JP2012116372A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device which can control electric motor using a presumed rotation angle when failure of a rotation angle sensor of the electric motor.SOLUTION: A control device 200 includes: a failure detection part 290 which detects a failure of a resolver 50; and a rotation angle estimation part 291 which presumes a rotation angle of the electric motor 11 based on an extended induced voltage. The control device 200, when the resolver 50 is normal, carries out drive control of the electric motor 11 based on steering torque T and rotation angle θfrom the resolver 50, and when the resolver 50 is failure, carries out drive control of the electric motor 11 based on the presumed rotation angle θpresumed by steering torque T and rotation angle estimation part 291. A base signal operation part 220 carries out enlargement setting of width of a second dead zone of a second base table 220b which is used in failure of the resolver 50, rather than width of a first dead zone of a first base table used when the resolver 50 is normal.

Description

  The present invention relates to an electric power steering device, and more particularly, when a rotation angle sensor that detects a rotation angle of a rotor of a motor (motor) fails, auxiliary torque generated by the motor is appropriately generated thereafter. The present invention relates to an electric power steering apparatus capable of performing the above.

In the electric power steering apparatus, the electric motor generates an auxiliary torque corresponding to the magnitude of the steering torque, and transmits the auxiliary torque to the steering system to reduce the steering force that the driver steers. Disclosed is a technology that compensates or corrects the damping of the base current (assist torque) determined by the steering torque and vehicle speed with the inertia (inertia) of the steering system, and controls the motor using the compensated and corrected current as a target current. (See Patent Documents 1 and 2).
Note that only the output from the steering torque sensor is input to the inertia compensation current value determining means of Patent Document 2, and no vehicle speed signal is input.

  In Patent Document 3, when the rotation angle sensor that detects the rotation angle of the rotor of the electric motor (brushless motor) fails, the rotation angle of the rotor is estimated based on the induced voltage of the coil of the brushless motor. A technique for controlling electric power steering is disclosed. In the technique of Patent Document 3, when the maximum induced voltage of the coil is less than a predetermined value, the steering direction detected by the steering torque sensor is determined, and a rotating magnetic field is generated in the rotational direction corresponding to the steering direction. Discloses a technique for driving and controlling an electric motor.

  Patent Document 4 discloses a sensorless control technique that does not use a rotation angle sensor for rotation control of a brushless motor, and particularly discloses a technique for rotationally driving the brushless DC motor from a stopped state.

JP 2002-59855 A (FIG. 2) Japanese Patent Laid-Open No. 2000-177615 (FIG. 2) JP 2009-46015 A (FIG. 2) JP 2009-142073 A

  However, in the technique described in Patent Document 3, when the maximum induced voltage of the coil of the brushless motor is less than a predetermined value, the steering direction detected by the steering torque sensor is determined, and the motor rotates in the rotation direction corresponding to the steering direction. Since the rotational angular velocity of the brushless motor and the rotational velocity of the rotating magnetic field do not match or the rotational control of the motor is switched due to a failure of the rotational angle sensor, the rotating magnetic field is generated to control the magnetic field to be generated. When the magnetic field is inappropriate for the rotor magnetic poles, the driver feels a discontinuous change in the steering reaction force. In addition, since the driver does not feel that the electric power steering control has failed due to the failure of the rotation angle sensor, the driver feels uncomfortable.

The technique described in Patent Document 4 is a technique for resuming the rotation control of a rotating brushless motor when the output from the inverter is stopped for some reason in the rotation control of the brushless motor. In the apparatus, when the rotation angle sensor of the brushless motor fails, it cannot be directly used for the purpose of resuming the control of the electric power steering apparatus without using the signal from the rotation angle sensor.
Incidentally, Patent Document 4 discloses a technique using an extended induced voltage observer.

  An object of the present invention is to provide an electric power steering apparatus that can control an electric motor using an estimated rotation angle when a rotation angle sensor of the electric motor of the electric power steering apparatus fails.

In order to solve the above-described problem, an electric power steering apparatus according to claim 1 includes a steering torque sensor that detects a steering torque input to a steered wheel, an electric motor that assists the operation of the steered wheel by generating an assist torque, Rotation by a rotation angle sensor for detecting the rotation angle of the motor, failure detection means for detecting a failure of the rotation angle sensor, rotation angle estimation means for estimating the rotation angle of the motor based on the induced voltage of the motor, and rotation by the failure detection means If no failure of the angle sensor is detected, the motor is driven and controlled based on the steering torque detected by the steering torque sensor and the rotation angle detected by the rotation angle sensor, and the failure detection means detects the failure of the rotation angle sensor. The motor is driven based on the steering torque detected by the steering torque sensor and the rotation angle estimated by the rotation angle estimation means. A motor drive control means Gosuru, in which comprises,
The motor drive control means has a dead zone in which the motor is not driven with respect to the steering torque when the failure detection means does not detect a failure of the rotation angle sensor, with the first upper limit value and the first lower limit value as widths. 1 is set as a dead zone, and when a failure of the rotation angle sensor is detected by the failure detection means, the dead zone in which the motor is not driven with respect to the steering torque is set as the second upper limit value and the second lower limit value as the width. As the second dead zone, the upper limit value and the lower limit value are both set wider than the first dead zone,
When the detected steering torque exceeds the second upper limit value or the second lower limit value of the second dead zone, the rotation angle estimation means is induced by rotation of the electric motor by the operation of the driver's steering wheel. Estimate the rotation angle based on the voltage,
The motor drive control means starts driving control of the motor based on the estimated rotation angle.

According to the first aspect of the present invention, the motor drive control means sets the dead zone in which the motor is not driven with respect to the steering torque when the failure detection means does not detect the failure of the rotation angle sensor as the first upper limit value. And a first dead zone having a width of the first lower limit value, and when a failure of the rotation angle sensor is detected by the failure detection means, a dead zone that does not drive the motor with respect to the steering torque is set to the second dead zone. As the second dead zone having the upper limit value and the second lower limit value as the width, both the upper limit value and the lower limit value are set wider than the first dead zone. When the detected steering torque exceeds the second upper limit value or the second lower limit value of the second dead zone, the rotation angle estimation means is caused by the rotation of the electric motor by the operation of the steering wheel of the driver. The rotation angle is estimated based on the generated induced voltage.
Accordingly, when a failure of the rotation angle sensor is detected by the failure detection means, the second upper limit value or the second upper limit value of the second dead zone in which the steering torque detected by the driver manually operating the steered wheels is increased. When the lower limit value of 2 is exceeded, the electric motor becomes higher in rotation speed due to the manual operation of the steered wheels due to the generation of absolute steering torque that is larger than the first upper limit value and the first lower limit value. As a result, the rotation angle can be estimated more accurately based on a larger induced voltage generated by the electric motor.

Then, when the detected steering torque exceeds the second upper limit value or the second lower limit value, the motor drive control means starts driving control of the motor based on the estimated accurate rotation angle. The electric motor can be driven and controlled by the accurately estimated rotation angle without generating an auxiliary torque in the direction opposite to the direction of operation of the steering wheel of the driver.
According to the invention described in claim 1, in the technique described in Patent Document 3, when the maximum induced voltage is less than a predetermined value, the operation direction of the steered wheel indicated by the steering torque is determined, and a constant rotating magnetic field is determined. For example, when the rotational speed of the rotating magnetic field is slower than the actual rotational angular speed of the electric motor, the driver is given a feeling of strangeness that the steering reaction force increases.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect of the present invention, the electric power steering apparatus is in a state where the electric motor drive control means detects a steering torque exceeding the second dead zone in the steering torque sensor. When a failure of the rotation angle sensor is detected by the detection means, the drive control of the electric motor is not performed based on the detected steering torque and the estimated rotation angle.

  According to the second aspect of the present invention, in the state in which the motor drive control means detects the steering torque exceeding the second dead zone in the steering torque sensor, the failure detection means detects a failure of the rotation angle sensor. In such a case, the drive control of the electric motor is not performed based on the detected steering torque and the estimated rotation angle.

Therefore, when a failure of the rotation angle sensor is detected by the failure detection means, the driver feels that the output of the auxiliary torque from the electric motor has been lost due to a sudden increase in the steering reaction force, and recognizes the failure of the rotation angle sensor. be able to.
In the case of the drive control of the electric motor as in the technique described in Patent Document 3, the rotation of the electric motor from the rotation angle sensor is determined until the motor drive control means determines that the rotation angle sensor has failed. What has been drive control of the motor based on the angle until now is the estimated motor rotation angle output from the rotation angle estimation means immediately after it is determined that the rotation angle sensor has failed. Based on this, drive control of the electric motor is performed, and discontinuity of the drive control occurs, and the driver feels the discontinuity of the steering reaction force from the steered wheels.

Therefore, according to the second aspect of the present invention, it is possible to prevent such a discontinuity of the drive control from occurring and cause the driver to feel the discontinuity of the steering reaction force from the steered wheels. Can recognize that the rotation angle sensor has failed.
Of course, after that, when the absolute value of the steering torque decreases and falls within the range of the second dead zone, and then the steering torque exceeds the second upper limit value or lower limit value of the second dead zone, the steering torque and The drive control of the electric motor can be started based on the estimated rotation angle.

  According to a third aspect of the present invention, in addition to the configuration of the first or second aspect of the invention, the motor drive control means sets at least the width of the first dead zone in accordance with an increase in the vehicle speed. Then, the first dead zone of the first dead zone that is enlarged according to the increase in the vehicle speed with respect to the second upper limit value and the second lower limit value of the second dead zone that are applied when a rotation angle sensor failure is detected. When the upper limit value of 1 and the first lower limit value exceed the second upper limit value and the second lower limit value, the first dead zone is used as the second dead zone.

