Automatic door control system

An automatic control system for controlling the operation of a sliding door system employs an electric motor for driving the sliding door system. An encoder is mounted to the shaft of the motor for generating signals which are decoded to detect the operational position of the sliding door system. A clock paced sequential logic circuit produces speed and directions signals in accordance with the detected operational position to control the speed and direction of the electric motor. Means are provided for recording the last stop position and slowing the sliding door system prior to reaching the last stop position. Safety means are provided to de-energize the motor in the event of malfunction of the motor speed control. The system also includes a reduced opening stop feature and a means for automatically establishing a sliding door reference position.

BACKGROUND OF THE INVENTION 
This invention relates to automatic sliding door systems of a type wherein 
a door panel or a pair of cooperating panels are driven between opened and 
closed positions along a linear path. More particularly, this invention 
relates to a sliding door system employing an automatically controlled 
direct current motor which provides a rotary drive for driving one or more 
sliding doors. 
In automatic conventional sliding door systems employing a pair of 
cooperating doors which open and close in tandem along a linear track, an 
electric motor functions as the prime mover of the doors. The doors are 
connected to a upwardly disposed tooth belt which is suspended between a 
pair of pulleys. The rotary drive of the motor is translated into linear 
motion of the doors. Header mounted switches or other microswitches 
positioned along the track are conventionally employed to sense the actual 
position of at least one of the doors and to employ the door position 
information to control the operation of the motor. The present invention 
is a new and improved automatic door control system which does not require 
header mounted switches or microswitches to determine the actual position 
of the doors. 
BRIEF SUMMARY OF THE INVENTION 
Briefly stated, the invention in a preferred form is an automatic control 
system for a sliding door system of a type wherein at least one door is 
moved along a linear path between closed and opened positions by means of 
the rotary drive of an electric motor. The control system employs a motor 
which produces bidirectional multispeed rotary drive. A motor control unit 
controls the direction and speed of the motor means and produces dynamic 
braking in the motor. A position control unit responsive to the rotary 
drive of the motor determines the linear position and direction of 
movement of a sliding door driven by the motor and produces position 
signals indicative thereof. A sensor detects an activating event and 
produces a corresponding operate signal. A motion control unit responsive 
to the position signals and the operate signal sequentially controls and 
paces the operation of the sliding door system by transmitting direction 
and speed signals to the motor control unit. In a preferred form, an 
encoder in the form of a four-slot rotor and two reflective sensors are 
mounted to the drive shaft of the motor. The position control unit employs 
signals generated by the encoder to determine opening and closing check 
zones and a closed position of the sliding door system and to produce 
corresponding signals indicative thereof. The motion control unit employs 
an eight-state, clock paced sequential logic circuit to generate direction 
and speed signals in accordance with signals produced by the position 
control unit. The motor control unit employs a pulse width modulator, a 
dynamic braking resistor, and a switching power transistor to selectively 
control the speed and direction of the motor and to brake the motor. 
The motor control unit includes a speed control. The motor is de-energized 
on malfunction of the speed control. A reduced opening feature to 
adjustably limit the linear opening of the door is also provided. A memory 
records the last position at which a door stops and controls the closing 
speed of the door in relation to the last stop position. A re-opening 
feature is provided so that the door may be re-opened in the event that 
the door is stopped by an obstacle. Automatic means are provided to 
establish a reference open position. The motor operates at selective 
opening and closing speeds in accordance with linear position of the 
sliding door system. 
A method for automatically controlling the operation of a sliding door 
system comprises driving the sliding door system by means of the rotary 
drive of a multispeed bidirectional motor and generating signals from the 
rotary drive. The operational position of the door system is detected by 
means of decoding the signals generated by the rotary drive of the motor 
and producing corresponding operational position signals. The method 
includes generating corresponding motor speed and motor direction signals 
by processing the operational position signals by means of a clock paced, 
timer controlled, sequential logic circuit, and selectively controlling 
the speed, direction, and braking of the motor in accordance with the 
speed and direction signals. 
The method for controlling a sliding door system includes the steps of 
recording the last stop position of the sliding door system and slowing 
the sliding door system prior to reaching the last stop position. The 
method includes automatically establishing a reference position of the 
sliding door system. 
An object of the invention is to provide a new and improved automatic 
control system for a sliding door system. 
Another object of the invention is to provide a new and improved automatic 
control system for a sliding door system which does not require header 
switches or microswitches for sensing the actual position of a door. 
Another object of the invention is to provide a new and improved automatic 
door control system incorporating an automatic speed control and having 
means for disabling the motor drive in the event of a malfunction in the 
speed control. 
A further object of the invention is to provide a new and improved 
automatic door control system having means for automatically establishing 
a reference position for the sliding door system. 
A yet further object of the invention is to provide a new and improved 
automatic door control system which operates in an efficient, reliable, 
and safe manner and wherein the last stop position of the door system is 
recorded and used as a reference position in the next closing sequence. 
Other objects and advantages of the invention will become apparent from the 
drawing and the specification.

DETAILED DESCRIPTION OF THE INVENTION 
With reference to the drawing wherein like numerals represent like parts 
throughout the several figures, an automatic door control system in 
accordance with the invention is generally designated by the numeral 10. 
