JP2008284977A - Electric power steering controlling system and motor drive control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering controlling system that can perform motor drive control which does not deteriorate steering feeling to the steering operation by a driver even with a structure to detect phase currents of a motor by a current detector provided on a common line at the ground side of an inverter. <P>SOLUTION: This electric power steering controlling system comprises: the inverter 30, which converts a DC voltage supplied from a DC power source 60 into an AC voltage by pulse width modulation control and supplies the AC voltage to a motor 50; a current detection circuit 40, which detects a current flowing through the common line L (a shunt resistor R1) at the ground side of a switching circuit 32 constituting the inverter 30; and a control system 20, which selects a control mode corresponding to an output state of the motor 50 out of a plurality of control modes m1, m2, m3, which are set in consideration of the state that the accuracy of current detection by a current detection circuit 40 is deteriorated, and performs the motor drive control. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an electric power steering control device and a motor drive control method, and more specifically, an electric power steering capable of detecting a current of each phase of a motor from a current flowing in a common line on the ground side of an inverter that supplies a drive voltage to the motor. The present invention relates to a control device and a motor drive control method.

2. Description of the Related Art Conventionally, there is known an electric power steering device that applies a steering assist force to a steering mechanism by driving a motor in accordance with a steering torque applied to a steering (handle) by a driver. In recent years, many brushless motors have been adopted as motors used in the electric power steering apparatus.

FIG. 1 is a schematic configuration diagram of a conventional electric power steering control device. An electric power steering control device (hereinafter referred to as an EPS control device) 1 includes a control unit 2 composed of a microcomputer, an inverter 3, and a current detection circuit 4.
Is connected to a motor 50 provided in a steering mechanism (not shown) of the vehicle.

The control unit 2 includes various sensors such as a torque sensor 5 that detects the steering state of the steering, a vehicle speed sensor 6 that detects the vehicle speed, and a rotation angle sensor 7 that detects the rotation angle (electrical angle) of the motor 50.
The steering torque signal detected by the torque sensor 5, the vehicle speed signal detected by the vehicle speed sensor 6, the rotation angle signal detected by the rotation angle sensor 7, etc. are input to the control unit 2, and the current is detected. The current value of each phase of the motor 50 detected by the circuit 4 is input to the control unit 2. The motor 50 employs a three-phase brushless motor that includes a rotor as a magnetic field made of permanent magnets and a stator made of U-phase, V-phase, and W-phase three-phase coils.

The inverter 3 has a function of converting a DC voltage supplied from a battery 60 serving as a DC power source into a three-phase AC voltage by pulse width modulation (PWM) control and supplying the converted voltage to the motor 50. And a switching circuit 32.

The switching circuit 32 includes switching elements UH and UL connected in series for the U phase, and V
The switching elements VH and VL connected in series for the phase and the switching elements WH and WL connected in series for the W phase are connected in parallel between the battery 60 and the ground GND. The connection point between the switching elements UH and UL, the switching element V
A connection point between H and VL and a connection point between the switching elements WH and WL are connected to a U-phase terminal u, a V-phase terminal v, and a W-phase terminal w of the motor 50, respectively.

A current detecting shunt resistor Ru is interposed between the U-phase switching element UL and the ground GND, and a current detecting shunt resistor Rv is provided between the V-phase switching element VL and the ground GND. A current detecting shunt resistor Rw is interposed between the W-phase switching element WL and the ground GND. Each switching element UH, UL,...
A feedback diode (not shown) is connected in parallel.

The PWM drive circuit 31 is based on the PWM signal of each phase output from the control unit 2,
Each switching element UH, UL constituting the switching circuit 32 for each V phase and W phase,...
A pulse modulation circuit that outputs a switching signal for turning on / off is configured.

Next, drive control of the motor 50 performed by the control unit 2 will be described. First, a command torque T * is calculated from a steering torque signal detected by the torque sensor 5, and current command values Id for the d-axis (field component) and q-axis (torque component) are calculated based on the command torque T *. * And Iq * are calculated. On the other hand, the currents Iu, Iv, and Iw of each phase of the motor 50 detected by the current detection circuit 4 are dq converted based on the rotation angle (electrical angle) θ to calculate the output current values Id and Iq for the d-axis and the q-axis, respectively. To do.

Next, proportional integral control (PI control) is performed so that the deviation between the current command values Id *, Iq * and the output current values Id, Iq is eliminated, and the voltage command values Vd *, Vq * is calculated.

