Patent Publication Number: US-2007120668-A1

Title: Security System Using Piezoelectric Sensors

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is a continuation-in-part of U.S. patent application Ser. No. 09/522,087 filed Mar. 10, 2000. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
      Not Applicable  
     BACKGROUND OF THE INVENTION  
      1. Field of Invention  
      This invention pertains to a system for monitoring an outdoor perimeter. More particularly, this invention relates to a system for monitoring and distinguishing between a variety of occurrences along a perimeter bounded by a single conductor wire that communicates with piezoelectric sensors.  
      2. Description of the Related Art  
      Residential and light commercial security systems have become an increasingly popular addition to many homes and businesses. These systems are typically based on the electronic detection of a breach in the perimeter of a structure. A breach is detected at either the perimeter itself or the interior of the structure. The perimeter is generally defined as the entrance/egress points to a structure such as doors and windows. Perimeter breaches are generally detected by magnetic sensors which monitor the opening and closing of doors and windows and by frequency sensors attuned to the sound of glass breakage. Interior breaches are generally detected by heat and motion detectors which monitor moving objects having a temperature greater than the ambient temperature. While providing a warning of intrusion, both the detection of perimeter and interior breaches occur after damage to the structure or entry has been obtained. For security purposes it is desirable that the bounded perimeter of interest be divided into zones which define the approximate property lines and/or selected sections thereof.  
      Similarly, motion sensors are used to turn on outdoor lighting thereby providing a deterrent to intrusion onto the property. However, these sensors are indiscriminate in that they may be triggered by small animals, children, or other moving objects which are not considered security risks. Further, because of the difficulty in accurately setting the range, and the accurate detection zone of each sensor, setting up a comprehensive coverage area limited to the boundaries of one&#39;s property is difficult at best. Finally, it should be noted that while the external sensors could be connected to a central alarm system, the inability to discriminate between legitimate security risks and stray animals and the difficulty in defining the protection area render such a system unreliable.  
      Ideally, a monitoring system could identify and announce activity along the monitored perimeter. Accordingly, there is a need for a monitoring system which allows a boundary of protection to be easily defined. Further, there is a need for a monitoring system capable of identifying potential threats to security so as to avoid false alarms.  
     BRIEF SUMMARY OF THE INVENTION  
      In accordance with various features of the present invention a system for monitoring and distinguishing between various activities along a perimeter bounded by a single conductor wire is provided. The system includes at least one piezoelectric sensor in communication with the conductor wire which bounds a protected zone such as the perimeter of the property or selected sections thereof. The signal generated by the activation of the piezoelectric sensor is read by a signal processing device to determine if a security breach has occurred. If a security breach has occurred, an appropriate alarm is energized.  
      The described security system is adaptable for use as a pet containment system as well. The pet that is being contained wears a signal receiver that also delivers a behavior-correcting electroshock stimulus. The signal-producing conductor wire defines the property&#39;s perimeter as described above. When the pet wearing the signal receiver traverses the signal-producing conductor wire, a corrective electroshock stimulus is delivered to the animal. This negative stimulus conditions the pet to remain within the property&#39;s perimeter as defined by the conductor wire and in this way contains the pet. The pet containment application of this security system is designed to function with previously installed pet containment systems. The signal produced by the conductor wire, for example, is capable of reproducing the signal produced by the previously used signal-producing wire boundary in order to avoid the cost involved in purchasing new signal receivers for the pet. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
      The above-mentioned features of the invention will become more clearly understood from the following detailed description of the invention read together with the drawings in which:  
       FIG. 1  is a block diagram of a system for monitoring a wire bounded perimeter showing various features of the transponder of the present invention;  
       FIG. 2  is a block diagram of a system for monitoring a wire bounded perimeter showing various embodiments of the sensors of the present invention;  
       FIG. 3  is a block diagram of a sensor showing various features of the present invention;  
       FIG. 4  is a piecewise external to internal diagram of an activity measurement device for indicating occurrences along a perimeter.  
       FIG. 5  is a perspective view of another embodiment of an activity measurement device for indicating occurrences along a perimeter.  
