Showing papers on "Angular displacement published in 1996"

The Importance of Body Stiffness in Undulatory Propulsion

Abstract: During steady swimming in fish, the dynamic form taken by the axial undulatory wave may depend on the bending stiffness of the body. Previous studies have suggested the hypothesis that fish use their muscles to modulate body stiffness. In order to expand the theoretical and experimental tools available for testing this hypothesis, we explored the relationship between body stiffness, muscle activity, and undulatory waveform in the mechanical context of dynamically bending beams. We propose that fish minimize the mechanical cost of bending by increasing their body stiffness, which would allow them to tune their body's natural frequency to match the tailbeat frequency at a given swimming speed. A review of the literature reveals that the form of the undulatory wave, as measured by propulsive wavelength, is highly variable within species, a result which calls into question the use of propulsive wavelength as a species-specific indicator of swimming mode. At the same time, the smallest wavelength within a species is inversely proportional to the number of vertebrae across taxa ( r 2 = 0.21). In order to determine if intact fish bodies are capable of increasing bending stiffness, we introduce a method for stimulating muscle in the body of a dead fish while it is being cyclically bent at physiological frequencies. The bending moment (N m) and angular displacement (radians) are measured during dynamic bending with and without muscle stimulation. Initial results from these whole body work loops demonstrate that largemouth bass possess the capability to increase body stiffness by using their muscles to generate negative mechanical work.

Quadrature axis winding for sensorless rotor angular position control of single phase permanent magnet motor

Abstract: A single phase permanent magnet motor includes a rotor, a stator, and a quadrature axis winding positioned out-of-phase from a main winding of the stator for generating an output signal representative of rotor angular position. An integrator can be coupled to the quadrature axis winding for phase retarding the output signal, and a comparator can be coupled to the integrator for detecting zero crossings of the phase retarded output signal to provide a commutation signal. The quadrature axis winding can be positioned about ninety electrical degrees out-of-phase from the main winding of the stator, and the integrator can be adapted to phase retard the output signal by a number of degrees which decreases as a speed of the motor increases. At low speeds the phase retard is preferably at about ninety degrees so that the phase retarded signal becomes in-phase with the main stator winding back EMF voltage. The motor may further include a rectifier coupled to the quadrature axis winding for rectifying the output signal, and a lowpass filter for filtering the rectified output signal to provide a signal proportional to velocity. Also the single phase motor is commutated for maximum torque production.

Method and device for angular measurement of a rotatable body

Abstract: A method and a device for measuring the angle of a rotatable body, in particular a body rotatable by more than 360°, are described. In this case this rotatable body cooperates with at least two further rotatable bodies, for example gear wheels, whose angular positions are determined with the aid of two sensors. The angular position of the rotatable body is determined from the angular positions detected in this way. So that unequivocal statements can be made, it is necessary for all three rotatable bodies or gear wheels to have defined predetermined numbers of teeth. The method and the device can be used, for example, for determining the steering angle of a motor vehicle.

Angular position sensor

Abstract: An angular position sensor having high angular resolution and which provides an immediate indication of the angular position being measured upon the application of power to the position sensor is disclosed. A quadrature disk having a continuous notch or recess in the outer periphery thereof is rotatable with respect to quadrature sensors positioned in a spaced-apart relationship with respect to one another. Differing radii on the quadrature disk cause the actuation and deactuation of the quadrature sensors as the disk passes thereunder producing sharply defined output signal transitions. While this is occurring, the Hall-effect sensor produces a sine wave output. The orientation of the quadrature disk with respect to the quadrature sensors is such that the output signal transitions produced by the quadrature sensors correspond with the maximum and minimum values of the sine wave produced by the Hall-effect sensor. The resulting rotation and quadrant data from the quadrature sensors and the Hall-effect sensor are applied as inputs to a microprocessor where a determination of the angular orientation of the member connected to the angular position sensor is made with respect to any arbitrary reference point.

