Electric power steering device

Abstract

A control device (4) that calculates an assist torque command value for a motor (5) and outputs the assist torque command value to the motor comprises: a steering angle calculation unit (21) that calculates a steering angle; a pinion shaft torque calculation unit (24) that calculates a pinion shaft torque on the basis of the state quantity of an EPS device; a movement suppression determination unit (25) that determines whether or not the steering state of a steering shaft is in a steering cut-in state on the basis of at least two of the steering angle, the steering angular velocity, and the pinion shaft torque, and permits suppression of movement of a rack shaft when the steering state is determined to be in the steering cut-in state, on the basis of a condition when the determination is made; a movement suppression determination angle acquisition unit (26) that acquires a corrected steering angle when the suppression of movement of the rack shaft is permitted; and an end position correspondence angle determination unit (27) that determines a positive / negative end position correspondence angle corresponding to the reciprocating movement direction of the rack shaft, using the movement suppression determination angle of the steering angle acquired when the suppression of movement is permitted.

Description

Electric power steering device

[0001] The present disclosure relates to an electric power steering device.

[0002] Electric power steering (EPS) devices (hereinafter simply referred to as EPS) using a motor as a drive source are known as power steering devices mounted on vehicles. The EPS uses information from various sensors to realize advanced driver-assistance systems (ADAS) functions (hereinafter simply referred to as ADAS functions), such as an automatic parking function that detects parking spaces and automatically assists with steering operations, and a lane keeping function that recognizes white lines on the road and controls the vehicle to stay within the recognized white lines.

[0003] Furthermore, the EPS has a set range of steering angle for the front wheels of the vehicle on which the EPS is installed, and the steering angle cannot exceed either end of this range. Specifically, the range of steering angle is set by the contact of the end of the rack shaft (rack end) with the rack housing.

[0004] Therefore, when the steering wheel is turned close to the maximum steering angle (end position) at which the steering wheel can be turned, if further turning is performed at a large steering angular velocity to increase the absolute value of the steering angle, the rack end will collide with the rack housing, causing an impact in the steering system. This so-called end impact impact is also transmitted to the steering wheel, causing problems such as a worsening of the steering feel and an increase in hitting noise.

[0005] In the automatic parking function, which is one of the ADAS functions, if the accurate end position cannot be detected, a margin is left from the actual end position to prevent impact from hitting the end, and the steering is stopped at a position before that, or the steering speed is reduced, which increases the time required for automatic parking. Therefore, the automatic parking function may be limited until the end position is obtained. Furthermore, not only the automatic parking function but also other ADAS functions may be limited until the end position is obtained.

[0006] As an example of acquiring the end position, in Patent Document 1, when the steering torque becomes equal to or greater than a certain threshold value, a stored limit position is detected as the steering angle corresponding to the end position.

[0007] Patent No. 7063428

[0008] The configuration disclosed in Patent Document 1 may determine that an end hit has occurred when traveling on an uneven road such as an off-road course, or when a tire hits a curb, and may detect a steering angle corresponding to an incorrect end position. As a result, the steering angle acquired in a later control flow is discarded, which may delay acquisition of the steering angle corresponding to the end position and limit the automatic parking function. There is a need for a system that can acquire a steering angle corresponding to the end position even when traveling on an uneven road or when a tire hits a curb, thereby reducing the chances of the ADAS function being limited.

[0009] The present disclosure discloses technology for solving the above-mentioned problems, and aims to provide an electric power steering device that can obtain a steering angle corresponding to the end position more quickly than conventional devices, even when traveling on rough roads or when the tires hit a curb, thereby reducing the chances of the ADAS function being restricted.

[0010] an electric power steering device disclosed in the present disclosure, comprising: a steering shaft for supporting a steering wheel and for transmitting a steering torque generated by steering the steering wheel to a rack shaft; a motor for generating an assist torque on the steering shaft; a steering gear for transmitting the shaft torque of the steering shaft to the rack shaft; and a control device for calculating an assist torque command value for the motor based on the steering torque and outputting the command value to the motor, wherein the control device comprises: a steering angle calculation unit which receives an input of a rotational angle position of the motor and calculates a steering angle corresponding to a rotation direction from a starting point of the steering shaft; a pinion shaft torque calculation unit which calculates a pinion shaft torque of the steering gear based on the steering torque, a steering angular velocity which is a time change amount of the steering angle, the change amount of the steering angular velocity, and the assist torque; a movement suppression determination unit which determines whether the steering state of the steering shaft is in a turned state based on at least two of the steering angle, the steering angular velocity, and the pinion shaft torque, and determines whether movement of the rack shaft of the steering gear can be suppressed based on the steering angle when it is determined that the steering shaft is in a turned state; a movement suppression determination angle acquisition unit that acquires the steering angle as a movement suppression determination angle when it is determined that movement of the rack shaft can be suppressed based on the steering angle; and an end position corresponding angle determination unit that determines end position corresponding angles in each of the positive and negative directions of reciprocating movement of the rack shaft based on the acquired movement suppression determination angles.

[0011] According to the electric power steering device of the present disclosure, even when traveling on rough terrain or when the tires hit a curb, the steering angle corresponding to the end position can be obtained more quickly than before, thereby reducing the chances of the ADAS function being restricted.

[0012] 1 is a diagram showing a configuration of an electric power steering device according to Embodiment 1. FIG. 2 is a block diagram showing a configuration of a control device for an electric power steering device according to Embodiment 1. FIG. 3 is a flowchart showing an operation in a movement suppression determination unit according to Embodiment 1. FIG. 4 is a flowchart showing an operation in a movement suppression determination angle acquisition unit according to Embodiment 1. FIG. 5 is a diagram showing the first half of a flowchart showing an operation in an end position corresponding angle determination unit according to Embodiment 1. FIG. 6 is a diagram showing the second half of a flowchart showing an operation in an end position corresponding angle determination unit according to Embodiment 1.

[0013] A preferred example of an electric power steering (EPS) device according to the present disclosure will be described below. Note that the same reference numerals in the various drawings indicate the same or corresponding parts.

[0014] Embodiment 1. A power steering device according to Embodiment 1 will now be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of an electric power steering device according to Embodiment 1. In FIG. 1, the electric power steering device 1 includes a steering shaft 8 to which a steering wheel 2 (also referred to as the steering wheel 2) is attached, a rack-and-pinion mechanism 9, a rack shaft 10, and a cylindrical rack housing 11 into which the rack shaft 10 is inserted. As a result, rotation of the steering shaft 8 caused by steering of the steering wheel 2 is converted into axial reciprocating motion of the rack shaft 10 by the rack-and-pinion mechanism 9. The steering shaft 8 is made up of, in order from the steering wheel 2 side, a column shaft 12, an intermediate shaft 13, and a pinion shaft 14. Connected to both ends of the rack shaft 10, in order from the side closest to the rack shaft 10, are a rack end 15 formed by a ball joint, a tie rod 16, a knuckle (not shown), and wheels 17 (also referred to as the front wheels 17).

