Motor control device, electric power steering device, and vehicle

An electric motor can be accurately drive-controlled even when a failure occurs in a motor electric angle detection unit. When at least one of a resolver and an angle computation unit is diagnosed as abnormal in an initial diagnosis after a system restart, a motor electric angle initial value is estimated on a basis of a response output of a three-phase electric motor in response to input of a motor drive signal to the three-phase electric motor, a motor electric angle estimation value is calculated on a basis of an output shaft rotation angle detection value detected by an output-side rotation angle sensor and a relative offset amount estimated on a basis of the estimated motor electric angle initial value, and the three-phase electric motor is drive-controlled on a basis of the calculated motor electric angle estimation value.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Japanese Patent Application No. 2015-159584 (filed on Aug. 12, 2015), the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a motor control device that drive-controls a multi-phase electric motor incorporated in an electric power steering device.

BACKGROUND ART

As a motor control device that controls an electric motor of an electric power steering device that is incorporated in a vehicle, for example, a control device of a multi-phase rotary machine described in PTL 1 is disclosed.

In the conventional example described in PTL 1, a position sensor such as a resolver detects a rotor rotation position θ, and, on the basis of command voltages Vd1 and Vq1 and the rotor rotation position θ, a U-phase command voltage Vuu*1, a V-phase command voltage Vvu*1, and a W-phase command voltage Vwu*1 that are three-phase voltage command values are calculated.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

However, the conventional example of PTL 1 described above does not consider a case of failure in the position sensor for detecting the rotor rotation position, and therefore it is difficult to accurately drive and control the multi-phase rotary machine after a failure therein.

Accordingly, the present invention has been accomplished by focusing on the unsolved problem in the above conventional example, and it is an object of the present invention to provide a motor control device, an electric power steering device, and a vehicle that allow an electric motor to be accurately driven and controlled even when a failure occurs in a motor electric angle detection unit that detects a motor electric angle.

Solution to Problem

In order to achieve the object, a motor control device according to a first aspect of the present invention includes a motor electric angle initial value estimation unit that, when a motor electric angle detection unit that detects a motor electric angle of a multi-phase electric motor that generates a steering assist force is diagnosed as being abnormal in an initial diagnosis after a system restart, estimates an initial value of the motor electric angle on a basis of a response output of the multi-phase electric motor in response to input of a motor drive signal to the multi-phase electric motor; a motor electric angle estimation unit that estimates the motor electric angle on a basis of a steering angle detected by a steering angle detection unit that detects a steering angle of the steering and the initial value estimated by the motor electric angle initial value estimation unit; and a motor drive control unit that, when the motor electric angle detection unit is normal, drive-controls the multi-phase electric motor on a basis of the motor electric angle detected by the motor electric angle detection unit, and when the motor electric angle detection unit is diagnosed as being abnormal in the initial diagnosis after the system restart, drive-controls the multi-phase electric motor on a basis of a motor electric angle estimation value estimated by the motor electric angle estimation unit.

Additionally, an electric power steering device according to a second aspect of the present invention includes the motor control device according to the first aspect.

Furthermore, a vehicle according to a third aspect of the present invention includes the electric power steering device according to the second aspect.

Advantageous Effects of Invention

According to the present invention, when the motor electric angle detection unit is diagnosed as being abnormal in the initial diagnosis after a system restart, the initial value of the motor electric angle can be estimated on the basis of a response output of the multi-phase electric motor according to input of a motor drive signal to the multi-phase electric motor. Then, the motor electric angle can be estimated on the basis of the estimated initial value of the motor eclectic angle and a steering angle of the steering, and, on the basis of the motor electric angle estimation value, the multi-phase electric motor can be drive-controlled. Accordingly, even when abnormality occurs in the motor electric angle detection unit before or during a system shutdown, the multi-phase electric motor can be drive-controlled equivalently to when the motor electric angle detection unit is normal.

In addition, since the electric power steering device is formed by including the motor control device having the above advantageous effects, the multi-phase electric motor can be drive-controlled by the motor electric angle estimation value even when an abnormality occurs in the motor electric angle detection unit before or during a system shutdown, thereby allowing continuation of a steering assist function of the electric power steering device.

Furthermore, since the vehicle is formed by including the electric power steering device having the advantageous effect, continuation of the steering assist function of the electric power steering device becomes possible even when an abnormality occurs in the motor electric angle detection unit, so as to improve the reliability.

DESCRIPTION OF EMBODIMENTS

Next, first through third embodiments of the present invention will be described with reference to the drawings. In the following descriptions of the drawings, the same or similar parts are denoted by the same or similar reference signs. However, it is to be noted that the drawings are schematically illustrated, and thus dimensional relationships, ratios, and the like may be different from actual ones.

In addition, the first through the third embodiments represented below exemplify devices and methods for embodying the technical ideas of the present invention, and thus the technical idea of the present invention does not specify materials, shapes, structures, arrangements, and the like of constituent components to those described below. Various changes can be added to the technical ideas of the present invention within the technical scope defined by the appended claims.

First Embodiment

A vehicle1according to an embodiment of the present invention includes front wheels2FR and2FL serving as right and left steered wheels and rear wheels2RR and2RL, as depicted inFIG. 1. The front wheels2FR and2FL are steered by an electric power steering device3.

The electric power steering device3includes a steering wheel11, and a steering force applied to the steering wheel11from a driver is transmitted to a steering shaft12. The steering shaft12includes an input shaft12aand an output shaft12b. One end of the input shaft12ais connected to the steering wheel11, and the other end thereof is connected to one end of the output shaft12bvia a steering torque sensor13.

Then, the steering force transmitted to the output shaft12bis transmitted to a lower shaft15via a universal joint14, and is further transmitted to a pinion shaft17via a universal joint16. The steering force transmitted to the pinion shaft17is transmitted to tie rods19via a steering gear18to steer the front wheels2FR and2FL serving as the steered wheels. Herein, the steering gear18is formed as a rack and pinion type including a pinion18aconnected to the pinion shaft17and a rack18bengaged with the pinion18a. Accordingly, the steering gear18converts a rotational movement transmitted to the pinion18ato a translatory movement in a vehicle width direction by the rack18b.

A steering assist mechanism20that transmits a steering assist force to the output shaft12bis connected to the output shaft12bof the steering shaft12. The steering assist mechanism20includes a deceleration gear21which is formed by, for example, a worm gear mechanism and is connected to the output shaft12band a three-phase electric motor22that generates the steering assist force, that is connected to the deceleration gear21, and that serves as a multi-phase electric motor formed by, for example, a three-phase brushless motor.

The steering torque sensor13detects a steering torque that is applied to the steering wheel11and transmitted to the input shaft12a. The steering torque sensor13is configured to convert the steering torque into a torsion angle displacement of an unillustrated torsion bar13ainterposed between the input shaft12aand the output shaft12b, convert the torsion angle displacement into an angular difference between an input-side rotation angle sensor13barranged on an input shaft12aside and an output-side rotation angle sensor13carranged on an output shaft12bside, and detect the angular difference, as depicted inFIG. 2.

Additionally, in the first embodiment, the input-side rotation angle sensor13band the output-side rotation angle sensor13care sensors that detect a relative rotation angle.

In addition, as depicted inFIG. 3, the three-phase electric motor22has the structure of a SPM motor that includes a stator22S having teeth Te that are formed protrudingly inward on an inner peripheral surface thereof to form slots SL and serve as magnetic poles and a surface magnet type rotor22R with eight poles that has permanent magnets PM on a surface thereof and is rotatably arranged to face the teeth Te on the inner peripheral side of the stator22S. Herein, the number of the teeth Te of the stator22S is set to the number of phases×2n (n represents an integer of 2 or more) where when, for example, n=2, the motor22has a structure with 8 poles and 12 slots.

