Steering control device and steering device

Abstract

The error between the virtual rack end position and the actual rack end position is reduced. The terminal position learning unit (46) comprises: a first storage unit (72) which stores the steering position farthest from the neutral position of the steering mechanism among the steering positions detected by the position detection unit (14) when the rotational force applied to the steering mechanism is less than a first specified value; a second storage unit (76) which stores the steering position farthest from the neutral position among the positions after the steering position detected by the position detection unit (14) is shifted by a second specified value in the neutral direction of the steering mechanism; and a third storage unit (78) which stores the steering position farthest from the neutral position among the steering positions stored in the first storage unit (72) and the second storage unit (76) as the terminal position stored in the terminal position learning unit (46).

Description

Technical Field

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

[0002] When the steering angle increases and reaches the maximum mechanical steering angle in the vehicle's steering mechanism, the rack shaft of the steering mechanism reaches the end of its stroke and cannot be further increased. This state where the rack shaft reaches the end of its stroke is called "end collision." In addition, the end of the rack shaft's stroke is sometimes referred to as a "rack end."

[0003] If an end collision occurs at a high steering speed, a large impact and a knocking sound (unusual noise) may be generated, which may make the driver feel uncomfortable. Patent document 1 describes the following technology: the maximum value of the absolute value of the steering angle is learned as the rack end position, and the steering reaction force is increased before the rack end position of the steering angle is reached, thereby alleviating the impact during the end collision.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-104476 Summary of the invention

[0007] Problems to be solved by the invention

[0008] However, there is looseness between the sensor for detecting the steering angle and the rack of the steering mechanism due to elastic bodies such as gears and backlash, etc. Therefore, an error occurs between the virtual rack end position learned based on the steering angle detected by the sensor (hereinafter sometimes referred to as "virtual rack end position") and the actual rack end position (hereinafter sometimes referred to as "actual rack end position").

[0009] If an error occurs in the virtual rack end position, even if the steering reaction force is increased before reaching the virtual rack end position, a desired output required to mitigate shock or noise during an end collision cannot be obtained, and unexpected shock or noise may occur.

[0010] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to reduce the error between the virtual rack end position and the actual rack end position.

[0011] Means for solving problems

[0012] To achieve the above object, a steering control device according to one embodiment of the present invention includes: a position detection unit that detects a steering position of a steering mechanism of a vehicle; and 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.

[0013] The terminal position learning unit includes: a first storage unit, which stores the steering position farthest from the neutral position of the steering mechanism among the steering positions detected by the position detection unit when the rotational force applied to the steering mechanism is less than a first specified value; a second storage unit, which stores the steering position farthest from the neutral position after the steering position detected by the position detection unit is offset by a second specified value in the neutral direction of the steering mechanism; and a third storage unit, which stores the steering position stored in the first storage unit and the second storage unit, whichever is farther from the neutral position, as the terminal position stored in the terminal position learning unit.

[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, the error between the virtual rack end position and the actual rack end position can be reduced. 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 an explanatory diagram of an example of the learned value of the terminal position when the column output shaft torque of (a) is generated.

[0024] Figure 8 (a) is a conceptual diagram of the actual rack end position. Figure 8(b) is a conceptual diagram of the virtual rack end position when there is no offset error. Figure 8 (c) is a conceptual diagram of the virtual rack end position when there is an offset error. Figure 8 (d) is a conceptual diagram of the state where the left virtual rack end position is learned after the offset error occurs. Figure 8 (e) is a conceptual diagram of correction of the steering angle detected by the steering angle sensor and resetting of the learned value of the right virtual rack end position. Figure 8 (f) is a further concept of learning the state of the virtual rack end position on the left side, Figure 8 (g) is a conceptual diagram of a state where the position of the end of the virtual rack on the right side has been learned. DETAILED DESCRIPTION

[0025] The embodiments of the present invention are described in detail with reference to the accompanying drawings. In addition, the embodiments of the present invention shown below illustrate devices and methods for implementing the technical ideas of the present invention, but the technical ideas of the present invention do not specify the structures and configurations of the components as described below. The technical ideas of the present invention can be modified in various ways within the technical scope specified by the claims described in the claims.