The control system is particularly adaptable for controlling direct 
current motor 12 which provides a rotary drive for driving a sliding door 
system generally designated by the numeral 14. 
Sliding door system 14 is exemplary of a number of sliding door systems 
with which the control system may be employed. Sliding door system 14 
includes a pair of cooperating door panels 16 and 18. Door panels 16 and 
18 are movable for sliding motion along a linear path between a closed 
position wherein the door panels cooperate to close an entranceway and an 
open position (illustrated by dashed lines) wherein the door panels 
retract to opposite sides of the entranceway to provide access to the 
entranceway. The full open position may be established by rubber bumpers 
20 which are mounted on the door jamb 22. Door panel 16 is connected to an 
upper section of a continuous tooth belt 24 and door panel 18 is connected 
to a lower section of tooth belt 24. Tooth belt 24 is suspended between an 
idler pulley 26 and a drive pulley 28. Drive pulley 28 is rotatably driven 
by the DC motor 12 for linearly moving door panels 16 and 18 in 
cooperating opposite directions. The door panels may connect at the top to 
a wheel assembly which slides along a track (not illustrated). The 
foregoing sliding door system 14 is of a conventional form which is set 
forth for purpose of illustrating a preferred application for the 
invention herein and should not be deemed a limitation of the invention. 
The present invention is also adaptable for incorporation into a sliding 
door system employing a single sliding panel. 
A pulse encoder 30 is mounted to the drive shaft of motor 12. In preferred 
form, encoder 30 employs a four-slot rotor coupled to the drive shaft and 
two reflective sensors to generate trains of position pulses, X and Y. The 
two sensors are positioned so that the X and Y signals appear in 
quadrature allowing for the detection of direction of movement of the 
drive shaft of motor 12, and consequently the direction of movement of 
door panels 16 and 18 of the sliding door system. 
A position control unit 32 processes the X and Y signals and generates 
various signals which are indicative of the operational position of the 
door panels 16 and 18. An OCK signal indicates that the doors are opening 
in a check speed zone or slow-down zone, a CCK signal indicates that the 
doors are closing in a check speed zone or slow-down zone, a CP signal 
indicates that the doors are in the closed position, and a ROS signal 
indicates that the doors are opening in a reduced opening mode. A clock 34 
generates a train of clocking pulses. The clocking pulses are employed by 
the position control unit 32 to generate a RATE signal which is indicative 
of the speed of motor 12. 
A motion control unit 36 receives the OCK, ROS, CCK, CP, and RATE signals 
and generates speed and direction signals for a motor drive unit 38. The 
motion control unit 36 receives an OP signal to initiate an opening cycle. 
The OP signal is generated by a sensor 40 which detects an activating 
condition such as movement or presence in a specified area or the OP 
signal may be generated by a safety sensor 42. The motion control unit 36 
also receives an RO signal from a reduced opening switch 44 and a BO 
signal from breakout switches 46. 
An initialization circuit 48 monitors the power supply and generates a 
power on/off reset signal (POR) and an initialization signal (INIT) for 
transmittal to the motion control unit 36. Clocking pulses from clock 34 
are also transmitted to the motion control unit 36. The motion control 
unit 36 generates a DS signal indicative that the doors are in a stopped 
mode. The DS signal is transmitted to the position control unit 32 for 
redetermination of the closed door reference position. 
The motion control unit 36 generates direction command signals F and R and 
speed level signals A and B. The F, R, A, and B signals are transmitted to 
the motor drive unit 38 which has circuitry for controlling motor 12. An 
enabling SWM signal is transmitted from the motor drive unit 38 to the 
motion control unit 36. The SWM signal functions to permit the control 
system to operate only if the speed control circuitry in motor drive unit 
38 is operational. 
Control system 10 is adapted for controlling a sliding door system such a 
system 14 and functions to accomplish operational objectives, safety 
objectives, and initialization procedures. A further detailed description 
of control system 10 including the operation thereof may best be 
understood by reference to a detailed description of a preferred 
operational sequence of sliding door system 14. Door panels 16 and 18 move 
in opposite directions from a closed position wherein the panels cooperate 
to close off an entranceway to an open position wherein the panels retract 
to a full open position. For purposes of discussion, the full open 
position is defined as the linear position where the extreme vertical 
edges of the panels abut against bumpers 20. In the closed position, 
vertical edges of the panels converge to abut each other. For purposes of 
illustration, it will be assumed that the panels are centrally disposed 
relative to the entranceway, are substantially identical, and are 
equidistant from a central vertical axis at any given instant in the 
operation of the sliding door system. Under such circumstances, the 
sliding door system can be illustrated by reference to the edge of one of 
the door panels and the sliding door system may be conceptually reduced to 
reference to a single panel or door. The movement of the sliding door 
system 14 between the opened and closed positions results in the 
longitudinal displacement of the door edge a distance D between the door 
fully opened (DFO) position and the door fully closed (DFC) position. The 
linear position of a door edge at the DFO and DFC positions is illustrated 
by vertical lines in FIG. 1. 
In the normal condition, the door may be viewed as in the DFC position. 