According to the invention described in claim 3, the electric motor drive control means is applied when at least the width of the first dead zone is enlarged according to the increase of the vehicle speed and a failure of the rotation angle sensor is detected. With respect to the second upper limit value and the second lower limit value of the second dead zone, the first upper limit value and the first lower limit value of the first dead zone, which are set to be enlarged according to the increase in the vehicle speed, are the second upper limit value. When the value exceeds the value and the second lower limit value, the first dead zone is used as the second dead zone.
If it is determined that the rotation angle sensor is out of order and the drive control of the electric motor is continued based on the estimated rotation angle and steering torque, the first upper limit is increased as the vehicle speed increases according to the vehicle speed. The first upper limit value and the first lower limit value are set to be widened, and the second upper limit value and the second lower limit value are set as widths for the same vehicle speed. If the width of the second dead zone is set to be wider than the width of the first dead zone, the rotation angle estimated due to the failure of the rotation angle sensor is driven in the middle and high vehicle speed range. When used for the control, the driver feels that the steering force is heavier than the normal steering sensation, giving a sense of discomfort.
Therefore, according to the third aspect of the present invention, this can be prevented. For example, when the steering wheel is operated during a lane change during high-speed traveling, the rotation angle sensor operates normally, and the drive control of the motor is performed based on the steering torque and rotation angle. Therefore, based on the steering torque and the estimated rotation angle, the operation feeling given to the driver can be made the same as when the drive control of the electric motor is performed.

  According to a fourth aspect of the present invention, there is provided the electric power steering apparatus according to any one of the first to third aspects, wherein the rotation angle estimating means is an induced voltage generated along with the rotation of the rotor of the electric motor. It includes an extended induced voltage observer for calculating and detecting.

  According to the fourth aspect of the present invention, the rotation angle estimating means includes the extended induced voltage observer for calculating and detecting the induced voltage generated along with the rotation of the rotor of the electric motor. After detecting the failure of the motor, the driver operates the steered wheel only by hand, and the induced voltage generated by the rotation of the rotor of the motor is calculated and detected by the expanded induced voltage observer. Can be calculated based on the induced voltage.

  According to the present invention, when the rotation angle sensor of the motor of the electric power steering apparatus fails, the rotation angle is accurately estimated based on the induced voltage, and thereafter, the motor can be controlled using the estimated rotation angle. An electric power steering apparatus can be provided.

It is a lineblock diagram of the electric power steering device which is an embodiment of the present invention. It is a functional block block diagram of the control apparatus of embodiment. It is explanatory drawing of the method in which a base signal calculating part sets a base target electric current value using a 1st base table. It is explanatory drawing of the method in which a base signal calculating part sets a base target electric current value using a 2nd base table. It is explanatory drawing of the method in which a damper correction signal calculating part sets a damper correction electric current value using a damper table. It is a flowchart which shows the flow of control of the electric power steering device when it is detected that the resolver has failed. It is a continuation of the flowchart of FIG. It is a continuation of the flowchart of FIG. It is explanatory drawing of the drive control of the electric motor of the electric power steering device accompanying the steering in each case when the resolver in the stop state of the vehicle is normal and at the time of failure, (a) is an explanatory view of the time transition of the steering torque, (B) is explanatory drawing of the time transition of the rotational angular velocity of an electric motor, and an electric motor drive current.

  An electric power steering apparatus according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram of an electric power steering apparatus according to an embodiment of the present invention, and FIG. 2 is a functional block configuration diagram of a control apparatus according to the embodiment.

<< Overall configuration of electric power steering system >>
In FIG. 1, an electric power steering device 100 includes a main steering shaft 3 provided with a steering handle (steering wheel) 2, a shaft 1, and a pinion shaft 5 having two universal joints (universal joints) 4, 4. Are connected by The pinion gear 7 provided at the lower end of the pinion shaft 5 meshes with the rack teeth 8a of the rack shaft 8 that can reciprocate in the vehicle width direction. The left and right steered wheels 10 are connected. With this configuration, the electric power steering apparatus 100 can change the traveling direction of the vehicle when the steering handle 2 is steered.
Here, the rack shaft 8, the rack teeth 8a, and the tie rods 9 and 9 constitute a turning mechanism.
The pinion shaft 5 is supported by the steering gear box 20 through the bearings 6a, 6b, and 6c at its lower, middle, and upper portions.

The electric power steering apparatus 100 includes an electric motor 11 that supplies an auxiliary torque for reducing the steering force by the steering handle 2, and a worm gear 12 provided on the output shaft of the electric motor 11 is connected to the pinion shaft 5. Is meshed with a worm wheel gear 13 provided on the wheel. That is, the worm gear 12 and the worm wheel gear 13 constitute a speed reduction mechanism.
Here, the rotator of the electric motor 11, the worm gear 12, the worm wheel gear 13, the pinion shaft 5, the rack shaft 8, the rack teeth 8a, the tie rods 9, 9 and the like connected to the electric motor 11 constitute a steering system.
The electric motor 11 is a three-phase brushless motor including a stator (not shown) having a plurality of field coils and a rotor (not shown) that rotates inside the stator.

  The electric power steering device 100 includes a control device 200, an inverter 60 that drives the electric motor 11, a resolver (rotation angle sensor) 50, a pinion torque applied to the pinion shaft 5, that is, a steering torque sensor 30 that detects a steering torque. A differential amplifier circuit 40 that amplifies the output of the steering torque sensor 30 and a vehicle speed sensor 35 are provided.

The inverter 60 includes a plurality of switching elements such as, for example, a three-phase FET bridge circuit, and outputs a DUTY signal (displayed as “DUTYu”, “DUTYv”, “DUTYw” in FIG. 2) from the control device 200. It is used to generate a rectangular wave voltage and drive the electric motor 11. Further, the inverter 60 uses, for example, current sensors S _Iu , S _Iv , S _Iw (see FIG. 2) such as Hall elements (refer to FIG. 2) for three-phase actual current values I (“Iu”, “Iv” in FIG. 2). , “Iw”), and a function for inputting to the control device 200.

The inverter 60 includes a voltage sensor S _Vuvw that individually detects the induced voltage values Vu, Vv, and Vw that are generated when the electric motor 11 is rotated and rotated by the operation of the steering handle 2 without being driven and controlled. The voltage signal from the voltage sensor S _Vuvw is input to an A / D port (analog / digital conversion port) (not shown) of the control device 200 and input to a rotation angle estimation unit 291b at the time of rotation of the rotation angle estimation unit 291 described later. .
Incidentally, although the field coil of the electric motor 11 is not shown in the figure, it is star-connected, and when the driver operates the steering handle 2 with only a manual force when the inverter 60 is not outputting a driving current, the electric motor 11 is The generation of induced voltage values Vu, Vv, Vw of each of the three phases driven by rotation can be detected individually. In FIG. 2, voltage sensors that individually detect the induced voltage values Vu, Vv, and Vw of each of the three phases are collectively represented by the voltage detection sensor S _Vuvw .
In FIG. 2, the current sensors S _Iu , S _Iv , S _Iw and the voltage sensor S _Vuvw built in the inverter 60 are illustrated outside the inverter 60 for the sake of convenience.

The resolver 50 detects the rotation angle θ _M of the rotor of the electric motor 11 and outputs an angle signal corresponding to the rotation angle θ _M. For example, the resolver 50 is magnetically provided on a magnetic rotor provided with a plurality of uneven portions at equal intervals in the circumferential direction. This is a variable reluctance type resolver in which a detection circuit for detecting a change in resistance is brought close.
In FIG. 2, the exciting winding of the resolver 50 is omitted, and a sin output winding 50a and a cos output winding 50b are shown. The rotation angle calculation unit 50c included in the resolver 50 calculates the rotation angle θ _M by arctan calculation based on output signals from the sin output winding 50a and the cos output winding 50b and inputs the rotation angle θ _M to the control device 200.

  Returning to FIG. 1, the steering torque sensor 30 detects the pinion torque applied to the pinion shaft 5, that is, the steering torque T. For example, the anisotropy in the reverse direction is detected at two positions in the axial direction of the pinion shaft 5. A magnetic film is deposited so that the detection coil is spaced from the pinion shaft 5 on the surface of each magnetic film. The differential amplifier circuit 40 amplifies the difference in permeability change between the two magnetostrictive films detected by the detection coil as an inductance change, and inputs a signal indicating the steering torque T to the control device 200.

  The vehicle speed sensor 35 detects the vehicle speed VS of the vehicle as the number of pulses per unit time, and outputs a signal indicating the vehicle speed VS.

"Control device"
Next, the configuration and function of the control device 200 will be described with reference to FIG. 2 and with reference to FIGS. 1, 3, 4, and 5 as appropriate. FIG. 3 is an explanatory diagram of a method in which the base signal calculation unit sets the base target current value using the first base table. FIG. 4 illustrates the base target current value of the base signal calculation unit using the second base table. FIG. 5 is an explanatory diagram of a method for setting, and FIG. 5 is an explanatory diagram of a method for the damper correction signal calculation unit to set the damper correction current value using the damper table.
The control device 200 includes a microcomputer having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc., an interface circuit, and a program stored in the ROM. The function described in is realized.

2 includes a base signal calculation unit 220, an inertia compensation signal calculation unit 210, a damper correction signal calculation unit 225, a q-axis PI control unit 240, a d-axis PI control unit 245, a two-axis three-phase conversion unit 262, PWM conversion unit 263, three-phase biaxial conversion unit 265, d-axis current generation unit 285, failure detection unit (failure detection means) 290, rotation angle estimation unit (rotation angle estimation unit) 291, rotation angle signal switching unit 292, rotation An angular velocity calculation unit 293 and the like are included.
Here, the inertia compensation signal calculation unit 210, the base signal calculation unit 220, the damper correction signal calculation unit 225, the q-axis PI control unit 240, the d-axis PI control unit 245, the adder 250, the subtracters 251, 252, 253, 2 The shaft three-phase conversion unit 262, the PWM conversion unit 263, the three-phase two-axis conversion unit 265, the rotation angle signal switching unit 292, and the rotation angular velocity calculation unit 293 constitute "motor drive control means" described in the claims. .

(Base signal calculation unit 220)
Based on the signal indicating the steering torque T from the differential amplifier circuit 40 (see FIG. 1) and the signal indicating the vehicle speed VS from the vehicle speed sensor 35 (see FIG. 1), the base signal calculation unit 220 is based on the electric motor 11 (see FIG. generating a base target current value I _B is a target value serving as a reference for the auxiliary torque output by the first reference). Generation of the base target current value I _B, based on the steering torque T and the vehicle speed VS, which is set in advance by experimental measurements or the like, when the signal of the rotation angle theta _M from the resolver 50 is normally received This is performed by referring to the first base table 220a used or the second base table 220b used when the signal of the rotation angle θ _M from the resolver 50 is not normally received.
The base signal calculation unit 220 inputs a dead zone upper limit torque | ± T _NR2 |, which will be described later, according to the vehicle speed VS of the second base table 220b to the rotation angle signal switching unit 292.