Then, the voltage command values Vd * and Vq * are inversely converted by dq based on the electrical angle θe to obtain the voltage command values Vu *, Vv * and Vw * for each phase of the motor 50, and the obtained voltage command values Vu *.
, Vv *, Vw * are converted into PWM command values PWMu *, PWMv *, PWMw * for each phase,
The converted PWM command value of each phase is output to the PWM drive circuit 31 of the inverter 3.

In the PWM drive circuit 31, the timing for turning on / off the switching elements UH, UL,... Of the switching circuit 32 is determined by a triangular wave comparison method based on the PWM command value. For example, a three-phase AC command wave Vu *, Vv *, Vw * as shown in FIG. 2A is compared with a triangular wave K (generally called a carrier wave or a carry wave). As shown in FIG. 2 (b), the on / off timing of the switching elements UH, UL,... Is determined from the intersection of the three-phase AC command waves Vu *, Vv *, Vw * and the triangular wave K. A three-phase alternating current is allowed to flow.

2A is a diagram conceptually showing the relationship between the triangular wave K and the three-phase AC command wave.
FIG. 2B is an enlarged view showing the relationship between the operation waveform of the triangular wave K, the three-phase AC command wave, and the angular switching element, and the relationship of the current detection waveform of each phase. In FIG. 2 (b), the three-phase AC command wave is simply indicated by a straight line, and in order to simplify the display, the switching elements UH, VH, WH on the power supply side and the switching elements UL, VL on the ground side are shown. The dead time for preventing short circuit with WL is omitted.

In the EPS control device 1 configured as described above, the current values Iu, Iv, and Iw flowing in each phase of the motor 50 are detected in order to perform the current feedback control. The detection of these current values is performed by the shunt resistor Ru. , Rv, Rw, for example, timing when current flows, for example, FIG.
, The peak of the triangular wave K that is not easily affected by switching noise or the like during the period in which all the switching elements UH, VH, WH on the DC power supply side are turned off and all the switching elements UL, VL, WL on the ground side are turned on ) It is performed at the timing of P1, and at this timing, it is possible to detect the current flowing in each phase of the motor 50 at a time.

However, in the conventional EPS control device 1 described above, the shunt resistor Ru for current detection is used.
, Rv, Rw are the switching elements UL, VL, WL on the lower side of the switching circuit 32, respectively.
Are connected in series with each other and ground GND, so that a shunt resistor for current detection is 3
The number of parts must be provided, and the number of parts is large, resulting in a cost increase.

Therefore, an apparatus configured to detect the current flowing through the motor with one shunt resistor has also been proposed. FIG. 3 shows a circuit configuration of an inverter configured to detect a current value flowing through the motor with one shunt resistor. However, components having the same functions as those of the inverter 3 shown in FIG.

The inverter 3A includes a PWM drive circuit 31 and a switching circuit 32A. The switching circuit 32A includes switching elements UH and UL for U phase, switching elements VH and VL for V phase, and W The phase switching elements WH and WL are connected in parallel between the battery 60 and the ground GND, and the shunt is connected to the common line L on the ground side of the switching elements UL, VL and WL. A resistor R1 is interposed.

Hereinafter, a method for detecting the current flowing through the motor 50 with the shunt resistor R1 will be described.
FIG. 4A is a diagram showing the relationship between the triangular wave K and the three-phase AC command wave at the time of high output,
FIG. 4B is an enlarged view showing the relationship between the triangular wave K, the three-phase AC command wave, the operation waveform of each switching element, and the current detection waveform detected from the voltage across the shunt resistor R1. In FIG. 4B, the three-phase alternating current command wave is simply indicated by a straight line, and the dead time for preventing a short circuit is omitted in order to simplify the display.

In the output state shown in FIG. 4B, the on / off states of the switching elements UH, UL,... Have four states (sections) a to d.
In the section a, the switching elements UH, VH, and WH on the power supply side are all turned on, and the switching elements UL, VL, and WL on the ground side are all turned off.
This is a non-energized state in which current circulates between H, VH, and WH and the motor 50.

In section b, the switching elements VH and WH on the power supply side are ON, and the switching element U on the ground side
L is in an ON state, and power is supplied from the battery 60 to the motor 50 via the inverter 3A. At this time, the phase current Iu flowing into the U phase flows into the common line L (shunt resistor R1). Is flowing.

In section c, the switching element WH on the power supply side is ON, the switching elements UL, V on the ground side
L is in an ON state, and power is supplied from the battery 60 to the motor 50 via the inverter 3A. At this time, the common line L (shunt resistor R1) is supplied to the phase flowing out from the W phase. Current Iw is flowing.

In the section d, the switching elements UH, VH, WH on the power supply side are all OFF, the switching elements UL, VL, WL on the ground side are all ON, and the switching element U on the ground side
This is a non-energized state in which current circulates between L, VL, WL and the motor 50.

