Abstract:
The fluid power generator is provided. The fluid power generator includes: a rotating member that rotates by fluid force; a generator motor that is mechanically linked with the rotating member and that is configured to function both as a generator and as a motor; a rotation speed meter that measures a rotation speed of the generator motor; and a controller that controls the generator motor, wherein the controller has a control mode to keep the rotation of the rotating member irrespective of a variation in flow rate of the fluid.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the priority based on Japanese Patent Applications No. 2008-34329 filed on Feb. 15, 2008; and No. 2009-12565 filed on, Jan. 23, 2009, the disclosures of which are hereby incorporated by reference in their entireties. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fluid power generator, as well as to a motor device having a function of electric power regeneration. 
     2. Description of the Related Art 
     For reduction of carbon dioxide, power generations by utilizing natural energies, such as wind power generation, hydraulic power generation, and photovoltaic power generation, have been attracting a great deal of attention. Enhancement of the efficiency of such natural energy power generations is of great importance to solve the environmental problems. 
     A fluid power generator may be constructed, for example, with application of a brushless motor structure. One example of the brushless motor structure is disclosed in JP 2001-298982A. 
     One typical example of the fluid power generator is a wind power generator. A prior art structure of the wind power generator adopts a heavy weight of blades, in order to prevent rotation of the blades from being stopped by a decrease of wind force and to prevent a decrease in power generation efficiency with a variation in rotation speed caused by the varying wind force. The heavy blades enhance the inertial force of rotation and keep the rotation of the generator. 
     This prior art structure, however, undesirably expands the dimensions of the whole wind power generator in order to support the heavy blades and requires the enhanced intensity of a support member for supporting the heavy blades in the wind power generator. Such drawbacks are not characteristic of the wind power generator but are commonly found in various fluid power generators. Efficient regeneration of electric power in a motor drive is also highly demanded. 
     SUMMARY 
     An object of the present invention is to provide technology that is able to keep the rotation of a fluid power generator irrespective of a variation in flow rate of a fluid. Another object of the present invention is to provide technology that is able to provide a motor device having a function of regenerating electric power by a different technique from the conventional technique. 
     According to an aspect of the present invention, a fluid power generator is provided. The fluid power generator comprises: a rotating member that rotates by fluid force; a generator motor that is mechanically linked with the rotating member and that is configured to function both as a generator and as a motor; a rotation speed meter that measures a rotation speed of the generator motor; and a controller that controls the generator motor, wherein the controller has a control mode to keep the rotation of the rotating member irrespective of a variation in flow rate of the fluid. 
     The fluid power generator according to this aspect of the invention controls the generator motor functioning both as the generator and as the motor in such a manner as to allow the rotation of the fluid power generator to be kept irrespective of a variation in flow rate of the fluid. 
     According to another aspect of the present invention, a motor device having a function of electric power regeneration is provided. The motor device comprises: a position signal generator that generates a position signal representing a relative position of an electromagnetic coil to a permanent magnet in the motor device; a driving signal generator that generates a driving signal specifying a voltage application time period of the electromagnetic coil, based on the position signal; and a regeneration signal generator that generates a regeneration signal specifying an electric power regeneration time period of the electromagnetic coil, based on the position signal, wherein the voltage application time period is set to appear periodically during each half cycle period of the position signal, and the electric power regeneration time period is set to appear in a residual time period other than the voltage application time period. 
     The motor device according to this aspect of the invention allows regeneration of electric power in the residual time period without application of the voltage to the electromagnetic coil, while periodically being driven with application of the voltage. 
     The technique of the invention is not restricted to the power generator or the motor device having any of the arrangements discussed above but is also actualized by diversity of other applications, for example, a power generation method, a power generation system, a motor device control method, a motor device control system, integrated circuits for attaining such methods and systems, computer programs for the same purpose, and recording media in which such computer programs are recorded. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram schematically illustrating the general configuration of a power generator  1000  in a first embodiment of the invention; 
         FIG. 2A  is a sectional view showing the schematic structure of the main body of the generator motor  100 ; 
         FIGS. 2B through 2D  respectively show the structures of the A-phase coil array  14 A of the stator  10 , the rotor  30 , and the B-phase coil array  24 B of the stator  10 ; 
         FIG. 3  is a flowchart showing a control routine of the power generator  1000 ; 
         FIG. 4  is an explanatory view showing the internal structure of the driving signal/power generation signal generator  300 ; 
         FIG. 5  is one timing chart showing variations of the respective signals generated by the driving signal/power generation signal generator  300 ; 
         FIG. 6  is another timing chart showing variations of the respective signals generated by the driving signal/power generation signal generator  300 ; 
         FIG. 7  is a circuit diagram showing the internal structure of the driving circuit assembly  400  and the power generation circuit assembly  500  with regard to the A-phase coil array  14 A; 
         FIG. 8  is a block diagram schematically illustrating the general configuration of a motor device  1000   b  in a second embodiment of the invention; 
         FIG. 9  is one timing chart showing variations of the respective signals generated by the driving signal/regeneration signal generator  300   b ; and 
         FIG. 10  is another timing chart showing variations of the respective signals generated by the driving signal/regeneration signal generator  300   b.    
