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Showing papers on "Angular displacement published in 1982"


Journal ArticleDOI
TL;DR: The left foot of five normal human subjects was rotated in a fixed stochastic pattern about a constant ankle angle and the torques opposing these rotations were measured to calculate the dynamic stiffness transfer functions relating ankle angular position to ankle torque.

212 citations


Patent
02 Mar 1982
TL;DR: In this paper, a method and apparatus for controlling the angular position of a motor by controlling the revolution of the motor in response to a given positioning command value commanding a predetermined angular position was presented.
Abstract: A method and apparatus for controlling the angular position of a motor by controlling the revolution of the motor in response to a given positioning command value commanding a predetermined angular position of the motor shaft so as to stop the motor shaft at the predetermined angular position, wherein the acceleration of the motor being accelerated in the initial acceleration stage of the motor position control operation is calculated, and on the basis of the calculated acceleration and a commanded maximum velocity, the remainder angular distance between the deceleration starting angular position and the desired angular position of the motor and the deceleration command value in the deceleration stage are calculated so as to control the deceleration of the motor on the basis of the calculated values.

53 citations



Patent
25 Feb 1982
TL;DR: In this paper, the rotational speed of a rotating body was detected by the combination of the number of zero-crossing pulses appearing within a predetermined period of time and the phase angle of the sine-wave signal generated from the encoder.
Abstract: In a speed detecting apparatus for detecting the rotational speed of a rotating body mechanically coupled thereto, an encoder generates one cycle of a sine-wave signal each time its angular position of rotation changes by a predetermined unit amount. A zero-crossing pulse is generated at each zero-crossing point of the sine-wave signal generated from the encoder, and the phase angle of the sine-wave signal is detected on the basis of the zero-crossing point of the sine-wave signal generated from the encoder. In a high speed range, the rotational speed is detected on the basis of the ratio between the number of zero-crossing pulses and the time interval between a first one and a last one of the plural zero-crossing pulses. On the other hand, in a low speed range, the rotational speed is detected on the basis of the combination of the number of the zero-crossing pulses appearing within a predetermined period of time and the phase angle of the sine-wave signal.

35 citations


Journal ArticleDOI
TL;DR: In this article, deviations in a time-integrated sonar-echo signal caused by angular motion of the sonar transducer have been calculated, due to the change in orientation of the transducers between the times of transmission of the acoustic pulse and reception of the resultant echoes.
Abstract: Deviations in a time‐integrated sonar‐echo signal caused by angular motion of the sonar transducer have been calculated. The effects are due to the change in orientation of the transducer between the times of transmission of the acoustic pulse and reception of the resultant echoes. The transmission and reception beams are then aimed in different directions than in the static case. If the beams are narrow enough in relation to the augular displacement, then the departures of the integrated echo from the static case will be significant. The deviations are presented for several beamwidths as a function of angular displacement of the transducer. The results quantify the expected outcome—the change in echo‐integration values from the corresponding static case increases with both increasing angular displacement and decreasing beamwidth. In an example calculation, a ship‐mounted transducer is shown to roll in conjunction with the ship an angle of 4° between the times of transmission and subsequent reception of e...

28 citations



Patent
04 Aug 1982
TL;DR: A transducer for sensing the angular position or rate of change of displacement of a housing of a borehole survey instrument with respect to a reference position is described in this article.
Abstract: A transducer for sensing the angular position or rate of change of displacement of a housing of a borehole survey instrument with respect to a reference position includes a rotor magnetically suspended within a stator which is in turn secured to the housing. The rotor is constrained by the magnetic suspension to rotate about a single axis relative to the stator. A frame of reference is established for the transducer, against which subsequent measurements are compared. Optical sensing means are included for sensing the movement of the rotor about the axis of motion to develop an indication of the angular position or rate of change of position of the housing.

21 citations


Journal ArticleDOI
TL;DR: In this paper, a relatively elementary description of the state of rotational displacement, in place of the known description in terms of a Rodriguez vector, which involves a symmetric treatment of the rotations about the two surface tangent vectors, without a participation in this of the rotation about the surface normal vector.
Abstract: We supplement an earlier consideration of two-dimensional finite-deformation shell theory in terms of independent descriptions of states of translational and rotational displacement by the avoidance of the previously made a priori assumption concerning the form of components of force strain. We furthermore introduce a relatively elementary description of the state of rotational displacement, in place of the known description in terms of a Rodriguez vector, which involves a symmetric treatment of the rotations about the two surface tangent vectors, without a participation in this of the rotation about the surface normal vector.

