JP7371509B2 - Motor control devices, electric actuator products and electric power steering devices - Google Patents

Description

The present invention relates to a motor control device that controls an electric motor, and an electric actuator product and an electric power steering device that include a motor controlled by the motor control device.

If a large current continues to flow through the electric motor, the temperature of the power supply line that supplies power from the power supply or the parts and wiring disposed near the power supply line increases, and there is a risk that they will burn out. Additionally, there is a risk that the solder used to attach the parts will melt and the parts will fall.
Patent Document 1 listed below describes a technique in which the current command value is limited by the limit value by gradually decreasing or increasing the limit value according to the maximum value of the time average of the phase current function.
In Patent Document 2 listed below, an overheat protection characteristic that specifies the correspondence between a current value and an overheat protection coefficient is stored for each component for motor current supply, and the overheat protection coefficient is determined according to the current flowing through the component. Techniques have been described to gradually decrease or increase the current limit.

Japanese Patent Application Publication No. 2002-238293 Japanese Patent Application Publication No. 2014-093832

The temperature of parts and wiring placed in or near the power supply line is affected by the magnitude of the power supply current flowing through the power supply line, and the magnitude of the power supply current is influenced by the applied voltage applied from the power supply to the driving element and the electric motor. Varies depending on motor rotation speed. For this reason, if the current command value is limited by a limit value set according to the phase current as in Patent Document 1, the output of the electric motor may be unnecessarily limited.
Further, the technique disclosed in Patent Document 2 suppresses the heat generation amount of the component by gradually decreasing or increasing the current upper limit value according to the current flowing through the component, regardless of the actual temperature of the component. Considering that the component temperature depends on the ambient temperature, it is necessary to provide a margin for the current upper limit value in order to suppress the component temperature below the allowable temperature, which may unnecessarily limit the output of the electric motor.

For this reason, when used, for example, to control an electric motor of an electric power steering device of a vehicle, assist torque is unnecessarily limited. As a result, the steering wheel cannot be steered to the rack end, which may cause problems in steering performance, such as difficulty in turning at intersections or inability to park accurately.
The present invention has been made with a focus on the above-mentioned problems, and uses a highly accurate current upper limit value to avoid excessive current limitation while suppressing the rise in temperature of components and wiring placed in or near the power supply line. The purpose is to

According to one aspect of the present invention, a motor control device for controlling an electric motor is provided. A motor control device includes a drive element that is connected in series between a power supply and an electric motor and converts the power supply current output from the power supply into a drive current that flows through the electric motor, and a rotation element that detects the motor rotation speed of the electric motor. A speed detection section, an inverter applied voltage detection section that detects the voltage applied to the drive element as the inverter applied voltage, and a temperature detection section that detects the temperature of components placed in or near the power supply line from the power supply to the drive element. a current command value calculation part that calculates a current command value for controlling the drive current, and a plurality of current command value calculation parts that limit the current command value so as to respectively limit the power supply current below a plurality of predetermined upper limit values. a current limit value determination unit that determines the current limit value in accordance with at least the motor rotation speed detected by the rotation speed detection unit and the inverter applied voltage detected by the inverter applied voltage detection unit; and a plurality of current limit value determination units determined by the current limit value determination unit. A current limit value interpolation unit that interpolates the current limit value of , and calculates a current limit value according to the component temperature detected by the temperature detection unit, and a current command that is limited by the current limit value calculated by the current limit value interpolation unit. and an element control section that controls the drive element based on the value.

According to another aspect of the present invention, there is provided an electric actuator product including the above motor control device and an electric motor controlled by the motor control device.
According to still another aspect of the present invention, the electric power source includes the above-mentioned motor control device and an electric motor controlled by the motor control device, and the electric motor provides a steering assist force to a steering system of a vehicle. A steering device is provided.

According to the present invention, it is possible to suppress the rise in temperature of the power supply line or components and wiring disposed in the vicinity thereof while avoiding excessive current limitation using a highly accurate current upper limit value.

FIG. 1 is a configuration diagram showing an overview of an example of an electric power steering device according to an embodiment. FIG. 2 is a block diagram showing an example of the functional configuration of the controller in FIG. 1. FIG. FIG. 2 is an explanatory diagram of components arranged at or near a power supply line. FIG. 3 is an explanatory diagram of the characteristics of the q-axis current limit value. FIG. 3 is a block diagram showing an example of a functional configuration of a drive current limiting section. FIG. 3 is a block diagram showing an example of a functional configuration of a rotation speed input processing section. FIG. 2 is a block diagram showing an example of a functional configuration of a current limit value determining section. FIG. 3 is a block diagram showing an example of a functional configuration of a limit value determining section. (a) and (b) are diagrams showing an example of a limit value table and a fluctuation value table used in the limit value determination unit 80a. (a) and (b) are diagrams showing an example of a limit value table and a variation value table used by the limit value determination unit 80b. (a) and (b) are diagrams showing an example of a limit value table and a fluctuation value table used by the limit value determination unit 80c. (a) is a block diagram showing an example of the functional configuration of a current limit value interpolation section, and (b) and (c) are explanatory diagrams of interpolation of the q-axis current limit value. FIG. 3 is a block diagram showing an example of a q-axis current limiting section. It is a flow chart of an example of a motor control method of an embodiment. FIG. 3 is a diagram showing experimental results of motor control according to the present invention. It is an enlarged view of a range where the component temperature is around 50 [° C.]. It is an enlarged view of a range where the component temperature is around 60 [° C.]. It is an enlarged view of a range where the component temperature is around 80 [° C.].

Embodiments of the present invention will be described in detail with reference to the drawings.
Note that the embodiments of the present invention shown below exemplify devices and methods for embodying the technical idea of the present invention. is not limited to the following: The technical idea of the present invention can be modified in various ways within the technical scope defined by the claims.

(composition)
In the following description, a case will be described in which a motor control device according to an embodiment of the present invention drives a polyphase motor that generates a steering assist force in an electric power steering device. However, the motor control device according to the embodiment of the present invention is not limited to this, and can be applied to various motor control devices that drive multiphase motors.

FIG. 1 shows a configuration example of an electric power steering device according to an embodiment. A column shaft 2 of the steering handle 1 is connected to a tie rod 6 of a steering wheel via a reduction gear 3, universal joints 4A and 4B, and a pinion rack mechanism 5. The column shaft 2 is provided with a torque sensor 10 that detects the steering torque of the steering handle 1, and a motor (electric motor) 20 that assists the steering force of the steering handle 1 is connected to the column shaft via a reduction gear 3. It is connected to 2.

A controller (ECU: Electronic Control Unit) 30 that controls the power steering device is supplied with electric power from the battery 14 which is a DC power source, and receives an ignition key signal from the ignition key 11. Based on the steering torque Th detected by the vehicle speed sensor 12 and the vehicle speed Vh detected by the vehicle speed sensor 12, a steering assist command value of the assist command is calculated using an assist map etc., and based on the calculated steering assist command value. The current I supplied to the motor 20 is controlled.