       FIG. 6  is a block diagram of an alternate embodiment of the system of the present invention incorporating a pet containment transmitter to provide additional functionality;  
       FIG. 7  is a block diagram of an alternate embodiment of the transponder of  FIG. 1  replacing the memory and comparison devices with a digital signal processor;  
       FIG. 8  diagrammatically illustrates the placement of the conductor wire to define a perimeter zone which is monitored for the containment of a pet or the egress of a small child;  
       FIG. 9  diagrammatically depicts the control panel of the signal processing device which detects zone and/or perimeter breach and other conditions;  
       FIG. 10  illustrates a zoning method in accordance with various features of the present invention for determining a location of a breach of the perimeter; and  
       FIG. 11  illustrates a block diagram of a calibration circuit which allows the piezoelectric sensor that is positioned about the perimeter to distinguish between various occurrences or activities causing a zone breach in varying soil conditions proximate the buried cable.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      A system for monitoring a wire-bounded perimeter is illustrated generally at  10  in the figures. The system for monitoring a wire bounded perimeter, or monitoring system  10 , uses at least one sensor  12  located at a predetermined location around a protected area  14  to identify activity at the perimeter of the protected area  14 .  
       FIG. 1  illustrates a block diagram of the monitoring system  10  of the present invention. The monitoring system  10  includes a single-conductor wire  16  which bounds an area defined as the protected area  14 . Electrically connected to the conductor wire  16  at predetermined locations are a series of sensors  12  and a transponder  18 . In the illustrated embodiment, the transponder  18  includes a processing device  20 , a gateway  22 , a comparison device  24 , a memory device  26 , an indicator device  28 , an external interface  30 , and a power supply  32 . Corresponding elements of the monitoring system  10  are labeled with like numerals.  
      The transponder  18  serves as the controller for the monitoring system  10 . Specifically, the transponder  18  supplies power, receives data from the sensors  12 , processes the received data, displays information about the processed data, and communicates with external devices, such as a conventional residential and light commercial security system (not shown). The processing device  20  sequences the operation of these functions. One skilled in the art will recognize that the processing device can be implemented in a variety of ways including discrete logical components (not shown) and a microprocessor (not shown). In the illustrated embodiment, the processing device  20  is a microprocessor for allowing the functionality of the transponder  18  to be varied, with minimal hardware changes, through the use of software. Typical functions of the processing device  20  include providing timing to control signal traffic across the conductor wire  16 , requesting information from the sensors  12 , and analyzing the information received from the sensors  12 . Additionally, the processing device  20  generates an output which is sent to an external interface  30 . The external interface  30  translates the output into a form which is usable by a conventional residential and light commercial security system, allowing the monitoring system  10  of the present invention to be integrated with an existing structural intrusion detection system. Such integration allows the monitoring system  10  to be monitored by an off-premises security monitoring company if desired.  
      Many of these functions compete for transmission time across the single conductor wire  16 . The gateway  22  manages access to the conductor wire  16 . One skilled in the art will recognize that a variety of electrical components can be used to implement the gateway  22  including switches, multiplexers, gates, and universal asymmetric receiver-transmitters (UARTs). In the illustrated embodiment, the gateway  22  is a UART responsive to the processing device  20 . Among the signals competing for use of the conductor wire  16  are information signals directed to one or more sensors  12  from the processing device  20  and information signals from one or more sensors  12  directed to the processing device  20 . In general, the conductor wire  16  carries a power signal from the power supply  32 . Data signals are encoded into the base signal by applying a modulation technique, such as frequency shift keying.  
      To monitor activity near the perimeter of the protected area  14 , the transponder  18  requests information from each sensor  12  by sending a data packet containing the appropriate command characters to the particular sensor  12 . When energized, each sensor  12  detects local activity and sends the detected activity signal to the transponder  18  for processing. The transponder  18  compares the detected activity to a variety of exemplary activity signals. Using the comparison result, the transponder then categorizes detected activity within one of the predetermined classes. One skilled in the art will recognize that various types of sensors  12  can be used depending upon the desired monitoring capabilities of the system, including, but not limited to, seismic, infrared, and audio sensors. Further, one skilled in the art will recognize that various levels of sophistication in the discrimination process can be used to provide more specific identification of the activity source.  
       FIG. 2  illustrates a block diagram of the present invention with emphasis on various embodiments of the sensors  12 . The sensors  12  each include a communication interface  34 , a transceiver  36 , a DC power source  38 , and an activity measuring device  40 . Wired sensors  12 A,  12 B,  12 C, and  12 D are shown in the figures. In each of the wired sensors  12 A,  12 B,  12 C, and  12 D, the communication interface  34  is a transformer physically coupled to the wire  16 .  
