Abstract:
There are provided a method for detecting an abnormality of a resolver, an angle detection device, a motor, and a transportation device, by which the abnormality can be detected promptly without the necessity of any complicated operations. There is provided a circuit configured to switch between a sine wave and a direct current voltage to be supplied, as an excitation signal of a resolver ( 2 ). Then, immediately after the power is turned on, the direct current voltage is applied to the resolver ( 2 ), and the output voltages of the phases of the resolver ( 2 ) are measured when the direct current voltage is applied. In this situation, the output voltages of the phases are compared with each other. When none of them matches each other, it is determined that an abnormality (short-circuit abnormality, short-circuiting) occurs at the resolver ( 2 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a method for detecting an abnormality of a resolver configured to detect a rotating position of a rotating body, an angle detection device having a function of detecting the abnormality of the resolver, and a motor and a transportation device each having the angle detection device. 
       BACKGROUND ART 
       [0002]    In one technology, as a method for detecting an abnormality of a resolver to be used for detecting a rotating angle of an electric motor or the like, for example, there is a technique disclosed in Patent Literature 1. In this technique, in synchronization with a maximum value or a minimum value of an excitation signal of the resolver, each resolver output signal is sampled, and when an offset of the sampled value falls out of a given range near 0, it is determined that an abnormality occurs at the resolver. 
         [0003]    In addition, as another method for detecting the abnormality of the resolver, for example, there is a technique disclosed in Patent Literature 2. In this technique, different values are set to the respective voltage transformation ratios between the excitation coil and the respective three resolver coils, and when three rotor electrical angles (operation electrical angles) operated from the three-phase resolver signal indicate different values from one another, it is determined that a short-circuit abnormality occurs at the resolver. 
       CITATION LIST 
     Patent Literature 
     PLT 1: JP 2001-343253 A 
     PLT 2: JP 2013-044679 A 
     SUMMARY 
     Technical Problem 
       [0004]    In the technique disclosed in Patent Literature 1, however, as the abnormality of the resolver is detected by the offset of the sampling signal, an abnormality cannot be detected unless the rotating angle reaches 180 degrees of the electrical angle at maximum. Therefore, until the abnormality detection is performed, the motor is controlled by using an abnormal signal and an adverse effect may be given to the motor revolution behavior. 
         [0005]    Besides, in the technique disclosed in Patent Literature 2, amplitude components are respectively extracted from the three-phase resolver signal, and the operation electrical angle is operated in three methods from the extracted amplitude values. Hence, complicated operations are needed for detection of the short-circuit abnormality of the resolver. 
         [0006]    Therefore, it is an object of the present disclosure to provide a method for detecting an abnormality of a resolver, an angle detection device, a motor, and a transportation device, by which the abnormality can be detected promptly without the necessity of any complicated operations. 
       Solution to Problem 
       [0007]    In order to address the above issues, in one embodiment of the present disclosure, there is provided a method for detecting an abnormality of a resolver, the method including: applying a direct current voltage to the resolver configured to output rotating positional information of a rotating body, as an electrical signal; and comparing output voltages of phases of the resolver, when the direct current voltage is applied to detect the abnormality of the resolver. 
         [0008]    In this manner, although the resolver is excited by use of a sine wave in general, the direct current voltage is applied to the resolver and the resolver signal output as a result is confirmed, so as to determine whether or not an abnormality occurs at the resolver. In this manner, by use of the fact that the resolver output signals when the direct current is applied to the resolver have all the same potentials in a normal state, the output voltages of the respective phases of the resolver are compared with each other to detect an abnormal state. Therefore, no complicated operation is necessary. Further, the abnormal state can be detected without rotating a rotor. 
         [0009]    In addition, in the above-described method for detecting the abnormality of the resolver, when the output voltages of phases of the resolver do not match each other, it may be determined that the abnormality occurs at the resolver. 
         [0010]    Accordingly, the abnormal state of the resolver can be detected with a simple configuration appropriately. 
