Steering control device and steering device

Abstract

The purpose of the present invention is to suppress erroneous learning when re-learning a rack end position. A steering control device is provided with: a position detection unit (14) that detects the steering position of a steering mechanism of a vehicle; a terminal position learning unit (46) that learns the terminal position of the steering mechanism on the basis of the steering position detected by the position detection unit; and a re-learning determination unit (53) that determines whether or not re-learning of the terminal position is necessary. The re-learning determination unit (53) is provided with: an end contact detection unit (90) that detects the occurrence of end contact in a state in which the steering mechanism is steered to an end position, and acquires an end contact steering angle, which is a steering angle when the occurrence of end contact is detected; an end contact steering angle range determination unit (91) that determines whether or not the deviation of the end contact steering angle acquired a plurality of times is equal to or less than a predetermined threshold value; and a re-learning unit (93) that resets the learned terminal position to an initial value when the deviation is equal to or less than a predetermined threshold value.

Description

Technical Field

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

[0002] When the steering angle increases in the vehicle's steering mechanism and reaches the maximum mechanical steering angle, the rack shaft of the steering mechanism reaches the end of the stroke and the steering angle cannot be increased further. The state in which the rack shaft reaches the end of the stroke as described above is called "end contact". In addition, the end of the rack shaft's stroke is sometimes described as "rack end".

[0003] When the end contact occurs at a high steering speed, a large impact or knocking sound (unusual noise) may be generated, which may make the driver feel uncomfortable. Patent documents 1 and 2 describe the following technology: the maximum absolute value of the steering angle is learned as the rack end position, and when the steering angle detected by the sensor is near the learned rack end position, the increase of the steering angle is suppressed to alleviate the impact when the end contacts.

[0004] Hereinafter, the virtual rack end position learned based on the steering angle detected by the sensor may be referred to as “virtual rack end position”, and the actual rack end position physically may be referred to as “actual rack end position”.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 7131737

[0008] Patent Document 2: Japanese Patent No. 7136398 Summary of the invention

[0009] Problems to be solved by the invention

[0010] Sometimes the rack shaft is replaced after the virtual rack end position has been learned. In this case, consider the following situations: a rack shaft with a different length from the rack shaft that should have been installed is mistakenly installed, or the installation position of the rack shaft changes before and after the rack shaft is replaced. In this case, it is necessary to relearn the virtual rack end position. When relearning the virtual rack end position, an inappropriate virtual rack end position may be learned due to sudden back-steering, collision between the tire and the curb, etc.

[0011] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to suppress erroneous learning when relearning the rack end position.

[0012] Means for solving problems

[0013] In order to achieve the above-mentioned object, a steering control device according to one embodiment of the present invention comprises: a position detection unit that detects a steering position of a steering mechanism of a vehicle; a terminal position learning unit that learns the terminal position of the steering mechanism based on the steering position detected by the position detection unit; and a relearning determination unit that determines whether relearning of the terminal position is required. The relearning determination unit comprises: an end contact detection unit that detects the occurrence of end contact as a state in which the steering mechanism is turned to the terminal position, and obtains an end contact steering angle as a steering angle when the end contact is detected; an end contact steering angle range determination unit that determines whether a deviation of the end contact steering angles obtained multiple times is less than a prescribed threshold value; and a relearning unit that resets the learned terminal position to an initial value when the deviation is less than the prescribed threshold value.

[0014] Furthermore, a steering device according to another aspect of the present invention includes: the above-mentioned steering control device; and an actuator that is driven and controlled by the steering control device to steer a steered wheel of a vehicle.

[0015] Effects of the Invention

[0016] According to the present invention, it is possible to suppress erroneous learning when relearning the rack end position. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural diagram showing an example of an electric power steering device according to an embodiment.

[0018] Figure 2 Yes means Figure 1 A block diagram of an example of the functional structure of the controller shown.

[0019] Figure 3 This is an explanatory diagram of an example of the range of the steering angle in which the impact relaxation control is performed.

[0020] Figure 4 This is a block diagram showing an example of the functional configuration of the impact relaxation control unit.

[0021] Figure 5 (a) is a characteristic diagram showing a characteristic example of a spring constant table. Figure 5 (b) is a characteristic diagram showing a characteristic example of a viscosity constant table.

[0022] Figure 6 This is a block diagram showing an example of the functional structure of the terminal position learning unit.

[0023] Figure 7 (a) is an explanatory diagram of an example of changes in column output shaft torque accompanying changes in steering angle, Figure 7 (b) is produced Figure 7 (a) is an explanatory diagram of an example of a learned value of a terminal position when a column outputs a shaft torque.

[0024] Figure 8 (a) is a conceptual diagram of the actual rack end position. Figure 8 (b) is a conceptual diagram of the state before the learning of the virtual rack end position begins. Figure 8 (c) is a conceptual diagram of the state where the virtual rack end position on the right side is learned. Figure 8 (d) is a conceptual diagram of the state where the virtual rack end position on the left is learned. Figure 8 (e) is a conceptual diagram of a state in which the learning of the virtual rack end is considered to be completed. Figure 8 (f) is a conceptual diagram of a state in which the learning of the virtual rack end is continued until it reaches the vicinity of the actual rack end.

[0025] Fig. 9 (a) is a conceptual diagram of the actual rack end position. Fig. 9 (b) means Figure 8 (f) Conceptual diagram of the same state, Fig. 9 (c) is a conceptual diagram of the state just after the offset error occurs. Fig. 9 (d) is a conceptual diagram of a state in which the learning position of the left virtual rack end position is updated. Fig. 9 (e) is a conceptual diagram of the correction of the steering angle detected by the steering angle sensor and the resetting of the learning value of the right virtual rack end position. Fig. 9 (f) is a conceptual diagram of a state in which the learning position of the virtual rack end position on the left is further updated. Fig. 9 (g) is a conceptual diagram of a state in which the learning of the virtual rack end is considered to be completed. Fig. 9 (h) is a conceptual diagram of a state in which the learned position of the left virtual rack end position is further updated.

[0026] Fig.10 Yes means Figure 8 (b) to (f) and Fig. 9 A table showing examples of limit values ​​in states (b) to (h).

[0027] Fig.11 This is a block diagram showing an example of the functional configuration of the relearning determination unit.

[0028] Fig.12 (a) is an explanatory diagram of an example of determining the necessity of the end contact steering angle. Fig.12 (b) is an explanatory diagram of an example of determining whether or not the end contact steering angle can be obtained.

[0029] Fig.13 (a) and (b) are explanatory diagrams of an example of rack stroke determination.

[0030] Fig.14 (a) to (c) are explanatory diagrams of an example of determination of the end contact steering angle range.

[0031] Fig.15 This is an example of a state transition diagram of a vehicle state.

[0032] Fig.16 It is an explanatory diagram of an example of a method of calculating the rack stroke minimum value Stmin, the rack stroke maximum value Stmax, the learning threshold value θlth, the rack end maximum value θevmax, and the initial value θint.

[0033] Fig.17 This is a flowchart of an example of the steering control method according to the embodiment.

[0034] Fig.18 yes Fig.17 A flowchart of an example of a single-side end contact process.

[0035] Fig.19 yes Fig.18 A flowchart of an example of a processing of abutting both side ends. DETAILED DESCRIPTION

[0036] Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0037] In addition, the embodiments of the present invention shown below illustrate devices and methods for implementing the technical concept of the present invention, but the technical concept of the present invention does not limit the structure and configuration of the components to the following contents. The technical concept of the present invention can be modified in various ways within the technical scope specified by the technical solution described in the claims.

[0038] (structure)

[0039] Figure 1 The schematic structural diagram of an example of an electric power steering device according to an embodiment of the present invention is shown. The column shaft (steering shaft) 2i, 2o of the steering wheel (steering wheel) 1 is connected to the steering wheels 8L, 8R via the reduction gear (worm gear) 3, the intermediate shaft 4, the pinion rack mechanism 5, the tie rods 6a, 6b and further via the hub units 7a, 7b constituting the reduction mechanism.

[0040] The column input shaft 2i and the column output shaft 2o are connected via a torsion bar (not shown), and the torsion bar is twisted by a deviation in the rotation angle between the column input shaft 2i and the column output shaft 2o.

[0041] The intermediate shaft 4 has a shaft member 4c and universal joints 4a and 4b attached to both ends of the shaft member. The universal joint 4a is connected to the column output shaft 2o, and the universal joint 4b is connected to the pinion rack mechanism 5.

[0042] The rack and pinion mechanism 5 includes a pinion 5a connected to a pinion shaft to which the steering force is transmitted from the universal joint 4b and a rack 5b meshing with the pinion 5a. The rack 5b converts the rotational motion transmitted to the pinion 5a into a linear motion in the vehicle width direction.

[0043] The steering shaft 2 (column shafts 2i, 2o) is provided with a torque sensor 10 for detecting a steering torque Th. In addition, the steering shaft 2 (column shafts 2i, 2o) is provided with a steering angle sensor 14 for detecting a steering angle θh of the steering wheel 1.

[0044] A motor 20 assisting the steering force of the steering wheel 1 is connected to the column output shaft 2o via a reduction gear 3. A controller 30 controlling an electric power steering (EPS) device is supplied with power from a battery 13 and receives an ignition key signal via an ignition key 11.

[0045] In addition, the unit for applying the steering assist force is not limited to the motor, and various actuators can be used.

[0046] The controller 30 calculates the current command value of the auxiliary control command based on the steering torque Th detected by the torque sensor 10, the vehicle speed Vh detected by the vehicle speed sensor 12, and the steering angle θh detected by the steering angle sensor 14, and controls the current supplied to the motor 20 by obtaining the voltage control command value Vref by compensating the current command value.

[0047] The steering angle sensor 14 is not essential, and the steering angle θh may be calculated by adding a rotation angle obtained from a rotation angle sensor that detects the rotation angle of the rotating shaft of the motor 20 and a torsion angle of the torsion bar of the torque sensor 10 .

[0048] The controller 30 may include, for example, a computer including a processor and peripheral components such as a storage device. The processor may be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit).

[0049] The storage device may include any of a semiconductor storage device, a magnetic storage device, and an optical storage device. The storage device may include a register, a cache memory, a ROM (Read Only Memory) used as a main storage device, and a RAM (Random Access Memory) and other memories.

[0050] The functions of the controller 30 described below are implemented, for example, by a processor of the controller 30 executing a computer program stored in a storage device.

[0051] Alternatively, the controller 30 may be formed by dedicated hardware for executing each information processing described below.

[0052] For example, the controller 30 may include a functional logic circuit set in a general-purpose semiconductor integrated circuit. For example, the controller 30 may include a programmable logic device (PLD: Programmable Logic Device) such as a field programmable gate array (FPGA: Field-Programmable Gate Array).

[0053] Figure 2 1 is a block diagram showing an example of the functional structure of the controller 30 of the embodiment. The controller 30 includes a basic command value calculation unit 40, an adder 41, a subtractor 42, a current control unit 43, a PWM (Pulse Width Modulation) control unit 44, an inverter (INV) 45, a terminal position learning unit 46, a control rotation displacement setting unit 47, a differential unit 48, a shock mitigation control unit 49, a current detector 50, a learning state determination unit 51, a shock mitigation control output limiting unit 52, and a relearning determination unit 53.

[0054] The basic command value calculation unit 40 calculates a basic current command value Iref1 as a control target value of the drive current of the motor 20 based on the steering torque Th from the torque sensor 10 and the vehicle speed Vh from the vehicle speed sensor 12 .

[0055] In the present embodiment, the basic current command value Iref1 for generating the steering assist force of the motor 20 in the right steering direction is defined as a positive value, and the basic current command value Iref1 for generating the steering assist force in the left steering direction is defined as a negative value.

[0056] The adder 41 corrects the basic current command value Iref1 by adding the surge relaxation control output Iref2 ′ outputted from the surge relaxation control output limiting unit 52 to the basic current command value Iref1 , and outputs the corrected basic current command value Iref1 as the current command value Iref3 .

[0057] The shock relief control output limiting unit 52 limits the upper limit value of the shock relief control output Iref2 output from the shock relief control unit 49 using the limit value 0, Limit1 or Limit2 output from the learning state determination unit 51, and limits the lower limit value of the shock relief control output Iref2 using the limit value 0, (-Limit1) or (-Limit2), thereby setting the shock relief control output Iref2'.

[0058] When the steering angle θh approaches the rack end position, the impact mitigation control unit 49 mitigates the impact and knocking sound (unusual noise) caused by the end contact by suppressing the increase of the steering angle θh. The control of the impact mitigation control unit 49 to mitigate the impact and knocking sound caused by the end contact is sometimes described as "impact mitigation control".

[0059] The impact mitigation control unit 49 outputs a current command value that suppresses the increase of the steering angle θh as the impact mitigation control output Iref2 in order to mitigate the impact and knocking sound caused by the end contact. The impact mitigation control output Iref2 when turning right has a negative value and reduces the magnitude of the positive basic current command value Iref1. On the other hand, the impact mitigation control output Iref2 when turning left has a positive value and reduces the magnitude of the negative basic current command value Iref1. For example, the impact mitigation control unit 49 may output a current command value that generates a steering reaction force.

[0060] The impact mitigation control output limiting unit 52 limits the upper limit value of the impact mitigation control output Iref2 during left turning to the limit value 0 or the positive limit values ​​Limit1 and Limit2 output from the learning state determination unit 51, and limits the lower limit value of the impact mitigation control output Iref2 during right turning to the limit value 0 or the negative limit values ​​(-Limit1) and (-Limit2).

