Steering Controls

Abstract

The present invention relates to a steering control device. A steering control device includes an electronic control unit configured to i) detect an absolute steering angle, ii) determine whether movement of a rotation shaft to one of the right and left sides has been restricted, iii) acquire a limit position determination angle corresponding to the absolute steering angle detected when the electronic control unit determines that movement of the rotation shaft has been restricted, and iv) set an end position corresponding angle based on the limit position determination angle, the end position corresponding angle being an angle indicating that the rotation shaft is located at a right end position or a left end position, and the end position corresponding angle is associated with the absolute steering angle.

Description

Technical Field

[0001] The invention relates to a steering control device. Background Art

[0002] In the related art, an electric power steering system (EPS) including an actuator with a motor as a driving source is referred to as a vehicle steering system. As such an EPS, there is an EPS that obtains the steering angle of a steering wheel as an absolute angle within a range including a range exceeding 360° and performs various types of control based on the steering angle. As an example of such control, for example, Japanese Unexamined Patent Application Publication No. 2016-155519 (JP 2016-155519 A) discloses performing an end contact mitigation control for mitigating (i.e., reducing) the influence of so-called end contact in which a rack end, which is an end of a rack shaft, contacts a rack housing.

[0003] In the EPS described in JP 2016-155519 A, the rack end position at which the movement of the rack shaft is physically restricted by the end contact is associated with the steering angle, and the angle is stored as the end position corresponding angle. In the EPS, the influence of the end contact is mitigated (i.e., reduced) by reducing the target value of the motor torque output from the motor based on the distance between the steering angle and the end position corresponding angle. Summary of the invention

[0004] For example, depending on the specifications of the vehicle, the end position corresponding angle may be lost, for example, when the ignition is turned off or when the battery is replaced. When the end position corresponding angle is lost in this way, for example, the end contact mitigation control may not be performed. Therefore, it is necessary to learn the end position corresponding angle. At this time, the end position corresponding angle needs to accurately correspond to the actual end angle at which the end contact actually occurs.

[0005] In the configuration described in JP 2016-155519 A, the end position corresponding angle is set based on the steering angle in a state where the rack shaft is determined to be in contact with the rack housing. In this configuration, the condition for determining that the rack shaft is in contact with the rack housing includes a condition that a state in which a change in the steering angle is equal to or less than a predetermined value continues despite the steering torque being input to the EPS.

[0006] As a condition where end contact occurs, for example, a situation can be conceived where the driver quickly performs turn steering and performs return steering immediately after the rack end contacts the rack housing. In this instantaneous end contact, a state where the change in the steering angle is equal to or less than a predetermined value does not continue. Therefore, in the configuration described in JP 2016-155519 A, the rack shaft may not be determined to be in contact with the rack housing, and thus the end position corresponding angle may not be set.

[0007] The present invention provides a steering control device capable of learning an end position corresponding angle accurately corresponding to an actual end angle.

[0008] The present invention also provides a steering control device capable of setting an end position corresponding angle based on instantaneous end contact.

[0009] An aspect of the present invention relates to a steering control device configured to control a steering system, the steering system including a housing; a rotating shaft accommodated in the housing so that the rotating shaft reciprocates; and an actuator that applies a motor torque using a motor as a driving source to reciprocate the rotating shaft. The steering control device includes an electronic control unit configured to i) detect an absolute steering angle as a rotation angle of a rotating shaft, the rotation angle of the rotating shaft being convertible into a rotation angle of a rotating wheel connected to the rotating shaft, and the absolute steering angle being expressed as an absolute angle within a range including a range exceeding 360°, ii) determine whether the movement of the rotating shaft to one of the right and left sides has been restricted, iii) acquire a limit position determination angle corresponding to the absolute steering angle detected when the electronic control unit determines that the movement of the rotating shaft has been restricted, and iv) set an end position corresponding angle based on the limit position determination angle, the end position corresponding angle being an angle indicating that the rotating shaft is located at a right end position or a left end position, and the end position corresponding angle is associated with the absolute steering angle. In the steering control device according to this aspect, after having acquired the value of the limit position determination angle, the electronic control unit may not acquire another value of the limit position determination angle until surrounding environment change determination is established as to whether the surrounding environment around the vehicle has changed.

[0010] For example, when the movement of the rotating shaft is limited due to the contact of the rotating wheel with the curb, the restricted position determination angle obtained at this time is an angle different from the actual end angle. Therefore, when the end position corresponding angle is set based on only a single restricted position determination angle, the end position corresponding angle may be an angle different from the actual end angle. Therefore, it is conceivable to set the end position corresponding angle based on multiple values ​​of the restricted position determination angle. Therefore, for example, when one value of the restricted position determination angle among multiple values ​​of the restricted position determination angle is obtained at the time of contact with the curb and other values ​​of the restricted position determination angle are obtained at the time of end contact, the end position corresponding angle can be prevented from becoming an angle different from the actual end angle. However, for example, when multiple values ​​of the restricted position determination angle are obtained at the time of contact with the curb, there is a concern that even if the end position corresponding angle is set based on multiple values ​​of the restricted position determination angle, the end position corresponding angle may also become an angle different from the actual end angle.

[0011] In this regard, according to the above configuration, after the value of the limit position determination angle has been set, when the surrounding environment around the vehicle has changed, another value of the limit position determination angle is acquired. Therefore, it is possible to prevent a situation from occurring in which each of the multiple values ​​of the limit position determination angle is data acquired when the movement of the rotation axis is restricted due to contact with a curb or the like. As a result, it is possible to set the end position corresponding angle that accurately corresponds to the actual end angle.

[0012] In the steering control device according to this aspect, the condition for establishing the determination of the change in the surrounding environment may include a condition that the return steering amount is equal to or greater than a return determination threshold. With this configuration, since the condition for establishing the determination of the change in the surrounding environment includes a condition for performing the return steering, it is possible to appropriately determine whether the surrounding environment has changed.

[0013] In the steering control device according to this aspect, the condition for establishing the determination of the change in the surrounding environment may include a condition that the vehicle speed is equal to or greater than a driving threshold indicating a non-stop state of the vehicle. With this configuration, since the condition for establishing the determination of the change in the surrounding environment includes the condition that the vehicle is driving, it is possible to appropriately determine whether the surrounding environment has changed.

[0014] In the steering control device according to this aspect, the electronic control unit can be configured to determine whether the movement of the rotating shaft has been restricted when the vehicle speed is equal to or less than a low speed threshold indicating low speed driving of the vehicle, regardless of whether the signal input from the vehicle speed sensor and indicating the vehicle speed is normal, and when the signal indicating the vehicle speed is abnormal, the conditions for establishing the determination of the surrounding environment change may not include the condition that the vehicle speed is greater than the driving threshold.

[0015] With this configuration, even when the signal input from the vehicle sensor and indicating the vehicle speed is abnormal, the limit position determination angle can be acquired, and thus the end position corresponding angle can be quickly set. When the signal indicating the vehicle speed is abnormal, the surrounding environment change determination does not include a comparison between the vehicle speed and the running threshold value, and thus it is possible to prevent the occurrence of a situation in which the surrounding environment change determination is not established due to the abnormality of the signal indicating the vehicle speed.

[0016] In the steering control device according to this aspect, the electronic control unit may be configured to perform dynamic limit determination and static limit determination, and determine that the movement of the rotating shaft has been limited when one of the dynamic limit determination and the static limit determination is established. When the sign of the steering torque for moving the rotating shaft to one side and the sign of the rotation direction of the motor for moving the rotating shaft to the one side are defined as positive, and the sign of the steering torque for moving the rotating shaft to the side opposite to the one side and the sign of the rotation direction of the motor for moving the rotating shaft to the side opposite to the one side are defined as negative, the condition for establishing the dynamic limit determination may include a condition that the absolute value of the steering torque is equal to or greater than a first steering torque threshold value and a condition that the sign of the angular velocity change as the change in the angular velocity of the motor is opposite to the sign of the steering torque and the absolute value of the angular velocity change is greater than the first angular velocity change threshold value, and the condition for establishing the static limit determination may include a condition that the absolute value of the steering torque is equal to or greater than a second steering torque threshold value greater than the first steering torque threshold value and a condition that the absolute value of the angular velocity change is equal to or less than a second angular velocity change threshold value less than the first angular velocity change threshold value.

[0017] With this configuration, when the movement of the rotating shaft has been restricted in various ways, the limit position determination angle can be acquired and the end position corresponding angle can be quickly set. Here, for example, it is assumed that after the movement of the rotating shaft has been restricted due to the contact of the rotating wheel with a curbstone or the like, a turn steering is quickly performed (i.e., the steering wheel is quickly turned) and the turn steering is continued without any change. In this case, a dynamic limit determination and a static limit determination can be established. Therefore, when the limit position determination angle is acquired at the time when these two determinations are established, both values ​​of the limit position determination angle are data acquired when the movement of the rotating shaft is restricted due to contact with a curbstone or the like. Therefore, in the configuration for performing dynamic limit determination and static limit determination, the effect caused by acquiring another value of the limit position determination angle when the surrounding environment around the vehicle has changed after the value of the limit position determination angle has been acquired is very good.

[0018] According to this aspect of the invention, it is possible to learn the end position corresponding angle which accurately corresponds to the actual end angle.

[0019] In the steering control device according to this aspect, the electronic control unit may be configured to perform dynamic limit determination, and determine that the movement of the rotating shaft has been limited when the dynamic limit determination is established. When the sign of the steering torque for moving the rotating shaft to one side and the sign of the rotation direction of the motor for moving the rotating shaft to one side are defined as positive, and the sign of the steering torque for moving the rotating shaft to the side opposite to the one side and the sign of the rotation direction of the motor for moving the rotating shaft to the side opposite to the one side are defined as negative, the conditions for establishing the dynamic limit determination may include a condition that the absolute value of the steering torque is equal to or greater than a first steering torque threshold, and a condition that the sign of the angular velocity change as the change in the angular velocity of the motor is opposite to the sign of the steering torque and the absolute value of the angular velocity change is greater than the first angular velocity change threshold.

[0020] When the rotating shaft is rapidly moved to one side by the driver's steering operation and end contact occurs in a state where the motor is rapidly rotating, the motor is likely to stop quickly. Therefore, when the movement of the rotating shaft has been limited in this manner, for example, when a positive steering torque equal to or greater than a first steering torque threshold is input, the change in the angular velocity of the motor is less than the negative first angular velocity change threshold. That is, when instantaneous end contact occurs, a dynamic limit determination can be established. Therefore, with this configuration, for example, when a turn steering is rapidly performed and an instantaneous end contact occurs, it can be determined that the movement of the rotating shaft has been limited, and the limit position determination angle can be obtained and the end position corresponding angle can be set.

