JP6024976B2 - Steering angle sensor reliability determination device - Google Patents

Description

  The present invention relates to a reliability determination device for a steering angle sensor.

A vehicle is provided with a steering angle sensor for detecting a steering angle, which is a rotation angle of a steering wheel as a steering member. The steering angle sensor is used to control an electric power steering device and other on-vehicle equipment. For this reason, it is important to determine whether or not the detection value of the steering angle sensor ensures reliability.
Based on only the output signal of the steering angle sensor, the reliability of the detected value of the steering angle sensor is determined by determining whether or not the steering angle sensor is faulty, whether or not the output line of the steering angle sensor is broken, etc. How to do is well known. Such a reliability determination method is called self-diagnosis diagnosis. In the self-diagnosis diagnosis, it can be determined whether or not the detected value of the steering angle sensor has a relatively low level of reliability, but the detected value of the steering angle sensor ensures a higher level of reliability. It is difficult to determine whether or not

  As a method for determining whether or not the detected value of the steering angle sensor has secured a higher level of reliability, for example, the following method (hereinafter referred to as "conventional high level reliability determination method") has been developed. Has been. That is, if the absolute value of the steering angle detected by the steering angle sensor is equal to or less than the predetermined value when the vehicle speed is equal to or higher than the predetermined speed and the lateral acceleration is substantially zero, the steering angle sensor It is determined that the detected value secures a high level of reliability. This determination method is based on the idea that the vehicle is traveling straight when the vehicle speed is equal to or higher than the predetermined speed and the lateral acceleration is substantially zero.

JP 2009-276098 JP 2004-42691 A

Since the conventional high-level reliability determination method described above is effective only when the vehicle is running, steering is performed immediately after the ECU (Electronic Control Unit) mounted on the vehicle is turned on. It cannot be determined whether or not the detection value of the angle sensor ensures a high level of reliability.
An object of the present invention is to provide a reliability determination device for a steering angle sensor that can determine whether or not the detection value of the steering angle sensor ensures a high level of reliability immediately after the power is turned on. Objective.

  The invention according to claim 1 is a reliability determination device for a steering angle sensor (11) for detecting a steering angle (θh) which is a rotation angle of the steering member (2), and is interlocked with the rotation of the steering member. A turning mechanism (4) for turning the steered wheels, an electric motor (18) for applying a steering assist force to the turning mechanism, and a rotation angle sensor for detecting a rotation angle (θs) of the electric motor. (25) When the ignition-off command is input, the steering angle detected by the steering angle sensor and the rotation angle detected by the rotation angle sensor are nonvolatile as the steering angle and rotation angle when the power was turned off last time. Means (73, S3) stored in the directional memory (74), the steering angle detected by the steering angle sensor immediately after the power is turned on, the rotation angle detected by the rotation angle sensor, and the nonvolatile memory Remembered Reliability determination means (71, S13 to S15) for determining the reliability of the detected value of the steering angle sensor based on the steering angle and the rotation angle when the power was previously turned off. It is a reliability determination device. In addition, although the alphanumeric character in parentheses represents a corresponding component in an embodiment described later, of course, the scope of the present invention is not limited to the embodiment. The same applies hereinafter.

  In the present invention, immediately after the power is turned on, the steering angle detected by the steering angle sensor, the rotation angle detected by the rotation angle sensor, the steering angle and the rotation angle at the previous power-off time stored in the nonvolatile memory, Based on this, the reliability of the detection value of the steering angle sensor is determined. Thereby, immediately after the power is turned on, it is possible to determine whether or not the detection value of the steering angle sensor ensures a high level of reliability.

  According to a second aspect of the present invention, the reliability determination means includes an absolute value of a difference between a steering angle detected by the steering angle sensor and a steering angle at the previous power-off time, and a rotation detected by the rotation angle sensor. Whether the absolute value of the difference between one of the angle and the absolute value of the difference between the previous rotation angle and the other and the other is less than or equal to a predetermined value Means (71, S13) for determining whether or not, means (71, S14) for determining that the detected value of the steering angle sensor is highly reliable when it is determined that the condition is satisfied, The reliability determination of the steering angle sensor according to claim 1, further comprising means (71, S15) for determining that the reliability of the detected value of the steering angle sensor is low when it is determined that the condition is not satisfied. Device.

