Steering angle detection device and electric power steering device

Abstract

A steering angle based on the steering angle when the vehicle is in a straight-moving state is calculated with high accuracy. The steering angle detection device comprises: a first storage unit (34) storing a steering angle neutral point correction value, which is a difference between a central value of the extreme steering angles in right steering and left steering and the steering angle when the vehicle is in a straight-moving state; a second storage unit (34) storing an initial position of a movable part of an actuator of a steering mechanism when the vehicle is in a straight-moving state; a first steering angle calculation unit (32) calculating a first steering angle based on the central value of the extreme steering angles in right steering and left steering based on a detected value of the position of the movable part of the actuator; and a second steering angle calculation unit (35) calculating a second steering angle when the vehicle is in a straight-moving state based on a detected value of the position of the movable part of the actuator, the steering angle neutral point correction value, the initial position and the first steering angle.

Description

Technical Field

[0001] The invention relates to a steering angle detection device and an electric power steering device. Background Art

[0002] Patent Document 1 below describes a technique in which the respective limit steering angles when the steering wheel is turned right and left are detected, the intermediate value thereof is set as the neutral point of the steering angle, and the steering angle is obtained based on the neutral point.

[0003] In the following description, the limit steering angles for right and left steering are sometimes expressed as "rack-end steering angles". For example, if the value of the steering angle to the right of the neutral position is positive and the value of the steering angle to the left is negative, the rack-end steering angle for right steering is the maximum steering angle when the steering wheel is turned to the right to the limit, and the rack-end steering angle for left steering is the minimum steering angle when the steering wheel is turned to the left to the limit.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 4323402 Summary of the invention

[0007] Problems to be solved by the invention

[0008] However, the center value of the left and right rack end steering angles may not always match the steering angle when the vehicle is traveling straight, and errors may also occur in the detection of the rack end steering angle. Therefore, the technology described in Patent Document 1 cannot accurately calculate the steering angle based on the steering angle when the vehicle is traveling straight.

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to calculate a steering angle with high accuracy based on the steering angle when the vehicle is in a straight-moving state.

[0010] Means for solving problems

[0011] In order to achieve the above-mentioned object, a steering angle detection device according to one embodiment of the present invention comprises: a position detection unit that detects a steering angle of a steering mechanism; an actuator that drives the steering mechanism; a first storage unit that stores a steering angle neutral point correction value, which is a difference between a central value of each of the limit steering angles of right steering and left steering and a steering angle when the vehicle is in a straight-moving state; a second storage unit that stores an actuator initial position, which is a position of a movable part of the actuator when the vehicle is in a straight-moving state; an actuator position detection unit that detects the position of the movable part of the actuator as a first actuator position; a first steering angle calculation unit that calculates, based on the first actuator position, a steering angle of the steering mechanism based on the central value of each of the limit steering angles of right steering and left steering as a first steering angle; and a second steering angle calculation unit that calculates, based on the first actuator position, a second steering angle that is a steering angle of the steering mechanism when the vehicle is in a straight-moving state.

[0012] To achieve the above object, an electric power steering device according to another aspect of the present invention includes the above-mentioned steering angle detection device, and drives an actuator based on a second steering angle to apply a steering assist force to a steering mechanism.

[0013] Effects of the Invention

[0014] According to the present invention, it is possible to calculate with high accuracy the steering angle based on the steering angle when the vehicle is in a straight-moving state. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic structural diagram showing an example of an electric power steering device according to an embodiment.

[0016] Figure 2 yes Figure 1 A block diagram showing an example of the functional configuration of a steering angle detection unit shown in FIG.

[0017] Figure 3 (a) to (c) are explanatory diagrams of an example of a steering angle detection method according to an embodiment.

[0018] Figure 4 (a) is a flowchart of an example of initial setting processing, and (b) is a flowchart of an example of steering angle information restoration processing.

[0019] Figure 5 (a) and (b) are explanatory diagrams of an example of a steering angle detection method according to a modified example. DETAILED DESCRIPTION

[0020] Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0021] In addition, the embodiments of the present invention shown below illustrate devices and methods for implementing the technical concept of the present invention, but the technical concept of the present invention does not limit the structure and configuration of the components to the following contents. The technical concept of the present invention can be modified in various ways within the technical scope specified by the claims described in the claims.

