Abstract: A position controller for motors for increasing the position loop gain of a full-close control system without causing recurrence of vibration. The controller where a position signal representing the position of a movable table and outputted from straight-line motion position sensing means attached to a straight-line motion mechanism is used as a position feedback signal comprises differentiating means (2) for differentiating a straight-line motion position signal and outputting a straight-line motion speed signal, subtracting means (4) for calculating the difference between a speed command signal and the straight-line motion speed signal, integrating means (3) for integrating a difference signal outputted form the subtracting means, proportional gain means (1) for receiving the output signal from the integrating means, and adding means (19) for adding the output signal form the proportional gain means to the speed command signal and outputting a new speed command Vr.

Abstract: The present invention provides an airflow control loop that uses averaged airflow measurements without the problems that are normally encountered with averaging measurements, such as the delay introduced into the airflow control loop. This is accomplished, in the present invention, through a predictive control scheme. The predictive control scheme of the airflow control loop calculates the damper sensitivity, calculates the damper runtime needed to achieve setpoint, and then runs the damper for the determined period of time. In addition to the unique airflow control loop used to maintain the constant airflow into the room, the present invention also implements a digital form of proportional, integral, and derivative (PID) control to maintain the room temperature. The digital form of PID control uses non-linear gains which vary according to how far the measured temperature is from setpoint.

Abstract: An industrial process material flow within an industrial process is controlled by a process control loop that includes a process controller, a field device controller and a field device in the process as well as process variable feedback from the process to the process controller. Both the process controller and the field device controller, such as a valve controller, are fine-tuned so that their interaction is taken into account and controller parameters, which provide an optimal control loop performance are found. This results in a significant improvement in the control loop performance, i.e., in a lower process variability, as compared with the traditional tuning method, which does not take into account the interaction between the two controllers.

Abstract: A sensorless vector control apparatus includes a speed controller for receiving a speed command value from a user and outputting a synchronous speed; a ‘d’ and ‘q’ axis voltage command unit for receiving the synchronous speed and outputting a ‘d’ axis voltage and a ‘q’ axis voltage; a voltage converter for receiving the ‘q’ axis voltage and the ‘d’ axis voltage, and converting the two phase voltages into three phase voltages; and an inverter for receiving the three phase voltages and controlling a speed of an induction motor. Since the vector control may be performed over the whole velocity range without using a speed sensor, the sensorless vector control apparatus may be used with advantage.

Abstract: A controller capable of monitoring a receiving circuit for receiving machine information. Machine information from a machine is received by a plurality of independent systems and the external signals received by the plurality of systems are compared, thereby, a receiving state of the receiving circuit is monitored. The controller includes a plurality of independent receiving units for receiving the external signal and monitoring units for comparing signals received by the plurality of receiving units, to monitor the receiving units based on a result of the comparison.

Abstract: The invention includes systems and methods for controlling the position of a device. In one aspect, the invention is a method comprising the steps of providing a device, the device having a position, a velocity, and an acceleration; providing a control signal, the position of the device being responsive to the control signal; and varying the control signal, as the device approaches a desired location, according to a nonlinear function of the position, the velocity, and the acceleration wherein the velocity and the acceleration converge on zero as the device approaches the desired position. A number of alternative nonlinear functions may be used. In another aspect, the invention is an apparatus that controls the position of a device according to the nonlinear function described above.

Abstract: The present a step controller includes a switching circuit having at least two outputting states, especially a three-level switch (DPS1) with negative feedback, and a PI or PID controller having an integrator (I1). The integrator is inactive during the positioning pulse of the three-level switch. The integrator (I1) is provided with a correcting element (CORR) which reduces the reset time (Tn) for a large input signal (xd). In this way, linear behavior of the step controller can be attained over the entire positioning range of a positioning element.

Abstract: A method and apparatus are provided for positioning a head over a disc in a disc drive while maintaining servo loop stability. The apparatus includes an actuator-head assembly having a large-scale actuator and a micro-actuator that are both able to move the head over the disc. A saturation adjustment component detects when a micro-actuator controller is producing a micro-actuator control value that will saturate the micro-actuator. Using the micro-actuator control value, the saturation adjustment component generates a saturation error value. An adaptive anti-windup circuit transfers control to the large-scale actuator when the saturation error value is generated by the saturation adjustment component.

