Showing papers on "Angular displacement published in 1997"

Stereoscopic Digital Particle Image Velocimetry for Application in Wind Tunnel Flows

Abstract: A particle image velocimetry system capable of accurately recovering the out-of-plane velocity component has been realized based on a stereoscopic viewing arrangement. To allow a large viewing angle with long focal length objective lenses, the angular displacement or Scheimpflug imaging configuration is employed in which the image, object and lens planes intersect in a common line. The varying magnification factor associated with this imaging configuration is accounted for using an accurate and simple-to-use calibration procedure based on solving the projection equations for each of the two cameras. A pair of high-resolution cameras, both capable of recording image pairs in the microsecond range, are synchronized to a pulsed Nd-YAG laser. By placing the cameras on either side of the light sheet the favourable light scattering characteristics of micron-sized seeding particles in forward scatter provide images at significantly higher illumination than at normal or backscatter viewing angles. Ultimately designed for use in industrial wind tunnels, the camera system is capable of working with non-symmetric arrangements. It has been successfully tested in a laboratory environment by imaging the unsteady flow field of a vortex ring passing through a laser light sheet. Adaptive processing software capable of dynamically adjusting the sample location of the interrogation windows to the local displacement vector significantly improves data yield. The algorithm requires only the selection of the final window/overlap size. The hierarchical interrogation approach permits the processing of images whose displacement dynamic range exceeds the interrogation window size.

Method and apparatus for angular position and velocity based determination of body sway for the diagnosis and rehabilitation of balance and gait disorders

Abstract: A method and apparatus for the diagnosis and rehabilitation of abnormal postural sway of a subject during standing or the performance of movement tasks is provided. Body sway sensors, such as angular velocity transducers, are attached to the body, such as the upper torso, of the subject. Output signals from the body sway sensors are transformed into detailed body sway angular displacement and velocity information by a system processor. The body sway angular displacement and velocity information may be displayed to an operator for diagnosis of the subject's balance or gait disorders. The angular displacement and velocity information may also be provided as feedback to the subject, to augment the signals normally used by the subject's brain to help stabilize body sway and improve balance. Rehabilitory feedback may be in visual, auditory, and/or tactile form, and/or in the form of electrical stimulation of the vestibular nerve. For visual feedback, a lightweight imaging system mounted on a pair of eyewear may be used to project a body sway angle and angular velocity feedback display into an eye of the subject. An angular position and velocity based body sway diagnosis system in accordance with the present invention may be used to monitor simultaneously the body sway of multiple subjects, and to provide rehabilitory feedback to such subjects, without interfering with or restricting the normal movement activities of the subjects.

Vision-based six-degree-of-freedom computer input device

Abstract: A vision-based controller provides translational and rotational control signals to a computer or other input driven device. The controller includes a tracked object, positioned in space and having at least a first reference point and a second reference point. The tracked object is capable of three dimensional rotational and translational movement. At least one imaging device, positioned at a distance from the tracked object, generates an image of the tracked object, at plural succeeding times. A processor unit receives the image, comprised of pixel values, from the imaging device; identifies pixels corresponding to a current center of the tracked object, the first reference point and the second reference point; determines a current dimension (i.e., size or radius) of the tracked object; calculates a translational and rotational displacement of the tracked object based on the above information; and generates control signals in accordance with the transitional and rotational displacement.

Convergent beam scanner linearizing method and apparatus

Abstract: A method of position encoding in convergent beam scanned imaging systems (10) is provided that reduces distortion. Distortion of a scanned image is introduced in convergent beam systems through the application of mirror "pullback" at the limits of the scanning sector, which is required to retain focus over the field of view or scanning sector. The rotational position of a scanner mirror (14) is not proportional to the spatial scanned angle or object space angle (δ) due to this pullback, and thus introduces distortion. Various components of the pullback motion are utilized to provide the compensation required to overcome this distortion. A process is provided that determines the position of a mirror position detector such that the pullback translation motion of the scanner mirror (14) is used to compensate for the nonlinear rotational motion of the scanner mirror (14). This is accomplished by locating the mirror position detector (16) at a predetermined radial distance and angular position with respect to the scanner mirror (14) point of rotation and sensing the rotation of the scanner mirror (14) and pullback. By appropriately selecting the angular position of the mirror position detector (16) with respect to the scanner mirror (14) center of rotation and the direction of pullback, the output of the mirror position detector becomes a substantially linearized representation of the object space angle (δ). Significant reductions in distortion can thus be obtained via optimizing the angular position of the mirror position detector (16) through an iterative mathematical approach performed by a computer.