[0021] In the steering control device according to this aspect, the conditions for establishing the dynamic limit determination may include the conditions that the sign of the angular velocity of the motor is the same as the sign of the steering torque and the absolute value of the angular velocity of the motor is greater than the first angular velocity threshold.

[0022] As described above, after the rotating shaft moves to one side by the steering operation of the driver and the momentary end contact occurs, the motor rotates in the direction in which the rotating shaft moves to one side until the motor quickly stops. Therefore, with this configuration, since the condition for establishing the dynamic limit determination includes the condition that the angular velocity of the motor is greater than the first angular velocity threshold value having the same sign as the sign of the steering torque, it is possible to accurately determine whether the momentary end contact has occurred.

[0023] In the steering control device according to this aspect, the electronic control unit may be configured to determine a static limit determination in addition to the dynamic limit determination, and when one of the dynamic limit determination and the static limit determination is established, determine that the movement of the rotation axis has been limited. The conditions for establishing the static limit determination may include a condition that the absolute value of the steering torque is equal to or greater than a second steering torque threshold value greater than the first steering torque threshold value, and a condition that the absolute value of the angular velocity change is equal to or less than a second angular velocity change threshold value less than the first angular velocity change threshold value.

[0024] When the rotating shaft moves to one side by the driver's steering operation and end contact occurs, the motor hardly rotates although the turning steering continues. Therefore, when the movement of the rotating shaft has been limited in this way, for example, in a state where a positive steering torque equal to or greater than the second steering torque threshold is input, the absolute value of the angular velocity change of the motor is equal to or less than the second angular velocity change threshold. That is, for example, when the steering wheel remains stationary after end contact has occurred, a static limit determination can be established. Therefore, using this configuration, for example, when the steering wheel remains stationary after end contact has occurred, it can be determined that the movement of the rotating shaft has been limited and the limit position determination angle can be obtained and the end position corresponding angle can be set.

[0025] In the above configuration, when one of the dynamic limit determination and the static limit determination is established, it is determined that the movement of the rotation axis is limited, and the limit position determination angle is acquired. Therefore, when the movement of the rotation axis has been limited in various ways, the limit position determination angle can be acquired and the end position corresponding angle can be set more quickly.

[0026] In the steering control device according to this aspect, the conditions for establishing a static limit determination may include the conditions that the sign of the angular velocity of the motor is the same as the sign of the steering torque and the absolute value of the angular velocity of the motor is greater than a first angular velocity threshold and equal to or less than a second angular velocity threshold.

[0027] When the turning steering is continued even after the end contact occurs as described above, strictly speaking, the motor rotates slightly due to the elastic deformation of the steering system. Therefore, with this configuration, since the conditions for establishing the static limit determination include the condition that the angular velocity of the motor is greater than the first angular velocity threshold value having the same sign as the steering torque and is equal to or less than the second angular velocity threshold value, it is possible to accurately determine whether the end contact continues to occur.

[0028] In a steering control device according to this aspect, the electronic control unit can be configured to obtain a value obtained by performing rigidity compensation on the absolute steering angle detected when the electronic control unit determines that the movement of the rotating shaft has been restricted based on the mechanical elastic deformation of the steering system caused by the torque applied to the steering system as a limit position determination angle.

[0029] With this configuration, an accurate limit position determination angle can be acquired in consideration of the elastic deformation of the steering system when determining that the movement of the rotation shaft has been restricted.

[0030] In the steering control device according to this aspect, the electronic control unit may be configured to calculate the torque applied to the steering system using the steering torque, the motor torque, and the inertia torque based on the angular velocity change.

[0031] With this configuration, since the steering torque, the motor torque, and the inertia torque are used as the torque applied to the steering system, the elastic deformation amount of the steering system when determining that the movement of the rotation axis has been restricted can be accurately calculated, and a more accurate limit position determination angle can be obtained. In particular, in dynamic limit determination, the inertia torque increases due to the rapid stop of the motor, and therefore the effect is good.

[0032] According to this aspect of the invention, the end position corresponding angle can be set based on the instantaneous end contact. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and in which:

[0034] Figure 1 is a diagram schematically showing the configuration of an electric power steering system;

[0035] Figure 2 is a block diagram showing a steering control device;

[0036] Figure 3 is a block diagram showing a limit value setting unit;

[0037] Figure 4 is a block diagram showing an end position corresponding angle management unit;

[0038] Figure 5 is a diagram schematically showing the relationship between the absolute steering angle and the pinion shaft torque;

[0039] Figure 6 is a flowchart showing a processing routine for acquiring a limit position determination angle, which is executed by a limit position determination angle acquisition unit;

[0040] Figure 7 is a flowchart showing a processing routine of dynamic limit determination performed by a limit position determination angle acquisition unit;

[0041] Figure 8 is a flowchart showing a processing routine of static limit determination performed by a limit position determination angle acquisition unit; and

[0042] Fig. 9 : is a flowchart showing a processing routine of surrounding environment change determination performed by the limit position determination angle acquisition unit. DETAILED DESCRIPTION

[0043] Hereinafter, a steering control device according to a first embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1 As shown, an electric power steering system (EPS) 2 as a steering system controlled by a steering control device 1 includes a steering mechanism 5 that rotates a steering wheel 4 based on a driver's operation of a steering wheel 3. The EPS 2 also includes an EPS actuator 6 that applies a steering force to the steering mechanism 5 for assisting the steering operation.

[0044] The steering mechanism 5 includes a steering shaft 11 to which the steering wheel 3 is fixed, a rack shaft 12 as a rotation shaft connected to the steering shaft 11, a rack housing 13 as a housing in which the rack shaft 12 is inserted so that the rack shaft 12 reciprocates, and a rack and pinion mechanism 14 that converts the rotational motion of the steering shaft 11 into the reciprocating motion of the rack shaft 12. The steering shaft 11 has a configuration in which a column shaft 15, an intermediate shaft 16, and a pinion shaft 17 are sequentially connected from the side where the steering wheel 3 is located.

[0045] The rack shaft 12 and the pinion shaft 17 are arranged in the rack housing 13 at a predetermined crossing angle. The rack and pinion mechanism 14 has a configuration in which rack teeth 12a formed on the rack shaft 12 and pinion teeth 17a formed on the pinion shaft 17 are meshed with each other. The tie rod 19 is rotatably connected to both ends of the rack shaft 12 via rack ends 18, each of which is formed by a spherical joint provided at one shaft end. The distal end of the tie rod 19 is connected to a steering knuckle (not shown) equipped with the rotating wheel 4. Therefore, in the EPS 2, the rotational motion of the steering shaft 11 based on the steering operation is converted into a reciprocating motion in the axial direction of the rack shaft 12 through the rack and pinion mechanism 14, and the reciprocating motion in the axial direction is transmitted to the steering knuckle via the tie rod 19, thereby changing the rotation angle of the rotating wheel 4, that is, the driving direction of the vehicle.

[0046] The position of the rack shaft 12 at which the rack end 18 contacts the left end of the rack housing 13 is a position at which the steering wheel 3 can be turned to the right to the greatest extent, and this position corresponds to the rack end position as the right end position. The position of the rack shaft 12 at which the rack end 18 contacts the right end of the rack housing 13 is a position at which the steering wheel 3 can be turned to the left to the greatest extent, and this position corresponds to the rack end position as the left end position.

[0047] The EPS actuator 6 includes a motor 21 as a driving source and a reduction mechanism 22 such as a worm gear. The motor 21 is connected to the column shaft 15 via the reduction mechanism 22. The EPS actuator 6 applies the motor torque as an auxiliary force to the steering mechanism 5 by reducing the rotational motion of the motor 21 using the reduction mechanism 22 and transmitting the reduced rotation to the column shaft 15. According to the present embodiment, a three-phase brushless motor is used as the motor 21.

[0048] The steering control device 1 is connected to the motor 21 and controls the operation of the motor 21. The steering control device 1 includes a central processing unit (CPU) and a memory, not shown, and the CPU executes a program stored in the memory in each predetermined calculation cycle. Thus, various controls are performed.

[0049] A vehicle speed sensor 31 that detects a vehicle speed SPD of the vehicle and a torque sensor 32 that detects a steering torque Th applied to the steering shaft 11 according to a steering operation of the driver are connected to the steering control device 1. A rotation sensor 33 that detects a rotation angle θm of the motor 21 as a relative angle within a range of 360° is connected to the steering control device 1. The steering torque Th and the rotation angle θm are detected as positive values ​​when the steering wheel 3 is turned to the right and as negative values ​​when the steering wheel 3 is turned to the left. That is, in the present embodiment, the sign of the steering torque Th that moves the rack shaft 12 to the right side corresponding to one side and the sign of the rotation direction of the motor 21 are defined as positive, and the sign of the steering torque Th that moves the rack shaft 12 to the left side corresponding to the side opposite to the one side and the sign of the rotation direction of the motor 21 are defined as negative. The steering control device 1 controls the operation of the EPS actuator 6, that is, the assist force applied to the steering mechanism 5 to enable the rack shaft 12 to reciprocate, by supplying drive power to the motor 21 based on a signal indicating a state quantity input from the sensor.

[0050] The configuration of the steering control device 1 will be described below. Figure 2 As shown, the steering control device 1 includes a microcomputer 41 that outputs a motor control signal Sm and a drive circuit 42 that supplies drive power to the motor 21 based on the motor control signal Sm. In other words, the steering control device 1 includes an electronic control unit (ECU), which includes the above-mentioned central processing unit (CPU) and the above-mentioned memory. A known PWM inverter including a plurality of switching elements such as FET is used as the drive circuit 42 according to the present embodiment. The motor control signal Sm output from the microcomputer 41 determines the on-state and off-state of the switching element. Therefore, the switching element is turned on and off in response to the motor control signal Sm, and the mode of power supply to the motor coils of each phase is switched, thereby converting the DC power of the vehicle power supply 43 into three-phase drive power and outputting it to the motor 21.

[0051] The control blocks to be described below are realized by a computer program executed by the microcomputer 41, detect the state quantity at each predetermined sampling cycle, and execute the calculation processing assigned to the following control blocks at each predetermined calculation cycle.

