JP4154323B2 - Resolver zero correction method for multiphase motors - Google Patents

Description

  The present invention corrects the resolver zero point by locking the motor rotation at a predetermined electrical angle and comparing the resolver output at that time with the predetermined electrical angle. It relates to a correction method.

  When supplying alternating current to the coil of a multiphase motor, it is necessary to determine the phase of the alternating current in synchronization with the phase of the rotor. For this purpose, the phase of the rotor is detected by a resolver provided on the rotating shaft of the motor. Yes. Due to variations in the resolver itself and position errors when it is attached to the motor, the resolver zero point (position where the output is zero) does not match the motor's predetermined phase. The zero point was corrected.

In order to automate this correction work, the phase of the alternating current supplied to the coil of the motor is compared with the output of the resolver, and the deviation is used to correct the phase of the rotor detected by the resolver. It is known.
Japanese Patent Laid-Open No. 10-201275

  By the way, although the said conventional thing estimates the phase of a rotor based on the phase of the alternating current supplied to the coil of a motor, the phase of alternating current and the phase of a rotor are fluctuate | varied with the load added to the motor in driving | operation. For this reason, the phase of the rotor estimated based on the phase of the alternating current does not necessarily match the actual phase, which may reduce the correction accuracy of the resolver zero point.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to improve the accuracy of the zero point correction of the resolver of the multiphase motor.

  In order to achieve the above object, according to the first aspect of the invention, the rotation of the motor is locked at a predetermined electrical angle, and the output of the resolver at that time is compared with the predetermined electrical angle. A resolver zero point correction method for a resolver in a multi-phase motor that corrects a resolver zero point, wherein a first direct current is passed through a motor coil to rotate the motor at a first electrical angle at which the torque becomes zero. In the first step of locking, the motor is applied at the second electrical angle different from the first electrical angle and having a torque of 0 by passing a second direct current different from the first direct current through the coil of the motor. And a third step of correcting the zero point of the resolver by comparing the second electrical angle with the output of the resolver. Zero point correction method It proposed.

  Note that the U-phase coil 61U, the V-phase coil 61V, and the W-phase coil 61W of the embodiment correspond to the coils of the present invention.

  According to the configuration of the first aspect, when the first direct current is applied to the motor coil in the first step, the rotation of the motor is locked at any one of the plurality of first electrical angles where the torque becomes zero. When a second direct current different from the first direct current is applied to the motor coil in the subsequent second step, the motor is different from the first electrical angle and has a torque of 0 at a predetermined second electrical angle. The rotation of is locked. By performing the first step prior to the second step, it is ensured that the electrical angle when starting the second step is one of the plurality of first electrical angles, so the torque becomes zero. Even if there are a plurality of second electrical angles, the predetermined second electrical angle at which the rotation of the motor is locked is always the same. Therefore, the zero point of the resolver can be accurately corrected by comparing the predetermined second electrical angle with the output of the resolver in the third step.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

  1 to 9 show an embodiment of the present invention. FIG. 1 is an overall perspective view of an electric power steering apparatus, FIG. 2 is an enlarged sectional view taken along line 2-2 of FIG. 1, and FIG. FIG. 4 is a diagram showing the motor drive circuit, FIG. 5 is a diagram showing the motor drive circuit during the first energization, and FIG. 6 is a diagram showing the change in torque with respect to the electrical angle during the first energization. FIG. 7 is a diagram showing a motor drive circuit at the time of second energization, FIG. 8 is a graph showing a change in torque with respect to an electrical angle at the time of second energization, and FIG. 9 explains the action of the zero point correction of the resolver. It is a flowchart.

  As shown in FIG. 1, the upper steering shaft 12 that rotates integrally with the steering handle 11 has a pinion shaft 17 that protrudes upward from the speed reducer 16 via an upper universal joint 13, a lower steering shaft 14, and a lower universal joint 15. Connected to. Tie rods 19 and 19 projecting from the left and right ends of the steering gear box 18 connected to the lower end of the speed reducer 16 are connected to knuckles (not shown) of the left and right wheels WL and WR. A three-phase AC motor M is supported on the speed reducer 16, and the operation of the motor M is controlled by an electronic control unit U to which a signal from a steering torque sensor St housed in the speed reducer 16 is input. .

  2 and 3, the speed reducer 16 is coupled to the lower case 21 integrated with the steering gear box 18, the intermediate case 23 coupled to the upper surface thereof with bolts 22 ..., and the upper surface thereof coupled to the bolts 24 ... The pinion shaft 17 is rotatably supported by the steering gear box 18 and the upper case 25 by ball bearings 26 and 27. A pinion 28 provided at the lower end of the pinion shaft 17 meshes with a rack 30 provided on a rack bar 29 supported inside the steering gear box 18 so as to be movable left and right. A pressing member 31 is slidably accommodated in a through hole 18 a formed in the steering gear box 18, and the pressing member 31 is attached to the rack bar 29 by a spring 33 disposed between the nut member 32 closing the through hole 18 a. By biasing toward the back, the deflection of the rack bar 29 is suppressed.

