JP5949949B2 - Steering control device - Google Patents

Description

  The present invention relates to a steer-by-wire steering control device in which a steering wheel and a steered wheel are mechanically separated.

Conventionally, as a steering control device, for example, there is a conventional technique described in Patent Document 1.
In the prior art described in Patent Document 1, the control amount for driving the reaction force motor is calculated by adding the control amount for the steering reaction force based on the steering rack axial force to the control amount for the steering reaction force based on the steering angle. Then, the reaction force motor is driven based on the calculated control amount. The control amount of the steering reaction force based on the steering angle includes a steering reaction force that returns the steering wheel to the neutral position. Thereby, in the prior art described in Patent Document 1, the influence of the external force acting on the steering wheel is reflected in the steering reaction force.

JP 2000-108914 A

Here, in general, when the vehicle turns while traveling backward, the tire lateral force is applied in the direction in which the turning angle increases because the point of application of the tire lateral force is set behind the ground contact center of the tire. There is a possibility that the steering rack axial force is generated in the direction in which the steering rack moves away from the neutral position. Therefore, in the prior art described in Patent Document 1, the control amount of the steering reaction force based on the steering angle and the control amount of the steering reaction force based on the steering rack axial force are reversed. Therefore, in the prior art described in Patent Document 1, if the magnitude relationship between the control amount of the steering reaction force based on the steering angle and the control amount of the steering reaction force based on the steering rack axial force changes, the sign of the steering reaction force changes. There was a possibility that the steering reaction force vibrated.
An object of the present invention is to make it possible to suppress the vibration of the steering reaction force when the vehicle turns while traveling backward, paying attention to the above points.

  In order to solve the above problem, in one aspect of the present invention, a feedforward axial force that is a force generated in the steering system in a direction to return the steering wheel to the neutral position is calculated. Next, it is a force generated in the steering system in the direction to return the steering wheel to the neutral position when moving forward based on the state quantity of the vehicle that varies with the lateral force of the tire acting on the steering wheel, and the steering wheel is moved to the neutral position when moving backward A feedback axial force, which is a force generated in the steering system in a direction to deviate from the steering system, is calculated. Subsequently, the calculated feedforward axial force and feedback axial force are distributed to set the final axial force. Subsequently, a steering reaction force is applied based on the set final axial force. At this time, if it is determined that the vehicle is traveling backward, the feedforward axial force is set as the final axial force.

  In one aspect of the present invention, for example, when the vehicle turns while traveling backward, even if the sign of the feedforward axial force and the feedback axial force is reversed, the sign of the final axial force is not switched. Therefore, switching of the driving direction of the reaction force actuator can be suppressed, and vibration of the steering reaction force can be suppressed.

2 is a conceptual diagram illustrating a configuration of a vehicle A. FIG. 3 is a block diagram illustrating a configuration of a control calculation unit 11. FIG. It is a block diagram showing the structure of the target reaction force electric current calculating part 11B. It is a block diagram showing the structure of feedforward axial force calculation part 11Ba. It is a figure for demonstrating the coefficient of the calculation formula of pinion axial force Th. It is a graph showing control map M1. It is a graph showing control map M2. 3 is a graph showing a relationship between a steering angle δ and a steering reaction force. It is a graph showing control map M3. It is a graph showing control map M4. It is a block diagram showing the structure of feedback axial force calculation part 11Bb. It is a graph showing a lateral G axial force, a current axial force, a yaw rate axial force, and an actual steering rack axial force. It is a graph showing blend axial force T _BR and actual steering rack axial force. It is a graph showing control map M5. It is a graph showing control map M6. It is a graph showing control map M7. It is a graph showing control maps M8a and M8b. It is a graph showing control map M9. It is a graph showing control map M10.

Next, an embodiment according to the present invention will be described with reference to the drawings.
(Constitution)
The vehicle A according to this embodiment is a vehicle including a steer-by-wire steering control device in which a steering wheel 1 and a front wheel (hereinafter also referred to as a steering wheel) 2 are mechanically separated.
FIG. 1 is a conceptual diagram illustrating a configuration of a vehicle A according to the present embodiment.
As shown in FIG. 1, the vehicle A includes a steering angle sensor 3, a turning angle sensor 4, a vehicle speed sensor 5, a lateral G sensor 6, a yaw rate sensor 7, and a shift sensor 12.
The steering angle sensor 3 detects the steering angle δ of the steering wheel 1. As a method of detecting the steering angle δ, for example, a method of calculating based on the rotation amount of the steering shaft can be employed. Then, the steering angle sensor 3 outputs a signal representing the detection result (hereinafter also referred to as a detection signal) to the control calculation unit 11 described later.

The turning angle sensor 4 detects the turning angle θ of the steered wheel 2. As a method of detecting the turning angle θ, for example, a method of calculating based on the amount of movement of the steering rack can be employed. Then, the turning angle sensor 4 outputs a detection signal to the control calculation unit 11.
The vehicle speed sensor 5 detects the vehicle speed V of the vehicle A. The vehicle speed sensor 5 outputs a detection signal to the control calculation unit 11.
The lateral G sensor 6 detects a lateral acceleration Gy acting on the vehicle A (a state quantity of the vehicle A varying with the tire lateral force Fd acting on the steered wheel 2). Then, the lateral G sensor 6 outputs a detection signal to the control calculation unit 11.
The yaw rate sensor 7 detects the yaw rate γ of the vehicle A (the state quantity of the vehicle A that varies with the tire lateral force Fd acting on the steered wheel 2). Then, the yaw rate sensor 7 outputs a detection signal to the control calculation unit 11.
The lateral G sensor 6 and the yaw rate sensor 7 are arranged on the spring (vehicle body).
The shift sensor 12 detects the position of the shift lever of the transmission. Examples of the position of the shift lever include a D range, an R range (reverse running position), and a P range. Then, the shift sensor 12 outputs a detection signal to the control calculation unit 11.

Further, the vehicle A includes a steering control unit 8 and a reaction force control unit 9.
The steered control unit 8 includes a steered motor 8A, a steered current detecting unit 8B, and a steered motor driving unit 8C.
The steered motor 8A is connected to the pinion shaft 10 via a speed reducer. The steered motor 8 </ b> A is driven by the steered motor driving unit 8 </ b> C and moves the steering rack to the left and right via the pinion shaft 10. Thereby, the steered motor 8A steers the steered wheel 2. As a method for driving the steered motor 8A, for example, a method of controlling a current flowing in the steered motor 8A (hereinafter also referred to as steered current) can be employed.
The steered current detection unit 8B detects the steered current (the state quantity of the vehicle A that varies with the tire lateral force Fd acting on the steered wheel 2). Then, the steering current detection unit 8B outputs a detection signal to the steering motor drive unit 8C and the control calculation unit 11.
Based on the target turning current calculated by the control calculation unit 11, the turning motor drive unit 8C turns the turning motor 8A so that the turning current detected by the turning current detection unit 8B matches the target turning current. Controls the steering current. Thereby, the steered motor driving unit 8C drives the steered motor 8A. The target turning current is a target value of the current flowing in the turning motor 8A.

The reaction force control unit 9 includes a reaction force motor 9A, a reaction force current detection unit 9B, and a reaction force motor drive unit 9C.
The reaction force motor 9A is connected to the steering shaft via a reduction gear. Then, the reaction force motor 9A is driven by the reaction force motor drive unit 9C and applies rotational torque to the steering wheel 1 via the steering shaft. Thereby, the reaction force motor 9A generates a steering reaction force. As a driving method of the reaction force motor 9A, for example, a method of controlling a current flowing in the reaction force motor 9A (hereinafter also referred to as reaction force current) can be adopted.
The reaction force current detection unit 9B detects a reaction force current. The reaction force current detection unit 9B outputs a detection signal to the reaction force motor drive unit 9C and the control calculation unit 11.
The reaction force motor drive unit 9C is based on the target reaction force current calculated by the control calculation unit 11 so that the reaction force current detected by the reaction force current detection unit 9B matches the target reaction force current. Controls the reaction force current. Thereby, the reaction force motor drive unit 9C drives the reaction force motor 9A. The target reaction force current is a target value of the current flowing through the reaction force motor 9A.

Further, the vehicle A includes a control calculation unit 11.
FIG. 2 is a block diagram illustrating the configuration of the control calculation unit 11.
As shown in FIG. 2, the control calculation unit 11 includes a target turning angle calculation unit 11A, a target reaction force current calculation unit 11B, and a target turning current calculation unit 11C.
The target turning angle calculation unit 11A is a target that is a target value of the turning angle θ (the rotation angle of the pinion shaft 10) based on the steering angle δ detected by the steering angle sensor 3 and the vehicle speed V detected by the vehicle speed sensor 5. Calculate the turning angle θ *. As a method of calculating the target turning angle θ *, for example, there is a method of adopting a multiplication value of the steering angle δ and the variable gear ratio of the steering angle δ and the turning angle θ. Then, the target turning angle calculation unit 11A outputs the calculation result to the target reaction force current calculation unit 11B.
The target reaction force current calculation unit 11B is based on the target turning angle θ * calculated by the target turning angle calculation unit 11A, the vehicle speed V detected by the vehicle speed sensor 5, and the turning current detected by the turning current detection unit 8B. To calculate the target reaction force current. Then, the target reaction force current calculation unit 11B outputs the calculation result to the reaction force control unit 9 (reaction force motor drive unit 9C).