[0061] The impact relaxation control unit 49 , the learning state determination unit 51 , and the relearning determination unit 53 will be described in detail later.

[0062] The current command value Iref3 calculated by the adder 41 is input to the subtractor 42, and the deviation (Iref3-Im) from the motor current value Im fed back is calculated. The deviation (Iref3-Im) is controlled by the current control unit 43 such as PI control, and the voltage control value Vref after current control is input to the PWM control unit 44 to calculate the duty, and the motor 20 is PWM driven via the inverter 45 using the PWM signal. The motor current value Im of the motor 20 is detected by the current detector 50 and input to the subtractor 42 for feedback.

[0063] The terminal position learning unit 46 learns virtual rack end positions θevr and θevl as the terminal positions of the steering mechanism based on the steering angle θh detected by the steering angle sensor 14. θevr is a virtual rack end position when turning right and has a positive value. θevl is a virtual rack end position when turning left and has a negative value.

[0064] Furthermore, an error may occur between the center position of the actual left and right rack end positions (hereinafter sometimes referred to as "rack neutral position") and the neutral position of the steering angle θh of the column shaft detected by the steering angle sensor 14 (hereinafter sometimes referred to as "steering angle neutral position"). Such an error may be referred to as "offset error" hereinafter.

[0065] The offset error is caused by, for example, incorrect assembly of the intermediate shaft 4. The terminal position learning unit 46 estimates the offset error Ofs and outputs a corrected steering angle θh1 obtained by subtracting the offset error Ofs from the steering angle θh detected by the steering angle sensor 14. The terminal position learning unit 46 will be described in detail later.

[0066] When the corrected steering angle θh1 approaches the rack end position and is within the range for implementing the impact relaxation control (hereinafter sometimes referred to as the "impact relaxation control implementation range"), the control rotational displacement setting unit 47 sets the control rotational displacement θr indicating the degree to which the corrected steering angle θh1 approaches the virtual rack end positions θevr and θevl.

[0067] Reference Figure 3 In the case of right steering (i.e., when the correction steering angle θh1 is a positive value), the range of threshold θthR<θh1 is the impact mitigation control implementation range, and in the case of left steering (i.e., when the correction steering angle θh1 is a negative value), the range of threshold θthL>θh1 is the impact mitigation control implementation range.

[0068] The threshold values ​​θthR and θthL are set based on the virtual rack end positions θevr and θevl, respectively. For example, the threshold value θthR for right steering may be a value obtained by subtracting a positive predetermined value Δθ from the virtual rack end position θevr (θevr-Δθ), and the threshold value θthL for left steering may be a value obtained by adding a predetermined value Δθ to the virtual rack end position θevl (θevl+Δθ).

[0069] The control rotational displacement θr is set to zero ("0"), for example, outside the impact mitigation control implementation range (i.e., θthL≤θh1≤θthR). Within the impact mitigation control implementation range for right steering, the larger the difference (θh1-θthR) obtained by subtracting the threshold value θthR from the correction steering angle θh1 is, the larger the control rotational displacement θr is set. On the other hand, within the impact mitigation control implementation range for left steering, the smaller the difference (θh1-θthL) obtained by subtracting the threshold value θthL from the correction steering angle θh1 is (i.e., the larger the absolute value |θh1-θthL| is), the smaller the negative control rotational displacement θr is set (the larger the absolute value |θr| is).

[0070] In other words, within the range where the correction steering angle θh1 is greater than the threshold θthR, the positive control rotational displacement θr increases as the correction steering angle θh1 increases, and within the range where the correction steering angle θh1 is less than the threshold θthL, the negative control rotational displacement θr decreases as the correction steering angle θh1 decreases.

[0071] For example, the control rotational displacement setting unit 47 may set the difference θh1-θthR as the control rotational displacement θr when the correction steering angle θh1 is greater than the threshold θthR, and may set the difference θh1-θthL as the control rotational displacement θr when the correction steering angle θh1 is less than the threshold θthL.

[0072] Reference Figure 2 The differentiation unit 48 differentiates the steering angle θh detected by the steering angle sensor 14 to calculate the steering angular velocity ω.

[0073] The shock mitigation control unit 49 sets the shock mitigation control output Iref2 based on the control rotational displacement θr and the steering angular velocity ω.

[0074] Figure 4 2 is a block diagram showing an example of the functional configuration of the impact relaxation control unit 49. The impact relaxation control unit 49 includes a spring constant table 60, multipliers 61 and 63, a viscosity constant table 62, an adder 64, an inverter 65, and a limiter 66.

[0075] The spring constant table 60 is a data table for calculating the spring constant k0 of the steering system. Figure 5 As shown in (a), the spring constant k0 has a characteristic of increasing rapidly (nonlinearly increasing) in the central part of the change region as the control rotation displacement θr increases. In addition, the characteristic when the control rotation displacement θr is a negative value is a linearly symmetrical characteristic with the spring constant k0 axis (vertical axis) as the symmetry axis.

[0076] In addition, the viscosity constant table 62 is a data table for calculating the viscosity constant μ of the steering system. Figure 5 As shown in (b), the viscosity constant μ has a characteristic of increasing relatively slowly as the control rotation displacement θr increases (nonlinear increase). In addition, the characteristic when the control rotation displacement θr is a negative value is a linearly symmetric characteristic with the viscosity constant μ axis (vertical axis) as the symmetry axis.

[0077] The spring constant k0 from the spring constant table 60 is multiplied by the control rotation displacement θr through the multiplier 61, and the multiplication result (k0×θr) is input to the adder 64. In addition, the viscosity constant μ from the viscosity constant table 62 is multiplied by the steering angular velocity ω through the multiplier 63, and the multiplication result (μ×ω) is input to the adder 64. The addition result (=k0×θr+μ×ω) of the adder 64 is input to the inverter 65 and the limiter 66, and the impact relaxation control output Iref2 after the sign is inverted and the maximum value is limited is set.

[0078] in addition, Figure 4 The structure of the impact mitigation control unit 49 is merely an example, and the present invention is not limited to the above structure. The impact mitigation control unit 49 only needs to have a structure capable of outputting the impact mitigation control output Iref2 that suppresses the increase of the steering angle θh when the correction steering angle θh1 approaches the rack end position.

[0079] Next, the details of the terminal position learning unit 46 are described. The terminal position learning unit 46 obtains the steering angle farthest from the steering angle neutral position among the steering angles θh detected by the steering angle sensor 14 when the rotational force applied to the steering mechanism is equal to or less than a first predetermined value (the maximum steering angle in the case of a positive steering angle θh and the minimum steering angle in the case of a negative steering angle θh) as the first candidate θm1 of the virtual rack end.

[0080] For example, the first candidate θm1 of the virtual rack end portion can be obtained when the column output shaft torque Tc applied to the column output shaft 2 o is equal to or smaller than the predetermined value T1.

[0081] The terminal position learning unit 46 may also determine, as the first candidate θm1 for the virtual rack end, the steering angle farthest from the steering angle neutral position among the steering angles θh detected by the steering angle sensor 14 when the rotational force applied to the steering mechanism is less than a first specified value and the operating force acting on the steering operating unit is less than a third specified value.

[0082] For example, the first candidate θm1 can be obtained when the column output shaft torque Tc is equal to or less than the predetermined value T1 and the steering torque Th is equal to or less than the predetermined value T2.

[0083] In addition, the terminal position learning unit 46 obtains the steering angle farthest from the steering angle neutral position among the angles obtained by shifting the steering angle θh detected by the steering angle sensor 14 in the direction of the steering angle neutral position by the second predetermined value (i.e., in the case of a positive steering angle θh, the angle obtained by subtracting the second predetermined value from the maximum steering angle, and in the case of a negative steering angle θh, the angle obtained by adding the second predetermined value to the minimum steering angle) as the second candidate θm2 of the virtual rack end. As the second predetermined value, for example, a maximum value considered to be an error can be set.

[0084] The terminal position learning unit 46 obtains the steering angle farthest from the steering angle neutral position among the first candidate θm1 and the second candidate θm2 as the virtual rack end positions θevr and θevl.

[0085] This can reduce the influence of the twist caused by the torque and the like, and can reduce the error between the virtual rack end positions θevr and θevl and the actual rack end positions.

[0086] Figure 6 : is a block diagram showing an example of the functional configuration of the terminal position learning unit 46. The terminal position learning unit 46 includes an output shaft torque calculation unit 70, a selection unit 71, a first storage unit 72, delay units 73 and 77, a change rate limiter 74, a correction position calculation unit 75, a second storage unit 76, a third storage unit 78, a limiter 79, a stroke calculation unit 80, an offset error calculation unit 81, a subtractor 82, and a terminal position correction unit 83.

[0087] The output shaft torque calculation section 70 calculates the column output shaft torque Tc applied to the column output shaft 2 o.

[0088] For example, the output shaft torque calculation unit 70 may calculate the column output shaft torque Tc by multiplying the current command value Iref3 of the motor 20 , the motor current value Im detected by the current detector 50 , the motor torque constant, and the reduction ratio of the reduction gear 3 to estimate the motor torque.

[0089] For example, the output shaft torque calculation unit 70 may calculate the sum of the motor torque estimated by multiplying the current command value Iref3 of the motor 20 by the motor torque constant and the reduction ratio of the reduction gear 3 and the steering torque Th detected by the torque sensor 10 as the column output shaft torque Tc.

[0090] In addition, for example, the output shaft torque calculation unit 70 can calculate the sum of the motor torque and the steering torque Th detected by the torque sensor 10 as the column output shaft torque Tc, and the motor torque is estimated by multiplying the motor current value Im detected by the current detector 50 by the motor torque constant and the reduction ratio of the reduction gear 3.

[0091] Alternatively, the output shaft torque calculation unit 70 may perform a second-order differentiation on the detection value of the angle sensor of the motor 20 to obtain the motor angular acceleration, multiply the value by the inertia moment to estimate the inertia torque, and add the inertia torque to the column output shaft torque Tc obtained in the above manner.

[0092] The column output shaft torque Tc is an example of “rotational force applied to the steering mechanism.” The steering torque Th is an example of “operation force acting on the steering operation part of the vehicle.”

[0093] The subtractor 82 calculates a corrected steering angle θh1 by subtracting the offset error Ofs calculated by the offset error calculation unit 81 from the steering angle θh detected by the steering angle sensor 14. The calculation of the offset error Ofs by the offset error calculation unit 81 will be described later.

[0094] The selection unit 71 selects one of the correction steering angle θh1 and the output of the delay unit 73 according to the values ​​of the column output shaft torque Tc and the steering torque Th, and outputs it to the first storage unit 72. The delay unit 73 delays and outputs the first candidate θm1 of the virtual rack end stored and output from the first storage unit 72.

[0095] For example, the selection unit 71 may select and output the corrected steering angle θh1 calculated based on the steering angle θh detected when the column output shaft torque Tc is less than or equal to a predetermined value T1 and the steering torque Th is less than or equal to a predetermined value T2 to the first storage unit 72 , and output the output of the delay unit 73 to the first storage unit 72 in other cases.

[0096] The first storage unit 72 stores, as a first candidate θm1 for the virtual rack end, one of the output of the delay unit 73 and the corrected steering angle θh1 that is farther from the steering angle neutral position.

[0097] Therefore, if the corrected steering angle θh1 calculated when the column output shaft torque Tc is less than the prescribed value T1 and the steering torque Th is less than the prescribed value T2 is farther from the steering angle neutral position than the first candidate θm1 stored in the first storage unit 72 until then, the first candidate θm1 stored in the first storage unit 72 is updated with the corrected steering angle θh1.

[0098] The selection unit 71 may select and output the correction steering angle θh1 to the first storage unit 72 when the column output shaft torque Tc is equal to or less than the predetermined value T1 , and may output the output of the delay unit 73 to the first storage unit 72 otherwise.

[0099] The change rate limiter 74 receives the first candidate θm1 output from the first storage unit 72 and the steering angle θo output from the third storage unit. The change rate limiter 74 limits the change rate of the first candidate θm1 with respect to the steering angle θo delayed by a delay unit (not shown), and outputs the first candidate θm1′ with the limited change rate to the third storage unit 78.

[0100] The correction position calculation unit 75 calculates an angle obtained by shifting the correction steering angle θh1 by a second predetermined value in the direction of the steering angle neutral position. That is, when the correction steering angle θh1 is positive, the correction position calculation unit 75 outputs an angle obtained by subtracting the second predetermined value from the correction steering angle θh1. When the correction steering angle θh1 is negative, the correction position calculation unit 75 outputs an angle obtained by adding the second predetermined value to the correction steering angle θh1.

[0101] The second storage unit 76 stores the output of the correction position calculation unit 75 and the output of the delay unit 77 whichever is farther from the steering angle neutral position as the second candidate θm2 of the virtual rack end. The delay unit 77 delays and outputs the second candidate θm2 of the virtual rack end stored and outputted from the second storage unit 76.

[0102] Therefore, if the output of the correction position calculation unit 75 (i.e., the angle obtained by offsetting the correction steering angle θh1 in the direction of the steering angle neutral position by the second specified value) is farther away from the steering angle neutral position than the second candidate θm2 stored in the second storage unit 76 until now, the second candidate θm2 stored in the second storage unit 76 is updated through the output of the correction position calculation unit 75.

[0103] The third storage unit 78 stores and outputs the steering angle θo that is away from the steering angle neutral position, of the first candidate θm1 ′ and the second candidate θm2 , the change rate of which is limited by the change rate limiter 74 .

[0104] The limiter 79 limits the magnitude of the steering angle θo output from the third storage unit 78 and outputs the resulting value as virtual rack end positions θevr and θevl.

