Abstract:
A system for powering a micro-robot including a thermoelectric system integrated with the micro-robot wherein the thermoelectric system includes a thermopile. A rechargeable battery operatively connected to the thermoelectric system to recharges the rechargeable battery using electricity generated by the thermopile from an environmental temperature gradient.

Description:
RELATED APPLICATION DATA  
       [0001]     The present application claims priority to U.S. Provisional Application No. 60/704,838 entitled “Systems and Methods for Powering Devices with a Thermoelectric System,” filed on Aug. 2, 2005. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT  
       [0002]     The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of Contract No. OF8630-03-C-0133 awarded by the U.S. Department of Defense. 
     
    
     TECHNICAL FIELD  
       [0003]     This invention relates generally to the field of thermoelectric generators and more particularly to the use of thermoelectric generators to power micro-robots and other micro-devices. BACKGROUND OF THE INVENTION  
         [0004]     Miniaturized robots, also mown as micro-robots, may be used in numerous situations and locations to receive and transmit data communications and perform various other requirements. Micro-robots may be positioned in remote locations to either transmit images or sounds or other types of data. Micro-robots may be used for commercial or military applications. For instance, in a commercial application, micro-robots may be used to locate and identify personnel trapped within buildings as a result of earthquake or terrorist attack. The micro-robots are sufficiently small enough to maneuver within the collapsed structure and navigate within very small confinements. Micro-robots may use various methods for maneuvering to its destination, including but not limited to hopping, vibrating, and rolling. Micro-robots currently rely upon “button batteries” for power supplies. The operational time for which such traditional button batteries can supply power is measured in hours. Therefore, without an improved system or method for providing extended power to the micro-robots, the use of micro-robots becomes extremely limited. In order for the micro-robots to operate over a long period of time, it will be necessary for the micro-robots to be able to recharge their batteries within the environment for which they are located. For example, within a collapsed structure, the only source of reliable power is heat. Optimally, a number of potential heat sources should be available to ensure rapid location of such power supplies.  
         [0005]     Therefore, there is a need in the art for systems and methods for providing extended power supply to micro-robots through the use of heat energy sources. 
     
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a diagram of the Seebeck Effect for thermoelectric systems according to an exemplary embodiment of the present invention.  
         [0007]      FIG. 2  is a thermopile of the thermoelectric system according to an exemplary embodiment of the present invention.  
         [0008]      FIG. 3  is an exemplary plot of ground and atmospheric temperatures.  
         [0009]      FIG. 4  is a hopping micro-robot for use with the thermoelectric system according to an exemplary embodiment of the present invention.  
         [0010]      FIG. 5  is a flow chart of the operation of a thermoelectric system integrated with a micro-robot according to an exemplary embodiment of the present invention.  
         [0011]      FIG. 6  is a vibrating micro-robot according to an exemplary embodiment of the present invention.  
         [0012]      FIG. 7  is a vibrating micro-robot for use with the thermoelectric system according to an exemplary embodiment of the present invention.  
         [0013]      FIG. 8  is a mini-WHEGS micro-robot according to an exemplary embodiment of the present invention.  
         [0014]      FIG. 9  is a scout micro-robot according to an exemplary embodiment of the present invention.  
         [0015]      FIG. 10  is an infrared sensor for a micro-robot according to an exemplary embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     The present invention now will be described more fully hereinafter with reference to the accompanying drawing, in which an exemplary embodiment of the invention is shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, this embodiment is provided so that this disclosure will be thorough and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.  
         [0017]     As illustrated in  FIG. 1 , continuously flowing electrical current may be created when a first wire  12  of a first material is joined with a second wire  14  of a second material and then heated at one of the junction ends  16 . This is known as the Seebeck Effect. The Seebeck effect has two main applications: Temperature Measurement (thermocouple) and Power Generation. A thermoelectric system is one that operates on a circuit that incorporates both thermal and electrical effects to convert heat energy into electrical energy or electrical energy to a decreasing temperature gradient. The combination of the two or more wires creates a thermopile  10  that is integrated into a thermoelectric system. When employed for the purposes of power generation, the voltage generated is a function of the temperature difference and the materials of the two wires used. A thermoelectric generator has a power cycle closely related to a heat engine cycle with electrons serving as the working fluid and can be employed as power generators. Heat is transferred from a high temperature source to a hot junction and then rejected to a low temperature sink from a cold junction or directly to the atmosphere. A temperature gradient between the temperatures of the hot junction and the cold junction generates a voltage potential and the generation of electrical power. Semi-conductors may be used to significantly increase the voltage output of thermoelectric generators.  