Abstract: A multi-purpose controller for variables which closely controls such variables to set point by making sequential corrections to the level of input to the system of the variable based on: system response time, relationship of controller output to the variable, deviation of the variable from set point, and change in system load as determined by change in error and change in system input. The controller has a self tuning capability and can provide generation of the set point according to a set of variable parameters. It can be configured as a stand alone controller, as an intelligent Input/Output device for another intelligent device, or be resident in another intelligent device such as a programmable controller, computer or other microprocessor based device.

Abstract: A method for generating a valve drive signal using a variable gain PI controller in a mass flow controller. The method includes multiplying an error signal with a proportional gain factor to generate a proportional signal. The method also includes implementing an integral function on the error signal. The integral function includes an integral gain factor which functions as the variable gain in the PI controller. For set-point signals less than a normalized predetermined percentage of the maximum set-point, the gain factor is equal to [ ( 1 0.1 - 1 ) ⁢   ⁢ A + B ] , where A is a first gain constant and B is a second gain constant.

Abstract: An data interface module is provided for allowing a user to remotely modify a predetermined number of operating parameters of a motor driven by a motor control and for displaying the same. The interface module includes a micro-controller interconnected to a communications network and a visual display structure. The visual display structure has a first screen which displays a scrollable list of the operating parameters and a second screen which displays a data value for a user selected one of the operating parameters. A user may modify the user selected operating parameter when the second screen is displayed.

Abstract: A control apparatus is disclosed that comprises a primary proportional, integral, differential (“PID”) controller capable of receiving a first setpoint and a first process variable and generating therefrom a second setpoint; and a secondary controller capable of receiving the second setpoint and a second process variable and generating therefrom an output control signal, wherein the primary PID controller is capable of receiving from the secondary controller a feedback signal 1) that indicates that a previous value of the second setpoint exceeds a limit associated with an output control signal of the secondary controller, and 2) that transfers a value of a signal from the secondary controller. The primary PID controller is then capable of limiting the contribution of the integral calculation component in a PID calculation that generates a new current value of the second setpoint.

Abstract: A servo control apparatus for performing a feedback control to a controlled system having characteristics represented by a characteristic equation including at least a second order term, a first order term and a zero order term, includes a disturbance estimating device that has an internal model having characteristics represented by a characteristic equation including only a second order term, and that estimates a disturbance applied to the controlled system by using the internal model, thereby generating an estimated disturbance value; and a compensating device that compensates the disturbance on the basis of the estimated disturbance value.

Abstract: A scanner motor acceleration method that uses a software driver and a flexible process method to enable a scanner to perform fast scanning operation without increasing motor cost or complex hardware design. Motor acceleration and deceleration may be done through software control on existing scanner hardware which do not support acceleration and deceleration function. Through positioning and speeding mechanisms of existing scanner hardware, and software which may be changed flexibly, scanner positioning function may be accurately performed without deviations.

Abstract: A speed controller circuit for a motor including a ramp function generator having a first input connected to a source of a speed demand signal and a second input connected to a ramp step signal. The ramp function generator develops a frequency ramp that has a slope is initiated by the speed demand signal which is adjusted in response to the ramp step signal. The ramp function generator also provides a frequency signal wherein the ramp function increases or decreases the frequency according to the speed demand. A V/F circuit to the ramp function generator and a space vector modulation circuit are connected to the V/F circuit. The output of the space vector modulation circuit is applied through power switching devices to the motor for speed control. A PI controller circuit is connected to a motor current feedback signal and to a maximum current signal, which provides the current limit of the control system.

Abstract: An integrated control and diagnostics system for a controlled system (e.g., a motor) includes a diagnostics module and a controller coupled to the motor. To optimize operation, the diagnostics information signal is used to modify the control provided by the controller as required. Moreover, the output of the control module is coupled to the diagnostics module so that the health assessment made by the diagnostics module can be based at least in part on the output of the controller. The invention uses a model-based diagnostics approach that allows integration of control algorithms with diagnostics algorithms to intelligently trade off optimizing performance to avert or accommodate failures, and to meet performance requirements in a wide range of applications.

Abstract: A method of estimating a motor torque constant including the steps of measuring a current and a speed of motor at sampling time during rotating of the motor and calculating the motor torque constant Kt* by a multiplicity of the measured current values and speed values.

