JP7342717B2 - 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.
Furthermore, the technique disclosed in Patent Document 2 suppresses the amount of heat generated by the component by gradually decreasing or increasing the current upper limit value in accordance with 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 calculation unit that calculates a current limit value as a limit value candidate according to 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; a current limit value selection section that selects one of a plurality of limit value candidates calculated by the current limit value selection section according to the component temperature detected by the temperature detection section; An element control section that controls the drive element based on the command 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 arranged in the vicinity thereof while avoiding excessive current restriction using a highly accurate 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 calculation section. FIG. 2 is a block diagram illustrating an example of a functional configuration of a limit value candidate calculation section. FIG. 3 is a block diagram showing an example of a functional configuration of a current limit value selection section. 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. (a) and (b) are diagrams showing simulation results when the component temperature is 60 [° C.]. (a) and (b) are diagrams showing simulation results when the component temperature is 100 [° C.]. (a) and (b) are diagrams showing simulation results when the component temperature is 120 [° C.]. (a) to (c) are diagrams showing simulation results when the component temperature is changed.

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 controls the q-axis current based on the component temperature Tp of the ECU components, the motor rotation speed Nr of the motor 20, the inverter applied voltage Vr, the d-axis current command value Id0, and the steering assist command value Iref. Limit command value Iq0.
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 the upper limit value specified according to the component temperature Tp.

In addition to the component temperature Tp, motor rotational speed Nr, inverter applied voltage Vr, d-axis current command value Id0, and steering assist command value Iref, the drive current limiter 43 controls the motor temperature Tm of the motor 20 and the inverter 50. 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 specified according to the component temperature Tp of the ECU component.
Specifically, a plurality of upper limit values Ib1, Ib2, . . . , Ibn of the power supply current are set according to the component temperature Tp.

For example, the temperature thresholds Tp1L, Tp1H, Tp2L, and Tp2H are set so that Tp1L<Tp1H<Tp2L<Tp2H, and the component temperature Tp rises from a temperature lower than the temperature threshold Tp1L and is lower than the temperature threshold Tp2L and higher than the temperature threshold Tp1H. The upper limit value may be switched from Ib1 to Ib2 when the temperature increases, and the upper limit value may be switched from Ib2 to Ib1 when the temperature decreases from a temperature higher than the temperature threshold Tp1H and becomes less than the temperature threshold Tp1L.

Similarly, when the component temperature Tp rises from a temperature lower than the temperature threshold Tp2L and exceeds the temperature threshold Tp2H, the upper limit value is switched from Ib2 to Ib3, and when the component temperature Tp rises from a temperature higher than the temperature threshold Tp2H and falls below the temperature threshold Tp2L and the temperature The upper limit value may be switched from Ib3 to Ib2 when it becomes higher than the threshold value Tp1H. By setting the temperature threshold value and the upper limit value in this way, the upper limit value can have a hysteresis characteristic with respect to the component temperature Tp.

The drive current limiter 43 limits the power supply current to below the upper limit value for each of the upper limit values Ib1 to Ibn based on the motor rotation speed Nr, the inverter applied voltage Vr, and the d-axis current command value Id0. Each of a plurality of q-axis current limit value candidates (hereinafter referred to as "limit value candidates") Iq_limc1, Iq_limc2, . . . , Iq_limcn for limiting the axis current command value Iq0 is calculated.

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).

If the q-axis current limit value Iq_lim calculated by the calculation formula (2) or (3) satisfies the above formula (4), the drive current limiter 43 controls the q-axis current limit value Iq_lim by the calculation formula (2) or (3). Calculate current limit value Iq_lim.
If the q-axis current limit value Iq_lim calculated by equation (2) or (3) does not satisfy the above equation (4), the q-axis current limit value Iq_lim is calculated by the following equation (5).

An overview of the characteristics of the q-axis current limit value Iq_lim with respect to the motor rotation speed will be described with reference to FIG. 4.
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, when calculating the q-axis current limit value Iq_lim, the upper limit value Ib_lim of the variables included in calculation formula (2) or (3) is fixed, thereby simplifying the calculation process and improving the controller 30's Reduce processing load.
Specifically, a plurality of arithmetic expressions are derived in which the upper limit value Ib_lim in the arithmetic expression (2) or (3) is fixed to the upper limit values Ib1 to Ibn, respectively set according to the component temperature Tp, and these multiple arithmetic expressions are Each of the limit value candidates Iq_limc1 to Iq_limcn is calculated using an arithmetic expression.