Figure 3 shows the function of the base target current value I _B stored in the first base table 220a. FIG. 3 shows an example in which the value of the steering torque T is positive. However, when the steering torque T is negative, the base target current value I _B is negative, and the width of the dead zone R _NR1 is also negative. Set to the side. When the steering torque T for the steering operation to the right side is positive (+) and the steering torque T for the steering operation to the left side is negative (−), in the following description, the difference between the left and right steering torques T is ± Therefore, the + side (right side) will be described as a representative, and the left side (− side) will be omitted as appropriate.
Incidentally, since the dead zone upper limit torque and the dead zone lower limit torque are also different in ± signs, explanation of the dead zone lower limit torque will be omitted as appropriate.

The case where the steering torque T is a positive value will be described with reference to FIG. 3 as an example. Unless the base signal calculation unit 220 receives a signal from the failure detection unit 290 that the resolver 50 has failed, was determined to be normal, using the first base table 220a, dead zone R _NR1 positive value side is provided when a positive value of the steering torque T is small to the base target current value I _B is set to zero, the steering torque T When the value becomes equal to or greater than the dead band upper limit torque T _NR1 which is the upper limit value of the positive value of the dead band R _NR1 , the base target current value I _B has a characteristic of increasing linearly with the gain G1. Further, the base signal calculation unit 220 has a characteristic that the output increases with a gain G2 at a predetermined steering torque value, and the output reaches a predetermined positive saturation value when the steering torque value further increases.

Here, the combined deadband R _NR1 and dead zone R _NR1 negative value side of the positive value side, corresponds to the "first dead zone" described in the claims hereafter, simply, "the normal dead zone R _NR1 ". The dead zone upper limit torque T _NR1 and the dead zone lower limit torque −T _NR1 correspond to “first upper limit value” and “first lower limit value” recited in the claims. Hereinafter, the dead band upper limit torque T _NR1 and the dead band lower limit torque −T _NR1 are referred to as “dead band upper limit torque | ± T _NR1 |” when they are displayed as absolute values without distinguishing between positive and negative.

In general, since the load on the road surface (road reaction force) varies depending on the traveling speed of the vehicle, the dead zone upper limit torque | ± T _NR1 | value, gains G1 and G2, and base target current value | I _B | The saturation value of is adjusted. The load is heaviest during stationary operation at zero vehicle speed, and the load is relatively light at medium and low speeds. Therefore, the base signal calculation unit 220 sets the absolute values of the gain (G1, G2) and the saturation value as the vehicle speed VS increases and increases the dead band upper limit torque | ± T _NR1 | The road surface information is given to the driver with a large manual steering area.
That is, a firm feeling of steering torque T is given as the vehicle speed VS increases.

Figure 4 shows the function of the base target current value I _B stored in the second base table 220b. 4 shows a vehicle speed VS as illustrated is shown the function of the base target current value I _B of the second base table 220b in the case of 0 km / h. FIG. 4 shows an example in which the value of the steering torque T is positive. However, when the value of the steering torque T is negative, the base target current value I _B is negative, and the dead zone R _NR1 , dead zone. The width of _RNR2 is also set to the negative side. First, the case where the steering torque T is a positive value will be described as an example in accordance with FIG. 4. In the base signal calculation unit 220, the resolver 50 (see FIG. 2) has failed from the failure detection unit 290 (see FIG. 2). when receiving a signal with there, judges the failure of the resolver 50, a positive value side using the second base table 220b, when a positive value of the steering torque T is small to the base target current value I _B is set to zero the dead zone R _NR2 is provided, the value of the steering torque T becomes a dead zone upper limit torque T _NR2 or an upper limit value of the positive values of the dead zone R _NR2, given in a straight line from the dead zone upper limit torque T _NR2 4 Increases to the positive saturation value of. In FIG. 4, the display is simplified and the dead zone upper limit torque T _{NR2 is} linearly increased to a predetermined positive saturation value, but a plurality of straight lines are linearly increased with the combination gains G1 and G2 as shown in FIG. The characteristics reaching a predetermined positive saturation value may be used.

Here, the positive-side dead zone R _NR2 and the negative-side dead zone −R _NR2 are combined to correspond to the “second dead zone” described in the claims. _NR2 ". The dead zone upper limit torque T _NR2 and the dead zone lower limit torque −T _NR2 correspond to the “second upper limit value” and the “second lower limit value” recited in the claims. Hereinafter, the dead band upper limit torque T _NR2 and the dead band lower limit torque −T _NR2 are referred to as “dead band upper limit torque | ± T _NR2 |” when they are displayed as absolute values without distinguishing between positive and negative.

FIG. 4 shows the dead zone R _NR1 in a normal state for comparison. Thus, the dead zone upper limit torque for the same vehicle speed VS | ± T _NR2 | values dead zone upper limit torque | is set larger than the value | ± T _NR1.

The function of the base target current value I _B stored in the second base table 220b is, for example, a fixed dead zone upper limit torque | ± T _NR2 | with respect to the vehicle speed VS, and a gain and a predetermined saturation value. However, when the vehicle speed VS is equal to or higher than a predetermined value, for example, 40 km / h or higher, the dead band upper limit torque | ± T _NR2 | is the dead band upper limit torque of the normal dead band R _NR1. The same value as the value of | ± T _NR1 | is set, and the function of the base target current value I _B corresponding to the vehicle speed VS faster than that is not set. This is because, as will be described later, the base signal calculation unit 220 performs control to switch the second base table 220b used when the resolver 50 fails to the first base table 220a again when a predetermined condition is satisfied. It is.

As described above, the dead zone upper limit torque | ± T _NR2 | is not limited to a fixed value for each vehicle speed VS. The value of the dead-band upper limit torque | ± T _NR2 | is the same as that described above because the motor 11 generates an induced voltage when the driver operates the steering handle 2 while driving the motor 11 without driving control of the motor 11. It is experimentally set in consideration of the case where the vehicle speed VS = 0 so that the three-phase induced voltage values Vu, Vv, and Vw can be accurately detected so that the rotational angular speed of the rotor of the electric motor 11 can be obtained. . However, since the steering resistance of the steered wheels 10 is smaller when the vehicle is in the running state than when the vehicle is stopped, the absolute value of the steering torque T necessary for steering without the auxiliary torque by the electric motor 11 is small. The value of the dead band upper limit torque | ± T _NR2 | corresponding to each vehicle speed VS is larger than the value of the dead band upper limit torque | ± T _NR1 | and is reduced as the vehicle speed VS increases. You may set so that.

(Damper correction signal calculation unit 225)
Returning to FIG. 2, the damper correction signal calculation unit 225 is provided to compensate for the viscosity of the steering system and to have a steering damper function for correcting this when the vehicle is degraded in convergence when the vehicle is traveling at high speed. It is calculated with reference to the damper table 225a of the damper correction signal calculator 225 using the rotational angular velocity ω _M of the electric motor 11. FIG. 5 shows a function of the damper correction current value _ID stored in the damper table 225a. FIG. 5 shows the case where the value of the rotational angular velocity ω _M of the electric motor 11 is positive, but when the value of the rotational angular velocity ω _M is negative, the value of the damper correction current value _ID becomes negative. First, the value of the rotational angular velocity omega _M with reference to FIG. 5 will be described the case of a positive example, the damper compensation current I _D as the rotational angular velocity omega _M is increased in the motor 11 is increased linearly, predetermined The damper correction current value rapidly increases at the rotational angular velocity ω _M and has a characteristic of a predetermined positive saturation value corresponding to the vehicle speed VS.

Similarly, if the value of the rotational angular velocity omega _M is negative, increases the damper compensation current I _D is linearly negative value direction as the rotational angular velocity omega _M of the electric motor 11 is increased in the negative value direction, a predetermined rotation The damper correction current value rapidly increases in the negative value direction at the angular velocity ω _M and has a characteristic that becomes a predetermined negative saturation value corresponding to the vehicle speed VS.
Further, as the value of the vehicle speed VS is higher, both the gain and the absolute value of the saturation value are increased, and the rotation torque of the electric motor 11, that is, the auxiliary torque output from the electric motor 11 according to the steering speed is based on the subtractor 251. and it is attenuated by subtracting the damper compensation current value I _D from the target current value I _B.

  In other words, when the steering wheel 2 is increased, as the rotational speed of the steering handle 2 increases, the value of the auxiliary torque current in the increasing direction to the electric motor 11 is reduced to make the steering feel of the steering handle 2 difficult to cut. When the direction handle 2 is returned, the current in the reaction force direction with respect to the return operation to the electric motor 11 is increased to make it difficult to return. Due to this steering damper effect, the convergence of the steering handle 2 can be improved and the turning motion characteristics of the vehicle can be stabilized.

(Subtractor 251)
Returning to FIG. 2 again, the subtractor 251 subtracts the damper correction current value I _D of the damper correction signal calculation unit 225 from the base target current value I _B of the base signal calculation unit 220 and inputs the result to the adder 250. .

(Inertia compensation signal calculation unit 210)
The inertia compensation signal calculation unit 210 compensates for the influence of the inertia of the steering system, and uses the rotation angular velocity ω _M (or rotation angular velocity ω _eM ) and steering torque T of the electric motor 11 and the inertia compensation signal calculation unit. Referring to the inertia table 210a 210, the inertia compensation current value I _I is calculated.

  The inertia compensation signal calculation unit 210 also compensates for a decrease in responsiveness due to the inertia of the rotor of the electric motor 11. In other words, when switching the rotation direction from the normal rotation to the reverse rotation, or from the reverse rotation to the normal rotation, the electric motor 11 tries to maintain the state by inertia, so the rotation direction is not immediately switched. Therefore, the inertia compensation signal calculation unit 210 performs control so that the switching of the rotation direction of the electric motor 11 coincides with the timing at which the rotation direction of the steering handle 2 is switched. In this way, the inertia compensation signal calculation unit 210 improves the response delay of the steering due to the inertia and viscosity of the steering system and provides a clean steering feeling. It is also practical for vehicle characteristics such as front engine front wheel drive (FF), front engine rear wheel drive (FR), recreation vehicle (RV) and sedan, and steering characteristics that vary depending on vehicle conditions such as vehicle speed and road surface. Sufficient properties are imparted.