[0105] Reference Figure 7 (a) and Figure 7 (b) of the present embodiment describes a learning example of the virtual rack end portion. For simplicity of description, the following case is described: if the offset error Ofs is set to 0 (i.e., the steering angle θh = the corrected steering angle θh1) and the steering angle θh detected when the column output shaft torque Tc is less than the predetermined value T1 is farther from the steering angle neutral position than the first candidate θm1 stored in the first storage unit 72, the first candidate θm1 is updated.

[0106] Figure 7 (a) is an explanatory diagram of an example of changes in the column output shaft torque Tc accompanying changes in the steering angle θh. The arrows in the diagram indicate the steering direction.

[0107] During the increase steering operation, when the steering angle θh exceeds θ1, the column output shaft torque Tc exceeds the specified value T1. During the subsequent return steering operation, when the steering angle θh is less than θ2 (θ2>θ1), the column output shaft torque Tc is less than the specified value T1.

[0108] Figure 7 (b) is produced Figure 7(a) is an explanatory diagram of an example of the learning value of the virtual rack end of the right steering when the column output shaft torque Tc is 0. The dotted line represents the steering angle θh, the single-dot chain line represents the first candidate θm1, the double-dot chain line represents the second candidate θm2, and the solid line represents the output θo from the third storage unit 78 (the virtual rack end positions θevr and θevl before being limited by the limiter 79). In addition, the single-dot chain line and the double-dot chain line are displayed in a staggered manner so as not to overlap with other lines.

[0109] When the steering angle θh increases at time t1 and the steering operation starts to increase, the steering angle θh (dashed line) is learned as the first candidate θm1 (one-dot chain line) during the period when the column output shaft torque Tc is less than the predetermined value T1 (i.e., the period when the steering angle θh is less than θ1). The first candidate θm1 (one-dot chain line) increases to θ1 during the process of increasing the steering operation.

[0110] In addition, an angle obtained by subtracting the second predetermined value from the steering angle θh is learned as a second candidate θm2 (two-dot chain line).

[0111] Therefore, during the period (from time t1 to time t2) when the first candidate θm1' after the rate of change is limited by the rate of change limiter 74 is larger than the second candidate θm2 (double dotted line), the first candidate θm1' is selected as the output θo (solid line) of the third storage unit 78, and when the second candidate θm2 exceeds the first candidate θm1' at time t2, the second candidate θm2 is selected as the output θo (solid line).

[0112] When the steering angle θh stops increasing and becomes constant at time t3, the second candidate θm2 (two-dot chain line) also stops increasing. Therefore, the first candidate θm1' whose change rate is limited by the change rate limiter 74 is selected as the output θo (solid line) of the third storage unit 78.

[0113] As described above, the first candidate θm1 (one-dot chain line) increases to θ1, so the output θo (solid line) of the third storage unit 78 increases to θ1 with a delay from the first candidate θm1. When reaching θ1 at time t4, the output θo (solid line) stops increasing.

[0114] Thereafter, when the steering angle θh starts to decrease and the back-steering operation starts, the steering angle θh decreases to θ2 at time t5. Then, the column output shaft torque Tc becomes equal to or less than the predetermined value T1. Therefore, the angle θ2 is learned as the first candidate θm1 (one-dot chain line).

[0115] Therefore, the first candidate θm1' whose change rate is limited by the change rate limiter 74 starts to increase and is selected as the output θo (solid line) of the third storage unit 78. The output θo (solid line) increases to θ2 at time t6 and then becomes constant.

[0116] If the output θo (solid line) of the third storage unit 78 learned as above, i.e., the virtual rack end positions θevr and θevl before being limited by the limiter 79, are compared with the case where only the angle obtained by subtracting the second predetermined value (e.g., the maximum error estimated value) from the steering angle θh is learned (two-dot chain line), the output θo of the third storage unit 78 can be learned as a steering angle farther from the steering angle neutral point. Therefore, the steering angle closer to the actual rack end position can be learned as the virtual rack end positions θevr and θevl.

[0117] Next, the learning state determination unit 51 will be described. Figure 2 The learning state determination unit 51 determines the learning state of the virtual rack end position by the terminal position learning unit 46 based on the virtual rack end positions θevr and θevl output from the terminal position learning unit 46 .

[0118] Based on the result of determining the learning state of the virtual rack end position, the learning state determination unit 51 outputs 0 or positive limit values ​​Limit1 and Limit2 to the impact relaxation control output restriction unit 52 as a limit value for limiting the upper limit value of the impact relaxation control output Iref2 during left steering.

[0119] The limit value Limit2 is a value greater than the limit value Limit1, and can be set to a sufficiently large value, for example, to effectively prevent impacts and knocking sounds (abnormal noises) caused by end abutment. On the other hand, the limit value Limit1 allows a certain degree of impacts and knocking sounds (abnormal noises), but can also be set to a value that prevents damage to the steering mechanism caused by end abutment.

[0120] In addition, the learning state determination unit 51 outputs any one of 0 or negative limit values ​​(-Limit1) and (-Limit2) as a limit value for limiting the lower limit value of the impact relief control output Iref2 during right steering to the impact relief control output limiting unit 52 based on the determination result of the learning state of the virtual rack end position.

[0121] Specifically, as initial values ​​before learning of the virtual rack end positions θevr and θevl, a positive initial value θint and a negative initial value (−θint) are stored in advance in the first storage unit 72 , the second storage unit 76 , and the third storage unit 78 .

[0122] The initial values ​​θint and (-θint) are appropriately set so that the virtual rack end position is not further outward than the actual rack end position (i.e., the initial values ​​θint and (-θint) make the virtual rack end position not further away from the steering angle neutral point than the actual rack end position). For example, it can be set as θint = (minimum rack stroke value Stmin - maximum rack end value θevmax).

[0123] Here, the rack stroke minimum value Stmin may be set to a minimum value (for example, a lower limit value of a manufacturing tolerance) of deviations of values ​​that can be calculated as the rack stroke between the virtual rack end positions θevr and θevl.

[0124] In addition, the "rack end maximum value θevmax" is the maximum value of the absolute value of the value that can be learned as the virtual rack end position θevr, θevl, and can be set as the rack end maximum value θevmax = (rack stroke maximum value Stmax / 2) + (estimated value of the offset error between the rack neutral position and the steering angle neutral position).

[0125] The rack stroke maximum value Stmax is the maximum value of the deviation of the value that can be calculated as the rack stroke between the virtual rack end positions θevr and θevl, and can be set to, for example, a value obtained by adding the learning error of the virtual rack end positions θevl and θevr to the upper limit of the manufacturing tolerance.

[0126] When the right virtual rack end position θevr output from the terminal position learning unit 46 is smaller than the prescribed learning threshold θlth, the learning state determination unit 51 determines that the learning of the right virtual rack end position θevr has not been performed, and outputs "0" as the limit value for limiting the lower limit value of the impact relief control output Iref2.

[0127] In the "learning threshold θlth", the minimum absolute value of the value that can be learned as the virtual rack end position θevr, θevl can be set. For example, it can be set to the learning threshold θlth = (rack stroke minimum value Stmin / 2) - (estimated value of the offset error between the rack neutral position and the steering angle neutral position).

[0128] Similarly, when the left virtual rack end position θevl is greater than the negative learning threshold (-θlth) (i.e., when the absolute value |θevl| is less than the absolute value |θlth|), it is determined that the learning of the left virtual rack end position θevl is not performed, and "0" is output as the limit value of the upper limit value of the impact mitigation control output Iref2.

[0129] When the right virtual rack end position θevr becomes equal to or greater than a predetermined learning threshold θlth, the learning state determination unit 51 determines that the right virtual rack end position θevr has been learned, and outputs “−Limit1” as a limit value for limiting the lower limit value of the shock relaxation control output Iref2.

[0130] Similarly, when the left virtual rack end position θevl is below the negative learning threshold (-θlth) (i.e., when the absolute value |θevl| is greater than the absolute value |θlth|), it is determined that the learning of the left virtual rack end position θevl has been performed, and "Limit1" is output as a limit value for limiting the upper limit value of the impact mitigation control output Iref2.

[0131] Furthermore, the learning state determination unit 51 calculates the distance between the right virtual rack end position θevr and the left virtual rack end position θevl as the rack stroke St.

[0132] When the absolute values ​​of the learned values ​​of the virtual rack end positions θevr and θevl become larger and the rack stroke St becomes longer than the minimum rack stroke Stmin, the learning state determination unit 51 determines that the learning of the virtual rack end positions θevr and θevl is completed, and outputs "-Limit2" as the limiting value for limiting the lower limit value of the impact mitigation control output Iref2, and outputs "Limit2" as the limiting value for limiting the upper limit value of the impact mitigation control output Iref2.

[0133] Next, an example of a case where the limit value output by the learning state determination unit 51 changes in accordance with a change in the learning state of the virtual rack end position will be described.

[0134] Figure 8 (a) is a conceptual diagram of the actual rack end position. Figure 8 (b) is a conceptual diagram of the state before the learning of the virtual rack end position begins. Figure 8 (c) is a conceptual diagram of the state where the virtual rack end position θevr on the right side is learned. Figure 8 (d) is a conceptual diagram of the state where the left virtual rack end position θevl is learned. Figure 8 (e) is a conceptual diagram of a state where the learning of the virtual rack ends θevr and θevl is considered to be completed. Figure 8 (f) is a conceptual diagram of a state where the learning of the virtual rack end is continued until it reaches the vicinity of the actual rack end.

[0135] in addition, Fig.10 The limit values ​​in the table are indicated in Figure 8 (b)~ Figure 8In the state (f), the limit value output by the learning state determination unit 51 is obtained.

[0136] exist Figure 8 (b)~ Figure 8 In (f), "0[deg]" indicates the neutral position of the steering angle. Fig. 9 (b)~ Fig. 9 The same is true for (h).

[0137] exist Figure 8 (b)~ Figure 8 In (f), the steering angle neutral position is roughly consistent with the rack neutral position (the center position of the actual rack end position).

[0138] In the state before the virtual rack end position learning starts ( Figure 8 In (b)), the right virtual rack end position θevr output from the terminal position learning unit 46 is based on the steering angle neutral position θint and is smaller than the learning threshold θlth.

[0139] Therefore, the learning state determination unit 51 determines that the learning of the right virtual rack end position θevr is not performed, and outputs "0" as the limit value for limiting the lower limit value of the shock relaxation control output Iref2 (see Fig.10 ).

[0140] In addition, the left virtual rack end position θevl output from the terminal position learning unit 46 is (-θint) based on the steering angle neutral position and is larger than the learning threshold value (-θlth). Therefore, the learning state determination unit 51 determines that the learning of the left virtual rack end position θevl is not performed, and outputs "0" as the limit value for limiting the upper limit value of the impact relaxation control output Iref2 (refer to Fig.10 ).

[0141] Then, if Figure 8 As shown in (c), the right virtual rack end position θevr is learned. Since the right virtual rack end position θevr is greater than the learning threshold θlth, the learning state determination unit 51 determines that the right virtual rack end position θevr has been learned, and outputs "-Limit1" as the limit value for limiting the lower limit value of the impact relief control output Iref2. On the other hand, since the left virtual rack end position θevl is unchanged, "0" is output as the limit value for limiting the upper limit value of the impact relief control output Iref2 (refer to Fig.10 ).

[0142] Then, if Figure 8As shown in (d), the left virtual rack end position θevl is learned. Since the left virtual rack end position θevl becomes less than the negative learning threshold value (-θlth), the learning state determination unit 51 determines that the left virtual rack end position θevl has been learned. However, since the rack stroke St is less than the rack stroke minimum value Stmin, it is determined that the learning of the virtual rack end positions θevr and θevl is not completed.

[0143] Therefore, "Limit1" is output as a limit value for limiting the upper limit value of the shock relaxation control output Iref2. In addition, "-Limit1" is output as a limit value for limiting the lower limit value.

[0144] Then, if Figure 8 As shown in (e), by learning the right virtual rack end position θevr, the rack stroke St becomes longer than the rack stroke minimum value Stmin. Therefore, the learning state determination unit 51 determines that the learning of the virtual rack end positions θevr and θevl has been completed, and outputs "Limit2" and "-Limit2" as the upper limit value and the lower limit value of the impact relaxation control output Iref2, respectively.

[0145] Thereafter, the virtual rack end positions θevr, θevl are repeatedly learned so as to be close to the actual rack end positions (see Figure 8 (f)).

[0146] The learning state determination unit 51 outputs “Limit2” and “−Limit2” as limit values ​​for limiting the upper limit value and the lower limit value of the shock relaxation control output Iref2 , respectively, until the rack stroke St exceeds the rack stroke maximum value Stmax.

[0147] Next, the operation when an offset error occurs between the rack neutral position and the steering angle neutral position will be described. Fig. 9 (a) is a conceptual diagram of the actual rack end position. Fig. 9 (b) is related to Figure 8 The same figure (f) shows the state without offset error, Fig. 9 (c) is a conceptual diagram of the state immediately after an offset error occurs.

[0148] Fig. 9 The steering angle neutral position of (b) is roughly consistent with the rack neutral position (the center position of the actual rack end position). Fig. 9 The steering angle neutral position of (c) is offset to the right by Δθ from the rack neutral position. That is, when the steering angle is turned to the left by Δθ from the steering angle neutral position, the rack 5b reaches the rack neutral position.

[0149] When an offset error occurs, shock mitigation control cannot be performed normally. Fig. 9 In the example of (c), since the right virtual rack end position θevr is located outside the actual rack end position, the necessary impact and noise cannot be reduced.