         [0018]      FIG. 2  illustrates a thermopile  20  constructed with an n-typed semiconductor material  22  and a p-type semiconductor material  24 . For increased electrical current, the n-type materials  22  are heavily doped to create excess electrons, while p-type materials  24  are used to create a deficiency of electrons. The thermopile  20  is not limited to this configuration and may be any thermopile sufficient to generate electricity from a temperature gradient.  
         [0019]     Thermoelectric generator technology is a functional, viable and continuous long-term electrical power source. Thermoelectric generators may be coupled with rechargeable battery technology, capacitor technology, or a combination of rechargeable batteries and capacitors to provide extended power supplies to micro-robots and other micro-devices.  
         [0020]     Due to the accessibility of temperature gradients occurring in natural and man-made environments, thermoelectric generators can provide a continuous power supply for devices in need of a power source. One of the most abundant, common, and accessible sources of energy is environmental heat. In buried hardened target environments, environmental heat may be the only feasible source of energy.  
         [0021]     Micro-robots may be used in numerous commercial and military conditions in environments which are very difficult to access, including hardened target environments, for payload delivery or other reconnaissance operations. Micro-robots include numerous and varying forms including but not limited to hopping micro-robots, vibrating micro-robots, walking micro-robots, and rolling micro-robots. Due to the remote operational location of many micro-robots, recharging of the batteries of a micro-robot may prove difficult. Thermoelectric systems may be employed to provide power to micro-robots. The thermoelectric system may include a thermoelectric generator that may be integrated with a micro-robot to provide electrical power. The thermoelectric generator includes a thermopile. In an exemplary embodiment, the thermopile is of the configuration of  FIG. 2 . Again, the thermopile is not limited to the configuration of  FIG. 2  and may be any thermopile sufficient to generate electricity from a temperature gradient.  
         [0022]     Heat energy may be extracted from a number of environmental sources thereby allowing for a number of potential “power stations” for the micro-robot. In addition to natural environmental sources, Table 1 illustrates numerous heat sources that the thermoelectric system of a micro-robot may employ.  
                                                   TABLE 1                           APPROX. MAXIMUM       ENVIRONMENTAL HEAT SOURCE   TEMPERATURE (F. °/C. °)*                                OFFICE SOURCES            Computer Power Unit (internal)   100/40        Computer Screen (CRT) (internal)   110/45        Coffee Makers   195/91        AC Units   80/30       Generators (Electrical)   140/60        Heaters (i.e. steam @ 25 psig)   266/130       Televisions (internal)   110/44        Refrigerator Compressors   90/30       Stoves   500/260       Ovens   500/260       Hot Water Heaters (Gas)   2500/1370       Dishwashers   140/60             LABORATORY SOURCES            Autoclaves   250/120       Hot Plates   450/230       Mixing Equipment   190/90        Power Generators   325/165       Hot Water Pipes   140/55        Steam Pipes (@ 25 psig)   266/130                  
 
         [0023]     In the absence of heat sources such as those listed in Table 1, the thermoelectric generator may use the thermal differential between the earth&#39;s surface and the earth&#39;s temperature as low as a foot below the earth&#39;s surface for a temperature gradient sufficient to create adequate electrical energy for a micro-robot.  FIG. 3  illustrates a plot of a temperature differential between the atmosphere at the earth&#39;s surface and 30 centimeters below the earth&#39;s surface. The plot of  FIG. 3  illustrates temperatures present at Royston, Hertfordshire in March 2000. One of ordinary skill in the art will appreciate that  FIG. 3  is for illustrative purposes only and does not represent the temperature gradient at all locations on earth and at all times.  
         [0024]     As shown in  FIG. 3 , at certain times the atmospheric temperature is greater than the subsurface temperature and at other times the atmospheric temperature is less than the subsurface temperature. However, for the thermoelectric generator to produce electricity only a temperature differential is required and, therefore, can produce electricity in either scenario. Generally, until a depth greater than 300 feet is reached, the temperature of the earth tends to decrease with depth. Thus, with a larger probe with higher surface area and greater depth into the earth surface, higher amounts of energy can be generated due to an increased temperature gradient with the earth&#39;s atmospheric conditions at the surface.  
         [0025]     The temperature gradient used to generate electrical energy may also be obtained from extreme conditions at the location of the micro-robot. For example, if a building is collapsed or on fire, the micro-robot may use the heat from the building or fire to create a temperature gradient to power the micro-robot. One of ordinary skill in the art will appreciate that any high heat source may be used to generate a temperature gradient to power the micro-robot.  
         [0026]      FIG. 4  illustrates an exemplary embodiment of a hopping micro-robot  40 . In this exemplary embodiment, the hopping micro-robot  40  navigates and maneuvers through use of a hopping mechanism including a bottom leg  42  and a top leg  44 . The hopping micro-robot may include a rechargeable battery  46  to provide electrical power. The rechargeable battery  46  may be located on the top leg  44  or any other location on the hopping micro-robot to supply power thereto. A thermopile  48  may be integrated with the micro-robot.  
