Abstract: Inductive position detector (10) is described which includes scale (20) having a longitudinal axis containing a train of magnetic balls (22), and a transducer (30) moveable relative to the scale (20). The transducer (30) includes means to induce a magnetic field in the scale (20). Magnetic markers (23) are provided at axially spaced locations along the scale (20). As the transducer (30) is moved along the scale (20), the pattern of magnetic markers (23) detected enables the position of the transducer to be determined.

Abstract: A deviation angle detector enlarges the application range by enlarging the detectable deviation angle range. The deviation angle detector has two resolvers, which have rotors, stators, and single excitation windings and multiple output windings that are coiled around the stators. The difference in rotation angles of the resolvers is detected as a deviation angle &Dgr;&THgr; by calculating the output signal that corresponds to the rotation angles of the resolvers digitally or in analog. The corresponding output windings of the resolvers are connected in series and the output signals are extracted from the serially connected output windings and calculated digitally or in analog.

Abstract: The invention provides a device to generate an rpm-dependent signal, or a tachogenerator, having a plurality of magnet elements with alternating polarity which are arranged and distributed around the circumference of the rotor shaft. The magnet elements preferably take the form of a magnetic ring which has alternatively polarized sections and is held on a support attached to the rotor shaft. The tachogenerator of the present invention has at least one coil parallel to the axis which is arranged on a second supporting device at an axial distance to the magnet elements. The magnets and coils are arranged spatially relative to each other and can be rotated in relation to each other with the rotation of the rotor shaft in order to induce an rpm-dependent signal in the coils. In accordance with the invention, a signal displacement device is provided which superimposes a DC voltage on the signals induced in the coils in order to generate a voltage-displaced signal.

Abstract: Magnetic forces are used as a controlled actuation mechanism to move and position objects of interest. In one embodiment, a first spherical surface has at least one magnetic positioner attached. A second spherical surface is positioned to move relative to the first spherical surface. A plurality of controlled electromagnets are spaced about the second spherical surface. Control logic energizes at least one of the controlled electromagnets to create magnetic interaction with at least one magnetic positioner to move the first spherical surface relative to the second spherical surface.

Abstract: An actuator comprises a magnet yoke (10a, 10b) and a carrier member (2) movable relative to the magnet yoke. The magnet yoke (10a, 10b) has at least one permanent magnet (14) and the carrier member (20) is positioned in the magnetic field produced by this magnet. The carrier member (20) has an auxiliary magnetic member (28) that produces a relative bias force between the carrier member (20) and the magnet yoke (10a, 10b). The bias force will be used to compensate for a weight applied to the device and acts as a bearing with a very large compliance. The carrier member (2) also comprises a coil (26). Passing current through the coil (26) produces a Lorentz force for further control of the actuator; alternatively, the device provides a velocity transducer by sensing the EMF generated in the coil by relative motion of the carrier member (20) and magnet yoke (10a, 10b).

Abstract: A system and method for connectionless sensing of the physical parameters of a shaft that is capable of continuous rotation. The system involving placing a circuit assembly on the rotating shaft, powering the circuit assembly through energy transferred from a stator coil across a gap to a rotor coil, sensing physical parameter data on the shaft and communicating this data across the gap from the rotor coil to a stator coil.

Abstract: An object of the present invention is to provide a rotary encoder that has a code member which rotates so as to draw an accurate circle as a shaft rotates. Such rotary encoder includes a casing; a detection element attached to the casing; and a rotatable rotor having a mounting aperture for inserting a shaft at the center thereof and being provided with a code member opposing to the detection element, in which an inner peripheral surface of the mounting aperture is provided with a spring member having a base and a plurality of tongues for energizing the shaft toward the center of the mounting aperture so as to set a position of the shaft at the center of the mounting aperture.

Abstract: A drive device, in particular a locking device, having an actuating drive for driving a moving element as well as a position detection device for detecting the position of the moving element, in which case the invention provides that the position detection device has a magnet element which is fitted to the moving element, as well as a Hall element which is arranged in the vicinity of the magnet element, in which case the Hall element is integrated in an electronic module.

Abstract: A handlebar accelerator for an electric bicycle has a bar, a tubular grip, and a joint. The grip has a ring formed at a first end thereof, a sector notch defined in the ring, and two magnetic elements respectively formed at two ends of the sector notch. The joint has a first hole defined at a first side for receiving one end of the grip, a second hole defamed at a second side for receiving one end of the bar, a channel defined therein for receiving the ring, a slot defined in the channel, a groove defined beside the channel, a passage in communication with the channel and the groove and extending outwards, and wires extending through the passage and electrically connected with a speed adjuster device. An examining element is secured in the slot and electrically connected with the wires.