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Next, aspects of the present invention will be described in the following order on the basis of embodiments:
     A. First Embodiment:   B. Modified Examples of First Embodiment:   C. Second Embodiment:   

     A. First Embodiment 
       FIG. 1  is a block diagram schematically illustrating the general configuration of a power generator  1000  in a first embodiment of the invention. The power generator  1000  has a generator motor  100 , a controller  200 , a wind speed meter  203 , a reference rotation speed storage unit  204 , a rotation speed comparator  205 , a rotation speed meter  206 , and an accumulator  700 . The controller  200  includes a CPU  202 , a driving signal/power generation signal generator  300 , a driving circuit assembly  400 , a power generation circuit assembly  500 , and a power generation current controller  600 . The generator motor  100  has blades  190  rotated by the wind force and two position sensors  16 A and  26 B provided to detect the relative positions of a rotor in the generator motor  100 . 
     The generator motor  100  has a power generation function of generating electric power by the wind force, a driving function of being driven as a motor to rotate the blades  190 , and a braking function of being driven as the motor in an opposite direction to the rotating direction of the blades  190  to control the rotation of the blades  190 . The generator motor  100  has a stator having two phase coil arrays (A-phase coil array and B-phase coil array) and a rotor having a permanent magnet array as described later in detail. 
     The two rotation sensors  16 A and  26 B are respectively attached to the A-phase coil array and to the B-phase coil array. For example, magnetic sensors may be adopted for the rotation sensors  16 A and  26 B. In application of the magnetic sensors for the rotation sensors  16 A and  26 B, the rotation sensor  16 A detects the magnetism of the permanent magnet array on the rotor and outputs a sensor signal SSA representing the position of the rotor relative to the A-phase coil array. Similarly the rotation sensor  26 B outputs a sensor signal SSB representing the position of the rotor relative to the B-phase coil array. The sensor signals SSA and SSB have periodical waveforms by rotation of the generator motor  100 . The frequencies of the sensor signals SSA and SSB are accordingly correlated to the rotation speed of the generator motor  100 . The waveforms of the sensor signals SSA and SSB are explained later in detail with reference to  FIGS. 5 and 6 . 
     The rotation speed meter  206  measures the rotation speed of the generator motor  100 , based on the frequency of the sensor signal SSA or the frequency of the sensor signal SSB. The reference rotation speed storage unit  204  stores reference rotation speeds therein. The ‘reference rotation speeds’ specify an upper limit value and a lower limit value of rotation speed ensuring adequate power generation. The lower limit value of the reference rotation speed and the upper limit value of the reference rotation speed are respectively referred to as ‘minimum reference rotation speed’ and ‘maximum reference rotation speed’. The minimum reference rotation speed is a lowest possible rotation speed that enables the rotation of the generator motor  100  to be kept. The two reference rotation speeds are arbitrarily updated by the CPU  202 . The rotation speed comparator  205  compares the minimum reference rotation speed and the maximum reference rotation speed with the actual rotation speed of the generator motor  100  measured by the rotation speed meter  206  and sends a result of the comparison to the CPU  202 . 
     The CPU  202  sends a command to the driving signal/power generation signal generator  300  based on the result of comparison received from the rotation speed comparator  205  to keep the actual rotation speed of the generator motor  100  in a specific range defined by the minimum reference rotation speed and the maximum reference rotation speed (hereafter referred to as ‘reference rotation speed range’). The CPU  202  also sends a command to the driving signal/power generation signal generator  300  based on a wind speed Vc measured by the wind speed meter  203 . The wind speed meter  203  may be omitted in a modified configuration where the CPU  202  does not utilize the wind speed Vc. The CPU  202  also sends a control command to the power generation current controller  600 . 
     The driving signal/power generation signal generator  300  generates a power generation signal REG and a driving signal DRV, in response to the command from the CPU  202  and the sensor signals SSA and SSB. The power generation signal REG rises to a high (H) level to enable the power generation function of the generator motor  100 . The driving signal DRV, on the other hand, rises to an H level to enable the driving function and the braking function of the generator motor  100 . Although not being specifically illustrated in  FIG. 1 , the driving signal DRV includes two A-phase driving signals DRVA 1  and DRVA 2  used to control the A-phase coil array and two B-phase driving signals DRVB 1  and DRVB 2  used to control the B-phase coil array. Similarly the power generation signal REG also has two A-phase power generation signals REGA 1  and REGA 2  and two B-phase power generation signals REGB 1 , and REGB 2 . This arrangement allows independent control of the A-phase coil array and the B-phase coil array. 
     The power generation circuit assembly  500  supplies the electric current, which is generated by the generator motor  100  at the H level of the power generation signal REG, to the power generation current controller  600 . The driving circuit assembly  400  excites the coil arrays of the generator motor  100  at the H level of the driving signal DRV and makes the generator motor  100  function as a motor. The power generation current controller  600  controls the amount of electric current to be supplied to the accumulator  700  according to the electric current supplied from the power generation circuit assembly  500 . 
