Abstract: In a DC braking method for stopping an induction motor, torque shock generated by an abrupt change of an output current phase is reduced to a predetermined value or less when a switch-over from a normal control state to a DC braking state. When a switch-over from a normal control state to a DC control state is performed, the generated torque shock is reduced to a predetermined value or less is provided. In this case, an abrupt change of an output voltage phase is inhibited by predictably operating the output voltage phase during the DC braking to control the power converter on the basis of a setup DC braking initiation frequency or a phase advanced until the DC braking is initiated, which is predetermined by a deceleration rate and the setup DC braking initiation frequency and the output voltage phase of a normal control state at the instant that a switch-over to the DC braking state is performed.

Abstract: A control method and a controller for an a.c. motor without using a speed sensor in which the speed estimated value or the magnetic flux estimated value of an all-dimensional magnetic flux speed observer can be made to correspond to that of an actual a.c. motor.

Abstract: A simple and accurate dead time dispersion measurement method and a voltage source inverter control method that can prevent the occurrence of an unstable phenomenon are provided. The control method controls a voltage source inverter of a PWM system, which includes a power semiconductor device controlling a level of a voltage, a frequency and a phase. According to the control method, before operation, voltage error information for each polarity of respective phase currents of the inverter is stored. And during the operation, the voltage error information is read to compensate for a voltage instruction value or a pulse width of a PWM instruction signal, so that a voltage error can be corrected.

Abstract: In a DC braking method for stopping an induction motor, torque shock generated by an abrupt change of an output current phase is reduced to a predetermined value or less when a switch-over from a normal control state to a DC braking state. When a switch-over from a normal control state to a DC control state is performed, a means for reducing the generated torque shock to a predetermined value or less is provided. In this case, an abrupt change of an output voltage phase is inhibited by predictably operating the output voltage phase during the DC braking to control the power converter on the basis of a setup DC braking initiation frequency or a phase advanced until the DC braking is initiated, which is predetermined by a deceleration rate and the setup DC braking initiation frequency and the output voltage phase of a normal control state at the instant that a switch-over to the DC braking state is performed.

Abstract: A simple and accurate dead time dispersion measurement method and a voltage source inverter control method that can prevent the occurrence of an unstable phenomenon are provided. The control method controls a voltage source inverter of a PWM system, which includes a power semiconductor device controlling a level of a voltage, a frequency and a phase. According to the control method, before operation, voltage error information for each polarity of respective phase currents of the inverter is stored. And during the operation, the voltage error information is read to compensate for a voltage instruction value or a pulse width of a PWM instruction signal, so that a voltage error can be corrected.

Abstract: To provided a control method and a controller for an a.c. motor without using a speed sensor in which the speed estimated value or the magnetic flux estimated value of an all-dimensional magnetic flux speed observer can be made to correspond to that of an actual a.c. motor. A controller for an a.c.

Abstract: The present invention relates to a surface emission apparatus for causing light, emitting from a light source arranged to a side of a light-emitting surface thereof, to emerge from the light-emitting surface. The surface emission apparatus includes a transparent light-guide plate in which reflecting shape portions formed with small projecting or concaving portions are arranged on its bottom surface portion opposing the light-emitting surface such that a density of the projecting or concaving portions is gradually increased in accordance with a distance from the light source. Light incident from the light source is reflected by the reflecting shape portions and emerges from the light-emitting surface. Since light emerging from the light source is reflected toward the light-emitting surface in accordance with the density of the reflecting shape portions, uniform light emission can be obtained throughout the entire light-emitting surface.

Abstract: The acceleration sensor has a first stationary substrate having a stationary electrode and a second stationary substrate having another stationary electrode and being opposed to the first stationary substrate with a given spacing. An electrically conductive diaphragm is disposed in the spacing and has a central segment fixed in the spacing through the pair of stationary substrates and a peripheral segment surrounding around and extending resiliently from the central segment to undergo displacement in the spacing relative to the stationary electrodes in response to an external acceleration force. The peripheral segment and the opposed stationary electrodes form variable capacitors effective to produce a capacitance change in response to the displacement of the peripheral segment to detect the external acceleration force.

Abstract: An apparatus for optically detecting displacement. The light source is provided for emitting a coherent primary light. A displacement member is disposed to undergo a displacement transversely of the primary light to receive the primary light on its face. The displacement member has on its face a diffractive pattern effective to diffract the primary light and a holographic lens pattern effective to converge the primary light to thereby convert the primary light into a secondary light. A detector is receptive of the secondary light to detect optically the displacement of the displacement member.