[0022] (structure)

[0023] Figure 1 The schematic structural diagram of an example of an electric power steering device according to an embodiment of the present invention is shown. The column shafts (steering shafts) 2i and 2o of the steering wheel (steering handle) 1 are connected to the steering wheels 8L and 8R via the reduction gear (worm gear) 3, the intermediate shaft 4, the pinion rack mechanism 5, the steering tie rods 6a and 6b, and further via the hub units 7a and 7b.

[0024] The column input shaft 2i and the column output shaft 2o are connected via a torsion bar (not shown), and the torsion bar is twisted by the deviation of the rotation angle between the column input shaft 2i and the column output shaft 2o.

[0025] The intermediate shaft 4 has a shaft member 4c and universal joints 4a and 4b attached to both ends of the shaft member. The universal joint 4a is connected to the column output shaft 2o, and the universal joint 4b is connected to the pinion rack mechanism 5.

[0026] The pinion rack mechanism 5 includes a pinion 5a connected to a pinion shaft that transmits steering force from a universal joint 4b, and a rack 5b that meshes with the pinion 5a and converts rotational motion transmitted to the pinion 5a into linear motion in the vehicle width direction.

[0027] The steering shaft 2 (column shafts 2i and 2o) is provided with a torque sensor 10 for detecting a steering torque Th.

[0028] The motor 20 assisting the steering force of the steering wheel 1 is connected to the column output shaft 2o via the reduction gear 3. A rotation angle sensor 21 for detecting a mechanical angle θm of the rotation shaft is provided on the rotation shaft of the motor 20. The mechanical angle θm is an example of the "first actuator position" described in the claims.

[0029] The rotation amount of the column output shaft 2o is obtained by dividing the rotation amount of the rotating shaft of the motor 20 by the reduction ratio R of the reduction gear 3. The controller 30 calculates the rotation angle of the column output shaft 2o obtained by dividing the mechanical angle θm by the reduction ratio R of the reduction gear 3 as the steering angle θt.

[0030] The motor 20 is an example of an "actuator" described in the claims. The reduction ratio R of the reduction gear 3 is an example of a "conversion coefficient" described in the claims. The actuator in the present invention is not limited to a motor, and various actuators can be used.

[0031] A controller 30 that controls an electric power steering (EPS) device is supplied with electric power from a battery 13 , and an ignition key signal is inputted via an ignition (IGN) key 11 .

[0032] The controller 30 calculates the current command value of the auxiliary control command based on the steering torque Th detected by the torque sensor 10, the vehicle speed Vh detected by the vehicle speed sensor 12, and the steering angle θt calculated according to the mechanical angle θm of the motor 20, and controls the current supplied to the motor 20 by obtaining the voltage control command value Vref by performing compensation on the current command value.

[0033] The controller 30 may include, for example, a computer including a processor and peripheral components such as a storage device. The processor may be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit).

[0034] The storage device may include any of a semiconductor storage device, a magnetic storage device, and an optical storage device. The storage device may include a register, a cache memory, a ROM (Read Only Memory) used as a main storage device, and a RAM (Random Access Memory) and other memories.

[0035] The functions of the controller 30 described below are implemented, for example, by a processor of the controller 30 executing a computer program stored in a storage device.

[0036] Furthermore, the controller 30 may be formed by dedicated hardware for executing each information processing described below.

[0037] For example, the controller 30 may include a functional logic circuit set in a general-purpose semiconductor integrated circuit. For example, the controller 30 may include a programmable logic device (PLD) such as a field programmable gate array (FPGA).

[0038] The controller 30 detects the steering angle θt of the steering mechanism. As described above, the controller 30 calculates the rotation angle of the column output shaft 2o as the steering angle θt by dividing the mechanical angle θm of the rotating shaft of the motor 20 by the reduction ratio R of the reduction gear 3.