      In the illustrated embodiment, a variety of DC power sources  38  are shown. First is a power conditioning in-line zener diode  38 A connected to the conductor wire  16  for generating a DC voltage drop used to power the sensor  14 A. Next is a DC transformer  38 B for converting the AC voltage traveling through the conductor wire  16  into a DC voltage. Finally, independent power sources  38 C, and  38 D are shown. Each of the independent power sources  38 C, and  38 D can be a battery or a solar cell. One skilled in the art will recognize that the independent power source  38 D provides the greatest benefit when used in a mobile sensor such that it can be readily moved without the need for connection to an external power source.  
      Each of the sensors  12  is provided with a unique identification, or address, allowing the transponder  18  to communicate with a particular sensor  12 . Communication is accomplished using a data packet having a header containing at least a frame synchronization code, at least one command character, at least one address character, and a security code. One skilled in the art will recognize that other information may be included, including, but not limited to, packet size and checksum information. In the illustrated embodiment, the data packet is transmitted using an RS-232 data format. The frame synchronization code is made up of sixteen (16) consecutive logical one bits coupled with no more than four (4) stop bits between the characters in the data packet. The command packet is transmitted through the conductor wire  16  using any appropriate modulation scheme. The preferred embodiment utilizes frequency shift keying (FSK) for transmitting the data packet. One method for implementing a FSK transmission is to use a higher frequency, such as 18 kHz, to transmit a logical one and a lower frequency, such as 14 kHz, to transmit a logical zero.  
       FIG. 3  illustrates the sensor  12  of the present invention. The transceiver  36  includes a sensor processing device  42 , a limiting amplifier  44 , a driving amplifier  46 , and a frequency tuner  48  in communication with a tightly wound ferrite core antenna  50  for monitoring an electromagnetic field for disruptions and for communicating with the transponder  18 . In the illustrated embodiment, the frequency tuner  48  is a capacitor selected to tune the transceiver  36  to the frequency having the desired sensitivity. In the stand-by, or receiver mode, the driving amplifier  46  is turned off allowing the ferrite core antenna  50  to pick up the signal being carried through the conductor wire  16 . The limiting amplifier  44  amplifies the received signals into logical ones and zeros which are presented to the sensor processing device  42  for period measurement using a frequency discrimination technique suited for a small microprocessor. In the illustrated embodiment, frequency discrimination is achieved by comparing the measured period to a predetermined threshold level. Conversely, in transmitter mode, the driving amplifier  46  is activated and the desired transmission frequency generated by the sensor processing device  42  for the current response character is impressed on the input to the driving amplifier  46  and broadcast by the ferrite core antenna  50 .  
      When a request is received by the sensor  12 , the activity measurement device  40  is activated to detect local activity. The activity measuring device  40  is positioned and adjusted such that activities near to or approaching the perimeter of the protected area  14  from the outside are detected. The detected activity signal is then encoded by the sensor processing device  32  and transmitted to the transponder  18 , of  FIG. 1 , by the transceiver  36 .  
       FIG. 4  is a piecewise external to internal diagram of an embodiment of the activity measurement device  40  of  FIG. 3 . The activity measurement device  40  includes an outer shield  52  and an insulating jacket  54  to provide rugged protection for an inner conductor  56  and a piezoelectric polymer  58 . The piezoelectric polymer  58  generates an electric signal in response to a mechanical stress, such as compression. Therefore, as an approaching entity steps on the ground proximate to the sensor  12 , the ground is compressed, thus compressing the sensor  12 , and ultimately compressing the activity measurement device  40 . The compressed activity measurement device  40  leads to a mechanical stress on the piezoelectric polymer  58  which generates an electrical signal indicating an occurrence at the perimeter. The electrical signal is transmitted from the piezoelectric polymer  58  to the conductor wire  16  by way of the inner conductor  56 . The conductor wire  16  then carries the electrical signal to the transponder  18 .  
       FIG. 5  illustrates another embodiment of the activity measurement device  40 . In this embodiment the activity measurement device  40  includes a base  60 , a structural support  62 , and a thin cut of the piezoelectric polymer  58 ′. The piezoelectric polymer  58 ′ is secured to the structural support  62  by way of a solder. The piezoelectric polymer  58 ′ is disposed on the support  62  such that a significant portion of the piezoelectric polymer  58 ′ extends beyond the support  62 . An activity measurement wire  64  is in electrical communication with the piezoelectric polymer  58 ′. The support  62  is secured to the base  60  so as to position the piezoelectric polymer  58 ′ above the base  60 . As an entity steps on the ground proximate to the sensor  14 , the activity measurement device  40  vibrates. Consequently, the extending portion of the piezoelectric polymer  58 ′ vibrates and generates and electrical signal in response the vibration. The generated signal is transmitted to the conductor wire  16  by way of the activity measurement wire  64 . The generated signal is then transmitted to the transponder  18  by way of the conductor wire  16 .  
