JP5880874B2 - Vehicle steering control device - Google Patents

Description

  The present invention includes a three-phase electric motor that applies torque that reduces an operation force input by a turning operation of a steering handle, a rotation angle acquisition unit that acquires a rotation angle of the electric motor, and a rotation of the steering handle. The present invention relates to a steering control device for a vehicle, comprising: a control unit that calculates a control amount for controlling the torque applied by the electric motor with respect to a dynamic operation; and a control unit that drives and controls the electric motor using the calculated control amount. .

  2. Description of the Related Art Conventionally, for example, a motor control device and an electric power steering device using the motor control device as shown in Patent Document 1 below are known. In this conventional motor control device, when an energization failure occurs in any phase of the motor, two energies other than the energization failure occurrence phase where the energization failure has occurred are set as energization phases, and an energization failure occurs for each energized phase. By executing the current control so as to generate a phase current that changes in a secant curve or a cosecant curve with a predetermined rotation angle corresponding to the generated phase as an asymptotic line, the output of the motor control signal is continued. ing. In addition, this conventional motor control device includes a rotation angle correction control unit that corrects (offsets) the rotation angle of the input motor, and at the time of two-phase driving in which two phases other than the conduction failure occurrence phase are used as the conduction phase. In order to compensate for the phase shift between the current command value and the actual current value in the current control, the rotation angle that is the basis of the current control is corrected. As a result, the motor can be smoothly rotated during the two-phase driving accompanying the occurrence of a failure in energization, and high output performance can be ensured.

JP 2009-27905 A

  In the above-described conventional device (electric power steering device), during two-phase driving, the rotation angle (electrical angle) of the motor is ensured in order to ensure high output performance by smoothing the rotation of the motor (electric motor) due to the occurrence of poor energization. ) Is corrected (offset). By the way, when correcting the rotation angle (electrical angle) of the electric motor, it is possible to smooth the rotation of the electric motor by increasing the correction amount. However, if the correction amount is increased too much, the torque output by the electric motor decreases, and the operating force input by the driver increases. That is, when correcting the rotation angle (electrical angle) of the electric motor using the correction amount during two-phase driving, smooth rotation of the electric motor, in other words, the steering feeling perceived by the driver, Ensuring the torque output by the motor, in other words, reducing the operating force input by the driver is in a trade-off relationship with each other. Therefore, when correcting the rotation angle (electrical angle) of the electric motor using the correction amount, a correction amount that can achieve the maximum compatibility between ensuring a good steering feeling and reducing the operating force is determined. There is a need to. In addition, for example, if the electric motor is simply enlarged in order to reduce the operating force, the fuel consumption may be deteriorated due to an increase in the weight of the vehicle, or the steering feeling may be deteriorated due to an increase in inertia of the rotating portion. .

  The present invention has been made to address the above-described problems, and one of its purposes is to ensure good steering feeling and reduce operating force even when the electric motor is driven in two phases. An object of the present invention is to provide a steering control device for a vehicle that can achieve both of these.

  In order to achieve the above object, a vehicle steering control apparatus according to the present invention includes a three-phase electric motor, rotation angle acquisition means, and control means. The three-phase electric motor applies a torque that reduces an operation force input by a turning operation of the steering handle. The rotation angle acquisition means acquires a rotation angle (electrical angle) of the electric motor. The control means calculates a control amount for controlling the torque applied by the electric motor in response to the turning operation of the steering handle, and drives and controls the electric motor using the calculated control amount. is there.

  One of the features of the vehicle steering control device according to the present invention is that the control means acquires the rotation angle detection means when the conduction failure occurs in any one of the phases of the electric motor. The control calculated by adding the correction amount to the rotation angle of the electric motor, calculating the control amount by correcting the rotation angle, and applying the current to a phase other than the phase in which the conduction failure has occurred. Steering load that is generated when the steered wheels are steered in accordance with the turning operation of the steering handle, wherein the electric motor is driven using the amount to continue the application of the torque. A first torque representing a difference between a load torque that is a function of the correction amount and a maximum value of an average value of torque generated by the electric motor, and the load torque , The correction amount Reversing torque in a region expressed as a function and in which the torque generated by the electric motor in association with the correction of the rotation angle by the addition of the correction amount is reversed with respect to the turning operation direction of the steering handle Is determined as a value when the second torques representing the difference between the two values coincide with each other. In this case, the first torque can be expressed as a COS function of the correction amount, and the second torque can be expressed as a SIN function of the correction amount.

  Further, in these cases, the control means increases the magnitude of the correction amount to a value when the first torque and the second torque coincide with the increase in the magnitude of the steering load. The rotation angle can be corrected by uniformly increasing and adding this correction amount.

  In these cases, the correction amount is determined to be a value when the first torque and the second torque coincide with each other within a range of 0.45 (rad) to 0.65 (rad). More preferably, the correction amount is set to a value when the first torque and the second torque coincide with each other within a range of 0.50 (rad) to 0.60 (rad). More specifically, the correction amount may be determined to be 0.55 (rad) as a value when the first torque and the second torque coincide with each other. In this case, when “deg” is used instead of “rad” as a unit of angle, the correction amount is within the range of 26 (deg) to 36 (deg), and the first torque and the The value when the second torque coincides may be determined, and more preferably, the correction amount is within a range of 28 (deg) to 34 (deg), and the first torque and the second torque. More specifically, the correction amount may be determined as 31 (deg) as a value when the first torque and the second torque match. ).

  According to these, when the electric motor is driven by the two-phase drive and the torque is continuously applied to the turning operation of the steering handle in accordance with the occurrence of the energization failure, the correction for correcting the rotation angle (electrical angle) of the electric motor is performed. The amount can be appropriately determined so as to achieve the maximum trade-off between a good steering feeling without a feeling of catching and a reduction in operating force input by the driver. Thus, even when the electric motor is driven by two-phase driving and torque application (assist control) for reducing the operation force input by the turning operation of the steering handle is continued, the driver The steering wheel can be easily turned while perceiving a very good steering feeling that is difficult to remember.

  In addition, as described above, it is possible to appropriately achieve both good steering feeling and reduction in operating force, so that it is not necessary to increase the output torque of the electric motor more than necessary. As a result, it is not necessary to enlarge the system in order to increase the output torque of the electric motor, and as a result, it is possible to suppress an increase in the weight of the vehicle and prevent deterioration in fuel consumption. Furthermore, since it is not necessary to increase the size of the electric motor in order to increase the output torque, it is possible to prevent, for example, deterioration of steering feeling due to an increase in inertia of the rotating portion of the electric motor.

  Further, the correction amount can be uniformly increased to a value when the first torque and the second torque coincide with the increase in the magnitude of the steering load (load torque). Thereby, especially when the turning load (load torque) is small, the magnitude of the correction amount for correcting the rotation angle (electric angle) of the electric motor can be reduced. For example, torque inversion generated by the electric motor And the vibration associated with torque reversal can be effectively suppressed.

