Showing papers on "Angular displacement published in 1998"

Catheter simulation device

Abstract: A device for tracking the translational and rotational displacement of an object having two degrees of freedom using a single point of contact with the object. The device is particularly useful in a catheter simulation device for surgery and interventional radiology applications. A spherical contact member is mounted for free rotation about all axes in force-transmitting contact with the surface of the object and a pair of shafts are mounted in tangential engagement with the spherical member to reflect the displacement imparted to the object relative to a reference position. This arrangement provides simultaneous tracking of the combined translational and rotational displacement of the object. Measuring the displacement of the object and a haptic applicator are included such that a load may be applied to the object to precisely control the degree of force required to cause displacement of the object. The actual forces applied to displace the object are also measured such that the device is capable of providing a realistic force reflection to simulate the feel of a surgical procedure, for example. A computerized control system and conventional recording device are employed to provide a programmed procedure which provides realistic "feel" to a user of an actual surgical procedure. The device is readily adaptable for interfacing with a virtual reality type program to simultaneously provide a visual simulation of the surgical procedure.

Single and dual end effector, multiple link robot arm systems having triaxial drive motors

Abstract: A robot arm system (8) includes a multiple link robot arm mechanism (10) mounted at a shoulder axis (16) to a torso link (12) that is capable of 360-degree rotation about a torso axis (14). The robot arm mechanism couples an upper arm (15) and a forearm (22) to a hand (30) that is capable of linear or radial motion relative to the shoulder axis. The robot arm system minimizes its moment of inertia by arranging first (50), second (52), and third (92) motors triaxially about the torso axis to permit rapid movement of the hand. The first motor is coupled through endless belts (55, 68) to rotate the forearm about an elbow axis (24), the second motor is coupled through an endless belt (74) to rotate the upper arm about the shoulder axis, and the third motor rotates the torso link about the torso axis. A motor controller (100) operates in at least three operational states. The first operational state maintains the position of the third motor and equally counter-rotates the first and second motors to cause linear extension or retraction of the hand. The second operational state equally rotates the first and second motors and maintains the position of the third motor to cause angular displacement of the hand about the shoulder axis. The third operational state equally rotates the first, second, and third motors so that the robot arm mechanism undergoes angular displacement about the torso axis. Coordinating the rotations of the first and second motors enables the robot arm mechanism to describe a compound curvilinear travel path for the hand. The rotatable torso link together with the robot arm motion permits simple, nonradial positioning of specimen processing stations (350) relative to the torso axis, extended hand reach, and corner reacharound capabilities. The consequence is a high-speed, high-throughput robot arm system that operates in a compact work space.

Electric motion platform and a control system for controlling the same

Abstract: A motion platform comprises a base, a top, a pair of positioning motor assemblies mounted to the base, and an arm assembly extending between each of the positioning motor assemblies and the top of the platform. Each of the arm assemblies is responsive to rotary motion of a respective one of the positioning motor assemblies and includes a rotating arm mounted at one end on the motor shaft and rotatable over a full 360-degree arc. Sensors detect the position of the arm assemblies and the speed and amount of rotation of the positioning motor assemblies. The motion platform further comprises a microcontroller, electrically connected to the positioning motor assemblies and responsive to input commands and to signals from the sensors, for controlling rotational speed, rotational direction and rotational extent of the positioning motor assemblies and thus angular displacement of the top of the motion platform relative the base. The motion platform has two degrees of freedom, pitch and roll, to mimic real world motion.