In the electric power steering device having such a configuration, the steering torque Th transmitted from the steering wheel 1 by the driver's steering wheel operation is detected by the torque sensor 10, and is calculated based on the detected steering torque Th and the vehicle speed Vh. The drive of the motor 20 is controlled by the steering assist command value, and this drive is applied to the steering system as an assist force (steering assist force) for the driver's steering operation, allowing the driver to operate the steering wheel with a light force. In other words, the steering assist command value is calculated from the steering torque Th and vehicle speed Vh output by the steering wheel operation, and how the motor 20 is controlled based on this steering assist command value determines how good or bad the feeling is when operating the steering wheel. , the performance of the electric power steering device is greatly influenced.

The controller 30 may include, for example, a computer including a processor and peripheral components such as a storage device. The processor may be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit).
The storage device may include any one of a semiconductor storage device, a magnetic storage device, and an optical storage device. The storage device may include memory such as a register, a cache memory, a ROM (Read Only Memory) used as a main storage device, and a RAM (Random Access Memory).
The functions of the controller 30 described below are realized, for example, by a processor executing a computer program stored in a storage device.

Note that the controller 30 may be formed of dedicated hardware for realizing the functions described below.
For example, the controller 30 may include a functional logic circuit set in a general-purpose semiconductor integrated circuit. For example, the controller 30 may include a programmable logic device (PLD) such as a field-programmable gate array (FPGA).

An example of the functional configuration of the controller 30 according to the embodiment will be described with reference to FIG. 2. The controller 30 includes a steering assist command value calculation section 40, a current command value calculation section 41, a drive current limiting section 43, subtractors 44 and 45, a proportional-integral (PI) control section 46, and a duty control section 40. (Duty) calculation section 47, space vector modulation section 48, PWM (Pulse Width Modulation) control section 49, inverter (INV) 50, 3-phase/2-phase conversion section 51, and rotation speed calculation section 52. , the motor 20 is driven by vector control.

The steering assist command value calculation unit 40 determines a steering assist command value Iref, which is a control target value (assist command) of the current supplied to the motor 20, based on the steering torque Th and the vehicle speed Vh.
The current command value calculation unit 41 converts the current command value, which is the target current of the current supplied to the motor 20, into the q-axis current command value of the rotor rotation coordinate system based on the steering assist command value Iref and the motor rotation speed Nr of the motor 20. Calculate as Iq0 and d-axis current command value Id0. The current command value calculation unit 41 outputs the q-axis current command value Iq0 to the drive current limiter 43, and outputs the d-axis current command value Id0 to the drive current limiter 43 and the subtracter 45.

The drive current limiter 43 acquires information on component temperatures Tp of components arranged on or near the power supply line from the battery 14 to the inverter 50.
With reference to FIG. 3, an example of components arranged on or near the power supply line will be described. The inverter 50 includes a bridge connected between a positive power line Lpp connected to the battery 14 and supplied with DC power, and a negative power line Lpn, which is a ground line.

The bridge includes upper arm drive elements (switching elements) Q1, Q3, and Q5, and lower arm drive elements (switching elements) Q2, Q4, and Q6.
Various components are arranged on or near the power lines Lpp and Lpn from the battery 14 to the drive elements Q1 to Q6. For example, a relay R and a choke coil L for cutting off power supply current are connected to the power supply line Lpp. The vicinity of the power supply line is an area where the temperature is expected to rise due to heat generation and heat conduction caused by the flow of power supply current. The electrolytic capacitor C connected to the input terminal of the inverter 50 and its wiring are examples of components near the power supply line. Hereinafter, components placed on or near the power supply line will be referred to as "ECU components."

The temperature detection unit 53 detects the component temperature Tp of any of the ECU components and outputs a detection signal to the controller 30. The temperature detection unit 53 may be arranged to detect the temperature of a component whose temperature increases or whose rate of temperature increase is significant among the ECU components.
Further, the inverter applied voltage detection section 54 detects the voltage (inverter applied voltage) Vr applied to the inverter 50 and outputs a detection signal to the controller 30.

See FIG. 2. The drive current limiter 43 limits the q-axis current command value Iq0 based on the component temperature Tp of the ECU component, the motor rotation speed Nr of the motor 20, the inverter applied voltage Vr, and the steering assist command value Iref.
Specifically, the drive current limiter 43 limits the q-axis current command value Iq0 so that the power supply current output by the battery 14 is equal to or less than an upper limit value depending on the component temperature Tp.

In addition to the component temperature Tp, motor rotational speed Nr, inverter applied voltage Vr, and steering assist command value Iref, the drive current limiter 43 controls the d-axis current command value Id0, the motor temperature Tm of the motor 20, and the The q-axis current command value Iq0 may be limited depending on the temperature information.
The drive current limiter 43 outputs the limited q-axis current command value Iq1 obtained by limiting the q-axis current command value Iq0 to the subtracter 44. Details of the drive current limiter 43 will be described later.

The subtracters 44 and 45 subtract the motor currents iq and id fed back from the motor 20 from the limited q-axis current command value Iq1 and the d-axis current command value Id0, respectively, to obtain the q-axis deviation current Δq and the d-axis deviation current. Calculate Δd. The q-axis deviation current Δq and the d-axis deviation current Δd are input to the PI control unit 46.

The PI control unit 46 calculates voltage command values vq and vd that set the q-axis deviation current Δq and the d-axis deviation current Δd to 0, respectively.
Duty calculating section 47 calculates a q-axis duty command value and a d-axis duty command value in PWM control of inverter 50 based on voltage command values vq and vd. The space vector modulator 48 converts the q-axis duty command value and the d-axis duty command value in the dq-axis space into three-phase duty command values, and outputs the three-phase duty command values to the PWM control unit 49 .

PWM control unit 49 generates a PWM signal with a duty ratio according to the three-phase duty command value as a gate signal for driving drive elements Q1 to Q6 of inverter 50, respectively.
The inverter 50 is driven by a gate signal generated by the PWM control unit 49, and the motor 20 is supplied with a current such that the q-axis deviation current Δq and the d-axis deviation current Δd become zero.

The rotation angle detection circuit 61 detects the motor angle (rotation angle) θ of the motor 20, and the rotation speed calculation unit 52 calculates the rotation angular velocity ω and the rotation speed Nr of the motor 20 based on the change in the motor angle θ.
The motor temperature acquisition unit 62 acquires temperature information about the motor temperature Tm of the motor 20. For example, the motor temperature acquisition unit 62 may directly detect the motor temperature Tm, or may estimate the motor temperature Tm based on the applied voltage and motor current of the motor 20.

Next, details of the drive current limiting section 43 will be explained. As described above, the drive current limiter 43 limits the q-axis current command value Iq0 so that the power supply current output by the battery 14 is equal to or less than the upper limit value depending on the component temperature Tp of the ECU component.
Specifically, a plurality of upper limit values Ib1, Ib2..., Ibn of the power supply current at a plurality of component temperatures Tp1, Tp2..., Tpn are respectively set.

For example, the component temperatures TL, TM, and TH are set so that TL<TM<TH, the upper limit value when the component temperature Tp is TL is set to Ib1, and the upper limit value when the component temperature Tp is TM. is set to Ib2, and the upper limit when the component temperature Tp is TH is set to Ib3.