It is the schematic which shows the structure of the electric power steering apparatus to which the steering control apparatus which concerns on this invention is applied. It is the schematic for demonstrating the structure and d / q coordinate system of the EPS motor of FIG. FIG. 2 is a circuit diagram schematically showing the drive circuit of FIG. 1. FIG. 2 is a functional block diagram functionally representing computer program processing (assist control) executed by the electronic control unit of FIG. 1. FIG. 5 is a functional block diagram functionally representing a first current control calculation unit and a second current control calculation unit in FIG. 4. In FIG. 4, it is a functional block diagram functionally representing assist control by two-phase driving when an energization failure occurs in the U phase. FIG. 4 is a schematic circuit diagram for explaining a switching state of a drive circuit when a conduction failure occurs in the U phase in FIG. 3. It is a graph for demonstrating the correction amount added to an electrical angle by the electrical angle correction | amendment part of the 2nd electric current control calculating part of FIG. 4 (FIG. 6). It is a graph for demonstrating the electric waveform of the phase current calculated by the phase current calculating part of the 2nd current control calculating part of FIG. 4 (FIG. 6). It is a graph for explaining the relationship between the output torque of the EPS motor and the phase current command value when the correction amount is not added to the electrical angle (not offset), that is, when the electrical angle is not corrected, in the two-phase drive. 6 is a graph for explaining a relationship between an output torque of an EPS motor and a phase current command value when a correction amount is added (offset) to an electrical angle, that is, when an electrical angle is corrected during two-phase driving. It is a graph for demonstrating the relationship between the load torque, the manual input torque, and the burden torque when the steering angle is rotated by correcting the electrical angle during two-phase driving. It is a graph for demonstrating determination of the correction amount optimal value. It is a graph for demonstrating the modification of this invention.

  Hereinafter, a vehicle steering control device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an electric power steering apparatus 10 to which a vehicle steering control apparatus according to this embodiment can be applied.

  The electric power steering apparatus 10 includes a steering handle 11 that is turned by a driver to steer left and right front wheels FW1 and FW2 as steered wheels. The steering handle 11 is fixed to the upper end of the steering shaft 12, and the lower end of the steering shaft 12 is connected to the steered gear unit U. A system including the steering handle 11, the steering shaft 12, and the steered gear unit U is also referred to as a steering system.

  The steered gear unit U is, for example, a gear unit adopting a rack and pinion type, and the rotation of the pinion gear 13 integrally assembled to the lower end of the steering shaft 12 is transmitted to the rack bar 14. Yes. The steered gear unit U has an electric motor 15 (hereinafter, this electric motor) for reducing (assisting) an operation force (more specifically, steering torque) input to the steering handle 11 by the driver. Is referred to as an EPS motor 15). An output torque (more specifically, assist torque) generated by the EPS motor 15 is transmitted to the rack bar 14.

  Here, as the EPS motor 15 mounted on the electric power steering apparatus 10, a three-phase DC brushless motor is employed. That is, as schematically shown in FIG. 2, the EPS motor 15 includes, for example, a rotor made of a permanent magnet and windings U, V, W (U ′, V ′) assembled on the stator side that accommodates the rotor. , W ′). In the EPS motor 15, a drive circuit 25 (inverter circuit) of the electric control circuit 20 described later is connected to the windings U, V, W (U ′, V ′, W ′). Yes.

  With this configuration, the rotational force of the steering shaft 12 accompanying the turning operation of the steering handle 11 by the driver is transmitted to the rack bar 14 via the pinion gear 13, and the assist torque of the EPS motor 15 is transmitted to the rack bar 14. Is done. As a result, the rack bar 14 is displaced in the axial direction by the rotational force from the pinion gear 13 and the assist torque of the EPS motor 15. Accordingly, the left and right front wheels FW1, FW2 connected to both ends of the rack bar 14 are steered in the left-right direction.

  In addition, the electric power steering apparatus 10 in this embodiment is implemented as a rack assist type in which the EPS motor 15 transmits assist torque to the rack bar 14 of the steered gear unit U. However, as another electric power steering apparatus 10, the EPS motor 15 is a pinion assist type in which assist torque is transmitted to the pinion gear 13, or the column main shaft in which the EPS motor 15 forms the steering shaft 12 via a predetermined reduction mechanism. Needless to say, a column assist type that transmits assist torque can be adopted.

  Next, the electric control device 20 that controls the operation of the above-described EPS motor 15 will be described. The electric control device 20 includes a vehicle speed sensor 21, a steering torque sensor 22, and a motor rotation angle sensor 23 as a rotation angle detection means. The vehicle speed sensor 21 detects the vehicle speed V of the vehicle and outputs a signal corresponding to the detected vehicle speed V. The vehicle speed V can also be acquired through communication with the outside, for example.

  As shown in FIG. 1, the steering torque sensor 22 is assembled to the steering shaft 12, detects the steering torque Th input by the driver to the steering shaft 12 by turning the steering handle 11, and detects this. A signal corresponding to the steering torque Th is output. The steering torque sensor 22 outputs, for example, a steering torque Th when the steering handle 11 is rotated to the right as a positive value, and the steering when the steering handle 11 is rotated to the left. Torque Th is output as a negative value. Here, in the present embodiment, for example, two sets of resolver sensors are employed as the steering torque sensor 22.

  The motor rotation angle sensor 23 is assembled to the EPS motor 15, detects a rotation angle (electrical angle) Θ from a preset reference rotational position, and outputs a signal corresponding to the electrical angle Θ. Here, in the present embodiment, as shown in FIG. 2, the motor rotation angle sensor 23 sets the direction parallel to the direction of the magnetic field generated by the rotor (permanent magnet) of the EPS motor 15 (that is, the N-pole direction) as d. The rotation angle of the d-axis with respect to the axial direction and the U-phase direction in the stator of the EPS motor 15 as a reference is detected as an electrical angle Θ. The motor rotation angle sensor 23 relates to the rotation direction of the EPS motor 15, for example, when the EPS motor 15 applies assist torque to the rack bar 14 in order to steer the left and right front wheels FW1, FW2 to the right. The electrical angle Θ is output as a positive value, and the electrical angle Θ when the assist torque is applied to the rack bar 14 in order to steer the left and right front wheels FW1, FW2 to the left is output as a negative value.

  Further, as shown in FIG. 1, the electric control device 20 includes an electronic control unit 24 as control means for controlling the operation of the EPS motor 15. The electronic control unit 24 includes a microcomputer including a CPU, a ROM, a RAM, and the like as main components, and controls the operation of the EPS motor 15. For this reason, at least the sensors 21 to 23 are connected to the input side of the electronic control unit 24, and the detection values detected by the sensors 21 to 23 are used as described later. The driving of the EPS motor 15 is controlled. On the other hand, a drive circuit 25 for driving the EPS motor 15 is connected to the output side of the electronic control unit 24.