[0026] (structure)

[0027] Figure 1 The schematic structural diagram of an example of an electric power steering device according to an embodiment of the present invention is shown. The column shafts (steering shafts) 2i and 2o of the steering wheel (steering handle) 1 are connected to the steering wheels 8L and 8R via the reduction gear (worm gear) 3, the intermediate shaft 4, the pinion rack mechanism 5, the steering tie rods 6a and 6b, and further via the hub units 7a and 7b.

[0028] The column input shaft 2i and the column output shaft 2o are connected via a torsion bar (not shown), and the torsion bar is twisted by the deviation of the rotation angle between the column input shaft 2i and the column output shaft 2o.

[0029] 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.

[0030] The pinion rack mechanism 5 includes a pinion 5a connected to a pinion shaft that transmits steering force from a universal joint 4b, and a rack 5b that meshes with the pinion 5a and converts the rotational motion transmitted to the pinion 5a into a linear motion in the vehicle width direction.

[0031] The steering shaft 2 (column shafts 2i and 2o) is provided with a torque sensor 10 for detecting a steering torque Th. In addition, the steering shaft 2 (column shafts 2i and 2o) is provided with a steering angle sensor 14 for detecting a steering angle θh of the steering wheel 1 .

[0032] 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.

[0033] In addition, the unit for applying the steering assist force is not limited to the motor, and various actuators can be used.

[0034] 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 performing compensation on the current command value.

[0035] The steering angle sensor 14 is not essential, and the steering angle θh may be calculated by adding the torsion angle of the torsion bar of the torque sensor 10 to the rotation angle obtained from the rotation angle sensor that detects the rotation angle of the rotation shaft of the motor 20 .

[0036] 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).

[0037] 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.

[0038] 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.

[0039] Alternatively, the controller 30 may be formed by dedicated hardware for executing each information processing described below.

[0040] For example, the controller 30 may include a functional logic circuit set in a general-purpose semiconductor integrated circuit. For example, the controller 30 may include a programmable logic device (PLD) such as a field programmable gate array (FPGA).

[0041] 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, subtractors 41, 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, and a shock mitigation control unit 49.

[0042] 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 .

[0043] The subtractor 41 corrects the basic current command value Iref1 by subtracting the surge relaxation control output Iref2 output from the surge relaxation control unit 49 from the basic current command value Iref1, and outputs the corrected basic current command value Iref1 as a current command value Iref3.

[0044] The impact mitigation control unit 49 mitigates the impact and knocking sound (unusual noise) caused by the end collision by suppressing the increase of the steering angle θh when the steering angle θh approaches the rack end position. The control of the impact mitigation control unit 49 to mitigate the impact and knocking sound caused by the end collision is sometimes described as "impact mitigation control".

[0045] 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 collision. For example, the impact mitigation control unit 49 may output a current command value that generates a steering reaction force. The details of the impact mitigation control unit 49 will be described later.

[0046] The current command value Iref3 calculated by the subtractor 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 ratio, 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.

[0047] The subtractor 41 is an example of a “command value correction unit” described in the claims, and the subtractor 42 , the current control unit 43 , the PWM control unit 44 , and the inverter 45 are examples of a “drive unit” described in the claims.

[0048] The terminal position learning unit 46 learns the 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 the virtual rack end position when turning right and has a positive value. θevl is the virtual rack end position when turning left and has a negative value.

[0049] In addition, an error (sometimes referred to as "offset error") sometimes occurs between the center position of the actual left and right rack end positions (sometimes referred to as "rack neutral position" below) and the neutral position of the steering angle θh of the column shaft detected by the steering angle sensor 14 (sometimes referred to as "steering angle neutral position" below).

