Steering control device and electric power steering device

Abstract

A steering control device (11) comprises: a target steering torque setting unit (22) that sets a target steering torque; a calculation unit (23) that calculates an assist steering torque which causes a steering torque to follow the target steering torque; and a current drive unit (12) that controls a current which flows through a motor to generate the assist steering torque. The target steering torque setting unit is provided with: a first torque calculation unit that determines a first torque on the basis of a post-shift steering angle, which is obtained by multiplying the rotational angular velocity of the motor by a steering angle gain to calculate a first shift amount that is the shift amount of the steering angle of the steering wheel and then adding the first shift amount to the steering angle, and a base map, in which a base torque exhibits the characteristic of gradually increasing in accordance with the post-shift steering angle; a second torque calculation unit that uses the rotational angular velocity of the motor to determine a second torque for imparting hysteresis to the target steering torque; and a target steering torque calculation unit that adds the first torque and the second torque and outputs the target steering torque.

Description

[Technical field]

[0001] The present disclosure relates to a steering control device and an electric power steering device. [Background technology]

[0002] An electric power steering device includes a motor that generates a steering assist torque for the steering wheel and a steering control device that controls the motor, and applies a steering assist force to the steering mechanism of a vehicle such as an automobile. Such an electric power steering device has the advantage of being lighter and more compact than a hydraulic power steering device.

[0003] The following Patent Document 1 discloses an electric power steering device that is capable of obtaining a constant steering feeling without being affected by changes in mechanical characteristics due to road surface conditions or aging deterioration of the steering mechanism. This electric power steering device obtains a constant steering feeling by setting the characteristics of the steering force relative to the steering angle (hereinafter referred to as "steering force angle characteristics") to be desired steering force characteristics (target steering force angle characteristics). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6129409 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in the electric power steering device disclosed in the above-mentioned Patent Document 1, the target steering force is calculated using a steering force characteristic model including a spring component, a viscosity component, and a friction component. On the other hand, in order to adjust the on-center feeling near the steering neutral position, it is necessary to increase or decrease the viscosity component (damper torque) or the friction component (friction torque). Here, since the viscosity component or the friction component is adjusted for a purpose other than the on-center feeling, there is a problem that changing the viscosity component or the friction component to adjust the on-center feeling may disrupt the steering feeling that has already been set.

[0006] The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a steering control device and an electric power steering device that can adjust the on-center feeling with a simple configuration while minimizing the impact on the steering feeling that has already been set. [Means for solving the problem]

[0007] In order to solve the above problem, a steering control device according to one aspect of the present disclosure includes a target steering torque setting unit that sets a target steering torque for a steering wheel, a calculation unit that calculates a steering assist torque required for making the steering torque follow the target steering torque based on a deviation between the target steering torque and a steering torque acting on a steering shaft of the steering wheel, and a current drive unit that controls a current flowing to a motor to generate the steering assist torque for the steering wheel, and the target steering torque setting unit calculates a target steering torque for the steering wheel by multiplying a rotational angular velocity of the motor by a steering angle gain. the first torque calculation unit calculates a first shift amount, which is a shift amount of a steering angle of a wheel, and calculates a first torque based on a post-shift steering angle obtained by adding the first shift amount to the steering angle and a base map showing a characteristic in which the magnitude of the base torque gradually increases as the magnitude of the post-shift steering angle increases; a second torque calculation unit calculates a second torque for imparting hysteresis to the target steering torque by using a rotational angular velocity of the motor; and a target steering torque calculation unit adds the first torque and the second torque together and outputs the sum as the target steering torque.

[0008] In addition, a power steering device according to one aspect of the present disclosure includes a steering torque detection unit that detects a steering torque acting on a steering shaft of a steering wheel, a steering state detection unit that detects a steering angle of a steering wheel, a motor that applies a steering assist torque to the steering shaft, a motor rotational angular velocity detection unit that detects the rotational angular velocity of the motor, and the above-mentioned steering control device that controls driving of the motor based on the detected steering torque, steering angle, and rotational angular velocity of the motor. Effect of the Invention