Upon the sensing of movement at the entranceway or the presence of a 
person or other activating event, the door starts moving to the DFO 
position. The initial acceleration of the door is determined by the 
current limit of motor 12 as established by the motor drive 38. When the 
door edge is at a preset distance from the DFO position, the moving door 
is slowed by means of dynamically braking the motor. The dynamic braking 
continues until the speed of the door (as measured by the motor speed) 
drops below a pre-established rate. At the pre-estabished rate, the motor 
is restarted in the driving mode at a relatively low check speed. The 
linear door movement continues at a low check speed until the extreme edge 
of the door contacts the bumper 20. The motor continues to be driven at a 
low preset current limit for about one second, and the motor is then 
turned off. The door is in the DFO position. Typically, the normal opening 
speed is approximately 2 feet/sec and the opening check speed is 
approximately 1/6 feet/sec. 
The door remains in the DFO position as long as the system activating event 
exists. When the activating event no longer exists, a time count is 
commenced. When the time count elapses, the door will commence moving in 
the closing direction toward the DFC position. At a predetermined distance 
from the DFC position, the movement rate of the door is slowed by 
dynamically braking the motor. The braking continues until the door 
reaches a preestablished low rate of speed at which time the motor is 
restarted in a driving mode at a low check speed. The movement continues 
at the check speed until the door reaches the DFC position. The motor 
continues to operate for about one second at a limited current and is then 
turned off. Typically, the normal closing speed is approximately 1 
feet/sec and the closing check speed is approximately 1/6 feet/sec. 
In the event of an activating condition, resulting in a consequent 
transmittal of an operate signal, during the sequence when the door is 
moving in the closing direction, the movement rate of the door is 
immediately slowed by dynamically braking the motor 12. The movement of 
the door is then restarted in the reverse opening direction. The 
previously described opening sequence is then continued from the position 
of reversal until the DFO position is attained. 
In the event that during the closing sequence an obstacle prevents the full 
closing of the door, the door edge contacts the obstacle with a limited 
force. If the door is stopped by the obstacle, the door automatically 
re-opens in the previously described opening sequence. During the 
succeeding closing sequence, the door will be slowed before reaching the 
position where the obstacle was encountered. In the event that the 
obstacle is still present, the door will nudge the obstacle at a low speed 
and with a low limited force. In the event that the obstacle remains, the 
motor will be turned off after the elapse of approximately one second. In 
the event that the obstacle is not encountered during the succeeding 
closing sequence, the door will continue to move at a slow speed until the 
door reaches the DFC position. The motor will then be turned off with a 
one second delay. 
During the next succeeding closing sequence, the door operates in a normal 
sequence; i.e., the door brakes and slows shortly before reaching the DFC 
position. The control system essentially records the latest stopping 
position and initiates a slow rate of movement slightly before reaching 
the latest stopping position during the next succeeding closing sequence. 
During the next closing sequence, the door will continue to move at a slow 
rate of speed until the door is forced to stop. The motor is subsequently 
turned off after an approximately one second delay. In the event that the 
door stops at a position which is outside of the slow-down zone as 
recorded from the preceding closing sequence, a re-opening sequence as 
previously described is undertaken. 
Sliding door system 14 may also incorporate additional operational 
features. In a reduced opening mode of operation, the door commences 
opening and after reaching a predetermined position before the DFO 
position, the door slows and stops. The width of the resulting reduced 
opening may be adjustable. The force at the door edge may be adjustably 
limited by limiting the motor current to the motor. Provision of this 
latter feature is advantageous for limiting the force at the door edge to 
a range within the requirements of applicable safety codes. Typically, the 
force at the door edge is set at approximately 28 pounds. 
With further reference to FIG. 2 and FIG. 3, position control 32 processes 
the X and Y signals emanating from pulse encoder 30 to determine the 
actual operational position of the door. Each of the X and Y signals 
assumes the form of a square wave in quadrature as a result of the form of 
the pulse encoder 30. A decoder 50 decodes the X and Y signals and 
generates pulses which are one clock unit in duration coinciding with each 
of the transitions of the X and Y signals. Consequently, in a preferred 
embodiment, a plurality of sixteen equidistant pulses are generated for 
each revolution of the drive shaft of motor 12. The relative position of 
the X and Y signals is indicative of the direction of rotation of the 
motor shaft. Decoder 50 generates output signals which are either a 
countup (CU) signal or a countdown (CD) signal. A countup/countdown 
prescaler 52 processes the CU and CD signals and transmits the processed 
signals to an eight bit up-down counter 54. Counter 54 essentially 
functions as a position indicator. 
With specific reference to FIG. 2, a longitudinal door position scale 
encompasses a length of 256 counts. The door fully open reference, DFO, is 
selected at a small count N1 in order to provide a margin of error to 
compensate for door mechanics and avoid other problems associated with 
placing the reference point at the origin of a number scale. The number N1 
is preset to counter 54 during the process of initializing the system. The 
count N at the DFC position which count is indicative of the maximum 
length of linear travel of the door varies in accordance with the door 
width and other factors related to the closing configuration of the door. 