Then, in two systems depicted inFIG. 4, a first three-phase motor winding L1and a second three-phase motor winding L2are wounded on the slots SL of the stator22S, and serve as multi-phase motor windings in which respective same-phase magnetic poles have the same phase with respect to the rotor magnet. In the first three-phase motor winding L1, respective one ends of U-phase coils U1aand U1b, V-phase coils V1aand V1b, and W-phase coils W1aand W1bare connected to each other to form a star connection. Furthermore, respective other ends of the U-phase coils U1aand U1b, the V-phase coils V1aand V1b, and the W-phase coils W1aand W1bare connected to a motor control device25to individually supply motor drive currents I1u, I1v, and I1w.

In addition, in the second three-phase motor winding L2, respective one ends of U-phase coils U2aand U2b, V-phase coils V2aand V2b, and W-phase coils W2aand W2bare connected to each other to form a star connection. Furthermore, respective other ends of the U-phase coils U2aand U2b, the V-phase coils V2aand V2b, and the W-phase coils W2aand W2bare connected to the motor control device25to individually supply motor drive currents I2u, I2v, and I2w.

Then, the respective phase coil portions U1a, U1b, V1a, V1b, W1a, and W1bof the first three-phase motor winding L1and the respective phase coil portions U2a, U2b, V2a, V2b, W2a, and W2bof the second three-phase motor winding L2are wound around the slots SL sandwiching the respective teeth Te in such a manner that energization current directions are the same.

In this manner, the respective phase coil portions U1a, U1b, V1a, V1b, W1a, and W1bof the first three-phase motor winding L1and the respective phase coil portions U2a, U2b, V2a, V2b, W2a, and W2bof the second three-phase motor winding L2are wound on mutually different12teeth Te1to Te12. Specifically, on the12teeth Te1to Te12, sequentially, the phase coils U1a, U1b, V1a, V1b, W1a, and W1bthat serve as the first system are wound in a counter-clockwise direction and in the same winding direction in order, and next, the phase coils U2a, U2b, V2a, V2b, W2a, and W2bthat serve as the second system are wound in the counter-clockwise direction and in the same winding direction in order. Furthermore, the phase coils U1a, U1b, V1a, V1b, W1a, and W1bserving as the first system are wound in the counter-clockwise direction and in the same winding direction in order, and lastly, the phase coils U2a, U2b, V2a, V2b, W2a, and W2bserving as the second system are wound in the counter-clockwise direction and in the same winding direction in order. Thus, the same-phase coil portions of the first three-phase motor winding L1and the second three-phase motor winding L2are wound thereon so as not to be simultaneously interlinked with the same magnetic flux formed by each magnetic pole permanent magnet PM of the rotor22R. Accordingly, each coil portion of the first three-phase motor winding L1and each coil portion of the second three-phase motor winding L2form a magnetic circuit that suppresses mutual magnetic interference to a minimum level.

Furthermore, as depicted inFIG. 5, the three-phase electric motor22includes a rotation position sensor23aformed by a resolver that detects a rotation position of the rotor. A detection value from the rotation position sensor23ais supplied to a motor electric angle detection circuit23, and the motor electric angle detection circuit23detects a motor electric angle θm. Hereinafter, the rotation position sensor23amay be described as “resolver23a”. In addition, the rotation position sensor23ais not limited to the resolver, and, for example, may be formed by another sensor such as a rotary encoder.

A steering torque T detected by the steering torque sensor13and a vehicle speed Vs detected by a vehicle speed sensor26are input to the motor control device25, and also, the motor electric angle θm output from the motor electric angle detection circuit23is input the motor control device25.

Additionally, a direct current from a battery27as a direct current source is input to the motor control device25. Herein, a negative electrode of the battery27is grounded, whereas a positive electrode thereof is connected to the motor control device25via an ignition switch28(hereinafter may be described as “IGN switch28”) that starts engine and also is directly connected to the motor control device25not via the IGN switch28.

A specific structure of the motor control device25is formed as depicted inFIG. 5. Specifically, the motor control device25includes a control computation device31that computes a motor current command value, first and second motor drive circuits32A and32B to which the motor current command value output from the control computation device31is individually input, and first and second motor current block circuits33A and33B interposed between output sides of the first and second motor drive circuits32A and32B and the first and second three-phase motor windings L1and L2of the three-phase electric motor22.

Although the depiction is omitted inFIG. 5, the steering torque T detected by the steering torque sensor13and the vehicle speed Vs detected by the vehicle speed sensor26depicted inFIG. 1are input to the control computation device31, and also, as depicted inFIG. 5, the motor electric angle θm output from the motor electric angle detection circuit23is input to the control computation device31. Furthermore, motor currents I1m(I1mu, I1mv, and I1mw) and I2m(I2mu, I2mv, and I2mw) output from current detection circuits34A and34B, which are output from the coils of the respective phases of the first three-phase motor winding L1and the second three-phase motor winding L2of the three-phase electric motor22, are input thereto.

Hereinafter, when it is unnecessary to distinguish the motor currents I1mfrom I2m, detection values thereof may be sometimes described as “motor current detection values Im (Imu, Imv, and Imw)”.

Additionally, as depicted inFIG. 5, motor phase voltages V1m(V1mu, V1mv, and V1mw) and V2m(V2mu, V2mv, and V2mw) detected by voltage detection circuits40A and40B interposed between the first and second motor drive circuits32A and32B and the first and second motor current block circuits33A and33B are input to the control computation device31.

Hereinafter, when it is unnecessary to distinguish between the motor phase voltages V1mand V2m, detection values thereof may be described as “motor voltage detection values Vm (Vmu, Vmv, and Vmw)”.

When the first and second motor drive circuits32A and32B are normal, the control computation device31calculates steering assist current command values I1* and12* by referring to a normal-time steering assist current command value calculation map which is depicted inFIG. 6and is set in advance on the basis of the steering torque T and the vehicle speed Vs. In addition, when the first and second motor drive circuits32A or32B are abnormal, the control computation device31calculates the steering assist current command values I1* and I2* by referring to an abnormal-time steering assist current command value calculation map which is depicted inFIG. 7and is set in advance on the basis of the steering torque T and the vehicle speed Vs.

In addition, on the basis of the calculated steering assist current command values I1* and I2* and the motor electric angle θm, the control computation device31calculates a target d-axis current command value Id* and a target q-axis current command value Iq* of a d-q coordinate systems. Additionally, the control computation device31performs a d-q phase to three phase conversion of the calculated d-axis current command value Id* and q-axis current command value Iq* to calculate a U-phase current command value Iu*, a V-phase current command value Iv*, and a W-phase current command value Iw*. Then, the control computation device31calculates current deviations ΔIu, ΔIv, and ΔIw between the calculated U-phase current command value Iu*, V-phase current command value Iv*, and W-phase current command value Iw* and added values of the current detection values of each phase detected by the current detection circuits34A and34B. Still furthermore, the control computation device31performs, for example, PI control computation or PID control computation of the calculated current deviations ΔIu, ΔIv, and ΔIw to calculate voltage command values V1* and V2* of the three phases for the first and second motor drive circuits32A and32B. Then, the control computation device31outputs the calculated voltage command values V1* and V2* of the three phases to the first and second motor drive circuits32A and32B.

In addition, the motor current detection values I1mu, I1mv, I1mw, I2mu, I2mu, and I2mwdetected by first and second abnormality detection circuits35A and35B interposed between the first and second motor current block circuits33A and33B and the first and second three-phase motor windings L1and L2of the three-phase electric motor22are input to the control computation device31.