[0050] Such an offset error is generated, for example, due to 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.

[0051] The control rotational displacement setting unit 47 sets the control rotational displacement θr when the corrected steering angle θh1 is close to the rack end position and is within the range for implementing the impact mitigation control (hereinafter sometimes referred to as the "impact mitigation control implementation range"). The control rotational displacement θr represents the degree of proximity between the corrected steering angle θh1 and the virtual rack end positions θevr, θevl.

[0052] 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.

[0053] 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).

[0054] The control rotational displacement θr is set to zero ("0"), for example, outside the impact mitigation control implementation range (i.e., θthL≤θh1≤θthR). In 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, in 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 (i.e., the larger the absolute value |θr|) is set.

[0055] In other words, in the range where the correction steering angle θh1 is larger than the threshold θthR, the positive control rotational displacement θr increases in accordance with the increase in the correction steering angle θh1, and in the range where the correction steering angle θh1 is smaller than the threshold θthL, the negative control rotational displacement θr decreases in accordance with the decrease in the correction steering angle θh1.

[0056] 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 larger than the threshold θthR, and may set the difference θh1-θthL as the control rotational displacement θr when the correction steering angle θh1 is smaller than the threshold θthL.

[0057] 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.

[0058] 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.

[0059] 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, and a limiter 65.

[0060] The spring constant table 60 is a data table for calculating the spring constant k0 of the steering system. Figure 5As 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.

[0061] 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 gradually and relatively gently as a whole (non-linear increase) as the control rotation displacement θr increases. 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.

[0062] The spring constant k0 from the spring constant table 60 is multiplied by the control rotation displacement θr in 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 in 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 limiter 65, and the impact relaxation control output Iref2 whose maximum value is limited is set.

[0063] 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.

[0064] 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 less than or equal to 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.

[0065] For example, the first virtual rack end candidate can be obtained when the column output shaft torque Tc applied to the column output shaft 2o is equal to or smaller than the predetermined value T1.

[0066] 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 less than a first specified value and the operating force acting on the steering operating unit is less than a third specified value, as a first candidate θm1 for the virtual rack end.

[0067] 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.

[0068] In addition, the terminal position learning unit 46 calculates the steering angle that is farthest from the steering angle neutral position among the angles after the steering angle θh detected by the steering angle sensor 14 is offset by the second specified value in the direction of the steering angle neutral position (i.e., the angle obtained by subtracting the second specified value from the maximum steering angle in the case of a positive steering angle θh, and the angle obtained by adding the second specified value to the minimum steering angle in the case of a negative steering angle θh) as the second candidate θm2 for the virtual rack end.

[0069] As the second predetermined value, for example, a maximum value considered to be an error may be set.

[0070] 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.

[0071] 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.

[0072] Figure 6 : is a block diagram showing an example of the functional structure 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.

[0073] The output shaft torque calculation section 70 calculates the column output shaft torque Tc applied to the column output shaft 2 o.

[0074] For example, the output shaft torque calculation unit 70 can calculate the motor torque as the column output shaft torque Tc, which is estimated by multiplying the current command value Iref3 to 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.

[0075] 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 to 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.

[0076] 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.

[0077] The output shaft torque calculation unit 70 may perform second-order differentiation on the detection value of the angle sensor of the motor 20 to obtain the motor angular acceleration, estimate the inertia torque by multiplying the inertia moment, and add the inertia torque to the column output shaft torque Tc obtained in the above manner.

[0078] 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.”

[0079] 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.

[0080] The selection unit 71 selects one of the correction steering angle θh1 and the output of the delay unit 73 based on 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.

[0081] For example, the selection unit 71 may select and output the corrected steering angle θh1 calculated based on the detected steering angle θh to the first storage unit 72 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, and output the output of the delay unit 73 to the first storage unit 72 in other cases.

[0082] 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.