The drive current limiter 43 selects a candidate corresponding to the upper limit value set for the component temperature Tp of the ECU component from among these limit value candidates Iq_limc1 to Iq_limcn, sets it as the q-axis current limit value Iq_lim, and controls the q-axis current. The command value Iq0 is limited to the q-axis current limit value Iq_lim or less.

See FIG. 5. The drive current limiter 43 includes a rotation speed input processor 70, a current limit value calculator 71, a current limit value selector 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 limit value candidates Iq_limc1 to Iq_limcn.
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 calculation unit 71 calculates a plurality of limits based on the rotation speed signal N output by the rotation speed input processing unit 70, the inverter applied voltage Vr output by the inverter applied voltage detection unit 54, and the d-axis current command value Id0. Each of value candidates Iq_limc1 to Iq_limcn is calculated.
The current limit value calculation unit 71 calculates limit value candidates Iq_limc1 to Iq_limcn according to the motor temperature Tm of the motor 20 and the temperature information of the inverter 50, in addition to the rotational speed signal N, the inverter applied voltage Vr, and the d-axis current command value Id0. may be calculated.

FIG. 7 shows an example of the functional configuration of the current limit value calculation section 71. The example of the current limit value calculation unit 71 shown in FIG. 7 calculates three limit value candidates Iq_limc1 to Iq_limc3. However, the number of limit value candidates determined in the present invention is not limited to three, and the number of limit value candidates may be two or more than three.
The current limit value calculation section 71 includes limit value candidate calculation sections 80a, 80b, and 80c.

The limit value candidate calculation unit 80a calculates a limit value candidate Iq_limc1. The limit value candidate 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.
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.

The limit value candidate calculation unit 80b determines the limit value candidate Iq_limc2. Limit value candidate Iq_limc2 is a limit value of q-axis current command value Iq0 for limiting the power supply current to below upper limit value Ib2, which is smaller than upper limit value Ib1.
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 candidate calculation unit 80c determines the limit value candidate Iq_limc3. Limit value candidate Iq_limc3 is a limit value of q-axis current command value Iq0 for limiting the power supply current to below upper limit value Ib3, which is smaller than upper limit value Ib2.
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.

FIG. 8 shows an example of the functional configuration of the limit value candidate calculation section 80a. The limit value candidate calculation unit 80a calculates a limit value that limits the q-axis current command value Iq0 so as to limit the power supply current to below the upper limit value Ib1, as a limit value candidate Iq_limc1, based on the calculation formulas (2) and (5). Calculate as
The limit value candidate calculation unit 80a includes coefficient multipliers 81, 82, and 83, term calculation units 84 and 85, adders 86 and 87, square root calculation units 88 and 89, a limiter 90, a multiplier 91, It includes a subtracter 92 and a limit value selection section 93.
The coefficient multiplier 81 multiplies the rotational speed signal N output by the rotational speed input processing section 70 by a coefficient (2π/60) to calculate the rotational angular velocity ω, and outputs it to the coefficient multiplier 82 and the term calculation section 84. .

The coefficient multipliers 82 and 83, the term calculation units 84 and 85, the adders 86 and 87, and the square root calculation unit 88 are derived by fixing the upper limit value Ib_lim of the power supply current in calculation formula (2) to the upper limit value Ib1. The calculation formula (6) is calculated.

The coefficient multiplier 82 calculates the product (−Kt·ω) of the rotational angular velocity ω and the coefficient “−Kt” and outputs the product to the adder 87.
The term calculation unit 84 calculates the term (Kt·ω) ² included in the calculation formula (6) and outputs it to the adder 86.
The term calculation unit 85 calculates the term (−4·Rr·(Rr·Id0 ² −Vr·Ib1+Ploss)) included in the calculation formula (6) and outputs it to the adder 86. Here, the d-axis current command value Id0 is substituted for Id.
The adder 86 adds the calculation results of the term calculation units 84 and 85. The square root calculation unit 88 calculates the square root of the addition result of the adder 86.

is calculated and output to the adder 87.
The adder 87 adds the multiplication result of the coefficient multiplier 82 and the calculation result of the square root calculation section 88. The coefficient multiplier 83 multiplies the addition result of the adder 87 by a coefficient (1/(2・Rr)), and calculates the right side of equation (6).

