Abstract:
Methods and apparatus for controlling the speed of an A.C. induction motor are disclosed and shown in operation for controlling the movement of a barrier. Included are voltage configuration circuits which selectively gate portions of the half-cycles of AC mains voltage to the induction motor. When the motor is started increasing amounts of mains AC voltage is applied to the motor and decreasing portions of the mains AC are applied to the motor during a stopping routine. The motor can also be energized with less than full mains AC to permit differences in barrier movement speed dependent on operating parameters.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to variable speed induction motors and the use of such in barrier movement operators.  
         [0002]     Barrier movement operators, such as gate and garage door operators comprise an electric motor connected to move a barrier between at least open and closed limits. In controlling the movement of the barrier, the motor and the barrier must be started in motion from rest and stopped from motion into the rest state. Sometimes, as is the case when an obstruction is in the path of the barrier, the barrier must be stopped then started again in a reverse direction. When the electric motor moving a barrier stops and/or starts abruptly the inertia of the at rest or moving barrier creates large forces. Such forces potentially reduce the lifetime of the barrier movement operator and create audible and visual appearances that the barrier movement operator is straining. Also, it may be desirable to move the barrier at different speeds during travel along different parts of the path of travel. For example, it may be desired to open the barrier at a faster speed than when it is closing.  
         [0003]     Some DC motor powered systems, such as that described in PCT/US02/24385, build up and diminish the power (torque) applied by the motor when the motion of the barrier is changed. Such building-up and diminishing may be done by timed increases and decreases of a DC voltage level or by pulse width modulating the DC power. DC motors require a powerful and costly source of DC voltage, relatively complex control circuitry and the more expensive DC motor itself. A need exists for methods and apparatus to control the power to an A.C. induction motor of a barrier movement operator in response to barrier control input signals. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]      FIG. 1  is a perspective view of a garage having mounted within it a garage door operator embodying the present invention;  
         [0005]      FIG. 2  is a block diagram of a controller mounted within the head unit of the garage door operator employed in the garage door operator shown in  FIG. 1 ;  
         [0006]      FIG. 3  is a circuit diagram of a motor control used in the head-end controller;  
         [0007]     FIGS.  4 A-E are wave forms for an example of gating A.C. voltage to an induction motor to sequentially increase (decrease) the effective applied voltage;  
         [0008]     FIGS.  5 A-P are wave forms for a first example of sequentially increasing (decreasing) the effective frequency and effective voltage applied to an A.C. motor;  
         [0009]     FIGS.  6 A-P are wave forms for a second example of sequentially increasing (decreasing) the effective frequency and effective voltage applied to an A.C. motor; and  
         [0010]      FIG. 7  is a block diagram of an alternative voltage configuration circuit. 
     
    
     DESCRIPTION  
       [0011]     Referring now to the drawings and especially to  FIG. 1 , more specifically a movable barrier operator or garage door operator is generally shown therein and referred to by numeral  10  includes a head unit  12  mounted within a garage  14 . More specifically, the head unit  12  is mounted to the ceiling  16  of the garage and includes a rail  18  extending therefrom with a releasable trolley  20  attached having an arm  22  extending to a multiple paneled garage door  24  positioned for movement along a pair of door rails  26  and  28 . The system includes a hand-held transmitter unit  30  adapted to send signals to an antenna  32  positioned on the head unit  12  and coupled to a receiver  80  as will appear hereinafter. A switch module  39  is mounted on a wall of the garage. The switch module  39  is connected to the head unit  12  by a pair of wires  39   a . The switch module  39  includes a light switch  39   b  and a command switch  39   d . An optical emitter  42  is connected via a power and signal line  44  to the head unit. An optical detector  46  is connected via wire  48  to the head unit  12 .  
