Abstract:
A wearable generator system in one embodiment includes a plurality of coils, each of the plurality of coils extending within a respective one of a plurality of planes, a magnet for generating a magnetic field, and a support attached to a support anchor point and to the magnet, and suspending the magnet at a position whereat the magnet is not frictionally engaged with a fixed surface, the support having a length selected such that the magnetic field is movable across each of the plurality of coils.

Description:
FIELD 
       [0001]    This invention relates to wearable power generating devices. 
       BACKGROUND 
       [0002]    The popularity of wearable and/or portable electronic devices has created a substantial market for such devices. Portable electronic devices include personal electronic devices, such as smart phone, cell phones, MP3 players, and Bluetooth, etc. One limitation of such devices is the amount of energy that can be conveniently stored in the devices. Accordingly, substantial resources have been devoted to maximizing the energy storage capacity for both a given volume and a given weight. Nonetheless, portable electronic devices are still limited by the amount of energy that can be stored in the devices. 
         [0003]    Consequently, portable electronic devices require frequent recharging. Moreover, as the device ages, the capacity of the energy storage system of the device deteriorates, necessitating more frequent charging. 
         [0004]    Recharging a portable electronic device is generally a simple matter. A number of convenience enhancing devices have been developed allowing portable electronic devices to be rapidly charged and to be charged using a variety of power sources such as 12v power systems commonly found in motorized vehicles. Additionally, backup batteries are commonly made available so that a fresh battery can be used to replace a depleted battery. 
         [0005]    Even with all of the advances in powering portable electronic devices, however, providing power can be a challenge. For example, many people enjoy using portable electronic devices while hiking. The availability of power sources for recharging portable electronic devices is very limited, however, along hiking trails. Even when charging sources are available, however, recharging the power system of the portable electronic device requires the portable electronic device or the power source to remain in a specific location. Even for quick charging systems, the delay in activities is an undesired consequence. 
         [0006]    In response to the foregoing limitations, the possibility of scavenging human power and either using it directly, or storing it for later use, to power portable electronic devices has been explored. Power harvesting generators which use human motion offer an attractive grid-free and portable energy source that can be used to power and recharge wearable and personal electronics. These generators harvest energy from everyday human motion, such as walking, running, standing up, and sitting down and use the harvested energy to charge the battery (or other storage reservoir) of a personal electronic device or even power the electronic devices directly. 
         [0007]    In general, power harvesting devices are mechanical-to-electrical energy converters that usually consist of a mass-spring system coupled to a frame which is displaced by outside vibrations, shocks, or other motion. The mass-spring system acts as a damper for the motion of the frame, thereby acquiring kinetic energy. Transduction of mechanical to electrical energy by mass-spring system can be electromagnetic (magnet moving relative to a coil), electrostatic (charged objects moving past each other), or piezoelectric (strain in a bending element produces output voltage). 
         [0008]    Transduction of human motion for powering wearable or portable electronics presents particular challenges. By way of example, frequencies of ordinary human motion (e.g. walking) are typically very low (˜1-2 Hz), the amplitudes of the movements are high (˜10 cm), and the weight and size of the device is limited to unobtrusive dimensions. As a consequence, the amount of power available from typical generating systems is limited to a few mW. Moreover, wearable electronics are becoming increasingly sophisticated and consuming more and more power. 
         [0009]    Another limitation of known systems is that the known systems harvest power in only one dimension. By way of example, a moving piston within a generator positioned in the heel of a shoe can be used to generate power. Of course, any energy available from motion in other directions, such as pivoting motions, is lost. 
         [0010]    Accordingly, there is a need for a lightweight generator that can be used to convert a movement into power. It would be beneficial if such a device were not limited to harvesting power available in a single dimension. 
       SUMMARY 
       [0011]    A wearable generator system in one embodiment includes a plurality of coils, each of the plurality of coils extending within a respective one of a plurality of planes, a magnet for generating a magnetic field, and a support attached to a support anchor point and to the magnet, and suspending the magnet at a position whereat the magnet is not frictionally engaged with a fixed surface, the support having a length selected such that the magnetic field is movable across each of the plurality of coils. 
         [0012]    In accordance with another embodiment, a wearable generator system includes at least one first coil, each of the at least one first coils extending within a respective one of at least one first plane, a first magnet for generating a first magnetic field, and a first support having a first portion fixedly positioned with respect to the at least one first coil and a second portion spaced apart from the first portion, the second portion fixedly attached to the first magnet at a location lower than the first portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  depicts a perspective view of a wearable generator system including a plurality of generator pouches, an energy storage pouch and a charging holster in accordance with principles of the present invention; 
           [0014]      FIG. 2  depicts a schematic diagram of the electrical circuit of the wearable generator system of  FIG. 1 ; 
           [0015]      FIG. 3  depicts a perspective view of a power harvester that is located in one of the generator pouches of  FIG. 1 ; 
           [0016]      FIG. 4  depicts the power harvester of  FIG. 3  after the wearer of the wearable generator system has moved from a first position; 
           [0017]      FIG. 5  depicts the power harvester of  FIG. 3  after the wearer of the wearable generator system has stopped moving; 
           [0018]      FIG. 6  depicts a simplified perspective view of the power harvester of  FIG. 3  showing the magnet field of the magnet of the power harvester with the magnet centrally located within a coil volume defined by the power harvester coils; 
           [0019]      FIG. 7  depicts a simplified perspective view of the power harvester of  FIG. 3  showing the magnet field of the magnet of the power harvester intersecting two different coils; and 
           [0020]      FIG. 8  depicts a partial cutaway perspective view of an alternative power harvester with a cube-shaped coil volume. 
       