The closed position, the closing check zone, the opening check zone, and 
the reduced opening stop are defined by subtracting corresponding 
pre-established counts N2, N3, N4, N5 from N. Consequently, each of the 
foregoing quantities is essentially expressed in terms of single variable 
N. 
Digital comparators 56, 58, 60, and 62 are connected to a eight bit P-bus 
64. The comparators compare the content of counter 54 with corresponding 
reference counts to generate the OCK signal, the CCK signal, the ROS 
signal, and the CP signals, respectively. The latter signals are 
correspondingly associated with the previously described opening and 
closing check zones, the reduced opening stop position of the door, and 
the closed position. The variable N is set as the content of an eight bit 
D-latch 66. D-bus 68 connects via full adders 70, 72, and 74 to 
comparators 58, 60, and 62, respectively. Adders 70, 72, and 74 add the 
complements of N3, N4, and N5, respectively to the N-count on D-bus 68 
thereby performing N-N3, N-N4, and N-N5 subtractions, respectively. The 
count on counter 54 is compared with the N2 count on comparator 56 and a 
corresponding open check (OCK) signal is generated. The count on counter 
54 is compared with the count on comparator 58 and a corresponding ROS 
signal is generated. The count on counter 54 is compared with the count on 
comparator 60 and a corresponding CCK signal is generated. The count on 
counter 54 is compared with the count on comparator 62 and a corresponding 
CP signal is generated. 
The input count to D-latch 66 is the same as the input count to P-bus 64. 
D-latch 66 releases the count to D-bus 68 upon transmittal of a latch 
enable (LE) signal. The LE signal is subject to the DS signal which is 
actuated when the door is stopped either in a fully closed position or any 
other position outside of the check zones. As a consequence, the door will 
(in any closing sequence) start slowing down at a constant distance from 
the previously recorded last door stop position. The mode of operation 
adjusts automatically for door width while leaving the check and reduced 
opening zones constant. Also, a re-opening sequence initiated by the door 
encountering an obstacle will cause the door to slow before reaching the 
obstacle (or obstacle position if removed) a second time and then nudging 
the obstacle (if again encountered) for approximately one second before 
being turned off. Counts N2, N4, and N5 are presettable by hex switches 
which allow a operator to adjust within limits the width of the reduced 
opening and of each of the slow-down or check zones. 
Decoder 50 also employs a time count generated by clock 34 and the X and Y 
signals to generate a RATE signal indicative of the actual speed of the 
motor. 
With reference to FIG. 4, the motion control unit 36 includes an eight 
state sequential logic circuit 80, the output of which is processed by an 
output logic circuit 82 to control motor drive unit 38. The input signals 
to the logic circuit 80 are the OP signal, the OCK signal, the ROS signal, 
the CCK signal and the CP signal. The control system condition for each 
state of the sequential eight state output from logic circuit 80 is 
designated in Chart I: 
______________________________________ 
CHART I 
STATE CONTROL SYSTEM CONDITION 
______________________________________ 
S0 DRIVE IS OFF; MOTOR IDLES 
IN CLOSED POSITION 
S1 FORWARD RELAY IS ON 
S2 DRIVE IS ON, DOORS ARE OPENING 
S3 DRIVE IS OFF, FORWARD RELAY IS ON 
S4 DRIVE IS OFF, MOTOR IDLES 
IN THE OPEN POSITION 
S5 REVERSE RELAY IS ON 
S6 DRIVE IS ON, DOORS ARE CLOSING 
S7 DRIVE IS OFF, FORWARD RELAY IS ON 
______________________________________ 
During the operation of the control system, the states of Chart I change 
sequentially in numerical order. Under certain circumstances, the S1 and 
S5 states can be loaded directly. The specific state is determined by the 
combination of the foregoing described input signals and the status of 
various timer systems as will be described below. 
The operation of the logic circuit 80 may be illustrated by reference to 
FIG. 5 wherein a simplified diagram of logic circuit 80 is illustrated. 
When the doors are fully closed, the OP signal is off, the logic circuit 
80 is in a S0 state, and the time on each of the timers has elapsed. The 
control system is in a stable idling state. A presettable four bit counter 
84 receives a count enable signal CE which is in a low state. Counter 84 
communicates with a decoder 86 which generates a corresponding S0, S1, S2, 
S3, S4, S5, S6, or S7 signal in accordance with the instruction from 
counter 84. The foregoin signals are indicative of the state of the logic 
circuit. 
Logic circuit 80 includes AND gates 88, 92, 94, 96, 98, and 100. The CCK 
signal and the S6 signal are applied to AND gate 88. The OCK signal and 
the S2 signal are applied to AND gate 90. An OR gate 102 receives the 
output signals from gates 88 and 90. The OP signal and the S0 signal are 
applied to AND gate 94. Output signals from gates 92 and 94 are each 
applied to OR gate 104. The OP signal and the S6 signal are applied to AND 
gate 96. The OP and S2 signals are applied to AND gate 98. Signals 
emanating from gates 96 and 98 are applied to OR gate 106. An ROS signal, 
an S2 signal, an INIT signal, and a reduced opening (RO) signal are 
applied to AND gate 100 to produce a reopening stop (RSTOP) signal which 
is applied to OR gate 108. A STOP signal generated from AND gate 110, a 
START signal generated from AND gate 112, and a REVERSE signal generated 
from AND gate 106 are also applied to OR gate 108. 