[0150] Therefore, the terminal position learning unit 46 estimates the offset error Ofs between the rack neutral position and the steering angle neutral position as described above, and outputs a corrected steering angle θh1 obtained by subtracting the offset error Ofs from the steering angle θh detected by the steering angle sensor 14 .

[0151] Reference Figure 6 The stroke calculation unit 80 calculates the rack stroke St. The offset error calculation unit 81 compares the rack stroke St with the rack stroke maximum value Stmax.

[0152] When the rack stroke St exceeds the rack stroke maximum value Stmax, the offset error calculation unit 81 determines that an offset error has occurred. Then, the difference obtained by subtracting the rack stroke maximum value Stmax from the rack stroke St is calculated as the offset error Ofs=(rack stroke St−rack stroke maximum value Stmax).

[0153] Fig. 9 (d) is a conceptual diagram of a state where the left virtual rack end position θevl is learned after an offset error occurs.

[0154] Since the steering angle neutral position is offset to the right of the rack neutral position, when the virtual rack end position θevl on the left is newly learned, the rack stroke St between the virtual rack end positions θevr and θevl exceeds the rack stroke maximum value Stmax. The offset error calculation unit 81 calculates the difference (rack stroke St-rack stroke maximum value Stmax) obtained by subtracting the rack stroke St from the rack stroke St as the offset error Ofs.

[0155] In the following description, the virtual rack end position learned when the rack stroke St exceeding the rack stroke maximum value Stmax is calculated among the left and right virtual rack end positions may be described as "one virtual rack end position". In addition, the virtual rack end position of the left and right virtual rack end positions that is not one virtual rack end position may be described as "the other virtual rack end position".

[0156] like Fig. 9As in the example (c) of FIG. 1 , if the steering angle neutral position is offset to the right from the rack neutral position, the left virtual rack end position becomes the virtual rack end position on one side, and the right virtual rack end position becomes the virtual rack end position on the other side. Conversely, if the steering angle neutral position is offset to the left from the rack neutral position, the right virtual rack end position becomes the virtual rack end position on one side, and the left virtual rack end position becomes the virtual rack end position on the other side.

[0157] Reference Figure 6 The subtractor 82 calculates a corrected steering angle θh1 by subtracting the offset error Ofs calculated by the offset error calculation unit 81 from the steering angle θh detected by the steering angle sensor 14 .

[0158] The terminal position correction unit 83 corrects the first candidate θm1 stored in the first storage unit 72, the second candidate θm2 stored in the second storage unit 76, and the steering angle θo stored in the third storage unit 78 based on the offset error Ofs. Fig. 9 (e) illustrates these correction processes.

[0159] The subtractor 82 subtracts the offset error Ofs from the steering angle θh, thereby obtaining Fig. 9 The steering angle shown in (e) moves from the neutral position (the position of "0[deg]").

[0160] On the other hand, Fig. 9 The left virtual rack end position θevl (i.e., the virtual rack end position on one side) learned in (d) is a learned value before the steering angle neutral position serving as the base point is moved. Therefore, if Fig. 9 If the steering angle neutral position is moved as shown in (e), the left virtual rack end position θevl needs to be corrected accordingly.

[0161] The terminal position correction unit 83 corrects the first candidate θm1 of the virtual rack end position on the left side stored in the first storage unit 72 using the offset error Ofs. The virtual rack end position on the left side is a negative value, so the offset error Ofs is added to perform correction. The second candidate θm2 and the steering angle θo stored in the second storage unit 76 and the third storage unit 78 are corrected in the same manner.

[0162] When one virtual rack end position is the right virtual rack end position (that is, when it is a positive value), the offset error Ofs is subtracted to perform correction.

[0163] In addition, the terminal position correction unit 83 adjusts the other virtual rack end position (at Fig. 9In the example of (e), the virtual rack end position θevr on the right side is corrected (reset) so that the rack stroke St between the virtual rack end positions θevr and θevl becomes the specified rack stroke minimum value Stmin. Thus, the virtual rack end position on the other side can be corrected to the inner side than the actual rack end position.

[0164] Reference Fig. 9 (f) When a new left virtual rack end position θevl is further learned, the offset error calculation unit 81 calculates the amount of change Δθevl of the virtual rack end position θevl before and after the update.

[0165] The offset error calculation unit 81 updates the offset error Ofs by adding the offset error Ofs before learning the new left virtual rack end position θev1 to the change amount Δθev1, thereby further moving the steering angle neutral position by the change amount Δθev1.

[0166] The terminal position correction unit 83 corrects the first candidate θm1 of one virtual rack end position (the left virtual rack end position) stored in the first storage unit 72 by the change amount Δθev1. The left virtual rack end position is a negative value, so the change amount Δθev1 is added to perform correction. The second candidate θm2 and the steering angle θo stored in the second storage unit 76 and the third storage unit 78 are also corrected in the same manner.

[0167] When one virtual rack end position is the right virtual rack end position (that is, when it is a positive value), correction is performed by subtracting the change amount Δθevl.

[0168] In addition, the virtual rack end position of the other side (at Fig. 9 In the example of (f), the virtual rack end position θevr on the right side is corrected (reset) so that the rack stroke St between the virtual rack end positions θevr and θevl becomes the rack stroke minimum value Stmin.

[0169] Reference Fig. 9 (g) When the new right virtual rack end position θevr (ie, the other virtual rack end position) is learned, the offset error calculation unit 81 does not update the offset error Ofs. That is, the steering angle neutral position is not moved.

[0170] Furthermore, the terminal position correction unit 83 does not correct the first candidate θm1 stored in the first storage unit 72, the second candidate θm2 stored in the second storage unit 76, and the steering angle θo stored in the third storage unit 78. Thus, only the right virtual rack end position θevr is updated so as to be away from the steering angle neutral position.

[0171] Reference Fig. 9 (h). Fig. 9 After the new right virtual rack end position θevr is learned in (g), even if the new left virtual rack end position θevl (i.e., the virtual rack end position on one side) is further learned, the right virtual rack end position θevr is not corrected (reset) in such a way that the rack stroke St becomes the specified minimum rack stroke value Stmin.

[0172] and Fig. 9 Similarly to (f), the offset error calculation unit 81 updates the offset error Ofs (i.e., corrects the steering angle neutral position) and moves, and the terminal position correction unit 83 corrects the left virtual rack end position θevl. At this time, the right virtual rack end position θevr is corrected by adding the offset error Ofs to the virtual rack end position θevr.

[0173] In addition, if the new right virtual rack end position θevr (i.e., the other virtual rack end position) is further achieved, the steering angle neutral position and the left virtual rack end position θevl (i.e., one virtual rack end position) are not changed, but only the right virtual rack end position θevr is changed.

[0174] Next, the operation of the learning state determination unit 51 when an offset error occurs is described. When the rack stroke St calculated based on the right virtual rack end position θevr and the left virtual rack end position θevl is longer than the rack stroke maximum value Stmax, the learning state determination unit 51 determines that an offset error has occurred.

[0175] When determining that an offset error has occurred, the learning state determination unit 51 resets the upper limit value and the lower limit value of the shock relaxation control output Iref2 to "0".

[0176] After that, similarly to the above description, when the right virtual rack end position θevr becomes equal to or greater than the prescribed learning threshold θlth, "-Limit1" is output as a limit value for limiting the lower limit value of the impact relief control output Iref2. When the left virtual rack end position θevl becomes equal to or less than the negative learning threshold (-θlth), "Limit1" is output as a limit value for limiting the upper limit value of the impact relief control output Iref2. If the rack stroke St is longer than the rack stroke minimum value Stmin, "Limit2" and "-Limit2" are output as limit values ​​for limiting the upper limit value and lower limit value of the impact relief control output Iref2, respectively.

[0177] Reference Fig. 9 (a)~ Fig. 9 (f) and Fig.10 , an example of a limit value output by the learning state determination unit 51 when an offset error occurs is described. Fig.10 The limit values ​​in the table are indicated in Fig. 9 (b)~ Fig. 9 In the state (h), the limit value output by the learning state determination unit 51 is obtained.

[0178] Fig. 9 (b) and Figure 8 The learning state determination unit 51 outputs "Limit2" and "-Limit2" as the upper limit value and the lower limit value of the shock relaxation control output Iref2, respectively.

[0179] If an offset error occurs due to a mis-assembly of the intermediate shaft 4 or the like, Fig. 9 At this stage, since the new virtual rack ends θevr and θevl have not yet been learned, the value of the rack stroke St calculated by the learning state determination unit 51 remains the same as Fig. 9 Therefore, the learning state determination unit 51 has not yet determined that an offset error has occurred, and has not yet reset the limit value to "0". Therefore, "Limit2" and "-Limit2" are output.

[0180] If in Fig. 9 If the new left virtual rack end position θevl is learned in (d), the rack stroke St becomes longer than the rack stroke maximum value Stmax. Therefore, the learning state determination unit 51 resets the upper and lower limits of the shock relaxation control output Iref2 to "0".

[0181] In addition, if Fig. 9 As shown in (e), the left virtual rack end position θevl becomes below the negative learning threshold (-θlth), so the learning state determination unit 51 determines that the learning of the left virtual rack end position θevl has been performed, and outputs "Limit1" as a limit value for limiting the upper limit value of the impact mitigation control output Iref2.

[0182] On the other hand, the right virtual rack end position θevr is corrected (reset) so that the rack stroke St between the virtual rack end positions θevr and θevl becomes the rack stroke minimum value Stmin, so the rack stroke St does not become longer than the rack stroke minimum value Stmin. Therefore, it is not determined that the learning of the virtual rack end positions θevr and θevl is completed, and the right virtual rack end position θevr is less than the learning threshold value θlth, so the output of "0" is maintained as the limit value for limiting the lower limit value of the impact relaxation control output Iref2. Fig. 9 The same is true for the state of (f).

[0183] Reference Fig. 9 (g). The new right virtual rack end position θevr (i.e., the other virtual rack end position) is learned. When the rack stroke St is longer than the rack stroke minimum value Stmin, the learning state determination unit 51 determines that the learning of the virtual rack end positions θevr and θevl is completed, and outputs "Limit2" and "-Limit2" as the upper limit value and lower limit value of the impact mitigation control output Iref2, respectively.

[0184] exist Fig. 9 Similarly, in (h), "Limit2" and "-Limit2" are output as limit values ​​for limiting the upper limit value and the lower limit value of the shock relaxation control output Iref2, respectively.

[0185] As described above, the steering control device of the present embodiment can limit the impact mitigation control output Iref2 in stages according to the learning degree of the virtual rack end position based on the comparison result between the learned virtual rack end position and the learning threshold value θlth, and the comparison result between the rack stroke St calculated based on the learned virtual rack end position and the rack stroke minimum value Stmin. Thus, the virtual rack end position can be learned while suppressing damage to the steering mechanism caused by the end contact.

[0186] Next, the relearning determination unit 53 will be described. Figure 2 The relearning determination unit 53 determines whether relearning of the virtual rack end positions θevl and θevr is necessary based on whether the occurrence of end contact is detected. In the following description, the virtual rack end positions θevl and θevr may be collectively referred to as "virtual rack end position θev".

[0187] When relearning the virtual rack end position θev, the relearning determination unit 53 outputs a relearning instruction signal Cmd for instructing relearning to the terminal position learning unit 46. Thus, for example, the virtual rack end position θev can be relearned in the following cases: when the rack shaft is replaced after learning the virtual rack end position θev, the rack shaft is replaced, and the end abuts due to a change in the mounting position of the rack shaft before and after the rack shaft is replaced by mistake to mount a rack shaft having a length different from that of the rack shaft that should have been installed.

[0188] Fig.11 2 is a block diagram showing an example of the functional configuration of the relearning determination unit 53. The relearning determination unit 53 includes an end contact detection unit 90, an end contact steering angle range determination unit 91, a counting unit 92, and a relearning unit 93.

[0189] The end contact detection section 90 detects the occurrence of the end contact based on the column output shaft torque Tc and the steering torque Th, and holds an end contact steering angle θabt which is a steering angle when the occurrence of the end contact is detected.

[0190] For example, the end contact detection unit 90 maintains the steering angle θdt when the steering torque Th is equal to or greater than a predetermined threshold value Tth1 (e.g., 8 [Nm]), and determines whether it is necessary to detect the end contact steering angle θabt based on the maintained steering angle θdt. For example, the end contact detection unit 90 may determine that it is necessary to detect the end contact steering angle θabt when the absolute value |θev-θdt| of the difference between the steering angle θdt and the virtual rack end position θev is greater than the steering angle threshold value θtha1, and may determine that it is not necessary to detect the end contact steering angle θabt when the absolute value |θev-θdt| of the difference between the steering angle θdt and the virtual rack end position θev is less than the steering angle threshold value θtha1.

[0191] Reference Fig.12 (a). Fig.12 (a) exemplifies a case where the steering wheel 1 is turned rightward. In the process when the steering wheel 1 is turned leftward, the right virtual rack end position θevr in the following description is replaced with the left virtual rack end position θevl.

[0192] When the steering angle when the steering torque Th is equal to or greater than the predetermined threshold value Tth1 is the steering angle θdt1 shown in the figure, the absolute value |θevr-θdt1| of the difference between the virtual rack end position θevr and the steering angle θdt1 is equal to or less than the steering angle threshold value θtha1, and the end contact detection unit 90 determines that it is not necessary to detect the end contact steering angle θabt. On the other hand, when the steering angle when the steering torque Th is equal to or greater than the predetermined threshold value Tth1 is the steering angle θdt2 shown in the figure, the absolute value |θevr-θdt2| of the difference between the virtual rack end position θevr and the steering angle θdt2 is greater than the steering angle threshold value θtha1, and the end contact detection unit 90 determines that it is necessary to detect the end contact steering angle θabt.