      Those skilled in art will recognize that the activity measurement device  40  may be another piezoelectric-based device without departing from the scope or spirit of the present invention. Those skilled in the art will also recognize that the activity measurement device  40  may be a device other than the discussed devices, such as seismic, infrared, and audio sensors, without departing from the scope or spirit of the present invention.  
      Returning now to the illustrated embodiment of  FIG. 1 , the processing device  20 , which includes digital signal processing capabilities, conditions the signal and the comparison device  24  compares the detected activity signal to exemplary activity profiles from selected sources, such as vehicles, animals, and humans, which are stored in the memory device  26 . A result generated from the comparison device  24  is generated and interpreted by the processing device  20 . In the illustrated embodiment, the processing device  20  is configured to generate one of four responses: vehicle, human, animal or no activity, along with the identification of the sensor  12  where the response was generated. Should activity meeting determined characteristics be detected, the processing device  20  generates an alert which is transmitted to a user through the indicator device  28  and/or to an external conventional residential and light commercial security system through the external interface  30 . One skilled in the art will recognize that the processing device  20  can be configured to selectively transmit alert signals to the various outputs. For example, in one embodiment, when an animal is detected, the monitoring system  10  displays an alert at the indicator device  28 , but does not pass any information on through the external interface  30 . Similarly, when a human is detected, alerts are sent to both the indicator device  28  and the external interface  30 . Further, one skilled in the art will recognize that the indicator device  28  can vary depending upon the type and amount of information offered to the user. In the illustrated embodiment, the indicator device  28  is a multi-line, alphanumeric display screen which can display the time, date, location, and type of activity. Other types of indications could be utilized, such as audio tones or light-emitting diodes representing a specific condition or location. Finally, one skilled in the art will recognize that other types of information can be communicated through the indicator device  28  including, but not limited to, diagnostic information and system status.  
       FIG. 6  illustrates an embodiment of the monitoring system  10  of the present invention incorporating an electronic pet containment function known to those skilled in the art. To implement the pet containment function, the transponder  18  additionally includes a signal generator  41  and a transmitter  43 . The signal generator  41  generates a radio frequency modulated electromagnetic signal of the type used in typical pet containment systems. The transmitter  43  transmits the containment signal through the conductor wire  16 . The pet  66  to be confined wears a receiver  86  configured to receive the containment signal and apply a corrective stimulus upon a predetermined trigger. Because the containment signal must coexist with the other information traveling along the conductor wire  16 , the containment signal is routed through the gateway  22  and the timing of the containment signal is controlled by the processing device  20 .  
       FIG. 7  illustrates a block diagram of an embodiment of the transponder  18  using an alternate method of classifying the detected activity signals. The transponder  18  replaces the comparison device  24  and the memory device  26  with a digital signal processing device  68 . The digital signal processing device  68  applies a digital filter to each detected activity signal. The filtered activity signal is then classified based on the response characteristics by the processing device  20 . The transponder  18  incorporating the digital signal processing device  68  is uniquely suited to use with a variety of sensor types. For example, the digital signal processing device  68  can be configured to apply to differing digital filters to each detected activity signal based upon the sensor type, thereby allowing the processing device  20  to identify activity in a number of differing forms and respond appropriately.  
      One skilled in the art will recognize that the ultimate function of the monitoring system  10  is to detect and categorize the activity prior to penetration of the protected area  14 . In this regard, various components of the system are interchangeably located without interfering with the objects of the present invention. Specifically, the digital signal processing device  68 , the comparison device  24 , the memory device  26 , and the processing device  20  may be located in each sensor  12  so that the transponder  18  simply collects the results and displays the information.  
      One skilled in the art will recognize that both the transponder  18  and the sensors  12  can include additional electronics, including modulators, demodulators, amplifiers, filters, etc., to enhance the basic function, accuracy, and reliability of the present invention without interfering with the scope of the present invention. Further, one skilled in the art will recognize that, within each of the sensors  12  and the transponders  18 , signals can be communicated between the various components using a variety of methods including the use of a bus.  