       FIG. 2A  is a sectional view showing the schematic structure of the main body of the generator motor  100 . The generator motor  100  has a substantially disk-shaped stator  10  and a substantially disk-shaped rotor  30 . The rotor  30  has a magnet array  34 M of multiple magnets and is fastened to a rotating shaft  112 . The magnets of the magnet array  34 M are magnetized in a vertical direction. The stator  10  has an A-phase coil array  14 A located above the rotor  30  and a B-phase coil array  24 B located below the rotor  30 . 
       FIGS. 2B through 2D  respectively show the structures of the A-phase coil array  14 A of the stator  10 , the rotor  30 , and the B-phase coil array  24 B of the stator  10 . In this illustrated example, the A phase-coil array  14 A and the B-phase coil array  24 B respectively have six coils, while the magnet array  34 M has six magnets. The number of the coils in each coil array and the number of the magnets in the magnet array are, however, not restricted to this number but may be set arbitrarily. 
       FIG. 3  is a flowchart showing a control routine of the power generator  1000 . The wind speed meter  203  measures the wind speed Vc at step S 10 . The CPU  202  selects one operation mode or a combination of multiple operation modes among five possible operation modes of the generator motor  100  according to the range of the observed wind speed Vc at step S 20 . The five operation modes include ‘driving mode’, ‘driving/power generation mixed mode’, ‘power generation mode’, ‘power generation/braking mixed mode’, and ‘braking mode’. 
     In the ‘driving mode’, both the A-phase coil array  14 A and the B-phase coil array  24 B activate only the driving function. In the ‘power generation mode’, both the A-phase coil array  14 A and the B-phase coil array  24 B activate only the power generation function. In the ‘braking mode’, both the A-phase coil array  14 A and the B-phase coil array  24 B activate only the braking function. 
     In the ‘driving/power generation mixed mode’, the generator motor  100  simultaneously activates the two functions, the driving function and the power generation function. In one typical example of the driving/power generation mixed mode, the A-phase coil array  14 A activates the driving function, while the B-phase coil array  24 B activates the power generation function. In another typical example of the driving/power generation mixed mode, at least one of the A-phase coil array  14 A and the B-phase coil array  24 B changes over the activated function between the driving function and the power generation function in one period of the sensor signal SSA or SSB. In the ‘power generation/braking mixed mode’, the generator motor  100  simultaneously activates the two functions, the power generation function and the braking function. 
     The rotation speed of the generator motor  100  increases during activation of the driving function of the coil array, and decreases during activation of the power generation function of the coil array. Activation of the braking function of the coil array further decreases the rotation speed of the generator motor  100 . Namely controlling the driving function, the power generation function, and the braking function of the coil array allows the rotation speed of the generator motor  100  to be controlled according to the operation status of the coil array. One concrete procedure of the control varies the duty ratios of the driving signal DRV and the power generation signal REG and changes over the operations of the respective coil arrays among a driving time period with activation of the driving function, a power generation time period with activation of the power generation function, and a braking time period with activation of the braking function, based on the observed wind speed Vc, so as to control the rotation speed of the generator motor  100 . 
     At step S 20 , the observed wind speed Vc is compared with four reference wind speeds Vth 1  through Vth 4  satisfying the relation of Vth 1 &lt;Vth 2 &lt;Vth 3 &lt;Vth 4 . 
     When the observed wind speed Vc is lower than the first reference wind speed Vth 1  or when the observed wind speed Vc is not lower than the first reference wind speed Vth 1  but is lower than the second reference wind speed Vth 2 , the CPU  202  determines whether the generator motor  100  is at stop at step S 25 . 
     When the observed wind speed Vc is lower than the first reference wind speed Vth 1  and the generator motor  100  is at stop, the generator motor  100  is not allowed to keep unassisted steady rotation with only the wind force (that is, a rotation speed rotatable with the minimum wind force) but is allowed to keep steady rotation with slight driving assistance. In this case, the driving mode and the subsequent driving/power generation mixed mode are selected as the operation mode of the generator motor  100 . In the condition of very weak wind force, the generator motor  100  is set in the driving mode to activate the driving function and increase the rotation speed to the level of steady rotation. When the rotation speed of the generator motor  100  reaches the level of steady rotation, the operation mode of the generator motor  100  shifts from the driving mode to the driving/power generation mixed mode to perform power generation with keeping the steady rotation of the generator motor  100  with assistance of the driving function to compensate for the insufficient wind force. For example, the operation mode of the generator motor  100  is controlled such as to make the A-phase coil array  14 A activate both the driving function and the power generation function and to make the B-phase coil array  24 B activate only the power generation function. The unassisted steady rotation of the generator motor  100  means that the generator motor  100  is rotated with only the wind force at the rotation speed of not lower than the minimum reference rotation speed under the condition of the constant wind force. 