  As shown in FIG. 3, the drive circuit 25 includes an inverter circuit unit 25a and a relay circuit unit 25b. The inverter circuit unit 25a constitutes a three-phase inverter circuit that converts a direct current supplied from the battery (power source) B and the smoothing reactor S through the power relay Rd or from the capacitor C into a three-phase alternating current. It is. The inverter circuit unit 25a includes switching elements SW11, SW12, SW21, and SW22 corresponding to the windings U, V, and W (U ′, V ′, and W ′) of the EPS motor 15 that is star-connected (Y-connected). , SW31, SW32. In the present embodiment, the windings U, V, W (U ′, V ′, W ′) are implemented using the star motor-connected EPS motor 15, but the windings U, V, W (U ′) , V ′, W ′) can also be implemented using an EPS motor with a delta connection.

  The switching elements SW11, SW12, SW21, SW22, SW31, and SW32 correspond to the switching element SW11, SW21, and SW31 on the High side (high potential side) and the switching elements SW12, SW22, and SW32 on the Lo side (low potential side), respectively. In addition, it corresponds to each of the three phases of the EPS motor 15, ie, the U phase, the V phase, and the W phase, and is configured by, for example, a MOSFET. The inverter circuit unit 25a is provided with current sensors (shunt resistors) J1, J2, J3 for detecting the current flowing through the EPS motor 15 in each phase. Signals representing the currents Iu, Iv, and Iw detected by these current sensors J1, J2, and J3 are output to the input side of the electronic control unit 24.

  As shown in FIG. 3, the relay circuit unit 25 b is connected to the U phase, V phase, and W phase of the EPS motor 15 (specifically, windings U, V, and W (U ′, V ′, W ′)). Each has a corresponding phase open relay R1, R2, R3. The phase open relays R1, R2, and R3 are respectively U phase, V phase, and W phase (specifically, windings U, V, and W (U ′, V ′, W) of the inverter circuit unit 25a and the EPS motor 15. It is a mechanical relay that allows or cuts off the electrical power to ')). Note that the phase open relays R1, R2, and R3 are not limited to mechanical relays, and for example, semiconductor relays may be employed.

  In the drive circuit 25 configured as described above, the inverter circuit unit 25a is on / off controlled and the relay circuit unit 25b is switch-controlled by a signal from the electronic control unit 24. As a result, the electronic control unit 24 switches the phase open relays R1, R2, and R3 constituting the relay circuit unit 25b to a state in which energization is allowed (closed state), and the switching elements SW11, SW12, SW21, and SW22 of the inverter circuit unit 25a. , SW31, SW32 are controlled (PWM control) to supply a three-phase drive current from the battery B or capacitor C to the EPS motor 15.

  On the other hand, the electronic control unit 24 switches the phase open relay of any of the phase open relays R1, R2, and R3 constituting the relay circuit unit 25b to a state in which energization is cut off (open state). A drive current is supplied to the EPS motor 15 via a phase open relay in a closed state other than the phase open relay switched to. Further, the electronic control unit 24 controls all of the switching elements SW11, SW12, SW21, SW22, SW31, and SW32 of the inverter circuit unit 25a to be off (open state), so that the phase open relays R1 and R2 of the relay circuit unit 25b are controlled. The drive current is not supplied to the EPS motor 15 regardless of the switching state of R3.

  Next, drive control of the EPS motor 15 by the electric control device 20 (more specifically, the electronic control unit 24) configured as described above, that is, assist control, is realized by computer program processing in the electronic control unit 24. This will be described with reference to the functional block diagram of FIG. The electronic control unit 24 controls the driving of the EPS motor 15 and applies an appropriate assist torque in order to reduce the burden associated with the turning operation of the steering handle 11 by the driver. For this reason, as shown in FIG. 4, the electronic control unit 24 includes an assist control unit 30 that calculates an assist amount representing an appropriate assist torque, and drives and controls the EPS motor 15 based on the calculated assist amount. Yes.

  As shown in FIG. 4, the assist control unit 30 includes a vehicle speed calculation unit 31, a torque value calculation unit 32, a current detection unit 33, and an electrical angle calculation unit 34. The vehicle speed calculation unit 31 inputs a signal corresponding to the vehicle speed V output from the vehicle speed sensor 21 and calculates the vehicle speed V. The torque value calculation unit 32 inputs a signal corresponding to the steering torque Th output from the steering torque sensor 22 and calculates the steering torque Th. The current detection unit 33 inputs signals corresponding to the currents Iu, Iv, and Iw flowing in the U phase, V phase, and W phase of the EPS motor 15 output from the ammeters J1, J2, and J3 provided in the drive circuit 25. Then, currents Iu, Iv, and Iw of each phase are detected. The electrical angle calculation unit 34 inputs a signal corresponding to the electrical angle Θ, which is the rotation angle of the EPS motor 15, output from the motor rotation angle sensor 23, and calculates the electrical angle Θ.

  The assist control unit 30 includes an assist current command value calculation unit 35, a first current control calculation unit 36, a second current control calculation unit 37, and a PWM conversion unit 38.

  The assist current command value calculation unit 35 receives the vehicle speed V from the vehicle speed calculation unit 31 and the steering torque Th from the torque value calculation unit 32, and should be applied to the steering system based on the vehicle speed V and the steering torque Th. Determine the target assist amount (target assist torque) Ta *. Then, the assist current command value calculator 35 drives and controls the EPS motor 15 through the drive circuit 25 according to a so-called vector control method so that the target assist amount Ta * is generated. In the vector control method, the current and voltage in the three phases of the EPS motor 15 are set in the d-axis direction component defined as described above, and the d-axis direction (that is, the direction of the magnetic field) as shown in FIG. Is a control method in which it is converted into a two-phase value with a component in the q-axis direction, which is a direction orthogonal to. Since the vector control method itself is well known, detailed description of the point of converting current and voltage in three phases into two phases and the point of converting current and voltage in two phases into three phases will be omitted.

  The assist current command value calculation unit 35 determines the d-axis target current Id * and the q-axis target current Iq * (hereinafter, the q-axis target current Iq *, in particular, the current according to the determined target assist amount Ta *. (Also referred to as command value iref). Since the EPS motor 15 in the present embodiment is a three-phase brushless DC motor, the torque (assist torque) generated by the EPS motor 15 is proportional to the q-axis current. Therefore, the assist current command value calculation unit 35 sets the d-axis target current Id * to “0” and calculates so that the q-axis target current Iq *, that is, the current command value iref is proportional to the target assist amount Ta *. To do. Then, the assist current command value calculation unit 35 outputs the calculated d-axis target Id * and q-axis target current Iq *, that is, the current command value iref, to the first current control calculation unit 36 and the second current control calculation unit 37. To do.

  The first current control calculation unit 36 calculates three-phase phase voltage command values Vu *, Vv *, and Vw * by executing current feedback control (d / q-axis current F / B) in the d / q coordinate system. Is. For this reason, the first current control calculation unit 36 calculates each phase voltage command value Vu *, Vv *, Vw * in a normal time when the current is properly supplied to the three phases of the EPS motor 15. In order to drive the EPS motor 15 by three phases, the phase voltage command values Vu *, Vv *, and Vw * are output to the PWM converter 38. Note that the drive control of the EPS motor 15 in normal times is not directly related to the present invention, and will be described briefly below.

