JP2012076693A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change a control quantity to a motor in response to an electric power consumption rate so as not to cause a sense of discomfort by torque clogging or the like, by restraining the electric power consumption of the motor to a limit or less.SOLUTION: The electric power consumption of a steering assisting motor is calculated or assisted, and an electric power consumption rate Prate is calculated based on the ratio of the electric power consumption of the steering assisting motor to a predetermined electric power limiting value, and a motor current command value Iq* is reduced in advance, as the calculated electric power consumption rate Prate approaches 1.

Description

  The present invention relates to an electric power steering apparatus including a steering means and a steering assist motor that assists the steering means.

A steering assist motor (hereinafter simply referred to as a “motor”) used in an electric power steering apparatus has its motor torque controlled by energizing a stator winding in accordance with the rotation of the motor. This relationship between the motor rotation speed (also referred to as rotation speed) and the motor torque is referred to as “motor output characteristics” in this specification.
The motor output characteristics include the power limit of the power source that drives the motor. By limiting the power of the motor based on the power limit of the power source, the current drawn from the power source can be kept below a certain level. Is prevented from malfunctioning due to overcurrent or overheating. FIG. 9 shows the relationship between the motor output characteristics and the power source power limit. The vertical axis of the graph represents motor torque, and the horizontal axis represents rotational speed.

In a normal design, a target output is set in a range that does not exceed the power supply power limit in the motor output characteristics, and the rotation of the motor is controlled to be the target output.
As shown in FIG. 10, in the control of a brushless motor, field weakening control for controlling the d-axis current to be negative is a technique for expanding the motor rotation speed to the high speed side even with the same voltage.

JP 2009-46005 JP 2009-22074 A

By the way, there is a case where power that temporarily exceeds the power limit of the power source is required, for example, when the vehicle is steered suddenly. In this case, the output of the motor is limited due to the power limit of the power source, so-called assist interruption occurs, the steering torque increases, and there is a problem that a feeling of strangeness such as a feeling of catching occurs.
This problem is conspicuous especially in the high-speed rotation (steering wheel steering) region where the field-weakening control is activated.

  Accordingly, an object of the present invention is to provide an electric motor designed to change the control amount to the motor in accordance with the power consumption rate so as not to give a sense of incongruity such as torque clogging while keeping the power consumption of the motor below the limit. A power steering device is provided.

  In order to achieve the above object, an electric power steering apparatus according to the present invention includes a steering assist motor for generating a steering assist force, an inverter drive circuit for driving the steering assist motor, and drive power to the inverter drive circuit. Power supply to be supplied; power consumption estimation means for calculating or estimating the power consumption of the power supply; and power consumption rate calculation means for calculating a power consumption rate from a ratio of the calculated or estimated power consumption to a predetermined power limit value And power control means for controlling the steering assist motor by changing a motor control amount in accordance with the power consumption rate calculated by the power consumption rate calculation means.

  With this configuration, when the calculated power consumption rate is large and the power consumption of the motor is close to the limit of the power source, a value that is changed in a direction lower than the predetermined motor control amount is applied as the motor control amount. be able to. For this reason, this phenomenon can be avoided when the power consumption rate increases rapidly and a sudden decrease in the motor control amount occurs. Therefore, there is no sense of incongruity such as torque clogging.

The motor control amount may be a motor current command value set by the power control means. In this case, the power control means supplies the motor to the steering assist motor according to the power consumption rate. Limit the current command value.
Further, the motor current command value may be corrected in accordance with a difference between the motor current command value and a current limit value representing an output limit of the steering assist motor.

The motor control amount may be a field-weakening control amount set by the power control unit. In this case, the power control unit supplies a d-axis current supplied to the steering assist motor according to the power consumption rate. Limit the command value.
The motor control amount may be a boosted voltage supplied to the steering assist motor. In this case, the power control means limits the boosted voltage according to the power consumption rate.

  The power consumption estimation means may detect the power consumption of the inverter drive circuit, may detect the voltage and current of a power supply that supplies power to the inverter drive circuit, calculates the rotational speed of the motor, and The power consumption may be detected based on the product of the motor torque or the motor current.