The drive current limiter 43 limits the q-axis current command value Iq0 based on the motor rotational speed Nr and the inverter applied voltage Vr so as to limit the power supply current to the upper limit value or less for each of the upper limit values Ib1 to Ibn. Each of a plurality of q-axis current limit values Iq_limc1, Iq_limc2, . . . , Iq_limcn is determined.
When the upper limit values Ib1, Ib2, .

An example of a method for calculating the q-axis current limit value according to the upper limit value of the power supply current will be described below.
The relationship between the input energy, output energy, and loss energy of the motor 20 and the drive circuit is given by the following equation (1).

In the above formula (1), Ib represents the power supply current output by the battery 14, Rr represents the resistance value of the part to which voltage is applied (for example, motor resistance or inverter internal resistance, etc.), and Id and Iq represent the d-axis current. and q-axis current, Kt represents the torque constant of the motor 20, and Ploss represents power loss due to iron loss, friction, etc.
By substituting the power supply current upper limit value Ib_lim for the power supply current Ib in the above formula (1) and solving the above formula (1) for the q-axis current, the calculation formula for the q-axis current limit value Iq_lim shown in the following formula (2) is obtained. get.

Now, when the rotational angular velocity ω of the motor 20 is expressed using the rotational speed N, the arithmetic expression (2) can be transformed into the following arithmetic expression (3).

On the other hand, since the q-axis current cannot exceed the maximum value Iref_max of the steering assist command value Iref, the q-axis current limit value Iq_lim is also limited by the following equation (4).

With reference to FIG. 4, an overview of the characteristics of the q-axis current limit value obtained from the arithmetic expression (3) and the conditional expression (4) will be explained.
The q-axis current limit value Iq_lim has a characteristic that depends on the motor rotation speed N. In a range where the motor rotational speed N is relatively low (0≦N<N1), the q-axis current limit value Iq_lim is equal to the maximum value Iref_max of the steering assist command value Iref. In this range, the q-axis current limit value Iq_lim does not contribute to limiting the q-axis current.
In a range where the motor rotational speed N is relatively high (N1≦N), the q-axis current limit value Iq_lim gradually decreases as the motor rotational speed N increases. When the q-axis current limit value Iq_lim becomes smaller than the q-axis current command value Iq0, the q-axis current command value Iq0 is limited to the q-axis current limit value Iq_lim.

In this embodiment, in order to reduce the processing load on the controller 30, a table of q-axis current limit values calculated in advance based on calculation formula (3) and conditional formula (4) is created and stored in the storage device. .
For example, in equation (3), the upper limit value Ib_lim may be fixed to each of Ib1 to Ibn, and a table may be created for each upper limit value Ib1 to Ibn.

The drive current limiter 43 reads each q-axis current limit value from these tables according to the input motor rotation speed Nr, and sets a plurality of q-axis current limit values Iq_limc1 to Iq_limcn based on the read q-axis current limit value. Determine each of the following. For example, the drive current limiter 43 corrects the q-axis current limit value read from the table according to the inverter applied voltage Vr input from the inverter applied voltage detector 54, and calculates the q-axis current limit values Iq_limc1 to Iq_limcn. Each may be determined.
The drive current limiter 43 calculates the q-axis current limit value Iq_lim according to the component temperature Tp by interpolating the plurality of q-axis current limit values Iq_limc1 to Iq_limcn according to the component temperature Tp of the ECU components, and calculates the q-axis current limit value Iq_lim according to the component temperature Tp. Limit the axis current command value Iq0 to below the q-axis current limit value Iq_lim.

See FIG. 5. The drive current limiter 43 includes a rotation speed input processor 70, a current limit value determiner 71, a current limit value interpolator 72, a rate limiter 73, a smoother 74, and a q-axis current limiter 75. .
The rotation speed input processing section 70 processes the rotation speed Nr of the motor 20 input from the rotation speed calculation section 52 to generate a rotation speed signal N used for determining the plurality of q-axis current limit values Iq_limc1 to Iq_limcn. do.
Specifically, the rotation speed input processing unit 70 compares the sign of the steering assist command value Iref and the sign of the motor rotation speed, and determines whether the direction of the motor current is equal to the direction of rotation of the motor. .

When the direction of the motor current and the direction of rotation of the motor are different, the steering handle 1 is in the reverse steering state. In this case, the motor 20 enters the regenerative state depending on the direction of the motor current and the direction of the back electromotive force. Therefore, the current flowing from the battery 14 becomes small or the motor 20 enters the power generation state, so there is no need to limit the power supply current.

Therefore, the rotation speed input processing section 70 outputs a rotation speed of 0 as the rotation speed signal N when the sign of the steering assist command value Iref and the sign of the motor rotation speed are different. As described above, when the motor rotation speed is 0, the q-axis current limit value Iq_lim does not contribute to limiting the q-axis current. If the direction of the motor current and the direction of rotation of the motor are different, the rotation speed input processing unit 70 sets the rotation speed signal N to 0 and cancels the restriction on the q-axis current.

See FIG. 6. The rotational speed input processing section 70 includes sign determination sections (sgn) 70a and 70b, a steering state determination section 70c, an absolute value calculation section (abs) 70d, and a selector 70e.
The sign determination units 70a and 70b determine the sign of the rotation speed Nr of the motor 20 calculated by the rotation speed calculation unit 52 and the steering assist command value Iref. The sign determination units 70a and 70b output the signs of the rotational speed Nr and the steering assist command value Iref to the steering state determination unit 70c.

The steering state determination unit 70c determines whether the steering wheel 1 is in an additional steering state or a reverse steering state, depending on whether the signs of the rotational speed Nr and the steering assist command value Iref are equal. Specifically, when the signs of the rotational speed Nr and the steering assist command value Iref are equal, the steering state determination unit 70c determines that the steering wheel 1 is in the additional steering state. When the rotational speed Nr and the steering assist command value Iref have different signs, the steering state determination unit 70c determines that the steering wheel 1 is in the reverse steering state.

When the steering wheel 1 is in the additional steering state, the steering state determining section 70c outputs a selection signal "1" to the selector 70e. When the steering wheel 1 is in the reverse steering state, the steering state determination unit 70c outputs a selection signal "0" to the selector 70e.
The absolute value calculation unit 70d calculates the absolute value |Nr| of the rotational speed Nr. When the steering state determining unit 70c outputs the selection signal "1", the selector 70e selects the absolute value |Nr| and outputs it as the rotational speed signal N. When the steering state determination unit 70c outputs the selection signal "0", the selector 70e selects the rotation speed 0 and outputs it as the rotation speed signal N.

See FIG. 5. The current limit value determination unit 71 determines a plurality of q-axis current limit values Iq_limc1 to Iq_limcn based on the rotation speed signal N output by the rotation speed input processing unit 70 and the inverter applied voltage Vr output by the inverter applied voltage detection unit 54. Determine the value.
The current limit value determining unit 71 determines a plurality of q-axis current limits according to the d-axis current command value Id0, the motor temperature Tm of the motor 20, and the temperature information of the inverter 50, in addition to the rotational speed signal N and the inverter applied voltage Vr. Values Iq_limc1 to Iq_limcn may be determined.

