JP5412825B2 - Motor control device and electric power steering device - Google Patents

Description

  The present invention relates to a motor control device for driving a brushless motor, and an electric power steering device including such a motor control device.

  2. Description of the Related Art Conventionally, an electric power steering device that applies a steering assist force to a steering mechanism of a vehicle by driving an electric motor according to a steering torque applied to a steering wheel (steering wheel) by a driver has been used. Conventionally, a brush motor has been widely used as an electric motor of an electric power steering apparatus. However, a brushless motor has also been used in recent years from the viewpoint of improving reliability and durability and reducing inertia.

  Such a brushless motor for assisting steering is driven by a motor drive circuit built in an electronic control unit (hereinafter referred to as “ECU”). Since electric power steering devices are required to be downsized, highly efficient, and low in cost, various proposals have been made regarding the integration of this ECU and a brushless motor.

  By the way, if there is a difference between phases in resistance components in a motor / drive circuit system including a brushless motor and a drive circuit, generation of ripples in the output torque of the motor (referred to as “torque ripple”) becomes a problem. In particular, in an electric power steering apparatus, since smoothness of the output torque of a motor is regarded as important from the viewpoint of improving steering feeling, it is required to suppress the occurrence of such torque ripple.

On the other hand, in the electric power steering device, the difference between each phase of the resistance component in the motor / drive circuit system including the brushless motor and the drive circuit (hereinafter referred to as “phase resistance difference”) is less than a predetermined value. A configuration has been proposed in which a resistance adjusting means for adjusting a resistance component in a motor / drive circuit system is provided (see, for example, paragraphs [0139] to [0143] and [0157] to [0161] of Patent Document 1).
JP 2005-319971 A

  However, if a resistance is added to eliminate the interphase resistance difference in the motor / drive circuit system, the efficiency and responsiveness in driving the brushless motor will be reduced. For this reason, it is preferable to form a wiring pattern on a circuit board (hereinafter referred to as “motor driving circuit board”) on which a motor driving circuit is mounted so as to eliminate the interphase resistance difference in the motor / driving circuit system.

  However, if the wiring pattern is formed so that the torque ripple is sufficiently reduced, the circuit pattern on the motor drive circuit board becomes complicated and the space for forming the circuit pattern increases. That is, in the motor drive circuit board, it is possible to design the wiring pattern so that the wiring resistance of the path from the power supply terminal to the ground terminal is uniform between the phases, but the wiring resistance does not affect the motor drive. It is difficult to make it sufficiently small and to arrange the switching elements constituting the motor drive circuit symmetrically. Therefore, the resistance component from the power supply terminal to the output terminal of the motor drive circuit (hereinafter referred to as “upper arm resistance”) and the resistance component from the output terminal to the ground terminal (hereinafter referred to as “lower arm resistance”) are aligned. When trying to form a wiring pattern, the circuit pattern becomes complicated and a large space is required for forming the circuit pattern, which increases the substrate size. As a result, in the electric power steering apparatus, the area occupied by the board in the ECU becomes large, which violates the above-described demand for downsizing and the like.

  Even if the circuit pattern is formed so that the upper arm resistance and the lower arm resistance are aligned on the motor drive circuit board, if the resistance values of these upper and lower arm resistances cannot be made sufficiently small, the actual resistance to the motor An error occurs between the applied voltage and the voltage to be applied. In this case, the motor cannot be driven and controlled exactly as intended, and in particular, when the motor is driven by open loop control, the target current cannot be supplied to the motor.

  Therefore, an object of the present invention is to provide a motor control device capable of reducing torque ripple while suppressing an increase in the size of a circuit board on which a drive circuit for a brushless motor is mounted. Another object of the present invention is to reduce an error in voltage applied to the brushless motor due to resistance components (upper and lower arm resistances of each phase) included in the drive circuit while suppressing an increase in the size of the circuit board. It is providing the motor control apparatus which can be suppressed. Still another object of the present invention is to provide an electric power steering apparatus including such a motor control apparatus.

A first invention is a motor control device for driving a brushless motor,
Control calculation means for obtaining a command value indicating each phase voltage to be applied to the brushless motor, and outputting the command value as a drive command value;
Correction means for correcting the drive command value;
Drive means for driving the brushless motor based on the drive command value corrected by the correction means ;
Current estimation means;
Current detection means ,
The driving means is configured by connecting a pair of switching elements composed of two switching elements connected in series to each other in parallel between the power supply terminal and the ground terminal by the number of phases of the brushless motor, and corresponding to each phase. A connection point between the two switching elements includes an inverter connected to the brushless motor as an output end;
The correction means includes an upper arm resistance that is a resistance component of each phase of the path from the power supply terminal to the output terminal of the inverter, and a lower arm resistance that is a resistance component of each phase of the path from the output terminal to the ground terminal. Based on the above, the drive command value is corrected for each phase ,
The current estimation means estimates a current to be supplied from the inverter to the brushless motor,
The current detection means detects a current supplied from the inverter to the brushless motor,
The correction means includes
Resistance value correcting means for correcting at least one resistance value of the upper and lower arm resistances based on a ratio between an estimated current value obtained by the current estimating means and a detected current value obtained by the current detecting means;
Command value correcting means for correcting the drive command value for each phase so as to compensate for a voltage shift at the output terminal with respect to the voltage indicated by the drive command value based on the resistance value corrected by the resistance value correcting means; It is characterized by including .
A second invention is a motor control device for driving a brushless motor,
Control calculation means for obtaining a command value indicating each phase voltage to be applied to the brushless motor, and outputting the command value as a drive command value;
Correction means for correcting the drive command value;
Drive means for driving the brushless motor based on the drive command value corrected by the correction means;
Voltage detection means,
The driving means is configured by connecting a pair of switching elements composed of two switching elements connected in series to each other in parallel between the power supply terminal and the ground terminal by the number of phases of the brushless motor, and corresponding to each phase. A connection point between the two switching elements includes an inverter connected to the brushless motor as an output end;
The correction means includes an upper arm resistance that is a resistance component of each phase of the path from the power supply terminal to the output terminal of the inverter, and a lower arm resistance that is a resistance component of each phase of the path from the output terminal to the ground terminal. Based on the above, the drive command value is corrected for each phase,
The voltage detection means detects a voltage of at least one phase at the output terminal of the inverter;
The correction means includes
The upper and lower arm resistances based on the voltage detection value of the phase detecting the voltage obtained by the voltage detection means and the current value indicating the current of the phase detecting the voltage supplied from the inverter to the brushless motor. Resistance value calculating means for calculating the resistance value of
Command value correction means for correcting the drive command value for each phase so as to compensate for a deviation in voltage at the output terminal with respect to the voltage indicated by the drive command value based on the resistance value calculated by the resistance value calculation means; It is characterized by including.
A third invention is a motor control device for driving a brushless motor,
Control calculation means for obtaining a command value indicating each phase voltage to be applied to the brushless motor, and outputting the command value as a drive command value;
Correction means for correcting the drive command value;
Drive means for driving the brushless motor based on the drive command value corrected by the correction means,
The driving means is configured by connecting a pair of switching elements composed of two switching elements connected in series to each other in parallel between the power supply terminal and the ground terminal by the number of phases of the brushless motor, and corresponding to each phase. A connection point between the two switching elements includes an inverter connected to the brushless motor as an output end;
The correction means includes an upper arm resistance that is a resistance component of each phase of the path from the power supply terminal to the output terminal of the inverter, and a lower arm resistance that is a resistance component of each phase of the path from the output terminal to the ground terminal. Based on the above, the drive command value is corrected for each phase according to the drive command value so that the voltage deviation at the output terminal caused by the difference between the upper arm resistance and the lower arm resistance is compensated,
The correction means includes
Storage means for storing a correction map indicating a correspondence relationship between a command value of a phase voltage to be applied to the brushless motor and a correction amount;
Correction calculation means for calculating the corrected drive command value by correcting the drive command value for each phase according to a correction amount associated with the drive command value output from the control calculation means by the correction map; It is characterized by including.

A fourth invention is an electric power steering device that applies a steering assist force to a steering mechanism of a vehicle by a brushless motor,
A motor control device according to any one of the first to third inventions;
The motor control device drives a brushless motor that applies a steering assist force to the steering mechanism.

According to any of the first , second, and third inventions , the drive command value indicating the voltage to be applied to the brushless motor is corrected for each phase based on the upper arm resistance and the lower arm resistance in the inverter, This compensates for a voltage shift at the output end caused by a voltage drop due to the upper and lower arm resistances. For this reason, it is possible to accurately apply the original voltage indicated by the drive command value before correction to the brushless motor while suppressing an increase in the circuit board size of the inverter. Thereby, it is possible to suppress the occurrence of torque ripple due to the difference between the upper arm resistance and the lower arm resistance in the inverter.
According to the first aspect of the invention, at least one of the upper and lower arm resistances is corrected based on the ratio between the estimated current value and the detected current value, and the output of the inverter is determined based on the corrected resistance value. The drive command value is corrected for each phase so that the voltage shift at the end is compensated. As a result, even if the resistance values of the upper arm resistance and the lower arm resistance vary or fluctuate due to characteristic variations of electronic components, etc., or temperature changes, the voltage that should be applied should be applied to the brushless motor with high accuracy and torque ripple can be reduced. Can be suppressed.
According to the second aspect of the invention, at least one phase voltage at the output terminal of the inverter is detected, and the voltage detection value of the phase where the voltage at the output terminal is detected and the voltage supplied from the inverter to the brushless motor are Based on the detected current value indicating the phase current, the resistance values of the upper and lower arm resistances are calculated, and based on the calculated resistance values, the voltage deviation at the output terminal of the inverter is compensated. The command value is corrected for each phase. As a result, even if the resistance values of the upper arm resistance and lower arm resistance vary or fluctuate due to variations in characteristics of electronic components, etc., and temperature changes, the voltage to be applied should be applied to the brushless motor with high accuracy and torque ripple. Can be suppressed.
According to the third aspect of the invention, the drive command value is corrected for each phase according to the drive command value indicating the voltage to be applied to the brushless motor, whereby the upper arm resistance and the lower arm resistance in the inverter are Even if there is a difference in the phase voltage, the phase voltage corresponding to the drive command value is applied to the brushless motor with high accuracy. Thereby, in the inverter, generation of torque ripple due to the difference between the upper arm resistance and the lower arm resistance is suppressed. In addition, since the drive command value indicating the voltage to be applied to the brushless motor is corrected for each phase so that the voltage deviation at the output terminal of the inverter is compensated, even if there is a resistance difference between the phases, The imbalance between the phases of the phase voltage applied to the motor is suppressed. Thereby, generation | occurrence | production of the torque ripple resulting from an interphase resistance difference can also be reduced. Therefore, an attempt to form a wiring pattern so that resistance components are aligned between the upper and lower arms of the inverter or between the phases in order to reduce torque ripple causes an increase in the size of the circuit board of the inverter. Therefore, by correcting the drive command value as described above, it is possible to reduce torque ripple while suppressing an increase in circuit board size. More specifically, according to the third aspect of the present invention, a correction map indicating the correspondence between the command value of the phase voltage to be applied to the brushless motor and the correction amount is prepared, and driving based on the correction map is performed. The above effect is obtained by correcting the command value for each phase. Such a correction map can be created by computer simulation for a system including a brushless motor and a motor control device, or by simple calculation based on an equivalent circuit for one phase for a motor / drive circuit system. . In other words, using the designed or measured values of the upper and lower arm resistances of the inverter and the phase resistance of the brushless motor, the voltage shift at the output terminal of each phase of the inverter is calculated by the computer simulation or the simple calculation based on the equivalent circuit. (Or, the relationship between the duty ratio of the inverter and the voltage deviation) is obtained, and a correction map can be created based on the voltage deviation or the like.