         [0027]     As illustrated in the flow chart of  FIG. 5 , the rechargeable battery may be recharged through the use of the thermopile of a thermoelectric system integrated with the micro-robot. The thermopile  52  contacts a heat source  51  such that a temperature gradient is formed within the wires of the thermopile at step  52 . The thermopile  52  then generates electricity by converting the thermal energy in the temperature gradient to electricity at step  53 . The electricity generated may then pass to a trickle charger at step  54  and the trickle charger then charges the rechargeable battery at step  55 . Once the rechargeable battery is charged, the battery can provide sufficient power to the needs of the micro-robot including the steps of mobility at step  56 , navigation at step  57 , or any other desired operation, such as pay load delivery at step  59 .  
         [0028]     The thermoelectric generator also may be used to charge an on board super capacitor of the micro-robot device at  58 . The super capacitor may be configured to store an abundance of electrical energy and also may expel the electrical energy in a slow controlled manner or in a burst of electricity. The super capacitor may supply power to the micro-robot and also may provide power for any potential weapon (i.e. explosive initiator) in a hard/overt kill capacity or to act as a weapon itself in a covert/soft kill capacity as well. For example, the super capacitor may operate as a weapon by short circuiting a Central Processing Unit, overloading a circuit of a desired device, and initiating a fire by expelling the abundance of electrical energy with a burst of electricity. One of ordinary skill in the art will appreciate that the use of a super capacitor is not limited to the examples enumerated herein but may be used to supply power, act as a weapon initiator, or act as a weapon itself in any manner. The thermoelectric generator also may be used to provide electrical energy to power any required devices on a micro-robot, including but not limited to sensors, processors, and mechanical operations.  
         [0029]     The recharging of the battery is not limited to the steps of  FIG. 5  and may include a system for recharging the battery that uses a thermopile. A capacitor may be used in place of a rechargeable battery to provide power to the micro-robot. The thermoelectric generator may be used to charge the capacitor with electrical energy. One of ordinary skill in the art will appreciate that any number of rechargeable batteries, capacitors, or combination of a rechargeable batteries and a capacitors are contemplated herein.  
         [0030]     The thermoelectric system may be affixed in any location on the micro-robot that allows for a temperature gradient to be exposed to the thermopile of the thermoelectric system. In an exemplary embodiment of the hopping micro-robot, the thermoelectric system is affixed to the bottom leg  44  such that the thermoelectric system interfaces a hot surface to expose itself to the temperature gradient between the hot surface and the atmosphere. The hot surface may include any material or substance that has a temperature higher than the atmosphere, including the items listed in Table 1.  
         [0031]     The thermoelectric system also may include a stake (not shown) that can be inserted into the ground to increase the thermal gradient with the hot surface. The thermopile may be integrated with the stake to produce electricity from the temperature gradient. One of ordinary skill in the art will appreciate that the thermoelectric system may be affixed anywhere on the micro-robot that is exposed to a temperature gradient.  
         [0032]     In another exemplary embodiment, the thermoelectric system may provide electrical energy to a vibrating micro-robot  60  as illustrated in  FIG. 6 . The vibrating micro-robot employs vibration (or micro-hopping) as a locomotion mechanism. Similar to the hopping micro-robot embodiment, thermoelectric system may be used to provide electrical energy to operate the locomotion of a vibrating micro-robot. The micro-robot  60  may employ a rechargeable battery  62  that powers vibrating motors  64 . The vibrating motors  64  vibrate to move the micro-robot  60  in a desired direction. A sensor  66  and related microprocessor and circuitry may be integrated in the vibrating micro-robot  60  to instruct the micro-robot on its destination. The sensor  66  may be any sensor capable of detecting a heat source such as an infrared sensor, heat sensor, or other light sensor.  
         [0033]      FIG. 7  illustrates an embodiment of a vibrating micro-robot  70  with an integrated thermoelectric system  72 . The thermoelectric system  72  may be positioned on a surface of the micro-robot that interfaces the heat source. A thermopile of the thermoelectric system could then generate electricity from the temperature gradient between a heat source and the atmosphere. The vibrating micro-robot  70  may further include at least one microcapacitor  74  to hold the electricity generated by the thermopile. It should be understood that the vibrating micro-robot may also include a rechargeable battery or any other type of battery or capacitor. The vibrating micro-robot may further include a radiator  78  for maximizing heat dissipation and increasing the heat difference between the hot side and cold side of the thermopile.  