[0039] Here, the rotating shaft of the motor 20 is connected to the column output shaft 2o via the reduction gear 3. Therefore, while the steering mechanism is turned from the neutral position to the right or left direction to the limit, the mechanical angle θm of the motor 20 changes further than the angle of 360 degrees for one rotation. Therefore, the steering angle θt of the steering mechanism cannot be determined uniquely based on the mechanical angle θm of the motor 20.

[0040] Therefore, the controller 30 holds the steering angle information related to the steering angle θt and updates it according to the change of the mechanical angle θm, thereby calculating the steering angle θt.

[0041] While the ignition key 11 is off, the number of rotations of the rotating shaft of the motor 20 is counted instead of detecting the mechanical angle θm. For example, the number of rotations of the rotating shaft of the motor 20 is counted per 1 / 4 rotation (ie, per quadrant).

[0042] When the ignition key 11 changes from off to on, based on the number of rotations n counted up to that moment and the mechanical angle θm detected at that moment, the rotation angle (360×n+θm) of the rotating shaft within the angle range of multiple rotations is calculated and divided by the reduction ratio R, thereby calculating the steering angle θt.

[0043] However, the steering angle information may disappear for various reasons. For example, when the vehicle is transported for a long time and the battery is removed from the vehicle to avoid battery consumption, the steering angle information disappears. If the steering angle information disappears, the steering angle θt becomes unknown based only on the mechanical angle θm of the motor 20.

[0044] In such a case, the neutral position of the steering mechanism can be obtained by detecting the left and right rack-end steering angles and calculating the median value of the rack-end steering angles.

[0045] However, the center value of the left and right rack-end steering angles does not necessarily coincide with the steering angle when the vehicle is in a straight-moving state. Therefore, even if the steering angle is calculated with the center value of the rack-end steering angle as the neutral position, it will not be the neutral position when the vehicle is in a straight-moving state. In other words, it will not be the steering angle based on the steering angle when the vehicle is in a straight-moving state. In addition, since errors also occur in the detection of the rack-end steering angle, the accuracy is also reduced due to the errors.

[0046] Therefore, the controller 30 of the embodiment includes a steering angle detection unit 31 that calculates a steering angle based on the steering angle when the vehicle is in a straight-moving state.

[0047] The steering angle detection unit 31 stores in advance a steering angle neutral point correction value Δθt, which is the difference between the center value of the left and right rack end steering angles and the steering angle when the vehicle is in a straight-ahead state. In addition, the motor initial position θm0 is also stored in advance, which is the mechanical angle θm of the rotation shaft of the motor 20 detected by the rotation angle sensor 21 when the vehicle is in a straight-ahead state. The motor initial position θm0 is an example of the "actuator initial position" described in the claims.

[0048] The steering angle detection unit 31 corrects the steering angle based on the center value of the left and right rack end steering angles based on the steering angle neutral point correction value Δθt and the motor initial position θm0, thereby accurately calculating the steering angle based on the steering angle when the vehicle is traveling straight.

[0049] Figure 2 2 is a block diagram showing an example of the functional configuration of the steering angle detection unit 31. The steering angle detection unit 31 includes a first steering angle calculation unit 32, a correction information generation unit 33, a storage unit 34, and a second steering angle calculation unit 35.

[0050] The first steering angle calculation unit 32 calculates the steering angle θt1 of the steering mechanism based on the center value of the left and right rack end steering angles. In other words, the steering angle θt1 is calculated so that the center value of the left and right rack end steering angles is in the neutral position. The steering angle θt1 is an example of the "first steering angle" described in the claims.

[0051] Hereinafter, the center value of the left and right rack end steering angles may be expressed as "L2L midpoint position θLn".

[0052] For example, the first steering angle calculation unit 32 detects the left and right rack end steering angles respectively, using an arbitrary steering angle θa (for example, a steering angle when the power is turned on before the steering angle information is stored) as a reference angle.