[0015] When the rack shaft 10 reciprocates, the positions at which it comes into contact with the rack ends 15 at both ends are the left and right end position corresponding steering angles θe (hereinafter also referred to as end position corresponding angles θe) at which the vehicle can be steered.

[0016] A torque sensor 3 is also provided on the steering shaft 8. When a steering torque is applied to the steering wheel 2 by steering by the driver, the torque sensor 3 detects the steering torque and outputs the detected steering torque Ts to the control device 4. The control device 4 calculates a current command value as an assist torque command value for the motor 5 based on the steering torque Ts detected by the torque sensor 3. Furthermore, the control device 4 calculates three-phase voltage commands Vu*, Vv*, Vw* corresponding to the current command value and outputs them to the motor 5. Note that the steering torque Ts is detected as a positive value when the vehicle is steered in one direction, and as a negative value when the vehicle is steered in the opposite direction.

[0017] The motor 5 generates an assist torque to assist the steering torque on the steering shaft 8 via the gear 7, and the steering torque and the assist torque are transmitted to the rack shaft 10, thereby changing the steering angle of the front wheels 17, which corresponds to the direction of travel of the vehicle.

[0018] The electric power steering of the first embodiment can be implemented in a vehicle that has an ADAS function and can control driving. Examples of the ADAS function include an automatic parking function that detects a parking space and automatically assists steering operation, and a lane keeping function that recognizes white lines on the road and controls the vehicle to drive within the recognized white lines, but the type is not particularly limited. Here, the control device 4 can also calculate a current command value corresponding to the ADAS function implemented in the vehicle.

[0019] The control device 4 is configured, as hardware, with, for example, a central processing unit (CPU) 18 or a processor and a storage device (see FIG. 1). The storage device includes a volatile storage device such as a random access memory (RAM) 19 and a read-only memory (ROM) 20, which is a non-volatile auxiliary storage device such as a flash memory. Alternatively, a hard disk may be used as an auxiliary storage device instead of the flash memory. The CPU 18 sequentially executes programs input from the ROM 20. In this case, the programs are input from the ROM 20 to the CPU 18 via the RAM 19. The CPU 18 may output data such as calculation results to the RAM 19 or may store data in the ROM 20 via the RAM 19. The above programs execute the various functions of the control device 4 (specifically, functions such as steering angle calculation, pinion shaft torque calculation, and movement suppression determination; see FIG. 2). While the above hardware may be provided as a single unit for the entire control device, it may also be provided with hardware with different specifications for each of the above functions.

[0020] The motor is also provided with a rotational position detection unit 6, which detects the rotational angular position θm (electrical angle) of the motor 5 as a relative angle within a range of 360° and outputs the detected value to the control device 4. In the first embodiment, the rotational position detection unit 6 is a unit that directly detects the rotational position, such as a resolver, but the rotational position may also be obtained by a known method of calculation based on a current detected by a current detection unit that is disposed in the control device and that is applied to the motor 5. Note that while the rotational angular position θm is taken to be a positive value when the motor is steered in a certain direction, it is detected as a negative value when the motor is steered in the opposite direction.

[0021] Next, the functions of the control device 4 will be described with reference to Fig. 2. Fig. 2 is a functional block diagram showing the configuration of the control device 4 of the electric power steering device according to this embodiment. Although Fig. 2 illustrates the basic functions of the control device 4, the control device 4 may further include configurations for realizing other functions. For example, the control device 4 may further include a section for calculating a current command value or a section for an ADAS function.

[0022] Here, the control device 4 includes a steering angle calculation unit 21, a differentiator 22, a steering angular velocity change amount calculation unit 23, a pinion shaft torque calculation unit 24, a movement suppression determination unit 25, a movement suppression determination angle acquisition unit 26, and an end position corresponding angle determination unit 27. The steering angle calculation unit 21 calculates a steering angle θs that corresponds to the absolute steering angle of the steering shaft 8 and can be converted into the steering angle of the front wheels 17. The rotational angle position θm of the motor 5 detected by the rotational position detection unit 6 is input to the steering angle calculation unit 21.

[0023] Next, the operation of the steering angle calculation unit 21 will be described. For example, after replacing the on-board power supply (not shown), the rotational angle position of the motor 5 when a start switch such as an ignition switch is turned on for the first time is set as the origin, and the number of rotations of the motor 5, where one rotation is 360°, is counted, and the absolute steering angle of the motor 5 is detected based on the number of rotations of the motor 5 and the rotational angle position θm of the motor 5. Furthermore, the steering angle calculation unit 21 multiplies the absolute steering angle of the motor 5 by a conversion coefficient based on the reduction ratio of the gear 7, thereby calculating the steering angle θs of the steering shaft 8 relative to the steering wheel 2 as an absolute steering angle that includes a range greater than 360°.

[0024] The electric power steering device 1 of the first embodiment has a function of accumulating the number of rotations of the motor 5 when the start switch is off, and when the start switch is turned on for the second time or later after the on-board battery is replaced, the origin (starting point) of the steering angle θs becomes the same as the origin set when the start switch was turned on for the first time. Note that the steering angle θs is a positive value when it is a rotation angle in a certain direction from the origin, and a negative value when it is a rotation angle in the other direction.

[0025] Next, the operation of the pinion shaft torque calculation unit 24 will be described. The steering torque Ts, rotational angular velocity ωs (hereinafter also referred to as steering angular velocity ωs), steering angular velocity change amount Δωs, and actual q-axis current value Iq detected by the torque sensor 3 are input to the pinion shaft torque calculation unit 24. The pinion shaft torque calculation unit 24 calculates the pinion shaft torque Tp, which is the total value of the torque (hereinafter also referred to as load torque) applied to the electric power steering device 1, from these state quantities.

[0026] Here, the steering angular velocity ωs corresponds to the rate of change of the steering angle θs calculated by the differentiator 22 using the steering angle θs output from the steering angle calculation unit 21 as an input. The steering angular velocity change amount Δωs corresponds to the rate of change of the steering angular velocity ωs calculated by the steering angular velocity change amount calculation unit 23 using the steering angular velocity ωs output from the differentiator 22 as an input.

[0027] The actual q-axis current value Iq is derived from the motor current Im detected by a motor current detection unit (not shown), and corresponds to the torque axis current which is the q-axis in the d-q coordinate system. Note that the method of deriving the actual q-axis current value Iq may differ from the above-described method depending on the configuration of the control device 4. The pinion shaft torque Tp corresponds to the axial force acting on the rack shaft 10. Here, the pinion shaft torque Tp is calculated using the steering torque Ts applied by the driver, the motor torque based on the actual q-axis current value Iq, and the inertia torque based on the steering angular velocity change amount Δωs, as shown in the following equation (1).

[0028] Tp=Ts+Iq×Kt−Δωs×(Jm+Jh) (1) In this equation (1), Kt is a constant determined by the torque constant of the motor 5 and the reduction ratio and efficiency of the gear 7. Furthermore, Jm is a constant determined by the moment of inertia of the motor 5 and the reduction ratio and efficiency of the gear 7. Furthermore, Jh is a constant determined by the moment of inertia of the handle 2 and the reduction ratio and efficiency of the gear 7.

