Abstract:
A Wireless Subterranean Soil Monitoring System. The system measures the complex permittivity around a subterranean antenna, and then responsively adjusts the antenna&#39;s tuning circuit according to the measured permittivity. Once tuned, the system will then execute the transmission of the probe data. Furthermore, the antenna design is adapted for subterranean use to further reduce the de-tuning effect of the adjacent soil.

Description:
[0001]    This application is filed within one year of, and claims priority to Provisional Application Ser. No. 62/194,762, filed Jul. 20, 2015. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates generally to agriculteral automation systems and, more specifically, to a Wireless Subterranean Soil Monitoring System. 
         [0004]    2. Description of Related Art 
         [0005]    The monitoring of the moisture of soil for the purpose of optimizing the growth of crops has become increasingly important today, particularly in the environment of large, corporate farming operations. There are two common practices associated with the installation of soil moisture probes in the soil. The most prevalent method involves the installation of a soil monitoring probe in the ground once the plant emerges after planting (actually a series of probes to cover an entire planted field). Each probe is then connected to a telemetry system that provides power and receives the measured data from the probe. The telemetry will regularly upload the received data to a central database using cellular or other wireless technology. Typically, the telemetry system is located in close proximity to the probe—somewhere in the actual field of crops. Before the crop is harvested the system (probes and telemetry equipment) is extracted and removed from the field. These annual installation and extraction operations are costly and further only permits the grower to obtain data during a portion of the year (just after planting until just before harvesting). 
         [0006]    A less common practice is to install the probe(s) in the soil and then trench the connecting cable to the perimeter of the field (typically about 100 meters away). This will allow the probe to reside in the field continuously for several years, providing data to the grower over the entire year. There are several drawbacks with the trenching method. First, it is a cumbersome and expensive exercise to trench the cable (to each probe). Second, there are several cases where normal field operations will result in one or more of the cables being severed, thereby breaking the connection to the probe. 
         [0007]    What is needed is a system and method that permits the probe to reside continuously in the field without the need for expensive trenching, and without the risk of damage to the equipment due to normal field operations. It is believed that a wireless probe transmission system that is buried in close proximity to each probe, is the solution to this problem. 
       SUMMARY OF THE INVENTION 
       [0008]    In light of the aforementioned problems associated with the prior systems and methods, it is an object of the present invention to provide a Wireless Subterranean Soil Monitoring System. The system should measure the complex permittivity around a subterranean antenna, and then responsively adjust the antenna&#39;s tuning circuit according to the measured permittivity. Once tuned, the system should then execute the transmission of the probe data. Furthermore, the antenna structural design should be adapted for subterranean use to further reduce the de-tuning effect of the adjacent soil. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The objects and features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages, may best be understood by reference to the following description, taken in connection with the accompanying drawings, of which: 
           [0010]      FIG. 1  is a cutaway side view a conventional soil moisture monitoring network; 
           [0011]      FIG. 2  is a top view of the network of  FIG. 1 ; 
           [0012]      FIG. 3  is a cutaway side view of a preferred embodiment of the wireless soil moisture monitoring network of the present invention; 
           [0013]      FIG. 4  is a partial cutaway side view of the subterranean sensor/transmitter assembly of the network of  FIG. 3 ; 
           [0014]      FIG. 5  is a flowchart depicting the transmission method of probes within the network of  FIG. 3 ; and 
           [0015]      FIG. 6  is a flowchart of the communications method of the network of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventors of carrying out his/their invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the generic principles of the present invention have been defined herein specifically to provide a Wireless Subterranean Soil Monitoring System. 
         [0017]    This invention describes a system that can reside next to the probe in the field, buried at any depth. It contains a battery pack, interface to the probe, a temporary data storage and a wireless transceiver. The invention solves the problem of being able to transmit and receive data via an antenna that is subject to varying permittivity of the adjacent soil. 
         [0018]    Any antenna that receives and transmits data must first be optimized to maximum efficiency in its typical environment. In the case where the antenna is buried in soil, the antenna efficiency will significantly degrade as the soil changes its complex permittivity due to the commonly-occuring changes in water and fertilizer content (in the soil). 