Therefore, in the high output state shown in FIG. 4, it is possible to detect the U-phase phase current Iu in the section b and the W-phase phase current Iw in the section c within one carrier of the triangular wave K. In other words, when any one of the switching elements UH, VH, and WH on the power supply side is ON, the current of the phase can be detected, and when the two phases are ON, the current of the remaining phase can be detected. Current detection for two phases can be performed within one carrier, and the current feedback control described above can be performed using the detected current value.

However, when the above-described control method for detecting the phase current with the shunt resistor R1 is adopted, the current is supplied only in the section where one of the switching elements UH, VH, and WH on the power source side is ON, or the section where the two phases are ON. For example, in the case of a low output with small values of the three-phase AC command waves Vu *, Vv *, Vw * as shown in FIG. , Shorter than the time required for current detection (A / D sampling period),
There is a problem that it is difficult to detect current with high accuracy, and as a result, the followability by current feedback control is deteriorated, and the steering feeling for the driver's steering operation may be reduced.
JP 2003-284374 A JP 2004-168128 A JP 2004-248444 A

Means for solving the problems and their effects

The present invention has been made in view of the above-described problem, and even when the motor phase current is detected by one current detector provided on a common line on the ground side of the inverter, steering with respect to the steering operation of the driver is performed. An object of the present invention is to provide an electric power steering control apparatus and a motor drive control method capable of performing motor drive control without reducing feeling.

In order to achieve the above object, an electric power steering control device (1) according to the present invention includes an inverter that converts a DC voltage supplied from a DC power source into an AC voltage by pulse width modulation control and supplies the AC voltage to the motor, and the inverter Current detecting means for detecting a current flowing in a common line on the ground side of the switching circuit constituting the switching circuit, and the output state of the motor from among a plurality of control modes set in consideration of current detection accuracy by the current detecting means And a control means for performing motor drive control by selecting a corresponding control mode.

According to the electric power steering control device (1), when the output state is such that the current detection accuracy by the current detection means is low, the output state of the motor corresponds to the output state of the motor from among the plurality of control modes. Decreasing follow-up of current feedback control due to a decrease in current detection accuracy by the current detection unit by selecting an appropriate control mode that is not affected by a decrease in current detection accuracy by the detection unit It is possible to prevent the steering feeling from being lowered by the driver's steering operation. Therefore, even if it is the structure which performs an electric current detection by the said electric current detection means, the electric power steering control excellent in the steering property which does not make a driver | operator feel uncomfortable can be performed.

A motor drive control method according to the present invention is a motor drive control method for converting a DC voltage supplied from a DC power source into an AC voltage via an inverter and supplying the converted voltage to a motor, wherein the switching circuit constituting the inverter A control mode corresponding to the output state of the motor is selected from a plurality of control modes set in consideration of current detection accuracy by a current detection means for detecting a current flowing in the common line on the ground side, and the selected control The motor drive control corresponding to the mode is performed.

According to the motor drive control method, when the output state is such that the current detection accuracy by the current detection unit is low, the current detection unit corresponds to the output state of the motor from among the plurality of control modes, that is, the current by the current detection unit. By selecting an appropriate control mode that is not affected by a decrease in detection accuracy and performing motor drive control, it is possible to prevent deterioration in follow-up performance of current feedback control due to a decrease in current detection accuracy by the current detection means. Can do.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an electric power steering control device and a motor drive control method according to the present invention will be described with reference to the drawings. FIG. 6 is a block diagram schematically showing a main part of the electric power steering control device (EPS control device) according to the embodiment. However, the same components as those of the conventional EPS control apparatus shown in FIG.

The electric power steering control device (EPS control device) 10 includes a CPU 21 and a RAM 22.
The control unit 20 including the ROM 23, the inverter 30, and the current detection circuit 40 are configured to include a motor (3) provided in a vehicle steering mechanism (not shown). Phase brushless motor) 50.

Further, a torque sensor 5 that detects the steering state of the steering, a vehicle speed sensor 6 that detects the vehicle speed, a rotation angle sensor 7 that detects the rotation angle (electrical angle) of the motor 50, and a power supply voltage of the battery 60 that is a DC power source are detected. Various sensors such as a power supply voltage sensor 8 are connected to the control unit 20, a steering torque signal detected by the torque sensor 5, a vehicle speed signal detected by the vehicle speed sensor 6,
A rotation angle signal detected by the rotation angle sensor 7, a voltage signal detected by the power supply voltage sensor 8, and the like are input to the control unit 20, and a current flowing through the common line L on the ground side of the switching circuit 32 </ b> A constituting the inverter 30. Is detected by the current detection circuit 40 and output to the control unit 20.

