Electricity: motive power systems – Positional servo systems – With particular motor control system responsive to the...
Reexamination Certificate
1999-08-27
2001-03-20
Ip, Paul (Department: 2837)
Electricity: motive power systems
Positional servo systems
With particular motor control system responsive to the...
C318S132000, C318S254100, C318S689000
Reexamination Certificate
active
06204625
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a driving apparatus for stepping motors which are employed in office automation devices, information equipment and the like. More particularly, it relates to a driving apparatus which can provide stepping motors with accurate positioning control.
BACKGROUND OF THE INVENTION
A conventional driving apparatus of stepping motors is disclosed in the Japanese Patent Application non-examined publication No. H06-343294.
FIG. 4
shows a block diagram of the conventional driving apparatus.
In
FIG. 4
, driving circuit
302
magnetizes sequentially the coils of two-phase stator of stepping motor
301
, thereby driving motor
301
in a stepping manner. Up-down counter
351
counts an instruction signal, i.e. a stepping signal, which drives motor
301
in a stepping manner. Read-only-memories (ROM)
352
and
353
receive the count values by counter
351
, and output prerecorded magnetizing-signal-data responsive to the counted value. Digital to analog converters (D/A converters)
354
and
355
receive the digital magnetizing signal data from ROMs
352
and
353
, convert the data into analog voltage data, and finally output the analog data into driving circuit
302
. Driving circuit
302
receives voltage signals from D/A converters
354
and
355
, amplifies the voltage signal, and applies the resultant voltage to motor
301
, whereby motor
301
can be driven as described above.
In the structure discussed above, the data stored in ROMs
352
and
53
are set to draw a pseudo-sine-wave so that a number of steps required rotating the motor one turn increases, thereby narrowing a step angle per step. As a result, the motor rotates smoothly.
However, in the conventional structure discussed above, irregular torque such as detent torque affects the operation whereby accurate positioning control of the motor cannot be expected. The motor produces toque in order to maintain the original position against outside torque that tries to rotate the rotor without magnetizing the stator coils. The maximum value of this torque is called detent torque.
When an encoder is coupled to motor
301
so that rotating information of motor
301
is fed back to a control circuit, i.e. closed-loop-positioning-control is provided, an accurate positioning can be realized; however, it requires a complicated circuit.
SUMMARY OF THE INVENTION
The present invention addresses the problem discussed above, and aims to provide a driving apparatus of stepping motors with the same accuracy inherent in an encoder, lower noise as well as less vibrations, and a simple circuit structure.
The driving apparatus of stepping motors of the present invention comprises the following elements:
a stepping motor, an encoder, a control circuit and a driving circuit.
The encoder detects the mover position of a stepping motor. The control circuit outputs a pseudo-sine-wave-signal to be synchronized with a clock signal, when an instruction pulse signal is provided. The pseudo-sine-wave-signal is used for driving the stepping motor in a micro step manner. The control circuit halts outputting the pseudo-sine-wave-signal, when a mover-position-signal is provided from the encoder.
The driving circuit amplifies the pseudo-sine-wave-signal to drive the stepping motor.
The construction discussed above allows the driving apparatus to control the spin of motor at the same accuracy inherent in the encoder, whereby positioning accuracy by micro-step driving can be increased and positional displacement due to the irregular torque can be eliminated. As a result, smooth driving is achieved, and noises as well as vibrations can be reduced.
REFERENCES:
patent: 4223261 (1980-09-01), White
patent: 4710691 (1987-12-01), Bergstrom et al.
patent: 4746843 (1988-05-01), Taenzer
patent: 5602681 (1997-02-01), Nakayama et al.
patent: 58-90614 (1983-05-01), None
patent: 6-343294 (1994-12-01), None
patent: 9-219988 (1997-08-01), None
patent: 10-174497 (1998-06-01), None
Ip Paul
Matsushita Electric - Industrial Co., Ltd.
Ratner & Prestia
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