JP2009171726A - Motor control unit and electric power steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To drive a brushless motor so as to suppress the generation of torque ripple caused by resistance differences among phases. <P>SOLUTION: An open loop control unit 22 obtains command voltage values v<SB>d</SB>, v<SB>q</SB>on dq axes based on command current values i<SB>d</SB><SP>*</SP>, i<SB>q</SB><SP>*</SP>on dq axes, the number Φ of armature winding interlinkage magnetic flux and the angular speed ω<SB>e</SB>of a rotor in the motor. A dq axes/three-phase conversion unit 23 converts the command voltage values v<SB>d</SB>, v<SB>q</SB>into phase voltage command values Vu, Vv, Vw. A data acquisition unit 41 obtains angle dependence data indicating dependence on an electrical angle indicated by a second-order harmonic component concerning the electrical angle of the d-axis component or the q-axis component of motor current based on a current detection value i<SB>a</SB>and an electrical angle θ. A correction coefficient determination unit 42 determines a correction coefficient for correcting the phase voltage command values so as to reduce the dependence based on the angle dependence data. A correction execution unit 43 corrects the phase correction values Vu, Vv, Vw obtained by the dq axes/three-phase conversion unit 23 based on the determined correction coefficient. <P>COPYRIGHT: (C)2009,JPO&INPIT

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.

  In general, a motor control device detects a current flowing through a motor in order to control torque generated by the motor, and performs PI control (proportional integral control) based on a difference between the current to be supplied to the motor and the detected current. A motor control device that drives a three-phase brushless motor is provided with two or three current sensors in order to detect a current of two or more phases.

In relation to the present invention, Patent Document 1 discloses that a d-axis voltage command value and a q-axis voltage command value are obtained using a motor circuit equation. Patent Document 2 discloses that the d-axis current command value is corrected according to the temperature of the motor.
JP 2001-187578 A JP 2000-184773 A

  In the motor control device included in the electric power steering device, the current sensor needs to detect a large current of 100 A or more. This current sensor is large in size and hinders downsizing of the control device of the electric power steering device. For this reason, in a motor control device included in an electric power steering device or the like, reduction of current sensors is an issue. If the number of current sensors can be reduced, the cost and power consumption of the motor control device can be reduced.

  Possible ways to reduce the number of current sensors are to reduce the number of current sensors to one and perform the same feedback control as before, or remove all current sensors and perform open loop control according to the motor circuit equation. It is done.

Among these methods, the former method has a problem that, depending on the rotational position of the rotor of the motor, a single current sensor may not be able to detect multiple phases of current necessary for feedback control, and the motor control becomes discontinuous. There is. In contrast, the latter method does not cause such a problem. However, unlike the case of feedback control for current, the latter method causes ripples (called “torque ripples”) in the output torque of the motor when there is a difference in resistance value between phases due to the following factors: There's a problem.
i) When a relay is arranged in two phases for fail-safe, a resistance difference corresponding to the contact resistance of the relay is generated.
ii) The contact resistance of the connector for connecting the motor control device and the motor differs between phases.

  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.

  Therefore, an object of the present invention is to provide a motor control device capable of driving a brushless motor so that generation of torque ripple due to resistance difference between phases is suppressed. Another object of the present invention is to provide an electric power steering apparatus provided with such a motor control device.

A first invention is a motor control device for driving a brushless motor,
Control arithmetic means for obtaining a phase voltage command value indicating a phase voltage to be applied to the brushless motor;
Current detecting means for detecting a current flowing through the brushless motor;
Rotational position detecting means for detecting the rotational position of the rotor in the brushless motor;
The dependence of the ratio of the current flowing in the brushless motor on the q-axis or d-axis component to the q-axis or d-axis command value relative to the electrical angle of the brushless motor indicated by the ratio of the ratio to the electrical angle is reduced. Correction means for correcting the phase voltage command value based on the detection result of the current detection means and the detection result of the rotational position detection means,
A motor control device comprising: drive means for driving the brushless motor based on the phase voltage command value corrected by the correction means.

According to a second invention, in the first invention,
The control calculation means calculates q-axis and d-axis components of a voltage to be applied to the brushless motor as q-axis and d-axis voltage command values, respectively, and applies the q-axis and d-axis voltage command values to the brushless motor. The phase voltage command value is obtained by converting each phase component of the voltage to be
The correction means includes
Based on the detection result of the current detection means, the ratio of the q-axis component of the current flowing to the brushless motor to the q-axis voltage command value and the ratio of the d-axis component of the current flowing to the brushless motor to the d-axis voltage command value Data acquisition means for calculating at least one and storing the calculated ratio as angle-dependent data in association with the electrical angle of the brushless motor based on the detection result of the rotational position detection means;
Correction coefficient determining means for determining a correction coefficient for correcting the phase voltage command value so that the dependence on the electrical angle indicated by the second harmonic component is reduced based on the angle dependency data;
Correction execution means for correcting the phase voltage command value based on the correction coefficient determined by the correction coefficient determination means.

According to a third invention, in the first invention,
The control calculation means determines q-axis and d-axis components of the current to be passed to the brushless motor as q-axis and d-axis current command values, respectively, and applies the brushless motor to the brushless motor based on the q-axis and d-axis current command values. The q-axis and d-axis components of the voltage to be applied are calculated as q-axis and d-axis voltage command values, respectively, and the q-axis and d-axis voltage command values are converted into respective phase components of the voltage to be applied to the brushless motor. To obtain the phase voltage command value,
The correction means includes
Based on the detection result of the current detection means, the ratio of the q-axis component of the current flowing to the brushless motor to the q-axis current command value and the ratio of the d-axis component of the current flowing to the brushless motor to the d-axis current command value Data acquisition means for calculating at least one and storing the calculated ratio as angle-dependent data in association with the electrical angle of the brushless motor based on the detection result of the rotational position detection means;
Correction coefficient determining means for determining a correction coefficient for correcting the phase voltage command value so that the dependence on the electrical angle indicated by the second harmonic component is reduced based on the angle dependency data;
Correction execution means for correcting the phase voltage command value based on the correction coefficient determined by the correction coefficient determination means.

According to a fourth invention, in the first invention,
The correction means is based on the current and rotational position detection values obtained by the current detection means and the rotational position detection means when the current detection value obtained by the current detection means is smaller than a predetermined threshold value, The phase voltage command value is corrected so that the dependence on the electrical angle indicated by the second harmonic component is reduced.

According to a fifth invention, in the first invention,
The correcting means is based on the second harmonics based on the detected current and rotational position values obtained by the current detecting means and the rotational position detecting means when the angular velocity of the brushless motor rotor is equal to or less than a predetermined threshold value. The phase voltage command value is corrected so that the dependence on the electrical angle indicated by the wave component is reduced.

A sixth 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 fifth inventions;
The motor control device drives a brushless motor that applies a steering assist force to the steering mechanism.

  According to the first aspect of the invention, the phase voltage command value is corrected so that the dependence of the current (motor current) flowing in the brushless motor on the electrical angle of the q-axis or d-axis component is reduced, so that The difference in resistance value (phase resistance difference) between the motor currents is reduced or eliminated, and torque ripples generated in the brushless motor due to the phase resistance difference are suppressed.

