Abstract: An example actuator assembly includes an actuator configured to move a rod. A variable differential transformer (VDT) is situated adjacent to the actuator. The VDT includes a core coupled to the rod such that movement of the rod causes a corresponding movement of the core. A plurality of windings surround the core for measuring displacement of the core. A shield surrounds the plurality of windings and shields the plurality of windings from a magnetic field of the actuator. The shield having a maximum permeability of 50,000-500,000. A LVDT configuration method is also disclosed.

Abstract: Embodiments herein relate to a sensor fault measurement system. The system includes a sensor having a primary winding, a first secondary winding and a second secondary winding and a wiring harness operably connected to the primary winding, first secondary winding and second secondary winding of the sensor. The system also includes a controller operably connected to the wiring harness. The controller includes a bias network configured to apply a common mode DC voltage bias of opposite sign to the first sensor output and the second sensor output respectively, and a fault sense circuit configured to monitor the DC voltage bias on first sensor output and the DC voltage bias on second sensor output, and identify a sensor fault if at least one of the DC voltage bias on first sensor output and the DC voltage bias second sensor output is impacted beyond a selected threshold.

Abstract: A measurement method using an inductive displacement sensor including a magnetic core and transformer with a primary winding and two secondary windings.

Abstract: A gap compensated torque sensing system and methods for using the same are provided. The system can include a sensor head in communication with a controller. The sensor head can contain a torque sensor and a proximity sensor coupled to the sensor head. The torque and proximity sensors can each sense magnetic fluxes passing through the target and a gap between the sensor head and the target. The controller can estimate torque applied to the target from magnetic fluxes sensed by the torque sensor. The controller can determine an improved gap measurement that is independent of electromagnetic properties of the target from magnetic fluxes sensed by the torque and proximity sensors. The estimated torque can be modified by the improved gap measurement to compensate for changes in magnetic properties of the target due to variations in the gap. In this manner, the accuracy of the torque measurements can be increased.

Abstract: Systems and methods of detecting failures in an assembly that uses a variable differential transformer sensor. In one embodiment, a signal processor receives an excitation signal applied to the sensor, and detects a zero-crossing of the excitation signal. The signal processor receives an output signal of the variable differential transformer sensor in response to the excitation signal, and detects a zero-crossing of the output signal. The signal processor detects a fault in the assembly responsive to a determination that the zero-crossing of the output signal is separated from the zero-crossing of the excitation signal by more than the detection threshold.

Abstract: An earthmoving machine comprises a sensor, an implement, and control architecture comprising a controller and configured to facilitate movement in response to a signal indicative of a measured implement position and an implement control value comprising a gain value associated with implement speed. The controller is programmed to execute machine readable instructions to generate a noise value that is based on an error between the signal and a target signal, determine whether the noise value is acceptable to lock the gain value, adjust the gain value to control the implement speed when the noise value is unacceptable until the noise value is acceptable, and operate the machine based on the locked gain value.

Abstract: A linear variable differential transformer (LVDT) having an electrical stroke includes a probe axially movable along a length of the LVDT electrical stroke, a primary winding extending axially over the length of the LVDT electrical stroke, and a secondary winding extending axially over the length of the LVDT electrical stroke. The LVDT further includes a tertiary winding extending axially over less than the length of the LVDT electrical stroke, the tertiary winding at least partially overlapping with the secondary winding. An advantage of the LVDT in accordance with the present disclosure is that the accuracy of the position calculated from the tertiary winding is greater relative to the total stroke of the LVDT than that calculated from the secondary winding. This is accomplished while still fitting within the envelope of a standard single output LVDT.

Abstract: Provided is a stage apparatus that includes a first movable unit; a linear motor that includes a stator coil array arranged over a stroke range in a predetermined direction of the first movable unit and a mover magnet fixed to the first movable unit; a second movable unit that is arranged to face the first movable unit via a space and relatively moves with respect to the first movable unit in the predetermined direction; and a switch unit that forms a closed circuit including coils in the stator coil array and a resistance during operation of a dynamic brake, wherein the resistance value of a first coil located at a center region of the stroke range in the stator coil array is larger than that of a second coil located toward an end side of the stroke range rather than the center region in the stator coil array.