[0029] Next, the operation of the movement suppression determination unit 25 will be described. The movement suppression determination unit 25 receives the steering angle θs, the steering angular velocity ωs, and the pinion shaft torque Tp as input. Based on these state quantities, the movement suppression determination unit 25 determines whether the steering angle is being turned, which increases the absolute value of the steering angle. If the movement suppression determination unit 25 determines that the steering angle is being turned, the movement suppression determination unit 25 corrects the steering angle θs based on the mechanical elastic deformation occurring in the electric power steering device according to the magnitude of the acquired pinion shaft torque Tp. The movement suppression determination unit 25 determines whether the corrected steering angle θs is equal to or greater than a maximum steering angle θmax, which is the maximum value of the steering range controlled by the driver, or whether the corrected steering angle θs is equal to or smaller than a minimum steering angle θmin, which is the minimum value of the steering range controlled by the driver. If the corrected steering angle θs is equal to or greater than the maximum steering angle θmax or equal to or smaller than the minimum steering angle θmin, the movement suppression determination unit 25 updates the steering range Sa with a value obtained by subtracting the minimum steering angle θmin from the maximum steering angle max.

[0030] Then, it is determined whether the steering range Sa is equal to or greater than the steering range threshold Sth, and if the steering range Sa is equal to or greater than the steering range threshold Sth, a positive direction movement suppression judgment permission flag (hereinafter, for simplicity, also referred to simply as the positive direction permission flag) or a negative direction movement suppression judgment permission flag (hereinafter, for simplicity, also referred to simply as the negative direction permission flag), which indicates the state of permission for movement suppression judgment in the positive or negative direction, is set to "permission" and output to the movement suppression judgment angle acquisition unit 26.

[0031] Next, the operation of the movement suppression determination angle acquisition unit 26 will be described. When the movement suppression determination unit 25 determines that the steering state of the steering shaft 8 related to the steering wheel 2 is in a turning state where the steering angular velocity ωs > 0 when the steering angle θs > 0, or the steering angular velocity ωs < 0 when the steering state of the steering shaft 8 related to the steering wheel 2 is in a steering angle θs < 0, the movement suppression determination unit 25 corrects the acquired steering angle θs based on the mechanical elastic deformation occurring in the electric power steering device according to the magnitude of the acquired pinion shaft torque Tp. The determination that the steering state of the steering shaft is in a turning state is not limited to the method of referring to the signs of the steering angle θs and the steering angular velocity ωs. The movement suppression determination unit 25 may determine that the steering state of the steering shaft 8 related to the steering wheel 2 is in a turned-in state in which the pinion shaft torque Tp > 0 holds when the steering angle θs > 0, or that the steering state of the steering shaft 8 related to the steering wheel 2 is in a turned-in state in which the pinion shaft torque Tp < 0 holds when the steering angle θs < 0. The movement suppression determination unit 25 may also determine that the steering state of the steering shaft 8 related to the steering wheel 2 is in a turned-in state in which the pinion shaft torque Tp > 0 holds when the steering angular velocity ωs > 0, or that the steering state of the steering shaft 8 related to the steering wheel 2 is in a turned-in state in which the pinion shaft torque Tp < 0 holds when the steering angular velocity ωs < 0. In other words, it is sufficient to determine whether the steering state of the steering shaft is in a turned-in state based on at least two of the steering angle θs, the steering angular velocity ωs, and the pinion shaft torque Tp.

[0032] This correction process is a process for obtaining the accurate position of the rack shaft by subtracting from the steering angle θs the mechanical elastic deformation that occurs in the steering device, which is the main component of the electric power steering device, such as the steering shaft 8, rack and pinion mechanism 9, rack shaft 10, rack housing 11, and rack end 15, depending on the magnitude of the pinion shaft torque Tp.

[0033] For example, in the case of an electric power steering device 1 classified as a column type in which the motor 5 is attached to the column shaft 12, the correction may be performed using a table of correction amounts defined by the rigidity values ​​of the steering shaft 8 around the axis, the rack and pinion mechanism 9 around the axis, and the rack shaft 10, and the value of the pinion shaft torque Tp. Alternatively, the correction may be performed using the following predefined equations (2) and (3): Corrected steering angle θs = θs - (angle) deformation amount (2) (angle) deformation amount = Tp / steering device rigidity value (3) The above correction process may be applied not only to column types, but also to pinion type electric power steering in which the motor 5 is attached to the pinion shaft 14, and rack type electric power steering in which the motor 5 is attached to the rack shaft 10. However, in the case of pinion type electric power steering or rack type electric power steering, the steering shaft 8, which has low rigidity, is not present in the motor torque transmission path, and the mechanical deformation amount is negligibly small, so the end position corresponding angle (described below) can be obtained with high accuracy without correcting the steering angle.

[0034] Incidentally, when the steering angle fluctuates due to steering by the driver, the steering range of the driver can be calculated by obtaining the maximum and minimum values ​​of the steering angle. Since it is considered that the movement of the rack shaft is not restrained by end contact within this steering range, by setting the steering angle being outside the steering range as one of the conditions for determining whether or not to perform a movement restraint determination, it is possible to prevent a movement restraint determination from being erroneously established if the steering angle is within the steering range, for example, even if the tire hits a curb while traveling on an uneven road such as an off-road course.

[0035] Furthermore, because there is a minimum steering range within which the driver must steer before the movement of the rack shaft is restricted by end contact, one of the conditions for determining whether or not to perform a movement restriction determination may be whether the steering range is equal to or greater than a predetermined threshold. An example of the minimum steering range within which the driver must steer before the movement of the rack shaft is restricted by end contact is half the minimum standard value of the stroke amount of the rack shaft. Half the minimum standard value of the stroke amount corresponds to the minimum steering range within which the driver must steer from when the vehicle is traveling straight until the end contact occurs.

[0036] In consideration of this, in the above configuration, the movement suppression determination unit monitors the steering angle to obtain the maximum and minimum steering angle values, and when the steering angle is equal to or greater than the maximum steering angle value or equal to or less than the minimum steering angle value, calculates the steering range, which is the sum of the absolute values ​​of the maximum steering angle and the minimum steering angle value, and allows the movement suppression determination to be performed after confirming that the steering range is equal to or greater than half of the minimum standard value of the stroke amount, for example. Therefore, even when traveling on an uneven road or when the tire hits a curb, the chances that the movement suppression determination will be established in situations other than end hits are reduced, and the steering angle corresponding to the end position can be obtained early.

