Sonar location monitor

[0002] Not applicable.

[0003] Not applicable.

[0004] The present invention relates generally to a personnel location device or system, and, more particularly, to a sonar location monitor for indicating and/or determining the location of a person (i.e., a swimmer) in a water environment (such as a lake, pool, or beach swimming area).

[0005] Swimmer safety is an important concern in all water sports and activities. Lifeguards are assigned the responsibility of protecting the lives of the swimming public. However lifeguards can monitor only limited portions of a swimming pool, water park, or beach area and have particular difficulty in seeing what goes on near the bottom. In many instances, despite the presence of lifeguards, help for a swimmer in trouble comes far too late to prevent drowning. Even with adequate staffs, lifeguards often find it difficult to monitor large numbers of swimmers.

[0006] There have been attempts at developing automatic alarm equipment to warn the staff of swimmers in danger. Several of these inventions have focused on protecting children from drowning in backyard pools. (See, e.g., U.S. Pat. Nos. 3,953,843 3,969,712 4,079,364 4,121,200 4,187,502 4,747,085 5,049,859.) The devices described by these patents simply monitor the presence of an unauthorized swimmer or object in the pool. These devices are designed for very small pools and do not possess any location or tracking capabilities.

[0007] Some devices for detecting a swimmer in the water are known. Many of these detection methods rely on some variation of an acoustic technique. For example U.S. Pat. No. 4,337,527 describe a system that uses ultrasonic transmission through water to identify underwater targets. A human operator listening to headphones classifies the target and determines its location. U.S. Pat. No. 4,459,689 describes an apparatus utilizing combination energy transmitting and receiving transducer for detecting and locating objects within a plurality of zones. U.S. Pat. No. 4,635,242 describes an underwater signaling device utilizing acoustic sound generators. Several devices for detecting swimmers in distress are known. (See, e.g., U.S. Pat. Nos. 4,932,009 and 5,097,254.) However, these devices do not pinpoint the location of the distressed swimmer.

[0008] Therefore, of particular interest is the development of a system for monitoring a large number of swimmers in a pool, beach area, or water park. Such a system would be capable not only of monitoring the status of a large number of swimmers but would also be capable of pinpointing the location of a swimmer in distress with sufficient warning to permit a timely rescue.

[0009] All references cited herein are incorporated by reference.

[0010] The present invention is similar to a system disclosed in U.S. Pat. No. 5,907,281 by the same inventors (the entire disclosure of which is hereby incorporated by reference) in that its use overcomes many of the disadvantages of the prior art in tracking swimmers in pools, beaches, and water parks. The prior methods do not possess automatic location and tracking capability. In fact many of the systems cited above are designed for simple detection of a water disturbance and as such can identify only the presence or absence of an object in the pool.

[0011] An objective of the invention is to provide an improved apparatus or system for detecting and locating swimmers at risk in a timely manner that would facilitate their rescue and prevent many of the drownings that occur each year. This objective can also encompass locating non-swimmers or small children who enter the water.

[0012] The invention provides a low frequency SONAR surveillance system for tracking the location of swimmers who may be in peril. By definition, SONAR stands for SOund NAvigation and Ranging. The invention includes the equipping of each swimmer with an individual Sonar Swimmer Location Monitor (SSLM) that transmits a series of ultrasonic pulses when specified safety thresholds of time and depth are exceeded. The invention utilizes a “pinger” to generate pulses that can be received by a network of hydrophones deployed around the perimeter of the pool. A hydrophone is an underwater microphone or transducer designed to detect or receive sound underwater. The invention also is capable of amplifying, filtering, and processing the received signals resulting in a graphical and/or numerical display of the distressed swimmer's location. The invention is also capable of triggering an alarm (audible or visual) whenever specified safety thresholds are exceeded.

[0013] The invention provides a miniaturized electronic device, or SSLM, that can be worn by a swimmer to enhance his/her safety during recreational swimming in crowded pools, beaches, and water parks. The SSLM can detect or measure swimmer distress by any number of criteria, including, but not limited to, detecting water pressure, water depth, the amount of time spent in the water, submersion in water, and/or any combination of these.

[0014] The invention provides a device to transmit omnidirectional ultrasonic pulses from a miniature transducer called a pinger contained in the SSLM.

[0015] The invention also provides a receiver network composed of hydrophones deployed at strategic locations around the pool. In one preferred embodiment the invention provides a system in which the hydrophones are deployed in the four corners of the pool as well as along each side of the pool.

