on the combustion dynamics of fuel, (including the features of the combustion temperature trends, delayed ignition time and time of complete combustion) and on its environmental characteristics. A rotary-type hydrodynamic oscillator at high angular velocity (10000 rpm) was used in supercavitation mode. It is shown that the technology of cavitation water treatment leads to a change in the dynamics of CWSF’s combustion and to an additional decrease in NOx emissions by 1.6 times, CO2 by 1.3 times.

High acceleration and angular velocity micro vibrating platform with IMU integration

Integrated multiple degree of freedom (DOF) micro vibrating platform is an emerging approach for self-calibration of long-term drifts in scale factor and offset of multi-axis MEMS-based inertial measurement units (IMU). A 3-DOF piezoelectric micro vibrating platform based on PZT-SOI with high acceleration and angular velocity by wafer-level fabrication is presented. To achieve the motion of out-of-plane movement and X/Y plane tilt, the structural optimization of the supporting folded beams has been investigated and analyzed, aiming to keep the optimal balance between stiffness, elastic coefficient and system damping ratio for the vibrating platform. The IMU is integrated on the vibrating platform with electrical connection by a two-layer routing scheme by silicon dioxide isolation. The out-of-plane acceleration and X/Y tilting angular velocity of the integrated system reach up to 34.8 g and 2500°/s, respectively. The micro vibrating platform with high dynamic performances plays an important role in the applications for MEMS inertial sensors with high measurement ranges.

Improving Walking Ability in People With Neurologic Conditions: A Theoretical Framework for Biomechanics-Driven Exercise Prescription

The purpose of this paper is to discuss how knowledge of the biomechanics of walking can be used to inform the prescription of resistance exercises for people with mobility limitations. Muscle weakness is a key physical impairment that limits walking in commonly occurring neurologic conditions such as cerebral palsy, traumatic brain injury, and stroke. Few randomized trials to date have shown conclusively that strength training improves walking in people living with these conditions. This appears to be because (1) the most important muscle groups for forward propulsion when walking have not been targeted for strengthening, and (2) strength training protocols have focused on slow and heavy resistance exercises, which do not improve the fast muscle contractions required for walking. We propose a theoretical framework to improve exercise prescription by integrating the biomechanics of walking with the principles of strength training outlined by the American College of Sports Medicine to prescribe exercises that are specific to improving the task of walking. The high angular velocities that occur in the lower limb joints during walking indicate that resistance exercises targeting power generation would be most appropriate. Therefore, we propose the prescription of plyometric and ballistic resistance exercise, applied using the American College of Sports Medicine guidelines for task specificity, once people with neurologic conditions are ambulating, to improve walking outcomes. This new theoretical framework for resistance training ensures that exercise prescription matches how the muscles work during walking.

Направленная самосборка микро- и нанопроводов оксида цинка

Methods of directed self-assembly of micro- and nanorods of zinc oxide using centrifugal force have been developed in the framework of the sol-gel method. Fibrous structures of zinc oxide, previously obtained in the sol, are artificially ordered on the far periphery of the substrate by centrifuging at high angular velocities.

Microwave phased array for aerological radar

The use of radars with phased antenna arrays in aerological atmospheric sounding systems significantly increases the technical characteristics of the radio channel, ensures reliable auto-tracking in the near zone at high angular velocities of the aerological probe, and reduces the overall dimensions of the radar station. Modelling and optimization of the parameters of the phased array and phase shifters were carried out in the NI AWR Design Environment. The results of the study showed that when designing a radar station, it is possible to reduce the level of side lobes of the phased array antenna pattern and the effect of reflections from the underlying surface under operating conditions significantly.

The method of attaining high rolling angular velocity of the bat in baseball batting

The method of attaining high rolling angular velocity of the bat in baseball batting

On the measurement of ski boot viscoelasticity

ObjectivesSince the polymeric materials commonly used for ski boots feature viscoelastic properties, the results of ski boot flexion tests are expected to be influenced by flexion velocity. Devices testing at all skiing specific ankle angular velocities are currently not available. Therefore, the aims of this study were to (i) develop a system allowing the testing of ski boots at high ankle angular velocities, (ii) quantify the effect of ankle angular velocity on viscoelasticity and (iii) determine the repeatability of the system. Design and MethodA test bench and a lower limb prosthesis were developed to determine tibia angle and applied torque. To assess the effect of angular velocity, two pairs of ski boots were tested at 5°/s, 50°/s, 75°/s and 100°/s. To assess stiffness variation and measurement repeatability, ten different used ski boots of different manufacturers were tested twice. ResultsFour ski boot flexion stiffness parameters and two energy dissipation factors were reported. The repeatability of the stiffness and the energy dissipation parameters was better than 4% and 3%, respectively. Stiffnesses and dissipation factors increased with increasing angular velocity. ConclusionIn the present study a reliable system facilitating the testing of ski boots at velocities of up to 100°/s was developed. To comprehensively characterise the viscoelastic properties of ski boots, we propose to report four ski boot stiffness parameters and two energy dissipation factors. An ankle angular velocity above 50°/s was recommended to perform mechanical tests of ski boots if employed in slalom-like skiing.