get. The limiter 90 limits the upper limit value of the multiplication result of the coefficient multiplier 83 to calculate a q-axis current limit value Iq_lim2, and outputs it to the limit value selection section 93.
On the other hand, the multiplier 91 calculates the square value ^Id02 of the d-axis current command value Id0, and the subtracter 92 subtracts the square value ^Id02 from the square value ^Iref_max2 of the maximum value Iref_max of the steering assist command value Iref. The square root calculation unit 89 calculates the square root of the subtraction result of the subtractor 92, and calculates the term on the right side of the calculation formula (5).

is calculated and output to the limit value selection section 93 as the q-axis current limit value Iq_lim3.
The limit value selection unit 93 selects the smaller value of the q-axis current limit values Iq_lim2 and Iq_lim3 and outputs it to the current limit value selection unit 72 as the limit value candidate Iq_limc1.

The limit value candidate calculation units 80b and 80c also have the same configuration as the limit value candidate calculation unit 80a. However, the coefficient multipliers 82 and 83, the term calculation units 84 and 85, the adders 86 and 87, and the square root calculation unit 88 of the limit value candidate calculation unit 80b calculate the upper limit value Ib_lim of the power supply current in calculation formula (2). An arithmetic expression (7) derived by fixing Ib2 to the upper limit value Ib2 is calculated.

Further, the coefficient multipliers 82 and 83, the term calculation units 84 and 85, the adders 86 and 87, and the square root calculation unit 88 of the limit value candidate calculation unit 80c calculate the upper limit value Ib_lim of the power supply current in the calculation formula (2). An arithmetic expression (8) derived by fixing Ib3 to the upper limit value Ib3 is calculated.

See FIG. 9. The current limit value selection unit 72 selects a candidate corresponding to the upper limit value set for the component temperature Tp detected by the temperature detection unit 53 from among the limit value candidates Iq_limc1 to Iq_limcn determined by the current limit value calculation unit 71. Select and output as q-axis current limit value Iq_lim0.
The current limit value selection unit 72 selects the q-axis current limit value Iq_lim0 from the three limit value candidates Iq_limc1 to Iq_limc3, corresponding to the current limit value calculation unit 71 shown in FIG.

The current limit value selection section 72 includes a selection signal generation section 94 and selectors 95 and 96.
The selection signal generation unit 94 generates a selection signal for selecting a candidate corresponding to the upper limit value specified for the component temperature Tp detected by the temperature detection unit 53 from among the limit value candidates Iq_limc1 to Iq_limc3. The selection signal generation section 94 includes flag setting sections 97 and 98.

For example, the flag setting unit 97 switches the ML determination flag FML from "0" to "1" when the component temperature Tp rises from a temperature lower than the temperature threshold Tp1L and becomes less than the temperature threshold Tp2L and higher than the temperature threshold Tp1H. , when the temperature drops from higher than the temperature threshold Tp1H and becomes less than the temperature threshold Tp1L, the ML determination flag FML is switched from "1" to "0".
The flag setting unit 98 switches the HM determination flag FHM from "0" to "1" when the component temperature Tp rises from a temperature lower than the temperature threshold Tp2L and exceeds the temperature threshold Tp2H, and switches the HM determination flag FHM from "0" to "1" when the component temperature Tp rises from a temperature lower than the temperature threshold Tp2L and exceeds the temperature threshold Tp2H. When the temperature decreases and becomes less than the temperature threshold Tp2L and higher than the temperature threshold Tp1H, the HM determination flag FHM is switched from "1" to "0".

When the ML determination flag FML is “1”, the selector 95 selects the limit value candidate Iq_limc2 and outputs it to the selector 96.
When the ML determination flag FML is “0”, the selector 95 selects the limit value candidate Iq_limc1 and outputs it to the selector 96.

When the HM determination flag FHM is "1", the selector 96 selects the limit value candidate Iq_limc3 and outputs it as the q-axis current limit value Iq_lim0.
When the HM determination flag FHM is "0", the selector 96 selects the output of the selector 95 and outputs it as the q-axis current limit value Iq_lim0.

As a result, when the component temperature Tp rises from a temperature lower than the temperature threshold Tp1L and becomes less than the temperature threshold Tp2L and higher than the temperature threshold Tp1H, the limit value candidate Iq_limc2 is selected as the q-axis current limit value Iq_lim0.
When the component temperature Tp falls from a temperature higher than the temperature threshold Tp1H and becomes less than the temperature threshold Tp1L, the limit value candidate Iq_limc1 is selected as the q-axis current limit value Iq_lim0.