The control computation device31compares the motor current detection values I1muto I1mwand I2muto I2mwfor receiving with the respective phase current command values Iu*, Iv*, and Iw* calculated by itself. Then, the control computation device31includes an abnormality detection unit31athat, on the basis of results of the comparison, detects an open-circuit failure and a short-circuit failure of field effect transistors (FETs) Q1to Q6as switching elements that form first and second inverter circuits42A and42B that will be described later.

When detecting an open-circuit failure or a short-circuit failure of the field effect transistors (FETs) forming the first and second inverter circuits42A and42B, the abnormality detection unit31aoutputs an abnormality detection signal SAa or SAb having a logical value of “1” to a gate drive circuit41A or41B of the first and second motor drive circuits32A or32B in which the abnormality has been detected.

The first and second motor drive circuits32A and32B, respectively, include the gate drive circuits41A and41B having an abnormal-time current control unit41aand the first and second inverter circuits42A and42B.

The voltage command values V1* and V2* of the three phases output from the control computation device31are input to the gate drive circuits41A and41B. Then, the gate drive circuits41A and41B form gate signals on the basis of the input voltage command values V1* and V2* of the three phases.

The gate signals output from the gate drive circuits41A and41B are input to the first and second inverter circuits42A and42B. Then, the first and second inverter circuits42A and42B supply drive currents to the three-phase electric motor22on the basis of the input gate signals.

When the voltage command values V1* and V2* are input from the control computation device31, the gate drive circuits41A and41B, respectively, form six gate signals by pulse width modulation (PWM) based on the voltage command values V1* and V2* and a triangular wave carrier signal Sc. Then, the gate drive circuits41A and41B output the gate signals to the first and second inverter circuits42A and42B.

In addition, when the abnormality detection signal SAa input from the control computation device31has a logical value of “0” (normal), the gate drive circuit41A outputs three high-level gate signals to the first motor current block circuit33A. In addition, the gate drive circuit41A outputs two high-level gate signals to the first power supply block circuit44A. Furthermore, when the abnormality detection signal SAa has the logical value of “1” (abnormal), the gate drive circuit41A causes the abnormal-time current control unit41ato simultaneously output three low-level gate signals to the first motor current block circuit33A to block motor current, and additionally, to simultaneously output two low-level gate signals to the first power supply block circuit44A to block battery power.

Similarly, when the abnormality detection signal SAb input from the control computation device31has the logical value of “0” (normal), the gate drive circuit41B outputs three high-level gate signals to the second motor current block circuit33B, and additionally outputs two high-level gate signals to the second power supply block circuit44B. Furthermore, when the abnormality detection signal SAb has the logical value of “1” (abnormal), the gate drive circuit41B causes the abnormal-time current control unit41ato simultaneously output three low-level gate signals to the second motor current block circuit33B to block motor current, and additionally, to simultaneously output two low-level gate signals to the second power supply block circuit44B to block battery power.

A battery current of the battery27is input to each of the first and second inverter circuits42A and42B via a noise filter43and the first and second power supply block circuits44A and44B, and smoothing electrolytic capacitors CA and CB are connected to input sides thereof.

The first and second inverter circuits42A and42B include the field effect transistors (FETs) Q1to Q6as the six switching elements, and have a structure in which three switching arms SAu, SAv, and SAw each having two field effect transistors connected in series are connected in parallel. Then, the gate signals output from the gate drive circuits41A and41B are input to gates of the respective field effect transistors Q1to Q6. Accordingly, a U-phase current Iu, a V-phase current Iv, and a W-phase current Iw are output from among the field effect transistors of the respective switching arms SAu, SAv, and SAw to the first and second three-phase motor windings L1and L2of the three-phase electric motor22via the first and second motor current block circuits33A and33B.

In addition, although unillustrated, a voltage across a shunt resistance interposed between each of the switching arms SAu, SAv, and SAw of the first and second inverter circuits42A and42B and a ground is input to the current detection circuits34A and34B. Then, the current detection circuits34A and34B detect the motor currents I1m(I1muto I1mw) and I2m(I2muto I2mw).

Additionally, the first motor current block circuit33A includes three current blocking field effect transistors QA1, QA2, and QA3. A source of the field effect transistor QA1is connected to a connection point of the field effect transistors Q1and Q2of the switching arm SAu of the first inverter circuit42A, and a drain thereof is connected to a U-phase coil L1uof the first three-phase motor winding L1via the first abnormality detection circuit35A. Additionally, a source of the field effect transistor QA2is connected to a connection point of the field effect transistors Q3and Q4of the switching arm SAv of the first inverter circuit42A, and a drain thereof is connected to a V-phase coil L1vof the first three-phase motor winding L1via the first abnormality detection circuit35A. Furthermore, a source of the field effect transistor QA3is connected to a connection point of the field effect transistors Q5and Q6of the switching arm SAw of the first inverter circuit42A, and a drain thereof is connected to a W-phase coil L1wof the first three-phase motor winding L1via the first abnormality detection circuit35A.

Additionally, the second motor current block circuit33B includes three current blocking field effect transistors QB1, QB2, and QB3. A source of the field effect transistor QB1is connected to a connection point of the field effect transistors Q1and Q2of the switching arm SBu of the second inverter circuit42B, and a drain thereof is connected to a U-phase coil L2uof the second three-phase motor winding L2via the second abnormality detection circuit35B. Additionally, a source of the field effect transistor QB2is connected to a connection point of the field effect transistors Q3and Q4of the switching arm SBv of the second inverter circuit42B, and a drain thereof is connected to a V-phase coil L2vof the second three-phase motor winding L2via the second abnormality detection circuit35B. Furthermore, a source of the field effect transistor QB3is connected to a connection point of the field effect transistors Q5and Q6of the switching arm SBw of the second inverter circuit42B, and a drain thereof is connected to a W-phase coil L2wof the second three-phase motor winding L2via the second abnormality detection circuit35B.

Then, the field effect transistors QA1to QA3and QB1to QB3, respectively, of the first and second motor current block circuits33A and33B are connected in the same direction in such a manner that cathodes of parasitic diodes D thereof face sides where the first and second inverter circuits42A and42B are arranged.

In addition, the first and second power supply block circuits44A and44B, respectively, have a series circuit structure in which drains of two field effect transistors (FETs) QC1, QC2and QD1, QD2are connected to each other and the parasitic diodes are oriented in opposite directions. Then, sources of the field effect transistors QC1and QD1are connected to each other and connected to an output side of the noise filter43. Furthermore, sources of the field effect transistors QC2and QD2are connected to sources of the respective field effect transistors Q1, Q2, and Q3of the first and second inverter circuits42A and42B.

Next, a description will be given of a specific structure of the motor electric angle detection circuit23according to the first embodiment.

The motor electric angle detection circuit23of the first embodiment includes a main motor electric angle detection circuit23b, a sub motor electric angle detection circuit23c, an electric angle selection unit23d, a RAM50, and a ROM51, as depicted inFIG. 8.

The main motor electric angle detection circuit23bincludes an angle computation unit60and a resolver abnormality diagnosis unit61.

The angle computation unit60computes a first motor electric angle θm1on the basis of a sin signal and a cos signal according to a rotation angle of the three-phase electric motor22output from the resolver23a. Then, the angle computation unit60outputs the computed first motor electric angle θm1to the electric angle selection unit23d.

The resolver abnormality diagnosis unit61detects abnormality in the resolver23aand outputs an abnormality detection signal SAr.

In addition, although the depiction is omitted inFIG. 5, an output shaft rotation angle detection value θos output from the output-side rotation angle sensor13cand the current detection values Im output from the current detection circuits34A and34B are input to the sub motor electric angle detection circuit23c. Furthermore, an ignition signal IGN indicating ON/OFF of the IGN switch28output from the IGN switch28, the first motor electric angle θm1from the angle computation unit60, and the abnormality detection signal SAr from the resolver abnormality diagnosis unit61are input thereto.

