Electricity: motive power systems – Positional servo systems – Plural servomotors
Patent
1984-07-10
1987-02-03
Dobeck, Benjamin
Electricity: motive power systems
Positional servo systems
Plural servomotors
318 51, 318 71, 318 52, 318798, G05B 1132
Patent
active
046410694
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
BACKGROUND OF THE INVENTION
This invention relates to a plural motor changeover control system which, by means of the same control apparatus, controls changeover among a plurality of motors the outputs of which differ.
In a machine tool or the like equipped with a plurality of motors having different outputs, the motors are driven alternatively. By way of example, in a turning center or the like, a turning machining motor is driven when turning machining is performed, thereby to rotate a workpiece at a commanded rotational velocity to carry out the turning operation. When a screw hole, hole or keyway is to be formed after the turning operation, a spindle is positioned at a predetermined point, upon which a motor for rotary tool is driven to rotate the tool, thereby drilling a hole into the stationary workpiece. Since the motor for the turning operation and the motor for the rotary tool are so arranged that while one is being driven the other is not, it has been contemplated to control the motors by a single servo control apparatus. If it were possible to apply such a servo control apparatus commonly for the two motors, the results would be very beneficial as it would make it possible to greatly simplify the arrangement and reduce the cost of the equipment. If the maximum outputs of the turning motor and rotary tool motor were identical, common application of the servo control apparatus would be very simple to achieve. In general, however, the maximum outputs of these motors differ by a wide margin, so that common application is difficult. Even if a servo control apparatus were to be applied to both motors, neither a significant simplification nor a significant reduction in cost would be achieved.
Moreover, in order to achieve such common application, it would be necessary to provide a switching circuit for the signal lines that transmit feedback signals from the motors, in addition to a switching circuit for the power lines that transmit the motor drive signals. These switching circuits use separately installed switching units that rely upon relay circuits. When relays are used, however, it is necessary to provide a power supply for driving the relays. This requires a great amount of space and complicated wiring.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a plural motor changeover control system which makes it possible to commonly apply a control unit with ease, and which is simple in construction and low in cost.
Another object of the present invention is to provide a plural motor changeover control system which has a signal line switching circuit of a simple arrangement, and which is improved to dispense with the need for a driving power supply and a great amount of space.
A plural motor changeover control system according to the present invention is for using a plurality of motors, the outputs of which differ, by successively switching among the motors. The system has a single servo control circuit used in controlling the plurality of motors, and velocity error-amplitude command tables having characteristics corresponding to the plurality of motors the outputs of which differ. A conversion table corresponding to a motor designated for operation from among the plurality of motors is selected, and an amplitude command is fetched from the selected conversion table, which command corresponds to a velocity error, which is a difference between an actual velocity of the designated motor and a commanded velocity. The amplitude command is applied to the servo control circuit to control the designated motor. The system is additionally provided with a signal line switching circuit for switching among, and applying to the servo control circuit, feed back signals from the plurality of motors, the signal line switching circuit being an analog switch.
According to the present invention, an advantage is provided wherein a servo control circuit is commonly applied to enable changeover control of a plurality of motors having different outputs. In addition, to
REFERENCES:
patent: 4257103 (1981-03-01), Suzuki et al.
patent: 4297624 (1981-10-01), Komiya
patent: 4422027 (1983-12-01), Mohlere
patent: 4433275 (1984-02-01), Imazeki et al.
patent: 4464615 (1984-08-01), Rodi
Fujioka Yoshiki
Hirota Mitsuhiko
Dobeck Benjamin
Fanuc Ltd
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