JP2012239281A - Motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor controller capable of slowing the variation in motor torque, and of enhancing the steering feeling.SOLUTION: A speed command setting unit 21 sets a rotor rotational speed corresponding to a q-axis current command value for generating, from a motor 5, a steering torque Th detected by a torque sensor 1 and a motor torque (assist torque) corresponding to a vehicle speed Vs detected by a vehicle speed sensor 2 as a speed command value ω. A speed deviation operation unit 22 operated the deviation (ω-ω) between the speed command value ωset by the speed command setting unit 21 and a rotor rotational speed ω operated by a speed operation unit 34. A speed control unit 23 operates a q-axis current command value Iby performing proportional integration operation (PI operation) for the deviation (ω-ω) operated by the speed deviation operation unit 22.

Description

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

  Conventionally, there is a vector control method as one of the control methods of a brushless motor. In the vector control method, the current values of the U phase, V phase, and W phase in the three-phase fixed coordinate system are converted into two-phase currents in the two-phase rotating coordinate system, and the motor is controlled using these two-phase currents. . The two-phase rotational coordinate system is a coordinate system defined by a d-axis along the magnetic pole direction of the rotor and a q-axis orthogonal to the d-axis. The two-phase current in the two-phase rotating coordinate system includes a d-axis current component and a q-axis current component.

FIG. 3 is a block diagram showing a configuration of a motor control device that controls a brushless motor for an electric power steering device by conventional vector control.
The conventional motor control device 100 drives a brushless motor 5 (hereinafter referred to as “motor 5”) for an electric power steering device (EPC). The motor control device 100 includes a microcomputer 111, a drive circuit 112 that supplies power to the motor 5, current sensors 113 and 114 for detecting U-phase current and V-phase current flowing in the motor 5, and a rotor of the motor 5. A rotation angle sensor 115 such as a resolver for detecting the rotation angle is provided.

The microcomputer 111 includes a q-axis current command value setting unit 121, a q-axis current deviation calculation unit 122, a q-axis current control unit 123, a d-axis current command value setting unit 124, and a d-axis current deviation calculation unit 125. , A d-axis current control unit 126, a coordinate conversion unit 127, a PWM control unit 128, a current detection unit 129, a coordinate conversion unit 130, and a rotation angle calculation unit 131.
The rotation angle calculation unit 131 calculates the rotor rotation angle θ based on the output signal of the rotation angle sensor 115. The current detection unit 129 obtains phase currents of the U phase, the V phase, and the W phase based on the output signals of the current sensors 113 and 114 for each predetermined calculation cycle. The coordinate conversion unit 130 converts the three-phase phase current obtained by the current detection unit 129 into a two-phase current in the two-phase rotation coordinate system using the rotor rotation angle calculated by the rotation angle calculation unit 131. . The two-phase current in the two-phase rotating coordinate system includes a d-axis current component and a q-axis current component. Of the two-phase currents obtained by the coordinate conversion unit 130, the d-axis current component is referred to as a d-axis current detection value _Id, and the q-axis current component is referred to as a q-axis current detection value _Iq .

The q-axis current command value setting unit 121 generates a q-axis current for generating a motor torque (assist torque) from the motor 5 according to the steering torque Th detected by the torque sensor 1 and the vehicle speed Vs detected by the vehicle speed sensor 2. Set command value I _q ^* . More specifically, the q-axis current command value I _q ^* is set using a map (table) that stores the q-axis current command value I _q ^* corresponding to the steering torque and the vehicle speed.

The q-axis current deviation calculation unit 122 calculates a deviation (I _q ^* −I _q ) between the q-axis current command value I _q ^* and the q-axis current detection value I _q obtained by the coordinate conversion unit 130. The q-axis current control unit 123 performs a proportional-integral calculation (PI calculation) on the deviation (I _q ^* −I _q ) obtained by the q-axis current deviation calculation unit 122 to thereby supply q to the motor 5. An axis voltage (hereinafter referred to as “q-axis voltage command value V _q ^* ”) is calculated.