         [0011]    Further, in another embodiment of the present disclosure, there is provided an angle detection device, including: a resolver configured to output rotating positional information of a rotating body, as an electrical signal; a sine wave generator configured to generate a sine wave signal; a direct current voltage generator configured to generate a direct current voltage; an excitation signal supplier configured to select one of the sine wave signal generated by the sine wave generator or the direct current voltage generated by the direct current voltage generator, and to supply the selected one to the resolver as an excitation signal; a voltage measurement portion configured to measure output voltages of phases of the resolver; and an abnormality detector configured to detect an abnormality of the resolver, by comparing the output voltages of the phases of the resolver measured by the voltage measurement portion, when the excitation signal supplier supplies the direct current voltage generated by the direct current voltage generator, as the excitation signal. 
         [0012]    In this manner, it is possible to switch between the sine wave and the direct current voltage to be supplied to the resolver. Hence, after the direct current voltage is applied and the abnormality is determined, switching is made to the sine wave so that the general angle detection can be carried out. 
         [0013]    Moreover, in the above-described angle detection device, the excitation signal supplier may be configured to select the direct current voltage generated by the direct current voltage generator and to supply the direct current voltage to the resolver, as the excitation signal, immediately after power is turned on. 
         [0014]    In this manner, immediately after the power is turned on, the direct current voltage is applied to the resolver and the abnormality is determined. Hence, it is possible to confirm that the resolver is in a normal state, and then it is possible to detect the angle. Thus, the reliability of the angle detection can be improved. 
         [0015]    Furthermore, in yet another embodiment of the present disclosure, there is provided a motor including the above-described angle detection device. 
         [0016]    Additionally, in further another embodiment of the present disclosure, there is provided a transportation device configured to transport a transportation target by using the above-described motor. 
       Advantageous Effects 
       [0017]    According to the present disclosure, the abnormality of the resolver can be detected promptly without the necessity of the rotor revolution. In addition, since an abnormal determination is made possible by a simple comparing operation, it is possible to achieve an abnormality detection function at a low cost. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0018]      FIG. 1  is a schematic configuration view of an angle detection device in one embodiment of the present disclosure; 
           [0019]      FIG. 2  is a circuit diagram illustrative of a configuration of the angle detection device; 
           [0020]      FIG. 3  is a flow chart illustrative of a short-circuit abnormality determination procedure; and 
           [0021]      FIG. 4  is a schematic configuration view illustrative of the angle detection device in another embodiment of the present disclosure. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0022]    Hereinafter, embodiments of the present disclosure will be described with reference to the attached drawings. 
         [0023]      FIG. 1  is a schematic configuration view of an angle detection device, in one embodiment of the present disclosure. 
         [0024]    In the drawing, reference numeral  1  indicates a motor (rotating body), reference numeral  2  indicates a resolver configured to detect a rotating position of the motor  1 . Herein, the motor  1  is, for example, a direct drive motor included in a transportation device, and serves as a drive source configured to drive a transportation target  10 . 
         [0025]    In addition, a servo motor includes the motor  1 , a resolver  2 , and a drive unit  3 , to be described later. It is to be noted that a mega torque motor can be used as the motor  1 . 
         [0026]    The resolver  2  is configured to include a cylindrical stator, and a rotor configured to hold a rotation shaft and arranged rotatably in the stator, and to change a reluctance between the rotor and the stator depending on the location of the rotor so that one cycle of a fundamental wave component of the reluctance change indicates one revolution of the rotor. In other words, the inner diameter center of the rotor is aligned with the inner diameter center of the stator, the outer diameter center of the rotor is configured to be eccentric by only a certain eccentric amount from the inner diameter center thereof to change the thickness of the rotor. Hence, the reluctance changes depending on the location of the rotor. 
         [0027]    The resolver  2  is a three-phase resolver configured, when a since wave shaped excitation signal is given from the outside, to output a resolver signal of phase A changing depending on the turning angle of the rotation shaft, a resolver signal of phase B, which is different in phase by 120 degrees from the resolver signal of phase A, and a resolver signal of phase C, which is different in phase by 120 degrees from the resolver signal of phase B. 