(Adder 250, subtractor 252, q-axis PI controller 240)
The adder 250 adds the input from the subtractor 251 and the inertia compensation current value I _{I of the} inertia compensation signal calculation unit 210. The q-axis target current value Iq ^* that is the output signal of the adder 250 is a q-axis current target signal that defines the output torque of the electric motor 11 and is input to the subtractor 252.

The subtractor 252 is configured to be able to input a calculation stop command Sc signal from the rotation angle signal switching unit 292. When the resolver 50 is detected to be normal, the calculation stop command Sc is input. Not. When it is detected that the resolver 50 is out of order, a calculation stop command Sc from the rotation angle signal switching unit 292 is input. Then, after the subtraction calculation in the subtractor 252 is stopped by the calculation stop command Sc, the electric motor 11 that is not driven and controlled by the control device 200 is forcedly operated by the driver's steering handle 2 (see FIG. 1). When the rotation angle estimation unit 291b, which will be described later with the rotation angle estimation unit 291, is rotated and rotated, the rotation angle θ _M of the rotor of the motor 11 can be estimated almost accurately. The calculation stop command Sc from 292 is canceled. As a result, the subtractor 252 again subtracts the q-axis actual current value Iq output from the three-phase two-axis conversion unit 265 from the q-axis target current value Iq ^* , and the resulting deviation value ΔIq ^* is the q-axis PI control unit. Input to 240.
Incidentally, the rotation angle estimated by the rotation angle estimation calculation unit 291b or the rotation angle estimation calculation unit 291c of the rotation angle estimation unit 291 in FIG. 2 and output from the rotation angle signal switching unit 292 is the estimated rotation angle. θ _eM is distinguished from the rotation angle θ _M detected by the resolver 50.

When the calculation stop command Sc from the rotation angle signal switching unit 292 is input to the subtractor 252, the q-axis actual current value Iq is not subtracted from the q-axis target current value Iq ^* , and the q-axis A 0 (zero) signal is input to the PI control unit 240 as the deviation value ΔIq ^* which is a control signal.

The q-axis PI control unit 240 performs feedback control of P (proportional) control and I (integral) control so that the deviation value ΔIq ^* decreases, and obtains a q-axis target voltage value Vq ^* that is a q-axis target signal. Are input to an extended induced voltage observer 291a, which will be described later, of the biaxial three-phase conversion unit 262 and the rotation angle estimation unit 291.

(D-axis current generation unit 285, subtractor 253, d-axis PI control unit 245)
The d-axis current generation unit 285 generates “0” as the target value of the d-axis target current value Id ^* of the electric motor 11, but performs field-weakening control by setting the d-axis target current value Id ^* as necessary. be able to.
The subtractor 253 is configured to be able to input a signal of a calculation stop command Sc from the rotation angle signal switching unit 292. When it is detected that the resolver 50 is normal, the calculation stop command Sc from the rotation angle signal switching unit 292 is not input. When the resolver 50 is detected as malfunctioning, the calculation stop command Sc from the rotation angle signal switching unit 292 is input, and the subtraction calculation in the subtractor 253 is stopped. Thereafter, the electric motor 11 that is not driven and controlled by the control device 200 is forcibly rotated by the driver's operation of the steering handle 2 (see FIG. 1), and the rotation angle estimation unit 291 causes the rotor of the electric motor 11 to rotate. When the rotation angle θ _M can be estimated almost accurately, the calculation stop command Sc from the rotation angle signal switching unit 292 is canceled. As a result, the subtracter 253 again performs a subtraction process of the d-axis actual current value Id input from the three-phase two-axis conversion unit 265 from the d-axis target current value Id ^* input from the d-axis magnetic current generation unit 285. The resulting deviation value ΔId ^* is input to the d-axis PI control unit 245.

When the calculation stop command Sc from the rotation angle signal switching unit 292 is input to the subtractor 253, the d-axis actual current value Id is not subtracted from the d-axis target current value Id ^*. A 0 (zero) signal is input to the PI control unit 245 as the deviation value ΔId ^* which is a control signal.
The d-axis PI control unit 245 performs PI feedback control of P (proportional) control and I (integral) control so that the deviation value ΔId ^* decreases, and obtains a d-axis target voltage value Vd ^* that is a d-axis target signal. Obtained and input to the biaxial three-phase converter 262 and the expansion induced voltage observer 291a.

(2-axis 3-phase converter 262, PWM converter 263)
The two-axis three-phase conversion unit 262 converts the input q-axis target voltage value Vq ^* and d-axis target voltage value Vd ^* from the dq coordinate system using the rotation angle θ _M or the estimated rotation angle θ _eM to 3 Convert to phase signals Uu ^* , Uv ^* , Uw ^* . Here, the dq coordinate system rotates by being fixed to a rotor having two axes, a d axis that is a magnetic pole axis and a q axis that is an axis that is electrically rotated 90 degrees with respect to the d axis. It is a fixed coordinate system.
The PWM converter 263 is a DUTY signal (a PWM (Pulse Width Modulation) signal) having a pulse width proportional to the magnitudes of the three-phase signals Uu ^* , Uv ^* , Uw ^* (“DUTYu” in FIG. 2). ”,“ DUTYv ”,“ DUTYw ”).
A signal indicating the rotation angle θ _M of the motor 11 or the estimated rotation angle θ _eM is input from the rotation angle signal switching unit 292 to the two-axis three-phase conversion unit 262 and the PWM conversion unit 263, and the rotation of the rotor Calculation and control are performed according to the angle θ _M or the estimated rotation angle θ _eM .
Hereinafter, the estimated rotation angle θ _eM is simply referred to as “estimated rotation angle θ _eM ”. Here, the “estimated rotation angle θ _eM ” corresponds to the “estimated rotation angle” recited in the claims.

(Three-phase two-axis conversion unit 265)
The three-phase two-axis conversion unit 265 converts the three-phase actual current values Iu, Iv, Iw of the motor 11 detected by the current sensors S _Iu , S _Iv , S _Iw of the inverter 60 into the rotation angle θ _M or the estimated rotation angle θ. _{The eM} is used to convert the d-axis actual current value Id and the q-axis actual current value Iq in the dq coordinate system, and the d-axis actual current value Id is input to the subtractor 253 and the expansion induced voltage observer 291a. The current value Iq is input to the subtractor 252 and the extended induced voltage observer 291a.
Incidentally, the generated torque of the electric motor 11 is proportional to the q-axis current, the d-axis actual current value Id is a field weakening current, and represents a demagnetizing field applied to the magnet magnetic field.

(Failure detection unit 290)
The failure detection unit 290 determines whether the output signal from the resolver 50 is in a normal state or in a failure state based on the output signals from the sin output winding 50a and the cos output winding 50b input to the rotation angle calculation unit 50c. When a failure state is detected, a signal indicating a resolver failure is input to the base signal calculation unit 220 and the rotation angle signal switching unit 292.
The failure determination of the resolver 50 in the failure detection unit 290 is a well-known technique and will not be described in detail. For example, paragraphs [0017] to [0023] of Japanese Patent Application Laid-Open No. 2009-12664 describe a technique of a resolver 50 failure determination method.

(Rotation angle estimation unit 291)
The rotation angle estimator 291 includes the above-described extended induced voltage observer 291a, a rotation rotation angle estimation calculator 291b, and a rotation angle estimation calculator 291c.
The rotation angle estimation unit 291 receives the failure determination of the resolver 50 from the failure detection unit 290, and when the calculation start command Sd is input from the rotation angle signal switching unit 292, the function starts, and the resolver 50 is normal. While being determined, the function is in a standby state. By doing so, when the resolver 50 is normal, the CPU of the microcomputer of the control device 200 reduces the load without calculating the function of the rotation angle estimation unit 291.
Receiving the calculation start command Sd from the rotation angle signal switching unit 292, the rotation angle estimation unit 291 starts the calculation. Specifically, it is a two-stage process as follows.

First, in the first stage, in response to the calculation start command Sd from the rotation angle signal switching unit 292, the rotation-time rotation angle estimation calculation unit 291b performs a filtering process on the three-phase induced voltage from the voltage sensor S _VUVW , A sine wave signal is extracted from the rectangular wave signal to start estimating the motor rotation angle θ _M. Here, the motor rotation angle θ _M estimated by the rotation-time rotation angle estimation calculation unit _291b is referred to as an estimated rotation angle θ _eM1 . The estimated rotation angle θ _eM1 is output to the rotation angle signal switching unit 292. A method for estimating and calculating the estimated rotation angle θ _eM1 from the three-phase induced voltage by the rotation-time rotation angle estimation calculation unit 291b is well known, and detailed description thereof is omitted.
Rotation angle signal switching unit 292 receives an input of the estimated rotation angle theta _EM1 from the rotation angle estimation calculation section 291b during co-rotation, a dead zone upper limit torque steering torque T is input from the base signal computing part 220 | ± T _NR2 After confirming that the value is equal to or greater than the value of |, a command for canceling the calculation stop command Sc is output to the subtracters 252, 253 and the rotation angular velocity calculation unit 293, and input from the rotation rotation angle estimation calculation unit 291b. The estimated rotation angle θ _eM1 is _input as an estimated rotation angle θ _eM to the rotation angular velocity calculation unit 293, the biaxial three-phase conversion unit 262, and the PWM conversion unit 263.

Thereafter, the q-axis PI control unit 240 and the d-axis PI control unit 245 are input with the deviation value ΔIq ^* and the deviation value ΔId ^* , respectively, and calculate the q-axis target voltage value Vq ^* and the d-axis target voltage value Vd ^* . Then, it starts to be input to the extended induced voltage observer 291a again at a constant period in the CPU.
The extended induced voltage observer 291a receives the d-axis target voltage value Vd ^* and the q-axis target voltage value Vq ^* one step before in the repetitive calculation at a constant period in the CPU from the two-axis three-phase conversion unit 262, and The estimated rotation angular velocity ω _eM calculated by the rotation angular velocity calculation unit 293 one step before in the repetitive calculation at a constant period in the CPU is input. Further, the d-axis actual current value Id and the q-axis actual current value Iq are input from the three-phase two-axis converter 265 to the extended induced voltage observer 291a.