The inverter 30 has a function of converting a DC voltage supplied from the battery 60 into a three-phase AC voltage by PWM control and supplying the same to the motor 50, and has a circuit configuration substantially similar to the inverter 3A shown in FIG. Thus, only one shunt resistor R1 is interposed in the common line L on the ground side of the switching elements UL, VL, WL.

Next, functions of the control unit 20 in the EPS control apparatus 10 will be described. Figure 7 shows EPS
3 is a block diagram for explaining a function of a control unit 20 in the control device 10. FIG.
The CPU 21 includes a control mode selection unit 21a, a command torque calculation unit 21b, a current command value calculation unit 21c, a voltage command value calculation unit 21d, an estimated voltage command value calculation unit 21e, a two-phase / three-phase conversion unit 21f, a PWM conversion unit 21g, The first output current conversion unit 21h and the second output current conversion unit 21i are included. In addition to the control mode determination map 23a, voltage command value correction parameter information 23b for performing speculative control (feedforward control), the ROM 23 stores an operation program of the CPU 21 and the like.

The control mode selection means 21 a is based on the steering torque Trq detected by the torque sensor 5, the motor angular velocity ω obtained from the electrical angle θ detected by the rotation angle sensor 7, and the power supply voltage Vb detected by the power supply voltage sensor 8. To select the control mode. That is, the detection data of the steering torque Trq, the motor angular velocity ω, and the power supply voltage Vb are applied to the control mode determination map 23a stored in the ROM 23, and the control mode corresponding to these detection data is determined.

FIG. 8 is a conceptual diagram for explaining the control mode determination map 23a. In the control mode determination map 23a, each determination region of the first control mode m1, the second control mode m2, and the third control mode m3 is based on the relationship between the steering torque Trq, the motor angular velocity ω, and the power supply voltage Vb. Is set.

The first control mode m1 is when the motor 50 is in a predetermined low output state (a state in which steering assist is almost unnecessary) (in other words, the current detection section b and the section c shown in FIGS. 4 and 5 can be sufficiently secured). The control mode is selected when the current detection accuracy in the current detection circuit 40 is likely to decrease. When the first control mode m1 is selected, the motor drive control is performed by the estimation control (feed forward control) for estimating the voltage command value instead of the current feedback control using the current value detected by the current detection circuit 40. Is supposed to do.

The second control mode m2 is when the motor 50 is in a predetermined high output state (a state where steering assist is necessary) and the steering is in a predetermined low speed steering state (a state where the steering is gently steered) ( In other words, the control selected in the case where the current detection section b and the section c shown in FIGS. 4 and 5 include a phase that can be sufficiently secured and a phase that can secure only the current detection section b having a high current value. Mode. When the second control mode m2 is selected, the current value (peak current value) is detected from the current detection section with the higher current value, the output current value is obtained from the peak current value for one phase, Current feedback control is performed.

The third control mode m3 is when the motor 50 is in a predetermined high output state (a state where steering assist is necessary) and the steering is in a predetermined high speed steering state (a state where the steering is steered sharply). In other words, this is the control mode selected when the current detection interval b and interval c shown in FIGS. When the third control mode m3 is selected, a two-phase current value is detected, the detected current value is dq converted to obtain an output current value, and current feedback control is performed.

Based on the steering torque Trq detected by the torque sensor 5, the vehicle speed s detected by the vehicle speed sensor 6, and the electrical angle θ detected by the rotation angle sensor 7, the command torque calculation means 21 b calculates the target value of the steering assist torque. The command torque T * is calculated and output to the current command value calculation means 21c.

Based on the command torque T *, the current command value calculation means 21c calculates the d-axis command current value Id *, q
The shaft command current value Iq * is calculated and output to the estimated voltage command value calculating means 21e when the first control mode m1 is selected, while the second or third control mode m2 or m3 is selected. If it is, it is output to the voltage command value calculation means 21d.

These command current values Id * and Iq * are the d axis in the same direction as the permanent magnet and q orthogonal to the same in the rotating coordinate system synchronized with the rotating magnetic flux generated by the permanent magnet on the rotor of the motor.
The command current value Id * designates the magnitude of the field current of the motor, and the command current value Iq * designates the magnitude of the torque generated by the motor.

The voltage command value calculation means 21d includes the command current values Id * and Iq *, the d-axis output current value Id (or Id1) converted by the first or second output current conversion means 21h and 21i, and the q-axis output current. Each deviation from the value Iq (or Iq1) is calculated, and based on each deviation, the output current value Id (or I
d1), a d-axis command voltage value Vd * (or Vd1 *) q-axis command voltage value Vq * (or Vq1 *) for causing Iq (or Iq1) to follow the command current values Id * and Iq *, Output to the two-phase / three-phase conversion means 21f.