         [0028]    The resolver  2  and the drive unit  3  are connected by an electrical cable  5  through a connector  4 . The electrical signal (resolver signal) output from the resolver  2  is transmitted to the drive unit  3  through the electrical cable  5 . 
         [0029]    The drive unit  3  is configured to have a position detection function of detecting the rotating position (turning angle) of the motor  1 , and an abnormality detection function of detecting a short-circuit abnormality between phases of the resolver  2 . The position detection function is a function of acquiring a resolver signal transmitted from the resolver  2  as rotating positional information of the motor  1 , and detecting a rotating position (turning angle) of the motor  1  based on the resolver signal. In addition, the abnormality detection function is a function of detecting short-circuiting/short-circuit abnormality of the resolver  2 , immediately after the power is turned on. 
         [0030]    This drive unit  3  is configured to include an excitation signal generation block  11 , a short-circuit abnormality detection signal generation block  12 , a change-over switch  13 , and a current amplification circuit  14 . 
         [0031]    The excitation signal generation block  11  is configured to generate a sine wave signal, and then to output the sine wave signal. In addition, the short-circuit abnormality detection signal generation block  12  is configured to generate a direct current voltage as a short-circuit abnormality detection signal, and then to output the short-circuit abnormality detection signal. 
         [0032]    The change-over switch  13  is configured to switch between the sine wave signal from the excitation signal generation block  11  and the direct current voltage from the short-circuit abnormality detection signal generation block  12  in response to a switch signal S 1  from an abnormality determination controller  19  to be described later, to output to the current amplification circuit  14 . Herein, the change-over switch  13  is configured to select and output the sine wave signal from the excitation signal generation block  11  when the switch signal S 1 =0, and to select and output the direct current voltage from the short-circuit abnormality detection signal generation block  12  when the switch signal S 1 =1. 
         [0033]    The current amplification circuit  14  is configured to amplify the signal output from the change-over switch  13 , and to supply the amplified signal as an excitation signal to the resolver  2  through the electrical cable  5 . 
         [0034]    Furthermore, the drive unit  3  is configured to include an angle detection signal reception block  15 , an R/D conversion block  16 , and a CPU  17 . In addition, the CPU  17  is configured to include an angle detector  18 , an abnormality determination controller  19 , and a short-circuit abnormality determination unit  20 . 
         [0035]    The angle detection signal reception block  15  is configured to receive inputs of the three-phase resolver signal output from the resolver  2  when the excitation signal is applied. Herein, the resolver signal is a three-phase analog signal of the phase A, the phase B, and the phase C, each being different in phase by 120 degrees. The angle detection signal reception block  15  is configured to convert the three-phase resolver signal that has been input into a two-phase signal and to output the two-phase signal to the R/D conversion block  16 , and in addition, to detect the voltage of the three-phase resolver signal that has been input and to output the detected voltage to the short-circuit abnormality determination unit  20 , to be described later, of the CPU  17 . 
         [0036]    In other words, the angle detection signal reception block  15  has a configuration illustrated in  FIG. 2 . As illustrated in  FIG. 2 , the angle detection signal reception block  15  is configured to include shunt resistances R 1 , R 2 , and R 3 , and to detect voltages (V A , V B , and V C ) of the resolver by using the shunt resistances R 1  to R 3 . In this situation, the resistance values of the shunt resistances R 1  to R 3  are all set to the same values. The respective phase voltages V A  to V C  are converted into digital values by A/D converters  21   a  to  21   c , and then are input into the CPU  17  (the short abnormality determination unit  20 ). 
         [0037]    Further, after the three-phase resolver signal are converted to the two-phase resolver signal with a three phase/two phase converter, the angle detection signal reception block  15  is configured to input the two-phase resolver signal into the R/D conversion block (RD converter)  16 . 