Abstract: A method and arrangement for adaptively compensating for load changes, particularly in connection with an electric motor drive which comprises a motor, the shaft of the motor being connected to a load (3) having a known moment of inertia; a device (2), such as an inverter, to control the motor, a torque controller being arranged in connection with the device; and a speed controller (1) arranged to control the speed of the motor. The method comprises steps of determining, during the load change, an estimate (Mh) for an external torque disturbance which causes load changes, and employing the torque disturbance estimate (Mh) determined during the previous load change for compensating for the external torque disturbance in controlling the torque of the motor.

Abstract: A method of controlling a motor comprises providing a motion control system and causing the shaft of the motor to move from an initial state to a new state, such as from an initial position or velocity to a new position or velocity. Coefficients for each of a plurality of polynomial segments of a motion profile are determined. The plurality of polynomial segments and the corresponding coefficients for each respective segment characterize planned movement of the shaft through each respective segment. In a particularly preferred aspect, each segment is defined by a plurality of polynomials, which include a first polynomial that describes shaft position with respect to time, a second polynomial that describes shaft velocity with respect to time, and a third polynomial that describes shaft acceleration with respect to time.

Abstract: A method and apparatus for tuning control loop parameters in a motion control system, is provided. In one embodiment, tuning of the proportional and integral gains of a servocontroller's velocity loop compensator is provided, as well as tuning of the cutoff frequencies of the servocontroller's low pass filters. In this embodiment, random noise excitation is added to the velocity command during a plurality of movement types for a machine tool axis. During each movement type, frequency response measurements are taken. Then, a composite frequency response can be selected by concatenating portions of the various frequency response measurements, so as to simulate a worst case scenario for the machine tool axis. From this composite response, an open loop response can be calculated and displayed, as well as bandwidth, phase margin, and gain margin values. The user can then enter the compensator parameters which were used when this data was taken, as well as proposed parameters.

Abstract: A deviation between a target value of a quantity of state and an actual value of the quantity of state that is caused to follow the target value or a time-integral of the deviation is filtered. Based on the filtered value, a switching surface &sgr; is calculated. Based on a value of the switching surface &sgr;, a control input value u is outputted. The filter is set through comparison in Bode diagrams between a design model of a control system based on an ordinary sliding mode control method and a characteristic variation model of the control system, and by performing compensation in such a direction as to cancel out the variation. The filtering process makes it possible to properly control the control system having a dead time by the sliding mode control method.

Abstract: The present invention relates to a method and a device for executing phase compensation in a control system of a motor-driven vehicle, in which the time derivative for an output signal (y) from a circuit (1) contained in the control system is limited relative to the time derivative for an input signal (u) to the circuit (1) if the time derivative for the input signal (u) exceeds a predetermined value. An error signal (&egr;) is formed between the output signal (y) and the signal (x) present in the circuit (1), the time derivative of which is not limited in relation to the time derivative for the input signal (u). The error signal (&egr;) is filtered via an asymptotically stable filter (3) to form a signal (&dgr;), which is fed back and subtracted from the input signal (u) of the circuit (1) to form the signal (x). A conventional rate limiter may be used to form the output signal (y) from the signal (x).

Abstract: A method and apparatus for tuning control loop parameters in a motion control system, is provided. In one embodiment, tuning of the proportional and integral gains of a servocontroller's velocity loop compensator is provided, as well as tuning of the cutoff frequencies of the servocontroller's low pass filters. In this embodiment, random noise excitation is added to the velocity command during a plurality of movement types for a machine tool axis. During each movement type, frequency response measurements are taken. Then, a composite frequency response can be selected by concatenating portions of the various frequency response measurements, so as to simulate a worst case scenario for the machine tool axis. From this composite response, an open loop response can be calculated and displayed, as well as bandwidth, phase margin, and gain margin values. The user can then enter the compensator parameters which were used when this data was taken, as well as proposed parameters.

Abstract: A motor speed controller with high speed response characteristics.

Abstract: An induction motor control system (10) for electric vehicles having a DC power supply (12), an inverter (14), an induction motor (16), and a clamping unit (26). The clamping unit (26) applies a clamping value iq_clamp to a real torque current command iq*. The clamping value iq_clamp is calculated in a maximum torque current calculation unit 28 and is based on predetermined maximum settings for the motor power Pmax and torque Tmax. The clamping value iq_clamp is applied such that the torque current command iq* cannot exceed the clamping value iq_clamp, whereby the induction motor produces 16 output power Pout and torque Tout that is always less than the predetermined maximum settings, Pmax and Tmax.