20 citations


Patent
Reinhold Stroezel1, Wilhelm W. Schwarze1, Karl Roll1, Alfred Hettich1, Wolfgang Raidt1 
27 Sep 1982
TL;DR: A transducer arrangement for torque and angular displacement measurement, especially in power screwdrivers, operates in accordance with the eddy current principle as mentioned in this paper, where a torsionally deformable member, especially shaft, is interposed between the driving and driven members, being connected thereto for joint rotation therewith.
Abstract: A transducer arrangement for torque and/or angular displacement measurement, especially in power screwdrivers, operates in accordance with the eddy current principle. The transducer arrangement is constructed as a self-contained structural unit having its own transducer casing which is connected by appropriate coupling and connecting parts to the housing of the power screwdriver and to the driving and driven members of the screwdriver. A torsionally deformable member, especially shaft, is interposed between the driving and driven members, being connected thereto for joint rotation therewith. When torque is applied to the deformable member, its end portions are angularly displaced relative to one another. Two slotted members, especially sleeves, are respectively connected to the end portions of the deformable member for joint angular displacement therewith, and they influence the magnetic field in the vicinity of the deformable member in proportion to their relative angular displacement. The changes in the magnetic field are detected by an electric coil arrangement whose impedance changes accordingly, and the thus obtained signal is evaluated to obtain the magnitude of the applied torque. A cable connected to the coil arrangement and extending to the exterior of the casing through an opening provided in the latter is accommodated in a tube. The tube extends along a handgrip portion of the housing of the screwdriver to protect the hand of the user.

20 citations


Patent
11 Feb 1982
TL;DR: In this paper, a dual-coil bobbin eddy current inspection probe is presented for detecting flaws in a tubular workpiece in a single scan, with one coil having an angular position about the axis about 90° relative to the angular position of the other coil, and the angle of intersection of the planes containing the coils being about 60°.
Abstract: Apparatus is described for detecting flaws in a tubular workpiece in a single scan. The coils of a dual coil bobbin eddy current inspection probe are wound at a 45° angle to the transverse axis of the probe, one coil having an angular position about the axis about 90° relative to the angular position of the other coil, and the angle of intersection of the planes containing the coils being about 60°.

18 citations


Patent
30 Dec 1982
TL;DR: In this article, an automatic focusing camera comprising optical object distance detecting means having a light emitting element for measuring an object distance and a light receiving element for receiving the reflected light from an object, provision being made of rotating means which rotates about an optical axis of a camera lens.
Abstract: In an automatic focusing camera comprising optical object distance detecting means having a light emitting element for measuring an object distance and a light receiving element for receiving the reflected light from an object, provision being made of rotating means which rotates about an optical axis of a camera lens and which has scanning means cooperating with the light receiving element to detect the object distance as a function of an angular displacement of the rotating means.

Patent
25 May 1982
TL;DR: In this paper, an apparatus for balancing a body to correct for unbalance determined during a measurement run on a balancing machine is described, where the body to be balanced is rotated at a measuring speed by compressed air and the unbalance is determined.
Abstract: An apparatus for balancing a body to correct for unbalance determined during a measurement run on a balancing machine. The body to be balanced is rotated at a measuring speed by compressed air and the unbalance is determined. A braking device then is applied to the body to brake the body and rotate the body at a low speed. When a predetermined portion of the body is located in a desired angular position, a stopping device, such as a pawl, is actuated to stop rotation of the body. Appropriate mass is then added to or removed from the body to correct the unbalance. If necessary, the pawl is released, and body is incrementally rotated so that unbalance can be corrected on several portions of the body. The apparatus, instead of balancing the body, is usable to mark the body as to the location of unbalance.

Patent
13 Apr 1982
TL;DR: In this article, a microcomputer calculates the position of the eyes of the driver seated on the seat from the outputs of displacement detectors 18A to 18D which detect displacements caused by operating the switches 16A to 16D.
Abstract: PURPOSE:To improve the utility and safety by permitting at least one of the angles of a back mirror, a meter and an air conditioner blow-out port to be set to an optimum angle to the driver automatically according to the displacement of seat forwards or backwards, a reclining operation and so forth. CONSTITUTION:When adjusting the fore-and-aft position of the driver's seat, reclining angle, etc. a seat control switch until 16 which consists of switches 16A to 16D for moving the seat in the fore-and-aft direction, backward rotation of the seat, vertical movement of the heat rest and rotation of the head rest is operated. As a result, a microcomputer 14 calculates the position of the eyes of the driver seated on the seat 2 from the outputs of displacement detectors 18A to 18D which detect displacements caused by operating the switches 16A to 16D. According to the results of calculation, the microcomputer 14 controls angular displacement mechanisms for a meter 4, an air conditioner 6, a room mirror 8 and left and right fender mirrors and 10, and 12. Thus, the parts 4, 6, 8, 10 and 12 are controlled to the optimum angles.