[0083] Therefore, if the corrected steering angle θh1 calculated when the column output shaft torque Tc is less than the predetermined value T1 and the steering torque Th is less than the predetermined value T2 is farther from the steering angle neutral position than the first candidate θm1 previously stored in the first storage unit 72, the first candidate θm1 stored in the first storage unit 72 is updated using the corrected steering angle θh1.

[0084] 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.

[0085] 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 delayed steering angle θo and outputs the first candidate θm1′ with the limited change rate to the third storage unit 78 .

[0086] The correction position calculation unit 75 calculates the angle obtained by shifting the correction steering angle θh1 in the direction of the steering angle neutral position by the second predetermined value. That is, when the correction steering angle θh1 is positive, the angle obtained by subtracting the second predetermined value from the correction steering angle θh1 is output. When the correction steering angle θh1 is negative, the angle obtained by adding the second predetermined value to the correction steering angle θh1 is output.

[0087] 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.

[0088] Therefore, if the output of the correction position calculation unit 75 (i.e., the angle after the correction steering angle θh1 is offset by the second specified value in the direction of the steering angle neutral position) is farther away from the steering angle neutral position than the second candidate θm2 previously stored in the second storage unit 76, the output of the correction position calculation unit 75 is used to update the second candidate θm2 stored in the second storage unit 76.

[0089] 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 .

[0090] The limiter 79 limits the magnitude of the steering angle θo output from the third storage unit 78 and outputs the same as virtual rack end positions θevr and θevl.

[0091] Reference Figure 7 (a) and Figure 7(b) describes an example of learning the virtual rack end of the present embodiment. For simplicity of description, the following case is described: the offset error Ofs is set to 0 (i.e., the steering angle θh = the corrected steering angle θh1), and if 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 previously stored in the first storage unit 72, the first candidate θm1 is updated.

[0092] 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.

[0093] During the yaw increase steering, when the steering angle θh exceeds θ1, the column output shaft torque Tc exceeds the specified value T1, and during the subsequent return steering, when the steering angle θh is less than θ2 (θ2>θ1), the column output shaft torque Tc is less than the specified value T1.

[0094] Figure 7 (b) is produced Figure 7 1 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 (a). 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.

[0095] If the steering angle θh increases and the yaw increase steering starts at time t1, 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). During the yaw increase steering process, the first candidate θm1 (one-dot chain line) increases to θ1.

[0096] In addition, an angle obtained by subtracting a second predetermined value from the steering angle θh is learned as a second candidate θm2 (two-dot chain line).

[0097] Therefore, during the period (time t1-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. If the second candidate θm2 exceeds the first candidate θm1' at time t2, the second candidate θm2 is selected as the output θo (solid line).

[0098] Then, 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.

[0099] 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.

[0100] After that, when the steering angle θh starts to decrease and the wheel steering 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).

[0101] 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.

[0102] When the output θo (solid line) of the third storage unit 78 learned as described above, i.e., the virtual rack end positions θevr and θevl before being limited by the limiter 79, are compared with the case where the angle obtained by subtracting the second predetermined value (e.g., the maximum error estimated value) from the steering angle θh is learned (double-dashed line), the output θo of the third storage unit 78 can be learned as a steering angle further away from the steering angle neutral point. Therefore, a steering angle closer to the actual rack end position can be learned as the virtual rack end positions θevr and θevl.

[0103] Next, the operation when an offset error occurs between the rack neutral position and the steering angle neutral position will be described. Figure 8 (a) is a conceptual diagram of the actual rack end position. Figure 8 (b) is a conceptual diagram of the virtual rack end positions θevr and θevl when there is no offset error. Figure 8 (c) is a conceptual diagram of virtual rack end positions θevr and θevl when there is an offset error.

[0104] exist Figure 8 (b) and Figure 8 In (c), the position of "0[deg]" indicates the neutral position of the steering angle. Figure 8 (d)~ Figure 8 The same is true for (g). Figure 8The steering angle neutral position of (b) is consistent with the rack neutral position (the center position of the actual rack end position). Figure 8 The steering angle neutral position of (c) is offset from the rack neutral position to the right by Δθ. That is, if the steering angle is turned to the left by Δθ from the steering angle neutral position, the rack 5b is in the rack neutral position.