Measuring device for contactless determination of relative angular position with an improved linear range

Abstract: A measuring device for contactless determination of relative angular position including a stator (10) provided with slotlike stator air gaps (14, 15), a rotor (12) rotatable relative to the stator with a main gap between it and the stator and a Hall element (16) arranged in at least one of the stator air gaps. Two ring magnets (21, 22) having magnetic polarities opposite to each other are provided in the interior wall of the stator (10). To measure a rotational angle of greater than ±75° with a linear response measurement curve, the first ring magnet (15) extends around the rotor (11) over an angular range of greater than 180°. When the null point of the magnetic induction B is shifted to the beginning of the linear range of the mechanical measuring range, particularly small rotation angles can be measured with a comparatively reduced measurement error.

Apparatus and method for generating digital position signals for a rotatable shaft

Abstract: An apparatus and method for generating digital electrical signals which are representative of the angular position and rotational velocity of a rotatable shaft in a servomechanism includes a resolver which is connected to the rotatable component. The resolver generates analog electrical output signals which are representative of an excitation signal modulated by both the sine and cosine of the electrical angular position of the motor. The output signals from the resolver are fed to a digital signal processing circuit which employs software algorithm techniques to define a plurality of tasks which are implemented sequentially to obtain the desired angular position and velocity signals. First, the sine and cosine signals are read from the resolver through respective analog-to-digital converters. The sine and cosine signals are demodulated by multiplication with the excitation signal, and the undesired higher frequency components are deleted by filtering. Then, the demodulated sine and cosine signals are conditioned to insure quadrature and to correct for amplitude and offset variations. Next, an electrical angular position signal for the rotatable member is determined by combining the demodulated and conditioned sine and cosine signals, and a correction is made for repeatable harmonic errors. A calculation is then made to o determine the rotational velocity of the rotatable member. The electrical angular position signal is next corrected for velocity related errors to generate an actual electrical position signal. Lastly, an actual mechanical position signal for the rotatable member is calculated. The actual mechanical position signal can be fed to a position controller circuit as a feedback signal to provide a closed loop servomechanism.

A robust capacitive angular position sensor

Abstract: A noncontacting robust capacitive angular position sensor currently under development for industrial and automotive application is presented. The main advantages of this low-cost system are its simplicity, high accuracy (/spl plusmn/0,2/spl deg/) and resolution (/spl plusmn/0,04/spl deg/) over the range of up to 360/spl deg/, excessive temperature operating capability, insensitivity to dirt, moisture and dew on the sensor electrodes and fast measurement speed. The paper describes the working principle, derives the required relationships for computing the rotor position and discusses the sensor's properties in relation to those of established encoder principles. The sensitivity of the sensor to mechanical errors like radial and axial axis offset, tilted axis, and tilted electrodes is explained. Finally the sensor electronics and its realization is discussed and data obtained from prototype sensors is presented.

Wind energy conversion device with angled governing mechanism

Abstract: A wind energy conversion device includes a support frame that pivots on a vertical yaw axis, and a rotor/bushing assembly coupled to the support frame through a governing coupling that permits the rotor/bushing assembly to pivot on a governing axis relative to the support frame. The governing axis is inclined from the vertical preferably by about 30° to provide a substantial gravitational bias of the rotor/bushing assembly toward a normal operating position when wind velocities are below a predetermined threshold. The governing axis also is laterally offset from a drive axis about which the wind rotates a propeller of the rotor/bushing assembly. This facilitates alignment of the rotor/bushing assembly so that the drive axis intersects the yaw axis. As a result, wind induced thrust does not generate a torque about the yaw axis. Wind velocities above the threshold pivot the rotor/bushing assembly counter to the gravitational force, thus to move a propeller structure of the rotor/bushing assembly out of its normal orientation perpendicular to the wind direction, thus reducing wind-induced thrust and rotational speed. A tail assembly, mounted to the support frame, maintains the support frame in a predetermined angular position relative to the wind direction as the rotor/bushing assembly pivots. In an alternative construction, the tail assembly is mounted to the rotor/bushing assembly, so that governing action pivots and tilts the tail assembly.