Spatial orientation in humans : perception of angular whole-body displacements in two-dimensional trajectories

Abstract: Vestibular perception of whole-body passive rotation in the horizontal plane was studied by applying two-dimensional (2D) motion to eight blindfolded healthy volunteers: pure rotations in place, corner-like trajectories and arcs of a circular trajectory were randomly applied by means of a remotely controlled robot. Angles embedded in the 2D trajectories were 45°, 90°, 135° and 180°. Stimulation of semicircular canals was the same for all trajectories but was accompanied by concurrent otolith stimulation during circular motion. Subjects participated in two successive experimental sessions. In the first session they were instructed to use a pointer to reproduce the total angular displacement after the motion (REPRODUCTION); in the second session they had to keep pointing towards a remote (15 m) memorised target during the motion (TRACKING). In REPRODUCTION subjects tended to overestimate their rotation angle by 28 ± 11% (mean ± SD). There was no systematic effect of the trajectory. Overestimation also occurred when subjects were required to rotate in darkness by 180° (by controlling a joystick). In TRACKING there was virtually no overestimation (6 ± 17%) and the movement of the pointer matched the dynamics of angular motion. We conclude that (a) the brain can separate and memorise the angular component of complex 2D motion; however, a large inter-individual variability in estimating its amplitude exists; (b) in the range of linear accelerations used in the study, no appreciable effect of otolith-canal perceptual interaction was shown; (c) angular displacements can be dynamically transformed into matched pointing movements; (d) overestimation seems to be typical of delayed judgements of angular displacement and of self-controlled rotations in place. This could be due to the characteristics of the physiological calibration of the vestibular input.

Method for the determination of the distance and the angular position of an object

Abstract: A method of determining distances and angular positions of stationary and moving objects (3), for example in an area to be monitored in connection with for instance swing doors. The determination is done by means of triangulation where light, which in the main part is collimated, is transmitted (1) into the area at different angles and in a certain sequence. The reflected light is correspondingly registered on a position-sensitive sensor (5) which is positioned at a certain distance from the transmitter (1). The position (5a, 5b), where the reflected light falls on the sensor (5), represents the distance, and the moment when the light is received represents the angular position of the detected object. The values are compared to stored reference values which change when the angle of the door's opening is changed.

Ambient-temperature passive magnetic bearings: Theory and design equations

Abstract: Research has been underway at the Lawrence Livermore National Laboratory to build a theoretical and experimental base for the design of ambient-temperature passive magnetic bearings for a variety of possible applications. in the approach taken the limitations imposed by Earnshaw`s theorem with respect to the stability of passive magnetic bearing systems employing axially symmetric permanent-magnet elements are overcome by employing special combinations of elements, as follows: Levitating and restoring forces are provided by combinations of permanent-magnet-excited elements chosen to provide positive stiffnesses (negative force derivatives) for selected displacements (i.e., those involving translations or angular displacement of the axis of rotation). As dictated by Eamshaw`s theorem, any bearing system thus constructed will be statically unstable for at least one of the remaining possible displacements. Stabilization against this displacement is accomplished by using periodic arrays (`Halbach arrays`) of permanent magnets to induce currents in close-packed inductively loaded circuits, thereby producing negative force derivatives stabilizing the system while in rotation. Disengaging mechanical elements stabilize the system when at rest and when below a low critical speed. The paper discusses theory and equations needed for the design of such systems.