Multiple link robot arm system implemented with offset end effectors to provide extended reach and enhanced throughput

Abstract: Two multiple link robot arms (10) are mounted to a torso link (11), and each of them includes an offset hand (30) and two motors (50, 52) capable of independent operation that provides movement of the offset hand along along combinations of angular, radial, linear, and curvilinear paths. The first motor rotates a forearm (22) about an elbow axis (24), and the second motor rotates an upper arm (14) about a shoulder axis (16). A motor controller (54) controls the first and second motors in two operational states that respectively enable linear extension or retraction of the robot arm radial to the shoulder axis and enable angular displacement of the hand about the shoulder axis. A distal end (34) of each offset hand is offset such that during first operational state motion, the distal end follows paths parallel to lines radial to the shoulder axis. The offset distance (240) is set so that when properly rotated in the second operational state, both offset hands can follow a common hand extension line (44) that is a perpendicular bisector between the shoulder axes of the robot arms. This allows specimens (206) retrieved by either offset hand to be placed on a processing station (208) located along the hand extension line.

System for determination of a location in three dimensional space

Abstract: An optical improvement for angular position sensors, which may be used to determine the spatial coordinates of a small source of light (or other energy) in a 3-dimensional volume. Such sensors normally include a linear photosensitive image detector such as a photodiode array or a charge-coupled device (CCD). An irregular pattern of parallel slits is described which increases the amount of light gathered while avoiding the undesirable characteristics of lens optics for this application. One optimal type of irregular pattern is the uniformly redundant array. A mathematical correlation function together with a polynomial interpolation function can determine the displacement of the image on the detector and thereby the location of the source relative to one angular dimension. Given the locations and orientations of several sensors in a 3-dimensional coordinate system and given the angles measured by each, the location of the point source can be computed.

Device for determining the angular position of a rotating shaft

Abstract: In order to improve the measurement possibilities with regard to a rotating shaft, including the whole angle area (0 to 360°), a rotation angle sensor is mounted that is provided with a radial-bipolar ring-shaped magnetic element ( 3 ), three air gaps ( 5, 6, 7, 8 ) displaced by an equal angle (φ) being connected with said shaft, and with a stator element ( 4 ) of a magnetoconductive material, while a Hall integrated circuit element ( 1, 2 ) is inserted in at least two adjacent air gaps ( 5, 6, 7, 8 ). The two Hall integrated circuit elements ( 1, 2 ) can be connected to an evaluation unit ( 9 ) which records a voltage curve of the measured circuit for each circuit element ( 1, 2 ), assigns each flow voltage measure to a position angle on the Hall integrated circuit voltage curves, calculates from the position angles assigned to the flow voltage values the actual position angle and gives it as the start signal (A 1 , A 2 ).

Angle sensor having lateral magnetic field sensor element and axial magnetic field direction measuring element for determining angular position

Abstract: An angle sensor includes a lateral magnetic field sensor element (1) for producing a sensor signal (US) which is dependent on the angular position of a target object (6) which is rotatable about an axis of rotation (5). The lateral magnetic field (8) is produced by a magnet (4) which also produces an axial magnetic field (7). Magnetic field sensor elements have a linear characteristic only over an angular range of up to at most 180°. According to the invention, however, in addition to the field sensor element (1) there is also provided a measuring element (2) which determines the direction of an axial magnetic field (7) also produced by magnet (4) and which traverses the measuring element (2). An evaluation circuit (9) is thereby enabled to determine the angular position of the target object (6) from the sensor signal (US) produced by the magnetic field sensor element (1) and the direction signal (UR) produced by the additional measuring element (2), which determination can be performed over an angular range exceeding 180°.

Guidance system having a body fixed seeker with an adjustable look angle

Abstract: A missile guidance system with a fixed body missile seeker having an adjustable look angle. The missile seeker has a fixed camera whose look angle is adjustable to keep a moving target within the field of view of the camera. The target is tracked by a tracker to generate target angle and line of sight rate signals. The target angle signal is input to pointing angle adjustment apparatus which adjusts the look angle of the camera. The pointing angle adjustment apparatus may comprise a stepper motor that controls the angular position of a gimbal on which the camera is mounted. Alternatively, the pointing angle adjustment apparatus may comprise one or more stepper motors that control an adjustable zoom lens or a plurality of optical wedges, respectively. A body angular rate output signal of a body-fixed inertial measurement system is summed with the line of sight rate signals from the tracker to determine the inertial line of sight rate of the moving target. The inertial line of sight rate is driven to zero or a low fixed value by a control system to accurately track a target. The control system and missile dynamics generate a body angle signal that is input to a difference circuit along with a camera pointing angle signal output by the pointing angle adjustment apparatus. The difference circuit generates a desired camera pointing angle that is input to the pointing angle adjustment apparatus to point the camera at the target.