Abstract: An earthmoving machine comprises a sensor, an implement, and control architecture comprising a controller and configured to facilitate movement in response to a signal indicative of a measured implement position and an implement control value comprising a gain value associated with implement speed. The controller is programmed to execute machine readable instructions to generate a surface-based cost function (SBCF) value based on the signal, determine whether the SBCF value is acceptable to lock the gain value, and generate a noise value that is based on an error between the signal and a target signal when the SBCF value is unacceptable, determine whether the noise value is acceptable to lock the gain value, adjust the gain value to control the implement speed when the noise value is unacceptable until the SBCF value or the noise value is acceptable, and operate the machine based on the locked gain value.

Abstract: Apparatus and methods of detecting failures in systems having a four-wire variable differential transformer sensor. In one embodiment, a method of detecting failures includes monitoring a source frequency of an Alternating Current (AC) voltage applied to an input of a four-wire variable differential transformer sensor, and monitoring an output frequency for an output of the sensor. The method further includes comparing the output frequency with the source frequency, and detecting a failure if the output frequency is different than the source frequency.

Abstract: The invention relates to position sensors of the linearly variable induction difference type. When cost constraints prevent the use of transformers with guaranteed phase-shift tolerance to achieve an accuracy objective, it is advantageous to provide an independent demodulation of the signals of the two windings. The error signal thus has a lower dependence on the phase shift and the accuracy is typically enhanced by a factor greater than an order of magnitude.

Abstract: A control apparatus for a machine that can be operated at high precision in a stable control state is provided by driving a movable body with control parameters suited to the mechanical state. A control parameter calculation circuit is provided to obtain control parameters for a drive apparatus control circuit for driving actuators in accordance with the conditions of actuator rotational velocity, the orientation of the movable body, and the position of the movable body, and a control parameter K for the drive apparatus control circuit is varied.

Abstract: In a circuit arrangement having a linear variable differential transformer as a displacement sensor or force sensor, having a selection circuit which is connected to the primary coil of the transformer and which provides an output current for triggering the primary coil, and having an analysis circuit which is connected to the secondary coils of the transformer and which provides a message signal, a control circuit used for triggering the selection circuit and the analysis circuit and for processing the measurement signal provided by the analysis circuit is connected to the primary coil in order to calculate the temperature of the circuit arrangement, and is configured such that it determines the temperature-dependent ohmic resistance of the primary coil and calculates from it the temperature and corrects accordingly the measurement signal provided by the analysis circuit.

Abstract: Analog circuitry is disclosed for conditioning a signal from linear and rotary variable differential transformers having a primary winding, a pair of secondary windings and a movable core. The circuitry includes a unique closed loop negative feedback mechanism which, over time, adjusts the frequency of a voltage controlled oscillator so that a steady-state condition is achieved within the circuitry, whereby the total integrated value of the secondary winding voltages at an integrator remains equal to a reference voltage, thereby reducing the computational burden associated with solving an equation to determine the position of the movable core of the transformer.

Abstract: The present invention is intended to provide a ultra-precision high sensitivity displacement measuring device which has such a high resolution as to be able to make submicron measurement.

Abstract: A variable differential transformer system (10), both linear and rotary (L/RVDT) includes a primary coil (12) drive by a primary drive (20) having a triangle wave generator whose frequency is set by an external frequency control (R.sub.osc and C.sub.osc) which includes compensation for gain temperature error. Secondary coils (14, 16) have a common connection for balanced loading with an input stage arrangement (R7, R8, R9, R10) providing low common mode range and a way to differentiate between normal operation and coil faults detected by a fault detection network (28). Synchronous demodulation (22) extracts both magnitude and direction from the secondary coil signals. Electronic calibration (24) is shown which compensates for sensor offset and gain. Sensor offset calibration is accomplished by adding a percentage of the synchronous demodulation reference wave form to the differential secondary signal.

Abstract: A system for creating a position reference signal includes a linear variable differential transformer (LVDT), a magnetically permeable core capable of entering and existing the chamber of the LVDT, a positioning means for moving the core in forward and backward directions through a home location in which the core is within said LVDT, and a signal conditioner means for receiving the signals from the secondary windings and outputting a value so that when the core approaches the home location from the forward direction, the value first changes polarity only when the core passes through the home location. Preferably, the value is always positive or always negative when the core is at a location outside of the chamber.