Patent
21 Apr 1982
TL;DR: A rotational angle sensor as discussed by the authors is an example of such a device, which includes a casing, a movable body rotatably supported by a permanent magnet, a magnetically soft member adjacent to the permanent magnet and an electrical coil wound on the member.
Abstract: A rotational angle sensor device includes a casing, a movable body rotatably supported on the casing, a permanent magnet secured to the movable body, a magnetically soft member adjacent to the permanent magnet, and an electrical coil wound on the magnetically soft member. The movable body is responsive to a rotational angle or angular displacement caused by an external object, in response to which the permanent magnet moves in relation to the magnetically soft member, causing variations in the external flux. Those variations in external flux cause corresponding variations in the time interval from the instant at which a voltage is applied to the electrical coil to the instant at which the coil current reaches a certain level. The variations in the time interval are detected to determine the rotational angle caused by the external object. The magnetically soft member is preferably formed from an amorphous magnetically soft material. Various embodiments of the rotational angle sensor device are disclosed.

Patent
16 Mar 1982
TL;DR: In this paper, the amplitude of a sine wave reference signal Vp is modulated into a value proportional to the magnitude of the x component of a displacement vector quantity generated at a point 9 involved with a detector 1A, and an output signal corresponding to a y displacement component is given to the arithmetic section 2 as a cosine wave signal Vy shifted by 90 degrees in the phase via an amplifier 12B and a phase shifter 13.
Abstract: PURPOSE:To facilitate the indication of plane pole coordinates by measuring rectangular coordinate components of a two-dimensional vector quantity so as to be converted into a sine wave and a cosine wave with an amplitude proportional to the magnitude thereof and detecting the phase of a sine wave signal from the addition of the two waves. CONSTITUTION:An x component of a displacement vector quantity generated at a point 9 involved is detected with a detector 1A, the amplitude of a sine wave reference signal Vp is supplied from the power source 4 modulated into a value proportional to the magnitude of the x component and the output sine wave signal Vx is inputted into an arithmetic section 2. Likewise, an output signal corresponding to a y displacement component from a detector 1B is given to the arithmetic section 2 as a cosine wave signal Vy shifted by 90 deg. in the phase via an amplifier 12B and a phase shifter 13. The signals Vx and Vy are added at an arithmetic section 2 to be converted into a sine wave signal Vo including a phase angle theta, which is detected with a phase detector section 3A. This facilitates the indication of a plane pole coordinate in which the amplitude of Vo corresponds to the magnitude of a radius vector and the angular displacement thereof to the phase angle theta.

Patent
01 Sep 1982
TL;DR: In this paper, a capacity type rotation detecting apparatus is proposed, where a fixed first plate and a rotational second plate are arranged to face each other and are respectively made of an electrically insulating material.
Abstract: A capacity type rotation detecting apparatus includes a fixed first plate and a rotational second plate which are arranged to face each other and are respectively made of an electrically insulating material. Provided on the first plate are a plurality of electrodes arranged circumferentially and forming a pair of sets of input rotational angle detection electrodes and a pair of sets of input reference angular position detection electrodes and at least two capacitive coupling signal transmitting electrically conductive rings. Also provided on the second plate are at least one set of output rotational angle detection electrodes and at least one set of output reference angular position detection electrodes arranged to face the respective pairs of sets of electrodes on the first plate and at least two capacitive coupling signal transmitting electrically conductive rings which are respectively connected to the at least two sets of electrodes on the second plate and respectively arranged to face the at least two rings on the first plate. The capacity type rotation detecting apparatus further includes first and second periodic signal supply circuits which have different repetition periods and respectively supply detecting signals of opposite phase to the respective pairs of sets of input electrodes on the first plate, and a rotational angle signal generating circuit and a reference angular position signal generating circuit responsive to respective signals generated at the at least two rings on the first plate to generate a rotational angle detection signal and a reference angular position detection signal, respectively, thereby simultaneously providing detection signals accurately without any delay irrespective of the rotational speeds of the second plate.

