Showing papers on "Angular displacement published in 2004"

Estimation of displacement vectors and strain tensors in elastography using angular insonifications

Abstract: In current practice, only one out of three components of the tissue displacement vector and one of nine components of the strain tensor are accurately estimated and imaged in ultrasound elastography. Since, only the axial component of both the displacement and strain are imaged, other important elastic parameters, such as shear strains and the Poisson's ratio, also are not imaged. Moreover, reconstruction of the Young's modulus would be significantly improved if all components of the strain tensor were available. In this paper, we describe a new method for estimating all the components of the tissue displacement vector following a quasi-static compression. The method uses displacements estimated from radiofrequency echo-signals along multiple ultrasound beam insonification directions. At each spatial location in the compressed medium, orthogonal tissue displacements in both the axial and lateral direction with respect to the direction of the applied compression are estimated by curve fitting angular displacement vector data calculated for all insonification directions. Following displacement estimation in orthogonal directions, components of the corresponding normal and shear strain tensors are estimated. Simulation and experimental results demonstrate the utility of this technique for the computation of the normal and shear strain tensors.

A real-time optical sensor for simultaneous measurement of three-DOF motions

Abstract: The need for simultaneous measurement of multiple degree-of-freedom (DOF) motions can be found in numerous applications such as robotic assembly, precision machining, optical tracking, wrist actuators, and active joysticks. Conventional single-axis encoders, though capable of providing high-resolution (linear or angular) measurements, rely on mechanical linkages (that often introduce frictions, backlashes, and singularities) to constrain the device so that the three-DOF (3-DOF) motion can be deduced from the individual orthogonal measurements. We present here a noncontact optical sensor for 3-DOF planar and spherical orientation measurements. We begin with the operational principle of a microscopic-surface-based optical sensor. The design concept and theory of a dual-sensor system capable of measuring 3-DOF planar and spherical motions in real time are then presented. Along with a detailed analysis, the concept feasibility of two prototype 3-DOF dual-sensor systems for measuring the instantaneous center of rotation and the angular displacement of a moving surface is demonstrated experimentally. It is expected that the analysis will serve as a basis for optimizing key design parameters that could significantly influence the sensor performance.

Compressor control system for a portable ventilator

Abstract: A method and apparatus for controlling a brushless DC (BLDC) motor over a wide range of angular speeds is presented Analog magnetic sensors provide continuous signal measurements related to the rotor angular position at a sample rate independent of rotor angular speed In one embodiment, analog signal measurements are subsequently processed using an arctangent function to obtain the rotor angular position The arctangent may be computed using arithmetic computation, a small angle approximation, a polynomial evaluation approach, a table lookup approach, or a combination of various methods In one embodiment, the BLDC rotor is used to drive a Roots blower used as a compressor in a portable mechanical ventilator system

Device for measuring the relative angular position of two bodies with respect to a point, and articular prosthesis provided therewith

Abstract: A device for measuring the relative angular position of two bodies with respect to a point is provided with a first measuring element and a second measuring element, relatively movable with respect to one another and connectable to a first body and a second body, respectively; the first measuring element includes a first inclination sensor, which has a first detection axis and supplies a first inclination signal, correlated to a first angle of inclination of the first detection axis with respect to a reference axis, and the second measuring element includes a second inclination sensor, which has a second detection axis and supplies a second inclination signal, correlated to a second angle of inclination of the second detection axis with respect to the reference axis.

Roll angular displacement measurement system with microradian accuracy

Abstract: A novel compact roll angular displacement measurement system is presented. It consists of a linearly orthogonally polarized, heterodyne laser source as the detection probe beam, a wave-retardation plate or a set of a half-wave plate plus a wave-retardation plate as the angle-sensing element to form an interferometric system. The roll angular displacement of a moving device can be detected by measuring the phase difference between the reference and measurement beams. The experimental results fit well with the theoretical analysis and a measurement resolution of sub-microradian over a half-degree is achieved experimentally.