FIG. 7 shows an example of the functional configuration of the current limit value determining section 71. The example of the current limit value determination unit 71 shown in FIG. 7 determines three q-axis current limit values Iq_limc1 to Iq_limc3. However, the number of q-axis current limit values determined by the current limit value determination unit 71 is not limited to three, and two q-axis current limit values may be determined. Four or more q-axis current limit values may be determined. The current limit value determining section 71 includes limit value determining sections 80a, 80b, and 80c.

The limit value determination unit 80a determines the q-axis current limit value Iq_limc1. The q-axis current limit value Iq_limc1 is a limit value of the q-axis current command value Iq0 for limiting the power supply current to below the upper limit value Ib1 when the component temperature Tp of the ECU component is TL.
For example, the maximum power supply current allowed by the electric power steering device of the embodiment may be set as the upper limit value Ib1. In this case, the q-axis current limit value Iq_limc1 may be used not only when the component temperature Tp of the ECU component is TL, but also as a limit value when the component temperature Tp is lower than TL.

The limit value determination unit 80b determines the q-axis current limit value Iq_limc2. The q-axis current limit value Iq_limc2 is a limit value of the q-axis current command value Iq0 for limiting the power supply current to below the upper limit value Ib2, which is smaller than the upper limit value Ib1, when the component temperature Tp is TM.
For example, the upper limit value Ib2 may be set so that the power consumption of the ECU components is approximately 1/2 that when the power supply current of the upper limit value Ib1 flows. For example, the upper limit value Ib2 may be set to Ib1×5/7.

The limit value determination unit 80c determines the q-axis current limit value Iq_limc3. The q-axis current limit value Iq_limc3 is a limit value of the q-axis current command value Iq0 for limiting the power supply current to below the upper limit value Ib3, which is smaller than the upper limit value Ib2, when the component temperature Tp is TH.
For example, the upper limit value Ib3 may be set to the minimum power supply current required for steering at maximum load and steering to the rack end. For example, the upper limit value Ib3 may be set to Ib1×3/7. In this case, the q-axis current limit value Iq_limc3 may be used not only when the component temperature Tp of the ECU component is TH, but also as a limit value when the component temperature Tp is higher than TH.

FIG. 8 shows an example of the functional configuration of the limit value determining section 80a. The limit value determining section 80a includes a limit value table reading section 81, a variation value table reading section 82, a limiter 83, a subtracter 84, a multiplier 85, a coefficient multiplier 86, an adder 87, and a limiter 88. Equipped with.

The limit value table reading unit 81 stores a limit value table in which the q-axis current limit value for limiting the power supply current to below the upper limit value Ib1 is associated with the rotational speed signal N.
The limit value table reading unit 81 reads the q-axis current limit value from the limit value table according to the rotation speed signal N output by the rotation speed input processing unit 70, and sets the read q-axis current limit value as the q-axis current reference limit value. Output as Iq_limb.

FIG. 9A shows an example of a table of q-axis current limit values for limiting the power supply current to below the upper limit value Ib1. The thick solid line shows a table of q-axis current limit values according to the rotational speed signal N, and the upper limit value Ib_lim is fixed to Ib1, the inverter applied voltage Vr is fixed to a predetermined reference voltage Vref, and the calculation formula ( 3) and conditional expression (4). The reference voltage Vref may be, for example, the lower limit of the allowable applied voltage of the inverter 50.
That is, a limit value table is created by calculating a limit value Iq_lim in advance for each rotational speed signal N according to the following equations (5) and (6).

In an actual circuit, the d-axis current included in arithmetic expression (3) and conditional expression (4) varies. Therefore, when creating a limit value table, a table of q-axis current limit values for a plurality of d-axis currents Id=0, Id1, Id2, and Id3 is calculated, respectively. The thin solid line, the broken line, the one-dot chain line, and the two-dot chain line indicate a table of q-axis current limit values at d-axis current Id=0, Id1, Id2, and Id3.
Then, the range of the d-axis current Id flowing in each rotational speed signal N is predicted, and these tables are selected or set according to the rotational speed signal N while considering the trade-off between protection performance and torque performance of the motor 20. A limit value table with a thick solid line is created by interpolating between the values.

Refer to FIG. In an actual circuit, the inverter applied voltage Vr varies depending on the steering state and vehicle state. Therefore, the q-axis current reference limit value Iq_limb is corrected according to the inverter applied voltage Vr. The higher the inverter applied voltage Vr is, the less power supply current is consumed, and the restriction on the q-axis current is relaxed.
The fluctuation value table reading unit 82 stores a fluctuation value table in which the rotational speed signal N is associated with the fluctuation value ΔIq_lim of the q-axis current limit value with respect to the standard deviation ΔV between the inverter applied voltage Vr and the reference voltage Vref.

FIG. 9(b) shows an example of a variation value table. In the fluctuation value table shown in (b) of FIG. 9, the upper limit value Ib_lim is fixed to Ib1 in calculation formula (3), the d-axis current is fixed to 0 [A], and the inverter applied voltage is set to (Vref + ΔV). The difference is calculated in advance by subtracting the q-axis current limit value when the inverter applied voltage is set to Vref from the q-axis current limit value when the inverter applied voltage is set to Vref.
That is, a fluctuation value table is created by calculating a fluctuation value ΔIq_lim in advance for each rotational speed signal N according to the following equation (7).

Refer to FIG. The variation value table reading unit 82 reads the variation value ΔIq_lim from the variation value table according to the rotation speed signal N output by the rotation speed input processing unit 70 and outputs the read variation value ΔIq_lim to the multiplier 85.
The limiter 83 limits the upper limit of the inverter applied voltage Vr, and the subtracter 84 calculates a deviation voltage (Vr-Vref) between the inverter applied voltage Vr, whose upper limit is limited, and the reference voltage Vref.
The multiplier 85 and the coefficient multiplier 86 multiply the fluctuation value ΔIq_lim read from the fluctuation value table by the deviation voltage (Vr-Vref) and the coefficient Gv (=1/ΔV) to obtain a correction value ΔIq_lim×Gv. Calculate ×(Vr−Vref).

The adder 87 corrects the q-axis current reference limit value Iq_limb by adding the correction value ΔIq_lim×Gv×(Vr-Vref), so that the q-axis current limit value Iq_limc1=Iq_limb+ΔIq_lim×Gv×(Vr-Vref). calculate.
The limiter 88 limits the upper limit value of the q-axis current limit value Iq_limc1 and outputs it to the current limit value interpolation unit 72.

Note that, as is clear from equation (3), the q-axis current limit value also varies depending on the torque constant Kt, the resistance value Rr, and the d-axis current Id. The torque constant Kt varies depending on the motor temperature Tm, and the resistance value Rr varies depending on the motor temperature Tm and the temperature of the inverter 50.
Therefore, the limit value determination unit 80a may further use the motor temperature Tm, the temperature of the inverter 50, and the d-axis current Id to correct the q-axis current reference limit value Iq_limb.

