Abstract:
This invention deals with a barrier operator system comprising a direct current (dc) motor coupled to a barrier, where the dc motor is driven by a string of voltage pulses. The system has a barrier operator that is programmed to determine various qualities including the speed of the motor from a generated voltage and a position of the barrier using the speed. Further, the barrier operator has the capability to adjust the speed of the motor based upon the determined position of the barrier using the speed.

Description:
CROSS-REFERENCE To RELATED APPLICATION  
       [0001]     This application is a continuation of prior application Ser. No. 11/241,091, filed Sep. 30, 2005, and entitled “System and Method for Determining Barrier Motor Parameters without using Sensors” of Eric Michael Gregori which is hereby incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The field of the invention relates to moveable barrier operators and, more specifically, to determining characteristics of these systems.  
       BACKGROUND  
       [0003]     Different types of moveable barrier operators have been sold over the years and these systems have been used to actuate various types of moveable barriers. For example, garage door operators have been used to move garage doors and gate operators have been used to open and close gates.  
         [0004]     Such barrier movement operators may include a wall control unit, which is connected to send signals to a head unit thereby causing the head unit to open and close the barrier. In addition, these operators often include a receiver unit at the head unit to receive wireless transmissions from a hand-held code transmitter or from a keypad transmitter, which may be affixed to the outside of the area closed by the barrier or other structure.  
         [0005]     Barrier operators sometimes include the ability to determine the torque of the motor. The torque may be used in a variable speed motor to determine whether the barrier has reached an obstruction. In previous systems, the operator received information related to the torque of the motor by using a tachometer (or some other type of sensor or sensing device), reading the speed of the motor, and deriving the torque from the amount of speed reduction of the motor.  
         [0006]     Positional information concerning the barrier may also be determined and used in operator systems, for example, to determine when to slow down the barrier as the barrier approaches a limit such as the ground. In previous systems, tachometers (or other types of sensors or sensing devices) were used to determine the position of the barrier. In one example, the number of tachometer pulses was measured from a limit or a pass point, in order to determine the position of the barrier.  
         [0007]     Unfortunately, the above-mentioned previous systems required the use of an extra component, the tachometer, which significantly increased the cost of the system. In addition, when a tachometer was used, other additional circuitry and/or software were frequently required to allow this additional component to operate. Another problem associated with previous systems was that only certain types of sensors or sensing devices could be used with certain types of motors, so that the user could not easily change motor types. This lack of flexibility added to user frustration, for instance, when a certain type of motor was not available or too costly for the user.  
       SUMMARY  
       [0008]     A system and method are provided that determine different operating characteristics of a motor without using additional sensors and/or software. The approaches described herein are cost effective to implement, simple to use, and allow a user the flexibility to choose from a large variety of motors types to suit their application and needs.  
         [0009]     In accordance with the principles described herein, a barrier operator may determine the current and/or motor voltage of a direct current (dc) motor and thereby derive information concerning a moveable barrier being driven by the motor. For instance, motor current can be determined and used to determine motor torque. The torque can then be used to determine whether the barrier has reached an obstruction. In another example, back electromagnetic force (emf) motor voltage can be ascertained and used to determine motor speed. The speed, in turn, may be used to determine the position of the barrier. In still another example, the back emf motor voltage can be measured and used to determine motor speed. The speed, in turn, can be used to determine motor torque and the torque can be used to determine whether an obstruction exists in the path of the barrier. All of these approaches do not require the use of costly sensors or sensing devices (such as tachometers).  
         [0010]     In one of these embodiments, a barrier operator includes a first measuring apparatus for measuring a current used by a direct current (dc) motor to move a barrier. The barrier operator also includes a second measuring apparatus for measuring a generated voltage of the dc motor. The generated voltage (i.e., the back emf) is created by operating the motor as a generator.  
         [0011]     A controller is coupled to the first measuring apparatus and the second measuring apparatus. The controller may be programmed to calculate a torque of the dc motor by using the measured motor current, and then to determine when an obstruction exists in the path of the barrier based upon the calculated torque. The controller may also be programmed to determine a speed of the motor from the generated voltage and determine a position of the barrier using the speed.  
         [0012]     The dc motor may be driven by a variety of voltage signals having varying characteristics. For example, the dc motor may be driven by a string of voltage pulses, which contain a plurality of on intervals and off intervals. Preferably, the generated voltage (emf) across the motor is measured during the off intervals.  
         [0013]     In others of these embodiments, the barrier operator may only include a measuring apparatus to measure a back emf motor voltage. This measured voltage may be used to determine the speed of the motor and the speed may be used to determine the position of the barrier. In other examples, the speed may be used to directly determine the torque of the motor and the torque may then be used to determine whether an obstruction exists in the path of the barrier.  