  According to the second aspect of the invention, at least one of the ratio of the current (motor current) flowing through the brushless motor to the q-axis voltage command value of the q-axis component and the ratio of the d-axis component of the motor current to the d-axis voltage command value is calculated. Then, the calculated ratio is acquired as angle dependency data in association with the electrical angle. Since this angle dependency data is data based on the ratio of the motor current to the voltage command value, the influence on the q-axis or d-axis component of the motor current due to the change in the applied voltage to the brushless motor is removed, and the motor current This properly shows the dependence of the q-axis or d-axis component on the electrical angle. Based on such angle dependency data, the phase voltage command value is corrected so that the dependency of the current flowing in the brushless motor on the electrical angle of the q-axis or d-axis component is reduced. Therefore, torque ripple generated in the brushless motor due to the interphase resistance difference can be more reliably suppressed.

  According to the third aspect of the invention, at least one of a ratio of the current (motor current) flowing through the brushless motor to the q-axis current command value of the q-axis component and a ratio of the d-axis component of the motor current to the d-axis current command value is calculated. Then, the calculated ratio is acquired as angle dependency data in association with the electrical angle. Since this angle dependence data is data based on the ratio of the motor current to the current command value, the motor current due to a change in current to be supplied to the brushless motor, that is, a change in current command value (or a corresponding change in applied voltage). The influence of the motor current on the q-axis or d-axis component is removed, and the dependence of the motor current on the electrical angle of the q-axis or d-axis component is appropriately shown. Based on such angle dependency data, the phase voltage command value is corrected so that the dependency of the current flowing in the brushless motor on the electrical angle of the q-axis or d-axis component is reduced. Therefore, the torque ripple generated in the brushless motor due to the interphase resistance difference can be more reliably suppressed.

  According to the fourth aspect of the present invention, the detected value of the motor current and the detected value of the rotor rotational position of the motor used for correcting the phase voltage command value are less than a predetermined threshold value. Get when you are small. That is, since the motor current is smaller than the threshold value, the current detection value and the rotational position detection value for correction are acquired when the increase in resistance value due to heat generation is small. As a result, since the detected current value and the detected rotational position value obtained when the interphase resistance difference is relatively larger than the resistance value are used for correcting the phase voltage command value, the interphase resistance difference is accurately compensated. Correction is possible, and the generation of torque ripple due to the interphase resistance difference can be more reliably suppressed.

  According to the fifth aspect of the invention, the detected value of the motor current and the detected value of the rotor rotational position of the motor used for correcting the phase voltage command value are less than a predetermined threshold value for the angular velocity of the brushless motor rotor. Get when it is. That is, the current detection value and the rotational position detection value are acquired when the back electromotive force is small and the voltage applied to the resistance of each phase is relatively large. By using such a current detection value and rotational position detection value, it is possible to perform correction for accurately compensating for the interphase resistance difference, and the generation of torque ripple due to the interphase resistance difference can be more reliably suppressed.

  According to the sixth aspect, since the phase voltage command value indicating the voltage to be applied to the brushless motor that gives the steering assist force is corrected, the occurrence of torque ripple due to the interphase resistance difference is suppressed. An electric power steering apparatus with good steering feeling can be provided.

<1. Electric power steering device>
FIG. 1 is a schematic diagram showing the configuration of an electric power steering apparatus according to an embodiment of the present invention, together with the configuration of a vehicle related thereto. The electric power steering apparatus shown in FIG. 1 includes 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 (hereinafter referred to as ECU) 10. This is a column assist type electric power steering device.

  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 T 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 T, 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.

  The electric power steering device according to the embodiment of the present invention is characterized by a control device (motor control device) that drives the brushless motor 1. Therefore, hereinafter, a motor control device included in the electric power steering device according to each embodiment will be described.

<2. First Embodiment>
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 phase compensator 11, a microcomputer (hereinafter abbreviated as “microcomputer”) 20, a three-phase / PWM (Pulse Width Modulation) modulator 12, a motor drive circuit 13, and a current sensor 14.

  The ECU 10 receives the steering torque T 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 phase compensator 11 performs phase compensation on the steering torque T. 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 12 and the motor drive circuit 13 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 12 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 13 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. By controlling the conduction state of the MOS-FET using the PWM signal, three-phase driving currents (u-phase current, v-phase current and w-phase current) are supplied to the brushless motor 1.

  The current sensor 14 functions as a current detection unit that detects a current flowing through the brushless motor 1. The current sensor 14 is constituted by, for example, a resistor or a Hall element, and only one current sensor 14 is provided between the motor drive circuit 13 and the power source. In the example shown in FIG. 2, the current sensor 14 is provided between the motor drive circuit 13 and the negative side (ground) of the power supply. However, the current sensor 14 is provided between the motor drive circuit 13 and the positive side of the power supply. It may be provided.

While the brushless motor 1 is rotating, the current value detected by the current sensor 14 changes according to the PWM signal. Within one cycle of the PWM signal, there are a case where the current sensor 14 detects a one-phase driving current and a case where the sum of the two-phase driving 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 14 while the brushless motor 1 is rotating. The current value i _a detected by the current sensor 14 is input to the microcomputer 20.

  The microcomputer 20 executes a program stored in a memory (not shown) built in the ECU 10 to thereby execute a command current calculation unit 21, an open loop control unit 22, a dq axis / three-phase conversion unit 23, and an angle calculation unit. 24, the angular velocity calculation unit 25, the Φ calculation unit 26, the data acquisition unit 41, the correction coefficient determination unit 42, and the correction execution unit 43. The command current calculation unit 21, the open loop control unit 22, and the dq axis / three-phase conversion unit 23 constitute a control calculation unit that obtains a phase voltage command value used to drive the brushless motor 1.

  The microcomputer 20 should be given to the motor drive circuit 13 according to the circuit equation of the motor based on the current command value indicating the amount of current to be supplied to the brushless motor 1 and the angular velocity of the rotor of the brushless motor 1 as shown below. A voltage command value indicating the voltage is obtained.

The angle calculation unit 24 calculates a rotation angle (hereinafter referred to as an angle θ) 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 25 obtains the angular velocity ω _e of the rotor of the brushless motor 1 based on the angle θ. 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 angle θ. That is, the angle calculation unit 24 calculates the electrical angle θ in the brushless motor 1.

The command current calculation unit 21 obtains the d-axis component and the q-axis component of the current to be supplied to the brushless motor 1 based on the steering torque T after phase compensation (the output signal of the phase compensator 11) and the vehicle speed S (hereinafter referred to as “the current value to be supplied to the brushless motor 1”). The former value is called d-axis current command value i _d ^* , and the latter value is called q-axis current command value i _q ^* ). More specifically, the command current calculation unit 21 has a built-in table (hereinafter referred to as an assist map) that stores the correspondence between the steering torque T and the command current using the vehicle speed S as a parameter, and refers to the assist map. To obtain the current command value. By using the assist map, when a certain amount of steering torque is applied, the current to be supplied to the brushless motor 1 in order to generate a steering assist force having an appropriate magnitude according to the magnitude is shown. The d-axis current command value i _d ^* and the q-axis current command value i _q ^* can be obtained.