      Referring now to  FIG. 8 , the conductor wire  16  is shown in an installation about the perimeter  70  of a dwelling  72 . It is noted that the conductor wire  16  is offset from the property boundary or perimeter  70  and defines a protected zone. The bicycle  74  is an article that will be detected if it moves over the containment boundary as illustrated diagrammatically at  76 . More specifically, if the bicycle is ridden over the sensor  12  disposed about the protected zone, generation of an activity signal by the sensor  12  proximate the boundary at  76  will alert the homeowner that the article, bicycle, has been moved to a prohibited area. The activity signal generated by the cable as a result of the bicycle stressing the sensor  12  will generate an alarm or alert at location  78  on the indicator device  28  shown in  FIG. 9 .  
      The indicator device  28  operates in a manner similar to the indicator device  28  shown in  FIGS. 1, 6  and  7 , and comprises part of a the transponder  18 . It will be noted that perimeter zones A, B, C and D are notes at  80   a - 80   d  in  FIG. 9 . These zones correspond to the sensors  12  shown in  FIG. 10  at  82   a - 82   d , respectively. The stressing of any of sensors  12  causes a corresponding alert to be energized on the indicator  28 . The piezoelectric polymer generates a voltage differential measured as a local activity signal which is transmitted through the conductor wire  16  when stressed. The indicator  28  is connected to a suitable processing device such as the processing device  20  in  FIG. 7  through connector  84  shown in  FIG. 9 . The activity signal from the sensors  12  is processed in a manner as described above in connection with  FIG. 6 , with the exception that the conductor wire  16  carries the sensor  14  activity signal to the gateway  22  where it is processed.  
      The voltage generated by the compression of the piezoelectric sensor  12 , or local activity signal, is read as a filtered local activity signal by the digital signal processing device  68 . The digital signal processing device  68  turns the local activity signal into a filtered local activity signal. Both the magnitude and the pattern of the voltage in the local activity signal are interpreted by the digital processing device  68  as it is converted into a filtered activity signal. The digital signal processing device  68  relays the filtered activity signal to a comparison device  24  that compares the filtered local activity signal to at least one reference signal. This comparison result is then relayed to the processing device  20  and the system takes appropriate measures according to the result. It is in this way determined whether or not the entity generating the local activity signal is a security risk.  
      The indicator device  28  also includes CONTACT ON, PERIMETER ALERT, CABLE BREAK and PWR (power) displays as shown in  FIG. 9  for signaling an operator that these conditions exist when the respective display is energized. The indicator device  28  is connected to the conductor wire  16  as shown diagrammatically in  FIG. 9  through the processing device  20  and the gateway  22  such as those shown in  FIG. 6 . Moreover, the conductor wire  16  can mark the perimeter for containment of a pet  66  wearing a receiver  86  as is described above in connection with the pet  66  in  FIG. 6 .  
      The stress on the sensor  12  varies with soil conditions. Typically sandy soil is less responsive than dry soil. In order to overcome this drawback, a calibration unit  88  is integrated into the system in the preferred embodiment as is shown in  FIG. 11 . This unit periodically sends a calibrated shock or pulse to the soil, and the received signal is used as a calibration signal. The gain of the circuit together with other performance components could be adjusted to compensate for the differing soil conditions. As desired, the calibration unit could be triggered by a unique signal produced in the sensor  12 . Alternatively, an autonomous device with a unique vibration signature could be used for activity detection purposes.  
      In the calibration unit  88  of  FIG. 11 , a signal driver  90  from the monitoring system  10  is directed towards the calibration unit  88  through the conductor wire  16 . A signal is directed from the calibration unit  88  to the perimeter detection circuiting through leads  84  for each zone circuiting to be adjusted. Comparisons of the signals to and from the perimeter detection circuiting allows adjustment of the calibration unit. This adjustment can be accomplished by the dial  92  of the indicator  28 .  
      What has been disclosed is an external perimeter monitoring system using strategically placed piezoelectric sensors connected to a transponder by conductor wire conductors through which data signals and power signals are sequenced. Activity detected at the sensors are analyzed to classify the source of the activity and an alert is generated if necessary. The external perimeter monitoring system is capable of interfacing with a conventional residential or light commercial security system to allow off-premises monitoring. Further, an alternate embodiment of the external perimeter monitoring system is integrated with a conventional electronic pet confinement system allowing the conductor wire to serve as a radio frequency antenna defining the confinement boundary with the confinement signal added to the data signal and power signal sequencing.  
      While a preferred embodiment has been shown and described, it will be understood that it is not intended to limit the disclosure, but rather it is intended to cover all modifications and alternate methods falling within the spirit and the scope of the invention as defined in the appended claims.