Showing papers on "Angular displacement published in 2001"

Reciprocal angular acceleration of the ankle and hip joints during quiet standing in humans.

Abstract: Human quiet standing is often modeled as a single inverted pendulum rotating around the ankle joint, under the assumption that movement around the hip joint is quite small. However, several recent studies have shown that movement around the hip joint can play a significant role in the efficient maintenance of the center of body mass (COM) above the support area. The aim of this study was to investigate how coordination between the hip and ankle joints is controlled during human quiet standing. Subjects stood quietly for 30 s with their eyes either opened (EO) or closed (EC), and we measured subtle angular displacements around the ankle (θ a ) and hip (θ h ) joints using three highly sensitive CCD laser displacement sensors. Reliable data were obtained for both angular displacement and angular velocity (the first derivative of the angular displacement). Further, measurement error was not predominant, even among the angular acceleration data, which were obtained by taking the second derivative of the angular displacement. The angular displacement, velocity, and acceleration of the hip were found to be significantly greater (P<0.001) than those of the ankle, confirming that hip-joint motion cannot be ignored, even during quiet standing. We also found that a consistent reciprocal relationship exists between the angular accelerations of the hip and ankle joints, namely positive or negative angular acceleration of ankle joint is compensated for by oppositely directed angular acceleration of the hip joint. Principal component analysis revealed that this relationship can be expressed as: $$\ddot \theta _h = \gamma \ddot \theta _a $$ with γ=–3.15±1.24 and γ=–3.12±1.46 (mean ±SD) for EO and EC, respectively, where ' $$\ddot \theta $$ ' is the angular acceleration. There was no significant difference in the values of γ for EO and EC, and these values were in agreement with the theoretical value calculated assuming the acceleration of COM was zero. On the other hand, such a consistent relationship was never observed for angular displacement itself. These results suggest that the angular motions around the hip and ankle joints are not to keep the COM at a constant position, but rather to minimize acceleration of the COM.

Tilt input device

Abstract: The invention herein is an input device for a graphic display, where cursor movements are controlled using pitch and roll rotations of the device by the user. Pitch rotational input corresponds to cursor movement along the vertical Y axis of the graphic display, and roll rotational input corresponds to cursor movement along the horizontal X axis. The top side and bottom side of the housing are cubic curved to allow for comfort to the user and ease of rotating device. The device of the invention can operate on all surfaces and in freespace. The invention includes angular displacement sensing methods for two types of technologies in common use, rotary encoder sensors and optical position tracking sensors. One embodiment of the invention allows the user to select the asis vertical axis from which the sensors will measure angular displacement. This feature will allow the device to be operated at multiple angles; traditionally, as on a desktop surface in the horizontal plane, and at custom positions, such as holding the device angled down by one's side or with their arms crossed.

Nonlinear excitation model of ball bearing waviness in a rigid rotor supported by two or more ball bearings considering five degrees of freedom

Abstract: This research presents a nonlinear model to analyze the ball bearing vibration due to the waviness in a rigid rotor supported by two or more ball bearings. The waviness of a ball and each races is modeled by the superposition of sinusoidal function, and the position vectors of inner and outer groove radius center are defined with respect to the mass center of the rotor in order to consider five degrees of freedom of a general rotor-bearing system. The waviness of a ball bearing is introduced to these position vectors to use the Hertzian contact theory in order to calculate the elastic deflection and nonlinear contact force resulting from the waviness while the rotor has translational and angular motion. They can be determined by solving the nonlinear equations of motion with five degrees of freedom by using the Runge-Kutta-Fehlberg algorithm. Numerical results of this research are validated with those of prior researchers. The proposed model can calculate the translational displacement as well as the angular displacement of the rotor supported by two or more ball bearings with waviness. It also characterizes the vibration frequencies resulting from the various kinds of waviness in rolling elements, the harmonic frequencies resulting from the nonlinear load-deflection characteristics of ball bearing, and the sideband frequencies resulting from nonlinearity of the waviness interaction. @DOI: 10.1115/1.1398289#

Linear output non-contacting angular position sensor

Abstract: A linear output and non-contacting angular position sensor has a rotatable arc segment magnet arranged to rotate about the stationary components of the sensor, which include a pair of stationary flux concentrators, separated by a Hall probe; or, the magnet may be arranged to rotate at the center of the sensor with the stationary components fixed outside the magnet. With either arrangement, the Hall probe produces a direct 0 to 5 V d.c. output which varies linearly with the rotational angle of the magnet as the magnet rotates through a predetermined angle. The predetermined angle of rotation is generally equal to the arc formed by the flux concentrators and the arc of the magnet is generally 20-40% greater than the arc of the flux concentrators.