The q-axis current command value i _q ^{* obtained} by the command current calculation unit 21 is a signed current value, and the sign indicates the steering assist direction. For example, when the sign is positive, steering assistance for turning to the right is performed, and when the sign is minus, steering assistance for turning to the left is performed. Further, the d-axis current command value i _d ^* is typically set to zero.

The open loop control unit 22 obtains the d-axis component and the q-axis component of the voltage to be applied to the brushless motor 1 based on the d-axis current command value i _d ^* , the q-axis current command value i _q ^* and the angular velocity ω _e ( Hereinafter, the former value is referred to as a d-axis voltage command value v _d and the latter value is referred to as a q-axis voltage command value v _q ). The d-axis voltage command value v _d and the q-axis voltage command value v _q are calculated using the motor circuit equations shown in the following equations (1) and (2).
v _d = (R + PL _d ) i _d ^* −ω _e L _q i _q ^* (1)
v _q = (R + PL _q ) i _q ^* + ω _e L _d i _d ^* + ω _e Φ (2)
In equations (1) and (2), v _d is a d-axis voltage command value, v _q is a q-axis voltage command value, i _d ^* is a d-axis current command value, i _q ^* is a q-axis current command value, 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, and Φ is the U, V, W-phase armature winding chain √ (3/2) times the maximum value of the number of magnetic flux exchanges, 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 driving circuit 13 in the ECU 10, the wiring resistance, and the like. This is the same in other embodiments.

The dq-axis / 3-phase converter 23 converts the d-axis voltage command value v _d and the q-axis voltage command value v _q obtained by the open loop control unit 22 into a voltage command value on the three-phase AC coordinate axis. More specifically, the dq-axis / three-phase conversion unit 23 uses the following equations (3) to (5) based on the d-axis voltage command value v _d and the q-axis voltage command value v _q to determine the u-phase voltage command value. Request V _u, v-phase voltage instruction value V _v and w-phase voltage instruction value V _w.
V _u = √ (2/3) × {v _d × cos θ−v _q × sin θ} (3)
V _v = √ (2/3) × {v _d × cos (θ-2π / 3)
−v _q × sin (θ−2π / 3)} (4)
V _w = −V _u −V _v (5)
The angle θ included in the above formulas (3) and (4) is an electrical angle obtained by the angle calculation unit 24. The u-phase voltage command value V _u , the v-phase voltage command value V _v, and the w-phase voltage command value V _w are also collectively referred to as “phase voltage command values V _u , V _v , V _w ”.

The data acquisition unit 41 includes a current value i _a detected by the current sensor 14, an electrical angle θ calculated by the angle calculation unit 24, a q-axis voltage command value v _q calculated by the open loop control unit 22, and Is entered. Data acquisition unit 41, first u-phase flowing to the brushless motor 1 based on the current value i _a and v-phase current (hereinafter, the former value u-phase current detection value i _u, the latter value v-phase current detection value i _v )), and convert these into current values on the dq coordinate axes. More specifically, the data acquisition unit 41, based on the u-phase current detection value i _u and the v-phase current detection value i _v, obtaining a q-axis current detection value i _q using the following equation (6).
i _q = √2 × {i _v × cos θ−i _u × cos (θ−2π / 3)} (6)

Next, the data acquisition unit 41 compares the q-axis current detection value i _{q with} the q-axis voltage command value v _q (hereinafter referred to as “voltage vs. q-axis current gain value” or “q-axis current gain value”) i _q / v _q is obtained when v _q ≠ 0, and this q-axis current gain value i _q / v _q is associated with the electrical angle θ calculated by the angle calculation unit 24 at the time of current detection by the current sensor 14, Store in the data acquisition unit 41. Data acquisition unit 41 in this manner, stores the q-axis current gain value i _q / v _q is in association with an electrical angle of that point each time it is calculated the q-axis current gain value i _q / v _q Go. As a result, data indicating q-axis current gain values i _q / v _q for various electrical angles θ of 0 to 360 degrees (hereinafter referred to as “angle dependency data”) is obtained in the data acquisition unit 41. As will be described later, since the dependence of the q-axis current on the electrical angle θ is based on the second harmonic component, the range of the electrical angle θ when acquiring the angle dependence data is a range narrower than 0 to 360 degrees. For example, it may be in the range of 90 to 270 degrees (this is the same in the modified examples and other embodiments described later).

The correction coefficient determination unit 42 corrects the phase voltage command values V _u , V _v , and V _w to be corrected by the correction execution unit 43 as will be described later, based on the angle dependency data obtained as described above. The coefficients g _u , g _v and g _w are determined.

The correction execution unit 43 includes the correction coefficients g _u , g _v , and g _w described above, the armature winding linkage magnetic flux number Φ calculated by the Φ calculation unit 26, and the angular velocity ω calculated by the angular velocity calculation unit 25. _e is input, and the correction execution unit 43 corrects the phase voltage command values V _u , V _v , and V _w according to the following equations (7) to (9).
_{V uc = (V u -e u} ) · g u + e u ... (7)
V _vc = (V _v −e _v ) · g _v + e _v (8)
V _wc = (V _w −e _w ) · g _w + e _w (9)
In the above formula (7) ~ (9), e u, e v, e w are each, u phases in the brushless motor 1, v-phase, a counter electromotive force of the w-phase (induced voltage). Incidentally, the q-axis component of the back electromotive force of the brushless motor 1 is ω _e Φ, and the d-axis component is zero. Therefore, the correction execution unit 43 converts the d-axis component and the q-axis component of the back electromotive force into back electromotive forces on the three-phase AC coordinate axis by the following equations (10) to (12), and obtains each phase obtained by the conversion. the counter electromotive force e _u, e _v, the equation using e _w (7) the phase voltage command values V _uc corrected according ~ (9), V _vc, calculates a V _wc.
e _u = √ (2/3) × {0 × cos θ−ω _e Φ × sin θ} (10)
e _v = √ (2/3) × {0 × cos (θ−2π / 3)
−ω _e Φ × sin (θ−2π / 3)} (11)
e _w = −e _u −e _v (12)
The angle θ included in the equations (10) and (11) is an electrical angle obtained by the angle calculation unit 24.

As described above, the microcomputer 20 obtains the current command values i _d ^* and i _q ^* on the dq coordinate axis, obtains the voltage command values v _d and v _q on the dq coordinate axis according to the motor circuit equation, and the d axis. In addition, a process of converting the q-axis voltage command values v _d and v _q into the phase voltage command values V _u , V _v and V _w and a process of correcting the phase voltage command values V _u , V _v and V _w are performed. The three-phase / PWM modulator 12 outputs three types of PWM signals based on the corrected phase voltage command values V _uc , V _vc , V _wc obtained by the microcomputer 20. As a result, sinusoidal currents corresponding to the corrected voltage command values V _uc , V _vc , and V _wc for each phase flow 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 Φ calculating unit 26 receives the current value i _a detected by the current sensor 14, the electrical angle θ calculated by the angle calculating unit 24, and the angular velocity ω _e calculated by the angular velocity calculating unit 25. Φ calculator 26 first current value i _a the basis seek current of u-phase and v-phase flowing in the brushless motor 1 (hereinafter, the former value u-phase current detection value i _u, the latter value the v-phase current detection Value i _v ) and converting these into current values on the dq coordinate axis using the following equations (13) and (14), the d-axis current detection value i _d and the q-axis current detection value i _q are obtained. Ask.
i _d = √2 × {i _v × sin θ−i _u × sin (θ−2π / 3)} (13)
i _q = √2 × {i _v × cos θ−i _u × cos (θ−2π / 3)} (14)

Next, when ω _e ≠ 0, the Φ calculating unit 26 uses the following formula ( _q) based on the q-axis voltage command value v _q , the d-axis current detection value i _d , the q-axis current detection value i _q and the angular velocity ω _e. 15) is used to determine the number of armature winding linkage magnetic fluxes Φ included in the equation (2).
Φ = {v _q − (R + PL _q ) i _q −ω _e L _d i _d } / ω _e (15)
Equation (15) substitutes d-axis current detection value i _d and q-axis current detection value i _q for d-axis current command value i _d ^* and q-axis current command value i _q ^* of equation (2), and The equation is solved for Φ.