A 555 type reversal timer 114 provides an output which is applied together 
with the output from OR gate 104 to AND gate 112. The trigger of timer 114 
receives the output signal from OR gate 106. The threshold of timer 114 
communicates with a RATE circuit 116 and is activated as long as a 
capacitor charges to a preset voltage. The reset of timer 114 is 
responsive to a POR signal. The output from timer 114 is in a high state 
as long as the POR signal is resetting the timer and the threshold voltage 
is present. 
The OCK and CCK signals are applied to an OR gate 124. The output of OR 
gate 124 is transmitted to the trigger of a 555 type slowdown timer 118. 
The reset of timer 118 is responsive to the POR signal. The threshold of 
timer 118 communicates with a rate circuit including a slowdown adjustable 
potentiometer 122, a charging resistor, and a capacitor in circuit with 
the rate signal so that the threshold of timer 118 is activated as long as 
the capacitor charges to an adjustable pre-established voltage. The output 
signal from timer 118, an INIT signal, and an output signal from OR gate 
102 are applied to AND gate 110. A state sequence timer circuit 126 
generates a TIMER OUT signal which is applied together with a signal from 
OR gate 108 to OR gate 128. The output from OR gate 128 forms a count 
enable (CE) signal for counter 84. 
State sequence timer 126 includes an eight bit counter 129 and a five bit 
counter 130. Timer 129 functions to interpose a short time delay, and 
timer 130 functions to interpose a longer time delay to the logic circuit. 
Counter 129 is paced by clock 34. Counter 129 is reset by an output signal 
from OR gate 132. The S0 signal, S4 signal, and the signal generated by OR 
gate 108 are applied to OR gate 132. A S2 signal, S6 signal, and RATE 
signal are applied to OR gate 134 to produce a signal which resets counter 
130. The output signals from counters 128 and 130 are input to selector 
136. The output from counter 130 also provides a T signal. The S0 signal, 
S2 signal, S4 signal, and S6 signal are applied to OR gate 138. OR gate 
138 provides an output signal to selector 136 for selective activation of 
a switch connecting timers 129 and 130 for interposing various time delay 
intervals into the logic sequence. When the output signal from gate 138 is 
in a high state, the selector switch connects with the signal from timer 
130. 
A CP signal is fed to pulse shaper or monostable component 138. When timer 
118 times out, a signal is transmitted to a pulse shaper or monostable 
component 142. Transition signals from pulse shapers 138 and 142 are 
applied to OR gate 140. The output from OR gate 140 provides a preset 
enable (PE) signal for counter 84. 
When the sliding door system is in the DFC position and the OP signal is 
off, the logic circuit 80 is in the S0 state and timers 114, 118, and 
state sequence timer 126 are out. The control system is in a stable or 
idling state. The count enabling signal (CE) of counter 84 is in a low 
state. When the OP signal changes to a high state, the CE signal goes to a 
high state and counter 84 counts one clock pulse. Decoder 86 is 
transformed to an S1 state. The latter sequence results in setting the CE 
signal low and starts the state sequence timer 126. For the S1 state, 
timer 126 is preset at a short time interval by means of selector 136. 
Typically, the time interval is 32 msec. with a 4 kHz clock. The short 
time interval will also apply to the S3, S5, and S7 states. When timer 126 
times out, the output goes to a high state so that the CE signal from OR 
gate 128 advances counter 84, and decoder 86 is transformed to the state 
S2. The CE signal is returned to the low state provided that no inputs are 
changed. The CE signal starts the state sequence timer 126 for a longer 
time interval; e.g., typically on the order of approximately one second. 
In the S2 state, the motor 12 is activated so that the drive shaft is 
rotating and the RATE signal is present periodically resetting timer 126. 
Consequently, provided the input signals stay unchanged, timer 126 does 
not time out, and the S2 state is maintained indefinitely; i.e., the door 
is continuously opening. The door eventually enters the slowdown or 
opening check zone. Position control 32 senses the position of the door in 
the slowdown zone, and the resulting OCK signal is in a high state. 
Slowdown timer 118 is started. The STOP signal from AND gate 110 is in a 
high state. The resulting count enable CE signal via OR gates 108 and 128 
is now in a high state. Counter 84 advances one clock and decoder 86 is 
now in the S3 state. 
Timer 126 is restarted for another 32 msec. interval. The resulting CE 
signal is again in a high state and the counter advances one clock with 
the decoder being in the S4 state. In the S4 state, the motor drive is 
terminated and the motor 12 is in a braking mode. As long as the speed of 
the motor exceeds a preset value, the RATE signal keeps the slowdown timer 
118 in a high state by periodically resetting the timer. The preset rate 
threshold value may be established by means of an adjustable potentiometer 
122. As the motor decelerates, the time interval between successive rate 
pulses will increase. At a certain speed, slowdown timer 118 will time out 
resulting in the transmittal of a pulse via pulse shaper 142 to the 
counter preset enable line. The preset lines P1, P2, P3, and P4 are set to 
0001 which state will be loaded and appear at the decoder as the S1 state 
thus restarting the opening sequence. The STOP signal will remain in a low 
state due to the low state at the output of slowdown timer 118. The output 
logic will take into account that the system is now operating in the 
slowdown zone and will force the setting of the motor drive to operate at 
a check speed. The timer 126 will be restarted in the S2 state and will 
force the setting of the motor drive to operate at a check speed. The 
timer 126 will be restarted in the S2 state and will be reset by the RATE 
signal as previously described. 