Here, the configuration of the target reaction force current calculation unit 11B will be described.
FIG. 3 is a block diagram illustrating the configuration of the target reaction force current calculation unit 11B.
As shown in FIG. 3, the target reaction force current calculation unit 11B includes a feedforward axial force calculation unit 11Ba, a feedback axial force calculation unit 11Bb, a feedback axial force correction unit 11Bf, a final axial force calculation unit 11Bc, an axial force-steering reaction counter A force conversion unit 11Bd and a target reaction force current calculation unit 11Be are provided.
FIG. 4 is a block diagram illustrating the configuration of the feedforward axial force calculation unit 11Ba.
As shown in FIG. 4, the feedforward axial force calculation unit 11Ba generates a steering reaction force according to the equation (5) described later based on the steering angle δ detected by the steering angle sensor 3 and the vehicle speed V detected by the vehicle speed sensor 5. Calculated as feedforward axial force _TFF . And feedforward axial force calculation part 11Ba outputs a calculation result to final axial force calculation part 11Bc (refer FIG. 2).

FIG. 5 is a diagram for explaining the coefficients of the calculation formula for the pinion axial force Th.
Here, the relational expression between the steered pinion angle Θ and the pinion axial force Th is based on the equation of motion of a vehicle including a steering mechanism in which the steering wheel 1 and the steering wheel 2 are mechanically connected (1 ) Expression. As the steered pinion angle Θ, for example, there is a rotation angle of the pinion shaft 10. Specifically, the turning pinion angle Θ is a multiplication value of the steering angle δ and the variable gear ratio between the steering angle δ and the turning angle θ. Further, as the pinion axial force Th, for example, there is a steering reaction force applied to the steering wheel 1. The first term on the right side of the following equation (1) is a damping term representing a component based on the steered pinion angular velocity dΘ / dt among the components constituting the pinion axial force Th. The second term on the right side is an inertia term representing a component based on the steered pinion angular acceleration d ² Θ / dt ² among the components constituting the pinion axial force Th. Further, the third term on the right side is a proportional term representing a component based on the tire lateral force Fd (steering pinion angle Θ) among the components constituting the pinion axial force Th.
Th = Ks (Jrs ² + Cr · s) / (Jr · s ² + (Cr + Cs) s + Ks) · Θ + Cs (Jrs ³ + Cr · s ² ) / (Jr · s ² + (Cr + Cs) s + Ks) · Θ + (Ks + Cs · s) ) / (Jr · s ² + (Cr + Cs) s + Ks) · Fd (1)
However, as shown in FIG. 5, Ks is pinion rigidity, Cs is pinion viscosity, Jr is rack inertia, and Cr is rack viscosity.

In the above equation (1), the second term on the right side, that is, the inertia term, contains a lot of noise components, and is preferably excluded because it induces vibration in the calculation result of the pinion axial force Th. Further, the tire lateral force Fd can be expressed as Fd = f (V) · Θ, depending on the turning pinion angle Θ and the vehicle speed V. As f (V), for example, there is a function that changes according to the vehicle speed V. Therefore, the above equation (1) can be expressed as the following equation (2).
^{Th = Ks (Jrs 2 + Cr} · s) / (Jr · s 2 + (Cr + Cs) s + Ks) · Θ + (Ks + Cs · s) / (Jr · s 2 + (Cr + Cs) s + Ks) · f (V) · Θ ...... ... (2)

FIG. 6 is a graph showing the control map M1.
Here, as a method of setting the variable f (V), for example, a method of reading the variable f (V) corresponding to the absolute value of the vehicle speed V from the control map M1 can be adopted. An example of the control map M1 is a map in which a variable f (V) corresponding to the absolute value of the vehicle speed V is registered. Specifically, as shown in FIG. 6, when the absolute value of the vehicle speed V is 0, the control map M1 sets the variable f (V) to a first set value (for example, 0.0). Further, in the range where the absolute value of the vehicle speed V is equal to or higher than the first set vehicle speed V ₁ (> 0), the variable f (V) is set to the second set value (> first set value. 1.0). Further, the control map M1 linearly increases the variable f (V) in accordance with the absolute value of the turning angular velocity dθ / dt in the range where the absolute value of the vehicle speed V is 0 or more and less than the first set vehicle speed V _1. Let Specifically, the control map M1 follows a linear function representing the relationship between the absolute value of the vehicle speed V and the variable f (V) when the absolute value of the vehicle speed V is greater than or equal to 0 and less than the first set vehicle speed V _1. Set the variable f (V). The linear function sets the variable f (V) to the first set value (0.0) when the absolute value of the vehicle speed V is 0, and the variable f (V) when the absolute value of the vehicle speed V is the first set vehicle speed V1. Let V) be the second set value (1.0). Thus, feedforward axial force calculating unit 11Ba the absolute value of the vehicle speed V is in the case of the first less than the set vehicle speed V ₁ decreases the absolute value of the more proportional component having a small absolute value of the vehicle speed V (reduced ). Further, the feedforward axial force calculating unit 11Ba, when the absolute value of the vehicle speed V is first set vehicle speed V ₁ or more, regardless of the size of the vehicle speed V, is not performed to reduce the absolute value of the proportional component.

The above equation (2) can be equivalently expressed as the following equation (3).
Th = P (s + 2 · ζ · ωn) s / (s ² + 2 · ζ · ωn · s + ωn ² ) δ + I · (s + 2 · ζ · ωn) / (s ² + 2 · ζ · ωn · s + ωn ² ) · f (V ) ・ Δ
= P (s + 2 · ζ · ωn) / (s ² + 2 · ζ · ωn · s + ωn ² ) dδ / dt + I · (s + 2 · ζ · ωn) / (s ² + 2 · ζ · ωn · s + ωn ² ) · f (V ) ・ Δ ……… (3)
However, P and I are control constants, ζ is a damping coefficient, and ωn is a natural frequency. As a method for setting ζ and ωn, for example, a method of setting a design value or a method of identifying from an experimental result can be adopted.
Therefore, the pinion axial force Th, that is, the steering reaction force generated in the steering wheel 1 can be expressed by the following equation (4) based on the above equation (3).
Th = P (s + 2 · ζ · ωn) / (s ² + 2 · ζ · ωn · s + ωn ² ) dδ / dt + I · (s + 2 · ζ · ωn) / (s ² + 2 · ζ · ωn · s + ωn ² ) · f ( V) ・ δ ……… (4)

Then, equation (4), that is, based on a formula of the pinion shaft force Th, as a method of calculating the feedforward axial force T _FF of the present embodiment employs the following equation (5).
T _FF = P · P ₁ · P ₂ (s + 2 · ζ · ωn) / (s ² + 2 · ζ · ωn · s + ωn ² ) dδ / dt + I · (s + 2 · ζ · ωn) / (s ² + 2 · ζ · ωn · S + ωn ² ) · f (V) · δ + Correction damping component = Damping component · P ₁ · P ₂ + Proportional component + Correction damping component (5)
However, the damping component is P (s + 2 · ζ · ωn) / (s ² + 2 · ζ · ωn · s + ωn ² ) dδ / dt, and the proportional component is I · (s + 2 · ζ · ωn) / (s ² + 2 · ζ · ωn · s + ωn ² ) · f (V) · δ. The correction damping component is a damping component based on the steering angular velocity dδ / dt, and generates a steering reaction force in a direction opposite to the steering angular velocity dδ / dt.

FIG. 7 is a graph showing the control map M2.
Here, as a method of setting the gain P ₁ , for example, a method of reading the gain P ₁ corresponding to the absolute value of the steering angular velocity dδ / dt from the control map M2 can be adopted. The control map M2, for example, there is a map that has registered the gain P ₁ corresponding to the absolute value of the steering angular velocity d? / Dt. Specifically, as shown in FIG. 7, when the steering angular velocity dδ / dt is 0, the control map M2 sets the gain P ₁ to a third set value (for example, 1.0). In the range where the absolute value of the steering angular velocity dδ / dt is not less than the first set steering angular velocity dδ ₁ / dt (> 0), the gain P ₁ is set to the fourth set value (< The third set value is set to 0.5, for example. Further, in the control map M2, in the range where the absolute value of the steering angular velocity dδ / dt is not less than 0 and less than the first set steering angular velocity dδ ₁ / dt, the gain P ₁ is linearly changed according to the absolute value of the steering angular velocity dδ / dt. Decrease. Specifically, the control map M2 indicates that the absolute value of the steering angular velocity dδ / dt and the gain P ₁ are in the range where the absolute value of the steering angular velocity dδ / dt is not less than 0 and less than the first set steering angular velocity dδ ₁ / dt. The gain P ₁ is set in accordance with a linear function representing the relationship. In the linear function, when the steering angular velocity dδ / dt is 0, the gain P ₁ is set to the third set value (1.0), and the absolute value of the steering angular velocity dδ / dt is the first set steering angular velocity dδ ₁ / dt. In this case, the gain P ₁ is set to the fourth set value (0.5). Thereby, when the absolute value of the steering angular velocity dδ / dt is less than the first set steering angular velocity dδ ₁ / dt, the feedforward axial force calculation unit 11Ba increases the damping component as the absolute value of the steering angular velocity dδ / dt increases. Decrease the absolute value of (correct). Further, when the absolute value of the steering angular velocity dδ / dt is equal to or higher than the first set steering angular velocity dδ ₁ / dt, the feedforward axial force calculation unit 11Ba gains P regardless of the magnitude of the steering angular velocity dδ / dt. The absolute value of the damping component based on ₁ is not corrected.