[0009] According to the present disclosure, it is possible to adjust the on-center feeling with a simple configuration while minimizing the effect on the steering feeling that has already been set. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram showing a configuration of a main part of an electric power steering device according to a first embodiment of the present disclosure. [Diagram 2] 1 is a block diagram showing a configuration of a main part of a control unit as a steering control device according to a first embodiment of the present disclosure. [Diagram 3] 5 is a flowchart showing an overview of the operation of a control unit serving as a steering control device according to embodiment 1 of the present disclosure. [Figure 4] 2 is a block diagram showing an example of an internal configuration of a target steering torque setting unit according to the first embodiment of the present disclosure. FIG. [Diagram 5] FIG. 4 is a diagram showing an example of a steering angle shift gain used in a first torque calculation unit in the first embodiment of the present disclosure. [Figure 6A] FIG. 4 is a block diagram showing a configuration example of a base calculation unit provided in a first torque calculation unit in the first embodiment of the present disclosure. [Figure 6B] FIG. 11 is a block diagram showing another example configuration of the base calculation unit provided in the first torque calculation unit in the first embodiment of the present disclosure. [Figure 7A]FIG. 6B is a diagram showing an example of a base map used in the base calculation unit shown in FIG. 6A. [Figure 7B] FIG. 6C is a diagram showing an example of a base map used in a base calculation unit shown in FIG. 6B. [Figure 8] FIG. 4 is a diagram showing an example of a hysteresis gain used in a second torque calculation section in the first embodiment of the present disclosure. [Figure 9A] FIG. 4 is a block diagram showing an example configuration of a third torque calculation unit according to the first embodiment of the present disclosure. [Figure 9B] FIG. 11 is a block diagram showing another example configuration of the third torque calculation unit in the first embodiment of the present disclosure. [Figure 10A] FIG. 9B is a diagram showing an example of a damper gain map used in the third torque calculation section shown in FIG. 9A. [Figure 10B] FIG. 9C is a diagram showing an example of a damper torque map used in a third torque calculation section shown in FIG. 9B. [Figure 11] 4 is a block diagram showing an example of an internal configuration of a torque feedback calculation unit according to the first embodiment of the present disclosure. FIG. [Figure 12] FIG. 4 is a diagram showing a relationship between a steering angle when a steering wheel is steered and a target steering torque in the first embodiment of the present disclosure. [Figure 13] FIG. 3 is a diagram showing a relationship between a steering angle when a steering wheel is steered and a target steering torque (base torque) in the first embodiment of the present disclosure. [Figure 14] 13 shows the movement locus of the steering angle when the driver releases the steering wheel from a turned state. [Figure 15] FIG. 11 is a block diagram showing a configuration of a steering angle shift calculation unit according to a second embodiment of the present disclosure. [Figure 16] FIG. 11 is a diagram showing an example of a steering angle application range adjustment map used in a steering angle shift calculation section in the second embodiment of the present disclosure. [Figure 17] FIG. 11 is a diagram showing a relationship between a steering angle when a steering wheel is steered and a target steering torque (base torque) in the second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a steering control device and an electric power steering device according to embodiments of the present disclosure will be described in detail with reference to the drawings. In each embodiment, the same or corresponding parts are denoted by the same reference numerals, and descriptions of overlapping parts will be omitted.

[0012] [First embodiment] <Electric power steering device> Fig. 1 is a block diagram showing a configuration of a main part of an electric power steering device according to embodiment 1 of the present disclosure. As shown in Fig. 1, the electric power steering device PS according to this embodiment includes a steering wheel 1, a steering shaft 2, steered wheels 3, a steering angle sensor 4, a torque sensor 5 (steering torque detection unit), a motor 6, a reduction gear 7, a vehicle speed sensor 8, a current sensor 9, a motor rotation angle sensor 10, and a control unit 11 (steering control device).

[0013] The steering wheel 1 is a so-called handle, and is operated by the driver of the vehicle to apply a steering angle to the steered wheels 3 of the vehicle. The steering shaft 2 is connected to the steering wheel 1, and rotates in response to the rotation of the steering wheel 1. The steered wheels 3 are provided on both the left and right sides of the vehicle, and are steered in response to the rotation of the steering shaft 2. The mechanism for steering the steered wheels 3, including the steering wheel 1 and the steering shaft 2, is referred to as the "steering".

[0014] The steering angle sensor 4 is disposed on the steering wheel 1 and detects the steering angle of the steering wheel 1. The torque sensor 5 is disposed on the steering shaft 2 and detects the steering torque acting on the steering shaft 2. The motor 6 is connected to the steering shaft 2 via a reduction gear mechanism 7 and applies a steering assist torque to the steering shaft 2. The vehicle speed sensor 8 detects the vehicle speed of the vehicle. The current sensor 9 detects the current flowing through the motor 6. The motor rotation angle sensor 10 detects the rotation angle of the motor 6.

[0015] The control unit 11 controls the driving of the motor 6 based on the detection results of the steering angle sensor 4, the torque sensor 5, the vehicle speed sensor 8, the current sensor 9, and the motor rotation angle sensor 10 to generate a steering assist torque for the steering. Specifically, the control unit 11 calculates the steering assist torque to be applied to the steering shaft 2 based on the above detection results, and controls the current of the motor 6 required to generate the steering assist torque. The control unit 11 will be described in detail below.

[0016] Steering control device Fig. 2 is a block diagram showing a configuration of a main part of a control unit as a steering control device according to the first embodiment of the present disclosure. As shown in Fig. 2, the control unit 11 includes a differentiator 24a, a target steering torque setting unit 22, a torque feedback calculation unit 23 (calculation unit), and a current driving unit 12. The differentiator 24a differentiates the rotation angle of the motor 6 detected by the motor rotation angle sensor 10 to calculate the rotation angular velocity of the motor 6 (hereinafter referred to as "motor rotation angular velocity"). The differentiator 24a, together with the motor rotation angle sensor 10, constitutes a motor rotation angular velocity detection unit 24 that detects the motor rotation angular velocity.

[0017] The target steering torque setting unit 22 sets a target steering torque for the steering. Here, the steering angle of the steering wheel 1 detected by a steering state detection unit 21 including the steering angle sensor 4, the vehicle speed of the vehicle detected by the vehicle speed sensor 8, and the motor rotation angular velocity detected by a motor rotation angular velocity detection unit 24 are input to the target steering torque setting unit 22. The target steering torque setting unit 22 sets a target steering torque for the steering using these detection results. The details of the target steering torque setting unit 22 will be described later.