For example, similar to the above fluctuation value table, a table that associates the rotational speed signal N with the fluctuation value of the q-axis current limit value with respect to the deviation of the torque constant Kt, the resistance value Rr, and the d-axis current Id is created using the calculation formula (3 ) is calculated and stored in advance based on the rotational speed signal N, and the fluctuation value is read out from the table in accordance with the rotational speed signal N.
On the other hand, the torque constant Kt and resistance value Rr are calculated based on the motor temperature Tm and the temperature of the inverter 50, and the deviation between the torque constant Kt, resistance value Rr, and d-axis current Id and these reference values is calculated. . A correction value may be obtained by multiplying the fluctuation value read from the table by these deviations, and the correction value may be added to the q-axis current reference limit value Iq_limb to correct the q-axis current reference limit value Iq_limb.

Limit value determining sections 80b and 80c also have the same configuration as limit value determining section 80a. However, the limit value table and the variation table stored by the limit value determination units 80b and 80c are different from the limit value table and the variation value table stored by the limit value determination unit 80a.

(a) of FIG. 10 shows a limit value table stored in the limit value table reading section 81 of the limit value determining section 80b. The limit value table in FIG. 10(a) is a table of q-axis current limit values for limiting the power supply current to below the upper limit value Ib2.
Similar to the table in FIG. 9(a), the thick solid line shows the table of q-axis current limit values according to the rotational speed signal N, and the thin solid line, broken line, one-dot chain line, and two-dot chain line indicate the table of d A table of q-axis current limit values for axis current Id=0, Id1, Id2, and Id3 is shown. The same applies to the table in FIG. 11(a).

These tables are calculated in the same way as the table in FIG. 9A, with the upper limit value Ib_lim fixed at Ib2 and the inverter applied voltage Vr fixed at a predetermined reference voltage Vref.
FIG. 10(b) shows a fluctuation value table stored in the fluctuation value table reading section 82 of the limit value determination section 80b. The fluctuation value table shown in FIG. 10(b) is calculated in the same way as the fluctuation value table shown in FIG. 9(b), with the upper limit value Ib_lim fixed at Ib2.

(a) of FIG. 11 shows a limit value table stored in the limit value table reading section 81 of the limit value determining section 80c. The limit value table in FIG. 11(a) is a table of q-axis current limit values for limiting the power supply current to below the upper limit value Ib3.
These tables are calculated in the same way as the table in FIG. 9A, with the upper limit value Ib_lim fixed at Ib3 and the inverter applied voltage Vr fixed at a predetermined reference voltage Vref.
FIG. 11(b) shows a fluctuation value table stored in the fluctuation value table reading section 82 of the limit value determination section 80c. The fluctuation value table shown in FIG. 11(b) is calculated in the same manner as the fluctuation value table shown in FIG. 9(b), with the upper limit value Ib_lim fixed at Ib3.

See FIG. 5. The current limit value interpolation unit 72 interpolates the plurality of q-axis current limit values Iq_limc1 to Iq_limcn determined by the current limit value determination unit 71 according to the component temperature Tp detected by the temperature detection unit 53, and It is output as the q-axis current limit value Iq_lim0.
The example of the current limit value interpolation unit 72 shown in FIG. 12 corresponds to the current limit value determination unit 71 shown in FIG. Calculate.

The current limit value interpolation section 72 includes interpolation value calculation sections 90 and 91 and a selection section 92.
The interpolated value calculation unit 90 calculates the q-axis current limit value when the component temperature Tp is in the range from TL to TM by interpolating the q-axis current limit value Iq_limc1 and the q-axis current limit value Iq_limc2.
Refer to FIG. 12(b). The interpolated value calculation unit 90 outputs the q-axis current limit value Iq_limc1 when the component temperature Tp is TL. When the component temperature Tp is TM, the q-axis current limit value Iq_limc2 is output. When the component temperature Tp is greater than TL and less than TM, interpolation obtained by interpolating between the q-axis current limit value Iq_limc1 and the q-axis current limit value Iq_limc2 by the component temperature Tp detected by the temperature detection unit 53 is performed. Output the value.

The interpolated value calculation unit 91 calculates the q-axis current limit value when the component temperature Tp is in the range from TM to TH by interpolating the q-axis current limit value Iq_limc2 and the q-axis current limit value Iq_limc3.
Refer to FIG. 12(c). The interpolated value calculation unit 91 outputs the q-axis current limit value Iq_limc2 when the component temperature Tp is TM. When the component temperature Tp is TH, the q-axis current limit value Iq_limc3 is output. When the component temperature Tp is greater than TM and less than TH, interpolation obtained by interpolating between the q-axis current limit value Iq_limc2 and the q-axis current limit value Iq_limc3 by the component temperature Tp detected by the temperature detection unit 53 is performed. Output the value.
Note that the interpolation value calculation units 90 and 91 may calculate the interpolation value by linear interpolation, or may calculate the interpolation value using a nonlinear function.

The selection unit 92 selects one of the maximum value Iq_limc1 and the minimum value Iq_limc3 of the plurality of q-axis current limit values Iq_limc1 to Iq_limc3, and the outputs of the interpolation value calculation units 90 and 91, from the component detected by the temperature detection unit 53. It is selected according to the temperature Tp and output as the q-axis current limit value Iq_lim0 according to the component temperature Tp.
Specifically, when the component temperature Tp is less than TL, the selection unit 92 selects the maximum value Iq_limc1 as the q-axis current limit value Iq_lim0.

When the component temperature Tp is greater than or equal to TL and less than TM, the selection unit 92 selects the output of the interpolation value calculation unit 90 as the q-axis current limit value Iq_lim0. When the component temperature Tp is greater than or equal to TM and less than TH, the selection unit 92 selects the output of the interpolation value calculation unit 91 as the q-axis current limit value Iq_lim0. When the component temperature Tp is equal to or higher than TH, the selection unit 92 selects the minimum value Iq_limc3 as the q-axis current limit value Iq_lim0.

In this embodiment, the q-axis current limit value Iq_lim0 is fixed to the q-axis current limit value Iq_limc1 in the range where the component temperature Tp is less than TL, and the q-axis current limit value Iq_lim0 is fixed to q-axis current limit value Iq_limc1 in the range where the component temperature Tp is higher than TH. Although the shaft current limit value Iq_limc3 is fixed, the present invention is not limited thereto. The current limit value interpolation unit 72 may calculate the q-axis current limit value Iq_lim0 in a range where the component temperature Tp is less than TL or greater than or equal to TH by extrapolation based on the plurality of q-axis current limit values Iq_limc1 to Iq_limc3.

See FIG. 5. The rate limiter 73 alleviates transient fluctuations in the q-axis current limit value Iq_lim0.
When the steering state of the steering wheel 1 is switched between the additional steering state and the reverse steering state, the value of the q-axis current limit value Iq_lim0 suddenly changes because the rotational speed input processing unit 70 switches the rotational speed signal N. Changes to As a result, there is a possibility that a sudden change in the output value of the q-axis current limit value or chattering may occur.
The rate limiter 73 generates a q-axis current limit value Iq_lim1 obtained by alleviating transient fluctuations in the q-axis current limit value Iq_lim0, and outputs it to the smoothing unit 74.