The d-axis current command value setting unit 124 sets the d-axis current command value I _d ^* . For example, the d-axis current command value I _d ^* is set to zero. The d-axis current deviation calculation unit 125 calculates a deviation (I _d ^* −I _d ) between the d-axis current command value I _d ^* and the d-axis current detection value I _d obtained by the coordinate conversion unit 130. The d-axis current control unit 126 performs a proportional-integral calculation (PI calculation) on the deviation (I _d ^* −I _d ) obtained by the d-axis current deviation calculation unit 125 to thereby supply d to the motor 5. An axis voltage (hereinafter referred to as “d-axis voltage command value V _d ^* ”) is calculated. A current command value is composed of the q-axis current command value I _q ^* set by the q-axis current command value setting unit 121 and the d-axis current command value I _d ^* set by the d-axis current command value setting unit 124. .

The coordinate conversion unit 127 uses the rotor rotation angle θ calculated by the rotation angle calculation unit 131 to convert the d-axis voltage command value V _d ^* and the q-axis voltage command value V _q ^* into the U phase in the three-phase fixed coordinate system. , V-phase and W-phase voltage command values V _U ^* , V _V ^* , and V _W ^* .
The PWM control unit 128 includes a U-phase PWM control signal, a V-phase PWM control signal, and a W-phase PWM having a duty corresponding to each of the U-phase, V-phase, and W-phase voltage command values V _U ^* , V _V ^* , and V _W ^*. A control signal is generated and supplied to the drive circuit 112.

The drive circuit 112 is composed of a three-phase inverter circuit. The power elements constituting the inverter circuit are controlled by a PWM control signal supplied from the PWM control unit 128, so that voltages corresponding to the three-phase voltage command values V _U ^* , V _V ^* , and V _W ^* are It is applied to the stator winding of each phase.

International Publication No. 2007/119755 JP 2009-112104 A

In the above-described conventional motor control device, the q-axis current command value I _q ^* for generating the motor torque from the motor 5 in accordance with the steering torque detected by the torque sensor 1 and the vehicle speed detected by the vehicle speed sensor 2, Set based on the map. In such a motor control device, the motor response to the steering torque (motor torque response) is fast, and the motor torque and the steering torque tend to fluctuate. As a result, for example, vibration may occur in the steering wheel or the steering torque may change abruptly. For this reason, there exists a problem that a favorable steering feeling cannot be obtained.

  An object of the present invention is to provide a motor control device capable of slowing fluctuations in motor torque and improving steering feeling.

In order to achieve the above object, an invention according to claim 1 is a motor control device (6) for controlling a brushless motor (5) for an electric power steering device, the current to be supplied to the brushless motor. Fluctuation value detection means (1, 2) for detecting a fluctuation value necessary for setting the command value, and for generating torque corresponding to the fluctuation amount detected by the fluctuation value detection means from the brushless motor. A speed command value setting means (21) for setting a speed command value (ω ^* ) corresponding to the current command value, a current detection means (31) for detecting a current flowing through the brushless motor, and a rotor of the brushless motor. Obtained by the speed detection means (34) for detecting the rotational speed (ω), the speed command value set by the speed command value setting means, and the speed detection means. Rolling on the basis of the speed, by performing feedback control, a current command value calculating means for calculating a current command value (22, 23, 26), the current command value calculated by the current command value calculating means (I _q ^* , I _d ^* ) and control means (24, 25, 27, 28, 29, 30) for controlling the current supplied to the brushless motor based on the motor current detected by the current detection means; Is a motor control device. In addition, although the alphanumeric character in parentheses represents a corresponding component in an embodiment described later, of course, the scope of the present invention is not limited to the embodiment. The same applies hereinafter.

