Showing papers on "Angular velocity published in 1988"

Angular momentum loss in low-mass stars

Abstract: The wind models discussed by Mestel (1984) are used here to formulate a general expression for the rate of angular momentum loss by magnetic stellar winds as a function of magnetic field configuration, rotation rate, and stellar model properties. The sensitivity of the rotation velocity to the various wind model parameters, the initial angular momenta, and the time dependence of the angular velocity for each mass is shown. The theoretical results are compared with observational ones, and it is found that the existence of very rapidly rotating stars in young clusters implies that low-mass stars are formed with a large spread of angular momentum. The high efficiency of angular momentum loss through magnetic stellar winds causes the rotation velocity to become less dependent on initial angular momentum J0 with time; by 300 million yur, the rotation velocity becomes independent of J0. This results in a decrease with time in the spread of rotation velocities as a function of stellar mass in young clusters.

Postural movements induced by rotations of visual scenes.

Abstract: The effect of visual information processing of a rotating visual scene on postural responses of a standing subject was studied. Rotation of a scene induced postural sway movements involving rotations in the ankle joint. For modulation frequencies of rotation below 0.3 Hz, a clear correlation was found between the visual stimulus and the postural movements in the lateral direction. The amplitude of postural movements appeared to be independent of the angular velocity of the rotation of the scene if the angular velocity exceeded 5 deg/sec for sinusoidally modulated rotations or 10 deg/sec (rms values) for randomly modulated rotations. To facilitate distinction between the contributions from visual information processing of the incoming visual stimuli and from the motor system, a model is presented that explains some aspects of visuo-motor interaction.

Multidirectional optical scanner

Abstract: A multidirectional scan pattern is generated by two mirrors, each inclined at a tilt angle and rotated about an axis at an angular speed. The size and shape of the pattern are controlled by adjusting the tilt angles and the angular speeds.

Eye movements induced by off-vertical axis rotation (OVAR) at small angles of tilt.

Abstract: Off-vertical rotation (OVAR) in darkness induced continuous horizontal nystagmus in humans at small tilts of the rotation axis (5 to 30 degrees). The horizontal slow eye velocity had two components: a mean velocity in the direction opposite to head rotation and a sinusoidal modulation around the mean. Mean velocity generally did not exceed 10 deg/s, and was less than or equal to the maximum velocity of optokinetic after-nystagmus (OKAN). Both the mean and modulation components of horizontal nystagmus increased with tilt angle and rotational velocity. Vertical slow eye velocity was also modulated sinusoidally, generally around zero. The amplitude of the vertical modulation increased with tilt angle, but not with rotational velocity. In addition to modulations in eye velocity, there were also modulations in horizontal and vertical eye positions. These would partially compensate for head position changes in the yaw and pitch planes during each cycle of OVAR. Modulations in vertical eye position were regular, increased with increases in tilt angle and were separated from eye velocity by 90 deg. These results are compatible with the interpretation that, during OVAR, mean slow velocity of horizontal nystagmus is produced by the velocity storage mechanism in the vestibular system. In addition, they indicate that the otolith organs induce compensatory eye position changes with regard to gravity for tilts in the pitch, yaw and probably also the roll planes. Such compensatory changes could be utilized to study the function of the otolith organs. A functional interpretation of these results is that nystagmus attempts to stabilize the image on the retina of one point of the surrounding world. Mean horizontal velocity would then be opposite to the estimate of head rotational velocity provided by the output of the velocity storage mechanism, as charged by an otolithic input during OVAR. In spite of the lack of actual translation, an estimate of head translational velocity could, in this condition, be constructed from the otolithic signal. The modulation in horizontal eye position would then be compensatory for the perceived head translation. Modulation of vertical eye velocity would compensate for actual changes in head orientation with respect to gravity.