Dual axis mechanically actuated motion platform

Abstract: A dual axis mechanically actuated motion platform which allows a user to move him or herself through a wide range of angular displacement in two intersecting axes individually or simultaneously by apply manual pressure to a lever in the direction of desired angular displacement. The motion platform is comprised of a base frame, a user support platform mounted on top of a universal joint, and a bearing mounted, preloaded offset linkage system coupled to a joystick lever. The offset linkage system creates enough increased mechanical advantage to move the seat platform in concert with the movement of the joystick lever, providing the user with the feeling of controlling an aircraft and the attendant sensations of pitch and roll motion.

Method and apparatus for sensor-less control of permanent magnet synchronous motor

Abstract: A permanent magnet synchronous motor having multiple-phase armature windings and a rotor is subjected to sensor-less control. Phase voltages are generated in response to voltage command values. The generated phase voltages are applied to the armature windings. Phase currents through the armature windings are detected. The detected phase currents depend on the voltage command values. An angular position and an angular velocity of the rotor are calculated from the detected phase currents. The voltage command values are adjusted in response to the calculated angular position and the calculated angular velocity of the rotor to implement feedback control of the motor. An angular velocity of the rotor is estimated from a time-domain variation in the calculated angular position of the rotor. A determination is made as to whether or not the calculated angular velocity of the rotor and the estimated angular velocity of the rotor are substantially equal to each other. The calculated angular position of the rotor is changed by a predetermined phase value and is thereby corrected when it is determined that the calculated angular velocity of the rotor and the estimated angular velocity of the rotor are not substantially equal to each other.

Safety device for vehicles

Abstract: Safety devices and methods of detecting the rotation of a vehicle are disclosed. The safety devices include micromechanical gyros for determining the angular position and angular speed of rotation of the vehicle about one of its axes, a control unit for comparing the angular position and angular speed of rotation with predetermined threshold values for those values in which at least one of the threshold values is variable and is based upon a predetermined operational condition of the vehicle, and at least one protective device actuatable by the control unit based upon that comparison. The methods disclosed include determining the angular position and angular speed of rotation of the vehicle about at least one axis, comparing the angular position and angular speed of rotation with predetermined threshold values for those values, at least one of the threshold values being variable and based upon at least one predetermined operational condition for the vehicles, and actuating at least one protective device based upon that comparison.

Target angular motion effects on ISAR imaging

Abstract: The authors investigate the effects of target roll, pitch and yaw motions in ISAR image reconstruction. They determine the impulse response of an imaging system in the presence of angular motions and evaluate the conditions under which pitch, roll and yaw have negligible effect on image focus. The theoretical analysis is finally validated by presenting and discussing some simulation results.

Apparatus for controlling speed of a rotary motor

Abstract: A speed control apparatus for a rotary motor includes a motor for rotating at a speed based on a torque command and which outputs a present angular position and a present angular speed of the motor. A speed measuring unit is provided for obtaining a speed error representing the difference between a reference angular speed and a present angular speed. A speed controller is provided for outputting a current command for controlling a rotational speed of the motor. A learning compensator is provided for correcting an effect of a disturbance expressed as a function of an angular position and an angular speed applied to the motor, via a repetitive learning process using the reference angular speed, any one of the speed error from the speed measuring unit and the current command output from the speed controller and the present angular position of the motor, for removing a high frequency noise generated in the repetitive learning process, and for outputting a resultant disturbance correction value. A speed command compensator is provided for obtaining a corrected current command by adding the current command value output from the speed controller and the disturbance correction value obtained in the learning compensator; and a current controller is provided for receiving the corrected current command and outputting a torque command to the motor. Thus, the apparatus stores in advance the correction value obtained in the learning compensator and effectively performs a speed control using the stored value.