Abstract: An apparatus capable of high accuracy position and motion control utilizes one or more linear commutated motors to move a guideless stage in one long linear direction and small yaw rotation in a plane. A carrier/follower holding a single voice coil motor (VCM) is controlled to approximately follow the stage in the direction of the long linear motion. The VCM provides an electromagnetic force to move the stage for small displacements in the plane in a linear direction perpendicular to the direction of the long linear motion to ensure proper alignment. One element of the linear commutated motors is mounted on a freely suspended drive assembly frame which is moved by a reaction force to maintain the center of gravity of the apparatus. Where one linear motor is utilized, yaw correction can be achieved utilizing two VCMs.

Abstract: A DC motor drive circuit includes a switching circuit that drives the coils of a small permanent magnetic DC motor. The drive circuit is preferably implemented in an integrated circuit device, such as a silicon CMOS device. Integrated into the same integrated circuit device is a magnetic sensor arranged to detect the position of the permanent magnet as it passes a defined point, or points, in its revolution, and control circuitry to derive the timing waveforms for driving the coils. The integrated power devices for driving the coils are also arranged to limit the rise and fall times of the applied voltages and currents so as to reduce or eliminate the generation of unwanted RFI. Additional circuitry is also integrated into the same integrated circuit device to derive the necessary power to operate the magnetic sensor, the control circuitry and the switching circuitry from the connections between the switching circuitry and the coils so as to remove the need for a separate power supply connection.

Abstract: A sensor for facilitating the measurement of temperature and magnetic field is described. The sensor comprises an optical cable having a distal end encompassed in a sheath of giant magnetoresistive material. Temperature changes alter the spectrum emissivity of the giant magnetoresistive material. Magnetic field changes alter the spectrum changes that occur from distorting the optical fiber that occur when the giant magnetoresistive material distorts the optical fiber.

Abstract: A position sensor or controller generates a response signal in existing armature windings of an actuator and detects the response signal to determine the position of the armature. To generate the response signal, the actuator includes a sensor excitation winding near the armature. Two sensor excitation windings can be provided, above and below the armature, to cancel out z components and thus allow for a variable gap. The sensor excitation winding or windings are supplied with an excitation signal to induce the response signal in the armature windings. The response signal is derived by differentially amplifying and frequency filtering a raw output of the armature windings. The response signal is demodulated to determine position. If a position controller rather than a mere sensor is desired, the position signal can be buffered, PID compensated, amplified, and fed back to the armature windings.

Abstract: An electric motor for moving or adjusting parts of vehicles such as windshield wipers and sunroofs have switching devices for shutting of the electric motor in at least one predetermined position of the movable part, for example also for shutting off the electric motors when the parts are disposed in their end positions. For this purpose, the switching devices have at least one permanent magnet that is for the actuation of switching contacts and, for example, is disposed on a switching gear, and have at least one sensor that is sensitive to magnetic fields. Different switching gears are stored for different sizes of parts to be moved. The invention sets forth a switching gear as an annular disk made of a magnetizable material, wherein the material is preferably comprised of a permanent magnet powder and a thermoplastic bonding. Such an annular disk is magnetized either in the immediate vicinity of an associated drive device or when installed in this drive device.

Abstract: A power window apparatus is provided for detecting pinching in accordance with the opened/closed position of the window and a state of rotation of a motor, the apparatus having a position sensor which detects a safety-control suspension region of the window and which is an accurate sensor. A spiral guide groove is formed in the inner surface of a housing opposite to a rotational plate which is rotated by an output shaft of a motor which opens/closes a window. A follower which is guided by the spiral guide groove is able to move along a straight guide groove provided for the rotational plate in the radial direction. Terminals in the form of conductive films are provided for a printed circuit board accommodated in the housing. When the rotational plate has been rotated, the follower is guided by the spiral guide groove so as to be moved in the straight guide groove. Thus, a slide member provided for the follower is brought into contact with the terminals so that the terminals are conducted with each other.