[0053] During the period from the right turn or the left turn limit to the other turn limit, the mechanical angle θm of the rotating shaft of the motor 20 changes by more than 360 degrees. Therefore, the first steering angle calculation unit 32 can count the number of rotations n of the rotating shaft, and calculate the angle of each rotating shaft when reaching the left and right turn limits as the rotation angle (360×n+θm) within the angle range of the rotation of multiple turns. Each rotation angle is divided by the reduction ratio R to calculate the left and right rack end steering angles.

[0054] The first steering angle calculation unit 32 obtains the central value of these rack end steering angles and sets it as the L2L midpoint position θLn. The steering angle detected based on an arbitrary steering angle θa is corrected using the L2L midpoint position θLn (for example, by subtracting the L2L midpoint position θLn), thereby calculating the steering angle θt1 based on the L2L midpoint position θLn.

[0055] The correction information generating unit 33 generates the difference between the L2L midpoint position θLn and the steering angle when the vehicle is in a straight-moving state as a steering angle neutral point correction value Δθt and stores it in the storage unit 34. In addition, the correction information generating unit 33 stores the mechanical angle θm when the vehicle is in a straight-moving state as the motor initial position θm0 in the storage unit 34. The storage unit 34 is an example of the “first storage unit”, “second storage unit”, and “third storage unit” described in the claims.

[0056] The correction information generating unit 33 may generate the steering angle neutral point correction value Δθt and the motor initial position θm0 at the time of factory shipment, for example, and store them in the storage unit 34 .

[0057] For example, the correction information generating unit 33 stores a value (−θt1) obtained by inverting the sign of the output θt1 of the first steering angle calculating unit 32 when the vehicle is traveling straight in the storage unit 34 as the steering angle neutral point correction value Δθt.

[0058] The second steering angle calculation unit 35 corrects the steering angle θt1 based on the mechanical angle θm, the steering angle neutral point correction value Δθt, and the motor initial position θm0, thereby calculating a corrected steering angle θt2 based on the steering angle of the steering mechanism when the vehicle is in a straight-moving state. The corrected steering angle θt2 is an example of the "second steering angle" described in the claims.

[0059] The second steering angle calculation unit 35 calculates the steering angle θnt based on the point after the L2L midpoint position θLn is corrected by the steering angle neutral point correction value Δθt. Hereinafter, the steering angle θnt based on the point after the L2L midpoint position θLn is corrected by the steering angle neutral point correction value Δθt is expressed as "L2L midpoint steering angle θnt". For example, the second steering angle calculation unit 35 can calculate the L2L midpoint steering angle θnt=θt1-Δθt by subtracting the steering angle neutral point correction value Δθt from the steering angle θt1. The L2L midpoint steering angle θnt is an example of the "third steering angle" described in the claims.

[0060] The second steering angle calculation unit 35 converts the L2L midpoint steering angle θnt into a mechanical angle θnm. Hereinafter, the mechanical angle θnm will be referred to as “L2L mechanical angle θnm”.

[0061] Specifically, the second steering angle calculation unit 35 converts the L2L midpoint steering angle θnt into a mechanical angle scale by multiplying the L2L midpoint steering angle θnt by the reduction ratio R. Hereinafter, the L2L midpoint steering angle (θn×R) converted into a mechanical angle scale is expressed as “converted L2L midpoint steering angle θntc”.

[0062] The second steering angle calculation unit 35 calculates the remainder mod(θntc, 360) of the converted L2L midpoint steering angle θntc with 360 degrees of angle change per rotation as the L2L mechanical angle θnm. The L2L mechanical angle θnm is an example of the “third actuator position” described in the claims.

[0063] The second steering angle calculation unit 35 calculates a mechanical angle θm2=θm-θm0 based on the motor initial position θm0 by correcting the mechanical angle θm detected by the rotation angle sensor 21 using the motor initial position θm0. Hereinafter, the mechanical angle θm2 is referred to as a "second motor mechanical angle θm2".

[0064] Figure 3 (a)~ Figure 3 The single-dot chain line in (c) represents the L2L midpoint steering angle θntc after conversion, the solid line represents the L2L mechanical angle θnm, and the dotted line represents the second motor mechanical angle θm2.