The sub motor electric angle detection circuit23cincludes a relative offset amount estimation unit62and a motor electric angle estimation unit63.

The relative offset amount estimation unit62estimates a relative offset amount θoff between an origin θmd of the motor electric angle θm (hereinafter may be described as “motor electric angle origin θmd”) and a reference value θosr of the output shaft rotation angle detection value θos. Then, the estimated relative offset amount θoff is output to the motor electric angle estimation unit63.

The motor electric angle estimation unit63reads, from the ROM51, a deceleration ratio RGr of the deceleration gear21and the number P of pole pairs of the rotor22R of the three-phase electric motor22that are stored in advance. Then, on the basis of the read deceleration ratio RGr and the number P of pole pairs, the output shaft rotation angle detection value θos detected by the output-side rotation angle sensor13c, and the relative offset amount θoff estimated by the relative offset amount estimation unit62, the motor electric angle estimation unit63calculates a motor electric angle estimation value θme. Furthermore, the motor electric angle estimation unit63outputs the calculated motor electric angle estimation value θme as a second motor electric angle θm2to the electric angle selection unit23d.

Specifically, the motor electric angle estimation unit63calculates the motor electric angle estimation value θme according to the following formula (1):
θme=θos×RGr×P+θoff  (1)

In other words, the output shaft rotation angle detection value θos is multiplied by the deceleration ratio RGr and the number P of pole pairs, and then, the relative offset amount θoff is added to a result of the multiplication, thereby calculating the motor electric angle estimation value θme.

The electric angle selection unit23dselects the first motor electric angle θm1output from the main motor electric angle detection circuit23bwhen the abnormality detection signal SAr output from the resolver abnormality diagnosis unit61of the main motor electric angle detection circuit23bhas the logical value of “0” representing the absence of abnormality. Then, the selected first motor electric angle θm1is output as the motor electric angle θm to the above-described control computation device31. On the other hand, when the abnormality detection signal SAr has the logical value of “1” representing the presence of abnormality, the electric angle selection unit23dselects the second motor electric angle θm2output from the sub motor electric angle detection circuit23c. Then, the selected second motor electric angle θm2is output as the motor electric angle θm to the control computation device31.

Next, a description will be given of a specific structure of the relative offset amount estimation unit62according to the first embodiment.

The relative offset amount estimation unit62of the first embodiment includes a first relative offset amount estimation unit70, a second relative offset amount estimation unit71, and a relative offset amount selection unit72, as depicted inFIG. 9.

When the resolver23aand the angle computation unit60are normal, the first relative offset amount estimation unit70estimates a first relative offset amount θoff1on the basis of the output shaft rotation angle detection value θos detected by the output-side rotation angle sensor13cand the motor electric angle detection value θm1detected by the main motor electric angle detection circuit23b. Then, the estimated first relative offset amount θoff1is stored in the RAM50.

Herein, when the resolver23aand the angle computation unit60are normal, the motor electric angle origin θmd is known, and therefore it is possible to easily estimate a relative offset amount with respect to the reference value θosr of the output shaft rotation angle.

In addition, the reference value θosr is obtained by multiplying an output shaft rotation angle detection value upon system start (at a time when the IGN switch28is turned ON from an OFF state) by the number P of pole pairs and the deceleration ratio RGr.

Additionally, in order to complement the motor electric angle θm by output shaft rotation angle detection value θos*P*RGr, it is necessary to make the motor electric angle origin θmd (0 degrees) coincident with the reference value θosr of the output shaft rotation angle. For example, as depicted inFIG. 10, when the reference value θosr is not coincident with the origin θmd, an angle error occurs in the output shaft rotation angle detection value θos*P*RGr (amount of displacement from reference value θosr) with respect to the motor electric angle θm indicated by a solid line in the drawing, as indicated by a dot-and-dash line in the drawing. Due to that, a significant deviation will occur with respect to an actual motor electric angle θm.

Accordingly, it is necessary to obtain in advance, as a relative offset amount, how much the reference value θosr of the output shaft rotation angle deviates with respect to the motor electric angle origin θmd and add the relative offset amount (correct with the relative offset amount) when estimating the motor electric angle.

The second relative offset amount estimation unit71estimates a second relative offset amount θoff2when the abnormality detection signal SAr has the value representing the presence of abnormality in an initial diagnosis by the resolver abnormality diagnosis unit61after a system restart in which the IGN switch28is again turned ON from a system stop in which the ING switch28is in an OFF state. Then, the estimated second relative offset amount θoff2is stored in the RAM50. In addition, the resolver abnormality diagnosis unit61of the first embodiment is configured to perform diagnosis immediately after the IGN switch28is turned on and the system starts.

Herein, in a case where, for example, the resolver23ahas had a failure during a previous system start or a failure has occurred, for example, in the resolver23aduring the system stop, the resolver23ais diagnosed as being abnormal in an initial diagnosis after the present system start. In this case, all angle data and the like obtained during the previous system start will be lost. Additionally, there is also a case where a driver operates the steering wheel11during a system stop.

Accordingly, when the resolver23ais diagnosed as being abnormal in an initial diagnosis after a system restart, it is necessary to estimate the motor electric angle origin θmd and estimate the second relative offset amount θoff2on the basis of the estimated motor electric angle origin θmd.

(Second Relative Offset Amount Estimation Unit71)

Next, a description will be given of a specific structure of the second relative offset amount estimation unit71according to the first embodiment.

The second relative offset amount estimation unit71of the first embodiment includes a harmonic command output unit110, an electric angle initial value estimation unit111, an electric angle initial value correction unit112, a first magnetic saturation command output unit113, and an offset amount estimation processing unit114, as depicted inFIG. 11.

The harmonic command output unit110outputs a first voltage output command Voi1to the control computation device31when the abnormality detection signal SAr has the value representing the presence of abnormality in the initial diagnosis after the system restart. Herein, the first voltage output command Voi1is an output command for a harmonic voltage command at such a level that the rotor22R of the three-phase electric motor22does not rotate and no magnetic saturation occurs in the stator22S.

The control computation device31of the first embodiment generates a voltage command for energization with a harmonic voltage according to input of the first voltage output command Voi1, and outputs the generated voltage command to the gate drive circuits41A and41B. In this way, energization with harmonic voltage to the three-phase electric motor22is performed via the first and second inverter circuits42A and42B.

The electric angle initial value estimation unit111acquires, via the current detection circuits34A and34B, the current detection value Im of a current that flows to the three-phase electric motor22in response to application of the harmonic voltage, and detects a first current peak value Imp1that is a peak value of the acquired current detection value Im.

Herein, in response to the application of the harmonic voltage, a current which is dependent on the motor electric angle θm flows to the three-phase electric motor22. Specifically, the first current peak value Imp1as the peak value of the above-mentioned current has information of the motor electric angle.

Thus, in the first embodiment, a relationship between the first current peak value Imp1and information θmi of the motor electric angle θm (hereinafter may be described as “motor electric angle information θmi”) is prepared as a map in advance, and the map (hereinafter may be described as “electric angle information map”) is stored in the ROM51.

The electric angle initial value estimation unit111reads the motor electric angle information θmi by referring to the electric angle information map stored in the ROM51from the detected first current peak value Imp1, and estimates a motor electric angle initial value θms on the basis of the read motor electric angle information θmi. Then, the estimated motor electric angle initial value θms is output to the electric angle initial value correction unit112.

In response to the input of the motor electric angle initial value θms, the electric angle initial value correction unit112outputs an output command for a voltage command (hereinafter may be described as “first magnetic saturation voltage command”) which is large to the extent that the rotor22R of the three-phase electric motor22does not rotate and magnetic saturation occurs in the stator22S to the first magnetic saturation command output unit113.