Performance test and improvement of piezoelectric torsional actuators

Abstract: This paper presents the design, test and improvement of a newly developed piezoelectric torsional actuator which generates large angular displacement using piezoceramics and a torsion bar. Because the proposed piezoelectric torsional actuator can generate torsional displacement, directly invoking the shear mode of the piezoelectric material, no complicated additional mechanism is needed. The electrodes are formed from a cylindrical piezoceramic poled along the axial direction and divided into six segments that are arranged radially and bonded to each other in opposite poling directions with conductive adhesive. The key to designing such an actuator is to match the torsional resonant frequency of the actuator with the excitation frequency. Finite element analysis for the piezoelectric actuator is performed to find the torsional resonant mode; an experimental investigation in terms of electrical impedance and torsional displacement measurement was conducted to verify the mode. As a result a maximum angular displacement of 0.18° was measured. To magnify the torsional displacement, a torsion bar was attached on top of the actuator. Thus, the torsional displacement was magnified by a factor of three. A resonance decrease due to the added mass of the torsion bar was observed and a theoretical investigation was performed using a two degrees of freedom lumped model.

An Infinite Dimensional Distributed Base Controller for Regulation of Flexible Robot Arms

Abstract: An exponentially stable variable structure controller is presented for regulation of the angular displacement of a one-link flexible robot arm, while simultaneously stabilizing vibration transient in the arm. By properly selecting the sliding hyperplane, the governing equations which form a nonhomogenous boundary value problem are converted to homogenous ones, and hence, analytically solvable. The controller is then designed based on the original infinite dimensional distributed system which, in turn, removes some disadvantages associated with the truncated-model-base controllers. Utilizing only the arm base angular position and tip deflection measurements, an on-line perturbation estimation routine is introduced to overcome the measurement imperfections and ever-present unmodeled dynamics. Depending on the composition of the controller, some favorable features appear such as elimination of control spillovers, controller convergence at finite time, suppression of residual oscillations and simplicity of the control implementation. Numerical simulations along with experimental results are provided to demonstrate and validate the effectiveness of the proposed controller.

3D angle measurement instrument

Abstract: A 3D angle measurement instrument includes a casing having a top and bottom with side walls extending therebetween. A gyroscope is positioned within the casing and electrically connected to a battery power source. The gyroscope is capable of measuring acceleration and deceleration velocities of the casing indicative of angular rotation thereof. A microprocessor is positioned within the casing and is electrically connected to the gyroscope and battery. The microprocessor receives an output signal from the gyroscope and is capable of calculating an angular displacement value using the output signal and a corresponding time factor. The angular displacement value is displayed on an electronic display in angular degrees from a reference point.

Device for determining the absolute angular position of a turning component

Abstract: A fixed magnetic sensor ( 16 ) is used to determine absolute angular position of a turning component ( 3, 4 ). A detection device ( 27 ) detects an angular position of a multipole magnetic ring ( 11 ) near a reference angular position. A resetting device ( 28 ) resets the angular position of the multipole magnetic ring ( 11 ) detected by detection device ( 27 ). The resetting device ( 28 ) is capable of assigning a value called “offset” to the value of the absolute angular position of the multipole magnetic ring ( 11 ). A determination device ( 29 ) determines the absolute angular position of the multipole magnetic ring ( 11 ) on all of the turns made by a turning component ( 3, 4 ) ascertained from the offset value and variations in the angular position.

Apparatus and method to angularly position micro-optical elements

Abstract: A micro-opto-electro-mechanical transducer in which an optical element is angularly positioned by electrical field coupling. Movable electrodes of two orthogonally disposed, differential variable capacitors are coupled to the optical element constrained by structural means to angular displacement around two free-axes of rotation. Cooperating stationary capacitor electrodes with surface contoured regions facing the movable electrodes are affixed to the structural means. A thin dielectric layer of high permittivity material provides a region of fixed spacing between the capacitor electrodes. The surface contoured regions constrain the approach of the movable electrodes with angular displacement of the optical element. Both the open-loop gain and the equilibrium voltage-angle response of the transducer is largely independent of displacement. Electrostatic force feedback maintains the optical element at voltage programmed positions of static equilibrium over a wide angular range of tip and tilt. In simpler embodiments, the optical element is angularly positioned in one direction around one axis of rotation. A preferred method of control allows an electrode of each variable capacitor to be electrically grounded.