According to the fourth aspect of the present invention, torque ripple can be reduced while suppressing an increase in the circuit board size of the inverter for driving the brushless motor. Therefore, the steering fee can be reduced while responding to requests for downsizing and high efficiency in the electric power steering device. The ring can be improved.

<1. Electric power steering device>
FIG. 1 is a schematic diagram showing the configuration of an electric power steering device using a motor control device according to the present invention, together with the configuration of a vehicle related thereto. The electric power steering apparatus shown in FIG. 1 is a column assist provided with a brushless motor 1, a speed reducer 2, a torque sensor 3, a vehicle speed sensor 4, a position detection sensor 5, and an electronic control unit (ECU) 10 as a motor control apparatus. This is an electric power steering device of the type.

  As shown in FIG. 1, a steering wheel (steering wheel) 101 is fixed to one end of the steering shaft 102, and the other end of the steering shaft 102 is connected to a rack shaft 104 via a rack and pinion mechanism 103. Both ends of the rack shaft 104 are connected to a wheel 106 via a connecting member 105 composed of a tie rod and a knuckle arm. When the driver rotates the handle 101, the steering shaft 102 rotates, and the rack shaft 104 reciprocates accordingly. As the rack shaft 104 reciprocates, the direction of the wheels 106 changes.

  The electric power steering device performs the following steering assistance in order to reduce the driver's load. The torque sensor 3 detects a steering torque Ts applied to the steering shaft 102 by operating the handle 101. The vehicle speed sensor 4 detects the vehicle speed S. The position detection sensor 5 detects the rotational position P of the rotor of the brushless motor 1. The position detection sensor 5 is composed of, for example, a resolver.

  The ECU 10 is supplied with electric power from the in-vehicle battery 100 and drives the brushless motor 1 based on the steering torque Ts, the vehicle speed S, and the rotational position P. The brushless motor 1 generates a steering assist force when driven by the ECU 10. The speed reducer 2 is provided between the brushless motor 1 and the steering shaft 102. The steering assist force generated by the brushless motor 1 acts to rotate the steering shaft 102 via the speed reducer 2.

  As a result, the steering shaft 102 is rotated by both the steering torque applied to the handle 101 and the steering assist force generated by the brushless motor 1. As described above, the electric power steering apparatus performs steering assist by applying the steering assist force generated by the brushless motor 1 to the steering mechanism of the vehicle.

<2. First Embodiment>
<2.1 Motor controller configuration>
FIG. 2 is a block diagram showing the configuration of the motor control device according to the first embodiment of the present invention. The motor control device shown in FIG. 2 is configured using an ECU 10 and drives a brushless motor 1 having u-phase, v-phase, and w-phase three-phase windings (not shown). The ECU 10 includes a microcomputer (hereinafter abbreviated as “microcomputer”) 20, a three-phase / PWM (Pulse Width Modulation) modulator 41, a motor drive circuit 43, and a current sensor 45.

  The ECU 10 receives the steering torque Ts output from the torque sensor 3, the vehicle speed S output from the vehicle speed sensor 4, and the rotational position P output from the position detection sensor 5. The microcomputer 20 functions as control means for obtaining a voltage command value used for driving the brushless motor 1. Details of the function of the microcomputer 20 will be described later.

  The three-phase / PWM modulator 41 and the motor drive circuit 43 are configured by hardware (circuit) and function as motor drive means for driving the brushless motor 1 using the voltage of the voltage command value obtained by the microcomputer 20. . The three-phase / PWM modulator 41 generates three types of PWM signals (U, V, and W shown in FIG. 2) having a duty ratio corresponding to the three-phase voltage command value obtained by the microcomputer 20. The motor drive circuit 43 is a PWM voltage source inverter circuit including six MOS-FETs (Metal Oxide Semiconductor Field Effect Transistors) as switching elements. The six MOS-FETs are controlled by three types of PWM signals and their negative signals. That is, two MOS-FETs are assigned to each phase in the motor drive circuit 43, and the two MOS-FETs are connected in series to form a switching element pair. An inverter is configured by connecting in parallel the number of phases between the power supply terminal and the ground terminal. And the connection point of two MOS-FETs (switching element pair) corresponding to each phase is connected to the brushless motor 1 as an output terminal of the phase in the inverter. The conduction state of two MOS-FETs corresponding to each phase is controlled by two PWM signals corresponding to the phase (two PWM signals having an inversion relationship with each other), whereby the u-phase, v-phase, and w-phase are controlled. The voltages obtained at the output terminals Nu, Nv, and Nw are applied to the brushless motor 1 as u-phase voltage, v-phase voltage, and w-phase voltage, respectively. By thus applying a voltage to the brushless motor 1, the u-phase current, the v-phase current, and the w-phase current are supplied from the motor drive circuit 43 to the brushless motor 1.

  The current sensor 45 outputs detection signals indicating the u-phase current and the v-phase current supplied to the brushless motor 1, and these detection signals are input to the microcomputer 20.

  The microcomputer 20 executes a program stored in a memory (not shown) built in the ECU 10, whereby a q-axis current command value determination unit 21, a d-axis current command value determination unit 22, subtractors 23 and 24, q-axis current PI control unit 31, d-axis current PI control unit 32, first coordinate conversion unit 33, second coordinate conversion unit 34, correction calculation unit 36, correction storage unit 37, current detection unit 14, and angle calculation unit 15 Function as. The q-axis current command value determination unit 21, the d-axis current command value determination unit 22, the subtractors 23 and 24, the q-axis current PI control unit 31, the d-axis current PI control unit 32, and the first and second coordinate conversion units. 33, 34, the current detection unit 14, and the angle calculation unit 15 constitute control calculation means for obtaining phase voltage command values Vu, Vv, Vw indicating the phase voltage to be applied to the brushless motor 1 as drive command values. The correction calculation unit 36 includes three adders 36u, 36v, and 36w corresponding to the u, v, and w phases of the brushless motor 1, and the correction storage unit 37 includes u phase, v phase, and w phase corrections. Maps 37u, 37v, and 37w are stored. The correction calculation unit 36 and the correction storage unit 37 constitute a correction unit that corrects the phase voltage command values Vu, Vv, and Vw.

  The microcomputer 20 indicates the voltage to be applied to the motor drive circuit 43 based on the current command value indicating the current to be supplied to the brushless motor 1 and the rotation angle (electrical angle) of the rotor of the brushless motor 1 as shown below. The phase voltage command values Vuc, Vvc, Vwc are obtained. In the following description, for the sake of convenience, when an explanation is given focusing on any one of the u phase, the v phase, and the w phase, the focused phase is referred to as an “x phase” (others). The same applies to the above embodiment).

The q-axis current command value determining unit 21 is a q-axis indicating a q-axis component of the current to be supplied to the brushless motor 1 based on the steering torque Ts detected by the torque sensor 3 and the vehicle speed S detected by the vehicle speed sensor 4. The current command value i _q ^* is determined. The q-axis current command value i ^* _q is a current value corresponding to the torque to be generated by the brushless motor 1 and is input to the subtracter 23. On the other hand, the d-axis current command value determining unit 22 determines a d-axis current command value i _d ^* indicating the d-axis component of the current to be supplied to the brushless motor 1. Since the d-axis component of the current flowing through the brushless motor 1 is not related to torque, typically i _d ^* = 0. The d-axis current command value i _d ^* is input to the subtractor 24.

  Based on the detection signal from the current sensor 45, the current detection unit 14 converts the detected values of the u-phase current and the v-phase current out of the current supplied from the motor drive circuit 43 to the brushless motor 1 to the u-phase current detected value Iu It is output as the v-phase current detection value Iv. These u-phase and v-phase current detection values Iu and Iv are given to the first coordinate conversion unit 33. Further, the angle calculation unit 15 obtains an electrical angle θ indicating the rotational position of the rotor of the brushless motor 1 based on the rotational position P detected by the position detection sensor 5. This electrical angle θ is given to the first and second coordinate conversion units 33 and 34. As shown in FIG. 3, when the u axis, the v axis, and the w axis are set for the brushless motor 1, and the d axis and the q axis are set for the rotor 6 of the brushless motor 1, the u axis and the d axis are set. Is an electrical angle θ.

The first coordinate conversion unit 33 uses the electrical angle θ to change the u-phase and v-phase current detection values Iu and Iv to the q-axis and d-axis, which are values on the dq coordinate, according to the following expressions (1) and (2). The current detection values i _q and i _d are converted.
i _d = √2 × {Iv × sin θ−Iu × sin (θ−2π / 3)} (1)
i _q = √2 × {Iv × cos θ−Iu × cos (θ−2π / 3)} (2)
The q-axis and d-axis current detection values i _q and i _d thus obtained are input to the subtracters 23 and 24, respectively.

The subtractor 23 calculates a q-axis current deviation (i ^* _q− i _q ) that is a deviation between the q-axis current command value i ^* _q and the q-axis current detection value i _q, and the q-axis current PI control unit 31 Then, the q-axis voltage command value v _q is obtained by the proportional-integral control calculation for the q-axis current deviation (i ^* _q− i _q ). Subtractor 24 calculates a d-axis current deviation (i ^* _d -i _d) is a deviation between the d-axis current command value i ^* _d and d-axis current detection value i _d, d-axis current PI control unit 32 obtains a d-axis voltage command value v _d by the proportional integral control operations on the d-axis current deviation (i ^* _d -i _d). The q-axis and d-axis voltage command values v _q and v _d thus obtained are input to the second coordinate conversion unit 34.

The second coordinate conversion unit 34 uses the electrical angle θ to change the q-axis and d-axis voltage command values v _q and v _d to a phase on the three-phase AC coordinate according to the following equations (3) to (5). Are converted into voltage command values Vu, Vv, and Vw (hereinafter, these phase voltage command values Vu, Vv, and Vw are converted into “u-phase voltage command value Vu”, “v-phase voltage command value Vv”, and “w-phase”, respectively. Also referred to as “voltage command value Vw”).
Vu = √ (2/3) × {v _d × cos θ−v _q × sin θ} (3)
Vv = √ (2/3) × {v _d × cos (θ-2π / 3)
−v _q × sin (θ−2π / 3)} (4)
Vw = −Vu−Vv (5)
These phase voltage command values Vu, Vv, and Vw are respectively supplied to adders 36u, 36v, and 36w of the correction calculation unit 36, and u-phase, v-phase, and w-phase correction maps 37u stored in the correction storage unit 37. , 37v, 37w, respectively.

  The x-phase correction map 37x (x = u, v, w) is a map for associating the x-phase voltage command value with the correction amount necessary for the voltage command value. Correction amounts corresponding to the x-phase voltage command value Vx are obtained from the x-phase correction map 37x, and these correction amounts are respectively given to the adders 36x corresponding to the x-phase in the correction calculation unit 36 (x = u, v, w).

  In the correction calculation unit 36, the adder 36x corresponding to the x phase corrects the x phase voltage command value Vx by adding the correction amount obtained from the x phase correction map 37x to the x phase voltage command value Vx (x = U, v, w). The corrected u-phase, v-phase and w-phase voltage command values Vuc, Vvc, Vwc obtained in this way are applied to the three-phase / PWM modulator 41.

