Electricity: motive power systems – Positional servo systems – Plural servomotors
Patent
1996-02-06
1997-07-08
Ro, Bentsu
Electricity: motive power systems
Positional servo systems
Plural servomotors
318600, 318611, 318630, G05D 312, G05D 320
Patent
active
056464959
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a digital servo control for controlling feed shafts of robot arms and machine tools, and more particularly to a tandem control method for controlling a plurality of servo motors to drive a common movable member (i.e. a common axis).
BACKGROUND ART
For a robot or machine tool, sometimes a single drive motor is not good enough to effectively accelerate or decelerate its movable member when such movable member is of large size, or the movable member cannot be moved stably due to the backlash between the motor and the movable member. In such a case, a tandem control is employed, wherein torque commands are given to two motors to control a common shaft by these two motors.
FIGS. 14 through 17 are views showing several examples of tandem control systems based on conventional digital servomechanisms. FIG. 14 shows a first example of the tandem control wherein a movable member is linearly moved. More specifically, a pair of main motor 100 and sub motor 110 is provided to control the drive of a linearly movable rack 120 as a movable member. The main motor 100 transmits a driving force to the rack 120 via a speed reduction device 101 and a pinion 102. Also, the sub motor 110 transmits another driving force to the rack 120 via another speed reduction device 111 and another pinion 112.
FIG. 15 shows a second example of the tandem control system wherein a movable member is rotated. More specifically, a pair of main motor 100 and sub motor 110 is provided to control the rotational movement of a rotary rack 120 as a movable member. Transmission of driving forces from respective motors is made via speed reduction devices 101, 111 and pinions 102, 112 in the same manner as the first example of the tandem control system.
FIG. 16 shows a third example of the tandem control system designed for linearly moving the movable member, wherein the drive of the movable member 121 is controlled by two motors, namely the main motor 100 and sub motor 110 through two screw members 103 and 113 connected to the main motor and the sub motor respectively. The movable member 121 engages with both the two screw members 103 and 113, whose one ends are fixed to the fixing member 122, in order to have its drive controlled through the screw members 103 and 113 which are respectively driven by the two motors.
Furthermore, FIG. 17 shows a fourth example of the tandem control system designed for linearly moving, wherein a movable member 123 is driven by main motor 100 and sub motor 110 via a screw member 104 whose ends are connected respectively to the main motor 100 and the sub motor 110.
FIG. 18 is a block diagram showing a circuit arrangement for performing a tandem control based on a conventional digital servomechanism. The control blocks shown in FIG. 18 constitute a circuit for controlling a machine table 12 by a numerical control unit 1. A main servo motor 6 and a sub servo motor 7 are both connected to the machine table 12 via transmission mechanisms 10 and 10, respectively. Each of servo motors 6 and 7 is driven by a command signal sent from a servo amplifier 4 which is controlled by a current command sent from a digital servo control unit 3. Position feedback Mfb and Sfb (Mfb represents a position feedback of the main servo motor 6, while Sfb represents a position feedback of the sub servo motor 7) and speed feedback Vf1 and Vf2 (Vf1 represents a speed feedback of the main servo motor, while Vf2 represents a speed feedback of the sub servo motor) from servo motors 6 and 7 to the digital servo control unit 3 are made through detectors 8 and 9. For current feedback, current is fed back from each of servo amplifiers 4 and 5 to the digital servo control unit 3. Furthermore, a machine position feedback amount Tfb is fed back from the machine table 12 to the digital servo control unit 3 through a detector 13.
Furthermore, the numerical control unit 1 is connected to the digital servo control unit 3 via a shared RAM 2, to share the data between them.
Moreover, FIG. 19 is a block diagram showing a princ
REFERENCES:
patent: 4065074 (1977-12-01), Anderson et al.
patent: 4289996 (1981-09-01), Barnes et al.
patent: 4591772 (1986-05-01), Hollow
patent: 4841211 (1989-06-01), Neko
patent: 4985841 (1991-01-01), Iwagaya
patent: 5181441 (1993-01-01), Okada
Maeda Kazuomi
Sonoda Naoto
Toyozawa Yukio
Fanuc Ltd.
Ro Bentsu
LandOfFree
Tandem control method based on a digital servomechanism does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Tandem control method based on a digital servomechanism, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Tandem control method based on a digital servomechanism will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2410463