Abstract: According to the present invention, in a first acceleration after power is turned ON, currents flowing through U-phase and V-phase of a servo motor output terminal are detected, and misconnection of the motor output terminal is detected by monitoring a pattern of the current wave form.

Abstract: A position controller has a command generator for generating position instructions, a position control unit for controlling a position by inputting a position instruction and the position of a motor being an object to be controlled, and outputting a speed instruction so that they become coincident with each other, a speed control unit for controlling a speed by inputting a speed instruction and a speed of the motor and outputting a torque instruction so that the speed instruction and speed become coincident with each other.

Abstract: A method and apparatus for tuning control loop parameters in a motion control system, is provided. In one embodiment, tuning of the proportional and integral gains of a servocontroller's velocity loop compensator is provided, as well as tuning of the cutoff frequencies of the servocontroller's low pass filters. In this embodiment, random noise excitation is added to the velocity command during a plurality of movement types for a machine tool axis. During each movement type, frequency response measurements are taken. Then, a composite frequency response can be selected by concatenating portions of the various frequency response measurements, so as to simulate a worst case scenario for the machine tool axis. From this composite response, an open loop response can be calculated and displayed, as well as bandwidth, phase margin, and gain margin values. The user can then enter the compensator parameters which were used when this data was taken, as well as proposed parameters.

Abstract: A method and apparatus for correcting DC offset in a frequency to voltage converter. An analog frequency to voltage converter receives a frequency signal and outputs a voltage signal having a level that is indicative of the frequency of the frequency signal. The frequency signal is also input into a digital processor which converts the frequency signal into a reference signal that is fed back and summed with the voltage signal. The processor integrates the difference between the reference signal and the output signal to drive the output signal to be equal to the reference signal thereby nullifying DC offset in the output signal. The invention can be applied to controlling the DC bus voltage in a variable frequency AC drive.

Abstract: When a steplike reference signal is supplied while a switch is open, an offset signal for compensating for the dead time of a pneumatic device is generated by an offset generator and supplied as a manipulated variable for the pneumatic device. When a feedback increases in level and a speed higher than a reference speed is detected by a speed detector, the switch is closed by a switching signal, switching from a PD control mode to a PID control mode. The pneumatic device thus controlled has a reduced response time and can made a quick response.

Abstract: A motor control apparatus for adjusting a gain by identifying an inertia includes a speed control section for determining a torque command and controlling a speed of a motor such that an actual speed of the motor coincides with an inputted speed command; an estimation section for simulating and creating a model of the speed control section so that the motor speed coincides with the speed of the model; and an identifying section for identifying an inertia on a basis of a ratio between a first value which is obtained by time-integrating a first speed deviation of the speed control section during a specified period and a second value which is obtained by time-integrating a second speed deviation of the estimation section during the same period as the specified period, wherein identification of the inertia is performed only in a case where the motor speed within the speed control section and the speed of the model within the estimation section are not zero and coincide to each other, and the inertia is identified

Abstract: To drive a lens part by a servo motor, an automatic controller turns on the first switch to input a desired value to an error amplifier from a final controlling element, and turns off the second switch to activate a feedback circuit which performs negative feedback. On the other hand, if the desired value is 0, or if the final controlling element does not work, the automatic controller turns off the first switch to shut out the desired value from the final controlling element, and turns on the second switch to activate the feedback circuit which performs positive feedback. This enables hand operation of the lens part with support of the positive feedback.

Abstract: There is provided a method of controlling a two-degree-of-freedom control system for controlling a controlled object. The method includes the steps of generating a first signal for feedforward control using a target value and generating a second signal for feedback control using an output signal from the controlled object. The method further includes the steps of outputting a plurality of the first signals while the second signal is outputted once, and controlling the controlled object by using the first signal and the second signal. In the present invention, plurality of the first signals include signals with different time widths.

Abstract: A method for detecting optimal controller parameters for a digital speed control is proposed, wherein an rpm control circuit is charged with different test signals, and the resulting rpm progression is determined. This rpm progression is subsequently evaluated with respect to triggering time and transient response for different controller parameters, and thereafter the most advantageous controller parameters are set in the controller of the control circuit.

Abstract: Control of time-dependent states, such motion, is facilitated in a manner that avoids explicit solution to the governing equations, but which permits specification of both an initial and a final acceleration. This permits the operator to restrict jerk by exerting control over the final acceleration (e.g., by setting this equal to the initial acceleration, or constraining it to within an allowed maximum), but without explicitly computing parameter values for jerk. More generally, the approach is useful in controlling any system in which states evolve with respect to a specific parameter (frequently, but not necessarily, time), and whose evolution can be described by a defined set of algebraic equations.