Flight control during ?free yaw turns? inDrosophila melanogaster

Abstract: 1. A new method for studying flight control in flies is introduced. In this set-up (thread paradigm) the fly is free to rotate around its vertical body axis but is otherwise kept stationary. The fly's orientation is continuously monitored optoelectronically. For statistical evaluation flight traces are divided into ‘turns’ (summed successive angular displacements until the direction of turning changes). 2. In the thread paradigm flies perform quick turning maneuvers corresponding to torque spikes at the torque compensator and to body saccades in free flight. In between, flies maintain a rather straight course. This obvious observation is reflected in bimodal velocity and turn histograms, both of which are composed approximately of a Gaussian and an exponential distribution. 3. The frequency of body saccades declines exponentially (decline constant 0.026/°), angular peak velocities increase linearly (12.5(°/s)/°=12.5/s), and the duration of saccades saturates (at about 250 ms) with increasing size of saccade. After a quick rising phase (40–60 ms) body saccades show, as a mean, an exponential drop of angular velocity with a time constant of about 40 ms. 4. The pattern dependency of the turning behavior resembles that measured using the torque compensator. The size of body saccades is influenced by the visual pattern wavelength. The direction of a body saccade may depend on that of the preceding one thus revealing its special status as part of a larger behavioral sequence. 5. Experiments with constant torque bias reveal an internal reference of zero torque. Corresponding measurements using the torque compensator suggest an efficacy model to be applicable in characterizing torque traces with constant rotatory bias. This new model allows simulation of constant-bias torque traces by applying a single efficacy factor to no-bias torque traces.

Trajectory planning in robotic continuous-path applications

Abstract: Trajectory planning of robot motions for continuous-path operations is formulated in configuration space, resorting to the intrinsic properties of the path traced by point of the end effector. It is shown that, by referring the orientation of the end effector to a unique orthogonal frame defined at every point of the aforementioned path, a systematic procedure for trajectory planning in configuration space is derived. The computations required to determine the angular velocity and angular acceleration of the path frame reduce to computing the Darboux vector of the path and its time derivative. >

Motion perceptions induced by off-vertical axis rotation (OVAR) at small angles of tilt.

Abstract: Off-vertical axis rotation in darkness induces a perception of body motion which lasts as long as rotation continues. Perceived body motion is the combination of two simultaneous displacements. The most easily perceived is a translation without rotation along a conical path, at the frequency of the actual rotation. Meanwhile, the subjects feel as if they were always facing towards the same direction. The summit of the cone is generally below the head, from the waist to below the feet, and subjects have a sense of progression in the direction opposite to actual spinning. Some subjects feel, on the contrary, the summit of the cone above their heads, and the progression in the direction of spinning. Subjects also perceived another body motion, although it was faint for some of them. It consists of a rotation at low velocity in the same direction as progression along the cone. The axis of the cone is perceived as slowly rotating along a larger cone. These motion perceptions increase with tilt angle and rotation velocity. They probably result from the analysis by the Central Nervous System of the acceleration acting on the otoliths. The perceived trajectory would be reconstructed from estimates of gravity, and kinematic variables such as head translational acceleration and velocity, and head rotational velocity. The same variables would account for OVAR-induced nystagmus. Motion sickness would result from the impossibility of reconstructing a consistent body movement from most sets of values of these variables.

Least squares method and apparatus for determining track eccentricity of a disk

Abstract: A transducer head (12), held in a fixed position as a preformatted disk (16) is rotated a full revolution, reads any sector address (30) accessible to the head. The addresses read come from a plurality of track revolutions (19) that depend on the magnitude of the eccentricity of the disk. A computer (52), programmed with a least squares algorithm, first coordinates (1) data corresponding to the angular position of the disk each time an address is read, with (2) data corresponding to the actual radius of each address. The computer then transforms the array of data coordinated into a sinusoidal track eccentricity compensating signal of the form D cos (wt + E) where the amplitude D is a constant computed from the least squares algorithm corresponding to the distance between the center of the disk and its rotational axis, the phase E, which is also a constant computed by least squares, corresponds to the angle the center of the disk is from an angular reference position, and wt is a variable equal to the product of disk angular speed and time.