         [0034]     In addition to hopping micro-robots and vibrating micro-robots, thermoelectric generators may be used to provide electrical power to any micro-robot including mini-WHEGS micro-robots  80  shown in  FIG. 8 , Scout micro-robots  90  shown in  FIG. 9 , or any other type of micro-robots or micro device where power can be generated with a thermoelectric generator. One of ordinary skill in the art will appreciate that the use of thermoelectric systems to provide sufficient power to micro-robots is not limited to the types of micro-robots disclosed herein but is applicable to any micro-robot or micro device.  
         [0035]     The thermoelectric system also may include a sensor for locating thermal conditions to allow for recharging the batteries or charging the capacitors. The sensors may include heat sensors, light detecting sensors, or any other sensing device operable to determine a thermal source. In an exemplary embodiment, the thermoelectric system may incorporate a light tracking sensor which allows the micro-robot to track a source of light in a dark environment.  FIG. 10  illustrates an embodiment of a micro infrared seeker which can be used to identify potential heat sources. The micro infrared sensor of the micro-robot may direct the micro-robot to move to the light. The source of light may provide a sufficient temperature gradient for the thermoelectric generator to generate electricity. In another exemplary embodiment, infrared sensors may be integrated with the thermoelectric system to allow the micro-robot to autonomously locate a heat source for recharging the battery or capacitor. The thermoelectric generator may be used to power the sensor as well as locomotive components of the micro-robot. The sensors alternatively may be powered by an auxiliary battery. The thermoelectric system may also include a device that determines how much power remains in the battery or capacitor that powers the micro-robot. The amount of remaining power may be used to determine if recharging of the battery or capacitor is needed.  
         [0036]     The thermoelectric system may further include a microprocessor for guidance, command, and control of the sensors and the micro-robot. In an exemplary embodiment, based on the operational parameters desired, the microprocessor of the thermoelectric system may be programmed to determine the best available source of thermal heat in order to determine the most efficient means for recharging the batteries. If a rapid charge is required, the microprocessor may command the micro-robot to locate a thermal source that creates a large temperature gradient. Likewise, if a rapid charge is not required, the microprocessor may be programmed to command the micro-robot to find a less conspicuous location to charge the battery or capacitor. One of ordinary skill in the art will appreciate that the microprocessor does not have to be part of the thermoelectric system. A microprocessor on the micro-robot may be programmed to guide, command, and control the micro-robot and the sensors. One of ordinary skill in the art will appreciate that standard guidance and control techniques may be implemented to guide and control the micro-robots movement to the heat source.  
         [0037]     In addition to micro-robots, the thermoelectric generators may be used to power other devices that require power over extended periods of time. In the exemplary embodiment of  FIG. 11 , a thermoelectric system may be used to power a weather station  1100  or the individual components of a weather station. An illustration of a weather station is shown in  FIG. 11 . In order to conserve power, the invention proposes the “seeding” of large areas with dozens (or hundreds) of individual sensors (i.e. humidity sensors, temperature sensors, wind velocity sensors, wind direction sensors, etc.) which in and of themselves consume little power. Micro-transmitters may be connected to sensors which may periodically send data to a central data fusion center and a broad picture of the environmental conditions over a wide area could be painted, thereby providing a more accurate weather account than an individual weather station. The sensors require little power and may be powered by the thermal gradient between the surface of the earth and the sub-surface of the earth. In an exemplary embodiment, the thermal gradient may be achieved through a sub-surface depth of between one and three feet. One of ordinary skill in the art will appreciate that any sub-surface depth that creates a temperature gradient is contemplated herein.  
         [0038]     The weather stations  1100  are often used in remote locations and may be required for use for an amount exceeding the battery life. The thermoelectric generator may be used to provide electrical power to the weather station. In an exemplary embodiment, the weather station rests on the earth&#39;s surface. The thermoelectric system may include a stake that is inserted into the earth&#39;s surface. The temperature of the earth generally decreases with depth at depths up to  100  feet. Therefore, the temperature at the end of the stake is typically lower than the temperature at the earth&#39;s surface. The difference between the temperature at the end of the stake and the earth&#39;s surface provides the temperature gradient sufficient for creating electrical energy through the thermopile of the thermoelectric system. One of ordinary skill in the art will appreciate that the temperature gradient may be attained from any source and is not limited to the use of a stake in the ground.  
         [0039]     In another embodiment of the present invention, the thermoelectric system may be integrated with an unattended ground sensor. An unattended ground sensor may be used for a number of applications such as intrusion detection, sound detection, IR detection, etc. The sensor would be coupled with a miniature RF transmitter (as would the previously referenced weather sensors) and would transmit its data to a central data collection command post to alert authorities in the event of intrusion into restricted areas.  
         [0040]     It should be apparent that the foregoing relates only to exemplary embodiments of the present invention and that numerous changes and modifications may be made herein without departing from the spirit and scope of the invention as defined herein.