Motor control device and electric power steering device

Abstract

The purpose of the present invention is to suppress saturation of a duty ratio in a high-load state and reduction of the duty ratio in a high-rotation-speed region. A motor control device is provided with: a d-axis current command value calculation unit (41) that sets a first d-axis current command value for weakening a magnetic field; a first current limiting unit (43) which is provided in a subsequent stage of the d-axis current command value calculation unit (41), limits the basic q-axis current command value so as to satisfy a motor rated current condition, and calculates a first q-axis current command value; a second current limiting unit (44) which is provided in the subsequent stage of the first current limiting unit (43), limits the first d-axis current command value and the first q-axis current command value so as not to exceed the battery allowable upper limit current, and calculates a second d-axis current command value and a second q-axis current command value; a voltage command value calculation unit (45, 47) that calculates a voltage command value on the basis of the second d-axis current command value and the second q-axis current command value; and a voltage limiting unit (48) that limits the voltage command value and suppresses saturation of the duty ratio.

Description

Technical Field

[0001] The invention relates to a motor control device and an electric power steering device. Background Art

[0002] A motor control device that controls an electric motor sometimes needs to calibrate the control output. For example, a motor control device installed in an electric power steering device calibrates the control output according to system requirements and customer requirements. Patent document 1 below proposes a motor control device that avoids duty saturation of PWM control of a motor (i.e., a state in which a voltage command value exceeds the maximum voltage that can be applied to a drive circuit) and limits the d-axis current to an arbitrary value.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2020 / 095479 Pamphlet Summary of the invention

[0006] Problems to be solved by the invention

[0007] The motor control device of Patent Document 1 has problems such as duty saturation in a high load state and a reduction in duty ratio in a high rotation speed range.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress saturation of the duty ratio in a high load state and reduction of the duty ratio in a high rotation speed region associated with correction of a control output of a motor control device.

[0009] Means for solving problems

[0010] In order to achieve the above-mentioned object, a motor control device of one embodiment of the present invention comprises: a torque control unit, which sets a basic q-axis current command value for controlling the torque generated by the motor; and a d-axis current command value calculation unit, which sets a first d-axis current command value for magnetic field weakening based on the basic q-axis current command value and the rotation speed of the motor; a first current limiting unit, which is arranged at the rear stage of the d-axis current command value calculation unit, and calculates the first q-axis current command value by limiting the basic q-axis current command value according to the first d-axis current command value in such a way that the drive current of the motor does not exceed the rated current of the motor; and a second current limiting unit, which is arranged at the rear stage of the first current limiting unit, and calculates the first q-axis current command value by limiting the basic q-axis current command value according to the first d-axis current command value in such a way that the output current of the battery does not exceed the specified upper limit. a voltage command value calculation unit, which calculates the first d-axis voltage command value and the first q-axis voltage command value based on the second d-axis current command value and the second q-axis current command value; a voltage limiting unit, which calculates the second d-axis voltage command value and the second q-axis voltage command value by limiting the first d-axis voltage command value and the first q-axis voltage command value respectively in a manner that suppresses duty cycle saturation of PWM control based on the first d-axis voltage command value and the first q-axis voltage command value; and a drive circuit, which drives the motor based on the second d-axis voltage command value and the second q-axis voltage command value.

[0011] An electric power steering device according to another aspect of the present invention applies a steering assist force to a steering system of a vehicle by means of a motor controlled by the above-mentioned motor control device.

[0012] Effects of the Invention

[0013] According to the present invention, it is possible to suppress duty saturation in a high load state and a decrease in duty ratio in a high rotation speed region associated with correction of a control output of a motor control device. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic structural diagram showing an example of an electric power steering device according to an embodiment.

[0015] Figure 2 Yes means Figure 1 A block diagram showing an example of the functional configuration of the controller described herein.

[0016] Figure 3 : is a block diagram showing an example of the functional configuration of the d-axis current command value calculation unit.

[0017] Figure 4 (a) is a diagram showing an example of setting of a d-axis current upper limit value set by the field current limiting unit, and (b) is a timing chart showing an example of limitation of a d-axis current command value.

[0018] Figure 5 This is a block diagram showing an example of the functional configuration of a feedback (FB) control unit.

[0019] Figure 6 This is a block diagram showing an example of the functional configuration of the voltage limiter.

[0020] Figure 7 This is a block diagram showing an example of the functional configuration of a voltage upper limit value setting unit.

[0021] Figure 8 (a) and (b) are schematic diagrams of the first and second examples of the setting example of the first determination gain, and (c) and (d) are schematic diagrams of the first and second examples of the setting example of the second determination gain.

[0022] Fig. 9 This is a flowchart of an example of a motor control method according to an embodiment.

[0023] Fig.10 This is a schematic structural diagram showing an example of a linear motion table device using the motor control device of the present invention. DETAILED DESCRIPTION

[0024] The embodiments of the present invention are described in detail with reference to the accompanying drawings. In addition, the embodiments of the present invention shown below illustrate devices and methods for implementing the technical ideas of the present invention, but the technical ideas of the present invention do not limit the structure and configuration of the components to the following contents. The technical ideas of the present invention can be modified in various ways within the technical scope specified by the technical solutions described in the claims.

[0025] (structure)

[0026] Figure 1 The schematic structural diagram of an example of an electric power steering device according to an embodiment is shown. A steering shaft (steering shaft, handle shaft) 2 of a steering wheel (steering handle) 1 is connected to steered wheels 8L, 8R via a reduction gear (worm gear) 3 constituting a reduction mechanism, universal joints 4a, 4b, a pinion rack mechanism 5, tie rods 6a, 6b, and further via hub units 7a, 7b.

[0027] The rack and pinion mechanism 5 includes a pinion 5a connected to a pinion shaft to which the steering force is transmitted from the universal joint 4b and a rack 5b meshing with the pinion 5a. The rack 5b converts the rotational motion transmitted to the pinion 5a into a linear motion in the vehicle width direction.

[0028] The steering shaft 2 is provided with a torque sensor 10 for detecting a steering torque Th. In addition, the steering shaft 2 is provided with a steering angle sensor 14 for detecting a steering angle θh of the steering wheel 1 .

[0029] A motor 20 assisting the steering force of the steering wheel 1 is connected to the steering shaft 2 via a reduction gear 3. A controller 30 controlling an electric power steering (EPS) device is supplied with power from a battery 13 and receives an ignition key signal via an ignition key 11.

[0030] The motor 20 is a multi-phase AC motor, and is driven by vector control of the controller 30. In the present embodiment, a case where the motor 20 is a three-phase AC motor is exemplified.

[0031] The controller 30 is an electronic control unit (ECU) that calculates a current command value for an assist control command based on the steering torque Th detected by the torque sensor 10, the vehicle speed Vh detected by the vehicle speed sensor 12, and the steering angle θh detected by the steering angle sensor 14, and controls the current supplied to the motor 20 by obtaining a voltage command value Vref by compensating the current command value.

[0032] The steering angle sensor 14 is not essential, and the steering angle θh may be calculated by adding a rotation angle obtained from a rotation angle sensor that detects the rotation angle of the rotation shaft of the motor 20 and a torsion angle of the torsion bar of the torque sensor 10 .

[0033] In addition, the steering angle of the steered wheels 8L, 8R may be used instead of the steering angle θh. For example, the steering angle may be detected by detecting the displacement amount of the rack 5b.

[0034] 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).

[0035] The storage device may include any of a semiconductor storage device, a magnetic storage device, and an optical storage device. The storage device may include a register, a cache memory, a ROM (Read Only Memory) used as a main storage device, and a RAM (Random Access Memory) and other memories.

[0036] The functions of the controller 30 described below are implemented, for example, by a processor of the controller 30 executing a computer program stored in a storage device.

[0037] In addition, the controller 30 may be formed by dedicated hardware for executing each information processing described below.