  FIG. 8 is a graph showing the relationship between the steering angle δ and the steering reaction force. This graph shows each steering control device (a mechanical steering control device in which the steering wheel 1 and the steering wheel 2 are mechanically coupled) and a steering-by-wire method that does not consider the saturation of the damping component. For each steering control device). In the mechanical steering control device, the damping component included in the steering reaction force is saturated as the steering angular velocity dδ / dt increases. Therefore, in the mechanical steering control device, as shown in FIG. 8, when the damping component is saturated, the Lissajous figure composed of the steering angle δ and the steering reaction force regardless of the magnitude of the steering angular velocity dδ / dt. The shape of is constant. However, in a steer-by-wire steering control device that does not consider saturation of the damping component included in the steering reaction force, the steering reaction force continues to increase as the steering angular velocity dδ / dt increases. In contrast, the control calculation unit 11 of the present embodiment decreases the absolute value of the damping component as the absolute value of the steering angular velocity dδ / dt increases. Therefore, the control calculation unit 11 of the present embodiment can suppress an increase in the absolute value of the damping component when the steering angular velocity dδ / dt is large. Therefore, the control calculation part 11 of this embodiment can suppress that a damping component becomes excessive. Thereby, the control calculating part 11 of this embodiment can provide a more suitable steering feeling.

FIG. 9 is a graph showing the control map M3.
Further, as a method of setting the gain P _2, for example, it can be employed a method of reading a gain P ₂ corresponding to the absolute value of the vehicle speed V from the control map M3. The control map M3, for example, there is a map that has registered the gain P ₂ corresponding to the absolute value of the vehicle speed V. Specifically, as shown in FIG. 9, the control map M3 is the gain P ₂ fifth set value when the absolute value of the vehicle speed V is zero (e.g., 0.5) is set to. Further, in the range where the absolute value of the vehicle speed V is equal to or higher than the second set vehicle speed V ₂ (> 0), the gain P ₂ is set to the sixth set value (> 5th set value, for example, 1. Set to 0). Further, the control map M3 linearly increases the gain P ₂ according to the absolute value of the vehicle speed V in the range where the absolute value of the vehicle speed V is 0 or more and less than the second set vehicle speed V ₂ . Specifically, the control map M3 is the absolute value and the second predetermined vehicle speed V ₂ less than the range from 0 or more of the vehicle speed V, the gain P according to a linear function representing the relationship between the absolute value and the gain P ₂ of the vehicle speed V Set ₂ Linear function, when the absolute value of the vehicle speed V is zero the gain P ₂ fifth set value and (0.5), when the absolute value of the vehicle speed V is a second set speed V ₂ of the gain P ₂ The sixth set value (1.0) is assumed. Thus, feedforward axial force calculating unit 11Ba the absolute value of the vehicle speed V is in the case of the second lower than the set vehicle speed V _2, the smaller the absolute value of the more damping component having a small absolute value of the vehicle speed V (corrected ). Further, when the absolute value of the vehicle speed V is equal to or higher than the second set vehicle speed V ₂ , the feedforward axial force calculation unit 11Ba calculates the absolute value of the damping component based on the gain P ₂ regardless of the magnitude of the vehicle speed V. Do not make corrections.

  As described above, the control calculation unit 11 of the present embodiment decreases the absolute value of the damping component as the absolute value of the vehicle speed V decreases. Here, in the mechanical steering control device in which the steering wheel 1 and the steered wheels 2 are mechanically coupled, when the vehicle speed V decreases, the tire lateral force Fd of the steered wheels 2 decreases, and the steering reaction force Is reduced. On the other hand, the control calculation part 11 of this embodiment can reduce a steering reaction force by making the absolute value of a damping component small, so that the absolute value of the vehicle speed V is small. Thereby, the control calculating part 11 of this embodiment can provide a more suitable steering feeling.

FIG. 10 is a graph showing the control map M4.
Further, as a method of setting the correction damping component, for example, a method of reading the correction damping component corresponding to the absolute value of the steering angular velocity dδ / dt from the control map M4 can be employed. As the control map M2, for example, there is a map in which a correction damping component corresponding to the absolute value of the steering angular velocity dδ / dt is registered. Specifically, as shown in FIG. 10, the control map M4 is set for each vehicle speed V. Each control map M4 sets the correction damping component to the seventh set value (for example, 0.0) when the steering angular velocity dδ / dt is zero. Further, the control map M4 indicates that the correction damping component is used regardless of the magnitude of the steering angular velocity dδ / dt in the range where the absolute value of the steering angular velocity dδ / dt is equal to or larger than the second set steering angular velocity dδ ₂ / dt (> 0). Set to the eighth set value (constant value). Further, in the control map M4, the steering angular velocity dδ / dt is 0.0 or more, and the absolute value of the steering angular velocity dδ / dt is a third set steering angular velocity dδ ₃ / dt (0 <dδ ₃ / dt <dδ ₂ / dt). In the range below, the correction damping component is linearly increased according to the absolute value of the steering angular velocity dδ / dt. Specifically, each control map M4 has an absolute value of the steering angular velocity dδ / dt and a correction damping in a range where the absolute value of the steering angular velocity dδ / dt is not less than 0 and less than the third set steering angular velocity dδ ₃ / dt. A correction damping component is set according to a linear function representing the relationship with the component. In the linear function, when the absolute value of the steering angular velocity dδ / dt is 0, the correction damping component is set to the seventh set value (0.0), and the absolute value of the steering angular velocity dδ / dt is the third set steering angular velocity dδ _3. When / dt, the correction damping component is set to the ninth set value (0 <9th set value <8th set value). Each control map M4 indicates that the absolute value of the steering angular velocity dδ / dt is within a range where the absolute value of the steering angular velocity dδ / dt is not less than the third setting steering angular velocity dδ ₃ / dt and less than the second setting steering angular velocity dδ ₂ / dt. The correction damping component is linearly increased according to the value. Specifically, the control map M4 indicates that the absolute value of the vehicle speed V is within a range where the absolute value of the steering angular velocity dδ / dt is greater than or equal to the third set steering angular velocity dδ ₃ / dt and less than the second set steering angular velocity dδ ₂ / dt. The correction damping component is set according to a linear function representing the relationship between the correction damping component and the correction damping component. The linear function is that when the absolute value of the steering angular velocity dδ / dt is the third set steering angular velocity dδ ₃ / dt, the correction damping component is the ninth set value, and the absolute value of the steering angular velocity dδ / dt is the second set steering. When the angular velocity is dδ ₂ / dt, the correction damping component is set to the eighth set value. Thereby, the feedforward axial force calculation unit 11Ba corrects the larger the absolute value of the steering angular velocity dδ / dt when the absolute value of the steering angular velocity dδ / dt is less than the second set steering angular velocity dδ ₂ / dt. Increase the absolute value of the damping component. Further, the feedforward axial force calculating unit 11Ba, when the absolute value of the steering angular velocity d? / Dt is the second set steering angular velocity d? ₂ / dt or more, regardless of the magnitude of the steering angular velocity d? / Dt, correction The absolute value of the damping component is set to a predetermined constant value.

Thus, control arithmetic unit 11 of the present embodiment adds the correction damping component absolute value larger the absolute value of the steering angular velocity d? / Dt increases feedforward axial force T _FF. Therefore, when the absolute value of the steering angular velocity dδ / dt increases at the start of turning the steering wheel 1, the control calculation unit 11 of the present embodiment can increase the rising of the steering reaction force. Thereby, the control calculating part 11 of this embodiment can provide a more suitable steering feeling.
In addition, when the absolute value of the steering angular velocity dδ / dt is equal to or greater than the second set steering angular velocity dδ ₂ / dt, the control calculation unit 11 of the present embodiment uses a predetermined constant value as a correction damping component. Therefore, when the driver turns the steering wheel 1 and the absolute value of the steering angular velocity dδ / dt becomes equal to or higher than the second set steering angular velocity dδ ₂ / dt, fluctuations in the correction damping component can be suppressed. . Therefore, the control calculation unit 11 of the present embodiment does not sense a change in the steering reaction force due to the variation in the correction damping component, and can prevent the driver from feeling uncomfortable with the steering feeling.

FIG. 11 is a block diagram illustrating a configuration of the feedback axial force calculation unit 11Bb.
As shown in FIG. 11, the feedback axial force calculation unit 11Bb includes a current axial force calculation unit 11Bba, a blend axial force calculation unit 11Bbb, a steering angular velocity detection unit 11Bbc, a steering determination unit 11Bbd, and a feedback axial force calculation execution unit 11Bbe. .
The current axial force calculation unit 11Bba calculates a steering rack axial force (an axial force of the steering rack; hereinafter also referred to as a current axial force) based on the steering current detected by the steering current detection unit 8B. To do. In the following formula (6), first, the steering current, the torque constant [Nm / A] for calculating the output torque of the steered motor 8A based on the steered current, and the motor torque of the steered motor 8A are transmitted. Multiply by the motor gear ratio. Subsequently, in the following equation (6), the multiplication result is divided by the pinion radius [m] of the pinion gear of the steering motor 8A, and the division result is multiplied by the efficiency when the output torque of the steering motor 8A is transmitted. The multiplication result is calculated as the current axial force. And current axial force calculation part 11Bba outputs a calculation result to blend axial force calculation part 11Bbb and feedback axial force calculation execution part 11Bbe.
Current axial force = (steering current x motor gear ratio x torque constant [Nm / A] / pinion radius [m]) x efficiency (6)

  Here, the steering current varies when the steering wheel 1 is steered, the target turning angle θ * varies, and a difference occurs between the target turning angle θ * and the actual turning angle θ. Further, the steered current is also generated when the steered wheel 2 is steered, the tire lateral force Fd acts on the steered wheel 2, and a difference occurs between the target steered angle θ * and the actual steered angle θ. fluctuate. Further, the steering current is caused by a road surface disturbance acting on the steered wheel 2 due to road surface unevenness or the like, and a tire lateral force Fd acting on the steered wheel 2 to obtain a target steered angle θ * and an actual steered angle θ. It also fluctuates due to differences. Therefore, the feedback axial force calculation unit 11Bb can calculate the steering rack axial force (current axial force) reflecting the influence of the tire lateral force Fd acting on the steered wheels 2 based on the steering current. Here, the current axial force is generated when a difference occurs between the target turning angle θ * and the actual turning angle θ. Therefore, the phase of the current axial force advances as compared with the actual steering rack axial force and lateral G axial force, as shown in FIG.