[0105] If an offset error occurs, the shock mitigation control cannot be performed normally. Figure 8 In the example of (c), the right virtual rack end position θevr is located outside the actual rack end position, so the required reduction of shock and abnormal noise cannot be achieved.

[0106] 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 .

[0107] Reference Figure 6 The stroke calculation unit 80 calculates the distance between the right virtual rack end position θevr and the left virtual rack end position θevl as the rack stroke St.

[0108] The offset error calculation unit 81 compares the rack stroke St with a predetermined rack stroke maximum value.

[0109] As the rack stroke maximum value, a maximum value that can be calculated as the rack stroke St may be set in consideration of possible errors (deviations) in the left and right virtual rack end positions θevl and θevr.

[0110] When the rack stroke St exceeds the rack stroke maximum value, the offset error calculation unit 81 determines that an offset error has occurred. Then, the difference obtained by subtracting the rack stroke maximum value from the rack stroke St is calculated as the offset error Ofs=(rack stroke St-rack stroke maximum value).

[0111] Figure 8 (d) is a conceptual diagram of a state where the left virtual rack end position θevl is learned after an offset error occurs.

[0112] 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 maximum rack stroke value. The offset error calculation unit 81 calculates the difference (rack stroke St-rack stroke maximum value) obtained by subtracting the rack stroke St from the rack stroke St as the offset error Ofs.

[0113] In the following description, the virtual rack end position learned when the rack stroke St exceeding the maximum rack stroke value is calculated among the left and right virtual rack end positions is sometimes expressed as "one virtual rack end position". In addition, the virtual rack end position of the other side of the left and right virtual rack end positions that is not the virtual rack end position of one side is sometimes expressed as "the other virtual rack end position".

[0114] like Figure 8 As 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.

[0115] 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 .

[0116] 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. Figure 8 (e) of the present invention will explain these correction processes.

[0117] The offset error Ofs is subtracted from the steering angle θh by the subtractor 82, as shown in FIG. Figure 8 As shown in (e), the steering angle neutral position (the position of "0[deg]") moves.

[0118] On the other hand, Figure 8 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 Figure 8 If the steering angle neutral position is moved as in (e), the left virtual rack end position θevl needs to be corrected accordingly.

[0119] 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 by the offset error Ofs. Since the virtual rack end position on the left side is a negative value, the offset error Ofs is added for 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.

[0120] 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.

[0121] In addition, the terminal position correction unit 83 adjusts the other virtual rack end position (at Figure 8 In 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 minimum rack stroke value. The minimum rack stroke value can be set to, for example, the minimum value of the deviation of the value that can be calculated as the rack stroke St. In this way, the virtual rack end position of the other side can be corrected to be closer to the inside than the actual rack end position.

[0122] Reference Figure 8 (f) If 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.

[0123] The offset error calculation unit 81 updates the offset error Ofs by adding the change amount Δθev1 to the offset error Ofs before learning the new left virtual rack end position θev1. As a result, the steering angle neutral position is further moved by the change amount Δθev1.

[0124] 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.

[0125] 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.

[0126] In addition, at the other virtual rack end position (at Figure 8 In the example of (f), 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 prescribed rack stroke minimum value.

[0127] Reference Figure 8 (g). Figure 8 (e), Figure 8As described in (f) of FIG. 1 , after correcting (resetting) the right virtual rack end position θevr (i.e., the other virtual rack end position) in such a way that the rack stroke St becomes the predetermined rack stroke minimum value, as shown in FIG. Figure 8 As shown in (g), when a new right virtual rack end position θevr 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.

[0128] 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 , or the steering angle θo stored in the third storage unit 78 .

[0129] Thus, only the right virtual rack end position θevr is adjusted to be away from the steering angle neutral position.