[0037] When the sign of the pinion shaft torque, which corresponds to the sum of torques applied to the steering shaft and moves the rack shaft in one direction, and the sign of the direction of rotation of the motor are each positive, and the sign of the pinion shaft torque and the sign of the direction of rotation of the motor that move the rack shaft in the direction opposite to the one direction are each negative, conditions for the movement suppression determination to be established include: the absolute value of the pinion shaft torque being equal to or greater than a first pinion shaft torque threshold; and the sign of a steering angular velocity change amount, which is the amount of change in steering angular velocity calculated by differentiating the steering angle, being opposite to the sign of the pinion shaft torque, and the absolute value of the steering angular velocity change amount being greater than a first steering angular velocity change amount threshold. Here, the first pinion shaft torque threshold refers to the sum of the motor inertia torque and the steering wheel inertia torque that are generated on the pinion shaft when the motor or the steering wheel suddenly decelerates when the motor or the steering wheel hits an end while rotating at high speed during high-speed steering. Furthermore, the second pinion shaft torque threshold value, which will be described later, is the sum of the motor torque and the steering torque when the steering is maintained at the end position, and is normally greater than the first pinion shaft torque threshold value. The first steering angular velocity change amount threshold value is set in consideration of the steering angular velocity change amount when the motor suddenly decelerates when an end contact occurs while the motor is rotating at high speed during high-speed steering. The pinion shaft torque is calculated using the steering torque applied to the steering shaft by the driver, the motor torque by the motor, and the inertia torque based on the angular velocity change amount of the motor. The above movement suppression determination is referred to as a high-speed movement suppression determination because it determines that end contact occurs during high-speed steering and the movement of the rack shaft is suppressed.

[0038] If the rack shaft moves in one direction at high speed due to steering by the driver and end contact occurs while the motor is rotating at high speed, the motor will attempt to stop suddenly. If the movement of the rack shaft is restricted at this time, for example, when a positive pinion shaft torque equal to or greater than the first pinion shaft torque threshold is input, the steering angular velocity change amount linked to the movement of the motor will be less than the negative first steering angular velocity change amount threshold. In other words, if the driver steers at high speed and end contact occurs, the high-speed movement suppression determination may be established.

[0039] If the steering torque applied by the driver, rather than the pinion shaft torque, is used as the condition for establishing the high-speed movement suppression determination, it is expected that, for example, when traveling on an uneven road, the steering torque will increase instantaneously due to vibrations transmitted from the road surface, causing the high-speed movement suppression determination to be established except when the end hits, and delaying the acquisition of the end position corresponding angle. By using the pinion shaft torque as the condition for establishing the high-speed movement suppression determination, even if the steering torque increases instantaneously, the motor torque will not instantaneously follow, and the increase in the absolute value of the pinion shaft torque will be suppressed, thereby reducing the chances of the high-speed movement suppression determination being erroneously established.

[0040] In the above electric power steering device, the movement suppression determination angle acquisition unit performs a low-speed movement suppression determination, separate from the high-speed movement suppression determination, for determining whether movement of the rack shaft is suppressed during steering at low speed, and determines that movement of the rack shaft is suppressed. Conditions for the low-speed movement suppression determination to be established include: the absolute value of the pinion shaft torque being equal to or greater than a second pinion shaft torque threshold (see the above description) that is greater than the first pinion shaft torque threshold; the absolute value of the steering angular velocity change being equal to or less than a second steering angular velocity change threshold that is smaller than the first steering angular velocity change threshold; and the absolute value of the steering angular velocity being equal to or less than the first steering angular velocity change threshold. Here, the second steering angular velocity change threshold is set taking into account the steering angular velocity change when the steering is held at the end position after end abutting during steering at low speed and the motor hardly rotates. The first steering angular velocity change amount threshold is set taking into consideration the steering angular velocity change amount when the motor suddenly decelerates when the motor hits the end while rotating at high speed during high-speed steering.

[0041] When the rack shaft moves in one direction due to steering by the driver and end contact occurs, the motor hardly rotates even if steering is continued. If the movement of the rack shaft is suppressed at this time, for example, in a state where a positive pinion shaft torque equal to or greater than the second pinion shaft torque is input, the absolute value of the steering angular velocity change amount is equal to or less than the second steering angular velocity change amount, and the absolute value of the steering angular velocity is equal to or less than the first steering angular velocity threshold. In other words, if end contact occurs after the driver steers at a low speed, or if the driver steers to maintain the steering position after end contact, the low-speed movement suppression determination is established, and the movement suppression determination angle can be acquired.

[0042] In consideration of this, in the above configuration, the movement suppression determination angle acquisition unit determines that the movement of the rack shaft is suppressed when either the high-speed movement suppression determination or the low-speed movement suppression determination is satisfied, and acquires the movement suppression determination angle. Therefore, even when the movement of the rack shaft is suppressed under various steering conditions, the movement suppression determination angle can be acquired, and the steering angle corresponding to the end position can be acquired quickly.

[0043] If the movement of the rack shaft is restricted when traveling on an uneven road such as an off-road course or when a tire collides with a curb, the movement restriction determination angle acquired at this time will be smaller than the absolute value of the movement restriction determination angle acquired at the time of end contact. Therefore, if the steering direction in which the sign of the pinion shaft torque and the sign of the rotational direction of the motor are positive is defined as the positive direction, and the direction in which the sign of the pinion shaft torque and the sign of the rotational direction of the motor opposite to the positive direction are negative is defined as the negative direction, then when the first stroke amount calculated based on the movement restriction determination angles in the positive and negative directions of the rack shaft (a value calculated by subtracting the movement restriction determination angle in the negative direction from the movement restriction determination angle in the positive direction) is equal to or greater than the minimum stroke amount, which is the minimum value of the standardized values ​​of the stroke amount, and is equal to or less than the maximum stroke amount, which is the maximum value of the standardized values ​​of the first stroke amount, the left and right movement restriction determination angles can be considered to have been acquired at the time of end contact.

[0044] In light of this, in the above configuration, the end position corresponding angle determination unit compares the first stroke amount calculated based on the rack shaft movement suppression determination angles in the positive and negative directions with the minimum and maximum stroke amounts. If the first stroke amount is equal to or greater than the minimum stroke amount and equal to or less than the maximum stroke amount, the end position corresponding angle determination unit determines the rack shaft movement suppression determination angles in the positive and negative directions as the end position corresponding angles. Therefore, the determined end position corresponding angles accurately correspond to the steering angle at which end contact occurred. Furthermore, if the first stroke amount is smaller than the minimum stroke amount or larger than the maximum stroke amount, the unit determines that the rack shaft movement suppression occurred due to a factor other than end contact or that the first stroke amount is outside the range of specified values, and discards the obtained movement suppression determination angle and the determined end position corresponding angle.

[0045] In the above-mentioned electric power steering device, when the end position corresponding angle determination unit acquires multiple movement suppression judgment angles in only one of the positive and negative directions, it is preferable that the end position corresponding angle determination unit determines the end position corresponding angle in that one direction based on the multiple movement suppression judgment angles in that one direction.

[0046] In the above configuration, even if it is not possible to obtain only the movement suppression judgment angle in one direction due to, for example, the vehicle's driving conditions, the end position corresponding angle determination unit determines the end position corresponding angle in one direction, and the ADAS function is not restricted when steering in that one direction.