Control device of leg type moving robot

Abstract: PROBLEM TO BE SOLVED: To appropriately control the actual floor reaction by detecting the actual floor reaction to calculate the moment around the center point, determining the amount of rotation to correct the target position and/or posture so that the position and/or posture of the leg part is rotated, and to displace the joint of a robot. SOLUTION: A two-foot walking robot 1 is provided with a joint on a leg part link 2. A six-axis force sensor 44 is mounted on a foot joint, the three- direction components of the force and the moment are measured, and presence/ absence of landing of a foot part and the floor reaction are detected. An inclination sensor 60 is installed on an upper body 24 to detect the inclination and the angular velocity. A rotary encoder to detect an amount of the rotation is provided on an electric motor for a joint. First and second arithmetic units are provided in a control unit 26, and the first arithmetic unit calculates the angular displacement command of the joint, and feeds it to a RAM. The second arithmetic unit reads the measured value to detect the command from the RAM, calculates the control value, and outputs it to the electric motor. The floor reaction can be appropriately controlled without generating the interference.

A 3D optical profilometer using a compact disc reading head

Abstract: The design, construction and performance of a novel optical profilometer based on the laser reading head of a compact disc player is described. The instrument is capable of self-guided scanning along arbitrary contours by utilizing the focus and radial tracking signals from the sensor head. The sensor is mounted on an x, y, motorized stage. The radial tracking signal provides the feedback for the angular position of the sensor, ensuring that the optical axis of the sensor is always perpendicular to the profile preventing the signal loss that occurs in conventional profilometers due to deflection of the light beam. The focus signal has a sensitivity in the nanometre range which makes the precision of the stages used to perform the scanning movements the dominant limiting factor for the measuring accuracy. The sensor head intermittently follows the contour, collecting datapoints at a predetermined lateral resolution. The profile is digitized in the form of x, y, and coordinates for each scanpoint. The accuracy of the instrument was verified by scanning standard measures with flat and circular cross sections. The mechanical structure of the prototype instrument was purpose built for the measurement of rigid corneal contact lenses. Various lenses have been measured and profile graphs are illustrated.

Laser-speckle angular-displacement sensor: theoretical and experimental study

Abstract: A novel, to our knowledge, method for the measurement of angular displacement for arbitrarily shaped objects is presented in which the angular displacement is perpendicular to the optical axis. The method is based on Fourier-transforming the scattered field from a single laser beam that illuminates the target. The angular distribution of the light field at the target is linearly mapped on a linear image sensor placed in the Fourier plane. Measuring this displacement facilitates the determination of the angular displacement of the target. It is demonstrated both theoretically and experimentally that the angular-displacement sensor is insensitive to object shape and target distance if the linear image sensor is placed in the Fourier plane. A straightforward procedure for positioning the image sensor in the Fourier plane is presented. Any transverse or longitudinal movement of the target will give rise to partial speckle decorrelation, but it will not affect the angular measurement. Furthermore, any change in the illuminating wavelength will not affect the angular measurements. Theoretically and experimentally it is shown that the method has a resolution of 0.3 mdeg (≈5 μrad) for small angular displacements, and methods for further improvement in resolution is discussed. No special surface treatment is required for surfaces giving rise to fully developed speckle. The effect of partially developed speckle is considered both theoretically and experimentally.

Axial and angular displacement fiber-optic sensor.