For example, the rate limiter 73 determines that the difference obtained by subtracting the q-axis current limit value Iq_lim1 output in the previous control cycle from the q-axis current limit value Iq_lim0 input in the current control cycle is greater than the positive rising threshold RISE_RATE. If it is larger, the sum of the q-axis current limit value Iq_lim1 output in the previous control cycle and the rising threshold RISE_RATE is output as the q-axis current limit value Iq_lim1.

In addition, the rate limiter 73 determines that the difference obtained by subtracting the q-axis current limit value Iq_lim1 output in the previous control cycle from the q-axis current limit value Iq_lim0 input in the current control cycle is greater than the negative falling threshold FALL_RATE. If the current limit value Iq_lim1 is also small, the sum of the q-axis current limit value Iq_lim1 output in the previous control cycle and the falling threshold value FALL_RATE is output as the q-axis current limit value Iq_lim1.

If the difference obtained by subtracting the q-axis current limit value Iq_lim1 output in the previous control cycle from the q-axis current limit value Iq_lim0 input in the current control cycle is greater than or equal to the falling threshold FALL_RATE and less than the rising threshold RISE_RATE, The input q-axis current limit value Iq_lim0 is output as is as the q-axis current limit value Iq_lim1.

The smoothing unit 74 smoothes the q-axis current limit value Iq_lim1, thereby alleviating a sudden change in the output value of the q-axis current limit value when the rotational speed signal N is switched, and eliminating chattering.
For example, the smoothing unit 74 may be a filter that calculates a time-weighted average value of the q-axis current limit value Iq_lim1. The smoothing unit 74 outputs the final q-axis current limit value Iq_lim obtained by smoothing the q-axis current limit value Iq_lim1 to the q-axis current limit unit 75.

The q-axis current limiter 75 limits the q-axis current command value Iq0 output from the current command value calculator 41 to a value equal to or less than the q-axis current limit value Iq_lim. The q-axis current limiter 75 outputs a limited q-axis current command value Iq1 obtained by limiting the q-axis current command value Iq0.
See FIG. 13. The q-axis current limiter 75 includes a sign inverter 100, comparators 101 and 102, and selectors 103 and 104.

Comparator 101 compares q-axis current command value Iq0 and positive q-axis current limit value Iq_lim. When the q-axis current command value Iq0 is greater than or equal to the positive q-axis current limit value Iq_lim, the comparator 101 outputs a selection signal “1” to the selector 103. When the q-axis current command value Iq0 is less than the positive q-axis current limit value Iq_lim, the comparator 101 outputs a selection signal “0” to the selector 103.

The sign inverter 100 inverts the sign of the q-axis current limit value Iq_lim and outputs a negative q-axis current limit value (-Iq_lim). Comparator 102 compares q-axis current command value Iq0 and a negative q-axis current limit value (-Iq_lim). When the q-axis current command value Iq0 is less than or equal to the negative q-axis current limit value (-Iq_lim), the comparator 102 outputs a selection signal “1” to the selector 104. When the q-axis current command value Iq0 is larger than the negative q-axis current limit value (-Iq_lim), the comparator 102 outputs a selection signal “0” to the selector 104.

When the comparator 101 outputs the selection signal "1" (that is, when the q-axis current command value Iq0 is greater than or equal to the positive q-axis current limit value Iq_lim), the selector 103 selects the q-axis current limit value Iq_lim. Output to selector 104.
When the comparator 101 outputs the selection signal "0" (that is, when the q-axis current command value Iq0 is less than the positive q-axis current limit value Iq_lim), the selector 103 selects the q-axis current command value Iq0. Output to selector 104.

When the comparator 102 outputs the selection signal "1" (that is, when the q-axis current command value Iq0 is less than or equal to the negative q-axis current limit value (-Iq_lim)), the selector 104 outputs the negative q-axis current limit value. The value (-Iq_lim) is selected and output as the limited q-axis current command value Iq1.
When the comparator 102 outputs the selection signal "0" (that is, when the q-axis current command value Iq0 is larger than the negative q-axis current limit value (-Iq_lim)), the selector 104 outputs the output of the selector 103. Select and output as the limited q-axis current command value Iq1. As described above, the limited q-axis current command value Iq1 is limited to a value that is less than or equal to the positive q-axis current limit value (Iq_lim) and greater than or equal to the negative q-axis current limit value (-Iq_lim).

Note that the battery 14 is an example of a power source described in the claims. The controller 30, the temperature detection section 53, the inverter applied voltage detection section 54, the rotation angle detection circuit 61, and the motor temperature acquisition section 62 are an example of a motor control device described in the claims. The rotation angle detection circuit 61 and the rotation speed calculation section 52 are examples of a rotation speed detection section described in the claims. The limit value table and the variation value table are examples of the first table and the second table described in the claims. The limit value table and the variation value table may be approximated by polynomials or the like and stored as approximate expressions in the first storage section and the second storage section. The proportional integral control section 46, the duty calculation section 47, the space vector modulation section 48, and the PWM control section 49 are examples of the element control section described in the claims.

(motion)
An example of the motor control method according to the embodiment will be described with reference to FIG. 14.
In step S1, the rotation angle detection circuit 61 and the rotation speed calculation unit 52 detect the rotation speed Nr of the motor 20.
In step S2, the inverter applied voltage detection unit 54 detects the inverter applied voltage Vr, which is the voltage applied to the inverter 50.

In step S3, the temperature detection section 53 detects the component temperature Tp of any of the ECU components.
In step S4, the current command value calculation unit 41 calculates the q-axis current command value Iq0 and the d-axis current command value Id0.

In step S5, the current limit value determination unit 71 determines a plurality of q-axis current limit values Iq_limc1 based on the rotation speed signal N output by the rotation speed input processing unit 70 and the inverter applied voltage Vr detected by the inverter applied voltage detection unit 54. .about.Iq_limcn.
In step S6, the current limit value interpolation unit 72 interpolates the plurality of q-axis current limit values Iq_limc1 to Iq_limcn to calculate the q-axis current limit value Iq_lim0 according to the component temperature Tp of the ECU component detected by the temperature detection unit 53. do.

In step S7, the rate limiter 73 generates a q-axis current limit value Iq_lim1 obtained by alleviating transient fluctuations in the q-axis current limit value Iq_lim0, and the smoothing unit 74 smoothes the q-axis current limit value Iq_lim1. The q-axis current limit value Iq_lim obtained by The q-axis current limiter 75 calculates the limited q-axis current command value Iq1 by limiting the q-axis current command value Iq0 by the q-axis current limit value Iq_lim.
In step S8, the controller 30 drives the motor 20 based on the d-axis current command value Id0 and the limited q-axis current command value Iq1.