When the door system reaches the fully open DFO position, the door movement 
will terminate and timer 126 will time out after one second. The decoder 
will then advance to the S3 state and subsequently advance to the S4 state 
where the logic circuit will idle until such time as the OP signal is off. 
In summary, the foregoing sequence of events of opening the door system 
from the DFC position to the DFO position commences with logic circuit 80 
in the S0 state. The OP signal advances the logic circuit to the S1 state. 
After a 32 msec. interval, the logic circuit is advanced to the S2 state. 
The OCK signal advances the logic circuit to the S3 state. After a 32 
msec. delay, the logic circuit is advanced to the S4 state. The slowdown 
timer 118 returns the logic circuit to the S1 state. After 32 msec. 
interval, the circuit is advanced to the S2 state. After the doors hit the 
bumper 20 and a one second interval, the logic circuit is advanced to the 
S3 state. After a 32 msec. interval, the logic circuit is advanced to the 
S4 state. 
The OP signal must go off (the OP signal on) in order to initiate the 
closing sequence. The closing sequence commences with the logic circuit 80 
in the S4 state. The OP signal advances the logic circuit to the S5 state. 
After a 32 msec. delay, the logic circuit is advanced to the S6 state. The 
door is now closing. When the door enters the closing check zone, the CCK 
signal advances the circuit to the S7 state. After 32 msec. delay, the 
logic circuit is returned to the S0 state. After transmittal of a CP 
signal indicative that the door is closed and a one second delay, the 
logic circuit is advanced to the S7 state. After a 32 msec. delay, the 
logic circuit is advanced to the S0 state. The foregoing 32 msec. and 1 
sec. time intervals are selected to provide efficient operation of the 
control system. Other time intervals could also be implemented. 
In the event that the OP signal reappears while the door is closing; i.e., 
state S6, OR gate 106 generates a REVERSE signal which sets the CE signal 
high and advances the logic circuit to the S7 state. After a 32 msec. 
delay, the logic circuit is returned to the S0 state. The REVERSE signal 
also starts the reversal timer 114. The RATE signal from rate circuit 116 
will prevent the timer from timing out until the motor decelerates; i.e., 
is braking in the S0 state at a speed below a preset speed. The START 
signal leading from AND gate 112 will be off until the timer 114 times 
out. When the speed of the motor has dropped to the preset levels, the 
START signal will be activated and the reversal timer 114 will advance 
logic circuit 80 to the S1 state and after 32 msec. to the S2 state 
wherein a new opening sequence is enacted as previously described. 
A feature of the present invention is the incorporation of a reduced 
opening stop whereby the door is opened to a given maximum opening width 
which width may be selectively changed. In the reduced opening mode of 
operation, the RO signal is in a high state. When the opening door 
approaches the reduced opening stop position, the ROS signal goes to a 
high state. The RSTOP signal leading form AND gate 100 will set the CE 
signal high so that the logic circuit will advance to the S3 state and 
after 32 msec. to the S4 state. The logic circuit will remain in the S4 
state until a closing sequence as previously described is commenced. The 
latter described reduced opening mode occurs when the reduced opening stop 
is positioned outside the opening check zone which is the normal 
situation. If the OCK signal is generated prior to the ROS signal, then 
the opening sequence and the reduced opening mode will also involve the 
normal slowdown in the opening check zone as previously described. 
The system control also incorporates a passive door handling feature. If, 
while the door system is in the DFC position and the logic circuit is in 
the S0 state, an attempt is made to open the door by manual means, the 
door will move freely for a short distance until the CP signal is set to a 
high state. The CP signal will result an the S5 state being loaded in the 
logic circuit and the door will automatically reclose in the closing 
sequence. If the door is prevented from reclosing, and held for one second 
in a position where CP is low, a reopening sequence as described below 
will follow. 
The control system provides for reopening the doors if the doors are 
stopped by an obstacle between the open and close check zones. With 
reference to FIG. 7, logic circuit 82 includes a reopening circuit 
designated generally as 144. Circuit 144 generates a reopening (REOP) 
signal in the event that state sequence timer 126 times out when the logic 
circuit is in the S6 state with no CP signal present. The AND gate 148 
receives the T and S6 signals as well as the CP signal and provides a REOP 
output signal. A DS signal indicative that a door is stopped is also 
produced each time either a reopening is initiated or the door is fully 
closed. The CP signal and the S0 state signal are applied to AND gate 150 
producing an output signal to the OR gate 152 which also receives the REOP 
signal. The output from OR gate 152 is inverted to form the DS signal 
which is transmitted to the position control 32. 
