Abstract: A spindle positioning method for high-speed positioning of a spindle by making the best use of the decelerating capability of a spindle motor. When a fixed-position stop command is generated while the operation of the spindle motor is controlled according to speed control, the motor rotation speed is reduced in accordance with the speed control to a speed N lower than or equal to a maximum rotational speed N1, which defines a constant torque region, and a control mode is switched from the speed control mode to position control mode at a point where the rotational speed is reduced to the speed N. Simultaneously, a value specifying the relation between the present position and target stop position of the motor with respect to one revolution of the spindle is set in an error counter as an initial position deviation.

Abstract: A slip frequency control method for induction motors, capable of achieving accurate control and excellent in control response.To effect determination of a slip frequency (fs) and an excitation magnetic flux frequency (.omega.0) by software processing to reduce a control error and a control delay caused if hardware elements are employed for the determination of these parameters, a vector control processor divides, in a speed control routine (101-104), the sum of a slip frequency, obtained by dividing the product of a secondary current command (I2) and a proportional constant (K2) by an excitation magnetic flux command (.PHI.), and a remainder (.alpha.') in the preceding routine by a routine executing frequency (CV), so as to derive a slip amount (A) and a remainder (.alpha.) in the present routine. In a current control routine (201 to 205) executed at intervals of a period shorter than that of the speed control routine, the processor divides the sum of the derived slip amount and the remainder (.beta.

Abstract: A main spindle rotation control method capable of preventing a workpiece from being twisted during the delivery of the workpiece between two main spindles of a machine. When the rotating speeds of first and second main spindles (100, 200) reach a synchronous rotating velocity as a result of a speed loop control executed by velocity control sections (111, 211) of first and second spindle control circuits (110, 210), position loop control is executed by position control sections (112, 212) of these control circuits, and each main spindle is driven to be decelerated in accordance with the rotational phase of each main spindle, and the velocity loop control is then executed again, to bring the main spindles to rotate in the same phase and at the same synchronous rotating speed. When the delivery of the workpiece (300) between the main spindles is started under this condition, integral control in both the velocity control sections is invalidated.

Abstract: A spindle rotation control method is provided capable of driving two spindles of a machine at the same speed with the same rotational phase. In response to a synchronizing control command from a numerical control apparatus, speed control is performed based on first and second speed commands calculated by using equations represented as a function of a synchronous speed command and parameters determined by the arrangement of a spindle rotational control system. When rotational speeds of the spindles reach the synchronous (same) rotational speed, first and second position deviation quantities corresponding to the synchronous rotational speed are calculated by using an equation represented as a function of a position control gain, and speed commands are converted into first and second moving commands, so as to perform position control loop processing based on the moving commands and the first and second spindle rotational quantities, and speed control based on a position control loop output.

Abstract: A control unit capable of driving a compound lathe so that an end face of a rotating workpiece can be tapped. The control unit (100) comprises first and second control circuits (110, 120) for controlling the rotation of first and second spindles (10, 20) respectively fitted with the workpiece (60) and a tapper (70). At start of tapping operation, the second control circuit executes position loop control in accordance with a deviation (.epsilon.) between position feedback signals (PCC1, PCC2) related to the two spindles, thereby equalizing rotational speeds of the two spindles, and then causes the second spindle to rotate at a speed higher than that of the first spindle by a tapping speed in accordance with the deviation (.epsilon.

Abstract: In a machine tool having first and second spindles, which are connected to respective spindle motors and control circuits each control circuit including a velocity controller and a position controller, and which simultaneously grasp the same workpiece, in which state the workpiece is subjected to machining. At such time, a digital velocity command provided by, e.g., a numerical control unit, is supplied to the two spindles simultaneously, switches for isolating the position controller from the velocity controller at each spindle is controlled at the respective spindle, a synchronous operation mode, which changes over the velocity command to a position command, is established, and the digital velocity command value is processed as a position command, whereby the two spindles are subjected to identical positional control. As a result, the rpm's of the spindles are synchronized and the workpiece can be machined and separated into two parts without subjecting it to excessive force.