The fluctuation value detecting means may include a torque sensor that detects a steering torque. Further, the fluctuation value detecting means may include a torque sensor that detects the steering torque and a vehicle speed sensor that detects the vehicle speed.
In the speed command value setting means, a speed command value corresponding to a current command value for generating torque corresponding to the fluctuation amount detected by the fluctuation value detection means from the brushless motor is set. In the current command value calculation means, the current command value is calculated by performing feedback control based on the speed command value set by the speed command value setting means and the rotational speed obtained by the speed detection means. Thereby, the response of the motor to the fluctuation amount detected by the fluctuation value detecting means can be delayed as compared with the conventional example. As a result, since the fluctuation of the motor torque (assist torque) can be slowed, the steering feeling can be improved.

According to a second aspect of the present invention, the speed command value setting means generates a basic current command value (I _qo ^* ) for generating torque from the brushless motor according to the fluctuation amount detected by the fluctuation value detection means. Basic current command value setting means (41) for setting, and conversion means (42) for converting the basic current command value set by the basic current command value setting means into a speed command value (ω ^* ), A motor control device according to claim 1.

  According to a third aspect of the present invention, the speed command value setting means is detected by the fluctuation value detection means based on a map storing a relationship between a fluctuation amount that is a detection target of the fluctuation value detection means and a speed command value. The motor control device according to claim 1, wherein the motor control device is configured to obtain a speed command value corresponding to the amount of fluctuation to be performed.

FIG. 1 is a block diagram showing an electrical configuration of an electric power steering apparatus to which a motor control apparatus according to an embodiment of the present invention is applied. FIG. 2 is a block diagram illustrating a configuration example of the speed command value setting unit. FIG. 3 is a block diagram showing an electrical configuration of a conventional motor control device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram showing an electrical configuration of an electric power steering apparatus to which a motor control apparatus according to an embodiment of the present invention is applied.
This electric power steering apparatus includes a torque sensor 1 that detects a steering torque applied to a steering wheel 10 of a vehicle, a vehicle speed sensor 2 that detects the speed of the vehicle, and a steering assisting device 3 via a speed reduction mechanism 4. A motor 5 that applies force and a motor control device 6 that drives and controls the motor 5 are provided.

The motor control device 6 drives the motor 5 according to the steering torque Th detected by the torque sensor 1 and the vehicle speed Vs detected by the vehicle speed sensor 2, thereby realizing appropriate steering assistance according to the steering situation and the vehicle speed.
In this embodiment, the motor 5 is a three-phase brushless motor, and a U-phase, V-phase, and W-phase disposed in a rotor (not shown) as a field magnet and a stator (not shown) facing the rotor. Stator windings (not shown).

The motor control device 6 is controlled by the microcomputer 11, a drive circuit (inverter circuit) 12 that is controlled by the microcomputer 11 and supplies power to the motor 5, and a U-phase current and a V-phase current that flow through the motor 5. Current sensors 13 and 14 and a rotation angle sensor 15 such as a resolver for detecting the rotation angle of the rotor are provided.
The microcomputer 11 includes a CPU and a memory (ROM, RAM, etc.), and functions as a plurality of function processing units by executing a predetermined program. The plurality of function processing units include a speed command value setting unit 21, a speed deviation calculation unit 22, a speed control unit 23, a q-axis current deviation calculation unit 24, a q-axis current control unit 25, and a d-axis current. Command value setting unit 26, d-axis current deviation calculation unit 27, d-axis current control unit 28, coordinate conversion unit 29, PWM control unit 30, current detection unit 31, coordinate conversion unit 32, rotation angle A calculation unit 33 and a speed calculation unit 34 are included.

The rotation angle calculation unit 33 calculates the rotor rotation angle θ based on the output signal of the rotation angle sensor 15 at every predetermined calculation cycle Ts. The speed calculation unit (speed detection means) 34 calculates the rotation speed ω of the rotor based on the rotor rotation angle θ calculated by the rotation angle calculation unit 33. When the rotor rotation angle calculated this time by the rotation angle calculation unit 33 is θ _n and the previously calculated rotor rotation angle is θ _n−1 , the rotor rotational speed ω is obtained based on the following equation (1), for example. It is done.