It is a block diagram for demonstrating the electrical structure and control function of an electric power steering apparatus. It is an illustration figure for demonstrating the structure of a motor. It is a graph which shows the relationship between the power consumption rate Prate and the power consumption rate gain PrateGain. 4 is a flowchart showing operations of a power consumption rate calculation unit 37 and a correction unit 22. It is a partial flowchart which shows the modification of FIG. It is a graph which shows the relationship between the power consumption rate Prate and d-axis current command value Id ^* . It is a block diagram for demonstrating the electric constitution of the electric power steering apparatus which concerns on a modification. It is a graph which shows the relationship between the power consumption rate Prate and the boost voltage Vboost. It is the graph which drew the motor output characteristic and the power supply power limit in a superimposed manner. It is the graph which showed the difference in motor output characteristics with and without weak field control.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram for explaining an electrical configuration and a control function of an electric power steering apparatus (an example of a vehicle steering apparatus) according to a first embodiment of the present invention.
This electric power steering device includes a torque sensor 1 for detecting a steering torque T applied to a steering wheel 10 as an operation member for steering a vehicle, and a steering assist force via a speed reduction mechanism 8 to a steering mechanism 2 of the vehicle. A motor 3 (steering assist motor) that gives power, a power supply 30 for driving the motor 3, a rotation angle sensor (for example, a motor resolver) 5 for detecting the rotation angle (electrical angle) of the motor 3, and the motor 3 A motor control device 6 for driving control and a vehicle speed sensor 7 for detecting the speed of the vehicle on which the electric power steering device is mounted are provided. The above-described rotation angle sensor 5, torque sensor 1 and vehicle speed sensor 7 are connected to the motor control device 6.

The motor control device 6 drives the motor 3 through the inverter drive circuit 12 in accordance with the steering torque detected by the torque sensor 1 and the vehicle speed detected by the vehicle speed sensor 7, so that an appropriate steering assist according to the steering situation and the vehicle speed is achieved. Is realized.
In this embodiment, the motor 3 is a three-phase motor. As schematically illustrated in FIG. 2, the U phase and the V phase are arranged in a rotor 50 as a field and a stator 55 facing the rotor 50. And W-phase stator windings 51, 52, 53. The motor 3 may be of an inner rotor type in which a stator is disposed facing the outside of the rotor, or may be of an outer rotor type in which a stator is disposed facing the inside of a cylindrical rotor.

Three-phase fixed coordinates (UVW coordinate system) are defined in which the U, V, and W axes are taken in the direction of the stator windings 51, 52, and 53 of each phase. Further, a two-phase rotational coordinate system (dq coordinate) in which the d axis (magnetic pole axis) is taken in the magnetic pole direction of the rotor 50 and the q axis (torque axis) is taken in the direction perpendicular to the d axis in the rotation plane of the rotor 50. System).
The dq coordinate system is a rotating coordinate system that rotates with the rotor 50. In the dq coordinate system, since only the q-axis current contributes to the torque generation of the rotor 50, the d-axis current may be set to zero or a negative value and the q-axis current may be controlled according to the desired torque. The rotation angle θ _M of the rotor 50 is the rotation angle of the d axis with respect to the U axis. d-q coordinate system is an actual rotating coordinate system that rotates in accordance with the rotor angle theta _M. With the use of the rotor angle theta _M, coordinate conversion may be made between the UVW coordinate system and the d-q coordinate system.

Returning to FIG. 1, the motor control device 6 includes a current detection unit 13 and an inverter drive circuit 12.
The current detector 13 detects the current flowing through the stator windings 51, 52, 53 (see FIG. 2) of the motor 3. More specifically, the current detection unit 13 includes current detectors that detect phase currents in the three-phase (U-phase, V-phase, and W-phase) stator windings 51, 52, and 53, respectively.

The parts other than the current detection unit 13 and the inverter drive circuit 12 of the motor control device 6 are configured by a microcomputer including a CPU and a memory (ROM, RAM, etc.), and a plurality of programs are executed by executing a predetermined program. Functions as a function processing unit.
The plurality of function processing units include a target motor torque generation unit 20, a current command value generation unit 21, a correction unit 22, a current deviation calculation circuit 23, a PI (proportional integration) control unit 24, a dq / UVW A conversion unit 25, a PWM (Pulse Width Modulation) control unit 26, a UVW / dq conversion unit 27, a rotation angle calculation unit 31, and a power consumption rate calculation unit 37 are included.