     When the observed wind speed Vc is not lower than the first reference wind speed Vth 1  but is lower than the second reference wind speed Vth 2  and the generator motor  100  is at stop, the level of wind force does not allow an unassisted start of rotation of the generator motor  100  but keeps the rotation of the generator motor  100  at the rotation speed of not lower than the level of steady rotation. In this case, the driving mode and the subsequent power generation mode are selected as the operation mode of the generator motor  100 . In the condition of relatively weak wind force, the generator motor  100  is not allowed to start rotation with only the wind force. The generator motor  100  is accordingly set in the driving mode to activate the driving function and increase the rotation speed to the level of steady rotation (the rotation speed rotatable with the minimum wind force). When the rotation speed of the generator motor  100  reaches the level of steady rotation, the driving function is inactivated and the operation mode of the generator motor  100  shifts from the driving mode to the power generation mode. In the power generation mode, the generator motor  100  generates electric power with the A-phase coil array  14 A and the B-phase coil array  24 B by the unassisted rotation with only the wind force. 
     When it is determined at step S 25  that the generator motor  100  is not at stop, the driving mode is not selected but either the driving/power generation mixed mode or the power generation mode is selected according to the range of the observed wind speed Vc as the operation mode of the generator motor  100 . 
     When the observed wind speed Vc is not lower than the second reference wind speed Vth 2  but is lower than the third reference wind speed Vth 3 , the power generation mode is selected as the operation mode of the generator motor  100 . In the condition of adequate wind force having appropriate strength for power generation, the level of wind force allows an unassisted start of rotation of the generator motor  100  and keeps the rotation of the generator motor  100  at the rotation speed of not lower than the level of steady rotation. In this case, the generator motor  100  is set in the power generation mode to generate electric power with the A-phase coil array  14 A and the B-phase coil array  24 B. 
     When the observed wind speed Vc is not lower than the third reference wind speed Vth 3  but is lower than the fourth reference wind speed Vth 4 , the power generation/braking mixed mode is selected as the operation mode of the generator motor  100 . In the condition of relatively strong wind force, the level of wind force makes the rotation of the generator motor  100  exceed the maximum reference rotation speed. In this case, the generator motor  100  is set in the power generation/braking mixed mode to perform power generation with keeping the rotation speed of the generator motor  100  to or below the maximum reference rotation speed. For example, the operation mode of the generator motor  100  is controlled such as to make the A-phase coil array  14 A activate both the braking function and the power generation function and to make the B-phase coil array  24 B activate only the power generation function. 
     When the observed wind speed Vc is not lower than the fourth reference wind speed Vth 4 , the braking mode is selected as the operation mode of the generator motor  100 . In the condition of very strong wind force, the level of wind force makes the rotation speed of the generator motor  100  significantly exceed the maximum reference rotation speed. In this case, the generator motor  100  is set in the braking mode to brake the generator motor  100  with the A-phase coil array  14 A and the B-phase coil array  24 B. Such control effectively prevents an abnormal increase in rotation speed of the generator motor  100  to an extremely high rotation speed over the maximum reference rotation speed to thereby protect the internal mechanism of the generator motor  100  from damages. 
     After selection of the operation mode of the generator motor  100  according to the range of the wind speed Vc at step S 20 , the rotation speed of the generator motor  100  is controlled to be kept in the reference rotation speed range according to the level of wind force as discussed above (steps S 30 , S 32 , and S 35 ). A concrete procedure changes over the operations of the respective coils arrays among the driving time period, the power generation time period, and the braking time period, based on the observed wind speed Vc. In the case of selection of either the power generation mode or the power generation/braking mixed mode at step S 20 , the amount of electric current supplied to the accumulator  700  may be regulated by the power generation current controller  600  (see  FIG. 1 ) according to the observed wind speed Vc (step S 32 ). Such regulation enables the rotation speed of the generator motor  100  to be kept in the reference rotation speed range. 
     In the case of selection of the driving/power generation mixed mode at step S 20 , it is determined at step S 40  whether control of the generator motor  100  is to be continued. At least one of the following conditions may be adopted for such determination: 
     (1) when the wind speed Vc has been not higher than a preset reference wind speed for more than a predetermined reference time period, the control for keeping the steady rotation of the generator motor  100  (rotation speed rotatable with the minimum wind force) is to be stopped; and 
     (2) when a result of subtraction of an amount of electric power consumed by the driving function of the generator motor  100  in a specific time period from an amount of electric power generated by the power generation function of the generator motor  100  in the specific time period is less than a preset reference amount of electric power, the control for keeping the steady rotation of the generator motor  100  (rotation speed rotatable with the minimum wind force) is to be stopped. 
     When it is determined at step S 40  that the control for keeping the steady rotation of the generator motor  100  (rotation speed rotatable with the minimum wind force) is to be stopped, the control of the generator motor  100  is stopped at step S 50 . This effectively prevents the operation of the power generator  1000  from being continued for a long time period in the state of consuming electric power for driving the generator motor  100  (in the driving/power generation mixed mode). 