  As described above, the three-phase / PWM modulator 41 outputs three types of PWM signals U, V, and W having a duty ratio corresponding to these corrected phase voltage command values Vuc, Vvc, and Vwc and their negative signals. Generate. The motor drive circuit 43 is controlled by these three types of PWM signals and their negative signals, so that three-phase drive currents (u-phase current, v-phase current and w-phase current) are supplied to the brushless motor 1. The As a result, the brushless motor 1 rotates and generates torque.

  Of the current paths from the motor drive circuit 43 to the brushless motor 1, current sensors 45 are inserted in the u-phase and v-phase current paths, and the current sensor 45 is connected to the brushless motor 1 as described above. Detection signals indicating the u-phase and v-phase currents supplied to. Further, the rotational position P of the rotor of the brushless motor 1 is detected by the position detection sensor 5 as described above. A detection signal indicating the u-phase and v-phase currents and a detection signal indicating the rotational position P are input to the microcomputer 20 and used for driving control of the brushless motor 1 as described above.

<2.2 Correction of phase voltage command value>
In order to suppress the ripple (torque ripple) included in the output torque of the brushless motor 1, the motor drive circuit board (circuit board on which the motor drive circuit 43 is mounted) of the motor / drive circuit system does not cause a difference in resistance between phases. A circuit pattern is preferably formed. However, even if the wiring pattern is formed so that there is no difference between the resistance components of the path from the power supply terminal to the ground terminal, the path from the power supply terminal to the output terminal of the motor drive circuit 43 for each phase. If there is a difference between the resistance component (hereinafter referred to as “upper arm resistance”) and the resistance component of the path from the output terminal to the ground terminal (hereinafter referred to as “lower arm resistance”), torque ripple occurs. . On the other hand, not only does the resistance difference between phases not occur in the motor / drive circuit system, but if the wiring pattern is formed so that the upper arm resistance and the lower arm resistance are equal for each phase, the motor drive circuit A circuit pattern on the substrate becomes complicated, and a space for forming the circuit pattern increases.

  Therefore, in this embodiment, in order to suppress an increase in the area of the motor drive circuit board, a difference generated between the upper arm resistance and the lower arm resistance (hereinafter, referred to as “upper and lower resistance difference”) is allowed for each phase. . The phase voltage command values Vu, Vv, and Vw are corrected by the correction means including the correction calculation unit 36 and the correction storage unit 37 so that the upper and lower resistance differences are compensated for each phase so as to suppress the occurrence of torque ripple. Is done. Hereinafter, the details of the correction by the correcting means will be described.

  In the present embodiment, the correction amount to be added to the phase voltage command values Vu, Vv, Vw in the correction calculation unit 36 to compensate for the upper / lower resistance difference is obtained with reference to a correction map prepared for each phase. . That is, the correction amount added to the u-phase, v-phase, and w-phase voltage command values Vu, Vv, Vw is determined by the u-phase, v-phase, and w-phase correction maps 37, 37v, 37w. The correction amounts are respectively associated with the phase voltage command values Vu, Vv, and Vw. Such u-phase, v-phase, and w-phase correction maps 37u, 37v, and 37w can be set so that the specific correspondence between the phase voltage command value and the correction amount is different. The correction map is created and used in the same way. Therefore, in the following description, the u phase, the v phase, and the w phase are represented by the x phase.

  FIG. 4 is a circuit diagram for explaining the creation of the x-phase correction map 37 x in the present embodiment, and shows the circuit configuration of the motor / drive circuit system including the motor drive circuit 43 and the brushless motor 1. The resistance component from the power supply terminal Npw to the x-phase output terminal Nx, that is, the upper arm resistance of the x-phase is composed of the ON resistance of the switching element (FET) and the wiring resistance in the upper arm, and the x-phase output terminal Nx to the ground terminal The resistance component up to Ngd, that is, the lower arm resistance of the x phase consists of the ON resistance and the wiring resistance of the switching element (FET) in the lower arm. Although not shown in FIG. 4, when the brushless motor 1 is rotating, a counter electromotive force is generated in each phase of the brushless motor 1. Hereinafter, the creation of the x-phase correction map will be described with reference to FIG. 4 (x = u, v, w).

  In the circuit board (motor drive circuit board) on which the motor drive circuit 43 is mounted, even if the wiring pattern is formed so that the resistance component of the path from the power supply terminal Npw to the ground terminal Ngd is equal between the phases, If there is a difference (upper and lower resistance difference) between the upper arm resistance Rhx and the lower arm resistance Rlx for the x phase, the voltage Vxa at the output terminal Nx deviates from the original voltage. In the present embodiment, the correction amount of the x-phase voltage command value Vx for compensating for this voltage deviation is given by the x-phase correction map 37x.

The voltage Vxa at the x-phase output terminal Nx of the motor drive circuit 43 is the voltage of the DC power supply supplied to the motor drive circuit 43 as Vb, and the duty ratio that is the ratio of the ON period of the switching element of the upper arm of the x-phase. Assuming that Dx represents, ideally (when Rhx = Rlx = 0),
Vxa = Dx · Vb (6)
It becomes. However, in reality, the upper arm resistance Rhx and the lower arm resistance Rlx have non-zero values, and Rhx ≠ 0 and Rlx ≠ 0. Therefore, the voltage Vxa at the output terminal is given by the above equation (6). It deviates from the value Dx · Vb. In the following, the resistance values of the upper arm resistance Rhx and the lower arm resistance Rlx are also indicated by symbols Rhx and Rlx, respectively (the same applies to other embodiments).

On the other hand, the x-phase voltage command value Vx output from the control calculation means (the second coordinate conversion unit 34) is an x-phase duty ratio Dx indicating the ratio of the ON period of the switching element of the x-phase upper arm of the motor drive circuit 43. Corresponding to
Dx = Vx / Vb (7)
It is. Since Rhx ≠ 0 and Rlx ≠ 0 as described above, when the two switching elements corresponding to the x phase are driven with the duty ratio Dx given by the equation (7), the output terminal of the motor drive circuit 43 For Nx, a voltage equal to the phase voltage command value Vx cannot be obtained.

  On the other hand, in the present embodiment, the upper arm resistance Rhx, the lower arm resistance Rlx, and the resistance component (hereinafter referred to as “motor phase resistance”) Rm of the brushless motor 1 are used for various phases. The deviation of the actual output terminal voltage Vxa from the ideal output terminal voltage Vxa (= Dx · Vb = Vx) corresponding to the duty ratio Dx is obtained in advance for the duty ratio Dx. For each of the various duty ratios Dx, a correction amount of the phase voltage command value Vx (= Dx · Vb) for compensating for the voltage deviation at the duty ratio Dx is determined, and the correction amount and the phase voltage command value Vx Alternatively, data that associates the duty ratio Dx is stored in the correction storage unit 37 as an x-phase correction map 37x (x = u, v, w).

  In the present embodiment, the correction amount obtained for each phase is added to the phase voltage command values Vu, Vv, Vw with reference to the u-phase, v-phase, and w-phase correction maps 37u, 37v, 37w created in this way. Thus, corrected phase voltage command values Vuc, Vvc, Vwc are obtained. Then, according to the corrected phase voltage command values Vuc, Vvc, Vwc, each switching element (FET) of the motor drive circuit 43 as a PWM voltage source inverter is driven (ON / OFF). As a result, the voltages Vua, Vva, Vwa obtained at the output terminals Nu, Nv, Nw of the motor drive circuit 43 are applied to the brushless motor 1.

<2.3 Specific examples of correction map creation>
In order to create the correction maps 37u, 37v, and 37w for each phase used in the present embodiment, the design values or actual measurement values of the upper arm resistance Rhx, the lower arm resistance Rlx, and the motor phase resistance Rm are used for each phase. It is necessary to determine how much the output terminal voltage Vxa (of the motor drive circuit 43) at various duty ratios Dx deviates from the ideal value (= phase voltage command value Vx). Such a voltage shift at the output terminal Nx is obtained by calculating the operation of the system including the motor control device including the motor drive circuit 43 and the brushless motor 1 using a design value or an actual measurement value of the resistors Rhx, Rlx, Rm. It can be obtained by simulation.

  Without performing such computer simulation, an equivalent circuit showing a configuration for one phase in the motor / drive circuit system (FIG. 4) including the motor drive circuit 43 and the brushless motor 1 is expressed based on a simple model, The voltage deviation at the output terminal Nx can also be obtained based on the equivalent circuit for each phase. Hereinafter, a method of obtaining the voltage deviation of the output terminal Nx in the x phase using this simple model and creating the x-phase correction map 37x based on the voltage deviation will be described (x = u, v, w).

  FIGS. 5A and 5B are circuit diagrams showing the configuration of the x phase, which is one phase of the motor / drive circuit system shown in FIG. In the simple model using the circuit configuration for one phase, the back electromotive force in the brushless motor 1 is not considered. FIG. 5A shows a case where the x-phase current flows from the motor drive circuit 43 to the brushless motor 1, and FIG. 5B shows a case where the x-phase current flows from the brushless motor 1 to the motor drive circuit 43. Show. 5A and 5B, the resistance component including the ON resistance and the wiring resistance of the switching element (hereinafter referred to as “upper switching element”) SWXh in the upper arm is shown as the upper arm resistance Rhx. The resistance component including the ON resistance and the wiring resistance of the switching element SWXl (hereinafter referred to as “lower switching element”) in the arm is indicated as a lower arm resistance Rlx. Rm represents an x-phase resistance component in the brushless motor 1.

As shown in FIG. 5A, when the x-phase current flows from the motor drive circuit 43 to the brushless motor 1, when the upper switching element SWXh is in the ON state, the x-phase current Ix is Ix = (Vb−Vm) / (Rhx + Rm) (8)
Therefore, the voltage Vxu of the output terminal Nx at this time is
Vxu = (Vb−Vm) Rm / (Rhx + Rm) + Vm (9)
It becomes. Here, Vb is a voltage of a DC power source supplied to the motor drive circuit 43, and Vm is a voltage at the neutral point Nn of the brushless motor 1. Further, since the brushless motor 1 is an inductive load, in this case, even if the upper switching element SWXh is turned off and the lower switching element SWXl is turned on, the current Ix expressed by the above formula (8) continues to flow. . Therefore, the voltage Vxd of the output terminal Nx when the lower switching element SWXl is in the on state is
Vxd = −Ix · Rlx
=-(Vb-Vm) Rlx / (Rhx + Rm) (10)
It becomes. Therefore, the output terminal voltage Vxa corresponding to the x-phase voltage applied to the brushless motor 1 is expressed by the following equation from the equations (9) and (10) using the duty ratio Dx which is the ratio of the ON period of the upper switching element SWXh. It can be expressed as
Vxa = Dx.Vxu + (1-Dx) .Vxd
= (Vb-Vm) {Dx. (Rm + Rlx) -Rlx} / (Rhx + Rm)
+ Dx · Vm (11)

By the way, an ideal x-phase voltage corresponding to the duty ratio Dx, that is, the voltage Vxo of the output terminal Nx when Rhx = Rlx = 0 is
Vox = Dx · Vb (12)
It is. Further, since the voltage deviation at the output end Nx is Vxa−Vxo, in this embodiment, the correction amount ΔVx is set to ΔVx = Vxo−Vxa (13)
And Therefore, when design values or actual measurement values of the resistors Rhx, Rlx, and Rm are given (Vb and Vm are known), the case where the x-phase current flows from the motor drive circuit 43 to the brushless motor 1, that is, Dx> 0.5. The correction amount ΔVx for various duty ratios Dx can be obtained from the equations (11) to (13).

