Abstract:
The Voltage Dosimeter is a method and apparatus that automatically controls voltage producing sources to deliver varying voltage to reduce the need for constant voltage production and it provides switching ability between devices by maintaining the negative electrode voltage of voltage producing sources in a predetermined range. In the preferred embodiment a maximal reactive gas flow rate produces the first positive electrode voltage dosage of a fuel cell, then positive electrode voltage doses repeatedly sequence at predetermined intervals from smallest to largest until the current negative electrode voltage is in the desired range. Then the reactive gas flow rate and positive electrode voltage dosage are selected. The method continues with the delivery of the selected reactive gas flow rate and positive electrode voltage dose by the voltage producing source so as to maintain the negative electrode voltage in the desired range.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
       [0001]     Adolph Mondry—System and method for automatically maintaining a blood oxygenation level. U.S. Pat. No. 5,682,877, Nov. 4, 1997—herein referred to as 877. The flow sheets of that device are similar to those of the Voltage Dosimeter.  
         [0002]     Meland Kantak—Internal fuel staging for improved fuel cell performance. P.N. application 20020081479—herein referred to as 479. A similar device is used in the Voltage Dosimeter.  
         [0003]     Thomas L Cable—High performance fuel cell interconnect with integrated flow paths and method for making same. P.N. application 200300877498—herein referred to as 498. A similar device is used in the Voltage Dosimeter.  
       FEDERALLY SPONSORED RESEARCH GRANTS  
       [0004]     There are no Federally sponsored research grants available to those involved in the research and development of this device.  
       BACKGROUND OF THIS INVENTION  
       [0005]     Fuel cells and many devices that are voltage producing sources, such as solar cells, must constantly generate the full amount of voltage needed to operate all connected circuits. Connections between these devices will be needed as requirements expand. It is desirable to have a device available, which automatically controls circuit voltage to minimize the need for constant voltage generation in fuel cells and other voltage producing devices without compromising circuit function, and which provides automatic switching.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     It is an object of the present invention to provide a method and apparatus to control voltage in fuel cells and other voltage producing sources to produce and deliver appropriate varying circuit voltage to decrease voltage production by placing the negative electrode of the voltage producing source in a predetermined range. It is a further object of this invention to provide automatic switching between these devices to provide extra voltage when needed.  
         [0007]     In carrying out the above objects and other stated objects and features of the present invention a method and apparatus is provided as a Voltage Dosimeter for maintaining a desired voltage level at the negative electrode (herein named the entrance voltage) of a voltage producing source, and includes delivering a first voltage producing dose to the positive electrode (herein named the exit voltage) of the voltage producing source producing an exit voltage dose selected from one of a plurality of exit voltage doses between a first exit voltage dose and a second exit voltage dose. The method includes delivering a second voltage producing dose to the circuit while repeatedly sequencing through the plurality of sequential exit voltage doses beginning with the first exit voltage dose and proceeding to an adjacent exit voltage dose in the sequence after a predetermined time interval has elapsed. The second voltage producing dose is delivered until the entrance voltage level attains the desirable level, at which point corresponding exit voltage and voltage producing doses are selected from the plurality of sequential voltage producing and exit voltage doses. The method also includes delivering the selected exit voltage and voltage producing doses so as to maintain the desired entrance voltage level.  
         [0008]     In the preferred embodiment the method and apparatus automatically selects an appropriate reactive gas dose to maintain a desired entrance voltage level of a fuel cell, for which the system is particularly suited, and is the preferred voltage producing source, and includes delivering a first reactive gas flow rate to the fuel cell, producing an exit voltage dose in the fuel cell selected from one of a plurality of exit voltage doses between a first exit voltage dose and a second exit voltage dose. The method includes delivering the second reactive gas flow rate to the fuel cell while repeatedly sequencing through the plurality of sequential exit voltage doses beginning with the first exit voltage dose and proceeding to an adjacent exit voltage dose in the sequence after a predetermined time interval has elapsed. The second reactive gas flow rate is delivered until the entrance voltage attains the desirable level, at which point a corresponding exit voltage dose and reactive gas flow rate are selected from the plurality of sequential exit voltage doses and reactive gas flow rates. The method also includes delivering the selected exit voltage dose and the reactive gas flow rate so as to maintain the desired entrance voltage level.  
         [0009]     The advantages of the Voltage Dosimeter are minimal needs for constant voltage production in fuel cells and other voltage producing sources, the availability of switching voltage between these devices as the need arises, and a reduction in the cost of electricity.  
         [0010]     The above objects, features, and other advantages will be readily appreciated by one of ordinary skill in the art from the following detailed description of the best mode for carrying out the invention, when taken in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1 / 6  demonstrates a perspective view of the first embodiment of the present invention.  