Electronic position and speed sensing device

Abstract: A position and speed sensor comprising a circular element (1) rotatably driven about its axis. The circular element (1) has two position indicators (3, 4) of different angular width. A sensor means (5) is fixed in position with respect to and adjacent to the circular element (1). The sensor means (5) has a sensing element for sensing the passage of each of the position indicators (3, 4) past the sensing element. An electrical signal is produced by the sensor means (5) corresponding to the passage of each of the sensed position indicators (3, 4). The signal has a duration corresponding to the angular widths of the sensed position indicators (3, 4). Also included is a means to process the electrical signal to produce information as to the angular position and angular velocity of the circular element. A method for reverse rotation detection using the position and speed sensor means (5) is also disclosed.

Vibration correction apparatus and optical device

Abstract: It is an object of the present invention to obtain optimum driving characteristics by correcting a deterioration in vibration correction characteristics, which is caused by a mechanical degradation such as shaft friction or deformation caused by the temperature and time change of vibration correction unit, or variations caused by the difference between individual devices. In order to achieve this object, a vibration correction apparatus for correcting the movement of an image which is caused by a vibration includes a calibration function by which an angular velocity detected by an angular velocity detection unit is integrated and converted into an angular displacement signal to generate a vibration signal, a variable angle prism (VAP) is driven on the basis of the vibration signal, the offsets of the frequency characteristic, the driving limit, and the initial position are detected from the response characteristics obtained when a predetermined test driving signal is supplied to the VAP, and the offsets are corrected.

Friction welding apparatus

Abstract: Variable amplitude, linear reciprocation of an output ram (28) is produced by converting rotary motion into linear motion using a swash plate (12) connected by a bending element (40) to drive a crank (34) The rotary prime mover (2) and swash plate (12) are mounted on a pivotable frame (4) so as the axial throw of the swash plate (12) is determined by the angular offset (θ) of the rotational axes (10,38) of the swash plate (12) and crank (34) When the axes (10,38) are coincident the throw, and therefore the ram stroke, is zero but progressive angular displacement produces a progressively increased stroke Thus, the frequency of reciprocation is determined by the angular speed of the prime mover, and the stroke is controllably variable between maximum and zero

Method and apparatus for controlling synchronous motor

Abstract: In a novel method and apparatus for controlling a synchronous motor, an angular position transducer, in whose output winding three-phase voltages with amplitude variations of N (N: an integer of 1 or more) cycles per revolution is induced, is directly coupled to a synchronous motor with 2N poles so that the demodulated a-phase voltage of the transducer has its positive peak value multiplied by the cosine of a selected angle as MMF phase angle when a direct axis of the motor is located in the position of its a-phase winding axis The instructions to control three-phase currents of an inverter feeding the motor are produced by multiplying the current phase instructions by the amplitude instruction The former is directly obtained using the three-phase voltages demodulated from the output of the transducer and the latter is derived from the detected speed deviation or torque instruction A changeover device is used for the current phase instruction to produce the reverse torque necessary in the four-quadrant drive of synchronous reluctance motors and interior permanent magnet synchronous motors Although the latter is the same as the conventional method, the former simplifies the apparatus because of analog processing not using expensive R/D converters Therefore, the present invention is effective to reduce costs and to increase reliability of the control apparatus synchronous motors

Calibration of an articulating probe head for a coordinate positioning machine

Abstract: A method is disclosed whereby a probe head which articulates a probe on the moveable arm of a coordinate measuring machine is calibrated to reduce the effect of errors, such as misalignment of the rotary axes of the head, and droop of the head and the probe. The method involves measurement of the probe position at a number of orientations of the head, the angle of orientation being determined by encoders within the head. Pairs of adjacent orientations at which the probe position is measured define segments, over which it is assumed that all errors change linearly. From the measured probe positions, a value of actual angular displacement between measured probe positions is calculated. The position of the probe at a given angular orientation within a segment may then be determined from the encoder reading at that orientation, and the ratio of the actual angular displacement between measured probe positions to the difference in the encoder readings at the orientations defining the segment (and corresponding to these measured positions). The size of the segments depends upon the linearity with which the droop changes with changing angular orientation of the head; as the change in droop becomes less linear, the segment size decreases in order to ensure that the assumption of linearity remains valid.