Harmonic weighting functions at the sliding interface of a finite-element machine model incorporating angular displacement

Abstract: The formulation presented in this paper couples the magnetic vector potential and the tangential component of the magnetic field strength at a sliding interface in the air gap of a two-dimensional finite-element machine model using harmonic weighting functions which enable the use of fast Fourier transforms in combination with a simple, diagonal operator to account for the angular displacement between stator and rotor. The method applies to models where the stator and rotor meshes are nonequidistant and nonmatching at the interface. The approach substantially reduces the cost of system assembly and preconditioner setup during a transient simulation and offers convenient ways for dealing with skewing and for torque computation.

Angular position sensor working to measure high linearity magnetic flux density

Abstract: An angular position sensor is provided which is designed to an angular position of a rotary shaft. The angular position sensor has a magnet affixed to the rotary shaft. The magnet has an N-pole and an S-pole and is so geometrically shaped as to produce magnetic flux which is substantially uniform in amount within a range extending around each of centers of the N-pole and the S-pole. This improves the linearity of a change in sensor output upon rotation of the rotary shaft.

Belt drive control method and its device, belt device, image forming device, process cartridge, program, and recording medium

Abstract: PROBLEM TO BE SOLVED: To provide a belt drive control method and its device in which a belt is driven at a constant moving speed without being affected by the fluctuation in the thickness of the belt while increase in the cost is suppressed, to provide a belt device, a process cartridge, an image forming device, a program and a recording medium. SOLUTION: Detection is made for rotational angular displacement or rotational angular velocity of a follower roller 502, alternating components in the rotational angular velocity having the frequency corresponding to the periodic thickness fluctuation along the peripheral direction of a belt 500 are extracted based on the detection results and rotation of a driving roller 501 is controlled based on the amplitude and the phase of the alternating components. COPYRIGHT: (C)2005,JPO&NCIPI

Drive control method, drive control device, belt apparatus, image forming apparatus, image reading apparatus, computer product

Abstract: Driving of a pulse motor is controlled in such a manner that a rotating body driven by the pulse motor rotates at a uniform angular velocity. Angular displacement of the rotating body is detected, a difference between a detection value of the angular displacement and a target value of angular displacement set in advance is calculated, and a drive pulse frequency of a drive pulse signal to be used for driving the pulse motor is calculated based on the difference and a reference drive pulse frequency. Whether the difference is added to the reference drive pulse can be selected.

Rest-to-Rest Motion for Planar Multi-Link Flexible Manipulator Through Backward Recursion

Abstract: In this work is considered the problem of rest-to-rest motion in a desired pre-fixed time for planar flexible manipulators. We introduce a simple idea permitting the minimization of end-effector residual vibration when reaching a desired angular equilibrium position, in a pre-fixed desired travelling time. The results hold without considering internal elastic damping effect, using a classical controller with feedforward plus joint feedback terms. The new approach concerns the computation of the feedforward control, which is based on backward integration of the elastic dynamics, starting from a rest position of the flexible arms. This backward integration yields basically elastic trajectories permitting to reach the final desired end-effector position without oscillation. The feedback controller is then used to stabilize locally the actual states along these desired trajectories. However, for fast rest to rest motion, the feedback compensator fails to drive the system states along the desired trajectories, this being due to the relatively large initial elastic error. To overcome this limitation, proper joint motion is planned between the desired initial and final positions through optimization techniques, the goal being the minimization of the initial elastic error associated to these joint trajectories. The optimal planning technique is formulated as a Pontryagin optimal control problem. This scheme is validated via numerical tests as well as experiments on a flexible two-link planar manipulator. @DOI: 10.1115/1.1649976#

360-Degree magnetoresistive rotary position sensor

Abstract: A 360-degree magnetoresistive rotary position sensor comprises a magnetic linear sensor and a magnetic angular sensor, formed on a semiconductor substrate. The linear sensor detects a sense of a magnetic field, and the angular sensor detects an angular position of the magnetic field up to 180-degree. With the linear sensor indicating that a positive sense of the magnetic field is detected, the angular sensor detects a first 180-degrees of angular position. With the linear sensor indicating that a negative sense of the magnetic field is detected, the angular sensor detects a second 180-degrees of angular position. As a result, the position sensor detects a full 360 degrees of rotation.