When the component temperature Tp rises from a temperature lower than the temperature threshold Tp2L and exceeds the temperature threshold Tp2H, the limit value candidate Iq_limc3 is selected as the q-axis current limit value Iq_lim0.
When the component temperature Tp decreases from a temperature higher than the temperature threshold Tp2H and becomes less than the temperature threshold Tp2L and higher than the temperature threshold Tp1H, the limit value candidate Iq_limc2 is selected as the q-axis current limit value Iq_lim0.
In this way, the q-axis current limit value Iq_lim has a hysteresis characteristic with respect to the component temperature Tp.

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. 10. 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 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.

(Modified example)
In the above embodiment, the limit value candidates Iq_limc1 to Iq_limcn are calculated using the resistance Rr and the torque constant Kt of the calculation formula (2) or (3) as fixed constants, but the present invention is not limited to this.
The current limit value calculation unit 71 may acquire temperature information of the motor 20 and change the resistance Rr and the torque constant Kt according to the temperature information of the motor 20. That is, the current limit value calculation unit 71 may calculate the limit value candidates Iq_limc1 to Iq_limcn according to the temperature information of the motor 20.
Alternatively, the temperature information of the inverter 50 may be acquired and the resistance Rr may be changed according to the temperature information of the inverter 50. That is, the current limit value calculation unit 71 may calculate the limit value candidates Iq_limc1 to Iq_limcn according to the temperature information of the inverter 50.

(motion)
An example of the motor control method according to the embodiment will be described with reference to FIG. 11.
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 calculation unit 71 calculates, based on the rotation speed signal N output by the rotation speed input processing unit 70, the inverter applied voltage Vr detected by the inverter applied voltage detection unit 54, and the d-axis current command value Id0, Each of a plurality of limit value candidates Iq_limc1 to Iq_limcn is calculated.
In step S6, the current limit value selection unit 72 selects a q-axis current limit from among the limit value candidates Iq_limc1 to Iq_limcn calculated by the current limit value calculation unit 71 according to the component temperature Tp of the ECU component detected by the temperature detection unit 53. Select the value Iq_lim0.

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.

(simulation result)
Hereinafter, with reference to FIGS. 12(a) and (b), FIGS. 13(a) and (b), FIGS. 14(a) and (b), and FIGS. 15(a) to (c), , the simulation results of the operation of the motor control device of this embodiment will be described.
In this simulation, the limited q-axis current command value Iq1, d-axis current command value Id0, and power supply current were calculated when the motor rotational speed was changed at different component temperatures Tp.

The temperature threshold values Tp1L, Tp1H, Tp2L, and Tp2H were set to Tp1L=70 [°C], Tp1H=80 [°C], Tp2L=110 [°C], and Tp2H=120 [°C], respectively.
Further, the upper limit values Ib1 to Ib3 of the power supply current were set so that Ib2=Ib1×5/7 and Ib3=Ib1×3/7.

The broken line in (a) of FIG. 12 indicates the motor rotation speed, the thick solid line indicates the limited q-axis current command value Iq1, and the thin solid line indicates the d-axis current command value Id0. The same applies to FIG. 13(a) and FIG. 14(a).
The broken line in FIG. 12(b) indicates the motor rotation speed, and the thick solid line indicates the power supply current. The same applies to FIG. 13(b) and FIG. 14(b).

(a) and (b) of FIG. 12 show simulation results when the component temperature Tp is 60 [° C.]. Under the condition that the motor rotation speed is increased from 0 [rpm] to 5000 [rpm], the limited q-axis current command value Iq1 is appropriately limited based on the upper limit value Ib_lim=Ib1, and the power supply current is suppressed to below Ib1. It can be confirmed that the

(a) and (b) of FIG. 13 show simulation results when the component temperature Tp is 100 [° C.]. Under the condition that the motor rotation speed is increased from 0 [rpm] to 5000 [rpm], the q-axis current command value Iq1 after limitation is appropriately limited based on the upper limit value Ib_lim=Ib2=Ib1*5/7, and the power supply It can be confirmed that the current is suppressed to Ib1*5/7 or less.