(Experimental result)
Below, with reference to FIGS. 15 to 18, experimental results using the motor control device of this embodiment will be shown. In the experiment, the temperatures TH, TM, and TL were set to TH = 80 [°C], TM = 60 [°C], and TL = 50, respectively, and end contact was repeated with low-medium speed steering at one end of the rack. I went.
In addition, the upper limit value of the power supply current when the component temperature Tp is below the temperature TL is set to Ib1, and the upper limit value when the component temperature Tp is the temperature TM is set to Ib1 × (5/7), The upper limit when Tp is equal to or higher than the temperature TH was set to Ib1×(3/7).

The thin broken line shows the steering assist command value Iref, the thin solid line shows the limited q-axis current command value Iq1, the thick solid line shows the power supply current Ib, the one-dot chain line shows the component temperature Tp of the ECU parts, and the thick broken line shows the The motor rotation speed of the motor 20 is shown.
See FIG. 15. It can be confirmed that the power supply current is gradually limited from Ib1 to Ib1×(3/7), so that the temperature rise of the ECU parts becomes gradual, and the temperature rise of the ECU parts is gradually suppressed.

FIG. 16 is an enlarged view of a range where the component temperature Tp of the ECU components is around 50 [° C.].
It can be confirmed that while the component temperature Tp is below 50 [°C], the power supply current increases to around the upper limit value Ib1, but when the component temperature Tp exceeds around 50 [°C], the power supply current is gradually restricted. .

Additionally, when the power supply current is large, the q-axis current command value Iq1 after limitation is limited, and when the power supply current is small or in a regenerative state, the q-axis current command value Iq1 after limitation increases to the maximum value Iref_max. can be confirmed.
Therefore, even if the power supply current is limited due to an increase in the component temperature Tp, the maximum q-axis current Iref_max is output, although it is low-medium speed steering, and steering to the rack end is possible.

FIG. 17 is an enlarged view of a range in which the component temperature Tp of the ECU components is around 60 [° C.].
While the component temperature Tp was below 60[℃], a power supply current equal to or higher than the upper limit value Ib1×(5/7) was supplied, but when the component temperature Tp exceeded 60[℃], the power supply current gradually decreased. It can be confirmed that it is limited to Ib1×(5/7) or less. This confirms that the rise in component temperature Tp is also gradually suppressed.

Additionally, when the power supply current is large, the q-axis current command value Iq1 after limitation is limited, and when the power supply current is small or in a regenerative state, the q-axis current command value Iq1 after limitation increases to the maximum value Iref_max. can be confirmed.
Therefore, even if the power supply current is limited due to an increase in the component temperature Tp, the maximum q-axis current Iref_max is output, although it is low-medium speed steering, and steering to the rack end is possible.

FIG. 18 is an enlarged view of a range where the component temperature Tp of the ECU components is around 80 [° C.].
It can be confirmed that when the component temperature Tp becomes around 80 [° C.], the power supply current is limited to Ib1×(3/7) or less. The increase in the component temperature Tp has also leveled off, confirming that the temperature increase in the ECU components has been suppressed.

Additionally, when the power supply current is large, the q-axis current command value Iq1 after limitation is limited, and when the power supply current is small or in a regenerative state, the q-axis current command value Iq1 after limitation increases to the maximum value Iref_max. can be confirmed.
Therefore, even if the power supply current is limited due to an increase in the component temperature Tp, the maximum q-axis current Iref_max is output, although it is low-medium speed steering, and steering to the rack end is possible.

(Effects of embodiment)
(1) The motor control device that controls the motor 20 is connected in series between the battery 14 as a power source and the motor 20, and is a drive device that converts the power supply current output from the battery 14 into a drive current that flows through the motor 20. Elements Q1 to Q6, a rotation angle detection circuit 61 and a rotation speed calculation unit 52 that detect the motor rotation speed of the motor 20, and an inverter applied voltage detection unit 54 that detects the inverter applied voltage that is the voltage applied to the inverter 50. A temperature detection section 53 that detects the component temperature of components arranged on or near the power supply line from the battery 14 to the drive elements Q1 to Q6, and a current command value calculation section that calculates a current command value for controlling the drive current. 41 and a plurality of current limit values for limiting the current command value so as to respectively limit the power supply current to below a plurality of predetermined upper limit values, at least the rotation angle detection circuit 61 and the rotation speed calculation unit 52 have detected. A current limit value determining unit 71 determines the motor rotation speed and the inverter applied voltage detected by the inverter applied voltage detecting unit 54, and temperature detection is performed by interpolating the plurality of current limit values determined by the current limit value determining unit 71. A current limit value interpolation unit 72 is provided that calculates a current limit value according to the component temperature detected by the unit 53. The proportional-integral control unit 46, the duty calculation unit 47, the space vector modulation unit 48, and the PWM control unit 49 control the drive elements Q1 to Q1 based on the current command value limited by the current limit value calculated by the current limit value interpolation unit 72. Controls Q6.

With this, the upper limit value of the power supply current is set in advance, and the upper limit value of the power supply current is set in accordance with the component temperature Tp of the component placed on or near the power supply line, and the upper limit value of the power supply current is set in advance in accordance with the component temperature Tp of the component placed in the power supply line or its vicinity. The drive current of the motor 20 can be controlled so that the power supply current is limited to below the upper limit value. For this reason, it is possible to suppress an increase in the component temperature Tp of components disposed on or near the power supply line while avoiding excessive current restriction using the highly accurate upper limit value.
For example, in the case of an electric power steering device that uses an electric motor to apply steering assist force to the steering system of a vehicle, it is possible to control the steering wheel 1 so that it can be steered to the rack end while suppressing a rise in component temperature Tp.
Further, by interpolating a plurality of current limit values, it is possible to calculate a current limit value that continuously changes depending on the component temperature Tp. This allows the power supply current to be gradually restricted without the driver being aware of it.

(2) The current limit value determining unit 71 determines each of the plurality of current limit values based on the current limit value read from a table storing current limit values calculated in advance according to the motor rotation speed and the inverter applied voltage. You may do so.
By calculating the current limit value in advance and storing it in a table, the processing load on the controller 30 can be reduced.

(3) The current limit value is calculated in advance according to the relationship established between the input power based on the inverter applied voltage and power supply current, the motor rotation speed, the output power based on the current command value, and the power loss. May be stored.
By calculating the current limit value in this way, the power supply current can be accurately limited.

(4) The current limit value determining unit 71 includes a limit value table storing current limit values corresponding to the motor rotation speed at a predetermined inverter applied voltage, and includes a limit value table that stores current limit values corresponding to the motor rotation speed at a predetermined inverter applied voltage. Each of the plurality of current limit values may be determined by correcting the current limit value read from the limit value table according to the rotation speed according to the inverter applied voltage detected by the inverter applied voltage detection section 54.
Thereby, the power supply current can be accurately limited according to fluctuations in the voltage applied to the inverter.