[0038] 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).

[0039] Next, the subject of the limiting function of the control output of the motor 20 executed by the controller 30 is described. The limiting function of the control output of the motor 20 is developed for the following purposes: (1) calculating the amount of weak excitation current for satisfying the following performance requirement of the steering angle of the steered wheels relative to the steering of the steering wheel; (2) satisfying the system current upper limit and the battery current upper limit; and (3) preventing duty saturation.

[0040] However, the motor control device of Patent Document 1 has the following problems 1 and 2.

[0041] (Issue 1) Duty saturation may not be prevented under high load conditions.

[0042] (Problem 2) The duty ratio may decrease in the high rotation speed range.

[0043] Therefore, the motor control device according to the embodiment aims to solve the first and second problems.

[0044] Furthermore, in the motor control device of the embodiment, in addition to Problem 1 and Problem 2, it is an object to solve Problem 3 and Problem 4 described below.

[0045] (Problem 3) As described later, in the motor control device of the embodiment, an integrator is used for feedback control of the motor current, and therefore, there is a possibility that the integrated value is excessively accumulated.

[0046] (Question 4) With the recent demand for higher output, the use of motors with low inductance and low inertia has become widespread. Therefore, a countermeasure against overcurrent caused by back electromotive force during high-speed rotation is required.

[0047] In the present invention, a solution to the above-mentioned problems 1 to 4 is configured based on the following principles.

[0048] It is believed that the main causes of duty saturation (issue 1) under high load conditions are errors caused by the steady deviation or transient characteristics of the feedback control of the motor current, inappropriate locations for current limitation, and restrictions on the duty dimension imposed in the current dimension. Therefore, duty saturation is prevented by limiting the voltage command value.

[0049] The main reason for the reduction in duty ratio in the high rotation speed region (problem 2) is considered to be excessive restriction of the q-axis current command value. Therefore, the restriction method of the q-axis current command value is modified to prioritize restriction of the q-axis current command value.

[0050] To address the excessive accumulation of the integral value in the feedback control of the motor current (issue 3), an anti-saturation function is newly added.

[0051] As a countermeasure against overcurrent (issue 4), a d-axis current command value as large as possible is passed during high-speed rotation to reduce the back electromotive force using a weak magnetic field. In order to pass the d-axis current command value as large as possible, the q-axis current command value is limited with priority.

[0052] In order to realize these corresponding policies, the inventors of the present invention have restructured and changed the configuration of each functional structure of the controller 30 . Figure 2 : is a block diagram showing an example of the functional structure of the controller 30. The controller 30 includes a torque control unit 40, a d-axis current command value calculation unit 41, an angular acceleration regulator 42, a first current limiting unit 43, a second current limiting unit 44, a feedforward (FF) control unit 45, a three-phase / two-phase conversion unit 46, a feedback (FB) control unit 47, a voltage limiting unit 48, a two-phase / three-phase conversion unit 49, a PWM (Pulse Width Modulation) control unit 50, and an inverter (INV) 51.

[0053] The torque control unit 40 calculates a basic q-axis current command value Iqr0 as a current command value for controlling the generated torque of the motor 20 based on at least the steering torque Th and the vehicle speed Vh.

[0054] The d-axis current command value calculation unit 41 sets a first d-axis current command value Idr1 for field weakening based on the basic q-axis current command value Iqr0 , the rotation speed ω of the motor 20 , and the power supply voltage VR supplied from the battery 13 .

[0055] Figure 3 2 is a block diagram showing an example of the functional configuration of the d-axis current command value calculation unit 41. The d-axis current command value calculation unit 41 includes a current command value setting unit 41a, an exciting current command value calculation unit 41b, and an exciting current limiting unit 41c.

[0056] The current command value setting unit 41a sets the q-axis current command value Iqt for calculating the basic d-axis current command value Idr0 in the subsequent excitation current command value calculation unit 41b based on the basic q-axis current command value Iqr0, the rotation speed ω, the power supply voltage VR and the past value Idz of the d-axis current command value.

[0057] Here, the basic d-axis current command value Idr0 is set to be suitable for the q-axis current command value Iqt that satisfies the conditions of the rated current of the motor 20 and the allowable upper limit current of the battery 13 .

[0058] As the past value Idz of the d-axis current command value, as described later, a past value of the second d-axis current command value Idr2 calculated by the second current limiting unit 44 (for example, the second d-axis current command value Idr2 calculated in the previous control cycle) may be used.

[0059] In the following description, the condition of the rated current of the motor 20 may be expressed as “system current limit”, and the condition of the allowable upper limit current of the battery 13 may be expressed as “battery current limit”.

[0060] Regarding the system current limitation, the current command value setting unit 41a sets the limitation gain Gq1 for the q-axis current command value according to the following equation (1) so that the d-axis current command value and the q-axis current command value are equal to or less than the system maximum current Imax (for example, the rated current of the motor).

[0061] In addition, a process of preventing division by "0" is performed during the calculation of the formula (1). In addition, a clipping process (0 to 1) is performed so that the calculation result does not exceed 1.

[0062] [Mathematical formula 1]

[0063]

[0064] Regarding the battery current limit, the current command value setting unit 41a sets the limit gain Gq2 for the q-axis current command value so that the battery current Ibat output from the battery 13 becomes less than the prescribed allowable upper limit Ibatmax. The current command value setting unit 41a sets the limit gain Gd1 for the d-axis current command value according to the following formula (2) so that the d-axis current command value does not exceed the allowable upper limit Ibatmax. In addition, the "0" division prevention process and the limit process are also implemented in the formula (2).

[0065] [Mathematical formula 2]

[0066]

[0067] In addition, the constant R represents the resistance value of each phase winding of the motor 20, and Ploss represents the loss caused by iron loss, friction, etc. The current command value setting unit 41a sets the limit gain Gq2 for the q-axis current command value through the following formula (3) based on the limit gain Gd1 set in the above formula (2). In addition, the constant Kt represents the torque constant of the motor 20. In addition, the "0" division prevention process and the limit process are also implemented in the formula (3).

[0068] [Mathematical formula 3]

[0069]

[0070] The current command value setting unit 41 a multiplies the basic q-axis current command value Iqr0 by the smaller gain of the limit gains Gq1 and Gq2 to calculate the q-axis current command value Iqt=min(Gq1, Gq2)×Iqr0.

[0071] The excitation current command value calculation unit 41b calculates the basic d-axis current command value Idr0 as the excitation current command value for field weakening according to the following formula (4) based on the q-axis current command value Iqt set by the current command value setting unit 41a, the rotation speed ω and the power supply voltage VR. In addition, the constant L represents the inductance of each phase of the motor, and the constant Ψ represents the number of magnetic flux linkages determined by the motor.

[0072] [Formula 4]

[0073]

[0074] The field current limiting unit 41 c calculates the first d-axis current command value Idr1 by limiting the basic d-axis current command value Idr0 to the direction of the field weakening current.

[0075] The limit value of the d-axis current command value is determined in consideration of the balance between the steering angle follow-up performance requirement for the steering wheel and the operating sound. However, in this embodiment, for the above-mentioned problem 4 (overcurrent countermeasure), it is necessary to pass as large a d-axis current command value as possible.

[0076] Therefore, the field current limiting unit 41c calculates the first d-axis current command value Idr1 by limiting the basic d-axis current command value Idr0 to be equal to or less than the d-axis current upper limit value IdUL, and changes the d-axis current upper limit value IdUL according to the rotation speed ω.

[0077] Figure 4 (a) is a diagram showing an example of setting of the d-axis current upper limit value IdUL set by the excitation current limiting unit 41c. In the range where the rotation speed ω is less than the threshold value ωth, the d-axis current upper limit value IdUL is set to a relatively small first limit value Id1, and in the range where the rotation speed ω is greater than the threshold value ωth, the d-axis current upper limit value IdUL is set to a second limit value Id2 greater than the first limit value Id1.