On the other hand, when the x-phase current flows from the brushless motor 1 to the motor drive circuit 43 as shown in FIG. 5B, when the lower switching element SWXl is in the ON state, the x-phase current Ix is Ix = Vm / (Rlx + Rm (14)
Therefore, the voltage Vxd of the output terminal Nx at this time is
Vxd = Vm · Rlx / (Rlx + Rm) (15)
It becomes. Since the brushless motor 1 is an inductive load, in this case, even if the lower switching element SWXl is turned off and the upper switching element SWXh is turned on, the current Ix expressed by the above formula (14) continues to flow. . Therefore, the voltage Vxu at the output terminal Nx when the upper switching element SWXh is in the on state is
Vxu = Vb−Ix · Rhx
= Vb-Vm.Rhx / (Rlx + Rm) (16)
It becomes. Therefore, the output terminal voltage Vxa corresponding to the x-phase voltage applied to the brushless motor 1 is obtained from the equations (15) and (16) using the duty ratio Dx which is the ratio of the ON period of the upper switching element SWXh at Nx. It can be expressed as:
Vxa = Dx.Vxu + (1-Dx) .Vxd
= Vm. {Rlx-Dx. (Rhx + Rlx)} / (Rlx + Rm)
+ Dx · Vb (17)

By the way, an ideal x-phase voltage corresponding to the duty ratio Dx, that is, the voltage Vxo of the output terminal Nx when Rhx = Rlx = 0 is
Vox = Dx · Vb (18)
It is. Accordingly, given design values or actually measured values of the resistors Rhx, Rlx, and Rm, when the x-phase current flows from the brushless motor 1 to the motor drive circuit 43, that is, when Dx <0.5, various duty ratios Dx are obtained. The correction amount ΔVx can be obtained from equations (17), (18), and (13).

  As described above, the correction amount ΔVx for various duty ratios Dx can be obtained from the equations (11) to (13) and the equations (17) to (18). An x-phase correction map 37x that associates ΔVx can be created (x = u, v, w).

FIG. 6 is a diagram illustrating an example of a correction map created based on the equivalent circuit of FIGS. 5A and 5B based on the simple model. However, in FIG. 6, for convenience, the correspondence relationship between the duty ratio Dx and the correction amount ΔVx is as follows: Rhx> Rlx, Rhx = Rlx ≠ 0, Rhx <Rlx, and Rhx = Rlx = 0 ( The four cases (ideal case) are shown simultaneously. As described above, if the design values or actually measured values of the resistances Rhx, Rlx, and Rm of the motor drive circuit 43 and the brushless motor 1 of the motor control apparatus that is to implement the present invention are used (power supply voltage Vb, neutral point voltage) As a correction map for associating the correction amount ΔVx with the duty ratio Dx for each phase, a correction map 37x corresponding to the resistance values of the resistors Rhx, Rlx, Rm can be created. That is, the correction map 37x (x = u, v, w) reflecting the upper and lower stage resistance difference and the interphase resistance difference can be created. The correction map 37x created in this way varies depending on the curves (polygonal lines) corresponding to any of the three cases except the ideal case (Rlx = Rhx = 0) of the four cases shown in FIG. The duty ratio Dx and the correction amount of the phase voltage command value Vx are associated with each other. Here, the duty ratio Dx can be expressed as Dx = Vx / Vb using the x-phase voltage command value Vx (before correction). Therefore, the x-phase correction map 37x can be used as a map for associating the correction amount ΔVx with the x-phase voltage command value Vx (x = u, v, w).

<2.4 Effect>
According to the present embodiment as described above, the phase voltage command value Vx (x = u, v, w) calculated by the control calculation means is the design value or actual measurement value of the upper arm resistance Rhx, the lower arm resistance Rlx, and the like. Is corrected for each phase by the correction calculation unit 36 with reference to the correction map 37x created based on the above (see FIG. 2), and as a PWM voltage source inverter according to the corrected phase voltage command values Vuc, Vvc, Vwc Each switching element (FET) of the motor drive circuit 43 is driven (ON / OFF). As a result, even when there is a difference (upper and lower stage resistance difference) between the upper arm resistance Rhx and the lower arm resistance Rlx in the motor drive circuit 43, the voltages according to the phase voltage command values Vu, Vv, Vw are accurately obtained. Applied to the brushless motor 1. The phase voltage command values Vu, Vv, and Vw are corrected for each phase according to each phase voltage command value Vx with reference to the correction maps 37u, 37v, and 37w created for each phase. Even when there is an interphase resistance difference in the circuit system, imbalance between the phases of the phase voltages Vua, Vva, Vwa applied to the brushless motor 1 is suppressed.

  Therefore, according to this embodiment, torque ripple in the brushless motor 1 can be reduced. By the way, if it is attempted to suppress the occurrence of torque ripple by forming a wiring pattern so that the upper and lower stage resistance difference and the interphase resistance difference in the motor drive circuit 43 as an inverter are eliminated, the size of the motor drive circuit board is increased. Invite. On the other hand, according to the present embodiment, torque ripple is reduced by correcting the phase voltage command values Vu, Vv, and Vw, so that an increase in the size of the motor drive circuit board can be avoided, and an increase in wiring resistance is also achieved. Can be avoided. For this reason, in the electric power steering device using the motor control device according to the present embodiment, torque ripple can be achieved while responding to requests for miniaturization, high efficiency, low cost, etc. by suppressing the size increase of the motor drive circuit board. The steering feeling can be improved by suppressing the above.

<3. Second Embodiment>
Next, a motor control device according to a second embodiment of the present invention will be described.
In general, an error occurs in the applied voltage applied from the motor drive circuit to the motor due to a voltage drop due to the upper and lower arm resistances in the motor drive circuit. Such an error in the voltage applied to the motor can be suppressed by correcting the phase voltage command values Vu, Vv, and Vw as in the first embodiment.

  By the way, when the motor control device is manufactured, the resistance values of the upper and lower arm resistances vary due to variations in characteristics of electronic components and the like, and the resistance values vary depending on the operating temperature environment. For this reason, in the first embodiment, the correction accuracy of the phase voltage command values Vu, Vv, and Vw decreases due to variations and fluctuations in the resistance value, and the error in the voltage applied to the motor cannot be sufficiently suppressed. There is. In the case where the motor is driven by open loop control, such an applied voltage error is particularly problematic in order to pass a target current to the motor.

  Therefore, in this embodiment, even if the resistance values of the upper and lower arm resistors in the motor drive circuit vary or fluctuate, the phase voltage command value is accurately corrected and the above error in the voltage applied to the motor is sufficiently suppressed. It is configured to be able to.

<3.1 Motor drive device>
FIG. 7 is a block diagram showing the configuration of the motor control device according to the present embodiment. Similarly to the first embodiment, this motor control device also drives the brushless motor 1 having three-phase windings (not shown) of u phase, v phase and w phase in the electric power steering device shown in FIG. And is configured using the ECU 10. Of the components in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 7, the ECU 10 used in the motor control device according to the present embodiment includes a microcomputer 60, a three-phase / PWM (Pulse Width Modulation) modulator 41, a motor drive circuit 43, and a current sensor 46. ing.

  The ECU 10 receives the steering torque Ts output from the torque sensor 3, the vehicle speed S output from the vehicle speed sensor 4, and the rotational position P output from the position detection sensor 5. The microcomputer 60 functions as control means for obtaining a voltage command value used for driving the brushless motor 1. Details of the function of the microcomputer 60 will be described later.

  The three-phase / PWM modulator 41 generates three types of PWM signals (U, V, W shown in FIG. 7) having a duty ratio corresponding to the three-phase voltage command value obtained by the microcomputer 60. As in the first embodiment, these PWM signals U, V, and W and their negative signals are given to a motor drive circuit 43 as a PWM voltage source inverter, and the u phase, v phase, The voltages obtained at the w-phase output terminals Nu, Nv, and Nw are applied to the brushless motor 1 as u-phase voltage, v-phase voltage, and w-phase voltage, respectively. As a result, the u-phase current, the v-phase current, and the w-phase current are supplied from the motor drive circuit 43 to the brushless motor 1.

  The current sensor 46 detects a current supplied from the motor drive circuit 43 to the brushless motor 1, that is, a current flowing through the brushless motor 1. The current sensor 46 is constituted by, for example, a resistor or a Hall element, and only one current sensor 46 is provided between the motor drive circuit 13 and the power source.

  While the brushless motor 1 is rotating, the current value detected by the current sensor 46 changes according to the PWM signal. Within one cycle of the PWM signal (hereinafter referred to as “PWM cycle”), there are a case where the current sensor 46 detects a one-phase drive current and a case where the sum of the two-phase drive currents is detected. Since the sum of the three-phase drive currents becomes zero, the remaining one-phase drive current can be obtained based on the sum of the two-phase drive currents. Therefore, the three-phase drive current can be detected by using one current sensor 46 while the brushless motor 1 is rotating. The current value Ia detected by the current sensor 46 is input to the microcomputer 60.

  The microcomputer 60 executes a program stored in a memory (not shown) built in the ECU 10, whereby a q-axis current command value determination unit 21, a d-axis current command value determination unit 22, an open loop control unit 51, It functions as a dq axis / 3-phase converter 54, a correction unit 61, a current estimation unit 58, an angle calculation unit 15, an angular velocity calculation unit 55, and a Φ calculation unit 56. The q-axis current command value determination unit 21, the d-axis current command value determination unit 22, the open loop control unit 51, the dq-axis / 3-phase conversion unit 54, the angle calculation unit 15, the angular velocity calculation unit 55, and the Φ calculation unit 56 are A control calculation means for obtaining phase voltage command values Vu, Vv, Vw indicating phase voltages to be applied to the brushless motor 1 is configured.

  As will be described below, the microcomputer 60 indicates the voltage to be applied to the motor drive circuit 43 based on the current command value indicating the current to be supplied to the brushless motor 1 and the rotation angle (electrical angle) of the rotor of the brushless motor 1. The phase voltage command values Vuc, Vvc, Vwc are obtained.

The q-axis current command value determination unit 21 determines a q-axis current command value i _qc indicating the q-axis component of the current to be supplied to the brushless motor 1 and determines the d-axis current command value, as in the first embodiment. The unit 22 determines a d-axis current command value i _dc indicating the d-axis component of the current to be supplied to the brushless motor 1. The q-axis current command value i _qc and the d-axis current command value i _dc are input to the open loop control unit 51.

As in the first embodiment, the angle calculation unit 15 obtains an electrical angle (hereinafter referred to as “angle θ”) indicating the rotation angle of the rotor of the brushless motor 1 based on the rotation position P detected by the position detection sensor 5. . The angular velocity calculation unit 55 obtains the angular velocity ω _e of the rotor of the brushless motor 1 based on the angle θ. The angle θ is input to the Φ calculating unit 56, the dq axis / three-phase converting unit 54, and the correcting unit 61, and the angular velocity ω _e is input to the open loop control unit 51 and the Φ calculating unit 56.