[0018] The torque feedback calculation unit 23 calculates a steering assist torque required for making the steering torque follow the target steering torque, based on the deviation between the target steering torque set by the target steering torque setting unit 22 and the steering torque detected by the torque sensor 5. The current driving unit 12 controls the current flowing through the motor 6 in order to generate the steering assist torque calculated by the torque feedback calculation unit 23 in the steering.

[0019] Incidentally, among the components of the control unit 11, the components excluding the current driver 12 (the differentiator 24a, the target steering torque setting unit 22, and the torque feedback calculation unit 23) are realized by a microcomputer having a CPU (Central Processing Unit) and a memory. The memory provided in the microcomputer may include both a volatile memory and a non-volatile memory. The current driver 12 is realized by, for example, an analog circuit having a plurality of switching elements such as FETs (field effect transistors).

[0020] Fig. 3 is a flowchart showing an outline of the operation of the control unit as a steering control device according to the first embodiment of the present disclosure. The process of the flowchart shown in Fig. 3 is repeatedly performed at a predetermined control period. When the process is started, first, the control unit 11 acquires the steering angle detected by the steering state detection unit 21, the vehicle speed detected by the vehicle speed sensor 8, the steering torque detected by the torque sensor 5, and the motor rotation angle detected by the motor rotation angle sensor 10. Then, the differentiator 24a of the control unit 11 differentiates the acquired motor rotation angle to obtain the motor rotation angular velocity (step S11).

[0021] Next, the target steering torque setting unit 22 of the control unit 11 sets a target steering torque using the acquired steering angle and vehicle speed, and the motor rotation angular velocity obtained by differentiation (step S12). Next, the torque feedback calculation unit 23 of the control unit 11 calculates a steering assist torque required to make the steering torque follow the target steering torque, based on the deviation between the target steering torque set by the target steering torque setting unit 22 and the steering torque detected by the torque sensor 5 (step S13). Next, the current driving unit 12 of the control unit 11 controls the current flowing through the motor 6 to generate the steering assist torque calculated by the torque feedback calculation unit 23 in the steering (step S16).

[0022] 4 is a block diagram showing an example of an internal configuration of the target steering torque setting unit in the first embodiment of the present disclosure. As shown in FIG. 4, the target steering torque setting unit 22 includes a first torque calculation unit 25, a second torque calculation unit 28, a third torque calculation unit 29, and a target steering torque calculation unit 30.

[0023] The first torque calculation unit 25 includes a steering angle shift calculation unit 26 and a base calculation unit 27, and calculates a first torque, which is a base torque, using the steering angle, the motor rotational angular velocity, and the vehicle speed. The steering angle shift calculation unit 26 includes a multiplier 26a and an adder 26b, and calculates a post-shift steering angle. The multiplier 26a multiplies the motor rotational angular velocity by a steering angle shift gain Dg (steering angle gain) to calculate a first shift amount, which is a shift amount of the steering angle of the steering wheel 1. The adder 26b adds the first shift amount to the steering angle to calculate a post-shift steering angle. The base calculation unit 27 calculates the first torque based on the post-shift steering angle calculated by the steering angle shift calculation unit 26 and a base map that indicates a characteristic in which the magnitude of the base torque gradually increases as the magnitude of the post-shift steering angle increases.

[0024] Fig. 5 is a diagram showing an example of a steering angle shift gain used in the first torque calculation unit in the first embodiment of the present disclosure. The steering angle shift gain Dg shown in Fig. 5 gradually increases in value as the vehicle speed increases up to a certain vehicle speed, but becomes constant when the vehicle speed exceeds the certain vehicle speed. When such a steering angle shift gain Dg is used, the steering angle shift gain Dg is changed in accordance with the vehicle speed in the first torque calculation unit 25. Note that the steering angle shift gain Dg shown in Fig. 5 changes in value depending on the vehicle speed, but may be a gain that does not change regardless of the vehicle speed.

[0025] Fig. 6A is a block diagram showing a configuration example of a base calculation unit provided in the first torque calculation unit in the first embodiment of the present disclosure. The base calculation unit 27 shown in Fig. 6A includes a base map 27a, a sign determination unit 27b, and a multiplier 27c. The base map 27a is a map in which a base torque according to a post-shift steering angle is defined. Fig. 7A is a diagram showing an example of a base map used in the base calculation unit shown in Fig. 6A. The base map 27a shown in Fig. 7A has a characteristic that the magnitude of the base torque in the positive direction gradually increases as the magnitude (absolute value) of the post-shift steering angle increases.

[0026] Also, different base maps 27a are prepared for each vehicle speed. In the example shown in FIG. 7A, different base maps 27a are prepared for each of "low vehicle speed", "medium vehicle speed", and "high vehicle speed". When such base maps 27a are prepared, the first torque calculation unit 25 changes the base map 27a according to the vehicle speed. However, it is not necessary to prepare different base maps 27a for each vehicle speed. The sign determination unit 27b determines whether the sign of the post-shift steering angle is positive (+1) or negative (-1). The multiplier 27c multiplies the magnitude of the base torque obtained using the base map 27a by the sign determined by the sign determination unit 27b.