[0078] For example, the threshold ωth can be set by converting the maximum steering angular velocity that may occur during emergency avoidance into the rotation speed of the motor 20. This can achieve a balance between quietness of the normal steering operation sound and the following performance of the steering angle relative to the steering wheel during emergency avoidance.

[0079] The field current limiting unit 41 c may include a change rate limiter that limits the time change of the first d-axis current command value Idr1 .

[0080] Figure 4 (b) is a timing chart of an example of limiting the first d-axis current command value Idr1. When the basic d-axis current command value Idr0 is input at time t1, the increase rate of the first d-axis current command value Idr1 is limited by the change rate limiter and gradually increases, reaching the first limit value Id1 at time t2.

[0081] Thereafter, when the rotation speed ω of the motor 20 increases and exceeds the threshold ωth at time t3, the d-axis current upper limit value IdUL increases to the second limit value Id2. As a result, the increase rate of the first d-axis current command value Idr1 is limited by the change rate limiter and gradually increases, reaching the second limit value Id2 at time t4.

[0082] Reference Figure 2 The angular acceleration regulator 42 sets a compensation value Δq of the q-axis current command value for suppressing torque fluctuations based on the rotation speed ω of the motor 20 .

[0083] The first current limiting unit 43 compensates the basic q-axis current command value Iqr0 by the compensation value Δq, and limits the compensated basic q-axis current command value (Iqr0+Δq) so that the drive current of the motor 20 does not exceed the system current limit, thereby calculating the first q-axis current command value Iqr1.

[0084] Specifically, the limit gain Gq3 is set according to the following equation (5). In the equation (5), a "0" division prevention process and a limiter process are also performed.

[0085] [Mathematical formula 5]

[0086]

[0087] The first current limiting unit 43 calculates a first q-axis current command value Iqr1 = Gq3 × (Iqr0 + Δq) by multiplying the basic q-axis current command value (Iqr0 + Δq) by the limit gain Gq3.

[0088] The second current limiting unit 44 calculates a second d-axis current command value Idr2 and a second q-axis current command value Iqr2 by limiting the first d-axis current command value Idr1 and the first q-axis current command value Iqr1 so that the battery current Ibat does not exceed the battery current limit.

[0089] Specifically, the limit gain Gd2 for the d-axis current command value and the limit gain Gq4 for the q-axis current command value are set according to the following equations (6) and (7). In addition, the "0" division prevention process and the limit process are also implemented in equations (6) and (7).

[0090] [Mathematical formula 6]

[0091]

[0092] The second current limiting unit 44 calculates a second d-axis current command value Idr2 = Gd2 × Idr1 by multiplying the first d-axis current command value Idr1 by the limit gain Gd2 , and calculates a second q-axis current command value Iqr2 = Gq4 × Iqr1 by multiplying the first q-axis current command value Iqr1 by the limit gain Gq4 .

[0093] The FF control unit 45 calculates the FFd-axis voltage command value Vdff and the FFq-axis voltage command value Vqff as voltage command values ​​for the motor 20 by feedforward control based on the second d-axis current command value Idr2 and the second q-axis current command value Iqr2 , respectively.

[0094] For example, the FF control unit 45 may calculate dq-axis non-interference voltage command values ​​that cancel out the interference voltages that interfere with each other between the d-axis and the q-axis as the FF d-axis voltage command value Vdff and the FF q-axis voltage command value Vqff.

[0095] In addition, for example, the FF control unit 45 may calculate a feedforward output based on a two-degree-of-freedom control structure as the FFd-axis voltage command value Vdff and the FFq-axis voltage command value Vqffd-axis.

[0096] The FFd-axis voltage command value Vdff and the FFq-axis voltage command value Vqff are examples of the “first d-axis voltage command value” and the “first q-axis voltage command value” described in the claims, respectively.

[0097] The three-phase / two-phase conversion unit 46 converts the detection values ​​of the three-phase current of the motor 20 detected by the motor current detector 21 into a d-axis current id and a q-axis current iq.

[0098] The FB control unit 47 calculates the FB d-axis voltage command value Vdfb as the d-axis voltage command value for the motor 20 by feedback control based on the current deviation ΔId of the d-axis current detection value id of the drive current of the motor 20 with respect to the second d-axis current command value Idr2 .

[0099] The FB control unit 47 calculates a FBq-axis voltage command value Vqfb as a q-axis voltage command value for the motor 20 by feedback control based on a current deviation ΔIq of a detected value iq of the q-axis current of the drive current of the motor 20 relative to a second q-axis current command value Iqr2 .

[0100] The FBd-axis voltage command value Vdfb and the FBq-axis voltage command value Vqfb are examples of the “first d-axis voltage command value” and the “first q-axis voltage command value” described in the claims, respectively.

[0101] The FB control unit 47 calculates the FBd-axis voltage command value Vdfb and the FBq-axis voltage command value Vqfb by at least one of proportional control (P control), integral control (I control) or differential control (D control) based on the current deviations ΔId and ΔIq, or a combination thereof.

[0102] Figure 5 This is a block diagram showing an example of the functional configuration of the FB control unit 47 when the FBd-axis voltage command value Vdfb and the FBq-axis voltage command value Vqfb are calculated by proportional-integral-derivative (PID) control.

[0103] The FB control unit 47 includes a subtractor 47a, gain multiplication units 47b, 47d, and 47f, an approximate differential unit 47c, an integrator 47e, and an adder 47g.

[0104] The subtractor 47a calculates a current deviation ΔId=(Idr2-id) of the d-axis current detection value id from the second d-axis current command value Idr2 and a current deviation ΔIq=(Iqr2-iq) of the q-axis current detection value iq from the second q-axis current command value Iqr2.

[0105] The gain multiplication unit 47 b outputs the multiplication result of the current deviation ΔId and the proportional gain Kp and the multiplication result of the current deviation ΔIq and the proportional gain Kp to the adder 47 g.

[0106] The approximate differential unit 47c calculates the differential values ​​of the current deviations ΔId and ΔIq. For example, the approximate differential unit 47c can calculate the differential values ​​by multiplying the current deviations ΔId and ΔIq by the transfer function s / (Ts+1) obtained by combining the differential operation and the low-pass filter. The gain multiplication unit 47d outputs the multiplication result of the differential value of the current deviation ΔId and the differential gain Kd and the multiplication result of the differential value of the current deviation ΔIq and the differential gain Kd to the adder 47g.

[0107] The integrator 47e calculates the integrated values ​​of the current deviations ΔId and ΔIq. The gain multiplier 47f outputs the multiplication result of the integrated value of the current deviation ΔId and the integrated gain Ki and the multiplication result of the integrated value of the current deviation ΔIq and the integrated gain Ki to the adder 47g.

[0108] The adder 47g outputs the sum of the multiplication result of the current deviation ΔId and the proportional gain Kp, the multiplication result of the differential value of the current deviation ΔId and the differential gain Kd, and the multiplication result of the integral value of the current deviation ΔId and the integral gain Ki as the FBd-axis voltage command value Vdfb.

[0109] The adder 47g outputs the sum of the multiplication result of the current deviation ΔIq and the proportional gain Kp, the multiplication result of the differential value of the current deviation ΔIq and the differential gain Kd, and the multiplication result of the integral value of the current deviation ΔIq and the integral gain Ki as the FBq axis voltage command value Vqfb.

[0110] The integrator 47e includes a delay element 47e1, an adder 47e2, and a gain multiplication unit 47e3.

[0111] The delay element 47e1 delays the integral component of the current deviation ΔId and the integral component of the current deviation ΔIq as the output of the integrator 47e and inputs them to the adder 47e2. That is, the delay element 47e1 inputs the past value (previous value) of the output of the integrator 47e to the adder 47e2.