[0016] The invention is capable of being automatically powered on whenever it is simply immersed in water, or immersed in water at a pre-selected depth and/or period of time, and automatically powering down whenever it leaves the water. The invention further is capable of powering “ON” in a monitor mode. In the monitor mode the unit does not transmit even though it is “ON.” The invention can also provide an alarm that is activated whenever the SSLM is powered “ON.” This mode of operation is useful for detecting persons that are not supposed to be in the water, such as small children who are outfitted with a monitor.

[0017] The invention is also capable of telemetering the data from the swimming area receivers to a central processor via wireless telemetry.

[0018] Yet another objective of the invention is to utilize computer systems to detect, display, and record all swimmer events of a potentially high risk nature occurring at pools, beaches, and water parks. The invention further is capable of recording all swimmer distress events in computer memory for playback and analysis at a later date if needed.

[0019] Other objectives and advantages of the SSLM system will be readily appreciated as the invention becomes better understood by reference to the following detailed descriptions when considered in conjunction with the accompanying drawings.

[0020] FIG. 1 is a diagrammatic illustration of the Sonar Swimmer Location System (SSLM) embodying the invention;

[0021] FIG. 2 is a plan view of a typical SSLM hydrophone array deployment scheme; and

[0022] FIGS. 3 (3A-3G) is a schematic diagram of a single receiver channel.

[0023] As used herein, “low frequency” refers to a range of 500-75,000 Hz and includes both sonic and ultrasonic frequencies.

[0024] The present invention is a low frequency sonar surveillance system for tracking the location of swimmers who may be in danger. Each swimmer is equipped with an individual Sonar Swimmer Location Monitor (SSLM) which transmits a series of ultrasonic pulses when specified thresholds monitored by the SSLM (such as depth and time) are exceeded. The invention transmits omnidirectional pulses through the water from a transducer contained in the SSLM to a network of receiving transducers deployed around the perimeter of the pool or water park. The invention amplifies, filters, and processes the received signals resulting in a graphical and/or numerical display of the distressed swimmer's location. The invention is also capable of triggering an alarm (audible or visual) whenever specified thresholds are exceeded.

[0025] In various environments the SSLM identifies swimmer distress by detecting water pressure, water depth, the amount of time spent in the water, and/or submersion in water. However, any criteria related to possible swimmer distress may be employed. The device also may be designed to interpret contact with water as a distress event, for example, to locate small children who have fallen into a swimming area.

[0026] Another embodiment of the present invention additionally can automatically power the SSLM whenever it is immersed in water and automatically power down whenever it leaves the water.

[0027] Other embodiments of the present invention include a capability of telemetering the data from the receivers to the central processor via wireless telemetry.

[0028] Still other embodiments of the invention include a capability of recording all swimmer events related to the use of the SSLM in computer memory for playback and analysis at a later date if necessary.

[0029] In a preferred embodiment, as a distressed swimmer sinks beneath the surface of the water, his/her SSLM senses an anomaly caused by exceeding a threshold water pressure for a threshold time period and activates a pinger to begin sending its pulsed alarm signal. The alarm signal is detected by one or more of the hydrophones and amplified and filtered by the receivers before passing it on to the central processor. The location of the distressed swimmer is determined by computer algorithms designed to process the signals received by the network of receivers. The signal processing algorithms minimize errors resulting from background noise, interference, and reflections from pool boundaries. As the alarm signal is flashed on the video display screen, an accompanying audible and/or visual alarm and location display is provided in the vicinity of the lifeguard station to alert the guard personnel of the swimmer distress.

[0030] In a preferred embodiment the invention comprises a process whereby the device worn by the swimmer is activated when certain predefined thresholds of depth and time are exceeded simultaneously. The SSLM is packaged in a miniature waterproof enclosure that is normally attached to a belt (other locations are possible) worn by the swimmer. In an alarm situation, the SSLM sends out ultrasonic pulses from a pinger contained in the device. Sufficient battery power is provided in the SSLM device to provide repetitive pulse transmission for a prescribed period of time. Sound waves propagate in water with little attenuation so receiving the signals over the limited dimensions of the pool or water park will not be difficult. The main problem will be dealing with the reflections that result from the boundaries of the pool or water park. Location errors resulting from these reflections are minimized in the data processing algorithms.

[0031] The receivers utilize low noise preamps, bandpass amplifiers, and low pass filters to provide primary signal conditioning. The receiver outputs are then cabled to a central processor with a CRT monitor that shows the outline of the pool and displays the location of any alarm signals that are detected. An alternate method of transmitting the receiver output signals to the central processor is one that uses short-range wireless telemetry. The SSLM terminal equipment may include video and audio alarm systems as well as a provision for recording all significant events.

