Abstract: The invention relates to a reference-point return method for returning a movable element of a machine to a reference point using solely a linear scale, without relying upon a limit switch. The method includes providing the linear scale (1) with a second scale portion (2) for stipulating a deceleration starting position and a reference-point position, in addition to first scale portion (3, 4) for generating two-phase signals for position detection, generating signals (S.sub.1, S.sub.2) indicative of the deceleration starting position (D) and reference-point position (O) from the second scale portion (2) of the linear scale, slowing a reference point return rapid-traverse velocity (Va) to a reference-point return rapid-traverse velocity (Vb) using the deceleration starting signal (S.sub.1), and effecting return to the reference point by stopping movement in response to the reference-point signal (S.sub.2).

Abstract: A servomotor control method controls a servomotor stably at a high speed. A control loop is switched from a PI control mode to an I-p control mode by varying a gain coefficient of a proportional arithmetic unit (1). This achieves a control process having the advantages of both the PI and I-p control modes.

Abstract: A speed control method for a servomotor, capable of smoothly rotating the servomotor without causing pulsating rotation even when the servomotor rotates at low speeds. On the basis of the numbers of feedback pulses (P2k(m-1)-k+1, . . . , P2km) detected and stored at intervals of a period (TS/2k) equal to a value obtained by dividing an estimated speed calculation period (TS) by an integer multiple of 2, the number (A) of feedback pulses in each estimated speed calculation period and the number (B) of pulses in a time period from a midpoint ((m-1)TS-TS/2) of an estimated speed calculation period immediately before each estimated speed calculation period to a midpoint (mTS-TS/2) of each estimated speed calculation period are calculated, and an estimated speed indicative of an actual rotation speed of the servomotor is further calculated on the basis of the thus calculated numbers (A, B) of pulses.

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 servomotor velocity control apparatus constructs a digital servo system including a compensating circuit (2) having a variable gain. The integration gain of the compensating circuit (2) is set and controlled by a gain setting unit (5) so as to be inversely proportional to estimated servomotor velocity computed from a velocity signal fed back in discrete fashion. It is possible to perform high-speed positioning based on an actual velocity signal which prevails when velocity is low.

Abstract: A servo motor controlling method for controlling both speed and current of a servo motor under digital control. An integration gain unit (22) and a loop proportional gain unit (26) of the current controlling loop are subjected to correction by respective gain units (23, 27) so as to be increased depending upon the rotational speed of the servo motor. Since a current loop gain is increased depending upon the rotational speed of the servo motor, the oscillation of the current loop does not occur at the time of low speed drive and stop, and the shortage of torque due to the lowering of the current loop gain at the time of high speed drive can be prevented.

Abstract: The invention provides a servomotor control apparatus which performs standard mode-type velocity control. An acceleration signal is formed by a differential computation or difference computation, from a velocity signal fed back from a servomotor. An acceleration value of the servomotor (d) is estimated by a criterion model (2) of a velocity control system utilizing a current command T(S) formed in a velocity control loop. The computed acceleration and the estimated acceleration are compared and the current command T(S) is corrected in conformity with the results of the comparison.

Abstract: A multiple-articulated robot control apparatus eliminates robot arm vibration by feedback-compensating disturbance due to interference torque when the robot arms are driven. The apparatus includes an arithmetic circuit (8) for computing mutual interference torque values for respective ones of the arms, a status observing circuit (2) for reproducing a status variable from a torque command and actual velocity of each servomotor, a conversion circuit (4) for converting an output of the status observing means into a corrective value of torque produced by disturbance acting upon the servomotor, and a correcting circuit (9) for correcting an error signal of the torque command of the servomotor by the converted corrective value and the interference torque value. Disturbance of each arm with regard to driving torque is eliminated. The apparatus is adapted to correct estimated disturbance torque.

Abstract: The invention is a servomotor control apparatus for controlling the positioning of a movable element of an industrial robot or NC machine tool. An NC unit or a robot controller detects displacement from a movable element that is to be positioned, such as a table, forms a position command regarding a servomechanism, and has a correction circuit (A) which receives quadrant data (BLF) regarding a backlash correction command. When there is a quadrant reversal for each axis of the movable element, frictional torque corresponding to the axis is stored and a torque correction command (FR) corresponding thereto is outputted. A torque command of a fully-closed loop servo system for performing control based on a fed back position detection signal is corrected by the torque correction command. The servomotor control apparatus can be applied to semi-closed loop servo system in which a backlash correction is possible, and not just to a fully-closed loop servo system.

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: In a robot control apparatus, the results of processing regarding inertia terms of a motion equation are stored in accordance with the position of a robot arm. The computation period of the inertia terms can be set to be larger than a drive torque computation period. The robot is controlled with the same precision and, moreover, drive torque can be computed at a shorter computation time.