  As shown in FIG. 5, the first current control calculation unit 36 includes a three-phase / two-phase conversion unit 361. The three-phase / two-phase conversion unit 361 inputs currents Iu, Iv, and Iw that actually flow in the U phase, V phase, and W phase of the EPS motor 15 from the current detection unit 33, and outputs an electrical angle from the electrical angle calculation unit 34. Θ is input, and actual currents Iu, Iv, Iw are converted into actual currents Id, Iq in d / q coordinates based on a known conversion matrix using electrical angle Θ. The q-axis actual current Iq is input to the subtractor 362 together with the current command value iref output from the assist current command value calculation unit 35, that is, the target current Iq *, and the d-axis actual current Id is the assist current command value. The target current Id * (Id * = 0) output from the calculation unit 35 is input to the subtracter 363.

  The subtractor 362 calculates the q-axis current deviation ΔIq between the input current command value iref, that is, the target current Iq * and the q-axis actual current Iq. Then, the subtracter 362 supplies the calculated q-axis current deviation ΔIq to the q-axis F / B control unit 364. On the other hand, the subtractor 363 calculates a d-axis current deviation ΔId between the input target current Id * and the d-axis actual current Id. Then, the subtracter 363 supplies the calculated d-axis current deviation ΔId to the d-axis F / B control unit 365.

  The F / B control units 364 and 365 are fed back in order to cause the actual current Iq to follow the q-axis current command value iref, that is, the target current Iq *, and to follow the actual current Id to the d-axis target current Id *. Execute control. That is, the F / B control units 364 and 365 respectively multiply the q-axis current deviation ΔIq and the d-axis current deviation ΔId input from the subtracters 362 and 363 by a predetermined F / B gain (PI gain) to obtain q The shaft voltage command value Vq * and the d-axis current command value Vd * are calculated. The F / B control units 364 and 365 then supply the calculated q-axis voltage command value Vq * and d-axis voltage command value Vd * to the two-phase / three-phase conversion unit 366, respectively.

  The two-phase / three-phase conversion unit 366 receives the electrical angle Θ from the electrical angle calculation unit 34 and also receives the q-axis voltage command value Vq * and the d-axis voltage command value Vd * from the F / B control units 364 and 365. To do. Then, the two-phase / three-phase converter 366 converts the q-axis voltage command value Vq * and the d-axis voltage command value Vd * into three-phase phase voltage command values Vu *, Vv *, Convert to Vw *.

  As described above, when the two-phase / three-phase conversion unit 366 converts the three-phase phase voltage command values Vu *, Vv *, and Vw *, the first current control calculation unit 36 converts the converted phase voltage command value. Vu *, Vv *, and Vw * are output to the PWM converter 38. The PWM converter 38 inputs the phase voltage command values Vu *, Vv *, Vw *, and based on the input phase voltage command values Vu *, Vv *, Vw *, the target duty ratio Du *, Dv *, Dw *. To decide. Then, the PWM converter 38 outputs drive signals corresponding to the determined target duty ratios Du *, Dv *, Dw * to the drive circuit 25.

  Thereby, in the drive circuit 25, switching control of switching elements SW11, SW12, SW21, SW22, SW31, and SW32 is switched by the PWM method based on the output drive signal, that is, the target duty ratio Du *, Dv *, Dw *. By converting the three-phase voltage command values Vu *, Vv *, and Vw * into three-phase AC voltages Iu, Iv, and Iw, the EPS motor 15 generates assist torque that matches the target assist amount Ta *. .

  By the way, for the EPS motor 15, the currents Iu, Iv, Iw of each phase output by the current detection unit 33, the electrical angle Θ output by the electrical angle calculation unit 34, and the rotational angular velocity obtained by time-differentiating the electrical angle Θ. Based on dΘ / dt, duty ratio Du *, Dv *, Dw * of each phase, wire breakage of windings U, V, W (U ′, V ′, W ′), contact failure of drive circuit 25, etc. It is possible to detect the presence / absence of a poorly energized phase caused by. More specifically, in the detection of the occurrence of an energized defective phase, for example, the phase current iX of the X phase (X = U, V, or W) is equal to or less than a predetermined current value set in advance, and the rotational angular velocity When dΘ / dt is within the target range of the disconnection determination, when the state where the duty ratio DX * corresponding to the X phase is not within the predetermined range corresponding to the predetermined current value and the target range continues to the X phase. It is detected that an energization failure has occurred.

  When the energization failure occurs in the X phase as described above, the assist control unit 30 drives the EPS motor 15 by so-called two-phase driving. A drive signal is generated by the control calculation unit 37 and the PWM conversion unit 38, and the assist torque (assist amount) is continuously applied to the turning operation of the steering handle 11 by the driver. Here, in the following description, as shown in FIG. 6, an energization failure occurs in the U phase of the EPS motor 15 among the U phase, the V phase, and the W phase, and only the V phase and the W phase are energized. A two-phase drive for driving the EPS motor 15 will be described as an example.

  As described above, when a power failure occurs in the U phase, a power failure has occurred among the switching elements SW11, SW12, SW21, SW22, SW31, SW32 of the inverter circuit unit 25a constituting the drive circuit 25. The switching elements SW11 and SW12 corresponding to the U-phase are kept off (open state), or, as shown in FIG. 7, the occurrence of poor conduction among the phase-opening relays R1, R2, and R3 of the relay circuit unit 25b. The phase open relay R1 corresponding to the U phase is maintained in the open state, so that no drive current is supplied to the U phase of the EPS motor 15. Therefore, as shown in FIG. 6, no signal is output from the current sensor J1 provided in the drive circuit 25 corresponding to the U phase, and as a result, the current detection unit 33 converts the current Iu flowing in the U phase to, for example, , “0” is output.

The second current control calculation unit 37 calculates the phase voltage command values Vu **, Vv **, and Vw ** by executing phase current feedback control (phase current F / B). Therefore, the second current control calculation unit 37 includes an electrical angle correction unit 371 as shown in FIG. The electrical angle correction unit 371 determines the phase of the phase current command value iX * (= iv * (x) or iw * (x)) calculated as described later in the phase current feedback control during the two-phase driving. Correction (offset) is performed. For this reason, the electrical angle correction unit 371 calculates a corrected electrical angle x corrected by adding the correction amount λ to the electrical angle Θ of the EPS motor 15 input from the electrical angle calculation unit 34 according to the following formula 1.

尚、前記式２中の関数sign(Th)は、引数である操舵トルクThの値が正の値であれば「＋１」、負の値であれば「−１」、「０」であれば「０」を出力するものである。又、前記式２中のλ０は、後に詳述する補正量最適値を表す。 However, the correction amount λ in the equation 1 is the direction of the steering torque Th input from the torque value calculation unit 32 or the change direction of the electrical angle Θ input from the electrical angle calculation unit 34 (or the rotational angular velocity dΘ / dt). That is, it is determined according to the steering direction. For example, when the steering torque Th is used, it is expressed by the following formula 2.