[0027] In such a base calculation unit 27, one base map 27a is specified according to the input vehicle speed. The magnitude of a base torque (first torque) is obtained using the post-shift steering angle input to the base calculation unit 27 and the specified base map 27a. In addition, the sign of the input post-shift steering angle is determined by a sign determination unit 27b. Then, the magnitude of the base torque (first torque) obtained using the base map 27a is multiplied by the sign of the post-shift steering angle determined by the sign determination unit 27b in a multiplier 27c, thereby obtaining the base torque (first torque).

[0028] Fig. 6B is a block diagram showing another example of the configuration of the base calculation unit provided in the first torque calculation unit in the first embodiment of the present disclosure. The base calculation unit 27 shown in Fig. 6B includes only the base map 27a. The base map 27a shown in Fig. 6B is a map in which a base torque according to a post-shift steering angle is defined, similar to the base map 27a shown in Fig. 6A. Fig. 7B is a diagram showing an example of the base map used in the base calculation unit shown in Fig. 6B.

[0029] As shown in FIG. 7B, the base map 27a shown in FIG. 6B has a characteristic that the magnitude of the base torque in the positive direction gradually increases as the magnitude of the steering angle in the positive direction after the shift increases, and the magnitude of the base torque in the negative direction gradually increases as the magnitude of the steering angle in the negative direction after the shift increases. The base map 27a shown in FIG. 6B is also prepared differently for each vehicle speed. In the example shown in FIG. 7B, similar to the example shown in FIG. 7A, different base maps 27a are prepared for each of "low vehicle speed", "medium vehicle speed", and "high vehicle speed". When such a base map 27a is prepared, the first torque calculation unit 25 changes the base map 27a according to the vehicle speed. However, it is not necessary to prepare different base maps 27a for each vehicle speed.

[0030] In such a base calculation unit 27, one base map 27a is specified according to the input vehicle speed. A base torque (first torque) is calculated using the post-shift steering angle input to the base calculation unit 27 and the specified base map 27a.

[0031] The second torque calculation unit 28 calculates a second torque, which is a friction torque, based on the motor rotation angular velocity and the vehicle speed. m As can be seen from the following equation, the second torque (friction torque) is expressed by the following equation: m As increases, it reaches a certain size and becomes saturated.

[0032]

number

[0033] Fig. 8 is a diagram showing an example of a hysteresis gain used in the second torque calculation unit in the first embodiment of the present disclosure. The hysteresis gain Tf shown in Fig. 8 is gradually decreased in value as the vehicle speed increases up to a certain vehicle speed, and is gradually increased in value as the vehicle speed increases beyond the certain vehicle speed. Note that the hysteresis gain Tf shown in Fig. 8 is changed in value depending on the vehicle speed, but may be changed in value regardless of the vehicle speed.

[0034] In addition, the second torque calculation unit 28 may perform low-pass filtering on the calculated second torque (friction torque) using a low-pass filter. Here, the cutoff frequency of the low-pass filter is set to a value that can extract a frequency component set to include the steering frequency of the driver. Generally, the driver's limit steering frequency is about 5 [Hz], and the resonance frequency of the steering shaft 2 is around 10 [Hz], so the cutoff frequency is set to a value greater than 0 and equal to or less than 10 [Hz].

[0035] The third torque calculation unit 29 calculates a third torque, which is a damper torque, based on the motor rotational angular velocity and the vehicle speed.

[0036] Fig. 9A is a block diagram showing an example of a configuration of a third torque calculation unit according to the first embodiment of the present disclosure. The third torque calculation unit 29 shown in Fig. 9A includes a damper gain map 29a and a multiplier 29b. The damper gain map 29a is a map in which a damper gain according to a motor rotation angular velocity is defined. Fig. 10A is a diagram showing an example of the damper gain map used in the third torque calculation unit shown in Fig. 9A.

[0037] 10A has a characteristic that when the magnitude (absolute value) of the motor rotation angular velocity exceeds a certain value, the magnitude of the damper gain gradually increases as the magnitude (absolute value) of the motor rotation angular velocity increases. Note that the magnitude of the damper gain is zero until the magnitude (absolute value) of the motor rotation angular velocity reaches a certain value.

[0038] Also, a different damper gain map 29a is prepared for each vehicle speed. In the example shown in FIG. 10A, a different damper gain map 29a is prepared for each of "low vehicle speed", "medium vehicle speed", and "high vehicle speed". When such damper gain maps 29a are prepared, the third torque calculation unit 29 changes the damper gain map 29a according to the vehicle speed. However, it is not necessary to prepare a different damper gain map 29a for each vehicle speed. The multiplier 29b multiplies the motor rotation angular velocity by the damper gain calculated using the damper gain map 29a.

[0039] In such a third torque calculation unit 29, one damper gain map 29a is specified according to the input vehicle speed. A damper gain is calculated using the motor rotation angular velocity input to the third torque calculation unit 29 and the specified damper gain map 29a. Then, the damper gain calculated using the damper gain map 29a and the motor rotation angular velocity are multiplied by a multiplier 29b to calculate a damper torque (third torque).