Abstract: A projection exposure apparatus controls the position of a mask so that the mask is in a desired position without reducing throughput even if the size of the mask is increased. For example, a controller adjusts the pressure of air blown from air holes so that a reticle is floated at a desired distance above a reticle floating plate. The controller also controls the driving of linear motors having stators and sliders, thereby adjusting the pressing force of control bars in contact with the sides of the floating reticle to press the sides of the reticle and control the two-dimensional position of the reticle. Therefore, it is possible to control a mask so that the mask is placed in a desired position without reducing throughput.

Abstract: In an electric motor, a Hall sensor (3) is arranged in the vicinity of the outer circumference of the rotor (2) and of at least one of the permanent magnets (4-7) provided for operationally exciting the electric motor. At least one of the permanent magnets (4-7) is provided for generating the magnetic field inducing the Hall sensor (3). The rotor (2) has rotor teeth (2.1) and/or rotor slots (2.2) on the air-gap side and, in operation, produces magnetic field pulsations in proportion to the rotor speed.

Abstract: An electric motor control system for a motor vehicle rear wiper assembly that provides OEM custom wiper features such as programmable wiper angle, speed and parking capabilities. The system includes a single Hall effect sensor, in combination with a gear mechanism that is magnetized in a geometrically sequenced pattern, to provide high resolution and rotational direction and/or speed information to the encoder for motor control purposes.

Abstract: A three-phase brushless dc motor driving circuit can use only one Hall signal. The magnitude and phase of the Hall signal is used for commutation in order to perform soft switching, and an index marker circuit can determine the starting point of motor rotation. A clock signal is output at extreme points of the Hall signal generated by the Hall sensor. Based on the clock signal, three step voltage signals are generated, each step voltage signal having three voltage levels, signal periods three times that of the Hall signal and 120 and 240 degree phase differences with the other two step voltage signals. The direction of current flow in each stator coil is controlled based on the voltage difference each of the step voltage signals and the Hall signal. Index marker detection is performed by demagnetizing a portion of a magnet in a rotor of the motor and using an additional extreme point resulting in the Hall signal to output an index marker.

Abstract: In a displacement pick-up for detecting the displacement of an actuator driven by a rotating drive element, which has an indexing mechanism (11) with a first indexing wheel (13), driven by the drive element and having an indexing cam (19), and a rotatable second indexing wheel with encompassing teeth (20), and which also has a device (12) for detecting the rotary position of the second indexing wheel (15), for the sake of achieving high freedom from noise the teeth (20) on the second indexing wheel (15) and the indexing cam (19) meshing with them on the first indexing wheel (13) are embodied with large surface areas, and the two indexing wheels (13, 15) are magnetized in such a way that their respective immediately adjacent faces repel one another.

Abstract: The upper limit value and lower limit value of a control target value are alternately supplied to a single D/A converter in synchronism with a clock, an analog output from the D/A converter is compared with an output from a PBR serving as a position detector, and a motor is driven by the difference voltage, thereby positioning the control object. In this case, control of the moving direction and drive/stop of the motor is performed by a combination between the setting states of the upper and lower limit values and the polarity of the difference voltage, and the switching operation of the selector is stopped during a control operation, thereby making it possible to smoothly perform the control operation at a high speed. The control system can be digitized as a whole by detecting a position by an encoder, and integration of the system can be enhanced, thereby realizing a compact and stable control system.

Abstract: A circuit configuration for the evaluation of inductive sensor signals in motor vehicles is described. An input stage comprising an input circuit and a reference circuit and a threshold value stage comprising a peak value rectifier circuit, converter circuit, comparator circuit, and adjustment circuit are provided for the recognition of the crossover of an alternating voltage sensor signal.

Abstract: A valve positioning system according to the present invention includes a force motor which responds to a command signal corresponding to a desired valve flow rate by energizing magnetic coils with a current to produce a flux force which moves the valve. Preferably two Hall effect sensors sense the actual position and provide a feedback signal to a control loop which compares the sensed position with the commanded position. The valve is positioned by adjusting the energizing current provided to the magnetic coils. The system optionally includes circuitry to compensate for the error in the actual position relative to the commanded position produced by changes in current in the magnetic coils.

Abstract: A displacement detector for enabling a precise detection of a displaced quantity of the core. The displacement detector is provided with a displaceable core, a detecting coil the inductance of which varies in response to a displaced quantity and a reference resistor, wherein a transient response voltage in case of a pulse voltage being applied to the inductance and the reference resistor is detected to enable detection of the absolute value of the inductance and thereby the change in the inductance which corresponds to the displaced quantity is detected independently of the peak value or the frequency of the pulse voltage. The displacement detector is preferably used in a torque sensor for an electric powered steering system, wherein the core of the displacement detector is formed of nonmagnetic metal material, the structure is simple, and a sensitive detection of a displaced quantity of the steering torque is possible.