Abstract: A mobile body controlling gear is provided that can suppress an occurrence of yaw motion due to an offset when the P control is switched to the PID control. The yaw-axis control signal Ep is added to the control signal from the P/PID controller. The added signal is input to the actuator. The yaw-axis driving unit performs yaw-axis control. The yaw-axis angular velocity detection sensor signal Sa is compared with the reference signal r. Then the P/PID controller receives the comparison signal. The reference value memory holds the yaw-axis control signal Ep immediately before the P/PID switching unit switches the P control mode to the PID control mode. The yaw-axis control signal Ep is handled as the reference signal rb for the PID control. The reference value rb is added to the angular velocity zero detection reference value rz and to the yaw-axis control signal Ep. The resultant sum is input to the PID terminal of the P/PID switching unit.

Abstract: The present invention propose a driving apparatus for an image processing system. A DC motor with a feedback controlling system is utilized as the driving apparatus. With the design of the present invention, the accuracy of the position control can be increased and the prior art problem of missing steps and unequalled steps can be eliminated. The driving apparatus of the present invention includes a DC motor, a position detecting device, an error counter, a controlling circuit, and a driving circuit. The position detecting device is employed for detecting positions of the DC motor in order to generate feedback signals. The error counter is responsive to input signals and the feedback signals for generating error signals. The controlling circuit is responsive to the error signals for controlling the DC motor. The driving circuit is responsive to the controlling circuit for driving the DC motor.

Abstract: An active control mechanism and method for stabilizing a servo-controlled actuator system such as an actuator system in a data recording disk drive by compensating the vibrational modes of the actuator's arm assembly. The control mechanism has a sensing arrangement which can include one or more individual sensors attached to the actuator at locations where they generate signals in phase with the vibrational modes, and especially with all the major vibrational modes, of the arm assembly. A control mechanism derives from the signals an adjustment signal consisting of three corrective terms--a stiffening correction, an active damping correction and an inertia reduction correction--and the adjustment signal is used in the feedback control loop to stabilize the actuator system.

Abstract: A motor controller controls the operation of an electric motor (28). The motor controller includes sensors (30, 97, 102) for sensing at least one dynamic operating characteristic of the motor and for providing a signal indicative of the at least one sensed dynamic motor operating characteristic. A variable gain regulator (190) receives a current command request signal having a value and provides a motor current control signal having a value functionally related to the value of the received current command request signal and a gain control value. A gain scheduler (196) is operatively coupled to the variable gain regulator (190) and to the sensor (30, 97, 102) for providing the gain control value to the variable gain regulator (196) in response to the sensed at least one dynamic motor operating characteristic to thereby control the amount of gain of the variable gain regulator (190).

Abstract: A high precision pointing mechanism (10), particularly for use in space applications. The precision mechanism includes a motor assembly (26) connected to a displaceable elbow (24). A controller (166) determines a motor torque command (170) in accordance with a position error (168). The position error is used to generate proportional gain (172), derivative gain (182), and integral gain (194) compensation terms. The sum of the proportional compensation component (172) and derivative compensation component (182) is used to generate a proportional-derivative compensation component. The proportional-derivative compensation component is input to a hyperbolic tangent function (188), which substantially models the friction characteristic of the high precision pointing mechanism (10). The output from the hyperbolic tangent function (188) is used in combination with the proportional-derivative compensation component and the integral compensation component to generate the motor torque command (170).

Abstract: An apparatus for moving a stage, supported by a base, to a target position. The apparatus includes a motor for driving the stage in X and Y directions, a laser interferometer for measuring a current position of the stage in the X and Y directions and a controller for generating a control signal for controlling the motor to move the stage to the target position in the X and Y directions on the basis of the target position and for dynamically setting a transfer function associated with generation of the control signal in correspondence with the current measured position. The controller sets the transfer function so that a gain decreases as the stage moves toward a peripheral portion of the base.

Abstract: To drive a lens part by a servo motor, an automatic controller turns on the first switch to input a desired value to an error amplifier from a final controlling element, and turns off the second switch to activate a feedback circuit which performs negative feedback. On the other hand, if the desired value is 0, or if the final controlling element does not work, the automatic controller turns off the first switch to shut out the desired value from the final controlling element, and turns on the second switch to activate the feedback circuit which performs positive feedback. This enables hand operation of the lens part with support of the positive feedback.