         [0012]     As shown in  FIG. 2 , the garage door operator  10 , which includes the head unit  12  has a controller  70  which includes the antenna  32 . The controller  70  includes a power supply  72  ( FIG. 4 ) which receives alternating current from an alternating mains voltage source, such as 120 volt AC ( 71 ) and converts the alternating current to required levels of DC voltage. The controller  70  includes an RF receiver  80  coupled via a line  82  to supply demodulated digital signals to a microcontroller  84 . The receiver  80  is energized by a power supply  72 . The microcontroller is also coupled by a bus  86  to a non-volatile memory  88 , which non-volatile memory stores user codes, and other digital data related to the operation of the control unit  70 . An obstacle detector  90 , which comprises the emitter  42  and infrared detector  46  is coupled via the obstacle detector bus  92  to the microcontroller. The obstacle detector includes lines  44  and  48 . The wall switch  39  is connected via the connecting wires  39   a  to the microcontroller  84 .  
         [0013]     The microcontroller  84 , in response to switch closures and received codes, will send signals over a logic line  102  to a logic module  104  connected to an alternating current motor  106  having a power take-off shaft  108  coupled to the transmission  18  of the garage door operator. A tachometer  110  is coupled to the shaft  108  and provides an RPM signal on a tachometer line  112  to the microcontroller  84 ; the tachometer signal being indicative of the speed of rotation of the motor. A limit identifier  93  which identifies the position of the movable barrier along its path of travel. Limit identifier may comprise limit switches or a software function to count tachometer signals to identify barrier position. The limit switches are shown in  FIG. 2  as a functional box  93  connected to microcontroller  84  by leads  95 . AC supply line  71  is also coupled to microcontroller  84  to identify the phase of the alternating current on the supply line.  
         [0014]     The controller  70  responds to input signals from the various input circuits of  FIG. 2  by controlling the movement of the door  24  or other barrier. For example, when a door command is received from transmitter  30  or wall control  39  microcontroller  84  determines the present state of the barrier movement operator and stops or begins movement of the barrier. During barrier movement the tachometer  110  input signals are analyzed to detect obstructions and, in some instances, to determine the position of the barrier. When a moving barrier achieves a travel limit as identified by limit identifier  93  the barrier may be stopped. Also, the controller  70  is programmed to illuminate light  81  in response to a light control signal from wall control  39  or anytime that the motor is powered to move the barrier.  
         [0015]     Logic unit  104  is illustrated in schematic form in  FIG. 3 . AC mains voltage is applied between input terminals  121  and  122  of logic unit  104  and voltages derived from the AC mains voltage are used to control the direction and speed of barrier motion and to illuminate light  81 . The AC mains voltage used herein is the common  60  HZ 120V AC of Public Distribution departments. As such, it is basically a sine wave having 60 cycles per second, each cycle being comprised of two half cycles of alternating polarity. Incoming AC voltage is applied via a step down transformer  124  to rectifying and filtering circuitry  126  to produce a DC voltage for powering various circuitry of the control  70 . Additionally, a portion of the stepped down voltage wave form is sent via a transistor  128  and output port  127  to microcontroller  84 . The wave form at port  127  is used by microcontroller  84  to produce gating signals in synchronism with the AC mains voltage. Although the present description relates to 60 HZ 120V AC the principles taught can easily be applied to other frequencies e.g., 50 HZ and other voltages e.g., 240.  
         [0016]     The common or neutral conductor conveying mains voltage to input terminal  122  is also connected to a common input of light  81  and motor  106 . The hot input terminal  121  is connected to one terminal of a normally open contact set  131  of a light control relay  130 . Whenever the light  81  is to be illuminated microcontroller  84  grounds light input terminal  133  causing DC current to flow through relay  130  closing the contact set  131 . Light  81  is connected to a terminal  135  of logic unit  104  to receive AC voltage from relay contact set  131  whenever relay  130  is operating to close contact set  131 .  
