Abstract: An apparatus for controlling resonance suppression of a machine tool according to the present disclosure includes: a numerical control part; a main operation part; a PLC configured to execute a control command by means of communication with the numerical control part or the main operation part; a servo drive configured to execute the control command of the PLC; a servo motor part configured to operate under control of the servo drive; and a power conversion part electrically connected to the servo motor part and the servo drive and configured to apply electrical energy to the servo motor part, wherein the power conversion part controls resonance suppression in accordance with an operation of the servo motor part by adjusting electrical energy to be applied to the servo motor part based on a signal from the servo drive.

Abstract: This motor control device receives a speed command from an upper layer system control device having a position controller, the motor control device having: a position command estimator that calculates an estimate of a position command on the basis of the speed command and a motor axis position response; and a speed command generator that generates an actual speed command on the basis of the estimate so that an end section of a machine connected to the motor does not oscillate, wherein the actual speed command is output from the speed command generator to a speed controller.

Abstract: A motor control device includes an acceleration detecting section configured to detect an acceleration of a control object, and an acceleration control section configured to control an acceleration of a motor driving the control object based on the detected acceleration, in which the acceleration control section includes a vibration component extraction filter configured to extract a vibration component generated between the motor and the control object, and the vibration component extraction filter changes a filter characteristic frequency according to at least one of a position and a mass of the control object.

Abstract: The invention pertains to measuring, adjusting and/or controlling a distance between a machining head, particularly a laser machining head, and a workpiece, comprising a measurement light source, a beam splitter that splits the light of the measurement light source into a measurement light beam and a reference light beam, a reference arm, through which the reference light beam is guided, an optical system for coupling the measurement light beam into a processing beam path featuring a focusing lens, an optical device for superimposing the measurement light beam, and a measurement and evaluation unit.

Abstract: A method for detecting oscillation in a signal coupling device includes at least one oscillation detection step. The oscillation detection step includes the steps of determining an undamped signal level of a signal on a signal path of the signal coupling device in a first step, reducing a gain of the signal path in a second step, and determining a damped signal level of the signal on the signal path and a deviation between the undamped signal level and the damped signal level at least once in a third step. An oscillation is detected if at least one deviation determined in the third step of the at least one oscillation detection step is higher than or equal to a predetermined oscillation threshold value. A device for detecting oscillation in a signal coupling device and a signal coupling device are also provided.

Abstract: A vibration control system for a variable speed cooling system includes a programmable controller in communication with a variable frequency drive (VFD). The programmable controller is programmed to command the VFD to operate at frequencies only outside of one or more frequency lockout bands automatically calculated by the programmable controller based on a comparison of newly acquired variable speed cooling system vibration data with previously stored variable speed cooling system vibration specification data.

Abstract: The invention relates generating timing signals registering the passage of a component past a sensor. The invention relates particularly to the generation of timing signals in real time for health monitoring of a mechanical system, for example for detecting excessive distortion or vibration of rotor blades in a turbine.

Abstract: A radio communication device includes an oscillation circuit and a modulation path. The oscillation circuit is configured to perform PLL control by using a reference frequency oscillated by a reference oscillator. The modulation path is configured to modulate a reference signal outputted from the reference oscillator, by a signal of a comparison frequency as a modulation wave.

Abstract: A system for determining motor speed of a brush DC motor in an apparatus, including a first filter for receiving a substantially DC component of the motor current and parameters corresponding to the brush DC motor, for calculating a speed estimate thereof; an adaptive bandpass filter having a center frequency corresponding to the speed estimate of the first filter, for receiving the motor current and substantially isolating a periodic current fluctuation thereof; a block for determining a frequency of the periodic current fluctuation, the current fluctuation corresponding to motor speed of the brush DC motor. The adaptive bandpass filter uses debounce filtering to reduce rapid filter passband switching, and a run-in period prior to passband switching to obviate transient effects of filter switching.

Abstract: A control device controls an inverter controlling an output of a motor by PWM control. The control device calculates a reference frequency based on a torque and a rotation speed of the motor, calculates a random coefficient using two data tables, and calculates, as a random frequency, a value obtained by adding, to a reference frequency, a value obtained by multiplying a prescribed width by the random coefficient. The control device calculates control limit lines based on the rotation speed of the motor, and corrects the random frequency so as to fall within a range that is higher than the control limit line and lower than the control limit line. The control device generates a carrier signal having a random frequency as a carrier frequency.