[0052] The vehicle speed SPD, the steering torque Th, and the rotation angle θm of the motor 21 are input to the microcomputer 41. The phase current values ​​Iu, Iv, and Iw of the motor 21 detected by the current sensor 44 and the power supply voltage Vb of the vehicle power supply 43 detected by the voltage sensor 45 are also input to the microcomputer 41. The current sensor 44 is provided on the connection line 46 between the drive circuit 42 and the motor coil of each phase. The voltage sensor 45 is provided on the connection line 47 between the vehicle power supply 43 and the drive circuit 42. Figure 2 In FIG. 4 , for convenience of description, a group of current sensors 44 of a phase is shown as one current sensor 44, and a group of connection lines 46 of a phase is shown as one connection line 46. The microcomputer 41 outputs a motor control signal Sm based on an input state amount.

[0053] Specifically, the microcomputer 41 includes a method for calculating the current command value Id * andIq * The current command value calculation unit 51 is based on the current command value Id * andIq * A motor control signal generating unit 52 outputs a motor control signal Sm, and an absolute steering angle detecting unit 53 detects an absolute steering angle θs.

[0054] The steering torque Th, the vehicle speed SPD, and the absolute steering angle θs are input to the current command value calculation unit 51. The current command value calculation unit 51 calculates the current command value Id based on the input state quantities. * andIq * . Current command value Id * andIq * are the target values ​​of the current to be supplied to the motor 21, and are the current command value on the d-axis and the current command value on the q-axis in the d / q coordinate system, respectively. * represents the target value of the motor torque output from the motor 21. In the present embodiment, the d-axis current command value Id * Basically fixed to zero. For example, when assisting right-hand steering, the current command value Id * andIq * has a positive value, and when assisting left steering, the current command value Id * andIq * Has negative value.

[0055] Current command value Id * andIq *, phase current values ​​Iu, Iv and Iw, and the rotation angle θm of the motor 21 are input to the motor control signal generating unit 52. The motor control signal generating unit 52 generates the motor control signal Sm by performing current feedback control in the d / q coordinate system based on the input state quantity.

[0056] Specifically, the motor control signal generating unit 52 calculates the d-axis current value Id and the q-axis current value Iq, which are actual current values ​​of the motor 21 in the d / q coordinate system, by mapping the phase current values ​​Iu, Iv, and Iw onto the d / q coordinate system based on the rotation angle θm. Then, the motor control signal generating unit 52 performs current feedback control so that the d-axis current value Id follows the d-axis current command value Id. * And the q-axis current value Iq follows the q-axis current command value Iq * The q-axis current value Iq calculated in the process of generating the motor control signal Sm is output to the current command value calculation unit 51 .

[0057] The motor control signal generating unit 52 outputs the generated motor control signal Sm to the drive circuit 42. Thus, by supplying the drive power based on the motor control signal Sm to the motor 21 and outputting the drive power based on the q-axis current command value Iq from the motor 21, * The motor torque, the auxiliary force is applied to the steering mechanism 5.

[0058] The rotation angle θm is input to the absolute steering angle detection unit 53. The absolute steering angle detection unit 53 detects the absolute motor angle based on the rotation angle θm, which is expressed as an absolute angle within a range including a range exceeding 360°. The absolute steering angle detection unit 53 in the present embodiment integrates (i.e., accumulates) the number of revolutions of the motor 21 with the rotation angle θm as the origin when the start switch such as the ignition switch is turned on for the first time after the vehicle-mounted power source 43 has been replaced, and detects the absolute motor angle based on the integrated number of revolutions and the rotation angle θm. Then, the absolute steering angle detection unit 53 detects the absolute steering angle θs indicating the steering angle of the steering shaft 11 by multiplying the absolute motor angle by a conversion factor based on the reduction ratio of the reduction mechanism 22. In the steering control device 1 according to the present embodiment, even when the start switch is turned off, the rotation of the motor 21 is monitored and the number of revolutions of the motor 21 is integrated normally. Therefore, even when the start switch is turned on for the second time or later after the vehicle-mounted power source 43 has been replaced, the origin of the absolute steering angle θs is the same as the origin set when the start switch was turned on for the first time.

[0059] As described above, since the rotation angle of the rotating wheel 4 is changed by the rotation of the steering shaft 11, the absolute steering angle θs indicates the rotation angle of the rotating shaft that can be converted into the rotation angle of the rotating wheel 4. The absolute motor angle and the absolute steering angle θs have a positive value when they are angles toward the right side from the origin, and have a negative value when they are angles toward the left side from the origin.

[0060] The configuration of the current command value calculation unit 51 will be described in detail below. The current command value calculation unit 51 includes an assist command value calculation unit 61 that calculates the q-axis current command value Iq * The auxiliary command value Ias of the basic component * ; Limit value setting unit 62, which is set as the q-axis current command value Iq * and a protection processing unit 63, which limits the assist command value Ias * The absolute value of the auxiliary command value Ias * The absolute value of is equal to or less than the limit value Ig. The current command value calculation unit 51 also includes an end position corresponding angle management unit 65 that manages the end position corresponding angles θs_re and θs_le, which are absolute steering angles θs corresponding to the right rack end position and the left rack end position and are stored in the memory 64.

[0061] The steering torque Th and the vehicle speed SPD are input to the assist command value calculation unit 61. The assist command value calculation unit 61 calculates the assist command value Ias based on the steering torque Th and the vehicle speed SPD. * Specifically, the assist command value calculation unit 61 calculates the assist command value Ias * , so that the assist command value Ias becomes larger as the absolute value of the steering torque Th becomes larger and the vehicle speed SPD becomes lower. * Has a larger absolute value. The calculated auxiliary command value Ias * The signal is output to the protection processing unit 63 .

[0062] As will be described later, in addition to the auxiliary command value Ias * In addition, the limit value Ig set by the limit value setting unit 62 is input to the protection processing unit 63. * When the absolute value of is equal to or less than the limit value Ig, the protection processing unit 63 sets the auxiliary command value Ias * The value is taken as the q-axis current command value Iq * The assist command value Ias is output to the motor control signal generating unit 52 without any change. * When the absolute value of is greater than the limit value Ig, the protection processing unit 63 will increase the auxiliary command value Ias by *The absolute value of is limited to the limit value Ig and the value obtained is used as the q-axis current command value Iq * Output to the motor control signal generating unit 52.

[0063] The rated current Ir as the maximum current corresponding to the torque preset as the motor torque that can be output from the motor 21, the end position corresponding angles θs_re and θs_le, and the like are stored in the memory 64. The left end position corresponding angle θs_le is the absolute steering angle θs corresponding to the left rack end position, and the right end position corresponding angle θs_re is the absolute steering angle θs corresponding to the right rack end position. As will be described later, the setting of the end position corresponding angles θs_re and θs_le is managed by the end position corresponding angle management unit 65. For example, in the present embodiment, a memory of a type that retains the end position corresponding angles θs_re and θs_le as long as the vehicle-mounted power supply 43 is not disassembled is used as the memory 64.

[0064] The following will describe the configuration of the limit value setting unit 62. The absolute steering angle θs, vehicle speed SPD, power supply voltage Vb, rated current Ir, and end position correspondence angles θs_re and θs_le are input to the limit value setting unit 62. The limit value setting unit 62 sets the limit value Ig based on the input state quantities.

[0065] Specifically, Figure 3 As shown, the limit value setting unit 62 includes a steering angle limit value calculation unit 71 that calculates a steering angle limit value Ien based on the absolute steering angle θs, a voltage limit value calculation unit 72 that calculates a voltage limit value Ivb as another limit value based on the power supply voltage Vb, and a minimum value selection unit 73 that selects the smaller one of the steering angle limit value Ien and the voltage limit value Ivb.

[0066] The absolute steering angle θs, the vehicle speed SPD, the rated current Ir, and the end position corresponding angles θs_re and θs_le are input to the steering angle limit value calculation unit 71. As will be described later, when the end separation angle Δθ is equal to or less than the predetermined angle θ1, the steering angle limit value calculation unit 71 calculates the steering angle limit value Ien based on the input state quantity, and the steering angle limit value Ien decreases as the end separation angle Δθ decreases, and the end separation angle Δθ indicates the minimum distance of the absolute steering angle θs from the right end position corresponding angle θs_re or the left end position corresponding angle θs_le. The calculated steering angle limit value Ien is output to the minimum value selection unit 73. When the right end position corresponding angle θs_re and the left end position corresponding angle θs_le are not set in the memory 64, the steering angle limit value calculation unit 71 does not calculate the steering angle limit value Ien.

[0067] The power supply voltage Vb is input to the voltage limit value calculation unit 72. When the absolute value of the power supply voltage Vb is equal to or less than the preset voltage threshold value Vth, the voltage limit value calculation unit 72 calculates a voltage limit value Ivb that is less than the rated voltage for supplying the rated current Ir. Specifically, when the absolute value of the power supply voltage Vb is equal to or less than the voltage threshold value Vth, the voltage limit value calculation unit 72 calculates a voltage limit value Ivb having an absolute value that decreases as the absolute value of the power supply voltage Vb decreases. The calculated voltage limit value Ivb is output to the minimum value selection unit 73.

[0068] The minimum value selection unit 73 selects the smaller of the input steering angle limit value Ien and the input voltage limit value Ivb as the limit value Ig, and outputs the selected one to the protection processing unit 63. When the steering angle limit value Ien is output as the limit value Ig to the protection processing unit 63, the q-axis current command value Iq * The absolute value of is limited to the steering angle limit value Ien. Therefore, when the end separation angle Δθ is equal to or less than the predetermined angle θ1, the q-axis current command value Iq is increased as the end separation angle Δθ decreases. * The end contact relaxation control is performed by reducing the absolute value of the end contact of the rack end 18 and the rack housing 13. As will be described later, when both the right end position corresponding angle θs_re and the left end position corresponding angle θs_le are stored in the memory 64, the normal end contact relaxation control is performed, and when one of the right end position corresponding angle θs_re and the left end position corresponding angle θs_le is stored in the memory 64, the temporary end contact relaxation control is performed.

[0069] When the voltage limit value Ivb is output to the protection processing unit 63 as the limit value Ig, the q-axis current command value Iq * The absolute value of the q-axis current command value Iq is limited to the voltage limit value Ivb. Therefore, when the absolute value of the power supply voltage Vb is equal to or less than the voltage threshold value Vth, the operation for making the q-axis current command value Iq * Power supply protection control in which the absolute value of decreases as the absolute value of the power supply voltage Vb decreases.