Method of starting a permanent-magnet synchronous motor equipped with angular position detector and apparatus for controlling such motor

Abstract: An angular position detector for generating trains of A- and B-phase pulses which are 90° out of phase with each other and a C-phase pulse per rotation are mounted on a permanent-magnet synchronous motor such that a magnetic pole origin of permanent magnets and a position where the C-phase pulse is generated agree with each other. After a power supply voltage is applied and in an initial stage before the permanent-magnet synchronous motor is operated normally, a motor control apparatus operates a current control loop with an alternating current command having a constant amplitude and a low frequency to supply an alternating current having a low frequency to the permanent-magnet synchronous motor for thereby rotating the rotor of the permanent-magnet synchronous motor from a stop at a low speed. The motor control apparatus then detects arrival at a magnetic pole reference when a C-phase pulse is detected, and detects an angular displacement of the magnetic poles of the rotor using counts of the A- and B-phase pulses counted in synchronism with the rotation of the rotor after the C-phase pulse is detected.

Single step coarse registration and inspection of circular objects

Abstract: A very fast, memory efficient, single-step solution for coarse alignment with determination of angular displacement, and inspection for surface defects on circular objects with non-symmetric patterns and random orientation is described. A suitable geometric partition model of an image is constructed that includes a plurality of spatial bins that can be used for rotation estimation and defect detection. In one embodiment for inspection of circular objects, the geometric partitioning includes 256 spatial bins constituted by concentric circular rings divided into sectors. The number of sectors and thickness of the rings are such that the approximate number of pixels in each region is the same. A set of numbers that encode rotational position and gray level information on the plurality of spatial bins of a reference object are acquired during training and used during run-time wherein the same information relative to a circular object being inspected is computed, and the data are correlated to determine both the coarse rotation and gray level difference in pertinent ones of the plurality of spatial bins.

Method for determining the absolute rotor position of in field controlled synchronous machines and device for carrying out this method

Abstract: The rotor position detection system provides the absolute rotor position from the estimated angular position of the rotor, with the corresponding torque component set to zero and the flux component set to a value above zero, so that the rotor is displaced into the estimated position upon a disparity between the estimated position and the actual position. The rotation rate for the latter movement of the rotor is evaluated, to provide a regulation value for providing a correction angle, allowing the estimated rotor angular position to be corrected to provide the actual angular position.

Determination of angular position optical fibers having axial asymmetries and aligning and splicing such fibers

Abstract: In the determination of the angular rotational position of an axial asymmetry, such as of optically inhomogeneous regions, in an optically transparent body, e.g. stress concentration zones of optical PM-fibers, where the body is located in arbitrary angular start positions, the body is illuminated during rotations thereof to different angular positions around its longitudinal axis. For different angular positions the difference is then determined between light, which has passed through the fiber end and in its position corresponds to the central part of the fiber, and light, which has passed through the fiber end and in its position corresponds to the region of the fiber located immediately outside the central part. These differences, considered as a function of the rotation angle, constitute a curve having a shape typical of the considered body. This curve is compared to a reference curve, for different translational positions of the reference curve, and that translation position is found, where a maximum agreement is obtained of the curves. The translation value of this translational position gives the angular offset of the body from a reference position. By this method a correct alignment can be made of for example two optical PM-fibers of different types and also the basic type of an unknown PM-fiber can be determined.

Modeling and fusion of radar and imaging sensor data for target tracking

Abstract: This paper presents a technique for fusing radar and imaging sensor data for target tracking. First, it is shown how angular position measurements can be computed from the two-dimensional intensity pattern provided by the imaging sensor. Then a model for the angular measurements is developed and accurate noise statistics are given. The measurement model that is derived differs from the one usually used in data fusion applications involving imaging sensors. In particular, it is shown that the noise is signal dependent and this affects the filtering equations which form the basis of the fusion operation. It is also shown that the two angular coordinates should not be decoupled because of the noise cross-correlation. The relationship between the imaging sensor’s angular measurements and the radar’s angular measurements is then explored by considering a simple example of a two-point target. It is shown that we cannot assume in general that the two sensors are measuring the same target point and that it is necessary to accommodate the difference between the two angular measurements within the data fusion process. A simple technique for accommodating this difference is developed and the equations necessary for fusing such measurements within the filtering framework are then presented. Finally, at the end of the paper it is pointed out that the same techniques can be applied to data fusion when tracking targets at very long ranges. The techniques developed in this paper are evaluated using a computer simulation with simulated data.