  A rotation shaft 34 of the motor M extending inside the reduction gear 16 is rotatably supported by the lower case 21 by a pair of ball bearings 35 and 36, and a worm 37 provided on the rotation shaft 34 of the motor M is a pinion. It meshes with a worm wheel 38 fixed to the shaft 17.

  Therefore, when the motor M is driven, the torque of the rotating shaft 34 is transmitted to the pinion shaft 17 via the worm 37 and the worm wheel 38, and the driver's steering operation is assisted by the motor M.

  FIG. 4 shows a motor drive circuit C that drives the motor M in response to a command from the electronic control unit U. The motor drive circuit C includes a three-phase bridge circuit 41, and its high voltage terminal TH is connected to a positive pole 45a of a 12V battery 45 mounted on a vehicle via a shunt resistor 42, a power relay 43 and a choke coil 44, and its low voltage. The terminal TL is grounded and connected to the negative electrode 45b of the battery 45. Between the high-voltage terminal TH and the low-voltage terminal TL of the three-phase bridge circuit 41, a first switching element 46a, a first output terminal TM1 and a second switching element 46b connected in series, and a third switching element connected in series 46c, second output terminal TM2 and fourth switching element 46d, and fifth switching element 46e, third output terminal TM3 and sixth switching element 46f connected in series are connected in parallel to each other. The first, second, and third output terminals TM1, TM2, and TM3 are connected to the U-phase coil 61U, the V-phase coil 61V, and the W-phase coil 61W of the motor M that are connected to the U-phase line 62U and the V-phase line, respectively. 62V and W phase line 62W are connected. The first to sixth switching elements 46a to 46f are configured by, for example, field effect transistors (FETs).

  The power relay 43 that turns on / off the supply of power from the battery 45 to the three-phase bridge circuit 41 is connected to a relay drive circuit 48 controlled by the electronic control unit U and turned on / off. A shunt resistor 42 disposed between the power relay 43 and the three-phase bridge circuit 41 is connected to a motor current detection circuit 49, and the motor current detection circuit 49 connected to the electronic control unit U is connected to both ends of the shunt resistor 42. Based on the potential difference and the resistance value of the shunt resistor 42, the current supplied from the battery 45 to the three-phase bridge circuit 41 is detected.

  The first to sixth switching elements 46a to 46f of the three-phase bridge circuit 41 are duty-controlled by the switching element drive circuit 51 connected to the electronic control unit U, so that the U phase coil 61U, the V phase coil 61V of the motor M, and Three-phase alternating current can be supplied to the W-phase coil 61W.

  A known resolver R that detects the electrical angle of the rotating shaft of the motor M is connected to the electronic control unit U, and the electronic control unit U has a function of correcting the zero point of the resolver R. That is, due to variations in the resolver R itself and a position error when it is attached to the motor M, the zero point of the resolver R (a position where the output becomes zero) does not coincide with the predetermined electrical angle of the motor M. Electrical correction is performed inside the electronic control unit U.

  Hereinafter, a method for correcting the zero point of the resolver R will be described.

  If the motor M can be accurately stopped (locked) at a predetermined electrical angle, the zero point correction can be performed by comparing the output of the resolver R at that time with the predetermined electrical angle. As shown in FIG. 7, the switching element drive circuit 51 turns on only the first switching element 46a and the sixth switching element 46f, for example, in response to a command from the electronic control unit U. Supply. This is called second energization. At this time, a combined torque of the torque generated by the U-phase coil 61U and the torque generated by the W-phase coil 61W is shown in FIG. When a direct current is supplied to the U-phase coil 61U and the W-phase coil 61W, the motor M rotates to an electrical angle of 210 ° where the torque becomes 0 and is stable there regardless of the electrical angle of the motor M. Lock to. That is, if the electrical angle is greater than 30 ° and less than 210 °, the motor M rotates clockwise and locks at an electrical angle of 210 °, and if the electrical angle is greater than 210 ° and less than 30 °, The motor M rotates counterclockwise and locks at an electrical angle of 210 °. However, since the torque of the motor M is 0 even when the electrical angle is 30 °, when the DC current is supplied to the U-phase coil 61U and the W-phase coil 61W, the electrical angle of the motor M is accidentally 30 °. There is a problem in that locking occurs at that position and locking becomes impossible at an original electrical angle of 210 °.

  Therefore, the first energization is performed prior to the second energization described above to prevent the motor M from stopping at an electrical angle of 30 °, and then the second energization described above is performed to perform the motor M. Is securely locked at an electrical angle of 210 °.