Abstract: A motor drive having a very large dynamic speed range comprises a PID position feedback control system (8) in which the motor position is readjusted on the basis of the difference between the instantaneous (x.sub.a) and the nominal (x.sub.s) position. A series of nominal positions (x.sub.s) is determined from a nominal speed (v) in a speed control unit (5). The successive nominal positions (x.sub.s (t)) in a series exhibit a constant difference (.DELTA.x) relative to one another and are presented to the PID position feedback control system (8) with fixed intervals (.DELTA.t). A drive of this kind is used, for example in the beam collimator of an X-ray device.

Abstract: At the periphery of a rotating disk (15) rotating in synchronization with an electric motor, first, second, and third sections (11a, 12a, . . . ) with different physical properties are disposed in sequence. Each of these first, second, and third sections has a width of an electrical angle of 120 degrees. One position detecting element (10) fixed to the motor body faces the first, second, and third sections, and as each section passes the element, a 3-phase position detecting signal corresponding to the section is obtained.

Abstract: A brushless motor drive circuit which can suppress switching pulses without using capacitors or other external components is provided. The brushless motor drive circuit has a hall element for generating two sinusoidal signals of opposite phase and a switching circuit which separates the two sinusoidal signals and cuts off the negative portion to produce two half cycle signals. The two half cycle signals are combined in the switching circuit, and the combined signal is applied to an automatic gain control circuit for providing a stable current to the hall element.

Abstract: The variable-reluctance servocontrolled linear motor comprises an electromagnet formed by a shell and by a winding around a displacement path, a magnetic portion mobile in the direction of displacement, guided mechanically so as to have a single degree of freedom with respect to the shell, under the effect of the force exerted by the electromagnet. A detector circuit is formed by an inductive or capacitive measurement sensor for the instantaneous value of the air gap and delivers a signal sd representative of the displacement of the mobile magnetic portion. A subtracter circuit receives a displacement control signal e and the signal sd representative of the displacement in order to deliver a displacement error signal .epsilon. for the mobile magnetic portion. A current amplifier circuit receives the error signal .epsilon. and delivers a supply current to the winding. A restoring element for the mobile magnetic portion exerts on the latter a restoring force opposed to the force exerted by the electromagnet.

Abstract: A stage mechanism suitable used in an exposure apparatus is disclosed, wherein heat generation of a coil assembly of a stage driving motor is prevented from adversely affecting a semiconductor substrate or measurement by a laser interferometer. A wafer chuck and the laser interferometer are disposed at a side of a base plate, and a stage and an electromagnetic coil for dirving the stage are disposed at the other side of the base plate. The wafer chuck and the stage are coupled to each other by a coupling member which extends through a bore formed in the base plate.

Abstract: An automobile is provided with a speed control system operably connected to a drive system of the automobile. The speed control system includes an accelerator pedal assembly having an accelerator pedal movably connected to a frame of the assembly, an actuator rod connected to the accelerator pedal, and an induction sensor stationarily connected to the frame. The sensor is adapted to generate an electrical output signal corresponding to the position of the actuator rod relative to the sensor without the actuator rod contacting the sensor. The accelerator pedal assembly is connected to the chassis of the automobile as a substantially modular unit.

Abstract: An electro-hydraulic fluid metering and control device with a position sensor having a plane of geometric symmetry. The control device includes a valve body with a plurality of ports and channels for fluid flow, a torque motor mounted on the valve body and responsive to an electrical driving signal, a valve, an armature operating in the torque motor and extending to operate the valve and position sensor and spring members for supporting the armature for pivotal movement to assure direct relationship between the valve and moving member of the position sensor.

Abstract: A position detecting method for detecting a position of a moving object such as a bearing or a lens by capturing a plurality of repetitive periodic waveforms coming from a position sensor and performing data processing on the captured waveforms. The method comprises the steps of moving the moving object by more than one period of the waveforms, obtaining a maximum value and a minimum value of the waveforms, obtaining an offset value and a gain of the waveforms based on the maximum value and the minimum value, correcting a gain and an offset value of data based on the obtained offset value and the gain of the waveforms to create corrected data, and processing the corrected data to detect the position of the moving object.