Based on the lateral acceleration Gy detected by the lateral G sensor 6, the blend axial force calculating unit 11Bbb calculates a steering rack axial force (hereinafter also referred to as a lateral G-axis force) according to the following equation (7). In the following equation (7), first, the front wheel load and the lateral acceleration Gy are multiplied, and the multiplication result is calculated as an axial force (axial force) applied to the steered wheel 2. Subsequently, in the following equation (7), the calculated axial force applied to the steered wheel 2 is multiplied by a constant (hereinafter also referred to as a link ratio) according to the link angle and suspension, and the multiplication result is represented by the horizontal G axis. Calculated as force.
Lateral G-axis force = Axial force applied to steering wheel 2 x Link ratio (7)
Axial force applied to steering wheel 2 = front wheel load x lateral acceleration Gy

Here, the lateral acceleration Gy is generated when the steered wheel 2 is steered, the tire lateral force Fd acts on the steered wheel 2, and the vehicle A turns. Therefore, the blend axial force calculation unit 11Bbb can calculate the steering rack axial force (lateral G axial force) reflecting the influence of the tire lateral force Fd acting on the steered wheels 2 based on the lateral acceleration Gy. Here, since the lateral G sensor 6 is disposed on the spring (vehicle body), detection of the lateral acceleration Gy is delayed. Therefore, the lateral G-axis force is delayed in phase as compared with the actual steering rack axial force, as shown in FIG.
In the present embodiment, an example is shown in which the lateral acceleration Gy detected by the lateral G sensor 6 is used when calculating the lateral G-axis force, but other configurations may be employed. For example, the yaw rate γ detected by the yaw rate sensor 7 may be multiplied by the vehicle speed V detected by the vehicle speed sensor 5, and the multiplication result γ × V may be used instead of the lateral acceleration Gy.

Also, the blend axial force calculation unit 11Bbb is based on the vehicle speed V detected by the vehicle speed sensor 5 and the yaw rate γ detected by the yaw rate sensor 7, and the steering rack axial force (hereinafter also referred to as the yaw rate axial force) according to the following equation (8). Is calculated. In the following formula (8), first, the front wheel load, the vehicle speed V, and the yaw rate γ are multiplied, and the multiplication result is calculated as an axial force applied to the steered wheel 2. Subsequently, in the following equation (8), the calculated axial force applied to the steered wheel 2 and the link ratio are multiplied, and the multiplication result is calculated as the yaw rate axial force.
Yaw rate axial force = axial force applied to steered wheel 2 x link ratio (8)
Axial force applied to steered wheel 2 = front wheel load x vehicle speed V x yaw rate γ
Here, the yaw rate γ is generated when the steered wheel 2 is steered, the tire lateral force Fd acts on the steered wheel 2, and the vehicle A turns. Therefore, the blend axial force calculation unit 11Bbb can calculate the steering rack axial force (yaw rate axial force) reflecting the influence of the tire lateral force Fd acting on the steered wheels 2 based on the yaw rate γ. Here, since the yaw rate sensor 7 is disposed on the spring (vehicle body), the detection of the yaw rate γ is delayed. For this reason, the phase of the yaw rate axial force is delayed compared to the actual steering rack axial force, as shown in FIG.

Further, the blend axial force calculation unit 11Bbb reads the current axial force from the current axial force calculation unit 11Bba. Subsequently, the blend axial force calculation unit 11Bbb is based on the read current axial force and the calculated lateral G axial force and yaw rate axial force, and the steering rack axial force (hereinafter also referred to as blend axial force) according to the following equation (9). Calculate T _BR . In the following equation (9), the lateral G-axis force is multiplied by the distribution ratio K1, the current axial force is multiplied by the distribution ratio K2, the yaw rate axial force is multiplied by the distribution ratio K3, and the sum of these multiplication results is the blend axis. Calculated as force T _BR . That is, the blend axial force T _BR is calculated based on a value obtained by multiplying the lateral G axial force by the distribution ratio K1, a value obtained by multiplying the current axial force by the distribution ratio K2, and a value obtained by multiplying the yaw rate axial force by the distribution ratio K3. . Then, the blend axial force calculation unit 11Bbb outputs the calculation result to the steering determination unit 11Bbd and the feedback axial force calculation execution unit 11Bbe. Here, the blend axial force T _BR has a positive value for the axial force that directs the steered wheel 2 in the right direction and a negative value for an axial force that directs the steered wheel 2 in the left direction.
T _BR = Lateral G Axial Force x K1 + Current Axial Force x K2 + Yaw Rate Axial Force x K3 (9)

Here, the distribution ratios K1, K2, and K3 are distribution ratios of the lateral G-axis force, current axial force, and yaw rate axial force. The magnitude relationship between the distribution ratios K1, K2, and K3 is K1>K2> K3. That is, the distribution ratio is set to a larger value in the order of the lateral G axial force, current axial force, and yaw rate axial force. For example, the distribution ratios K1, K2, and K3 are set to K1 = 0.6, K2 = 0.3, and K3 = 0.1, respectively. Thus, blending axial force calculating unit 11Bbb as a blend axial force T _BR, calculates a steering rack axial force that reflects the influence of the tire lateral force Fd acting on the steering wheel 2.

FIG. 13 is a graph showing the blend axial force T _BR and the actual steering rack axial force.
As described above, the blend axial force calculation unit 11Bbb of the present embodiment calculates the blend axial force T _BR based on the value obtained by multiplying the current axial force by the distribution ratio K2 and the value obtained by multiplying the lateral G axial force by the distribution ratio K1. calculate. Here, as shown in FIG. 12, the phase of the lateral G-axis force is delayed compared to the actual steering rack axial force. Further, the phase of the current axial force advances compared to the actual steering rack axial force. Therefore, the blend axial force calculation unit 11Bbb of the present embodiment can compensate for the phase lag due to the lateral G-axis force as shown in FIG. The blend axial force T _BR can be calculated. Therefore, the control calculation unit 11 of the present embodiment can apply a more appropriate steering reaction force by driving the reaction force motor 9A based on the blend axial force _TBR .

Further, the blend axial force calculation unit 11Bbb of the present embodiment calculates the blend axial force T _BR based on a value obtained by multiplying the current axial force by the distribution ratio K2 and a value obtained by multiplying the lateral G axial force by the distribution ratio K1. . Here, when a road surface disturbance is applied to the steered wheel 2 due to road surface unevenness or the like, and the tire lateral force Fd is applied to the steered wheel 2, the vehicle A has a target turning angle θ * and an actual turning angle θ. There will be a difference. Thus, blends axial force calculating unit 11Bbb of this embodiment, by adding the current axial force to the lateral G axial force, it can reflect the influence of the road surface disturbance acting on the steering wheel 2 to the blend axial force T _BR, more An appropriate blend axial force T _BR can be calculated. Therefore, the control calculation unit 11 of the present embodiment can apply a more appropriate steering reaction force by driving the reaction force motor 9A based on the blend axial force _TBR .

Further, the blend axial force calculation unit 11Bbb of the present embodiment increases the lateral G axial force distribution ratio K1 to a current axial force distribution ratio K2. Therefore, the blend axial force calculation unit 11Bbb of the present embodiment can reduce the distribution ratio of the current axial force. For example, even if the estimation accuracy of the current axial force is reduced due to the inertia of the steered motor 8A or the influence of friction, A decrease in the estimation accuracy of the blend axial force T _BR can be suppressed. Therefore, the control calculation unit 11 of the present embodiment can apply a more appropriate steering reaction force by driving the reaction force motor 9A based on the blend axial force _TBR .

Further, the blend axial force calculation unit 11Bbb of the present embodiment has a value obtained by multiplying the current axial force by the distribution ratio K2, a value obtained by multiplying the lateral G axial force by the distribution ratio K1, and a value obtained by multiplying the yaw rate axial force by the distribution ratio K3. Based on the above, the feedback axial force T _FB is calculated. Here, for example, when the vehicle A is in a spin state, the steering current and the lateral acceleration Gy increase, so that the detection result of the lateral G sensor 6 and the detection result of the steering current detection unit 8B are both maximum. Value (saturated value). On the other hand, the yaw rate γ also increases, but the increase amount of the yaw rate γ is relatively small compared to the increase amounts of the steering current and the lateral acceleration Gy, so that the detection result of the yaw rate sensor 7 reaches the maximum value (saturated value). Not reach. Therefore, the detection result of the yaw rate sensor 7 varies depending on the degree of spin state of the vehicle A. Therefore, the blend axial force T _BR can be changed according to the degree of the spin state of the vehicle A. As a result, the control calculation unit 11 of the present embodiment can apply a more appropriate steering reaction force by driving the reaction force motor 9A based on the blend axial force _TBR .

  The steering angular velocity detector 11Bbc calculates the steering angular velocity dδ / dt of the steering wheel 1 based on the steering angle δ detected by the steering angle sensor 3. And steering angular velocity detection part 11Bbc outputs a calculation result to blend axial force calculation part 11Bbb and steering determination part 11Bbd. Here, the steering angular velocity dδ / dt has a positive value when the steering wheel 1 rotates clockwise, and a negative value when the steering wheel 1 rotates counterclockwise.