The open loop control unit 51 indicates the d-axis component and the q-axis component of the target value of the voltage to be applied to the brushless motor 1 based on the d-axis current command value i _dc , the q-axis current command value i _qc and the angular velocity ω _e. The d-axis voltage command value v _dc and the q-axis voltage command value v _qc are obtained. The d-axis voltage command value v _dc and the q-axis voltage command value v _qc are calculated using the motor circuit equations shown in the following equations (19) and (20).
v _dc = (R + PL _d ) i _dc −ω _e L _q i _qc ... (19)
v _qc = (R + PL _q ) i _qc + ω _e L _d i _dc + ω _e Φ (20)
In Equations (19) and (20), ω _e is the rotor angular velocity, R is the circuit resistance including the armature winding resistance, L _d is the d-axis self-inductance, L _q is the q-axis self-inductance, Φ Is √ (3/2) times the maximum value of the u, v, w phase armature winding flux linkage, and P is a differential operator. Of these, R, L _d , L _q and Φ are treated as known parameters. The circuit resistance indicated by R includes the wiring resistance between the brushless motor 1 and the ECU 10, the resistance of the motor drive circuit 43 in the ECU 10, the wiring resistance, and the like.

The dq-axis / three-phase conversion unit 54 uses the angle θ to convert the d-axis voltage command value v _dc and the q-axis voltage command value v _qc obtained by the open loop control unit 51 into a voltage command value on the three-phase AC coordinate axis. That is, it converts into u-phase voltage command value Vu, v-phase voltage command value Vv, and w-phase voltage command value Vw. The u-phase voltage command value Vu, the v-phase voltage command value Vv, and the w-phase voltage command value Vw are collectively referred to as “phase voltage command values Vu, Vv, Vw”.

The current estimation unit 58 includes the q-axis and d-axis current command values i _qc and i _dc from the q-axis and d-axis current command value determination units 21 and 22 and the q-axis and d-axis voltage commands from the open loop control unit 51. Based on the values v _qc and v _dc , the q-axis component and the d-axis component of the current to be supplied from the motor drive circuit 43 to the brushless motor 1 are designed as the q-axis current estimated value Iqe and the d-axis current estimated value Iqe, respectively. Ask. Specifically, when the magnitude of the voltage vector calculated from the d-axis and q-axis voltage command values v _qc and v _dc is equal to or lower than the voltage of the battery 100 as the power source, that is, equal to or lower than the power source voltage, the q-axis and d If the shaft current command values i _qc and i _dc are the q-axis and d-axis current estimated values Iqe and Ide, respectively, and the calculated voltage vector exceeds the power supply voltage, the calculated voltage vector The q-axis and d-axis current estimated values Iqe and Ide are obtained by reducing the q-axis and d-axis current command values i _qc and i _dc according to the ratio of the magnitude of the power supply voltage to the height. These q-axis and d-axis current estimation values Iqe and Ide are output from the current estimation unit 58 and input to the correction unit 61. The method for determining the q-axis and d-axis current estimated values Iqe and Ide is not limited to the above method, and the q-axis component and the d-axis component of the current to be supplied from the motor drive circuit 43 to the brushless motor 1 ( The q-axis and d-axis current estimated values Iqe and Ide may be determined by other methods as long as the method can appropriately estimate the q-axis component and the d-axis component of the current that should flow through the brushless motor 1.

  The correction unit 61 corrects the phase voltage command values Vu, Vv, and Vw based on the q-axis current estimated value Iqe, the d-axis current estimated value Ide, and the current value Ia detected by the current sensor 46. The corrected phase voltage command values Vuc, Vvc, Vwc are input to the three-phase / PWM modulator 41.

  The three-phase / PWM modulator 41 generates three types of PWM signals U, V, and W having a duty ratio corresponding to these corrected phase voltage command values Vuc, Vvc, and Vwc. The motor drive circuit 43 is controlled by these three types of PWM signals U, V, and W and their negative signals. As a result, the voltage obtained at the output terminals Nu, Nv, Nw of the motor drive circuit 43 is applied to the brushless motor 1. As a result, a sinusoidal current corresponding to the voltage command values Vuc, Vvc, and Vwc of each phase flows through the three-phase windings of the brushless motor 1, and the rotor of the brushless motor 1 rotates. Accordingly, a torque corresponding to the current flowing through the brushless motor 1 is generated on the rotating shaft of the brushless motor 1. The generated torque is used for steering assistance.

The current value Ia detected by the current sensor 46, the angle θ calculated by the angle calculation unit 34, and the angular velocity ω _e calculated by the angular velocity calculation unit 35 are input to the Φ calculation unit 56. The Φ calculating unit 56 first determines the values of the u-phase and v-phase currents flowing through the brushless motor 1 based on the current value Ia, that is, the u-phase current detection value Iu and the v-phase current detection value Iv, and these are obtained on the dq coordinate axis. The d-axis current detection value i _d and the q-axis current detection value i _q are obtained by converting into current values.

Next, when ω _e ≠ 0, the Φ calculating unit 56 uses the following formula ( _q) based on the q-axis voltage command value v _qc , the d-axis current detection value i _d , the q-axis current detection value i _q, and the angular velocity ω _e. 21) is used to find the armature winding flux linkage number Φ included in the equation (20).
Φ = {v _qc − (R + PL _q ) i _q −ω _e L _d i _d } / ω _e (21)
Incidentally, equation (21) substitutes the d-axis current detection value i _d and the q-axis current detection value i _q on the d-axis current command value i _dc and the q-axis current command value i _qc of formula (20), the expression Is solved for Φ.

The Φ calculation unit 56 outputs the obtained Φ value to the open loop control unit 51. The open loop control unit 51 uses the Φ value calculated by the Φ calculation unit 56 when _{obtaining the} q-axis voltage command value v _qc using the equation (20). As described above, the microcomputer 60 obtains the armature winding interlinkage magnetic flux number Φ included in the circuit equation of the motor and uses the Φ value when _obtaining the q-axis voltage command value v _qc , but omits the Φ calculation unit 56. Alternatively, a predetermined value may be used as the Φ value.

In the present embodiment, the armature winding resistance R and the like used for _{obtaining the} d-axis voltage command value v _dc and the q-axis voltage command value v _qc in the open loop control unit 31 are treated as known parameters. , .PHI. Are appropriately corrected by the .PHI. Calculation unit 56 as parameter calculation means while treating them as known parameters. However, the present invention is not limited to such a configuration, and instead of the Φ calculating unit 56 or together with the Φ calculating unit 56, an R calculating unit as a parameter calculating unit is provided, and d-axis voltage command values v _dc and q When calculating the shaft voltage command value v _qc , R calculated by the R calculating unit may be used. Each parameter for _obtaining the d-axis voltage command value v _dc and the q-axis voltage command value v _qc may be treated as a fixed value or a calculated value based on the current command value.

<3.2 Details of Correction Unit>
FIG. 8 is a block diagram showing a configuration of the correction unit 61 in the present embodiment. The correction unit 61 includes a phase current calculation unit 612, a dq axis / 3-phase conversion unit 614, a resistance value correction unit 616, and a command value correction unit 618.

  The phase current calculation unit 612 obtains the u-phase current detection value Iu, the v-phase current detection value Iv, and the w-phase current detection value Iw from the current value Ia detected by the current sensor 46. These phase current detection values Iu, Iv, and Iw are input to the resistance value correction unit 616.

  The dq-axis / three-phase conversion unit 614 estimates the q-axis and d-axis current estimation values Iqe and Ide received from the current estimation unit 58 based on the angle θ calculated by the angle calculation unit 15 and estimates the current on the three-phase AC coordinate axis. Values, i.e., u-phase current estimated value Iue, v-phase current estimated value Ive, and w-phase current estimated value Iwe. These phase current estimated values Iue, Ive, and Iwe are input to the resistance value correction unit 616 and the command value correction unit 618.

The resistance value correction unit 616 uses the phase current detection values Iu, Iv, Iw and the phase current estimation values Iue, Ive, Iwe, and the upper arm resistance Rhx and the lower arm of each phase in the motor drive circuit 43 according to the following equations. The resistance Rlx is corrected (x = u, v, w).
Rhxc = Rhx × Ixe / Ix (23)
Rlxc = Rlx × Ixe / Ix (24)
Here, Rhxc represents the corrected upper arm resistance of the x phase, and Rlxc represents the corrected lower arm resistance of the x phase. Design values or measured values are used as the resistance values of the upper arm resistance Rhx and the lower arm resistance Rlx of each phase in the initial state of the motor control device.

  FIGS. 9A and 9B are circuit diagrams showing the configuration of the x phase, which is one phase of the motor drive circuit 43, and FIG. 10 shows x when the upper arm resistance Rhx and the lower arm resistance Rlx are considered. FIG. 6 is a waveform diagram of a voltage at a phase output terminal Nx (hereinafter referred to as “x-phase output terminal voltage”). Here, the upper switching element SWXh and the lower switching element SWXl shown in FIGS. 9A and 9B are FETs as x-phase switching elements in the motor drive circuit 43, but the upper and lower arm resistances Rhx and Rlx. Are expressed including the ON resistances of the upper and lower switching elements SWXh and SWXl, respectively.

In one period T of the PWM signal X (X = U, V, W), in the ON period of the upper switching element SWXh (the OFF period of the lower switching element SWXl) tx, the current actually flowing in the upper arm or the x-phase current detection When the value is Ix, the x-phase output terminal voltage Vxh at this time is
Vxh = Vb−Rhx · Ix (25)
It becomes. On the other hand, in the off period of the upper switching element SWXh (the on period of the lower switching element SWXl) (T-tx), if the current actually flowing in the lower arm or the x-phase current detection value is Ix, the x-phase output terminal at this time The voltage Vxl is
Vxl = 0−Rlx · Ix (26)
(See FIG. 10).

Therefore, the voltage (hereinafter referred to as “x-phase actual voltage”) Vxa actually applied to the brushless motor 1 from the x-phase output terminal Nx of the motor drive circuit 43 is:
Vxa = {Vxh · tx + Vxl · (T−tx)} / T
= {(Vb−Rhx · Ix) · tx + (0−Rlx · Ix) · (T−tx)} / T
= {(Vb.tx + 0. (T-tx)} / T
-{Rhx.tx + Rlx. (T-tx)}. Ix / T (27)
It becomes. Thus, the error Δex caused by the upper arm resistance Rhx and the lower arm resistance Rlx at the x-phase actual voltage Vxa is
Δex = − {Rhx · tx + Rlx · (T−tx)} · Ix / T (28)
It turns out that it becomes.

  Therefore, the error Δex is greatly affected by the upper arm resistance Rhx when tx> (T−tx), and at this time, Ix> 0 (FIG. 9A). On the other hand, when tx <(T−tx), the influence of the lower arm resistance Rlx is large, and at this time, Ix <0 (FIG. 9B). Therefore, in the present embodiment, when Ix> 0, based on the x-phase current detection value Ix, the upper arm resistance Rhx is corrected according to Equation (23), and the corrected upper arm resistance Rhxc is newly replaced with Rhx. When Ix <0, the lower arm resistance Rlx is corrected according to the equation (24), and the corrected lower arm resistance Rlxc is newly replaced with Rlx. In the resistance value correction unit 616, the upper arm resistance Rhx and the lower arm resistance Rlx are updated in this manner.

  However, since the fluctuation of the resistance value is sufficiently gradual compared with the period of the control calculation for driving the motor, in this embodiment, the period of the control calculation, that is, the phase voltage command value Vu, A period longer than the period for obtaining Vv and Vw is set. This update cycle may be several milliseconds to several seconds, for example, may be updated only once when the motor control device is started, and may be updated when the phase currents Iu, Iv, Iw are detected. . Further, an average value or a representative value of several resistance values calculated may be used. Note that the correction method (updating method) of the resistance values of the upper arm resistance Rhx and the lower arm resistance Rlx is not limited to the above, and based on the ratio between the phase current estimated value Ixe and the phase current detection value Ix, What is necessary is just to correct | amend the resistance value of lower arm resistance Rhx and Rlx appropriately (update).