Abstract: A monolithic interface circuit for use with a linear variable differential transformer (LVDT) position transducer. The interface circuit includes a drive circuit for providing an excitation signal of selectable frequency and amplitude to the LVDT primary winding. The interface circuit further includes a decoder responsive to signals induced in the LVDT secondary windings for computing the position p of the LVDT core as a solution to the equation p=K(A-B)/(A+B), where A and B represent the signals induced in the primary winding and K is a constant scale factor. The decoder includes circuitry for rectifying and filtering the secondary signals, a charge balance loop responsive to the detected signals for providing a binary signal having a duty cycle representative of B/(A+B), and an output circuit responsive to the binary signal for providing the position output. The decoder provides excellent scale factor stability and linearity and is relatively insensitive to variations in primary drive amplitude.

Abstract: A device for measuring the position of an element utilizing a linear variable differential transducer. The primary of the transducer is excited by using a single pulse, causing an induced pulse to be created at the secondary coil. The induced pulse is compensated for the effects of distortion. The induced pulse is sampled and compared with the input pulse to determine the amount of attenuation caused by the transducer, from which the position of an element attached to the transducer can be calculated.

Abstract: An auxiliary resolver position tracking (RPT) system for an industrial robot includes a resolver excitation and monitoring system which is powered by an uninterruptable power supply which includes a battery. The RPT system generates trapezoidal excitation pulses for the resolvers in the robot when no external excitation signal is applied, for example when the robot is shut down. Since there is relatively little motion to be detected in these instances, the RPT system switches between a slow position sampling rate, when no motion is detected, and a fast sampling rate when motion is detected. When operating on battery power, the RPT only switches to the fast sampling rate when motion is detected. To ensure that no motion data is lost when the system switches back to the slow sampling rate, the high sampling rate is maintained for a time sufficient to capture any residual motion of the robot.

Abstract: A waveform generator for a resolver transducer or the like is described. Such generator forms two 3-level waveforms which approximate sinusoidal waveforms for the excitation and/or output detection of such a resolver. Each of the sinusoidal waveforms is formed by combining a pair of digitally programmed bi-state signals which have their phases shifted relative to one another by an amount proportional to an angular input variable. The result is that the amplitude of these sinusoidal waveforms which are formed are representative of the sine and cosine of such variable.

Abstract: An electro-hydraulic servo mechanism comprising: a hydraulic actuator formed with a pair of hydraulic chambers and having an output member which is displaced by a differential pressure between the hydraulic chambers, the output member being connected with an object to be controlled; an electro-hydraulic converter for varying the differential pressure between the hydraulic chambers in response to an electric signal; a first differential transformer for outputting a first induced electromotive force proportional to the displacement of the output member; a control circuit for generating the electric signal in response to the output of the first differential transformer and to an external command signal and for outputting the electric signal to the electro-hydraulic converter; a pressure receiving member that is displaced in response to the differential pressure between the hydraulic chambers; and a second differential transformer for outputting a second induced electromotive force proportional to the displacemen

Abstract: A linear variable displacement transducer (LVDT) has a core connected to an actuator such as a torque motor. The outputs of the LVDT are demodulated and subtracted to provide a displacement signal which is compared with a desired displacement to provide closed loop control of the torque motor. The desired displacement is formed by multiplying a demand signal by the sum of the demodulated LVDT outputs so as to provide temperature compensation.

Abstract: An electro-hydraulic positioning system which has automatic calibration capabilities is disclosed. The system includes a microprocessor which accesses calibration parameters stored in a non-volatile memory unit. The microprocessor adjusts the position demand according to the stored calibration parameters. The system may be placed in an atuomatic calibration mode. In which case, update calibration parameters are automatically determined and stored. The system also includes a microcontroller which monitors system operating variables and reports deviations of the variables from expected values for same.

Abstract: A monlithic interface circuit for use with a linear variable differential transformer (LVDT) position transducer. The interface circuit includes a drive circuit for providing an excitation signal of selectable frequency and amplitude to the LVDT primary winding. The interface circuit further includes a decoder responsive to signals induced in the LVDT secondary windings for computing the position p of the LVDT core as a solution to the equation p=K(A-B)/(A+B), where A and B represent the signals induced in the primary winding and K is a constant scale factor. The decoder includes circuitry for rectifying and filtering the secondary signals, a charge balance loop responsive to the detected signals for providing a binary signal having a duty cycle representative of B/(A+B), and an output circuit responsive to the binary signal for providing the position output. The decoder provides excellent scale factor stability and linearity and is relatively insensitive to variations in primary drive amplitude.