Abstract: A torque sensor for use in detecting torsion of a power steering device or the like of a vehicle.

Abstract: An apparatus for detecting a relative displacement of a magnetic record medium and a magnetic sensor a method for manufacturing the above apparatus are disclosed. A magnetization pattern is recorded on the magnetic record medium and the relative displacement is detected by means of at least two magnetic detectors arranged on a common substrate with a given pitch. The common substrate is relatively inclined with respect to an arranging direction of the magnetization pattern to derive a desired phase difference between output signals generated from respective two magnetic detectors. The two magnetic detectors are connected into a bridge circuit to derive a detection output signal representing only the relative displacement without being affected by a noise magnetic field.

Abstract: A magnetoresistance element is arranged in a plane parallel to the end face of a PG yoke and is situated on the outer side of a circle described by revolution of the PG yoke end face and in close proximity to the end face to detect a characteristic flux component emitted from the PG yoke end face. The magnetoresistance element is disposed in such a manner that an acute angle is formed between the direction of a current flowing in the element and a normal line extending from the axis of rotation of a recording medium. A flux component hardly influenced by the area of the PG yoke end face is thus detected.

Abstract: An apparatus for detecting a displacement of a magnetic sensor including four magnetoresistive elements with respect to a magnetic record medium having a magnetic track on which a magnetization pattern has been recorded with a given pitch is disclosed. First and second magnetoresistive elements are arranged side by side in a direction perpendicular to the direction of the magnetization pattern, and third and fourth magnetoresistive elements are arranged on the first and second magnetoresistive elements, respectively via insulating layers. The first and third magnetoresistive elements are mutually biased magnetically and second and fourth magnetoresistive elements are mutually biased magnetically. The first, second, third and fourth magnetoresistive elements are connected into a bridge circuit and diagonal points of the bridge circuit are connected to positive and negative inputs of a differential amplifier.

Abstract: A magnetic detection apparatus for use in an encoder includes a first magnetic sensor for detecting an external magnetic field and a second magnetic sensor for detecting a signal magnetic field. The first magnetic sensor is constructed by two magnetoresistive elements and a conductive layer arranged therebetween for applying a magnetic bias thereto. The second magnetic sensor is constructed by two magnetoresistive elements, first conductive layer arranged therebetween for applying a magnetic bias thereto and second conductive layer arranged on one side of two magnetoresistive elements for canceling an effect of the external magnetic field by feeding back a differential output derived from the first magnetic sensor thereto. In such a construction, it is possible to derive from the second magnetic sensor only a signal representing the signal magnetic field without being affected by the external magnetic field.

Abstract: A magnetic sensor including first and second electromagnetic elements arranged one on the other is manufactured by depositing on a glass substrate a first magnetoresistive film of Fe-Ni permalloy, an insulating film of SiO.sub.2 and a second magnetoresistive film of Fe-Ni permalloy successively in this order and then these three films are simultaneously etched by a single etching treatment with aid of a photomask to form first and second magnetoresistive elements. Then, through-holes are formed in the second magnetoresistive film and insulating film to expose parts of the first magnetoresistive film. Next, an insulating photoresist film of polyimide is applied on the second magnetoresistive film and openings are formed in the insulating photoresist film at positions of the bottom of the through-holes and at positions corresponding to junctions to the second magnetoresistive film.

Abstract: A non-contact magnetic potentiometer comprising a rotatably supported first yoke, a second yoke arranged as opposed to the first yoke at a slight spacing, a pair of permanent magnets fixed as inclined on the surface of the first yoke opposed to the second yoke and magnetized in the thickness direction, and a Hall effect device fixed on the second yoke as opposed to the pair of permanent magnets, whereby the structure and manufacture can be simplified and an output voltage of any desired wave form can be obtained. This potentiometer is provided with a means for preventing the influences of the temperature and the variation with the lapse of years.

Abstract: A non-contact magnetic potentiometer comprising a rotatably supported first yoke, a second yoke arranged as opposed to the first yoke at a slight spacing, a pair of permanent magnets fixed as inclined on the surface of the first yoke opposed to the second yoke and magnetized in the thickness direction, and a hall effect device fixed on the second yoke as opposed to the pair of permanent magnets, whereby the structure and manufacture can be simplified and an output voltage of any desired wave form can be obtained. This potentiometer is provided with a means for preventing the influences of the temperature and the variation with the lapse of years.