         [0019]    The present invention can best be understood by initial consideration of  FIG. 1 . 1    FIG. 1  is a cutaway side view a conventional soil moisture monitoring network  6 . As discussed previously, there are a series of soil moisture probes  10  buried in the soil  8  around the planted area. The probes  10  are individually connected to the probe controller/transmitter  22  by control conduits  20  (buried cables). The difference between the two most prevalent prior systems is the depth at which the conduits  20  are buried. As used throughout this disclosure, element numbers enclosed in square brackets [ ] indicates that the referenced element is not shown in the instant drawing figure, but rather is displayed elsewhere in another drawing figure. 
         [0020]    In normal operation, the controller/transmitter  22  will poll each probe  10  on a regular periodicity to obtain the mosture readings of the soil  8  adjacent to each probe  10 . The probes  10  are aligned horizontally, and provide distinct moisture readings at depths along the length of each probe  10 . On a regular basis (or when requested), the controller/tranmitter  22  will transmit the moisture data to a centralized data repository by an attached external communications tower  24 . As discussed above, the transmission is wireless by either cellular or some other approach. The probe controller/transmitter typically has an internal power supply (e.g. a battery), and may be equipped with a solar panel to recharge the onboard battery pack for prolonged, continuous use. 
         [0021]      FIG. 2  is a top view of the network  6  of  FIG. 1 . As seen here, the conduits  20  traverse the planted field (this would be the non-trenched approach). It is clear from this view that any attempt at tilling or otherwise operating heavy equipment in the field is guaranteed to impact the criss-crossing cables (conduits  20 ). It is this problem that is solved by the present invention, first introduced in  FIG. 3 . 
         [0022]      FIG. 3  is a cutaway side view of a preferred embodiment of the wireless soil moisture monitoring network  23  of the present invention. The network  23  is comprised of one or more subterranean sensor/transmitter assemblies  30 . Each sensor/transmitter assembly  30  has a soil moisture probe  10  interconnected with a subterranean transmitter  32 . The sensor&#39;/transmitter assemblies  30  communicate wirelessly with the probe communications tower  36 . 
         [0023]    The probe network controller/receiver/transmitter (PNCRT)  34  does double-duty—it handles the conventional communications with the central data repository, to transmit the soil moisture data by cellular or other wireless means via the external communications tower  24 . It further handles the wireless communications with the individual sensor/transmitter assemblies  30 . Like the probe controller/transmitter of the prior system, the PNCRT  34  also will have an onboard power supply (typically a battery), and usually will have a solar panel to keep the onboard battery fully charged. 
         [0024]    As should be apparent from this drawing figure, there are no longer cables interconnecting the central probe control system and the individual probes  10 . Consequently, the expense and damage risk presented by the criss-crossing control conduits [ 20 ] has been eliminated. One note regarding the identification of the probe communications tower  36  and the external communications tower  24  - these are identified as separate entities for the purpose of explanation only. It is possible that only a single tower is employed, depending upon a number of factors, including location, installation requirements, and wireless communication technology, among others. If we now turn to  FIG. 4 , we can examine the features of this new probe assembly. 
         [0025]      FIG. 4  is a partial cutaway side view of the subterranean sensor/transmitter assembly  30  of the network [ 23 ] of  FIG. 3 . There are two main components to the assembly  30 : the soil moisture probe  10 , and the subterranean transmitter  32 . The probe  10  could be any suitable soil moisture probe, but would preferrably be of the type discussed in a companion patent application entitled “Soil Moisture and Electrical Conductivity Probe.” There is a short local control conduit (cable)  37  interconnecting the probe  10  and the transmitter  32 , but this is expected to be very short, and to be completely buried under the soil  8 , at or below the level of the transmitter  32 . 
         [0026]    The transmitter  32  is typically a hollow, elongate tube that is sealed at both ends. Conventional 2-inch diameter PVC pipe has proven to be very suitable, but other materials could also be used. The key is that the walls of the housing  38  be long-lasting for prolonged underground stays, while also being “transparent” to the wireless transmissions between the transmitter  32  and the PNCRT [ 34 ]. A prototype transmitter  32  has functioned very well with a housing  38  that is 8 (eight) feet in length. 
