Patent Application
20160039340
1. Field of the Invention
The disclosures herein relate generally to proximity detection and collision avoidance systems.
2. Background of the Invention
Each year, there are tens of thousands of injuries related to forklifts. Forklift accidents are a leading cause of occupational injuries. In 2013, there were 70 forklift fatalities. According to 2008 data from the U.S. Department of Labor's Bureau of Labor Statistics, the number one cause of lift truck related work fatalities is pedestrians being struck by a vehicle. Industrial accidents are a major cause of workplace injury. Lack of situational awareness can result in collisions between industrial equipment, like forklifts, or collisions between pedestrians and industrial equipment. In short, there exists a significant need for advances in proximity detection and collision avoidance systems.
The present invention pertains to a selective proximity detection system. A selective proximity detection system comprises at least one proximity tag, a plurality of sensor nodes, and at least one alert node. A sensor nodes comprises a proximity detector capable of detecting proximity with respect to the proximity tag, and a motion detector. In a preferred embodiment, a motion detector is an infrared detector. In alternate embodiments, a motion detector may employ video, radar motion sensing, or sensing of scattered RF signals, preferably FM broadcast signals whose half wavelength is comparable in dimension to the height of a typical person. In a preferred embodiment, a proximity detector is a NFER locator-receiver and a proximity tag is a NFER tag transmitter. In alternate embodiments, a NFER locator-receiver may employ a directional electrically small antenna array. In alternate embodiments, a proximity detector may employ ZigBee, WiFi, Bluetooth, passive scattering of ambient RF signals or other means of proximity detection. Also in a preferred embodiment, the proximity detector is normally off until the microprocessor turns the proximity detector on in response to a motion detection by the motion detector, thus saving power and maximizing battery life. A sensor node conveys motion detection data and proximity detection data to an alert mode via a datalink. In preferred embodiments, a datalink is a low-power Bluetooth data link.
An alert node selects from among a variety of alert responses based upon the motion detection data and proximity detection data. The alert node employs a warning device such as a light or audible alarm which may be either co-located on incorporated in the alert node or remote from the alert node.
In preferred embodiments, a selective proximity detection system employs a remote digital device to configure and/or monitor the selective proximity detection system.
In alternate embodiments, a selective proximity detection system employs a process comprising the steps of
The signal may be an FM broadcast band signal and the plurality of thresholds may include thresholds to distinguish between pedestrians and heavy equipment like forklifts.
In still further alternate embodiments, a selective proximity detection system determines a location of a scatterer by the steps of:
The calibration and location transmissions may involve FM broadcast band signals, and the received signal characteristics may include a plurality of signal amplitudes.
Additional advantages of the invention will become evident on review of the drawings and specification.
The appended drawings illustrate only exemplary embodiments of the invention and therefore do not limit its scope because the inventive concepts lend themselves to other equally effective embodiments.
Selective Proximity Detection System A selective proximity detection system helps avoid collisions between industrial equipment as well as collisions between pedestrians and industrial equipment. In a preferred embodiment, a selective proximity detection system comprises a plurality of proximity tag transmitters, a plurality of sensor nodes, and a plurality of alert nodes.
Applicants discovered that orthogonal magnetic antennas offer unique advantages for transmission and reception in real-time location systems, particularly Near-Field Electromagnetic Ranging (NFER) systems and in other applications like proximity detection. Details may be found in “Near-field location system and method,” (Ser. No. 11/272,533, filed Nov. 10, 2005, now U.S. Pat. No. 7,307,595, issued Dec. 11, 2007). Additional compact antenna designs are shown in applicant's “Space efficient magnetic antenna system,” (Ser. No. 11/473,595, filed Jun. 22, 2006, now U.S. Pat. No. 7,755,552 issued Jul. 13, 2010). Other antenna concepts of value in an RTLS and elsewhere are disclosed in Applicant's co-pending “Planar antenna system,” (Ser. No. 12/857,528, filed Aug. 16, 2010, now U.S. Pat. No. 8,436,780 issued May 7, 2013), and “Space efficient magnetic antenna method,” (Ser. No. 12/834,821, filed Jul. 12, 2010, now U.S. Pat. No. 8,922,440 issued Dec. 30, 2014). All these disclosures are hereby incorporated by reference.