Steering determining unit 11Bbd, based on the steering angular velocity d? / Dt which blends axial force blends axial force calculating unit 11Bbb calculated T _BR and steering angular velocity detection unit 11Bbc detects the driver of the steering wheel 1 additional steering operation and cut It is determined which of the return operations is being performed. The rounding-up operation is, for example, a steering operation in a direction in which the steering wheel 1 (steering angle δ) is away from the neutral position. Further, as the return operation, for example, there is a steering operation in a direction in which the steering wheel 1 (steering angle δ) approaches the neutral position. Specifically, the steering determination unit 11Bbd determines that the blend axial force T _BR is a positive value and the steering angular velocity dδ / dt is a positive value, or the blend axial force T _BR is a negative value and the steering angular velocity dδ / If dt is a negative value, it is determined that the steering wheel 1 is being increased, and the variable K4 is set to 1.0. The variable K4 is a flag that indicates whether the steering wheel 1 is being turned on or turned off. The variable K4 is set to 1.0 when the steering wheel 1 is turned up and is set to 0.0 when the switchback operation is performed. Further, the steering determination unit 11Bbd determines that the blend axial force T _BR is a positive value and the steering angular velocity dδ / dt is a negative value, or the blend axial force T _BR is a negative value and the steering angular velocity dδ / dt is positive. If the value is a value, it is determined that the steering wheel 1 is not being increased, and the variable K4 is set to zero. Then, the steering determination unit 11Bbd outputs the set variable K4 to the feedback axial force calculation execution unit 11Bbe.

The feedback axial force calculation execution unit 11Bbe receives the current axial force, blend axial force T _BR , steering angular velocity dδ / dt, and current axial force calculation unit 11Bba, blend axial force calculation unit 11Bbb, steering angular velocity detection unit 11Bbc, and steering determination unit 11Bbd. Read variable K4. Subsequently, the feedback axial force calculation execution unit 11Bbe performs steering rack axial force (hereinafter referred to as feedback shaft) according to the following equation (10) based on the read current axial force, blend axial force T _BR , steering angular velocity dδ / dt, and variable K4. Force T _FB ). Then, the feedback axial force calculation execution unit 11Bbe outputs the calculation result to the feedback axial force correction unit 11Bf.
Feedback axial force T _FB = Current axial force × GB + Blend axial force T _BR × (1-GB) (10)

However, GB is a numerical value (hereinafter referred to as a distribution ratio) representing a distribution ratio GB of the current axial force and a distribution ratio (1-GB) of the blend axial force _TBR . As a result, the feedback axial force calculation execution unit 11Bbe adds the current axial force and the blend axial force T _BR at a ratio of GB: (1-GB) based on the distribution ratio GB, thereby obtaining the feedback axial force T _FB . calculate.
Here, as a method of setting the distribution ratio GB, for example, a method of setting the distribution ratio GB by the distribution ratio setting unit 11Bbf based on the determination result output by the steering determination unit 11Bbd can be adopted. The distribution ratio setting unit 11Bbf reads the steering angular velocity dδ / dt and the variable K4 from the steering determination unit 11Bbd. Subsequently, the distribution ratio setting unit 11Bbf calculates the distribution ratio GB according to the following equation (11) based on the read steering angular velocity dδ / dt and the variable K4.
GB = K4 × K5 (11)

However, K5 is a numerical value indicating the distribution ratio GB of the current axial force and the distribution ratio (1-GB) of the blend axial force _TBR when K4 is 1.0, that is, when the steering wheel 1 is increased. is there. Thereby, the feedback axial force calculation execution unit 11Bbe adds the current axial force and the blend axial force T _BR at a ratio of K5: (1-K5) based on the variable K5 when the steering wheel 1 is increased. The feedback axial force T _FB is calculated. Note that when K4 is 0.0, i.e., at the time of switching back operation of the steering wheel 1, regardless of the variable K5, the blend axial force T _BR feedback axial force T _FB.
Here, as a method for setting the variable K5, for example, a method of reading the variable K5 corresponding to the steering angular velocity dδ / dt from the control map M5 can be adopted. An example of the control map M5 is a map in which a variable K5 corresponding to the steering angular velocity dδ / dt is registered.

FIG. 14 is a graph showing the control map M5.
As shown in FIG. 14, the control map M5 shows that the steering angular velocity dδ / dt is large in the range where the absolute value of the steering angular velocity dδ / dt is not less than 0 and less than the fourth set steering angular velocity dδ ₄ / dt (> 0). Regardless, the variable K5 is set to the tenth set value (for example, 1.0). Further, the control map M5 has a variable K5 in the range where the absolute value of the steering angular velocity dδ / dt is not less than the fifth set steering angular velocity dδ ₅ / dt (> dδ ₄ / dt) regardless of the magnitude of the steering angular velocity dδ / dt. Is set to an eleventh set value (<tenth set value, for example, 0.0). Further, the control map M5 indicates that the absolute value of the steering angular velocity dδ / dt is within a range where the absolute value of the steering angular velocity dδ / dt is not less than the fourth set steering angular velocity dδ ₄ / dt and less than the fifth set steering angular velocity dδ ₅ / dt. Accordingly, the variable K5 is decreased linearly. Specifically, the control map M5 indicates that the steering angular velocity dδ / dt is in a range where the absolute value of the steering angular velocity dδ / dt is not less than the fourth set steering angular velocity dδ ₄ / dt and less than the fifth set steering angular velocity dδ ₅ / dt. The variable K5 is set according to a linear function that represents the relationship between the absolute value of and the variable K5. In the linear function, when the absolute value of the steering angular velocity dδ / dt is the fourth set steering angular velocity dδ ₄ / dt, the variable K5 is set to the tenth set value (1.0), and the absolute value of the steering angular velocity dδ / dt is the first value. The variable K5 is set to the eleventh set value (0.0) when the 5-set steering angular velocity is dδ ₅ / dt. As a result, the distribution ratio setting unit 11Bbf has the variable K4 of 1.0 (during the addition operation), and the absolute value of the steering angular velocity dδ / dt is less than the fourth set steering angular velocity dδ ₄ / dt (during low-speed steering). ), The distribution ratio GB is set to 1.0. Then, the feedback axial force calculating execution unit 11Bbe is a feedback axial force T _FB current axial force. Further, in the distribution ratio setting unit 11Bbf, the variable K4 is 1.0 (during the addition operation), and the absolute value of the steering angular velocity dδ / dt is equal to or greater than the fifth setting steering angular velocity dδ ₅ / dt (during high-speed steering). In this case, the distribution ratio GB is set to 0.0. Thus, the feedback axial force calculating execution unit 11Bbe is a blend axial force T _BR feedback axial force T _FB. Further, the distribution ratio setting unit 11Bbf has a variable K4 of 1.0 (at the time of rounding operation), the absolute value of the steering angular velocity dδ / dt is equal to or higher than the fourth setting steering angular velocity dδ ₄ / dt, and is set to the fifth setting. When the steering angular velocity is less than dδ ₅ / dt (during medium speed steering), the variable K5 is set as the distribution ratio GB. Thus, the feedback axial force calculating execution unit 11Bbe includes a feedback axial force T _FB what the sum of the value obtained by multiplying the (1-K5) to the value blended axial force T _BR multiplied by variable K5 current axial force To do. On the other hand, the distribution ratio setting unit 11Bbf sets 0.0 as the distribution ratio GB regardless of the steering angular velocity dδ / dt when the variable K4 is 0.0 (during the switching operation). Then, the feedback axial force calculating execution unit 11Bbe is a blend axial force T _BR feedback axial force T _FB.

As described above, the feedback axial force calculation execution unit 11Bbe of the present embodiment has an absolute value of the steering angular velocity dδ / dt that is less than the fourth set steering angular velocity dδ ₄ / dt when the steering wheel 1 is increased. In this case, the current axial force is set as the feedback axial force _TFB . Here, in the mechanical steering control device in which the steering wheel 1 and the steered wheels 2 are mechanically coupled, the tire lateral force Fd accompanying the steering of the steered wheels 2 when the steering wheel 1 is increased. And the friction generate a steering reaction force that returns the steering wheel 1 to the neutral position. Further, in the feedback axial force calculation execution unit 11Bbe of the present embodiment, the current axial force becomes equal to the sum of the tire lateral force Fd and the friction when the steering wheel 1 is increased. Therefore, the control calculation part 11 of this embodiment can give the steering reaction force which returns the steering wheel 1 to a neutral position similarly to a mechanical steering control apparatus by setting the current axial force to the feedback axial force _TFB. . Thereby, the control calculation part 11 of this embodiment can provide a more appropriate steering reaction force at the time of the steering wheel 1 turning operation.
Incidentally, the blend axial force T _BR does not include an element of friction accompanying steering of the steered wheel 2. Therefore, for example, in the method of using the blend axial force T _BR as the feedback axial force T _FB when the steering wheel 1 is increased, there is a possibility that the steering feeling may be uncomfortable.