The function sign (Th) in the expression 2 is “+1” if the value of the steering torque Th as an argument is a positive value, “−1” if it is a negative value, and “−1” if it is “0”. "0" is output. In addition, λ0 in the equation 2 represents an optimum correction amount that will be described in detail later.

  Here, as shown in FIG. 8, when the argument is the steering torque Th, the correction value λ becomes “−λ0” when the value of the steering torque Th is a negative value, and the value is “0”. In some cases, it is “0”, and when the value is positive, it is “+ λ0”. Also, when the argument is the rotational angular velocity dΘ / dt, the correction value λ is “−λ0” when the rotational angular velocity dΘ / dt is a negative value, as shown in FIG. When it is “0”, it is “0”, and when the value is positive, it is “+ λ0”. When the electrical angle correction unit 371 calculates the corrected electrical angle x, the electrical angle correction unit 371 supplies the calculated corrected electrical angle x to the phase current calculation unit 372.

The phase current calculation unit 372 excludes a predetermined electrical angle Θ (rotation angle) corresponding to a current-carrying phase during two-phase driving, and a target assist amount Ta *, that is, a current command value iref (q-axis target current Iq *). The phase current command value iX * is calculated so that the q-axis actual current Iq corresponding to is generated in the EPS motor 15. More specifically, in the present embodiment, in order to assume a case in which an energization failure occurs in the U phase, the phase current calculation unit 372 causes the phase current to flow in the V phase or W phase, which is a non-failure phase excluding the U phase. Calculates the command value iX *. In this case, as described above, the U phase in which the energization failure has occurred is electrically disconnected, and the phase current of the V phase and the phase current of the W phase are absolute values of each other, as is apparent from Kirchhoff's law. Are equal to each other and the phase current is reversed. Therefore, in the present embodiment, the phase current calculation unit 372 illustratively uses the V phase current as a reference, that is, uses the V phase as a control phase, and calculates the phase current command value iv * (x) according to the following Equation 3. . Here, the phase current command value iv * (x) is a periodic function having a period of 2π, and in the following description, 0 ≦ x <2π is indicated. When the W phase is the control phase, the phase current command value iw * (x) can be calculated according to the following equation 4.

  Here, iref in Equation 3 represents a current command value supplied from the assist current command value calculator 35, and imax in Equation 3 represents a maximum value of current that can be supplied to the V phase. Further, x in Equation 3 represents a corrected electrical angle supplied from the electrical angle correction unit 371. Furthermore, θ1 that determines the range of the corrected electrical angle x in the above equation 3 is represented by equation 9 described later. As a result, when an energization failure occurs in the U phase, the phase current command value iv * (x) expressed by the above equation 3 (or the phase current command value iw * (x) expressed by the above equation 4). As shown in FIG. 9, the current waveform according to the equation changes into a secant curve having asymptotic lines of “π / 2 (90 deg)” and “3π / 2 (270 deg)” of the electrical angle Θ. Thus, when the phase current command value iv * (x) or the phase current command value iw * (x) is calculated as the phase current command value iX * of the control phase, the phase current calculation unit 372 calculates the calculated phase current command. The value iX *, that is, the phase current command value iv * (x) or the phase current command value iw * (x) is supplied to the subtractor 374.

  Further, the second current control calculation unit 37 includes a control phase selection unit 373. The control phase selection unit 373 controls one phase (V phase or W phase) of the remaining two phases (V phase and W phase) other than the phase (U phase in this embodiment) in which the energization failure has occurred. Choose as. Then, the control phase selection unit 373 acquires the actual phase current iX (= Iv or Iw) of the control phase and the selected phase (V phase or W phase) from the current detection unit 33 and supplies it to the subtractor 374.

  The subtractor 374 subtracts the actual phase current iX (= Iv or Iw) from the input phase current command value iX *, that is, the phase current command value iv * (x) or the phase current command value iw * (x). The current deviation ΔiX is calculated. Then, the subtractor 374 supplies the calculated phase current deviation ΔiX to the F / B control unit 375.

  The F / B control unit 375 makes the actual phase current iX (= Iv or Iw) follow the phase current command value iX *, that is, the phase current command value iv * (x) or the phase current command value iw * (x). Execute feedback control. That is, the F / B control unit 375 multiplies the phase current deviation ΔiX input from the subtractor 374 by a predetermined F / B gain (PI cane) to thereby obtain a phase voltage command for the control phase (V phase or W phase). Calculate the value VX * (= VV * or VW *). Then, the F / B control unit 375 supplies the calculated phase voltage command value VX * (= VV * or VW *) to the phase voltage command value calculation unit 376.

  The phase voltage command value calculation unit 376 calculates the phase voltage command values Vu **, Vv **, Vv **, Vv **, based on the phase voltage command value VX * (= VV * or VW *) for the control phase (V phase or W phase). Calculate Vw **. That is, the phase in which the energization failure has occurred cannot be energized, and the phase of each energized phase during two-phase driving is shifted by π / 2. Therefore, the phase voltage command value of the phase where the conduction failure has occurred is “0”, and the phase voltage command values of the remaining two conduction phases can be calculated by inverting the sign of the phase voltage command value VX * for the control phase. It becomes. For this reason, in this embodiment, an energization failure has occurred in the U phase, and the V phase is selected as the control phase. Therefore, the phase voltage command value calculation unit 376 has the phase voltage command values Vu ** and Vv *. * And Vw ** are calculated as Vu ** = 0, Vv ** = VX * (= VV *), and Vw ** = − VX * (= VV *).

  Thus, when each phase voltage command value Vu **, Vv **, Vw ** is calculated by the phase voltage command calculation unit 376, the second current control calculation unit 37 calculates the calculated each phase voltage command value. Vu **, Vv **, and Vw ** are output to the PWM converter 38. In the PWM conversion unit 38, the phase voltage command values Vu **, Vv **, Vw * are the same as when the phase voltage command values Vu *, Vv *, Vw * are output from the first current control calculation unit 36. Based on *, target duty ratios Du *, Dv *, and Dw * are determined. Then, the PWM converter 38 outputs drive signals corresponding to the determined target duty ratios Du *, Dv *, Dw * to the drive circuit 25.

  Thus, in the drive circuit 25, the switching of the switching elements SW21, SW22, SW31, and SW32 is controlled by the PWM method based on the output drive signal, that is, the target duty ratios Du *, Dv *, and Dw *. The voltage command values Vu **, Vv **, Vw ** are converted into three-phase AC voltages Iu (= 0), Iv, Iw, and the EPS motor 15 generates assist torque that matches the target assist amount Ta *. .

  As described above, in the second current control calculation unit 37, the electrical angle correction unit 371 adds the correction amount λ (correction amount optimum value λ0) to the electrical angle Θ of the EPS motor 15, and the corrected electrical angle x Is calculated. Hereinafter, the correction amount λ and the correction amount optimum value λ0 that are added to correct the electrical angle Θ will be described in detail.