[0130] Furthermore, after newly learning the right virtual rack end position θevr (i.e., the other virtual rack end position), the terminal position correction unit 83 stops correcting (resetting) the right virtual rack end position θevr so that the rack stroke St becomes the specified rack stroke minimum value.

[0131] After that, even if a new left virtual rack end position θevl (i.e., one virtual rack end position) 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 minimum value of the specified rack stroke, but Figure 8 (f) Similarly, the offset error Ofs is updated (i.e., the steering angle neutral position is corrected), and the left virtual rack end position is corrected. 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.

[0132] In addition, if a new right virtual rack end position θevr (i.e., the other virtual rack end position) is further learned, the steering angle neutral position and the left virtual rack end position θevl (i.e., the one virtual rack end position) remain unchanged, and only the right virtual rack end position θevr changes.

[0133] (Variation Example)

[0134] The selection unit 71 of the terminal position learning unit 46 selects one of the corrected steering angle θh1 and the output of the delay unit 73 based on the values ​​of the column output shaft torque Tc and the steering torque Th, and outputs it to the first storage unit 72. Here, with respect to the corrected steering angle θh1, the deformation amount of the mechanism part caused by the column output shaft torque Tc may also be corrected and input to the selection unit 71. The selection unit 71 may select one of the corrected steering angle θh1 and the output of the delay unit 73 after the deformation amount is corrected based on the values ​​of the column output shaft torque Tc and the steering torque Th, and output it to the first storage unit 72. In this way, the influence of the torsion of the steering mechanism can be further reduced. The deformation amount can be calculated based on the column output shaft torque Tc and the rigidity (spring constant) of the mechanism part. Figure 7 In the equation ( θ1 ) , the rigidity is the ratio of the change in the column output shaft torque Tc at the point indicated by the symbol θ1 or θ2 to the change in the steering angle θh, and can be obtained by experiments or the like.

[0135] Figure 7 The characteristics shown change 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 may be obtained by experiment or the like and stored as a steering speed correction amount characteristic, and the steering angle θh may be corrected according to the steering speed and the steering speed correction amount characteristic.

[0136] By comparing the threshold values ​​θthR and θthL set to a predetermined value Δθ from the virtual rack end position toward the rack center with the correction steering angle θh1, it is determined whether the correction steering angle θh1 is near the virtual rack end positions θevr and θevl. After learning the virtual rack end positions θevr and θevl, the reference point of the steering angle θh from the steering angle sensor 14 may change (error). This occurs, for example, when the straight driving state is detected and the reference point of the steering angle θh is corrected. If such a change (error) occurs, the impact mitigation control output may not have the desired characteristics.

[0137] Therefore, the threshold value θthR = θevr - Δθ1 and the threshold value θthL = θevl + Δθ1 can be set using the prescribed value Δθ1 obtained by adding the value Δm after considering the change (error) of the reference point of the steering angle θh to the prescribed value Δθ. The value Δm is an example of the "fourth prescribed value" described in the claims. The threshold values ​​θthR and θthL are positions obtained by setting the prescribed value Δθ1 from the virtual rack end position toward the center of the rack. In this way, even if there is a change (error) in the reference point of the steering angle θh, the impact mitigation control output becomes the desired characteristic.

[0138] 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 is a steering control device that generates a force for steering the steering wheel of a vehicle through an actuator. For example, it can also be applied to a steer-by-wire (SBW) type steering device that mechanically separates the steering wheel from the steering wheel. In this case, the steering torque Th may not be added to the motor torque when the column output shaft torque Tc is calculated.