Further, the estimated voltage command value calculating means 21e calculates a d-axis command voltage value Vd * and a q-axis command voltage value Vq * corresponding to the command current values Id * and Iq *, respectively, resulting from the impedance difference between the motor phases. The command voltage values Vd * and Vq * are determined based on the correction parameter information 23b such as the electrical angle and temperature stored in the ROM 23 so that torque ripple due to amplitude difference of each phase current or offset deviation does not occur. The corrected d-axis estimated command voltage value Vd2 * and q-axis estimated command voltage value Vq2 * are calculated and output to the two-phase / three-phase conversion means 21f.

The two-phase / three-phase conversion means 21f is configured to output a command voltage value Vd * (or Vd1 *), Vq * (or Vq1
*) Or estimated command voltage values Vd2 * and Vq2 * are inversely converted (three-phase conversion) to calculate voltage command values Vu *, Vv * and Vw * for each phase of the motor, and output to the PWM conversion means 21g. To do.

The PWM converter 21g converts the voltage command values Vu *, Vv *, and Vw * of each phase of the motor 50 into PW
M command values (PWM signals) are converted into PWMu *, PWMv *, and PWMw *, respectively, and the converted PWM command values PWMu *, PWMv *, and PWMw * are converted into inverters 30 (PW
Output to the M drive circuit 31).

In addition, the current detection circuit 40 uses the first output current conversion unit 21h or the second output current conversion unit to convert the resistance voltage value generated at both ends of the shunt resistor R1 interposed in the common line L on the ground side of the inverter 30. 21i is a circuit that outputs to 21i.

The first output current conversion unit 21h functions when the second control mode m2 is selected by the control mode selection unit 21a, and is a value among the current values detected within one carrier of the triangular wave K. Based on the following formula 2 using the current value (peak current value) Ip having the larger (absolute value), the current command values Id * and Iq * calculated by the current command value calculation means 21c, and the electrical angle θ, The q-axis output current value Iq1 is calculated and output to the voltage command value calculation means 21d so as to perform current feedback control.

Hereinafter, a method for obtaining the q-axis output current value Iq1 will be described. First, assuming that the currents flowing in the three phases are Iu, Iv, and Iw, the peak current value Ip is Ip = MAX (Iu, Iv, Iw
w).
Here, Iu = √ (2/3 × (Iq ² + Id ² )) × Sin (θ−φ),
Iv = √ (2/3 × (Iq ² + Id ² )) × Sin (θ−φ−3π / 2),
Iv = √ (2/3 × (Iq ² + Id ² )) × Sin (θ−φ + 3π / 2). Here, θ is an electrical angle (rad), and φ is a phase delay (rad) with respect to the electrical angle (φ = Atan (Id * / Iq *)).

Further, as can be seen from the relationship diagram between the electrical angle θ and the motor current value shown in FIG. 9, the peak current value Ip has the same waveform repeated every electrical angle 60 ° (π / 3). It can be expressed as
Ip = √ (2/3 × (Iq ² + Id ² )) × Sin (ψ−2π / 3−φ).
ψ = θ−φ−π / 3 × TRUNC (θ × π / 3-1) (θ> φ)
ψ = θ−φ + π / 3 (θ ≦ φ)
TRUNC is a function for deriving an integer part in parentheses.

Thus, the absolute value ABS (Iq) of the q-axis output current value Iq can be calculated by the following equation 2.
ABS (Iq) = √ (2/3 × (Iq ² / Sin (ψ-2π / 3−φ) −Id ² ).
Note that the d-axis command current value Id * is substituted as an estimated value for the d-axis output current value Id in Equation 2, φ is obtained from Atan (Id * / Iq *), and the peak current value Iq is The actually detected peak current value is substituted, and ψ is substituted with the value obtained from the electrical angle θ.

Further, the direction (sign) of the peak current value Iq is determined by obtaining the motor angular velocity ω from the electrical angle θ and by positive / negative of the angular velocity ω. That is, if the angular velocity ω> 0, Iq = ABS (Iq
), Iq = −ABS (Iq) if angular velocity ω ≦ 0.

The second output current conversion means 21i functions when the third control mode m3 is selected by the control mode selection means 21a, and the two-phase current value detected by the current detection circuit 40; The current values of the remaining phases calculated based on the current values of the two phases are obtained, and the output current values Iu, Iv, and Iw of these three phases are used as the d-axis output current value Id and the q-axis output current value Iq. The voltage is converted and output to the voltage command value calculation means 21d so as to perform current feedback control.