そして、ここで、
Ｖｄ ：ｄ軸電圧値
Ｖｑ ：ｑ軸電圧値
Ｒａ ：固定子の巻線抵抗
Ｐ ：微分演算子
Ｌｄ ：ｄ軸インダクタンス
Ｌｑ ：ｑ軸インダクタンス
Ｋｅ ：速度起電力係数
ω_M ：回転角速度
ｅ_ed ：ｄ軸の誘起電圧
ｅ_eq ：ｑ軸の誘起電圧
である。 The extended induced voltage observer 291a calculates the d-axis induced voltage e _ed and the q-axis induced voltage e _eq by the following equation (1), and inputs them to the rotation angle estimation calculation unit 291c.

And where
Vd: d-axis voltage value Vq: q-axis voltage value Ra: stator winding resistance P: differential operator Ld: d-axis inductance Lq: q-axis inductance Ke: speed electromotive force coefficient ω _M : rotational angular velocity e _ed : d Axis induced voltage e _eq : q axis induced voltage.

When the subtractors 252 and 253 and the rotation angular velocity calculation unit 293 resume the calculation, the extended induced voltage observer 291a calculates the induced voltage e _ed of the d axis and the induced voltage e _eq of the q axis as follows by repeated calculation. Output to the rotation angle estimation calculation unit 291c. The rotation angle estimation calculation unit 291c estimates and calculates the motor rotation angle of the electric motor 11 based on the d-axis induced voltage e _ed and the q-axis induced voltage e _eq (hereinafter, the estimated motor rotation angle is calculated). This is input to the rotation angle signal switching unit 292 (referred to as an estimated rotation angle θ _eM2 ).
In equation (1), the d-axis voltage value Vd and the q-axis voltage value Vq are output by the biaxial three-phase conversion unit 262 one step before the d-axis target voltage value Vd ^* and By replacing the q-axis target voltage value Vq ^* with ω _M as the angular velocity ω _M one step before input from the rotational angular velocity calculation unit 293, the d-axis induced voltage e _ed and the q-axis induced voltage e _eq Can be easily calculated by the extended induced voltage observer 291a, and can be input to the rotation angle estimation calculation unit 291c.
Then, as a second stage, the rotation angle estimation calculation unit 291c performs an arctan (inverse tangent function) calculation based on the d-axis induced voltage e _ed and the q-axis induced voltage e _eq to obtain the estimated rotation angle θ _eM2 . Calculate and input to the rotation angle signal switching unit 292. Incidentally, the second right side of the formula (1) is generally referred to as “extended induced voltage”.
However, Equation (1) is an example of a premise that there is an estimation error. However, if there is no estimation error, the second term of Equation (1) is changed to the q-axis component as shown in Equation (2). Only an induced voltage is generated. However, Eex is a thing as described in Formula (3).

The rotation angle estimation calculation unit 291c calculates the estimated rotation angle θ _eM2 based on the d-axis induced voltage e _ed and the q-axis induced voltage e _eq from the extended induced voltage observer 291a, and _sends it to the rotation angle signal switching unit 292. A signal indicating that the output has started is input to the turning rotation angle estimation calculation unit 291b, and the estimation calculation of the estimated rotation angle θ _{eM1 in} the turning rotation angle estimation calculation unit 291b is stopped.

(Rotation angle signal switching unit 292, rotation angular velocity calculation unit 293)
The rotation angle signal switching unit 292 includes a signal indicating the rotation angle θ _M from the resolver 50, a signal indicating the estimated rotation angle θ _eM1 from the rotating rotation angle estimation calculation unit 291b, and a rotation angle estimation calculation unit 291c. A signal indicating the estimated rotation angle θ _eM2 , a failure detection signal when the failure detection unit 290 detects a failure of the resolver 50, and a signal indicating the steering torque T from the steering torque sensor 30 (see FIG. 1) are input. The
When the signal that detects the failure of the resolver 50 is not input from the failure detection unit 290, the rotation angle estimation unit 291 is instructed to enter a stand-by state to stop computation, and the rotation angle input from the resolver 50 θ _M is input to the rotation angular velocity calculation unit 293, the 2-axis 3-phase conversion unit 262, the PWM conversion unit 263, and the 3-phase 2-axis conversion unit 265.
The rotational angular velocity calculation unit 293 calculates the rotational angular velocity ω _M by time differentiation of the input rotational angle θ _M and inputs the rotational angular velocity ω _M to the damper correction signal calculation unit 225 and also to the rotation angle estimation unit 291. Incidentally, since the rotation angle estimation unit 291 is in a standby state, the rotation angle velocity ω _M is only inputted and no calculation is performed.

The rotation angle signal switching unit 292 outputs a calculation stop command Sc to the subtracters 252 and 253 and the rotation angular velocity calculation unit 293 when a signal that detects the failure of the resolver 50 is input, and temporarily controls the drive of the motor 11. While stopping, a calculation start command Sd is output to the rotation angle estimation unit 291. Thereafter, as a first step, the rotation angle signal switching unit 292 determines that the absolute value of the steering torque T is determined according to the vehicle speed VS at that time based on the second base table 220b described above. | _TNR2 | When the dead zone upper limit torque | ± T _NR2 | is greater than or equal to the value below the upper limit, the estimated rotation angle θ _eM1 estimated from the rotation angle estimation calculation unit 291b at the time of rotation is _set as the estimated rotation angle θ _eM in two axes. The three-phase converter 262, the PWM converter 263, the three-phase two-axis converter 265, and the rotation angular velocity calculator 293 start outputting. At the same time, the calculation stop command Sc output to the subtracters 252 and 253 and the rotation angular velocity calculation unit 293 is canceled, the calculation is restarted, and the state is returned to the drive control state. That is, the drive control of the electric motor 11 is resumed based on the estimated rotation angle θ _eM and the estimated rotation angular velocity ω _eM .

After that, when the estimated rotation angle θ _eM2 from the rotation angle estimation calculation unit 291c is input as the second stage, the estimated rotation angle θ _eM2 estimated from the rotation angle estimation calculation unit 291c is _set as the estimated rotation angle θ _eM. The two-axis three-phase conversion unit 262, the PWM conversion unit 263, the three-phase two-axis conversion unit 265, and the rotation angular velocity calculation unit 293 are switched, and the drive control of the electric motor 11 is performed based on the estimated rotation angle θ _eM and the estimated rotation angular velocity ω _eM. To continue.
Thereafter, sensorless drive control of the electric motor 11 by the rotation angle estimation unit 291 is performed, but the rotation angle signal switching unit 292 indicates that when the rotation of the motor 11 is stopped, that is, when the estimated rotation angular velocity ω _eM indicates zero. Again, the state returns to the state where the signal for detecting the failure of the resolver 50 is inputted.

  Next, with reference to FIGS. 6 to 9 as appropriate and with reference to FIG. 2 as appropriate, a method of driving control of the electric motor 11 when the resolver 50 fails will be described. FIGS. 6 to 8 are flowcharts showing a control flow of the electric power steering apparatus when it is detected that the resolver has failed. FIG. 9 is an explanatory diagram of the drive control of the electric motor of the electric power steering device in accordance with the steering operation when the rotation angle sensor in the stop state of the vehicle is normal and at the time of failure, and (a) is the steering torque. (B) is an explanatory view of the time transition of the rotational angular velocity of the motor and the motor drive current.

In step S01, the rotation angle signal switching unit 292 checks whether or not a resolver failure signal is received from the failure detection unit 290. If a resolver failure signal is received (Yes), the process proceeds to step S04. If a resolver failure signal is not received (No), the process proceeds to step S02.
In step S02, control device 200 executes normal electric power steering control (“executes EPS control”).

That is, the rotation angle signal switching unit 292 outputs the rotation angle θ _M input from the resolver 50 to the rotation angular velocity calculation unit 293 to calculate the rotation angular velocity ω _M. The inertia compensation signal calculation unit 210 calculates the inertia compensation current value I _I by referring to the inertia table 210 a using the rotational angular velocity ω _M and the steering torque T of the electric motor 11 and inputs the calculated value to the adder 250.
Base signal computing part 220, since the failure detection unit 290 does not receive the signal of the resolver fault, using the steering torque T and the vehicle speed VS, calculating a base target current value I _B with reference to the first base table 220a And output to the subtracter 251. The damper correction signal calculation unit 225 refers to the damper table 225 a using the rotation angular velocity ω _M , calculates a damper correction current value _ID , and inputs the calculated value to the subtracter 251.

The subtractor 251 subtracts the damper correction current value I _D from the base target current value I _B and inputs it to the adder 250. The adder 250 adds the inertia compensation current value I _I and the base target current value I _B corrected with the damper correction current value _ID , and inputs the result to the subtractor 252 as the q-axis target current value Iq ^* .
The subtractor 252 calculates a deviation value ΔIq ^* by subtracting the q-axis actual current value from the q-axis target current value Iq ^* , and inputs the deviation value ΔIq ^* to the q-axis PI control unit 240. The q-axis PI control unit 240 calculates the q-axis target voltage value Vq ^* and inputs it to the two-axis three-phase conversion unit 262.
Further, when the field weakening control is not performed, the d-axis current generation unit 285 inputs “zero” as the d-axis target current value Id ^* to the subtractor 253, and the subtractor 253 generates the d-axis target current value Id ^* from the d-axis target current value Id ^*. The deviation value ΔId ^* is calculated by subtracting the actual current value Id and input to the d-axis PI control unit 245. The d-axis PI control unit 245 calculates the d-axis target voltage value Vd ^* and inputs it to the two-axis three-phase conversion unit 262.

The biaxial three-phase converter 262 converts the three-phase signals Uu ^* , Uv ^* , Uw ^* using the rotation angle θ _M and inputs the signals to the PWM converter 263. Incidentally, the expansion induced voltage observer 291a is in a standby state, and does not perform any calculation just by inputting the d-axis target voltage value Vd ^* and the q-axis target voltage value Vq ^* .
The PWM converter 263 uses the rotation angle θ _M to display a DUTY signal corresponding to the magnitude of the three-phase signals Uu ^* , Uv ^* , Uw ^* (“DUTYu”, “DUTYv”, “DUTYw” in FIG. 2). ) And input to the inverter 60. The inverter 60 supplies each phase current of the three-phase actual current values Iu, Iv, and Iw corresponding to the DUTY signal to the motor 11 and drives it.