[0047] In the above-mentioned electric power steering device, when the difference between the maximum and minimum values ​​of the multiple movement suppression judgment angles in one direction is set as the movement suppression judgment angle difference in the one direction, it is preferable that the end position corresponding angle determination unit determines only the end position corresponding angle in the one direction based on the multiple movement suppression judgment angles in the one direction if the movement suppression judgment angle difference in the one direction is smaller than a predetermined threshold value for the movement suppression judgment angle difference.

[0048] When the movement suppression determination angle difference in one direction is smaller than the movement suppression difference threshold, the multiple movement suppression determination angles in one direction are considered to be angles near the actual end position. Therefore, in the above configuration, when the movement suppression determination angle difference is smaller than the movement suppression determination angle difference threshold, the end position corresponding angle determination unit determines only the end position corresponding angle in one direction based on the multiple movement suppression determination angles in one direction, thereby preventing the end position corresponding angle from deviating from the actual end position. In the above electric power steering device 1, when the end position corresponding angle in only the positive direction has been determined, the end position corresponding angle determination unit 27 may determine the steering angle calculated by subtracting a predetermined stroke amount from the positive direction end position corresponding angle as the negative direction end position corresponding angle, and when the end position corresponding angle in only the negative direction has been determined, may determine the steering angle calculated by adding a predetermined stroke amount to the negative direction end position corresponding angle as the positive direction end position corresponding angle. In this case, the predetermined stroke amount may be a minimum stroke amount that is the smallest value of the standard values ​​of the stroke amount, or may be a standard value of the distance between both ends of the movable range of the steering angle, and a value obtained by subtracting a margin from this standard value to take various variations into consideration. By determining the end position corresponding angle in only one direction and simultaneously determining the end position corresponding angle in the opposite direction, the ADAS function can be quickly enabled.

[0049] In the above-described electric power steering device, it is desirable to perform a steering angle correction on the steering angle that is compared between the maximum steering angle and the minimum steering angle in the movement suppression determination unit based on a mechanical elastic deformation of the electric power steering device that occurs due to a torque applied to the electric power steering device.

[0050] According to the above configuration, an accurate steering angle can be obtained by taking into consideration mechanical elastic deformation according to the torque applied to the electric power steering device. It is preferable to calculate the torque applied to the electric power steering device using the steering torque, the motor torque, and an inertia torque based on a steering angular velocity change amount calculated as a change amount of the steering angular velocity which is a derivative of the steering angle.

[0051] Next, a process for outputting a positive direction permission flag or a negative direction permission flag, which indicates the state of the positive direction or negative direction movement suppression determination result by the movement suppression determination unit 25, will be described. As shown in the flowchart of FIG. 3, the movement suppression determination unit 25 determines whether the steering wheel is being turned (step S101). If it is determined that the steering wheel is being turned (YES in step S101), it determines whether the steering angle θs corrected based on the mechanical elastic deformation occurring in the electric power steering device according to the magnitude of the acquired pinion shaft torque Tp is equal to or greater than the maximum steering angle θmax (step S102). If the corrected steering angle θs is equal to or greater than the maximum steering angle θmax (YES in step S102), the maximum steering angle θmax is updated to be equal to the corrected steering angle θs (step S103). Furthermore, the steering range Sa, which is the sum of the absolute value of the maximum steering angle θmax and the absolute value of the minimum steering angle θmin, is calculated (step S104), and it is determined whether the steering range Sa is equal to or greater than the steering range threshold Sth (step S105). If the steering range Sa is equal to or greater than the steering range threshold Sth (YES in step S105), the positive direction movement suppression determination permission flag is set to 1 (permitted) (step S106).

[0052] On the other hand, if the steering range Sa is smaller than the steering range threshold Sth (if step S105 is NO), the positive direction movement suppression determination permission flag is set to 0 (prohibited) and the negative direction movement suppression determination permission flag is set to 0 (prohibited) (step S107).

[0053] Here, the maximum steering angle θmax and the minimum steering angle θmin both have initial values ​​of 0, and if the corrected steering angle θs is greater than the maximum steering angle θmax, the maximum steering angle θmax is updated to a value equal to the corrected steering angle θs, and if the corrected steering angle θs is smaller than the minimum steering angle θmin, the minimum steering angle θmin is updated to a value equal to the corrected steering angle θs.

[0054] If the corrected steering angle θs is equal to or less than the maximum steering angle θmax (if step S102 is NO), it is determined whether the steering angle θs corrected based on the mechanical elastic deformation occurring in the electric power steering device according to the magnitude of the acquired pinion shaft torque Tp is equal to or less than the minimum steering angle θmin (step S108). If the corrected θs is equal to or less than the minimum steering angle θmin (if step S108 is YES), the minimum steering angle θmin is updated to be equal to the corrected steering angle θs (step S109). Furthermore, a steering range Sa is calculated as the sum of the absolute values ​​of the maximum steering angle max and the minimum steering angle θmin (step S110), and it is determined whether the steering range Sa is equal to or greater than a steering range threshold Sth (step S111). If the steering range Sa is equal to or greater than the steering range threshold Sth (YES in step S111), the negative direction movement suppression determination permission flag is set to 1 (permitted) (step S112).

[0055] On the other hand, if the movement suppression judgment unit 25 determines that the steering wheel is not in a turning state (if step S101 is NO), if the corrected steering angle θs is smaller than the maximum steering angle θmax and larger than the minimum steering angle θmin (if step S108 is NO), if the corrected steering angle θs is smaller than the maximum steering angle θmax and equal to or smaller than the minimum steering angle θmin, and the steering range Sa is equal to or smaller than the steering range threshold value Sth (if step S111 is NO), the movement suppression judgment unit 25 sets the positive direction movement suppression judgment permission flag = 0 (prohibited) and the negative direction movement suppression judgment permission flag = 0 (prohibited) (step S113).

[0056] The movement suppression determination angle acquisition unit 26 receives state quantities (hereinafter also referred to as steering state quantities) including the steering angle θs, the steering angular velocity ωs, the steering angular velocity change amount Δωs that is the output of the steering angular velocity change amount calculation unit, a positive direction permission flag, a negative direction permission flag, a positive direction end position corresponding angle determination flag (also referred to as a θpe determination flag), and a negative direction end position corresponding angle determination flag (also referred to as a θne determination flag) as input. Based on these state quantities, the movement suppression determination angle acquisition unit 26 may, in the following description, simply refer to the positive direction movement suppression determination angle θi when it is not specified that the positive direction or the negative direction is the movement suppression determination angle.

[0057] As described above, there are two conditions for the movement suppression determination to be established: a high-speed movement suppression determination and a low-speed movement suppression determination. Therefore, the movement suppression determination angle acquisition unit 26 performs at least one of the two conditions for the movement suppression determination to be established: a high-speed movement suppression determination and a low-speed movement suppression determination. When performing two types of movement suppression determination, the high-speed movement suppression determination is performed first. If the high-speed movement suppression determination is not established, the low-speed movement suppression determination is performed. Here, the reason for performing the high-speed movement suppression determination first is that when an end collision occurs during steering at high speed, the time during which the absolute value of the steering angular velocity change amount increases is short. Therefore, the time during which the high-speed movement suppression determination, which checks whether the steering angular velocity change amount is greater than the first steering angular velocity change amount, is established is shorter than the time during which the low-speed movement suppression determination is established. Therefore, performing the high-speed movement suppression determination first increases the chances of the movement suppression determination being established.