The Φ calculating unit 26 outputs the obtained Φ value to the open loop control unit 22. The open loop control unit 22 uses the Φ value calculated by the Φ calculation unit 26 when _{obtaining the} q-axis voltage command value v _q using the equation (2). As described above, the microcomputer 20 obtains the armature winding linkage magnetic flux number Φ included in the motor circuit equation, and uses the Φ value when obtaining the q-axis voltage command value v _q .

The Φ calculating unit 26 may obtain the Φ value at an arbitrary timing as long as ω _e ≠ 0. For example, the Φ calculating unit 26 may obtain the Φ value at a predetermined time interval, obtain the Φ value only once after the start of the driving of the brushless motor 1, or the Φ value when the state such as temperature changes. You may ask for. In addition, since an error is likely to occur in the Φ value obtained when ω _e is close to zero, the Φ calculation unit 26 may obtain the Φ value only when ω _e is equal to or greater than a predetermined threshold.

  As described above, the motor control device according to the present embodiment obtains the voltage command value by open loop control according to the motor circuit equation based on the current command value and the angular velocity of the rotor, and the current value detected by the current sensor. Φ included in the circuit equation of the motor is obtained based on the above, and the Φ value is used when obtaining the voltage command value. Therefore, according to the motor control device according to the present embodiment, even when the Φ value included in the circuit equation of the motor fluctuates due to manufacturing variation or temperature change, the Φ value is obtained based on the current value detected by the current sensor. The brushless motor can be driven with high accuracy, and a desired motor output can be obtained.

  Further, the motor control device according to the present embodiment is provided with only one current sensor. Therefore, according to the motor control device according to the present embodiment, it is possible to reduce the size, cost and power consumption of the motor control device by reducing the number of current sensors. Furthermore, since the motor control device according to the present embodiment performs open loop control, the motor control does not become discontinuous, unlike the motor control device that performs feedback control using one current sensor. Therefore, according to the motor control device according to the present embodiment, it is possible to suppress sound and vibration.

<2.1 Principle of correction>
In this embodiment, the torque ripple caused by the difference between the u-phase, v-phase, and w-phase regarding the value of the circuit resistance including the armature winding resistance (hereinafter, this difference is referred to as “phase resistance difference”). A correction unit 40 is provided to correct the phase voltage command values V _u , V _v , and V _w to suppress the occurrence. The correction unit 40 includes the data acquisition unit 41, the correction coefficient determination unit 42, and the correction execution unit 43 described above. The correction execution unit 43 is a correction obtained by the data acquisition unit 41 and the correction coefficient determination unit 42. The phase voltage command values V _u , V _v , and V _w are corrected according to the above-described equations (7) to (9) using the coefficients g _u , g _v , and g _w . Hereinafter, correction of such phase voltage command values V _u , V _v , and V _w will be described with reference to FIGS.

FIG. 4 is a diagram for explaining the principle of the correction, and shows the relationship between the q-axis current that is the q-axis component of the current flowing through the brushless motor 1 and the electrical angle θ. More specifically, the relationship between the q-axis current i _qo and the electrical angle θ when there is no interphase resistance difference and the relationship between the q-axis current i _qa and the electrical angle θ when there is an _inter- phase resistance difference are shown. . Now, the circuit resistances including the armature winding resistances for the u-phase, v-phase, and w-phase are respectively called “u-phase resistance”, “v-phase resistance”, and “w-phase resistance” (or collectively referred to as “phase These are collectively referred to as “resistors”, and are represented by the symbols “Ru”, “Rv”, and “Rw”, respectively. The symbols “Ru”, “Rv”, and “Rw” also indicate the values of the u-phase resistance, the v-phase resistance, and the w-phase resistance, respectively.

As shown in FIG. 4, when there is no resistance difference between these phase resistances Ru, Rv, Rw (Ru = Rv = Rw), that is, when there is no interphase resistance difference, the q-axis current i _qo is an electrical angle θ. Regardless of the value (fixed). On the other hand, the q-axis current i _qa when there is an interphase resistance difference depends on the electrical angle θ. More specifically, the q-axis current i _{qa in the} case where there is an interphase resistance difference includes a second harmonic component with respect to the electrical angle θ, as shown in FIG. This is because the u, v, and w phase voltages (sine wave-like) applied to the brushless motor 1 have the same amplitude, but if there is a phase difference, u, v, Since the amplitude _differs between the w-phase currents i _u , i _v , and i _w , the q-axis current i _q obtained from the equation (6) is not fixed to a constant value, and the second harmonic component for the electrical angle θ is It is because it contains. The amplitude and phase of the second harmonic component vary depending on the magnitude relationship of the resistance values among the phase resistances Ru, Rv, Rw.

Therefore, by correcting the phase voltage command values V _u , V _v , and V _w according to the phase of the q-axis current i _q in the brushless motor 1, the dependence of the q-axis current i _{q on} the electrical angle is reduced or eliminated. Thus, it is possible to suppress the occurrence of torque ripple due to the interphase resistance difference. The correction unit 40 in the present embodiment corrects the phase voltage command values V _u , V _v , and V _w so as to suppress torque ripple based on such a principle. The details of this correction method will be described below.

<2.2 Correction method>
In the present embodiment, the q-axis current gain value i _q / v _q that is the ratio of the q-axis current detection value i _{q to} the q-axis voltage command value v _{q is} calculated by the data acquisition unit 41 of the correction unit 40 as described above. Data obtained for various electrical angles θ and indicating q-axis current gain values i _q / v _q for various electrical angles θ of 0 to 360 degrees is stored in the data acquisition unit 41 as angle dependency data. Here, storing the data indicating the q-axis current gain value i _q / v _q instead of the q-axis current detection value i _q eliminates the influence on the q-axis current due to the change in the voltage applied to the brushless motor 1. This is because the data indicating the dependence of the q-axis current on the electrical angle θ is appropriately acquired.