         [0012]      FIG. 2 / 6  is a graphical demonstration of the flow charts of the Voltage Dosimeter.  
         [0013]      FIG. 3 / 3 - 5 / 6  are flow charts dealing with the voltage and reactive gas strategy of the present invention for use in the Voltage Dosimeter.  
         [0014]      FIG. 6 / 6  is a flow chart for relating parameters in the Voltage Dosimeter.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]     Referring now to  FIG. 1 / 6 , a first embodiment of the present invention is shown. This embodiment indicated by reference number  1  in  FIG. 1 / 6  is the best mode in implementing this invention and is particularly suited for use as a Voltage Dosimeter.  FIG. 1 / 6  includes two voltometers  2  and  3 —one volometer  2 , which measures exit voltage—v 1 —at the positive electrode  4  of a voltage delivery system and a second voltometer  3 , which measures entrance voltage—v 2 —at the negative electrode  5  of a voltage delivery system. Two band pass electrical filters  7  and  8  are connected to each voltometer  2  and  3 , then to an electronic control unit (ECU)  9 , which exercises control strategy, and processing and analyzing voltage data to maintain v 2  in a specific range. The ECU  9  preferably operates on power delivered from either D.C. or A.C. power supplies allowing portability to the Voltage Dosimeter System.  
         [0016]     With continuing reference to  FIG. 1 / 6  a fuel cell  10  as described in U.S. patent application Ser. No. 498 is added as the preferred embodiment of a voltage delivery system. The two reactive gas flow rates at the inlets  11  are controlled by two ECU  9  controlled variably opening solenoid valves  12  with Coulomb controlling circuits, as was taught in 877 and U.S. Pat. No. 5,008,773. Reactive gases pass through an electrolyte solution  13 , then react at the electrodes  14 . A typical reaction is 2H2+O2=2H2O+4e−+heat, thus producing voltage in an electric wire  15  with resistance  16 . A circuit  6 , such as that of a family dwelling, is pictured. Adequate voltage delivery here is the object of the present embodiment. A battery  17  is supplied for use when extra power is needed. Optional DC/AC converters  17  and AC//DC converters  6  are included for better use of conventional appliances.  
         [0017]     Referring now to  FIG. 2 / 6 , the method of device function is demonstrated graphically. Voltage is placed on the ordinate and time, reactive gas flow rate, and voltage producing dosage are placed on the abscissa of a Cartesian plane. Maximum reactive gas flow rate or voltage producing dosage occurs at tr on the abscissa, the significance of which will be presented later. Measured and calculated logarithmic functions are used in the preferred embodiment as exit voltage doses, but any measured and estimated transcendental function with an inverse may be used.  
         [0018]     Referring again to  FIG. 1 / 6 , as will be seen, conditions on v 2 —the entrance voltage—control reactive gas flow rate  11  and thus v 1 —exit voltage, circuit voltage, circuit voltage dosage, and finally entrance voltage—v 2 —itself.  
         [0019]     Referring now to  FIG. 2 / 6 , the illustrated method of reactive gas flow rate and exit voltage dosage selection starts with the administration of an extreme reactive gas flow rate—herein referred to as the selector dose of the reactive gas flow rate which produces the maximum or minimum voltage producing and exit voltage dose at the positive electrode of the fuel cell or of any voltage producing device—as in curve A or B. Curve A is represented by y=log to the base a of x. Curve A activates at x=0.  
         [0020]     Line CG is the desired voltage of v 2 —herein referred to as the selection parameter, which is a range in the actual device. At the intersection of line CG and curve A or B (call it X), line D points to point E on the abscissa as the selected reactive gas flow rate or voltage producing dose. This is determined by graphical means and, as will be seen, the flow charts. The virtual exit voltage dose logarithm is curve F, which activates at point E, the selected voltage producing dose, and is boosted by curves A, B, H—an overshoot of curve A—and curve I—a deactivation of curve H—to produce line G, which is the selected exit voltage dose and here is an exit voltage as well, because it is a horizontal line, and is represented by y=log to the base b of tr, where tr is the t value of the flattening out of the logarithm y=log to the base b of t (curve F) at tr seconds. Line G is completely determined by the intersection (X) described above and in the flow charts, as will be seen, thus the determination of lines F and G by the above methods is unnecessary. Curve F and G start in the x coordinate system at x=t and in the t coordinate system at t=0, when curve A deactivates. Curve F and G deactivate when curve A activates. Curve J is the virtual curve of curves A and H. K marks the Circulation time. It marks the time from the initial reactive gas flow rate to the first recording of v 1 . Its accuracy is essential for proper flow chart function with respect to time. Its calculation and that of tr will be demonstrated. The voltage producing dose is circulation time dependent. The exit voltage dose is not, since it is a function of time. At line CG v 1  usually differs from v 2  in value. At the above mentioned intersection (X) v 2  is in its desired range and v 1  is selected as the selected exit voltage dosage, which determines the selected voltage producing dosage. Until the above intersection (X) the line CG can not be placed on the Cartesian plane.  