Estimation of the Rotational Terms of the Dynamic Response Matrix

Abstract: The dynamic response of a structure can be described by both its translational and rotational receptances. The latter ones are frequently not considered because of the difficulties in applying a pure moment excitation or in measuring rotations. However, in general, this implies a reduction up to 75% of the complete model. On the other hand, if a modification includes a rotational inertia, the rotational receptances of the unmodified system are needed. In one method, more commonly found in the literature, a so called T-block is attached to the structure. Then, a force, applied to an arm of the T-block, generates a moment together with a force at the connection point. The T-block also allows for angular displacement measurements. Nevertheless, the results are often not quite satisfactory. In this work, an alternative method based upon coupling techniques is developed, in which rotational receptances are estimated without the need of applying a moment excitation. This is accomplished by introducing a rotational inertia modification when rotating the T-block. The force is then applied in its centroid. Several numerical and experimental examples are discussed so that the methodology can be clearly described. The advantages and limitations are identified within the practical application of the method.

Method for at least partially compensating for errors in ink dot placement due to erroneous rotational displacement

Abstract: A method of at least partially compensating for errors in ink dot placement by at least one of a plurality of nozzles due to erroneous rotational displacement of a printhead module relative to a carrier, the nozzles being disposed on the printhead module, the method comprising the steps of: (a) determining the rotational displacement; (b) determining at least one correction factor that at least partially compensates for the ink dot displacement; and (c) using the correction factor to alter the output of the ink dots to at least partially compensate for the rotational displacement.

Gyrostabilizer for small boats

Abstract: A gyrostabilizer system that counteracts the natural rolling motion of a small boat or vessel. The invention constitutes an improvement in prior art systems of this type in that the system weighs less because it has a much lighter rotor made of composite materials spinning at much higher speeds. The gyrostabilizer system includes a lightweight rotor spinning at very high speeds to attain a large angular momentum. The mass of the rotor is concentrated away from the spin axis of the rotor to maximize angular momentum while minimizing weight. The rotor is mounted in a frame that, in turn, is mounted on gimbals so that the frame can be rotated about an axis that is normal to the longitudinal roll axis of the vessel. When the rotor is rotated about the gimbals, a torque is created that opposes the torque created by the sea and reduces the rolling motion of the vessel. The rotor may be mounted in an evacuated chamber to reduce air drag. Rotation of the rotor frame around the gimbal axis is controlled by an active servo system using information provided by roll angular position and angular velocity sensors.

Measurement Uncertainty of Stereoscopic-PIV for Flow with Large Out-of-plane Motion

Abstract: A stereoscopic-PIV system was developed to operate with the light sheet oriented perpendicular to the main flow direction, which makes it possible to measure the streamwise vorticity. The SPIV system is based on an angular displacement of 45 degrees of the two cameras and a 3D calibration based reconstruction method. It was expected that the large out of plane motion would limit the accuracy of the measurements, which was therefore investigated in detail for laminar and turbulent pipe flow. The laminar flow measurements revealed the importance of a precise alignment of the light sheet with respect to the calibration plane. Small misalignments lead to unacceptably large so called registration errors. Although the registration error was described by several authors before, it has never been properly quantified . We explain and predict the amount of registration error and check this with direct measurements. After alignment, the laminar velocity profile and turbulence statistics were reproduced with very high accuracy, which proves the applicability of SPIV to flows with large out of plane motion. At the end of the paper an example is presented of the application of the SPIV system to the study of transition in pipe flow.

Position determination that is responsive to a retro-reflective object

Abstract: Utilizing frequency-dependent diffraction (also referred to as dispersion) to determine the angular position of a retro-reflective object within a scanning space. The technique involves dispersing an electromagnetic beam into a scanning space by frequency. If a retro-reflective object is located within the scanning space, the object will retro-reflect a portion of the dispersed beam having a frequency that is associated with the angular position of the retro-reflective object within the scanning space. The frequency of the retro-reflected beam is used to determine the angular position of the retro-reflective object within the scanning space. When a second beam is dispersed into the scanning space and a portion of the second beam is retro-reflected in the manner just described, a second angular position of the retro-reflective object can be found. Coordinates of the retro-reflective object are determinable by triangulation using the two angular positions. These are absolute, as opposed to relative, coordinates.