Abstract: An intensity-based fiber-optic sensor for measuring axial and angular displacement has been designed and tested in a controlled laboratory environment. In addition, a mathematical model allowing the simultaneous calculation of the three desired parameters needed to characterize the tilt and the position of a surface under investigation is described. Preliminary tests show good agreement between the theory and the experimental results and show the sensor’s potential for application in the manufacturing industry for position and vibration control. The sensor shows significant improvement in angular range over previously reported methods. An axial displacement range of 2 mm, with an accuracy of 40 μm, and an angular displacement range of 40 mrad, with an accuracy of 0.5 mrad, are demonstrated. Suggestions for further improvement of the range and the sensitivity of the sensor are also described.

Method of controlling attitude of a momentum biased spacecraft during long-duration thruster firings

Abstract: A method is provided for controlling the attitude of a momentum biased spacecraft about all three mutually orthogonal axes during a thruster firing maneuver without separately sensing angular displacement, angular rate, or angular acceleration about the spacecraft yaw axis The method includes a transient phase during which a yaw feedforward torque is computed based on the known pitch/yaw coupling due to thruster geometry, and a steady state phase, during which feedback gains are adjusted to estimate yaw attitude based on coupling of a steady state disturbance torque about the roll axis of the spacecraft and a steady state disturbance torque about the yaw axis of the spacecraft

Small-angle measurement by use of a single prism

Abstract: A new method of angle measurement based on the internal reflection effect is proposed that uses a single right-angle prism. We measure the angular displacement between a laser beam and the prism by detecting the changes in reflectance as a function of the angle of incidence. We achieve high linearity of measurement by taking the inverse of reflectance as the output. The inverse of reflectance is obtained from the intensities of the reflected and the transmitted beams measured by two photodiodes. Experiments with a prototype device have demonstrated that angle measurement with a range of ?500 arc sec, a nonlinearity error of ?0.1%, and a resolution of 0.1 arc sec can be readily achieved. The measurement range can be further increased with some sacrifice of linearity.

Adaptive absolute steering angle sensor

Abstract: The invention relates to an adaptive absolute steering angle sensor for the absolute determination of a turning angle, especially for determining the steering angle in a motor vehicle by way of a code applied across a 360 ° angular range for determining the angle. The code and a sensor system are arranged in such a way that they are able to rotate in relation to each other. Absolute determination of the angle is carried out by reading the contrast information using a micro processor which determines both the angular position of the code and the fine resolution of the angles on the basis of the relative position of the recognized angle to the image on the photodetector system. At the same time the overall function of the system is verified and adjusted during each measurement. The code is determined using a photodetector system, positioned in a single place, and used for determining the angle, whereby an unbroken segment of code track is shown on at least one photodetector line and at least one code word is detected to which corresponds a predetermined angle. The position of the code word in relation to the fixed position of the photodetector line is measured.

Design of spherical 4R mechanisms : Function generation for the entire motion cycle

Abstract: Spherical 4R mechanisms are studied for which the crank is relatively smaller than the remaining links. The theory of small-crank mechanisms is applied to obtain approximate descriptions for the follower angular displacement in terms of the input crank angle. The follower angle is presumed to comprise a mean and a perturbational motion. This results in an approximate expression in which the follower displacement is given as a linear combination of simple harmonic functions of the first and second harmonics of the crank angle. The approximate equations are utilized for synthesis of spherical 4R mechanisms for function generation. In contrast to the conventional design procedures, the use of the approximate equations allows the synthesis of spherical mechanisms in which a prescribed function is satisfied for the entire motion of the mechanism. In addition to design examples, sample error charts are provided to assist the designer in ascertaining feasible ranges for design and corresponding orders of error.

Method and apparatus for detecting rotational direction of a two cycle engine

Abstract: A system for determining the direction of rotation of the crankshaft of an internal combustion engine includes a sensor assembly for generating a crank rotation direction signal. The sensor assembly includes a stator having a sprocket fixed to the crank and having a plurality of teeth. The rotation of the crank, and the sprocket with the crank, results in changes in the magnetic field, and such changes or flux create a current in a conductor. The rotor also includes, at one angular location about the sprocket, a first interruption that serves as a first reference point or marker. The interruption in the sprocket teeth creates an irregularity in the magnetic flux and, consequently in the generated current or signal. The rotor also includes a second interruption or marker at an angle other than 1800 from the first marker. The second interruption differs physically from the first interruption, so that a second irregularity which is distinguishable from the first irregularity occurs in the generated signal. The pattern of the generated signal, in combination with the known angular displacement of the first and second markers, provides sufficient information from which the direction of rotation of the crankshaft can be readily determined.