Next, the processing operation performed by the control unit 20 in the electric power steering control device 10 according to the embodiment will be described based on the flowchart shown in FIG. This processing operation is executed every predetermined cycle (for example, 0.4 milliseconds). For example, it is performed by timer interrupt processing.

First, in step S1, the steering torque Trq, the motor angular velocity ω, and the power supply voltage Vb are detected, and in the next step S2, these detected values are applied to the control mode determination map 23a to determine the corresponding control mode.

If it is determined in step S2 that the first control mode m1 is applicable, the process proceeds to step S3. In step S3, a command torque T that is a target value of the steering assist torque based on the steering torque Trq, the vehicle speed s, and the electrical angle θ. Processing for calculating * is performed, and in the next step S4, processing for calculating the d-axis command current value Id * and the q-axis command current value Iq * is performed based on the command torque T *, and then the process proceeds to step S5.

In step S5, a d-axis command voltage value Vd * and a q-axis command voltage value Vq * corresponding to the command current values Id * and Iq * are calculated. In the next step S6, correction parameter information 23b such as an electrical angle and temperature is calculated. The command voltage values Vd * and Vq * are corrected based on the d-axis estimated command voltage value Vd2 *.
, Perform a guess control (feed forward control) to calculate the q-axis estimation command voltage value Vq2 *,
Thereafter, the process proceeds to step S7.

In step S7, the estimated command voltage values Vd2 * and Vq2 * are inversely converted (three-phase conversion) to calculate the voltage command values Vu2 *, Vv2 * and Vw2 * of each phase, and the next step S8 Then, the voltage command values Vu2 *, Vv2 *, and Vw2 * for each phase are converted into the PWM command values (PW for each phase).
M signal) PWMu2 *, PWMv2 *, and PWMw2 * are converted. In step S9, the converted PWM command values PWMu2 *, PWMv2 *, and PWMw2 * of the respective phases are converted into inverters 30.
The process of outputting to (PWM drive circuit 31) is performed, and then the process ends.

On the other hand, if it is determined in step S2 that it corresponds to the second control mode m2, step S2 is executed.
In step S10, the command torque T * is calculated in the same manner as in step S3. In the next step S11, the d-axis command current value Id * and the q-axis command current value Iq * are the same as in step S4. Is performed, and then the process proceeds to step S12.

In step S12, processing for detecting the peak current value Ip of the phase having the largest current value (absolute value) in one carrier of the triangular wave K is performed. In this case, in addition to setting the value of the higher phase of the two phases detected as the peak current value Ip, a peak hold circuit may be provided in the current detection circuit 40 to detect the peak current in one carrier.

In the next step S13, the detected peak current value Ip, current command value Id *, Iq *,
Then, the q-axis output current value Iq1 is calculated by substituting the electrical angle θ into the above-described equation 2, and then the process proceeds to step S14.

In step S14, the command current values Id * and Iq *, the output current value Id1 (in this case, the same value as the command current value Id * is adopted), and each deviation (ΔId1, ΔIq1) from Iq1 are calculated. Based on each deviation, a d-axis command voltage value Vd1 * and a q-axis command voltage value Vd1 * for causing the output current values Id1 and Iq1 to follow the command current values Id * and Iq * are calculated, and then the process proceeds to step S15. .

In step S15, the command voltage values Vd1 * and Vq1 * are subjected to dq reverse conversion (three-phase conversion),
Processing for calculating voltage command values Vu1 *, Vv1 *, Vw1 * for each phase is performed, and the next step S
16, the voltage command values Vu1 *, Vv1 *, and Vw1 * for each phase are converted into PWM command values (PW for each phase).
M signal) PWMu1 *, PWMv1 *, and PWMw1 * are converted, and in the next step S17, the converted PWM command values PWMu1 *, PWMv1 *, and PWMw1 * of each phase are output to the inverter 30 (the PWM drive circuit 31 thereof). Is performed, and then the process is terminated.

On the other hand, if it is determined in step S2 that it corresponds to the third control mode m3, step S2 is executed.
In step S18, the command torque T * is calculated in the same manner as in step S3. In step S19, the d-axis command current value Id * and the q-axis command current value Iq * are the same as in step S4. Is performed, and then the process proceeds to step S20.