Abstract: The motor speed detection apparatus detects rotational speed of a motor. The apparatus includes an FG coil (21) and a magnet (22) to be relatively moved with rotation of the motor, the FG coil outputting an alternating-current signal to be sampled by the apparatus, an A/D converter (1) to convert the alternating-current signal into a digital signal, an integrator (2) to perform time integration on the digital signal, a first determiner (3, 9) to determine which one of plural threshold ranges includes an integration value obtained by the integrator, a second determiner (3, 8) to determine whether change of the integration value is increase or decrease, and a logical product calculator (3, 10) to produce a binary signal showing a logical product of determination results of the first and second determiners. The apparatus calculates the rotational speed based on a production cycle of the binary signal.

Abstract: A motor control device main unit includes a pressure command signal generation module, a simulated pressure control module, a simulated position calculation module, a simulated pressure signal generation module, a pressure control module, a speed control module, and a current control module. The speed control module receives a motor speed command signal, which is a signal of a sum of an actual motor speed command value of an actual motor speed command signal from the pressure control module and a simulated speed calculated value of a simulated motor speed signal. The speed control module carries out speed control calculation based on a motor speed command value of the motor speed command signal and an actual motor speed of an actual motor speed signal.

Abstract: When a servo device receives the frequency setting signal as a control signal through the receiver from the transmitter, it select the information in conformity with the received frequency setting signal among the driving frequency setting information as stored in advance. When the handling signal is input as the control signal by the transmitter, the servo device is configured to transform the difference data taken synchronously with the difference data timing signal from the pulse width comparison part into the selected driving frequency. The servo device is configured to generate the driving signal from the transformed difference data signal of the desired corresponding count value range, and to perform drive control the driving feature.

Abstract: Motor control circuits and associated methods to control an electric motor provide an ability to synchronize a rotational speed of the electric motor with an external clock signal, resulting in reduced jitter in the rotational speed of the electric motor.

Abstract: A system for controlling a motor (3) includes a driver circuit (5) for generating a drive voltage (v) to generate a phase current (i) in the motor. Phase current sensing circuitry (10,21) digitizes the phase current. A first circuit (23) provides a reconstructed digital representation of a BEMF signal (vbemf) of the motor to generate an error-corrected synchronization signal (SYNC) in response to the phase current and a detected error in the motor speed, an amplitude feedback signal (15), and information (iR,iL,?iL,vL) indicative of a resistance (Rm) and an inductance (Lm) of the motor. A motor drive signal (15) having an error-corrected frequency is generated in response to the synchronization signal. A PWM circuit (16) produces a PWM signal (17) having a frequency equal to the error-corrected frequency of the synchronization signal (SYNC) and a duty cycle controlled according to the detected error.

Abstract: A stepper motor driver system includes: a digital signal controller configured to digitally synthesize synthesized analog voltage signals that will induce a desired velocity of a stepper motor when applied to a pair of stepper motor windings; and voltage amplifiers, communicatively coupled to the digital signal controller, configured to amplify the synthesized analog voltage signals to produce amplified analog voltage signals and to output the amplified analog voltage signals; where the digital signal controller is configured to synthesize the analog voltage signals by affecting at least one of a phase or an amplitude of each of the analog voltage signals as a function of the desired velocity of the stepper motor.

Abstract: A motor controller capable of detecting an oscillation of a feedback loop and performing gain adjustment while updating a gain value of a control unit is provided. The motor controller includes an electric motor, an operation-amount detector, a control unit, a machine, a disturbance signal generator which generates a sweep sine wave, a compensation-driving-force detector, a vibration calculator, an oscillation detector, a vibration storage, a simulated open-loop gain calculator, a gain changer, and an automatic gain changer, and detects an oscillation by processing a response signal in time series on the basis of a first threshold regarding to a magnitude of vibration and a second threshold regarding a frequency.

Abstract: According to one embodiment, a digital converter is provided to process output signals of a resolver attached to a rotating apparatus. These output signals are converted into digital signals by ?? AD converters. Multiplication units receive the digital signals outputted from the ?? AD converters. A subtraction unit subtracts the outputs of the multiplication units. A synchronous detection unit detects the output of the subtraction unit based on a synchronization signal synchronously. An angular velocity calculation unit adjusts a proportional gain of an output of the synchronous detection unit, compensates the phase thereof, and calculates the angular velocity of the rotating apparatus. A rotational angle calculation unit calculates a rotational angle by integrating the angular velocity. Cosine and sine output units output a cosine and a sine corresponding to the obtained rotational angle to the multiplication units, respectively.