New torsional actuator based on shear piezoelectric response

Abstract: A torsional actuator generating angular displacement from the piezoelectric shear strain was developed. The actuator is a tube consisting of an even number of the segments poled along the length, which are adhesively bonded together, and the joints act as electrodes to apply the driving voltage. The experimental data measured on the prototype actuator: (i) prove the proposed concept of the torsional actuator, (ii) show that the actuator functions well under the torque load, and (iii) demonstrate that is has superior characteristics compared to previously reported designs of torsional actuators. In addition, one of the obvious advantages of the present design of the actuator is its simplicity: the piezoelectric shear strain is transformed directly into the angular displacement, whereas in the previously reported actuators, the conversion mechanism into the torsional motion was rather complicated which thus required a sophisticated design of the whole system.

Bond head having dual axes of motion

Abstract: A bond head is provided for a wire bonding machine having a linear axis frame, a rotary axis frame, a bond tool and a wire clamp. The linear axis frame is vertically linearly displacable along a linear axis, while the rotary axis frame is rotationally displacable along a rotary axis. A pivotal connector is provided which pivotally connects the rotary axis frame to the linear axis frame, enabling the rotary axis frame to rotate independent of linear displacement of the linear axis frame. The bond tool is connected to the rotary axis frame and is vertically linearly displacable in response to vertical linear displacement of the linear axis frame and rotationally displacable in response to rotational displacement of the rotary axis frame. The wire clamp is connected to the linear axis frame and is vertically linearly displacable in response to vertical linear displacement of the linear axis frame, while the wire clamp is maintained rotationally stationary during rotational displacement of the rotary axis frame. The bond head also includes a linear motion assembly and a rotary motion assembly. The linear motion assembly has a linear driver, a linear position detector and a linear driver controller. The rotary motion assembly correspondingly has a rotary driver, a rotary position detector and a rotary driver controller.

An angular displacement interferometer based on total internal reflection

Abstract: This paper describes a new angular displacement interferometer based on the internal-reflection effect. In order to make use of the internal-reflection effect, a novel prism assembly is designed, which yields a very compact optical configuration. As a result, the linearity of the angular displacement interferometer is greatly improved. Both the linearization of the measurement equation and the experimental verification of the analysis have been conducted and the results are presented here in detail. The main factors affecting the angle measurement are also addressed. The results of the experimental verification are in good agreement with the theoretical analysis.

Method and apparatus for determining angular displacement, surface translation, and twist

Abstract: A method and apparatus for determining angular displacement of one or more parts of an object (10) comprising detecting in at least one first image sensor first and second one or more distributions of Fourier-transformed speckles before and after angular displacement, respectively, and determining the displacement of the detected images; a method and apparatus for determining twist of a rotating shaft between two or more parts of the shaft subjected to a load; a method and apparatus for simultaneously determining angular displacements and surface translations of one or more parts of an object; and a method of determining the radius of angular displacement of one or more parts of an object.

Method and device for accurately measuring a longitudinal contour of a measuring object, such as a screw thread and similar geometries

Abstract: Method and device for accurately measuring a longitudinal contour of a measuring object, wherein use is made of clamping members for retaining a measuring object to be measured; a scanning arm which is pivotable about an axis transverse to a longitudinal center line of the clamped measuring object and whose free end comprises one scanning needle, the scanning arm being mounted on a driving device which, in operation, can move the scanning arm in one linear direction of movement parallel to the longitudinal center line of the measuring object, and means being provided for detecting the angular displacement of the scanning arm and the position of the scanning arm in said one linear direction of movement; and a processor for processing information regarding the angular displacement and the position of the scanning arm, wherein a contour measurement is made in such a manner that the scanning needle moves along a contour flank in downward direction only, i.e. in the direction of the bottom of a profile groove.