Biased rotatable combdrive actuator methods

Abstract: A method for rotating a combdriven device about an axis uses applied bias force along with applied voltage between first and second comb fingers to controllably rotate the device about one or two axis. One mode of the present invention includes measuring the position of a rotating element and providing feedback to control the angular position thereof by changing bias force and/or drive voltage. The present invention can be employed with prior-art staggered combdrives, single layer self-aligned combdriven devices, and in a broad range of applications in optical telecommunication switching, video, biomedical, inertial sensors, and in storage magnetic disk drives.

Direct measurement of the vorticity field in digital particle images

Abstract: A new method called direct measurement of vorticity (DMV) for digital particle images is described in this paper. Unlike previous methods for calculating the vorticity in particle image velocimetry (PIV), the vorticity is determined directly from the average angular displacement of rotation between two matched patterns. In order to improve the stability and precision of the angular displacement, polar coordinates are used instead of Cartesian coordinates to depict gray level patterns. The results of a Monte Carlo simulation of an Oseen-vortex flow indicate that the accuracy of the DMV method is independent of the spatial resolution of the velocity sampling, and the errors in the velocity field will not be propagated into the vorticity field as occurs with some finite difference methods. Therefore, the DMV method is a good method to be used to extract the vorticity field from velocity data that has higher levels of uncertainty.

System for calibrating the axes on a computer numeric controlled machining system and method thereof

Abstract: A method and system for calibrating a machine capable of automatically calibrating the axes of the machine by comparing an initial calibration state of a particular axis with a subsequent motion of the machine along the same axis. The machine adjusts the motion along such axis based on the angular displacement by modifying the reference data in the computer memory of the machine to accord with the subsequent motion along the axis.

A planar capacitive sensor for angular measurement

Abstract: This paper presents a new approach for the design of capacitive angular position and angular speed sensors. The idea is to combine the transmitter and receiver plates into a single sensor plane. This approach allows us to reduce the number of sensor components to a single sensor PCB-with transmitter, receiver, and sensor electronics-and the rotor. Another advantage is the easy mounting procedure if one end of the rotating axle is accessible. A prototype of this sensor has been developed with a measurement range of 180/spl deg/ with an uncertainty below 0.20.

Axis deviation detection device for vehicular radar device

Abstract: PROBLEM TO BE SOLVED: To accurately detect an axis deviation angle θ of an axial line 7 determined in advance and an axial line 21 of straight running of a vehicle by scanning and deflecting a beam radiated to detect a distance between objects 18 and 19 to be detected on both right and left sides of the axial line 7 determined in advance in a substantially horizontal plane around a vertical axial line 6. SOLUTION: A radar means 25 is mounted on a vehicle 13 for angular displacement drive so that a beam from the radar means 25 scans by a drive means 5 to receive a reflection beam. While the vehicle 13 runs on a left running lane 16 of a straight road, a linear guard rail 18 provided on a road side on the left side is detected for a plurality of times in which scanning angles differ on the left side of the axial line 7 determined in advance, virtual straight lines yLa, yRa connecting a plurality of each detection position are obtained by computing, and the axis deviation angle θ corresponding to the inclination k is obtained by computing.

Apparatus for sensing an angular position of a wheel of a vehicle about a steering axis

Abstract: Apparatus for sensing an angular position of a steerable wheel of a vehicle, such as a work machine or the like, about a steering axis thereof. The apparatus includes a support frame having an upper arm and a lower arm defining a space through which the steering axis passes, and a wheel hub located in the space for supporting the wheel. The steering axis extends through a predetermined bottom axial surface portion of the wheel hub, and a lower kingpin is mounted in a passage through the lower arm and supports the wheel hub in the space for rotation about the steering axis. The lower kingpin includes an axial passage therethrough extending between an upper axial opening facing the bottom axial surface portion of the wheel hub and an externally located bottom opening. A sensor is mounted in connection with the bottom opening of the lower kingpin, the sensor including an element rotatable about a rotational axis, the sensor being operable for sensing a rotational position of the rotatable element about the rotational axis, and a pin extending through the axial passage through the kingpin and having a first end pivotably connected to the wheel hub for rotation therewith, and a second end connected to the element for rotating the element when the wheel hub is rotated about the steering axis.

Angular position indicator for cranes

Abstract: An angular position indicator for cranes which uses a combination of electronic, optical and mechanical components. It is intended for use on fixed or mobile Cranes and designed to operate in harsh industrial environments. Wireless communication replaces fixed electrical hardwiring that would otherwise be required between system components. The angular position indicator uses an angular displacement transducer of unique design. The angular position indicator performs pattern recognition of optical apertures using analog measurements of the illumination of optical detectors. The design allows for a substantial increase in measurement resolution as compared to digital optical encoders with the same number of optical channels.

Development of computer-based environment for simulating the voluntary upper-limb movements of persons with disability.