Further, when the steering wheel 1 is switched back, the feedback axial force calculation execution unit 11Bbe of the present embodiment performs the current axial force and the lateral G axial force regardless of the absolute value of the steering angular velocity dδ / dt. And blend axial force T _BR that is distributed at a preset distribution ratio is defined as feedback axial force T _FB . Here, in the mechanical steering control device in which the steering wheel 1 and the steered wheels 2 are mechanically coupled, the tire lateral force Fd accompanying the steering of the steered wheels 2 when the steering wheel 1 is switched back. Thus, a steering reaction force that returns the steering wheel 1 to the neutral position is generated. Therefore, in the mechanical steering control device, when the steering wheel 1 is switched back, the driver reduces the holding force of the steering wheel 1 and slides the steering wheel 1 with the palm of the hand, thereby making the steering wheel 1 neutral. The steering wheel 2 was returned to the neutral position. On the other hand, in the feedback axial force calculation execution unit 11Bbe of the present embodiment, the blending axial force T _{BR is set} to the feedback axial force T _FB so that even if the steering current is reduced and the current axial force is reduced, steering is performed. It can suppress that the steering reaction force which returns the wheel 1 to a neutral position reduces. Therefore, the feedback axial force calculation execution unit 11Bbe according to the present embodiment is similar to the mechanical steering control device in that the driver reduces the holding force of the steering wheel 1 and slides the steering wheel 1 with the palm of the steering wheel. The wheel 1 can be returned to the neutral position. Thereby, the control calculating part 11 of this embodiment can provide a more appropriate steering reaction force when the steering wheel 1 is switched back.

Further, the feedback axial force calculation execution unit 11Bbe of the present embodiment determines that the steering wheel 1 is being increased, and the absolute value of the steering angular velocity dδ / dt is the fourth set steering angular velocity dδ ₄ / dt. If it is determined as above, the current axial force and the blend axial force T _BR are distributed to set the feedback axial force T _FB, and the current axial force is distributed as the absolute value of the steering angular velocity dδ / dt decreases. Increase the ratio. Therefore, the feedback axial force calculation execution unit 11Bbe of the present embodiment performs, for example, the steering wheel δ straddling the neutral position during the steering wheel 1 switching operation, and the steering wheel 1 is continuously increased in the same direction. If we, as the absolute value of the steering angular velocity d? / dt during turning-increasing operation is gradually reduced, can gradually transition from a blend axial force T _BR to current axial force feedback axial force T _FB. Thereby, the control calculating part 11 of this embodiment can provide a more appropriate steering reaction force.

Returning to FIG. 3, the final axial force calculation unit 11Bc includes the steering angle δ, the vehicle speed V, the lateral force from the steering angle sensor 3, the vehicle speed sensor 5, the lateral G sensor 6, the feedforward axial force calculation unit 11Ba, and the feedback axial force correction unit 11Bf. read direction acceleration Gy, feedforward axial force T _FF and the feedback axial force T _FB. Subsequently, the final axial force calculator 11Bc calculates the steering angular velocity dδ / dt of the steering wheel 1 based on the read steering angle δ. Subsequently, the final axial force calculating unit 11Bc, based on the read steering angle [delta], the vehicle speed V, the lateral acceleration Gy, feedforward axial force T _FF and the feedback axial force T _FB, calculated steering angular velocity d? / Dt, the following ( The steering rack axial force (hereinafter referred to as final axial force) is calculated according to the equation (12). Then, the final axial force calculation unit 11Bc outputs the calculation result to the axial force-steering reaction force conversion unit 11Bd.
Final axial force = Feed forward axial force T _FF × GF + Feedback axial force T _FB × (1-GF) (12)

Here, GF is a numerical value representing a distribution ratio of the distribution ratio GF and the feedback axial force T _FB feedforward axial force T _FF (1-GF) (hereinafter, referred to as distribution ratio) is. Thus, the final axial force calculating unit 11Bc, based on the distribution ratio GF, the feedforward axial force T _FF and the feedback axial force T _FB GF: by combined at a ratio of (1-GF), the final axial force calculate.
Thus, the final axial force calculating unit 11Bc of the present embodiment calculates the final axial force based on the feedback axial force T _FB and feedforward axial force T _FF. Here, the feedback axial force T _FB changes according to a change in the road surface state or a change in the vehicle state in order to reflect the influence of the tire lateral force Fd acting on the steering wheel 2. In contrast, the feedforward axial force T _FF, since not reflect the influence of tire lateral force Fd, smoothly changes regardless of the change or the like of the road surface condition. Therefore, the final axial force calculating unit 11Bc, in addition to the feedback axial force T _FB, it calculates the final axial force on the basis of the feedforward axial force T _FF, it can be calculated more appropriate final axial force.

The final axial force calculation unit 11Bc includes a distribution ratio calculation unit 11Bca. The distribution ratio calculation unit 11Bca has a distribution ratio GF ₁ based on the axial force difference, a distribution ratio GF ₂ based on the lateral acceleration Gy, a distribution ratio GF ₃ based on the vehicle speed V and the steering angle δ, and a distribution based on the steering angular speed dδ / dt. based on the ratio GF _4, it sets the distribution ratio GF. As the axial force difference, for example, the difference between the feedforward axial force _TFF and the feedback axial force _TFB can be employed. Specifically, the axial force difference, a subtraction result obtained by subtracting the feedback axial force T _FB from the feedforward axial force T _FF. Further, as a method of setting the distribution ratio GF is, for example, and any smaller value of the distribution ratio GF ₂ based on the distribution ratio GF ₁ and lateral acceleration Gy based on the axial force difference, based on the vehicle speed V and steering angle δ A method of multiplying the distribution ratio GF _{3 by the} distribution ratio GF ₄ based on the steering angular velocity dδ / dt and setting the multiplication result as the distribution ratio GF can be adopted.

FIG. 15 is a graph showing the control map M6.
Method for setting distribution ratio GF _1, for example, can be employed a method of reading the distribution ratio GF ₁ which corresponds to the absolute value of the axial force difference from the control map M6. The control map M6, for example, there is a map that has registered the distribution ratio GF ₁ which corresponds to the absolute value of the axial force difference. Specifically, as shown in FIG. 15, the control map M6 has a large axial force difference in a range where the absolute value of the axial force difference is 0 or more and less than the first set axial force difference Z ₁ (> 0). Regardless, the distribution ratio GF ₁ is set to the twelfth set value (for example, 1.0). The first set axial force difference Z _1, for example, can be employed an axial force difference estimation accuracy of the feedforward axial force T _FF starts lowering. Further, in the control map M6, in the range where the absolute value of the axial force difference is equal to or larger than the second set axial force difference Z ₂ (> Z ₁ ), the distribution ratio GF ₁ is set to the thirteenth set value regardless of the magnitude of the axial force difference. (<Twelfth set value. For example, 0.0). As the second set axial force difference Z _2, for example, can be employed an axial force difference estimation accuracy of the feedforward axial force T _FF is lower than the estimation accuracy of the feedback axial force T _FB. Further, in the control map M6, in the range where the absolute value of the axial force difference is not less than the first set axial force difference Z ₁ and less than the second set axial force difference Z ₂ , the distribution ratio GF is determined according to the absolute value of the axial force difference. Decrease ₁ linearly. Specifically, the control map M6 is in and a second set axial force difference Z ₂ than the range in absolute value first set axial force difference Z ₁ or more axial force difference, distribution and the absolute value of the axial force difference ratio setting the distribution ratio GF ₁ according to the primary function representing the relationship between the GF _1. The primary function 12 set value distribution ratio GF ₁ when the absolute value of the axial force difference is first set axial force difference Z ₁ (1.0) and then, the absolute value of the axial force difference is the second setting axis When the force difference is Z ₂ , the distribution ratio GF ₁ is set to the thirteenth set value (0.0).

Thus, the final axial force calculating unit 11Bc of the present embodiment, when the absolute value of the axial force difference is first set axial force difference Z ₁ or more, the absolute value of the first setting the axial force of the axial force difference The distribution ratio GF ₁ (the distribution ratio GF of the feedforward axial force TFF) is made smaller than when the difference is less than Z ₁ . Therefore, the final axial force calculating unit 11Bc of the present embodiment, for example, reduces the road surface mu, the estimation accuracy of the feedforward axial force T _FF is decreased, when the axial force difference is increased, the feedback axial force T _FB distribution ratio (1-GF) can be increased. Therefore, the final axial force calculation unit 11Bc of the present embodiment can apply a more appropriate steering reaction force.

FIG. 16 is a graph showing the control map M7.
Here, as a method of setting the distribution ratio GF _2, for example, it can be employed a method of reading the distribution ratio GF ₂ corresponding to the absolute value of the lateral acceleration Gy from the control map M7. The control map M7, for example, there is a map that has registered the distribution ratio GF ₂ corresponding to the absolute value of the lateral acceleration Gy. Specifically, as shown in FIG. 16, the control map M7 has a lateral acceleration Gy in a range where the absolute value of the lateral acceleration Gy is 0 or more and less than the first set lateral acceleration Gy ₁ (> 0). The distribution ratio GF ₂ is set to the fourteenth set value (for example, 1.0) regardless of the size of. As the first set lateral acceleration Gy _1, for example, it can be adopted lateral acceleration Gy estimation accuracy of the feedforward axial force T _FF starts lowering. Further, the control map M7 is lateral acceleration in the range absolute value of the second set lateral acceleration Gy ₂ (> Gy ₁₎ more Gy, the lateral acceleration distribution ratio GF ₂ regardless of the size of the Gy 15 Set to a set value (<14th set value, eg, 0.0). As the second set lateral acceleration Gy _2, for example, can be adopted lateral acceleration Gy estimation accuracy of the feedforward axial force T _FF is lower than the estimation accuracy of the feedback axial force T _FB. Further, the control map M7 is distributed according to the absolute value of the lateral acceleration Gy in a range where the absolute value of the lateral acceleration Gy is not less than the first set lateral acceleration Gy ₁ and less than the second set lateral acceleration Gy _2. linearly decreasing the ratio GF _2. Specifically, the control map M7 is a lateral acceleration and a second set lateral acceleration Gy ₂ below the range in absolute value first set lateral acceleration Gy ₁ or more Gy, and the absolute value of the lateral acceleration Gy The distribution ratio GF ₂ is set according to a linear function representing the relationship with the distribution ratio GF ₂ . In the linear function, when the absolute value of the lateral acceleration Gy is the first set lateral acceleration Gy ₁ , the distribution ratio GF3 is set to the 14th set value (1.0), and the absolute value of the lateral acceleration Gy is the second set. the distribution ratio GF3 15th set value when a lateral acceleration Gy ₂ and (0.0).