  According to a second aspect of the present invention, the reliability determining means has an absolute value of a difference between a steering angle detected by the steering angle sensor and a steering angle at the time of previous power-off being equal to or less than a first predetermined value, and Means (71) for determining whether or not a condition that the absolute value of the difference between the rotation angle detected by the rotation angle sensor and the rotation angle at the previous power-off is less than or equal to a second predetermined value is satisfied; When it is determined that the detected value of the steering angle sensor is high, the means (71) for determining that the detected value of the steering angle sensor is high, and when it is determined that the condition is not satisfied, The steering angle sensor reliability determination apparatus according to claim 1, further comprising means (71) for determining that the reliability of the detected value is low.

FIG. 1 is a schematic diagram showing a schematic configuration of an electric power steering apparatus to which a steering angle sensor reliability determining apparatus according to an embodiment of the present invention is applied. FIG. 2 is a schematic diagram showing an electrical configuration of the ECU. FIG. 3 is a schematic diagram schematically showing the configuration of the electric motor. FIG. 4 is a block diagram showing the configuration of the motor control unit. FIG. 5 is a graph showing a setting example of the q-axis basic current command value I _qo ^* with respect to the detected steering torque Th. FIG. 6 is a graph showing a setting example of the damping compensation value I _{qc with} respect to the vehicle speed V. FIG. 7 is a block diagram illustrating a configuration of a reliability determination unit of the steering angle sensor. FIG. 8 is a flowchart showing the operation of the angle storage processing unit. FIG. 9 is a flowchart showing the operation of the first reliability determination unit.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of an electric power steering apparatus to which a steering angle sensor reliability determining apparatus according to an embodiment of the present invention is applied.
The electric power steering apparatus 1 includes a steering wheel 2 as a steering member for steering the vehicle, a steering mechanism 4 that steers the steered wheels 3 in conjunction with the rotation of the steering wheel 2, and steering by the driver. And a steering assist mechanism 5 for assisting. The steering wheel 2 and the steering mechanism 4 are mechanically coupled via a steering shaft 6 and an intermediate shaft 7.

  The steering shaft 6 includes an input shaft 8 connected to the steering wheel 2 and an output shaft 9 connected to the intermediate shaft 7. The input shaft 8 and the output shaft 9 are connected via a torsion bar 10 so as to be relatively rotatable on the same axis. That is, when the steering wheel 2 is rotated, the input shaft 8 and the output shaft 9 rotate in the same direction while rotating relative to each other.

  A steering angle sensor 11 and a torque sensor 12 are provided around the steering shaft 6. The steering angle sensor 11 detects a steering angle θh that is the rotation angle of the steering wheel 2 (the rotation angle of the steering shaft 6). The steering angle sensor 11 detects the amount of rotation (rotation angle) of the steering wheel 2 in both forward and reverse directions from the neutral position (reference position) of the steering wheel 2, and the amount of rotation in the right direction from the neutral position is, for example, A positive value is output, and the amount of rotation from the neutral position to the left is output as a negative value, for example. The torque sensor 12 detects the steering torque Th applied to the steering wheel 2 based on the relative rotational displacement amount of the input shaft 8 and the output shaft 9. The steering angle θh detected by the steering angle sensor 11 and the steering torque detected by the torque sensor 12 are input to the ECU 30.

  The steered mechanism 4 includes a rack and pinion mechanism including a pinion shaft 13 and a rack shaft 14 as a steered shaft. The steered wheel 3 is connected to each end of the rack shaft 14 via a tie rod 15 and a knuckle arm (not shown). The pinion shaft 13 is connected to the intermediate shaft 7. The pinion shaft 13 rotates in conjunction with the steering of the steering wheel 2. A pinion 16 is connected to the tip of the pinion shaft 13.

  The rack shaft 14 extends linearly along the left-right direction of the vehicle (the direction orthogonal to the straight direction). A rack 17 that meshes with the pinion 16 is formed at an intermediate portion in the axial direction of the rack shaft 14. By the pinion 16 and the rack 17, the rotation of the pinion shaft 13 is converted into the axial movement of the rack shaft 14. The steered wheels 3 can be steered by moving the rack shaft 14 in the axial direction.