[0058] The conditions for the high-speed movement suppression judgment to be established include that the absolute value of the pinion shaft torque Tp is equal to or greater than the first pinion shaft torque Tpth1, and that the sign of the steering angular velocity change amount Δωs, which is the change amount of the steering angular velocity ωs, is opposite to the sign of the pinion shaft torque Tp, and the absolute value of the steering angular velocity change amount Δωs is greater than the first steering angular velocity change amount threshold value Δωsth1.

[0059] Conditions for the low-speed movement suppression judgment to be established include the absolute value of the pinion shaft torque Tp being equal to or greater than a second pinion shaft torque Tpth2 that is greater than the first pinion shaft torque Tpth1, the absolute value of the steering angular velocity change amount Δωs being equal to or less than a second steering angular velocity change amount threshold Δωsth2 that is smaller than the first steering angular velocity change amount threshold Δωsth1, and the absolute value of the steering angular velocity ωs being equal to or less than the first steering angular velocity threshold ωsth1.

[0060] The high-speed movement suppression determination detects a state in which the movement of the rack shaft 10 is restricted when end contact occurs after the driver steers at a relatively high speed. The low-speed movement suppression determination detects a state in which the movement of the rack shaft 10 is restricted when end contact occurs after the driver steers at a low speed, or when the driver steers to maintain the steering position after end contact. Therefore, even when the movement of the rack shaft is suppressed under various steering conditions, the movement suppression determination angle θi can be obtained early.

[0061] The movement suppression judgment angle acquisition unit 26 of this embodiment 1 acquires, as the movement suppression judgment angle θi, an angle corrected based on the mechanical elastic deformation that occurs in the electric power steering device 1 depending on the magnitude of the pinion shaft torque Tp, relative to the steering angle θs when it is determined that the movement of the rack shaft 10 is suppressed as a result of the high-speed movement suppression judgment or the low-speed movement suppression judgment.

[0062] Next, a description will be given of a processing procedure related to outputting the movement suppression determination angle θi by the movement suppression determination angle acquisition unit 26. Note that, for convenience of explanation, the following will use Fig. 4 to describe a case where the rack shaft 10 moves in the positive direction and the movement suppression determination angle θi in the positive direction is acquired, but the same processing is also performed when the rack shaft 10 moves in the negative direction and the movement suppression determination angle θi in the negative direction is acquired.

[0063] 4, the movement suppression determination angle acquisition unit 26 determines whether the positive direction end position determination flag is 0 (undetermined) (step S201). The positive direction end position determination flag is output from the end position corresponding angle determination unit 27, which will be described later, and is initially set to 0 (undetermined).

[0064] If the positive direction end position determination flag is 0 (undetermined) (YES in step S201), it is determined whether the positive direction movement suppression determination angle acquisition permission flag is 1 (permitted) (step S202). The positive direction end position movement suppression determination angle acquisition permission flag is output from the movement suppression determination angle acquisition permission unit and is initially set to 0 (prohibited).

[0065] If the positive direction movement suppression determination angle acquisition flag is 1 (permitted) (if step S202 is YES), it is determined whether the positive direction movement suppression determination is established (step S203). If the positive direction movement suppression determination is established (if step S203 is YES), an angle corrected based on the mechanical elastic deformation generated in the electric power steering device 1 according to the magnitude of the pinion shaft torque Tp with respect to the steering angle θs when the positive direction movement suppression determination is established is acquired as the positive direction movement suppression determination angle θpi (step S204).

[0066] On the other hand, if the positive direction end position determination flag is 1 (determined) (if step S201 is NO), or the positive direction movement suppression determination angle permission flag is 0 (prohibited) (if step S202 is NO), or the positive direction movement suppression determination is not established (if step S203 is NO), the movement suppression determination angle acquisition unit 26 does not perform any subsequent processing (ends).

[0067] Next, the operation of the end position corresponding angle determination unit 27 will be described. The end position corresponding angle determination unit 27 receives a plurality of movement suppression determination angles θi from the movement suppression determination angle acquisition unit 26. The end position corresponding angle determination unit 27 determines a positive direction end position corresponding angle θpe and a negative direction end position corresponding angle θne based on the movement suppression determination angles θi. Furthermore, the end position corresponding angle determination unit 27 outputs a positive direction end position corresponding angle determination flag and a negative direction end position corresponding angle determination flag, which indicate whether the end position corresponding angles in both the positive and negative directions have been determined, to the movement suppression determination angle acquisition unit 26. In the following description, when the positive direction end position corresponding angle and the negative direction end position corresponding angle are not specified as being in the positive direction or the negative direction, they may be simply referred to as the end position corresponding angle θe.

[0068] When the end position corresponding angle determination unit 27 acquires the movement suppression determination angles θi in both the positive and negative directions, it calculates a first stroke amount Ws1, which is the sum of the absolute value of the movement suppression determination angle θi in the positive direction and the absolute position of the movement suppression determination angle θi in the negative direction. Thereafter, if the first stroke amount Ws1 is equal to or greater than a minimum stroke amount Wsmin, which is the minimum standard value of the stroke amount, and equal to or less than a maximum stroke amount Wsmax, which is the maximum standard value of the stroke amount, the end position corresponding angle determination unit 27 determines the acquired movement suppression determination angles θi in both the positive and negative directions as the positive direction end position corresponding angle θpe and the negative direction end position corresponding angle θne, respectively, and sets both the positive and negative direction end position corresponding angle determination flags to 1 (determined). If the first stroke amount Ws1 is smaller than the minimum stroke amount Wsmin, or if the first stroke amount Ws1 is larger than the maximum stroke amount Wsmax, the end position corresponding angle determination unit 27 does not determine the positive direction end position corresponding angle θpe or the negative direction end position corresponding angle θne, and discards the input movement suppression judgment angle θi.

[0069] On the other hand, when the end position corresponding angle determination unit 27 acquires the movement suppression determination angle θi in one direction, either positive or negative, multiple times, it calculates the difference between the maximum and minimum values ​​of the multiple movement suppression determination angles θi. If the difference between the maximum and minimum values ​​of the multiple movement suppression determination angles θi is equal to or less than the end position corresponding angle difference threshold Δθth, the end position corresponding angle determination unit 27 determines the average value of the multiple movement suppression determination angles θi as the end position corresponding angle θe in the corresponding direction. Note that the end position corresponding angle difference threshold Δθth is a threshold for determining whether the movement suppression determination angle θi is within the range of acquisition accuracy of the movement suppression determination angle θi acquired by the movement suppression determination angle acquisition unit 26, and is preset to a value determined based on the standard deviation of the movement suppression determination angle calculated from the multiple movement suppression determination angles acquired in advance through experiments, etc. On the other hand, if the maximum and minimum values ​​of the multiple movement suppression determination angles θi are greater than the end position corresponding angle difference threshold Δθth, the end position corresponding angle determination unit 27 discards the multiple movement suppression determination angles θi in one direction.