     On elapse of a predetermined time period (step S 60 ) after the control of the rotation speed of the generator motor  100  according to the wind speed Vc at one of steps S 30 , S 32 , and S 35 , the control routine goes back to step S 10  to measure the wind speed Vc and to step S 20  to select one operation mode or a combination of multiple operation modes among the five operation modes. Even in the selection of the driving/power generation mixed mode at step S 20 , the control routine may omit the determination at step S 40  and directly goes to step S 60 . 
       FIG. 4  is an explanatory view showing the internal structure of the driving signal/power generation signal generator  300 . The driving signal/power generation signal generator  300  includes a signal control module  302 , a hysteresis level setting module  308 , an intermediate voltage output module  310 , an A-phase driving signal generator circuit  312 , an A-phase power generation signal generator circuit  314 , a B-phase driving signal generator circuit  316 , and a B-phase power generation signal generator circuit  318 . 
     The signal control module  302  has a duty ratio setter  304  and a base signal generator  306 . The hysteresis level setting module  308  has resistors  320  and  324  and an electronic variable resistor  322 . The intermediate voltage output module  310  has resistors  326  and  330  and an electronic variable resistor  328 . 
     The A-phase driving signal generator circuit  312  includes comparators  332  and  334  and AND gates  336  and  338 . The A-phase power generation signal generator circuit  314  includes a comparator  340 , an inverter  342 , negative-logic AND gates  344  and  346 , and NAND gates  348  and  350 . The B-phase driving signal generator circuit  316  includes comparators  352  and  354  and AND gates  356  and  358 . The B-phase power generation signal generator circuit  318  includes inverters  360  and  362 . 
     The duty ratio setter  304  of the signal control module  302  sets a resistance value Rv in the electronic variable resistor  322 , in response to a command from the CPU  202  (see  FIG. 1 ). The base signal generator  306  of the signal control module  302  generates an A-phase base signal FSA and a B-phase base signal FSB, in response to a command from the CPU  202 . The A-phase base signal FSA has a high (H) level to activate both the driving function and the power generation function of the A-phase coil array  14 A and has a low (L) level to activate only the power generation function of the A-phase coil array  14 A. The B-phase base signal FSB, on the other hand, has an H level to activate only the driving function of the B-phase coil array  24 B and has an L level to activate only the power generation function of the B-phase coil array  24 B. 
     In the A-phase driving signal generator circuit  312 , the comparator  332  compares a voltage value V 1  between the resistor  320  and the electronic variable resistor  322  with the A-phase sensor signal SSA and outputs a signal Q 332  representing a result of the comparison. The comparator  334  compares a voltage value V 2  between the electronic variable resistor  322  and the resistor  324  with the A-phase sensor signal SSA and outputs a signal Q 334  representing a result of the comparison. The AND gate  336  performs a logical AND of the A-phase base signal FSA and the signal Q 332  and generates the first A-phase driving signal DRVA 1  representing the logical product. The AND gate  338  performs a logical AND of the A-phase base signal FSA and the signal Q 334  and generates the second A-phase driving signal DRVA 2  representing the logical product. 
     In the A-phase power generation signal generator circuit  314 , the comparator  340  compares the A-phase sensor signal SSA with a voltage representing an intermediate value of the amplitude of the A-phase sensor signal SSA (hereafter referred to as ‘intermediate voltage’) and outputs a changeover signal Q 340  representing a result of the comparison. The intermediate voltage is obtained from the electronic variable resistor  328 . The inverter  342  outputs an inverted signal Q 342  of the changeover signal Q 340 . The OR gate  344  functioning as the negative-logic AND gate inputs the signal Q 332  and the inverted signal Q 342  and outputs a signal Q 344 . The OR gate  346  functioning as the negative-logic AND gate inputs the signal Q 334  and the changeover signal Q 340  and outputs a signal Q 346 . The NAND gate  348  performs a logical AND of the A-phase base signal FSA and the signal Q 344  and generates the first A-phase power generation signal REGA 1  as an inverted output of the logical product. The NAND gate  350  performs a logical AND of the A-phase base signal FSA and the signal Q 346  and generates the second A-phase power generation signal REGA 2  as an inverted output of the logical product. 
     In the B-phase driving signal generator circuit  316 , the comparator  352  compares the voltage value V 1  with the B-phase sensor signal SSB and outputs a signal Q 352  representing a result of the comparison. The comparator  354  compares the voltage value V 2  with the B-phase sensor signal SSB and outputs a signal Q 354  representing a result of the comparison. The AND gate  356  performs a logical AND of the B-phase base signal FSB and the signal Q 352  and generates the first B-phase driving signal DRVB 1  representing the logical product. The AND gate  358  performs a logical AND of the B-phase base signal FSB and the signal Q 354  and generates the second B-phase driving signal DRVB 2  representing the logical product. 
     In the B-phase power generation signal generator circuit  318 , the inverters  360  and  362  respectively invert the B-phase base signal FSB and output the first B-phase power generation signal REGB 1  and the second B-phase power generation signal REGB 2 . 