When the steering wheel 2 is steered (rotated), this rotation is transmitted to the pinion shaft 13 via the steering shaft 6 and the intermediate shaft 7. The rotation of the pinion shaft 13 is converted into an axial movement of the rack shaft 14 by the pinion 16 and the rack 17. Thereby, the steered wheel 3 is steered.
The steering assist mechanism 5 includes an electric motor 18 for generating a steering assist force, and a speed reduction mechanism 19 for transmitting the output torque of the electric motor 18 to the steering mechanism 4. In this embodiment, the electric motor 18 is a three-phase brushless motor. The speed reduction mechanism 19 includes a worm gear mechanism that includes a worm shaft 20 and a worm wheel 21 that meshes with the worm shaft 20. The speed reduction mechanism 19 is accommodated in a gear housing 22 as a transmission mechanism housing.

The worm shaft 20 is rotationally driven by the electric motor 18. The worm wheel 21 is coupled to the steering shaft 6 so as to be rotatable in the same direction. The worm wheel 21 is rotationally driven by the worm shaft 20.
When the worm shaft 20 is rotationally driven by the electric motor 18, the worm wheel 21 is rotationally driven and the steering shaft 6 rotates. The rotation of the steering shaft 6 is transmitted to the pinion shaft 13 via the intermediate shaft 7. The rotation of the pinion shaft 13 is converted into the axial movement of the rack shaft 14. Thereby, the steered wheel 3 is steered. That is, the wheel 3 is steered by rotating the worm shaft 20 by the electric motor 18.

  The rotation angle of the rotor of the electric motor 18 (rotor rotation angle (electrical angle)) is detected by a rotation angle sensor 25 such as a resolver. An output signal of the rotation angle sensor 25 is input to the ECU 30. The ECU 30 further receives a vehicle speed V detected by the vehicle speed sensor 26, a lateral acceleration Gy detected by the lateral acceleration sensor 27, and the like. The electric motor 18 is controlled by an ECU 30 as a motor control device.

FIG. 2 is a schematic diagram showing an electrical configuration of the ECU 30.
The ECU 30 includes a microcomputer 50, a drive circuit (inverter circuit) 41 that is controlled by the microcomputer 50 and supplies electric power to the electric motor 18, and a current detection unit 42 that detects a motor current flowing through the electric motor 18. Yes.
The electric motor 18 is, for example, a three-phase brushless motor, and includes a rotor 100 as a field and U-phase, V-phase, and W-phase stator windings 101, 102, and 103, as schematically shown in FIG. And a stator 105. The electric motor 18 may be of an inner rotor type having a stator opposed to the outside of the rotor, or may be of an outer rotor type having a stator opposed to the inside of a cylindrical rotor.

  Three-phase fixed coordinates (UVW coordinate system) are defined in which the U, V, and W axes are taken in the direction of the stator windings 101, 102, and 103 of each phase. Further, a two-phase rotational coordinate system (dq coordinate system) in which the d axis (magnetic pole axis) is taken in the magnetic pole direction of the rotor 100 and the q axis (torque axis) is taken in a direction perpendicular to the d axis in the rotation plane of the rotor 100. The actual rotating coordinate system) is defined. The dq coordinate system is a rotating coordinate system that rotates with the rotor 100. In the dq coordinate system, since only the q-axis current contributes to the torque generation of the rotor 100, the d-axis current may be set to zero and the q-axis current may be controlled according to the desired torque. The rotation angle (electrical angle) θs of the rotor 100 is the rotation angle of the d axis with respect to the U axis. The dq coordinate system is an actual rotating coordinate system according to the rotor angle θs. By using this rotor angle θs, coordinate conversion between the UVW coordinate system and the dq coordinate system can be performed.

  The microcomputer 50 includes a CPU and a memory (ROM, RAM, non-volatile memory, etc.), and functions as a plurality of function processing units by executing a predetermined program. The plurality of function processing units include a motor control unit 60 and a steering angle sensor reliability determination unit 70. Note that when the ignition key is turned off, an ignition off command is input to the microcomputer 40.

  The motor control unit 60 controls the drive circuit 41 according to the steering torque Th detected by the torque sensor 12, the vehicle speed V detected by the vehicle speed sensor 26, and the steering angle θh detected by the steering angle sensor 11. Appropriate steering assistance according to the steering situation is realized. The reliability determination unit 70 of the steering angle sensor includes a vehicle speed V detected by the vehicle speed sensor 26, a steering angle θh detected by the steering angle sensor 11, a lateral acceleration Gy detected by the lateral acceleration sensor 27, and a rotation angle sensor 25. The reliability of the steering angle sensor is determined using the rotation angle θs of the electric motor 18 calculated based on the output signal. Hereinafter, the operation of the motor control unit 60 and the operation of the reliability determination unit 70 of the steering angle sensor will be sequentially described.