Single-Plane Auto-Balancing of Rigid Rotors

Abstract: This paper presents an analytical study of single-plane automatic balancing of statically and dynamically unbalanced rigid rotors, considering also the effect of partial unbalance compensation and vibration reduction. We consider a rotor equipped with a self- balancing device consisting of a circular track with moving balls to compensate for rotor unbalance. The investigations include an analysis of the equations of motion and determination of conditions for existence and stability of synchronous motions. Different solutions for the existence conditions correspond to different types of synchronous motions, including compensatory motions, with the elements’ positions providing complete or partial compensation of unbalanced forces as well as reduction of vibrations. A stability analysis serves to determine the actual angular position of elements at any rotational speed and to find the speed range with stable unbalance compensation. Numerical simulations confirm the analytical results except for those in the immediate vicinity of critical speeds.

Belt drive control unit, belt device and image forming apparatus

Abstract: PROBLEM TO BE SOLVED: To provide a belt drive control unit capable of accurately extracting amplitude and phase of an AC component, corresponding to thickness variation in a peripheral direction of a belt with a processing unit which is less expensive than Fourier transform, and to provide a belt device and an image forming apparatus. SOLUTION: Angular displacement or angular speed of a driven roller 14 is detected in an encoder rotation sensing station 610, and from the detection result, amplitude/phase of a belt AC component of the angular displacement or angular speed, having frequency corresponding to thickness variation of a belt, is extracted by orthogonal detection in a belt cycle variation sensing station 608. On the basis of the extracted amplitude and phase, an objective function is produced in an objective function calculating part 607, and from this objective function, an objective reference signal is produced in an objective reference signal producing part 606. The objective reference signal is compared by a comparator 605, with an FB signal from the detection result obtained in the encoder rotation sensing station 610; and by controlling a motor 17 on the basis of the comparison result, the rotation of the driven roller is controlled. COPYRIGHT: (C)2006,JPO&NCIPI

Pulse width modulation based digital incremental encoder

Abstract: A digital incremental encoder for generating an output signal indicative of an angular position, a direction of rotation, and a speed of rotation of a shaft. A counter receives a PWM signal indicative of the angular position of the shaft and a clock signal from an angular position sensor, and generates a multi-bit output. A latch latches the multi-bit output, a first bit and a second bit of which are used to generate the output signals that include the first bit. The first bit and the second bit may be XOR'd together to generate an XOR output included in the output signals. A direction of rotation may be derived from a quadrature phase relationship between the first bit and the XOR output. The angular position sensor may be an NCAPS or MT-NCAPS. A linear position sensor may be used instead of an angular position sensor to generate the PWM signal.

Handwheel-operated device

Abstract: A handwheel-operated device comprising a fixed body, a handwheel and a moveable body, the handwheel being rotatable relative to the fixed body and the moveable body moveable relative to the fixed body, and the device further comprising a first motor operable to actuate the moveable body, first sensor means responsive to the rotation of the handwheel and first control means operable in conjunction with the first sensor means to cause the first motor to rotate upon an angular displacement and/or angular velocity of the handwheel.

Single track brush-based position encoder for rotating shaft

Abstract: A position sensor generates a signal representative of the angular position and, if desired, angular velocity of a rotating object using only a single circular track and plural brushes that ride on the track when the object rotates. The single circular track can have plural segments, and the sensor can generate more than one signal cycle per revolution.

Rigid body equations of motion for modeling and control of spacecraft formations. Part 1: Absolute equations of motion

Abstract: In this paper, we present a tensorial (i.e., coordinate-free) derivation of the equations of motion of a formation consisting of N spacecraft each modeled as a rigid body. Specifically, using spatial velocities and spatial forces we demonstrate that the equations of motion for a single free rigid body (i.e., a single spacecraft) can be naturally expressed in four fundamental forms. The four forms of the dynamic equations include (1) motion about the system center-of-mass in terms of absolute rates-of-change, (2) motion about the system center-of-mass in terms of body rates of change, (3) motion about an arbitrary point fixed on the rigid body in terms of absolute rates-of-change, and (4) motion about an arbitrary point fixed on the rigid body in terms of body rates-of-change. We then introduce the spatial Coriolis dyadic and discuss how a proper choice of this non-unique tensor leads to dynamic models of formations satisfying the skew-symmetry property required by an important class of nonlinear tracking control laws. Next, we demonstrate that the equations of motion of the entire formation have the same structure as the equations of motion of an individual spacecraft. The results presented in this paper form the cornerstone of a coordinate-free modeling environment for developing dynamic models for various formation flying applications.