[0193] When it is determined that it is necessary to detect the end contact steering angle θabt, after the steering torque Th becomes greater than the specified threshold value Tth1, the end contact detection unit 90 maintains the steering angle θcd when the column output shaft torque Tc is less than the specified threshold value Tth2 (for example, 35 [Nm]) and the steering torque Th is less than the specified threshold value Tth1 as a candidate for the end contact steering angle θabt (hereinafter sometimes referred to as "end contact steering angle candidate").

[0194] When the absolute value |θev-θcd| of the difference between the end contact steering angle candidate θcd and the virtual rack end position θev is greater than the steering angle threshold value θtha2, the end contact detection unit 90 obtains the end contact steering angle candidate θcd as the end contact steering angle θabt. When the absolute value |θev-θcd| is less than the steering angle threshold value θtha2, the end contact detection unit 90 does not obtain the end contact steering angle candidate θcd as the end contact steering angle θabt but discards it. For example, the steering angle threshold value θtha2 can be set to a value that is smaller than the steering angle threshold value θtha1 by a predetermined margin Δ. For example, the predetermined margin Δ can be set based on the detection error of the steering angle θh.

[0195] Reference Fig.12 (b). Fig.12 (b) illustrates a case where the steering wheel 1 is turned to the right. In the process when the steering wheel 1 is turned to the left, the right virtual rack end position θevr in the following description is replaced with the left virtual rack end position θevl.

[0196] In the case of the end contact steering angle candidate θcd1, the absolute value |θevr-θcd1| of the difference between the virtual rack end position θevr and the end contact steering angle candidate θcd1 is less than the steering angle threshold value θtha2, so the end contact detection unit 90 does not obtain the end contact steering angle candidate θcd1 as the end contact steering angle θabt and discards it. On the other hand, in the case of the end contact steering angle candidate θcd2, the absolute value |θevr-θcd2| of the difference between the virtual rack end position θevr and the end contact steering angle candidate θcd2 is greater than the steering angle threshold value θtha2, so the end contact detection unit 90 obtains the end contact steering angle candidate θcd2 as the end contact steering angle θabt.

[0197] Next, the end contact detection unit 90 calculates the rack stroke approximation Sta based on the acquired end contact steering angle θabt. If the rack stroke approximation Sta is not a value within the allowable range, the acquired end contact steering angle θabt can be discarded and excluded from the object of the determination process of the deviation of the end contact steering angle θabt in the end contact steering angle range determination unit 91 described later.

[0198] Fig.13 (a) shows a calculation example of the rack stroke approximation value Sta when the end contact does not occur when the steering wheel 1 is turned to one of the left and right sides, and when the end contact occurs when the steering wheel 1 is turned to the other of the left and right sides to obtain the end contact steering angle θabt. Fig.13 (b) shows an example of calculating the rack stroke approximation value Sta when the end contact occurs when the steering wheel 1 is turned to the left and to the right, and the end contact steering angle θabtl and the steering angle θabtr are obtained on the left and right sides, respectively.

[0199] like Fig.13 As shown in (a), when the end contact steering angle θabt is obtained when the steering wheel 1 is turned to the right, the end contact detection unit 90 calculates the absolute value of the difference between the left virtual rack end position θevl and the right steering angle θabt as the rack stroke approximation Sta.

[0200] When the error between the rack stroke approximation value Sta and the predetermined value is not within the threshold value, it is considered that the steering wheels 8L, 8R collide with a curb or the like when the steering wheel 1 is turned and cannot be turned to the rack end. Therefore, when the error between the rack stroke approximation value Sta and the predetermined value is not within the threshold value, the end contact detection unit 90 may discard the steering angle θabt without using it for determining whether relearning is required.

[0201] In the process of acquiring the end contact steering angle θabt when the steering wheel 1 is turned to the left, the left virtual rack end position θevl in the above description is replaced with the right virtual rack end position θevr.

[0202] In the following description, the end contact steering angle θabt obtained when the steering wheel 1 is turned to the left is sometimes described as the “left end contact steering angle”, and the end contact steering angle θabt obtained when the steering wheel 1 is turned to the right is sometimes described as the “right end contact steering angle”.

[0203] like Fig.13 As shown in (b), when the end contact steering angle θabtl on the left and the end contact steering angle θabtr on the right are obtained, the absolute value of the difference between these end contact steering angles θabtl and θabtr is calculated as the rack stroke approximation Sta. The end contact detection unit 90 compares the minimum value of the rack stroke of the rack shaft that may be incorrectly installed on the vehicle (hereinafter sometimes recorded as "minimum error stroke Sterr") with the rack stroke approximation Sta. When the rack stroke approximation Sta is greater than the minimum error stroke Sterr, the end contact detection unit 90 determines that the end contact steering angles θabtl and θabtr are appropriate. When the rack stroke approximation Sta is less than the minimum error stroke Sterr, the end contact detection unit 90 determines that the detection of the end contact steering angle θabt is an erroneous detection. The end contact detection unit 90 outputs the determination result to the counting unit 92.

[0204] Reference Fig.11 The end contact steering angle range determination unit 91 determines whether the deviation of the right end contact steering angle θabt obtained multiple times by the end contact detection unit 90 is less than a predetermined threshold value θtha3. Similarly, the end contact steering angle range determination unit 91 determines whether the deviation of the left end contact steering angle θabt obtained multiple times by the end contact detection unit 90 is less than a predetermined threshold value θtha3.

[0205] Below, refer to Fig.14 (a)~ Fig.14 In (c), the calculation method of the deviation of the end contact steering angle θabt on the right side is described, but the calculation method of the deviation of the end contact steering angle θabt on the left side is also the same.

[0206] Reference Fig.14 (a). Fig.14In (a), the triangular mark indicates the end abutment steering angle θabt most recently obtained by the end abutment detection unit 90. Hereinafter, the end abutment steering angle θabt most recently obtained by the end abutment detection unit 90 is sometimes described as the “most recent end abutment steering angle”. The circular mark indicates the end abutment steering angle θabt obtained by the end abutment detection unit 90 and stored in the end abutment steering angle storage unit 94 at a time point before the most recent end abutment steering angle θabt (triangular mark) is obtained. Hereinafter, the end abutment steering angle θabt stored in the end abutment steering angle storage unit 94 is sometimes described as the “stored end abutment steering angle”. Fig.14 (b) and Fig.14 The same is true in (c).

[0207] like Fig.14 As shown in (a), when the difference between the most recent end contact steering angle θabt (triangle mark) and the minimum value θmin and the maximum value θmax of the stored end contact steering angle θabt (circle mark) is less than the predetermined threshold value θtha3, the end contact steering angle range determination unit 91 determines that the deviation of these end contact steering angles θabt is less than the predetermined threshold value θtha3. In this case, the end contact steering angle range determination unit 91 stores the most recent end contact steering angle θabt (triangle mark) in addition to the stored end contact steering angle θabt (circle mark) in the end contact steering angle storage unit 94.

[0208] Reference Fig.11 Each time the end contact detection unit 90 obtains the end contact steering angle θabt (triangle mark), the counting unit 92 counts the number of times the end contact steering angle range determination unit 91 determines that the deviation of the end contact steering angle θabt is less than the predetermined threshold value θtha3. In other words, the number of times the end contact steering angle with a deviation less than the predetermined threshold value θtha3 is obtained is counted.

[0209] The counting unit 92 includes a vehicle state determination unit 95 , end contact counters 96oL, 96oR, 96bL, 96bR, virtual end contact counters 97oL, 97oR, 97bL, 97bR, and center return counters 98oL, 98oR, 98bL, 98bR.

[0210] In the following description, the end abutment counters 96oL, 96oR, 96bL, and 96bR are sometimes collectively referred to as “end abutment counters 96”, the virtual end abutment counters 97oL, 97oR, 97bL, and 97bR are collectively referred to as “virtual end abutment counters 97”, and the center return counters 98oL, 98oR, 98bL, and 98bR are sometimes recorded as “center return counters 98”.

[0211] The vehicle state determination unit 95 determines whether the vehicle is in a stopped state or a running state based on the vehicle speed Vh detected by the vehicle speed sensor 12 . Fig.15 It is an example of a state transition diagram of a vehicle state. If the vehicle speed Vh becomes greater than the vehicle speed threshold value Vth when the vehicle is in a stopped state, the vehicle state determination unit 95 determines that the vehicle state has changed to a running state. When the vehicle state is in a running state, when the vehicle speed Vh is less than the vehicle speed threshold value Vth and the count value of the end contact counter 96 is "0", it is determined that the vehicle state has changed to a stopped state. As described above, the counting unit 92 has four end contact counters 96oL, 96oR, 96bL and 96bR, so the vehicle state determination unit 95 can determine whether the vehicle state has changed to a stopped state for each of these counters.

[0212] Reference Fig.11 When the vehicle is in the driving state, the end contact counter 96 counts and stores the number of times the end contact steering angle range determination unit 91 determines that the deviation of the end contact steering angle θabt is less than the predetermined threshold value θtha3 each time the end contact steering angle θabt (triangle mark) is obtained.

[0213] That is, when the vehicle is in the driving state, when the end contact steering angle range judgment unit 91 determines that the difference between the most recent end contact steering angle θabt (triangle mark) and the minimum value θmin and the maximum value θmax of the stored end contact steering angle θabt (circular mark) is below the specified threshold value θtha3, the end contact counter 96 increases the count value by 1.

[0214] On the other hand, when the vehicle is in a stopped state, each time the end contact steering angle θabt (triangle mark) is obtained, the virtual end contact counter 97 counts the number of times the end contact steering angle range determination unit 91 determines that the deviation of the end contact steering angle θabt is below the specified threshold value θtha3 and stores the number of counts.

[0215] That is, when the vehicle is in a stopped state, when the end contact steering angle range judgment unit 91 determines that the difference between the minimum value θmin and the maximum value θmax of the most recent end contact steering angle θabt (triangle mark) and the stored end contact steering angle θabt (circular mark) is below the specified threshold value θtha3, the virtual end contact counter 97 increases the count value by 1.

[0216] The end contact counter 96oL and the virtual end contact counter 97oL are counters that count the number of times the end contact steering angle range determination unit 91 determines that the deviation of the left end contact steering angle θabt is less than a predetermined threshold value θtha3 when end contact occurs when turning to the left and does not occur when turning to the right.

[0217] In addition, the end abutment counter 96oR and the virtual end abutment counter 97oR are counters that count the number of times the end abutment steering angle range determination unit 91 determines that the deviation of the right end abutment steering angle θabt is below the specified threshold θtha3 when no end abutment occurs when turning to the left and end abutment occurs when turning to the right.

[0218] In addition, the end abutment counter 96bL and the virtual end abutment counter 97bL are counters that count the number of times the end abutment steering angle range determination unit 91 determines that the deviation of the left end abutment steering angle θabt is below the specified threshold θtha3 when end abutment occurs both when turning to the left and when turning to the right.

[0219] In addition, the end contact counter 96bR and the virtual end contact counter 97bR are counters that count the number of times the end contact steering angle range determination unit 91 determines that the deviation of the right end contact steering angle θabt is below the specified threshold θtha3 when end contact occurs both when turning to the left and when turning to the right.

[0220] When the vehicle state changes from the stopped state to the running state, the counting unit 92 substitutes the count value of the virtual end contact counter 97 for the count value of the end contact counter 96. That is, the count value of the end contact counter 96 is replaced by the count value of the virtual end contact counter 97. In addition, the count value of the virtual end contact counter 97 is reset to "0".

[0221] Reference Fig.14 (c). When the nearest end contact steering angle θabt (triangle mark) is closer to the neutral position of the steering mechanism than the stored end contact steering angle θabt (circle mark), and the difference between the maximum value θmax of the stored end contact steering angle θabt (circle mark) (i.e., the end contact steering angle θabt farthest from the neutral position) and the nearest end contact steering angle θabt (triangle mark) is greater than the prescribed threshold value θtha3, the end contact steering angle range determination unit 91 determines that the deviation of these end contact steering angles θabt is not less than the prescribed threshold value θtha3. Hereinafter, such a state is sometimes described as a "neutral side deviation state".

[0222] When the most recent end contact steering angle θabt (triangle mark) is in the neutral side deviation state, the end contact steering angle range determination unit 91 discards the most recent steering angle θabt (triangle mark).

[0223] In addition, the center return counter 98 counts and stores the number of times the most recent end contact steering angle θabt (triangle mark) is determined to be in a neutral side deviation state. That is, when the end contact steering angle range determination unit 91 determines that the most recent end contact steering angle θabt (triangle mark) is in a neutral side deviation state, the center return counter 98 increases the count value by 1.

[0224] The center return counter 98oL counts the number of times the end contact steering angle range determination unit 91 determines that the left end contact steering angle θabt is in the neutral side deviation state when end contact occurs when turning left and does not occur when turning right.

[0225] The center return counter 98oR counts the number of times the end contact steering angle range determination unit 91 determines that the right end contact steering angle θabt is in the neutral side deviation state when end contact does not occur when turning to the left and occurs when turning to the right.

[0226] The center return counter 98bL counts the number of times the end contact steering angle range determination unit 91 determines that the left end contact steering angle θabt is deviated from the neutral side when the end contact occurs both when turning left and when turning right.