[0139] (Effects of Embodiments)

[0140] (1) A steering control device comprises: a position detection unit that detects a steering position of a steering mechanism of a vehicle; and a terminal position learning unit (46) that learns the terminal position of the steering mechanism based on the steering position detected by the position detection unit. The terminal position learning unit (46) comprises: a first storage unit (72) that stores a steering position farthest from a neutral position of the steering mechanism among the steering positions detected by the position detection unit when a rotational force applied to the steering mechanism is less than a first specified value; a second storage unit (76) that stores a steering position farthest from a neutral position among the positions after the steering position detected by the position detection unit is shifted by a second specified value in a neutral direction of the steering mechanism; and a third storage unit (78) that stores the steering position stored in the first storage unit (72) and the second storage unit (76) that is farther from the neutral position as the terminal position stored in the terminal position learning unit (46).

[0141] This makes it possible to learn a virtual rack end position that is less affected by the torsion of the steering mechanism caused by the rotational force applied to the steering mechanism. Therefore, the error between the virtual rack end position and the actual rack end position can be reduced.

[0142] When the rotational force applied to the steering mechanism is less than a first predetermined value, the steering position detected by the position detection unit can be corrected with a correction amount (first correction amount) corresponding to the rotational force. In addition, the steering position can also be corrected with a correction amount (second correction amount) corresponding to the steering speed. At least one of the first correction amount and the second correction amount can be used. In this way, it is possible to learn a virtual rack end position that further reduces the torsion of the steering mechanism caused by the rotational force applied to the steering mechanism and the influence caused by the steering speed.

[0143] (2) The terminal position learning unit 46 may also include: a stroke calculation unit 80, which calculates the rack stroke St of the steering mechanism based on the steering position detected by the position detection unit and the other terminal position of the left and right terminal positions stored in the third storage unit 78 when the position detection unit detects a steering position that is farther from the neutral position than the terminal position of one of the left and right terminal positions of the steering mechanism stored in the third storage unit 78; a steering position correction unit 82, which corrects the steering position detected by the position detection unit based on the excess amount of the rack stroke St over the threshold when the rack stroke St calculated by the stroke calculation unit 80 exceeds the threshold; and a terminal position correction unit 83, which corrects the terminal position of one side stored in the first storage unit 72, the second storage unit 76 and the third storage unit 78 in a manner that separates the terminal position of the other side from the terminal position of the other side by a specified interval when the rack stroke St calculated by the stroke calculation unit 80 exceeds the threshold.

[0144] Thus, even if there is an offset error between the rack neutral position and the steering angle neutral position, it is possible to perform shock alleviation control suitable for the state of the vehicle after the virtual rack end position is learned so as to absorb the offset error.

[0145] (3) The terminal position learning unit 46 can store the steering position farthest from the neutral position of the steering mechanism among the steering positions detected by the position detection unit in the first storage unit 72 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 of the vehicle is less than a third specified value.

[0146] Thereby, it is possible to learn a virtual rack end position in which the rotational force applied to the steering mechanism and the operation force acting on the steering operation portion have little influence on the torsion of the steering mechanism.

[0147] (4) The terminal position learning unit 46 may calculate the rotational force applied to the steering mechanism based on the current command value for the motor 20 that drives the steering mechanism or the current flowing through the motor 20 .

[0148] Alternatively, the terminal position learning unit 46 may calculate the rotational force applied to the steering mechanism based on the sum of a rotational torque calculated based on a current command value for the motor 20 driving the steering mechanism or a current flowing through the motor 20 and an operating force acting on the steering operating unit.

[0149] The terminal position learning unit 46 may add the inertia torque obtained from the angular acceleration and the inertia moment of the steering mechanism to the above-mentioned rotational force.

[0150] Thereby, the virtual rack end position can be learned based on the rotational force applied to the steering mechanism.

[0151] Description of Reference Numerals

[0152] 1…steering wheel, 2i…column input shaft, 2o…column output shaft, 3…reduction gear, 4…intermediate shaft, 4a, 4b…universal joint, 4c…shaft member, 5…pinion rack mechanism, 5a…pinion, 5b…rack, 6a, 6b…steering tie rod, 7a, 7b…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, 42, 82…subtractor, 43…current control unit, 44…PWM control unit, 45 …inverter, 46…terminal position learning unit, 47…controlled rotation displacement setting unit, 48…differentiating unit, 49…impact mitigation control unit, 50…current detector, 60…spring constant table, 61, 63…multiplier, 62…viscosity constant table, 64…adder, 65, 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.