In the correction coefficient determination unit 42 of the correction unit 40, based on the angle dependency data acquired as described above, the electrical angle at which the q-axis current gain value i _q / v _q becomes maximum (hereinafter referred to as “peak electrical angle”). ) Θp is obtained, and the correction coefficients g _u , g _v , and g _{w in} the above-described equations (7) to (9) are determined according to the peak electrical angle θp. The second harmonic component of the electrical angle θ included in the q-axis current gain value i _q / v _q has two peaks in the range of θ = 0 to 360 degrees. For determining g _u , g _v , and g _w , the peak electrical angle θp included in the range of θ = 90 to 270 degrees is used. However, the range of the electrical angle θ used for determining the correction coefficients g _u , g _v , and g _w is not limited to this. Further, as can be seen from the above equations (7) to (9), when the value of the correction coefficient g _x (x = u, v, w) is 1, the voltage applied to the resistance Rx of the phase ( (Amplitude) is the same as before the correction, and when the value of the correction coefficient g _x (x = u, v, w) is larger than 1, the voltage (the amplitude) applied to the resistance Rx of the phase is higher than that before the correction. Also grows.

  Further, the following matters are derived from the above equation (6). That is, when the phase resistances Ru, Rv, and Rw are in the relationship of Rv> Rw, Ru, for example, as shown in FIG. 5A, the peak electrical angle θp exists in the range of θ = 90 to 150 degrees, and Ru> When there is a relationship of Rv, Rw, for example, as shown in FIG. 5B, there is a peak electrical angle θp in the range of θ = 150 to 210 degrees, and when there is a relationship of Rw> Ru, Rv, for example, FIG. As shown in (c), the peak electrical angle θp exists in the range of θ = 210 to 270 degrees.

Therefore, the correction coefficient determining unit 42 in the present embodiment determines the correction coefficients g _u , g _v , and g _w as follows. In the following, correction coefficient based on the angular dependence data g _u, g _v, at the time the determination of g _w is not at all made, these correction factors g _u, g _v, appropriate initial values as g _w, for example " It is assumed that 1 "(a value corresponding to no correction) is set.

(A1) When 90 [deg] ≦ θp <150 [deg] A value obtained by increasing the current v-phase correction coefficient g _v is newly set as a v-phase correction coefficient g _v . This means that the applied voltage to the v-phase resistance Rv is made larger than before correction in order to reduce the amplitude difference between the v-phase current and the u-phase and w-phase currents.
(A2) When 150 [deg] ≦ θp <210 [deg] A value obtained by increasing the current u-phase correction coefficient g _u is newly set as a u-phase correction coefficient g _u . This means that the applied voltage to the u-phase resistor Ru is made larger than before correction in order to reduce the amplitude difference between the u-phase current and the v-phase and w-phase currents.
(A3) When 210 [deg] ≦ θp <270 [deg] A value obtained by increasing the current w-phase correction coefficient g _w is newly set as a w-phase correction coefficient g _w . This means that the voltage applied to the w-phase resistor Rw is made larger than before correction in order to reduce the amplitude difference between the w-phase current and the u-phase and v-phase currents.

According to the corrections (A1) to (A3) described above, the amplitude difference among the u-phase, v-phase, and w-phase currents is reduced or eliminated, so the q-axis current i _q with respect to the electrical angle θ. As a result, the torque ripple in the brushless motor 1 is suppressed. Hereinafter, specific examples of such correction will be further described.

For example, when the peak electrical angle θp obtained based on the angle dependency data is 150 [deg] as shown in FIG. 6A, the phase resistances Ru, Rv, and Rw are Ru = Rv> Rw. There is a relationship. In this case, in the correction coefficient determination unit 42, the current u-phase and v-phase correction coefficients g _u and g _v are changed to, for example, 1.1 times the value. When the peak electrical angle θp obtained based on the angle dependency data is 165 [deg] as shown in FIG. 6B, the phase resistances Ru, Rv, and Rw are Ru>Rv> Rw. There is a relationship. In this case, in the correction coefficient determination unit 42, the current u-phase correction coefficient g _u is changed to a value that is 1.1 times the current value, and the current v-phase correction coefficient g _v is changed to a value that is, for example, 1.05 times the current value. Is done. Furthermore, when the peak electrical angle θp obtained based on the angle dependency data is 180 [deg] as shown in FIG. 6C, the phase resistances Ru, Rv, and Rw are Ru> Rv = Rw. There is a relationship. In this case, in the correction coefficient determination unit 42, the current u-phase correction coefficient _gu is changed to, for example, 1.1 times the value. Furthermore, when the peak electrical angle θp obtained based on the angle dependency data is 195 [deg] as shown in FIG. 6D, the phase resistances Ru, Rv, Rw are Ru>Rw> Rv. Therefore, in the correction coefficient determination unit 42, the current u-phase correction coefficient g _u is changed to, for example, 1.1 times the value, and the current w-phase correction coefficient g _w is, for example, 1.05 times the value. Is changed to the value of

In the above, the magnification when changing the current correction coefficients g _u , g _v , and g _w or the value after the change is the second harmonic of the electrical angle θ included in the q-axis current gain value i _q / v _q. It is determined according to the fluctuation range (amplitude) of the component. The numerical values “1.1 times” and “1.05 times” shown above are merely examples, and actually, the experimental data or the computer simulation results are used to determine the q-axis current relative to the electrical angle θ. The correction coefficient determination unit 42 adjusts the determination method of the correction coefficients g _u , g _v , and g _w so that appropriate correction coefficients g _u , g _v , and g _w that can suppress the dependency are determined. Is preferred.

In the correction execution unit 43, the phase voltage command values V _u , V _v , and V _w are determined according to the above equations (7) to (9) using the correction coefficients g _u , g _v , and g _w determined as described above. It is corrected. Such corrected phase voltage command values V _uc , V _vc , V _wc are used for driving the brushless motor 1 as described above.

  As described above, according to the present embodiment, the phase voltage command value is corrected so that the dependence of the q-axis current on the electrical angle θ indicated by the second harmonic component related to the electrical angle θ of the q-axis current is reduced or eliminated. Therefore, the resistance difference between the phases is compensated, and the occurrence of torque ripple due to the resistance difference between the phases is suppressed. Therefore, by using the motor control device according to the present embodiment to drive the brushless motor 1 that generates the steering assist force in the electric power steering device as shown in FIG. 1, a good steering feeling can be given to the driver. Can be provided.

<3. Modification of First Embodiment>
Next, a modification of the above embodiment will be described. Note that, among the constituent elements of the modified example described below, the same or corresponding parts as those of the above-described embodiment are denoted by the same reference numerals and detailed description thereof is omitted.

In the above embodiment, data indicating the q-axis current gain values i _q / v _q for various electrical angles θ of 0 to 360 degrees is acquired as the angle dependency data by the data acquisition unit 41, and based on the angle dependency data. The correction coefficients g _u , g _v , and g _w are determined by the correction coefficient determination unit 42. Instead, the d-axis current gain value i _d / (variable voltage) for various electrical angles θ of 0 to 360 degrees. Data indicating v _d may be acquired by the data acquisition unit 41 as angle dependency data, and the correction coefficients g _u , g _v , and g _w may be determined by the correction coefficient determination unit 42 based on the angle dependency data. . According to this configuration, the dependency of the d-axis current i _{d on} the electrical angle θ is reduced or reduced by correcting the phase voltage command values V _u , V _v , V _w using the correction coefficients g _u , g _v , g _w. This eliminates the amplitude difference between the u-phase, v-phase, and w-phase currents, so that torque ripple in the brushless motor 1 can be suppressed as in the above embodiment.