With reference to FIG. 8, logic circuit 82 includes an output logic circuit 
145 which provides command signals for the motor drive control. The S1 
state, S2 state, and S3 state signals from decoder 86 are applied via OR 
gate 154 to produce a forward (F) signal. The S5 state, S6 state, and S7 
state signals from decoder 86 are applied via OR gate 156 to produce a 
reverse (R) signal. The S2 state and S6 state signals are applied via OR 
gate 158 to produce a signal leading to AND gate 160 and AND gate 162. The 
S6 state signal and the OCK signal are applied via OR gate 164 to produce 
a signal leading to AND gate 160. AND gate 160 provides an A-drive level 
mode (A) signal. The S2 state signal, CCK signal, and CP signal are 
applied via OR gate 166 to produce a signal leading to AND gate 162. AND 
gate 162 produces an output signal for a B-drive level mode (B) signal. 
Applicable building and safety codes require that the sliding doors be 
provided with a breakout means to allow the doors to be forcibly opened in 
an emergency situation. A breakout switch 46 may be provided to generate a 
signal indicative of a breakout condition. In a preferred form breakout 
switch 46 includes a mechanically or magnetically actuated switch which 
generates a high state signal when the sliding doors are in the 
operational sliding mode. If the breakout switch 46 is open, the 
corresponding breakout (BO) signal is in a low state and the INH signal is 
in a high state which results in resetting the presettable counter 84 to a 
0 count. 
A switching monitor (SWM) signal is generated in the motor drive unit 38 
and is fed back to the motion control unit 36 so that the control system 
will start only if the speed control circuitry in the motor drive unit is 
operational. In the event of a failure in the speed control circuitry, the 
SWM signal will disable operation of the control system. With reference to 
FIG. 6, a safety circuit designated generally as 168 employs an 
optocoupler or phototransistor 170. The SWM signal derived from the motor 
drive 38 is interfaced via optocoupler 170. The phototransistor is in the 
on state if the switching of the speed control transistor 218 occurs. A 
555 type timer 172 has an output which is set high by the power on reset 
(POR) signal. The output state will be maintained as long as the voltage 
at the timer threshold does not exceed two-thirds of the supply voltage. 
During the closing sequence when the logic circuit 80 is in the S6 state, 
capacitor 174 commences charging. The SWM signal will normally be on after 
a short delay beyond the commencement of the motor drive operation. 
Therefore, the SWM signal will discharge capacitor 174 before it reaches 
the threshold voltage. In the event that the motor drive unit 38 does not 
operate properly and the SWM signal is off, timer 172 will time out in 
approximately 100 milliseconds. The timer output signal, the POR signal, 
and the BO signal are applied to AND gate 176 to produce an INH signal 
leading to the reset of counter 84. Consequently, if the SWM signal is 
off, the logic circuit will be reset to the S0 state. To restart 
operation, the power supply must be turned off and on to reset timer 72 by 
means of a new POR pulse. The INH signal also is inverted to produce an 
enable (E) signal. 
With reference to FIG. 9, a reset circuit is generally designated by the 
numeral 178. When power is applied to the control system, an operational 
amplifier 180 generates a power on reset (POR) pulse. The timing of the 
pulse is determined by a capacitor 182 and resistor 184. The POR signal is 
applied to all of the timers and counters of the control system. The INH 
signal from safety circuit 168 will reset counter 84 to the 0 count. 
FIG. 10 illustrates the operate timer and the initialization circuit 48. 
Operate delay timer 186 is a 555 type device. The operate contact 41 of 
sensor 40 is normally open so that the sensor output signal is in a low 
state. The sensor output signal and REOP signal are applied to AND gate 
188 to produce an output to the trigger pin of timer 186. For as long as 
the output from sensor 70 is in a low state, the trigger of timer 186 will 
also be in low state and the timer output in a high state; i.e., the 
output signal from timer 186 is on. When the sensor contact opens, the OP 
signal will go off with a time delay defined by the values of capacitor 
190 and resistors 192 and 194. A potentiometer 196 is employed to regulate 
the time delay interval. AND gate 188 will also interpose a time delay for 
the reopening signal going off. A D-type flip-flop 198 synchronizes the 
output signal from timer 186 with the pace of the clock 34 so that the OP 
signal is synchronized with the POR signal. The POR signal is also applied 
to a D-type flip-flop 200 which sets the INIT signal in a high state. The 
INIT signal sets the content of the counter 54 to a preset count N1. Thus, 
a temporary memory for initialization is provided for each POR signal. The 
INIT signal disables the RSTOP signal from AND gate 100. The INIT signal 
disables the stop signal from AND gate 110. The INIT signal and the RATE 
signal connect via AND gate 202 to enable the discharge transistor 204. 