[0112] The adder 47e2 outputs the sum of the current deviation ΔId and the output of the delay element 47e1, and the sum of ΔIq and the output of the delay element 47e1. Specifically, the sum obtained by adding the current deviation ΔId to the past value of the integral component of the current deviation ΔId is output. In addition, the sum obtained by adding the current deviation ΔIq to the past value of the integral component of the current deviation ΔIq is output.

[0113] The gain multiplication unit 47e3 calculates the multiplication result obtained by multiplying the voltage limiting gain Gv set by the voltage limiting unit 48 and the output of the adder 47e2 as the output of the integrator 47e (i.e., the integral component of the current deviations ΔId, ΔIq), and outputs it to the gain multiplication unit 47f and inputs it to the delay element 47e1.

[0114] By multiplying the output of the adder 47e2 by the voltage limit gain Gv, the integrated value in the integrator 47e can be reduced, so that an anti-saturation function of the integrated value can be realized.

[0115] For example, as described later, by setting the voltage limit gain Gv to a value smaller than "1", accumulation of the integral value by the integrator 47e can be suppressed. Also, by setting the voltage limit gain Gv to "0", for example, the integral value of the integrator 47e can be reset to "0".

[0116] Reference Figure 2 The voltage limiting unit 48 calculates the second d-axis voltage command value Vd and the second q-axis voltage command value Vq by limiting the voltage command values ​​Vdff, Vdfb, Vqff, and Vqfb in a manner that suppresses duty cycle saturation of PWM control based on the FFd-axis voltage command value Vdff, the FBd-axis voltage command value Vdfb, the FFq-axis voltage command value Vqff, and the FBq-axis voltage command value Vqfb.

[0117] Figure 6 2 is a block diagram showing an example of the functional configuration of the voltage limiter 48. The voltage limiter 48 includes a voltage upper limit value setting unit 48a, a disturbance voltage suppressing unit 48b, a voltage limit gain setting unit 48c, a limiter 48d, a multiplier 48e, and an adder 48f.

[0118] The voltage upper limit value setting unit 48a sets the voltage upper limit value VDutyMax as the upper limit value of the voltage command value that does not produce duty saturation. When the motor 20 is in power operation and regeneration, the dead time of the converter 51 acts on the upper limit value in different directions. Therefore, the voltage upper limit value setting unit 48a sets the voltage upper limit value VDutyMax during power operation according to the following formula (8), and sets the voltage upper limit value VDutyMax during regeneration according to the following formula (9).

[0119] [Formula 7]

[0120]

[0121] Since the voltage utilization efficiency is improved by superimposing the third harmonic on the three-phase voltage command value of the motor 20, the upper limit value of the voltage command value can be increased to 100% of the power supply voltage VR. The duty ratio range of PWM control, 0 to 100 [%], corresponds to the range from the lower limit of the negative voltage to the upper limit of the positive voltage. Therefore, in the above equations (8) and (9), the power supply voltage VR is multiplied by a coefficient corresponding to the upper limit of each positive and negative side.

[0122] In addition, the reduction amount (2×DeadTime / PWMTime) caused by the dead time DeadTime of the inverter 51 is subtracted or added according to whether the motor 20 is in the power running state or the regeneration state. In addition, PWMTime represents the PWM cycle of the PWM control unit 50. The dead time DeadTime often deviates between the design value and the actual value, so a properly set dead time compensation value may be subtracted or added according to whether the motor 20 is in the power running state or the regeneration state.

[0123] In addition, the ratio (slope) of the change in the terminal voltage of the motor 20 to the change in the duty cycle due to the dead time compensation is reduced. In order to compensate for this, the inverse of the conversion coefficient VRDutyConvFactor is multiplied by the calculation formula of the above formulas (8) and (9). The conversion coefficient VRDutyConvFactor acts in the direction of reducing the voltage command value when converting to the duty cycle, so the reduction is compensated by increasing the voltage upper limit value VDutyMax.

[0124] Furthermore, the constant DutyMaxRate is set by subtracting a margin for ensuring quantization error and current detection accuracy based on calculations in the subsequent stage from a value of "1" (ie, DutyMaxRate=100[%]-quantization error-margin).

[0125] Figure 7 2 is a block diagram showing an example of the functional configuration of the voltage upper limit value setting unit 48a. The voltage upper limit value setting unit 48a includes a first gain setting unit 48a1, a second gain setting unit 48a2, a selector 48a3, multipliers 48a4, 48a6, 48a7, and a subtractor 48a5.

[0126] The first gain setting unit 48a1 determines whether the motor 20 is in the power running state or the regeneration state based on the battery current Ibat, and outputs a first determination gain G1 indicating the determination result. When the motor 20 is in the power running state, the first determination gain G1 has a value of "1", and when the motor 20 is in the regeneration state, the first determination gain G1 has a value of "-1".

[0127] Figure 8 (a) is a schematic diagram of a first example of setting examples of the first determination gain G1. For example, the first determination gain G1 can be set to a value of "-1" when the battery current Ibat is less than a value I1 less than a value "0", and can be set to a value of "1" when the battery current Ibat is greater than a value "0", and can be linearly and gradually increased from a value "-1" to a value "1" as the battery current Ibat increases within a range from a value I1 to a value "0", or can be nonlinearly and gradually increased.

[0128] The battery current Ibat for which the first determination gain G1 is set to the value “1” may be set to a value I2 smaller than “0” with a margin. Figure 8 (b) is a schematic diagram of a second example of the setting example of the first determination gain G1. This is because if the sign of the first determination gain G1 is set incorrectly, duty saturation will occur.

[0129] For example, a value I2 greater than value I1 and less than value "0" can be set, and the first judgment gain G1 can be set to value "1" when the battery current Ibat is greater than value I2. In the range of battery current Ibat from value I1 to value I2, as the battery current Ibat increases, the first judgment gain G1 is gradually increased linearly or nonlinearly from value "-1" to value "1".

[0130] Reference Figure 7 The second gain setting unit 48a2 determines whether the duty cycle is close to the upper limit based on the voltage limit gain Gv described later, and outputs a second determination gain G2 indicating the determination result. When the duty cycle is close to the upper limit, the second determination gain G2 has a value of "1", and when the duty cycle is not close to the upper limit, the second determination gain G2 has a value of "-1".

[0131] Figure 8 (c) is a schematic diagram of a first example of the setting example of the second determination gain G2. For example, the second determination gain G2 is set to a value of "-1" when the voltage limit gain Gv is less than a value Gv1 less than a value "1", and is set to a value of "1" when the voltage limit gain Gv is greater than a value "1". When the voltage limit gain Gv is in the range from the value Gv1 to the value "1", the second determination gain G2 gradually increases linearly from the value "-1" to the value "1" as the voltage limit gain Gv increases, or may gradually increase nonlinearly.

[0132] The voltage limit gain Gv in which the second determination gain G2 is set to the value “1” may be provided with a margin and set to a value Gv2 smaller than “1”. Figure 8 (d) is a schematic diagram of a second example of the setting example of the second determination gain G2. This is because if the sign of the second determination gain G2 is set incorrectly, duty saturation will occur.

[0133] For example, a value Gv2 greater than the value Gv1 and less than the value "1" can be set, and the second judgment gain G2 can be set to the value "1" when the voltage limiting gain Gv is greater than the value Gv2. When the voltage limiting gain Gv is in the range from the value Gv1 to the value Gv2, as the voltage limiting gain Gv increases, the second judgment gain G2 is gradually increased linearly or nonlinearly from the value "-1" to the value "1".

[0134] Reference Figure 7The selector 48a3 outputs the larger gain of the first determination gain G1 and the second determination gain G2 to the multiplier 48a4. The multipliers 48a4, 48a6, 48a7 and the subtractor 48a5 calculate the voltage upper limit value VDutyMax according to the calculation formulas (8) and (9) above.