[0040] Fig. 9B is a block diagram showing another example of the configuration of the third torque calculation unit in the first embodiment of the present disclosure. The third torque calculation unit 29 shown in Fig. 9B includes a damper torque map 29c, a sign determination unit 29d, and a multiplier 29e. The damper torque map 29c is a map in which the damper torque according to the motor rotation angular velocity is defined. Fig. 10B is a diagram showing an example of the damper torque map used in the third torque calculation unit shown in Fig. 9B.

[0041] Damper torque map 29c shown in Fig. 10B has the same characteristics as damper gain map 29a shown in Fig. 10A. That is, damper torque map 29c shown in Fig. 10B has a characteristic that when the magnitude (absolute value) of the motor rotation angular velocity exceeds a certain value, the magnitude of the damper torque gradually increases as the magnitude (absolute value) of the motor rotation angular velocity increases. Note that the magnitude of the damper torque is zero until the magnitude (absolute value) of the motor rotation angular velocity reaches a certain value.

[0042] In addition, a different damper torque map 29c is prepared for each vehicle speed. In the example shown in FIG. 10B, a different damper torque map 29c is prepared for each of "low vehicle speed", "medium vehicle speed", and "high vehicle speed". When such a damper torque map 29c is prepared, the third torque calculation unit 29 changes the damper torque map 29c according to the vehicle speed. However, it is not necessary to prepare a different damper torque map 29c for each vehicle speed. The sign determination unit 29d determines whether the sign of the motor rotation angular velocity is positive (+1) or negative (-1). The multiplier 29e multiplies the magnitude of the damper torque calculated using the damper torque map 29c by the sign determined by the sign determination unit 29d.

[0043] In the third torque calculation unit 29, one damper torque map 29c is specified according to the input vehicle speed. The magnitude of the damper torque (third torque) is calculated using the motor rotation angular velocity input to the third torque calculation unit 29 and the specified damper torque map 29c. The sign of the input motor rotation angular velocity is determined by a sign determination unit 29d. Then, the magnitude of the damper torque (third torque) calculated using the damper torque map 29c is multiplied by the sign of the motor rotation angular velocity determined by the sign determination unit 29d in a multiplier 29e, thereby calculating the damper torque (third torque).

[0044] The target steering torque calculation unit 30 includes adders 30a and 30b, and adds together the base torque (first torque) calculated by the first torque calculation unit 25, the friction torque (second torque) calculated by the second torque calculation unit 28, and the damper torque (third torque) calculated by the third torque calculation unit 29. Specifically, the friction torque (second torque) and the damper torque (third torque) are added together by the adder 30b, and the torque output from the adder 30b and the base torque (first torque) are added together by the adder 30a. The target steering torque calculation unit 30 outputs the torque obtained by the addition as the target steering torque.

[0045] Fig. 11 is a block diagram showing an example of an internal configuration of a torque feedback calculation unit in the first embodiment of the present disclosure. As shown in Fig. 11, the torque feedback calculation unit 23 includes a subtractor 31, a first steering assist torque calculation unit 32, a second steering assist torque calculation unit 33, a third steering assist torque calculation unit 34, and an adder 35. Such a torque feedback calculation unit 23 calculates a steering assist torque required to make the steering torque follow the target steering torque, based on the deviation between the target steering torque set by the target steering torque setting unit 22 and the steering torque detected by the torque sensor 5.

[0046] The subtractor 31 determines the deviation between the target steering torque set by the target steering torque setting unit 22 and the steering torque detected by the torque sensor 5. The first steering assist torque calculation unit 32 includes an integrator 32a and a multiplier 23b, and calculates a first steering assist torque by integrating the deviation determined by the subtractor 31 with the integrator 32a and multiplying the integrated deviation by an integral control gain KTI with the multiplier 32b.

[0047] The second steering assist torque calculation unit 33 includes a multiplier 33a, and calculates a second steering assist torque by multiplying the motor rotation angular velocity by a speed control gain KTV using the multiplier 33a. The third steering assist torque calculation unit 34 includes a multiplier 34a, and calculates a third steering assist torque by multiplying the deviation obtained by the subtractor 31 by a proportional control gain KTP using the multiplier 34a.

[0048] The adder 35 adds the first steering assist torque calculated by the first steering assist torque calculation unit 32, the second steering assist torque calculated by the second steering assist torque calculation unit 33, and the third steering assist torque calculated by the third steering assist torque calculation unit 34. Then, the adder 35 outputs the torque obtained by the addition as the steering assist torque.

[0049] Here, since the steering assist torque includes an integral control component (first steering assist torque), the driver's steering torque follows the target steering torque. This allows the driver to steer with an appropriate torque. Furthermore, when the driver releases his / her hands from the steering wheel 1, the motor speed control component (second steering assist torque) obtained by multiplying the motor rotation angular velocity by the speed control gain KTV makes it possible to adjust the steering torque to a value between the target steering torque and zero. This allows the steering torque to follow the target steering torque, thereby realizing smooth steering. Furthermore, by using the motor speed control component (second steering assist torque), it is possible to ensure stability of control even when the motor 6 and the torque sensor 5 are located apart from each other. Furthermore, since differentiation of the target steering torque is not necessary, noise can be suppressed, and smooth and stable steering can be realized.