ω = (θ _n −θ _n−1 ) / Ts (1)
The rotor rotational speed ω calculated by the speed calculation unit 34 is given to the speed deviation calculation unit 22 as a speed detection value.
The current detection unit 31 obtains U-phase, V-phase, and W-phase phase currents on the basis of the output signals of the current sensors 13 and 14 for each predetermined calculation cycle Ts. The coordinate conversion unit 32 uses the rotor rotation angle θ calculated by the rotation angle calculation unit 33 to convert the three-phase current obtained by the current detection unit 31 into a two-phase current in the two-phase rotation coordinate system. To do. The two-phase rotational coordinate system is a coordinate system defined by a d-axis along the magnetic pole direction of the rotor and a q-axis orthogonal to the d-axis. The two-phase current in the two-phase rotating coordinate system includes a d-axis current component and a q-axis current component. Of the two-phase currents obtained by the coordinate conversion unit 32, the d-axis current component is referred to as a d-axis current detection value _Id, and the q-axis current component is referred to as a q-axis current detection value _Iq .

The speed command value setting unit 21 generates a motor torque (assist torque) from the motor 5 according to the steering torque Th detected by the torque sensor 1 and the vehicle speed Vs detected by the vehicle speed sensor 2. Is set as the speed command value ω ^* . Details of the speed command value setting unit 21 will be described later.
The speed deviation calculation unit 22 calculates a deviation (ω ^* −ω) between the speed command value ω ^* set by the speed command value setting unit 21 and the rotor rotational speed ω calculated by the speed calculation unit 34.

The speed control unit 23 calculates a q-axis current command value I _q ^* by performing a proportional integration calculation (PI calculation) on the deviation (ω ^* −ω) calculated by the speed deviation calculation unit 22. The q-axis current command value I _q ^* is a q-axis current command value for generating a motor torque (assist torque) corresponding to the steering torque Th and the vehicle speed Vs from the motor 5. The speed control unit 23 is provided to slow down the response of the motor 5 (response of the motor torque) to the steering torque Th and the vehicle speed Vs so as to slow the fluctuation of the motor torque (assist torque).

The q-axis current deviation calculation unit 24 calculates a deviation (I _q ^* −I _q ) between the q-axis current command value I _q ^* and the q-axis current detection value I _q obtained by the coordinate conversion unit 32. The q-axis current control unit 25 performs a proportional-integral calculation (PI calculation) on the deviation (I _q ^* −I _q ) obtained by the q-axis current deviation calculation unit 24 to thereby supply q to the motor 5. An axis voltage (hereinafter referred to as “q-axis voltage command value V _q ^* ”) is calculated.

The d-axis current command value setting unit 26 sets the d-axis current command value I _d ^* . For example, the d-axis current command value I _d ^* is set to zero. The d-axis current deviation calculation unit 27 calculates a deviation (I _d ^* −I _d ) between the d-axis current command value I _d ^* and the d-axis current detection value I _d obtained by the coordinate conversion unit 32. The d-axis current control unit 28 performs a proportional-integral calculation (PI calculation) on the deviation (I _d ^* −I _d ) obtained by the d-axis current deviation calculation unit 27 to thereby supply d to the motor 5. An axis voltage (hereinafter referred to as “d-axis voltage command value V _d ^* ”) is calculated.

The speed deviation calculation unit 22, the speed control unit 23, and the d-axis current command value setting unit 26 constitute current command value calculation means. That is, the current command value is configured from the q-axis current command value I _q ^* calculated by the speed control unit 23 and the d-axis current command value I _d ^* set by the q-axis current command value setting unit 26. Since the torque generated from the motor 5 corresponds to the motor current, the current command values I _q ^* and I _d ^* can be rephrased as “torque command values” for commanding the torque to be generated from the motor 5.