The rotation angle calculation unit 31 calculates the rotation angle (electrical angle; hereinafter referred to as “rotation angle θ _M ”) of the rotor 50 of the motor 3 based on the output signal of the rotation angle sensor 5. This rotation angle θ _M is output as a conversion angle θ _S for coordinate conversion.
The target motor torque generator 20 generates a target motor torque T _M ^* based on the steering torque (detected steering torque) detected by the torque sensor 1 and the vehicle speed detected by the vehicle speed sensor 7. Specifically, the target motor torque generating unit 20 is based on the detected vehicle speed and the target motor torque T according to the detected steering torque based on the relationship of the target motor torque T _M ^* to the detected steering torque set in advance for each vehicle speed. Generate _M ^* .

For the detected steering torque, for example, the torque for steering in the left direction is a positive value, and the torque for steering in the right direction is a negative value. The target motor torque T _M ^* is a positive value when a steering assist force for leftward steering is to be generated from the motor 3, and when a steering assist force for rightward steering is to be generated from the motor 3. Negative value.
The target motor torque T _M ^* generated by the target motor torque generation unit 20 is given to the current command value generation unit 21.

The current command value generation unit 21 generates a current to be passed through the coordinate axes of the dq coordinate system as a current command value. Specifically, the d-axis current command value Id ^* and the q-axis current command value Iq ^* are generated. More specifically, the current command value generation unit 21 sets the q-axis current command value Iq ^* to a significant value, and sets the d-axis current command value Id ^* to zero or a negative value (set to a negative value). Is the case of field weakening control). More specifically, the current command value generation unit 21 divides the target motor torque T _M ^* generated by the target motor torque generation unit 20 by the torque constant K _T of the motor 3 to thereby obtain a q-axis current command value. Iq ^* is calculated. This q-axis current command value may be referred to as “motor current command value” in this specification. The q-axis current command value Iq ^* and the d-axis current command value Id ^* generated by the current command value generation unit 21 are given to the current deviation calculation circuit 23 via the correction unit 22.

The current detection unit 13 includes a U-phase current I _U , a V-phase current I _V , and a W-phase current I _W of the motor 3 in the inverter drive circuit 12 (hereinafter, these are collectively referred to as “three-phase detection current I _UVW ”). Is detected. The three-phase detection current I _UVW detected by the current detection unit 13 is given to the UVW / dq conversion unit 27.
The UVW / dq converter 27 converts the three-phase detection current I _UVW into a d-axis current Id and a q-axis current Iq on the two-phase rotational coordinate system (dq coordinate system) (hereinafter referred to as “two”). The coordinates are converted to “phase detection currents Id, Iq”. For this coordinate conversion, the conversion angle θ _S obtained by the rotation angle calculation unit 31 is used.

The power consumption rate calculation unit 37 is based on the two-phase detection currents Id and Iq obtained by the UVW / dq conversion unit 27 and the voltage V _dq supplied from the power supply 30 to the inverter drive circuit 12. Find Pinv. The power consumption Pinv of the inverter drive circuit 12 is a value corresponding to the power consumption of the power source (battery) 30.

Pinv = VdId + VqIq (1)
The power consumption rate calculation unit 37 sets an inverter power limit value Pinv_lim. The inverter power limit value Pinv_lim is the maximum limit value of the power consumption of the inverter drive circuit 12, and an excessive load is applied to the power supply when exceeding this limit value. The power consumption rate calculation unit 37 further obtains a power consumption rate Prate based on the inverter power limit value Pinv_lim and the power consumption Pinv.

Prate = Pinv / Pinv_lim (2)
This power consumption rate Prate is a value indicating how much the current power consumption of the inverter drive circuit 12 is compared to the inverter power limit value Pinv_lim. Pinv_lim falls within the range of 0 = <Pinv_lim = <1.
The correction unit 22 sets a power consumption rate gain PrateGain based on the power consumption rate Prate. This is a value obtained as a function of the power consumption rate Prate. A specific example of the function form of the power consumption rate gain PrateGain is shown in FIG. According to this figure, if A and B are constants in the range from 0 to 1, and the power consumption rate Prate is from 1 to A, the power consumption rate gain PrateGain is 1. When the power consumption rate Prate exceeds A, the power consumption rate gain PrateGain decreases from 1. When the power consumption rate Prate reaches 1, the power consumption rate gain PrateGain becomes B. Thus, “A” is the upper limit value of the power consumption rate Prate for maintaining the power consumption rate gain PrateGain at 1, and “B” is the power consumption when the power consumption rate Prate reaches the maximum value 1. This is the value of the rate gain PrateGain.

The correction unit 22 corrects the q-axis current command value Iq ^* using the power consumption rate gain PrateGain. When the corrected q-axis current command value Iq ^* is expressed as “Iq ^* ′”,
Iq ^* ′ = Iq ^* × PrateGain (3)
It is.