Abstract: Methods and apparatus are provided for operation of a voltage source inverter. A method of operating a voltage source inverter having an output with multiple voltage phases having a DC voltage level, the method comprising sensing a low output frequency condition; determining a DC voltage offset responsive to the low output frequency condition; and applying the DC voltage offset when operating the voltage source inverter resulting in a change to the DC voltage level of the multiple voltage phases.

Abstract: A method of controlling a current of a three-phase electric motor with a three-phase controller. The firing angles are adjusted so as to leave a range of firing angles in which DC components appear.

Abstract: A motor drive circuit includes a first amplifier circuit to amplify a difference between first and second position detection signals with a gain becoming smaller according to drop in power supply voltage, to output a first amplification signal, the first and second position detection signals being signals indicating a rotational position of a rotor in a motor, having a frequency corresponding to a rotation speed of the motor, and being opposite in phase to each other; a second amplifier circuit to amplify the difference between the first and second position detection signals with the gain, to output a second amplification signal opposite in phase to the first amplification signal; and a drive circuit to amplify the difference between the first amplification signal and the second amplification signal with a predetermined gain to be saturated at the power supply voltage, to output a driving voltage for driving the motor.

Abstract: A machine having a drive that directly or indirectly excites vibrations in the machine over a frequency range when the drive is connected to the power supply. A sensor detects a time-dependent signal that is characteristic of the excited vibrations. The time-dependent signal is transmitted to a control device that analyzes the frequency of the time-dependent signal and relates the frequency analysis to the excitation that produces the excitation and uses this relationship to determine a state of at least one element of the machine. The control device outputs a message to an operator of the machine on the basis of the state that is determined. Preferably, the control device applies an interference variable that has at least one frequency inside the frequency range to the drive so as to excite vibrations. The interference variable may be a sinusoidal interference variable whose frequency passes through the frequency range, or a pseudobinary interference variable whose spectrum covers the frequency range.

Abstract: A speed controller used in a control loop of a motor includes a comparator, a processing device, and an arithmetic logical unit (ALU). The comparator compares a received instruction speed or a received measured speed of the motor with a predetermined speed value, outputs a first signal to the processing device when the received speed is greater than the predetermined speed value, or outputs a second signal to the processing device when the received speed is equal to or less than the predetermined speed value. The processing device receives a speed difference between the instruction speed and the measured speed. The processing device outputs a first proportional value when the first signal is received, or outputs a second proportional value when the second signal is received. The ALU outputs an instruction current to the control loop by calculating the proportional value according to a predetermined calculation rule.

Abstract: A drive unit includes a rotating electrical machine; a rotation sensor that detects a rotational position of a rotor of the rotating electrical machine, and a storage medium. In an inspecting step of measuring a counter electromotive force by mechanically driving the rotating electrical machine after the rotating electrical machine and the rotation sensor are assembled together, positional error information of the rotation sensor obtained based on information of the counter electromotive force and output information from the rotation sensor is stored in the storage medium. The storage medium is integrally provided to the drive unit in such a state that the storage medium is readable upon assembling a control device that controls the rotating electrical machine.

Abstract: An electric motor control device includes a power supply unit that supplies power to a three-phase electric motor; a three-phase current sensor that individually detects three respective phase currents of the three-phase electric motor; a summing unit that calculates a three-phase sum by adding the three phase currents detected by the three-phase current sensor; a detected current correction unit that calculates correction amounts for at least two of the three phase currents based on a phase and an amplitude of the three-phase sum and then corrects phase current detection values by the calculated correction amounts; and a motor control unit that controls a power supply by the power supply unit to the three-phase electric motor by feedback control based on the three phase currents after correction by the detected current correction unit and on target currents.

Abstract: Methods and systems for controlling a power inverter in an electric drive system of an automobile are provided. A signal controlling the power inverter is modified utilizing a first voltage distortion compensation method if a modulation index of the signal is less than a first modulation index value. The signal is modified utilizing a second voltage distortion compensation method if the modulation index is at least equal to the first modulation index value.

