Abstract: A method for estimating a load acting on a machine tool and controlling a life of the machine tool based on the estimated load. When predetermined machining is effected on a predetermined workpiece, a disturbance load torque acting on a motor for a spindle or a motor for a feed shaft is estimated by a disturbance estimating observer. When the estimated disturbance load becomes not lower than a set reference value, a timer is reset and started. If the estimated disturbance load torque is kept not smaller than the set reference value until the timer reaches a predetermined set time, a tool change command is issued to stop the machining. Since the tool life is determined in accordance with the magnitude of the load acting on the tool, the tool life is controlled objectively and accurately.

Abstract: The present invention relates to motor control at the time of reversal of direction of feed axes of a machine tool using a servomotor. The present invention includes a disturbance torque estimating unit for estimating a disturbance torque and estimating a frictional torque. The value in a speed loop integrator is divided into a frictional torque component and an acceleration torque component. An integrator target value for the time of reversal of motor rotation is obtained in accordance with the acceleration torque component and a value obtained by inverting the sign of the frictional torque component. Backlash acceleration correction is effected using a value obtained by applying a certain offset to a speed command so that the integrator target value is reached, as a backlash acceleration value. In estimating the frictional torque, a ratio of torque constant to inertia is estimated automatically, and the frictional torque is estimated by using this ratio.

Abstract: Rotation of a code plate fixed to a shaft of a detecting object is detected for producing a one-rotation signal and an incremental signal corresponding to a division of one revolution into a plurality of equal sections. The incremental signal is counted by a counter, thereby detecting an absolute position using an encoder. The counter is cleared in response to a one-rotation signal arriving first after the encoder starts its detecting operation. The counter continues to count the incremental signal in proportion to rotation of the shaft of the detecting object after its count value is once cleared, without clearing the count value in response to subsequent one-rotation signals. Thus, the counter obtains an absolute distance from a position where the counter received the first one-rotation signal to a present position.

Abstract: To control a servo motor, after the sign of a shift command is inverted, a first offset amount Vmo is added to a speed command during a period the motor rotates by the amount of "a" so that inversion of sign of an integral value of the speed loop is made to occur earlier, thereby accelerating the reversal of the direction of the motor. Then, after the motor has rotated by an amount "b", a second offset amount Vto is added to the speed command, thereby causing the motor to generate a torque that is large enough for an object connected to the motor to start moving to overcome the frictional force. The first offset amount is determined based on a value of an integrator in the speed loop at the time the direction of the shift command is inverted so that the servo motor is reversed by the correct amount. The second offset value is reversed determined based on the acceleration at the moment of inversion, so that its value is optimized corresponding to the frictional force.

Abstract: An AC synchronous motor control method in which the optimum phase advancing control is executed not only in acceleration but also in deceleration of a motor. When a value P, which is obtained by multiplying a motor's revolutionary speed by a torque command, is positive or equal to "0", a proportional constant of a linear equation for calculating a phase advancing compensation amount .delta. is set to k, whereas, when the above value P is negative, the above proportional constant is set to k' (k'<k). Then, the phase advancing compensation amount .delta. is calculated by using the proportional constant k or k', and the calculated compensation amount .delta. is added to a rotor phase .theta., thus advancing the phase of current commands. The motor is controlled by executing current loop processing on the basis of a current command T thus obtained.

Abstract: A method of controlling a servomotor, characterized by faster convergence of both positional deviations and velocity deviations, higher responsibility as well as an improved resistivity against a disturbance, and being free from any mechanical resonance. An adjustment gain G is increased when a torque command Tc1 received from a conventional velocity control is small, whereas the adjustment gain G is decreased when the torque command Tc1 is large. A torque command Tc2 obtained by multiplying the Tc1 to the output from the velocity control section by the adjustment gain G is supplied to the servomotor. The gain is to be heightened in the case where the positional deviation and velocity deviation are both small and the torque command Tc1 is also small, to thereby ensure a higher responsibility and a rapid convergence. Moreover, the gain is to be suppressed when the torque command Tc1 is large, thus preventing the occurrence of a mechanical resonance.

Abstract: An abnormality detecting method for a servo system capable of quickly detecting an abnormal condition even in a low rotation speed range is provided.While a digital servo control section (11-13) is executes a servo control operation for controlling the drive of a servomotor in accordance with a torque command (Tc) derived from a speed feedback (VA) and a speed command (Vc) corresponding to an actual position deviation (Er), a simulator (14) integrates a speed command (Vcs) equal to the product of a position loop gain (PG) and an estimated position deviation (Ers) obtained by subtracting a position feedback (PAS) from a movement command (Me). The simulator thus derives the position feedback (PAS), and an excessive error detecting section (15) compares the difference (Er-Ers) between the actual position deviation and the estimated position deviation with a predetermined value (As).