Coning compensation in strapdown inertial navigation systems

Abstract: The invention is a method for compensating for coning in a strapdown inertial navigation system which utilizes groups of five successive incremental angles of rotation of a body-fixed coordinate system as measured by orthogonally-mounted gyros at regular measurement intervals, each group of five measurements being obtained during a group interval equal to five measurement intervals. The coning-compensated angular displacement of the body-fixed coordinate system about a fixed axis in space during a p'th group interval is obtained by summing the five measured incremental angles and a coning compensation term. The coning compensation term consists of the sum of: (1) one-half the cross-product of a first and a second vector sum, the second vector sum being the sum of the five incremental angles of rotation in a group and the first vector sum being the sum of the second vector sum over p groups; and (2) the weighted sum of three vector cross-products, the multiplier and the multiplicand of each vector cross-product being a weighted sum of five measured incremental angles. The coning-compensated angular displacement can be summed over p to obtain an accurate estimate of the vector angle of rotation over a plurality of group intervals.

Magneto-resistive angle sensing device with a temperature-stable zero point

Abstract: The contactless magneto-resistive angle sensing device (1) includes two sensor components (10,11) oriented at a fixed angle relative to each other, a controllable power supply (PW) to heat and maintain the sensor components (10,11) at different temperatures, a magnet (MG) producing a magnetic field (B) in which the sensor components are arranged and an evaluating device (12) to receive output signals (U1,U2) from the sensor components (10,11). Each sensor component (10,11) includes magneto-resistive resistors (MR) connected in a respective bridge (B1,B2) having input terminals (I1,I1';I2,I2') for supply of current and output terminals (O1,O1';O2,O2') for the output signal (U1,U2). In a rotating magnetic field the evaluating device (12) analyzes the output signals (U1,U2) as a function of field angle and temperature to determine a reference angle at which the output signals of the angle sensing device have a minimum temperature dependence and stores the reference angle as a zero point for subsequent angular measurements. The sensor components are then mounted on a rotatable part whose angular position is to be subsequently measured at an angular position in relation to a stationary magnetic corresponding to the reference angle.

Angularly oscillating, variable displacement compressor

Abstract: A pump or compressor wherein the volumetric displacement of a piston cylinder assembly is variable. The piston is connected to a crank slider or eccentric mechanical drive, the crankshaft of which oscillates alternately clockwise through a controllably variable angle θ and counterclockwise through substantially the same angle θ, the angle θ being measured from the angular position of the crankshaft or eccentric at which separation between piston and the closed end of the bore is a minimum (Top Dead Center). The angle of crank oscillation controls the degree of volumetric displacement of the piston. The crank shaft is connected to a torsional spring so as to substantially resonate the rotational inertia of the moving parts. An oscillating electric motor supplies the oscillating torque to drive the mechanism at constant frequency but controllably variable angular amplitude.

Method and apparatus for measuring the thickness of non-circular elongated workpieces

Abstract: The invention relates to a method for measuring the thickness of non-circular elongated workpieces in which the thickness of the workpiece is measured along three measuring axis, the measurements are fed into a computer to determine minimum and maximum values and associated angular positions of the measuring axis, the measuring systems are rotated to a zero measuring position and the measured thicknesses are correlated by an algorithm, and the computer computes the degree for which angular position of the mimimum and maximum changes when the workpiece is advanced.

Rotational digital subtraction angiography phantom

Abstract: A gantry (18) that carries an x-ray source (14) and an x-ray detector (16) rotates around a test phantom (10) in a forward direction. A plurality of forward projection images are generated and stored in a forward image memory (42). The angle at which each forward direction projection image is generated is stored in a position memory (56). The gantry is then rotated in a reverse direction and a reverse direction image is generated at generally the same angular positions as in the forward rotation direction. The forward and reverse direction projection images of the phantom are analyzed to determine an offset or error between each corresponding forward and reverse angular image position. The offsets are stored in an angular position look-up table (80) and a pixel reregistration look-up table (82). In subsequent reverse scans, the angular position at which the reverse direction projection images are taken are altered in accordance with the angular offset for the corresponding angular position. The forward sweep images are video pixel position shifted in accordance with the video pixel offset for the corresponding angular position to bring the forward and reverse direction projection images into registration.