A significant advantage of the selective proximity detection system 400 is that workers, like pedestrian 414, do not need to carry any device in order to be warned regarding a potential collision with heavy equipment like forklift 415. Thus, the selective proximity detection system 400 protects workers, truck drivers, and facility guests without requiring them to remember to use, carry, or employ some device. The selective proximity detection system 400 offers significant advantages over prior art systems that require workers, guests, and other pedestrians to carry a device in order to be protected.
In addition, because the selective proximity detection system 400 can identify when a motion detection correlates to a proximity detection of heavy equipment like forklift 415, it triggers an alert or warning only when heavy equipment is present, and not when two pedestrians approach a corner or intersection. This selectivity offers substantial advantages over prior art systems that rely on motion detection alone and therefore have a significant problem with unnecessary alerts for pedestrian-pedestrian interactions. The selective proximity detection system 400 thus avoids “warning fatigue” that may lead to over stimulated workers ignoring an alert since so many alerts are false alarms in prior art motion detection only systems.
Remote digital device 420 allows a user to configure selective proximity detection system 400 via datalinks to component devices like sensor nodes 402, and a alert node 403. In a preferred embodiment, remote digital device 420 is a tablet or smartphone employing a Bluetooth data link in preferred embodiments. Detection thresholds, ranges, alert modes, and algorithms may be configured to suit a users' particular deployment needs. A Bluetooth data link may further employ encryption or other security measures to avoid unauthorized tampering with settings and configuration. Further, remote digital device 420 enables a user to monitor battery status and other critical parameters of the selective proximity detection system 400.
In a typical deployment of a preferred embodiment, a piece of industrial equipment (such as forklifts 433) will have associated proximity tags 426. If an alert node 428 receives motion detection data from a sensor node 427 and proximity detection data from a different sensor node 427, an alert node 428 provides warning of a potential pedestrian-forklift collision by illuminating a warning light 429 with a first pattern (for instance, solid or continuous on). If an alert node 428 receives proximity detection data from two or more sensor nodes 427, an alert node provides warning of a potential forklift-forklift collision by illuminating a warning light 429 with a second pattern (for instance, flashing). Motion detection alone from different sensors will not trigger an alert.
In the example of
A second forklift with associated proximity tag #2 triggers a proximity detection at sensor node #4. Alert node #2 receives a proximity detection from sensor node #4, but in the absence of any addition detections, does not trigger associated warning light #2. Sensor nodes may be associated with a plurality of alert nodes. For instance, alert node #1 and alert node #2 both receive detection data from sensor node #3.
The selective proximity detection system 425 is selective in that it can provide different alerts or warnings based on the nature of a potential collision—one alert response to aid forklift drivers to avoid a forklift-forklift collision, a different alert response to aid a forklift driver and pedestrian to avoid a forklift-pedestrian collision, and an alert response to aid pedestrians to avoid collisions with each other. In addition, a selective proximity detection system can be configured to avoid alerting for a potential pedestrian-pedestrian collision. This “null” alert response avoids the warning fatigue, loss of awareness, and potential for accidents associated with a system that delivers excess false alarms. Thus a pedestrian knows that a particular alert response means a forklift is present and can take appropriate action to avoid injury. A selective proximity detection system 425 can provide a range of warning levels and different alert responses to avoid false alerts and help ensure that alerts are taken seriously and not ignored due to excessive false alarms.
A wide variety of alternate algorithms are possible, so the logic diagrams of
Antennas for use with NFER systems are electrically-small, typically much smaller than the wavelength. For instance, an NFER system operating at 1 MHz with a wavelength λ=300 m may employ antennas about 30 cm in dimension (λ/1000) or smaller. These electrically small antennas typically exhibit omnidirectional or dipole-like patterns. Applicant's “Directive electrically-small antenna system and method,” (Ser. No. 13/436,956, filed Apr. 1, 2012) presents further antennas of use in conjunction with a low-frequency, near-field proximity detection or location system. This application is incorporated in its entirety by reference.
In a preferred embodiment, motion detection and proximity detection for a selective proximity detection system are instantiated in separate systems. This has the advantage of detecting pedestrians without those pedestrians being associated with a proximity tag. An interesting alternative embodiment employs changes in the signal strength of scattered ambient signals so as to provide proximity detection and location information for a passive target such as a pedestrian.