Abstract: A feedback-type position control method by which position control can be effected properly and easily in various machines. A pulse number converter (5) obtains the sum of a remainder (Rn-1) for a preceding cycle and the product of the number (xn) of feedback pulses delivered from a pulse coder (4) within a predetermined period and a first conversion coefficient (A) (S1 to S3). If the sum is positive or zero, position feedback pulses corresponding in number to a quotient (yn') obtained by dividing the absolute value of the sum by a second conversion coefficient (B) are delivered, and a remainder (Rn') resulting from the division is stored as a remainder (Rn) used to obtain the sum for the next cycle (S4 to S8).

Abstract: An improved servomotor control method where a multiplier ratio DMR is computed in advance by an arithmetic unit (20) from a traveling distance L of a movable machine element per revolution of a servomotor, a traveling distance R per pulse of a move command, and a number N of incremental pulses generated by an absolute position-detecting pulse coder (18) per revolution of the servomotor. A move command (.DELTA.R.sub.n) is accumulated by a move command accumulator (11), an absolute position (P.sub.A ') output by the absolute position-detecting pulse coder (18) is multiplied by the multiplier ratio DMR. A difference (E.sub.r) between a value (P.sub.c) obtained by accumulating the move commands and the result (P.sub.A) of the multiplication operation is computed as a position error, and rotation of the servomotor (17) is controlled by using the position error.

Abstract: An overcurrent detector realized by using a computer. The apparatus is provided with an overcurrent detector (5) which calculates the temperature rise .theta.(n) =K.sub.1 P(n)+K.sub.2 .theta.(n-1), based on a current (In) flowing in an electric machine, under the conditions that the machine has an electric resistance (r), the machine works in a known ambient temperature, the allowable temperature rise (.theta.(max)) of the machine is known, a first coefficient (K.sub.1) and a second coefficient (K.sub.2) are predetermined. The overcurrent detector (5) further compares the temperature rise (.theta.(n)) with a difference between the allowable temperature rise (.theta.(max)) of the machine and the ambient temperature at which the machine is used, and determines that the machine is in an overcurrent position, when the former exceeds the latter.

Abstract: A reference-point return method for a numerical control system. When a return is made to a reference point, a numerical control unit (21) reads an absolute position of a motor (23) within one revolution thereof from an absolute position detector (24), obtains a distance B from a predetermined motor point (a grid point) to the absolute position that has been read, and initially sets the distance B as a command position REF.sub.n from the grid point. Thereafter, the numerical control unit (21) outputs a move command value .DELTA.R.sub.n to a digital servo-circuit (22) every predetermined time .DELTA.T, updates a commanded position REF.sub.n in accordance with the equationREF.sub.n +.DELTA.R.sub.n .fwdarw.REF.sub.nobtains REF.sub.n after a deceleration limit switch (25) is depressed, and outputs (N-REF.sub.n) to the digital servo-circuit (22) as a final commanded traveling distance .DELTA.R.sub.n to return the movable element to a reference-point position set at a predetermined grid point.

Abstract: A servo-control circuit that suppresses an incomplete integration term, which is contained in an integration gain of a velocity feedback loop in a velocity control block (5), when an error between a position signal from a mechanical system and a move command exceeds a predetermined reference value. As a result, a torque command applied to a current control block (6) is controlled so as to minimize a torque which causes overshoot along a static friction characteristic of the mechanical system. Thus, an effect equivalent to that achieved in an analog servo system by non-linearly manipulating a coefficient at the charge and discharge time of a CR time-constant circuit can be realized in a computerized digital servo-control system.

Abstract: A digital servor system can swiftly stop a moving object, having a small friction resistance to the motion, at the position where the object should stop, without vibration thereof. A velocity command generating device (3) calculates a velocity command (V.sub.cmd) based on the deviation value of a position fedback from a position command detected by a position deviation detecting device (2). A velocity deviation detecting device (5) calculates a deviation (E) of a velocity fedback from the velocity command (V.sub.cmd). A torque command generating device (6) calculates a torque command (T.sub.cmd) giving a delay processing to the deviation (E), and outputs the torque command (T.sub.cmd) to a motor driving means (7).

Abstract: A negative feedback control system includes a step of amplifying digital information by an amplifying operation at a high response speed and not including an integration. The negative feedback control system detects a predetermined amount of increase and decrease in the controlled variable, and outputs an increment signal or a decrement signal according to the predetermined amount of increase and decrease in the controlled variable, respectively, receives increment signals and the decrement signals from a controlled variable detecting unit 4, ignores the first successive n increment signals immediately after an arbitrary decrement signal, then begins to count each increment signal as a +1 unit from the n+1-th increment signal after the arbitrary decrement signal, and ignores the first successive n decrement signals immediately after an arbitrary increment signal, then begins to count each decrement signal as a -1 unit from the n+l-th decrement signal after the arbitrary increment signal (FIG.