Angle sensor, position sensor and automobile

Abstract: PROBLEM TO BE SOLVED: To provide a sensor to determine a larger angular position univocally in such an angle sensor containing a magnetic field sensor element that measures a sensor signal depending on the angular position of an object to be measured that is provided with a magnet and is rotatable around a rotary axis. SOLUTION: This sensor determines the angular position of an object 6 to be measured univocally in a range of 0 to 360 degrees. A well-known magnetic field sensor 1 has linear characteristic of angle range only up to 180 degrees. However, it is added with a measuring element 2 to determine the direction of a magnetic field 7 crossing a measuring element 2, in addition to the magnetic field sensor element 1. An evaluation circuit 9 having a proper structure is used so as to determine an angular position α according to the sensor signal from the element 1 and the direction signal from the added element 2. It can also determine the angular position in even a range of angle exceeding 180 degrees.

Compact camera with variable position handgrip

Abstract: A camera comprising a spindle for supporting an image recording disk to be rotated about a center axis, and a handgrip which is to be hand held at an angular position, is characterized in that the handgrip is supported for rotation about the center axis to vary the angular position at which the handgrip is hand held.

High resolution optical shaft encoder for motor speed control based on an optical disk pick-up

Abstract: Using a three-beam optical pick-up from a compact disk player and a flexible, shaft-mounted diffraction grating, we obtain information about the rotation speed and angular position of the motor’s spindle. This information may be used for feedback to the motor for smooth operation. Due to the small size of the focused spot and the built-in auto-focus mechanism of the optical head, the proposed encoder can achieve submicrometer resolution. With high resolution, reliable operation, and low-cost elements, the proposed method is suitable for rotary and linear motion control where accurate positioning of an object is required.

Methods and apparatus for determining bar code label location information

Abstract: A system for synchronization of the angular position of a rotating optical assembly in a bar code scanner having a rotating optical assembly. The optical assembly is rotated by a motor which produces a fixed number of pulses per rotation, the pulses occurring at equal intervals such that each pulse indicates a degree of angular rotation of the motor. The pulses are continuously monitored and counted. Timing is simultaneously monitored. A synchronization label is placed in the scanner such that light directed through the rotating optical assembly will strike the synchronization label and be reflected back to the rotating optical assembly when the rotating optical assembly is at a particular angular position, thus establishing an initial angular position of the rotating optical assembly. Once the initial angular position is established, timing is continuously monitored and pulses are continuously monitored and counted. When an event of interest, such as bar code scan occurs, the pulse count is evaluated and processed to determine an angular position of the rotating optical assembly with respect to the initial position as established at synchronization.

Method for calibrating rotary encoder with multiple calibration points

Abstract: One embodiment of the present invention provides a method for calibrating a rotary encoder including a rotatable disk including at least two index points located along a circumferentially extending row. These index points contain information specifying an angular position of the index point. This allows the rotary encoder to be calibrated by turning it through a sufficient angular displacement to ensure that an index point passes over a sensor. This sufficient angular displacement is less than a complete revolution because there are multiple index points along the circumference of the disk. This design allows a rotary encoder to be calibrated without turning it through a complete revolution. This is advantageous where turning the rotary encoder through a complete rotation is not possible or is inconvenient, for example in applications such as a wind direction indicator, a rudder position indicator or a joystick. Thus, one embodiment of the present invention includes a method for calibrating a rotary encoder including a rotatable disk with at least two index points located along a circumferentially extending row on the rotatable disk. The method includes turning the rotary encoder through a sufficient angular displacement to ensure that an index point passes over a first sensor in the rotary encoder, the sufficient angular displacement being less than a complete revolution. The method also includes reading an index point signal through the first sensor, and decoding the index point signal to obtain an angular position value for the index point. The method additionally includes using the angular position value to calibrate the rotary encoder.