Decentralised operating method for multi-motor drive system synchronous control e.g. of rotary printing machine

Abstract: The decentralised operating method uses a synchronisation bus (4) extending between all of the electric drive motors, each of which is provided with a drive regulator (1) incorporating a required angular position indicator (12), so that the synchronisation bus is only used for the required machine rotation rate and the interrupt signals. A control signal can be supplied to each required angular position indicator, for static or dynamic adjustment to a given setting for setting the drive to a given reference point or synchronisation.

Rotational displacement information detection apparatus

Abstract: This invention relates to an apparatus for detecting rotational information, and includes a disk attachable to a spindle, with relative rotational information of the disk to be detected. The apparatus also includes a a rotation detection grating on the disk, a main body unit independent from the disk, an optical detection unit fixed in the main body unit, a light source, a reference grating, and a light-receiving element fixed to the optical detection unit. The rotational information of the disk relative to the optical detection unit is detected by the light-receiving element by detecting a light beam which is emitted by the light source and goes via the rotation detection grating and the reference grating. A positioning block for positioning the spindle attachable to the disk is also included. The positioning block has a V-shaped portion which is arranged so that slope surfaces thereof are substantially symmetrical about a line that connects a rotation center of the spindle to be attached to the disk and the optical detection unit. The spindle is positioned by putting the spindle on the V-shaped portion.

Computer controlled collimator changer

Abstract: An apparatus controls a stereotactic radiosurgery dose applied to an object being treated by a linear accelerator mounted on a gantry. The linear accelerator is capable of generating a beam having a path and a beam centerline, directed toward the object, and the beam is capable of having a plurality of angular positions relative to the object. The apparatus includes a turntable that is rotatable about an axis of rotation and defines a plurality of openings passing therethrough. Each opening has a center and receives therein a beam collimator of a preselected size. The turntable is disposed so that each of the plurality of openings may be rotated to where the center of the opening is coincident with the beam centerline, thereby allowing the beam to pass therethrough. A drive rotates the turntable about the axis of rotation and a sensor determines the angular position of the beam relative to the object. A controller that is responsive to the angular position determining sensor controls the turntable rotating drive so that as the angular position of the beam relative to the object changes, a preselected collimator is in the path of the beam.

Linear and angular position sensor

Abstract: The position sensor has a casing(1) and a disc casing(6) surrounding a common axis(2), either one of the casings(1,6) can enclose the other with an airgap(e) between their respective mutually opposite faces. The two casings are movable with respect to each other, by rotation(4) around the axis(2) and/or linearly(5) along the axis(2). One of the casings(1) has a magnet(7) with an axial revolution surface(8) having a axial variable diameter. The other casing(6) has a flux return ring fitted with at least two probes(9,10) separated from each other by an angular distance which is a function of the number of pole pairs of the magnet. A first probe(9) is fitted on the part of the disc(6) crossed by a return magnetic flux which is at a minimum when the magnet and the disc are at a reference angular position with respect to each other and being designed to supply a variable output signal which is a function of the mutual rotation of the two casings. A second probe(10) is fixed on the disc part crossed by the return magnetic flux which is at its maximum when the disc and magnet are in another angular reference position and is designed to supply a variable signal which is a function of the value of the airgap which itself varies as a function of the mutual axial position of the two casings.

Contactless magnetic sensor for measuring angular displacement

Abstract: A sensor for measuring angular displacement has a central axis (3) about which a permanent magnet armature (2) with north and south poles (4, 5) is free to rotate in either direction such that its flux provides an index of its orientation detected by eg. a Hall element (6). A practical assembly is illustrated in which the two fixed pole shoes (8, 9) which encircle the magnetic armature (2) are shaped to limit the airgap and thereby inhibit leakage to maximise the flux density appearing at the sensor (6). Alternative configurations include a disc armature, refinements of magnetisation and variable geometry to assist calibration.