Abstract: A differential reactance permanent magnet transducer has a stator with at least two pole elements, each having an electrically conductive coil wound thereabout. The reluctances of the stator pole elements are periodically changed, in an electrically out-of-phase relationship to one another, due to the effects of permanent magnet elements moving in proximity thereto. Measurement of the reactance differentials that are thereby produced in coils mounted upon the two stator pole elements is utilized to sense the angular position of the transducer rotor. In addition to a high-resolution sensor zone and a commutation sensor zone, the transducer may include a home sensor zone to indicate a home position upon each revolution of the rotor. All of the coils employed on the stator are so arranged and electrically connected that no net back-EMF value is inductively generated from any coil as a result of movement of the rotor relative to the stator.

Abstract: A recording apparatus, which is provided with a carriage supporting a recording head or reciprocating along a platen, includes a magnetized scale of a magnetic linear encoder positioned along a moving direction of the carriage, and a magnetic head of the magnetic linear encoder, mounted on the carriage and adapted for reading the magnetized pattern of the scale. The scale is provided with at least two magnetized lines of mutually different pitches of magnetization, for recording position information relating to the recording operation, and position information relating to other functions.

Abstract: A linear encoder detects the position of relative motion of two objects by providing an electromagnetic conversion element on one of the objects opposing a magnetic circuit on the other object. The magnetic circuit is composed of a yoke in which a plurality of projections, each acting as a magnetic pole, are formed so as to be arranged in a row at prescribed intervals in the direction of relative motion of the two objects. A permanent magnet is joined to the yoke.

Abstract: An electromagnetic drive system includes a motor having a first motor section movable relative to a second motor section along a motion axis. The second motor section has three excitation coils. The first motor section includes a magnetic circuit generating a magnetic field in the excitation coils. The first motor section also includes a short-circuit winding for only high-frequency induction currents. This short-circuit winding is magnetically coupled to the excitation coils. The degree of electromagnetic coupling of at least one excitation coil depends on the position of the first motor section relative to the second motor section. The short-circuit winding provides a position-dependent electromagnetic coupling between the center excitation coil and the two outer excitation coils.

Abstract: A positioning device includes a table (5, 69), which is displaceable in two coordinate directions (X, Y) by means of Lorentz forces of electric linear motors over a base (3) and is guided over the base (3) by means of a static gas bearing, which has an air gap thickness independent of the coil systems and magnet systems (15-21, 37-43) in the motors. The positioning device is particularly suitable for the manufacture of masks with patterns for integrated circuits.

Abstract: The object of the present invention is to obtain an apparatus for realizing a high-speed numerical control of a load with good efficiency. Required numerical control of a load is carried out in such a manner that the motor drives the load connected to the motor as a DC motor in an initial stage of shifting movement of the load, and, when the braking torque is generated for deceleration, the motor starts to operate as a stepping motor in response to a predetermined number of electric pulses in its final stage. Furthermore, when an armature coil is deactivated while the motor is in operation, a back-flow preventing diode prevents a magnetic energy stored in the armature coil from returning to an electric power source, whereby the magnetic energy is used to charge a small-capacitance capacitor to a high voltage, causing an exciting current to decrease rapidly.

Abstract: A drive system capable of driving a driven member with a large force and precisely rapidly positioning the same is disclosed, with use of a control unit for efficiently driving a motor with a large torque. Upon storage of target position data from a computer in a counter circuit of a driving mode switching circuit, the driven member is driven at a high speed with a large force via a ball screw/nut mechanism by the motor which efficiently operates as a two-phase reluctance motor at a high speed with large torque. When a count of the counter circuit, decremented with movement of the driven member, reaches a first preset value, supply of a sequence of position detection signals, indicative of the motor rotational position, to an energization control circuit is changed by a signal switching circuit, so that the motor is driven in the deceleration mode until its speed reaches a preset speed, and then the motor is driven at a constant speed.

Abstract: Interface circuits for electromagnetic position transducers are provided to reduce the effects of capacitive coupling occurring in the conductive cabling between the position transducers and the associated interfaces located remotely therefrom. Capacitive coupling of excitation signals to the transducer output signals result in error signals appearing as cyclic error in measured positions. The magnitude of the coupled signals are substantially reduced by providing excitation signals symmetrical with respect to ground. The magnitude of the coupled signals are also reduced by presenting equal impedances relative to ground to the output signal return and signal paths. By reducing the effects of capacitively coupled signals, conducting cables for the excitation signals and the transducer output signals may be incorporated in a single shielded cable.