FIG. 4 is a block diagram illustrating a configuration of the motor control unit 60.
The motor control unit 60 includes a current command value setting unit 61, a current deviation calculation unit 62, a PI (proportional integration) control unit 63, a dq / UVW conversion unit 64, a PWM (Pulse Width Modulation) control unit 65, A UVW / dq converter 66 and a rotation angle calculator 67 are included.
The rotation angle calculator 67 calculates the rotation angle (electrical angle; hereinafter referred to as “rotor angle θs”) of the rotor of the electric motor 18 based on the output signal of the rotation angle sensor 25.

The current command value setting unit 61 sets a current value to be passed through the coordinate axes of the dq coordinate system as a current command value. The current command value setting unit 61 includes a basic current command value setting unit 61A, a damping compensation value calculation unit 61B, and an addition unit 61C.
The basic current command value setting unit 61A has a d-axis basic current command value I _do ^* and a q-axis basic current command value I _qo ^* (hereinafter referred to as “two-phase basic current command value I _doqo ^* ”). Set. More specifically, the basic current command value setting unit 61A sets the q-axis basic current command value I _qo ^* to a significant value, and _sets the d-axis basic current command value I _do ^* to zero. More specifically, the basic current command value setting unit 61A sets the q-axis basic current command value I _qo ^* based on the steering torque (detected steering torque) Th detected by the torque sensor 12.

A setting example of the q-axis basic current command value I _qo ^* with respect to the detected steering torque Th is shown in FIG. For the detected steering torque Th, for example, the torque for steering in the right direction is a positive value, and the torque for steering in the left direction is a negative value. The q-axis basic current command value I _qo ^* is a positive value when an operation assisting force for steering in the right direction from the electric motor 18 is to be generated, and an operation assisting force for steering in the left direction from the electric motor 18. When the value should be generated, a negative value is assumed. The q-axis basic current command value I _qo ^* is positive with respect to a positive value of the detected steering torque Th, and is negative with respect to a negative value of the detected steering torque Th. When the detected steering torque Th is zero, the q-axis basic current command value I _qo ^* is zero. The q-axis basic current command value I _qo ^* is set such that the absolute value of the q-axis basic flow command value I _qo ^* increases as the absolute value of the detected steering torque Th increases. The q-axis basic current command value I _qo ^* is set such that the absolute value thereof decreases as the vehicle speed V detected by the vehicle speed sensor 26 increases.

Based on the vehicle speed V detected by the vehicle speed sensor 26 and the steering angle θh detected by the steering angle sensor 11, the damping compensation value calculation unit 61B is configured to provide a damping compensation value I _qc for converging the steering wheel to the neutral position. Is calculated. Specifically, the damping compensation value calculation unit 61B calculates the damping compensation value I _qc based on the vehicle speed V and the steering speed ω obtained by time differentiation of the steering angle θh. A setting example of the damping compensation value I _{qc with} respect to the vehicle speed V is shown in FIG. The damping compensation value I _qc is set so as to increase as the vehicle speed V increases. In this example, the damping compensation value I _qc is set to change stepwise as the vehicle speed V increases. Further, the damping compensation value I _qc is set so as to increase as the steering speed ω increases.

The adding unit 61C _outputs a value _obtained by subtracting the damping compensation value I _qc from the q-axis basic current command value I _qo ^* as the q-axis current command value I _q ^* , and the d-axis basic current command value I _do ^* as the d-axis. Output as current command value I _d ^* . Hereinafter, the q-axis current command value I _q ^* and the d-axis current command value I _d ^* are collectively referred to as “two-phase current command value I _dq ^* ”.
The two-phase current command value I _dq ^* set by the current command value setting unit 61 is given to the current deviation calculation unit 62. The current detection unit 42 detects the U-phase current I _U , the V-phase current I _V and the W-phase current I _W (hereinafter collectively referred to as “three-phase detection current I _UVW ”) of the electric motor 18. To do. The three-phase detection current I _UVW detected by the current detection unit 42 is given to the UVW / dq conversion unit 66.