[0135] Reference Figure 6 The disturbance voltage suppressing unit 48b is provided at a subsequent stage of the FB control unit 47, and functions as a voltage disturbance observer that suppresses the influence of the back electromotive force and other disturbance voltages on the FBd-axis voltage command value Vdfb and the FBq-axis voltage command value Vqfb.

[0136] The interference voltage suppressing unit 48b includes a delay element 48b1, an adder 48b2, a filter 48b3, and a multiplier 48b4. The delay element 48b1 is an example of the "first delay element" and the "second delay element" described in the claims.

[0137] The delay element 48b1 delays the d-axis voltage command value (Gv×Vdobs) and the q-axis voltage command value (Gv×Vqobs) output from the disturbance voltage suppression unit 48b and inputs them to the adder 48b2. That is, the delay element 48b1 inputs the past values ​​(last values) of the d-axis voltage command value (Gv×Vdobs) and the q-axis voltage command value (Gv×Vqobs) to the adder 48b2.

[0138] The adder 48b2 outputs the sum of the past value of the d-axis voltage command value (Gv×Vdobs) and the FBd-axis voltage command value Vdfb, and also outputs the sum of the past value of the q-axis voltage command value (Gv×Vqobs) and the FBq-axis voltage command value Vqfb.

[0139] The filter 48 b 3 performs a filtering process for reducing noise on the output of the adder 48 b 2 , and calculates a d-axis voltage command value Vdobs and a q-axis voltage command value Vqobs as outputs of the voltage disturbance observer.

[0140] Specifically, the sum of the past value of the d-axis voltage command value (Gv×Vdobs) and the FBd-axis voltage command value Vdfb is filtered to calculate the d-axis voltage command value Vdobs. In addition, the sum of the past value of the q-axis voltage command value (Gv×Vqobs) and the FBq-axis voltage command value Vqfb is filtered to calculate the q-axis voltage command value Vqobs. For example, the filter 48b3 may be a low-pass filter.

[0141] The voltage limit gain setting unit 48c sets a voltage limit gain Gv for limiting the voltage command value to be equal to or less than the voltage upper limit value VDutyMax based on the outputs Vdobs and Vqobs of the voltage disturbance observer, the FFd-axis voltage command value Vdff, the FFq-axis voltage command value Vqff, and the voltage upper limit value VDutyMax.

[0142] Specifically, the voltage limit gain setting unit 48c calculates the voltage limit gain Gv (the following equation (10)) by the ratio of the resultant vector of the d-axis voltage command value and the q-axis voltage command value to the voltage upper limit value VDutyMax. The limiter 48d limits the upper limit value of the voltage limit gain Gv to "1" and the lower limit value to "0".

[0143] [Mathematical formula 8]

[0144]

[0145] The multiplier 48b4 of the disturbance voltage suppressor 48b multiplies the outputs Vdobs and Vqobs of the voltage disturbance observer by the voltage limit gain Gv, inputs the multiplication results (Gv×Vdobs) and (Gv×Vqobs) to the delay element 48b1, and outputs them to the adder 48f.

[0146] The multiplier 48e multiplies the FFd-axis voltage command value Vdff and the FFq-axis voltage command value Vqff by the voltage limit gain Gv, respectively, and outputs the multiplication results (Gv×Vdff) and (Gv×Vqff) to the adder 48f.

[0147] The adder 48f calculates the sum of the multiplication results (Gv×Vdobs) and (Gv×Vdff) as the second d-axis voltage command value Vd=Gv×(Vdobs+Vdff), and calculates the sum of the multiplication results (Gv×Vqobs) and (Gv×Vqff) as the second q-axis voltage command value Vq=Gv×(Vqobs+Vqff).

[0148] In this way, by limiting the voltage command value by multiplying the voltage limit gain Gv, it is possible to suppress saturation of the duty ratio to 100% in the PWM control based on the second d-axis voltage command value Vd and the second q-axis voltage command value Vq.

[0149] Reference Figure 2 The two-phase / three-phase conversion unit 49 converts the second d-axis voltage command value Vd and the second q-axis voltage command value Vq into three-phase voltage command values.

[0150] The three-phase voltage command value is input to the PWM control unit 50, and the motor 20 is PWM driven via the converter 51. The drive current of the motor 20 is detected by the motor current detector 21, converted into a d-axis current id and a q-axis current iq by the three-phase / two-phase conversion unit 46, and fed back to the subtractor 47a of the FB control unit 47.

[0151] (effect)

[0152] The d-axis current command value calculation unit 41 calculates the basic d-axis current command value Idr0 based on the above formula (4). Since the constants R and L in the formula are set to nominal values, errors caused by deviations in physical parameters and temperature changes occur. In addition, the detection value of the rotation speed ω of the motor 20 also generates errors due to delays, noise, etc. Therefore, it is difficult to completely prevent duty saturation by limiting the d-axis current command value.

[0153] Therefore, in the present embodiment, duty saturation is suppressed in the voltage limiting unit 48 at the subsequent stage, and calculation of the optimum d-axis current command value is attempted in the d-axis current command value calculation unit 41 .

[0154] Thus, in the present embodiment, duty saturation is not considered in the d-axis current command value calculation unit 41, but if the d-axis current command value based on the above formula (4) is directly used, the d-axis current command value may be excessively calculated. Therefore, based on the above formula (4), how each input parameter affects the d-axis current command value is studied. In order to increase the d-axis current command value in the negative direction (enhance the weak magnetic control), according to the above formula (4), as long as the motor speed ω increases, the power supply voltage VR decreases, and the q-axis current command value Iqt increases.

[0155] Next, the influence when the q-axis current command value Iqt used in calculating the basic d-axis current command value Idr0 deviates from the second q-axis current command value Iqr2 actually used in calculating the voltage command value is studied.

[0156] When the second q-axis current command value Iqr2 deviates to the larger side, the d-axis current command value is insufficient, so duty saturation occurs. As the main cause of this phenomenon, the output Δq of the angular acceleration regulator 42 is added to the basic q-axis current command value Iqr0. However, the output Δq of the angular acceleration regulator changes sharply, and the d-axis current command value is limited by the rate of change limiter, etc., so it is presumed that it cannot follow the sharp change. Therefore, the time for the second q-axis current command value Iqr2 to deviate to the larger side is short, and its influence is also limited. Therefore, the situation where the second q-axis current command value Iqr2 deviates to the larger side is not considered.

[0157] If the second q-axis current command value Iqr2 deviates to the smaller side, the basic d-axis current command value Idr0 becomes excessive, and the duty cycle cannot be used to the upper limit. As a main reason, the case where the q-axis current command value is limited in the later stage is considered. The limitation of the q-axis current command value in the later stage is based on the system current limitation of the limitation gain Gq3 of the above formula (5) and the battery current limitation based on the limitation gain Gq4 of the above formula (7).

[0158] Therefore, the current command value setting unit 41a calculates the q-axis current command value Iqt with these restrictions by using the above equations (1) and (3) and uses it to calculate the basic d-axis current command value Idr0, thereby calculating the optimal q-axis current command value.

[0159] In addition, a voltage limit gain Gv for applying voltage limitation is calculated in the voltage limiting unit 48 and multiplied by the voltage command value. When the voltage limit gain Gv is multiplied by the voltage command value in the disturbance voltage suppression unit 48b functioning as a voltage disturbance observer, the upper limit value of the integrator constituting the voltage disturbance observer can be limited, and thus it substantially functions as an anti-saturation function.

[0160] In addition, the voltage limiting unit 48 limits the d-axis voltage command value and the q-axis voltage command value by multiplying the gain (voltage limit gain Gv) of the same value. This is because, since the voltage disturbance observer is composed of an integrator, if the q-axis is limited first, even if the synthetic vector of the d-axis voltage command value and the q-axis voltage command value is limited by the upper limit value, the d-axis voltage command value will continue to rise to the upper limit value, and accordingly, the q-axis voltage command value will be sharply limited, which may cause a sharp change in the output.