[0050] Since the steering assist torque proportional control component (third steering assist torque) has a faster response than the steering assist torque integral control component (first steering assist torque), the tracking response can be made faster and overshoot can be reduced. As a result, when the driver is holding the steering wheel 1 and steering, the steering torque stably tracks the target steering torque, and smoother steering can be realized. Note that in this embodiment, a case where the torque feedback calculation unit 23 that performs torque feedback is provided as a configuration for achieving stability and tracking has been described as an example. However, as long as the deviation between the target steering torque and the steering torque can be fed back, the configuration is not limited to the one that performs torque feedback.

[0051] Next, the effect of providing the control unit 11 (steering control device) described above will be described. In a steering control device that sets a target steering torque according to the steering situation and controls the steering torque to follow the target steering torque, when the driver sets the steering feeling of the car, the target steering force angle characteristic is adapted so that the target steering torque has the desired characteristic. A specific adaptation method is assumed to be a steering method in which the steering wheel 1 is operated with a sine wave of about 0.2 [Hz] at the desired vehicle speed, and the lateral acceleration is 0.2 [G] or less.

[0052] In the technology disclosed in the above-mentioned Patent Document 1, when setting a target steering force angle characteristic to realize a desired feeling, a steering force characteristic model that is decomposed into a spring component (base torque), a viscous component (damper torque), and a friction component (friction torque) is used. In addition, in the technology disclosed in the above-mentioned Patent Document 1, the target steering torque can be set based on a plurality of center feel evaluation indexes that define the center feeling. However, when adjusting the on-center feeling characteristic near the neutral steering angle using the steering force characteristic model, there is a risk that the characteristic of the other steering angle ranges will be affected.

[0053] Fig. 12 is a diagram showing the relationship between the steering angle and the target steering torque when the steering wheel is steered in the first embodiment of the present disclosure. The target steering force angle characteristic A in Fig. 12 is a basic characteristic created by adding the base torque, the damper torque, and the friction torque. The target steering force angle characteristic B in Fig. 12 is a characteristic in this embodiment in which an on-center feeling characteristic is imparted to the target steering force angle characteristic A.

[0054] The target steering force angle characteristic C is a characteristic in the technology disclosed in Patent Document 1, in which an on-center feeling characteristic similar to the target steering force angle characteristic B is imparted to the target steering force angle characteristic A by adjusting a viscosity component. The target steering force angle characteristic D is a characteristic in the technology disclosed in Patent Document 1, in which an on-center feeling characteristic similar to the target steering force angle characteristic B is imparted to the target steering force angle characteristic A by adjusting a friction component.

[0055] As shown in Fig. 12, when an on-center feeling is to be imparted by using a viscous component or a friction component, the target steering force angle characteristic changes significantly from the initially set basic target steering force angle characteristic A. For this reason, it becomes necessary to re-adjust all of the base torque, damper torque, and friction torque.

[0056] Fig. 13 is a diagram showing the relationship between the steering angle when the steering wheel is steered and the target steering torque (base torque) in the first embodiment of the present disclosure. In the control unit 11 according to this embodiment, when sine wave steering is performed as in the adaptation method, the peak of the motor rotational angular velocity appears near the neutral position. Therefore, as shown in Fig. 13, when the steering angle shift calculation unit 26 is effective, it is possible to apply torque specifically near the neutral position of the base torque (first torque), so that the on-center feeling can be adjusted.

[0057] FIG. 14 shows the movement locus of the steering angle when the driver releases the steering wheel from a turned state. The movement locus TR1 is obtained in this embodiment. The movement locus TR2 is obtained when the third torque calculation unit 29 is disabled. The movement locus TR3 is obtained when the steering angle shift calculation unit 26 and the third torque calculation unit 29 are disabled. Referring to FIG. 14, in this embodiment, the steering angle shift calculation unit 26 and the third torque calculation unit 29 are provided, so that the behavior of the steering wheel 1 can be suppressed and high convergence can be achieved. As a result, the steering wheel 1 can be converged without overshooting and oscillation.

[0058] Furthermore, in this embodiment, the steering angle shift gain Dg of the steering angle shift calculation unit 26, the damper gain map 29a of the base calculation unit 27 that calculates the first torque, the second torque calculation unit 28 that calculates the second torque, and the damper gain map 29a of the third torque calculation unit 29 that calculates the third torque are all variable with respect to the vehicle speed. This makes it possible to set appropriate control gains in response to the characteristics of the road reaction torque that changes with the vehicle speed, and by flexibly setting the target steering torque according to the vehicle speed, a wide variety of steering feelings can be realized. Note that it is not necessary to make all gains variable with respect to the vehicle speed, and at least one gain or map may be variable with respect to the vehicle speed.