[0227] The center return counter 98bR counts the number of times the end contact steering angle range determination unit 91 determines that the right end contact steering angle θabt is in a state deviated from the neutral side when the end contact occurs both when turning left and when turning right.

[0228] When any count value of the center return counters 98oL, 98oR, 98bL, 98bR becomes equal to or greater than a predetermined threshold value, the end contact steering angle range determination unit 91 deletes the left and right end contact steering angles θabt (circle marks) stored in the end contact steering angle storage unit 94. In addition, the counting unit 92 resets the count values ​​of the end contact counters 96oL, 96oR, 96bL, 96bR, the virtual end contact counters 97oL, 97oR, 97bL, 97bR, and the center return counters 98oL, 98oR, 98bL, 98bR to "0".

[0229] Reference Fig.14(b). When the most recently acquired end contact steering angle θabt (triangle mark) is further away from the neutral position of the steering mechanism than the stored end contact steering angle θabt (circle mark), and the difference between the minimum value θmin of the stored end contact steering angle θabt (circle mark) (i.e., the end contact steering angle θabt closest to the neutral position) and the most recently acquired end contact steering angle θabt (triangle mark) is greater than a prescribed threshold value θtha3, the end contact steering angle range determination unit 91 determines that the deviation of these end contact steering angles θabt is not less than the prescribed threshold value θtha3. Hereinafter, such a state is sometimes described as an "end side deviation state".

[0230] When the most recent end contact steering angle θabt (triangle mark) is in an end side deviation state, the end contact steering angle range determination unit 91 eliminates the end contact steering angle θabt (circular mark) stored at a time before the most recent steering angle θabt (triangle mark) is obtained from the end contact steering angle storage unit 94, and stores the most recent steering angle θabt (triangle mark) in the end contact steering angle storage unit 94.

[0231] In addition, the count values ​​of the end contact counter 96, the virtual end contact counter 97, and the center return counter 98 are reset to "0". Furthermore, when the vehicle is in the running state, the end contact counter 96 is incremented by 1, and when the vehicle is in the stopped state, the virtual end contact counter 97 is incremented by 1.

[0232] Specifically, when end contact occurs when turning to the left and does not occur when turning to the right, and the most recent end contact steering angle θabt (triangle mark) is the end contact steering angle θabt on the left, the stored end contact steering angle θabt on the left (circle mark) is deleted from the end contact steering angle storage unit 94, and the most recent left steering angle θabt (triangle mark) is stored in the end contact steering angle storage unit 94. In addition, the count values ​​of the end contact counter 96oL, the virtual end contact counter 97oL, and the center return counter 98oL are reset to "0". In addition, when the vehicle state is the driving state, the end contact counter 96oL is increased by 1, and when the vehicle state is the stopped state, the virtual end contact counter 97oL is increased by 1.

[0233] In addition, when the end contact does not occur when turning to the left, and the end contact occurs when turning to the right, and the most recent end contact steering angle θabt (triangle mark) is the right end contact steering angle θabt, the stored right end contact steering angle θabt (circle mark) is deleted from the end contact steering angle storage unit 94, and the most recent right steering angle θabt (triangle mark) is stored in the end contact steering angle storage unit 94. In addition, the count values ​​of the end contact counter 96oR, the virtual end contact counter 97oR, and the center return counter 98oR are reset to "0". In addition, when the vehicle state is the driving state, the end contact counter 96oR is increased by 1, and when the vehicle state is the stopped state, the virtual end contact counter 97oR is increased by 1.

[0234] In addition, when the end contact occurs in both the left turn and the right turn and the most recent end contact steering angle θabt (triangle mark) is the left end contact steering angle θabt, the stored left end contact steering angle θabt (circle mark) is deleted from the end contact steering angle storage unit 94, and the most recent left steering angle θabt (triangle mark) is stored in the end contact steering angle storage unit 94. In addition, the count values ​​of the end contact counter 96bL, the virtual end contact counter 97bL, and the center return counter 98bL are reset to "0". In addition, when the vehicle state is the driving state, the end contact counter 96bL is increased by 1, and when the vehicle state is the stopped state, the virtual end contact counter 97bL is increased by 1.

[0235] In addition, when the end contact occurs in both the left turn and the right turn and the most recent end contact steering angle θabt (triangle mark) is the right end contact steering angle θabt, the stored right end contact steering angle θabt (circle mark) is deleted from the end contact steering angle storage unit 94, and the most recent right steering angle θabt (triangle mark) is stored in the end contact steering angle storage unit 94. In addition, the count values ​​of the end contact counter 96bR, the virtual end contact counter 97bR, and the center return counter 98bR are reset to "0". In addition, when the vehicle state is the driving state, the end contact counter 96bR is increased by 1, and when the vehicle state is the stopped state, the virtual end contact counter 97bR is increased by 1.

[0236] When the end contacts occur both when turning to the left and when turning to the right, the counting unit 92 receives the determination result from the end contact detection unit 90, and the determination result is the rack stroke approximation Sta ( Fig.13(b)) is obtained by comparing the absolute value of the difference between the left and right end contact steering angles θabt with the minimum error travel value Sterr.

[0237] When the rack stroke approximation value Sta is smaller than the minimum error stroke value Sterr, the counting unit 92 determines that an erroneous detection of the end contact steering angle θabt has occurred, and the count values ​​of the end contact counters 96bL and 96bR are saved to the virtual end contact counters 97bL and 97bR. That is, the count values ​​of the virtual end contact counters 97bL and 97bR are replaced by the count values ​​of the end contact counters 96bL and 96bR, and the count values ​​of the end contact counters 96bL and 96bR are reset to "0".

[0238] Thereafter, when the vehicle state changes to the traveling state in the vehicle state judgment process and it is determined that the end contact steering angle θabt can be reliably detected, the count values ​​of the virtual end contact counters 97bL and 97bR are returned to the end contact counters 96bL and 96bR.

[0239] In addition, if Fig.14 As shown in (a) of FIG. 1 , in the following description, a case where the deviation between the most recently acquired end contact steering angle θabt (triangle mark) and the stored end contact steering angle θabt (circle mark) is less than a predetermined threshold value θtha3 is sometimes described as “the most recently acquired end contact steering angle θabt is within the predetermined deviation range θtha3”. Fig.14 (b) and Fig.14 As shown in (c), in the following description, the situation where the most recent end contact steering angle θabt (triangle mark) is in an end side deviation state or a neutral side deviation state is sometimes described as "the most recently obtained end contact steering angle θabt is outside the prescribed deviation range θtha3".

[0240] Reference Fig.11 The relearning unit 93 determines whether or not relearning of the virtual rack end position θev is necessary based on the count value of the end contact counter 96 , and outputs a relearning instruction signal Cmd to the terminal position learning unit 46 when relearning of the virtual rack end position θev is necessary.

[0241] For example, when the count value of the end contact counter 96 exceeds a predetermined threshold value, the relearning unit 93 determines that the virtual rack end position θev needs to be relearned, and outputs a relearning instruction signal Cmd.

[0242] For example, when the end contact occurs when turning to the left and does not occur when turning to the right, and when the count value of the end contact counter 96oL for the left side exceeds the predetermined threshold value, the relearning unit 93 may output a relearning instruction signal Cmd indicating the relearning of the left virtual rack end position θevl to the terminal position learning unit 46. The terminal position learning unit 46 resets the left virtual rack end position θevl to the initial value (-θint) according to the relearning instruction signal Cmd. Therefore, the terminal position learning unit 46 relearns the left virtual rack end position θevl.

[0243] In addition, for example, when the end contact does not occur when turning to the left and the end contact occurs when turning to the right, and when the count value of the end contact counter 96oR for the right side exceeds the predetermined threshold value, the relearning unit 93 may output a relearning instruction signal Cmd indicating the relearning of the right virtual rack end position θevr to the terminal position learning unit 46. The terminal position learning unit 46 resets the right virtual rack end position θevr to the initial value (θint) based on the relearning instruction signal Cmd. Therefore, the terminal position learning unit 46 relearns the right virtual rack end position θevr.

[0244] In addition, for example, when end abutment occurs both when turning to the left and when turning to the right, and the sum of the count value of the end abutment counter 96bL for the left side and the count value of the end abutment counter 96bR for the right side is greater than a prescribed threshold value, the re-learning unit 93 calculates the rack stroke minimum value Stmin, the rack stroke maximum value Stmax, the learning threshold value θlth, the rack end maximum value θevmax and the initial value θint as the set values ​​used in the learning of the virtual rack end position θev based on the end abutment steering angle θabt stored in the end abutment steering angle storage unit 94 of the end abutment steering angle range determination unit 91.

[0245] Reference Fig.16 , an example of a method for calculating the rack stroke minimum value Stmin, the rack stroke maximum value Stmax, the learning threshold θlth, the rack end maximum value θevmax, and the initial value θint is described. Fig.16 In the figure, reference symbol “RC” indicates the center position of the left and right rack ends, and “0 [deg]” indicates the position where the steering angle θh detected by the steering angle sensor 14 becomes “0”.

[0246] The re-learning unit 93 calculates the sum of the absolute value of the maximum value of the left end abutment steering angle θabt (i.e., the steering angle closest to the neutral position among the left end abutment steering angle θabt) and the absolute value of the minimum value of the right end abutment steering angle θabt (i.e., the steering angle closest to the neutral position among the right end abutment steering angle θabt) as the virtual stroke Stp = |max(left end abutment steering angle θabt)|+|min(right end abutment steering angle θabt)|.

[0247] Next, the re-learning unit 93 calculates 1 / 2 of the absolute value of the difference between the absolute value of the maximum value of the left end abutting steering angle θabt and the absolute value of the minimum value of the right end abutting steering angle θabt as the virtual assembly error eθ=||max(left end abutting steering angle θabt)|-|min(right end abutting steering angle θabt)|| / 2.

[0248] The re-learning unit 93 calculates a subtraction result of subtracting a predetermined manual steering gear thermal expansion / contraction error and a learning error from the virtual stroke Stp as the rack stroke minimum value Stmin=(Stp-manual steering gear thermal expansion / contraction error-learning error).

[0249] The re-learning unit 93 calculates the sum of the thermal expansion / contraction error of the specified manual steering gear, the learning error, and the sensor error and the virtual stroke Stp as the maximum rack stroke Stmax = (Stp + thermal expansion / contraction error of the manual steering gear + learning error + sensor error).

[0250] The re-learning unit 93 calculates the sum of 1 / 2 of the rack stroke maximum value Stmax and the virtual assembly error eθ as the rack end maximum value θevmax=(Stmax / 2+eθ).

[0251] The re-learning unit 93 calculates a subtraction result obtained by subtracting the rack end maximum value θevmax from the rack stroke minimum value Stmin as an initial value θint=(Stmin-θevmax).

[0252] The re-learning unit 93 calculates a subtraction result obtained by subtracting the virtual assembly error eθ from 1 / 2 of the rack stroke minimum value Stmin as the learning threshold value θlth=(Stmin / 2−virtual assembly error eθ).

[0253] The relearning unit 93 outputs the calculated initial value θint and the rack stroke maximum value Stmax to the terminal position learning unit 46. In addition, the relearning unit 93 outputs the calculated rack stroke maximum value Stmax, the rack stroke minimum value Stmin, and the learning threshold value θlth to the learning state determination unit 51. The relearning unit 93 may be configured to output the rack end maximum value θevmax.

[0254] The terminal position learning unit 46 updates the initial value θint at the start of learning the virtual rack end positions θevr, θevl to the value recalculated by the relearning unit 93 . The rack stroke maximum value Stmax used for determining the offset error is updated to the value recalculated by the relearning unit 93 .

[0255] Furthermore, the learning state determination unit 51 updates the rack stroke maximum value Stmax, the rack stroke minimum value Stmin, and the learning threshold value θlth used for determining the learning state to the values ​​recalculated by the re-learning unit 93 .

[0256] The relearning unit 93 may output a relearning instruction signal Cmd indicating the relearning of the left virtual rack end position θevl and the right virtual rack end position θevr to the terminal position learning unit 46. The terminal position learning unit 46 resets the left virtual rack end position θevl to the initial value (-θint) and the right virtual rack end position θevr to the initial value (θint) according to the relearning instruction signal Cmd. Therefore, the terminal position learning unit 46 relearns the left virtual rack end position θevl and the right virtual rack end position θevr.

[0257] (action)

[0258] Fig.17 This is a flowchart of an example of the steering control method according to the embodiment.

[0259] In step S1 , the end contact detection unit 90 holds the steering angle θdt when the steering torque Th is equal to or greater than a predetermined threshold value Tth1 .

[0260] In step S2, the end contact detection unit 90 determines whether the absolute value |θev-θdt| of the difference between the maintained steering angle θdt and the virtual rack end position θev is greater than the steering angle threshold value θtha1. If the absolute value |θev-θdt| is not greater than the steering angle threshold value θtha1 (step S2: No), the process returns to step S1. If the absolute value |θev-θdt| is greater than the steering angle threshold value θtha1 (step S2: Yes), the process proceeds to step S3.

[0261] In step S3 , the end contact detection unit 90 holds the end contact steering angle candidate θcd when the column output shaft torque Tc becomes smaller than a predetermined threshold value Tth2 and the steering torque Th becomes smaller than a predetermined threshold value Tth1 after the steering torque Th becomes equal to or greater than the predetermined threshold value Tth1 .

[0262] In step S4, the end contact detection unit 90 determines whether the absolute value |θev-θcd| of the difference between the end contact steering angle candidate θcd and the virtual rack end position θev is greater than the steering angle threshold value θtha2. If the absolute value |θev-θcd| is not greater than the steering angle threshold value θtha2 (step S4: No), the process returns to step S1. If the absolute value |θev-θcd| is greater than the steering angle threshold value θtha2 (step S4: Yes), the process proceeds to step S5.