In step S20, a current value of two phases is detected in one carrier of the triangular wave K through the current detection circuit 40, and a process for obtaining a current value of the remaining phase based on the current value of the two phases is performed. Proceed to S21. Depending on the phase (electrical angle), it may be difficult to detect the current value of the two phases with high accuracy. Therefore, the electric angle at the time of sampling is an electric angle where it is difficult to detect the current value of the two phases with high accuracy. In some cases, the detection accuracy of the current value can be further improved if the detection of the two-phase current value at that timing is not performed. Alternatively, when the ON / OFF duty difference between the switching elements UH, UL,... (For example, the time width of the section b and the section c shown in FIGS. 4 and 5) is equal to or less than a predetermined value (shorter than the sampling period). If the detection of the two-phase current value at that timing is not performed, the current value detection accuracy can be further increased.

In the next step S21, the three-phase output current values Iu, Iv, Iw are converted into d-axis output current values Id,
And the process which converts into q-axis output electric current value Iq is performed, and it progresses to step S22 after that. In step S22, each deviation (ΔId, Iq *) between the command current values Id * and Iq * and the output current values Id and Iq.
ΔIq) is calculated, and the output current values Id and Iq are converted into command current values Id * and Iq based on the deviations.
Processing for calculating a d-axis command voltage value Vd * and a q-axis command voltage value Vd * for following the * is performed, and then the process proceeds to step S23.

In step S23, the command voltage values Vd * and Vq * are inversely converted (three-phase conversion) to calculate the voltage command values Vu *, Vv * and Vw * for each phase. In the next step S24, ,
The voltage command values Vu *, Vv *, and Vw * for each phase are converted into PWM command values (PWM signals) PWMu for each phase.
*, PWMv *, PWMw *, and in the next step S25, the converted PW of each phase
The M command values PWMu *, PWMv *, and PWMw * are converted into the inverter 30 (the PWM drive circuit 31 thereof).
) Is output, and then the processing ends.

According to the electric power steering control apparatus (EPS control apparatus) 10 according to the above embodiment, even if the current detection circuit 40 detects the current flowing through the shunt resistor R1, the steering torque Trq and the motor angular speed ω On the basis of the power supply voltage Vb, a control mode that is not easily affected by a decrease in current detection accuracy by the current detection circuit 40 is selected from a plurality of control modes, and motor drive control corresponding to the selected control mode is selected. Is done.

For example, when the motor 50 is in a predetermined low output state, the first control mode m1 is selected, and the current value detected by the current detection circuit 40 is not used (that is, current feedback control is not performed). ), Motor control is performed by feedforward control for estimating a voltage command value for performing pulse width modulation control. Therefore, it is possible to prevent the current feedback control from being performed in a state where the current detection accuracy by the current detection circuit 40 is lowered, and the steering that does not make the driver feel uncomfortable by the control to estimate the voltage command value is excellent. Electric power steering control can be performed.

Further, when the motor 50 is in a predetermined high output state and the steering is in a predetermined low speed steering state, the second control mode m2 is selected, and a one-phase signal that can be accurately detected by the current detection circuit 40 is selected. The output current value Iq1 * is estimated using the peak current value Ip, the motor electrical angle θ, and the current command values Id * and Iq *, and the motor is controlled by current feedback control using the output current value Iq1 *. Therefore, by using the one-phase peak current value Ip that can be detected with high accuracy, it is possible to perform current feedback control with good steering performance that does not impair followability.

Further, when the motor 50 is in a predetermined high output state and the steering is in a predetermined high speed steering state, the third control mode m3 is selected, and the current values of a plurality of phases that can be detected by the current detection circuit 40 Is converted into output current values Id and Iq, and motor control is performed by current feedback control using the converted output current values Id and Iq. Therefore, tracking is performed using two-phase current values that can be accurately detected. Current feedback control with good steering performance can be performed without impairing performance.

Therefore, in an output state in which the current detection accuracy at the shunt resistor R1 by the current detection circuit 40 is low, by selecting an appropriate control mode that is not easily affected by the decrease in the current detection accuracy by the current detection circuit 40, current detection is performed. It is possible to prevent the follow-up performance of the current feedback control due to the decrease in the current detection accuracy by the means, and it is possible to prevent the steering feeling from being lowered with respect to the driver's steering operation.

Further, since these controls can be realized by switching control between current feedback control and estimation control without using special vector control, motor control can be performed without increasing the calculation load of the CPU 21, and the processing speed can be reduced. It can be put into practical use without using a high CPU, and the cost of the apparatus can be reduced.