       FIG. 5  is one timing chart showing variations of the respective signals generated by the driving signal/power generation signal generator  300 . The timing chart of  FIG. 5  includes waveforms of an A-phase coil end-to-end signal and a B-phase coil end-to-end signal as signals between both ends of the A-phase coil array  14 A and the B-phase coil array  24 B. Waveforms of the A-phase coil end-to-end signal and the B-phase coil end-to-end signal are also included in the timing chart of  FIG. 6  discussed later. In the illustrated example of  FIG. 5 , the A-phase base signal FSA and the B-phase base signal FSB are set at the H level (not shown). The A-phase coil array  14 A activates the driving function and the power generation function, and the B-phase coil array  24 B activates only the driving function. Namely the power generator  1000  is controlled to mainly activate the driving function in the state of  FIG. 5 . 
     The duty ratio setter  304  ( FIG. 4 ) sets the resistance value Rv in the electronic variable resistor  322 , in response to a command from the CPU  202  ( FIG. 1 ). Setting the resistance value Rv determines the voltage values V 1  and V 2  and defines a hysteresis level as shown in  FIG. 5 . The ‘hysteresis level’ means a range of voltage between the voltage value V 1  and the voltage value V 2 . 
     The A-phase driving signal generator circuit  312  ( FIG. 4 ) generates the first A-phase driving signal DRVA 1  and the second A-phase driving signal DRVA 2  according to the hysteresis level as shown in  FIG. 5 . The first A-phase driving signal DRVA 1  has an H level in response to the A-phase sensor signal SSA of higher than the voltage value V 1 . The second A-phase driving signal DRVA 2  has an H level in response to the A-phase sensor signal SSA of lower than the voltage value V 2 . 
     The A-phase power generation signal generator circuit  314  ( FIG. 4 ) generates the first A-phase power generation signal REGA 1  and the second A-phase power generation signal REGA 2  as shown in  FIG. 5 . The first A-phase power generation signal REGA 1  has an H level in response to an H level of the changeover signal Q 340  and an L level of the first A-phase driving signal DRVA 1 . The second A-phase power generation signal REGA 2  has an H level in response to an L level of the changeover signal Q 340  and an L level of the second A-phase driving signal DRVA 2 . 
     The B-phase driving signal generator circuit  316  ( FIG. 4 ) generates the first B-phase driving signal DRVB 1  and the second B-phase driving signal DRVB 2  according to the hysteresis level as shown in  FIG. 5 . The first B-phase driving signal DRVB 1  has an H level in response to the B-phase sensor signal SSB of higher than the voltage value V 1 . The second B-phase driving signal DRVB 2  has an H level in response to the B-phase sensor signal SSB of lower than the voltage value V 2 . 
     The B-phase power generation signal generator circuit  318  ( FIG. 4 ) generates the first B-phase power generation signal REGB 1  and the second B-phase power generation signal REGB 2  as shown in  FIG. 5 . In the illustrated example of  FIG. 5 , the B-phase base signal FSB is set at the H level. The first B-phase power generation signal REGB 1  and the second B-phase power generation signal REGB 2  accordingly have an L level over the whole time period of  FIG. 5 . Namely with regard to the B-phase, only the driving function is activated, while the power generation function is inactive. 
     As described previously, one procedure of control varies the resistance value Rv corresponding to the wind speed Vc measured by the wind speed meter  203  and changes the duty ratios of the driving signal DRV and the power generation signal REG to control the rotation speed of the generator motor  100 . Another procedure of control varies the levels of the A-phase base signal FSA and the B-phase base signal FSB corresponding to the wind speed Vc measured by the wind speed meter  203  and changes the power generation time period and the driving time period with regard to each phase to control the rotation speed of the generator motor  100 . 
       FIG. 6  is another timing chart showing variations of the respective signals generated by the driving signal/power generation signal generator  300 . In the illustrated example of  FIG. 6 , the A-phase base signal FSA has the H level and the B-phase base signal FSB has the L level. The A-phase coil array  14 A accordingly activates both the driving function and the power generation function, while the B-phase coil array  24 B activates only the power generation function. The state of  FIG. 6  has a greater hysteresis level than that in the state of  FIG. 5  and accordingly has the smaller duty ratios of the first A-phase driving signal DRVA 1  and the second A-phase driving signal DRVA 2  and the greater duty ratios of the first A-phase power generation signal REGAL and the second A-phase power generation signal REGA 2  compared with those in the state of  FIG. 5 . The timing chart of  FIG. 6  shows the variations of the respective signals in the condition of weak wind force. The power generator  1000  sets the shorter driving time period for the A-phase coil array  14 A to assist the rotation of the generator motor  100 , while performing power generation during the power generation time period of the A-phase coil array  14 A and the whole time period of the B-phase coil array  24 B. 
     Setting the power generation signal REG at the H level during the non-driving time period having the driving signal DRV of the L level enables the A-phase coil array  14 A to perform power generation in the non-driving time period, while driving the A-phase coil array  14 A with the A-phase driving signals DRVA 1  and DRVA 2  in the driving time period. This arrangement desirably enhances the power generation efficiency. 