Abstract: A signal conditioner for a linear variable differential transformer having a first amplifier which senses the differences in amplitude between secondary alternating current voltages in the two secondaries respectively, and a second amplifier which compares the phase of the difference signal from the first amplifier with the phase of one of the secondary alternating voltages. A conditioned signal A.sub.out is output by the signal conditioner according to the equation A.sub.out =K.sub.1 V.sub.s1 +K.sub.2 (V.sub.s1 -V.sub.s2) where K.sub.1 and K.sub.2 are constants, and V.sub.s1 and V.sub.s2 are instantaneous voltages across the respective secondaries.

Abstract: A displacement detector includes a movable member of a magnetic material movable as a function of the displacement of an object which is to be detected, an AC signal source, a primary coil energizable by an AC signal supplied by the AC signal source for generating a magnetic field in the direction in which the movable member is movable, secondary coils located in at least two positions spaced along and disposed around the path of movement of the movable member, a third coil disposed in the range of movement of the movable member and around the path of movement of the movable member, first, second, and third rectifier circuits connected respectively to the secondary coils and the third coils, and a processing circuit for processing outputs supplied from the first, second, and third rectifier circuits. The displacement detector can be incorporated in an automotive power steering device having input and output shafts coaxially coupled to each other by a resilient member which is twistable about its own axis.

Abstract: A drive and position sensor having a drive shaft for positioning a driven part and connected to a magnetic core by a reduction gear to position the core axially relative to a primary and secondary coil so that the voltage in the secondary coil is a measure of the position of the driven part.

Abstract: A unipolar signal indication of core position is provided in an inductive displacement transducer, such as an LVDT, as the sum magnitude of the transducer's applied primary winding voltage signal and the transducer's induced secondary winding voltages.

Abstract: Phase information in a multiple-coil indictive displacement sensor is retained by summing the excitation signal with each of the secondary signals to provide augmented secondary signals which may then be converted to a digital format. A signal processor may then be employed to extract both the magnitude and phase information from the augmented secondary signals by subtracting the magnitude of the primary excitation signal from each of the augmented secondary signals. The resulting signals retain both phase and magnitude information.

Abstract: A linear servoactuator including an integrated split-secondary differential transformer position sensor and a fluid driven linear actuator controlled by solenoid poppet valves. Signals from the position sensor transformer are digitized and linearized by a control microcomputer by using digitized transformer signals as addresses for a programmable read only memory. The linearized output is compared to a command position to determine an error value. When the error reaches a predetermined magnitude, indicating that the actuator is approaching the command position, solenoid poppet valves are actuated by a pulse-width modulated signal from the microcomputer to progressively decrease the fluid flow to the actuator for deceleration.

Abstract: A signal conditioning circuit (30) using an oscillator (32) which feeds a counter (34) whose output addresses a programmable memory (42). The output of the programmable memory (42) provides a selected processed signal which is used for excitation of a transducer (12). The processed signals can have various phase shifts, frequencies, or amplitudes. The transducer (12) has a mechanical input (14) and provides a modulated signal output which is a function of the mechanical input. The output of the transducer (12) is fed to a phase sensitive demodulator (36). Demodulator (36) provides an output signal in response to the signal from transducer (12) and an appropriate demodulator drive signal. The output signal from demodulator (36) is indicative of the mechanical input to transducer (12). Averaging means (40) is connected to the output of the demodulator (36) to provide a DC signal which is proportional to the mechanical input to transducer (12).

Abstract: Apparatus for high resolution sensing of the position of a rapidly moving member. The apparatus includes at least two linear variable differential transformers (LVDT's) each having a magnetic core coupled to the movable member. A signal source and a phase shifter provide energizing signals to the primary coil of each LVDT. The energizing signals have the same frequency but are phase shifted relative to each other. The induced secondary voltages of the LVDT's are sampled by synchronous detectors, the outputs of which are combined by an adder into a high resolution output signal. When two LVDT's are utilized, the energizing signals have a relative phase shift of 90.degree. and the effective position sampling rate is doubled. The apparatus can be used to sense the operating frequency of a tunable magnetron.