[0263] In step S5, the vehicle state determination unit 95 determines whether the vehicle is in a stopped state or a running state. When the vehicle state changes from a stopped state to a running state, the counting unit 92 substitutes the count value of the virtual end contact counter 97 into the count value of the end contact counter 96. In addition, the count value of the virtual end contact counter 97 is reset to "0".

[0264] In step S6, the end contact detection unit 90 determines whether the end contact occurs when the steering wheel 1 is turned to the left and when it is turned to the right. If the end contact occurs on both the left and right sides (step S6: Yes), the process proceeds to step S8. If the end contact occurs only on one of the left or right sides (step S6: No), the process proceeds to step S7.

[0265] In step S7, the relearning determination unit 53 executes a one-side end contact process. For details of the one-side end contact process, refer to Fig.18 This will be described later. After that, the process proceeds to step S9.

[0266] In step S8, the relearning determination unit 53 executes the both-side end contact processing. Fig.19 This will be described later. After that, the process proceeds to step S9.

[0267] In step S9, the controller 30 determines whether the IGN key 11 is turned off. In the case where the IGN key 11 is not turned off (step S9: No), the process returns to step S1. In the case where the IGN key 11 is turned off (step S9: Yes), the process ends.

[0268] Fig.18 yes Fig.17The single-side end contact processing (S7) is a flowchart of an example of the single-side end contact processing. The single-side end contact processing is independently executed in the case where the end contact occurs when turning to the right (that is, the case where the end contact steering angle θabt on the right side is obtained) and the case where the end contact occurs when turning to the left (that is, the case where the end contact steering angle θabt on the left side is obtained).

[0269] In step S10, the end contact detection unit 90 calculates the rack stroke approximation Sta based on the most recently acquired end contact steering angle θabt. For example, when the right end contact steering angle θabt is acquired, the absolute value of the difference between the left virtual rack end position θevl and the right steering angle θabt is calculated as the rack stroke approximation Sta. When the left end contact steering angle θabt is acquired, the absolute value of the difference between the right virtual rack end position θevr and the left steering angle θabt is calculated as the rack stroke approximation Sta. When the error between the rack stroke approximation Sta and the predetermined value is not within the threshold value (step S10: No), the one-side end contact processing is terminated. When the error between the rack stroke approximation Sta and the predetermined value is within the threshold value (step S10: Yes), the processing proceeds to step S11.

[0270] In step S11, the end contact steering angle range determination unit 91 determines whether the most recently acquired end contact steering angle θabt is within the prescribed deviation range θtha3. When the most recently acquired end contact steering angle θabt is outside the prescribed deviation range θtha3 (step S11: No), the process proceeds to step S15. When the most recently acquired end contact steering angle θabt is within the prescribed deviation range θtha3 (step S11: Yes), the process proceeds to step S12.

[0271] In step S12, the counting unit 92 increases the count value of the end contact counter 96 or the virtual end contact counter 97 by 1. Specifically, when the vehicle is in a running state and the end contact steering angle θabt on the left side is obtained, the count value of the end contact counter 96oL is increased by 1. When the vehicle is in a running state and the end contact steering angle θabt on the right side is obtained, the count value of the end contact counter 96oR is increased by 1. When the vehicle is in a stopped state and the end contact steering angle θabt on the left side is obtained, the count value of the virtual end contact counter 97oL is increased by 1. When the vehicle is in a stopped state and the end contact steering angle θabt on the right side is obtained, the count value of the virtual end contact counter 97oR is increased by 1.

[0272] In step S13, the relearning unit 93 determines whether the count value of the end contact counter 96 exceeds a predetermined threshold value. If the count value of the end contact counter 96 does not exceed the predetermined threshold value (step S13: No), the one-side end contact processing is terminated. If the count value of the end contact counter 96 exceeds the predetermined threshold value (step S13: Yes), the processing proceeds to step S14.

[0273] In step S14 , the re-learning unit 93 outputs a re-learning instruction signal Cmd to the terminal position learning unit 46 .

[0274] Specifically, when the count value of the end contact counter 96oL on the left side exceeds a predetermined threshold value, a relearning instruction signal Cmd indicating relearning of the virtual rack end position θevl on the left side is output. The terminal position learning unit 46 resets the virtual rack end position θevl on the left side to an initial value (-θint) according to the relearning instruction signal Cmd. When the count value of the end contact counter 96oR on the right side exceeds a predetermined threshold value, a relearning instruction signal Cmd indicating relearning of the virtual rack end position θevR on the right side is output. The terminal position learning unit 46 resets the virtual rack end position θevl on the right side to an initial value (θint) according to the relearning instruction signal Cmd. Thereafter, the one-side end contact processing is terminated.

[0275] In step S15, the end contact steering angle range determination unit 91 determines whether the most recently acquired end contact steering angle θabt is in the neutral side deviation state. If the most recently acquired end contact steering angle θabt is in the end side deviation state (step S15: No), the process proceeds to step S19. If the most recently acquired end contact steering angle θabt is in the neutral side deviation state (step S15: Yes), the process proceeds to step S16.

[0276] In step S16, the counting unit 92 increases the count value of the center return counter 98 by 1. Specifically, when the most recently acquired end contact steering angle θabt is the left end contact steering angle θabt, the count value of the center return counter 98oL is increased by 1, and when the most recently acquired end contact steering angle θabt is the right end contact steering angle θabt, the count value of the center return counter 98oR is increased by 1.

[0277] In step S17, the counting unit 92 determines whether the count value of any of the center return counters 98oL and 98oR is greater than a predetermined threshold value. If the count value is not greater than the threshold value (step S17: No), the one-side end contact process is terminated. If the count value is greater than the threshold value (step S17: Yes), the process proceeds to step S18.

[0278] In step S18, the counting unit 92 resets the count values ​​of the end contact counters 96oL, 96oR, 96bL, 96bR, the virtual end contact counters 97oL, 97oR, 97bL, 97bR, and the center return counters 98oL, 98oR, 98bL, 98bR to "0". In addition, the end contact steering angle range determination unit 91 deletes the left and right end contact steering angles θabt stored in the end contact steering angle storage unit 94. Thereafter, the one-side end contact processing is terminated.

[0279] In step S19, the counting unit 92 resets the end contact counter 96oL and the virtual end contact counter 97oL, or the end contact counter 96oR and the virtual end contact counter 97oR to "0" according to whether any of the end contact steering angles θabt on the left and right sides is in the end side deviation state. In addition, the end contact steering angle range determination unit 91 eliminates the end contact steering angle θabt on either the left or right side stored in the end contact steering angle storage unit 94. Specifically, when the end contact steering angle θabt on the left side is in the end side deviation state, the counting unit 92 resets the end contact counter 96oL and the virtual end contact counter 97oL to "0", and the end contact steering angle range determination unit 91 eliminates the end contact steering angle θabt on the left side. When the right end contact steering angle θabt is in the end side deviation state, the counting unit 92 resets the end contact counter 96oR and the virtual end contact counter 97oR to "0", and the end contact steering angle range determination unit 91 cancels the right end contact steering angle θabt.

[0280] The process of step S20 is the same as that of step S12. After that, the one-side end contact process is terminated.

[0281] Fig.19 yes Fig.18 A flowchart of an example of the two side end contact processing (S8).

[0282] In step S30, the end contact steering angle range determination unit 91 determines whether the most recently acquired end contact steering angle θabt is within the prescribed deviation range θtha3. When the most recently acquired end contact steering angle θabt is outside the prescribed deviation range θtha3 (step S30: No), the process proceeds to step S36. In addition, the processes of steps S36 to S42 are independently performed in the case where the end contact occurs when turning to the right (i.e., the case where the right end contact steering angle θabt is acquired) and the case where the end contact occurs when turning to the left (i.e., the case where the left end contact steering angle θabt is acquired).

[0283] On the other hand, when the most recently acquired end contact steering angle θabt is within the predetermined deviation range θtha3 (step S30 : Yes), the process proceeds to step S31 .

[0284] In step S31, the counting unit 92 increases the count value of the end contact counter 96 or the virtual end contact counter 97 by 1. Specifically, when the vehicle is in a running state and the end contact steering angle θabt on the left side is obtained, the count value of the end contact counter 96bL is increased by 1. When the vehicle is in a running state and the end contact steering angle θabt on the right side is obtained, the count value of the end contact counter 96bR is increased by 1. Specifically, when the vehicle is in a stopped state and the end contact steering angle θabt on the left side is obtained, the count value of the virtual end contact counter 97bL is increased by 1. When the vehicle is in a stopped state and the end contact steering angle θabt on the right side is obtained, the count value of the virtual end contact counter 97bR is increased by 1.

[0285] In step S32, the end contact detection unit 90 calculates the absolute value of the difference between the left and right end contact steering angles θabt as the rack stroke approximation value Sta. For example, the end contact detection unit 90 may calculate the absolute value of the difference between the stored minimum value of the right end contact steering angle θabt (i.e., the steering angle closest to the neutral position among the stored right end contact steering angles θabt) and the stored maximum value of the left end contact steering angle θabt (i.e., the steering angle closest to the neutral position among the stored left end contact steering angles θabt) as the rack stroke approximation value Sta=|min(right end contact steering angle θabt)-max(left end contact steering angle θabt)|. If the rack stroke approximation value Sta is not equal to or greater than the minimum error stroke value Sterr (step S32: No), the process proceeds to step S35. When the rack stroke approximation value Sta is equal to or larger than the error stroke minimum value Sterr (step S32 : Yes), the process proceeds to step S33 .

[0286] In step S33, the relearning unit 93 determines whether the sum of the count value of the end contact counter 96bL and the count value of the end contact counter 96bR is greater than or equal to a predetermined threshold value. If the sum of the count values ​​is not greater than or equal to the predetermined threshold value (step S33: No), the both-side end contact processing is terminated. If the sum of the count values ​​is greater than or equal to the predetermined threshold value (step S33: Yes), the processing proceeds to step S34.

[0287] In step S34, the relearning unit 93 calculates the various setting values ​​(rack stroke minimum value Stmin, rack stroke maximum value Stmax, learning threshold value θlth, rack end maximum value θevmax, initial value θint) used in learning the virtual rack end position θev. The relearning unit 93 outputs the calculated initial value θint and rack stroke maximum value Stmax to the terminal position learning unit 46, and outputs the calculated rack stroke maximum value Stmax, rack stroke minimum value Stmin, and learning threshold value θlth to the learning state determination unit 51. The terminal position learning unit 46 and the learning state determination unit 51 update these setting values ​​to the values ​​received from the relearning unit 93.

[0288] The relearning unit 93 outputs the relearning instruction signal Cmd to the terminal position learning unit 46. The terminal position learning unit 46 resets the left virtual rack end position θevl to the initial value (-θint) and the right virtual rack end position θevr to the initial value (θint) according to the relearning instruction signal Cmd. Then, the two-side end contact processing is terminated.

[0289] In step S35, the counting unit 92 saves the count values ​​of the end contact counters 96bL and 96bR to the virtual end contact counters 97bL and 97bR. Then, the both-side end contact processing is terminated.

[0290] In step S36, the end contact detection unit 90 calculates the absolute value of the difference between the left and right end contact steering angles θabt as the rack stroke approximation Sta. If the rack stroke approximation Sta is not greater than the error stroke minimum value Sterr (step S36: No), the two-side end contact processing is terminated. If the rack stroke approximation Sta is greater than the error stroke minimum value Sterr (step S36: Yes), the processing proceeds to step S37.

[0291] In step S37, the end contact steering angle range determination unit 91 determines whether the most recently acquired end contact steering angle θabt is in the neutral side deviation state. If the most recently acquired end contact steering angle θabt is in the end side deviation state (step S37: No), the process proceeds to step S41. If the most recently acquired end contact steering angle θabt is in the neutral side deviation state (step S37: Yes), the process proceeds to step S38.

[0292] In step S38, the counting unit 92 increases the count value of the center return counter 98 by 1. Specifically, when the most recently acquired end contact steering angle θabt is the left end contact steering angle θabt, the count value of the center return counter 98bL is increased by 1, and when the most recently acquired end contact steering angle θabt is the right end contact steering angle θabt, the count value of the center return counter 98bR is increased by 1.

[0293] In step S39, the counting unit 92 determines whether the count value of any of the center return counters 98bL and 98bR is greater than a predetermined threshold value. If the count value is not greater than the threshold value (step S39: No), the two-side end contact processing is terminated. If the count value is greater than the threshold value (step S38: Yes), the processing proceeds to step S40.

[0294] The processing of step S40 is Fig.18 The processing of step S18 is the same as that of step S18. Then, the processing of the both-side end portions abutting each other is terminated.

[0295] In step S41, the counting unit 92 resets the end contact counter 96bL and the virtual end contact counter 97bL, or the end contact counter 96bR and the virtual end contact counter 97bR to "0" according to whether the end contact steering angle θabt on the left side or the right side is in the end side deviation state. In addition, the end contact steering angle range determination unit 91 deletes the end contact steering angle θabt on the left side or the right side stored in the end contact steering angle storage unit 94. Specifically, when the end contact steering angle θabt on the left side is in the end side deviation state, the counting unit 92 resets the end contact counter 96bL and the virtual end contact counter 97bL to "0", and the end contact steering angle range determination unit 91 deletes the end contact steering angle θabt on the left side. When the right end contact steering angle θabt is in the end side deviation state, the counting unit 92 resets the end contact counter 96bR and the virtual end contact counter 97bR to "0", and the end contact steering angle range determination unit 91 cancels the right end contact steering angle θabt.