In the above embodiment, the data indicating the q-axis current gain value i _q / v _q is acquired as the angle-dependent data instead of the data indicating the q-axis current detection value i _q itself. Data indicating the ratio i _q / i _q ^* of the detected current value i _{q to} the q-axis current command value i _q ^* (hereinafter referred to as “vs. command q-axis current gain value” or “q-axis current gain value”) is represented by i _q ^* You may make it acquire as angle dependence data when it is not ≠ 0. The q-axis current command value i _q ^* necessary for obtaining the angle dependency data is obtained from the command current calculation unit 21. Even with such a modification, the influence on the q-axis current due to the change in the current to be supplied to the brushless motor 1, that is, the change in the current command value (or the corresponding change in the applied voltage to the brushless motor 1) is removed. The data indicating the dependence of the q-axis current on the electrical angle θ can be appropriately acquired. Hereinafter, this modification will be described with reference to FIG.

Assuming that the electrical angle at which the q-axis current gain value i _q / i _q ^* is the maximum is also referred to as “peak electrical angle”, as in the case of the first embodiment, The following matters are derived. That is, when the phase resistances Ru, Rv, and Rw are in the relationship of Rv> Rw, Ru, as shown in FIG. 7A, the peak electrical angle θp exists in the range of θ = 90 to 150 degrees, and Ru> Rv , Rw, there is a peak electrical angle θp in the range of θ = 150 to 210 degrees as shown in FIG. 7B, and when Rw> Ru, Rv, the relationship is as shown in FIG. As shown in FIG. 4, there is a peak electrical angle θp in the range of θ = 210 to 270 degrees.

Therefore, also in this modification, the correction coefficient determination unit 42 determines the correction coefficients g _u , g _v , and g _{w in the same} manner as in the first embodiment. That is, when 90 [deg] ≦ θp <150 [deg], a value obtained by increasing the current v-phase correction coefficient g _v is newly set as the v-phase correction coefficient g _v . In the case of 150 [deg] ≦ θp <210 [deg] is newly the u-phase correction coefficient g _u a larger value of u-phase correction coefficient g _u the current. Further, when 210 [deg] ≦ θp <270 [deg], a value obtained by increasing the current w-phase correction coefficient g _w is newly set as a w-phase correction coefficient g _w . Then, the correction execution unit 43 of this modification uses such new correction coefficients g _u , g _v , and g _w and uses the phase voltage command values V _u and V _{v in} accordance with the above-described equations (7) to (9). , V _w is corrected.

Note that the magnification at the time of changing the current correction coefficients g _u , g _v , and g _w or the value after the change is the second harmonic of the electrical angle θ included in the q-axis current gain value i _q / i _q ^*. It is determined according to the fluctuation range (amplitude) of the component. In practice, appropriate correction coefficients g _u , g _v , and g _w are determined using experimental data or computer simulation results so that the dependence of the q-axis current on the electrical angle θ is suppressed. It is preferable to adjust the determination method of the correction coefficients g _u , g _v , and g _w by the correction coefficient determination unit 42. Other configurations in the present modification are the same as those in the above embodiment.

Even with the above-described modification, the amplitude difference between the u-phase, v-phase, and w-phase currents is reduced or eliminated, so that the dependency of the q-axis current i _{q on} the electrical angle θ is eliminated. As a result, torque ripple in the brushless motor 1 is suppressed.

In the embodiment and the modification, the timing at which the data acquisition unit 41 acquires the current gain values i _q / v _q , i _d / v _d or i _q / i _q ^* constituting the angle-dependent data, The timing at which the correction coefficient determination unit 42 determines new correction coefficients g _u , g _v , and g _w based on the angle dependency data and outputs them to the correction execution unit 43 is not particularly limited. Such current gain value acquisition timing and correction coefficient output timing may be set at a predetermined interval, for example, or when the state such as temperature is changed, the angle dependency data is acquired and new correction is performed. The coefficients g _u , g _v , and g _w may be output.

When the current gain values i _q / v _q constituting the angle-dependent data are acquired, the timing of data acquisition is not particularly limited as long as v _q ≠ 0, but the q-axis voltage command value v _q is If it is close to zero, an error is likely to occur, and the detection accuracy of the peak electrical angle θp decreases. Therefore, the current gain value i _q / v _q is set only when the q-axis voltage command value v _q is equal to or greater than a predetermined lower limit value. You may make it acquire. For the same reason, when the current gain value i _q / i _q ^* constituting the angle dependency data is acquired, an error is likely to occur when the q-axis current command value i _q ^* is close to zero, and the peak is obtained. Since the detection accuracy of the electrical angle θp decreases, the current gain value i _q / i _q ^* may be acquired only when the q-axis current command value i _q ^* is equal to or greater than a predetermined lower limit (threshold). . In addition, when the angular velocity ω _{e of} the rotor is large, the counter electromotive force is large and the applied voltage to the resistances Ru, Rv, Rw of each phase is small. Is likely to occur, and the detection accuracy of the peak electrical angle θp decreases. Therefore, the angle dependency data may be acquired only when the angular velocity ω _e is equal to or less than a predetermined upper limit value (threshold value). Further, since the counter electromotive force increases when the angular velocity ω _e is large, the torque ripple is small even if there is a resistance difference between the phases. Therefore, only when the angular velocity ω _e is equal to or lower than the predetermined upper limit value, the correction execution unit 43 may correct the phase voltage command values V _u , V _v , V _w (Equations (7) to (9)). reference).

By the way, when the current (motor current) flowing through the brushless motor 1 increases, the resistance increases due to heat generation, whereas the interphase resistance difference usually does not change with the current. Therefore, when the motor current is increased, the interphase resistance difference is relatively smaller than the resistance value, and as a result, the current difference between the phases is also reduced. For this reason, since the amplitude of the second harmonic component (with respect to the electrical angle θ) included in the current gain value i _q / v _q or i _q / i _q ^* is also reduced, the peak electric current obtained from the angle dependence data is reduced. The detection accuracy of the angle θp decreases. Therefore, a threshold value as an upper limit value is determined in advance from the viewpoint of heat generation with respect to the motor current (for example, q-axis current detection value i _q ), and the current gain value only when the detection value or command value of the motor current is smaller than the threshold value. It is preferable to obtain angle-dependent data by calculating i _q / v _q or i _q / i _q ^* .

Further, in the above-described embodiment and its modified examples, the angle dependency data for either one of the q-axis current gain value and the d-axis current gain value is used to determine the correction coefficients g _u , g _v , and g _w. However, it is also possible to obtain angle dependency data for both the q-axis current gain value and the d-axis current gain value and determine the correction coefficients g _u , g _v , and g _w based on the angle dependency data. Good.