[0070] In addition, when only the end position corresponding angle θe in one direction has been determined, the end position corresponding angle determination unit 27 acquires the movement suppression judgment angle θi in the opposite direction and determines the end position corresponding angle θe in the opposite direction based on the movement suppression judgment angle θi.

[0071] Specifically, when only the end position corresponding angle θe in one direction has been determined, the end position corresponding angle determination unit 27 acquires the movement suppression determination angle θi in the opposite direction and calculates a second stroke amount Ws2. The second stroke amount Ws2 is the sum of the absolute value of a value based on multiple movement suppression determination angles θi in one direction and the absolute value of the movement suppression determination angle θi in the opposite direction. In the first embodiment, the sum of the end position corresponding angle θe in one direction and the absolute value of the movement suppression determination angle θi in the opposite direction is calculated as the second stroke amount Ws2. Then, when the second stroke amount Ws2 is equal to or greater than a minimum stroke amount Wsmin, which is the minimum value of the standardized stroke amount, and equal to or less than a maximum stroke amount Wsmax, which is the maximum value of the standardized stroke amount, the end position corresponding angle determination unit 27 sets the movement suppression determination angle θi in the opposite direction as the end position corresponding angle θe in the opposite direction. On the other hand, if the second stroke amount Ws2 is smaller than the minimum stroke amount Wsmin, or if the first stroke amount Ws1 is larger than the maximum stroke amount Wsmax, the end position corresponding angle determination unit 27 discards the end position corresponding angle θe in one direction and the movement suppression judgment angle θi in the opposite direction.

[0072] Next, the processing procedure for determining the end position corresponding angle θe by the end position corresponding angle determination unit 27 will be described with reference to FIGS. 5A and 5B . As shown in the flowcharts of FIGS. 5A and 5B , the end position corresponding angle determination unit 27 determines whether the end position corresponding angle determination flags for both the positive and negative directions are set to 1 (determined) (step S301). If the end position corresponding angle determination flags for both the positive and negative directions are set to 1 (determined) (YES in step S301), the subsequent processing is not performed. Note that in FIGS. 5A and 5B , a in FIG. 5A and a in FIG. 5B are connected to each other, b in FIG. 5A and b in FIG. 5B, and c in FIG. 5A and c in FIG. 5B are connected to each other.

[0073] If the positive and negative end position corresponding angle determination flags are not set to 1 (determined) (if step S301 is NO), it is determined whether the positive and negative end position corresponding angle determination flags are set to 0 (undetermined) (step S302). If the positive and negative end position corresponding angle determination flags are set to 0 (undetermined) (if step S302 is YES), it is determined whether the positive and negative movement suppression determination angles θi have been acquired (step S303). If the positive and negative movement suppression determination angles θi have been acquired (if step S303 is YES), the first stroke amount Ws1 is calculated (step S304), and it is determined whether the first stroke amount Ws1 is equal to or greater than the minimum stroke amount Wsmin and equal to or less than the maximum stroke amount Wsmax (step S305). If the first stroke amount Ws1 is equal to or greater than the minimum stroke amount Wsmin and equal to or less than the maximum stroke amount Wsmax (YES in step S305), the positive and negative movement suppression determination angles θi used to calculate the first stroke amount Ws1 are determined as the positive end position corresponding angle θpe and the negative end position corresponding angle θne (step S306), and the positive and negative end position corresponding angle determination flags are set to 1 (determined) (step S307). Note that if the first stroke amount Ws1 is smaller than the minimum stroke amount Wsmin or if the first stroke amount Ws1 is greater than the maximum stroke amount Wsmax (NO in step S305), the obtained movement suppression determination angles θi are discarded (step S308).

[0074] On the other hand, if the end position corresponding angle determination unit 27 has not acquired both the positive and negative movement suppression determination angles θi (if step S303 is NO), it determines whether multiple movement suppression determination angles θi in one direction, either positive or negative, have been acquired (step S309). If multiple movement suppression determination angles θi in one direction have been acquired (if step S309 is YES), it calculates the difference Δθ between the maximum and minimum values ​​of the multiple acquired movement suppression determination angles θi in one direction (step S310) and determines whether Δθ is equal to or less than the end position corresponding angle difference threshold Δθth (step S311). If Δθ is equal to or less than the end position corresponding angle difference threshold Δθth (if step S311 is YES), it determines the end position corresponding angle θe in one direction based on the multiple movement suppression determination angles θi (step S312), and further sets the one-direction end position corresponding angle determination flag to 1 (determined) (step S313).

[0075] If multiple movement suppression determination angles θi in either the positive or negative direction have not been acquired (if NO in step S309), the subsequent processes are not performed. Also, if Δθ is greater than the end position corresponding angle difference threshold Δθth (if NO in step S311), the acquired movement suppression determination angle θi is discarded (step S308).

[0076] If the positive and negative end position corresponding angle determination flags are not set to 1 (determined) (if step S301 is NO) and the positive and negative end position corresponding angle determination flags are not set to 0 (undetermined) (if step S302 is NO), the end position corresponding angle determination unit 27 determines whether a movement suppression determination angle in a direction in which the end position corresponding angle is undetermined has been acquired (step S314).If a movement suppression determination angle in a direction in which the end position corresponding angle is undetermined has been acquired (if step S314 is YES), the end position corresponding angle determination unit 27 calculates the second stroke amount Ws2 (step S315) and determines whether the second stroke amount Ws2 is equal to or greater than the minimum stroke amount Wsmin and equal to or less than the maximum stroke amount Wsmax (step S316). If the second stroke amount Ws2 is greater than or equal to the minimum stroke amount Wsmin and less than or equal to the maximum stroke amount Wsmax (if step S316 is YES), the movement suppression judgment angle θi for the direction in which the end position corresponding angle is undetermined is determined as the end position corresponding angle θe for the corresponding direction (step S317), and further, the end position corresponding angle determination flag for the direction in which the end position corresponding angle is undetermined is set to 1 (determined) (step S318).

[0077] On the other hand, if the second stroke amount Ws2 is smaller than the minimum stroke amount Wsmin or larger than the maximum stroke amount Wsmax (if step S316 is NO), the end position corresponding angle determination unit 27 discards the movement suppression determination angle θi in the direction where the end position corresponding angle is undetermined and the end position corresponding angle θp in the determined direction (step S319), and sets the end position corresponding angle determination flags for both the positive and negative directions to 0 (undetermined) (step S320). Note that if the movement suppression determination angle in the direction where the end position corresponding angle is undetermined has not been obtained (if step S314 is NO), subsequent processing is not performed (the process ends).