Further, the correction unit 22 sets the q-axis current limit value _{Iq_lim} so that the current consumption of the motor 3 does not exceed the current limit value for motor protection. In the case of a brushless motor, the q-axis current limit value _{Iq_lim} is calculated using the inverter power limit value Pinv_lim,
_{Iq _lim = (Pinv_lim-V d} * × Id *) / V q * ··· (4)
Is required. The correction unit 22 outputs the q-axis current command value Iq ^* ′ as it is if the q-axis current command value Iq ^* ′ is equal to or less than _{Iq_lim} , but if the q-axis current command value Iq ^* ′ exceeds _{Iq_lim} The q-axis current command value Iq ^* ′ is reduced to _{Iq_lim} and output.

In the case of a motor with a brush, the inverter power consumption Pinv is replaced with the above equation (1),
Pinv = VmIm (1a)
It is calculated using (Vm: motor voltage, Im: motor current). The corrected q-axis current command value I _m ^* ′ is replaced with the above equation (3),
I _m ^* ′ = I _m ^* × PrateGain (3a)
Calculate with _{Instead of the} motor current limit value I _{m_lim} in the above equation (4),
I _{m_lim} = Pinv_lim / V _m (4a)
Calculate with As described above, similarly to the brushless motor, the power can be limited by the motor voltage and the motor current.

FIG. 4 is a flowchart showing operations of the power consumption rate calculation unit 37 and the correction unit 22.
The power consumption rate calculation unit 37 calculates the inverter power consumption Pinv using the equation (1) (step S1), calculates the power consumption rate Prate using the equation (2) (step S2), and FIG. A power consumption rate gain PrateGain (step S3) is set using the illustrated map.
The correction unit 22 is obtained from the current command value generation unit 21 using the above-described equation (3) (step S4), and corrected by applying this power consumption rate gain PrateGain to the q-axis current command value Iq ^*. Q-axis current command value Iq ^* 'is obtained (step S5). Further, the q-axis current limit value _{Iq_lim} is calculated using the equation (4) (step S6). The correction unit 22 compares the corrected q-axis current command value Iq ^* ′ with the q-axis current limit value _{Iq_lim,} and compares the q-axis current command value Iq ^* ′ with the q-axis current limit value _{Iq_lim.} If it is larger (Yes in step S7), the q-axis current command value Iq ^* ′ is rewritten so as to be the same value as the q-axis current limit value _{Iq_lim} (step S8). If the q-axis current command value Iq ^* ′ is equal to or less than the q-axis current limit value _{Iq_lim} (No in step S7), the q-axis current command value Iq ^* ′ is used without being rewritten. The q-axis current command value Iq ^* ′ is provided to the current deviation calculation circuit 23.

The current deviation calculation circuit 23 calculates a deviation between the q-axis current command value Iq ^* ′ and the d-axis current command value Id ^* and the two-phase detection currents Iq and Id given from the UVW / dq converter 27. These deviations are given to the PI control unit 24.
The PI control unit 24 performs a PI calculation on the current deviation calculated by the deviation calculation unit 23 to thereby provide a two-phase command voltage V _dq ^* (d-axis command voltage V _d ^* and q-axis command voltage to be applied to the motor 3. V _q ^* ) is generated. The two-phase instruction voltage V _dq ^* is given to the dq / UVW conversion unit 25.

The dq / UVW conversion unit 25 converts the two-phase instruction voltage V _dq ^* into the three-phase instruction voltage V _UVW ^* . For this coordinate conversion, the conversion angle θ _S obtained by the rotation angle calculation unit 31 is used. The three-phase command voltage V _UVW ^* includes a U-phase command voltage V _U ^* , a V-phase command voltage V _V ^*, and a W-phase command voltage V _W ^* . The three-phase instruction voltage V _UVW ^* is given to the PWM control unit 26.
The PWM control unit 26 includes a U-phase PWM control signal, a V-phase PWM control signal, and a W-phase PWM having a duty corresponding to the U-phase instruction voltage V _U ^* , the V-phase instruction voltage V _V ^*, and the W-phase instruction voltage V _W ^* , respectively. A control signal is generated and supplied to the inverter drive circuit 12.