[0070] The configuration of the steering angle limit value calculation unit 71 will be described below. The steering angle limit value calculation unit 71 includes an end separation angle calculation unit 81 that calculates the end separation angle Δθ and an angle limit component calculation unit 82 that calculates an angle limit component Iga that is a current limit determined based on the end separation angle Δθ. The steering angle limit value calculation unit 71 calculates the steering angle limit value Ien by subtracting the angle limit component Iga from the rated current Ir.

[0071] Specifically, the absolute steering angle θs and the end position corresponding angles θs_re and θs_le are input to the end separation angle calculation unit 81. When both the right end position corresponding angle θs_re and the left end position corresponding angle θs_le are stored in the memory 64, the end separation angle calculation unit 81 calculates the difference between the absolute steering angle θs in the latest calculation cycle and the left end position corresponding angle θs_le and the difference between the absolute steering angle θs in the latest calculation cycle and the right end position corresponding angle θs_re. Then, the end separation angle calculation unit 81 outputs the smaller absolute value of the calculated difference as the end separation angle Δθ to the angle limit component calculation unit 82 and the excess angular velocity calculation unit 83. On the other hand, when only one of the right end position corresponding angle θs_re and the left end position corresponding angle θs_le is stored in the memory 64, the end separation angle calculation unit 81 calculates the difference between the absolute steering angle θs in the latest calculation cycle and the end position corresponding angle θs_le or the end position corresponding angle θs_re. Then, the end separation angle calculation unit 81 outputs the calculated difference as the end separation angle Δθ to the angle limit component calculation unit 82 .

[0072] When neither the right end position corresponding angle θs_re nor the left end position corresponding angle θs_le is stored in the memory 64, the end separation angle calculation unit 81 does not calculate the end separation angle Δθ. Therefore, in the angle limit component calculation unit 82 to be described later, the angle limit component Iga is not calculated, and the steering angle limit value Ien is not calculated.

[0073] The end separation angle Δθ and the vehicle speed SPD are input to the angle limit component calculation unit 82. The angle limit component calculation unit 82 includes a map defining the relationship between the end separation angle Δθ and the vehicle speed SPD and the angle limit component Iga, and refers to the map to calculate the angle limit component Iga corresponding to the end separation angle Δθ and the vehicle speed SPD.

[0074] In this mapping, the angle limit component Iga is set to decrease as the end separation angle Δθ increases from the zero state, reaches zero when the end separation angle Δθ is a predetermined angle θ1, and is zero when the end separation angle Δθ is greater than the predetermined angle θ1. In this mapping, a region where the end separation angle Δθ is negative is also set, and when the end separation angle Δθ becomes less than zero, the angle limit component Iga increases in proportion to the decrease in the end separation angle Δθ, and remains constant after the angle limit component Iga becomes equal to the rated current Ir. The negative region in this mapping is set based on the assumption that in a state where the rack end 18 is in contact with the rack housing 13, when the rotation steering is further performed (that is, the steering wheel 3 is further rotated), the motor 21 rotates with the elastic deformation of the EPS 2. The predetermined angle θ1 is set to a small angle indicating a range close to the end position corresponding angles θs_re and θs_le. That is, the angle limit component Iga is set to decrease when the absolute steering angle θs changes from the end position corresponding angles θs_re and θs_le to the neutral steering position, and to be zero when the absolute steering angle θs is closer to the neutral steering position than near the end position corresponding angles θs_re and θs_le.

[0075] In this mapping, in the region where the end separation angle Δθ is equal to or less than the predetermined angle θ1, the angle limit component Iga is set to decrease as the vehicle speed SPD increases. Specifically, when the vehicle speed SPD is in the low speed region, the angle limit component Iga is set to be greater than zero, and when the vehicle speed SPD is in the medium speed or high speed region, the angle limit component Iga is set to zero. The calculated angle limit component Iga is output to the subtractor 83.

[0076] In addition to the angle limit component Iga, the rated current Ir is input to the subtractor 83. The steering angle limit value calculation unit 71 outputs a value obtained by subtracting the angle limit component Iga from the rated current Ir in the subtractor 83 to the minimum value selection unit 73 as the steering angle limit value Ien.

[0077] The configuration of the end position corresponding angle management unit 65 will be described below. Figure 2As shown, the vehicle speed SPD, the steering torque Th, the absolute steering angle θs, the q-axis current value Iq, and the motor angular velocity ωm obtained by differentiating the rotation angle θm are input to the end position corresponding angle management unit 65. The end position corresponding angle management unit 65 determines whether the movement of the rack shaft 12 to one of the right and left sides is restricted based on the input state quantity, and when it is determined that the movement of the rack shaft 12 is restricted, obtains a plurality of limit position determination angles θi corresponding to the absolute steering angle θs (that is, a plurality of values ​​of the limit position determination angle θi). Then, the end position corresponding angle management unit 65 stores the end position corresponding angles θs_re and θs_le based on the plurality of limit position determination angles θi in the memory 64. After storing the end position corresponding angles θs_re and θs_le in the memory 64 once, the end position corresponding angle management unit 65 does not perform the processing associated with the setting of the end position corresponding angles θs_re and θs_le until the end position corresponding angles θs_re and θs_le are lost.

[0078] Specifically, Figure 4 As shown, the end position corresponding angle management unit 65 includes: an angular velocity change calculation unit 91, a limit position determination angle acquisition unit 92, and an end position corresponding angle setting unit 93. The motor angular velocity ωm is input to the angular velocity change calculation unit 91. The angular velocity change calculation unit 91 calculates the angular velocity change Δωm as the change (i.e., the amount of change) of the motor angular velocity ωm based on the input motor angular velocity ωm. Then, the angular velocity change calculation unit 91 outputs the angular velocity change Δωm to the limit position determination angle acquisition unit 92. The angular velocity change calculation unit 91 in this embodiment outputs the value obtained by performing low-pass filtering on the angular velocity change Δωm to the limit position determination angle acquisition unit 92.

[0079] The vehicle speed SPD, the steering torque Th, the q-axis current value Iq, the motor angular velocity ωm, the angular velocity change amount Δωm, and the absolute steering angle θs are input to the limit position determination angle acquisition unit 92. As will be described later, the limit position determination angle acquisition unit 92 determines whether the movement of the rack shaft 12 to one of the right and left sides is restricted based on the input state amount, and when it is determined that the movement of the rack shaft 12 is restricted, acquires the limit position determination angle θi corresponding to the absolute steering angle θs.

[0080] The plurality of limit position determination angles θi from the limit position determination angle acquisition unit 92 are input to the end position corresponding angle setting unit 93. When the limit position determination angles θi of the right and left sides are acquired, the end position corresponding angle setting unit 93 sets the end position corresponding angles θs_re and θs_le based on the limit position determination angles θi of the right and left sides. The end position corresponding angle setting unit 93 determines which of the right and left sides each limit position determination angle θi is associated with based on the signs of the limit position determination angles θi.

[0081] Specifically, when acquiring the right and left limit position determination angles θi, the end position corresponding angle setting unit 93 first calculates the stroke width Wma, which is the sum of the absolute value of the right limit position determination angle θi and the absolute value of the left limit position determination angle θi. When the stroke width Wma is greater than the stroke threshold Wth, the end position corresponding angle setting unit 93 sets the acquired right and left limit position determination angles θi as the end position corresponding angles θs_re and θs_le without any change. The stroke threshold Wth1 is an angle range represented by the absolute steering angle θs, and is set to be slightly smaller than the angle range corresponding to the entire stroke range of the rack shaft 12. When the stroke width Wma is equal to or less than the stroke threshold Wth, the end position corresponding angle setting unit 93 does not set the end position corresponding angles θs_re and θs_le, discards the input limit position determination angle θi, and performs the same processing when acquiring the right and left limit position determination angles θi again.

[0082] On the other hand, when a plurality of limit position determination angles θi of only one side of the right side and the left side are acquired, the end position corresponding angle setting unit 93 sets only the end position corresponding angle θs_re or θs_le of the corresponding side based on the acquired limit position determination angle θi. Specifically, the end position corresponding angle setting unit 93 sets the average value of the plurality of limit position determination angles θi as the end position corresponding angle θs_re of the right side or the end position corresponding angle θs_le of the left side.

[0083] The acquisition of the limit position determination angle θi performed by the limit position determination angle acquisition unit 92 will be described below. When the signal indicating the vehicle speed SPD input from the vehicle speed sensor 31 is normal and the vehicle speed SPD is greater than the low speed threshold value Slo, the limit position determination angle acquisition unit 92 will not determine whether the movement of the rack shaft 12 is restricted. This is because, when the vehicle speed SPD is high to a certain extent and the steering wheel 3 is turned to the rack end position, end contact does not occur due to the rotation of the vehicle, etc. For example, when the vehicle speed SPD has an impossible value, or when the change in the vehicle speed SPD from a previous value is greater than a preset threshold value, the limit position determination angle acquisition unit 92 may determine that the signal indicating the vehicle speed SPD is abnormal. The low speed threshold value Slo is a vehicle speed indicating that the vehicle is traveling at a low speed, and is set in advance.

[0084] When the signal indicating the vehicle speed SPD is abnormal or when the vehicle speed SPD is equal to or less than the low speed threshold value Slo, the limit position determination angle acquisition unit 92 performs a dynamic limit determination. When the dynamic limit determination has been continuously established for a first predetermined time, the limit position determination angle acquisition unit 92 acquires the limit position determination angle θi corresponding to the absolute steering angle θs detected when the determination has been continuously established for the first predetermined time. On the other hand, in the case where the dynamic limit determination is not established, the limit position determination angle acquisition unit 92 performs a static limit determination. When the static limit determination has been continuously established for a second predetermined time, the limit position determination angle acquisition unit 92 acquires the limit position determination angle θi corresponding to the absolute steering angle θs detected when the determination has been continuously established for the second predetermined time.

[0085] The static limit determination is a determination for detecting a state in which the steering wheel remains stationary while the movement of the rack shaft 12 is restricted and a state in which slow turn steering is performed and the movement of the rack shaft 12 is restricted. The dynamic limit determination is a determination for detecting a state in which turn steering is performed relatively quickly and return steering (i.e., the steering wheel is returned) is performed immediately after the movement of the rack shaft 12 has been restricted.