The coordinate conversion unit 29 uses the rotor rotation angle θ calculated by the rotation angle calculation unit 33 to convert the d-axis voltage command value V _d ^* and the q-axis voltage command value V _q ^* into the U phase in the three-phase fixed coordinate system. , V-phase and W-phase voltage command values V _U ^* , V _V ^* , and V _W ^* .
The PWM control unit 30 includes a U-phase PWM control signal, a V-phase PWM control signal, and a W-phase PWM having a duty corresponding to each of the U-phase, V-phase, and W-phase voltage command values V _U ^* , V _V ^* , and V _W ^*. A control signal is generated and supplied to the drive circuit 12.

The drive circuit 12 includes a three-phase inverter circuit corresponding to the U phase, the V phase, and the W phase. The power elements constituting the inverter circuit are controlled by a PWM control signal supplied from the PWM control unit 30, so that voltages corresponding to the three-phase voltage command values V _U ^* , V _V ^* , and V _W ^* are applied to the motor 5. It is applied to the stator winding of each phase.
The speed deviation calculation unit 22 and the speed control unit 23 constitute a speed feedback control unit. By the operation of the speed feedback control means, the rotational speed of the motor 5 is controlled so as to approach the speed command value ω ^* set by the speed command value setting unit 21. The q-axis current deviation calculation unit 24, the q-axis current control unit 25, the d-axis current deviation calculation unit 27, and the d-axis current control unit 28 constitute current feedback control means. By the action of the current feedback control means, the motor current flowing through the motor 5 is controlled so as to approach the current command values I _q ^* and I _d ^* . Thereby, an appropriate assist torque (steering assist force) corresponding to the steering torque and the vehicle speed can be applied to the steering mechanism of the vehicle.

FIG. 2 is a block diagram illustrating a configuration example of the speed command value setting unit 21.
The speed command value setting unit 21 includes a basic q-axis current value command value setting unit 41 and a current command value-speed command value conversion unit 42.
The q-axis current command value setting unit 21 is a basic q-axis for generating motor torque (assist torque) from the motor 5 according to the steering torque Th detected by the torque sensor 1 and the vehicle speed Vs detected by the vehicle speed sensor 2. Sets the current command value I _qo ^* . More specifically, the basic q-axis current command value I _qo ^* is set using a map (table) that stores the basic q-axis current command value I _q0 ^* corresponding to the steering torque and the vehicle speed.

The current command value-speed command value conversion unit 42 converts the basic q-axis current command value I _qo ^* set by the q-axis current command value setting unit 21 into a speed command value ω ^* which is a command value of the rotor rotation speed. To do. This conversion method will be described.
The rotational speed ω of the motor 5 can be expressed by the following equation (2).
ω = (V−R · I) / Ke (2)
V: Motor terminal voltage I: Motor current R: Motor resistance (resistance between motor terminals)
Ke: Back electromotive force constant The rotational speed ωo of the motor 5 when there is no load can be expressed by the following equation (3).

ωo = V / Ke (3)
A difference (ωo−ω) between ωo and ω is expressed by the following equation (4).
ωo−ω = V / Ke− (V−R · I) / Ke
= R · I / Ke (4)
By transforming the equation (4), the equation (5) representing the relationship between the rotational speed ω and the motor current I is obtained.

ω = ωo-R · I / Ke (5)
Therefore, the conversion formula for converting the basic q-axis current command value I _qo ^* into the speed command value ω ^* is the formula (6).
ω ^* = ωo−R · I _qo ^* / Ke (6)
In the formula (6), ωo, R, and Ke are set in advance. The current command value-speed command value conversion unit 42 converts the basic q-axis current command value I _qo ^* set by the q-axis current command value setting unit 21 to the speed command value ω ^* based on the equation (6). Convert.

The speed command value setting unit 21 is detected by the steering torque Th detected by the torque sensor 1 and the vehicle speed sensor 2 using a map (table) storing the speed command value ω ^* corresponding to the steering torque and the vehicle speed. The speed command value ω ^* corresponding to the vehicle speed Vs may be obtained.
In the embodiment, the speed command value setting unit 21 sets the speed command value ω ^* corresponding to the steering torque Th and the vehicle speed Vs. Then, the speed control unit 23 performs proportional integral calculation (PI calculation) on the deviation (ω ^* −ω) between the speed command value ω ^* and the speed detection value ω, whereby the q-axis current command value I _q ^*. Is calculated. Therefore, the response of the motor 5 to the steering torque Th and the vehicle speed Vs (response of the motor torque) compared to the conventional example in which the q-axis current command value I _q ^* corresponding to the steering torque Th and the vehicle speed Vs is set based on the map. Can slow down. As a result, since the fluctuation of the motor torque (assist torque) can be slowed, the steering feeling can be improved.