[0032] Those skilled in the art recognize that the device worn by the swimmer may comprise any number of modes of detecting conditions related to the swimmer, that by way of example and not limitation can include the depth in the water, degree of movement, time spent at or under a certain depth or any one of a plethora of devices utilized for monitoring swimmer distress known in industry and in the art.

[0033] The following examples are offered by way of illustration and are not intended to limit the invention in any manner.

[0034] In the illustration provided in FIG. 1 there is shown a Sonar Swimmer Location Monitor (SSLM) System 10 which is designed to alert guard personnel when a swimmer is at risk. FIG. 2 illustrates a typical SSLM deployment scheme, and more particularly, an SSLM hydrophone array deployment scheme. The swimmer wears a small belt-mounted device called the SSLM 11 that senses depth over repetitive time intervals and decides when the individual is at risk. The transmitting transducer (pinger) 13 is thus triggered “ON” and sends out ultrasonic pulses that are received by a network of hydrophones 50 around the pool. Each hydrophone is connected to a receiver 15 and the outputs of the receivers are cabled to the central processor unit 17 that computes and displays the swimmer's location.

[0035] For smaller swimming areas that do not wish to invest in a complete computer and graphic user interface, a simplified alarm annunciator can be used to indicate the presence of an alarm situation without pinpointing the swimmer's location.

[0036] The SSLM transmitting device 11 worn by the swimmer is packaged in a waterproof container the approximate size of a pack of playing cards. It attaches to an adjustable belt or other means of fastening the device that is worn by the swimmer at all times he/she is in the water, or near the water. Battery power is automatically applied to the device whenever the unit is submerged in the water. Under nonemergency or non-distress conditions the drain on the battery will be insignificant, on the order of a few milliamps. Only when a potentially distressed swimmer event occurs and the unit triggers the transmitter “ON” does the current drain on the battery rise to about 100 milliamps. The SSLM unit 11 is designed for at least one hour of transmission under swimmer distress conditions. Because the application of power is automatic, the device can also be used to detect persons who fall into the water.

[0037] Under normal operation (for water parks, pools, beaches, and other swimming area applications), the SSLM unit 11 senses waterpressure/depth (e.g., via a pressure sensor 12) and triggers a counter (e.g., a depth discriminator 14) to count the time that a predefined water pressure is exceeded (for example, that pressure associated with a 3 ft. depth of the belt worn unit). When that water pressure is exceeded on a continuous basis for a predefined time interval (e.g., alarm discriminator 16), for example, 30 seconds, a potential swimmer distress is identified, and the pinger 13 begins transmitting. The ultrasonic waves emitted by the pinger 13 are received by one or more of the hydrophones 50 surrounding the swimming area and the SSLM location is quickly determined via triangulation algorithms and displayed by the central processor. Also, the guard personnel may be alerted by an audible and/or visual alarm that is sounded at their duty station, and with a remote display of the SSLM location.

[0038] FIG. 3 (3A-3G) is a schematic of one of the receiver channels 15. These units are packaged in water-resistant enclosures (since these are located generally near the terminals of the underwater hydrophone cables) and are securely mounted in a protected location. Preferably, the units are powered using long-life rechargeable batteries. The hydrophone cable is connected to the receiver input amplifier U3. The amplified signal is then fed to a bandpass amplifier U2 which is a superheterodyne amplifier that amplifies the signal by a factor of 1000. The typical bandpass characteristics of U2 include a center frequency of 25,000 Hz and a bandwith of 1,000 Hz. The remaining circuitry in the receiver consists of a two stage active low-pass filter (U1A and U1B) followed by a switched capacitor low-pass filter U5. The signal is then fed through another amplifier U4 to a two-stage detector-filter combination (U7A and U7B). Frequency is controlled by an oscillator-divider combination (U8 and U9A). The alarm signal is characterized as a repetitive tone pulse of 25,000 Hz ultrasonic energy operating at a 10 percent duty cycle at a rate of one pulse per second. In response to this signal, the receiver output is a dc pulse of 100 millisecond duration appearing every second.

[0039] The terminal equipment (central processor) 17 operates on these pulses in a straightforward manner. A central processing unit consisting of a computer and monitor is used in most cases. Normally they are equipped with a Graphic User Interface (GUI) enabling the computer to show the plan view of the water area of the pool, water park, or beach with flashing symbols to show the location of the SSLM transmissions.

[0040] All references mentioned in this specification are herein incorporated by reference.