[0161] In addition, regarding the setting of the voltage upper limit value VDutyMax by the voltage upper limit value setting unit 48 a , the dead time acts so as to reduce the duty during power running and to increase the duty during regeneration.

[0162] The above formula (8) is a calculation formula for the voltage upper limit value VDutyMax during power operation. If the switching of the action direction during regeneration is not considered, the upper limit of the duty cycle may deviate. Therefore, in this embodiment, power operation and regeneration are determined, and the sign of the reduction amount based on the dead time is switched.

[0163] However, if the sign is simply switched, a drastic change in the duty cycle will occur, which may cause overcurrent and operating noise. Therefore, the battery current Ibat is used as the condition for regeneration, and the voltage limit gain Gv is used as the condition for duty, and the judgment gains G1 and G2 are calculated based on these. However, since it is unknown which of these condition judgments is satisfied, the sign is switched based on the maximum value of the judgment gains G1 and G2, thereby realizing a gradual switching between the two judgment gains G1 and G2.

[0164] The FB control unit 47 has an anti-windup function for the integrated value in the integrator 47e. Generally speaking, the anti-windup function is intended to prevent the integrated value from being excessively accumulated when the output of the controller including the integrator is limited for some reason.

[0165] In a general configuration of an anti-windup function, some kind of processing is applied to the difference between the output before and after being limited, and the difference is fed back to limit the upper limit of the integral value.

[0166] In this embodiment, the output of the FB control unit 47 rarely exceeds the voltage upper limit, and the output of the disturbance voltage suppression unit (voltage disturbance observer) 48b provided at the subsequent stage exceeds the voltage upper limit in most cases. Therefore, a general anti-saturation structure cannot be used as it is.

[0167] In addition, it is preferred that the ratio of the output of the FB control unit 47 to the output of the interference voltage suppression unit 48b can be changed even when the voltage command value is limited by the voltage upper limit value (for example, preferably, when the rotational speed ω of the motor 20 decreases and the torque increases, the back electromotive force decreases and the q-axis current increases, so that the ratio of the output of the FB control unit 47 becomes larger and the ratio of the output of the interference voltage suppression unit 48b becomes smaller).

[0168] Therefore, in this embodiment, the integrated value of the integrator 47e of the FB control unit 47 and the outputs Vdobs and Vqob of the voltage disturbance observer of the disturbance voltage suppression unit 48b are multiplied by the same gain (voltage limiting gain Gv) to limit the load equally between the FB control unit 47 and the disturbance voltage suppression unit 48b.

[0169] (action)

[0170] Fig. 9 This is a flowchart of an example of a motor control method according to an embodiment.

[0171] In step S1, the torque sensor 10, the vehicle speed sensor 12 and the motor current detector 21 respectively detect the steering torque Th, the vehicle speed Vh and the drive current of the motor 20. In addition, the voltage sensor and the current sensor detect the power supply voltage VR and the battery current Ibat supplied from the battery 13.

[0172] In step S2 , the torque control unit 40 calculates a basic q-axis current command value Iqr0 based on at least the steering torque Th and the vehicle speed Vh.

[0173] In step S3 , the d-axis current command value calculation unit 41 sets a first d-axis current command value Idr1 based on the basic q-axis current command value Iqr0 , the power supply voltage VR, and the rotation speed ω of the motor 20 .

[0174] In step S4 , the first current limiting unit 43 calculates a first q-axis current command value Iqr1 by limiting the basic q-axis current command value Iqr0 based on the rated current of the motor 20 .

[0175] In step S5 , the second current limiting unit 44 calculates a second d-axis current command value Idr2 and a second q-axis current command value Iqr2 by limiting the first d-axis current command value Idr1 and the first q-axis current command value Iqr1 based on the battery upper limit current Ibatmax.

[0176] In step S6, the FF control unit 45 calculates the FFd-axis voltage command value Vdff and the FFq-axis voltage command value Vqff. The FB control unit 47 calculates the FBd-axis voltage command value Vdfb and the FBq-axis voltage command value Vqfb.

[0177] In step S7 , the voltage upper limit value setting unit 48 a sets the voltage upper limit value VDutyMax.

[0178] In step S8 , the voltage limit gain setting unit 48 c sets the voltage limit gain Gv based on the voltage upper limit value VDutyMax.

[0179] In step S9 , the voltage limiting unit 48 limits the FFd-axis voltage command value Vdff, FFq-axis voltage command value Vqff, FBd-axis voltage command value Vdfb, and FBq-axis voltage command value Vqfb by the voltage limiting gain Gv, thereby calculating the second d-axis voltage command value Vd and the second q-axis voltage command value Vq.

[0180] In step S10 , the PWM control unit 50 and the inverter 51 drive the motor 20 based on the second d-axis voltage command value Vd and the second q-axis voltage command value Vq. Thereafter, the process ends.

[0181] (Variation Example)

[0182] The motor control device of the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present invention.

[0183] For example, in the above-mentioned embodiment, an electric power steering device equipped with the motor control device is illustrated as an application example of the motor control device involved in the present invention, but the application scope of the motor control device involved in the present invention is not limited to this, and can be applied to various mechanical devices using the motor control device.

[0184] Fig.10 This is a schematic structural diagram showing an example of a linear motion table device using the motor control device of the present invention.

[0185] The linear motion table device includes a feed screw device, a table 71 , two linear guides (linear motion guide devices), and a base 74 .

[0186] The feed screw device includes a screw shaft 70, a nut 76, and a motor 77. The screw shaft 70 is inserted into the nut 76. The feed screw mechanism of the feed screw device is a ball screw in which the spiral groove of the screw shaft 70 and the spiral groove of the nut 76 are in point contact via balls (rolling elements). The motor 77 is coupled to one axial end of the screw shaft 70.

[0187] The two linear guides each have a guide rail 72, two sliders (moving bodies) 73, and a plurality of rolling bodies. In the linear guide, the guide rail 72 and the slider 73 each have a track surface forming a rolling path for the rolling bodies at positions facing each other. The two track surfaces extend in the longitudinal direction of the guide rail 72, and the slider 73 moves linearly along the guide rail 72 via the rolling bodies rolling in the rolling path under load.

[0188] Linear guides are arranged at both ends of the base 74 in a direction perpendicular to the moving direction Y of the table 71 , and a feed screw device is arranged between the two linear guides. The guide rail 72 and the screw shaft 70 are arranged parallel to the moving direction Y of the table 71 .

[0189] With this arrangement, the guide rail 72 is fixed to the base 74. The screw shaft 70 has rolling bearings mounted on both axial ends thereof, and housings 75 are fixed to the outer rings of the rolling bearings. Each housing 75 is fixed to the base 74. Thus, the screw shaft 70 is supported rotatably relative to the base 74.

[0190] The worktable 71 is disposed above the two sliders 73 of each linear guide and the nut 76 of the feed screw device, and is directly fixed to the sliders 73 and fixed to the nut 76 via a bracket. That is, the two sliders 73 of each linear guide and the nut 76 of the feed screw device are fixed to one surface of the worktable 71.

[0191] In this linear motion table, when the motor 77 is driven to operate the feed screw device, the screw shaft 70 rotates, and the nut 76 is linearly moved by the ball screw mechanism. In accordance with this, the table 71 is linearly moved while being guided by the linear guide.

[0192] The controller 78 sets a current command value for driving the motor 77 , calculates a voltage control command value Vref based on the current command value through the same processing as the controller 30 of the above-described embodiment, and controls the current supplied to the motor 20 .