At the transmission of the first sensor operate signal, the door system 
starts opening. Operate timer 186 is maintained in a high state by the 
RATE signal acting via the discharge transistor 204. The high state 
endures for as long as the doors move and is accomplished so as to prevent 
the removal of the OP signal before the doors reach a fully open state. At 
the same time, the rate pulses are counted in the opening direction on the 
eight bit counter 206. When the last bit of the counter goes to a high 
state, the counter is latched in the state via inverter 208. At the 
instant that the door reaches the DFO position, the door movement ceases 
and timer 186 is restarted. When the timer times out, its output will go 
to a low state. If the door moved more than a certain distance in the 
opening direction; i.e., inverter 208 output is low, an inverted output 
from OR gate 210 will reset flip-flop 200. Therefore, the position 
reference is established with the door fully open. The door will then be 
started in a closing direction. The door will move at a slow speed in a 
manner wherein the entire door width is essentially set inside the closing 
slowdown zone by the INIT signal. When the door finally reaches the DFC 
position and stops a DS signal occurs and, a fully closed position 
reference is memorized and normal operation is commenced. 
With further reference to FIG. 4, the DC motor is driven from a line 
voltage rectifier comprising a rectifier bridge 214 and a filter capacitor 
216. A speed controller in the form of a switching transistor stepdown 
convertor comprising a switching transistor 218, a free-wheeling diode 
220, and a pulse width modulator (PWM) control unit 222 is interposed to 
control the motor speed. The motor direction and consequently the 
direction of movement of the door system is established by energizing a 
forward relay 224 for the opening mode or energizing a reverse relay 226 
for a closing mode. A dynamic braking resistor 228 is employed so that 
when both the forward relay 224 and the reverse relay 226 are de-energized 
while the motor is moving, a dynamic braking action results with the 
braking energy being dissipated in braking resistor 228. The circuitry of 
the PWM control unit 222 controls the motor by varying the output voltage 
of the step-down converter in accordance with the required motor speed and 
the motor loading. The motor current is monitored by means of a current 
sense resistor 230. The rectifier voltage is monitored by means of a 
voltage sense resistor 232. The sensed current and voltage is transmitted 
to the PW control unit 222 for automatic compensation for line variations. 
The speed reference for the motor is determined by decoding the A and B 
logic signals as described in Chart II: 
______________________________________ 
CHART II 
SIGNAL STATE 
MOTOR OPERATIONAL MODE 
______________________________________ 
A = 0; B = 0 
MOTOR OFF 
A = 1; B = 0; 
MOTOR OPERATED AT CLOSING 
SPEED 
A = 0; B = 1; 
MOTOR OPERATED AT OPENING 
SPEED 
A = 1; B = 1; 
MOTOR OPERATING AT APPROACH 
OR CHECK SPEED 
______________________________________ 
The motor current limit is correspondingly selected in relation to the A 
and B signals. 
The circuitry of motor drive unit 38 works directly off-line requiring 
isolation of all of the interface signals. Optocouplers 234 and 236 
employed for the A signal and the B signal, respectively. As previously 
described, optocoupler 170 is employed with SWM signal. Relays 225 and 227 
isolate the F and R signals, respectively. 
Proper operation of the motor drive is in part dependent upon the 
coordination of the timing of the A signal, B signal, F signal, and R 
signal. When the motor is in a standing mode, the direction relay is 
energized first. After allowing sufficient time to compensate for the 
delays in the relay action, which time is approximately on the order of 30 
milliseconds, the A and B signals are transmitted as appropriate and the 
motor commences operation. To slow down the speed of the motor, the A and 
B signals are first set to zero. This results in turning off the switching 
transistor 218. The direction relay is turned off after allowing 
sufficient time; i.e., approximately on the order of 30 milliseconds, for 
the motor current to decay. Upon de-energizing the direction relays, the 
motor is connected across braking resistor 228. The current flowing in 
resistor 228 when the motor moves will produce the dynamic braking action. 
In the event that reversing is required, the motion control will delay 
re-energizing of the direction relays until the motor is sufficiently 
slowed down by the braking action. This latter delay avoids a DC plugging 
condition which is detrimental to both the motor and the motor drive. In 
addition, the foregoing mode of operation avoids breaking relatively large 
DC currents by the contact elements of the relays. 
A snubber circuit 238 functions to improve the turnoff process of the 
switching transistor 218. In addition, the snubber circuit incorporates a 
means for detecting the presence of the switching process. During the 
switching process, a negative DC voltage will develop on capacitor 240. 
The SWM signal results from the transmission of the presence of the 
voltage via optocoupler 170 to the motion control. To confirm that the 
switching transistor is operating, a failure of the switching transistor 
results in a lack of speed control such as for example the door system 
moving at high rates of speed and not slowing when required. If the SWM 
signal indicates a malfunction, the motion control will automatically open 
the direction relays. In the latter event, the control system is disabled 
by permanently removing the E signal, which signal, as illustrated in FIG. 
4, is the power supply for optocouplers 234 and 236 and relays 224 and 
226. 
PWM control unit 222 includes potentiometers for adjusting the opening 
speed, the closing speed, and the check speed of the doors of the door 
system. The motor torque, and consequently the force at the edge of the 
doors, is determined by the motor current. The control unit 222 also 
includes circuitry for limiting the motor current to preset values. 
The foregoing description of a control system for a sliding door system has 
been set forth for purposes of illustration and should not be deemed a 
limitation of the invention. Accordingly, various modifications, 
adaptations, and alternatives to the described automatic door control 
system may occur to one skilled in the art without departing from the 
spirit and scope of the present invention.