The inventors have discovered that FM broadcast band (88 MHz-108 MHz) signals are well-suited to this application. These FM broadcast band signals may be transmitted by an FM broadcast station, by a low-power transmitter operating in or around the FM broadcast band, or other source of RF signals whose frequencies are within or near the FM broadcast band. Their nominally 3 m wavelengths resonate strongly with scatterers about one half wavelength (˜1.5 m) in length. This is approximately the height of a typical person. In a preferred embodiment FM broadcast-band signals-of-opportunity may be employed. In alternate embodiments, signals-of-opportunity may be supplemented by or replaced by signals from beacons deliberately added or introduced to an environment within which a motion and proximity detection system might operate.
Applicants recently discovered that AM broadcast band signals are characterized by “near field” behavior, even many wavelengths away from the transmission tower. These localized near-field signal characteristics provide the basis for a “Method and apparatus for determining location using signals-of-opportunity” (Ser. No. 12/796,643, filed Jun. 8, 2010, now U.S. Pat. No. 8,018,383 issued Sep. 13, 2011). The techniques therein disclosed enable an RTLS comprising a mobile tag receiver employing signals-of-opportunity to determine precise location or position. Applicants noted that this signal-of-opportunity location approach could enable a suitable Locator-Receiver to determine its own position with respect to scattered FM band signals. More generically, passive receiver tag RTLS employing an uncooperative signal is described in Applicant's co-pending “Near-field electromagnetic location system and method,” (Ser. No. 12/977,067, filed Dec. 23, 2010) along with other improvements in the RTLS arts.
The embodiment of a selective proximity detection system hereinafter disclosed enables detection and location of a passive scatterer, such as a person, by exploiting the interaction of the person with the standing wave behavior in the area within several wavelengths of the Locator. In this discussion, the term “Locator” or “Locator-Receiver” may be employed to refer to a selective proximity detection system (PDS) hereinafter described employing detection and location of a passive scatterer of ambient RF signals.
In a preferred embodiment, antenna 727 further includes a minimum coupling orthogonal magnetic antenna array 729 as further described in Applicant's co-pending “Minimum coupling symmetric array,” application Ser. No. 14/313,932 filed Jun. 24, 2014. This application is incorporated by reference. Orthogonal magnetic antenna array 729 has the advantage of enabling a single channel receiver to capture all three orthogonal field components if used in conjunction with a multiplexer. Alternatively, the inputs of the three element in orthogonal magnetic antenna array 729 may be summed to achieve a good approximation to the total field amplitude and total signal power. A smart phone 726 typically has an analog-digital convertor (ADC) capability that can output audio frequency signals to the headphone jack to enable either varactor tuning or multiplexing. An averaged pulse width modulated (PWM) signal can yield a desired varactor tuning voltage, for instance. Orthogonal magnetic antenna array 729 further includes a plurality of interface PCBs 730 to support suitable tuning or multiplexing circuits.
In alternate embodiments, antenna 727 may comprise a single, larger antenna element. For instance, a 25 mm diameter magnetic antenna with a bandwidth of 250 kHz, adequate to detect a single FM radio signal, will exhibit an antenna gain of about −20 dBi to −24 dBi across the 88 MHz-108 MHz band. This is sufficient to detect most local station signals. A 12.5 mm diameter antenna with comparable bandwidth will be characterized by about −29 dBi to −33 dBi gain.
An untuned antenna will exhibit broader bandwidth but lower sensitivity. A 25 mm diameter antenna with 20 MHz bandwidth centered at 98 MHz so as to capture the entire FM band will exhibit −39 dBi-−43 dBi gain. A comparable 12.5 mm diameter antenna will have −48 dBi to −52 dBi gain. Ferrite loading may enhance the gain to a degree. Even these low gains are likely to be adequate to detect strongly local FM broadcast signals, however. As usual, there exists an engineering tradeoff between cost and complexity on the one hand and performance on the other.
A preferred embodiment employs multiple detection thresholds, allowing a selective proximity detection system to distinguish between scatterers. For instance, a forklift or large piece of industrial equipment will tend to have greater scattering than an individual pedestrian. Thus a plurality of detection thresholds can allow a proximity detection system to be selective and discriminate between a range of potential scatterers.
Process flow continues with transmitting a signal by the jth station in block 803. In a preferred embodiment a station is an FM broadcast station, although in alternate embodiments signals from other sources may supplement or replace FM broadcast signals.
Process flow continues with a proximity detection system (PDS) receiving a jth signal from the jth station in block 804. The jth signal may include a combination of direct and multipath components depending on scattering from structures, people, or other scatterers. Process flow then continues at block 805 with a PDS measuring a kth signal characteristic from the jth signal. Signal characteristics may include total power, amplitude of individual components received by orthogonal antennas, or phase or phase difference characteristics.