Abstract: Upper-limb orthotic systems have been designed for restoring the upper-limb functions of individuals with disabilities resulting from spinal cord injury (SCI), stroke and muscular dystrophy. These systems employ either functional electrical stimulation or external power. It is proposed that, instead of time-consuming and complicated monitoring using sensors and motion analysis, a software simulator with both angular displacement and acceleration parameters can facilitate the design of a control strategy for an orthosis. Reaching movements of three cervical SCI subjects are used to verify the simulator. A motion analysis system is used to measure the range of motion and joint angles during hand reaching. Results indicate that quaternion and spline curve techniques are suitable for interpolation of the hand reaching movements. The information needed for good simulation only compress the shoulder and elbow joint angles in a few key postures. Stimulated acceleration signals on the upper-arm segment have a high correlation coefficient (> 0.9) and a small root mean squared error (< 0.11 g) with a real bi-axial accelerometer.

Star-connected sensor

Abstract: In a rotary assembly comprising a rotor mounted in rotation in a stator about a mean axis or rotation, a radial position sensor comprises three induction sensors (51, 52, 53) distributed in the stator substantially at 120° from one another around the rotor and equidistant from the mean axis of rotation. The induction sensors (51, 52, 53) are cabled in star connection with a common connection point (54), and are powered by a balanced three-phase sinusoidal voltage source (55) with neutral point (56). The output voltage (Ve), present between the common connection point (54) and the neutral point (56) of the balanced three-phase sinusoidal voltage source (55), is processed by signal processing means (7, 8, 12) which determine its amplitude and its phase relative to the voltage delivered by the balanced three-phase sinusoidal voltage source (55). Thus, from only three sensors, two signals are obtained constituting the amplitude image and the angular position of the radial displacement of the rotor gravity axis in the stator.

Position control of an inertia-spring DC-motor system without mechanical sensors: experimental results

Abstract: In this article, two Generalized Proportional-Integral (GPI) feedback control schemes are proposed for the stabilization of the angular position of a DC-motor-actuated rotation inertia load, fixed to a wall by means of a rotation spring. The feedback schemes, which are not based on asymptotic observers nor calculations based on samplings, use only electrical variables measurements.

Angle measuring device

Abstract: An angle measuring device for measuring an angular position of a stationary object with respect to an object which is rotatable around an axis of rotation, that includes a rotor which is connected to the rotatable object which rotates about the axis of rotation and a stator that includes a scanning unit for scanning a graduation, which moves in relation to the scanning unit. A coupler is fastened to the stationary object or stator so as to seat the stator on the stationary object that has a contact face which extends transversely with respect to the axis of rotation. The coupler has a contact face that extends transversely with respect to the axis of rotation and engages the clamping face of the stationary object or stator so that a clamping force is generated so as to fasten the coupler to the stationary object and wherein the coupler is fixed against relative rotation, but is radially and/or axially elastic.

An application of EKF for the position control of a single link arm

Abstract: This study is on the development of an extended Kalman filter (EKF) used in conjunction with a simple PD+ controller for the position control of a direct drive system (DDS) The DDS consists of, specially, a single link arm driven by a permanent magnet synchronous motor (PMSM) and controlled by a DSP32 based motion control unit The EKF is used to estimate the angular position and velocity, beside the total inertia of the system, which is used to calculate the load information for the PD+ controller The estimation algorithm is based on the Bayes method known for its high accuracy Precision being the main objective of the study, the control input error usually ignored in past literature is also take into account in the filter design The control method thus developed demonstrates an improved performance over the classical PID in terms of accuracy and robustness through simulations and experiments that were carried out

Fluid circulation control valve for automobile engine cooling circuit, has one input and two or three outputs and output fluid regulating part, with a sloping end, which rotates inside the valve body

Abstract: The sloping end (38) of the valves regulating part (26) has a generally plane face (40) which forms with the axis of rotation (XX) an angle (A) of about 45 degrees. At least one of the fluid outputs (20,22,24) is a radial tube, and at least one is a tangential tube. The regulating part (26) is covered by a split ring which is made solid during rotation by a projecting pin. The split ring is made from a material having a low coefficient of friction. Fluid circulation circuit control valve having a body (12), with fluid input (18) and at least two fluid outputs (20,22,24), which delimits a cylindrical location for a regulating part (26). The part (26) is designed to turn around an axis (XX) and to take up different angular positions so as to control the fluid distribution through the outputs. The body (12) includes a base wall (14) containing fluid input (18) and a lateral cylindrical wall (16) containing the outputs (20,22,24) at axial heights and in chosen angular positions with respect to the axis (XX). The regulating part (26) has a sloping end (38) turned towards the base wall (14), this gives control of the fluid outputs with a defined law as a function of the angular position of the part (26) turning in the valve body (12).

