Electricity: motive power systems – Positional servo systems – Multiple mode systems
Patent
1993-10-13
1996-05-21
Martin, David S.
Electricity: motive power systems
Positional servo systems
Multiple mode systems
318603, 318461, G05B 1118
Patent
active
055192971
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spindle positioning method for enabling a spindle motor to stop at a desired position stably in a shortest possible period of time, by making the best use of the decelerating capability of the spindle motor.
2. Description of the Related Art
In a known method for stopping a rotating spindle motor at a desired position, the motor is first decelerated to a base speed for positioning control during a speed control stage; then, a control mode for the spindle motor is switched from the speed control mode to a position control mode; and a position loop control is carried out using the difference between a commanded stop position and a current position as a position deviation.
In order to shorten the time required for the positioning in the known method, the value of position gain may be increased. If, however, the position gain is increased disregarding the accelerating/decelerating characteristics of the spindle motor, the spindle motor may fail to follow the speed command, causing an undesired overshoot. Conversely, if the value of the position gain during the position loop control is set too small for fear of the occurrence of overshoot, the time required for the positioning will inevitably be prolonged. Thus, it is difficult to prevent overshoot and achieve quick positioning at the same time.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a spindle positioning method which is not only capable of preventing an undesired overshoot, but also capable of positioning a spindle of a machine tool at a desired stop position in a short time.
To achieve the above object, according to the present invention, when a fixed-position stop command is generated while operation of a spindle motor is controlled in accordance with speed control, the rotational speed of the spindle motor is reduced, according to the speed control, to a speed lower than or equal to a maximum rotational speed defining a constant torque region. A value specifying the relation between a present position and a commanded stop position of the spindle motor with respect to one revolution of the motor is set as an initial position deviation when the motor speed is reduced to the speed lower than or equal to a base speed, and an operation control mode for the motor is switched from the speed control mode to a position control mode. Linear acceleration/deceleration control is carried out thereafter until the commanded stop position is reached.
Further, the present invention provides a method of positioning a spindle at a desired rotational position, comprising the steps of: detecting the speed of a spindle motor and a rotational position of the spindle motor with respect to one revolution of the spindle when the speed of the spindle motor becomes lower than or equal to a base speed; obtaining a minimum amount of movement required if the spindle motor is decelerated along a deceleration line set based on the detected speed, as well as a distance from the detected rotational position to a target stop position; successively adding an amount of movement corresponding to one revolution of the spindle to the distance until the distance becomes greater than the minimum amount of movement and setting the obtained value as a position deviation; carrying out a position loop control, based on a speed command obtained, by multiplying the square root of the position deviation by a set position loop gain; and controlling operation of the spindle motor based on the speed command.
Preferably, the minimum amount of movement is obtained by dividing the square of the detected speed by a parameter value preset according to the deceleration line, and the position loop gain equals the square root of the parameter value.
Furthermore, the present invention provides a method comprising the steps of: (a) reducing the rotational speed of a spindle motor to a speed N, lower than or equal to a maximum rotational speed N1 which defines a constant torque region, when a f
REFERENCES:
patent: 4170865 (1987-12-01), Higomura
patent: 4965501 (1990-10-01), Hashimoto
patent: 5173647 (1992-12-01), Hashimoto
patent: 5194788 (1993-03-01), Hashimoto
EPS Search Report filed May 25, 1994.
Fukukura Masaaki
Kono Shinichi
Fanuc Ltd.
Martin David S.
LandOfFree
Spindle positioning method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Spindle positioning method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Spindle positioning method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2040467