Process flow continues in decision block 806. If there is another characteristic for the PDS to evaluate, the PDS increments k to k+1 and continues at block 805. If there is not another characteristic of the jth signal for the PDS to measure, process flow continues at decision block 807. If there is another signal for the PDS to evaluate, the PDS increments j to j+1 and continues at block 803. If there is not another signal for the PDS to receive, process flow continues at block 808.
In process block 808, a PDS compares K signals characteristics from each of the J signals to a baseline value. A baseline value may be a user set level, a hardwired level, or in a preferred embodiment a rolling average of received signal strength. In a preferred embodiment, a comparison calculates the sum of the absolute values of the deviations of the currently received signal characteristic values and compares them to the baseline obtained through a rolling average.
Process flow continues in decision block 809. If the result of the comparison of block 808 does not exceed the threshold of block 802, process flow continues in decision block 811. If the result of the comparison of block 808 exceeds the threshold, then process flow continues in block 810 with triggering of a detection by a PDS.
Triggering may be connected with a wide variety of useful actions including, but not limited to, sending an alert to a remote user, triggering a camera to record video or still photos, sounding an audio or visual alarm, or recording details of the triggering event in a database. A PDS may take such action or communicate data to another device.
In a preferred embodiment, multiple detection thresholds may have been set by a user in block 802, allowing a PDS to evaluate the scattering and distinguish between a range of potential scatterers, such as a discrimination between a pedestrian 414 and a forklift 415. The proximity detection system may employ a plurality of thresholds to determine an appropriate alert for a plurality of scatterers.
Process flow continues in decision block 811. If the PDS continues the process, process flow continues back at block 803 with transmission of a signal by the j=1 station. Otherwise the process terminates at end block 813. A first alternate embodiment process flow determines presence of a scatterer by receiving and measuring ambient RF signals.
The second alternate embodiment process flow diagram 900 illustrates a representative “calibration mode” on the left side and a representative “location detection mode” on the right side. In “calibration mode,” process flow commences at start block 901. The steps depicted in the flowcharts herein are not necessarily performed in the order drawn.
The process flow continues with the jth station (or equivalently, beacon) transmitting a calibration transmission in block 902. In preferred embodiments, the station is an FM broadcast station, and the signal is a direct signal, a scattered signal, or a combination of direct and scattered signals originating at the FM broadcast station.
Then in block 903, the Locator (for instance, proximity detection system 707 or proximity detection system 725) receives the calibration transmission with the scatterer (for instance, person 716) in the ith position. The Locator measures the kth signal characteristic of the jth signal with the scatterer at the ith position in block 904. In the most simple embodiments, K=1 and the signal characteristic is the total power. In alternate embodiments, K=3 and the signal characteristics are the three orthogonal signal amplitudes or powers. In still further alternate embodiments, K=6 inclusive of the three amplitudes from three orthogonal antennas and the three phase differences between signals from the three orthogonal antennas. Additional characteristics of the signals may be captured through a demodulation process. In typical embodiments, J=6 to 20 depending on the availability of signals, although with reduced accuracy a single locator-receiver may suffice determine its unknown position from a single signal (i.e. J=1) if a Locator employs K=6 signal characteristics. In a preferred embodiment the calibration transmission is a near-field signal dominated by the near-field scatter and standing waves of a distant FM broadcast station as depicted in simulation 701 of
The process flow continues with decision block 905. If all K characteristics have not yet been measured, then the process continues back at block 904 with measuring the next, i.e. (k+1)th, characteristic. Otherwise, the process continues with decision block 906. If additional calibration transmissions (or signals) are available, the process may continue at block 903 with the Locator receiving a calibration transmission from the (j+1)th station with the scatterer at the at the ith position. If the Locator has measured all J available signals, then the process continues at block 907 with storing K signal characteristic measurements for each of the J station (or equivalently beacon) signals with the scatterer at the ith position in the plurality of Calibration Data Sets 910. An associator or person performing the calibration provides truth data for the calibration mode allowing a processor or information handling system (IHS) to correlate the Calibration Data Set with the known ith scatterer position in block 907. Additional data or measurements including orientation or other sensor data may also be associated with the ith position in the plurality of Calibration Data Sets 910.
If all I desired scatterer positions have not yet been characterized, then the process continues back at block 902 with the first (j=1) station transmitting a calibration transmission to be received by a Locator with the scatterer at the (i+1)th position. Otherwise, the calibration mode process terminates in End Block 909.