       FIG. 7  is a circuit diagram showing the internal structure of the driving circuit assembly  400  and the power generation circuit assembly  500  with regard to the A-phase coil array  14 A. The same circuit structure is provided with regard to the B-phase coil array  24 B, although not being specifically illustrated. The driving circuit assembly  400  includes four transistors TR 1  through TR 4 . The first A-phase driving signal DRVA 1  is used to drive the transistors TR 1  and TR 4 , while the second A-phase driving signal DRVA 2  is used to drive the transistors TR 2  and TR 3 . When the first A-phase driving signal DRVA 1  has the H level to drive the transistors TR 1  and TR 4 , the electric current flows in a direction from a positive (+) terminal of the A-phase coil array  14 A (A-phase coil ‘+’) to a negative (−) terminal of the A-phase coil array  14 A (A-phase coil ‘−’). When the second A-phase driving signal DRVA 2  has the H level to drive the transistors TR 2  and TR 3 , on the other hand, the electric current flows in a direction from the A-phase coil ‘−’ to the A-phase coil ‘+’. Such inversion of the direction of electric current flowing through the A-phase coil array  14 A drives and rotates the generator motor  100 . In the condition of strong wind force that requires braking the generator motor  100 , on the other hand, the first A-phase driving signal DRVA 1  and the second A-phase driving signal DRVA 2  input into the transistors TR 1  through TR 4  are exchanged. In this application, the direction of electric current flowing through the A-phase coil array  14 A becomes opposite to the direction of electric current for driving the generator motor  100  and accordingly brakes the generator motor  100 . 
     The power generation assembly  500  includes four transistors TR 5  through TR 8 , four diodes D 1  through D 4 , and one capacitor C 1 . The first A-phase power generation signal REGA 1  is used to drive the transistors TR 5  and TR 8 , while the second A-phase power generation signal REGA 2  is used to drive the transistors TR 6  and TR 7 . When the first A-phase power generation signal REGA 1  has the H level to drive the transistors TR 5  and TR 8 , energy excited on the A-phase coil array  14 A flows through the A-phase coil ‘+’, the diode D 1 , and the transistor TR 5 , is charged into the capacitor C 1 , and returns through the transistor TR 8 , the diode D 4 , and the A-phase coil ‘−’. When the second A-phase power generation signal REGA 2  has the H level to drive the transistors TR 6  and TR 7 , energy excited on the A-phase coil array  14 A flows through the A-phase coil ‘−’, the diode D 2 , and the transistor T 6 , is charged into the capacitor C 1 , and returns through the transistor TR 7 , the diode D 3 , and the A-phase coil ‘+’. 
     In the condition of adequate wind force having appropriate strength for power generation, in the case of selection of the power generation mode, all the transistors TR 1  through TR 4  in the driving circuit assembly  400  are kept continuously off, while all the transistors TR 5  through TR 8  in the power generation circuit assembly  500  are kept continuously on. The generator motor  100  accordingly performs only power generation. 
     As described above, the control procedure of the embodiment selects the operation mode of the generator motor  100  according to the observed wind speed Vc and adequately controls the power generation time period and the driving time period of the generator motor  100 . This arrangement ensures adequate control of the rotation speed of the generator motor  100  irrespective of a variation in wind speed Vc. 
     B. Modified Examples of First Embodiment 
     The first embodiment and its applications discussed above are to be considered in all aspects as illustrative and not restrictive. There may be many modifications, changes, and alterations without departing from the scope or spirit of the main characteristics of the present invention. Some examples of possible modification are given below. 
     B1. Modified Example 1 
     The control procedure of the first embodiment uses the observed wind speed Vc to select and activate one operation mode or a combination of multiple operation modes among the five possible operation modes of the generator motor  100 . One modification may use the current rotation speed of the generator motor  100  to select and activate one operation mode or a combination of multiple operation modes among the five possible operation modes of the generator motor  100 . Another modification may use both the observed wind speed Vc and the current rotation speed of the generator motor  100  to select and activate one operation mode or a combination of multiple operation modes among the five possible operation modes of the generator motor  100 . 
     B2. Modified Example 2 
     In the power generator  1000  of the first embodiment, the generator motor  100  has the five operation modes. The generator motor  100  may have additional operation modes other than the five operation modes. The generator motor  100  may have only the power generation mode. The rotation speed of the generator motor  100  may be controlled according to the wind force in the power generation mode. 
     B3. Modified Example 3 
     In the power generator  1000  of the first embodiment, the generator motor  100  has the two phases, the A phase and the B phase (see  FIG. 2A ). The number of phases is, however, not restricted to the two phases, but the generator motor  100  may have a single phase or three or a greater number of phases. 
     B4. Modified Example 4 
     The first embodiment describes application of the invention to the wind power generator  1000 . The technique of the invention is, however, not restricted to the wind power generator but may be applicable to any of various power generators for fluid power generation with the force of a fluid such as hydraulic power units. 
     B5. Modified Example 5 
     The generator motor  100  of the first embodiment may be used alone, instead of being incorporated in the power generator  1000 . In application of the generator motor  100  as a power source of a moving body, the generator motor  100  is driven and operated as the motor in the driving time period, while working as the generator to generate electric power in the power generation time period other than the driving time period. Controlling the power generation time period and the driving time period regulates the speed of the moving body. 
