Abstract: A system for preventing objectionable large torque pulsations during the starting and synchronization of a line-start permanent magnet motor compares motor speed with motor synchronous speed and power source phase with the motor back-emf phasor. The motor starting armature is coupled to the power source and the PM armature is disconnected from the power source before motor speed has reached to within a predetermined margin of synchronous speed and before the back-emf phasor has dropped below a predetermined phase difference. After motor speed has approached synchronous speed to within the margin and the phase difference has dropped below the predetermined phase difference, connections are reversed so that the starting armature is disconnected from the power source and the PM armature is coupled to the power source.

Abstract: The presence of a disk cartridge in a disk drive is detected by obtaining a measure of the load on the spindle motor of the disk drive and comparing that measure to a threshold value. The measure of load on the spindle motor may comprise (i) the time the spindle motor takes to spin-up to its full operating speed, (ii) the time the spindle motor takes to coast down to its operating speed from a first speed in excess of the operating speed, (iii) the voltage applied across the coils of the spindle motor, or (iv) the current drawn by the spindle motor.

Abstract: By monitoring the load of the electric motor, it can be reliably determined when the electric motor runs up against a stop in the starting position of the awning, etc.The electric motor turns off automatically and resets an internal counter. When the awning, etc., is being extended, a certain number of pulses is counted per rotation of the electric motor, and after a certain predetermined count value is reached, which indicates that the awning, etc., has arrived at end position, the electric motor is turned off. Because the counting device is reset in the starting position, the electric motor automatically compensates for any change which may have occurred in the length of the fabric of the awning, etc., the next time an actuation is carried out.

Abstract: An electric power steering device for directly applying the power of an electric motor as an auxiliary steering power to a steering system to lower a steering force required of the driver, wherein a current detecting element in a motor current detecting unit is connected in series with the motor, and a drive control unit is operable to always drive, by a PWM signal, that side of switching elements of a bridge circuit to which the motor is connected. With this construction, a high-frequency pulse noise generated upon the PWM driving of the the switching element is absorbed by an inductance in the motor and hence a high-frequency pulse noise detected by the current detecting element can be controlled at an extremely small level. Thus, the electric power steering device can prevent generation of abnormal noises from the motor and oscillation or hunting of the steering system and provide stable steering characteristics.

Abstract: A traction control system for an ac locomotive optimizes traction performance by separately controlling the allowable creep level of each individual axle and by minimizing torsional vibration per axle. The traction control system includes a torque maximizer and a torsional vibration detector. The torque maximizer measures traction system performance levels and determines the desired torque maximizer state for maximizing traction performance of each individual axle. The torsional vibration detector digitally processes estimated torque feedback of each traction motor in order to detect an unacceptable level of torsional vibration. The outputs of the torque maximizer and the torsional vibration detector are provided to a creep modulator which processes these inputs in order to control the operating creep level of each locomotive axle. As a result, traction performance is improved while minimizing torsional vibration and operating noise levels due to wheel/rail squeal.

Abstract: In a controller of an electric power steering apparatus for use with an automotive vehicle, a regenerating condition determining section determines whether or not a motor of the vehicle is in a regenerating condition, and a regeneration control signal generating section generates a regeneration control signal to control the regenerating condition of the motor. A switching section selects between the motor control signal and the regeneration control signal in accordance with a result of determination by the regenerating condition determining section. With this arrangement, a motor current including a regenerative current that is caused to flow in the motor in response to a vehicle driver effecting during-stoppage steering maneuvering and then releasing a steering wheel can be controlled independently of a feedback loop of the controller.

Abstract: In the case of a motor controller for electronically commutated DC motors, an additional current and/or an additional voltage is passed at the commutation instant to that winding of the motor which is active at that time, in order to prevent torque drops. In order to compensate for torque drops at different motor loads, the duration and/or amplitude of the additional current and/or of the additional voltage are/is determined from the actual motor load.

Abstract: An electric appliance control system is provided for use with an electric power unit such as an electric lawn mower. The electric appliance control system includes a battery, a selectively operable switch, a relay having first and second contacts, a control means, a charger circuit and an operator presence switch. The relay is operable by the switch to connect the electric power unit to the battery. The first and second contacts of the relay pass amperage therethrough between the battery and the electric power unit. The first contact is normally open and the second contact is normally closed. The control means includes a negative temperature coefficient thermistor in series with the first contact and multiple thermistors arranged in parallel and utilized in series with the second contact. The negative temperature coefficient thermistor variably increases the amperage passing through the first contact of the relay upon the selective operation of the switch to connect the electric power unit to the battery.