  As described above, during the two-phase driving, the electrical angle correction unit 371 calculates the corrected electrical angle x, and the phase current calculation unit 372 uses the corrected electrical angle x to cause the target current amount Ta *, that is, the current command. The phase current command value iX * is calculated so that the q-axis actual current Iq corresponding to the value iref is generated in the EPS motor 15. As described above, when the phase current command value iX * is calculated using the corrected electrical angle x and the phase current feedback control is executed, the rotation of the EPS motor 15 during the two-phase driving can be smoothed. When the driver rotates the steering handle 11, a so-called good steering feeling without a feeling of catching can be perceived.

  In explaining this, now, when the electrical angle correction unit 371 does not correct the electrical angle Θ, that is, the phase current calculation unit 372 uses the electrical angle Θ output from the electrical angle calculation unit 34 as it is, the phase current command Assume a situation where the value iX * is calculated and phase current feedback control is executed. As shown in FIG. 9, the current waveform of the phase current command value iX * calculated at the time of two-phase driving is based on the principle, for example, when a conduction failure occurs in the U phase, the electrical angle Θ is π / 2 ( 90 deg) and 3π / 2 (270 deg) are asymptotic lines, and an infinite current is required. However, in reality, the EPS motor 15 has a rated current value, and it is necessary to limit the current of each phase, so that it is impossible to pass an infinite current to the EPS motor 15. Therefore, as described above, when a conduction failure occurs in the U phase, the phase current iv in the vicinity of π / 2 (90 deg) and 3π / 2 (270 deg) at the electrical angle Θ of the V phase that is the control phase, It is limited by the maximum current value imax that can be applied to the V phase.

  However, for example, when the phase current iv of the V phase that is the control phase is limited, the output torque generated by the EPS motor 15 is limited and reduced as shown in FIG. As a result, there may occur a situation where the assist torque provided by the EPS motor 15 is insufficient (or the assist torque becomes zero). In the situation where the assist torque is insufficient, the electric angle Θ of the EPS motor 15 approaches π / 2 (90 deg) and 3π / 2 (270 deg) in accordance with the turning operation of the steering handle 11 by the driver. The steering load generated when the left and right front wheels FW1 and FW2 that are the steered wheels are steered increases. More specifically, the operation force (operation torque Th) necessary for the turning operation of the steering handle 11 is large. To become a driver, the driver feels caught.

  On the other hand, the electrical angle correction unit 371 corrects the electrical angle Θ of the EPS motor 15 by adding the correction amount λ to the rotational direction of the EPS motor 15. More specifically, the phase of the electrical angle Θ is corrected by the correction amount λ. When the offset is corrected to the forward side, the torque increase region where the output torque increases in the rotational direction of the EPS motor 15 and the torque reversal where the output torque reverses with respect to the rotational direction of the EPS motor 15 as shown in FIG. Areas can appear intentionally. FIG. 11 shows an example in which the correction amount λ = 20 deg.

  Then, by intentionally appearing such a torque increase region and a torque reversal region, energy can be stored in the rotational motion of the EPS motor 15 in the torque increase region, and the rotation of the EPS motor 15 is accelerated in the steering direction. Can be made. On the other hand, in the torque reversal region, conversely, energy that decelerates the rotation of the EPS motor 15 and returns the electrical angle Θ toward the torque increase region can be stored. Therefore, for example, the rotation (electrical angle Θ) of the EPS motor 15 in the steering direction is decelerated by entering the torque reversal region from the torque increasing region, and the momentum of the rotation is lost, so that the assist decreasing region where the output torque decreases is exceeded. When this is not possible, the EPS motor 15 is rotated in the direction opposite to the steering direction and returned to the torque increase region again.

  As a result, the EPS motor 15 accumulates energy that rotates in the steering direction in the returned torque increase region and gives momentum to the rotation. If the momentum is insufficient, the EPS motor 15 returns from the torque reversal region to the torque increase region again, Energy that rotates in the steering direction in the increase region can be stored to give momentum to the rotation. By repeatedly moving between the torque increasing region and the torque reversing region, the EPS motor 15 can jump over the assist lowering region due to its inertia and reduce the feeling of catch perceived by the driver. Can do.

  By the way, in order to surely prevent the above-described assist lowering region from being jumped over, in other words, to securely catch, the torque increasing region and the torque reversing region can be surely increased by increasing the correction amount λ added to the electrical angle Θ. It is effective to be able to appear. On the other hand, if the correction amount λ to be added to the electrical angle Θ is excessively increased, as will be described later, the torque that can be generated by the EPS motor 15 decreases, so that the operating force (steering torque Th) input by the driver is reduced. There is a contradiction that increases. For this reason, it can be said that the prevention of the feeling of catch and the reduction of the operating force are in a trade-off relationship with each other.

  That is, even in a two-phase drive state in which the maximum output accompanying the current limitation is limited compared to the normal time, when the steering load is small, there is a margin in the torque that the EPS motor 15 can generate. It is possible to set the correction amount λ large with priority given to prevention of feeling. However, in a situation where the steering load increases and there is no margin in the torque that can be generated by the EPS motor 15, if the correction amount λ is set large in order to prioritize prevention of a feeling of catching, the steering torque Th input by the driver increases. It may cause a burden.

  Therefore, it is necessary to determine the correction amount λ that can achieve both the prevention of the feeling of catching and the reduction of the operating force, more specifically, the correction amount optimal value λ0. For this reason, the inventor of the present application has determined the correction amount λ (correction amount optimal value λ0) as described in detail below.

ただし、前記式５中のKtは、Kt＝Th／irefで決定されるトルク定数を表す。 When the torque increasing region and the torque reversal region as shown in FIG. 11 appear, the torque Tout generated by the EPS motor 15 (hereinafter referred to as generated torque Tout) can be expressed by the following equation (5). . The generated torque Tout is a periodic function of a period π, and in the following description, (π / 2) −λ ≦ θ <(3π / 2) −λ is shown.

However, Kt in Equation 5 represents a torque constant determined by Kt = Th / iref.

ここで、上述したように、前記式１に従って電気角Θに補正量λを加算した補正後電気角xを計算する。このため、発生トルク平均値Tavgの演算については、発生トルクToutがπ（１８０ｄｅｇ）の周期を持っているため、下記式７に示すように、−π／２〜π／２の範囲においてxについて積分して平均化すれば良い。

尚、前記式７中の電流指令値irefの最大値iref(max)及びθ１の各変数は、下記式８及び式９により定義される。

In this case, the average value Tavg of torque generated by the EPS motor 15 (hereinafter referred to as generated torque average value Tabg) is considered to be obtained by integrating the generated torque Tout by the electrical angle Θ, as shown in the following formula 6. be able to.

Here, as described above, the corrected electrical angle x obtained by adding the correction amount λ to the electrical angle Θ is calculated according to the equation 1. For this reason, in the calculation of the generated torque average value Tabg, since the generated torque Tout has a cycle of π (180 deg), as shown in the following equation 7, x is in the range of −π / 2 to π / 2. Integrate and average.

Each variable of the maximum value iref (max) and θ1 of the current command value iref in the equation 7 is defined by the following equations 8 and 9.