Abstract: A measurement system for converting the outputs of dissimilar transducers into digital numbers by means of a phase conversion technique. The outputs of a plurality of dissimilar transducers are generated as pairs of amplitude modulated sinusoidal signals. All AM signal pairs are converted into phase modulated signal pairs by a plurality of identical conversion circuits where the phase difference between at least one PM signal pair is linearly related to the measured parameter of the transducer associated therewith. The phase differences for each transducer is converted into a digital number by counting increments of time between the zero crossings of each pair of phase modulated signals and outputting the resulting count to a data buss of a control processor. Transducer parameters which are nonlinearly related to their phase differences are compensated by a correction factor which is calculated by knowing the error between any particular measured input and the linear input.

Abstract: A position transducer for indicating the position of a core member of a linear variable differential transformer produces DC level output signals proportional to changes occurring in the excitation and core displacement. Pulse signals from a clock source are converted to sinusoidal signals of a predetermined frequency and applied to the transformer. Movement of the core member varies the amplitude of the secondary waveform. To extract the position information the primary and secondary waveforms are applied to sample and hold circuits. These circuits receive gating signals to ensure the outputs of the primary and secondary sample and hold circuits acquire peak values of the sinusoidal input signals. The gating signals are derived by applying the sinusoidal primary waveform to a phase shift network. The resultant waveform is squared and used to trigger a one shot to produce a pulse train whose pulse width is 1/14 the period of excitation frequency.

Abstract: A precision drive system including a base plate; track means and an air bearing means movable relative to one another, one of the means being fixed to the base plate and the other being movable for carrying an object to be moved relative to the base plate; means for moving one of the track and air bearing means; means for driving the moving means; and a control circuit including a power circuit for operating the means for driving; a velocity sensor for detecting the velocity of the movable one of the track and air bearing means, and a velocity feedback circuit for introducing velocity error signals into the power circuit to correct velocity; a position sensor to detect the position of the movable one of the track and air bearing means and a position feedback circuit for introducing position error signals into the power circuit to correct position.

Abstract: A device for controlling the speed of movement of a mobile member relative to a fixed support member, said mobile member receiving its motion from first drive means is described. The main feature of said drive is that it comprises a speed transducer operated directly by said mobile member and arranged to supply an electrical signal proportional to said speed of movement of said mobile member to second comparison and processing means, to said second means there being also fed at least one electrical reference signal proportional to a predetermined value of said speed; the output signal of said second means, proportional to the difference between said signal of said transducer and said electrical reference signal, being fed to said first drive means.

Abstract: This invention relates to a digital-analog interface for insertion between the control circuit of a moving element and a transmitter of digital control signals.This interface comprises an inductive detector of the actual position of the moving element. The inductive detector has a single primary winding directly connected to an a.c. source and two secondary windings. The detector secondary windings are connected in parallel to one input of a summing circuit, through a first resistance of fixed value and through a second resistance of adjustable value, respectively. Means responsive to the transmitter digital control signals are provided to adjust the value of the second resistance. The output of the summing circuit is connected to the control circuit of the moving element.

Abstract: A system for duplicating a master part includes a gauge for measuring changes in the dimension therein of a master part to be duplicated and for providing control signals representative of changes from a predetermined dimension. The control signals are applied to a control circuit for controlling an adjustable tool block associated with a machine tool for machining a workpiece in response to the control signals from the gauge to assure that the workpiece dimension conforms to that of the master part.

Abstract: A positioning device for positioning a part, such as, a movable part of a machine tool, relative to a fixed part of the machine tool, comprises, a transmitter adapted to be secured to one of said fixed and movable parts and having spaced apart first and second transmitter surfaces and a differential transmitter adapted to be secured to the other of the first and second parts and having first and second heads adapted to be positioned in alignment with the respective first and second transmitter surfaces, so that the heads produce a control signal in accordance with the amount of the heads aligned with the surfaces. Control means are connected to the respective heads and to means for moving a machine part to position the machine part in accordance with the coverages of the heads on the first and second surfaces.