         [0038]    The R/D conversion block  16  is configured to convert an output signal from the resolver  2  into a digital angle data, and to input the digital angle data into the angle detector  18  of the CPU  17 , as illustrated in  FIG. 1 . The angle detector  18  is configured to acquire the angle data that has been output from the R/D conversion block  16 , and to use the angle data for various kinds of control (motor control and the like). 
         [0039]    In addition, the abnormality determination controller  19  of the CPU  17  is configured to output the switch signal S 1 =0, while a short-circuit abnormality determination process of determining a short-circuit abnormality of the resolver  2  is being performed, and to output the switch signal S 1 =1 in any other case. In one embodiment of the present disclosure, the short-circuit abnormality determination process is configured to be carried out for a certain period of time after the power is turned on, and the switch signal S 1 =1 is output. 
         [0040]    The short-circuit abnormality determination unit  20  of the CPU  17  is configured to carry out the short-circuit abnormality determination process based on the respective phase voltages V A  to V C  output from the angle detection signal reception block  15 , while the abnormality determination controller  19  is outputting the switch signal S 1 =1. A short-circuit abnormality determination result is configured to be output to the outside so that a given abnormality process should be carried out. For example, the drive control of the motor  1  can be stopped as an abnormality process. 
         [0041]    Next, a short-circuit abnormality determination process to be carried out by the CPU  17  will be described specifically. 
         [0042]      FIG. 3  is a flowchart illustrative of the short-circuit abnormal determination procedure. The short-circuit abnormality determination process starts, when the power is turned on. 
         [0043]    Firstly, at step S 1 , the abnormality determination controller  19  outputs the switch signal S 1 =1 to the change-over switch  13 . Accordingly, the change-over switch  13  is in a state indicated by a broken line of  FIG. 2 , and the short-circuit abnormality detection signal (DC voltage) generated by the short-circuit abnormality detection signal generation block  12  is applied to the three-phase resolver  2 . 
         [0044]    Next, at step S 2 , the short-circuit abnormality determination unit  20  acquires the voltages of the resolver output signals output from the three-phase resolver  2 . The voltages of the resolver output signals to be acquired here are values obtained by the A/D converters  21   a  to  21   c  converting the respective phase voltages V A  to V C  of the resolver  2  detected by the angle detection signal reception block  15  into digital values. 
         [0045]    At step S 3 , it is determined whether or not the respective phase voltage values acquired at step S 2  are all equal. Then, when it is determined that all values have equal potentials at step S 4 , processing goes to step S 4 , whereas when it is determined that all values do not have equal potentials at step S 4 , processing goes to step S 5 . 
         [0046]    At step S 4 , it is determined that the resolver signal is in a normal state, that is, it is determined that no short-circuit abnormality or short-circuiting occurs at the resolver  2 , a short-circuit abnormality determination result indicating “normal state” is output, and then the short-circuit abnormality determination process ends. 
         [0047]    On the other hand, at step S 5 , it is determined that the resolver signal is in a short-circuit state or in an open state, a short-circuit abnormality determination result indicating “abnormal state” is output, and then the short-circuit abnormality determination process ends. 
         [0048]    As described above, after the power is turned on, the DC voltage is applied to the three-phase resolver  2 , as the excitation signal. The impedance characteristic of the resolver coil is jωL (ω: angular acceleration, L: inductance), and the angular acceleration of the DC voltage is 0 rad/s 2 . Hence, when the DC voltage is applied, the impedance is 0Ω. Therefore, when the resolver signal is in a normal state, the voltages available at the shunt resistances R 1  to R 3  when the DC voltage is applied are all equal. On the other hand, when the resolver signal is in an abnormal state (short-circuit state, open state), the voltages available at the shunt resistances R 1  to R 3  when the DC voltage is applied are all different from one another. 
         [0049]    Thus, the abnormal state of the resolver  2  can be detected by use of the fact that the voltages made available at the shunt resistances R 1  to R 3  when the DC voltage is applied change depending on whether the resolver signal is in an abnormal state (short-circuit state, open state) or in a normal state. 
