Abstract: A spot welding system using a spot welding gun having a servomotor for driving welding tips capable of suppressing variation of pressing force due to influence of heat generated by welding current to obtain an uniform pressing force. A difference between the temperature T detected by a temperature sensor and an initial temperature T0 is multiplied by a coefficient A to obtain a pressing force compensation amount ?. A pressing force d estimated by an observer is subtracted from the compensated command pressing force p? and an obtained difference is multiplied by a constant K2 to obtain a torque command (current command) ? for driving the servomotor to press the objects by the welding tips. Since the commanded pressing force is compensated in accordance with the temperature, a constant and stable pressing force is produced without influence of the temperature variation.

Abstract: A control device for controlling the motion of a movable part in a machine while suppressing vibration generated in the movable part. The control device includes a state-variable estimating section for estimating a state variable of a controlled system in the machine and outputting an estimated state variable; a reference model for outputting an ideal controlled variable for the controlled system; a compensator for calculating a compensation value for correcting a control input for the controlled system, based on a difference between the estimated state variable and the ideal controlled variable; and a feedback control section for determining the control input, based on a deviation between a desired command value and one of the estimated state variable and the ideal controlled variable.

Abstract: A laser oscillator capable of executing a high-speed feedback control by reducing the control load of a main processor in the feedback control of the laser output. The laser is excited by an excitation source activated by one or more power supplies. The laser radiation is detected by a power sensor or a photodiode. A detected signal is A/D converted and fed to a sub processor or a high-speed DSP. The sub processor compares the current laser output value to a desired control value and calculates a deviation value in a predetermined period. The sub processor outputs a feedback signal to each of the power supplies according to a command from the main processor. Each power supply adjusts the supplied current to control the laser output. The main processor monitors conditions of the power supplies and controls a coolant circulation device. A factor regarding a load on a sequential control process, which may delay the feedback control, is eliminated and an analog circuit is unnecessary.

Abstract: A spot welding system using a spot welding gun having a servomotor for driving welding tips capable of suppressing variation of pressing force due to influence of heat generated by welding current to obtain an uniform pressing force. A position control of the welding tips is performed based on motion commands r, position feedback amounts y to obtain a torque command (current command) &tgr; to drive the servomotor. A difference between the temperature T detected by a temperature sensor and an initial temperature T0 is multiplied by a coefficient A to obtain a pressing force compensation amount &agr;. In a pressing force control, the pressing force compensation amount &agr; is subtracted from the commanded pressing force to obtain temperature compensated command pressing force P′.

Abstract: A method of and apparatus for detecting an abnormal load on a servo gun axis, capable of quickly detecting sticking of a welding tip to an object of welding before movement of a robot, without adversely affecting the object. A load applied to a servomotor for driving a welding tip of a welding gun is detected by an observer. An abnormal load signal is output when the estimated disturbance load deviates from a range defined by a reference &bgr; (&bgr;>0). A determination as to whether or not the estimated disturbance load is larger than the reference value +&bgr; is not made during a period of time from the start of a closing motion of the welding gun until the estimated disturbance load becomes smaller than a set value &agr;. When the welding tip is stuck to a workpiece, a negative estimated disturbance load smaller than −&bgr; is derived and an abnormal load Signal is outputted.

Abstract: A collision detecting method, in which a collision of a driven body driven by a servomotor is detected by a disturbance estimating observer. The method obtains a disturbance component which can be known in advance, subtracts the disturbance component from an input torque to generate a modified torque, and inputs the modified torque to a distrubance estimating observer.

Abstract: A method of obtaining a very robust adaptive PI control method irrespective of fluctuation of parameters of a control object, wherein (speed command r-actual speed y) is used as a state variable Suf. Estimated values J*, A*, Gr*, and C* of inertia, coefficient of dynamic friction, gravitational disturbance depending on a robot angle, and Coulomb's friction, respectively, are obtained and a torque command .tau. is obtained in accordance with the following equation so as to cancel an error between each of the estimated values and its actual value to zero..tau.=K2.multidot.Suf+(K1/s).multidot.Suf+J*.multidot.r'+A*.multidot.y+Gr*. multidot.sin .theta.+Cf*+.tau.1.The first and second terms of the right side of the above equation are identical with a torque command obtained by the PI control. Furthermore, r' represents an acceleration of command; .theta. represents a rotational angle of a robot arm; and .tau.1 represents a switching input corresponding to miscellaneous disturbance.

Abstract: A control method capable of preventing vibration of a control object and making a band sufficiently high in controlling a robot or a machine tool in semi-closed loop. A torque command u" is obtained by executing a feedback-control of the servomotor using the position and speed of a servomotor in the same manner as in the conventional method. A displacement amount d1 between the motor position and the position of the control object and a displacement speed d2 are estimated by an observer. A corrected torque command u is determined by subtracting, from the torque command u", values obtained by multiplying the displacement amount d1 and the displacement speed d2 by the adjustable gains (.alpha.-KpK1) and (.beta.-K1), respectively. The servomotor is driven based on the corrected torque command u thus obtained. There can be obtained effects equivalent to those that would be obtained when a feedback-control is performed using the position and speed of the control object. The adjustment values .alpha. and .beta.

Abstract: A control method for a servomotor which is controlled by a control system with a position control loop and a speed control loop, such that a degree of flexibility specified on working coordinates, on which the servomotor is situated, is converted into servo gains Kp and Kv for individual axes of the servomotor, and the servomotor is driven according to the converted servo gains Kp and Kv, whereby the degree of flexibility can be set on the working coordinates, and a driven body can be moved manually.

Abstract: A robotic arm is driven by a servomotor which is controlled through position and speed control loops. The position and speed control loops are adaptable in response to a flexible position control. Upon receipt of a flexible control command, a position gain and a proportional gain of the speed control loop are lowered in accordance with a set degree of flexibility. The output of an integrator of the speed control loop is also limited to a set clamp value. As a result, a torque command for controlling the servomotor never achieves an expressly large value even if a position deviation increases. In case an obstacle is placed in the transfer path of the robotic arm, the arm can be moved by human power to avoid the obstacle.

Abstract: A collision detecting method for quickly securely detecting a collision between a driven body driven by a servomotor and an obstacle by using an observer, thereby preventing machine components from be damaged by the collision. An estimated disturbance torque (y) is obtained in accordance with a torque command (I) and an actual motor speed (.theta.) by means of the observer (50) formed of blocks (S1 to 54) having transfer functions (Kt/J, K3, K4/S, 1/S), which depend individually on a torque constant, inertia, and parameters corresponding thereto, and a multiplier (61) having a transfer function (J.multidot.A) equivalent to the product of the inertia and a unit system conversion constant.

Abstract: A collision detecting method for quickly securely detecting a collision between a driven body driven by a servomotor and an obstacle by using an observer, thereby preventing machine components from being damaged by the collision. An estimated distrubance torque (y) is obtained in accordance with a torque command (I) and an actual motor speed (.theta.) by means of the observer (50) formed of blocks (51 to 54) having transfer functions (Kt/J, K3, K4/S, 1/S), which depend individually on a torque constant, inertia, and parameters corresponding thereto, and a multiplier (61) having a transfer function (J.multidot.A) equivalent to the product of the inertia and a unit system conversion constant.