In the embodiment and the modification described above, R, Φ, and the like used for _{obtaining the} d-axis voltage command value v _d and the q-axis voltage command value v _q in the open loop control unit 22 are treated as known parameters. However, for Φ, the value calculated by the Φ calculating unit 26 is used. That is, Φ is appropriately corrected by the Φ calculating unit 26 while being treated as a known parameter. However, the present invention is not limited to this, and an R calculator is provided instead of or together with the Φ calculator 26 to obtain the d-axis voltage command value v _d and the q-axis voltage command value v _q . In this case, R calculated by the R calculating unit may be used (this is the same in the embodiments described below). When the R calculation unit is provided, the R calculation unit, for example, when i _q ≠ 0, the q-axis voltage command value v _q , the d-axis current detection value i _d , and the q-axis current detection value i _{Based on q} and the angular velocity ω _e , the electric winding resistance R included in the above formulas (1) and (2) is obtained using the following formula.
R = (v _q −PL _q i _q −ω _e L _d i _d −ω _e Φ) / i _q

<4. Second Embodiment>
FIG. 8 is a block diagram showing the configuration of the motor control device according to the second embodiment of the present invention. The motor control device according to the present embodiment is obtained by replacing the microcomputer 20 and the current sensor 14 with the microcomputer 30 and the current sensor 15 in the motor control device according to the first embodiment. This motor control device performs feedback control when the current sensor 15 is operating normally, and performs open loop control when the current sensor 15 fails.

One current sensor 15 is provided on the path through which the three-phase drive current supplied to the brushless motor 1 flows, and individually detects the three-phase drive current. Three-phase current values detected by current sensor 15 (hereinafter referred to as u-phase current detection value i _u , v-phase current detection value _iv and w-phase current detection value i _w ) are input to microcomputer 30.

  The microcomputer 30 is obtained by adding a three-phase / dq axis conversion unit 31, a subtraction unit 32, a feedback control unit 33, a failure monitoring unit 34, and a command voltage selection unit 35 to the microcomputer 20. Also in the microcomputer 30, the correction unit 50 including the data acquisition unit 41, the correction coefficient determination unit 42, and the correction execution unit 53 is realized as in the first embodiment. Is slightly different from the case of the first embodiment (details will be described later).

3-phase / dq axis conversion section 31, based on the detected u-phase current detection value i _u and the v-phase current detection value i _v by the current sensor 15, d-axis current by using the following equation (16) (17) A detection value _id and a q-axis current detection value _iq are obtained.
i _d = √2 × {i _v × sin θ−i _u × sin (θ−2π / 3)} (16)
i _q = √2 × {i _v × cos θ−i _u × cos (θ−2π / 3)} (17)

Subtraction unit 32, d-axis current command value i _d ^* and the d-axis current detection value i _d deviation E _d, and a deviation E _q of the q-axis current command value i _q ^* and the q-axis current detection value i _q . The feedback control unit 33 performs a proportional-integral calculation shown in the following equations (18) and (19) on the deviations E _d and E _q , so that the d-axis voltage command value v _d ^# and the q-axis voltage command value v _q ^{# are obtained.} Ask for.
v _d ^# = K × {E _d + (1 / T) ∫E _d · dt} (18)
v _q ^# = K × {E _q + (1 / T) ∫E _q · dt} (19)
However, in Expressions (18) and (19), K is a proportional gain constant, and T is an integration time.

  The failure monitoring unit 34 checks whether or not the three-phase current values detected by the current sensor 15 are within the normal range, and determines whether the current sensor 15 is operating normally or has failed. The failure monitoring unit 34 determines “normal” when all three-phase current values are within the normal range, and determines “failure” when one-phase or more current values are outside the normal range. The failure monitoring unit 34 outputs a control signal indicating the determination result.

When the failure monitoring unit 34 determines that the command voltage selection unit 35 is normal, the command voltage selection unit 35 outputs the d-axis voltage command value v _d ^# and the q-axis voltage command value v _q ^# obtained by the feedback control unit 33, and the failure monitoring unit If it is determined in 34 that a failure has occurred, the d-axis voltage command value v _d and the q-axis voltage command value v _q obtained by the open loop control unit 22 are output.

  When the current sensor 15 is operating normally, the failure monitoring unit 34 determines that it is normal, and the command voltage selection unit 35 selects the output of the feedback control unit 33. At this time, the command current calculation unit 21, the dq axis / three-phase conversion unit 23, the angle calculation unit 24, the three-phase / dq axis conversion unit 31, the subtraction unit 32, and the feedback control unit 33 operate to perform feedback control. In addition to this, while the current sensor 15 is operating normally, the angular velocity calculation unit 25 and the Φ calculation unit 26 also operate. The Φ calculating unit 26 obtains the armature winding linkage magnetic flux number Φ included in the equation (2) using the equation (15) while the current sensor 15 is operating normally.

The data acquisition unit 41 and the correction coefficient determination unit 42 also operate in the same manner as in the first embodiment while the current sensor 15 is operating normally. That is, the data acquisition unit 41, the q-axis voltage from the u-phase current detection value i _u and the v-phase current detection value i _v are calculated based on the q-axis current detection value i _q and the feedback control section 33 from the current sensor 15 Using the command value v _q ^# and the electrical angle θ from the angle calculation unit 24, angle dependency data indicating q-axis current gain values i _q / v _q ^# with respect to various electrical angles θ is acquired. The correction coefficient determination unit 42 determines correction coefficients g _u , g _v , and g _w based on the angle dependency data. These correction coefficients g _u , g _v , and g _w are given to the correction execution unit 53. As in the case of the first embodiment, the correction execution unit 53 includes the correction coefficients g _u , g _v and g _w together with the armature winding linkage magnetic flux number Φ from the Φ calculation unit 26 and the angular velocity. An angular velocity ω _e is given from the calculation unit 25. Further, the correction execution unit 53 is also given a control signal indicating the determination result in the failure monitoring unit 34.

Incidentally, while the current sensor 15 is operating normally, d-axis current command value i _d ^* and the d-axis current detection value i _d deviation E _d, and, q-axis current command value i _q ^* and the q-axis current since the feedback control so that the deviation E _q of the detection value i _q is canceled performed normally, the occurrence of torque ripple caused by the interphase resistance difference is not a problem. Therefore, in the present embodiment, the correction execution unit 53 is based on the control signal from the failure monitoring unit 34 while the current sensor 15 is operating normally, that is, while feedback control is being performed, dq axis / 3. The phase voltage command values V _u , V _v , V _w output from the phase converter 23 are supplied to the three-phase / PWM modulator 12 as they are without correction. That is, V _u = V _uc , V _v = V _vc , V _w = V _wc . However, the phase voltage command values V _u , V _v , and V _w may be corrected using the correction coefficients g _u , g _v , and g _w even while feedback control is being performed.

Thereafter, when the current sensor 15 fails, the failure monitoring unit 34 determines that there is a failure, and the command voltage selection unit 35 selects the output of the open loop control unit 22. At this time, the command current calculation unit 21, the open loop control unit 22, the dq axis / 3-phase conversion unit 23, and the angle calculation unit 24 operate to perform open loop control. The open loop control unit 22 obtains the d-axis voltage command value v _d and the q-axis voltage command value v _q using the Φ value obtained while the current sensor 15 is operating normally. The d-axis voltage command value v _d and the q-axis voltage command value v _q are given to the dq-axis / 3-phase conversion unit 23 via the command voltage selection unit 35, where the phase voltage command values V _u , V _v , It is converted to V _w. These phase voltage command values V _u , V _v and V _w are given to the correction execution unit 53.