As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form. For example, in the above-described embodiment, the speed control unit 23 performs the proportional-integral calculation (PI calculation) on the deviation (ω ^* −ω) between the speed command value ω ^* and the speed detection value ω, thereby performing the q-axis current command. Although the value I _q ^* is being calculated, the speed control unit 23 performs proportional integral differential calculation (PID calculation), proportional calculation (P calculation) or proportional differential calculation (PD calculation) with respect to the deviation (ω ^* −ω). ) To calculate the q-axis current command value I _q ^* . However, from the viewpoint of slowing down the response of the motor torque to the fluctuation of the steering torque Th, the speed control unit 23 performs the q-axis current by performing a proportional integration calculation (PI calculation) on the deviation (ω ^* −ω). The command value I _q ^* is preferably calculated.

In the above embodiment, the speed command value setting unit 21 sets the rotor rotational speed corresponding to the motor torque corresponding to the steering torque Th and the vehicle speed Vs as the speed command value ω ^* , but the steering torque Th and the vehicle speed are set. The difference (ωo−ωx) between the rotor rotational speed corresponding to the motor torque corresponding to Vs (this speed will be expressed as “ωx”) and the no-load speed ωo may be set as the speed command value ω ^*. . In this case, a difference (ωo−ω) between the rotor rotation angle ω calculated by the speed calculation unit 34 and the no-load speed ωo is used as the speed detection value given to the speed deviation calculation unit 22.

  Although the embodiments of the present invention have been described above, various design changes can be made within the scope of the matters described in the claims.

  DESCRIPTION OF SYMBOLS 1 ... Torque sensor, 2 ... Vehicle speed sensor, 5 ... Motor, 6 ... Motor controller, 21 ... Speed command value setting part, 22 ... Speed deviation calculation part, 23 ... Speed control part, 24 ... q-axis current deviation calculation part, 25 ... q-axis current control unit, 26 ... d-axis current command value setting unit, 27 ... d-axis current deviation calculation unit, 28 ... d-axis current control unit, 29,32 ... coordinate conversion unit, 30 ... PWM control unit, 31 ... Current detector, 33 ... Rotation angle calculator, 34 ... Speed calculator

Claims (3)

A motor control device for controlling a brushless motor for an electric power steering device,
Fluctuation value detecting means for detecting a fluctuation value necessary for setting a current command value to be supplied to the brushless motor;
Speed command value setting means for setting a speed command value corresponding to a current command value for generating torque corresponding to the amount of fluctuation detected by the fluctuation value detecting means from the brushless motor;
Current detecting means for detecting a current flowing through the brushless motor;
Speed detecting means for detecting the rotational speed of the rotor of the brushless motor;
Current command value calculating means for calculating a current command value by performing feedback control based on the speed command value set by the speed command value setting means and the rotational speed obtained by the speed detecting means;
A motor control device including: a current command value calculated by the current command value calculation unit; and a control unit configured to control a current supplied to the brushless motor based on a motor current detected by the current detection unit. . The speed command value setting means includes a basic current command value setting means for setting a basic current command value for generating torque from the brushless motor according to the fluctuation amount detected by the fluctuation value detection means,
The motor control device according to claim 1, further comprising conversion means for converting the basic current command value set by the basic current command value setting means into a speed command value. The speed command value setting means is a speed corresponding to the fluctuation amount detected by the fluctuation value detection means, based on a map storing the relationship between the fluctuation amount to be detected by the fluctuation value detection means and the speed command value. The motor control device according to claim 1, wherein the motor control device is configured to obtain a command value.

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