In the above embodiment, the estimated command voltage values Vd2 * and Vq2 * are calculated by the speculative control only when the first control mode m1 is selected, but in another embodiment, Even when the second or third control mode m2 or m3 is selected, the estimation command voltage values Vd2 * and Vq2 * are always calculated by performing the estimation control, and when the second control mode m2 is selected, Find the difference between the command voltage values Vd1 *, Vq1 * and the estimated command voltage values Vd2 *, Vq2 *,
In the third control mode m3, the difference between the command voltage values Vd * and Vq * and the estimated command voltage values Vd2 * and Vq2 * is obtained, and the difference is a predetermined value (the detected current value or the like). When the value is greater than or equal to the value that can be determined to be abnormal), the mode shifts to the fail mode and the estimated command voltage value Vd2
It is good also as a structure which controls by the electric current value which attenuated * and Vq2 *, and according to such a structure, it can transfer to fail mode promptly at the time of abnormality.

It is a schematic block diagram of the conventional electric power steering control apparatus. (A) is the figure which showed the relationship between the triangular wave K and a three-phase alternating current command wave, (b) is the operation waveform of the triangular wave K, a three-phase alternating current command wave, and each switching element, and the electric current of each phase It is the enlarged view which showed the relationship with a detection waveform. It is a circuit block diagram of the inverter comprised so that the electric current value which flows into a motor with one shunt resistor could be detected. (A) is the figure which showed the relationship of the triangular wave K and the three-phase alternating current command wave at the time of high output, (b) is the operation waveform of the triangular wave K, the three-phase alternating current command wave, and each switching element, It is the enlarged view which showed the relationship with the electric current detection waveform detected from the both-ends voltage of shunt resistance R1. (A) is the figure which showed the relationship between the triangular wave K and the three-phase alternating current command wave at the time of low output, (b) is the operation waveform of the triangular wave K, the three-phase alternating current command wave, and each switching element, It is the enlarged view which showed the relationship with the electric current detection waveform detected from the both-ends voltage of shunt resistance R1. It is the block diagram which showed roughly the principal part of the electric power steering control apparatus which concerns on embodiment of this invention. It is a block diagram for demonstrating the function of the control part in the electric power steering control apparatus which concerns on embodiment. It is the figure which showed notionally the control mode determination map memorize | stored in the control part in the electric power steering control apparatus which concerns on embodiment. It is the figure which showed the relationship between the electrical angle (theta) of a motor, and the electric current value of each phase of a motor. It is the flowchart which showed the processing operation which the control part performs in the electric power steering control device which concerns on embodiment.

Explanation of symbols

10 Electric power steering control device (EPS control device)
20 control unit 21 CPU
22 RAM
23 ROM
30 Inverter 31 PWM drive circuit 32 Switching circuit R1 Shunt resistor 40 Current detection circuit 50 Motor 60 Battery (DC power supply)

Claims (6)

An inverter that converts a DC voltage supplied from a DC power source into an AC voltage by pulse width modulation control and supplies the AC voltage to the motor;
Current detecting means for detecting a current flowing in the common line on the ground side of the switching circuit constituting the inverter;
Control means for performing motor drive control by selecting a control mode corresponding to the output state of the motor from a plurality of control modes set in consideration of current detection accuracy by the current detection means. An electric power steering control device. The plurality of control modes include a first control mode that is selected when the motor is in a predetermined low output state, a motor that is in a predetermined high output state, and a steering that is in a predetermined low speed steering state. A second control mode selected in some cases, and a third control mode selected when the motor is in a predetermined high output state and the steering is in a predetermined high speed steering state,
2. The electric power steering control device according to claim 1, wherein the control mode is selected based on a steering torque indicating a steering state of the steering, an angular velocity of the motor, and a power supply voltage of the DC power source. . When the first control mode is selected from the plurality of control modes,
The control means performs motor control by feedforward control for estimating a voltage command value for performing the pulse width modulation control without using the current value detected by the current detection means. The electric power steering control device according to claim 2. When the second control mode is selected from the plurality of control modes,
The control means estimates an output current value using a one-phase peak current value detectable by the current detection means, an electrical angle of the motor, and a current command value obtained based on a command torque,
4. The electric power steering control device according to claim 2, wherein motor control is performed by current feedback control using the estimated output current value. When the third control mode is selected from the plurality of control modes,
The control means converts a current value of a plurality of phases that can be detected by the current detection means into an output current value, and performs motor control by current feedback control using the converted output current value. The electric power steering control device according to any one of claims 2 to 4. A motor drive control method for converting a DC voltage supplied from a DC power source into an AC voltage via an inverter and supplying the converted voltage to a motor,
A control mode corresponding to the output state of the motor among a plurality of control modes set in consideration of current detection accuracy by current detection means for detecting current flowing in a common line on the ground side of the switching circuit constituting the inverter Select
A motor drive control method comprising performing motor drive control corresponding to the selected control mode.

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