The first magnetic saturation command output unit113outputs a first saturation voltage output command Vsi1that is an output command for the first magnetic saturation voltage command to the control computation device31in response to the output command from the electric angle initial value correction unit112.

The control computation device31of the first embodiment generates the first magnetic saturation voltage command in response to the input of the first saturation voltage output command Vsi1, and outputs the generated first magnetic saturation voltage command to the gate drive circuits41A and41B. In this way, the energization to the three-phase electric motor22with a harmonic voltage which is large to the extent that magnetic saturation occurs (hereinafter may be described as “first magnetic saturation voltage”) is performed via the first and second inverter circuits42A and42B.

The electric angle initial value correction unit112acquires, via the current detection circuits34A and34B, the current detection value Im of a current that flows to the three-phase electric motor22in response to the application of the first magnetic saturation voltage, and detects a second current peak value Imp2that is a peak value of the acquired current detection value Im.

Herein, even in the case of application of the first magnetic saturation voltage, a current which is dependent on the motor electric angle θm flows to the three-phase electric motor22. The magnitude of a vector of the current has a feature that the magnitude of the vector is larger when oriented in a north pole direction than when oriented in a south pole direction. In other words, the second current peak value Imp2of the current has information for discriminating the directions (the north pole direction and the south pole direction) in which the vector of the first current peak value Imp1is oriented, and the motor electric angle initial value θms can be corrected on the basis of the information.

Thus, in the first embodiment, a relationship between the second current peak value Imp2and correction information Cm of the motor electric angle initial value θms (hereinafter may be described as “motor electric angle correction information Cm”) is prepared as a map in advance, and the map (hereinafter may be described as “correction information map”) is stored in the ROM51.

The electric angle initial value correction unit112reads the motor electric angle correction information Cm by referring to the correction information map stored in the ROM51from the detected second current peak value Imp2, and corrects the motor electric angle initial value θms on the basis of the read motor electric angle correction information Cm. Then, a corrected motor electric angle initial value θmsc is output to the offset amount estimation processing unit114.

The offset amount estimation processing unit114estimates the motor electric angle origin θmd on the basis of the corrected motor electric angle initial value θmsc, and estimates the second relative offset amount θoff2on the basis of the motor electric angle origin θmd and the reference value θosr of the output shaft rotation angle at the time of a system restart. Then, the estimated second relative offset amount θoff2is stored in the RAM50.

When the abnormality detection signal SAr has the value representing the presence of abnormality while system is running, the relative offset amount selection unit72selects the first relative offset amount θoff1, whereas when the abnormality detection signal SAr has the value representing the presence of abnormality in an initial diagnosis after a system restart, the relative offset amount selection unit72selects the second relative offset amount θoff2. Then, the relative offset amount selection unit72reads, from the RAM50, either one selected from the first relative offset amount θoff1and the second relative offset amount θoff2, and outputs the selected relative offset amount as the relative offset amount θoff to the motor electric angle estimation unit63.

Next, operation of the first embodiment will be described.

In an operation stopped state in which the IGN switch28is in an OFF state and thus the vehicle1is stopped, and also the steering assist control processing is stopped, the control computation device31and the motor electric angle detection circuit23of the motor control device25are in a non-operation state.

Due to this, various kinds of processing to be executed by the control computation device31and the motor electric angle detection circuit23are stopped. In this state, the three-phase electric motor22is out of operation, and thus output of a steering assist force to the steering mechanism is stopped.

When the IGN switch28is turned on from the operation stopped state, the control computation device31and the motor electric angle detection circuit23are brought into an operation state and start various kinds of processing such as processing for detecting the motor electric angle θm and steering assist control processing. At this time, it is assumed that the resolver23aand the angle computation unit60are normal.

In this case, the abnormality detection signal SAr has the value representing the absence of abnormality, and the electric angle selection unit23doutputs, as the motor electric angle θm, the first motor electric angle θm1computed by the angle computation unit60to the control computation device31.

On the basis of the motor electric angle θm, the control computation device31calculates the d-axis current command value Id* and the q-axis current command value Iq*. Then, on the basis of the d-axis current command value Id* and the q-axis current command value Iq*, the control computation device31calculates the three-phase voltage command values V1* and V2* for the first and second motor drive circuits32A and32B, and outputs the calculated three-phase voltage command values V1* and V2* to the first and second motor drive circuits32A and32B. Accordingly, the first and second motor drive circuits32A and32B drive-control the first and second inverter circuits42A and42B, thereby drive-controlling (controlling commutation of) the three-phase electric motor22.

On the other hand, when the resolver23aand the angle computation unit60are normal, the relative offset amount estimation unit62of the sub motor electric angle detection circuit23cperforms processing for estimating the first relative offset amount θoff1. Specifically, on the basis of the output shaft rotation angle detection value θos detected by the output-side rotation angle sensor13cand the motor electric angle θm output from the main motor electric angle detection circuit23bat the normal time, the first relative offset amount θoff1is estimated, and the estimated first relative offset amount θoff1is stored in the RAM50.

Then, when the resolver23aand the angle computation unit60are normal, the relative offset amount estimation unit62of the first embodiment outputs the first relative offset amount θoff1stored in the RAM50as the relative offset amount θoff to the motor electric angle estimation unit63.

The motor electric angle estimation unit63calculates, when the resolver23aand the angle computation unit60are normal, the motor electric angle estimation value θme from the output shaft rotation angle detection value θos detected by the output-side rotation angle sensor13c, the first relative offset amount θoff1, the deceleration ratio RGr (for example, 20.5), and magnetic pole pairs (for example, 4). Then, the motor electric angle estimation value θme is output as the second motor electric angle θm2to the electric angle selection unit23d.

After that, when a failure occurs in at least one of the resolver23aand the angle computation unit60while system is running and the abnormality detection signal SAr has the value representing the presence of abnormality, the electric angle selection unit23doutputs, as the motor electric angle θm, the second motor electric angle θm2input from the sub motor electric angle detection circuit23cto the control computation device31.

Accordingly, the control computation device31drive-controls (controls commutation of) the three-phase electric motor22on the basis of the second motor electric angle θm2estimated by the sub motor electric angle detection circuit23c.

Subsequently, it is assumed that the IGN switch28is once turned off and the system is stopped, and after that, the IGN switch28is turned on again and the system is restarted.

In this case, the abnormality detection signal SAr has the value representing the presence of abnormality due to an initial diagnosis by the resolver abnormality diagnosis unit61after the system restart, and the relative offset amount estimation unit62performs processing for estimating the second relative offset amount θoff2.

Specifically, the relative offset amount estimation unit62first causes the harmonic command output unit110to output the first voltage output command Voi1to the control computation device31, which then applies a harmonic voltage at such a level that the rotor22R does not rotate and no magnetic saturation occurs in the stator22S to the three-phase electric motor22. For example, assume that a harmonic voltage having a waveform as depicted inFIG. 12Ais applied. Next, the electric angle initial value estimation unit111detects the first current peak value Imp1from the current detection value Im of a current that flows to the three-phase electric motor22in response to the application of the harmonic voltage. For example, when assuming that a response current as indicated by a solid line L1inFIG. 12Bflows, a peak value indicated by “o” in the same drawing is detected as the first current peak value Imp1. The electric angle initial value estimation unit111acquires the motor electric angle information θmi by referring to the electric angle information map stored in the ROM51from the detected first current peak value Imp1, and estimates the motor electric angle initial value θms on the basis of the acquired motor electric angle information θmi.