[0065] The second steering angle calculation unit 35 calculates the motor position difference Δθm as follows based on the difference (θnm-θm2) between the L2L mechanical angle θnm and the second motor mechanical angle θm2. The motor position difference Δθm is an example of the “actuator position difference” described in the claims.

[0066] (1) When the difference (θnm-θm2) ≥ (-180) degrees and the difference (θnm-θm2) ≤ 180 degrees, Figure 3 As shown by arrow 40 in (a), the difference (θnm-θm2) is directly set as the motor position difference Δθm.

[0067] (2) When the difference (θnm-θm2) is less than (-180) degrees, Figure 3 As shown by arrow 41 in (b), the sum of the difference (θnm-θm2) plus 360 degrees is set as the motor position difference Δθm.

[0068] (3) When the difference (θnm-θm2)>180 degrees, Figure 3 As shown by arrow 42 in (c), the difference obtained by subtracting 360 degrees from the difference (θnm-θm2) is set as the motor position difference Δθm.

[0069] Figure 3(a)~ Figure 3 The two-dot chain line in (c) indicates a scaled angle θstc converted to a mechanical angle by multiplying the steering angle based on the steering angle when the vehicle is traveling straight by the reduction ratio R. Hereinafter, the angle θstc is referred to as "converted straight midpoint steering angle θstc".

[0070] from Figure 3 (a)~ Figure 3 As shown in (c), by subtracting the motor position difference Δθm from the converted L2L mid-point steering angle θntc, the converted L2L mid-point steering angle θntc can be corrected to the converted straight-ahead mid-point steering angle θstc. If the converted straight-ahead mid-point steering angle θstc is divided by the reduction ratio R, the steering angle based on the steering angle when the vehicle is in a straight-ahead state can be calculated.

[0071] Here, since the L2L mid-point steering angle θnt = (L2L mid-point steering angle θntc after conversion / reduction ratio R), the second steering angle calculation unit 35 calculates the difference (θnt-Δθm / R) obtained by subtracting the division result (Δθm / R) obtained by dividing the motor position difference Δθm by the reduction ratio R from the L2L mid-point steering angle θnt as the corrected steering angle θt2.

[0072] Therefore, if the following (condition 1) and (condition 2) are satisfied, the second steering angle calculation unit 35 can calculate the corrected steering angle θt2 as a steering angle based on the steering angle when the vehicle is in a straight-moving state.

[0073] (Condition 1) From the time when the steering angle neutral point correction value Δθt and the motor initial position θm0 are stored (for example, at the time of shipment) to the time when the corrected steering angle θt2 is calculated, the mechanism on which the motor 20 is mounted is not changed by parts replacement or the like.

[0074] (Condition 2) The error between the L2L midpoint position θLn used when storing the steering angle neutral point correction value Δθt and the L2L midpoint position θLn used when calculating the corrected steering angle θt2 is less than the mechanical angle of 180 degrees.

[0075] (action)

[0076] Next, refer to Figure 4 (a) and Figure 4 (b) An example of a steering angle detection method according to an embodiment is described. Figure 4 (a) is a flowchart of an example of initial setting processing for generating a steering angle neutral point correction value Δθt and a motor initial position θm0 and storing them in the storage unit 34 .

[0077] In step S1 , the first steering angle calculation unit 32 detects the left and right rack end steering angles, respectively, and detects the middle value thereof as the L2L midpoint position θLn.

[0078] In step S2 , the correction information generating unit 33 generates a difference between the L2L midpoint position θLn and the steering angle when the vehicle is traveling straight as a steering angle neutral point correction value Δθt, and stores it in the storage unit 34 .

[0079] In step S3 , the correction information generating unit 33 stores the mechanical angle θm when the vehicle is traveling straight as the motor initial position θm0 in the storage unit 34 .

[0080] After that, the initial setting process ends.

[0081] Figure 4 (b) is a flowchart of an example of a steering angle information recovery process for calculating the corrected steering angle θt2. This process is performed when the battery is reconnected.

[0082] In step S10 , the second steering angle calculation unit 35 reads the steering angle neutral point correction value Δθt and the motor initial position θm0 from the storage unit 34 .