     B6. Modified Example 6 
     In the power generator  1000  of the embodiment, the driving signal/power generation signal generator  300  ( FIG. 4 ) is designed to have a rise of the power generation signal REG at the moment of a fall of the driving signal DRV (see  FIGS. 5 and 6 ). The driving signal/power generation signal generator  300  may alternatively be designed to have a rise of the power generation signal REG on elapse of a preset time period after a fall of the driving signal DRV. 
     B7. Modified Example 7 
     In the power generator  1000  of the embodiment, the driving mode is activated when the generator motor  100  is at stop. The driving mode may be activated in the condition of the low wind speed Vc or the low rotation speed even when the generator motor  100  is not at stop. 
     C. Second Embodiment 
       FIG. 8  is a block diagram schematically illustrating the general configuration of a motor device  1000   b  in a second embodiment of the invention. The motor device  1000   b  of the second embodiment has the similar structure to that of the power generator  1000  of the first embodiment shown in  FIG. 1 , except that the blades  190  and the wind speed meter  203  are omitted from the structure of the second embodiment and that the generator motor  100  of the first embodiment is replaced by a motor  100   b  having a function of electric power regeneration in the structure of the second embodiment. The driving signal/power generation signal generator  300 , the power generation circuit assembly  500 , and the power generation current controller  600  in the power generator  1000  of the first embodiment are respectively replaced by a driving signal/regeneration signal generator  300   b , a regeneration circuit assembly  500   b , and a regenerative electric current controller  600   b  in the motor device  1000   b  of the second embodiment. These elements  300   b ,  500   b , and  600   b  of the second embodiment, however, have substantially the same internal structures and operations as those of the corresponding elements  300 ,  500 , and  600  of the first embodiment. 
     As in the power generator  1000  of the first embodiment, in the motor device  1000   b  of the second embodiment, the motor  100   b  is operated with a driving signal DRV and a regeneration signal REG (power generation signal) (see  FIGS. 5 and 6 ) to control the driving torque and the rotation speed and to regenerate electric power during a time period having an H level of the regeneration signal REG. The regenerated electric power is accumulated in the accumulator  700 . The regenerative electric current controller  600   b  regulates the regenerated electric current to control the braking force of the motor  100   b.    
       FIG. 9  is one timing chart showing variations of the respective signals generated by the driving signal/regeneration signal generator  300   b  ( FIG. 8 ). As mentioned above, the driving signal/regeneration signal generator  300   b  has substantially the same internal structure as that of the driving signal/power generation signal generator  300  of the first embodiment shown in  FIG. 4 . The driving signal/regeneration signal generator  300   b  sets an H-level time period of the driving signal DRVA 1  and an H-level time period of the driving signal DRVA 2  (that is, a voltage application time period or a driving time period) as substantially symmetrical time periods about a maximum point P 1  and about a minimum point P 2  of the A-phase sensor signal SSA. In the driving signal/regeneration signal generator  300   b , the duty ratio setter  304  (see  FIG. 4 ) may be designed to arbitrarily change the duration of the voltage application time period (duty ratio). The driving signal/regeneration signal generator  300   b  sets an H-level time period of the regeneration signal REGA 1  and an H-level time period of the regeneration signal REGA 2  (that is, an electric power regeneration time period) in a residual time period other than the voltage application time period. In the driving signal/regeneration signal generator  300   b , the duty ratio setter  304  (see  FIG. 4 ) may also be designed to arbitrarily change the duration of the electric power regeneration time period (duty ratio). 
       FIG. 10  is another timing chart showing variations of the respective signals generated by the driving signal/regeneration signal generator  300   b . The timing chart of  FIG. 10  has different waveforms of the driving signals DRVA 1  and DRVA 2  and the regeneration signals REGA 1  and REGA 2  from the waveforms in the timing chart of  FIG. 9 . In the illustrated example of  FIG. 10 , the electric power regeneration time periods are set as substantially symmetrical time periods about the maximum point P 1  and the minimum point P 2  of the A-phase sensor signal SSA. This arrangement enables regeneration of electric power in a time period of high energy conversion efficiency, thus allowing the accumulator  700  to be charged rapidly. In this manner, the driving signal/regeneration signal generator  300   b  arbitrarily changes the temporal positions of the electric power regeneration time period and the voltage application time period relative to the A-phase sensor signal SSA. 
     As described above, in the motor device  1000   b  of the second embodiment, the driving signal/regeneration signal generator  300   b  controls the temporal positions and the durations of the voltage application time period and the electric power regeneration time period in one period of the A-phase sensor signal SSA. This arrangement ensures precise control of the torque and the rotation speed generated in the voltage application time period of the motor  100   b  and the electric power regenerated in the electric power regeneration time period of the motor  100   b . The above description with regard to the control of the A phase is similarly applicable to the control of the B phase. The A phase and the B phase may be controlled independently.