The three-phase two-axis converter 265 uses the rotation angle θ _M to determine the d-axis actual current value Id based on the three-phase actual current values Iu, Iv, and Iw detected by the current sensors S _Iu , S _Iv , and S _Iw. The q-axis actual current value Iq is calculated, the d-axis actual current value Id is input to the subtractor 253 and the extended induced voltage observer 291a, and the q-axis actual current value Iq is input to the subtractor 252 and the expanded induced voltage observer 291a. To do.

  Incidentally, the extended induced voltage observer 291a is in a standby state, and does not perform any calculation just by receiving the d-axis actual current value Id and the q-axis actual current value Iq.

The resolver 50 detects the rotation angle θ _M and inputs the rotation angle θ _M to the rotation angle signal switching unit 292. The rotation angle signal switching unit 292 converts the input rotation angle θ _M into a biaxial three-phase conversion unit 262 and a PWM conversion unit. 263, a three-phase biaxial converter 265, and a rotational angular velocity calculator 293. The rotational angular velocity calculation unit 293 calculates the rotational angular velocity ω _M by differentiating the rotational angle θ _M with respect to time, and inputs the rotational angular velocity ω _M to the damper correction signal calculation unit 225 and the expansion induced voltage observer 291a.
Incidentally, the expansion induced voltage observer 291a is in a standby state, and does not perform any calculation just by inputting the rotational angular velocity ω _M.

  In step S03, the control device 200 checks whether or not ignition-off is detected. This ignition-off signal is acquired by CAN (Controller Area Network) communication from an engine ECU (not shown in FIG. 2). When the ignition-off is detected (Yes), the control is terminated, and when it is not detected (No), the process returns to Step S01.

When the process proceeds from step S01 to step S04, the rotation angle signal switching unit 292 stops the electric assist and activates the function of the rotation angle estimation unit 291. Specifically, the rotation angle signal switching unit 292 inputs a calculation stop command Sc to the subtractors 252, 253 and the rotation angular velocity calculation unit 293, and stops the calculation. Further, the rotation angle signal switching unit 292 also stops outputting the rotation angle θ _{M to} the biaxial three-phase conversion unit 262 and the PWM conversion unit 263. As a result, deviation values ΔIq ^* and ΔId ^* that are signals of the signals input to the PWM conversion unit 263 are not generated, and the rotation angle θ _M or the estimated rotation angle is added to the two-axis three-phase conversion unit 262 and the PWM conversion unit 263. Since θ _eM is not input either, the calculation is also stopped, and the three-phase drive current from the inverter 60 to the electric motor 11 is not supplied. That is, the electric assist is stopped.

Further, the rotation angle signal switching unit 292 inputs a calculation start command Sd to the rotation angle estimation unit 291 and shifts its function from the standby state up to that point to the calculation execution state.
Even when the electric assist of the electric power steering apparatus 100 (see FIG. 1) is stopped in step S04, the driver operates the steering handle 2 (see FIG. 1) to rotate the electric motor 11 and rotate it. When an induced voltage is generated in the three-phase winding 11 and is input to the rotation angle estimation unit 291, the rotation angle estimation calculation unit 291 b at the time of rotation is detected by the voltage sensor S _Vuvw in step S 05. Based on the three-phase induced voltage, the estimation calculation of the estimated rotation angle θ _eM1 is started. The estimated rotation angle θ _{eM1 that} has been estimated is input to the rotation angle signal switching unit 292.

At this stage, since the rotation angular velocity of the electric motor 11 is still small, the rotation angle estimation unit 291b at the time of rotation does not obtain a _precise value of the estimated rotation angle θ _eM1 , and the rotation angle signal switching unit 292 The estimated rotation angle θ _eM is not output to the biaxial three-phase conversion unit 262, the PWM conversion unit 263, and the rotation angular velocity calculation unit 293.

In step S06, the base signal calculation unit 220 receives the resolver failure signal from the failure detection unit 290, and changes the base table from the first base table 220a to the second base table 220b. Then, it calculates a base target current value I _B with reference to the second base table 220b using the steering torque T. The calculated base target current value I _B is output to the subtractor 251. Further, the value of the dead zone upper limit torque | ± T _NR2 | of the second base table 220b corresponding to the vehicle speed VS at that time is input to the rotation angle signal switching unit 292.
In step S07, the rotation angle signal switching unit 292 indicates that the absolute value of the steering torque T is less than the dead band upper limit torque | ± T _NR2 | of the second base table 220b from the dead band upper limit torque | ± T _NR2 | Check (| T | ≧ | ± T _NR2 |?). If the absolute value of the steering torque T is less than the dead band upper limit torque | ± T _NR2 | of the second base table 220b and indicates the dead band upper limit torque | ± T _NR2 | or more (Yes), the process proceeds to step S08. Otherwise (No), step S07 is repeated.

In step S08, the rotation angle signal switching unit 292 sets the estimated rotation angle θ _eM1 from the rotation-time rotation angle estimation unit _291b as the estimated rotation angle θ _eM , the biaxial three-phase conversion unit 262, the PWM conversion unit 263, and the rotation angular velocity. While starting to output to the calculation unit 293, the calculation stop command Sc output to the rotation angular velocity calculation unit 293 and the subtracters 252, 253 is cancelled.

In step S09, the rotation angular velocity calculation unit 293 calculates the estimated rotation angular velocity ω _eM by performing time differentiation on the estimated rotation angle θ _eM input in step S08. The calculated estimated rotation angular velocity ω _eM is input to the inertia compensation signal calculation unit 210 and the damper correction signal calculation unit 225 as a substitute value for the rotation angular velocity ω _M.
In step S10, the base signal computing part 220, using the second base table 220b, and calculates the base target current value I _B on the basis of the steering torque T and the vehicle speed VS, input to the subtractor 251.
In step S11, the damper correction signal calculation unit 225 uses the damper table 225a to calculate the damper correction current value _ID based on the estimated rotational angular velocity ω _eM and the vehicle speed VS, and outputs the calculated value to the subtracter 251. 1 subtracts the damper correction current value I _D from the base target current value I _B and outputs the result to the adder 250.

In step S 12, the inertia compensation signal calculation unit 210 calculates an inertia compensation current value I _I based on the estimated rotational angular velocity ω _eM and the steering torque T using the inertia table 210 a and inputs the calculated value to the adder 250. Thereafter, the process proceeds to step S13 in FIG. 7 according to the connector (A).
In step S13, the adder 250 adds the result of the subtractor 251 in step S11 and the inertia compensation current value I _I in step S12 to obtain a q-axis target current value Iq ^* . In step S14, the subtractor 252 receives the q-axis actual current value Iq input from the q-axis target current value Iq ^* from the three-phase biaxial conversion unit 265 (the q-axis actual current value Iq is still in the first stage of this repetition). = 0) is subtracted to obtain a deviation value ΔIq ^*, which is input to the q-axis PI control unit 240. In step S15, the q-axis PI control unit 240 calculates the q-axis target voltage value Vq ^* and inputs the q-axis target voltage value Vq ^* to the two-axis three-phase conversion unit 262 and the expansion induced voltage observer 291a (“q-axis target voltage value Vq ^* is Calculation").

When the field weakening control is not performed, the d-axis current generation unit 285 inputs “zero” as the d-axis target current value Id ^* to the subtractor 253, and in step S16, the subtractor 253 determines from the d-axis target current value Id ^*. By subtracting the d-axis actual current value Id (d-axis actual current value Id = 0 at the first stage of this repetition) input from the three-phase two-axis conversion unit 265, a deviation value ΔId ^* is obtained, and d Input to the axis PI control unit 245. In step S17, the d-axis PI control unit 245 calculates the d-axis target voltage value Vd ^* and inputs the d-axis target voltage value Vd ^* to the two-axis three-phase conversion unit 262 and the expansion induced voltage observer 291a (“d-axis target voltage value Vd ^* is Calculation").

Thereafter, in step S18, driving of the electric motor 11 is started. Specifically, the three-phase biaxial conversion unit 265 uses the estimated rotation angle θ _eM to determine the DUTY signal (“DUTYu” in FIG. 2) corresponding to the magnitude of the three-phase signals Uu ^* , Uv ^* , Uw ^* . “DUTYv” and “DUTYw” are generated and input to the inverter 60. Then, the inverter 60 supplies each phase current of the three-phase actual current values Iu, Iv, and Iw corresponding to the DUTY signal to the electric motor 11 and starts driving. The three-phase two-axis converter 265 uses the estimated rotation angle θ _eM to determine the d-axis actual current value based on the three-phase actual current values Iu, Iv, and Iw detected by the current sensors S _Iu , S _Iv , and S _Iw. Id, q-axis actual current value Iq is calculated, d-axis actual current value Id is input to subtractor 253 and extended induced voltage observer 291a, and q-axis actual current value Iq is input to subtractor 252 and expanded induced voltage observer 291a. input.

In step S19, the expansion induced voltage observer 291a and the rotation angle estimation calculation unit 291c start calculation of the estimated rotation angle θ _eM2 and input to the rotation angle signal switching unit 292. Then, the rotation angle signal switching unit 292 starts outputting the estimated rotation angle θ _eM2 as the estimated rotation angle θ _eM (“calculation start of the estimated rotation angle θ _eM2 ”). Specifically, the expansion induced voltage observer 291a receives the q-axis target voltage value Vq ^* , the d-axis target voltage value Vd ^* , and the three-phase two-axis input from the q-axis PI control unit 240 and the d-axis PI control unit 245, respectively. Based on the d-axis actual current value Id and the q-axis actual current value Iq input from the conversion unit 265, the d-axis induced voltage e _ed and the q-axis induced voltage e _eq are calculated, and the rotation angle estimation calculating unit 291c. To enter. Then, the rotation angle estimation calculation unit 291c starts calculating the estimated rotation angle θ _eM2 based on the d-axis induced voltage e _ed and the q-axis induced voltage e _eq . At this time, the rotational angle estimation calculation section 291b when the estimated rotation angle theta _eM2 from the rotation angle estimation calculation section 291c drag rotation receives an operation start signal stops the operation of the estimated rotation angle theta _EM1.
Thereafter, in step S20, sensorless control of the electric motor 11 is executed based on the estimated rotation angle θ _eM and the estimated rotation angular velocity ω _eM .
Specifically, the second base table 220b is used as a base table in the base signal calculation unit 220, and the q-axis PI control unit 240 calculates the q-axis target voltage value Vq ^* , the two-axis three-phase conversion unit 262, and It inputs into the expansion induced voltage observer 291a. The d-axis PI control unit 245 calculates the d-axis target voltage value Vd ^* and inputs the calculated d-axis target voltage value Vd ^* to the three-phase two-axis conversion unit 262 and the extended induced voltage observer 291a.