Method for calibrating an angular position sensor

Abstract: A method is provided to calibrate an angular position sensor by using an electrical coil to provide a magnetic field that simulates the presence of a permanent magnet. By successively selecting currents to flow through the electrical coil and by moving the electrical coil through at least two angular positions, the gain of an output relationship between a signal from a magnetically sensitive component and the angular position of the coil can be determined. By changing the intensity of the electrical current flowing through the coil, the intensity of the magnetic field emanating from the coil can be selected. In order to achieve the appropriate null offset characteristic of the device, the electrical coil is moved until a preselected output voltage is achieved. By comparing the angular position of the coil when the output voltage is achieved to an angular position of the coil for the desired output signal characteristic, a calibration angle can be determined. A ferromagnetic object is then magnetized with a magnetic field of the determined intensity and at an angle equal to the calibration angle.

Device for promtping use of vehicle seatbelts

Abstract: A device for prompting the use of a vehicle seatbelt. The device includes a sensor and an alarm. The sensor is attached to the seatbelt so that it assumes a first angular position when the seatbelt is in an inoperative position and a second angular position when the seatbelt is in an operative position. The sensor includes a motion sensor responsive to motion of the vehicle when the sensor is in the first angular position. The sensor generates a signal indicative of motion of the vehicle occurring while the sensor is in the first position. The alarm is responsive to the signal and generate an alarm to prompt use of the seatbelt.

Steering wheel angular position sensor

Abstract: Angle sensor, in particular for the steering gear of vehicles, with several sensor elements of the same design which are positioned separately in a circumferential direction on a facility which is fastened in a fixed position to the installation aligned at a vertical plane to the axis of the installation on a circular curve concentric with the axis of the installation and which cooperate with a code ring which is coupled to a component of the installation which can rotate around the axis. The angle sensor reduces space requirements and simplifies assembly. The code ring is equipped with n(n>1) geometrically equal code ring segments, each featuring the same codification. The sensor elements and each code ring segment extend over circumferential angle of (360/n)°.

Microcontroller-based measurement of angular position, velocity and acceleration

Abstract: A description of the current status and of the capabilities of digital techniques for the measurement of the three quantities of rotating motion control systems is presented in this work. The analysis covers the requirements of a digital system for the measurement of velocity and acceleration. The use of a 24 bit single-chip digital signal processor in a system developed is reported along with experimental results indicating high performance characteristics; single period response, zero output ripple, 4 decades dynamic range and very high accuracy figures.

Vehicle wheel balancing machine

Abstract: The balancing machine has a rotatable spindle (2) to receive a wheel (3). It also has a measuring device to measure the radii and the axial distance, relative to the machine, at the surfaces provided at the wheel rims for attaching balancing weights. The measurement device has a position generator to convert the measured parameters into machine readable signals, for the positioning of balance weights (12,13) The machine includes a light source (8) to generate a pointer type light beam (9) to a slit (6). The source is rotatable about an axis (7) perpendicular plane which also includes the axis of rotation of the spindle. The light source moves with the slit along a straight guide track (5) which is radial to the spindle and within the plane, or extends parallel to it. The light source moves such that the light beam is aligned parallel to the axis of rotation of the spindle to measure the radii and is aligned at an angle to it on the wheel to measure the axial distance. The light source is connected to position detectors which generate signals corresponding to the distance from the light beam to the spindle axis and the angular position of the beam.