Based on the control signal from the failure monitoring unit 34, the correction execution unit 53, when the current sensor 15 is in failure, corrects the correction coefficients g _u , from the correction coefficient determination unit 42 as in the case of the first embodiment. A phase voltage command according to the above-described equations (7) to (12) using g _v , g _w , the armature winding interlinkage magnetic flux Φ from the Φ calculating unit 26 and the angular velocity ω _e from the angular velocity calculating unit 25. The values V _u , V _v and V _w are corrected. The corrected phase voltage command values V _uc , V _vc , and V _wc are given to the three-phase / PWM modulator 12. The motor drive means comprising the three-phase / PWM modulator 12 and the motor drive circuit 13 drives the brushless motor 1 with the voltages of these phase voltage command values V _uc , V _vc , V _wc .

  As described above, when the current sensor is operating normally, the motor control device according to the present embodiment performs a proportional integral operation on the difference between the current command value and the current value detected by the current sensor to The command value is obtained, and when the current sensor fails, the voltage command value is obtained by performing open loop control according to the circuit equation of the motor based on the current command value and the angular velocity of the rotor. When performing open loop control, the Φ value (the number of armature winding linkage magnetic fluxes Φ) obtained while the current sensor is operating normally is used. Therefore, according to the motor control device according to the present embodiment, while the current sensor is operating normally, feedback control can be performed and the brushless motor can be driven with high accuracy. In addition, when the current sensor fails and feedback control cannot be performed, the open-loop control is performed using the armature winding interlinkage magnetic flux number Φ obtained during the feedback control, so that the brushless motor is highly accurate. To obtain a desired motor output.

Further, according to the present embodiment, when open-loop control is performed, the electrical angle θ of the q-axis current i _q or the d-axis current i _d using the correction coefficient obtained by the data acquisition unit 41 and the correction coefficient determination unit 42. The phase correction command value is corrected by the correction execution unit 53 so that the dependence on is reduced or eliminated. Thereby, generation | occurrence | production of the torque ripple resulting from a resistance difference between phases is suppressed. Therefore, even when the current sensor fails and feedback control cannot be performed, a good steering feeling can be obtained.

  In the present embodiment as well, the data acquisition unit 41 and the correction coefficient determination unit 42 can be modified in the same manner as the modification of the first embodiment.

<5. Other variations>
In the first embodiment and the modification, only one current sensor 14 is provided, but a plurality (two or three) may be provided. For example, when the u-phase and v-current sensor phase is provided, d-axis current detection value is used in the data acquisition unit 41 and the Φ calculator 26 i _d and the q-axis current detection value i _q is these obtained by converting the u-phase and v u-phase current detection value output from the current sensor phase i _u and the v-phase current detection value i _v into current values on the dq coordinate axis.

  In the motor control device according to the second embodiment, the feedback control and the open loop control are switched based on the determination result in the failure monitoring unit 34. However, the determination is not based on the determination in the failure monitoring unit 34 (for example, the driver Feedback control and open loop control may be switched).

  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.

It is a block diagram which shows the structure of the electric power steering apparatus which concerns on embodiment of 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 the principle of correction | amendment of the phase voltage command value in the said 1st Embodiment. It is a figure for demonstrating the correction method of the phase voltage command value in the said 1st Embodiment. It is a figure for demonstrating the specific example of the correction | amendment in the said 1st Embodiment. It is a figure for demonstrating the correction method of the phase voltage command value in the modification of the said 1st Embodiment. It is a block diagram which shows the structure of the motor control apparatus which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 6 ... Rotor, 10 ... ECU, 13 ... Motor drive circuit, 14, 15 ... Current sensor (current detection means), 20, 30 ... Microcomputer, 32 ... Subtraction part, 35 ... Command voltage selection part, 40, 50 ... Correction part .

Claims (6)

A motor control device for driving a brushless motor,
Control arithmetic means for obtaining a phase voltage command value indicating a phase voltage to be applied to the brushless motor;
Current detecting means for detecting a current flowing through the brushless motor;
Rotational position detecting means for detecting the rotational position of the rotor in the brushless motor;
The dependence of the ratio of the current flowing in the brushless motor on the q-axis or d-axis component to the q-axis or d-axis command value relative to the electrical angle of the brushless motor indicated by the ratio of the ratio to the electrical angle is reduced. Correction means for correcting the phase voltage command value based on the detection result of the current detection means and the detection result of the rotational position detection means,
A motor control device comprising: drive means for driving the brushless motor based on the phase voltage command value corrected by the correction means. The control calculation means calculates q-axis and d-axis components of a voltage to be applied to the brushless motor as q-axis and d-axis voltage command values, respectively, and applies the q-axis and d-axis voltage command values to the brushless motor. The phase voltage command value is obtained by converting each phase component of the voltage to be
The correction means includes
Based on the detection result of the current detection means, the ratio of the q-axis component of the current flowing to the brushless motor to the q-axis voltage command value and the ratio of the d-axis component of the current flowing to the brushless motor to the d-axis voltage command value Data acquisition means for calculating at least one and storing the calculated ratio as angle-dependent data in association with the electrical angle of the brushless motor based on the detection result of the rotational position detection means;
Correction coefficient determining means for determining a correction coefficient for correcting the phase voltage command value so that the dependence on the electrical angle indicated by the second harmonic component is reduced based on the angle dependency data;
The motor control device according to claim 1, further comprising correction execution means for correcting the phase voltage command value based on the correction coefficient determined by the correction coefficient determination means. The control calculation means determines q-axis and d-axis components of the current to be passed to the brushless motor as q-axis and d-axis current command values, respectively, and applies the brushless motor to the brushless motor based on the q-axis and d-axis current command values. The q-axis and d-axis components of the voltage to be applied are calculated as q-axis and d-axis voltage command values, respectively, and the q-axis and d-axis voltage command values are converted into respective phase components of the voltage to be applied to the brushless motor. To obtain the phase voltage command value,
The correction means includes
Based on the detection result of the current detection means, the ratio of the q-axis component of the current flowing to the brushless motor to the q-axis current command value and the ratio of the d-axis component of the current flowing to the brushless motor to the d-axis current command value Data acquisition means for calculating at least one and storing the calculated ratio as angle-dependent data in association with the electrical angle of the brushless motor based on the detection result of the rotational position detection means;
Correction coefficient determining means for determining a correction coefficient for correcting the phase voltage command value so that the dependence on the electrical angle indicated by the second harmonic component is reduced based on the angle dependency data;
The motor control device according to claim 1, further comprising correction execution means for correcting the phase voltage command value based on the correction coefficient determined by the correction coefficient determination means.   The correction means is based on the current and rotational position detection values obtained by the current detection means and the rotational position detection means when the current detection value obtained by the current detection means is smaller than a predetermined threshold value, The motor control device according to claim 1, wherein the phase voltage command value is corrected so that dependency on the electrical angle indicated by the second harmonic component is reduced.   The correcting means is based on the second harmonics based on the detected current and rotational position values obtained by the current detecting means and the rotational position detecting means when the angular velocity of the brushless motor rotor is equal to or less than a predetermined threshold value. The motor control device according to claim 1, wherein the phase voltage command value is corrected so that dependency on the electrical angle indicated by a wave component is reduced. 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 5, comprising:
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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