[0086] The limit position determination angle acquisition unit 92 of the present embodiment performs rigid compensation on the absolute steering angle θs detected when it is determined that the movement of the rack shaft 12 has been restricted as a result of dynamic limit determination or static limit determination, and the rigid compensation performs correction based on the mechanical elastic deformation of EPS2 caused by the torque applied to EPS 2, and the limit position determination angle acquisition unit 92 acquires the angle after rigid compensation as the limit position determination angle θi.

[0087] After having acquired one limit position determination angle θi (i.e., one value of the limit position determination angle θi), the limit position determination angle acquisition unit 92 will not acquire another limit position determination angle θi (i.e., another value of the limit position determination angle θi) before establishing a surrounding environment change determination as to whether the surrounding environment around the vehicle has changed.

[0088] The processing performed by the limit position determination angle acquisition unit 92 will be described in detail below in the order of dynamic limit determination, static limit determination, rigidity compensation, and surrounding environment change determination.

[0089] Dynamic limit determination

[0090] When the following three conditions are satisfied, the limit position determination angle acquisition unit 92 determines that the dynamic limit determination is established and the movement of the rack shaft 12 has been limited.

[0091] (a1) The absolute value of the steering torque Th is equal to or greater than the first steering torque threshold value Tth1. (a2) The sign of the motor angular velocity ωm is the same as that of the steering torque Th, and the absolute value of the motor angular velocity ωm is greater than the first angular velocity threshold value ωth1.

[0092] (a3) The sign of the angular velocity change Δωm is opposite to the sign of the steering torque Th, and the absolute value of the angular velocity change Δωm is greater than the first angular velocity change threshold value Δωth1. The first steering torque threshold value Tth1 is the steering torque when the return steering is performed immediately after the rack end 18 contacts the rack housing 13, and is set to an appropriate value greater than zero. The first angular velocity threshold value ωth1 is the angular velocity indicating that the motor 21 is in a stopped state, and is set to substantially zero. The first angular velocity change threshold value Δωth1 is a change in the angular velocity indicating that the motor 21 is rapidly decelerated, and is set to a relatively large value.

[0093] Static limit determination

[0094] When the following three conditions are satisfied, the limit position determination angle acquisition unit 92 determines that the static limit determination is established and the movement of the rack shaft 12 has been limited.

[0095] (b1) The absolute value of the steering torque Th is equal to or greater than the second steering torque threshold Tth2. (b2) The motor angular velocity ωm has the same sign as the steering torque Th, and the absolute value of the motor angular velocity ωm is greater than the first angular velocity threshold ωth1 and equal to or less than the second angular velocity threshold ωth2.

[0096] (b3) The absolute value of the angular velocity change Δωm is less than the second angular velocity change threshold value Δωth2. The second steering torque threshold value Tth2 is the steering torque required to hold the steering wheel 3 when the vehicle turns in a state where the rack end 18 is in contact with the rack housing 13, and is set to an appropriate value greater than the first steering torque threshold value Tth1. The second angular velocity threshold value ωth2 is an angular velocity indicating that the motor 21 rotates at a low speed, and is set to an appropriate value greater than zero. The second angular velocity change threshold value Δωth2 is a change in the angular velocity indicating that the motor 21 is substantially not accelerated or decelerated, and is set to a value that is smaller than the first angular velocity change threshold value Δωth1 and slightly greater than zero.

[0097] Rigidity compensation

[0098] The limit position determination angle acquisition unit 92 acquires, as the limit position determination angle θi, a value obtained by subtracting the mechanical elastic deformation induced in the EPS 2 from the absolute steering angle θs detected when it is determined that the movement of the rack shaft 12 has been restricted.

[0099] Specifically, the limit position determination angle acquisition unit 92 calculates the pinion shaft torque Tp, which is the sum of the torques applied to the EPS 2 when it is determined that the movement of the rack shaft 12 has been limited. The pinion shaft torque Tp corresponds to the axial force acting on the rack shaft 12. As represented by expression (1), the limit position determination angle acquisition unit 92 in the present embodiment calculates the pinion shaft torque Tp using the steering torque Th applied by the driver, the motor torque based on the q-axis current value Iq, and the inertia torque based on the angular velocity change Δωm of the motor 21.

[0100] Tp=Th+Iq×Km+Δωm×Kω...(1)

[0101] “Km” represents a coefficient determined by the motor constant of the motor 21, the reduction ratio and efficiency of the reduction mechanism 22, etc. “Kω” represents a coefficient determined by the inertia moment of the motor 21, the reduction ratio and efficiency of the reduction mechanism 22, etc.

[0102] like Figure 5 As shown, normally, when the driver performs a steering operation, the turning wheel 4 rotates, and the absolute steering angle θs increases according to the pinion shaft torque Tp applied to the EPS 2. For the following reason, at an angle slightly larger than the absolute steering angle θs corresponding to the actual rack end position, the absolute steering angle θs hardly increases even when the pinion shaft torque Tp increases. Since the movement of the rack shaft 12 has been restricted by the end contact, when the pinion shaft torque Tp increases, the motor 21 rotates slightly only due to the torsion of the steering shaft 11 constituting the EPS 2 or mechanical elastic deformation such as compression of the rack shaft 12. Since the slope of the pinion shaft torque Tp with respect to the absolute steering angle θs is proportional to the elastic coefficient Ke of the EPS 2, the absolute steering angle θs at a position where the pinion shaft torque Tp is zero on the line along the slope from the absolute steering angle θs serving as a base point substantially corresponds to the actual rack end position.

[0103] Taking this into consideration, the limit position determination angle acquisition unit 92 calculates the rotation angle of the motor 21 by multiplying the pinion shaft torque Tp by the elastic coefficient Ke of the EPS 2 based on the elastic deformation amount of the EPS 2. The limit position determination angle acquisition unit 92 acquires a value obtained by subtracting the rotation angle from the absolute steering angle θs detected when it is determined that the movement of the rack shaft 12 has been restricted as the limit position determination angle θi.

[0104] Changes in the surrounding environment

[0105] When the following two conditions are satisfied, the limit position determination angle acquisition unit 92 determines that the surrounding environment change determination is established and the surrounding environment around the vehicle has changed. The limit position determination angle acquisition unit 92 does not determine whether the condition (c2) is satisfied when the signal indicating the vehicle speed SPD is abnormal, and determines that the surrounding environment change determination is established when the condition (c1) is satisfied.

[0106] (c1) The return steering amount θba is equal to or greater than the return determination threshold value θth. (c2) When the signal indicating the vehicle speed SPD input from the vehicle speed sensor 31 is normal, the vehicle speed SPD is equal to or greater than the running threshold value Smin.

[0107] The return steering amount θba is the difference between the latest limit position determination angle θi and the absolute steering angle θs. The return determination threshold θth is the angle at which the driver is considered to have performed the return steering, and is preset to a relatively large value such as approximately 100°. The running threshold Smin is the minimum vehicle speed indicating that the vehicle has not stopped and is running, and is preset to a value greater than zero and less than the low speed threshold Slo.

[0108] flow chart

[0109] Refer to the following Figures 6 to 9 1, an example of a processing routine executed by the limit position determination angle acquisition unit 92 is described in the flowchart shown in FIG. In the following description, for the convenience of description, it is assumed that the rack shaft 12 moves to the right and the limit position determination angle θi on the right is acquired. However, when the rack shaft 12 moves to the left and the limit position determination angle θi on the left is acquired, the same processing routine is executed.

[0110] like Figure 6 As shown, when various state quantities are acquired at the time of acquiring the limit position determination angle θi (step 101), the limit position determination angle acquisition unit 92 determines whether a permission flag indicating permission to acquire the limit position determination angle θi is set (step 102). The permission flag is set in the initial state, and the permission flag is reset when the limit position determination angle θi is acquired. In the reset state, when the surrounding environment change determination is established, the permission flag is set again.

[0111] When the permission flag is not set (step 102: No), the limit position determination angle acquisition unit 92 does not perform subsequent processing and does not acquire the limit position determination angle θi in the same calculation cycle. On the other hand, when the permission flag is set (step 102: Yes), the limit position determination angle acquisition unit 92 determines whether the signal indicating the vehicle speed SPD is normal (step 103). When the signal indicating the vehicle speed SPD is normal (step 103: Yes), the limit position determination angle acquisition unit 92 determines whether the vehicle speed SPD is greater than the low speed threshold value Slo (step 104). When the vehicle speed SPD is greater than the low speed threshold value Slo (step 104: Yes), the limit position determination angle acquisition unit 92 does not perform subsequent processing and does not acquire the limit position determination angle θi in the same calculation cycle. On the other hand, when the signal indicating the vehicle speed SPD is not normal (step 103: No) and when the vehicle speed SPD is equal to or less than the low speed threshold value Slo (step 104: No), the limit position determination angle acquisition unit 92 performs dynamic limit determination (step 105).

[0112] like Figure 7 As shown, in the dynamic limit determination, the limit position determination angle acquisition unit 92 determines whether the steering torque Th is equal to or greater than the first steering torque threshold value Tth1 (step 201). When the steering torque Th is equal to or greater than the first steering torque threshold value Tth1 (step 201: yes), the limit position determination angle acquisition unit 92 determines whether the motor angular velocity ωm is greater than the first angular velocity threshold value ωth1 (step 202). That is, in step 202, the limit position determination angle acquisition unit 92 determines whether the sign of the motor angular velocity ωm is the same as the sign of the steering torque Th, and whether the absolute value of the motor angular velocity ωm is greater than the first angular velocity threshold value ωth1. When the motor angular velocity ωm is greater than the first angular velocity threshold value ωth1 (step 202: yes), the limit position determination angle acquisition unit 92 determines whether the angular velocity change Δωm is less than the negative first angular velocity change threshold value Δωth1 (step 203). That is, in step 203, the limit position determination angle acquisition unit 92 determines whether the sign of the angular velocity change Δωm is opposite to the sign of the steering torque Th, and whether the absolute value of the angular velocity change Δωm is greater than the first angular velocity change threshold value Δωth1. When the angular velocity change Δωm is less than the negative first angular velocity change threshold value Δωth1 (step 203: Yes), the limit position determination angle acquisition unit 92 determines that the dynamic limit determination is established, and the movement of the rack shaft 12 has been limited (step 204).