[0078] In the first embodiment described above, the control device 4 controls an electric power steering device 1 in which the motor 5 applies motor torque to the column shaft 12, but this is not limiting, and the control device may also control, for example, a steering device in which motor torque is applied to the rack shaft 10 via a ball screw nut. Furthermore, the control device is not limited to an EPS in which the steering unit steered by the driver and the steering unit that steers the front wheels are mechanically connected by an intermediate shaft 13 (also referred to as intermediate shaft 13) or the like, and the control device 4 may also control a steer-by-wire EPS in which the steering unit steered by the driver and the steering unit that steers the front wheels are separated.

[0079] Although exemplary embodiments are described in the present disclosure, the various features, aspects, and functions described in the embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are anticipated within the scope of the technology disclosed in this specification. For example, variations in, addition to, or omission of at least one component are included.

[0080] REFERENCE SIGNS LIST 1 Electric power steering device, 2 Steering wheel, 3 Torque sensor, 4 Control device, 5 Motor, 6 Rotational position detection unit, 7 Gear, 8 Steering shaft, 9 Rack and pinion mechanism, 10 Rack shaft, 11 Rack housing, 12 Column shaft, 13 Intermediate shaft, 14 Pinion shaft, 15 Rack end, 16 Tie rod, 17 Front wheel, 18 CPU, 19 RAM, 20 ROM, 21 Steering angle calculation unit, 22 Differentiator, 23 Steering angular velocity change amount calculation unit, 24 Pinion shaft torque calculation unit, 25 Movement suppression determination unit, 26 Movement suppression determination angle acquisition unit, 27 End position corresponding angle determination unit

Claims

1. A vehicle steering system comprising: a steering shaft for supporting a steering wheel and transmitting steering torque generated by steering the steering wheel to a rack shaft; a motor for generating an assist torque on the steering shaft; a steering gear for transmitting the shaft torque of the steering shaft to the rack shaft; and a control device for calculating an assist torque command value for the motor based on the steering torque and outputting the command value to the motor, wherein the control device comprises: a steering angle calculation unit which receives as input a rotational angle position of the motor and calculates a steering angle corresponding to the rotation direction from the starting point of the steering shaft; a pinion shaft torque calculation unit which calculates a pinion shaft torque of the steering gear based on the steering torque, a steering angular velocity which is a time change amount of the steering angle, the change amount of the steering angular velocity, and the assist torque; a movement suppression determination unit which determines whether the steering state of the steering shaft is in a turned state based on at least two of the steering angle, the steering angular velocity, and the pinion shaft torque, and determines whether movement of the rack shaft of the steering gear can be suppressed based on the steering angle when it is determined to be in a turned state; an end position corresponding angle determining unit that determines, based on the obtained movement suppression determination angles, end position corresponding angles in each of a positive direction and a negative direction, which are reciprocating movement directions of the rack shaft, when it is determined that movement of the rack shaft can be suppressed based on the steering angle; 2. An electric power steering device according to claim 1, wherein the steering angle is corrected based on elastic deformation of a steering device that occurs in accordance with the magnitude of the pinion shaft torque.

3. A steering shaft that supports a steering wheel and transmits steering torque generated by steering the steering wheel to a rack shaft; a motor that generates an assist torque on the steering shaft; a steering gear that transmits the shaft torque of the steering shaft to the rack shaft; and a control device that calculates an assist torque command value for the motor based on the steering torque and outputs it to the motor, wherein the control device comprises: a steering angle calculation unit that receives as input the rotational angle position of the motor and calculates a steering angle corresponding to the rotation direction from the starting point of the steering shaft; a pinion shaft torque calculation unit that receives as input the steering torque, a steering angular velocity that is the amount of change in the steering angle over time, the amount of change in the steering angular velocity, and a q-axis current value that is a torque current value derived from the motor current and calculates a pinion shaft torque of the steering gear; a movement suppression determination unit that determines whether the steering state of the steering shaft is in a deep turn state based on the steering angle, the steering angular velocity, and the pinion shaft torque, corrects the steering angle in response to elastic deformation of a steering device that occurs according to the magnitude of the steering torque when it is determined that the steering shaft is in a deep turn state, and determines whether movement of a rack shaft of the steering gear can be suppressed based on the corrected steering angle; a movement suppression determination angle acquisition unit that acquires the corrected steering angle as a movement suppression determination angle when it is determined that movement of the rack shaft can be suppressed based on the corrected steering angle; and an end position corresponding angle determination unit that determines end position corresponding angles in each of a positive direction and a negative direction, which are reciprocating movement directions of the rack shaft, based on the acquired movement suppression determination angles.

4. An electric power steering device as described in any one of claims 1 to 3, characterized in that the end position corresponding angle determination unit calculates the stroke amount of the rack shaft based on each end position corresponding angle of the rack shaft, and if the stroke amount is not within a predetermined range, discards the acquired movement suppression judgment angle and the determined end position corresponding angle.

5. An electric power steering device according to any one of claims 1 to 3, characterized in that the conditions under which the movement suppression determination unit permits the movement suppression are: when the steering state of the steering shaft is a steering angle θs > 0, the steering angular velocity ωs > 0; and when the steering state is a steering angle θs < 0, the steering angular velocity ωs < 0.

6. An electric power steering device according to any one of claims 1 to 3, characterized in that the movement suppression determination unit determines that the steering state of the steering shaft is in the turning state when the steering angle is positive and the steering angular velocity is positive, or when the steering angle is negative and the steering angular velocity is negative.

7. An electric power steering device according to any one of claims 1 to 6, characterized in that, when it is determined that the steering state of the steering shaft is a turned state, the movement suppression determination unit determines whether or not a steering angle corrected based on mechanical elastic deformation of the steering device generated in accordance with the magnitude of the pinion shaft torque acquired by the control device is equal to or greater than a maximum steering angle which is the maximum value of the steering range in which the steering wheel is steered, and if the corrected steering angle is equal to or greater than the maximum steering angle, updates the maximum steering angle to a value equal to the corrected steering angle, calculates the sum of the absolute value of the maximum steering angle and the absolute value of the minimum steering angle which is the minimum value of the steering range, and determines whether or not to permit suppression of movement of the rack shaft based on the result of determining whether or not the sum of the absolute values ​​is equal to or greater than a predetermined threshold.

8. An electric power steering device as described in any one of claims 1 to 3, characterized in that when the movement suppression judgment angle in only one of the positive and negative directions is obtained multiple times, the end position corresponding angle determination unit determines the end position corresponding angle in that one direction based on the multiple movement suppression judgment angles in that one direction.

9. An electric power steering device as described in any one of claims 2, 3, or 7, characterized in that when the steering state of the steering shaft is in the turned state, the steering angle and the movement suppression judgment angle are each corrected based on the amount of deformation of the steering device caused by the load torque on the steering device.

10. An electric power steering device as described in any one of claims 1 to 9, characterized in that when the end position corresponding angle is determined only in the positive direction, the end position corresponding angle determination unit determines the steering angle calculated by subtracting a predetermined stroke amount from the positive direction end position corresponding angle as the negative direction end position corresponding angle, and when the end position corresponding angle is determined only in the negative direction, the end position corresponding angle determination unit determines the steering angle calculated by adding a predetermined stroke amount to the negative direction end position corresponding angle as the positive direction end position corresponding angle.