         [0027]    The basic components of the transmitter  32  are a basic dipole antenna  40  extending outwardly to the opposing ends of the housing  38 . A probe local controller  44  controls the operation of the transmitter  32 , as well as the operation of the soil moisture probe  10 . There is a transceiver/tuner  42  within the housing  38  for communicating with the PNCRT [ 34 ], and a battery  46  to supply sufficient power to operate all of the components of the assembly  30  for at least a year. 
         [0028]    It has been proven that a low power, low frequency transmitter can be operated for at least one year on a readily-available battery  46  with the distance between the PNCRT [ 34 ] and the probes  10  being up to one mile. 
         [0029]    The interior of the housing  38  may be filled with air (or other gas), or it may be filled with foam (e.g. chemically-expanding foam). While air or other gas will provide the least barrier to wireless transmissions from the antenna  40 , it provides no structural rigidity. The benefit of foam  46  is that it provides substantial structural rigidity, while also water-proofing the internal components (and making them tamper-proof). This while also presenting a very small additional barrier to wireless transmissions. 
         [0030]    Having introduced the physical components of the device and system of the present invention, we will now examine the novel operational features necessary for the system to function effectively.  FIGS. 5 and 6  depict these features. 
         [0031]      FIG. 5  is a flowchart depicting the transmission method  48  for probes within the network of  FIG. 3 . There are a few key aspects to the successful operation of the wireless equipment previously described above: (1) the wireless probe transmitters must be capable of making their transmissions from underground; (2) that the antennas within the probe transmitters are equipped to adjust/tune the transmission characteristics in response to the changing permitivity characteristics of the soil surrounding the antenna housing; (3) that the network of several sensor/transmitter assemblies are capable of cooperating with one another in communicating with a single PNCRT; and (4) that all of these functions are carried out using very low power demand so that the sensor/transmitter assemblies can remain buried for a year or more without the need for a very expensive battery. 
         [0032]    To that end the method  48  (which is focused on a single probe/transmitter assembly) commences with the assembly [ 30 ] transmitting an initial time synchronization message to the PNCRT [ 34 ]  100 . The PNCRT [ 34 ] identifies the assembly [ 30 ], and returns a message that corrects any discrepancy between the internal time on the assembly [ 30 ], and that of the PNCRT [ 34 ], that is received by the assembly [ 30 ] and applied so that the assembly [ 30 ] has an internal clock that is correlated with the master clock in the PNCRT [ 34 ]. 
         [0033]    The receipt of this message will also cause the assembly [ 30 ] to adopt a time slot  104 . This means that for a particular transmission periodicity, this assembly [ 30 ] will always transmit at a pre-assigned time slot. This allows for several assemblies [ 30 ] within the same network [ 23 ] to proceed through a “round robin” set of sequential transmissions. This eliminates the need for handshakes between each assembly [ 30 ] and the PNCRT [ 34 ] (since the individual transmissions are one-directional), which simplifies the equipment design and reduces the power demand (thereby prolonging battery life). 
         [0034]    The assembly [ 30 ] will, just before transmitting data, will obtain a set of soil moisture data from its probe [ 10 ]  106 . The assembly [ 30 ] will then, utilizing the antenna itself as a field sensor, detect the complex impedence of the antenna  108 . This just-detected complex impedence information will be used by the assembly [ 30 ] to tune the antenna characteristics  110  so that the transmission power is optimized (and electrical demand is reduced). Only then will the assembly [ 30 ] make its transmission to the PNCRT [ 34 ]  112 . 
         [0035]    Going forward, the assembly [ 30 ] will continue to loop at its assigned time slot  116 , within the established periodicity for the network  114 , to repeat steps  106 - 112 . This loop of steps is referred to collectively as the probe data transmission and optimization method  50  (within the entire transmission method  48 ). 
         [0036]      FIG. 6  illuminates the application of the method of  FIG. 5 , as it is applied to a network of assemblies [ 30 ]. First, all of the probe assemblies [ 30 ] conduct their synchronoziation with the PNCRT [ 34 ]  120 , and then the individual assemblies [ 30 ] sequentially execute the Data Transmission and Optimization Method [ 50 ]  121 , etc. for “N” assemblies [ 30 ] that are members of the network [ 23 ]. This will continue to loop continuously until batteries expire or the network [ 23 ] is shut down for another reasons. 
         [0037]    Those skilled in the art will appreciate that various adaptations and modifications of the just-described preferred embodiment can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.