[0193] (Effects of Embodiments)

[0194] (1) A motor control device comprises: a torque control unit, which sets a basic q-axis current command value for controlling the torque generated by the motor; and a d-axis current command value calculation unit, which sets a first d-axis current command value for magnetic field weakening based on the basic q-axis current command value and the rotation speed of the motor; a first current limiting unit, which is arranged at the rear stage of the d-axis current command value calculation unit, and calculates the first q-axis current command value by limiting the basic q-axis current command value according to the first d-axis current command value so that the drive current of the motor does not exceed the rated current of the motor; and a second current limiting unit, which is arranged at the rear stage of the first current limiting unit, and limits the output current of the battery to a predetermined upper limit so that the output current of the battery does not exceed the specified upper limit. a first d-axis current command value and a first q-axis current command value are controlled to calculate a second d-axis current command value and a second q-axis current command value; a voltage command value calculation unit, which calculates a first d-axis voltage command value and a first q-axis voltage command value based on the second d-axis current command value and the second q-axis current command value; a voltage limiting unit, which calculates a second d-axis voltage command value and a second q-axis voltage command value by limiting the first d-axis voltage command value and the first q-axis voltage command value respectively in a manner that suppresses duty cycle saturation of PWM control based on the first d-axis voltage command value and the first q-axis voltage command value; and a drive circuit, which drives the motor based on the second d-axis voltage command value and the second q-axis voltage command value.

[0195] Thus, the motor control device according to the embodiment can suppress saturation of the duty ratio in a high load state and reduction of the duty ratio in a high rotation speed region.

[0196] (2) The d-axis current command value calculation unit can calculate the first d-axis current command value based on the following q-axis current command value: the q-axis current command value is obtained by limiting the basic q-axis current command value in a manner such that the drive current of the motor does not exceed the rated current of the motor based on the past value of the second d-axis current command value.

[0197] Thus, even if the q-axis current command value for calculating the voltage command value is limited based on the rated current of the motor, the deviation between the q-axis current command value for calculating the first d-axis current command value and the q-axis command value for calculating the voltage command value can be reduced. As a result, the duty cycle can be limited to a value lower than the upper limit by suppressing the calculation of an excessively large first d-axis current command value.

[0198] (3) The d-axis current command value calculation unit may calculate the first d-axis current command value based on the q-axis current command value obtained by limiting the basic q-axis current command value based on the past value of the second d-axis current command value so that the output current of the battery does not exceed the allowable upper limit.

[0199] Thus, even if the q-axis current command value for calculating the voltage command value is limited based on the upper limit current of the battery, the deviation between the q-axis current command value for calculating the first d-axis current command value and the q-axis command value for calculating the voltage command value can be reduced. As a result, the duty ratio can be limited to be lower than the upper limit while suppressing the calculation of an excessively large first d-axis current command value.

[0200] (4) The d-axis current command value calculation unit may limit the upper limit of the first d-axis current command value based on the rotation speed of the motor.

[0201] This makes it possible to achieve a balance between operating noise and overcurrent countermeasures.

[0202] (5) The voltage limiting unit may include: a voltage upper limit value setting unit, which sets a voltage upper limit value as an upper limit value of the applied voltage to the motor; and a voltage limiting gain setting unit, which sets a voltage limiting gain corresponding to the voltage upper limit value, and the voltage limiting unit calculates the second d-axis voltage command value and the second q-axis voltage command value by respectively limiting the first d-axis voltage command value and the first q-axis voltage command value according to the voltage limiting gain.

[0203] This can suppress saturation of the duty ratio in a high load state.

[0204] (6) The voltage upper limit setting unit can set the voltage upper limit based on at least one of the improvement in voltage utilization efficiency obtained by superimposing the third harmonic on the multi-phase voltage command value of the motor as a multi-phase motor, the voltage drop caused by the dead time, and the decrease in the ratio of the motor terminal voltage to the duty cycle caused by the dead time compensation.

[0205] Thereby, the voltage upper limit value for limiting the voltage command value can be appropriately set.

[0206] (7) The voltage limiting unit may include an interference voltage suppression unit, which outputs a first multiplication result obtained by multiplying the sum of the first d-axis voltage command value and the output of the first delay element by a voltage limiting gain, and a second multiplication result obtained by multiplying the sum of the first q-axis voltage command value and the output of the second delay element by the voltage limiting gain, and inputs the first multiplication result and the second multiplication result into the first delay element and the second delay element, respectively, and the voltage limiting unit outputs a second d-axis voltage command value including the first multiplication result and a second q-axis voltage command value including the second multiplication result.

[0207] Thus, the voltage command value can be limited based on the voltage limit gain. In addition, the influence of the disturbance voltage on the first d-axis voltage command value and the first q-axis voltage command value can be suppressed.

[0208] (8) The voltage limit gain setting unit may set the voltage limit gain based on the voltage upper limit value, the sum of the first d-axis voltage command value and the output of the first delay element, and the sum of the first q-axis voltage command value and the output of the second delay element.

[0209] Thus, the voltage limit gain can be calculated from the ratio of the resultant vector of the d-axis voltage command value and the q-axis voltage command value to the voltage upper limit value.

[0210] (9) The voltage command value calculation unit can output a first d-axis voltage command value including a d-axis integral component and a first q-axis voltage command value including a q-axis integral component, and suppress the d-axis integral component and the q-axis integral component based on a voltage limiting gain, wherein the d-axis integral component is an integral component of a deviation of a detected value of a d-axis current of a motor driving current relative to a second d-axis current command value, and the q-axis integral component is an integral component of a deviation of a detected value of a q-axis current of a motor driving current relative to a second q-axis current command value.

[0211] Thus, in the voltage command value calculation unit that calculates the voltage command value by integral control, an anti-saturation function of the integral value can be realized.

[0212] (10) The first d-axis voltage command value may include a feedforward d-axis voltage command value calculated by feedforward control based on the second d-axis current command value, and a feedback d-axis voltage command value calculated by feedback control based on a deviation of a detected value of a d-axis current of the motor drive current relative to the second d-axis current command value. In addition, the first q-axis voltage command value may include a feedforward q-axis voltage command value calculated by feedforward control based on the second q-axis current command value, and a feedback q-axis voltage command value calculated by feedback control based on a deviation of a detected value of a q-axis current of the motor drive current relative to the second q-axis current command value.

[0213] The interference voltage suppression unit can output a first multiplication result obtained by multiplying the sum of the feedback d-axis voltage command value and the output of the first delay element by the voltage limiting gain, and a second multiplication result obtained by multiplying the sum of the feedback q-axis voltage command value and the output of the second delay element by the voltage limiting gain, and input the first multiplication result and the second multiplication result into the first delay element and the second delay element, respectively.

[0214] The voltage limiting gain setting unit can set the voltage limiting gain based on the voltage upper limit value, the sum of "the feedback d-axis voltage command value and the output of the first delay element and the feedforward d-axis voltage command value", and the sum of "the feedback q-axis voltage command value and the output of the second delay element and the feedforward q-axis voltage command value".

[0215] The voltage limiting unit can output a second d-axis voltage command value including a third multiplication result obtained by multiplying the feedforward d-axis voltage command value by the voltage limiting gain and the first multiplication result, and output a second q-axis voltage command value including a fourth multiplication result obtained by multiplying the feedforward q-axis voltage command value by the voltage limiting gain and the second multiplication result.

[0216] Thus, it is possible to improve the responsiveness based on the feedforward control and suppress the influence of the disturbance based on the feedback control. In addition, the voltage command value can be limited based on the voltage limit gain. In addition, it is possible to suppress the influence of the disturbance voltage on the feedback d-axis voltage command value and the feedback q-axis voltage command value. In addition, the voltage limit gain can be calculated based on the ratio of the synthetic vector of the d-axis voltage command value and the q-axis voltage command value to the voltage upper limit value.