Subsequently, the relative offset amount estimation unit62causes the first magnetic saturation command output unit113to output the first saturation voltage output command Vsi1to the control computation device31, which then applies a harmonic voltage at such a level that the rotor22R does not rotate and magnetic saturation occurs in the stator S22(the first magnetic saturation voltage) to the three-phase electric motor22. Then, the electric angle initial value correction unit112detects the second current peak value Imp2from the current detection value Im of a current that flows to the three-phase electric motor22in response to the application of the first magnetic saturation voltage. For example, when assuming that a response current as indicated by a dot-and-dash line L2inFIG. 12Bflows, a peak value indicated by “0” in the same drawing is detected as the second current peak value Imp2. The electric angle initial value correction unit112acquires the motor electric angle correction information Cm by referring to the correction information map stored in the ROM51from the detected second current peak value Imp2, and corrects the motor electric angle initial value θms on the basis of the acquired motor electric angle correction information Cm.

Subsequently, the relative offset amount estimation unit62causes the offset amount estimation processing unit114to estimate the motor electric angle origin θmd on the basis of the corrected motor electric angle initial value θmsc, and to estimate the second relative offset amount θoff2on the basis of the motor electric angle origin θmd and the reference value θosr of the output shaft rotation angle acquired at the time of the system restart. Then, the estimated second relative offset amount θoff2is stored in the RAM50.

Furthermore, the relative offset amount estimation unit62causes the relative offset amount selection unit72to read the second relative offset amount θoff2from the RAM50since the abnormality detection signal SAr has the value representing the presence of abnormality due to the initial diagnosis after the system restart. Further, the relative offset amount estimation unit62causes the relative offset amount selection unit72to output the read second relative offset amount θoff2, as the relative offset amount θoff, to the motor electric angle estimation unit63.

Accordingly, the motor electric angle estimation unit63calculates the motor electric angle estimation value θme from the output shaft rotation angle detection value θos detected by the output-side rotation angle sensor13c, the second relative offset amount θoff2, the deceleration ratio RGr (for example, 20.5), and magnetic pole pairs (for example, 4). Then, the calculated motor electric angle estimation value θme is output as the second motor electric angle θm2to the electric angle selection unit23d.

Since the abnormality detection signal SAr has the value representing the presence of abnormality, the electric angle selection unit23doutputs, as the motor electric angle θm, the second motor electric angle θm2input from the sub motor electric angle detection circuit23cto the control computation device31.

Accordingly, the control computation device31drive-controls (controls commutation of) the three-phase electric motor22on the basis of the second motor electric angle θm2estimated by the sub motor electric angle detection circuit23c.

Additionally, the steering torque sensor13corresponds to a torque detection unit, the output-side rotation angle sensor13ccorresponds to a steering angle detection unit, the three-phase electric motor22corresponds to a multi-phase electric motor, and the resolver23aand the angle computation unit60correspond to a motor electric angle detection unit.

Additionally, the first and second inverter circuits42A and42B correspond to a motor drive circuit, the control computation device31corresponds to a control computation device, and the resolver abnormality diagnosis unit61corresponds to an abnormality diagnosis unit.

Effects of First Embodiment

(1) In the motor control device25according to the first embodiment, the electric angle initial value estimation unit111estimates the motor electric angle initial value θms on the basis of a response output (a response current) of the three-phase electric motor22in response to input of a motor drive signal (a harmonic voltage) to the three-phase electric motor22when at least one of the resolver23aand the angle computation unit60that detect the motor electric angle θm of the three-phase electric motor22that generates a steering assist force is diagnosed as being abnormal in an initial diagnosis after a system restart. The motor electric angle estimation unit63estimates the motor electric angle θm on the basis of the output shaft rotation angle detection value θos and the motor electric angle initial value θms (the second relative offset amount θoff2estimated on the basis thereof). When the resolver23aand the angle computation unit60are normal, the control computation device31and the motor electric angle detection circuit23drive-control the three-phase electric motor22on the basis of the first motor electric angle θm1detected by these components. On the other hand, when at least one of the resolver23aand the angle computation unit60is abnormal in an initial diagnosis after a system restart, the control computation device31and the motor electric angle detection circuit23drive-control the three-phase electric motor22on the basis of the second motor electric angle θm2estimated by the motor electric angle estimation unit63.

With this structure, when at least one of the resolver23aand the angle computation unit60is diagnosed as being abnormal in an initial diagnosis after a system restart, it is possible to estimate the motor electric angle initial value θms on the basis of a response output of the three-phase electric motor22in response to input of a motor drive signal to the three-phase electric motor22and estimate the motor electric angle θm on the basis of the estimated motor electric angle initial value θms and the output shaft rotation angle detection value θos.

Accordingly, the three-phase electric motor22can be driven equivalently to normal time after a system restart even in a case where the system has been restarted after having once been stopped from the time when at least one of the revolver23aand the angle computation unit60was diagnosed as being abnormal or where abnormality has occurred during a system stop.

(2) In the motor control device25according to the first embodiment, the steering torque sensor13detects the steering torque T transmitted to the steering mechanism. The output-side rotation angle sensor13cdetects a steering angle (the output shaft rotation angle detection value θos) of the steering. The three-phase electric motor22generates a steering assist force. The resolver23aand the angle computation unit60detect the motor electric angle θm of the three-phase electric motor22. The first and second inverter circuits42A and42B supply a drive current to the three-phase electric motor22. The control computation device31drive-controls the first and second inverter circuits42A and42B on the basis of the steering torque T detected by the steering torque sensor13and the motor electric angle θm detected by the resolver23aand the angle computation unit60.

In addition, the resolver abnormality diagnosis unit61diagnoses abnormality in the resolver23aand the angle computation unit60. When at least one of the resolver23aand the angle computation unit60that detect the motor electric angle θm of the three-phase electric motor22that generates a steering assist force is diagnosed as being abnormal in the initial diagnosis after the system restart, the electric angle initial value estimation unit111estimates the motor electric angle initial value θms on the basis of a response output (a response current) of the three-phase electric motor22in response to the input of a motor drive signal (a harmonic voltage) to the three-phase electric motor22.

Furthermore, the motor electric angle estimation unit63estimates the motor electric angle θm on the basis of the output shaft rotation angle detection value θos detected by the output-side rotation angle sensor13cand the motor electric angle initial value θms estimated by the electric angle initial value estimation unit111(the second relative offset amount θoff2estimated on the basis thereof). When at least one of the resolver23aand the angle computation unit60is diagnosed as being abnormal in an initial diagnosis by the resolver abnormality diagnosis unit61after a system restart, the control computation device31drive-controls the first and second inverter circuits42A and42B on the basis of the steering torque T detected by the steering torque sensor13and the motor electric angle estimation value θme estimated by the motor electric angle estimation unit63(the second motor electric angle θm2).

With this structure, when at least one of the resolver23aand the angle computation unit60is diagnosed as being abnormal in an initial diagnosis after a system restart, it is possible to estimate the motor electric angle initial value θms on the basis of a response output of the three-phase electric motor22in response to input of a motor drive signal to the three-phase electric motor22and estimate the motor electric angle θm on the basis of the estimated motor electric angle initial value θms and the output shaft rotation angle detection value θos.

Accordingly, the three-phase electric motor22can be driven equivalently to normal time after a system restart even in a case where the system has been restarted after having once been stopped from the time when at least one of the revolver23aand the angle computation unit60was diagnosed as being abnormal or where abnormality has occurred during a system stop.

(3) In the motor control device25according to the first embodiment, the electric angle initial value estimation unit111estimates the motor electric angle initial value θms on the basis of the current response at the time when the harmonic energization has been made to the three-phase electric motor22.

With this structure, it is possible to estimate the motor electric angle initial value θms on the basis of the current response which is dependent on the motor electric angle of the three-phase electric motor22in response to the harmonic energization to the three-phase electric motor22. For example, it is possible to estimate the motor electric angle initial value θms on the basis of motor electric angle information obtained from a peak value or the like of the response current.