Box-shaped Galactic Bulges. I. Equilibrium Models

Abstract: Simple self-consistent stellar distribution-function models are presented which have a box-shaped appearance and are cylindrically rotating. The distribution function is a function only of the two classical isolating integrals of an axisymmetric system, energy and the component of angular momentum parallel to the axis of symmetry. The major difference between these models and previous ones is the mode of truncation of the distribution function. The truncation contour has the same functional form as all of the other contours of the distribution function. This ensures that the mean rotation in the meridional plane of the models is identically cylindrical. It is argued that this mode of truncation is similar to what would be found in a system that has suffered significant dissipation. A second paper in this series presents comparisons of the models to photometric and kinematic observations of a number of box-shaped galactic bulges. 23 references.

Dragging of inertial frames by the rotating Earth: Proposal and feasibility for a ground-based detection

Abstract: We are proposing a ground-based experiment to detect the Lense-Thirring drag due to the rotating earth by an off-line comparison between an astrometric measurement of the Earth rotation and an inertial measurement of the angular velocity of the laboratory. It is shown that the former, by means of routine observations of Very Long Baseline Interferometry, has already reached the accuracy needed to perform a 3 % experiment on a time span of ∼1 yr. We propose to perform the latter by a dynamical detector of local rotation of novel conception, the Gyromagnetic Electron Gyroscope. Its principle of operation is briefly discussed together with its response to rotationlike gravitational fields.

Streak-line motion during steady and unsteady axisymmetric vortex breakdown

Abstract: Numerical calculations of vortex breakdown generated within a closed circular cylinder by rotation of one of the end walls have been performed. The solutions are used to compute steady streak‐line patterns for dye introduced both symmetrically and asymmetrically about the symmetry axis upstream of the breakdown bubble. Beginning from such a steady state, the end‐wall angular speed is impulsively increased and the asymmetric streak‐line pattern is observed during a portion of the subsequent period of unsteady flow.

Elliptical-drive oscillating compressor and pump

Abstract: A rotary apparatus uses vanes which oscillate with respect to one another, while simultaneously rotating within a chamber, to compress a gas or pump a liquid. The oscillating motion results from interaction of at least a single coupled pair of elliptical drive members. When the driver elliptical member is rotated at a constant angular velocity, it causes the driven elliptical member to rotate with a varying angular velocity. As the driven elliptical member is connected to at least one vane, that vane also rotates with a varying angular velocity. In a preferred embodiment, two pairs of meshing elliptical gears drive four vanes with an oscillating and rotating motion.

Nystagmus induced by off-vertical rotation axis in the cat

Abstract: 1) In the alert cat, nystagmus induced by off-vertical axis rotation (OVAR) was recorded following steps in head velocity or ramps of velocity at constant acceleration below canal threshold. Dependence of nystagmus characteristics on tilt angle of rotation axis and head velocity was studied. Similar results were obtained with both types of stimulation. 2) Mean and modulation amplitude of horizontal eye velocity increased with tilt angle in the range 0-30 degrees. 3) Both variables increased also with head velocity, but with different trends, probably because they are set by different mechanisms. When head rotational velocity was increased above 80 degrees/s, mean eye velocity progressively decreased to zero. 4) In spite of variations from one animal to another, some regularity was observed in the phase of eye velocity modulation. In several cases, a reduction in phase lead of eye velocity with respect to conventional origin of phases (nose-down position) was observed when head velocity increased. 5) Time constant of post-OVAR nystagmus decreased with the tilt angle of the rotation axis from gravity, but not with the orientation of the head with respect to rotation axis. 6) The results could be accounted for by a general equation describing the vestibulo-ocular reflex, provided that estimates of kinematic variables of head movement (head rotational and translational velocities), and visual target distance could be computed by the Central Nervous System.