The biaxial three-phase converter 262 converts the three-phase signals Uu ^* , Uv ^* , Uw ^* based on the d-axis target voltage value Vd ^* and the q-axis target voltage value Vq ^* using the estimated rotation angle θ _eM , This is output to the PWM converter 263 and the extended induced voltage observer 291a. The PWM conversion unit 263 uses the estimated rotation angle θ _eM to determine the DUTY signal corresponding to the magnitude of the three-phase signals Uu ^* , Uv ^* , Uw ^* (“DUTYu”, “DUTYv”, “DUTYw” in FIG. 2). Display) is generated and input to the inverter 60. The inverter 60 supplies each phase current of the three-phase actual current values Iu, Iv, and Iw corresponding to the DUTY signal to the motor 11 and drives it.

The three-phase two-axis converter 265 uses the estimated rotation angle θ _eM to determine the d-axis actual current value based on the three-phase actual current values Iu, Iv, and Iw detected by the current sensors S _Iu , S _Iv , and S _Iw. Id and q-axis actual current value Iq are coordinate-transformed, d-axis actual current value Id is input to subtractor 253 and extended induced voltage observer 291a, and q-axis actual current value Iq is subtracted by 252 and extended induced voltage observer. Input to 291a.

Then, the extended induced voltage observer 291a calculates the d-axis induced voltage e _ed and the q-axis induced voltage e _eq and inputs them to the rotation angle estimation calculating unit 291c. The rotation angle estimation calculation unit 291c calculates an estimated rotation angle θ _eM by performing an arctan (inverse tangent function) calculation based on the induced voltage e _ed of the d axis and the induced voltage e _{eq of the} q axis, and switches the rotation angle signal. To the part 292. The rotation angle signal switching unit 292 inputs a signal indicating the estimated rotation angle θ _eM to the rotation angular velocity calculation unit 293, the 2-axis 3-phase conversion unit 262, the PWM conversion unit 263, and the 3-phase 2-axis conversion unit 265. Thus, sensorless drive control of the electric motor 11 by the rotation angle estimation unit 291 is performed.

In step S21, it is checked whether or not the estimated rotational angular velocity ω _eM input from the rotational angle estimation calculation unit 291c has become zero (“ω _eM = 0?”). Specifically, it is determined that ω _eM = 0 when the absolute value of the estimated rotational angular velocity ω _eM is smaller than a predetermined threshold value close to zero. If ω _eM = 0 (Yes), the process returns to step S01 of FIG. 6 according to the connector (B). If not (No), the process proceeds to step S22.
In step S22, the control device 200 checks whether or not ignition-off is detected. When the ignition-off is detected (Yes), the control is terminated, and when it is not detected (No), the process proceeds to step S23 of FIG. 8 according to the connector (C).

In step S23, the base signal calculation unit 220 increases the vehicle speed VS so that the dead band upper limit torque | ± T _NR1 | of the first base table 220a becomes _{equal to} or greater than the dead band upper limit torque | ± T _NR2 | of the second base table 220b. Check whether or not. If the dead zone upper limit torque | ± T _NR1 | of the first base table 220a is equal to or greater than the dead zone upper limit torque | ± T _NR2 | of the second base table 220b (Yes), the process proceeds to step S24, and otherwise (No). Returns to step S20 of FIG. 7 according to the connector (D).

In step S24, the base signal calculation unit 220 checks whether or not the absolute value of the steering torque T is less than the dead band upper limit torque | ± T _NR1 | of the first base table 220a (| T | <| ± T _NR1 |? ). If the absolute value of the steering torque T is less than the dead zone upper limit torque | ± T _NR1 | of the first base table (Yes), the process proceeds to step S25, and if not (No), according to the connector (D), FIG. Return to step S20.
In step S25, the base signal calculation unit 220 changes the base table from the second base table 220b to the first base table 220a.
In step S26, EPS control by sensorless control of the electric motor 11 is executed based on the estimated rotation angle θ _eM and the estimated rotation angular velocity ω _eM . The processing in step S26 is “the second base table 220b is used as the base table in the base signal calculation unit 220, and the q-axis PI control unit 240 calculates the q-axis target voltage value Vq ^* ,” and “base The first base table 220a is used as the base table in the signal calculation unit 220, and the q-axis PI control unit 240 calculates the q-axis target voltage value Vq ^* and reads as "", and performs the process of step S20 described above. Because of this, redundant explanation is omitted.

In step S27, it is checked whether or not the estimated rotational angular velocity ω _eM input from the rotational angle estimation calculation unit 291c has become zero (“ω _eM = 0?”). This step S27 is the same process as step S21 described above. When ω _eM = 0 (Yes), the process returns to step S01 of FIG. 6 according to the connector (B). Otherwise (No), the process proceeds to step S28.

  In step S28, the control device 200 checks whether or not ignition-off is detected. If the ignition-off is detected (Yes), the control is terminated, and if it is not detected (No), Step S26 is continued.

  Next, referring to FIG. 9, referring to FIG. 1, FIG. 2, and FIG. 4, the resolver 50 (refer to FIG. 2) outputs the auxiliary torque in the base signal calculation unit 220 when normal and when the failure occurs (see FIG. 2). Explain the control to assist. FIG. 9 is an explanatory diagram of the drive control of the electric motor of the electric power steering apparatus with steering when the resolver is in a normal state and when the vehicle is in a stopped state, and (a) shows the time transition of the steering torque. (B) is explanatory drawing of the time transition of the rotational angular velocity of an electric motor, and an electric motor drive current. Here, it is an example in the case of a stationary operation of the steering handle 2 (see FIG. 1) with a vehicle speed VS of 0 km / h.

When the resolver 50 is normal, when the driver starts to steer the steering handle 2 at time t2 in FIG. 9A, the absolute value of the steering torque T increases from time t2, as shown by the middle solid line. . _Dead band upper limit torque of the dead zone R _NR1 (see FIG. 4) corresponding to the vehicle speed VS = 0 km / h of the first base table 220a (see FIG. 2) of the base signal calculation unit 220 of the steering torque T | ± T _NR1 | from the time t3 became more base signal computing part 220 starts to output a base target current value I _B. That is, as shown by the broken line in FIG. 9B, the motor driving current rises from time t3. The rotational angular velocity ω _M of the electric motor 11 (see FIG. 2) when the electric motor driving current rises is a value indicated by ω _M1 in FIG. 9B.

When the resolver 50 is in a failure state and the failure occurs at time t1 in FIG. 2A, the base signal calculation unit 220 switches to use the second base table 220b (see FIG. 2), and the time When the driver starts to steer the steering handle 2 at t2, the steering torque T increases from the time t2, as shown by the solid thick solid line. From the time t4 when the steering torque T becomes _{equal to} or greater than the dead band upper limit torque | ± T _NR2 | of the dead band R _NR2 (see FIG. 4) corresponding to the vehicle speed VS = 0 km / h of the second base table 220b of the base signal calculation unit 220. base signal computing part 220 starts to output a base target current value I _B. In other words, the motor drive current rises from time t4 as shown by the middle thick solid line in FIG. The rotational angular velocity ω _M of the electric motor 11 (see FIG. 2) when the electric motor driving current rises is a value indicated by ω _M3 in FIG. 9B.

The value of the estimated rotation angle θ _eM1 calculated in the rotation-time estimated rotation angle calculation unit 291b (see FIG. 2) of the rotation angle estimation unit 291 can be calculated with a rotational angular velocity ω _M2 ((b) in FIG. 9). ))), Set the value of the dead band upper limit torque | ± T _NR2 | based on the test data so that ω _M3 is sufficiently higher. As a result, the rotational angular velocity ω _M3 becomes a sufficiently large value, and the rotational angle estimating unit 291b at the time of rotation can calculate the estimated rotational angle θ _eM1 with high accuracy.
Incidentally, when the vehicle starts traveling, the absolute value of the steering torque T without the auxiliary torque of the electric motor 11 than the _{stationary state is} the rotational angular velocity ω _{M2 at} which the value of the estimated rotational angle θ _eM1 can be calculated experimentally with high accuracy. Therefore, the dead zone upper limit torque | ± T _NR2 | can be set low. Therefore, even if the vehicle speed VS increases as described above, the value of the dead zone upper limit torque | ± T _NR2 | is greater than the dead zone upper limit torque | ± T _NR1 | It does not need to be increased according to the increase in the vehicle speed VS to make it feel, and can be set to a fixed value as it is or to be decreased. Accordingly, the value of the dead band upper limit torque | ± T _NR1 | becomes equal to or greater than the value of the dead band upper limit torque | ± T _NR2 | as in steps S18 and S19 of the flowchart, and the base table is changed from the second base table 220b to the first base table 220a. You can change it.

According to this embodiment, when the failure of the resolver 50 (see FIG. 2) is not detected by the failure detection unit 290 (see FIG. 2), the control device 200 (see FIG. 2) A dead zone in which the motor 11 is not driven with respect to the steering torque T is set as a dead zone R _{NR1 in} a normal state having a dead zone upper limit torque T _NR1 and a dead zone lower limit torque −T _NR1 as widths, and a failure detection unit 290 causes a failure of the resolver 50. If detected, the dead zone in which the motor 11 is not driven with respect to the steering torque T is set as the dead zone R _NR2 at the time of failure having the dead zone upper limit torque T _NR2 and the dead zone lower limit torque −T _NR2 as the width. The lower limit torque is set to be wider than the first dead zone _RNR1 .
Therefore, when a failure of the resolver 50 is detected by the failure detection unit 290, the dead zone upper limit of the second dead zone R _NR2 in which the steering torque T detected by the driver manually operating the steering handle 2 is increased. when more than torque T _NR2 and dead band minimum torque -T _NR2, motor 11 by generating the steering torque T of the larger absolute value than when exceeding the dead zone upper limit torque T _NR1 and dead band minimum torque -T _NR1 of the first dead zone R _NR1 To a higher rotational speed. As a result, the rotation angle estimation calculation unit 291b of the rotation angle estimation unit 291 can estimate and calculate the estimated rotation angle θ _eM1 with higher accuracy based on a larger induced voltage generated by the electric motor 11.