[0083] In step S11 , the first steering angle calculation unit 32 detects the left and right rack end steering angles, respectively, and detects the middle value thereof as the L2L midpoint position θLn.

[0084] In step S12 , the first steering angle calculation unit 32 calculates the steering angle θt1 based on the L2L midpoint position θLn.

[0085] In step S13 , the second steering angle calculation unit 35 calculates the L2L mid-point steering angle θnt by subtracting the steering angle mid-point correction value Δθt from the steering angle θt1 .

[0086] In step S14 , the second steering angle calculation unit 35 calculates a second motor mechanical angle θm2 based on the motor initial position θm0 by correcting the mechanical angle θm detected by the rotation angle sensor 21 using the motor initial position θm0 .

[0087] In step S15, the second steering angle calculation unit 35 converts the L2L midpoint steering angle θnt into a motor mechanical angle, and then calculates a motor position difference Δθm based on the difference (θnm-θm2) between the L2L mechanical angle θnm and the second motor mechanical angle θm2.

[0088] In step S16 , the second steering angle calculation unit 35 subtracts the motor position difference Δθm divided by the reduction ratio R (Δθm / R) from the L2L midpoint steering angle θnt to calculate the corrected steering angle θt2 .

[0089] After that, the steering angle information restoration process ends.

[0090] (Effects of Embodiments)

[0091] (1) The rotation angle sensor 21 and the first steering angle calculation unit 32 detect the steering angle of the steering mechanism. The correction information generation unit 33 stores the steering angle neutral point correction value Δθt, which is the difference between the central value of the respective limit steering angles in the right turn and the left turn and the steering angle when the vehicle is in a straight state, and the motor initial position θm0, which is the angle of the rotation axis of the motor 20 when the vehicle is in a straight state, in the storage unit 34. The rotation angle sensor 21 detects the mechanical angle θm of the rotation axis of the motor 20. The first steering angle calculation unit 32 calculates the steering angle θt1 of the steering mechanism based on the central value of the respective limit steering angles in the right turn and the left turn based on the mechanical angle θm. The second steering angle calculation unit 35 calculates the corrected steering angle θt2 based on the steering angle of the steering mechanism when the vehicle is in a straight state based on the mechanical angle θm, the steering angle neutral point correction value Δθt, the motor initial position θm0, and the steering angle θt1.

[0092] Thus, even if the steering angle information is lost, it is possible to calculate the corrected steering angle θt2 based on the steering angle of the steering mechanism when the vehicle is traveling straight.

[0093] Furthermore, even if an error occurs in the detection of the rack end steering angle, it is possible to calculate the accurately corrected steering angle θt2 that does not include such an error.

[0094] (2) The second steering angle calculation unit 35 can calculate the second motor mechanical angle θm2, which is the mechanical angle of the rotating shaft of the motor 20 based on the motor initial position θm0, based on the mechanical angle θm and the motor initial position θm0, and calculate the corrected steering angle θt2 based on the L2L midpoint steering angle θnt obtained by correcting the steering angle θt1 using the steering angle neutral point correction value Δθt and the second motor mechanical angle θm2.

[0095] Before correction based on the second motor mechanical angle θm2, the steering angle θt1 is corrected using the steering angle neutral point correction value Δθt, thereby enabling correction based on the second motor mechanical angle θm2 even if the steering angle θt1 deviates by more than 180 degrees from the steering angle based on the steering angle of the steering mechanism when the vehicle is in a straight state.

[0096] (3) The second steering angle calculation unit 35 can calculate the motor position difference Δθm which is the difference between the L2L mechanical angle θnm corresponding to the L2L mid-point steering angle θnt and the second motor mechanical angle θm2, and correct the L2L mid-point steering angle θnt based on the value (Δθm / R) obtained by dividing the motor position difference Δθm by the reduction ratio R, thereby calculating the corrected steering angle θt2.

[0097] Thus, the corrected steering angle θt2 can be calculated based on the L2L mid-point steering angle θnt and the second motor mechanical angle θm2.