Thus, the final axial force calculating unit 11Bc of the present embodiment, when the absolute value of the lateral acceleration Gy is first set lateral acceleration Gy ₁ or more, the absolute value of the first set of lateral acceleration Gy The distribution ratio GF ₂ (the distribution ratio GF of the feedforward axial force TFF) is made smaller than when the lateral acceleration Gy is less than ₁ . Therefore, the final axial force calculating unit 11Bc of the present embodiment, for example, lateral acceleration Gy increases, when the estimation accuracy of the feedforward axial force T _FF is decreased, the distribution ratio (1 feedback axial force T _FB -GF) can be increased. Therefore, the final axial force calculation unit 11Bc of the present embodiment can apply a more appropriate steering reaction force.

FIG. 17 is a graph showing the control maps M8a and M8b.
Here, as a method of setting the distribution ratio GF _3, for example, the distribution ratio GF _3a corresponding to the absolute value of the absolute value and the steering angle δ of the vehicle speed V, the control GF _3b map M8a, read from M8b, read allocation ratio A method of multiplying GF _3a and GF _3b and making the multiplication result the distribution ratio GF ₃ can be adopted. The control map M8a, for example, there is a map that has registered the distribution ratio GF ₃ corresponding to the absolute value of the vehicle speed V. Specifically, as shown in FIG. 17 (a), the control map M8a is the absolute value range and less than the third set speed V ₃ 0 or more vehicle speed V is allocated regardless of the size of the vehicle speed V The ratio GF _3a is set to the 16th set value (for example, 0.5). As the third set vehicle speed V ₃ , for example, non-linearity of tire characteristics (non-linearity of the tire lateral force Fd with respect to the tire slip angle) due to the low vehicle speed V appears, and the estimation accuracy of the feedforward axial force _TFF decreases. The starting vehicle speed V can be adopted. Further, the control map M8a, to the extent the absolute value of the fourth set speed V ₄ (> V ₃₎ or more of the vehicle speed V, regardless of the magnitude of the vehicle speed V distribution ratio GF _3a seventeenth setting value (> first 16 Set value, for example, 1.0). As the fourth set vehicle speed V ₄ , for example, a vehicle speed V at which the estimation accuracy of the feedforward axial force T _FF is higher than the estimation accuracy of the feedback axial force T _FB can be employed. Further, the control map M8a, the absolute value of the vehicle speed V is in a range and the fourth less than the set vehicle speed V ₄ at the third set speed V ₃ or more, linearly increasing the distribution ratio GF _3a in accordance with the absolute value of the vehicle speed V Let Specifically, the control map M8a, to the extent and in the fourth less than the set vehicle speed V ₄ in absolute value the third set speed V ₃ or more of the vehicle speed V is a linear function representing the relationship between the distribution ratio GF _3a and the vehicle speed V Then, the distribution ratio GF _3a is set. The linear function is assigned when the absolute value of the vehicle speed V is the third set vehicle speed V ₃ and the allocation ratio GF _3a is the 16th set value (0.5), and when the vehicle speed V is the fourth set vehicle speed V _4. The ratio GF _3a is set to the seventeenth set value (1.0).

Thus, the final axial force calculating unit 11Bc of the present embodiment, when the absolute value of the vehicle speed V is the fourth less than the set vehicle speed V _4, the absolute value of the vehicle speed V is in the fourth set speed V ₄ or more Compared to the case, the distribution ratio GF _3a (the distribution ratio GF of the feedforward axial force TFF) is reduced. Therefore, the final axial force calculating unit 11Bc of the present embodiment, for example, the vehicle speed V is reduced, when the estimation accuracy of the feedforward axial force T _FF is decreased, the distribution ratio (1-GF feedback axial force T _FB ) Can be increased. Therefore, the final axial force calculation unit 11Bc of the present embodiment can apply a more appropriate steering reaction force.

Further, as the control map M8b, for example, there is a map in which a distribution ratio GF _3b corresponding to the absolute value of the steering angle δ is registered. Specifically, as shown in FIG. 17B, the control map M8b indicates that the steering angle δ is within a range where the absolute value of the steering angle δ is 0 or more and less than the first set steering angle δ ₁ (> 0). , regardless of the size of the distribution ratio GF _3b 18th set value (e.g., 1.0) is set to. As the first set steering angle δ ₁ , for example, a steering angle δ at which the estimation accuracy of the feedforward axial force _TFF starts to decrease can be employed. Further, the control map M8b, in the range absolute value of the second set steering angle [delta] ₂ (> [delta] ₁₎ more steering angle [delta], the distribution ratio GF _3b regardless of the size of the steering angle [delta] 19 set value ( <18th set value, for example, 0.6). As the second set steering angle δ ₂ , for example, a steering angle δ at which the estimation accuracy of the feedforward axial force T _FF is lower than the estimation accuracy of the feedback axial force T _FB can be employed. Further, in the control map M8b, in the range where the absolute value of the steering angle δ is not less than the first set steering angle δ ₁ and less than the second set steering angle δ ₂ , the distribution ratio GF _3b is set according to the absolute value of the steering angle δ. Decrease linearly. Specifically, the control map M8b indicates that the absolute value of the steering angle δ and the distribution ratio GF _3b are within a range where the absolute value of the steering angle δ is equal to or larger than the first set steering angle δ ₁ and less than the second set steering angle δ _2. The distribution ratio GF _3b is set according to a linear function representing the relationship between In the linear function, when the absolute value of the steering angle δ is the first set steering angle δ ₁ , the distribution ratio GF _3b is set to the 18th set value (1.0), and the absolute value of the steering angle δ is the second set steering angle. 19 set value distribution ratio GF3 when a [delta] ₂ and (0.6).

Thus, the final axial force calculating unit 11Bc of the present embodiment, when the absolute value of the steering angle [delta] is first set steering angle [delta] ₁ or more, the absolute value of the first set steering angle of the steering angle [delta] [delta] _The distribution ratio GF _3b (the distribution ratio GF of the feedforward axial force TFF) is made smaller than when it is less than ₁ . Therefore, the final axial force calculating unit 11Bc of the present embodiment, for example, steering angle δ is increased, when the estimation accuracy of the feedforward axial force T _FF is decreased, the distribution ratio of the feedback axial force T _FB (1- GF) can be increased. Therefore, the final axial force calculation unit 11Bc of the present embodiment can apply a more appropriate steering reaction force.

FIG. 18 is a graph showing the control map M9.
Here, as a method of setting the distribution ratio GF _4, for example, it can be employed a method of reading the distribution ratio GF ₄ corresponding to the absolute value of the steering angular velocity d? / Dt from the control map M9. The control map M9, for example, there is a map that has registered the distribution ratio GF ₄ corresponding to the absolute value of the steering angular velocity d? / Dt. Specifically, as shown in FIG. 18, the control map M9 indicates that the steering angular velocity is in the range where the absolute value of the steering angular velocity dδ / dt is 0 or more and less than the fourth set steering angular velocity dδ ₄ / dt (> 0). Regardless of the magnitude of dδ / dt, the distribution ratio GF ₄ is set to the 20th set value (for example, 1.0). The fourth set steering angular velocity d? ₄ / dt, for example, can be adopted steering angular velocity d? / Dt of estimation accuracy of the feedforward axial force T _FF starts lowering. Further, the control map M9 shows that the distribution ratio is within the range where the absolute value of the steering angular velocity dδ / dt is not less than the fifth set steering angular velocity d ₅ / dt (> dδ ₄ / dt) regardless of the magnitude of the steering angular velocity dδ / dt. the GF ₄ 21 set value (<20th set value. for example, 0.0) is set to. The fifth set steering angular velocity d? ₅ / dt, for example, can be adopted steering angular velocity d? / Dt of estimation accuracy of the feedforward axial force T _FF is lower than the estimation accuracy of the feedback axial force T _FB. Further, the control map M9 indicates that the absolute value of the steering angular velocity dδ / dt is within a range where the absolute value of the steering angular velocity dδ / dt is equal to or larger than the fourth set steering angular velocity dδ ₄ / dt and less than the fifth set steering angular velocity dδ ₅ / dt. linearly decreasing the distribution ratio GF ₄ in accordance with the. Specifically, the control map M9 indicates that the steering angular velocity dδ / dt is within a range where the absolute value of the steering angular velocity dδ / dt is not less than the fourth set steering angular velocity dδ ₄ / dt and less than the fifth set steering angular velocity d ₅ / dt. The distribution ratio GF ₄ is set according to a linear function that represents the relationship between the absolute value of the distribution ratio GF ₄ and the distribution ratio GF ₄ . When the absolute value of the steering angular velocity dδ / dt is the fourth set steering angular velocity dδ ₄ / dt, the linear function sets the distribution ratio GF ₄ to the twentieth set value (1.0) and the absolute value of the steering angular velocity dδ / dt. Is the fifth set steering angular velocity dδ ₅ / dt, the distribution ratio GF ₄ is set to the twenty-first set value (0.0).

As described above, the final axial force calculation unit 11Bc of the present embodiment calculates the absolute value of the steering angular velocity dδ / dt when the absolute value of the steering angular velocity dδ / dt is equal to or greater than the fourth set steering angular velocity dδ ₄ / dt. The distribution ratio GF ₄ (the distribution ratio GF of the feedforward axial force TFF) is made smaller than in the case where it is less than the fourth set steering angular velocity dδ ₄ / dt. Therefore, the final axial force calculation unit 11Bc of the present embodiment, for example, when the steering angular velocity dδ / dt increases and the estimation accuracy of the feedforward axial force T _FF decreases, the distribution ratio of the feedback axial force T _FB ( 1-GF) can be increased. Therefore, the final axial force calculation unit 11Bc of the present embodiment can apply a more appropriate steering reaction force.