Abstract: The invention discloses an Ultrafast Electro-Dynamic X, Y and Theta Positioning Stage. A positioning stage made according to this invention allows light payloads to be moved with extremely high linear and angular accelerations over finite distances and angles with a plane. An important feature of this invention is a momentum-cancelling design which allows reaction forces and torques on the fixed member to approach zero, thereby, allowing for a smooth and an ultrafast performance by the positioning stage.

Abstract: An electric power steering system which additionally includes a radial arm extending from a steering rod, an axial shaft extending in parallel with the axial center line of the steering rod, an axial bore formed in the casing of the system for guiding axial movement of the axial shaft substantially without any play, and a spring member urging the axial shaft against a side wall of the axial bore. Thus, rotation of the steering rod around its axial center line may be prevented with a relatively small force. Therefore, no excessive force needs to be applied to the axial shaft, and the axial shaft would not encounter any substantial resistance to its axial movement.

Abstract: A displacement transducer suitable for use in a magnetic bearing measures the flux density between a pair of components and divides a signal indicative of the magnetomotive force between the components by the flux density signal to obtain a signal indicative of displacement.

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: A spindle orientation control apparatus according to the invention provides a spindle (4) for which a magnetic sensor senses the spindle and outputs stopping-position proximity (LS) signal and a stopping position determination (MS). The spindle (4) is coupled via gear or belt (5) to a spindle motor (2) wherein the spindle is controlled to stop at a fixed position based on a velocity command conforming to velocity of the spindle motor (4). Velocity pulses for detecting the rotational velocity of the motor can be employed as position pulses. A velocity command value (VCMD) can be reduced by an amount corresponding to a number of fed back velocity pulses a. The velocity value is clamped at a predetermined level when the velocity command value of the spindle attains a predetermined level until a final changeover. The final the spindle changeover for making equal stop-position decision signal (MS) signal and the velocity command value when an edge of the stop-position proximity signal (LS) signal is detected.

Abstract: A sensor for detecting a number of revolutions of a rotary shaft is provided which comprises a ring magnet secured to the outer peripheral surface of the rotary shaft, the number of revolutions of which is to be detected, a Hall IC arranged near the outer peripheral surface of the rotary shaft, for detecting the magnetism of the ring magnet. The ring magnet has one circumferential half of the outer peripheral surface thereof magnetized to serve as the north pole and the other circumferential half of the outer peripheral surface thereof magnetized to serve as the south pole.

Abstract: In a screened inductance sensor having a drive winding, a sense winding, and a conductive screen for varying the induced voltage in the sense winding by reason of the eddy currents generated in the conductive screen in the presence of the drive field, a physical barrier is interposed between the region of the sensor in the windings are located and the region in which the screen is located. These regions are fully environmentally isolated from each other by the physical barrier. The construction is especially suited to screened inductance level gauges, in particular for fuel tanks, where the conductive screen is part of a float assembly in contact with the fuel, but the electrical windings are kept dry in a separate portion of the gauge.

Abstract: A motor control apparatus disclosed in this invention counts output signals from an encoder upon rotation of a rotor, and performs energization switching of a motor coil when the count value has reached a predetermined value.

Abstract: The invention relates to a system for monitoring the closing of a door or other such barrier, such as a sliding door of a vehicle. This system has a circuit outside of the door which serves to emit a signal indicating the open or closed state of the door. In the production of this signal, the need for any electromechanical limit switches or indicating devices mounted on the door and coupled galvanically with the circuit is avoided by providing, in accordance with the invention, a circuit that is mounted on the door. Both circuits have at least one inductive element. The inductive elements are coupled only inductively with one another, but are not in physical contact with one another, so that the production of the signal indicating the open or closed state of the door can be performed contactlessly.

Abstract: This invention is directed to electro-magnetic alignment apparatus which includes a monolithic stage, a sub-stage, an isolated reference structure, force actuators interposed between the monolithic stage and the sub-stage for suspending and positioning the monolithic stage in space, sensors for sensing the position of the monolithic stage and outputting a signal to control circuitry, which compares the sensed position with a commanded stage position and outputs an error signal to the force actuator, and actuators for controlling the position of the sub-stage to follow the approximate position of the monolithic stage.