Hitachi, Ltd.

Hiroshi Hayashida

Kunio Miyashita

Hiroshi Kimura

Shigeki Morinaga

Kosho Ishizaki

Ryoso Masaki

Toshiaki Okuyama

Yasuo Matsuda

Kanji Kawakami

Hiroshi Nagase

Yasunori Katayama

Toshihiko Matsuda

Hideki Nihei

Syooichi Kawamata

Masahiro Kayama

Mitsuyuki Honbu

Takeo Maeda

Takamasa Hori

Ichiro Hashimoto

Tadashi Okawa

Sadao Sekizawa

Junshiro Inamura

Kenzo Kamiyama

Hiroyuki Okamoto

An actuator suitable for use in a joint device for driving a robot arm or in a subject follow-up device in a video camera, etc., is designed to have a mobility of a freedom of two degrees or more and is adapted to drive a movable part directly using first piezoelectric motor elements each of which consists of piezoelectric elements having a non-ring-like configuration and an elastic body and second piezoelectric motor elements each of which consists of at most one ring-like piezoelectric element and an elastic member. The actuator exhibits a simplified structure, is small and lightweight, provides a powerful driving power and has a wide range of mobility.

Actuator

An actuator has a stepping motion function with a high stopping accuracy and resolution. The actuator includes a fixed portion and a movable portion constructed in combination so as to be movable relative to each other, a coil for imparting a moving force to the movable portion, a magnetic recording medium mounted on one of the fixed portion and the movable portion and recording magnetic signals, and a plurality of magnetic sensors mounted on the other thereof for detecting said magnetic signals in said magnetic recording medium, and wherein signals different in phase and output from said respective sensors are used by themselves, or signals inversely converted from the former signals are additionally used, and the coil is supplied with a driving force command by sequentially selecting and changing those signals.

Actuator with stepping motion function

A large number of teeth are formed on the outer circumference of a rotor. A stator is disposed around the rotor. The stator has multiple magnetic poles whose number is n times the number of phases. Each pole has formed on its surface a plurality of teeth at a pitch equal to the rotor tooth pitch. The teeth mounted on the adjacent magnetic poles are selected to deviate in pitch one-half or thereabout from the rotor teeth and the adjacent poles are to be opposite phases from each other.

Low-speed high-torque motor

A pulse width control apparatus and method for controlling motor speed wherein the number of pulses relating to more speed feedback data is counted so as to control the speed of the motor in accordance with a speed command data and a pulse width modulation signal based on the counted number of pulses. A free-running hardware timer and a soft-timer on a program controlled by an instruction execution time of a microcomputer are arranged so that ON-time data and OFF-time data of the pulse width modulation signal are selectively set in one and the other of the hardware and soft-timers in dependence on values of the ON and OFF times, respectively. The ON and OFF states of the pulse width modulation signal are changed when the contents of the hardware and soft-timers reach predetermined values so as to control the pulse width thereof.

Method and apparatus therefor in motor speed control

The invention discloses a movement detecting device for detecting the movement state of a moving body such as a rotating body, in which a magnetic recording medium on which N and S magnetic poles are alternately recorded at a constant interval is fixed symmetrically with respect to a rotary shaft of a rotating body whose rotation state is to be detected, and an MR element comprising magnet-resistive elements is mounted at a fixed position relative to the magnetic recording medium so that the rotation state of the rotating body can be detected from variation of the values of resistance of the magnet-resistive elements caused by the rotation of the body. N and S poles are recorded on the magnetic recording medium with a small pole pitch P. The magnet-resistive elements are formed to have a width sufficiently smaller than the pole pitch. The magnet-resistive elements constitute a first group and a second group, the magnet-resistive elements of each group being disposed with an interval equal to the pole pitch or half the pole pitch. The magnet-resistive elements are disposed in such a manner that the interval between the groups is deviated from the pole pitch, whereby a circuit comprising these magnet-resistive elements can detect the rotation of the rotating body.

Magneto resistive sensor for detecting movement of a rotating body

An encoder with a position detecting device is disclosed which is applicable to a brushless motor or the like, and includes a rotating body provided on a surface thereof with a magnetic material and magnetoresistive elements disposed opposite to and in close proximity to said magnetic material. The rotating body is provided with an encoding track in which a magnetic signal has been recorded in a predetermined direction of magnetization, and a position detecting track in which a magnetic signal has been recorded in a direction of magnetization intersecting with the predetermined direction of magnetization. The magnetoresistive elements are formed on an insulating substrate and face the tracks. Further, the magnetoresistive elements are arranged side by side in a radial direction of the rotating body and each of the magnetoresistive elements is placed so that the magnetoresistive element intersects the direction of magnetization in a track facing the magnetoresistive element, to make small the magnetoresistive element supporting substrate, thereby making the whole of the encoder small in size, and to prevent magnetic interference between the encoding track and position detecting track, thereby enhancing the performance of the encoder with the position detecting device.