Abstract: There is provided a bearingless step motor in which a rotating shaft can rotate while rising from a main body by a magnetic force without using a mechanical bearing. The bearingless step motor comprises a stator including stator cores having winding portions and a rotor including a rotating shaft and rotor cores. The rotor rotates by a magnetic interaction between the rotor cores and the stator cores. A first permanent magnet is mounted to the rotor and a second permanent magnet is mounted to the stator. The first permanent magnet and the second permanent magnet are arranged so that a repulsive force is generated between magnetic poles. There is little power consumption for raising the rotating shaft and a complicated system for controlling the rise of the rotating shaft is unnecessary. Thus, the motor can be manufactured with a light and compact structure.

Abstract: A motor controller includes: a notch filter arranged inside a control system; an oscillation frequency estimating section which estimates an oscillation frequency component in a motor; and a notch control section which controls a notch filter so as to change a notch frequency and a notch width. The notch control section changes a frequency between an oscillation frequency and a notch frequency set in a notch filter as a new notch frequency, while changing a notch width to a new notch width such that the notch width is larger after the change than before the change.

Abstract: An energy-saving magnetic bearing device with no bias current for making the relation between the excitation current and the magnetic force of the electromagnet linear is provided. In a magnetic bearing device for supporting a rotor 1 serving as the magnetic piece in a levitating state allowing free rotation at a specified position by the magnetic force of a pair of electromagnets 2, 3, the electromagnets 2, 3 are constituted to interpose the rotor 1 and face each other. A driver 204 is a PWM (pulse width modulation) type driver for controlling the excitation current in the electromagnets 2, 3 by modulating the pulse width of a voltage driven at a specified carrier frequency fc, and includes a resonator means for electrically resonating at a frequency equal to the carrier frequency fc.

Abstract: A control apparatus for an adjusting device in a motor vehicle is provided. The apparatus has a sensor, particularly a current sensor (S1), for generating a signal (U1 to U10, I1 to I3, ?t1 to ?t8) which is dependent on a motor movement by a motor in the adjusting device. The apparatus also has a power driver for controlling a motor current, and a processor (RE). The processor is designed and set up (i) to find a position (xm) from the sensor signal (U1 to U10, I1 to I3, ?t1 to ?t8), particularly from the ripple in the motor current, (ii) to associate a reference characteristic (Chref) of orderly signals (U1 to U10, I1 to I3, ?t1 to ?t8) from the sensor, particularly for the ripple, with a reference position (xref), (iii) to correct the position found (xm) on the basis of the reference characteristic (Chref) and the reference position (xref), and (iv) to control the motor current on the basis of the corrected position.

Abstract: An apparatus and a method for controlling an operation of a reciprocating compressor which can improve operational efficiency of the reciprocating compressor are provided. The apparatus for controlling the operation of the reciprocating compressor includes a resonance frequency operation unit for calculating a mechanical resonance frequency of the reciprocating compressor, an operating frequency reference value generation unit for comparing the calculated mechanical resonance frequency with a current operating frequency of the reciprocating compressor, and generating an operating frequency reference value according to the comparison result, and a controller for controlling a motor of the reciprocating compressor according to the generated operating frequency reference value.

Abstract: A method and a controller for controlling a magnetic bearing device, in which a rotor is suspended for rotation around a shaft, are disclosed. Sensor signals are transformed to yield tilt displacement signals (S?x, S?y) which correspond to tilting displacements of the shaft in predetermined directions (x, y). From the tilt displacement signals (S?x, S?y), tilt control signals A?x, A?y) are derived; these are transformed to yield actuator control signals for driving electromagnetic actuators in the magnetic bearing device. According to the invention, tilting displacements for which the tilt vector rotates about the device axis (z) with a first predetermined sense of rotation are controlled separately from tilting displacements for which the tilt direction vector rotates about the device axis (z) with a second sense of rotation opposite to the first predetermined sense of rotation. In this way, control of nutation and precession can be achieved without influence from blade vibrations or shaft bending modes.

Abstract: A small-sized and low-cost phase detection circuit which has improved noise immunity. The phase detection circuit comprises a multiplier for multiplying an input signal by a reference signal and outputting a first signal, an integration circuit for integrating the first signal and outputting a second signal, a phase estimation circuit for estimating phase information based on the second signal, and a reference signal generation circuit for generating the reference signal based on the estimated phase information. Since the phase is detected based on information representing an entire waveform, the influence of local noise can be diluted and noise immunity can be improved.