         [0014]     Thus, a system and method are provided that determine different operating characteristics of a motor without the requirement of additional costly sensors and/or software. The motor characteristics may be used to determine the position of a barrier and/or whether the barrier has encountered an obstruction. These approaches are cost effective and simple to implement, and allow the user the flexibility to choose from a large variety of motors.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a diagram of a system for determining the operating characteristics of a moveable barrier system according to the present invention;  
         [0016]      FIG. 2  is a diagram of a system for determining the operating characteristics of a motor sued in a moveable barrier system according to the present invention;  
         [0017]      FIG. 3  is a diagram of a system for determining the operating characteristics of a motor sued in a moveable barrier system according to the present invention;  
         [0018]      FIG. 4  is a diagram of a system for determining the operating characteristics of a motor sued in a moveable barrier system according to the present invention;  
         [0019]      FIG. 5  is a diagram of a system for determining the operating characteristics of a motor sued in a moveable barrier system according to the present invention;  
         [0020]      FIG. 6  is a diagram of a system for determining the operating characteristics of a motor sued in a moveable barrier system according to the present invention; and  
         [0021]      FIG. 7  is a graph of the average back emf versus average voltage across the motor of the system of  FIG. 6  according to the present invention. 
     
    
       [0022]     Skilled artisans will appreciate that elements in the figures are illustrated for ease of understanding and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of the various embodiments of the present invention.  
       DESCRIPTION  
       [0023]     Referring now to the drawings and especially  FIG. 1 , one example of a system for measuring the operating characteristics of a motor used in a moveable barrier system is described. A barrier operator  102  includes a motor  104  and a controller  106 . The motor  104  is coupled to a barrier  103 . The motor  104  may be any type of direct current (dc) motor.  
         [0024]     The barrier  103  may be any type barrier such as a swinging gate, sliding gate, garage door, swinging door, or shutters. In addition, the operator  102  may be a garage door operator, gate operator, or any other type of barrier operator. Other types of barriers and barrier operators are possible.  
         [0025]     A wall control unit  108  is coupled to the operator  102 . The wall control unit  108  may include control buttons for example, for opening the barrier  103 , closing the barrier  103 , or programming the barrier operator  102 .  
         [0026]     A portable transmitter  110  may be used to open and close the barrier  103 . For example, the transmitter  110  may transmit Radio Frequency (RF) signals that are received by the operator  102 , which, in turn, actuates the barrier  103 .  
         [0027]     In one example of the operation of the system of  FIG. 1 , the motor  104  is operated in a manner that generates a voltage (i.e., the back electromagnetic force (emf)). The speed of the motor  104  can then be determined from the generated back emf voltage. A position of the barrier  103  can be determined using the speed, and the speed of the motor  104  can be adjusted based upon the determined position of the barrier  103 .  
         [0028]     In addition, the current of the motor  104  can be measured. This current can be used to determine the torque of the motor  104 . Then, the torque can be used to determine if the barrier has reached an obstruction. For instance, if the torque exceeds some value or is within some range of values, the barrier  103  may be determined to have reached an obstruction.  
         [0029]     The motor  104  can be driven with a string of voltage pulses. This string of pulses includes a plurality of on intervals and off intervals. In one example, the generated back emf voltage is measured during the off intervals of the pulse string.  
         [0030]     Referring now to  FIG. 2 , one approach for determining the operating characteristics of a motor is described. A dc motor  202  is coupled to a power source  204 . The power source  204  may be any direct current (dc) power source. A measurement device  206  (or devices) is coupled to the motor  202 . The measurement device  206  may include any combination of electronic hardware and/or computer software to measure the voltage at different points in the system. In this regard, the measurement device may include a controller or microprocessor.  
         [0031]     Switches  208  and  210  are used to selectively connect and disconnect the motor  202  to the power source  204 . A transistor control device  212  is used to control the switches  208  and  210  via a transistor  214 . The transistor  214  may be a field effect transistor (FET) or other similar device.  
         [0032]     Positional information concerning a barrier  215  moved by the motor  202  is determined by measuring and analyzing the voltage across the motor  202  while the motor  202  is disconnected from the power source  204 . Specifically, when the motor  202  is disconnected from the power source  204 , the motor  202  acts as a generator. While acting as a generator, the back emf voltage generated and measured by the measurement device  206  is directly proportional to the speed of the motor  202 . The speed of the motor  202  may be measured at a periodic rate and is directly proportional to the distance traveled by the barrier  215 . In one example, the position of the barrier  215  can be computed as the second integral of motor speed over time.  