Patent
25 Aug 1982
TL;DR: In this paper, an electronic ignition control apparatus has RAM to initially store first and second signals indicative of the starting and terminating points for calculation of a time necessary for rotation of a predetermined angle defined by integer times as large as a predetermined angular interval of an output shaft of an engine.
Abstract: In an electronic ignition control apparatus having RAM to initially store first and second signals indicative of the starting and terminating points for calculation of a time necessary for rotation of a predetermined angle defined by integer times as large as a predetermined angular interval of an output shaft of an engine, a rotation time of the output shaft is calculated during rotation of an angle of the output shaft defined by the first and second signals from RAM to calculate an optimum spark advance angle in relation to the operating condition of the engine such that an angular position defined by integer times as large as the predetermined angular interval at the advance angle side of the calculated advance angle is determined to be stored in RAM as a third signal. Calculation of a time defined by the difference between the calculated advance angle and the angular position defined by the third signal is started upon arrival of the output shaft to the angular position defined by the third signal from RAM and completed to deenergize the ignition coil of the engine previously energized.

Patent
08 Jul 1982
TL;DR: In this paper, the angular adjustment of a single or multiple camshafts with respect to the crankshaft according to speed and load conditions is addressed using an adjustable mechanism.
Abstract: A device for the angular adjustment of a camshaft of a combustion engine according to speed and load conditions and to the angular position of the camshaft with respect to a driving wheel being controlled by an adjustable mechanism. The technical problem is the angular adjustment of the single or multiple camshafts with respect to the crankshaft according to speed and load conditions. Tooth pulses, or counting pulses, corresponding to the angular position of the crankshaft (2) and reference pulses corresponding to a particular angular reference position (singular tooth) are generated by a transducer, or pulse generator, controlled by the toothed ring associated with the crankshaft and the ignition circuit (13). An address counter (10) is reset by the reference pulses and incremented by the tooth pulses so that the output of the counter provides digital address signals corresponding to the actual angular position of the crankshaft (2). The output signals of the address counter and digital signals corresponding to load conditions are input to a correction processor with memory, (20) the output of which provides a camshaft adjustment signal. During pre-set engine operational periods, a buffer memory ( 21), controlled by the tooth-pulse time base signal, stores an adjustment signal used as a camshaft correcting variable, which is then delayed under asynchronous clocking and fed into an electromechanical control device (FIG. 3) which effects a rotary-then-linear displacement of a control member (31) and subsequently an angular corresponding displacement of the camshaft(s) to the correcting variable.

Patent
29 Sep 1982
TL;DR: In this paper, a device for controlling or measuring operational parameters of an axial piston machine is described, and the output signals from the sensors are separated into the pressure dependent signals, frequency dependent signals and angular displacement signals which upon multiplication are applied to a programmable data processing unit.
Abstract: Disclosed is a device for controlling or measuring operational parameters of an axial piston machine. The tilting plate which engages and adjusts the stroke of the piston is provided with two opposite pivot pins supported in fixed bearings. At least one pivot pin is provided with a shearing stress sensor preferably in the form of a magnetoelastic feeler which produces electrical signals the pulsation of which is indicative of rotational speed and the magnitude of the signal is proportional to pressure applied by the pistons and thus to the delivery of the machine. A second sensor is coupled to the tilting plate to indicate the angular displacement of the latter. The output signals from the sensors are separated into the pressure dependent signals, frequency dependent signals and angular displacement signals which upon multiplication are applied to a programmable data processing unit. The output of the unit is supplied to a solenoid operated proportional valve which controls pressure fluid for hydraulic setting motors which adjust the angular displacement of the tilting plate.

Patent
26 Jul 1982
TL;DR: In this article, a linear array of photodetectors is disposed on a planar surface mounted on the first body parallel to the axis about which the displacement is to be measured.
Abstract: An electro-optic sensor for precise, direct and continuous measurement of the angular displacement between two bodies. A linear array of photodetectors is disposed on a planar surface mounted on the first body parallel to the axis about which the displacement is to be measured. The line of the array is perpendicular to this axis. A light source disposed on the planar surface near the photodetector array transmits light through optics to a reflecting reference flat mounted on the second body. The optics collimates the transmitted light and causes the reflected image of the light source to be spread into a line on and perpendicular to the photodetector array. This line image moves along the linear array as angular displacement occurs between the two bodies. No mechanical moving parts are required in the sensor.