         [0017]     The voltage applied to light output terminal  135  is also applied via a voltage configuring circuit  138  to the center contact  140  of a double throw contact set  137  of a relay  139 . The normally closed contact  141  of relay  139  is connected to a down motor output terminal  143  and normally open contact  142  is connected to an up motor output terminal  145 . By operation of relay the voltage output of voltage configuration circuit  138  is applied to terminal  143  (down motor) when relay  139  is at rest and it is applied to output terminal  145  (up motor) when the relay  139  is energized. Relay  139  is energized when microcontroller  84  applies ground to input terminal  147 . Output terminals  143  and  145  are connected to down and up power input terminals of motor  106 .  
         [0018]     The voltage configuration circuit  138  is controlled by microcontroller  84  via input signals at terminal  149  to pass portions of the mains AC voltage on to relay contact  140  (relay  137 ). In the arrangement described herein microcontroller  84  provider input signals to terminal  149  to control voltage controlling circuit  138  to pass voltage to contact  140  which has a varying effective base frequency and a varying effective voltage. The main conductor path for AC voltage through the voltage configuration circuit  138  comprises conductor  151  to a main terminal of a triac  150  and conductor  152  which connects the other main terminal of triac  150  to relay contact  140 . Resistor and capacitor configurations  144  in  FIG. 3  are used in several known places to provide circuit protection and electrical noise reduction and could be eliminated from the circuit if these characteristics are not important. The gate input  155  to triac  150  is connected to a main terminal of an opto-triac  157 , the other main terminal of which is connected via a resistor  153  to receive mains AC voltage from relay  130 . Voltage is gated between the main terminals of opto-triac  157  whenever input terminal  149  is controlled by microcontroller  84  to provide a conductive path to ground. By the arrangements described, whenever relay contacts  131  are closed and microcontroller  84  provides a conductive path to ground at terminal  149 , a portion of an AC one-half cycle will be passed on to relay contact  141  for application to motor  106 .  
         [0019]     Microcontroller  84  controls the motor  106  by controlling the application of voltage to the motor relay  130 , by controlling whether an up or a down winding of the motor  106  is energized relay  139  and by controlling the nature of the energizing voltage (voltage configuration circuit  138 ). To move the barrier open (upward) microcontroller  84  closes relay contact  131 , controls voltage configuration circuit  138  to provide a desired configuration of output voltage and controls relay  139  to close relay contact  140  and  142 . To move the barrier toward the closed position microcontroller  84  closes relay contact  131 , controls voltage configuration circuit  138  to provide appropriate voltage and allows relay  139  to stay in the inactive state in which contact  140  and  141  are normally closed. Whenever the motor is to be stopped relay  130  may be opened or configuration circuit  138  can be controlled to pass no significant voltage to relay contact  140 .  
         [0020]     Voltage configuration circuit  138  operates under the control of microcontroller  84  to pass any portions of the incoming mains AC voltage which the microcontroller is programmed to pass. When full AC voltage is to be sent to motor control relay  139 , input  149  is grounded for the period of time that full voltage is to be sent. The grounding of terminal  149  causes a representation of the AC voltage on conductor  151  to be presented to gate conductor of triac  150  to which triac  150  responds by conveying nearly all of the voltage on main terminal conductor  151  to main terminal conductor  152 . When the ground connection at terminal  149  is removed, no voltage is applied to terminal  140 .  