    
    
     DESCRIPTION 
       [0021]    For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the invention is thereby intended. It is further understood that the present invention includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the invention as would normally occur to one skilled in the art to which this invention pertains. 
         [0022]    Referring to  FIG. 1 , there is depicted a representation of a wearable generator system generally designated  100 . The generator system  100  in this embodiment includes a belt  102  that can be fastened about a wearer using male clasp  104  and female clasp  106 . Supported on the belt  102  are plurality of generator pouches  108 ,  110 ,  112 , and  114 , an energy storage pouch  116 , a charging holster  118 , and an auxiliary pouch  120 . 
         [0023]    The generator pouches  108 / 110 / 112 / 114  house a respective one of the power harvesters  124   1-4  shown in  FIG. 2 . The power harvesters  124   1-4  generate electrical power which is directed to a conditioning and charging circuit  126  which is housed within the energy storage pouch  116 . The conditioning and charging circuit  126  includes one or more energy storage devices along with conditioning and control electronics. 
         [0024]    The conditioning and charging circuit  126  includes a processing circuit and a memory. The processing circuit may suitably be a general purpose computer processing circuit such as a microprocessor and its associated circuitry. The processing circuit is operable to carry out the operations attributed to it herein. Within the memory are program instructions. The program instructions are executable by the processing circuit and/or any other components as appropriate. 
         [0025]    The conditioning and charging circuit  126  control the components therein for conditioning energy received from the power harvesters  124   1-4  and using the conditioned energy to charge the energy storage devices. The conditioning and charging circuit  126  further direct energy from the energy storage devices or from the power harvesters  124   1-4  to a charging component  128  located in the charging holster  118 . The charging component  128  may include contacts for directly charging an electrical component placed into the charging holster  118  or coils for inductively charging an electrical component. In alternative embodiments, an electrical component such as a sensor or communications component may be hardwired into the charge control system  122 . 
         [0026]    The conditioning and charging circuit  126  may also direct energy from the energy storage devices or from the power harvesters  124   1-4  to a charging component  130  located in the auxiliary pouch  120 . The auxiliary pouch  120  may thus be used to charge replaceable batteries used in portable electronics. 
         [0027]    Each of the power harvesters  124   1-4  in this embodiment are identical and are described in more detail with reference to the power harvester  124   1  shown in simplified form in  FIG. 3 . The power harvester  124   1  includes a number of coils  132   x . Each of the coils  132   x  includes one or more turns of electrically conductive material and is electrically isolated from the other of the coils  132   x . A support line  138  (seen more clearly in  FIG. 4 ) is attached at one end to a support anchor point  140  and at another end to a magnet  142 . 
         [0028]    The magnet  142  is supported by the support line  138  in a manner which allows for movement of the magnet  142  within the space defined by the coils  132   x . For example, as a wearer accelerates in the direction of the arrow  144  of  FIG. 3 , the inertia of the magnet  142  causes the magnet  142  to be displaced from the location of  FIG. 3  to the location of  FIG. 4 . Such movement may be effected by using a rigid material for the support line  138  but allowing the support line  138  to swivel about the support anchor point  140 . Alternatively, a non-rigid material or even a resiliently stretchable material may be used to construct all or a portion of the support line  138 . In one embodiment, the support line  138  thus further allows for rotation of the magnet  142  such as in the direction of the arrow  146  of  FIG. 5 . 
         [0029]    The movement of the magnet  142  with respect to the coils  132   x  generates electricity as discussed with further reference to  FIGS. 6 and 7 .  FIG. 6  depicts a simplified view of the power harvester  124   1  showing only coils  132   1-3 . The coils  132   1-3  are each substantially positioned within a respective plane, each of the planes intersecting the planes in which the other of the coils  132   1-3  are positioned. By way of example, the planes in which the coils  132   2  and coils  132   3  lie intersect along the line  150  while the planes in which the coils  132   1  and coils  132   3  lie intersect along the line  152 . The coils  132   1-3  thus define a coil volume generally identified as  154  which is substantially in the form of a sphere. The magnet  142  is suspended within the coil volume  154  and the magnetic field  156  of the magnet  142  emanates from the magnet  142 . 
         [0030]    As the magnet  142  moves, such as from the position depicted in  FIG. 6  to the position depicted in  FIG. 7 , the magnetic field  156  moves across various of the coils  132   1-3 . As depicted in  FIG. 7 , the magnetic field  156  has crossed the coil  132   2  and the coil  132   3 . As the magnetic field  156  crosses the coils  132   2-3 , a current is generated in the coils  132   2-3  which is transferred to energy storage devices within the conditioning and charging circuit  126 . The conditioning and charging circuit  126  then boosts the voltage generated by the harvester to the one usable by a sensor, personal electronic device, or a battery or a capacitor as appropriate. 
         [0031]    More specifically, electromagnetic power harvesting uses the voltage induced in a conductive coil moving relative to a permanent magnet. Using Faraday&#39;s law, the voltage induced in a generator where a coil moves through a permanent magnetic field (V EMF ) can be expressed by: 
         [0000]    
       