Accordingly, even when at least one of the resolver23aand the angle computation unit60is diagnosed as being abnormal in an initial diagnosis after a system restart, it is possible to estimate a motor electric angle that can accurately control commutation of the three-phase electric motor22.

(4) In the motor control device25according to the first embodiment, the electric angle initial value correction unit112corrects the motor electric angle initial value θms on the basis of the current response at the time when the harmonic energization at such a level that magnetic saturation occurs has been applied to the three-phase electric motor22.

With this structure, it is possible to correct the motor electric angle initial value θms on the basis of a current response which is dependent on the motor electric angle of the three-phase electric motor22in response to the harmonic energization at such a level that magnetic saturation occurs applied to the three-phase electric motor22. For example, the motor electric angle initial value θms can be corrected on the basis of information obtained from a peak value or the like of the response current.

Accordingly, a more accurate motor electric angle initial value θms can be obtained.

(5) The electric power steering device3according to the first embodiment includes the motor control device25.

With this structure, functions and effects equivalent to those of the motor control device25described in the (1) to (4) above can be obtained, and also the steering assist control can be continued even upon failure of the resolver23aand the angle computation unit60, so that reliability of the electric power steering device3can be improved.

(6) The vehicle1according to the first embodiment includes the electric power steering device3including the motor control device25.

With this structure, functions and effects equivalent to those of the motor control device25described in the (1) to (4) above can be obtained, and also steering assist control can be continued even upon failure of the resolver23a, so that reliability of the vehicle1can be improved.

Second Embodiment

The second embodiment is different from the first embodiment in that the former includes a third relative offset amount estimation unit73instead of the second relative offset amount estimation unit71in the relative offset amount estimation unit62of the above first embodiment, and is the same as the first embodiment except for the difference.

Hereinafter, the same structural parts as those of the first embodiment are denoted by the same reference signs, and descriptions thereof will be omitted as appropriate, whereas different parts will be described in detail.

(Third Relative Offset Amount Estimation Unit73)

The third relative offset amount estimation unit73of the second embodiment includes a pulse command output unit115, the electric angle initial value estimation unit111, the electric angle initial value correction unit112, a second magnetic saturation command output unit116, and the offset amount estimation processing unit114, as depicted inFIG. 13.

The pulse command output unit115outputs a second voltage output command Voi2to the control computation device31when the abnormality detection signal SAr has the value representing the presence of abnormality in an initial diagnosis after a system restart. Herein, the second voltage output command Voi2is an output command for a pulse wave voltage command at such a level that the rotor22R of the three-phase electric motor22does not rotate and no magnetic saturation occurs in the stator22S.

The control computation device31of the second embodiment generates a voltage command for performing energization with a pulse wave voltage in response to input of the second voltage output command Voi2, and outputs the generated voltage command to the gate drive circuits41A and41B. Accordingly, the energization to the three-phase electric motor22, for example, with a pulse wave voltage depicted inFIG. 14is performed via the first and second inverter circuits42A and42B.

The electric angle initial value estimation unit111of the second embodiment acquires, via the current detection circuits34A and34B, the current detection value Im of a current that flows to the three-phase electric motor22in response to the application of the pulse wave voltage, and detects a third current peak value Imp3that is a peak value of the acquired current detection value Im.

Herein, a current which is dependent on the motor electric angle θm flows to the three-phase electric motor22in response to the application of the pulse wave voltage, similarly to the harmonic voltage of the first embodiment. Specifically, the third current peak value Imp3that is a peak value of the current has motor electric angle information.

Then, in the second embodiment, as in the above first embodiment, a relationship between the third current peak value Imp3and the motor electric angle information θmi is prepared as an electric angle information map in advance, and the electric angle information map is stored in the ROM51.

The electric angle initial value estimation unit111reads the motor electric angle information θmi by referring to the electric angle information map stored in the ROM51from the detected third current peak value Imp3, and estimates the motor electric angle initial value θms on the basis of the read motor electric angle information θmi. The estimated motor electric angle initial value θms is output to the electric angle initial value correction unit112.

The electric angle initial value correction unit112of the second embodiment outputs, in response to the input of the motor electric angle initial value θms, an output command for a voltage command with a pulse wave which is large to the extent (hereinafter may be described as “second magnetic saturation voltage command”) that the rotor22R of the three-phase electric motor22does not rotate and magnetic saturation occurs in the stator22S to the second magnetic saturation command output unit116.

The second magnetic saturation command output unit116outputs a second saturation voltage output command Vsi2that is an output command for the second magnetic saturation voltage command to the control computation device31in response to the output command from the electric angle initial value correction unit112.

The control computation device31of the second embodiment generates the second magnetic saturation voltage command in response to input of the second saturation voltage output command Vsi2, and outputs the generated second magnetic saturation voltage command to the gate drive circuits41A and41B. Accordingly, the energization with a pulse wave voltage (hereinafter may be described as “second magnetic saturation voltage”) which is large to the extent that the magnetic saturation occurs to the three-phase electric motor22is performed via the first and second inverter circuits42A and42B.

The electric angle initial value correction unit112acquires, via the current detection circuits34A and34B, the current detection value Im of a current that flows to the three-phase electric motor22in response to application of the second magnetic saturation voltage, and detects a fourth current peak value Imp4that is a peak value of the acquired current detection value Im.

Herein, even in the case of application of the second magnetic saturation voltage, a current which is dependent on the motor electric angle θm flows to the three-phase electric motor22. In other words, a current flows that has the same characteristics as those in the case of application of the first magnetic saturation voltage in the above first embodiment.

Thus, in the second embodiment, a relationship between the fourth current peak value Imp4and the motor electric angle correction information Cm is prepared as a correction information map in advance, and the correction information map is stored in the ROM51.

The electric angle initial value correction unit112reads the motor electric angle correction information Cm by referring to the correction information map stored in the ROM51from the detected fourth current peak value Imp4, and corrects the motor electric angle initial value θms on the basis of the read motor electric angle correction information Cm. Then, the corrected motor electric angle initial value θmsc is output to the offset amount estimation processing unit114.

The offset amount estimation processing unit114estimates the motor electric angle origin θmd on the basis of the corrected motor electric angle initial value θmsc from the electric angle initial value correction unit112, and estimates the second relative offset amount θoff2on the basis of the motor electric angle origin θmd and the reference value θosr of the output shaft rotation angle at the time of a system restart. Then, the estimated second relative offset amount θoff2is stored in the RAM50.

Additionally, the steering torque sensor13corresponds to a torque detection unit, the output-side rotation angle sensor13ccorresponds to a steering angle detection unit, the three-phase electric motor22corresponds to a multi-phase electric motor, and the resolver23aand the angle computation unit60correspond to a motor electric angle detection unit.

Additionally, the first and second inverter circuits42A and42B correspond to a motor drive circuit, the control computation device31corresponds to a control computation device, and the resolver abnormality diagnosis unit61corresponds to an abnormality diagnosis unit.

Effects of Second Embodiment

The second embodiment exhibits the following effects in addition to the effects of the first embodiment.

(1) In the motor control device25according to the second embodiment, the electric angle initial value estimation unit111estimates the motor electric angle initial value θms on the basis of the current response at the time when the pulse wave energization has been applied to the three-phase electric motor22.

With this structure, it is possible to estimate the motor electric angle initial value θms on the basis of the current response which is dependent on the motor electric angle of the three-phase electric motor22in response to the pulse wave energization applied to the three-phase electric motor22. For example, the motor electric angle initial value θms can be estimated on the basis of motor electric angle information obtained from a response current peak value or the like.

Accordingly, even when at least one of the resolver23aand the angle computation unit60is diagnosed as being abnormal in the initial diagnosis after the system restart, it is possible to estimate a motor electric angle that can control commutation of the three-phase electric motor22equivalently to normal time.