A “location detection mode” begins on the right side of the process flow diagram with Start Block 921. The steps depicted in the flowcharts herein are not necessarily performed in the order drawn. The process flow continues with the jth station transmitting a location transmission in block 922.
Then the process flow continues in block 923 with the Locator receiving the jth station's location transmission with the scatterer at the unknown position. The Locator measures the kth signal characteristic of the jth station signal with the scatterer at the unknown position in block 924.
The process flow continues with decision block 925. If all K characteristics have not yet been measured, then the process continues back at block 924 with measuring the (k+1)th characteristic. Otherwise, the process continues with decision block 926. If additional signals are available, the process may continue at block 923 with the Locator receiving a location transmission from the (j+1)th station while the scatterer is at the unknown position. If all J available signals have been measured, then the process continues at block 927 with storing K signal characteristics for each of the J station's location transmissions in Positioning Data Set 931. Positioning Data Set 931 thus includes signal characteristics of beacon signals received by the Locator with the scatterer at the unknown position. In a preferred embodiment the location transmission is a near-field signal of a nearby station, or standing waves or multipath signals of a distant station. Also, nothing in this disclosure should be construed so as to require the Locator employed in the location determination mode to be the same Locator as that employed in the calibration mode. In practice, many different yet functionally equivalent Locators may share a common calibration data set. Similarly, multiple Locators may be employed in generating a particular calibration data set.
The process flow continues in block 928 with employing Calibration Data Sets 910 and Positioning Data Set 931 to determine the unknown position of the scatterer. If another position needs to be determined, then the process continues back at block 922 with the Transmit Tag transmitting a location transmission from another unknown position or location. Otherwise, the location determination mode process terminates in End Block 930.
Applicants have developed a variety of algorithms for comparing Calibration Data Sets 910 and Positioning Data Set 931 to determine the unknown position of a transmitter or a receiver in a near-field or multipath heavy propagation environment. Near-Field Electromagnetic Ranging (NFER) technology offers a wireless physical layer optimized for real-time location in the most RF hostile settings. NFER® systems exploit near-field behavior within about a half wavelength of a tag transmitter to locate a tag to an accuracy of 1-3 ft, at ranges of 60-200 ft, all at an infrastructure cost of $0.50/sqft or less for most installations. NFER® systems operate at low frequencies, typically around 1 MHz, and long wavelengths, typically around 300 m.
Low frequency signals penetrate better and diffract or bend around the human body and other obstructions. This physics gives NFER® systems long range. There's more going on in the near field than in the far field. Radial field components provide the near field with an extra (third) polarization, and the electric and magnetic field components are not synchronized as they are for far-field signals. Thus, the near field offers more trackable parameters. Also, low-frequency, long-wavelength signals are resistant to multipath. This physics gives NFER® systems high accuracy. Low frequency hardware is less expensive, and less of it is needed because of the long range. This makes NFER® systems more economical in more difficult RF environments.
Near field electromagnetic ranging was first fully described in applicant's “System and method for near-field electromagnetic ranging” (Ser. No. 10/355,612, filed Jan. 31, 2003, now U.S. Pat. No. 6,963,301, issued Nov. 8, 2005). This application is incorporated in entirety by reference. Some of the fundamental physics underlying near field electromagnetic ranging was discovered by Hertz [Heinrich Hertz, Electric Waves, London: Macmillan and Company, 1893, p. 152]. Hertz noted that the electric and magnetic fields around a small antenna start 90 degrees out of phase close to the antenna and converge to being in phase by about one-third to one-half of a wavelength. This is one of the fundamental relationships that enable near field electromagnetic ranging. A paper by one of the inventors [H. Schantz, “Near field phase behavior,” 2005 IEEE Antennas and Propagation Society International Symposium, Vol. 3A, 3-8 July, 2005, pp. 237-240] examines these near-field phase relations in further detail. Link laws obeyed by near-field systems are the subject of another paper [H. Schantz, “Near field propagation law & a novel fundamental limit to antenna gain versus size,” 2005 IEEE Antennas and Propagation Society International Symposium, Vol. 3B, 3-8 July, 2005, pp. 134-137]. In addition to an active RTLS tag (or fixed locator—mobile beacon) architecture, the teachings of U.S. Pat. No. 6,963,301 encompass a passive location tag (or fixed beacon—mobile locator) architecture. In this architecture, the passive location tag (or passive RTLS tag) is a receiver that may be incorporated or associated with a vehicle or person to provide position information from signals emitted by fixed transmit beacons. A beacon may be an uncooperative source of electromagnetic radiation, like a signal from an AM broadcast station, an FM broadcast station or other signal-of-opportunity. In the sense taught by Applicants, a “passive RTLS tag” is passive in the sense that it does not emit signals in the process of obtaining location data, rather it receives and characterizes signals so as to determine location of an associated mover. Determination of location may be performed either locally (within the passive RTLS tag) or remotely (by conveying signal characterization data to a remote server for location determination).