[0113] On the other hand, when the steering torque Th is less than the first steering torque threshold Tth1 (step 201: No), when the motor angular velocity ωm is equal to or less than the first angular velocity threshold ωth1 (step 202: No), and when the angular velocity change Δωm is equal to or greater than the negative first angular velocity change threshold Δωth1 (step 203: No), the limiting position determination angle acquisition unit 92 does not perform subsequent processing.

[0114] like Figure 6 As shown, after the dynamic limit determination is performed in step 105, the limit position determination angle acquisition unit 92 determines whether the determination is established (step 106). When the dynamic limit determination is established (step 106: Yes), the limit position determination angle acquisition unit 92 increments the count value Cdy of the dynamic counter indicating the number of times the dynamic limit determination has been established (step 107), and clears the count value Cst of the static counter indicating the number of times the static limit determination has been established (step 108). Next, the limit position determination angle acquisition unit 92 determines whether the count value Cdy of the dynamic counter is equal to or greater than a predetermined count value Cth1 corresponding to the first predetermined time (step 109), and when the count value Cdy is less than the predetermined count value Cth1, the subsequent processing is not performed (step 109: No).

[0115] On the other hand, when the count value Cdy is equal to or greater than the predetermined count value Cth1 (step 109: Yes), the limit position determination angle acquisition unit 92 clears the count value Cdy of the dynamic counter (step 110). Then, the limit position determination angle acquisition unit 92 acquires the limit position determination angle θi by performing rigid compensation on the absolute steering angle θs acquired in the same calculation cycle (step 111), and sets a stop flag indicating that the acquisition of the limit position determination angle θi is stopped before the surrounding environment change determination is established (step 112).

[0116] When the dynamic limit determination is not established (step 106: No), the limit position determination angle acquisition unit 92 performs the static limit determination (step 113). Figure 8As shown, in the static limit determination, the limit position determination angle acquisition unit 92 determines whether the steering torque Th is equal to or greater than the second steering torque threshold value Tth2 (step 301). When the steering torque Th is equal to or greater than the second steering torque threshold value Tth2 (step 301: yes), the limit position determination angle acquisition unit 92 determines whether the motor angular velocity ωm is greater than the first angular velocity threshold value ωth1 and less than or equal to the second angular velocity threshold value ωth2 (step 302). That is, in step 302, the limit position determination angle acquisition unit 92 determines whether the sign of the motor angular velocity ωm is the same as the sign of the steering torque Th, and whether the absolute value of the motor angular velocity ωm is greater than the first angular velocity threshold value ωth1 and equal to or less than the second angular velocity threshold value ωth2. When the motor angular velocity ωm is greater than the first angular velocity threshold ωth1 and equal to or less than the second angular velocity threshold ωth2, that is, when the motor 21 rotates at a very low speed (step 302: yes), the limit position determination angle acquisition unit 92 determines whether the absolute value of the angular velocity change Δωm is less than the second angular velocity change threshold Δωth2 (step 303). When the absolute value of the angular velocity change Δωm is less than the second angular velocity change threshold Δωth2 (step 303: yes), the limit position determination angle acquisition unit 92 determines that the static limit determination is established, and the movement of the rack shaft 12 has been limited (step 304).

[0117] On the other hand, when the steering torque Th is less than the second steering torque threshold Tth2 (step 301: No), when the motor angular velocity ωm is equal to or less than the first angular velocity threshold ωth1 or greater than the second angular velocity threshold ωth2 (step 302: No), and when the absolute value of the angular velocity change Δωm is equal to or greater than the second angular velocity change threshold Δωth2 (step 303: No), the limiting position determination angle acquisition unit 92 does not perform subsequent processing.

[0118] like Figure 6 As shown, after the static limit determination has been performed in step 113, the limit position determination angle acquisition unit 92 determines whether the determination is established (step 114). When the static limit determination is established (step 114: Yes), the limit position determination angle acquisition unit 92 increments the count value Cst of the static counter (step 115), and clears the count value Cdy of the dynamic counter (step 116). Subsequently, the limit position determination angle acquisition unit 92 determines whether the count value Cst of the static counter is equal to or greater than a predetermined count value Cth2 corresponding to the second predetermined time (step 117), and does not perform subsequent processing when the count value Cst is less than the predetermined count value Cth2 (step 117: No).

[0119] On the other hand, when the count value Cst is equal to or greater than the predetermined count value Cth2 (step 117: Yes), the limit position determination angle acquisition unit 92 clears the count value Cst of the static counter (step 118). Then, the limit position determination angle acquisition unit 92 acquires the limit position determination angle θi by performing rigid compensation on the absolute steering angle θs acquired in the same calculation cycle (step 119), and sets the stop flag (step 120).

[0120] When the static limit determination is not established (step 114 : No), that is, when the movement of the rack shaft 12 is not limited, the limit position determination angle acquisition unit 92 clears the count value Cdy of the dynamic counter and the count value Cst of the static counter (steps 121 and 122 ).

[0121] like Fig. 9 As shown, in the surrounding environment change determination, when acquiring various state quantities (step 401), the limit position determination angle acquisition unit 92 determines whether the stop flag is set (step 402). When the stop flag is not set (step 402: No), that is, when the limit position determination angle θi is not acquired and it is not necessary to determine whether the surrounding environment around the vehicle has changed, the limit position determination angle acquisition unit 92 does not perform subsequent processing.

[0122] On the other hand, in the case where the stop flag is set (step 402: yes), the limit position determination angle acquisition unit 92 calculates the return steering amount θba (step 403), and determines whether the return steering amount θba is greater than the return determination threshold value θth (step 404). When the return steering amount θba is greater than the return determination threshold value θth (step 404: yes), the limit position determination angle acquisition unit 92 determines whether the signal indicating the vehicle speed SPD is normal (step 405). When the signal indicating the vehicle speed SPD is normal (step 405: yes), the limit position determination angle acquisition unit 92 determines whether the vehicle speed SPD is equal to or greater than the running threshold value Smin (step 406). When the vehicle speed SPD is equal to or greater than the running threshold value Smin (step 406: yes), the limit position determination angle acquisition unit 92 sets the permission flag (step 407), and resets the stop flag (step 408).

[0123] When the vehicle speed SPD is abnormal (step 405: No), the limit position determination angle acquisition unit 92 skips step 406, and performs setting of the permission flag and resetting of the stop flag in steps 407 and 408. When the return steering amount θba is equal to or less than the return determination threshold value θth (step 404: No), and when the vehicle speed SPD is less than the running threshold value Smin (step 406: No), the limit position determination angle acquisition unit 92 resets the permission flag (step 409).

[0124] The operation and advantageous effects of this embodiment will be described below. The limit position determination angle acquisition unit 92 performs dynamic limit determination and determines that the movement of the rack shaft 12 has been limited when the dynamic limit determination is established. The conditions for establishing the dynamic limit determination include a condition that the absolute value of the steering torque Th is equal to or greater than the first steering torque threshold value Tth1 and a condition that the sign of the angular velocity change Δωm is opposite to the sign of the steering torque Th and the absolute value of the angular velocity change Δωm is greater than the first angular velocity change threshold value Δωth1.

[0125] For example, when the rack shaft 12 is rapidly moved to the right by the driver's steering operation and the end contact occurs in a state where the motor 21 is rapidly rotating, the motor 21 may be rapidly stopped. Therefore, when the movement of the rack shaft 12 has been limited in this manner, for example, in a state where a positive steering torque Th equal to or greater than the first steering torque threshold Tth1 is input, the angular velocity change Δωm of the motor 21 is less than the negative first angular velocity change threshold Δωth1. That is, when instantaneous end contact occurs, a dynamic limit determination can be established. Therefore, in the present embodiment, for example, when instantaneous end contact occurs by performing a rapid turn steering, it can be determined that the movement of the rack shaft 12 has been limited, and the limit position determination angle θi can be acquired and the end position corresponding angles θs_re and θs_le can be set.

[0126] As described above, for example, after the rack shaft 12 moves to the right by the driver's steering and the momentary end contact occurs, the motor 21 rotates in the direction in which the rack shaft 12 moves to the right until the motor 21 quickly stops. Therefore, in the present embodiment, since the condition for establishing the dynamic limit determination includes the condition that the motor angular velocity ωm is greater than the first angular velocity threshold ωth1 having the same sign as that of the steering torque Th, it is possible to accurately determine whether the momentary end contact occurs.

[0127] The limit position determination angle acquisition unit 92 performs static limit determination, and determines that the movement of the rack shaft 12 has been limited when the static limit determination is established. The conditions for establishing the static limit determination include a condition that the absolute value of the steering torque Th is equal to or greater than a second steering torque threshold value Tth2 greater than the first steering torque threshold value Tth1, and a condition that the absolute value of the angular velocity change Δωm is equal to or less than a second angular velocity change threshold value Δωth2 less than the first angular velocity change threshold value Δωth1.

[0128] For example, when the rack shaft 12 moves to the right side by the driver's steering operation and end contact occurs, the motor 21 hardly rotates although the turning steering continues. Therefore, when the movement of the rack shaft 12 has been limited in this way, for example, in a state where a positive steering torque equal to or greater than the second steering torque threshold value Tth2 is input, the absolute value of the angular velocity change Δωm of the motor 21 is equal to or less than the second angular velocity change threshold value Δωth2. That is, for example, when the steering wheel remains stationary after the end contact occurs, a static limit determination can be established. Therefore, in the present embodiment, for example, when the steering wheel remains stationary after the end contact occurs, it can be determined that the movement of the rack shaft 12 has been limited, and the limit position determination angle θi can be obtained and the end position corresponding angles θs_re and θs_le can be set.

[0129] When the turning steering is continued even after the end contact has occurred as described above, strictly speaking, the motor 21 rotates slightly due to the elastic deformation of the EPS 2. Therefore, in the present embodiment, since the conditions for establishing the static limit determination include the conditions that the motor angular velocity ωm is greater than the first angular velocity threshold ωth1 having the same sign as the steering torque Th and is equal to or less than the second angular velocity threshold ωth2, it is possible to accurately determine whether the end contact has continued to occur.

[0130] The limit position determination angle acquisition unit 92 acquires, as the limit position determination angle θi, a value obtained by performing rigid compensation on the absolute steering angle θs detected when determining that the movement of the rack shaft 12 has been restricted, based on the mechanical elastic deformation of the EPS 2 due to the pinion shaft torque Tp applied to the EPS 2. Therefore, it is possible to acquire an accurate limit position determination angle θi in consideration of the elastic deformation of the EPS 2 when determining that the movement of the rack shaft 12 has been restricted.