[0098] (4) The second steering angle calculation unit may calculate the L2L mechanical angle θnm as the remainder mod(θnt×R, 360) of the product (θnt×R) of the L2L midpoint steering angle θnt and the reduction ratio R with 360 degrees as a divisor.

[0099] In this way, the L2L mechanical angle θnm used for calculating the motor position difference Δθm can be calculated.

[0100] (Variant 1)

[0101] The above embodiment is an example of a method for calculating the corrected steering angle θt2. The corrected steering angle θt2 can be calculated by various methods based on the mechanical angle θm, the steering angle neutral point correction value Δθt, the motor initial position θm0 and the first steering angle θt1. Modifications will be described below.

[0102] The second steering angle calculation unit 35 can also calculate the difference (θntc-θm2) obtained by subtracting the second motor mechanical angle θm2 from the converted L2L mid-point steering angle θntc, which is the product of the L2L mid-point steering angle θnt and the reduction ratio R, and calculate the motor position difference Δθm based on the remainder mod (θntc-θm2, 360) of the difference (θntc-θm2) obtained by using 360 degrees as the divisor.

[0103] And, if Figure 5 As shown in (a), when mod(θntc-θm2, 360)≤180 degrees, mod(θntc-θm2, 360) is set to the motor position difference Δθm.

[0104] On the other hand, Figure 5 As shown in (b), when mod(θntc-θm2, 360)>180 degrees, mod(θntc-θm2, 360)-360 degrees is set as the motor position difference Δθm.

[0105] Even when the motor position difference Δθm is set in this way, the corrected steering angle θt2 can be calculated.

[0106] (Variant 2)

[0107] The correction information generating unit 33 may calculate a difference (Δθt×R-θm0) obtained by subtracting the motor initial position θm0 from the product (Δθt×R) of the steering angle neutral point correction value Δθt and the reduction ratio R, and store it as the correction amount difference (Δθt×R-θm0).

[0108] The second steering angle calculation unit 35 may calculate a value (θt1×R−(Δθt×R−θm0)−θm) obtained by subtracting the correction amount difference (Δθt×R−θm0) and the mechanical angle θm from the product of the first steering angle θt1 and the reduction ratio R.

[0109] The value calculated in this way (θt1×R-(Δθt×R-θm0)-θm) can be arranged as (θt1-Δθt)×R-(θm-θm0)=(θntc-θm2), and is therefore equal to the difference (θntc-θm2) in Modification Example 1.

[0110] Even if the difference (θntc-θm2) is calculated in this way, the corrected steering angle θt2 can be calculated.

[0111] (Variant 3)

[0112] The second motor mechanical angle θm2 may be divided by the reduction ratio R to determine the correction amount for the L2L midpoint steering angle θnt based on the difference (θnt-θm2 / R) obtained by subtracting the scaled value θm2 / R converted into the rotation angle of the column shaft 2o from the L2L midpoint steering angle θnt.

[0113] For example, the mechanical angle θm can be changed by turning the steering wheel, thereby changing the difference (θnt-θm2 / R), and the difference (θnt-θm2 / R) when the absolute value becomes the smallest can be set as the correction amount. The L2L midpoint steering angle θnt can be corrected with the correction amount set in this way, thereby calculating the corrected steering angle θt2.

[0114] The corrected steering angle θt2 can also be calculated by such a method.

[0115] (Variant 4)

[0116] The steering angle θt may be calculated based on the rotation angle detected by a steering angle sensor attached to the column input shaft 2i or the column output shaft 2o.

[0117] Description of Reference Numerals

[0118] 1: Steering wheel; 2i: Column input shaft; 2o: Column output shaft; 3: Reduction gear; 4: Intermediate shaft; 4a, 4b: Universal joint; 4c: Shaft component; 5: Pinion and rack mechanism; 5a: Pinion; 5b: Rack; 6a, 6b: Steering rod; 7a, 7b: Hub unit; 8L, 8R: Steering wheel; 10: Torque sensor; 11: Ignition key; 12: Vehicle speed sensor; 13: Battery; 20: Motor; 21: Rotation angle sensor; 30: Controller; 31: Steering angle detection unit; 32: First steering angle calculation unit; 33: Correction information generation unit; 34: Storage unit; 35: Second steering angle calculation unit.