         
           
             
               V 
               EMF 
             
             = 
             
               
                 - 
                 
                   
                      
                     Φ 
                   
                   
                      
                     t 
                   
                 
               
               = 
               
                 
                   - 
                   
                      
                     
                        
                       t 
                     
                   
                 
                  
                 
                   ( 
                   
                     
                       Nlz 
                        
                       
                         ( 
                         t 
                         ) 
                       
                     
                      
                     
                       B 
                        
                       
                         ( 
                         t 
                         ) 
                       
                     
                   
                   ) 
                 
               
             
           
         
       
     
         [0000]    where N is the number of turns of the coil, B is the strength of the magnetic field, Φ is the magnetic flux, and/is the length of a side of one loop in the coil. The generated output power is given in general by P=V EMF   2 /R tot . 
         [0032]    Thus, each of the coils  132   2-3  generates electrical power. As is evident from  FIGS. 6 and 7 , the coils  132   2-3  are orientated differently. Accordingly, even if the movement of the magnet  142  is such that power generation is maximized for the coil  132   2 , the coil  132   3  still generates some amount of power. Given the multiple orientations of the coils  132   x  as depicted in  FIG. 3 , any movement of the magnet  142  will generate some power in at least one of the coils  132   x . The wearable generator system  100  is thus capable of generating power for a wide variety of movements. Consequently, the wearable generator system  100  may be positioned about an individual&#39;s waist, on an arm or a leg, etc. and still provide energy. 
         [0033]    Because the wearable generator system  100  is able to generate power without limitation as to the particular movement exhibited by the magnet  142 , power generation is maximized, in general, by maximizing movement of the magnet  142 . To this end, the support line  138  may be a flexible line such that kinetic energy of the magnet  142  is not lost through frictional contact. 
         [0034]    The support anchor point  140  is positioned such that when the belt  102  is positioned on a wearer, the support anchor point  140  is at the upper portion of the power harvester  124   1 . In embodiments wherein the orientation of the power harvester  124   1  is not controlled, or wherein the power harvester  124   1  is subject to large accelerations or inversion, an additional line or lines may be used to maintain the magnet  142  suspended within the coil volume  156 . In embodiments wherein additional lines are used to keep the magnet  142  suspended at different orientations of the power harvesters  124   x , some amount of slack in the lines is preferably provided. Accordingly, movement of the magnet is generally limited by a single one of the lines to maximize movement of the magnet  142 . 
         [0035]    Movement of a magnet positioned within a coil volume may further be adjusted by connecting lines to the magnet asymmetrically. By way of example,  FIG. 8  depicts an embodiment of a power harvester  170  with an asymmetrically suspended magnet  172 . The power harvester  170  includes a rectangular frame  174  with coils  176  positioned on all six sides of the frame  174 . The coils  176  thus define a rectangular coil volume in which the magnet  172  is suspended by a support line  178  attached to a support line anchor  180  on the frame  174 . A tether line  182  is attached to a tether anchor point  184  on the frame  174  and to the magnet  172 . Coil volumes of other shapes may be used for different applications. Additionally, while coils  176  are positioned on all sides of the frame  174 , some embodiments may utile coils on less than all of the sides. 
         [0036]    While the magnet  172  is supported at substantially the midpoint of the magnet  142  by the support line  178 , the tether  182  is attached to the magnet  172  closer to one end of the magnet  172 . Accordingly, as the magnet  172  moves to the left, the tether  182  will cause the magnet  172  to spin because the magnet  172  is asymmetrically supported by the support line  178  and the tether line  180 . Axial movement of the magnet  172  is thus converted to a spinning motion which causes a magnetic field of the magnet  172  to cross several of the coils  176 . Thus, contact between the magnet  172  and the frame  174  and coils  176  can be reduced, thereby reducing frictional loss, while increasing the crossing of coils  176  by the magnetic field of the magnet  172 . 
         [0037]    While the invention has been illustrated and described in detail in the drawings and foregoing description, the same should be considered as illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications and further applications that come within the spirit of the invention are desired to be protected.