         [0050]    It is to be noted that in  FIG. 1 , the excitation signal generation block  11  corresponds to a sine wave generator, the short-circuit abnormality detection signal generation block  12  corresponds to a direct current voltage generator, the change-over switch  13  and the current amplification circuit  14  correspond to an excitation signal supplier, the angle detection signal reception block  15  corresponds to a voltage measurement portion, and the short-circuit abnormality determination unit  20  corresponds to an abnormality detector. 
         [0051]    Thus, in one embodiment of the present disclosure, an abnormality of the resolver  2  can be determined without the need of the rotor revolution. Thus, when an abnormality occurs at the resolver  2 , the abnormality can be detected promptly. 
         [0052]    Furthermore, since the DC voltage is applied to the resolver  2  immediately after the power is turned on and an abnormality determination is made, it is possible to start the general angle detection after the resolver  2  is confirmed to be in a normal state. Therefore, it is possible to prevent the motor control with an abnormality signal. 
         [0053]    Now, as another method of detecting an abnormality of the resolver, different values are set to the respective voltage transformation ratios between the excitation coil and the respective three resolver coils, and when three rotor electrical angles (operation electrical angles) which have been operated from the three-phase resolver signal indicate different values from one another, it is determined that the short-circuit abnormality occurs at the resolver. 
         [0054]    In contrast, in one embodiment of the present disclosure, all the voltage transformation ratios of the resolver  2  that are same can be realized. In addition, as an abnormality of the resolver  2  can be detected in a simple comparing operation, such a method is achievable at a low cost. 
         [0055]    It is to be noted that in one embodiment of the present disclosure as described above, by comparing the respective phase voltages V A  to V C  of the resolver  2  with digital values converted by the A/D converters  21   a  to  21   c , respectively, determination of the short-circuit abnormality has been described. However, the short-circuit abnormality can be determined by use of a comparator. 
         [0056]    Further, in one embodiment of the present disclosure as described above, the case where the resolver configured to output the resolver signals of the phase A, the phase B, and the phase C is applied has been described. However, a resolver configured to output the resolver signal of four or more phases is also applicable. 
         [0057]    Furthermore, in one embodiment of the present disclosure as described above, as illustrated in  FIG. 4 , a servomotor can be configured with the motor  1 , the resolver  2 , an RD unit  6 , and the drive unit  7 . In this case, the RD unit  6  and the drive unit  7 , which are assembled with the resolver  2 , are configured to be connected with the electrical cable  5  through the connector  4 . 
         [0058]    The RD unit  6  is configured to have functions of the above-described angle detection signal reception block  15  and the R/D conversion block  16 . The drive unit  7  is configured to have functions of the excitation signal generation block  11 , the short-circuit abnormality detection signal generation block  12 , the change-over switch  13 , the current amplification circuit  14 , and the CPU  17 . Then, the signal output from the RD unit  6  is transmitted to the drive unit  7  through the electrical cable  5 , so that the angle detection of the resolver  2  and the short-circuit abnormality determination can be carried out. 
       INDUSTRIAL AVAILABILITY 
       [0059]    According to the method of detecting an abnormality of the resolver in the present disclosure, the abnormality of the resolver can be detected promptly without the need of the rotor revolution. In addition, as an abnormality determination is made possible by a simple comparing operation, the abnormality detection function can be realized at a low cost and it is useful. 
       REFERENCE SIGNS LIST 
       [0060]      1  . . . motor (rotating body),  2  . . . resolver,  3  . . . drive unit,  4  . . . connector,  5  . . . electrical cable,  11  . . . excitation signal generation block,  12  . . . short-circuit abnormality detection signal generation block,  13  . . . change-over switch,  14  . . . current amplification circuit,  15  . . . angle detection signal reception block,  16  . . . R/D conversion block,  17  . . . CPU,  18  . . . angle detector,  19  . . . abnormality determination controller,  20  . . . short-circuit abnormality determination unit,  21   a - 21   c  . . . A/D converter