The UVW / dq converter 66 converts the three-phase detection current I _UVW (U-phase current I _U , V-phase current I _V and W-phase current I _W ) in the UVW coordinate system detected by the current detection unit 42 into the dq coordinate system. _Are transformed into two-phase detection currents I _d and I _q (hereinafter collectively referred to as “two-phase detection current I _dq ”). For this coordinate conversion, the rotor angle θs (electrical angle) calculated by the rotation angle calculation unit 67 is used.

The current deviation calculation unit 62 calculates the deviation between the two-phase current command value I _dq ^* set by the current command value setting unit 61 and the two-phase detection current I _dq given from the UVW / dq conversion unit 66. More specifically, the current deviation calculation unit 62 calculates the deviation of the d-axis detection current I _d with respect to the d-axis current command value I _d ^* and the deviation of the q-axis detection current I _q with respect to the q-axis current command value I _q ^* . To do. These deviations are given to the PI control unit 63.

The PI control unit 63 performs a PI calculation on the current deviation calculated by the current deviation calculation unit 62, whereby a two-phase voltage command value V _dq ^* (d-axis voltage command value V _d ^* and q-axis voltage command value V _q ^* ) is generated. The two-phase voltage command value V _dq ^* is given to the dq / UVW converter 64.
The dq / UVW conversion unit 64 converts the two-phase voltage command value V _dq ^* into a three-phase voltage command value V _UVW ^* . For this coordinate conversion, the rotor angle θs (electrical angle) calculated by the rotation angle calculation unit 67 is used. The three-phase voltage command value V _UVW ^* includes a U-phase voltage command value V _U ^* , a V-phase voltage command value V _V ^*, and a W-phase voltage command value V _W ^* . The three-phase voltage command value V _UVW ^* is given to the PWM control unit 65.

The PWM control unit 65 includes a U-phase PWM command signal, a V-phase PWM control signal having a duty corresponding to the U-phase voltage command value V _U ^* , the V-phase voltage command value V _V ^*, and the W-phase voltage command value V _W ^* , respectively. A W-phase PWM control signal is generated and supplied to the drive circuit 41.
The drive circuit 41 includes a three-phase inverter circuit corresponding to the U phase, the V phase, and the W phase. The power elements constituting the inverter circuit are controlled by a PWM control signal supplied from the PWM control unit 65, whereby a voltage corresponding to the three-phase voltage command value V _UVW ^* is set to the stator winding 101 of each phase of the electric motor 18. , 102, 103.

The current deviation calculation unit 62 and the PI control unit 63 constitute a current feedback control unit. By the action of the current feedback control means, the motor current flowing through the electric motor 18 is controlled so as to approach the two-phase current command value I _dq ^* set by the current command value setting unit 61.
FIG. 7 is a block diagram illustrating a configuration of the reliability determination unit 70 of the steering angle sensor.

The steering angle sensor reliability determination unit 70 includes a first reliability determination unit 71, a second reliability determination unit 72, an angle storage processing unit 73, and a nonvolatile memory 74. Hereinafter, a value obtained by converting the rotor angle θs of the electrical angle into the rotor angle of the mechanical angle is referred to as “rotor mechanical angle θs”.
FIG. 8 is a flowchart showing the operation of the angle storage processing unit 73.

The angle storage processing unit 73 receives the steering angle θh detected by the steering angle sensor 11 when the ignition-off command is input, and the rotor mechanical angle detected by the rotation angle calculation unit 67 (see FIGS. 2 and 4). θs is stored in the nonvolatile memory 74.
Referring to FIG. 8, when the ignition off command is input (step S1: YES), angle storage processing unit 73 is detected by steering angle θh detected by steering angle sensor 11 and rotation angle calculation unit 67. The rotor mechanical angle θs is acquired (step S2). Then, the angle storage processing unit 73 stores the acquired steering angle θh and rotor mechanical angle θs in the nonvolatile memory 74 as the steering angle θh ′ and rotor mechanical angle θs ′ at the time of previous power-off (step S3). When the steering angle θh ′ and the rotor mechanical angle θs ′ at the time of the previous power-off are already stored in the nonvolatile memory 74, the angle storage processing unit 73 overwrites the data acquired in step S2, thereby Update the data. Thereafter, the angle storage processing unit 73 ends the process.