[0296] The process of step S42 is the same as the process of step S31. Then, the both side end contact process is terminated.

[0297] (Variation Example)

[0298] The above describes an embodiment in which the steering control device of the present invention is applied to an electric power steering device. However, the steering control device of the present invention can be widely applied to steering control devices other than electric power steering devices as long as it uses an actuator to generate a force to steer the steering wheel of the vehicle. For example, it can also be applied to a steer-by-wire (SBW) type steering device in which the steering wheel and the steering wheel are mechanically separated. In this case, the steering torque Th can also be not added to the motor torque when calculating the column output shaft torque Tc.

[0299] (1) The end contact detection unit 90 can correct the end contact steering angle θabt based on the deformation of the mechanism part based on the column output shaft torque Tc. This can reduce the influence of the torsion of the steering mechanism. The deformation can be calculated based on the column output shaft torque Tc and the rigidity (spring constant) of the mechanism part. Figure 7 Here, the rigidity is a ratio of a change in the column output shaft torque Tc to a change in the steering angle θh at a point indicated by reference symbol θ1 or θ2, and can be obtained by experiments or the like.

[0300] Figure 7 The characteristics shown vary according to the viscous resistance based on the steering speed. The steering speed may affect the rack end learning value. The change in the rack end learning value relative to the change in the steering speed can be obtained by experiment or the like and stored as a steering speed correction amount characteristic, and the end contact steering angle θabt can be corrected according to the steering speed and the steering speed correction amount characteristic.

[0301] (2) In the above-mentioned embodiment, when the rack stroke St between the left and right virtual rack end positions θev exceeds the rack stroke maximum value Stmax, the virtual rack end position θev at the stroke end where the end contact is not detected is reset so that the rack stroke St becomes the prescribed rack stroke minimum value. Alternatively, when either of the left and right virtual rack end positions θev exceeds the rack end maximum value θevmax, the other of the left and right virtual rack end positions θev is reset so that the rack stroke St becomes the prescribed rack stroke minimum value.

[0302] (Effects of Embodiments)

[0303] (1) A steering control device includes: a position detection unit that detects a steering position of a steering mechanism of a vehicle; a terminal position learning unit that learns the terminal position of the steering mechanism based on the steering position detected by the position detection unit; and a relearning determination unit that determines whether relearning of the terminal position is required. The relearning determination unit includes: an end contact detection unit that detects the occurrence of end contact as a state in which the steering mechanism is turned to the terminal position, and obtains an end contact steering angle as a steering angle when the end contact is detected; an end contact steering angle range determination unit that determines whether a deviation of the end contact steering angles obtained multiple times is less than a predetermined threshold value; and a relearning unit that resets the learned terminal position to an initial value when the deviation is less than the predetermined threshold value.

[0304] This can prevent the end contact from being erroneously detected and the terminal position from being relearned due to sudden wheel turning, collision between the tire and the curb, etc. before the end contact actually occurs. Therefore, erroneous learning of the terminal position can be prevented.

[0305] (2) The relearning unit can detect the occurrence of end abutment both when turning to the left and when turning to the right, and when the deviation of the end abutment steering angle when turning to the left and the deviation of the end abutment steering angle when turning to the right are respectively below specified thresholds, calculate the estimated rack stroke based on the end abutment steering angle, and reset the initial value based on the estimated rack stroke.

[0306] Thus, when a rack shaft having a length different from that of the rack shaft that should be installed is mistakenly installed, the learning initial value can be set according to the rack length of the rack shaft actually installed.

[0307] (3) A counting unit may be provided for counting the number of acquisitions of the end contact steering angle having a deviation equal to or less than a predetermined threshold value, and the relearning unit may reset the learned terminal position to an initial value when the number of acquisitions becomes equal to or greater than a first threshold number.

[0308] This makes it possible to more accurately determine whether the deviation in the end contact steering angle is equal to or smaller than a predetermined threshold.

[0309] (4) The steering angle range determination unit may store the acquired end contact steering angle and determine whether the deviation of the end contact steering angle is less than or equal to a predetermined threshold value based on the difference between the stored end contact steering angle and the steering angle when the end contact is detected. The counting unit may reset the count of the number of acquisitions when it is determined that the deviation of the end contact steering angle is not less than or equal to the predetermined threshold value.

[0310] This can suppress the terminal position from being erroneously relearned when the deviation in the end contact steering angle temporarily becomes equal to or smaller than a predetermined threshold.

[0311] (5) The counting unit may count the number of times it is determined that the following situations occur as the number of center returns: compared with the first steering angle, which is the steering angle farthest from the neutral position of the steering mechanism among the stored end contact steering angles, the second steering angle detected when the end contact occurs is closer to the neutral position, and the difference between the first steering angle and the second steering angle is not less than a prescribed threshold value, and the counting unit may reset the count of the number of times obtained when the number of center returns becomes greater than the second threshold number of times.

[0312] This can prevent the terminal position from being erroneously relearned in a state where the vehicle cannot be steered before the end portion actually comes into contact due to the tire coming into contact with a curb or the like.

[0313] (6) The counting unit may include a counting storage unit, which stores the number of times the end contact steering angle is obtained with a deviation of less than a predetermined threshold value during a period when the vehicle speed is greater than a vehicle speed threshold as the end contact count number, stores the number of times the end contact steering angle is obtained with a deviation of less than a predetermined threshold value during a period when the vehicle speed is less than the vehicle speed threshold as a virtual count number, and substitutes the value of the virtual count number into the end contact count number when the vehicle speed changes from less than the vehicle speed threshold to greater than the vehicle speed threshold. The relearning unit may reset the learned terminal position to an initial value when the end contact count number is greater than a first threshold number.

[0314] In the stopped state, the tire may come into contact with a curbstone or the like, and the end contact steering angle may be erroneously obtained before the end contact actually occurs. Therefore, by withholding relearning until the state is changed from the stopped state to the running state, erroneous learning can be suppressed.

[0315] (7) The end contact detection unit may calculate the rack stroke based on the learned terminal position learned on one of the left and right sides and the end contact steering angle obtained on the other of the left and right sides, when the end contact does not occur when turning to one of the left and right sides but the end contact occurs when turning to the other of the left and right sides. When the error of the calculated rack stroke is not within a predetermined allowable range, the end contact detection unit does not use the end contact steering angle obtained on the other of the left and right sides for calculating the deviation of the end contact steering angle.

[0316] If the error of the rack stroke calculated based on the end contact steering angle is not within a predetermined allowable range, the end contact steering angle may be erroneously detected. By not using such an end contact steering angle, erroneous learning can be suppressed.

[0317] (8) The end contact detection unit can calculate the rack stroke based on the situation of turning to the left and the end contact steering angle obtained on the right side when end contact occurs both when turning to the left and when turning to the right. When the calculated rack stroke is less than a specified lower limit value, the value of the end contact count number is substituted into the virtual count number, and the value of the end contact count number is reset to 0.

[0318] In this way, when the end contact occurs both when turning to the left and when turning to the right, and the rack stroke calculated based on the end contact steering angle is less than the specified lower limit, there may be a false detection of the end contact steering angle. Therefore, by moving the value of the end contact count number to the virtual count number and temporarily holding the relearning, false learning can be suppressed.

[0319] Description of Reference Numerals

[0320] 1…steering wheel, 2i…column input shaft, 2o…column output shaft, 3…reduction gear, 4…intermediate shaft, 4a, 4b…universal joint, 4c…shaft component, 5…pinion rack mechanism, 5a…pinion, 5b…rack, 6a, 6b…tie rod, 7a, 7b…wheel hub unit, 8L, 8R…steering wheel, 10…torque sensor, 11…ignition key, 12…vehicle speed sensor, 13…battery, 14…steering angle sensor, 20…motor 、30…controller、40…basic command value calculation unit、41、64…adder、42、82…subtractor、43…current control unit、44…PWM control unit、45…inverter、46…terminal position learning unit、47…control rotation displacement setting unit、48…differentiation unit、49…impact relief control unit、50…current detector、51…learning state determination unit、52…impact relief control output limiting unit、53…relearning determination unit、 60 ... spring constant table, 61, 63 ... multiplier, 62 ... viscosity constant table, 65 ... inverter, 66, 79 ... limiter, 70 ... output shaft torque calculation unit, 71 ... selection unit, 72 ... first storage unit, 73, 77 ... delay unit, 74 ... change rate limiter, 75 ... correction position calculation unit, 76 ... second storage unit, 78 ... third storage unit, 80 ... stroke calculation unit, 81 ... offset error calculation unit, 83 ... terminal position correction unit, 90…end contact detection unit, 91…end contact steering angle range determination unit, 92…counting unit, 93…re-learning unit, 94…end contact steering angle storage unit, 95…vehicle state determination unit, 96bL, 96bR, 96oL, 96oR…end contact counter, 97bL, 97bR, 97oL, 97oR…virtual end contact counter, 98bL, 98bR, 98oL, 98oR…center return counter.

Claims

1. A steering control device, characterized in that: The steering control device comprises: a position detection unit that detects a steering position of a steering mechanism of the vehicle; a terminal position learning unit that learns a terminal position of the steering mechanism based on the steering position detected by the position detection unit; and a relearning determination unit for determining whether relearning of the terminal position is required, The relearning determination unit comprises: an end contact detection unit that detects the occurrence of the end contact in a state where the steering mechanism is turned to the terminal position, and acquires an end contact steering angle as a steering angle when the occurrence of the end contact is detected; an end contact steering angle range determination unit that determines whether a deviation of the end contact steering angles acquired a plurality of times is equal to or smaller than a predetermined threshold value; and The re-learning unit resets the learned terminal position to an initial value when the deviation is equal to or smaller than a predetermined threshold value.

2. The steering control device according to claim 1, characterized in that: When the occurrence of end abutment is detected both when turning to the left and when turning to the right, and the deviation of the end abutment steering angle when turning to the left and the deviation of the end abutment steering angle when turning to the right are respectively below the specified threshold value, the relearning unit calculates the estimated rack stroke based on the end abutment steering angle, and resets the initial value based on the estimated rack stroke.

3. The steering control device according to claim 1, characterized in that: The steering control device includes a counting unit that counts the number of times the end contact steering angle is obtained with a deviation that is equal to or smaller than the predetermined threshold value. When the acquisition frequency becomes equal to or greater than a first threshold frequency, the re-learning unit resets the learned terminal position to the initial value.

4. The steering control device according to claim 3, characterized in that: The steering angle range determination unit stores the acquired end contact steering angle and determines whether a deviation of the end contact steering angle is less than or equal to the predetermined threshold value based on a difference between the stored end contact steering angle and the steering angle when the end contact is detected. The counting unit resets the count of the number of acquisitions when it is determined that the deviation of the end contact steering angle is not less than the predetermined threshold value.

5. The steering control device according to claim 4, characterized in that: The counting unit counts the number of times it is determined that the second steering angle at which the end contact occurs is closer to the neutral position than the first steering angle, which is the steering angle farthest from the neutral position of the steering mechanism among the stored end contact steering angles, and the difference between the first steering angle and the second steering angle is not less than the predetermined threshold value as the number of center returns. When the center return frequency becomes equal to or greater than a second threshold frequency, the count of the acquisition frequency is reset.

6. The steering control device according to claim 3, characterized in that: The counting unit includes a counting storage unit, which stores the number of times the end contact steering angle is obtained with a deviation of less than the prescribed threshold value during a period when the vehicle speed is greater than the vehicle speed threshold value as the end contact count number, and stores the number of times the end contact steering angle is obtained with a deviation of less than the prescribed threshold value during a period when the vehicle speed is less than the vehicle speed threshold value as the virtual count number, When the vehicle speed changes from less than the vehicle speed threshold to greater than the vehicle speed threshold, the value of the virtual count number is substituted into the end contact count number, The relearning unit resets the learned terminal position to an initial value when the end contact count number becomes equal to or greater than the first threshold number.

7. The steering control device according to claim 1, characterized in that: In a case where end contact does not occur when turning to one of the left and right sides but occurs when turning to the other of the left and right sides, the end contact detection unit calculates the rack stroke based on the learned terminal position learned on the one of the left and right sides and the end contact steering angle obtained on the other of the left and right sides, When the calculated error of the rack stroke is not within a predetermined allowable range, the end contact steering angle obtained on the other of the left and right sides is not used for calculation of the deviation of the end contact steering angle.

8. The steering control device according to claim 6, characterized in that: When the end contacts occur both when the vehicle is turning to the left and when the vehicle is turning to the right, the end contact detection unit calculates the rack stroke based on the situation of turning to the left and the end contact steering angle obtained on the right. When the calculated rack stroke is smaller than a predetermined lower limit value, the value of the end contact count number is substituted into the virtual count number, and the value of the end contact count number is reset to zero.

9. The steering control device according to any one of claims 1 to 8, characterized in that: The steering control device comprises: a command value calculation unit that calculates a current command value for an actuator that applies a steering assist force to the steering mechanism based on an operation of a steering operation unit acting on the vehicle; a command value correction unit that corrects the current command value calculated by the command value calculation unit when the steering position detected by the position detection unit is near the terminal position learned by the terminal position learning unit; as well as A drive unit controls driving of the actuator based on the current command value corrected by the command value correction unit.

10. A steering device, characterized in that: The steering device comprises: The steering control device according to claim 9; and An actuator is driven and controlled by the steering control device to steer the steering wheels of the vehicle.

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