Torsion transducer for magnetic storage disk drives

Abstract: A torsion transducer for providing electrical position and angular velocity signals for a device driven in a bidirectional partial rotational mode, such as commonly found in the rotary actuator arm of a disc drive for rotating computer memories. The torsion transducer comprises a torsion bar in the form of a wire, with one end attached to the rotating element of the actuator arm and the other to a piezoelectric transducer operating in the shear mode, which is anchored to the stationary frame of the device. As the torsion bar is twisted by the angular motion of the rotary element, torque is applied to the piezoelectric transducer, which then generates an electrical signal that can be processed to represent position and angular velocity of the rotary elements of the actuator arm.

Slow rotation of radiating viscous-fluid universe coupled with scalar field

Abstract: Investigations are being made on slowly rotating models of radiating viscous fluid coupled with scalar field in spherically-symmetric Einstein Universe, and some new analytic solutions are found to substantiate the possibility of the existence of such universes. The nature and role of the rotational velocity Ω(r, t) which is related to the local dragging of inertial frames and that of matter rotation ω(r, t) are studied. We also discuss the effects of the radiation field and the scalar field on the rotation. Rotating models which are expanding are obtained, where in all the cases the rotational velocities are found to decay with the time; and these models may be taken as good examples of real astrophysical situations.

Dynamical Evolution of the Rotation of Venus

Abstract: By considering the torque of the bodily tides, the effect of the core-mantle viscous coupling and the torque of the atmospheric tides have been obtained by numerical calculation: the evolution of the spin angular velocity Ω♀ and the obliquity β of the Venus are calculated numerically with the step-variable Runge-Kutta method of 7th order; and 7 sets of the probable Cytherean spin evolution have been obtained. It is indicated that the present spin state of Venus is the result of long-term evolution within the reasonable ranges of some disposable parameters. The early spin period is between 7 h to 2 d and the corresponding obliquity is about 90 ° ~ 100 °. The effects of the torques of body and atmospheric tides and the core-mantle viscous coupling of Venus on its spin angular velocity could nearly cancel out each other about a billion years ago. Therefore, Venus could have been captured in a spin-orbit resonant state by the gravitational torque of the Earth on the permanent deformation part of Venus; and this resonant state has lasted up to the present time.

Slowly-rotating charged viscous-fluid universes: Exact solutions

Abstract: By considering a spherically-symmetric metric, certain new analytic solutions for charged rotating viscous-fluid cosmological models in the Einstein universe are found out. Five different cases in which the nature and role of the rotational velocity Ω(r, t) is related to the local dragging of inertial frames and that of matter rotation ω(r, t), are investigated. Except for the case of ‘perfect dragging’, the electric field is found to have a damping effect on the rotation of matter. The damping effect is seen to be roughly analogous to the viscosity. In some solutions we find out the temporal restrictions for realistic astrophysical situations. Models which are rotating as well as expanding are also obtained and studied.

The steady state Navier–Stokes equations for incompressible flows with rotating boundaries

Abstract: When a rigid body performs a rotation in a fluid, the system of governing equations consists of conservation of linear momentum of the fluid and conservation of angular momentum of the rigid body. Since the torque at the interface involves the drag due to the fluid flow, the conservation of angular momentum may be viewed as a boundary condition for the field equations of fluid motion. The familiar no-slip condition becomes an additional equation in the system which not only governs the fluid motion, but also the motion of the rigid body. The unknown functions in the system of equations are the velocity field and the pressure field of the fluid motion and the angular velocity of the rigid body.In this paper we obtain existence and uniqueness results for the steady state problem in which a rigid body rotates about an axis of symmetry in a viscous incompressible fluid.