FIG. 9 is a flowchart showing the operation of the first reliability determination unit 71.
The first reliability determination unit 71 stores the steering angle θh detected by the steering angle sensor 11 immediately after the ECU 30 is turned on, the rotor mechanical angle θs detected by the rotation angle calculation unit 67, and the nonvolatile memory 74. Whether or not the reliability of the detected value of the steering angle sensor 11 is high is determined based on the stored steering angle θh ′ and rotor mechanical angle θs ′ at the previous power-off time.

Referring to FIG. 9, when the power supply of ECU 30 is turned on (step S <b> 11: YES), first reliability determination unit 71 detects steering angle θh detected by steering angle sensor 11 and rotation angle calculation unit 67. Is obtained (step S12).
Next, the first reliability determination unit 71 determines whether or not the reliability determination condition represented by the following equation (1) is satisfied, assuming that the reduction ratio of the reduction mechanism 19 is R (R> 1). (Step S13).

|| θh−θh ′ | — (| θs−θs ′ | / R) | <γ (1)
In equation (1), | θh−θh ′ | is the absolute value of the difference between the steering angle θh acquired in step S12 and the steering angle θh ′ at the previous power-off stored in the nonvolatile memory 74. In equation (1), | θs−θs ′ | is the absolute value of the difference between the rotor mechanical angle θs acquired in step S12 and the rotor mechanical angle θs ′ when the power was last turned off. (| Θs−θs ′ | / R) is a value obtained by dividing the absolute value | θs−θs ′ | by R, and the absolute value | θs−θs ′ | is converted into the rotation amount (rotation angle) of the steering wheel 2. It becomes the value. γ (γ> 0) is a threshold, and is set to 10, for example.

Therefore, in step S13, the reliability determination that the absolute value of the difference between the absolute value | θh−θh ′ | and the value obtained by converting the absolute value | θs−θs ′ | into the rotation angle of the steering wheel 2 is smaller than γ. It is determined whether or not the condition is satisfied.
When it is determined that the reliability determination condition is satisfied (step S13: YES), the first reliability determination unit 71 determines that the detection value of the steering angle sensor 11 is highly reliable (step). S14). That is, the first reliability determination unit 71 determines that the detection value of the steering angle sensor 11 ensures a high level of reliability. Thereafter, the first reliability determination unit 71 ends the current process.

When it is determined in step S13 that the reliability determination condition is not satisfied (step S13: NO), the first reliability determination unit 71 has low reliability of the detected value of the steering angle sensor 11. Is determined (step S15). That is, the first reliability determination unit 71 determines that the detection value of the steering angle sensor 11 does not ensure a high level of reliability. In this case, the first reliability determination unit 71 instructs the motor control unit 60 to change the motor control mode (step S16). For example, the first reliability determination unit 71 uses the current command value (two-phase current command value I _dq ^{*) to the} current command value setting unit 61 without using the steering angle θh detected by the steering angle sensor 11 ^. ) Is set. When the current command value setting unit 61 receives this instruction, thereafter, for example, the q-axis basic current command value I _qo ^* and the d-axis basic current command value I _do set by the basic current command value setting unit 61A. ^* Is output as q-axis current command value I _q ^* and d-axis current command value I _d ^* , respectively. That is, the current command value setting unit 61 sets the two-phase current command value I _dq ^* without using the steering angle θh detected by the steering angle sensor 11. Thereafter, the first reliability determination unit 71 ends the current process.

  Whether the reliability of the detected value of the steering angle sensor 11 is high after the processing by the first reliability determination unit 71 is completed and before the ignition-off command is input. The process for determining whether or not is continued. For example, the second reliability determination unit 71 continues when the vehicle speed V detected by the vehicle speed sensor 26 is equal to or higher than a predetermined speed and the lateral acceleration Gy detected by the lateral acceleration sensor 27 is substantially zero. In addition, it is determined whether or not the absolute value of the steering angle θh detected by the steering angle sensor 11 is equal to or less than a predetermined value. Then, if the absolute value of the steering angle θh is equal to or smaller than a predetermined value, the second reliability determination unit 71 determines that the reliability of the detected value of the steering angle sensor 11 is high, and the absolute value of the steering angle θh is predetermined. If it is larger than the value, it is determined that the reliability of the detected value of the steering angle sensor 11 is low. When it is determined that the reliability of the detection value of the steering angle sensor 11 is low, the second reliability determination unit 72 instructs the motor control unit 60 to provide a motor, similar to step S16 in FIG. An instruction to change the control mode is given.