Claims

1. A steering angle detection device, wherein: The steering angle detection device comprises: A position detection unit that detects a steering angle of the steering mechanism; an actuator, which drives the steering mechanism; a first storage unit storing a steering angle neutral point correction value, the steering angle neutral point correction value being a difference between a center value of the steering angle at each of right steering and left steering limits and the steering angle when the vehicle is in a straight-moving state; a second storage unit storing an actuator initial position, the actuator initial position being a position of a movable portion of the actuator when the vehicle is in a straight-moving state; an actuator position detection unit that detects a position of a movable portion of the actuator as a first actuator position; a first steering angle calculation unit that calculates, based on the first actuator position, a steering angle of the steering mechanism based on a median value of the steering angles at respective limits of right steering and left steering as a first steering angle; as well as A second steering angle calculation unit calculates a second steering angle based on the first actuator position, the steering angle neutral point correction value, the actuator initial position and the first steering angle, using as a reference the steering angle of the steering mechanism when the vehicle is in a straight-moving state.

2. The steering angle detection device according to claim 1, wherein: The second steering angle calculation unit calculates a second actuator position based on the first actuator position and the actuator initial position, the second actuator position being the position of the actuator with reference to the actuator initial position. The second steering angle calculation unit calculates the second steering angle based on a third steering angle obtained by correcting the first steering angle using the steering angle neutral point correction value and the second actuator position.

3. The steering angle detection device according to claim 2, wherein: The second steering angle calculation unit calculates an actuator position difference, which is a difference between a third actuator position corresponding to the third steering angle and the second actuator position. The second steering angle calculation unit calculates the second steering angle by correcting the third steering angle based on a product of a ratio of a change in the steering angle of the steering mechanism to a change in a position of a movable portion of the actuator and an actuator position difference.

4. The steering angle detection device according to claim 3, wherein: The second steering angle calculation unit calculates the third actuator position by obtaining the remainder obtained by dividing the product of the following conversion coefficient and the third steering angle by 360 degrees, wherein the conversion coefficient is the inverse of the ratio of the change in the steering angle of the steering mechanism to the rotation amount of the rotating shaft of the motor serving as the actuator.

5. The steering angle detection device according to claim 2, wherein: The second steering angle calculation unit calculates a remainder obtained by subtracting the second actuator position from the product of the following conversion coefficient and the third steering angle and dividing it by 360 degrees as an actuator position difference, wherein the conversion coefficient is the inverse of the ratio of the amount of change in the steering angle of the steering mechanism to the amount of rotation of the rotating shaft of the motor as the actuator, The second steering angle is calculated by correcting the third steering angle based on a value obtained by dividing the actuator position difference by the conversion coefficient.

6. The steering angle detection device according to claim 2, wherein: The steering angle detection device includes a third storage unit that stores a correction amount difference, the correction amount difference being a difference between a product of a conversion coefficient and the steering angle neutral point correction value and an actuator initial position, the conversion coefficient being an inverse of a ratio of a change amount of the steering angle of the steering mechanism to a rotation amount of a rotation shaft of a motor as the actuator, The second steering angle calculation unit calculates a remainder obtained by dividing a difference obtained by subtracting the correction amount difference and the first actuator position from the product of the first steering angle and the conversion coefficient by 360 degrees as an actuator position difference. The second steering angle calculation unit calculates the second steering angle by correcting the third steering angle based on a value obtained by dividing the actuator position difference by the conversion coefficient.

7. The steering angle detection device according to claim 2, wherein: The second steering angle calculation unit calculates the second steering angle by correcting the third steering angle based on a difference obtained by subtracting a product of a ratio of a change in the steering angle of the steering mechanism to a change in a position of a movable part of the actuator and a position of the second actuator from the third steering angle.

8. An electric power steering device, wherein: The electric power steering device comprises a steering angle detection device according to any one of claims 1 to 7, The actuator is driven based on the second steering angle to apply a steering assist force to the steering mechanism.

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