Electricity: motive power systems – Positional servo systems – With particular motor control system responsive to the...
Patent
1991-02-11
1993-03-16
Ip, Paul
Electricity: motive power systems
Positional servo systems
With particular motor control system responsive to the...
318696, 318254, 318653, G05B 1940, H02P 800
Patent
active
051947951
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a drive system for driving a driven member and a control unit for use in the drive system, and more particularly, to a control unit capable of highly efficiently driving an electric motor at a high speed with high torque and of rapidly and precisely positioning the motor to a desired rotational position, and to a drive system capable of driving a driven member with a large driving force and of rapidly and precisely positioning the driven member by use of the control unit.
BACKGROUND ART
A conventional stepping motor is used exclusively to drive a lightweight load. If the conventional stepping motor is so designed as to drive a heavy load, it becomes large in size and hence the inertia thereof increases. In this case, a stepping operation of the motor requires a long time, so that the motor cannot be driven at a high speed. Further, a large electric power is required to start and stop the electric motor upon start and completion of the stepping operation, and hence the energy efficiency is lowed. In addition, if a stepping angle is set to a small value to enhance the precision of positioning in the conventional DC motor, the motor output torque is lowered.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a control unit capable of highly efficiently driving an electric motor at a high speed with high torque and rapidly and precisely positioning the electric motor to a desired rotational position, and a drive system capable of driving a driven member with a large driving force and rapidly and precisely positioning the driven member by use of the control unit.
In order to attain the above object, according to one aspect of the present invention, a control unit is provided, which comprises a position detector for sequentially generating a series of position detection signals with rotation of a rotor of an electric motor; a stepping signal generator for sequentially generating a series of stepping signals; an energization control circuit for energizing and de-energizing exciting coils of the electric motor in response to corresponding ones of the position detection signals and the stepping signals; a driving mode switching circuit for switching a driving mode of the electric motor from a normal driving mode to a deceleration driving mode and then from the deceleration driving mode to a stepping driving mode; and a signal switching circuit for supplying the series of position detection signals in a normal sequence to the energization control circuit in the normal driving mode, supplying the series of position detection signals in a sequence different from the normal sequence to the energization control circuit in the deceleration driving mode, and interrupting supply of the series of position detection signals to the energization control circuit and sequentially supplying the series of stepping signals to the energization control circuit in the stepping driving mode.
According to another aspect of the present invention, a drive system is provided, which comprises an electric motor; a drive unit for driving a driven member with a driving force obtained by amplifying an output of the electric motor; and a control unit for controlling the electric motor; wherein the control unit includes the above-mentioned position detector, energization control circuit, driving mode switching circuit and signal switching circuit, and the driving mode switching circuit is operable to switch the driving mode in accordance with a remaining distance of the driven member to a target position.
Preferably, the drive unit includes a ball screw
ut mechanism. The position detector includes two position detection elements fixed on a stationary armature of the motor separately from each other, these position detection elements being operable to generate a series of position detection signals which are continuous with one another but not superposed on one another. Each position detection elements is disposed at that position at which the element is permitted to g
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patent: 4469995 (1984-09-01), Chiang et al.
patent: 4584506 (1986-04-01), Kaszmann
patent: 4591774 (1986-05-01), Ferris et al.
patent: 4963808 (1990-10-01), Torisawa et al.
patent: 5028073 (1991-07-01), Harms et al.
Bahn Itsuki
Chiba Jiro
Ip Paul
Sekogiken
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