Abstract: A motor starter for an electrical circuit includes separable contacts for switching an electrical current flowing between a power source and a motor; an operating mechanism responsive to a trip signal for opening and closing the separable contacts; a separable contact state detection circuit providing an operating signal having two states corresponding to the open and closed positions of the separable contacts; a current transformer sensing the electrical current flowing between the power source and the motor and providing a sensed current value; and an overload relay generating the trip signal as an I.sup.2 t function of the sensed current value and the two states of the operating signal. The overload relay employs a pair of thermal time constants which closely model the motor under both natural convection and forced air cooling conditions.

Abstract: The invention relates to a control device for stopping the operation of a single-phase asynchronous motor with a capacitor in the event an overload of this motor with respect to a threshold value is detected. This device is characterized in that it includes, on the one hand, device for measuring the phase shift between any one parameter, voltage or current (U1, U2, I2, I3) of the main phase (.phi.1) or the secondary phase (.phi.2) and another one of these parameters and, on the other hand, device for controlling the stoppage capable of interrupting the current supply to the motor in the event there is measured a time delay lower than a memorized threshold value.

Abstract: The microprocessor based controller for the fractional horsepower actuator motor includes a capacitive power backup system. The motor is used as an actuator and is coupled to an air damper or valve. In the event of a loss of power to the controller, the controller must drive the air damper or valve to a predetermined, failsafe position. The capacitive energy source stores sufficient power to drive the motor and the coupled air damper or valve to the predetermined failsafe position. The controller includes a sensor for determining the presence or absence of power and generating a failsafe control signal. A switch receives the failsafe control signal and passes power from either the main power supply or the capacitive energy storage unit. The controller includes a microprocessor and a memory. During a failsafe operation, the microprocessor drives the motor and hence the air damper or valve to the failsafe position at full power.

Abstract: A brushless motor includes a stationary member; a rotating member rotatably supported with respect to the stationary member; a stator provided in the stationary member and provided with a stator coil for generating current magnetic field under an exciting state; and a rotor magnet provided in the rotating member for obtaining a revolutionary power due to an electromagnetic mutual effect with the current magnet field of the stator coil. The rotor magnet is formed such that segment-shaped magnets are placed annularly with predetermined gaps circumferentially. The gaps are filled with a magnetic resin material.

Abstract: An on-car motor driving apparatus is equipped with a motor for moving a moving unit such as a window of a motor car, a motor driving controller which controls the revolution, stop, and rotational direction of the motor, and a current measuring and comparing device which measures the variation in current per unit time of the motor and compares the measured variation in current with a preset value. The on-car motor driving apparatus stops the revolution of the motor and/or reverses the rotational direction of the motor through the motor driving controller. The apparatus is further equipped with a voltage measuring device for measuring motor driving voltage and a voltage-based time setting device which changes the length of the unit time in accordance with the driving voltage value measured by the voltage measuring device. Line voltage is supplied to a differential amplifier only when the line voltage is supplied to the motor.

Abstract: Apparatus which automates the collection of motor temperature, flux and shaft current data for proactive motor maintenance. Motor speed is determined by an analysis of the flux frequency spectrum, and motor load is determined based on speed, from which a normalized thermal parameter is then determined. From a spectrum analysis of magnetic flux signals a set of peaks each characterized by a frequency and an amplitude is found, and a subset of peaks is identified in accordance with predetermined identity criteria for purposes of comparison. Temperature, magnetic flux and shaft current data are trended to provide early indications of degradation, as well as for recognizing faults.

Abstract: An adjusting motor is connected in series with a load and power supply to thereby adjust the voltage across the load, the speed of the motor being responsive to changes in the load voltage, and the load voltage in turn being adjusted as a result of changes in the counter electro-motive force or impedance of the motor. Further control of the voltage adjustment provided by the motor can be obtained by adding an auxiliary generator or a mechanical load to control the response of the motor to voltage changes in the load. Even further control of the voltage adjustment can be obtained by adding an adjustable power load to the auxiliary generator, and by controlling the motor or auxiliary generator based on feedback of load voltage or adjusting motor current levels to a central controller and electrical machine control device, and/or by making the controller responsive to input or set values.