Clinical features and early detection of sport-related concussion.

AimAthletes who suffer sport‐related concussions but continue playing have a high probability of experiencing more severe symptoms with any subsequent concussion. This study used data from the authors’ clinical department to retrospectively investigate the clinical characteristics of sport‐related concussion and factors associated with delays in examinations.MethodsThe study included 38 patients with sport‐related concussions who were treated at the authors’ hospital. The sports during which the injuries occurred, occasions of injury, factors affecting the time from injury until examination at hospital, and prognoses were evaluated retrospectively.ResultsSport‐related concussions most frequently occurred in rugby and judo, where tackling, throwing, and other types of physical contact can result in impacts to the head region at high angular or linear velocity with acceleration. Some subjects showed consciousness disturbance and/or clear subjective symptoms immediately after the injury and were therefore examined at the hospital rapidly. However, other subjects who suffered amnesia or less obvious symptoms continued to play after the injury and had delayed examinations. In addition, there was a tendency for examinations to be delayed when an on‐site physician was present.ConclusionsIn contact sports where injury‐resulting events occur, such as impacts to the head at high angular or linear velocity with acceleration, athletes should be immediately withdrawn from play and evaluated for concussion, even if there are no obvious head injuries or symptoms. The immediate ascertainment of symptoms after physical contact would improve the rapid detection of sport‐related concussion.

Isokinetic flexion strength recovery after ACL reconstruction: a comparison between all inside graft-link technique and full tibial tunnel technique

ABSTRACTIntroduction: Recently, a new minimally invasive single bundle technique for anatomic ACL reconstruction has been described, called the ‘All-Inside graft-link technique’. One of the advantages of this procedure is the reduced morbidity at the donor site as the graft choice is the quadrupled semitendinosus, thus sparing the gracilis tendon. The aim of this study was to evaluate isokinetic flexion strength recovery in patients who underwent a gracilis sparing technique compared to those with a full-tibial tunnel technique using a doubled gracilis and semitendinosus tendons (DGST) graft.Methods: Patients were divided into two groups: Group A (22 patients) who underwent ACL reconstruction performed with an All-Inside graft-link technique; Group B (22 patients) who underwent ACL reconstruction with an Out-In technique and DGST graft. At a mean follow-up of 13 months, quadriceps and hamstring isokinetic peak torque deficits were recorded.Results: In group A, the mean side to side peak torque flexion difference between the operated and non-operated limbs was −3% and the mean torque at 30° was −7.5% at high angular velocity (180°/sec); the mean peak flexion torque was 7.2% and the mean torque at 30° was 3.1% at low angular velocity (60°/sec).In group B, the mean side to side peak flexion torque was −3.5% and the mean torque at 30° was −7.6% at high angular velocity (180°/sec); the mean peak flexion torque was −7.2% and the mean torque at 30° was −11% at low angular velocity (60°/sec).A statistically significant difference was found between the two groups at lower angular velocity both for the mean peak flexion torque and the mean torque at 30° (p = 0.009), with better results in the study group.Discussion/conclusion: Gracilis sparing technique is a minimally invasive technique for ACL reconstruction and yielded a significantly better flexion strength recovery at lower angular velocity compared to a full tibial tunnel technique with DGST for ACL reconstruction.

Performance analysis and experimental study of traveling wave type rotary ultrasonic motor in high-rotation environment.

In this work, the performance evolution of a traveling wave type rotary ultrasonic motor (TRUM) in a high-rotating environment is studied. The dynamic model of the stator of the TRUM in the centrifugal field is established, and the centrifugal stiffening effect on the stator caused by the centrifugal force is described. Furthermore, the warping deflection of the stator caused by the centrifugal force is analyzed. It is found to change the original contact state and decrease the performance of the TRUM. The contact model between the stator and rotor in the centrifugal field is established. Moreover, the performance model of the TRUM in the centrifugal field is established, and the mechanism and varying trend of the mechanical performance of the TRUM in this condition are analyzed. Finally, the performance test system of the TRUM is set, and the mechanical performance of the TRUM at high angular velocities environment is measured. And the methods to improve the tolerance of the TRUM in the centrifugal field are put forward.