         [0033]     In still another example, the measured back emf voltage can be used to directly determine motor speed and the speed can be used to determine motor torque. The motor torque can then be used to determine whether an obstruction is present in the path of the barrier  215 .  
         [0034]     Torque information concerning the motor  202  can also be determined from the motor current. The current is determined by measuring the voltage across the transistor  214  when the transistor  214  is activated. The resistance between the drain and source (RDS(on)) is known so that the voltage can be calculated using Ohm&#39;s law. The voltage can be used to determine motor torque and whether an obstruction exists.  
         [0035]     In addition, torque information can be determined if the speed of the motor  202  is known. For example, the known supply voltage, known duty cycle of the supply voltage, and motor torque speed curves can be used to determine the torque of the motor  202  and whether an obstruction exists.  
         [0036]     Referring now to  FIG. 3 , another approach for determining the operating characteristics of a motor that is used to actuate a moveable barrier is described. In this example, the configuration of the transistor and other components has been adjusted with respect to the system illustrated in  FIG. 2 .  
         [0037]     A dc motor  302  is coupled to a power source  304  via a transistor  314 . The power source  304  may be any direct current (dc) power source. A measurement device  306  (or devices) is coupled to the motor  302 . The measurement device  306  may include any combination of electronic hardware and/or computer software to measure the voltage at different points in the system. In this regard, the measurement device  306  may include a controller or microprocessor.  
         [0038]     Switches  308  and  310  are used to selectively connect and disconnect the motor  302  to the power source  304 . A transistor control device  312  is used to control the switches  308  and  310  via the transistor  314 . The transistor  314  may be a field effect transistor (FET) or similar device.  
         [0039]     Positional information concerning a barrier  315  moved by the motor  302  is determined by measuring and analyzing the voltage across the motor  302  while the motor  302  is disconnected from the power source  304 . Specifically, when the motor  302  is disconnected from the power source  304 , the motor  302  acts as a generator. While acting as a generator, the back emf voltage generated and measured by the measurement device  306  is directly proportional to the speed of the motor  302 . The speed of the motor  302  may be measured at a periodic rate and is directly proportional to the distance traveled by the barrier  315 . In one example, the position of the barrier  315  can be computed as the second integral of motor speed over time.  
         [0040]     In still another example, the measured back emf voltage can be used to directly determine motor speed and the speed can be used to determine motor torque. The motor torque can then be used to determine whether an obstruction is present in the path of the barrier  315 .  
         [0041]     Torque information concerning the motor  302  can also be determined from the motor current. The current is determined by measuring the voltage across the transistor  314  when the transistor  314  is activated. The resistance between the drain and source (RDS(on)) is known so that the voltage can be calculated using Ohm&#39;s law. The voltage can be used to determine motor torque and whether an obstruction exists.  
         [0042]     In addition, torque information can be determined if the speed of the motor  302  is known. For example, the known supply voltage, known duty cycle of the supply voltage, and motor torque speed curves can be used to determine the torque of the motor  302  and whether an obstruction exists.  
         [0043]     Referring now to  FIG. 4 , still another approach for determining the operating characteristics of a motor that is used to actuate a moveable barrier is described. A dc motor  402  is coupled to a power source  404 . The power source  404  may be any direct current (dc) power source. A measurement device  406  (or devices) is coupled to the motor  402 . The measurement device  406  may include any combination of electronic hardware and/or computer software to measure the voltage at different points in the system. In this regard, the measurement device  406  may include a controller or microprocessor.  
         [0044]     Switches  408  and  410  are used to selectively connect and disconnect the motor  402  to the power source  404 . A transistor control device  412  is used to control the switches  408  and  410  via a transistor  414 . The transistor  414  may be a field effect transistor (FET) or other similar device. A resistor  416  is coupled to the transistor  414  and the measurement device  406 .  
         [0045]     Positional information concerning a barrier  415  moved by the motor  402  is determined by measuring and analyzing the voltage across the motor  402  while the motor  402  is disconnected from the power source  404 . Specifically, when the motor  402  is disconnected from the power source  404 , the motor  402  acts as a generator. While acting as a generator, the back emf voltage generated and measured at the measurement device  406  is directly proportional to the speed of the motor  402 . The speed of the motor  402  may be measured at a periodic rate and is directly proportional to the distance traveled by the barrier  415 . In one example, the position of the barrier  415  can be computed as the second integral of motor speed over time.  
         [0046]     In still another example, the measured voltage can be used to directly determine motor speed and the speed can be used to determine motor torque. The motor torque can then be used to determine whether an obstruction is present in the path of the barrier  415 .  