When the detected absolute value of the steering torque T exceeds the dead zone upper limit torque | ± T _NR2 |, the estimated rotation angle θ _eM1 is _set as the estimated rotation angle θ _eM, and the control device 200 drives the motor 11 based on the estimated rotation angle θ _eM1. By restarting the control, it is possible to drive and control the electric motor 11 without generating an auxiliary torque in the direction opposite to the operation direction of the driver's steering handle 2 by the accurate estimated rotation angle θ _eM .
According to the present embodiment, in the technique described in Patent Document 3, when the maximum induced voltage value of the electric motor 11 is less than a predetermined value, the operation direction of the steering handle 2 indicated by the steering torque T is determined and fixed. Due to the control to generate the rotating magnetic field, for example, when the rotational speed of the rotating magnetic field is slower than the actual rotational angular speed of the electric motor, it is solved that the driver feels strange that the steering reaction force increases. The

Further, as shown in step S08 of FIG. 6 in the flowchart, the control device 200 detects the absolute value of the steering torque T equal to or greater than the dead zone upper limit torque | ± T _NR2 | in the steering torque sensor 30 (see FIG. 1). In the state, when a failure of the resolver 50 is detected by the failure detection unit 290, the drive control of the electric motor 11 is not performed based on the detected steering torque T and the estimated rotation angle θ _eM .

Therefore, when the failure detection unit 290 detects a failure of the resolver 50, the driver feels that the output of the auxiliary torque from the electric motor 11 has been lost due to a sudden increase in the steering reaction force, and recognizes the failure of the resolver 50. be able to.
When the drive control of the electric motor is performed as in the technique described in Patent Document 3, the control device 200 is based on the rotation angle θ _M from the resolver 50 until it is determined that the resolver 50 is out of order. In the case where the drive control of the electric motor 11 has been performed until then, the electric motor 11 is based on the estimated rotation angle θ _eM suddenly output from the rotation angle estimation unit 291 immediately after it is determined that the resolver 50 has failed. As a result, the discontinuity of the drive control of the electric motor 11 occurs, and the driver feels the discontinuity of the steering reaction force from the steering handle 2.

Therefore, according to the present embodiment, it is possible to prevent such discontinuity of the drive control from occurring and cause the driver to feel the discontinuity of the steering reaction force from the steering handle 2, and to ensure that the driver resolves the resolver. It can be recognized that 50 has failed.
Of course, after that, the absolute value of the steering torque T decreases and becomes less than the dead zone upper limit torque | ± T _NR2 |, and after entering the range of the steering torque range of the dead zone R _NR2 at the time of failure, the absolute value of the steering torque T When the value exceeds the value of the dead zone upper limit torque | ± T _NR2 |, the drive control of the electric motor 11 can be started based on the steering torque T and the estimated rotation angle θ _eM .

The control device 200 enlarges at least the steering torque range of the normal dead zone R _NR1 in accordance with the increase in the vehicle speed VS, and applies an upper limit of the dead zone R _NR2 at the time of failure applied when a failure of the resolver 50 is detected. to dead band upper limit torque which is an upper limit value of the dead zone R _NR1 during normal | | ± T _NR2 | dead zone upper limit torque is a value ± T _NR1 | when becomes more values, as dead zone R _NR2 of failure The normal dead band R _NR1 is used.

If the control device 200 determines that the resolver 50 is out of order and continues driving control of the electric motor 11 based on the estimated rotation angle θ _eM and the steering torque T, the vehicle speed VS according to the vehicle speed VS is conventionally used. The range of the dead zone R _{NR1 in} the normal state is increased as the value increases, and the dead zone R _NR2 at the time of failure is set to be larger than the dead zone R _{NR1 in the} normal state with respect to the same vehicle speed VS. In other words, the dead zone upper limit torque | ± T _NR2 | of the dead zone R _NR2 at the time of failure is changed from the dead zone upper limit torque of the dead zone R _NR1 at the normal time | ± T _NR1 | to the same vehicle speed VS. Assuming that the setting is large, if the resolver 50 uses the estimated rotation angle θ _eM at the time of the failure for the drive control of the electric motor 11 in the range where the vehicle speed VS is medium and high, the driver can steer the steering feeling in the normal state. Feel the power heavy and discomfort It will be giving a.

Therefore, according to the present embodiment, it can be prevented. For example, in the operation of the steering handle 2 at the time of a lane change during high-speed traveling, the resolver 50 operates normally and the drive control of the electric motor 11 is performed based on the steering torque T and the rotation angle θ _M. The operation feeling given to the driver can be made the same when the resolver 50 is out of order and the drive control of the electric motor 11 is performed based on the steering torque T and the estimated rotation angle θ _eM .

Further, in the present embodiment, the rotation angle estimation unit 291 includes an extended induced voltage observer 291a that calculates and detects an induced voltage that occurs as the rotor of the electric motor 11 rotates, so that the failure detection unit 290 includes the resolver 50. After detecting the failure, the driver operates the steering handle 2 only manually to detect and detect the induced voltage generated by the rotation of the rotor of the electric motor 11 by the expanded induced voltage observer 291a. The unit 291 can accurately calculate the estimated rotation angle θ _eM of the electric motor 11 by repeated calculation based on the induced voltage.

In the present embodiment, when the resolver 50 is normal, the rotation angle estimation unit 291 is in a standby state without performing a calculation operation, but is not limited thereto, and the rotation angle estimation unit 291 is calculating, The angular signal switching unit 292 may adopt the estimated rotational angle θ _eM2 output from the rotational angle estimating unit 291 as the estimated rotational angle θ _eM and not output it.

2 Steering handle (steering wheel)
DESCRIPTION OF SYMBOLS 10 Steering wheel 11 Electric motor 30 Steering torque sensor 35 Vehicle speed sensor 50 Resolver (rotation angle sensor)
60 Inverter 100 Electric Power Steering Device 200 Control Device 210 Inertia Compensation Signal Calculation Unit (Motor Drive Control Unit)
220 Base signal calculation unit (motor drive control means)
220a First base table 220b Second base table 225 Damper correction signal calculation unit (motor drive control means)
240 q-axis PI control unit (motor drive control means)
245 d-axis PI controller (motor drive control means)
250 adder (motor drive control means)
251, 252, 253 Subtractor (motor drive control means)
262 2-axis 3-phase converter (motor drive control means)
263 PWM converter (motor drive control means)
265 3-phase 2-axis converter (motor drive control means)
280 Motor speed calculation unit (motor drive control means)
290 Failure detection unit (failure detection means)
291 Rotation angle estimation unit (rotation angle estimation means)
291a Extended induced voltage observer 291b Estimated rotation angle calculation unit 291c Estimated rotation angle calculation unit 292 Rotation angle signal switching unit (motor drive control means)
293 Rotational angular velocity calculation unit (motor drive control means)
R _NR1 normal dead zone (first dead zone)
R _Dead zone at the time of _NR2 failure (second dead zone)
-T _NR1 dead zone lower limit torque (first lower limit value)
T _NR1 deadband upper limit torque (first upper limit value)
-T _NR2 dead band lower limit torque (second lower limit value)
T _NR2 deadband upper limit torque (second upper limit value)

Claims (4)

A steering torque sensor for detecting a steering torque input to the steering wheel;
An electric motor for assisting the operation of the steered wheel by generating an auxiliary torque;
A rotation angle sensor for detecting a rotation angle of the electric motor;
Failure detection means for detecting a failure of the rotation angle sensor;
A rotation angle estimating means for estimating a rotation angle of the electric motor based on an induced voltage of the electric motor;
When the failure of the rotation angle sensor is not detected by the failure detection means, the motor is driven and controlled based on the steering torque detected by the steering torque sensor and the rotation angle detected by the rotation angle sensor, When a failure of the rotation angle sensor is detected by the failure detection means, drive control of the electric motor is performed based on the steering torque detected by the steering torque sensor and the rotation angle estimated by the rotation angle estimation means. Electric motor drive control means,
In an electric power steering apparatus comprising:
The electric motor drive control means includes
When the failure detection means does not detect a failure of the rotation angle sensor, a dead zone in which the motor is not driven with respect to the steering torque is defined as a first upper limit value and a first lower limit value as a width. Set it as a dead zone,
When a failure of the rotation angle sensor is detected by the failure detection means, a dead zone in which the electric motor is not driven with respect to the steering torque is set to a second upper limit value and a second lower limit value. As the dead zone, both the upper limit value and the lower limit value are set wider than the first dead zone,
The rotation angle estimating means includes
When the detected steering torque exceeds the second upper limit value or the second lower limit value of the enlarged second dead zone, an induction caused by rotation of the electric motor by operation of a steering wheel by a driver Estimating the rotation angle based on voltage,
The electric power steering apparatus, wherein the electric motor drive control means starts driving control of the electric motor based on the estimated rotation angle. The electric motor drive control means includes
When a failure of the rotation angle sensor is detected by the failure detection means in a state where the steering torque exceeding the second dead zone is detected by the steering torque sensor, the detected steering torque and the detected torque The electric power steering apparatus according to claim 1, wherein drive control of the electric motor is not performed based on the estimated rotation angle. The electric motor drive control means includes
At least the width of the first dead zone is enlarged according to an increase in vehicle speed,
The first upper limit value and the second lower limit value of the second dead zone that are applied when a failure of the rotation angle sensor is detected are enlarged according to an increase in the vehicle speed. When the first upper limit value and the first lower limit value of the dead zone exceed the second upper limit value and the second lower limit value, the first dead zone is used as the second dead zone. The electric power steering apparatus according to claim 1 or 2, wherein The rotation angle estimating means includes
The electric power steering apparatus according to any one of claims 1 to 3, further comprising an extended induced voltage observer that calculates and detects an induced voltage generated with rotation of a rotor of the electric motor.

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