Effects of low-intensity resistance training on muscular function and glycemic control in older adults with type2 diabetes.

Aims/IntroductionThe present study aimed to investigate the effects of low‐intensity resistance training with slow movement and tonic force generation (LST) on muscular function and glucose metabolism in older patients with type 2 diabetes.Materials and MethodsA total of 10 patients with type 2 diabetes (age 68.2 ± 9.7 years) engaged in LST training twice a week for 16 weeks. Before the long‐term intervention, they were subjected to the measurement of acute changes in blood factors relating to glycemic control as a result of a bout of LST. Body composition, muscular size and strength, and glycated hemoglobin were measured before and after the intervention.ResultsThe magnitudes of the acute changes in the blood factors were all small and were not considered harmful for glucose metabolism. The 16‐week LST training caused significant increases in thigh muscle thickness and strength, and decreases in body fat mass and glycated hemoglobin. The change in glycated hemoglobin showed a significant negative correlation with the change in the isokinetic knee extension peak torque measured at a high angular velocity (180°/s).ConclusionsThe LST training was shown to be effective for gaining muscular size and strength, and improving glycemic control in older patients with type 2 diabetes. The mechanisms underlying this effect might involve the improvement of contractile function in fast glycolytic fibers.

Water vortex hydropower technology: a state-of-the-art review of developmental trends

With the explosive growth of global energy demand coupled with effects of climate change, there is a significant shift towards green energy generation in recent years. Of the various renewable energy resources available, micro-hydro-power and pico-hydro-power remain very popular in both developed and developing countries. Since 2006, significant growth has spurted in the use of artificial free-surface vortices to generate low and ultra-low-head hydropower following the development of the so-called gravitational water vortex hydropower plant. The technology works on the principle of harnessing hydroelectric power from the high angular velocity experienced in the core of a whirlpool generated in a vortex chamber. In this article, a state-of-the-art review is undertaken on the vortex hydropower technology including a historical review of the technology, the underlying hydraulic principles of such devices, overview of research and technologies that have been deployed to date together with an evaluation of their performance and key findings. Currently, there are 19–22 known live vortex hydropower technologies operating internationally with key academic and commercial research activity in Europe and Asia. The average efficiency from these sites was found to be in the region of 53% which is lower than conventional propeller turbines but higher than waterwheel systems. It was found that the vortex plant, due to its ability to sustain relatively high efficiencies at low heads and small to medium flow rates, addresses a gap in the current turbine application chart. Its key advantage lies in the high-power densities produced compared with conventional technologies. The system also demonstrates potential to be able to function as a fish passage; however, stronger validation is required to prove this for a range of turbine systems. Finally, the authors propose a number of areas that should be investigated that should provide immediate improvements to the turbine in terms of performance.

Rotating network jets in the quiet Sun as observed by IRIS

Aims. We perform a detailed observational analysis of network jets to understand their kinematics, rotational motion, and underlying triggering mechanism(s). We analyzed the quiet-Sun (QS) data. Methods. IRIS high-resolution imaging and spectral observations (slit-jaw images: Si IV 1400.0 Å; raster: Si IV 1393.75 Å) were used to analyze the omnipresent rotating network jets in the transition region (TR). In addition, we also used observations from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observation (SDO). Results. The statistical analysis of 51 network jets is performed to understand their various mean properties, e.g., apparent speed (140.16 ± 39.41 km s−1), length (3.16 ± 1.18 Mm), and lifetimes (105.49 ± 51.75 s). The Si IV 1393.75 Å line has a secondary component along with its main Gaussian, which is formed due to the high-speed plasma flows (i.e., network jets). The variation in Doppler velocity across these jets (i.e., blueshift on one edge and redshift on the other) signify the presence of inherited rotational motion. The statistical analysis predicts that the mean rotational velocity (i.e., ΔV) is 49.56 km s−1. The network jets have high-angular velocity in comparison to the other class of solar jets. Conclusions. The signature of network jets is inherited in TR spectral lines in terms of the secondary component of the Si IV 1393.75 Å line. The rotational motion of network jets is omnipresent, which is reported first for this class of jet-like features. The magnetic reconnection seems to be the most favorable mechanism for the formation of these network jets.