[0131] Since the limit position determination angle acquisition unit 92 calculates the pinion shaft torque Tp based on the steering torque Th, the motor torque and the inertia torque, the elastic deformation amount of the EPS 2 when determining that the movement of the rack shaft 12 has been restricted can be accurately calculated, and the limit position determination angle θi can be set more accurately. In particular, in dynamic limit determination, the inertia torque increases due to the rapid stop of the motor 21, and therefore the effect is good.

[0132] The operation and advantageous effects of this embodiment will be described below. For example, when the movement of the rack shaft 12 has been restricted due to the contact of the rotating wheel 4 with the curb, the restricted position determination angle θi acquired at this time is an angle different from the actual rack end angle, which is the actual end angle at which the end contact actually occurs. Therefore, when the end position corresponding angle θs_re or θs_le of the corresponding side is set based on only a single restricted position determination angle θi, the end position corresponding angle θs_re or θs_le may be an angle different from the actual rack end angle. Therefore, it is conceivable that the end position corresponding angle θs_re or θs_le of the corresponding side is set based on a plurality of restricted position determination angles θi (i.e., a plurality of values ​​of the restricted position determination angle θi) on one side of the right side and the left side. Therefore, for example, even if one of the plurality of restricted position determination angles θi is acquired at the time of contact with the curb and the other restricted position determination angles θi are acquired at the time of end contact, it is possible to prevent the set end position corresponding angles θs_re and θs_le from being angles different from the actual rack end angle. However, for example, when multiple limit position determination angles θi are obtained at the time of contact with the curb, there is the following problem: even if the end position corresponding angle θs_re or θs_le of the corresponding side is set based on the multiple limit position determination angles θi of one of the right and left sides, the end position corresponding angle θs_re or θs_le may also be an angle different from the actual rack portion angle.

[0133] In view of this, after one limit position determination angle θi has been set, the limit position determination angle acquisition unit 92 acquires another limit position determination angle θi after the surrounding environment around the vehicle has changed. Therefore, it is possible to prevent a situation from occurring in which each of the plurality of limit position determination angles θi is data acquired when the movement of the rack shaft 12 has been restricted due to contact with a curb or the like. As a result, the end position corresponding angles θs_re and θs_le that accurately correspond to the actual rack end angles can be set.

[0134] Since the conditions for establishing the surrounding environment change determination include the condition that the return steering amount θba is equal to or greater than the return determination threshold θth and the condition that the vehicle speed SPD is equal to or greater than the running threshold Smin, it is possible to accurately determine whether the surrounding environment has changed.

[0135] Regardless of whether the signal indicating the vehicle speed SPD input from the vehicle speed sensor 31 is normal, when the vehicle speed SPD is equal to or less than the low speed threshold value Slo, the limit position determination angle acquisition unit 92 determines whether the movement of the rack shaft 12 has been limited. Therefore, since the limit position determination angle θi can be acquired even if an abnormality occurs in the signal indicating the vehicle speed SPD, the end position corresponding angles θs_re and θs_le can be quickly set. When the signal indicating the vehicle speed SPD is abnormal, the limit position determination angle acquisition unit 92 makes the surrounding environment change determination not include the comparison of the vehicle speed SPD with the running threshold value Smin. Therefore, it is possible to prevent the situation in which the surrounding environment change determination is not established due to the abnormality of the signal indicating the vehicle speed SPD.

[0136] The limit position determination angle acquisition unit 92 performs dynamic limit determination and determines that the movement of the rack shaft 12 has been limited when the dynamic limit determination is established. The conditions for establishing the dynamic limit determination include a condition that the absolute value of the steering torque Th is equal to or greater than the first steering torque threshold value Tth1 and a condition that the sign of the angular velocity change Δωm is opposite to that of the steering torque Th and the absolute value of the angular velocity change Δωm is greater than the first angular velocity change threshold value Δωth1.

[0137] For example, when the rack shaft 12 is quickly moved to the right by the driver's steering operation and the end contact occurs in a state where the motor 21 is rotating rapidly, the motor 21 may be stopped quickly. Therefore, when the movement of the rack shaft 12 has been limited in this way, for example, in a state where a positive steering torque Th equal to or greater than the first steering torque threshold Tth1 is input, the angular velocity change Δωm of the motor 21 is less than the negative first angular velocity change threshold Δωth1. That is, when instantaneous end contact occurs, a dynamic limit determination can be established. Therefore, in the present embodiment, for example, when the turning steering is performed rapidly and an instantaneous end contact occurs, it can be determined that the movement of the rack shaft 12 has been limited, and the limit position determination angle θi can be acquired and the end position corresponding angles θs_re and θs_le can be set.

[0138] As described above, for example, after the rack shaft 12 moves to the right by the driver's steering operation and the momentary end contact occurs, the motor 21 rotates in the direction in which the rack shaft 12 moves to the right until the motor 21 quickly stops. Therefore, in the present embodiment, since the condition for establishing the dynamic limit determination includes the condition that the motor angular velocity ωm is greater than the first angular velocity threshold ωth1 having the same sign as that of the steering torque Th, it is possible to accurately determine whether the momentary end contact occurs.

[0139] The limit position determination angle acquisition unit 92 performs static limit determination and determines that the movement of the rack shaft 12 has been limited when the static limit determination is established. The conditions for establishing the static limit determination include a condition that the absolute value of the steering torque Th is equal to or greater than a second steering torque threshold value Tth2 greater than the first steering torque threshold value Tth1, and a condition that the absolute value of the angular velocity change Δωm is equal to or less than a second angular velocity change threshold value Δωth2 less than the first angular velocity change threshold value Δωth1.

[0140] For example, when the rack shaft 12 moves to the right side by the driver's steering operation and end contact occurs, the motor 21 hardly rotates although the turning steering continues. Therefore, when the movement of the rack shaft 12 has been limited in this way, for example, in a state where a positive steering torque equal to or greater than the second steering torque threshold value Tth2 is input, the absolute value of the angular velocity change Δωm of the motor 21 is equal to or less than the second angular velocity change threshold value Δωth2. That is, for example, when the steering wheel remains stationary after the end contact occurs, a static limit determination can be established. Therefore, in the present embodiment, for example, when the steering wheel remains stationary after the end contact occurs, it can be determined that the movement of the rack shaft 12 has been limited, and the limit position determination angle θi can be obtained and the end position corresponding angles θs_re and θs_le can be set.

[0141] When the turning steering is continuously performed after the end contact occurs as described above, strictly speaking, the motor 21 rotates slightly due to the elastic deformation of the EPS 2. Therefore, in the present embodiment, since the conditions for establishing the static limit determination include the conditions that the motor angular velocity ωm is greater than the first angular velocity threshold ωth1 having the same sign as the steering torque Th and is equal to or less than the second angular velocity threshold ωth2, it is possible to accurately determine whether the end contact continues to occur.

[0142] The limit position determination angle acquisition unit 92 performs dynamic limit determination and static limit determination, and when one of the dynamic limit determination and the static limit determination is established, determines that the movement of the rack shaft 12 has been restricted. Therefore, when the movement of the rack shaft 12 has been restricted in various ways, the limit position determination angle θi can be acquired, and the end position corresponding angles θs_re and θs_le can be set more quickly.

[0143] For example, it is assumed that even after the movement of the rack shaft 12 has been restricted due to the contact of the turning wheel 4 with a curb or the like, the turning steering has been quickly performed and the turning steering is continuously performed. In this case, both the dynamic limit determination and the static limit determination can be established. Therefore, in the case where it is assumed that two limit position determination angles θi are acquired when both determinations are established, both limit position determination angles θi are data acquired when the movement of the rack shaft 12 has been restricted due to contact with the same curb. Therefore, in the configuration in which the dynamic limit determination and the static limit determination are performed, the effect caused by acquiring another limit position determination angle θi when the surrounding environment around the vehicle changes after setting one limit position determination angle θi as in the present embodiment is good.

[0144] The limit position determination angle acquisition unit 92 acquires, as the limit position determination angle θi, a value obtained by performing rigid compensation on the absolute steering angle θs detected when determining that the movement of the rack shaft 12 has been restricted, based on the mechanical elastic deformation of the EPS 2 due to the pinion shaft torque Tp applied to the EPS 2. Therefore, it is possible to acquire an accurate limit position determination angle θi in consideration of the elastic deformation of the EPS 2 when determining that the movement of the rack shaft 12 has been restricted.

[0145] Since the limit position determination angle acquisition unit 92 calculates the pinion shaft torque Tp based on the steering torque Th, the motor torque and the inertia torque, the elastic deformation amount of the EPS 2 when determining that the movement of the rack shaft 12 has been restricted can be accurately calculated, and a more accurate limit position determination angle θi can be set. In particular, in dynamic limit determination, the inertia torque increases due to the rapid stop of the motor 21, and therefore the effect is good.

[0146] The above embodiment may be modified as follows. Unless a technical conflict occurs, the above embodiment and the following modification example may be combined. In the embodiment, when the signal indicating the vehicle speed SPD is normal and the vehicle speed SPD is greater than the low speed threshold value Slo, it may also be determined whether the movement of the rack shaft 12 has been restricted. When the signal indicating the vehicle speed SPD input from the vehicle speed sensor 31 is abnormal, it may not be determined whether the movement of the rack shaft 12 has been restricted.

[0147] In an embodiment, when the signal indicating the vehicle speed SPD is abnormal, the surrounding environment change determination may further include comparing the vehicle speed SPD with the driving threshold value Smin. In the present embodiment, the limit position determination angle acquisition unit 92 determines whether the movement of the rack shaft 12 is limited by performing dynamic limit determination and static limit determination, but the present invention is not limited thereto, and may determine whether the movement of the rack shaft 12 is limited by performing only one of the dynamic limit determination and the static limit determination. By performing only the dynamic limit determination without performing the static limit determination, it may be determined whether the movement of the rack shaft 12 has been limited.

[0148] In an embodiment, the conditions for establishing the determination of the change in the surrounding environment include that conditions (c1) and (c2) are satisfied, but the present invention is not limited thereto, and for example, as long as it can be determined that the surrounding environment around the vehicle has changed, the determination related to condition (c1) may not be performed. For example, in addition to condition (c2) or instead of condition (c2), an imaging device such as a camera may be used to image the surrounding environment of the vehicle, and it may be determined whether the captured image has changed. For example, a positioning signal may be received from an artificial satellite of a global positioning system (GPS), and it may be determined based on the received positioning signal whether the position of the vehicle has changed by a predetermined distance or more. For example, it may be determined that the surrounding environment around the vehicle has changed as several minutes pass, and the conditions for determining the change in the surrounding environment may be appropriately modified.