Abstract: A position controller includes: a compensation torque control circuit which outputs a second torque signal T.sub.2 * and an initial value of an integration torque T.sub.iset on the basis of a real speed signal .omega..sub.M, a rotation angle instruction signal .theta..sub.M *, a real rotation angle signal .theta..sub.M, an integration torque signal T.sub.i of a speed control circuit, and a reference .theta..sub.drp *; a speed control circuit which outputs a first torque signal T.sub.1 * and the integration output T.sub.i on the basis of a speed instruction signal .omega..sub.M * and the real speed signal .omega..sub.M ; an adder which adds the first torque signal T.sub.1 * to the second torque signal T.sub.2 * and outputs a torque instruction signal; and a torque control circuit which controls the torque of the motor in accordance with the torque instruction signal.

Abstract: A method of driving a motor without initial back rotation includes the steps of identifying a rest position 22 of a storage medium 20, mapping the rest position of storage medium 20 to a motor drive sequence, and driving the motor with the motor drive sequence, thereby enabling motor start-up without back rotation. The method is applicable to unipolar and bipolar drive methods as well as inductive read type and magneto-resistive type heads.

Abstract: An electric power steering apparatus provides a steering power assist of a motor to the steering system of an associated automotive vehicle, so as to reduce necessary steering power to be applied by a driver. The steering apparatus includes an attenuation device in the form of a phase delay circuit or an active low-pass filter, which is provided in a feedback loop connecting a motor current detector and a control section of a control unit constituting the vehicle steering system. By the attenuation device attenuating relatively high frequency components of motor current detected by the motor current detector, there is achieved a high-performance electric power steering apparatus which is capable of reducing noise in the feedback loop, without affecting the motor current, to a sufficient degree to highly improve a response to a driver's steering operation.

Abstract: Device for driving a body by means of an electric motor, comprising mechanical means for measuring the displacement of said body which are kinematically linked to the body and are equipped with switches (ID, IM) actuated by the mechanical measurement means at certain points on the trajectory of the body. The device comprises means for initializing a phase for specific powering of the motor such as power supply at reduced torque for a timed duration (TP, x, C4) or power supply at reduced voltage or cut-off of the power supply, switched in by actuation of at least one of said switches.

Abstract: It is an object to obtain a press apparatus and a press controlling method which apply press working to a processed object with accurate press load and is capable of press working with accurate press load without affected by variations in thickness of the processed objects and variations in shut height of molds. A servo motor (51) is connected concentrically to a rotation transmitter (52), and a screw shaft (53) is provided passing through the center of the rotation transmitter (52). The driving force of the servo motor (51) is converted into a thrusting force of a press ram (54) by combining the rotation transmitter (52) and the screw shaft (53). Correct press load is applied to the processed objects and troubles in the press processing caused by variations in thickness of the processed objects can be prevented.

Abstract: Two motor sensors are disposed at two different angular positions of the motor to generate two pulse signals of different phases. The motor rotational speed and direction can be detected on the basis of these two pulse signals. The detected motor rotational direction is checked as to whether it is the same or opposite to that determined by the shift lever. If opposite, the battery car is determined to be being caused to move down on a sloping road, and the motor torque is corrected so that the battery car can be once stopped on condition that the accelerator pedal is slightly depressed. After that, when the accelerator pedal is further depressed and the accelerator pedal stroke reaches a stroke enough to generate a motor torque for starting the battery car on a sloping road, the ordinary drive control is executed.

Abstract: A system and methods to provide a desired operating area for a motor driving a fan for inducing a draft in a vent of a heating, ventilating and air conditioning system. The motor includes a stationary assembly and a rotatable assembly. The stationary assembly includes windings adapted to be energized in at least one preselected sequence. The rotatable assembly is in magnetic coupling relation to the stationary assembly and in driving relation to the fan. The system includes a commutating circuit responsive to a pressure signal representative of a minimum air pressure in the vent and a tachometer signal representative of the speed of the motor for controlling power switching devices. The power switching devices selectively connect a power supply to the windings to provide a motor current to the windings in the preselected sequence to produce an electromagnetic field for rotating the rotatable assembly at a motor operating speed.

Abstract: The method and the apparatus are for starting up a synchronous machine having a rotor and a stator provided with a winding. The rotor has an initial position with respect to the stator.

Abstract: A power steering system includes a housing and a first member supported by the housing for movement relative to the housing. A second member is supported by the housing for movement relative to the housing and the first member. Steerable vehicle wheels are moved in response to relative movement between the first and second members. A power steering resistance control system resists relative movement between the first and second members with a force which varies as a function of variations in vehicle speed. Material is located in a chamber circumscribing the first member. The material has a viscosity which varies as a function of the magnitude of an energy field acting thereon to vary the resistance to relative movement between the first and second members. The energy field is applied to act on the material with a magnitude that varies as a function of the vehicle speed.