         [0021]     FIGS.  4 A-E represent one example of controlling the effective voltage applied to terminal  140 .  FIG. 4 -E represents both the input AC mains sine wave as well as the output sine wave which will occur when terminal is grounded continuously for a period of time.  FIG. 4A  represents the application of a small (with respect to  FIG. 4E ) effective voltage to terminal  140 . It will be remembered that microcontroller  84  receives a representation of the AC mains voltage on a terminal  127  from which the timing of the half cycles of the AC mains voltage is determined. The wave form of  FIG. 4A  is achieved by grounding terminal  149  a predetermined period of time before the next zero crossing of the AC mains voltage. The period of grounding should not be so large as to be in effect at the next zero crossing of the mains voltage. The grounding causes the voltage applied to terminal  140  to reach substantially the full AC mains voltage level until the next zero crossing. When the current reaches zero the triac  150  ceases to conduct and will not begin again until the next grounding of terminal  149 . The line of pulses  160  on  FIG. 4A  represents the times for grounding the input terminal  149 .  FIG. 4B  represents a higher effective voltage and is achieved by grounding terminal  149  with a slightly greater period of time remaining before the next zero crossing than existed in  FIG. 4A .  FIGS. 4C and 4D  represent step increases in the effective voltage and as before are achieved by gating more of each applied half-cycle. Finally, in  FIG. 4E  the input  149  is substantially continuous grounded and the entire mains voltage is passed. FIGS.  4 A-E represent a small number of incremental increases in the effective voltage for purposes of illustration. When a barrier is beginning to move it may be desirable to control voltage configuration circuit  138  to produce many, e.g.,  128 , incremental increases in effective voltage during the first 1-4 seconds of barrier motion.  
         [0022]     The description above refers to increasing barrier speed by controlling voltage configuration circuit  138  by progressing from  FIG. 4A  to  4 E. The barrier can be gradually slowed by reversing the sequence from maximum speed e.g.,  FIG. 4E  and reducing the effective voltage by working backward through  FIG. 4D  to  FIG. 4A . The long term speed of barrier movement can also be controlled by the apparatus and methods discussed herein. Moving the barrier in the open direction may be achieved by progressing through the incremental effective voltage increases ending at the full AC mains voltage ( FIG. 4E ). This maximum voltage would result in a maximum speed of the barrier. On the other hand, when closing the barrier the effective voltage may only be increased to  FIG. 4C  as a maximum in which case the barrier would move more slowly than in the opening direction.  
         [0023]     The examples represented by FIGS.  4 A-E describe gradually changing the effective voltage applied to an AC induction motor  106  to slowly accelerate a barrier as well as slow it down and run at a chosen speed. FIGS.  5 A-P provide examples by which both the effective voltage and the effective frequency of voltage applied to a motor are controlled. Such may provide finer control over the barrier movement speed.  
         [0024]     As in the preceding example with regard to  FIG. 4A -E the  FIG. 5P  represents both the mains AC voltage as well as the output of the voltage configuration circuit at maximum effective frequency and effective applitude. In  FIG. 5A  which represents a low effective frequency and a low effective voltage a portion of every third half-cycle is gated to the terminal  140 . This reduces the effective frequency to that represented by the dashed line wave  162  in  FIG. 5A . The gating pulses to create the wave of  FIG. 5A  are shown on a line  164 . The length of the gating pulses is sequentially increased as before to create the resultant waves of  FIGS. 5B-5E . The beginning of each gating pulse defines the beginning of the voltage pulse passed to terminal  140  and the end occurs during a half cycle for which voltage passing should cease at the next zero crossing. As shown in  FIGS. 5F through 5J  the gating pulses  165  and  166  extend into two consecutive half-cycles. As the gating pulses continue to lengthen they extend into three consecutive half-cycles until, in  FIG. 5P , the gating pulses lengthen to become continuous gating the entire sine wave. As represented in  FIG. 5  the gating process begins with every third half-cycle and gradually increases until the entire source wave ( FIG. 5P ) is sent to the motor. In the beginning ( FIG. 5A ) only a small effective voltage is gated at a reduced effective frequency  162 . As gating increases the effective frequency increases as does the effective voltage. The sequence of FIGS.  5 A-P presents representative samples of the actual wave forms created. As with the example of  FIG. 4 , further change can stop at any of the wave forms for a steady speed slower than full speed ( FIG. 5P ) and the motor can be slowed by performing the steps of the example in reverse.  
