Electricity: motive power systems – Open-loop stepping motor control systems
Patent
1998-04-02
1999-08-24
Ip, Paul
Electricity: motive power systems
Open-loop stepping motor control systems
318685, 324429, 324433, 340636, 3542891, 35428912, H02P 822
Patent
active
059428724
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND INFORMATION
From the article "The Stepping Motor and the Duration of Its Step," Feinwerktechnik und Messtechnik 99(7-8):327-332, 1991, by Klaus Mayer, a stepping motor is known which has a permanent-magnet rotor arranged on a motor shaft, the rotor rotating within the rotating magnetic field of two coil systems. For the control of this motor, the coils are acted on alternately by current. For each sampling of action of the current, the rotor places itself in a given stable position. Movement from one such stable position into the following stable position in the direction of rotation of the rotor for another sampling of action of the current is referred to as a step. In this connection, one distinguishes between different types of stepping operation. There are known in this connection full-step operation, half-step operation, and micro-step operation. Micro-step operation is characterized by the fact that the current samplings for the coils of the stepping motor extend in discretely approximated sinusoidal curves. The division of the rotation of the rotor into individual micro-steps together with a maximum speed of revolution with which the rotor is to rotate gives the maximum control-step clock frequency with which the stepping motor is to be controlled. For example, a micro-step of 1/32.degree., referred to the pointer shaft of a geared stepping motor, with a maximum angular speed of rotation of the pointer of 400.degree./sec results in a control-step clock frequency of 12.8 kHz for the stepping motor.
SUMMARY OF THE INVENTION
The method of the present invention for controlling a stepping motor has the advantage, as compared to the related art, that, despite a low control-step clock frequency, a higher control resolution in the form of smaller partial steps is obtained, as a result of which the noise developed by the stepping motor is less, particularly at low speeds of rotation. Furthermore, the movement of a pointer which is driven in rotation by the stepping motor is more uniform. Furthermore, the expense for the circuitry is less, since circuits which provide a lower control-step clock frequency are generally less expensive and more reliable. A control circuit which is adapted to be connected in front of the stepping motor and is as a rule a microcontroller is thus relieved by the method from tasks which require lengthy calculating times.
If the first partial step is carried out with the step timing, the construction of the circuit is thereby simplified, since the step timing itself can serve for the triggering of the first partial step.
If the partial steps are carried out with a constant time delay after each first partial step, a particularly low circuit expense results for the production of the partial-step timing pulses.
If the time delay between the partial steps is decreased with increasing step clock frequency, there is thus obtained a constant number of partial steps for each full step, as a result of which there is no reduction in the resolution into partial steps upon an increase in the step timing frequencies.
The use of a phase-locked loop (PLL) circuit for the production of the partial-step clock frequency is particularly advantageous, since, on the one hand, there is thereby obtained the automatic following up of the partial-step clock frequency with the full step frequency and, on the other hand, divider-unrelated frequency ratios between partial-step clock frequency and step clock frequency can also be obtained.
The device of the present invention for controlling a stepping motor has the advantage, over the related art, that the control device need have only a low control step clock frequency and that, in this connection, nevertheless a higher control resolution in the form or smaller partial steps takes place, as a result of which the noise developed by the stepping motor is less, particularly at low speeds of rotation.
A monostable flip-flop constitutes a particularly economical means of obtaining a constant period of delay between the partial-step pulses.
BRIEF DE
REFERENCES:
patent: 4161679 (1979-07-01), Kohn et al.
patent: 4584512 (1986-04-01), Pritchard
patent: 4612841 (1986-09-01), Yoshikawa
patent: 4694410 (1987-09-01), Murata
patent: 5426371 (1995-06-01), Salley et al.
patent: 5521671 (1996-05-01), Aoki et al.
"The Stepping Motor and the Duration of Its Step," Feinwerktechnik and Messtechnik 99(7-8): 327-332, 1991 by Klaus Mayer*.
Herzog Bernhard
Kizler Alfred
Steger Roland
Ip Paul
Moto Meter GmbH
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