Complicated propagation environments do tend to perturb the near-field phase relations upon which NFER® systems rely. Applicants have overcome this problem using calibration methods described in “Near-field electromagnetic positioning system and method” (Ser. No. 10/958,165, filed Oct. 4, 2004, now U.S. Pat. No. 7,298,314, issued Nov. 20, 2007). Additional calibration details are provided in applicant's “Near-field electromagnetic positioning calibration system and method” (Ser. No. 11/968,319, filed Nov. 19, 2007, now U.S. Pat. No. 7,592,949, issued Sep. 22, 2009). Still further details of this calibration are provided in applicant's co-pending “Near-field electromagnetic calibration system and method” (Ser. No. 12/563,960 filed Sep. 21, 2009, now U.S. Pat. No. 7,859,452, issued Dec. 28, 2010). Systems and methods of calibration and determination of location pioneered in these applications are relevant to the present invention. These applications are all incorporated in entirety by reference.
Applicant's unique algorithms enable innovative techniques for displaying the probability density and other aspects of location information, as described in applicant's “Electromagnetic location and display system and method,” (Ser. No. 11/500,660, filed Aug. 8, 2006, now U.S. Pat. No. 7,538,715, issued May 26, 2009).
Further, the phase properties of near-field signals from orthogonal magnetic and other multiple antenna near-field transmission signals enable additional phase comparison states that can be used for location and communication, as described in applicant's co-pending “Multi-state near-field electromagnetic system and method for communication and location,” (Ser. No. 12/391,209, filed Feb. 23, 2009, now U.S. Pat. No. 8,253,626, issued Aug. 28, 2012).
Near-field electromagnetic ranging is particularly well suited for tracking and communications systems in and around standard cargo containers due to the outstanding propagation characteristics of near-field signals. This application of NFER® technology is described in applicant's “Low frequency asset tag tracking system and method,” (Ser. No. 11/215,699, filed Aug. 30, 2005, now U.S. Pat. No. 7,414,571, issued Aug. 19, 2008).
Applicants have also discovered that near-field electromagnetic ranging works well in the complicated propagation environments of nuclear facilities and warehouses. An NFER® system provides the RTLS in a preferred embodiment of applicants' co-pending “System and method for simulated dosimetry using a real-time location system” (Ser. No. 11/897,100, filed Aug. 29, 2007, now abandoned). An NFER® system also provides the real-time location system in a preferred embodiment of applicants' “Asset localization, identification, and movement system and method” (Ser. No. 11/890,350, filed Aug. 6, 2007, now U.S. Pat. No. 7,957,833 issued Jun. 7, 2011) and in applicants' “Inventory control system and method” (Ser. No. 13/153,640, filed Jun. 6, 2011, now U.S. Pat. No. 8,326,451 issued Dec. 4, 2012).
Applicants also discovered that a path calibration approach can yield successful location solutions particularly in the context of first responder rescues, as detailed in applicant's “Firefighter location and rescue equipment” (Ser. No. 13/021,711, filed Feb. 4, 2011).
All these applications are incorporated in entirety by reference.
The present invention has been described above with the aid of functional building blocks illustrating the performance of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. Any such alternate boundaries are thus within the scope and spirit of the claimed invention. One skilled in the art will recognize that these functional building blocks can be implemented by discrete components, application specific integrated circuits, processors executing appropriate software and the like or any combination thereof.
While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. One should understand that numerous variations may be made by one skilled in the art based on the teachings herein. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
| Number | Date | Country | |
|---|---|---|---|
| 60637779 | Dec 2004 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12834821 | Jul 2010 | US |
| Child | 14919113 | US | |
| Parent | 11473595 | Jun 2006 | US |
| Child | 12834821 | US | |
| Parent | 11272533 | Nov 2005 | US |
| Child | 11473595 | US |