Fuzzy Logic Control of the End-Point Vibration in an Experimental Flexible Beam

Abstract: This paper is concerned with the design and implementation of a fuzzy logic controller (FLC) to control the end-point vibration in a single flexible beam mounted on a two-degrees-of-freedom platform. The angular position of the hub and the signal from a strain gage mounted on the beam are used as the two inputs to the FLC. In order to add more damping, the strain gage signal is combined with the hub angular velocity represented by the output of a tachometer attached to the motor shaft. We discuss how to build the rule base for the flexible beam based on the relation between the angular displacement of the hub and the end-point deflection, as well as the effect of different scaling gains on the performance of the FLC. We present several experimental results showing the effectiveness of the FLC in reducing the end-point vibration of the flexible beam.

Relativistic Effects of our Galaxy's Motion on Circles-in-the-sky

Abstract: We study the geometric effects of our galaxy's peculiar motion on the circles-in-the-sky. We show that the shape of these circles-in-the-sky remains circular, as detected by a local observer with arbitrary peculiar velocity. Explicit expressions for the radius and center position of such an observed circle-in-the-sky, as well as for the angular displacement of points on the circle, are derived. In general, a circle is detected as a circle of different radius, displaced relative to its original position, and centered at a point which does not correspond to its detected center in the comoving frame. Further, there is an angular displacement of points on the circles. These effects all arise from aberration of cosmic microwave background radiation, exhausting the purely geometric effects due to the peculiar motion of our galaxy, and are independent of both the large scale curvature of space and the expansion of the universe, since aberration is a purely local phenomenon. For a Lorentz-boosted observer with the speed of our entire galaxy, the maximum (detectable) changes in the angular radius of a circle, its maximum center displacement, as well as the maximum angular distortion are shown all to be of order $\beta=(v/c)$ radians. In particular, two back-to-back matching circles in a finite universe will have an upper bound of $2|\beta|$ in the variation of either their radii, the angular position of their centers, or the angular distribution of points.

Apparatus for sensing angular position

Abstract: An apparatus for sensing a position of an object is provided that may include a magnet having a set of magnetic flux properties, the magnet mounted for movement about an axis relative to the object and a magnetic field-sensing device mounted in fixed relation to and spaced from the magnet, the magnetic field-sensing device calibrated to sense a change in at least one magnetic flux property in response to movement of the magnet relative to the object and generate a data signal indicative of a position of the object. In one aspect the magnet is configured to have a substantially diamond shaped cross section and the magnetic field-sensing device is calibrated to sense a change in flux density distribution in response to a change in an air gap defined between an exterior surface of the magnet and the magnetic field-sensing device.

Cutting unit for cutting continuous cigarette rods

Abstract: A cutting unit (1) for cutting continuous cigarette rods (3), wherein a cutting head (12) is locked in position on a fixed supporting body (9) by an automatically releasable locking device (24), and, to make a change in format, is rotated, with respect to the supporting body (9) and after the locking device (24) is released, about an axis (20) of rotation by an actuating device (22) negative-feedback-controlled by a detecting device (23) for determining angular displacement of the cutting head (12) about the axis (20) of rotation.

Sinusoidal phase-modulating laser diode interferometer for measuring angular displacement

Abstract: We propose a sinusoidal phase-modulating laser diode interferometer for measuring small angular displacement. The interferometer is based on a Fabry-Perot plate. It has a simple structure and is insensitive to external disturbance. Sinusoidal phase-modulating interferometry is used for improving the measurement accuracy. A charge-coupled device (CCD) image sensor is used for measuring the distance between the reflected beams from two faces of the Fabry-Perot plate. From the distance, the initial angle of incidence is calculated. Compared with Michelson interferometers and autocollimators, this interferometer has the advantage of compact size and simple structure. The numerical calculation and experimental results verify the usefulness of this novel interferometer. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

Three-coordinate koniogravimeter

Abstract: In the present invention, products of sliding rail, linear displacement transducer, angular displacement transducer, transmission screw and motor on the market are used to assemble a three coordinatemeasuring instrument with cylindrical coordinate system. The instrument has three parts of cross arm, vertical arm and base for realizing movement of three-dimensional direction to achieve purpose ofmeasuring workpieces in various outlines.