Patent
30 Apr 1982
TL;DR: In this article, an ultrasonic range measuring device is used in order to measure the distance between the object or reflector (11) and the measuring head (6) or the optical system (10), and a computer is used to evaluate the relationship between the transmitting point and receiving point of the emitted light pulse or pulses.
Abstract: In order to determine the spatial angular position between parts of an object and prescribed reference lines or reference surfaces, in particular to measure the track and camber of motor vehicle wheels in a simple way, a device is provided which consists of a measuring head (6), which can be connected to a reflector, e.g. a mirror (11), and is equipped with at least one row (9) of light-emitting elements (7) and a row (15) of light-receiving elements (8) with a collecting optical system (10). This collecting optical system (10) focuses the light pulses, reflected by the reflector (11), of the light-emitting elements (7) onto the light-receiving elements (8). An ultrasonic range measuring device (12) known per se can be accommodated in the measuring head (6) in order to measure the distance (13) between the object or reflector (11) and the measuring head (6) or the optical system (10). Finally, a computer (14) is provided in order to evaluate the relationships between the transmitting point and receiving point of the emitted light pulse or pulses and to measure, e.g., the track angle alpha of a motor vehicle wheel and/or the camber angle beta .

Journal ArticleDOI
TL;DR: A simple and robust torque magnetometer which has a wide sensitivity range, from 10-6 to 0.2 N m, is described in this paper, which is suitable for work down to liquid helium temperatures and up to about 450K.
Abstract: A simple and robust torque magnetometer which has a wide sensitivity range, from 10-6 to 0.2 N m, is described. The design is based on that of Aldenkamp et al. (1960) but uses a modified mutual inductance method for measurement of angular displacement which in conjunction with a lock-in amplifier provides a direct reading of torque. This output is fed, together with a voltage proportional to magnet angle, to an on-line microcomputer, Fourier analysis of the torque curve, including a shearing correction takes approximately one minute following the complete input of data. The instrument is suitable for work down to liquid helium temperatures and up to about 450K.

Patent
14 May 1982
TL;DR: In this article, a magnetic or an electromagnetic sensor arrangement and a rotating magnetic circuit driven by the rotating component to pass in front of the sensor is presented. But the sensor state is not modified during the rotation of the magnetic circuit.
Abstract: The device has a magnetic or an electromagnetic sensor (2) arrangement and a rotating magnetic circuit (1) driven by the rotating component to pass in front of the sensor (2). The magnetic circuit (1) is of a circular shape divided into two or any even number of sectors (8,13). Alternate sectors (13) have a slot (14) passing in front of the sensor (2), the other sectors have a solid part (11) passing in front of the sensor (2). The sensor (2) state is thus alternately modified during the rotation of the magnetic circuit (1). The device is simple, accurate, reliable, statically and dynamically balanced and gives the position when the component is rotating or at rest. The device can be used to detect the angular position of a rotor of a motor.

Journal ArticleDOI
Z Dvir1, T. Trousil1
TL;DR: A device for measuring several spatio-temporal parameters involved in the maintenance of dynamic balance, which consists of a single degree of freedom metastable platform, the angular position and total displacement of which are monitored by a set of two independent transducers.
Abstract: A device for measuring several spatio-temporal parameters involved in the maintenance of dynamic balance is presented. It consists of a single degree of freedom metastable platform, the angular position and total displacement of which are monitored by a set of two independent transducers. The introduction of a hydraulic mechanism, for damping of the platform's almost frictionless motion, makes this device suitable for the examination and possible treatment of patients who suffer from disturbances in their postural control mechanisms and who cannot steady themselves on the otherwise undamped platform. In addition the significance of incorporating a mini computer as an integral part of the system is discussed.

23 Jun 1982
TL;DR: In this paper, the design and implementation of a measurement system for the CMU Direct Drive Arm using High resolution Optical Shaft Encoders is described and compared with two methods of angular velocity measurement: velocity by change of position and velocity by frequency.
Abstract: : Accurate measurement of the angular position and angular velocity of the joints is essential in the control of a robot manipulator. This report analyses in detail the design and implementation of a measurement system for the CMU Direct Drive Arm using High resolution Optical Shaft Encoders. Two methods of angular velocity measurement--velocity by change of position and velocity by frequency--are analysed and compared. (Author)