Abstract: A control device for a brushless motor capable of stopping the brushless motor without any complicated control. The control device includes a rotation control section to which an output of a position detector detecting a polarity of a magnet field of a rotor on a side of a stator is fed and which generates a driving signal of a predetermined polarity based on the output of the position detector input thereto. Also it includes a motor driving section to which the driving signal is fed and which flows an excitation current through a driving coil for a phase determined depending on a polarity of the driving signal input thereto.

Abstract: A computer having a hard disk drive includes a battery voltage monitor which establishes a shut down condition of the computer if the supply voltage falls below a chosen level V.sub.L. Upon start up of the hard disk drive motor, current through the motor is limited so that supply voltage of the battery to a computer does not fall below level V.sub.1, which level is greater than the level V.sub.L. Additionally during start up, current in the motor is controlled so that voltage supplied by the battery to the computer does not rise above a threshold level V.sub.2 which is greater than V.sub.1.

Abstract: A soft start power control device for a liquid vacuum motor includes a detection component for shutting off the vacuum motor when the vacuum's recovery tank reach full capacity, and in-rush current limiting component for restraining the in-rush current to the motor when the power is switched on, whereby the motor slowly ramps up to its operating speed. The motor is switch by a triac. The device includes a component for preventing the triac from inadvertently triggering at commutation frequency. A snubber circuit is also connected in parallel with the triac to limit the dv/dt characteristic. The detection component includes a float switch to monitor the level of liquid in the recovery tank. The detection component disables the motor once the water reaches a predetermined high level, which then requires the operator to empty the recovery tank before restarting the motor.

Abstract: In a circuit arrangement for influencing the start-up and/or braking behavior of three-phase a.c. non-synchronous motors having phase windings (5, 6, 7), which are connected in star for continuous operation and have terminals for the phase conductors (1, 2, 3) and for a neutral conductor (4) the phase terminal of one phase winding (6, 7) is connected by a change-over switch (9, 11) to the neutral conductor (4) for start-up and/or braking. A corresponding circuit arrangement is disclosed also for three-phase a.c. non-synchronous machines in which the phase windings (5, 6, 7) have terminals for the phase conductors (1, 2, 3) and for a neutral conductor (4).

Abstract: A method for driving a weaving machine during slow motion includes the steps of carrying out the slow motion drive using the main drive motor, and controlling excitation of the main drive motor as a function of the load on the weaving machine parts which has been predetermined and stored in a memory as a function of weaving machine part positions. The required speed of the weaving machine parts to be driven may also be taken into account in controlling the main drive motor. A device for carrying out the method includes the main drive motor, a power phase controller for the main drive motor, detectors for detecting the positions of the weaving machine parts, and a comparator for comparing the positions with stored positions in order to take into account the load data which has been entered.

Abstract: A generating device of a phase current instruction value for an A.C. servomotor and the generating method thereof, drives a synchronous A.C. servomotor. A sine wave, namely, a phase current instruction value for commutation of the A.C. servomotor driver can be generated by receiving as an interrupt the detection signal of a commutation sensor which detects the reverse electromotive force of the a motor at the microprocessor. The pulse position of the present since wave is.The pulse position of present sine wave is determined by the interrupt signal of the microprocessor. The motor is driven and controlled by converting by way of a D-A converter to an analog signal the data for generating a sine wave according to the increase or decrease of an encoder pulse.

Abstract: An improved method of controlling an electro-hydraulic control system by developing a motor control command in relation to the desired force to be exerted by an electric motor on a mechanical element whose displacement determines the hydraulic pressure. The control command is comprised of two magnitude signals. The first magnitude signal must be sufficient to exert enough force to overcome a static friction characteristic of the mechanical element, and the second magnitude signal is selected to achieve a desired average current or voltage over that control period. The time constant for the control command is less than the mechanical time constant of the system, but greater than the the electrical time constant of the system. The control command may be implemented by using either current or voltage control.

Abstract: Method of supplying power to a single phase step motor of a time-piece, adapted to provide the motor with chopped voltage pulses of time-period T.sub.6 variable with respect to the load conditions and to the supply voltage of the motor, characterized in that each said impulsion of chopped voltage is composed of a sequence of elementary pulses of the same polarity and of a constant duration T.sub.4, and in that the durations T.sub.5i separating the said elementary voltage pulses vary according to load conditions and according to the supply voltage of the motor variable with respect to the load conditions and to the supply voltage of the motor.The invention finds a field of application in motors for time-pieces.