Abstract: An automatic weld line copying apparatus has a non-contact type sensor including a core wound with an exciting primary winding which in turn is wound with a secondary winding a plurality of secondary coils differentially. The sensor is compact and able to detect, without contact, the distance from the flat surface or edge line of an object to be welded thus making possible accurate and efficient automatic welding of a small welding assembly with a complicated weld line.

Abstract: A handle apparatus is for use with a device which has a movable component and a variable speed motor system which is responsive to an error signal for driving the movable component to desired positions corresponding to the error signal. The handle apparatus includes a central stationary support member which can be mounted to the movable component. The support member is adapted to receive a miniature force sensor which includes a linear variable differential transformer having an operative axis. The member receives one force sensor for each axis in which power-assist is desired; with the axis of each force sensor positioned corresponding to each axis of power-assist.

Abstract: A position indicator is disclosed which includes the combination of a linear voltage differential transformer (LVDT) and accuracy assurance circuitry. The LVDT includes a movable core connected to a mechanism whose position is to be indicated. The accuracy assurance circuitry permits the disclosed indicator to operate substantially independent of fluctuations in input voltage or frequency. This substantial independence is achieved in the following manner. First, the voltage across the LVDT is rectified by a first precision rectifier. Simultaneously, the LVDT tap voltage is rectified by a second precision rectifier. Each precision rectifier output is filtered and then applied to an analog divider which "cancels out" the effects of input voltage or frequency fluctuation. The divider output is an analog signal which is a true ratio of tap voltage to voltage across the LVDT. This true ratio signal accurately represents the position of the mechanism connected to the movable core.

Abstract: A phase-sensitive transducer apparatus comprises first and second relatively movable members, the first relatively movable member having a plurality of windings and the second relatively movable member having a winding. Means are included for applying a first input signal to one of the windings of the first relatively movable member and a second input signal to another of the windings of the first relatively movable member. An output signal is developed on the winding of the second relatively movable member. The first and second input signals are sinusoidal in nature of substantially identical frequency and peak amplitude and are phase-displaced by a predetermined amount, and the output signal is substantially constant in peak amplitude and variable in phase during relative movement of the first and second relatively movable members.

Abstract: A stator lamination compression mechanism simultaneously monitors the axial length of a series of laminations to be used in an electric motor. A linear variable differential transformer provides a movable coupling element connected to a sensing member monitoring the axial length of the compressed laminations. A specially designed sensing circuit responds to variations in magnitude and phase of a single ended output signal provided by the differential transformer and continuously tracks the movement of the coupling element. The monitor provides warnings when the axial length varies beyond predetermined selected magnitudes.

Abstract: A phase-sensitive transducer apparatus comprises first and second relatively movable members, the first relatively movable member having a plurality of windings and the second relatively movable member having a winding. Means are included for applying a first input signal to one of the windings of the first relatively movable member and a second input signal to another of the windings of the first relatively movable member, an output signal being induced on the winding of the second relatively movable member. The first and second input signals are sinusoidal in nature of substantially identical frequency and peak amplitude and are phase-displaced by a predetermined amount, and the output signal is substantially constant in peak amplitude and variable in phase during relative movement of the first and second relatively movable members.

Abstract: A phase-sensitive transducer apparatus comprises first and second relatively movable members wherein the first relatively movable member has a plurality of windings and the second relatively movable member has a winding. Means are included for applying a first input signal to one of the windings of the first relatively movable member and a second input signal to another of the windings of the first relative movable member. An output signal is induced on the winding of the second relatively movable member. The first and second input signals are sinusoidal in nature of substantially identical frequency and peak amplitude and are phase-displaced by a predetermined amount, and the output signal is substantially constant in peak amplitude and variable in phase during relative movement of the first and second relatively movable members.

Abstract: A device for positioning a part comprises a signal generator which, upon movement of said part within the vicinity of a required position of the part, produces a signal value which passes through zero at a point when said part is in said required position, and a servo system responsive to said signal value to transmit movement to said part until said signal value reaches zero. The signal generator may operate to define a predetermined stop position into which a part, for example a machine part or a workpiece, is to be moved, or, in cooperation with an appropriately movable member, it may be used to trace a predetermined pattern of movement so that the part to be moved follows said pattern.