The inverter drive circuit 12 includes a three-phase converter 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 26, so that a voltage corresponding to the three-phase instruction voltage V _UVW ^* is set to the stator windings 51 of each phase of the motor 3. 52 and 53.
In such a configuration, when a steering torque is applied to the steering wheel 10, this is detected by the torque sensor 1. Then, the target motor torque T _M ^* corresponding to the steering torque detected by the torque sensor 1 and the vehicle speed detected by the vehicle speed sensor 7 is generated by the target motor torque generator 20. Then, current command values Id ^* and Iq ^* corresponding to the target motor torque T _M ^* are generated by the current command value generation unit 21.

The correction unit 22 applies the power consumption rate gain PrateGain to the q-axis current command value Iq ^* acquired from the current command value generation unit 21 to obtain a corrected q-axis current command value Iq ^* ′, and the q-axis if a current command value Iq ^* 'exceeds the q-axis current limit value Iq _{_lim,} so that below the q-axis current limit value Iq _{_lim,} and outputs the reduced q-axis current command value Iq ^*.
The deviation between the motor current command values Id ^* and Iq ^* and the two-phase detection currents Id and Iq is obtained by the current deviation computing circuit 23, and PI computation is performed by the PI control unit 24 so as to lead this deviation to zero. A two-phase instruction voltage V _dq ^* corresponding to the calculation result is output from the PI control unit 24. This two-phase command voltage V _dq ^* is converted into a three-phase command voltage V _UVW ^* by the dq / UVW converter 25.

Then, by the operation of the PWM control unit 26, the inverter drive circuit 12 operates at a duty ratio corresponding to the three-phase instruction voltage V _UVW ^* , whereby the motor 3 is driven and the final current command values Id ^* , Iq ^The motor torque (assist torque) corresponding to ^* is given to the steering mechanism 2. In this way, steering assistance can be performed according to the steering torque and the vehicle speed, and the drive power to the motor can be appropriately suppressed according to the power consumption rate so that there is no sense of incongruity such as torque clogging during sudden steering. it can.

In the above embodiment, “if the q-axis current command value Iq ^* ′ is larger than the q-axis current limit value _{Iq_lim} (Yes in step S7), the q-axis current command value Iq ^* ′ is changed to the q-axis current limit value Iq. _Although it has been described that the value is rewritten to be the same value as _{_lim} (step S8), the following modifications are possible. The main part of the control according to this modification is shown in FIG.
In FIG. 5, following step S _<b> 6 of FIG. 4, the correction unit 22 compares the corrected q-axis current command value Iq ^* ′ with the q-axis current limit value _{Iq_lim,} and compares the q-axis current command value. 'if is greater than q-axis current limit value iq _{_lim} (Yes in step S7), the q-axis current command value Iq ^*' iq ^* difference between the q-axis current limit value _{^{Iq _lim ΔIq * = Iq * '}} -Iq _lim Is obtained (step S8a). The difference ΔIq ^* is multiplied by a gain b (0 ≦ b ≦ 1) and subtracted from Iq ^* ′ (step S8b) to obtain a value (Iq ^* ′ − b × ΔIq ^* ). This value is set as Iq ^* ', and the process proceeds to step S9 in FIG.

The gain b is a constant that takes a value from 0 to 1. If b = 1, this is the same as step S8 in FIG.
As shown in steps S8a and S8b of FIG. 5, the q-axis current command value Iq ^* 'is corrected according to the difference between the corrected q-axis current command value Iq ^* ' and the q-axis current limit value _{Iq_lim} . This is because if the q-axis current command value Iq ^* ′ is used for control, the q-axis current command value Iq ^* ′ may exceed the q-axis current limit value _{Iq_lim} due to a control response delay.

Next, an electric power steering device to which a motor control device according to another embodiment of the present invention is applied will be described. In the embodiments so far, the power consumption rate Prate is calculated using the equation (2), and the power consumption rate gain PrateGain is set based on the power consumption rate Prate using the function form of FIG. The q-axis current command value Iq ^* is corrected using the power consumption rate gain PrateGain.

However, when the field weakening control is performed, instead of or setting the power consumption rate gain PrateGain, the power consumption rate Prate approaches 1 from C (0 ≦ C ≦ 1) as shown in FIG. The d-axis current command value Id ^* can be controlled so as to approach 0 from a negative constant value (Id1 ^* ). By this control, the field-weakening control amount can be reduced in a region where the power consumption rate is high, the output torque of the motor can be reduced, and an uncomfortable feeling such as torque clogging can be prevented during sudden steering.