A directional model for the statistical analysis of movement in three dimensions

Abstract: SUMMARY Movement of an object in three dimensions involves rotation and translation. The data for analysis are the coordinates of landmarks on the object, recorded at several time points. Statistical models for describing the rotational component of the movement of an object are proposed in this work. Under the fixed-axis model, the object rotates around an axis that does not change in time. The angular position of the object is then characterised by its rotation axis and an angle giving the extent of the rotation of the object with respect to a reference point. More complicated models occur when the rotation axis varies in time. Under the fixed-angle model the quaternions for the time-varying orientations of the object are shown to lie in a two-dimensional great circle on the surface of the unit sphere in four dimensions. Simple estimators are given of the comnmon rotation axis and of the angles characterising the time varying orientation of the object. A score statistic for testing the fit of the fixed-axis model is constructed and methods for handling the autocorrelation of the errors at neighbouring data points are provided. The analysis of data, collected by an OPTOTRACK camera system on a rotating forearm, illustrates the methodology presented in this paper.

High bandwidth large stroke spin-stand for data storage component testing

Abstract: A high bandwidth, large stroke spin-stand for testing components of a disc drive includes a coarse positioning stage and a rotary micropositioning stage. The spin-stand is capable of positioning a transducer head relative to the data storage disc based on one or both of: (1) an angular position of a rotary actuator arm in the rotary micropositioning stage; and (2) servo data read from the data storage disc. The angular position of the rotary actuator arm is detected by an encoder. In one embodiment, position adjustments are based on the detected angular position. In another embodiment, position adjustments are based on servo data read from the data storage disc, but are also conditional on angular position being consistent with the servo data. In yet another embodiment, both angular position and servo data from a track are linearized to generate PES adjustment parameters that are recorded on the data storage disc to redefine the track as more circular or to linearize the PES.

Load movement testing apparatus and method

Abstract: PROBLEM TO BE SOLVED: To provide a load movement testing apparatus and method serving to make evaluations of high reliability by reproducing a situation of damage occurrence, corresponding to a variety of conditions and assuring high closeness and accuracy. SOLUTION: The method includes rotating a sample 2 following the rotation of a test wheel 51; combining the motions of both to set, for example, the speed of the test wheel 51 relative to the sample 2 over a wide range; causing angular displacement of the test wheel 51 on a horizontal plane in travel direction L as following the rotation of the test wheel 51; and causing traversing of both at the same time so as to control the test wheel 51 to move along a transverse direction, to thereby faithfully reproduce a situation of occurrence of deformation, wear or the like at, for example, the curve of a road.

Automatic self-calibration of an incremental motion encoder

Abstract: Our recently developed patented instrument, the Incremental Motion Encoder (IME) is able to monitor the rotation of mechanical systems. Using the disc from an Incremental Shaft Encoder, but with three or more read heads instead of one, the IME is able to resolve small transverse movements of the shaft as well as angular position. However, the accuracy of the measurements is limited by small distortions in the grating lines of the disc, due either to damage or to manufacturing errors. This paper presents algorithms which use data from the IME to compensate for such errors in the disc, thus enabling automatic self-calibration of the IME.

Angle measuring system and method of mounting it

Abstract: An angle measuring system that includes a stator and a rotor for measuring an angular position between a stationary first object and a second object, which is rotatable about an axis of rotation. A coupling couples the stator to the stationary first object so that the stator is fixed against relative twisting, but is also radially and/or axially resilient. A mounting element that clamps a face of the stationary first object by expanding in a radial direction with respect to the axis of rotation. An expansion element that interacts with the mounting element so as to cause the expanding in a radial direction and a screw that actuates the expansion element, wherein the screw is screwed into the stationary first object.

Rotation angle meter using a magnet and GMR sensor to generate a position signal. the meter and rotating part, the position of which is to be determine, are linked by gear wheels so that sensitivity is greatly increased

Abstract: Rotation angle meter comprises a magnet (2) and a GMR for generating an electrical position signal for determining the angular position of a rotating part (1). The magnet (2) is fixed to a rotating axle (4) with a gear wheel or rim (5). The rotating part also has a gear wheel or rim (6). The two gear wheels mesh directly together or via a mechanical transmission. An electronic circuit captures the voltage applied to the GMR caused by a full rotation of the magnet. By the gearing effect and transmission, the rotation angle meter can measure rotation angles of less than 10 or even 3 degrees of the rotating part, which corresponds to a full rotation of the rotating part.