[0149] In an embodiment, when conditions (a1) and (a3) ​​are satisfied, it can be determined that the dynamic limit determination is established even if condition (a2) is not satisfied. Regardless of whether the dynamic limit determination is continuously established for the first predetermined time, as long as the dynamic limit determination is established only in one calculation cycle, the limit position determination angle θi can be acquired.

[0150] In an embodiment, when conditions (b1) and (b3) are satisfied, it can be determined that the static limit determination is established even if condition (b2) is not satisfied. Regardless of whether the static limit determination is continuously established for the second predetermined time, as long as the static limit determination is established only in one calculation cycle, the limit position determination angle θi can be acquired.

[0151] In the embodiment, the pinion shaft torque Tp is calculated based on the steering torque Th, the motor torque and the inertia torque, but the present invention is not limited thereto, and for example, in order to reduce the calculation load, the pinion shaft torque Tp may be calculated based on the steering torque Th and the motor torque. The pinion shaft torque Tp used for the rigidity compensation performed on the absolute steering angle θs acquired as a result of the dynamic limit determination may be different from the pinion shaft torque Tp used for the rigidity compensation performed on the absolute steering angle θs acquired as a result of the static limit determination.

[0152] In the embodiment, the absolute steering angle θs acquired when it is determined that the movement of the rack shaft 12 has been restricted may be acquired without any change as the restriction position determination angle θi, and rigidity compensation may not be performed thereon.

[0153] In the embodiment, when a plurality of limit position determination angles θi of only one side of the right side and the left side are obtained, the average value thereof is set as the end position corresponding angle θs_re or θs_le of the corresponding side. However, the present invention is not limited thereto, and for example, the limit position determination angle θi having the largest absolute angle among the plurality of limit position determination angles θi may be set as the end position corresponding angle θs_re or θs_le of the corresponding side. When only one limit position determination angle θi is obtained, the limit position determination angle θi may be set as the end position corresponding angle θs_re or θs_le of the corresponding side.

[0154] In the embodiment, after one limit position determination angle θi has been acquired, even when the surrounding environment change determination to determine whether the surrounding environment around the vehicle has changed is not established, another limit position determination angle θi can be acquired as long as it is determined that the movement of the rack shaft 12 has been restricted.

[0155] In the embodiment, by monitoring the rotation of the motor 21 even when the ignition switch is turned off, the number of revolutions of the motor 21 from the origin is normally integrated, and the absolute motor angle and the absolute steering angle θs are detected. However, the present invention is not limited to this, and for example, a steering sensor that detects the steering angle as an absolute angle may be provided, the number of revolutions of the motor 21 from the origin may be integrated based on the steering angle detected by the steering sensor and the reduction ratio of the reduction mechanism 22, and the absolute motor angle and the absolute steering angle θs may be detected.

[0156] In an embodiment, by setting the auxiliary command value Ias * The end contact relaxation control is performed by limiting the steering angle limit value Ien, but the present invention is not limited to this. * The end contact relaxation control is performed by adding a steering reaction component, which increases as the rack shaft approaches the rack end position, that is, has the same value as the assist command value Ias. * The components with opposite signs to the ones with opposite signs.

[0157] In an embodiment, the auxiliary command value Ias * The protection process is performed, but the present invention is not limited thereto, and for example, the assist command value Ias may be adjusted by using the compensation value based on the torque differential value obtained by differentiating the steering torque Th. * The value obtained by the correction is subjected to protection processing.

[0158] In the embodiment, the limit value setting unit 62 includes a voltage limit value calculation unit 72 that calculates the voltage limit value Ivb based on the power supply voltage Vb, but the present invention is not limited thereto, and another calculation unit that calculates another limit value based on another state amount may be provided in addition to or in place of the voltage limit value calculation unit 72. A configuration may be adopted in which the limit value setting unit 62 does not include the voltage limit value calculation unit 72 and sets the steering angle limit value Ien to the limit value Ig without any change.

[0159] In the embodiment, the value obtained by subtracting the angle limit component Iga from the rated current Ir is used as the steering angle limit value Ien, but the present invention is not limited thereto. The value obtained by subtracting the angle limit component Iga and the current limit amount determined by the motor angular velocity from the rated current Ir can be used as the steering angle limit value Ien.

[0160] In the embodiment, the steering control device 1 controls the EPS 2 of the type in which the EPS actuator 6 applies the motor torque to the column shaft 15, but the present invention is not limited to this, and for example, the steering control device 1 may control a steering system of the type in which the motor torque is applied to the rack shaft 12 via a ball screw nut. The present invention is not limited to EPS. The steering control device 1 may control a steer-by-wire type steering device in which the power transmission between the steering unit operated by the driver and the rotating unit that rotates the rotating wheel is cut off; and may perform end contact mitigation control on the torque command value or the q-axis current command value of the motor of the rotating actuator provided on the rotating unit as in the present embodiment.

Claims

1. A steering control device, which is configured to control a steering system, the steering system include: case; a rotating shaft, the rotating shaft being accommodated in the housing so as to reciprocate; and an actuator, the actuator using a motor as a driving source to apply a motor torque to reciprocate the rotating shaft, the steering control device is characterized by comprising: An electronic control unit configured to: i) detecting an absolute steering angle as a rotation angle of a rotation shaft which can be converted into a rotation angle of a rotating wheel connected to the rotation shaft, and which is expressed as an absolute angle including a range exceeding 360°, ii) determining whether the movement of the rotation axis to one of the right side and the left side has been restricted, iii) acquiring a limit position determination angle corresponding to the absolute steering angle detected when the electronic control unit determines that the movement of the rotation shaft has been limited, and iv) setting an end position corresponding angle based on the limit position determination angle, the end position corresponding angle being an angle indicating that the rotation axis is located at the right end position or the left end position and the end position corresponding angle being associated with the absolute steering angle, After having acquired the value of the limit position determination angle, the electronic control unit does not acquire another value of the limit position determination angle until a surrounding environment change determination is established as to whether the surrounding environment around the vehicle has changed, The conditions for establishing the surrounding environment change determination include a condition that the vehicle speed is equal to or greater than a running threshold indicating a non-stop state of the vehicle, the electronic control unit is configured to determine whether the movement of the rotation shaft has been restricted when the vehicle speed is equal to or less than a low speed threshold indicating low speed travel of the vehicle, regardless of whether a signal input from a vehicle speed sensor and indicating the vehicle speed is normal; as well as When the signal indicating the vehicle speed is abnormal, the conditions for establishing the surrounding environment change determination do not include a condition that the vehicle speed is greater than the running threshold value.

2. The steering control device according to claim 1, It is characterized in that The conditions for establishing the surrounding environment change determination include a condition that the return steering amount is equal to or greater than a return determination threshold.

3. The steering control device according to claim 1, Features: the electronic control unit being configured to perform a dynamic limit determination and a static limit determination, and to determine that the movement of the rotation shaft has been limited when one of the dynamic limit determination and the static limit determination is established; as well as When the sign of the steering torque for moving the rotating shaft to one side and the sign of the rotation direction of the motor for moving the rotating shaft to the one side are defined as positive, and the sign of the steering torque for moving the rotating shaft to the side opposite to the one side and the sign of the rotation direction of the motor for moving the rotating shaft to the side opposite to the one side are defined as negative, The conditions for establishing the dynamic limit determination include a condition that the absolute value of the steering torque is equal to or greater than a first steering torque threshold value and a condition that the sign of an angular velocity change as a change in the angular velocity of the motor is opposite to the sign of the steering torque and the absolute value of the angular velocity change is greater than a first angular velocity change threshold value, and The conditions for establishing the static limit determination include a condition that the absolute value of the steering torque is equal to or greater than a second steering torque threshold value greater than the first steering torque threshold value and a condition that the absolute value of the angular velocity change is equal to or less than a second angular velocity change threshold value less than the first angular velocity change threshold value.

4. The steering control device according to claim 1, Features: the electronic control unit being configured to perform a dynamic limit determination and to determine that the movement of the rotation shaft has been limited when the dynamic limit determination is established; as well as When the sign of the steering torque for moving the rotating shaft to one side and the sign of the rotation direction of the motor for moving the rotating shaft to the one side are defined as positive, and the sign of the steering torque for moving the rotating shaft to the side opposite to the one side and the sign of the rotation direction of the motor for moving the rotating shaft to the side opposite to the one side are defined as negative, the conditions for establishing the dynamic limit determination include the condition that the absolute value of the steering torque is equal to or greater than a first steering torque threshold and the condition that the sign of the angular velocity change as the change of the angular velocity of the motor is opposite to the sign of the steering torque and the absolute value of the angular velocity change is greater than the first angular velocity change threshold.

5. The steering control device according to claim 4, It is characterized in that The conditions for establishing the dynamic limit determination include conditions that a sign of the angular velocity of the motor is the same as a sign of the steering torque and an absolute value of the angular velocity of the motor is greater than a first angular velocity threshold.

6. The steering control device according to claim 4, Features: the electronic control unit being configured to determine a static limit determination in addition to the dynamic limit determination, and to determine that the movement of the rotation shaft has been limited when one of the dynamic limit determination and the static limit determination is established; as well as The conditions for establishing the static limit determination include a condition that the absolute value of the steering torque is equal to or greater than a second steering torque threshold value greater than the first steering torque threshold value and a condition that the absolute value of the angular velocity change is equal to or less than a second angular velocity change threshold value less than the first angular velocity change threshold value.

7. The steering control device according to claim 6, It is characterized in that The conditions for establishing the static limit determination include the conditions that the sign of the angular velocity of the motor is the same as the sign of the steering torque and the absolute value of the angular velocity of the motor is greater than a first angular velocity threshold and equal to or less than a second angular velocity threshold.

8. The steering control device according to claim 4, It is characterized in that The electronic control unit is configured to acquire, as the limit position determination angle, a value obtained by performing rigidity compensation on the absolute steering angle detected when the electronic control unit determines that the movement of the rotation shaft has been limited, based on mechanical elastic deformation of the steering system due to torque applied to the steering system.

9. The steering control device according to claim 8, It is characterized in that The electronic control unit is configured to calculate a torque applied to the steering system using the steering torque, the motor torque, and an inertia torque based on the angular velocity change.

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