         [0025]     In the preceding discussion of FIGS.  5 A-P the wave form created is discontinuous. Accordingly, a fourier transform of the wave will show a base frequency and a number of harmonics. As longer and longer portions of a half-cycle are passed, the base frequency will remain, but other frequencies and harmonics will appear and their magnitude will change. At some point in the progression, as more and more of additional half-cycles are coupled to the motor, the original base frequency will diminish in significance to be replaced with higher base frequencies. Thus, by changing the wave shape of the applied signal as shown in FIGS.  5 A-P the effective frequency to which the motor responds is changed.  
         [0026]     In the example of  FIG. 5  the effective frequency was reduced by beginning to gate portions of every third half-cycle and increasing the amount gated. Greater initial effective frequency reductions can be achieved if the initial step involves the gating of every N th  half-cycle where N is an odd integer greater than one. The gating of odd half cycles guarantees that one will be a positive half-cycle and the subsequent half-cycle will be negative to balance out any significant DC component of the gated signal.  
         [0027]     FIGS.  6 A-P represent a second example of gating control to create increasing or decreasing effective frequencies and effective voltages. The example of  FIG. 6  has been found to be somewhat more compatible with some types of AC induction motors.  FIGS. 6A-6E  are, as shown in  FIGS. 5A-5E , created by gating increasing portions of every third half-cycle. In  FIG. 6F , when gating begins for a second half-cycle, a pulse  170  is also gated intermediate to two completed half-cycles and of opposite polarity to the adjacent half-cycle polarity. The gating pulses for  FIG. 6F  are shown on line  168 . As carried forward in  FIG. 6G-6N  the pulse  170  is expanded along with the main gated half-cycle until in  FIG. 6P  the completed sine wave is applied to terminal  140 .  
         [0028]     As discussed above, the increases (decreases) in effective voltage are performed in incremental steps. A feedback loop may be implemented in the system to control the performance of increasing (decreasing) steps when the motor is started or stopped. The feed back is implemented by microcontroller  84  which is pre-programmed to store a time based profile of desired motor start up speeds and stopping speeds. When the microcontroller  84  begins to control the motor to start up, the output of tachometer  110  is compared to the start up profile. When the motor is starting too slowly incremental effective voltage increasing steps will be omitted and the effective voltage will be raised until motor speed matches the start up profile. Similarly, when the motor speed exceeds the start up profile effective voltage increasing steps will be performed more slowly or skipped until the motor is at the profiled speed. Similar feed back corrections are made when the motor is being stopped to approximate the stopping speed profile.  
         [0029]     In the preceding description the wave form connected to the motor  106  is controlled by voltage configuration circuit  138  in response to gating signals from microcontroller  84 .  FIG. 7  illustrates an alternative to  FIG. 3  which includes an electrical H bridge  210  to configure the mains voltage before it is connected to the motor. The output of terminal  131  of relay  130  is connected to a bottom portion of the H bridge  210  and the top of H bridge  210  is connected to the AC mains neutral terminal. The right side of the H bridge comprises voltage configuration circuits  201  and  202  connected in series and the left side comprises voltage configuration circuits  203  and  204  connected in series. Each voltage configuration circuit  201 - 204  is substantially identical to voltage configuration circuit  138  of  FIG. 3 . Each voltage configuration circuit  201 - 204  is controlled by signals on an individual gating lead which are collectively referred to as leads  207 . Leads  207  are connected to receive control signals from microcontroller  84 . The neutral terminal of motor  106  is connected to a point  205  of the series connection between voltage configuration circuits  203  and  204  and the up and down terminals of motor  106  are selectively connected to a point  206  in the serial connections between voltage configuration circuits  201  and  202 . As in  FIG. 3  the state of up/down relay  139  is determined by microcontroller  84 . The microcontroller  84  can exert greater control over the wave form applied to motor  106  when the circuit of  FIG. 7  is used. For example, wave forms derived from both odd and even half-cycles of the mains voltage can be connected to the motor  106 .