By the way, as is clear from the equation 7, the average torque value Tavg generated by the EPS motor 15 can be expressed as a function of the correction amount λ. This can also be understood from the fact that when the electrical angle Θ is corrected using the correction amount λ, a torque increasing region and a torque reversal region appear as described with reference to FIG. In the generated torque average value Tabg calculated as the COS function of the correction amount λ according to the equation 7, the maximum value Tavg (max) is substituted with the maximum value iref (max) for the current command value iref, and Since θ1 = π / 6 according to Equation 9, it can be expressed by Equation 10 below.

ただし、この場合、上述したように、アシスト電流指令値演算部３５によって演算される電流指令値irefは運転者が操舵ハンドル１１を介して入力する操舵トルクThすなわち手入力トルクTh1の関数となる。このため、二相駆動状態におけるＥＰＳモータ１５の出力トルクが負荷トルクTLに対して十分な余裕があるときには、通常時と同様に電流指令値iref（出力トルク）と転舵トルクTLとがバランスするポイントで操舵トルクTh（すなわち手入力トルクTh1）が決定される。一方で、負荷トルクTLが二相駆動時における出力上限である前記式１０により表される最大値Tavg(max)を上回る場合には、電流指令値irefが最大値iref(max)で飽和して固定されるため、発生トルク平均値Tavgは、補正量λに応じた最大値Tavg(max)となる。 Now, assuming that the steering load TL (hereinafter also referred to as load torque TL) is constant, the driver turns the steering wheel 11 while the current command value iref is saturated at the maximum value iref (max). Steering torque Th1 (hereinafter referred to as manual input torque Th1) as a first torque necessary to operate and steer the left and right front wheels FW1 and FW2 that are steered wheels is calculated according to the following formula 11. Can do.

However, in this case, as described above, the current command value iref calculated by the assist current command value calculation unit 35 is a function of the steering torque Th input by the driver via the steering handle 11, that is, the manual input torque Th1. For this reason, when the output torque of the EPS motor 15 in the two-phase drive state has a sufficient margin with respect to the load torque TL, the current command value iref (output torque) and the steering torque TL are balanced as in the normal case. The steering torque Th (that is, the manual input torque Th1) is determined at the point. On the other hand, when the load torque TL exceeds the maximum value Tavg (max) expressed by the above equation 10 that is the upper limit of output during two-phase driving, the current command value iref is saturated at the maximum value iref (max). Since it is fixed, the generated torque average value Tabg is the maximum value Tavg (max) corresponding to the correction amount λ.

  By the way, as described above, when the EPS motor 15 rotates at a certain rotational speed (rotational speed), the torque reversal region can be jumped by acceleration in the torque increase region. However, if the rotational speed (rotational speed) of the EPS motor 15 decreases, there is a possibility that the electric motor Θ between the torque increasing region and the torque reversing region stops in balance with the load torque TL.

  Specifically, with reference to FIG. Assume that the rotation of the EPS motor 15 stops at a stable point. This a. At the stable point, the sum of the output torque of the EPS motor 15 and the manual input torque Th1 is balanced with the load torque TL. This a. When the driver tries to steer in the right direction in FIG. 12 at the stable point, the output torque of the EPS motor 15 decreases. Therefore, the driver decreases the output torque by the manual input torque Th1 (steering torque Th). Supplementing, b. It is necessary to advance the electrical angle Θ to the torque reversal point. Here, in the following description, a. From the stable point b. The steering torque Th as the second torque necessary until reaching the torque reversal point is referred to as a burden torque Th2.

  When the electric torque Θ of the EPS motor 15 enters the torque reversal region by inputting the burden torque Th2, as described above, the acceleration is once accelerated in the reverse direction, and c. Return to the acceleration start point. Then, rotation starts again in the steering direction (rightward in FIG. 12). Since the magnitude of the output torque of the EPS motor 15 at this time is larger than the magnitude of the load torque TL, the EPS motor 15 is inertial ( By virtue of the momentum), the rotation can be continued beyond the torque reversal region.

  That is, even if the rotation of the EPS motor 15 is stopped, a. From the stable point b. As long as it can proceed to the torque reversal point, the rotation can be continued beyond the torque reversal region. If the burden torque Th2 necessary for continuing the rotation of the EPS motor 15 is large as described above, a steering feeling that makes the driver feel like being caught becomes a result. In this case, as shown in FIG. 12, the larger the correction amount λ, the b. Torque reversal point is a. To move toward the stable point (leftward in FIG. 12), in other words, to advance the phase of the electrical angle Θ, the burden torque Th2 is reduced.

ただし、反転トルクTrevは、下記式１３に従って補正量λのＳＩＮ関数として表すことができる。

Here, if the EPS motor 15 outputs the output torque Trev (hereinafter referred to as reverse torque Trev) at the torque reversal point, the burden torque Th2 can be calculated according to the following equation 12.

However, the reverse torque Trev can be expressed as a SIN function of the correction amount λ according to the following equation (13).

  By the way, when the manual input torque Th1 expressed by the expressions 10 and 11 is compared with the burden torque Th2 expressed by the expressions 12 and 13, the manual input torque Th1 is expressed as a COS function of the correction amount λ. While the load torque Th2 is expressed as a SIN function of the correction amount λ, it shows a tendency to decrease as the correction amount λ increases while the correction amount λ increases. For this reason, when an arbitrary load torque (steering load) TL is given, the manually input torque Th1 and the burden torque Th2 with respect to the change in the correction amount λ are plotted as shown in FIG.

  In FIG. 13, in “A” in which the correction amount λ (offset) is 20 degrees, the burden torque Th2 is larger than the manual input torque Th1, so that the small hand is maintained while the EPS motor 15 is maintained in the rotating state. The steering handle 11 can be turned by the input torque Th1. However, when steering is again performed from the state where the rotation of the EPS motor 15 is stopped (that is, when advancing from a. Stable point to b. Torque reversal point in FIG. 12), it is necessary to input a large burden torque Th2. In the turning operation of the steering handle 11, the driver can easily feel a catching feeling.

  On the other hand, in FIG. 13, at “B” where the correction amount λ (offset amount) is approximately 31 degrees, the manual input torque Th1 and the burden torque Th2 are equal. For this reason, when the EPS motor 15 is in a rotating state, the driver feels that the turning operation of the steering handle 11 is heavy because the manual input torque Th1 is larger than that in the case of “A”. However, when the EPS motor 15 is rotating (during the turning operation of the steering handle 11), and when the steering is started again from the state where the rotation of the EPS motor 15 is stopped (that is, from a. Stable point to b. Torque reversal point in FIG. 12). ), The driver feels almost the same weight, making it difficult to remember.

Therefore, the correction amount λ in the above “B” can be determined as one optimum value as shown in the following equation 14 using the equations 10 to 13.