(a) and (b) of FIG. 14 show simulation results when the component temperature Tp is 120 [° C.]. Under the condition that the motor rotation speed is increased from 0 [rpm] to 5000 [rpm], the q-axis current command value Iq1 after limitation is appropriately limited based on the upper limit value Ib_lim=Ib3=Ib1*3/7, and the power supply It can be confirmed that the current is suppressed to Ib1*3/7 or less.

(a) to (d) of FIG. 15 show simulation results when the component temperature Tp is repeatedly changed in a trapezoidal waveform in the range of 60 [° C.] to 120 [° C.].
15(a) shows the component temperature Tp, the broken line in FIG. 15(b) shows the motor rotation speed, the thick solid line shows the q-axis current command value after restriction Iq1, and the thin solid line shows the d-axis current command value Id0, the broken line in FIG. 15(c) shows the motor rotation speed, and the thick solid line shows the power supply current.
Under the condition that the motor rotation speed is increased from 0 [rpm] to 5000 [rpm], the limited q-axis current command value Iq1 is appropriately limited based on the upper limit value Ib_lim according to the component temperature Tp, and the power supply current is It can be confirmed that it is dynamically suppressed within the range of Ib1 to Ib1*3/7.

(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 below a plurality of predetermined upper limit values, at least the rotation angle detection circuit 61 and the rotation speed calculation, as limit value candidates. A current limit value calculation unit 71 that calculates according to the motor rotation speed detected by the motor rotation speed detected by the inverter applied voltage detection unit 52 and the inverter applied voltage detected by the inverter applied voltage detection unit 54, and which of the plurality of limit value candidates calculated by the current limit value calculation unit 71. A current limit value selection section 72 is provided that selects a current limit value according to the component temperature detected by the temperature detection section 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 selected by the current limit value selection unit 72. Controls Q6.

As a result, a plurality of upper limit values for the power supply current are set in advance, and the motor is controlled so that the power supply current is limited to one of the upper limit values depending on the component temperature Tp of the components placed on or near the power supply line. 20 drive currents can be controlled. 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, since the current limit value selection unit 72 switches the current limit value in a stepwise manner according to the component temperature Tp, the power supply current can be quickly limited. Therefore, even if the component temperature Tp rises rapidly, the power supply current can be quickly restricted.

(2) The current limit value calculation unit 71 calculates a plurality of upper limits according to the 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 the power loss. Calculate limit value candidates for each value.
Thereby, the upper limit value of the power supply current included in the calculation formula of the limit value candidate can be treated as a fixed value, and the calculation process can be simplified.

(3) 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 calculation 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. .

(4) The current limit value calculation 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 driving 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.

(5) 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...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, 95, 96, 103, 104...Selector, 71 ...Current limit value calculation unit, 72...Current limit value selection unit, 73...Rate limiter, 74...Smoothing unit, 75...Q-axis current limit unit, 80a, 80b, 80c...Limit value candidate calculation unit, 81, 82, 83... Coefficient multiplier, 84, 85... Term operation section, 86, 87... Adder, 88, 89... Square root operation section, 90... Limiter, 91... Multiplier, 92... Subtractor, 93... Limit value selection section, 94... Selection signal generation section, 97, 98... Flag setting section, 100... Sign inverter, 101, 102... Comparator

Claims (6)

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 selected as limit value candidates for the motor, which is detected by at least the rotational speed detection unit. a current limit value calculation unit that calculates each according to the rotational speed and the inverter applied voltage detected by the inverter applied voltage detection unit;
a current limit value selection unit that selects one of the plurality of limit value candidates calculated by the current limit value calculation unit 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 limit value candidate selected by the current limit value selection unit;
Equipped with
The current limit value calculation unit calculates the plurality of values according to a relationship established between the inverter applied voltage and the input power based on the power supply current, the motor rotation speed, the output power based on the current command value, and the power loss. A motor control device characterized in that the limit value candidate is calculated for each upper limit value . 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 calculation unit calculates a current limit value for limiting the q-axis current command value. 3. The motor control device according to claim 1, wherein the current limit value calculation unit further calculates the limit value candidate according to at least temperature information of the electric motor and temperature information of the drive element. The motor control device according to any one of claims 1 to 3 , wherein the restriction on the drive current is canceled depending on the direction of the drive current and the rotational direction of the electric motor. A motor control device according to any one of claims 1 to 4 ,
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 4 ,
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.

Images