Abstract: A motor control device for controlling rotation of a motor by controlling a driving voltage applied to the motor is provided. The device includes a driving voltage control unit configured to control the driving voltage, and a detecting unit configured to detect rotation of the motor. The motor has operating characteristics indicative of relationship between the driving voltage and a rotation speed of the motor, where the operating characteristics have a specific dead-band range of driving voltages wherein the rotation speed of the motor is zero regardless of changes in the driving voltage. The driving voltage control unit performs a low rotation control operation including at least one alternating repetition of a first control operation and a second control operation.

Abstract: A detection device (8) detects radial deflections (x, y) of a rotating element (2) which is mounted in a base (1) by means of a magnetic bearing system (3) so as to rotated about a rotational axis (4) and feeds these deflections to a control device (9). Said control device uses the radial deflections (x, y) to determine control signals (Sx, Sy) for the magnetic bearing system (3) and outputs them to the magnetic bearing system (3). The detection device (8) also detects a rotary frequency (f) of the rotating element (2) and feeds it to the control device (9). The control device eliminates from the radial deflections (x, y) at least one frequency portion that comprises the portions of the radial deflections (x, y) having frequencies close to a filter frequency that has a defined ratio to the rotary frequency (f). The control device (9) uses the frequency portion to determine frequency control signals (Fx, Fy) in accordance with a frequency control model.

Abstract: The invention relates to a brushless DC motor control apparatus controlling the number of revolutions of a brushless DC motor having a rotor with n poles (where n is a natural number) that rotates due to a supply current with m phases (where m is a natural number) supplied to a stator, comprising: a rotation detector part, which counts the number of revolution pulses from the brushless DC motor caused by the rotation of the rotor, a revolution requirement amount input part, which receives the number of revolutions of the brushless DC motor as input and converts it to a corresponding revolution requirement amount, a comparison part, which compares the number of revolution pulses and the revolution requirement amount, and a current controller part, which controls the supply current supplied to the brushless DC motor according to comparison results from the comparison part.

Abstract: Provided is a motor control circuit in which the circuit structure is not complicated, which has a favorable response to the phase difference signal, and in which the signal variation caused by heat is small. This rotation control circuit of a motor includes: a PWM control circuit of the motor; a rotational speed sensor of the motor; a reference signal generation circuit 10; a phase comparing circuit; and a divider for dividing the detected rotational speed signal of the motor; wherein the phase difference between the signal from the divider and the signal based on the reference signal is sought with the phase comparing unit, and this phase difference signal is supplied to the PWM control circuit.

Abstract: A method of analyzing a limited rotation motor system is disclosed. The method includes the step of providing a motor control frequency domain signal that is representative of a frequency domain representation of the motor control signal responsive to a first digital signal that is representative of a motor control signal. The method also includes the step of providing a position detection frequency domain signal that is representative of a frequency domain representation of the position detection signal responsive to a second digital signal that is representative of a position detection signal.

Abstract: Disclosed is a method of controlling drive speed of a motor operating in overload conditions. The method includes the steps of: driving the motor at a predetermined reference speed; detecting phase voltage and phase current applied to the motor; determining whether or not the motor is operating in overload conditions based on the detected phase voltage and phase current; and controlling the motor according to whether or not the motor is operating in overload conditions. Accordingly, the present invention can prevent occurrence of over-current due to the instantaneous acceleration of the motor to a predetermined initial speed.

Abstract: A speed control means 7 for outputting a drive command signal for a motor 1 to make the speed of the motor 1 conform to the speed command signal based on a signal indicating the difference between the speed command signal and the detected speed of the motor; a filter 13 inserted in series with the speed control means 7 in the speed control loop, having a high frequency domain, a low frequency domain, and an intermediate frequency domain between the high frequency domain and the low frequency domain, a gain KL in the low frequency domain being larger than a gain KH in the high frequency domain, and having a phase lag characteristic so that the phase in the intermediate frequency domain is delayed; the speed control means 7 having a proportional controller 9 that multiplies input by a proportional gain KP and outputs the result, and the filter 13 being set so that phase lag occurs between a resonance frequency and an anti-resonance frequency of a mechanical system.

Abstract: By applying time-frequency analysis to a given standard iterative learning control or ILC an adaptive filter for the learned feed-forward loop is designed. This time varying filter varies according to the momentary frequency content of the error signal and allows to discriminate between areas of deterministic and stochastic error. Its application results in selective application of ILC to those intervals where error signals of high level are concentrated and allows application of a single ILC acquisition to different setpoint trajectories. The adaptive filter finds particular use in lithographic scanning systems where it is used for varying scan length.