Patent
19 May 1982
TL;DR: In this article, a mounting arrangement for an instrument, such as an inertial measurement unit (IMU), is presented, where a mounting frame is pivotable mounted to a platform for rotation about a vertical axis and a support frame is rotatably mounted to the mounting frame for rotation on a horizontal axis.
Abstract: In a mounting arrangement for an instrument, such as an inertial measurement unit, a mounting frame is pivotably mounted to a platform for rotation about a vertical axis and a support frame is rotatably mounted to the mounting frame for rotation about a horizontal axis The support frame supports the instrument A horizontal lock and motion assembly interconnects the mounting frame and platform, and allows adjustment of the angular position of the mounting frame about the vertical axis relative to the platform when the mounting frame is locked to the platform A vertical lock and motion assembly interconnects the support frame and mounting frame, and allows adjustment of the angular position of the support frame about the horizontal axis relative to the mounting frame when the support frame is locked to the mounting frame

Patent
Lawrence C. Faupell1
27 Dec 1982
TL;DR: An anti-rotation linkage as mentioned in this paper allows freedom of angular deflection in two coordinate directions of a first member, for example, a rocket motor nozzle, with respect to the primary axis of a second member.
Abstract: An antirotation linkage that allows freedom of angular deflection in two coordinate directions of a first member, for example, a rocket motor nozzle, with respect to the primary axis of a second member, a rocket motor in which the nozzle is mounted for angular displacement of the thrust vector for steering control, but which restricts rotation of the first member about such primary axis.

Patent
18 Nov 1982
TL;DR: In this paper, the first and second couplings are fixed to a movable part and the second coupling is supported by a fitting part 11 by the first coupling 51 which has elasticity, an angular moment is produced around an axis parallel to the board surface of the coupling 41.
Abstract: PURPOSE:To obtain a large rotation angle and reduce the energy consumption due to unnecessary displacement by a method wherein the first and the second couplings which produce an angular moment at a movable part while being bent by dimensional strain generated by a piezoelectric substance. CONSTITUTION:Dimensional strain generated by elongation of a piezoelectric substance 3 is transmitted to a movable part 21 nearly along a board surface of the first coupling 41. As one end of the movable part 21 is supported by a fitting part 11 by the second coupling 51 which has elasticity, an angular moment is produced around an axis parallel to the board surface of the coupling 41. Displacement of the angle is produced at the movable part 21 by this angular moment. Accordingly, if an arm is fitted and fixed to the movable part 21, the angular displacement produced at the movable part 21 can be enlarged and reciprocal movement of the tip of the arm can be obtained. The ends of couplings 41 and 51 which are fixed to the movable part 21 move according to the fluctuation of the maovable part 21 and bending is occurred at the couplings 41 and 51. But as the thickness of the boards of the couplings is small the energy consumption can be small.

Patent
16 Feb 1982
TL;DR: In this paper, an autocollimator is mounted on a rotatable support where it is desired to measure and calibrate the angular position of the support every fixed number of degrees, such as one or ten degrees.
Abstract: Apparatus for indicating with precision relative rotation in terms of integral numbers of relatively large basic angular intervals and small angular deviations from such intervals. A portion of the apparatus is typically mounted to a rotatable support where it is desired to measure and calibrate, with great precision, the angular position of the support every fixed number of degrees, such as one or ten degrees, and to measure offsets from integral numbers of such basic angular intervals. The apparatus comprises two slightly non-parallel mirror surfaces rotatable with the support and illuminated by an autocollimator. The mirrors provide multiple reflections of the illumination. The angle between the mirrors define the basic angular interval. The number of reflections varies with the number of basic angular intervals of support rotation. At each precise integral number of basic intervals, the illumination will return to a fixed location on the autocollimator viewing screen. The screen is mounted to indicate deviations from the exact multiple of basic intervals.

Patent
20 Jan 1982
TL;DR: In this paper, the angular displacement in mutually perpendicular planes is measured between a fixed point and a movable point whose distance or angular displacement from the fixed point is to be measured by precise timing of the movement of a reference point (75) on a rotatable element (31, 32) which is driven at a constant rate of speed through sensing elements (37, 40) corresponding to the location of the fixed and movable (76) points.
Abstract: Angular displacement in mutually perpendicular planes is measured between a fixed point and a movable point whose distance or angular displacement from the fixed point is to be measured by precise timing of the movement of a reference point (75) on a rotatable element (31, 32) which is driven at a constant rate of speed through sensing elements (37, 40) corresponding to the location of the fixed (75) and movable (76) points. In each plane, the ratio of the time required for movement from the fixed to the movable point (Time 'A') to the time required for full revolution between the fixed point (Time 'B') is converted into an angular unit of measurement which can be used to actuate a display (102) or otherwise record it. A series of measurements may be taken and averaged to minimize errors or spurious measurements.