The command value correction unit 618 receives the phase voltage command values Vu, Vv, Vw from the dq axis / 3-phase conversion unit 54, and is updated as described above by the resistance value correction unit 616 in the correction unit 61. Rhx and lower arm resistance Rlx are received, and phase voltage command values Vu, Vv, Vw are corrected as follows using the estimated phase current values Iue, Ive, Iwe together with Rhx. Assuming that the on period of the upper switching element SWXh corresponding to the x-phase voltage command value Vx is tx, the x-phase voltage (average value in the cycle T) to be applied to the brushless motor 1 at this time is {Vb · tx + 0 · (T-tx)} / T (29)
(X = u, v, w).

In order to make the x-phase actual voltage Vxa equal to the x-phase voltage, in order to compensate for the deviation of the x-phase actual voltage Vxa with respect to the x-phase voltage command value Vx (the deviation of the voltage at the x-phase output terminal), as shown in FIG. Consider changing the ON period of the upper switching element SWXh from tx to txc. That is, the ON period of the upper switching element SWXh is changed from tx to txc in order to compensate for the error Δex (formula (28)) caused by the upper and lower arm resistances Rhx and Rlx for the x-phase actual voltage Vxa. With this change, the x-phase actual voltage Vxa applied to the brushless motor 1 is {(Vb−Rhx · Ix) · txc + (0−Rlx · Ix) · (T−txc)} / T
... (30)
Therefore, the following formula is established from the above formulas (29) and (30).
{Vb · tx + 0 · (T−tx)} / T
= {(Vb-Rhx.Ix) .txc + (0-Rlx.Ix). (T-txc)} / T
... (31)
Here, Ix is an x-phase current or an x-phase current detection value that actually flows when the on period of the upper switching element SWXh is txc, and this on period txc is changed so that the error Δex is compensated. It is a thing. Therefore, in this embodiment, the phase current Ix is regarded as being equal to the x-phase current estimated value Ixe. The ON period tx corresponds to the x-phase voltage command value Vx before correction, and tx = (Vx / Vb) · T, and the ON period txc after the change corresponds to the corrected x-phase voltage command value Vxc. Txc = (Vxc / Vb) · T (x = u, v, w).

From the above equation (31), the corrected x-phase voltage command value Vxc can be calculated by the following equation (x = u, v, w).
Vxc = (Vx + Rlx · Ixe) · Vb / {Vb− (Rhx−Rlx) · Ixe} (32)

  The corrected phase voltage command values Vuc, Vvc, Vwc obtained as described above are output from the correction unit 61 and applied to the three-phase / PWM modulator 41. As described above, the three-phase / PWM modulator 41 generates three types of PWM signals U, V, and W having duty ratios corresponding to these corrected phase voltage command values Vuc, Vvc, and Vwc. The voltage obtained at the output terminals Nu, Nv, Nw by the motor drive circuit 43 being controlled by these three types of PWM signals and its negative signal is applied to the brushless motor 1. As a result, three-phase drive currents (u-phase current, v-phase current, and w-phase current) are supplied to the brushless motor 1.

<3.3 Effects>
According to the present embodiment as described above, the phase voltage command values Vu, Vv, and Vw are corrected based on the resistance values of the upper and lower arm resistors Rhx and Rlx, whereby the upper arm resistor Rhx and the like in the motor drive circuit are corrected. The error generated in the voltage applied to the motor due to the voltage drop caused by the lower arm resistance Rlx is compensated. For this reason, even if the resistance values of the upper arm resistance Rhx and the lower arm resistance Rlx are not negligible, an original voltage is applied to the brushless motor 1 while suppressing an increase in the board size of the motor drive circuit. Further, it is possible to suppress the occurrence of torque ripple due to the absence of the upper arm resistance and the lower arm resistance.

  In addition, according to the present embodiment, the resistance values of the upper arm resistance Rhx and the lower arm resistance Rlx are appropriately updated based on the ratio between the current estimated value and the current detection value, and the phase voltage is determined based on the updated resistance value. The command values Vu, Vv, Vw are corrected. Therefore, even if the resistance values of the upper arm resistance Rhx and the lower arm resistance Rlx vary or fluctuate due to variations in characteristics of electronic components, etc., or temperature changes, the voltage that should be originally applied is accurately applied to the motor, resulting in torque ripple. It is suppressed.

<3.4 Modification>
In the above embodiment, one current sensor 46 is inserted between the motor drive circuit 43 and the ground (FIG. 7), but may be inserted between the motor drive circuit 43 and the power supply line. Further, instead of such a current sensor 46, one current sensor may be provided for each phase, or a current sensor may be provided for each of the two phases of the three phases. In this way, the upper and lower arm resistances Rhx and Rlx of each phase can be easily corrected for each control calculation cycle based on the equations (23) and (24).

<4. Third Embodiment>
FIG. 12 is a block diagram showing the configuration of the motor control device according to the third embodiment of the present invention. As with the first and second embodiments, this motor control device is also a brushless motor 1 having three-phase windings (not shown) of u phase, v phase and w phase in the electric power steering device shown in FIG. And is configured using the ECU 10. Of the components in the present embodiment, the same components as those in the second embodiment are designated by the same reference numerals, and detailed description thereof is omitted.

  The motor control device according to the present embodiment includes a u-phase voltage sensor 48u, a v-phase voltage sensor 48v, and a w-phase voltage sensor 48w as voltage detection means for detecting the voltages of the output terminals Nu, Nv, and Nw in the motor drive circuit 43, respectively. I have. These voltage sensors 48u, 48v, and 48w output the detected values of the voltages at the output terminals Nu, Nv, and Nw as the u-phase voltage detection value V1, the v-phase voltage detection value V2, and the w-phase voltage detection value V3, respectively. .

  The correction unit 71 in the present embodiment uses the phase voltage detected values V1, V2, and V3 in addition to the q-axis current estimated value Iqe and the d-axis current estimated value Ide, and uses the phase voltage command values Vu and Vv. , Vw is corrected. In the following, phase voltage detection values V1, V2, and V3 in the on period txc of the upper switching element SWXh are denoted by Vuh, Vvh, and Vwh, respectively, and the phase voltage detection value V1 in the off period (T-txc) of the upper switching element SWXh. , V2, and V3 are denoted by Vul, Vvl, and Vwl, respectively (see FIG. 11).

  FIG. 13 is a block diagram showing the configuration of the correction unit 71. The correction unit 71 includes a dq axis / three-phase conversion unit 714, a resistance value calculation unit 716, and a command value correction unit 718.

  The dq-axis / 3-phase converter 714 converts the q-axis and d-axis current estimated values Iqe and Ide received from the current estimator 58 into the angle calculator 15 as in the dq-axis / 3-phase converter 614 in the second embodiment. Is converted into a u-phase current estimated value Iue, a v-phase current estimated value Ive, and a w-phase current estimated value Iwe.

The resistance value calculation unit 716 calculates the resistance values of the upper arm resistance Rhx and the lower arm resistance Rlx of each phase in the motor drive circuit 43 according to the following equation using the estimated phase current values Iue, Ive, Iwe (x = U, v, w).
Rhx = (Vb−Vxh) / Ixe (34)
Rlx = (0−Vxl) / Ixe (35)
Here, as described above, Vxh is an x-phase voltage detection value in the on period of the x-phase upper switching element SWXh, and Vxl is the off period of the x-phase upper switching element SWXh, that is, the lower switching element SWXl is on. It is the x-phase voltage detection value in the period.

  In calculating the resistance values of the upper arm resistance Rhx and the lower arm resistance Rlx of each phase, the phase current detection value Ix should be used instead of the phase current estimation value Ixe in the above formulas (34) and (35). It is. Therefore, when the current detection value Ix of each phase is easily obtained, it is preferable to use the phase current detection value Ix instead of the phase current estimation value Ixe in the calculation of the resistance value. However, when the phase voltage command value Vx is corrected, the phase current detection value Ix becomes substantially equal to the phase current estimation value Ixe. Therefore, in the present embodiment, the upper arm resistance is considered in view of the simplification of the configuration. As described above, the estimated phase current value Ixe is used to calculate the resistance values of Rhx and the lower arm resistance Rlx.

  The resistance value calculation unit 716 may calculate the resistance values of the upper and lower arm resistances Rhx and Rlx every time the command voltages Vu, Vv, and Vw of each phase are calculated, that is, every control calculation cycle. However, since the resistance values do not fluctuate rapidly, the calculation of these resistance values is performed in a period longer than the period for obtaining the phase voltage command values Vu, Vv, Vw in this embodiment. This calculation period may be several milliseconds to several seconds, for example, or may be calculated only once when the apparatus is activated. Furthermore, an average value or a representative value of the calculated resistance values for several times may be used.

  The command value correction unit 718 receives the phase voltage command values Vu, Vv, and Vw from the dq axis / three-phase conversion unit 54, and the upper and lower arm resistances Rhx, calculated by the resistance value calculation unit 716 in the correction unit 71. Rlx is received, and the phase voltage command values Vu, Vv, Vw are corrected by the same method as the command value correction unit 618 in the second embodiment using the estimated phase current values Iue, Ive, Iwe together with them. .

  That is, the corrected x-phase voltage command value Vxc is corrected so that the error Δex (see equation (28)) generated by the upper and lower arm resistances Rhx and Rlx is compensated for each phase actual voltage Vxa applied to the brushless motor 1. It is obtained by the aforementioned equation (32). The corrected phase voltage command values Vuc, Vvc, Vwc obtained in this way are output from the correction unit 71 and provided to the three-phase / PWM modulator 41, as in the first and second embodiments. .

  According to the present embodiment as described above, similarly to the first and second embodiments, the phase voltage command values Vu, Vv, Vw are corrected based on the resistance values of the upper and lower arm resistances Rhx, Rlx. Thus, an error that has occurred in the voltage applied to the motor due to a voltage drop due to the upper arm resistance Rhx and the lower arm resistance Rlx in the motor drive circuit is compensated. Further, the resistance values of the upper arm resistance Rhx and the lower arm resistance Rlx are appropriately calculated based on the estimated current value and the voltage detection value, and the phase voltage command values Vu, Vv, Vw are corrected based on the calculated resistance value. Therefore, even if the resistance values of the upper arm resistance Rhx and the lower arm resistance Rlx vary or fluctuate due to variations in characteristics of electronic components, etc., or temperature changes, the voltage that should be originally applied is accurately applied to the motor, resulting in torque ripple. It is suppressed.

  It is not necessary to calculate the resistance values of the upper and lower arm resistances Rhx and Rlx for each control calculation cycle of the brushless motor 1 (every time the phase voltage command value is calculated), and the phase voltages generated by the voltage sensors 48u, 48v, and 48w. It is not necessary to detect V1, V2, and V3 every control calculation cycle. For this reason, according to this embodiment, the calculation load of the microcomputer 70 is reduced. The voltage sensors 48u, 48v, and 48w may be any sensor that can sufficiently respond to the PWM cycle, and the method for realizing the voltage sensors is not limited. For example, when the microcomputer 70 includes an A / D converter, the voltages of the output terminals Nu, Nv, Nw in the motor drive circuit 43 are applied to a predetermined input port of the microcomputer 70 via a voltage dividing circuit or the like. By providing, the voltage sensors 48u, 48v, and 48w can be easily realized.

