Electricity: motive power systems – Positional servo systems – With particular motor control system responsive to the...
Patent
1995-01-31
1996-09-24
Cabeca, John W.
Electricity: motive power systems
Positional servo systems
With particular motor control system responsive to the...
388815, 318635, 327 66, 330257, 330288, G05B 902, H03F 345
Patent
active
055594166
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a control circuit, in particular for a direct current motor control in positioning systems.
Such a control circuit is known from the publication Siemens Components 27 (1989), No. 2, pages 79 to 82.
Positioning systems equipped with direct current motors are frequently used for keeping a mechanical variable, e.g. a linear movement or a tilting movement, in track with an adjustable electrical voltage. Such positioning systems may be used in an automobile for controlling the position of air duct dampers, or the position of headlights to compensate for variable load conditions. Motor positioning systems are also used in computers in applications such as positioning a magnetic head on a hard disk drive.
FIG. 9 shows a control circuit for positioning systems with direct current motors according to the prior art. The direct current motor to be controlled is connected between the output of a first operational amplifier OP1 and the output of a second operational amplifier OP2. A voltage divider constituted by a first voltage divider resistor R1, a second voltage divider resistor R.sub.2 and a third voltage divider resistor R.sub.3 is connected between a voltage supply V.sub.S and a reference potential GND. The inverting input of the first operational amplifier OP1 is connected to the connecting node between the second voltage divider resistor R.sub.2 and the third voltage divider resistor R3. The non-inverting input of the second operational amplifier is connected to the connecting node between the first voltage divider resistor R.sub.1 and the second voltage divider resistor R.sub.2. The non-inverting input of the first operational amplifier OP1 is connected to the inverting input of the second operational amplifier OP2; the two latter inputs are fed with an input voltage V.sub.IN. Between the outputs of the two operational amplifiers there is connected a direct current motor. Mechanically coupled therewith is a potentiometer R.sub.F detecting the actual value of the rotational position of the motor. This actual value is fed back via a feedback resistor R.sub.R to an input of operational amplifier OP1. This input furthermore is connected via a resistor R.sub.IN to the tap of a nominal value potentiometer R.sub.C.
FIG. 10 illustrates the transfer function of this known circuit according to FIG. 9. Plotted on the abscissa is the input voltage V.sub.IN, whereas the differential output voltage V.sub.OUT is plotted on the ordinate. When the input voltage V.sub.IN is lower than V.sub.1, the differential output voltage V.sub.OUT is negative and in its amount virtually corresponds to the supply voltage V.sub.S. The motor thereby rotates in a first direction, for example in a right-hand rotation. When the input voltage V.sub.IN is continuously increased until it exceeds a threshold value V.sub.1 corresponding to the potential at the connecting site between resistors R.sub.2 and R.sub.3, the differential output voltage V.sub.OUT changes to the value of zero volt. The motor stops. When upon further increase of the input voltage a threshold value V.sub.2 is exceeded, which corresponds to the potential at the connecting site between resistors R.sub.1 and R.sub.2, the differential output voltage V.sub.OUT increases to a positive value which virtually corresponds to the amount of the supply voltage V.sub.S. The motor then rotates in a second direction, namely in a left-hand rotation in the example assumed.
A problem of the circuit shown in FIG. 9 is that it displays a linear behavior in the range of the threshold values V.sub.1, V.sub.2 and in practical realization therefore requires an output compensation circuit (Boucherot member). In addition thereto, this circuit involves a sensitive reaction to interference voltages superimposed on the input voltage, especially when V.sub.IN after stopping of the motor is close to one of the thresholds V.sub.1 and V.sub.2.
It is desirable to have a control circuit which involves hysteresis in the switching thresholds V.sub.1 and V.sub.2 and furthermore is adapted to
REFERENCES:
patent: 3656006 (1972-04-01), Bourke et al.
patent: 4290000 (1981-09-01), Sun
patent: 5140591 (1992-08-01), Palara et al.
patent: 5160896 (1992-11-01), McCorkle
Cabeca John W.
Carlson David V.
Donohue Michael J.
SGS-Thomson Microelectronics GmbH
LandOfFree
Direct current motor control circuit in positioning systems does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Direct current motor control circuit in positioning systems, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Direct current motor control circuit in positioning systems will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1931113