  However, the motor rotation angle sensor 23 provided in the actual electric power steering apparatus 10 usually detects the electrical angle Θ with a detection error. For this reason, with respect to the correction amount λ, the detection error of the motor rotation angle sensor 23 that is allowed in performing the assist control described above, in other words, the detection accuracy of the motor rotation angle sensor 23 is taken into account, according to the above-described equation (14). It is appropriate to set a range including the determined correction amount optimum value λ0 = 0.55 rad. Specifically, the allowable range of the correction amount λ is preferably set to 0.45 rad <λ <0.65 rad, and 0 when the motor rotation angle sensor 23 has higher detection accuracy. More preferably, 50 rad <λ <0.60 rad is set.

  When “deg” is used instead of “rad” as the unit of angle, the correction amount optimum value λ0 = 31 deg is obtained as an approximate value. The setting range of the correction amount λ is preferably set to 26 deg <λ <36 deg, and more preferably 28 deg <λ <34 deg when the detection accuracy of the motor rotation angle sensor 23 is high.

  As can be understood from the above description, according to the above embodiment, the correction amount λ (optimum correction amount λ0) for correcting the electrical angle Θ of the EPS motor 15 during the two-phase driving is set to suppress the catching feeling and the operation force. Appropriate determination can be made so as to maximize the trade-off between reducing the (steering torque Th). As a result, even when the EPS motor 15 is driven by two-phase driving and assist control is continued, the driver does not feel uncomfortable and turns the steering wheel 11 while perceiving a very good steering feeling. Can be operated.

  In addition, since it is possible to appropriately achieve both the suppression of the feeling of catching and the reduction of the operating force (steering torque Th), it is not necessary to increase the output torque of the EPS motor 15 more than necessary. Thereby, it is not necessary to enlarge the system of the electric power steering apparatus 10 in order to increase the output torque of the EPS motor 15, and for example, an increase in the weight of the vehicle can be suppressed and deterioration of fuel consumption can be prevented. Furthermore, since it is not necessary to increase the size of the EPS motor 15 in order to increase the output torque, for example, it is possible to prevent deterioration in steering feeling due to an increase in inertia of the rotating portion of the EPS motor 15.

<Modification>
In the above embodiment, as shown in FIG. 8, a constant correction amount λ (correction amount optimum value λ0) is always added to the electrical angle Θ to correct the steering torque Th and the rotational angular velocity dΘ / dt. Implemented. Incidentally, the correction of the electrical angle Θ is necessary when the steering load TL (load torque TL) that can be estimated from the steering torque Th and the magnitude of the current command value iref is large. Therefore, instead of always adding a constant correction amount λ (correction amount optimal value λ0) to the electrical angle Θ as in the above embodiment, the magnitude of the steering load TL (load torque TL) (that is, steering) The correction amount λ can be increased uniformly to the correction amount optimum value λ0 as the torque Th increases or the current command value iref increases. In this case, in particular, since the magnitude of the correction amount λ for correcting the electrical angle Θ can be reduced when the steering load TL (load torque TL) is small, for example, the frequency of torque reversal as described above. The vibration associated with torque reversal can be effectively suppressed. Other effects are the same as in the above embodiment.

  In carrying out the present invention, the present invention is not limited to the above-described embodiments and modifications, and various modifications can be made without departing from the object of the present invention.

  For example, in the embodiment and the modification described above, the electrical angle calculation unit 34 calculates the electrical angle Θ using the electrical signal output from the motor rotation angle sensor 23. In this case, instead of or directly in addition to directly detecting the electrical angle Θ (rotation angle) of the EPS motor 15, for example, the EPS motor 15 is detected using a detection value obtained by another sensor mounted on the vehicle. It is also possible to estimate the electrical angle Θ (rotation angle) of the EPS motor 15 or to estimate the electrical angle Θ (rotation angle) of the EPS motor 15 using a calculated value obtained by other control. is there. Thus, even when the electrical angle Θ (rotation angle) of the EPS motor 15 is estimated and implemented, for example, as described above, the electrical angle Θ is set using the correction amount λ that is appropriately set. Since it can correct | amend, the effect equivalent to the said embodiment and modification can be anticipated.

  FW1, FW2 ... front left and right wheels, 10 ... electric power steering device, 11 ... steering handle, 12 ... steering shaft, 13 ... pinion gear, 14 ... rack bar, 15 ... EPS motor, 20 ... electric control device, 21 ... vehicle speed sensor, DESCRIPTION OF SYMBOLS 22 ... Steering torque sensor, 23 ... Motor rotation angle sensor, 24 ... Electronic control unit, 25 ... Drive circuit, 30 ... Assist control part, 31 ... Vehicle speed calculating part, 32 ... Torque value calculating part, 33 ... Current detection part, 34 ... Electrical angle calculation unit, 35 ... Assist current command value calculation unit, 36 ... First current control calculation unit, 37 ... Second current control calculation unit, 371 ... Electrical angle correction unit, 372 ... Phase current calculation unit, 373 ... Control Phase selector, 38 ... PWM converter, U ... steering gear unit

Claims (6)

For a three-phase electric motor that applies torque to reduce the operating force input by the steering handle turning operation, a rotation angle obtaining means for obtaining the rotation angle of the electric motor, and the steering handle turning operation A vehicle steering control device comprising: a control unit that calculates a control amount for controlling the torque applied by the electric motor; and a control unit that drives and controls the electric motor using the calculated control amount.
The control means includes
When an energization failure occurs in any one of the phases of the electric motor, the rotation angle is corrected by adding a correction amount to the rotation angle of the electric motor acquired by the rotation angle detection means. The control amount is calculated, and the electric motor is driven using the calculated control amount by two-phase driving to energize phases other than the phase where the energization failure has occurred, and the application of the torque is continued. Yes,
The correction amount is
The load torque, which is a turning load generated when turning the steered wheels in accordance with the turning operation of the steering handle, and the torque generated by the electric motor, which is expressed as a function of the correction amount. A first torque representing a difference between the average maximum value, and
It is expressed as a function of the load torque and the correction amount, and the torque generated by the electric motor in association with the correction of the rotation angle by adding the correction amount is relative to the turning operation direction of the steering handle. Thus, the vehicle steering control device is determined as a value when the second torque representing a difference from the reverse torque in a region where the reverse occurs. In the vehicle steering control device according to claim 1,
The first torque is expressed as a COS function of the correction amount,
The vehicle steering control device, wherein the second torque is expressed as a SIN function of the correction amount. In the vehicle steering control device according to claim 1 or 2,
The control means includes
As the turning load increases, the correction amount is uniformly increased to a value when the first torque and the second torque match, and this correction amount is added. Then, the vehicle steering control device corrects the rotation angle. In the steering control device for a vehicle according to any one of claims 1 to 3,
The correction amount is
A vehicle steering control device characterized in that the value is determined when the first torque and the second torque coincide with each other within a range of 0.45 (rad) to 0.65 (rad). . The vehicle steering control device according to claim 4,
The correction amount is
A vehicle steering control device characterized in that the value is determined when the first torque and the second torque coincide with each other within a range of 0.50 (rad) to 0.60 (rad). . In the vehicle steering control device according to any one of claims 1 to 5,
The correction amount is
A steering control device for a vehicle, wherein a value when the first torque and the second torque coincide with each other is determined to be 0.55 (rad).

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