Cam adjusting device for furniture

Abstract: An cam adjusting device (30) comprises a first and second element sliding reciprocally and a cam (32) pivoted to the first element by means of a pivot (33) rotating around an axis (48) to react with one of its lateral surfaces (35, 38) against a bearing surface (34, 37) on the second element, upon rotation of the cam around the axis thereby achieving sliding and adjustment of the reciprocal position of the first and second element. The cam is shaped so that, for any angular position of the cam in its active stroke the centre of rotation of the cam is substantially in the region of a straight line (41) passing through a point (36) of contact between a lateral surface of the cam and a bearing surface of the second element, said straight line being slanted at an angle φ identical to the angle of friction in the point of contact. A cam meeting this condition has been found maximize the amplitude of the adjustment without encountering instability. Using cam adjusting device (30), iron fittings, such as hinges, are easy to make.

Torsionsschwingungsdämpfer mit Koppelelementen

Abstract: A torsional vibration damper has an input flywheel 6 and an output flywheel 10 relatively rotatably connected together through coupling elements 49 which each include a resilient device 16 of which one end is connected to the input flywheel 6 and the other end to the output flywheel 10, so that a relative angular displacement of the two flywheels is always opposed by the force of the resilient device deformed by this relative displacement. The displacement behaviour of the resilient device 16 may be altered by the provision of centrifugal weights (28, 30, Fig 3) or (35, 36, Fig 4).

Investigation of the effects of design parameters on output characteristics of capacitive angular displacement sensors by finite element field modelling

Abstract: The effects of design parameters on performance characteristics of a capacitive angular displacement sensor used in limited angle torque motors are investigated. This is done by 2D finite element modelling and computation of electrostatic fields in the complex geometry of the sensor. Results are presented in terms of sensor's output characteristic showing the effects of some of its material and geometric parameters. The output characteristic investigated is the variation of sensor output voltage V with angular position /spl theta/ of the motor rotor, V=f(/spl theta/). The design parameters used comprise permittivities of various dielectric materials and angular width w/sub 1/ of the sensor.

Determining alignment between threaded parts using force and position data from a robot hand

Abstract: A technique for determining threaded part alignment using minimal force and angular position data is developed. This technique is based on backspinning a nut with respect to a bolt and measuring the force spike that occurs when the bolt "drops" into the nut. Kinematic models that describe the relationship between threaded parts during backspinning are presented and are used to show how angular alignment may be determined. The models indicate that it may be possible to distinguish between the aligned and misaligned cases between a bolt and a nut by using axial force data only. In addition, by tracking the in-plane relative attitude of the bolt during spinning, data can be obtained on the direction of the angular misalignment. Results from experiments using a bolt held in a Salisbury hand are presented.

Angular displacement transducer having flux-directing target and multi-sectored pole piece

Abstract: An angular displacement transducer has a highly magnetically permeable target which preferentially directs the flux of a fluctuating magnetic field through one of two or more cores. The fluctuating magnetic field induces voltages in secondary windings around the cores. Output signals which vary with the angle of the target about an axis are obtained by connecting pairs of secondary windings differentially. By choosing targets of different shapes the output voltage can be made to vary with angle as a sine wave or as a triangular wave. Transducers according to the invention can be rugged and accurate while retaining a simple construction.

Motion detection device for a photographic apparatus

Abstract: A motion detection device for a motion compensation system, suitable for use in a camera, to precisely and quickly compute an omega zero as a reference value for motion compensation, and to perform highly accurate camera motion compensation by using an angular displacement signal which has been accurately calculated with an omega zero as a reference. A mean computation device computes an integration mean value which is a central value of the angular velocity signal based on a signal output from an angular velocity sensor. A setting device sets an omega zero initial estimate value to compute the omega zero reference value. An omega zero computation device computes the omega zero value based on the integration mean value and the omega zero initial estimate value. An integration device converts the omega zero to an angular displacement signal. The integration average value and the omega zero initial estimate value are assigned weights by a reducing function that decreases as time progresses after the beginning of the computation function. A greater weight is placed on the omega zero initial estimate value immediately after the beginning of the computation function, while a greater weight is placed on the integration mean value as time passes after the beginning of the computation function.