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; and 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, The terminal position learning unit comprises: a first storage unit for storing, among the steering positions detected by the position detection unit when the rotational force applied to the steering mechanism is equal to or less than a first predetermined value, a steering position farthest from a neutral position of the steering mechanism; a second storage unit for storing a steering position farthest from the neutral position among positions obtained by shifting the steering position detected by the position detection unit in the neutral direction of the steering mechanism by a second predetermined value; as well as A third storage unit stores, as the terminal position stored in the terminal position learning unit, one of the steering positions stored in the first storage unit and the second storage unit that is farther from the neutral position.

2. The steering control device according to claim 1, characterized in that: The terminal position learning unit comprises: a stroke calculation unit that calculates the stroke of the steering mechanism based on the steering position detected by the position detection unit and the other of the left and right terminal positions stored in the third storage unit, when the position detection unit detects the steering position that is farther from the neutral position than one of the left and right terminal positions of the steering mechanism stored in the third storage unit; a steering position correction unit that corrects the steering position detected by the position detection unit based on an excess amount of the stroke over the threshold value when the stroke calculated by the stroke calculation unit exceeds a threshold value; and A terminal position correction unit that corrects the terminal position of the other party stored in the first storage unit, the second storage unit, and the third storage unit so that the terminal position of the one party is separated from the terminal position of the other party by a predetermined interval when the stroke calculated by the stroke calculation unit exceeds the threshold.

3. The steering control device according to claim 1, characterized in that: The terminal position learning unit stores in the first storage unit the steering position farthest from the neutral position of the steering mechanism among the steering positions detected by the position detection unit when the rotational force is less than the first specified value and the operating force acting on the steering operating unit of the vehicle is less than a third specified value.

4. The steering control device according to any one of claims 1 to 3, characterized in that: The terminal position learning unit calculates the rotational force based on a current command value for an actuator driving the steering mechanism or a current flowing through the actuator.

5. The steering control device according to any one of claims 1 to 3, characterized in that: The terminal position learning unit calculates the rotational force based on a sum of a rotational torque calculated based on a current command value for an actuator driving the steering mechanism or a current flowing through the actuator and an operation force acting on a steering operation unit of the vehicle.

6. The steering control device according to claim 4, characterized in that: The terminal position learning unit adds an inertia torque obtained from an angular acceleration and an inertia moment of the steering mechanism to the rotational force.

7. The steering control device according to claim 1, characterized in that: The terminal position learning unit uses at least one of a first correction amount corresponding to the rotational force and a second correction amount corresponding to the steering speed to correct the steering position detected by the position detection unit when the rotational force is below the first specified value to obtain a corrected steering position, and stores the steering position farthest from the neutral position of the steering mechanism among the corrected steering positions in the first storage unit.

8. The steering control device according to claim 3, characterized in that: The terminal position learning unit uses at least one of a first correction amount corresponding to the rotational force and a second correction amount corresponding to the steering speed to correct the steering position detected by the position detection unit when the rotational force is less than the first specified value and the operating force acting on the steering operating part of the vehicle is less than the third specified value to obtain the corrected steering position, and stores the steering position farthest from the neutral position of the steering mechanism among the corrected steering positions in the first storage unit.

9. The steering control device according to any one of claims 1 to 3, 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 applied to a steering operation unit of 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 the drive of the actuator based on the current command value corrected by the command value correction unit.

10. The steering control device according to claim 9, characterized in that: The steering control device includes a command value correction unit, which sets the position after the terminal position is moved by a fourth specified value in the neutral direction of the steering mechanism as a virtual terminal position, and corrects the current command value calculated by the command value calculation unit when the steering position is near the virtual terminal position.

11. 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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