Method for controlling velocity of a rotary motor and an apparatus therefor

Abstract: A velocity control method for a rotary motor and an apparatus adopting the same estimates and corrects a disturbance applied to the rotary motor to improve a velocity control characteristic. The disturbance is expressed as a function of an angular velocity and an angular position via a simple calculation process. The velocity control apparatus includes a learning compensator for receiving a velocity command, angular position information and the output of a velocity controller and correcting an effect of the disturbance which is expressed as a function of the angular velocity and the angular position, in addition to a general velocity control loop of a rotary motor composed of a velocity controller, a current controller, a motor and a velocity measuring unit. The learning compensator stores one period of the output of the velocity controller at a steady state of the velocity control loop and obtains a correction value using the stored value and the previous output value. The correction value obtained in the learning compensator is stored in advance and velocity control is performed using the stored value.

Control of the attitude of a satellite in low orbit involving solar acquisition

Abstract: For controlling the attitude of the body of an earth satellite placed on a low orbit, values of components of the geomagnetic field of the earth are measured along three axes of a frame of reference bound to the body. The values are derivated with respect to time, and multiplied by a gain. Currents responsive to the multiplicated derivatives are passed through magnetic torquers located along the three axes of the body to create magnetic torques that bias the body to a fixed angular position relative to the field lines of the geomagnetic field. Such steps are continuously carried out during eclipse periods. Out of eclipse periods, the pitch of the body is controlled by modifying an internal momentum in response to a signal provided by a solar sensor, so as to maintain solar generators carried by the body of the satellite oriented towards the Sun.

Angular displacement signalling device

Abstract: An angular displacement signalling device comprising a housing, a torque transmitting unit extending through the housing, first and second rotors fixed to respective first and second unit regions for rotation relative to the housing, an output member supported for movement with respect to the housing and the rotors, a transmission for transmitting drive between the output member and the first rotor so that the output member movement bears a predetermined relationship to movement of the first rotor, a first angular displacement signal generator comprising a first signal element fixed with respect to the output member and the second signal element fixed with respect to the housing, the signal elements coupled together and relatively moveable to produce a first angular displacement signal whose value changes in relation to the extent of the relative angular movement between the first rotor and the housing, and a second angular displacement signal generator comprising third and fourth signal elements coupled together to produce a second angular displacement signal having a value which varies in relation to the angular displacement between the first and second rotors.

System for measuring the angle of rotation

Abstract: A system for measuring the angle of rotation in order to determine the absolute angular position of the shaft of an electromotor is described which consists of a device for measuring the angle of rotation (10) and a control unit (11) connected to one another via an electric interface. The electric interface comprises an analog process data channel (8) and a digital parameter channel (9). The control unit (11) controls a change-over switch (7) of the process data channel (8) via the digital parameter channel (9). As a result thereof, a sine-cosine signal pair with one period for revolution is supplied via the process data channel (8) to the control unit (11) in order to determine the absolute angular position for the starting of the motor. Then, a sine-cosine signal pair with a high number of periods per revolution is supplied via the process data channel (8) in order to incrementally count the angle of rotation. An accurate correction of the incrementally counted angle takes place by means of a synchronizing signal generated by an index mark (15) and supplied via the parameter channel (9) to the control unit (11).

Angle measuring process and device for rotary bodies

Abstract: A process and device are disclosed for measuring the rotation angle of a rotary body, in particular a body capable of rotating over more than 360°. The rotary body co-operates with at least two other rotary bodies, for example toothed wheels, whose angular position is determined by means of two sensors. The relative position of the rotary body is derived from the thus determined angular positions. For clear indications to be given, all three rotary bodies or toothed wheels must have a predetermined number of teeth. The process and device may be used for example to determine the steering angle of a motor vehicle.

Inductive sensor measuring angular displacement or rotation from e.g. ferromagnetic sectored disc

Abstract: The unit measures rotation or angular displacement, producing a representative electrical signal. It comprises two principal parts. A measurement signal inducer (e.g. a sectored ferromagnetic disc) turning with the rotating body, and a stationary measurement sensor. This comprises a casing enclosing the components producing the signal, and a connecting cable led out from it. In the new design, the casing is assembled from two plastic shells (7, 7'). Once the components (5, 8, 9) have been fitted in, and the cable has been inserted, the shells are joined by adhering, ultrasonic welding or hot seal welding. Finally, a casting compound or hot melt adhesive is injected, to fill the casing. Also claimed is the corresponding method of making the measurement sensor.