Device for detecting the relative and absolute position of a moving body

An endless counting apparatus comprises a first memory for storing a code of a first predetermined number of bits sufficient to represent the maximum value of each coded input expressed according to the binary notation, a second memory for storing an endless-making code of a second predetermined number of bits of higher order than and contiguous to the less and least significant bits stored in the first memory, and a control circuit for adding or subtracting the value of the coded input to or from the contents of the first and second memories depending on the input value to be counted and applying the result of addition or subtraction to the first and second memories. A method for endless counting by such an apparatus comprises clearing the most significant bit of the endless making code stored in the second memory when the code stored in the second memory has attained a value which causes an overflow due to a carry from the contents of the first memory if the carry occurs, and setting the most significant bit of the endless-making code stored in the second memory when the code stored in the second memory has attained a value which causes an underflow due to a borrow from the contents of the first memory if the borrow occurs.

Method and apparatus for counting an infinite length with a counter of

A motor speed control method and system allow the motor to be accelerated to the steady state in the minimum time even under conditions of varying load torque, varying load inertia and varying power voltage. The motor is controlled by a voltage including a component of proportional term which is a function of a difference between a command speed and a detected speed, and a component of integral term which is summed during an acceleration phase. The acceleration of the motor during the starting process is measured and the integral term is modified basing on the result. The integral term may be memorized so that it is used as the integral term when the subsequent starting phase is completed. The integral term may be obtained from the acceleration and deceleration in the starting process.

Method and system for controlling speed of electric motor

A control process and apparatus for positioning an electric motor provided with a rotation angle detector at a designated position positively at a high speed without being accompanied with hunting notwithstanding variation in the motor current and inertia of a load. The control process activated upon starting of the motor and ending at the stoppage of the motor at the designated position includes a first control region in which acceleration of the motor having been started is detected and subsequently a constant speed operation of the motor is effected at a maximum speed. A deceleration initiating time point is determined in dependence on the acceleration. A second control region is provided in which the motor is decelerated in accordance with a deceleration pattern determined in dependence on a rotation angle extending between a position corresponding to the deceleration initiating time point and the commanded stop position, and motor torque and inertia of load is detected at the deceleration initiating time point. During a third control region the motor is progressively decelerated by reducing correspondingly the gain of voltage (current) applied to the motor when the motor position approaches to the commanded stop position. The control process also includes a fourth control region in which, when the motor stops short of or beyond the commanded position, the duty ratio of voltage applied to the motor is progressively increased to thereby re-start the motor toward the commanded position, and a fifth control region in which the motor is held at the commanded stop position.

Method and apparatus for position control of an electric motor

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.

Method for controlling angular position and apparatus therefor

Disclosed is a magnetic rotary encoder used in combination with a rotary body having plural pieces of magnetic information recorded on at least one circumferentially running track. The rotary encoder comprises a substrate having a surface disposed opposite to the rotary body and at least one magnetoresistive element formed on the surface of the substrate. The magnetoresistive element is formed on the substrate surface as an integral pattern including at least two portions extending substantially in the radial direction of the rotary body in a relation opposite to the magnetic information recorded portion of the rotary body, two lead connection terminal portions formed at the outer ends of the radially extending portions respectively, and a circumferentially extending portion interconnecting the radially extending portions at their ends, so as to form a single electrical signal path which passes both of the radially extending portions and terminates in the two lead connection terminal portions. These lead connection terminal portions are disposed outside of the outer peripheral edge of the rotary body.

Magnetic rotary encoder

Disclosed is a magnetic head for use to constitute a position encoder which comprises a magnetic recording medium carrying records provided by a plurality of unit magnets arrayed with a constant pitch .lambda. on the surface of a moving member. The magnetic head is fixedly disposed opposite to the magnetic recording medium to constitute the position encoder. The magnetic head comprises a bridge circuit of four U-shaped arms each of which is formed by a pair of magnetoresistive elements spaced apart by an interval of (.lambda./2)(1+n), where n is zero or a positive integer.

Magnetic head for sensing the position of a moving member

An induction motor is operated by a power supply of variable voltage and variable frequency. The voltage and frequency of the variable-voltage variable-frequency power supply is changed by a control circuit to accelerate or decelerate the induction motor. For slowly controlling the speed of the induction motor, the ratio of the output voltage to the output frequency of the variable-voltage variable-frequency power supply is maintained substantially constant. The control circuit includes a voltage correcting means which, in response to a command for sudden acceleration or deceleration of the speed of the motor, corrects the output voltage of the power supply in accordance with the acceleration or deceleration rate and the prevailing magnitude of the output frequency of the variable-voltage variable-frequency power supply.

Variable speed control apparatus for induction motor

A control system for a brushless motor is disclosed which comprises an AC power supply, a rectifier circuit including controlled rectifier elements for converting the alternating current supplied by the AC power supply into a direct current, an inverter circuit including controlled rectifier elements for converting the direct current produced by the rectifier circuit into an alternating current, a motor driven by the inverter circuit and a position detector for detecting a signal representing rotational positions of the motor. The controlled rectifier elements of the inverter circuit are fired in predetermined sequence in response to detection signals from the position detector, while the DC output current of the rectifier is continually controlled at each commutation of the inverter circuit at low motor speeds. A predetermined number of signals in synchronism with each commutation of the inverter circuit are included in one cycle, so that the DC output current of the rectifier circuit is controlled for continual operation by the use of signals with different delay times behind the aforementioned signals concurrent with the commutation of the inverter.

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Mito, Japan

Hiroshi Hayashida