Cylinder abnormality detecting device for internal combustion engine

Abstract: PURPOSE: To promptly further accurately detect only a cylinder of abnormality by changing angular speed reference value in the next cylinder to a value larger than the normal updated value, when a rotary angular speed of an output shaft decreases lower than the angular speed reference value in an internal combustion engine. CONSTITUTION: A rotary angular speed of an output shaft in an internal combustion engine M1 is detected by a means M2, synchronizing with a stroke of each cylinder. While it is discriminated by a means M3 whether or not a rotary angular speed of a predetermined stroke in each cylinder is smaller than the angular speed reference value set from a rotary angular speed before the predetermined stroke. Further the angular speed reference value in the next cylinder is changed by a means M4 being based on the rotary angular speed. When the rotary angular speed is smaller than the angular speed reference value, a cylinder of abnormality is detected by a means M5. Here the angular speed reference value is changed by a means M6 to a value larger than the value updated in the means M4. Thus, even when an irregular misfire or the like is generated in the other cylinder, the cylinder of abnormality is promptly further accurately detected. COPYRIGHT: (C)1990,JPO&Japio

On the control of magnetically levitated robot wrists

Abstract: The author deals with the problem of controlling six-degrees-of-freedom magnetically levitated robot wrists. This control problem is greatly simplified by the use of the Euler quaternion representation of rotation. It is shown that both the approximate and exact linearizations of the equations of motion are fully decoupled second-order systems, and therefore simple scalar PD/PID (proportional-derivative/proportional-integral-derivative) compensators can be used for their control. The author presents a novel nonlinear angular velocity or angular momentum observer and shows that it has global and eventually exponential convergence. The author presents simulation results and discusses some implementation issues and experimental results. The simulations, using the magic wrist parameters, showed that these controllers perform well. >

Linear internal waves generated by density and velocity perturbations in a linearly stratified fluid

Abstract: A generalized theoretical analysis and finite-difference solutions of the Navier-Stokes equations of the initial-value problem are applied to obtain the linear internal wave fields generated by a density perturbation and two rotational velocity perturbations in an inviscid linearly stratified fluid. The velocity perturbations are those due to an axisymmetric swirl and a vortex pair. Solutions obtained correspond to the strong stratification limit.The theoretical results of the rotational perturbation cases show an oscillating non-propagating disturbance, which is absent in the density-perturbation case. The swirl-flow solution shows an oscillatory behaviour in both the angular momentum deposited in the fluid and in the torque exerted by the external gravitational force field. The vortex-flow solution shows a vertical ray pattern.The equi-partitioning of energy is reached at about 0.4 of a Brunt-Vaisala (B.V.) period. The potential energy-kinetic energy conversion, or vice versa, takes place between 0.15 and 0.3 B.V. periods.

Balance shaft driving device for engine

Abstract: PURPOSE:To suppress the variation of torque and vibration over the entire revolution range by controlling the offset quantity in variable ways by controlling the revolution and the vertical shift of a pair of balance shafts according to the angular speed of a crankshaft, angle and the engine load. CONSTITUTION:A pair of balance shafts 1 and 1' each having a variable height is installed in offset state at equal intervals at the right and left sides onto the body of an engine 3, and when the crankshaft of the engine 3 is revolved at an angular speed of omega in the clockwise direction, the balance shaft 1 revolves at an angular speed of 2omega in the counterclockwise direction. Revolution control is performed according to the angular speed omega of the crankshaft, angle, and the engine load by a controller 17, and each offset quantity of a pair of balance shafts 1 and 1' is controlled in variable ways by the vertical shift control. Therefore, even if the load of the engine 3 varies, the corresponding offset moment is generated, and the variation of torque is suppressed over the entire revolution range from the low speed to the high speed, and vibration is suppressed.

Angular velocity measuring device

Abstract: PURPOSE: To accomplish accurate measurement by deciding data obtained when output from an angle sensor does not change for a certain time as offset data and performing offset correction. CONSTITUTION: The output from an angular velocity sensor 2 is inputted in a computation device 12 through a sensor amplifier 3 and an AD converter 4. When it is understood based on the output from the steering angle sensor 13 that a vehicle travels straight for several seconds, the computation device 12 arithmetically averages the data outputted from the angular velocity sensor 2, which is incorporated just before, and the obtained average is set as the offset data. The computation device 12 subtracts the newest offset data from the angular velocity data obtained on and after that an executes the offset correction. COPYRIGHT: (C)1990,JPO&Japio