  In the above embodiment, the phase voltage detection values V1, V2, and V3 by the voltage sensor are required to calculate the resistance values of the upper and lower arm resistors Rhx and Rlx used to correct the phase voltage command values Vu, Vv, and Vw. However, before the calculations of the equations (34) and (35) are performed using these phase voltage detection values V1, V2, and V3 (Vxh, Vxl), a filter operation (smoothing process) corresponding to a low-pass filter is performed. Is preferred. In this way, it is possible to reduce a correction error due to noise in the detection signal.

In the above embodiment, the estimated phase current values Iue, Ive, Iwe are used to calculate the resistance values of the upper and lower arm resistances Rhx, Rlx. Instead, the detected phase current values Iu, Iv, Iw are used. May be used. In this case, the phase current detection values Iu, Iv, and Iw are obtained from the current value Ia detected by the current sensor 46 by providing the correction unit 71 with the phase current calculation unit 612 (FIG. 8) in the second embodiment. be able to. On the other hand, in the above embodiment, since the phase current detection value is not used for calculating the resistance values of the upper and lower arm resistances Rhx and Rlx, the q-axis voltage command value v _qc and the d-axis voltage in the open loop control unit 51 are used. If the current detection value is changed so as not to be used for the calculation of Φ necessary for the calculation of the command value v _dc , the current sensor 46 becomes unnecessary.

In the above embodiment, the u-phase voltage detection value V1, the v-phase voltage detection value V2, and the w-phase voltage detection value V3 are obtained by detecting the voltages at the output terminals Nu, Nv, and Nw in the motor drive circuit 43. In addition, as shown in FIG. 14, the voltages at the upper and lower ends (the connection point to the power supply line and the connection point to the ground) in the motor drive circuit 43 are detected to detect the upper end voltage detection value V4 and the lower end voltage detection value V5. May be obtained. In this case, the resistance values of the upper and lower arm resistances Rhx and Rlx of each phase can be calculated by the following formula (x = u, v, w).
Rhx = (V4-Vxh) / Ixe (37)
Rlu = (V5-Vxl) / Ixe (38)

<5. Other Embodiments>
FIG. 15 is a block diagram showing a configuration of a motor control device according to another embodiment of the present invention. Similarly to the first to third embodiments, this motor control device is also a brushless motor 1 having three-phase windings (not shown) of u phase, v phase and w phase in the electric power steering device shown in FIG. And is configured using the ECU 10. Of the components in the present embodiment, the same components as those in the third embodiment are designated by the same reference numerals, and detailed description thereof is omitted.

  Similar to the third embodiment, the motor control device according to the present embodiment includes a u-phase voltage sensor 48u and a v-phase voltage sensor as voltage detection means for detecting the voltages at the output terminals Nu, Nv, and Nw in the motor drive circuit 43, respectively. 48v, w-phase voltage sensor 48w is provided. These voltage sensors 48u, 48v, and 48w output the detected values of the voltages at the output terminals Nu, Nv, and Nw as the u-phase voltage detection value V1, the v-phase voltage detection value V2, and the w-phase voltage detection value V3, respectively. .

  The correction unit 81 in the present embodiment uses the dq-axis / 3-phase conversion unit based on the phase voltage detection values V1, V2, and V3 without using the q-axis current estimation value Iqe and the d-axis current estimation value Ide. The phase voltage command values Vu, Vv, Vw output from 54 are corrected. For this reason, in this embodiment, unlike the third embodiment (FIG. 12), the current estimation unit 58 is not provided. Hereinafter, the operation of the correction unit 81 in the present embodiment will be described with reference to FIGS. 11 and 15.

Assuming that the on period of the upper switching element SWXh corresponding to the x-phase voltage command value Vx is tx, the x-phase voltage (average value in the cycle T) to be applied to the brushless motor 1 at this time is {Vb · tx + 0 · (T−tx)} / T (39)
(X = u, v, w).

In order to make the x-phase actual voltage Vxa equal to the x-phase voltage, in order to compensate for the deviation of the x-phase actual voltage Vxa with respect to the x-phase voltage command value Vx (the deviation of the voltage at the x-phase output terminal), as shown in FIG. Consider changing the ON period of the upper switching element SWXh from tx to txc. That is, the ON period of the upper switching element SWXh is changed from tx to txc in order to compensate for the error Δex (formula (28)) caused by the upper and lower arm resistances Rhx and Rlx in the x-phase actual voltage Vxa. With this change, the x-phase actual voltage applied to the brushless motor 1 is {Vxh · txc + Vxl · (T−txc)} / T (40)
It becomes. Here, the detected phase voltage values V1, V2, and V3 in the on period txc of the upper switching element SWXh are denoted by Vuh, Vvh, and Vwh, respectively, and the detected phase voltage values V1, V1 in the off period (T-txc) of the upper switching element SWXh. V2 and V3 are denoted by Vul, Vvl, and Vwl, respectively (see FIG. 11).

From the above equations (39) and (40), the following equation is established.
{Vb · tx + 0 · (T−tx)} / T
= {Vxh · txc + Vxl · (T−txc)} / T (41)
The corrected x-phase voltage command value Vxc is obtained from the following equation (x = u, v, w) from the above equation (41) and tx = (Vx / Vb) · T, txc = (Vxc / Vb) · T. .
Vxc = {Vx + (0−Vxl)} · Vb / (Vxh−Vxl) (42)

  The corrected phase voltage command values Vuc, Vvc, Vwc obtained in this way are output from the correction unit 81 and applied to the three-phase / PWM modulator 41. In addition, when a voltage is applied to the brushless motor 1 according to such corrected phase voltage command values Vuc, Vvc, and Vwc, the current flowing through the brushless motor 1 is normally the phase voltage used for the correction. The detection values V1, V2, and V3 change compared to the current at the time of detection. For this reason, since the phase voltage detection values Vxh and Vxl usually change after the correction, the above equation (41) does not necessarily hold. However, when such correction is repeated, the above equation (41) is established.

  According to the embodiment as described above, as in the first to third embodiments, the error generated in the voltage applied to the motor due to the voltage drop due to the upper arm resistance Rhx and the lower arm resistance Rlx in the motor drive circuit is Compensation is performed by correcting the phase voltage command values Vu, Vv, and Vw. Further, the voltages at the output terminals Nu, Nv, Nw in the motor drive circuit 43 are sequentially detected, and the phase voltage command values Vu, Vv, Vw are corrected based on the detected values. Therefore, as in the second and third embodiments, even if the resistance values of the upper arm resistance Rhx and the lower arm resistance Rlx vary or fluctuate due to characteristic variations of electronic components and temperature changes, the voltage to be originally applied Is accurately applied to the motor, and torque ripple is suppressed.

In the above embodiment, the u-phase voltage detection value V1, the v-phase voltage detection value V2, and the w-phase voltage detection value V3 are obtained by detecting the voltages at the output terminals Nu, Nv, and Nw in the motor drive circuit 43. In addition to this, as shown in FIG. 14, the voltages at the upper and lower ends (the connection point to the power supply line and the connection point to the ground) in the motor drive circuit 43 are detected to detect the upper end voltage detection value V4 and the lower end voltage detection value. You may make it obtain V5. In this case, the corrected x-phase voltage command value Vxc is calculated by the following equation instead of the above equation (42).
Vxc = {Vx + (V5−Vxl)} · V4 / (Vxh−Vxl) (43)

  Next, still another embodiment of the present invention will be described. FIG. 16 is a block diagram showing the configuration of the motor control device according to this embodiment. Similarly to the first to third embodiments, this motor control device is also a brushless motor 1 having three-phase windings (not shown) of u phase, v phase and w phase in the electric power steering device shown in FIG. And is configured using the ECU 10. Of the components in the present embodiment, the same components as those in the second embodiment are designated by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, the upper and lower arm resistances Rhx and Rlx of each phase in the motor drive circuit 43 are measured at the time of manufacturing the motor control device, and their measured values (these measured values are also indicated by symbols Rhx and Rlx). Is stored (x = u, v, w). As this resistance value memory | storage part 59, the flash memory etc. which were incorporated in the microcomputer 90 can be used, for example.

  The correction unit 91 in the present embodiment reads the measured values of the upper and lower arm resistances Rhx and Rlx of each phase from the resistance value storage unit 59, and uses these measurement values to correct the correction unit 71 in the third embodiment. Similarly to the command value correction unit 718 (FIG. 13), the corrected phase voltage command value Vxc is calculated according to the equation (32) (x = u, v, w). As is clear from the above, in this embodiment, the resistance value calculation unit 716 in the third embodiment is not necessary.

  The measurement of the upper and lower arm resistances Rhx and Rlx of each phase in the motor drive circuit 43 can be performed as follows. That is, with the x-phase upper switching element SWXh turned on, by measuring a voltage between the power supply terminal Npw and the output terminal Nx while passing a predetermined current through the upper switching element SWXh, A measured value of the arm resistance Rhx can be obtained (see FIG. 9). Similarly, the measured value of the lower arm resistance Rlx of the x phase can be obtained (x = u, v, w).

  The current to be passed through the motor drive circuit 43 for measuring the resistance value at the time of manufacture is not limited as long as it is a value suitable for measurement. For example, the current that should flow during actual operation or when it is actually operated. A flowing current may be used. Further, for measuring the voltage value and the current value, a measuring device outside the apparatus (for testing) is used here, but sensors (not shown) built in the motor drive circuit 43, a current sensor 46, and a voltage sensor are used. May be used.

  According to the present embodiment as described above, the phase voltage command values Vu, Vv, and Vw are corrected based on the measurement values stored in the resistance value storage unit 59, whereby the upper arm resistance Rhx in the motor drive circuit 43 is corrected. In addition, the error generated in the voltage applied to the motor due to the voltage drop caused by the lower arm resistance Rlx is compensated. In addition, even if the resistance values of the upper arm resistance Rhx and the lower arm resistance Rlx vary due to variations in characteristics of electronic components and the like at the time of manufacturing the motor control device, the phase voltage command is based on the measured values at the time of manufacturing the resistance values. Since the values Vu, Vv, and Vw are corrected, the voltage that should be originally applied is accurately applied to the motor, and torque ripple is suppressed. Furthermore, according to the present embodiment, it is possible to reduce the detection circuit (current sensor, voltage sensor) necessary for correcting the phase voltage command value and reduce the calculation load as compared with the other embodiments described above.

<6. Other variations>
In the second and third embodiments, in the resistance value correction unit 616 or the resistance value calculation unit 716, the current estimation unit 58 and the resistance value correction (update) and calculation of the upper arm resistance Rhx and the lower arm resistance Rlx are performed. The phase current estimated value Ixe obtained by the dq axis / 3-phase converters 614 and 714 is used (Equations (23) and (24), Equations (34) and (35)). _Instead , a value obtained by converting the q-axis and d-axis current command values i _qc and i _dc into a command value on the three-phase AC coordinate axis, that is, a phase current command value Ixc may be used (x = u, v, w). . In particular, in the region where the rotational speed (per unit time) of the brushless motor 1 is low, the counter electromotive force is small, and therefore the phase current estimated value Ixe and the phase current command value Ixc are almost equal, so the phase current command value Ixc is used. Even if the resistance value is corrected, an error does not substantially occur.

  Further, in order to accurately correct or calculate the resistance value by the equations (23) and (24) or the equations (34) and (35), it is preferable that the back electromotive force in the brushless motor 1 is small, and the current value is large. Is preferred. Further, the smaller the current value, the smaller the voltage drop due to the upper and lower arm resistances Rhx and Rlx of the motor drive circuit 43. Therefore, the correction in the resistance value correction unit 616 and the calculation of the resistance value in the resistance value calculation unit 716 may be performed only in a region where the rotation speed (per unit time) of the brushless motor 1 is lower than a predetermined value. Alternatively, it may be performed only in a region where the current value of each phase is larger than a predetermined value.

