Control system for an automatic door

As a driving power source for an automatic door, a brushless D.C. motor is employed, and the position and the speed of a door member are determined by making use of detection pulses issued from magnetic pole position detectors which are associated with the brushless D.C. motor without providing any additional detector means separately. On the basis of the current position and the current speed of the door as determined from the detection pulses and of a programmed sequence of opening and closing operations for the door as stored in a control system, the opening and closing movements of the door member are controlled.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a control system for controlling operation 
of an automatic door. 
2. Description of the Prior Art 
Heretofore, as a control system for an automatic door, there have been 
known various systems such as a control system including limit switches 
for detecting the position of a door, a control system in which a rotation 
detector is provided on a rotary shaft of a drive motor or another rotary 
shaft and numerical control of the drive motor is effected on the basis of 
the detected rotational data, a control system in which teeth on a timing 
belt for coupling a drive motor to a door are detected and counted and 
numerical control of the drive motor is effected on the basis of the 
counted data, or the like. 
However, in these known control systems in the prior art, it was 
necessitated to provide any type of door position detector means 
separately from drive means for a door. Hence, the number of component 
parts of the system could not be reduced, and so, it was difficult to 
achieve simplification of the construction and reduction of manufacturing 
costs. 
SUMMARY OF THE INVENTION 
It is a principal object of the present invention to provide a control 
system for an automatic door that is free from the above-described 
shortcoming in the prior art. 
A more specific object of the present invention is to provide a control 
system for an automatic door in which there is no need to provide door 
position detector means separately from drive means for the door and hence 
reduction of manufacturing costs can be achieved. 
The improvements in the control system for an automatic door according to 
the present invention exist in that a brushless D.C. Motor, referred to 
herein as a D.C. brushless motor, is employed as a drive motor for a door, 
and magnetic pole position detection signals generated by a magnetic pole 
position detector inherently provided within a D.C. brushless motor 
circuit are utilized for detecting the door position in a position control 
circuit and for detecting the speed of movement of the door in a speed 
control circuit. 
According to one feature of the present invention, there is provided a 
control system for an automatic door which comprises a D.C. brushless 
motor coupled to a door member via speed reduction means to transmit 
driving power to the door member and adapted to deliver magnetic pole 
position detection pulses. A position control circuit is included 
responsive to the magnetic pole position detection pulses delivered from 
the D.C. brushless motor for determining the position of the door member 
and thereby generating a speed command signal indicating the direction and 
magnitude of the speed of the door member. Also included is a speed 
control circuit responsive to the magnetic pole position detection pulses 
and the speed command signal which applies a drive control signal to the 
D.C. brushless motor so that the motor is driven at such rotational speed 
that the door member is moved at the speed indicated by the speed command 
signal.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In the following, the present invention will be described in greater detail 
in connection to one preferred embodiment of the invention. 
Referring now to FIG. 1, a D.C. brushless motor M is coupled to a driving 
pulley 2 via a reduction gear 1, a door drive belt 4 is wrapped around the 
driving pulley 2 and a driven pulley 3, and a door 5 is connected to the 
belt 4 via a connecting member 6 so that the door 5 can be moved in the 
opening or closing direction by rotating the D.C. brushless motor M in the 
normal or reverse direction, respectively. 
In this D.C. brushless motor M, as shown in FIG. 2, generally armature 
windings 11 form a stator and a field magnet 12 forms a rotor. In 
addition, three magnetic pole position detectors 13 each constructed of a 
Hall effect element, a magnetic reluctance element or a photoelectric 
element are disposed on the stator at an angular interval of 120.degree. 
(only one magnetic pole position detector 13 is illustrated in FIG. 2), so 
that three pulse trains having their phases shifted by 120.degree. from 
one another are delivered from these magnetic pole position detectors 13 
in response to rotation of the field magnet 12 forming the rotor. In a 
control circuit section enclosed by a chain line frame C, the angular 
position and rotational speed of the field magnet 12 forming a rotor are 
determined on the basis of the magnetic pole position detection pulses P 
consisting of these three pulse trains, and a drive control signal is 
applied to the D.C. brushless motor M on the basis of the position and 
speed data. In the D.C. brushless motor M, a power switch circuit 10 
associated therewith (See FIG. 2) switches D.C. drive currents fed to the 
respective armature windings 11 in accordance with the drive control 
signal to generate the necessary drive torque. 