         [0047]     Torque information concerning the motor  402  can also be determined from the motor current. The current is determined by measuring the voltage across the resistor  416  when the transistor  414  is activated. The resistance of the resistor  416  is known so that the voltage can be calculated using Ohm&#39;s law. The voltage can be used to determine motor torque and whether an obstruction exists.  
         [0048]     Referring now to  FIG. 5 , yet another approach for determining the operating characteristics of a motor that is used to actuate a moveable barrier is described. In this example, the configuration of the transistor and other components has been adjusted with respect to the system illustrated in  FIG. 4 .  
         [0049]     A dc motor  502  is coupled to a power source  504  via a transistor  514 . The power source  504  may be any direct current (dc) power source. A measurement device  506  (or devices) is coupled to the motor  502 . The measurement device  506  may include any combination of electronic hardware and/or computer software to measure the voltage at different points in the system. In this regard, the measurement device  506  may include a controller or microprocessor.  
         [0050]     Switches  508  and  510  are used to selectively connect and disconnect the motor  502  to the power source  504 . A transistor control device  512  is used to control the switches  508  and  510  via the transistor  514 . The transistor  514  may be a field effect transistor (FET) or other similar device. A resistor  516  is coupled to the transistor  514  and the measurement device  506 .  
         [0051]     Positional information concerning a barrier  515  moved by the motor  502  is determined by measuring and analyzing the voltage across the motor  502  while the motor  502  is disconnected from the power source  504 . Specifically, when the motor  502  is disconnected from the power source  504 , the motor  502  acts as a generator. While acting as a generator, the back emf voltage generated and measured by the measurement device  506  is directly proportional to the speed of the motor  502 . The speed of the motor  502  may be measured at a periodic rate and is directly proportional to the distance traveled by the barrier  515 . In one example, the position of the barrier  515  can be computed as the second integral of motor speed over time.  
         [0052]     In still another example, the measured voltage can be used to directly determine motor speed and the speed can be used to determine motor torque. The motor torque can then be used to determine whether an obstruction is present in the path of the barrier  515 .  
         [0053]     Torque information concerning the motor  502  can also be determined from the motor current. The current is determined by measuring the voltage across the resistor  516  when the transistor  514  is activated. The resistance of the resistor  516  is known so that the voltage can be calculated using Ohm&#39;s law. The voltage can be used to determine motor torque and whether an obstruction exists.  
         [0054]     Referring now to  FIG. 6 , yet another approach for determining the operating characteristics of a motor that is used to actuate a moveable barrier is described. A dc motor  602  is coupled to a summing amplifier  604  and a Field Effect Transistor (FET)  606 . A micro-processor  608  is coupled to the summing amplifier  604 . The microprocessor  608  may be any suitable microprocessor that is capable of performing voltage measurements.  
         [0055]     When the microprocessor  608  deactivates the FET  606 , the back emf voltage at an input of the microprocessor  608  is read by the microprocessor  608 . As the speed to the motor  602  increases, the voltage at the input of the microprocessor  608  also rises. The magnitude of this voltage depends upon the speed of the motor  602  only and is independent of the load of the motor  602 .  
         [0056]     The voltage measured can be used to determine speed, and the speed can be used to determine a position of a barrier  610 , which is coupled to the motor  602 . Alternatively, the speed can be used to determine the torque of the motor  602 , and the torque can be used to determine whether an obstruction exists in the path of the barrier  610 .  
         [0057]     Referring now to  FIG. 7 , a graph of the performance characteristics of the system of  FIG. 6  is described. The data describes the voltage at the drain of the FET  606  when a Pulse Width Modulated (PWM) signal originating from the microprocessor  602  is used to drive the FET  606 . In this example, the motor supply voltage is a full wave rectified Alternating Current (AC) with a peak voltage of around 28 volts.  
         [0058]     The PWM signal transmitted by the microprocessor  608  is synchronized with the supply voltage. The data shown in the graph shows that the average voltage on the drain of the FET  606  (while the FET is deactivated) is inversely proportional to the speed (RPM) of the motor.  
         [0059]     The back emf voltage of the motor  602  is read by the microprocessor  608  as the average voltage at the drain of the FET  606  while the FET is deactivated. This average voltage is, in turn, inversely proportional to the actual shaft speed of the motor. The determined speed can be used to determine the position of the barrier  610 . Based upon the position of the barrier  610 , the speed may be adjusted. For instance, if the speed is high when the position of the barrier is near the ground, the speed may be slowed in order that the barrier not crash into the ground.  
         [0060]     While there has been illustrated and described particular embodiments of the present invention, it will be appreciated that numerous changes and modifications will occur to those skilled in the art, and it is intended in the appended claims to cover all those changes and modifications which fall within the true scope of the present invention.