[0059] In this embodiment, the steering state detection unit 21 is provided with a steering angle sensor 4, and the steering angle detected by the steering angle sensor 4 is used in the steering angle shift calculation unit 26. However, instead of the detection result of the steering angle sensor 4, the motor rotation angle detected by the motor rotation angle sensor 10 may be converted into a steering angle and used. For example, the motor rotation angle detected by the motor rotation angle sensor 10 may be converted into the angle of the steering shaft 2 using the reduction ratio of the reduction mechanism 7 and used. Furthermore, when the motor rotation angle is a relative angle with respect to the angle of the steering shaft 2, a yaw rate sensor or the like (not shown) provided in the vehicle may determine that the vehicle is traveling straight ahead, and the relative angle may be offset to 0 to be used as the absolute angle of the steering shaft 2.

[0060] [Embodiment 2] <Electric power steering device> The configuration of the electric power steering device according to this embodiment is basically the same as the configuration of the electric power steering device PS shown in Fig. 1. Therefore, a detailed description of the electric power steering device according to this embodiment will be omitted.

[0061] Steering control device The basic configuration of the steering control device according to this embodiment is similar to that of the steering control device (control unit 11) according to embodiment 1. However, the configuration of the steering angle shift calculation unit 26 of the first torque calculation unit 25 provided in the target steering torque setting unit 22 of the control unit 11 is different. The steering angle shift calculation unit 26 will be described below.

[0062] Fig. 15 is a block diagram showing a configuration of a steering angle shift calculation unit in the second embodiment of the present disclosure. As shown in Fig. 15, the steering angle shift calculation unit 26 according to this embodiment is configured by adding a steering angle application range adjustment map 26c and a multiplier 26d to the steering angle shift calculation unit 26 shown in Fig. 4. The steering angle shift calculation unit 26 shown in Fig. 4 and the steering angle shift calculation unit 26 in this embodiment shown in Fig. 15 are different in the method of calculating a first shift amount, which is a shift amount of the steering angle of the steering wheel 1.

[0063] Fig. 16 is a diagram showing an example of a steering angle application range adjustment map used in the steering angle shift calculation unit in the second embodiment of the present disclosure. The steering angle application range adjustment map 26c shown in Fig. 16 shows a characteristic in which the steering angle application range adjustment gain gradually decreases as the magnitude (absolute value) of the steering angle of the steering wheel 1 increases.

[0064] Also, different steering angle application range adjustment maps 26c are prepared for each vehicle speed. In the example shown in Fig. 16, different steering angle application range adjustment maps 26c are prepared for each of "low vehicle speed", "medium vehicle speed", and "high vehicle speed". When such steering angle application range adjustment maps 26c are prepared, the first torque calculation unit 25 changes the steering angle application range adjustment map 26c according to the vehicle speed. However, it is not necessarily necessary to prepare different steering angle application range adjustment maps 26c for each vehicle speed.

[0065] Multiplier 26d multiplies the first shift amount output from multiplier 26a by the steering angle application range adjustment gain obtained using steering angle application range adjustment map 26c to calculate a second shift amount, which is the shift amount of the steering angle after the steering angle application range adjustment.

[0066] In the steering angle shift calculation unit 26, the steering angle shift gain Dg is specified according to the input vehicle speed, and the specified steering angle shift gain Dg and the motor rotation angular velocity are multiplied by the multiplier 26a to calculate a first shift amount (a shift amount of the steering angle of the steering wheel 1). Also, one steering angle application range adjustment map 26c is specified according to the input vehicle speed, and a steering angle application range adjustment gain is obtained using the input steering angle and the specified steering angle application range adjustment map 26c. The first shift amount and the steering angle application range adjustment gain are multiplied by the multiplier 26d to calculate a second shift amount (a shift amount of the steering angle after the steering angle application range adjustment). Then, the second shift amount is added to the steering angle by the adder 26b, and the post-shift steering angle is calculated.

[0067] FIG. 17 is a diagram showing the relationship between the steering angle and the target steering torque (base torque) when the steering wheel is steered in the second embodiment of the present disclosure. In this embodiment, by providing the steering angle application range adjustment map 26c, the steering angle after the steering angle shift can be gradually reduced as the steering angle increases. Therefore, as shown in FIG. 17, in this embodiment, the effect range of the steering angle shift calculation unit that imparts the on-center feeling can be narrowed down to a more limited range than in the first embodiment. This makes it possible to suppress the influence on the steering force angle characteristics that are adjusted with an intention other than the intention of adjusting the on-center feeling characteristics.

[0068] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments, and can be freely modified within the scope of the present disclosure. For example, the electric power steering device PS described in the above embodiments may be of a column type or a rack-and-pinion type. In addition, in terms of performing feedback control based on the target steering torque, it is also applicable to a steer-by-wire reaction device that includes at least a torque sensor. In addition, the figures used in the description of the above embodiments show examples, and are not limited thereto.

[0069] Each of the components (target steering torque setting section 22 and torque feedback calculation section 23) of the control unit 11 described above has an internal computer system. A program for realizing the functions of each of the components of the control unit 11 described above may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed to perform processing in each of the components of the control unit 11 described above. Here, "reading a program recorded on a recording medium into a computer system and executing it" includes installing the program into a computer system. The "computer system" referred to here includes hardware such as an OS and peripheral devices.