Abstract: An apparatus for Position Error Signal (PES) measurement in a disk drive servo system includes a variable-gain amplifier that receives an analog servo signal; a multiplier coupled to the variable-gain amplifier; a low-pass filter coupled to the multiplier; a digital-to-analog converter; an analog summer that is coupled to the low-pass filter and to the digital-to-analog converter; an analog-to-digital converter coupled to the analog summer; a digital summer coupled to the analog-to-digital converter, and a phase-locked loop that provides timing signals to the multiplier, the digital-to-analog converter and the analog-to digital converter. The invention enables an output of the variable-gain amplifier to be multiplied with the clocking signal of the phase-locked loop. The multiplication output signal is then filtered by the low-pass filter.

Abstract: The invention relates to a device for displacing an object, which device includes a drive device for moving the object along an axis of motion, a control unit which is coupled to the drive device, a set-point generator which is coupled to the control unit and is arranged to determine from secondary conditions a jerk set profile and set points for a plurality of sampling periods for a trajectory to be traveled and to apply the set points to the control unit per sampling period. A problem solved by the invention consists in that secondary conditions such as, for example the maximum velocity or the desired final position, can be changed during a motion along a trajectory. To this end, during the displacement along the trajectory and in response to a change of the secondary conditions, a jerk set profile and associated set points are derived in the set-point generator from the secondary conditions for the sampling periods as from a sampling period succeeding the change.

Abstract: To provide magnetic bearing devices capable of preventing undesirable consequences caused by conical mode or parallel mode resonance which is liable to occur during acceleration of a rotor. A band-pass filter 24 is connected in series with a PID control circuit 12 is for improving stiffness in a specific frequency band. A displacement of a rotor 2 detected by a displacement detector 30 is entered to a switcher 32. On the other hand, a rotational speed sensor 7 detects the revolving speed, and a compensator switching discriminator 26 causes a switch 32s of the switcher 32 to connect to an output terminal 32b or to an output terminal 32c when the revolving speed coincides with preset revolving speed data. The preset revolving speed data defines specific revolving speeds occurring below and above a frequency band which includes a first conical mode resonant frequency and a second conical mode resonant frequency.

Abstract: A method of estimating the gain of a servo control system including an actuator, in which input data supplied to the actuator and the actuator's position data are applied to a gain estimate formula in a closed loop discrete value system for controlling the actuator, so as to estimate the gain of the servo control system.

Abstract: Letting a differential value of a command value of a position command to a position control loop be an input variable, a feed forward compensation value is calculated depending on the input variable and a combination of a proper vibration frequency and an attenuation constant of a vibration in a moving direction of a moving mechanism to be set in a parameter setting manner, and a feed forward compensation is effected for the command value of the position command to the position control loop by the feed forward compensation value.

Abstract: A process and apparatus for positioning an object being moved along a path to a destination using a pole changing three-phase induction motor having at least two fixed driving speeds. The object is initially accelerated along the path of movement to the highest driving speed of the motor, during which the acceleration curve is determined and stored. The acceleration data is then used to calculate the location along the path in advance of the destination at which the motor is switched off and braked until reaching the next lower driving speed, whereupon the motor is operated at the next lower driving speed for a predetermined path length. The motor is then again switched off and braked until its driving speed reaches zero closely proximate the destination, at which point a motor in a gear assembly attached to the motor is operated for final low speed positioning of the object at the destination with a high degree of accuracy.

Abstract: A disturbance load estimation method for a servomotor in which an disturbance load externally exerted on the servomotor can be accurately estimated even when the voltage is saturated. Actual values (Ir, Is, It) of three-phase alternating current determined by current loop processing (term 1) are converted by DQ conversion, and an effective current component (Iq) that contributes to a torque generated by the servomotor is obtained (term 4). Based on the obtained effective current component, a motor acceleration is estimated (term 5), a difference between the estimated acceleration and an actual motor acceleration (term 6) is obtained, and the disturbance load is estimated based on the acceleration difference (term 7).

Abstract: A simple modification to a proportional integral controller allows for non-linear control strategies while maintaining the simplicity of set up and tuning of the loop through modifying the proportional and/or integral gains K.sub.p, K.sub.j by a linear or parabolic function of the feedback error signal. Provision is made for symmetrical or asymmetrical gain modification functions.