(5) The current limit value determination unit 71 includes a variation table that associates the variation value of the current limit value with the motor rotation speed with respect to the standard deviation between the inverter applied voltage and the reference voltage, and the rotation angle detection circuit 61 and the rotation The rotation angle detection circuit 61 and the rotation speed calculation section are configured according to the fluctuation value read from the fluctuation value table according to the motor rotation speed detected by the numerical calculation section 52 and the inverter applied voltage detected by the inverter applied voltage detection section 54. Each of the plurality of current limit values may be determined by correcting the limit value read from the limit value table according to the motor rotational speed detected by 52.
By calculating the variation value of the current limit value with respect to the deviation of the inverter applied voltage in advance and storing it in a table, it is possible to suppress the load of correction processing according to the variation of the inverter applied voltage.

(6) The current limit value interpolation unit 72 includes one or more interpolation value calculation units 90 and 91 that calculate interpolated values between a plurality of current limit values according to the component temperature Tp, and interpolation value calculation units 90 and 91. A selection unit 92 may be provided that selects the calculated interpolated value and either the maximum value or the minimum value of the plurality of current limit values according to the component temperature Tp.
Thereby, interpolated values of a plurality of current limit values can be calculated according to the component temperature Tp.

(7) The current command value calculation section 41 calculates the q-axis current command value and the d-axis current command value for controlling the drive current, and the current limit value determination section 71 calculates the q-axis current command value and the d-axis current command value for controlling the drive current. A current limit value may be determined.
By controlling the q-axis current command value so that the power supply current is limited to the upper limit value or less, it is possible to suppress the rise in component temperature Tp of components placed in or near the power supply line while avoiding excessive current restriction. .

(8) The current limit value determination unit 71 may further determine the current limit value according to at least the temperature information of the motor 20 and the temperature information of the drive elements of the inverter 50.
Thereby, changes in the torque constant and resistance value due to the temperature of the motor 20 and changes in the resistance value due to the temperature of the driving element can be taken into consideration, and the power supply current can be more accurately restricted.

(9) The drive current limiter 43 may release the limit on the drive current depending on the direction of the drive current and the rotational direction of the motor 20.
Thereby, when the motor 20 is in the regenerative state (for example, when the steering wheel 1 is in the reverse steering state), unnecessary current restriction can be canceled.

DESCRIPTION OF SYMBOLS 1... Steering handle, 2... Column shaft, 3... Reduction gear, 4A, 4B... Universal joint, 5... Pinion rack mechanism, 6... Tie rod, 10... Torque sensor, 11... Ignition key, 12... Vehicle speed sensor, 14... Battery, 20... Motor, 30... Controller, 40... Steering assist command value calculation section, 41... Current command value calculation section, 43... Drive current limiting section, 44, 45, 84... Subtractor, 46... Proportional integral control section, 47... Duty calculation section, 48... Space vector modulation section, 49... PWM control section, 50... Inverter, 52... Rotation speed calculation section, 53... Temperature detection section, 54... Inverter applied voltage detection section, 61... Rotation angle detection circuit , 62...Motor temperature acquisition section, 70...Rotational speed input processing section, 70a, 70b...Sign determination section, 70c...Steering state determination section, 70d...Absolute value calculation section, 70e, 103, 104...Selector, 71...Current Limit value determination section, 72... Current limit value interpolation section, 73... Rate limiter, 74... Smoothing section, 75... Q-axis current limit section, 80a, 80b, 80c... Limit value determination section, 81... Limit value table reading section , 82... Fluctuation value table reading section, 83, 88... Limiter, 85... Multiplier, 86... Coefficient multiplier, 87... Adder, 90, 91... Interpolation value calculation section, 92... Selection section, 100... Sign inverter , 101, 102... comparator

Claims (10)

A motor control device that controls an electric motor,
a drive element connected in series between a power source and the electric motor to convert a power supply current output from the power source into a drive current flowing to the electric motor;
a rotational speed detection unit that detects a motor rotational speed of the electric motor;
an inverter applied voltage detection unit that detects the voltage applied to the drive element as an inverter applied voltage;
a temperature detection unit that detects a component temperature of a component disposed on or near a power supply line from the power supply to the drive element;
a current command value calculation unit that calculates a current command value for controlling the drive current;
A plurality of current limit values for limiting the current command value such that the power supply current is respectively limited to a plurality of predetermined upper limit values or less are determined at least at the motor rotation speed and the inverter detected by the rotation speed detection section. a current limit value determination unit that determines each according to the inverter applied voltage detected by the applied voltage detection unit;
a current limit value interpolation unit that interpolates the plurality of current limit values determined by the current limit value determination unit to calculate a current limit value according to the component temperature detected by the temperature detection unit;
an element control unit that controls the drive element based on the current command value limited by the current limit value calculated by the current limit value interpolation unit;
Equipped with
The current limit value determining unit determines the plurality of currents based on a current limit value read from a limit value storage unit that stores the current limit value calculated in advance according to the motor rotation speed and the inverter applied voltage. A motor control device characterized in that each of the limit values is determined . The limit value storage unit has a limit value calculated in advance according to a relationship established between the input power based on the inverter applied voltage and the power supply current, the motor rotation speed, the output power based on the current command value, and power loss. The motor control device according to claim 1 , wherein the current limit value is stored. The limit value storage unit includes a first table storing the current limit value according to the motor rotation speed at a predetermined voltage applied to the inverter,
The current limit value determination unit determines the current limit value read from the first table according to the motor rotation speed detected by the rotation speed detection unit, and the current limit value read out from the first table according to the inverter applied voltage detected by the inverter applied voltage detection unit. determining each of the plurality of current limit values by correcting the current limit values;
The motor control device according to claim 1 or 2, characterized in that: The limit value storage unit includes a second table that associates a variation value of the current limit value with respect to a standard deviation between the inverter applied voltage and a reference voltage and the motor rotation speed,
The current limit value determination section is configured to calculate the fluctuation value read from the second table according to the motor rotation speed detected by the rotation speed detection section and the inverter applied voltage detected by the inverter applied voltage detection section. determining each of the plurality of current limit values by correcting the current limit value read from the first table according to the motor rotation speed detected by the rotation speed detection unit;
The motor control device according to claim 3 , characterized in that: The current limit value interpolation unit is
one or more interpolated value calculation units that calculate interpolated values between the plurality of current limit values according to the component temperature;
a selection unit that selects the interpolation value calculated by the interpolation value calculation unit and either a maximum value or a minimum value of the plurality of current limit values according to the component temperature;
The motor control device according to any one of claims 1 to 4 , characterized in that it comprises: further comprising a current command value calculation unit that calculates a q-axis current command value and a d-axis current command value for controlling the drive current,
The motor control device according to claim 1 , wherein the current limit value determination unit determines a current limit value for limiting the q-axis current command value. 7. The current limit value determination unit further determines each of the plurality of current limit values according to at least temperature information of the electric motor and temperature information of the drive element. The motor control device according to item 1. The motor control device according to any one of claims 1 to 7 , wherein the restriction on the drive current is canceled depending on the direction of the drive current and the rotation direction of the electric motor. A motor control device according to any one of claims 1 to 8 ,
an electric motor controlled by the motor control device;
An electric actuator product comprising: A motor control device according to any one of claims 1 to 8 ,
an electric motor controlled by the motor control device;
An electric power steering device comprising: an electric power steering device, wherein the electric motor applies a steering assist force to a steering system of a vehicle.

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