[0217] Description of Reference Numerals

[0218] 1…steering wheel, 2…steering shaft, 3…reduction gear, 4a, 4b…universal joint, 5…pinion-rack mechanism, 5a…pinion, 5b…rack, 6a, 6b…tie rod, 7a, 7b…hub unit, 8L, 8R…steering wheel, 10…torque sensor, 11…ignition key, 12…vehicle speed sensor, 13…battery, 14…steering angle sensor, 20, 77…motor, 21…motor current detector, 30…controller, 40…torque control unit, 41…d-axis current command value calculation unit, 41a…current command value setting unit, 41b…field current command value calculation unit, 41c…field current limiting unit, 42…angular acceleration regulator, 43…first current limiting unit, 44…second current limiting unit, 45…feedforward control unit, 46…three-phase / two-phase conversion unit, 47…feedback control unit, 47a, 48 a5...subtractor, 47b, 47d, 47e3, 47f...gain multiplication unit, 47c...approximate differential unit, 47e...integrator, 47e1, 48b1...delay element, 47e2, 47g, 48b2, 48f...adder, 48...voltage limiter, 48a...voltage upper limit value setting unit, 48a1...first gain setting unit, 48a2...second gain setting unit, 48a3...selector, 48a4...second gain setting unit, 48a5...second gain setting unit, 48a6...second gain setting unit, 48a7...second gain setting unit, 48a8...second gain setting unit, 48a9...second gain setting unit, 48a1...second gain setting unit, 48a1...second gain setting unit, 48a2...second gain setting unit, 48a3...second gain setting 8a4, 48a6, 48a7, 48b4, 48e...multiplier, 48b...interference voltage suppression unit, 48b3...filter, 48c...voltage limiting gain setting unit, 48d...limiter, 49...two-phase / three-phase conversion unit, 50...PWM control unit, 51...converter, 70...screw shaft, 71...work table, 72...guide rail, 73...slider, 74...base, 75...housing, 76...nut.

Claims

1. A motor control device, characterized in that: The motor control device comprises: a torque control unit that sets a basic q-axis current command value for controlling the motor to generate torque; a d-axis current command value calculation unit that sets a first d-axis current command value for field weakening based on the basic q-axis current command value and the rotation speed of the motor; a first current limiting unit provided at a subsequent stage of the d-axis current command value calculating unit, for calculating a first q-axis current command value by limiting the basic q-axis current command value according to the first d-axis current command value so that the drive current of the motor does not exceed the rated current of the motor; a second current limiting unit, which is provided at a subsequent stage of the first current limiting unit and calculates a second d-axis current command value and a second q-axis current command value by limiting the first d-axis current command value and the first q-axis current command value respectively so that the output current of the battery does not exceed a prescribed allowable upper limit; a voltage command value calculation unit that calculates a first d-axis voltage command value and a first q-axis voltage command value based on the second d-axis current command value and the second q-axis current command value; a voltage limiting unit that calculates a second d-axis voltage command value and a second q-axis voltage command value by limiting the first d-axis voltage command value and the first q-axis voltage command value respectively in a manner that suppresses saturation of a duty ratio of PWM control based on the first d-axis voltage command value and the first q-axis voltage command value; and A drive circuit drives the motor based on the second d-axis voltage command value and the second q-axis voltage command value.

2. The motor control device according to claim 1, characterized in that: The d-axis current command value calculation unit calculates the first d-axis current command value based on the following q-axis current command value: the q-axis current command value is obtained by limiting the basic q-axis current command value based on a past value of the second d-axis current command value so that the drive current of the motor does not exceed the rated current of the motor.

3. The motor control device according to claim 1, characterized in that: The d-axis current command value calculation unit calculates the first d-axis current command value based on a q-axis current command value obtained by limiting the basic q-axis current command value based on a past value of the second d-axis current command value so that the output current of the battery does not exceed the allowable upper limit.

4. The motor control device according to claim 1, characterized in that: The d-axis current command value calculation unit limits an upper limit of the first d-axis current command value based on a rotation speed of the motor.

5. The motor control device according to claim 1, characterized in that: The voltage limiting unit includes: a voltage upper limit value setting unit that sets a voltage upper limit value as an upper limit value of a voltage applied to the motor; and a voltage limit gain setting unit for setting a voltage limit gain corresponding to the voltage upper limit value, The voltage limiting unit calculates a second d-axis voltage command value and a second q-axis voltage command value by limiting the first d-axis voltage command value and the first q-axis voltage command value, respectively, according to the voltage limit gain.

6. The motor control device according to claim 5, characterized in that: The voltage upper limit setting unit sets the voltage upper limit based on at least one of an improvement in voltage utilization efficiency caused by superimposing third harmonics on a multi-phase voltage command value of the motor as a multi-phase motor, a voltage drop caused by dead time, and a decrease in the ratio of the motor terminal voltage to the duty cycle caused by dead time compensation.

7. The motor control device according to claim 5, characterized in that: The voltage limiting unit includes an interference voltage suppression unit, which outputs a first multiplication result obtained by multiplying the sum of the first d-axis voltage command value and the output of the first delay element by the voltage limiting gain, and a second multiplication result obtained by multiplying the sum of the first q-axis voltage command value and the output of the second delay element by the voltage limiting gain, and inputs the first multiplication result and the second multiplication result into the first delay element and the second delay element respectively, and the voltage limiting unit outputs the second d-axis voltage command value including the first multiplication result and the second q-axis voltage command value including the second multiplication result.

8. The motor control device according to claim 7, characterized in that: The voltage limit gain setting unit sets the voltage limit gain based on the voltage upper limit value, the sum of the first d-axis voltage command value and the output of the first delay element, and the sum of the first q-axis voltage command value and the output of the second delay element.

9. The motor control device according to claim 7 or 8, characterized in that: The voltage command value calculation unit outputs the first d-axis voltage command value including the d-axis integral component and the first q-axis voltage command value including the q-axis integral component, and suppresses the d-axis integral component and the q-axis integral component based on the voltage limiting gain, wherein the d-axis integral component is an integral component of a deviation of a detected value of a d-axis current of the driving current of the motor relative to the second d-axis current command value, and the q-axis integral component is an integral component of a deviation of a detected value of a q-axis current of the driving current of the motor relative to the second q-axis current command value.

10. The motor control device according to claim 7 or 8, characterized in that: The first d-axis voltage command value includes: a feedforward d-axis voltage command value calculated by feedforward control based on the second d-axis current command value; and a feedback d-axis voltage command value calculated by feedback control based on a deviation of a detected value of a d-axis current of a drive current of the motor relative to the second d-axis current command value. The first q-axis voltage command value includes: a feedforward q-axis voltage command value calculated by feedforward control based on the second q-axis current command value; and a feedback q-axis voltage command value calculated by feedback control based on a deviation of a detected value of a q-axis current of a drive current of the motor relative to the second q-axis current command value. The disturbance voltage suppression unit outputs a first multiplication result obtained by multiplying the sum of the feedback d-axis voltage command value and the output of the first delay element by the voltage limit gain, and a second multiplication result obtained by multiplying the sum of the feedback q-axis voltage command value and the output of the second delay element by the voltage limit gain, and inputs the first multiplication result and the second multiplication result into the first delay element and the second delay element, respectively. The voltage limit gain setting unit sets the voltage limit gain based on the voltage upper limit value, the sum of “the feedback d-axis voltage command value and the output of the first delay element and the feedforward d-axis voltage command value”, and the sum of “the feedback q-axis voltage command value and the output of the second delay element and the feedforward q-axis voltage command value”, The voltage limiting unit outputs the second d-axis voltage command value including a third multiplication result and the first multiplication result, and outputs the second q-axis voltage command value including a fourth multiplication result and the second multiplication result, wherein the third multiplication result is obtained by multiplying the feedforward d-axis voltage command value by the voltage limiting gain, and the fourth multiplication result is obtained by multiplying the feedforward q-axis voltage command value by the voltage limiting gain.

11. An electric power steering device, characterized in that: The electric power steering device comprises: The motor control device according to claim 1; and a motor controlled by the motor control device, The electric power steering device applies a steering assist force to a steering system of a vehicle through the motor.

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