Abstract: A diagnostic system is disclosed for analyzing a limited rotation motor system. The diagnostic system includes a first transform unit, a second transform unit, a closed loop frequency response unit, and a diagnostic system. The first transform unit is for receiving a first digital signal that is representative of a motor control signal, and is for providing a motor control frequency domain signal that is representative of a frequency domain representation of the motor control signal. The second transform unit is for receiving a second digital signal that is representative of a position detection signal, and is for providing a position detection frequency domain signal that is representative of a frequency domain representation of the position detection signal. The closed loop frequency response unit is for identifying a representation of the frequency response of the limited rotation motor responsive to the position detection frequency domain signal and the motor control frequency domain signals.

Abstract: Steering apparatus includes at least one motor for generating a steering assisting force in a direction to steer a steerable wheel, two drive circuits having respective switching elements for PWM-controlling the motor, and a controller for differentiating, between the drive circuits, a control frequency at which the switching element is switched on and off. The differentiated PWM switching timing can effectively reduce switching noise and magnetostrictive sound of the motor.

Abstract: A motor control device that can reduce electrical noise is provided. A motor control device includes an inverter, a current controller, a high frequency wave superpositioner, and a high frequency wave setter. An inverter applies a current to the motor. A current controller outputs a voltage to the inverter according to a current applied to the motor from the inverter. A high frequency wave superpositioner applies a high frequency wave to the voltage from the current controller as a superpositioned wave to infer a position of a rotor in the motor. A high frequency wave setter varies at least one characteristic of the superpositioned wave applied by the high frequency wave superpositioner.

Abstract: An interrupt signal is generated at each of rising timings of PWM signals which are produced on the basis of phase-shifted triangular wave carrier signals for phases, and voltage command values for the phases. At timings of the interrupt signals, A/D conversion of motor currents of the phases detected by a shunt is started. Interrupt signals are also produced at timings of valleys of the triangular wave carrier signals. Additionally, peak interrupt signals and valley interrupt signals are respectively produced at timings of peaks and valleys of triangular wave carrier signals for phases. Based on each of the peak interrupt signals, normality/abnormality of a switching element of an upper side of the phase corresponding to the interrupt signal is checked, and, based on each of the valley interrupt signals, normality/abnormality of a switching element of a lower side of the phase corresponding to the interrupt signal is checked.

Abstract: A method for determining at least one time constant of a reference model, which is designed as a 2nd order time-delay element of a machine. The method includes detecting an oscillation frequency of an undamped machine oscillation and determining an optimized value of a time constant of the reference model as a function of the detected oscillation frequency of the undamped machine oscillation.

Abstract: In an electric motor control apparatus including an electric motor 4 for driving a load machine, a rotation detector 3 for detecting a rotating angle of the electric motor 4, and a servo control device 2 for controlling the electric motor 4, a calculating device 1 automatically calculates protruded shapes to be a resonance frequency and an anti-resonance frequency from frequency characteristics obtained from an operation command signal 8 and a rotation detector signal 9, and furthermore, calculates errors of frequency characteristics calculated by frequency characteristic equations 20 for a 2-inertia model and a rigid body model from a frequency characteristic obtained by a measurement, and compares the minimum values of calculated values in the frequency characteristics of the 2-inertia model and the rigid body model and measured values respectively, thereby automatically modeling the characteristic of the machine.

Abstract: A controlled magnetic bearing apparatus which generates a control signal based on a sensor signal from a displacement sensor for detecting a radial displacement of a rotor to suppress whirling of the rotor due to an external force synchronized with a rotational movement, and can hence support the rotor stably in a levitated state.

Abstract: An operation control method of a reciprocating compressor is disclosed in which, in case that a motor is overloaded, an operation frequency is increased to render magnetic fluxes of a magnet and an input current are mutually offset, so that a reciprocating compressor can be stably driven even in case of the overload. For this purpose, while the reciprocating compressor using an inverter is operated at a rated frequency, a current load of the motor is measured and the measured load is compared with a pre-set reference load. Upon comparison, if the measured load is greater than the reference load, it is determined as an overload and the operation frequency is increased by as much as a certain value higher than an oscillation frequency, for performing an overload operation.

Abstract: The invention provides a method for controlling an electric motor and an apparatus for controlling the same, which lower vibrations generated due to low rigidity of a control object, secure vibration-suppressing performance without depending on instruction patterns and characteristics of a control object, and achieve high positioning accuracy.