Abstract: Method for controlling an electric drive motor coupled to a reciprocating mechanical system such as an oil well walking beam pump by inserting a pair of power-off pulses in a reciprocation period of the pump motor energization cycle, with one pulse in a top-of-cycle region and the other pulse in a bottom-of-cycle region to reduce rod stress and motor electrical power consumption and increase pump displacement and efficiency.

Abstract: In the transistor power output stages disclosed herein, short-circuit protection is provided with respect to output terminals through which a reversible motor or other load is to be energized. An output stage connected between the load and one of the supply leads provides current gain for energizing the load at a current level which is a function of the level of drive current provided to the output stage. Drive current is provided only at a first level independently of the voltage at the output terminal and a sensing means provides drive current at an increased level when the voltage at the output terminal is in a normal range, e.g. close to the voltage at the respective supply lead.

Abstract: A brushless motor includes a rotor having permanent magnets and a coil for rotating the rotor. In the motor, a switching element is connected between the coil and a power source, a magnetic sensor is provided for detecting the position of one of the permanent magnets of the rotor to control the switching operation of the switching element, and a delay circuit is provided for delaying a signal from the magnetic sensor and then applying the delayed signal to the switching element.With this arrangement, the apparent hysteresis width of the magnetic sensor can be broadened and the prior art problem is avoided wherein variations in the hysteresis width of the magnetic sensor results in disabled rotation of the rotor.

Abstract: An apparatus detects stoppage of a motor of a power driven screwdriver due to the excess load. After detecting stoppage, power to the motor is increased gradually to a predetermined value to firmly tighten the screw. The time of increase of power is determined at an arbitrary value.

Abstract: A direct current, brushless, biphase motor with four unipolar windings and electronic drive, presents a geometry of the teeth and of the magnet generated field so that in each winding a trapezoidal e.m.f. is generated to allow the electronic drive to feel or sense the best switching point on the oblique side of such trapezoidal wave without the use of Hall probes; the two phases are embodied to obtain conduction on 180.degree. per winding, thus as two single-phases in parallel; the two single-phases may be embodied in a different way to permit the electronic selection of the use of three distinct motors in the motor: first single-phase, second single-phase and third biphase.

Abstract: The problem of providing aircraft engine starting is solved with an engine start control apparatus operating a generator (12) as a synchronous motor. The motor (12) receives power from a main inverter (46) and an excitation inverter (48) through an exciter (14) operating as a rotary transformer. These inverters (46, 48) are controlled by a control unit (22) which provides for constant power characteristics in the field weakening range. The control unit (22) includes a pulse width modulation (PWM) generator (100) which is responsive to a voltage command (102) and a commutation command (104) to develop switching signals (88) for controlling the switches (S1-S6) in the main inverter (46). The voltage command (102) is used to vary the duty cycle of the PWM signals. The commutation angle command (104) is used to control the timing of the PWM signals. The voltage command (102) and the commutation angle command (104) are controlled using closed loop current control.

Abstract: A method and electronic circuit for controlling a brushless direct current motor, the motor having stator coils and a rotor with permanent magnets, in which the rotor position is detected by induced voltages. A control circuit has an inverter for supplying current (I.sub.1, I.sub.2, I.sub.3) to the stator coils (1, 2, 3); a circuit detecting the relative position of the rotor-stator from the induced voltages; and a control circuit processing information (I.sub.m) of current being supplied by the inverter to the stator coils, reference speed (W.sub.ref) and on rotor position (P.sub.1, P.sub.2, PP.sub.3) by sending control signals (S1 to S6) to the inverter. The control circuit comprises a main logic circuit or digital memory, delay elements connected in series, a circuit controlling the supply of current to the motor, a circuit detecting the minimum speed limit of the motor, a circuit for converting the frequency/voltage, a voltage comparator circuit and a Proportional-Integral-Derivative circuit.

Abstract: An electric floor cleaner is of the type arranged to drive a three-phase motor, whose rated voltage is substantially equal to a voltage obtained by voltage doubling and rectifying a single-phase commercial power line and then by converting a voltage doubled d.c. voltage into three-phase a.c. by an inverter. The voltage and frequency of the three-phase a.c. output from the inverter are controlled for a predetermined period of time after a power switch is put into a turned on state from a turned off state. It is therefore possible to reduce the starting current to a small value enabling the use of a larger rated output motor than a motor in a conventional system within an allowable current limit of a commercial power line.