[0070] Furthermore, a "computer system" may include multiple computer devices connected via a network including the Internet or communication lines such as a WAN, LAN, or leased line. Furthermore, a "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into a computer system. In this way, the recording medium storing the program may be a non-transitory recording medium such as a CD-ROM.

[0071] The recording medium also includes a recording medium installed inside or outside and accessible from a distribution server to distribute the program. The program may be divided into a plurality of parts, each of which may be downloaded at a different timing and then combined by each component of the control unit 11, and each of the divided programs may be distributed by a different distribution server. Furthermore, the "computer-readable recording medium" includes a recording medium that holds a program for a certain period of time, such as a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network. The program may be a recording medium for implementing part of the above-mentioned functions. Furthermore, the program may be a recording medium that can realize the above-mentioned functions in combination with a program already recorded in the computer system, that is, a so-called difference file (difference program). [Explanation of symbols]

[0072] 1... steering wheel, 2... steering shaft, 5... torque sensor, 6... motor, 11... control unit, 12... current drive section, 21... steering state detection section, 22... target steering torque setting section, 23... torque feedback calculation section, 24... motor rotation angular velocity detection section, 25... first torque calculation section, 26... steering angle shift calculation section, 26c... steering angle application range adjustment map, 27... base calculation section, 28... second torque calculation section, 29... third torque calculation section, 29a... damper gain map, 29c... damper torque map, 30... target steering torque calculation section, PS... electric power steering device

Claims

1. A target steering torque setting unit that sets a target steering torque based on a steering angle of a steering wheel and a rotational angular velocity of a motor that generates a steering assist torque with respect to a steering shaft; a calculation unit that calculates a steering assist torque required for making the steering torque follow the target steering torque based on a deviation between the target steering torque and a steering torque acting on the steering shaft; a current driving unit that controls a current flowing through the motor to generate the steering assist torque; Equipped with the target steering torque setting unit is a first torque calculation unit that calculates a first shift amount, which is a shift amount of a steering angle of a steering wheel, by multiplying a rotational angular velocity of the motor by a steering angle gain, and calculates a first torque based on a post-shift steering angle obtained by adding the first shift amount to the steering angle and a base map that indicates a characteristic in which a magnitude of a base torque gradually increases as a magnitude of the post-shift steering angle increases; a second torque calculation unit that calculates a second torque for applying a friction torque to the target steering torque by using a rotational angular velocity of the motor; a target steering torque calculation unit that adds the first torque and the second torque and outputs the sum as the target steering torque; A steering control device comprising:

2. The first torque calculation unit includes a steering angle shift calculation unit that calculates the post-shift steering angle; a base calculation unit that calculates the first torque based on the post-shift steering angle and the base map; The steering control device according to claim 1 .

3. The steering angle shift calculation unit further includes a steering angle application range adjustment map in which a steering angle application range adjustment gain corresponding to the steering angle is defined, multiplying the first shift amount by a steering angle application range adjustment gain corresponding to the steering angle obtained from the steering angle application range adjustment map to calculate a second shift amount which is a shift amount of the steering angle after the steering angle application range adjustment, and adding the steering angle to the second shift amount to calculate the post-shift steering angle. The steering control device according to claim 2.

4. 4. The steering control device according to claim 3, wherein the steering angle application range adjustment map is a map showing a characteristic in which the steering angle application range adjustment gain gradually decreases as the magnitude of the steering angle increases.

5. The steering control device according to claim 3 , wherein the first torque calculation unit changes at least one of the steering angle gain, the base map, and the steering angle application range adjustment map in accordance with a vehicle speed.

6. The steering control device according to claim 1 , wherein the second torque calculation unit calculates the second torque using a rotational angular velocity of the motor and a magnitude of the friction torque defined for each vehicle speed.

7. The target steering torque setting unit further includes a third torque calculation unit that calculates a third torque as a damper torque based on a rotational angular velocity of the motor, The target steering torque calculation unit adds up the first torque, the second torque, and the third torque and outputs the sum as the target steering torque. The steering control device according to claim 1.

8. the third torque calculation unit further includes a damper gain map in which a damper gain according to a rotational angular velocity of the motor is defined, specifying a damper gain according to a rotational angular velocity of the motor using the damper gain map, and multiplying the specified damper gain by the rotational angular velocity of the motor to obtain the third torque. The steering control device according to claim 7.

9. The steering control device according to claim 8 , wherein the third torque calculation unit changes the damper gain map in accordance with a vehicle speed.

10. the third torque calculation unit further includes a damper torque map in which a damper torque corresponding to a rotational angular velocity of the motor is defined, determining the third torque based on the rotational angular velocity of the motor and the damper torque map; The steering control device according to claim 7.

11. The steering control device according to claim 10 , wherein the third torque calculation unit changes the damper torque map in accordance with a vehicle speed.

12. a steering torque detection unit that detects a steering torque acting on a steering shaft of a steering wheel; a steering state detection unit that detects a steering angle of a steering wheel; a motor for applying a steering assist torque to the steering shaft; a motor rotation angular velocity detection unit that detects a rotation angular velocity of the motor; A steering control device according to any one of claims 1 to 11, which controls driving of the motor based on the detected steering torque, the detected steering angle, and the detected rotational angular velocity of the motor; An electric power steering device comprising:

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