         [0021]     Before describing the flow charts it is useful to explain the terminology employed. The most recent base state keeps v 2  (the entrance voltage) in its desirable range. V 1  (the exit voltage) and v 2  are measured in all states. The washout state washes out overshoots. It also determines the voltage producing dose or in the fuel cell the reactive gas flow rate, as will be seen. For the fuel cell Voltage Dosimeter exit voltage doses are functions of reactive gas flow rates. For other voltage producing devices, exit voltage doses are functions of other voltage producing dosage mechanisms—motion, magnetism, heat or technologies producing heat.  
         [0022]     Referring now to  FIG. 3 / 6 - 5 / 6 , flow charts are shown, which illustrate the system and method for the proper selection of exit voltage doses, voltage producing doses, and reactive gas flow rates.  
         [0023]     Referring to  FIG. 3 / 6 , Step  400  determines various system parameters, which may be predetermined and stored in memory, calculated by an ECU (such as ECU  9  in  FIG. 1 / 6 ) or entered by a system operator. The system parameters include the following: 
    MIN R=minimum dose of voltage production and exit voltage given for each range.     MAX R=maximum dose of voltage production and exit voltage given for each range.     V 1 =exit voltage.     V 2 =entrance voltage. When it equals zero for ten seconds, the device deactivates and reactivates when the battery discharges in response to the closing of a circuit switch.     Tv 1 =desired exit voltage.     dL=low v 2  threshold.     dH=high v 2  threshold.     TSS=series state delay time.     Tcirc=circulation delay time.     Twash=washout delay time.     TR=desired response time or reaction time 
 
 To calculate dH and dL close all circuits. Increase v 1  until all circuits first function properly. Measure v 2 . This is dL. Do the same with the smallest circuit. This is dH. 
   
 
         [0035]     As shown in  FIG. 3 / 6  the ECU now passes control to Step  402 , which measures v 1  and v 2 . At Step  404  a maximum exit voltage and voltage producing dose of the last range is administered. This is represented graphically by curve A of  FIG. 2 / 6  and is called the selector dose. It represents the maximum exit voltage dose. The possible exit voltage dose is set for the lowest dose of the lowest range.  
         [0036]     With continuing reference to  FIG. 3 / 6  at Step  406  v 1  is maintained while pausing Tcirc seconds, then x is set to 0 seconds. Step  406  is called an adjustment state. It coordinates the flow charts with respect to time. Initial circulation times may be estimated or measured.  
         [0037]     Referring once again to  FIG. 3 / 6  the ECU passes control to Step  408 , which continues to deliver exit voltage to v 1 . Step  408  is referred to as a series state—Tss—and is necessary to coordinate the progression through various possible doses within a time period determined by tr. The calculation of Tss depends on the current operating state. Some representative calculations are illustrated in  FIG. 6 / 6  for a single ranged implementation as discussed in greater detail below.  
         [0038]     Still referring to  FIG. 3 / 6  a test is performed at Steps  409  and  410 . It asks—is v 2  greater than dH?—and, is v 2  less than dL?, respectively. They split control into three pathways. Negative answers to both conditions direct control to Step  426 , where 1. The definitive current exit voltage dose is set to the possible dose, while the preliminary voltage producing dose is set one circulation time into the future. 2. A pause for the circulation time takes place. Then, 3. t is set to 0. This represents preliminary voltage producing dose and definitive exit voltage dose selection.  
         [0039]     Now referring to  FIG. 4 / 6  processing continues with the ECU directing control to Step  428 , which pauses to washout high valued functions from the selected dose. The state is completed when all involved functions equal a straight line—the selected exit voltage dose. For convenience in the representation of the method in the flow charts the ECU was represented to set t=0 in Step  426 . This actually occurs at the start of the washout state. The ECU directs in the washout state the determination of the selected value of point E of  FIG. 1 / 6 —the definitive selected voltage producing dose or the selected reactive gas flow rate in the case of the fuel cell Voltage Dosimeter—then activates these doses. The exit voltage dose remains the selected dose as curve G in  FIG. 1 / 6 . Both of the above dosages continue until activation of MIN R or MAX R.  FIG. 430  measures voltage values for the Conditions below. Steps  409  and  410  represent a second test and ask the same questions as the above mentioned first test—Is v 2  greater than dH or less than dL, respectively? If either answer yes, control is directed to Steps  431  and  434 , respectively, where a predetermined fraction of tr is either subtracted or added, respectively to tr. This pathway determines tr only if the circulation time is correct. The circulation time is calculated by keeping the last three base state values in memory. When control is directed to or beyond a noncontiguous base state from which control was originally assumed a predetermined amount of time is added to the circulation time. This will correct abnormally short circulation times. For abnormally long circulation times—if control passes consecutively to two ascending or descending base states, a predetermined amount of time is subtracted from the circulation time.  