Further, in this electric power steering apparatus, when the booster circuit 28 for boosting the voltage of the power supply 30 is provided, a control for lowering the boosted voltage Vboost as the power consumption rate Prate approaches 1 is adopted. Can do.
FIG. 7 is a block diagram for explaining the electrical configuration of the electric power steering apparatus. The difference from FIG. 1 is that the booster circuit 28 is in accordance with the power consumption rate Prate which is the output signal of the power consumption rate calculation unit 37. The step-up voltage changes. As shown in FIG. 8, the booster circuit 28 decreases the boosted voltage Vboost as the power consumption rate Prate approaches 1 from D (0 ≦ D ≦ 1) (V1 → V2). As a result, by reducing the motor voltage in a region where the power consumption rate is high, it is possible to reduce the output torque of the motor and to prevent a sense of incongruity such as torque clogging during sudden steering.

In the embodiments so far, the power consumption Pinv of the inverter drive circuit 12 has been obtained in order to estimate the power consumption of the power source (battery) 30 (the above formula (1)). However, a configuration may be adopted in which the voltage and current of the power source (battery) 30 are directly detected to determine the power consumption of the power source (battery) 30.
Further, using the rotation angle θ _M of the rotor 50 of the motor 3 output from the rotation angle calculation unit 31 (for example, by differential calculation), the rotation speed of the motor is calculated, and based on the product of this and the motor current Im. The power consumption of the power source (battery) 30 may be estimated.

  3, 6, and 8 shown so far show examples in which the power consumption rate gain, the field weakening current, and the boost voltage change linearly, the correction unit 22 and the boost circuit 28 of the present invention The control is not limited to this. For example, the power consumption rate Prate may change in a curved line in the range of 0 to 1 (secondary curve, exponential curve, sine wave curve, etc.). Further, instead of storing and using the function forms of the power consumption rate gain, field weakening current, and boosted voltage shown in FIGS. 3, 6, and 8 in the memory, values corresponding to the respective power consumption rates Prate are set in advance. It may be written in a table in memory and used.

  In addition, when emergency avoidance during high-speed traveling, the q-axis current command value, the boost voltage, and the field-weakening control amount are not limited. When the vehicle speed is high, these control amounts can be set not to be limited. It is also possible to combine each control of the q-axis current command value, the boost voltage, and the field weakening control.

  DESCRIPTION OF SYMBOLS 3 ... Steering auxiliary motor, 12 ... Inverter drive circuit, 22 ... Correction | amendment part, 30 ... Power supply, 37 ... Power consumption rate calculating part

Claims (9)

A steering assist motor for generating steering assist force;
An inverter drive circuit for driving the steering assist motor;
A power supply for supplying drive power to the inverter drive circuit;
Power consumption estimation means for calculating or estimating the power consumption of the power source;
A power consumption rate calculating means for calculating a power consumption rate from a ratio between the calculated or estimated power consumption and a predetermined power limit value;
An electric power steering apparatus comprising: power control means for controlling the steering assist motor by changing a motor control amount in accordance with the power consumption rate calculated by the power consumption rate calculation means. The motor control amount is a motor current command value set by the power control means,
The electric power steering apparatus according to claim 1, wherein the power control unit limits the motor current command value supplied to the steering assist motor according to the power consumption rate.   The electric power steering apparatus according to claim 2, wherein the power control means sets a power consumption rate gain according to the power consumption rate, and multiplies the q-axis current command value by the power consumption rate gain.   The power control means responds to a difference between a q-axis current command value multiplied by the power consumption rate gain and a q-axis current limit value representing an output limit of the steering assist motor. The electric power steering apparatus according to claim 3, wherein correction is further performed. The motor control amount is a field-weakening control amount set by the power control means,
The electric power steering apparatus according to claim 1, wherein the power control unit limits a d-axis current command value supplied to the steering assist motor according to the power consumption rate.   The electric power steering apparatus according to claim 1, wherein the motor control amount is a boosted voltage supplied to the steering assist motor, and the power control unit limits the boosted voltage according to the power consumption rate.   The electric power steering apparatus according to any one of claims 1 to 6, wherein the power consumption estimation means detects power consumption of an inverter drive circuit.   The electric power steering apparatus according to any one of claims 1 to 6, wherein the power consumption estimation means detects a power consumption by detecting a voltage and a current of a power supply that supplies power to the inverter drive circuit.   The electric power steering according to any one of claims 1 to 6, wherein the power consumption estimation means calculates a rotation speed of a motor and obtains power consumption based on a product of the rotation speed and a motor torque or a motor current. apparatus.

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