  According to the embodiment, immediately after the ECU 30 is powered on, it can be determined whether or not the detection value of the steering angle sensor 11 ensures a high level of reliability. When it is determined that the detected value of the steering angle sensor 11 does not ensure a high level of reliability, the motor control mode is set such that the electric motor 18 is controlled without using the detected value of the steering angle sensor 11. Can be changed.

  As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form. For example, when a control device that performs some control using the steering angle θh detected by the steering angle sensor 11 other than the motor control unit 60 is mounted on the vehicle, the first reliability determination unit 71 When it is determined that the reliability determination condition in step S13 of FIG. 9 is not satisfied, the control device may be instructed to perform control without using the steering angle θh.

  In the embodiment, in step S13 of FIG. 9, the first reliability determination unit 71 determines whether or not the reliability determination condition represented by the equation (1) is satisfied. It may be determined whether or not the reliability determination condition of | θh−θh ′ | <α and | θs−θs ′ | <β is satisfied. | Θh−θh ′ | is the absolute value of the difference between the steering angle θh acquired in step S <b> 12 of FIG. 9 and the steering angle θh ′ at the previous power-off stored in the nonvolatile memory 74. | Θs−θs ′ | is the absolute value of the difference between the rotor mechanical angle θs acquired in step S12 of FIG. 9 and the rotor mechanical angle θs ′ when the power was turned off the last time. α (α> 0) is a first threshold value, and β (β> 0) is a second threshold value. α is set to 10, for example. β is set to 10 × R, for example, where R (R> 1) is the reduction ratio of the speed reduction mechanism 19. For example, when the reduction ratio R is 20, β is set to 200.

  In addition, various design changes can be made within the scope of matters described in the claims.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus, 8 ... Input shaft, 9 ... Output shaft, 11 ... Steering angle sensor, 25 ... Rotation angle sensor, 67 ... Rotation angle calculating part, 18 ... Electric motor, 30 ... ECU, 70 ... Steering angle sensor , Reliability determination unit, 71... First reliability determination unit, 73... Angle storage processing unit, 73.

Claims (3)

A reliability determination apparatus for a steering angle sensor for detecting a steering angle that is a rotation angle of a steering member,
A steering mechanism that steers the steered wheels in conjunction with the rotation of the steering member;
An electric motor for providing a steering assist force to the steering mechanism;
A rotation angle sensor for detecting a rotation angle of the electric motor;
When an ignition-off command is input, the steering angle detected by the steering angle sensor and the rotation angle detected by the rotation angle sensor are stored in the nonvolatile memory as the steering angle and rotation angle at the previous power-off time. Means,
Immediately after the power is turned on, the steering angle detected by the steering angle sensor, the rotation angle detected by the rotation angle sensor, and the steering angle and rotation angle at the previous power-off time stored in the nonvolatile memory And a reliability determination device for determining the reliability of the detected value of the steering angle sensor. The reliability determination means includes
The absolute value of the difference between the steering angle detected by the steering angle sensor and the steering angle at the previous power-off time, and the absolute value of the difference between the rotation angle detected by the rotation angle sensor and the rotation angle at the previous power-off time Means for determining whether or not a condition that an absolute value of a difference between a value corresponding to one of the other and the other value is equal to or less than a predetermined value is satisfied;
Means for determining that the reliability of the detected value of the steering angle sensor is high when it is determined that the condition is satisfied;
The reliability determination device for a steering angle sensor according to claim 1, further comprising means for determining that the reliability of the detected value of the steering angle sensor is low when it is determined that the condition is not satisfied. The reliability determination means includes
The absolute value of the difference between the steering angle detected by the steering angle sensor and the steering angle at the previous power-off is not more than a first predetermined value, and the rotation angle detected by the rotation angle sensor and the previous power-off Means for determining whether or not a condition that an absolute value of a difference from the rotation angle is equal to or smaller than a second predetermined value is satisfied;
Means for determining that the reliability of the detected value of the steering angle sensor is high when it is determined that the condition is satisfied;
The reliability determination device for a steering angle sensor according to claim 1, further comprising means for determining that the reliability of the detected value of the steering angle sensor is low when it is determined that the condition is not satisfied.

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