  As shown in FIG. 5, at the time of the first energization, the switching element drive circuit 51 turns on only the first switching element 46a, the fourth switching element 46d, and the sixth switching element 46f, for example, according to a command from the electronic control unit U. A direct current is supplied through the path of the U-phase coil 61U → V-phase coil 61V and the path of the U-phase coil 61U → W-phase coil 61W. At this time, a combined torque generated by the U-phase coil 61U, the V-phase coil and the W-phase coil 61W is shown in FIG. When a direct current is supplied to the U-phase coil 61U, the V-phase coil 61V, and the W-phase coil 61W, the motor M basically rotates to an electrical angle of 180 ° where the torque becomes 0 and stably locks there. However, since the torque of the motor M is 0 even when the electrical angle is 0 °, if the electrical angle of the motor M is accidentally 0 °, the motor M may be locked at that position. In any case, the motor M can be locked at the position where the electrical angle is 180 ° or 0 °, that is, at the position where the electrical angle is not 30 °, by the first energization described above.

  Therefore, since it is guaranteed that the electrical angle of the motor M is not 30 ° at the time when the subsequent second energization is started, the motor M can be reliably locked at an electrical angle of 210 ° by the second energization. . Therefore, the zero point correction of the resolver R can be completed by making the output of the resolver R correspond to an electrical angle of 210 ° at this time.

  The above operation will be further described based on the flowchart of FIG.

  First, in step S1, the first to sixth switching elements 46a to 46f are all turned OFF to free the motor M, and then in step S2, the fourth switching element 46d communicating with the V-phase coil 61V and the sixth switching element communicating with the W-phase coil 61W. The switching element 46f is turned on, and the first switching element 46a connected to the U-phase coil 61U is turned on at a duty ratio of 20% in step S3, so that the motor M is locked at an electrical angle of 180 ° in step S4 (FIG. 5). reference). At this time, if the electrical angle of the motor M happens to be 0 °, the motor M may lock at an electrical angle of 0 °. In other words, the motor M is locked at either an electrical angle of 180 ° or 0 ° by the steps S1 to S4. Steps S2 to S4 correspond to the first energization described above.

  In the subsequent step S5, the fourth switching element 46d that communicates with the V-phase coil 61V is turned OFF, so that the first switching element 46a that communicates with the U-phase coil 61U and the sixth switching element 46f that communicates with the W-phase coil 61W are turned on. Thus (see FIG. 7), the motor M is locked at an electrical angle of 210 ° in step S6. Steps S5 and S6 correspond to the second energization described above. If step S5 is performed and the electrical angle of the motor M is 30 °, the motor M is locked at the electrical angle of 30 ° instead of being locked at the electrical angle of 210 ° in step S5. Since the electrical angle when performing S5 is guaranteed to be 180 ° or 0 °, the motor M is always locked at the electrical angle of 210 ° in step S6.

  In step S7, the output a ° of the resolver R is read. In step S8, the first switching element 46a that communicates with the U-phase coil 61U and the sixth switching element 46f that communicates with the W-phase coil 61W are turned off. The correction value b ° (= 210 ° −a °) is calculated by subtracting the output a ° of the resolver R from the actual electrical angle of 210 °. In step S10, the correction value b ° is stored in the electronic control unit U. Therefore, thereafter, the electrical angle of the motor M can be detected with high accuracy by correcting the output a ° of the resolver R with the correction value b °.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. It is.

  For example, in the embodiment, the motor M is locked with an electrical angle of 180 ° (or 0 ° electrical angle) in the first step, and the motor M is locked with an electrical angle of 210 ° in the second step. The electrical angle for locking is not limited to the embodiment.

  The present invention can be applied to any multiphase motor other than the three-phase motor M, and the use of the motor M is not limited to the electric power steering apparatus.

Overall perspective view of electric power steering device 2-2 line enlarged sectional view of FIG. 3-3 sectional view of FIG. Diagram showing motor drive circuit The figure which shows the motor drive circuit at the time of 1st electricity supply The graph which shows the change of the torque with respect to the electrical angle at the time of 1st electricity supply The figure which shows the motor drive circuit at the time of 2nd electricity supply The graph which shows the change of the torque with respect to the electrical angle at the time of 2nd electricity supply Flow chart explaining the action of the zero point correction of the resolver

Explanation of symbols

61U U-phase coil (coil)
61V V-phase coil (coil)
61W W phase coil (coil)
M motor R resolver

Claims (1)

A multi-phase motor that locks the rotation of the motor (M) at a predetermined electrical angle and corrects the zero point of the resolver (R) by comparing the output of the resolver (R) with the predetermined electrical angle. A resolver zero-point correction method in
A first step of energizing the coil (61U, 61V, 61W) of the motor (M) with a first direct current and locking the rotation of the motor (M) at a first electrical angle at which the torque becomes zero;
A second direct current different from the first direct current is applied to the coils (61U, 61V, 61W) of the motor (M), and the second electric current is different from the first electrical angle and has a torque of zero. A second step of locking the rotation of the motor (M) at the corner;
A third step of comparing the second electrical angle and the output of the resolver (R) to correct the zero point of the resolver (R);
A method for correcting a zero point of a resolver in a multiphase motor.

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