(2) In the motor control device25according to the second embodiment, the electric angle initial value correction unit112corrects the motor electric angle initial value θms on the basis of the current response at the time when the pulse wave energization at such a level that magnetic saturation occurs has been applied to the three-phase electric motor22.

With this structure, it is possible to correct the motor electric angle initial value θms on the basis of the current response which is dependent on the motor electric angle of the three-phase electric motor22in response to the pulse wave energization at such a level that magnetic saturation occurs applied to the three-phase electric motor22. For example, the motor electric angle initial value θms can be corrected on the basis of information obtained from a response current peak value or the like.

Accordingly, a more accurate motor electric angle initial value θms can be obtained.

Third Embodiment

The third embodiment is different from the above first embodiment in that the former includes a fourth relative offset amount estimation unit74instead of the second relative offset amount estimation unit71in the relative offset amount estimation unit62of the first embodiment, and is the same as the first embodiment except for the difference.

Hereinafter, the same structural parts as those in the first embodiment are denoted by the same reference signs, and descriptions thereof will be omitted as appropriate, whereas different parts will be described in detail.

(Fourth Relative Offset Amount Estimation Unit74)

The fourth relative offset amount estimation unit74of the third embodiment includes the harmonic command output unit110, the electric angle initial value estimation unit111, the electric angle initial value correction unit112, a step command output unit117, and the offset amount estimation processing unit114, as depicted inFIG. 15.

The electric angle initial value correction unit112of the third embodiment outputs an output command for a step wave voltage command (hereinafter may be described as “step voltage command”) at such a level that the rotor22R of the three-phase electric motor22does not rotate to the step command output unit117in response to the input of the motor electric angle initial value θms.

The step command output unit117outputs a step voltage output command Vsi3that is an output command for the step voltage command to the control computation device31in response to the output command from the electric angle initial value correction unit112.

The control computation device31of the third embodiment generates the step voltage command in response to the input of the step voltage output command Vsi3, and outputs the generated step voltage command to the gate drive circuits41A and41B. Accordingly, the energization with a step wave voltage (hereinafter may be described as “step wave voltage”) to the three-phase electric motor22is performed via the first and second inverter circuits42A and42B.

The electric angle initial value correction unit112acquires, via the current detection circuits34A and34B, the current detection value Im of a current that flows to the three-phase electric motor22in response to the application of, for example, a step wave voltage as indicated inFIG. 16, and detects a fifth current peak value Imp5that is a peak value of the acquired current detection value Im.

Herein, even in the case of application of the step wave voltage, a current which is dependent on the motor electric angle θm flows to the three-phase electric motor22. Thus, in the third embodiment, a relationship between the fifth current peak value Imp5and the motor electric angle correction information Cm is prepared as a correction information map in advance, and the correction information map is stored in the ROM51.

The electric angle initial value correction unit112reads the motor electric angle correction information Cm by referring to the correction information map stored in the ROM51from the detected fifth current peak value Imp5, and corrects the motor electric angle initial value θms on the basis of the read motor electric angle correction information Cm. Then, the corrected motor electric angle initial value θmsc is output to the offset amount estimation processing unit114.

The offset amount estimation processing unit114estimates the motor electric angle origin θmd on the basis of the corrected motor electric angle initial value θmsc from the electric angle initial value correction unit112. Furthermore, the offset amount estimation processing unit114estimates the second relative offset amount θoff2on the basis of the motor electric angle origin θmd and the reference value θosr of the output shaft rotation angle at the time of a system restart. Then, the estimated second relative offset amount θoff2is stored in the RAM50.

Additionally, the steering torque sensor13corresponds to a torque detection unit, the output-side rotation angle sensor13ccorresponds to a steering angle detection unit, the three-phase electric motor22corresponds to a multi-phase electric motor, and the resolver23aand the angle computation unit60correspond to a motor electric angle detection unit.

Additionally, the first and second inverter circuits42A and42B correspond to a motor drive circuit, the control computation device31corresponds to a control computation device, and the resolver abnormality diagnosis unit61corresponds to an abnormality diagnosis unit.

Effects of Third Embodiment

The third embodiment exhibits the following effects in addition to the effects of the first and second embodiments.

(1) In the motor control device25according to the third embodiment, the motor electric angle initial value θms is corrected on the basis of the current response at the time when the step-shaped wave energization has been applied to the three-phase electric motor22.

With this structure, it is possible to correct the motor electric angle initial value θms on the basis of the current response which is dependent on the motor electric angle of the three-phase electric motor22in response to the step-shaped wave energization applied to the three-phase electric motor22. For example, the motor electric angle initial value θms can be corrected on the basis of information obtained from a response current peak value or the like.

Accordingly, a more accurate motor electric angle initial value θms can be obtained.

(1) The above embodiments have been configured to estimate the motor electric angle on the basis of the output shaft rotation angle detection value θos detected by the output-side rotation angle sensor13cforming the steering torque sensor13. However, the invention is not limited to the configuration. For example, the motor electric angle may be estimated on the basis of a rotation angle detected by another sensor as long as it is a sensor that detects the rotation angle of a shaft that rotates by operation of the steering wheel11, such as that the motor electric angle is estimated on the basis of an input shaft rotation angle θ is detected by the input-side rotation angle sensor13b.

(2) The above embodiments have described the case where the d-axis current command value Id* and the q-axis current command value Iq* are calculated on the basis of the steering assist current command value by the steering assist control processing of the control computation device31, the dq-phase to three-phase conversion of these values is performed to calculate the U-phase current command value Iu*, the V-phase current command value Iv*, and the W-phase current command value Iw*, and the current deviations ΔIu, ΔIv, and ΔIw between the values Iu*, Iv*, and Iw* and added values of the current detection values of the respective phases are calculated. However, the present invention is not limited to the above configuration. The added values of the current detection values of the respective phases may be dq-axis converted, deviations ΔId and ΔIq between the dq-axis converted values and the d-axis current command value Id* and the q-axis current command value Iq* may be calculated, and the deviations ΔId and ΔIq may be dq-phase to three-phase converted.

(3) The above embodiments have described the example in which the present invention is applied to the column assist electric power steering device. However, the present invention is not limited to this configuration, and, for example, the present invention may be applied to a rack assist or pinion assist electric power steering device.

While the present invention has been described with reference to the limited number of embodiments, the scope of the invention is not limited thereto, and modifications of the respective embodiments based on the above disclosure are obvious to those skilled in the art.

REFERENCE SIGNS LIST

1Vehicle3Electric power steering device11Steering wheel12Steering shaft12bOutput shaft13Steering torque sensor13cOutput-side rotation angle sensor18Steering gear20Steering assist mechanism22Three-phase electric motor23Motor electric angle detection circuit23aResolver23bMain motor electric angle detection circuit23cSub motor electric angle detection circuit23dElectric angle selection unit25Motor control device26Vehicle speed sensor27Battery28IGN switch31Control computation device32A First motor drive circuit32B Second motor drive circuit33A First motor current block circuit33B Second motor current block circuit34A,34B Current detection circuit35A First abnormality detection circuit35B Second abnormality detection circuit41A,41B Gate drive circuit42A First inverter circuit42B Second inverter circuit43Noise filter44A First power supply block circuit44B Second power supply block circuit60Angle computation unit61Resolver abnormality diagnosis unit62Relative offset amount estimation unit63Motor electric angle estimation unit70First relative offset amount estimation unit71,73,74Second, third, fourth relative offset amount estimation unit72Relative offset amount selection unit110Harmonic command output unit111Electric angle initial value estimation unit112Electric angle initial value correction unit113,116First, second magnetic saturation command output unit114Offset amount estimation processing unit115Pulse command output unit117Step command output unit