Abstract: There are provided a method and an apparatus for absolute position detection, in which position detection is performed with high accuracy by interpolation between feedback pulses generated as an object of position detection moves, and the power-on command displacement can be calculated with high accuracy, the method and the apparatus entailing only small electric power consumption. A stored value in an absolute counter (2), which is indicative of an approximate absolute position of an object of position detection, is updated each time a feedback pulse is generated from a feedback pulse generating circuit (1), and is retentively stored in the counter even after the power is turned off. As the object of position detection moves, moreover, the count value of interpolation pulses, generated during the time interval which elapses from the instant that the power is turned on again until the first one of the feedback pulses is generated, is temporarily stored in a correction counter (5).

Abstract: A numerical control apparatus according to the invention reliably eliminates the influence on positional accuracy of static resistance and dynamic resistance, which act as disturbance upon a servo loop, when a semi-closed loop forms a servo system for positioning, by numerical control, a machine tool or the like driven by a servomotor. The numerical control apparatus has a backlash correction function and supplies the servo system with a backlash correction data BL(i) distinguished from an ordinary move command BL(i). In order to eliminate a shift from a commanded position due to the aforementioned disturbance, an offset command corresponding to frictional torque Fa in the mechanical system of the machine tool or the like is applied to the servo system as a torque correction signal FR(i) in accordance with the backlash correction data BL(i).

Abstract: A position control system has a speed control loop for generating a torque command signal for a motor from the speed deviation between a speed command and an actual speed. The position control system includes command subdividing means (2) for subdividing the speed deviation (.epsilon.(i)) into a predetermined minute amount (.epsilon..sub.2 (i)=.alpha.) and a remaining amount (.epsilon..sub.1 (i)=.epsilon.(i)-.alpha.), integrating meand (3) for integrating the remaining amount (.epsilon..sub.1 (i)), and incompletely integrating means (4) for incompletely integrating the minute amount (.epsilon..sub.2 (i)). The output from the integrating means (3) and the output from the incompletely integrating means (4) are added, and the sum is issued as a torque command signal.

Abstract: An output torque of a servomotor is controlled to prevent overrun of an injection mechanism in an injection molding machine. The injection mechanism is driven by the servomotor to perform an injection operation of the injection mechanism. The injection molding machine includes a torque limit circuit which limits a value of a torque instruction output from a servo circuit of the injection mechanism operating in an injection direction to a value of a torque limit instruction from a numerical control apparatus and does not perform a torque limit operation of a drive instruction in a direction opposite to the injection direction. Therefore, the servomotor for driving the injection mechanism can be rapidly decelerated to prevent overrun of the injection mechanism.

Abstract: A velocity control apparatus according to the invention is used in order to acccept feedback data, for velocity control of a servomotor or the like. The disclosed apparatus provides velocity information in the form of discrete data from a pulse coder or the like, and forms a prescribed control command by digitally processing the data in a microprocessor. In a case where the above mentioned data are sampled at a predetermined sampling rate during a processing period so as to accommodate processing by the microprocessor, a lag element results when the data are accepted within the computer as velocity information which causes an inaccuracy in servomotor control. Accordingly, a detection signal forming unit (5) processes the discrete count data as the sum of count data synchronized to the sampling rate which is the processing period subdivided into a fraction, in which fraction the denominator is an integer.

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 robot control apparatus has servo CPUs (c.sub.1, c.sub.2) provided in control loops of respective servomotors (e.sub.1, e.sub.2) for driving and controlling loads about plural drive axes (.theta..sub.1, .theta..sub.2) of a robot arm. Since these servo CPUs execute drive torque calculations necessary for servomotor control, the cost of the control apparatus can be reduced. Also provided is a shared RAM (b) capable of being accessed commonly by the servo CPUs. Information about other axes stored in the RAM is read out and, when current loop processing is not being carried out, non-linear torque calculations necessary for servo-control are performed. As a result, current loop processing is not impeded and servomotor control can be carried out in a highly precise manner.

Abstract: An interface system for a servo controller has a speed controller (7), a current controller (9), etc., which have heretofore been disposed on the side of a servomotor, disposed in a control circuit (15) on the side of an NC apparatus. The present position and speed data from the servomotor are fed back and are stored in a common RAM, and control signals for a driver circuit, such as an inverter (12), are supplied from the NC apparatus side to the servomotor side. A system bus on the NC apparatus side is directly connected to a local bus on the servomotor side.

Abstract: A velocity control system in which, when an observer is used to estimate velocity based on position information from a rotary encoder, load torque, which is a cause of a steady-state estimation error, is estimated at the same time and velocity is controlled by using the estimated value. Velocity control of the motor is executed by feeding back the position information from the rotary encoder to an integration element in the I-P controller.