The control circuit section C comprises a position control circuit 7, a 
speed control circuit 8 and a D.C. power supply circuit 9 which can be 
switched on and off externally of the control circuit section C. The 
magnetic pole position detection pulses P delivered from the magnetic pole 
position detectors 13 in the D.C. brushless motor M are input to the 
position control circuit 7 and the speed control circuit 8. 
The position control circuit 7 has its power supplied from the D.C. power 
supply circuit 9, and is connected to an access sensor switch SW such as a 
door mat switch, an infrared sensor, a capacitive sensor, etc. which 
senses the presence of a human body or other object at an automatic door 
and issues an actuation signal for the position control circuit 7. This 
position control circuit 7 determines the direction of rotation of the 
motor M on the basis of the phase relations among the three pulse trains 
delivered from the respective magnetic pole position detectors 13, and 
also determines the position of the door 5 by counting up or counting down 
the pulses depending upon the direction of rotation (starting from a 
reference position of the door 5). It is to be noted that the pulses 
forming the three pulse trains are generated for every 1/3 revolutions or 
1/6 revolutions of the rotor depending upon whether pulses of one polarity 
or pulses of both polarities are taken into consideration. 
Within the position control circuit 7 is stored a program consisting of a 
predetermined sequence of operations for opening and closing the door 5 in 
response to the actuation signal sent from the access sensor switch SW. 
Hence, after the access sensor switch SW has sensed presence of an object 
at the automatic door, the position control circuit 7 issues a speed 
command signal indicating the direction and magnitude of the desired speed 
of the door 5 on the basis of the stored sequence program and the 
determined current position of the door 5, and this speed command signal 
is applied to the speed control circuit 8. 
The speed control circuit 8 calculates and determines the speed of the door 
5 on the basis of the magnetic pole position detection pulses P issued 
from the magnetic pole position detectors 13 in the D.C. brushless motor 
M, and as a result of comparison between the desired direction and 
magnitude of the speed of the door 5 indicated by the speed command signal 
applied from the position control circuit 7 and the current direction and 
magnitude of the speed of the door 5, it determines the necessary 
acceleration of the D.C. brushless motor M and issues a drive control 
signal having a polarity and a magnitude corresponding to the direction 
and magnitude of the necessary acceleration, which is applied to the D.C. 
brushless motor M so that the motor may be driven at such rotational speed 
that the door 5 can be moved at the desired speed indicated by the speed 
command signal. 
In the control system for an automatic door having the above-described 
construction, when an object such as a human body comes close to the 
automatic door, the access sensor switch SW is operated and an actuation 
signal is applied to the position control circuit 7 in the control circuit 
section C. In response to the actuation signal, the position control 
circuit 7 generates a speed command signal on the basis of a stored 
program of the predetermined sequence of operations and the current 
position of the door 5 on the basis of the magnetic pole detection pulses 
P, and applies the speed command signal to the speed control circuit 8, 
which in turn applies a drive control signal to the D.C. brushless motor M 
to open and close the door 5 according to the predetermined sequence of 
operations. 
During the movement of the door 5, the pulses delivered from the magnetic 
pole position detectors 13 in the D.C. brushless motor M are applied to 
the position control circuit 7 as well as to the speed control circuit 8 
for use in determining the current position and the current speed of the 
door 5. 
In addition, owing to the employment of the D.C. brushless motor, the buzz 
noise generated by an A.C. motor in the automatic door in the prior art 
can be eliminated, and thereby noises generated upon opening and closing 
the automatic door can be reduced. Moreover, since control of rotational 
speed and torque of a D.C. brushless motor is easily achieved, 
controllability of the opening/closing speed of the automatic door is 
excellent. In the case of employing an AC/DC converter as the D.C. power 
supply circuit 9, even in an area of a foreign country where the A.C. 
voltage of the commercial power line is different from that in Japan, the 
control system according to the present invention can be adapted to the 
different A.C. voltage in a relatively simple manner only by modifying the 
circuit of the AC/DC converter. 
The principal advantage of the present invention resides in that owing to 
the use of a D.C. brushless motor as a drive source, the detection pulses 
issued from the magnetic pole position detectors which is inherently 
associated with the motor for controlling rotation of the motor, can be 
utilized for determining the position of the door, hence there is no need 
to provide a position detector for the door separately from the drive 
motor, thus the number of component parts are reduced, and thereby 
reduction of manufacturing costs are realized. 
While the principle of the present invention has been described above in 
connection to one preferred embodiemnt of the invention, it is intended 
that all matter contained in the above description and illustrated in the 
accompanying drawing shall be interpreted to be illustrative and not as a 
limitation to the scope of the invention.