  In each of the above embodiments, the correction map is created, the resistance values of the upper and lower arm resistors Rhx and Rlx are corrected, or the resistance values of the upper and lower arm resistors Rhx and Rlx are calculated for each phase (see FIG. 2, formulas (23) (24) and formulas (34) (35)), instead of these, a common correction map is created for each phase, and resistance values of the upper and lower arm resistances Rhx and Rlx are corrected. Alternatively, the calculation may be performed for each phase. Further, the phase voltage command value Vx may be corrected by using the resistance values of the upper and lower arm resistors Rhx and Rlx corrected or calculated for a specific phase in common for each phase (x = u, v, w). Even in these cases, the same effects as those of the above embodiments can be obtained by correcting the phase voltage command Vx for each phase. In this case, although the degree of the effect obtained differs from the case of each said embodiment, a structure can be simplified rather than each said embodiment.

  In each of the above embodiments, the phase voltage command values Vu, Vv, and Vw are corrected as command values indicating the phase voltage to be applied to drive the brushless motor 1 (this is referred to as “drive command value” in this specification). The phase voltage command values Vuc, Vvc, and Vwc obtained as described above are given to the three-phase / PWM modulator 41 from the microcomputer, and the three-phase / PWM modulator 41 receives the (corrected) phase voltage command values Vuc, Vvc, Based on Vwc, PWM signals U, V, and W are generated as signals for controlling each switching element in the motor drive circuit 43. However, instead of these phase voltage command values Vuc, Vvc, Vwc, on periods tuc, tvc, twc or duty ratios tuc / T, tvc / T, twc / Tc corresponding to these phase voltage command values Vuc, Vvc, Vwc Is output from the correction unit in the microcomputer as a drive command value, and the PWM signal U is output by the three-phase / PWM modulator 41 based on the ON periods tuc, tvc, twc or the duty ratios tuc / T, tvc / T, twc / T. , V, W may be generated.

For example, in the second embodiment (FIG. 7), when the on-period txc (after change) of the upper switching element SWXh is used as the drive command value (x = u, v, w), the equation (32) Instead of the indicated phase voltage command value Vxc, an ON period txc represented by the following equation (33) is calculated by the correction unit 61 and provided to the three-phase / PWM modulator 41. FIG. 17 is a block diagram showing the configuration of the correction unit 61 in this case together with the three-phase / PWM converter 41. Unlike the configuration shown in FIG. 8, the correction unit 61 shown in FIG. 17 includes a converter 617 that converts the phase voltage command value Vx given from the dq axis / 3-phase conversion unit 54 into the on period tx = Vx / Vb. (X = u, v, w), the command value correction unit 618b calculates the changed on-period txc by correcting these on-periods tx according to the following equation (33). These changed on periods tuc, tvc, twc are given to the three-phase / PWM modulator 41. In this case, the three-phase / PWM modulator 41 uses the PWM signals U, tc, twc based on these on periods tuc, tvc, twc. V and W are generated. 17 is the same as the configuration shown in FIG. 8, and the same components are denoted by the same reference numerals.
txc = {(Vb-0) .tx + Rlx.Ixe.T} / {Vb- (Rhx-Rlx) .Ixe}
... (33)

Further, for example, when the on-period txc (after the change) of the upper switching element SWXh is used as the drive command value in the other embodiment (FIG. 15), the phase voltage command value Vxc represented by the equation (42) is used. Thus, an ON period txc represented by the following equation is calculated by the correction unit 81 and is supplied to the three-phase / PWM modulator 41 (x = u, v, w).
txc = {(Vb-0) .tx + (0-Vxl) .T} / (Vxh-Vxl)
In this case, the three-phase / PWM modulator 41 generates PWM signals U, V, and W based on these on periods tuc, tvc, and twc. In this case, as shown in FIG. 14, the upper and lower ends of the motor drive circuit 43 (the connection point to the power supply line and the connection point to the ground) are detected to detect the upper end voltage detection value V4 and the lower end voltage. When configured to obtain the value V5, an ON period txc represented by the following equation is calculated by the correction unit 81 and is supplied to the three-phase / PWM modulator 41 (x = u, v, w).
txc = {(V4-V5) .tx + (V5-Vxl) .T} / (Vxh-Vxl)

  Among the above embodiments, the first embodiment is described on the assumption of feedback control, and the other embodiments are described on the assumption of open loop control. However, the present invention is applicable to any control method, and the control method employed in each embodiment may be interchanged between feedback control and open loop control. However, the influence on the motor current or the motor torque due to the error of the motor applied voltage caused by the upper and lower arm resistances Rhx and Rlx in the motor drive circuit 43 is generally more in the case of open loop control than in the case of feedback control. large. For this reason, the present invention is particularly effective in the case of open loop control.

  The present invention can be applied not only to the above-described column assist type electric power steering apparatus but also to a pinion assist type or rack assist type electric power steering apparatus. The present invention can also be applied to motor control devices other than the electric power steering device. Further, in each of the above embodiments, the number of phases of the brushless motor 1 as a driving target is three, but as is apparent from the above description, the motor control device for driving a brushless motor having a number of phases other than three phases is also used. The present invention can be applied.

It is a block diagram which shows the structure of an electric power steering apparatus provided with the motor control apparatus which concerns on this invention. It is a block diagram which shows the structure of the motor control apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the three-phase alternating current coordinate and dq coordinate in a three-phase brushless motor. It is a figure for demonstrating preparation of the correction map in the said 1st Embodiment. It is a circuit diagram which shows the equivalent circuit for 1 phase for calculating | requiring the voltage shift required for preparation of the correction map in the said 1st Embodiment. It is a figure for demonstrating the correction map produced based on the equivalent circuit shown in FIG. It is a block diagram which shows the structure of the motor control apparatus which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the correction | amendment part in the said 2nd Embodiment. It is a circuit diagram for demonstrating the error of the voltage applied to the motor resulting from upper stage and lower stage arm resistance. It is a wave form diagram for demonstrating the error which arises by the upper stage and lower stage arm resistance about the applied voltage to a motor. It is a wave form diagram for demonstrating the correction | amendment (correction | amendment of phase voltage command value) for compensating the error which arises by the upper stage and lower stage arm resistance about the applied voltage to a motor. It is a block diagram which shows the structure of the motor control apparatus which concerns on the 3rd Embodiment of this invention. It is a block diagram which shows the structure of the correction | amendment part in the said 3rd Embodiment. It is a circuit diagram for demonstrating the modification of the said 3rd Embodiment. It is a block diagram which shows the structure of the motor control apparatus which concerns on other embodiment of this invention. It is a block diagram which shows the structure of the motor control apparatus which concerns on other embodiment of this invention. It is a block diagram which shows the structure of the correction | amendment part in the other modification of the said 2nd Embodiment of this invention with a 3 phase / PWM modulator.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 6 ... Rotor, 10 ... ECU, 20 ... Motor control part, 36 ... Correction calculating part, 37 ... Correction memory | storage part, 43 ... Motor drive circuit, 45 ... Current sensor 10, 60, 70, 80, 90 ... Microcomputer.

Claims (4)

A motor control device for driving a brushless motor,
Control calculation means for obtaining a command value indicating each phase voltage to be applied to the brushless motor, and outputting the command value as a drive command value;
Correction means for correcting the drive command value;
Drive means for driving the brushless motor based on the drive command value corrected by the correction means ;
Current estimation means;
Current detection means ,
The driving means is configured by connecting a pair of switching elements composed of two switching elements connected in series to each other in parallel between the power supply terminal and the ground terminal by the number of phases of the brushless motor, and corresponding to each phase. A connection point between the two switching elements includes an inverter connected to the brushless motor as an output end;
The correction means includes an upper arm resistance that is a resistance component of each phase of the path from the power supply terminal to the output terminal of the inverter, and a lower arm resistance that is a resistance component of each phase of the path from the output terminal to the ground terminal. Based on the above, the drive command value is corrected for each phase ,
The current estimation means estimates a current to be supplied from the inverter to the brushless motor,
The current detection means detects a current supplied from the inverter to the brushless motor,
The correction means includes
Resistance value correcting means for correcting at least one resistance value of the upper and lower arm resistances based on a ratio between an estimated current value obtained by the current estimating means and a detected current value obtained by the current detecting means;
Command value correcting means for correcting the drive command value for each phase so as to compensate for a voltage shift at the output terminal with respect to the voltage indicated by the drive command value based on the resistance value corrected by the resistance value correcting means;
The motor control apparatus characterized by including . A motor control device for driving a brushless motor,
Control calculation means for obtaining a command value indicating each phase voltage to be applied to the brushless motor, and outputting the command value as a drive command value;
Correction means for correcting the drive command value;
Drive means for driving the brushless motor based on the drive command value corrected by the correction means ;
Voltage detection means ,
The driving means is configured by connecting a pair of switching elements composed of two switching elements connected in series to each other in parallel between the power supply terminal and the ground terminal by the number of phases of the brushless motor, and corresponding to each phase. A connection point between the two switching elements includes an inverter connected to the brushless motor as an output end;
The correction means includes an upper arm resistance that is a resistance component of each phase of the path from the power supply terminal to the output terminal of the inverter, and a lower arm resistance that is a resistance component of each phase of the path from the output terminal to the ground terminal. Based on the above, the drive command value is corrected for each phase ,
The voltage detection means detects a voltage of at least one phase at the output terminal of the inverter ;
The correction means includes
The upper and lower arm resistances based on the voltage detection value of the phase detecting the voltage obtained by the voltage detection means and the current value indicating the current of the phase detecting the voltage supplied from the inverter to the brushless motor. Resistance value calculating means for calculating the resistance value of
Command value correction means for correcting the drive command value for each phase so as to compensate for a deviation in voltage at the output terminal with respect to the voltage indicated by the drive command value based on the resistance value calculated by the resistance value calculation means;
The motor control apparatus characterized by including . A motor control device for driving a brushless motor,
Control calculation means for obtaining a command value indicating each phase voltage to be applied to the brushless motor, and outputting the command value as a drive command value;
Correction means for correcting the drive command value;
Drive means for driving the brushless motor based on the drive command value corrected by the correction means,
The driving means is configured by connecting a pair of switching elements composed of two switching elements connected in series to each other in parallel between the power supply terminal and the ground terminal by the number of phases of the brushless motor, and corresponding to each phase. A connection point between the two switching elements includes an inverter connected to the brushless motor as an output end;
The correction means includes an upper arm resistance that is a resistance component of each phase of the path from the power supply terminal to the output terminal of the inverter, and a lower arm resistance that is a resistance component of each phase of the path from the output terminal to the ground terminal. The drive command value is corrected for each phase according to the drive command value so that the voltage shift at the output end caused by the difference between
The correction means includes
Storage means for storing a correction map indicating a correspondence relationship between a command value of a phase voltage to be applied to the brushless motor and a correction amount;
Correction calculation means for calculating the corrected drive command value by correcting the drive command value for each phase according to a correction amount associated with the drive command value output from the control calculation means by the correction map;
The motor control apparatus characterized by including . An electric power steering device that applies a steering assist force to a steering mechanism of a vehicle by a brushless motor,
A motor control device according to any one of claims 1 to 3 ,
The electric power steering device according to claim 1, wherein the motor control device drives a brushless motor that applies a steering assist force to the steering mechanism.

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