         [0040]     Referring now to  FIG. 5 / 6 , if both conditions in the second test answer no, the ECU places control in Step  436 , the base state. Steps  438  and  440  represent the third test and ask the same questions (is v 2 &gt;dH or &lt;dL?) as those of the previous tests with different consequences. They determine the stability of the base state (both conditions answer no if it is stable). If it is unstable, the ECU directs control to either Step  463 , if Step  438  answers yes, or  446 , which 1. Minimizes or maximizes the current dose, respectively 2. Pauses for the circulation time, then 3. sets x=0. These doses continue until dose selection. It should be noted that Steps  431 ,  434 , the yes part of  418 , and the no part of Steps  433  and  440  all yield control to Step  436 , the base state. The ECU then directs control from Step  463  to Step  411 , and from Step  446  to Step  412 .  
         [0041]     Referring again to  FIG. 3 / 6 , the ECU directs control from Step  464  (evaluated later), and if Step  414  in  FIG. 4 / 6  (the first condition of fourth test to be elucidated soon) answers no, to Step  408  to maintain the current exit voltage dose for Tss. Control is then directed to Step  409 , which, if along with Step  410 —the first test—the answer is yes to both conditions, control is passed to Steps  411  and  412 , respectively, which decrement and increment the possible dose, respectively, then both pass control to Condition  414 .  
         [0042]     Referring now to  FIG. 4 / 6 , Steps  414  and  418  represent the fourth and final test with different conditions than the other tests. These conditions ask if the present possible dose is the last dose available, and if the present range is the last one available, respectively. If Step  414  answers no, control is directed by the ECU to Step  408  in  FIG. 3 / 6 , which maintains a current dose for Tss. If the condition answers yes, control is directed to Step  418 , which determines if the present range is the last range available. If it answers no, control is directed to Step  464 , in which control enters a new range, sets the current exit voltage and voltage producing dose to MAX R or MIN R of the new range, pauses for the circulation time, then sets x=0. Control is then directed to Step  408 , which maintains a current exit voltage dose for Tss. If Step  418  answers yes, the ECU directs control to Step  436 , the base state.  
         [0043]     Referring now to  FIG. 6 / 6  a flow chart is shown illustrating representative calculations of Tss according to the present invention. One of these calculations or an analogous calculation is performed for each series state of  FIG. 3 / 6 - 5 / 6 , such as illustrated at Steps  408 ,  411 , and  412 .  
         [0044]     Returning to  FIG. 6 / 6  at Step  480  a test is performed to determine if the system has reached a base state. If not, the series state delay is estimated as: Tss=tr/IR. If the result is true, the process continues with Step  484 , where a test is performed to determine whether v 2 &lt;dL. If true, then Step  486  determines whether the most recent base state is a minimum for the current range. If it is true, the series state delay is calculated by Step  488  as Tss=tr/(IR−1). Step  498  then returns control to the series state which initiated the calculation.  
         [0045]     With continuing reference to  FIG. 6 / 6 , if the test at Step  486  is true, then the series state delay is calculated by Step  490  as Tss=tr(MAX R−MIN R)/(IR−1)(MAX R−BASE STATE) before control is released to the series state via Step  498 . If the test performed at Step  484  is false, then Step  492  performs a test to determine if the most recent base state is the maximum for the current range. If the result of Step  492  is true, then Step  496  calculates the series state delay as Tss=tr/(IR−1). Control is then returned to the appropriate series state via Step  498 . If the result of the test at Step  492  is false, then the series state delay is calculated by Step  494  as Tss=tr(MAX R−MIN R)/(IR−1)(BASE STATE−MIN R). Step  498  then returns control to the appropriate series state.  FIG. 6 / 6  applies to a single range. One of ordinary skill in the art should appreciate that the calculations may be modified to accommodate a number of possible ranges.  
         [0046]     It should be apparent by any one skilled in the art that the flow charts provide a method and apparatus for a Voltage Dosimeter.  
         [0047]     Other Voltage Dosimeters use other means to produce voltage. Fission reactors, mechanical/magnetic reactors, fusion reactors, solar cells, steam/turbine reactors, and fossil fuel burning reactors can function as Voltage Dosimeters controlling voltage in corresponding circuits by the same method and with same apparatus as the fuel cell Voltage Dosimeter. The range used for v2 depends on the application. Switching function between voltage producing devices employs Step  418  of  FIG. 4 / 6 —last range available?—If it answers yes, control passes to Step  436 , the base state, where voltage passes from the device. For all other steps, voltage is transfered to the device.