Abstract: The invention concerns a method to control the stops of an intermittently operating electric motor. The motor current is measured at even intervals and a mean value is created from the measured values. An actual value is compared with said mean value and a signal is given to stop the motor if the actual value deviates from the mean value a predetermined amount. Each new measured value replaces the first measured value in the series.

Abstract: A fault management system for a switched reluctance motor detects faults through phase current differential sensing and phase flux differential sensing and isolates any fault by deactivating any faulted phase. Motor operation continues through the remaining phases. A speed control circuit maintains the normal operating speed of the motor, despite the deactivation of one or more phases. Starting the motor when stopped in a "dead zone" created by a faulted phase is accomplished by using the intact phases to generate negative torque to move the rotor out of the dead zone.

Abstract: A manually assistable electric driving device for a lid of an automobile luggage compartment has a clutch mechanism disposed between an electric motor and an output member drivingly connected to the lid. The clutch mechanism is so constructed that, when the lid is being driven by the motor in either direction, the lid can be manually moved in the same direction and at a speed higher than the speed caused by the motor drive.

Abstract: A motor controller is adaptable to a wide range of motor currents by using an integrator circuit having an additional feedback arrangement for affecting the effective time constant of the integrator under specified conditions. The operational amplifier has an amplifier having a first input, a second input, and an output, an input resistor connected between an input of the operational amplifier and the first input of the amplifier, and a feedback impedance connected between the output of the amplifier and the first input of the amplifier. A voltage at the input of the operational amplifier is compared with a voltage at the first input of the amplifier. An auxiliary current path for the feedback impedance is provided when the voltage at the input of the operational amplifier has a predetermined relationship to the voltage at the input of the amplifier.

Abstract: For setting in operation a converter drive for an asynchronous machine with an intermediate-current link and phase-sequence quenching, the commutations in the inverter are synchronized with the commutations in the controlled rectifier and/or all commutating capacitors are discharged before the start-up and/or the direction of commutation is cyclically changed during the startup. This makes it possible to start up the converter also if the intermediate-link current has gaps, and the asynchronous machine is loaded only with hunting torques.

Abstract: A brushless D.C. motor drive circuit provides full available D.C. bus voltage to the motor during periods of motor speed acceleration and deceleration and modulated D.C. voltage to the motor during periods when no demands are made on the motor to accelerate or decelerate, thus avoiding time-lag problems inherent in the type of conventional brushless D.C. motor drive circuits which employ pulse-width modulators to continuously provide modulated D.C. voltage to the motor.

Abstract: Motor protection relay is taught in which a microprocessor is utilized in conjunction with a reduced voltage motor starter and the electrical motor system which it operates upon to cause the motor to start in stages. The microprocessor-based system infers a start by the presence of a minimal amount of electrical current flowing in the three-phase system which supplies power to the motor starter and thence to the motor. After the start has been inferred, the microprocessor controlled protection device will issue a transition command for the second stage of the start operation where higher voltage is placed across the motor terminals when the in-rush current has fallen to a predetermined programmable value which approximates full load current, for example. An "incomplete sequence" feedback line is provided which is supplied from the auxiliary contacts of the low voltage starter to the microprocessor.

Abstract: For use with overhead axes of a machine tool or the axes which ride astride one another of a robot, the gravitational effect can be eliminated for controlled drives if a control variable which opposes the gravitational effect is inserted into the control loop of the controller. By this arrangement, a wide control range can be achieved for the overall machine tool or system.

Abstract: A control circuit of a direct current servomotor which constantly rotates a floppy disk. A drive pin is connected to a motor shaft of the direct current servomotor, and the floppy disk is driven to rotate at a such state that engagement of the drive pin with a drive hole of the floppy disk chucks up the floppy disk on the servomotor. The direct current servomotor consists of a brushless motor that hall devices detect its magnet pole position and choose among the excited phases of the stator coils. The motor rotates to the reverse direction at the start-up by means of inversion of the input electric current flow to the hall devices in a short while and change-over of the magnet pole detecting direction. The reverse rotation at the motor start-up moves the drive pin on to the rear end of the drive hole, and the subsequent normal rotation firmly starts up the motor.

Abstract: A brushless DC motor control system comprises a commercially available semiconductor commutator supplying field current to stator windings of the DC motor, a current detector connected to a negative-side terminal of the semiconductor commutator, a signal conversion circuit converting the output signal of the current detector to a signal correlated to the load of the motor, and a microcomputer controlling the semiconductor commutator according to the output signal of the signal conversion circuit in the motor starting mode.