Thus, the final axial force calculating unit 11Bc the absolute value of the first set axial force difference Z less than ₁ axial force difference, the absolute value of the first set lateral acceleration Gy less than ₁ lateral acceleration Gy, an absolute vehicle speed V When the value is greater than or equal to the fourth set vehicle speed V ₄ , the absolute value of the steering angle δ is less than the first set steering angle δ ₁ , and the absolute value of the steering angular velocity dδ / dt is less than the fourth set steering angular velocity dδ ₄ / dt. Uses the feedforward axial force _TFF as the final axial force. Also, the final axial force calculating unit 11Bc the absolute value of the axial force difference is the second set axial force difference Z ₂ or more, the absolute value of the lateral acceleration Gy and the second set lateral acceleration Gy ₂ or more, and the steering angular velocity d? / When the absolute value of dt is at least one of the fifth set steering angular velocity dδ ₅ / dt or more, the feedback axial force T _FB is set as the final axial force. Further, the final axial force calculation unit 11Bc has an absolute value of the axial force difference that is greater than or equal to the first set axial force difference Z ₁ and less than the second set axial force difference Z ₂ , and the absolute value of the lateral acceleration Gy is the first set lateral force. Direction acceleration Gy ₁ or more and less than second set lateral acceleration Gy ₂ , vehicle speed V absolute value is less than fourth set vehicle speed V ₄ , steering angle δ absolute value is first set steering angle δ ₁ or more, and steering angular velocity When the absolute value of dδ / dt is equal to or greater than the fourth set steering angular velocity dδ ₄ / dt, a value obtained by multiplying the feedforward axial force T _FF by the distribution ratio GF and the feedback axial force T _FB are allocated (1-GF ) Multiplied by the sum is taken as the final axial force.

Therefore, the final axial force calculation unit 11Bc determines that the vehicle A has a high road surface μ (dry road surface), a high vehicle speed V, a small steering angle δ, and a small steering angular velocity dδ / dt (hereinafter, a specific situation). In this case, the feedforward axial force _TFF is set as the final axial force. Here, the feedforward axial force T _FF, since not reflect the influence of tire lateral force Fd, smoothly changes regardless of the change or the like of the road surface condition. Therefore, the final axial force calculation unit 11Bc can realize a stable steering feeling when the vehicle A is in a specific situation. On the other hand, when the vehicle A is in a situation other than the specific situation (hereinafter also referred to as a normal situation), the final axial force calculation unit 11Bc and the feedback axial force T _FB or the feed forward axial force T _FF are fed back. The sum of the axial force T _FB is the final axial force. Here, the feedback axial force T _FB changes according to a change in the road surface state or a change in the vehicle state in order to reflect the influence of the tire lateral force Fd acting on the steering wheel 2. Therefore, when the vehicle A is in a normal situation, the final axial force calculation unit 11Bc has a steering feeling similar to that of a mechanical steering control device in which the steering wheel 1 and the steering wheel 2 are mechanically coupled. And a natural steering feeling can be realized.

Returning to FIG. 3, the axial force-steering reaction force conversion unit 11Bd calculates a target steering reaction force based on the final axial force calculated by the final axial force calculation unit 11Bc. The target steering reaction force is a target value of the steering reaction force. As a method for calculating the target steering reaction force, for example, a method of reading the target steering reaction force corresponding to the vehicle speed V and the final axial force from the control map M10 can be employed. The control map M10 is a map in which a target steering reaction force corresponding to the final axial force is registered for each vehicle speed V.
FIG. 19 is a graph showing the control map M10.
As shown in FIG. 19, the control map M10 is set for each vehicle speed V. Further, the control map M10 sets the target steering reaction force to a larger value as the final axial force is larger.
Returning to FIG. 3, the target reaction force current calculation unit 11Be calculates a target reaction force current according to the following equation (13) based on the target steering reaction force calculated by the axial force-steering reaction force conversion unit 11Bd. Then, the target reaction force current calculation unit 11Be outputs the calculation result to the reaction force motor drive unit 9C.
Target reaction force current = Target steering reaction force × Gain (13)

In this embodiment, the target reaction force current calculation unit 11Be calculates the target reaction force current based on the target steering reaction force calculated by the axial force-steering reaction force conversion unit 11Bd. A configuration can also be adopted. For example, the target reaction force current calculation unit 11Be corrects the target steering reaction force by adding a correction reaction force, an end contact reaction force, or the like to the target steering reaction force calculated by the axial force-steering reaction force conversion unit 11Bd, The target reaction force current may be calculated based on the corrected target steering reaction force. As the corrective reaction force, for example, there is a steering reaction force applied when the target steering reaction force is corrected. Further, as the end contact reaction force, for example, there is a steering reaction force applied when the turning angle θ reaches the maximum value.
The feedback axial force correction unit 11Bf determines whether the vehicle A is traveling backward based on the position of the shift lever detected by the shift sensor 12. Here, the feedback axial force correction unit 11Bf determines that the vehicle A is traveling backward when it detects that the shift lever is in the R range (reverse traveling position). Then, the feedback shaft force correction unit 11Bf, when it is determined that the vehicle A is retracted traveling, final axis feedforward axial force T _FF feedforward axial force calculating unit 11Ba is calculated as the feedback axial force T _FB It outputs to force calculation part 11Bc. On the other hand, the feedback shaft force correction unit 11Bf, when the vehicle A is judged not to be reverse drive outputs a feedback axial force T _FB feedback axial force calculating unit 11Bb is calculated as the final axial force calculating unit 11Bc .

(Operation other)
Next, the operation of the steering control device for vehicle A will be described.
It is assumed that the driver operates the steering wheel 1 while the vehicle A is traveling backward. Then, the control calculation unit 11 calculates the target turning angle θ * based on the steering angle δ and the vehicle speed V (target turning angle calculation unit 11A in FIG. 2). Subsequently, the control calculation unit 11 calculates a target turning current based on a subtraction result obtained by subtracting the actual turning angle θ from the calculated target turning angle θ * (target turning current calculation unit 11C in FIG. 2). . Thereby, the steering control unit 8 steers the steered wheels 2 according to the operation amount of the steering wheel 1. Then, the vehicle A turns while traveling backward.

At the same time, the control calculation unit 11 calculates a feedforward axial force T _FF based on the steering angle δ and the vehicle speed V (feedforward axial force calculating unit 11Ba of Figure 3). Subsequently, the control calculation unit 11 calculates a current axial force based on the steering current (current axial force calculation unit 11Bba in FIG. 11). Subsequently, the control calculation unit 11 calculates a lateral G-axis force based on the lateral acceleration Gy (blend axial force calculation unit 11Bbb in FIG. 11). Subsequently, the control calculation unit 11 calculates the yaw rate axial force based on the yaw rate γ and the vehicle speed V (blend axial force calculation unit 11Bbb in FIG. 11). Subsequently, the control calculation unit 11 calculates the blend axial force T _BR based on the calculated current axial force, lateral G-axis force, and yaw rate axial force (blend axial force calculation unit 11Bbb in FIG. 11). Then, the control calculation unit 11 distributes the calculated current axial force and the blend axial force T _BR by GB: (1-GB) to calculate the feedback axial force T _FB (feedback axial force calculating unit in FIG. 3). 11Bb).

Subsequently, the control calculation unit 11 determines that the vehicle A is traveling backward based on the position (R range) of the shift lever (feedback axial force correction unit 11Bf in FIG. 3). Subsequently, the control calculation unit 11 replaces the calculated feedback axial force T _FB with the feedforward axial force T _FF (feedback axial force correction unit 11Bf in FIG. 3). Thus, the control arithmetic unit 11 corrects the feedback axial force T _FB feedback axial force calculating unit 11Bb is calculated. Subsequently, the control calculation unit 11 distributes the calculated feed forward axial force T _FF and the corrected feedback axial force T _FB , that is, the feed forward axial force T _FF with GF: (1−GF), The final axial force is calculated (final axial force calculation unit 11Bc in FIG. 3). Thereby, the control calculation part 11 makes final axial force the feedforward axial force _TFF . Subsequently, the control calculation unit 11 calculates a target steering reaction force based on the calculated final axial force (axial force-steering reaction force conversion unit 11Bd in FIG. 3). Subsequently, the control calculation unit 11 calculates a target reaction force current based on the calculated target steering reaction force (target reaction force current calculation unit 11Be in FIG. 3). Subsequently, the control calculation unit 11 drives the reaction force motor 9A based on the calculated target reaction force current (reaction force motor drive unit 9C in FIG. 2). As a result, the reaction force control unit 9 applies a steering reaction force in a direction to return the steering wheel 1 to the neutral position.

Here, in general, when the vehicle A makes a turn while traveling backward, the applied point of the tire lateral force Fd is set behind the ground contact center of the tire, so that the tire lateral direction increases in the direction in which the turning angle increases. A force Fd acts, and a steering rack axial force is generated in a direction that causes the steering rack to deviate from the neutral position. Therefore, the current axial force is generated in a direction that causes the steering rack to deviate from the neutral position. The yaw rate axial force is also generated in a direction that causes the steering rack to deviate from the neutral position. Therefore, the feedback axial force T _FB causes the steering rack to deviate from the neutral position based on these axial forces. Therefore, the feedforward axial force T _FF, positive and negative feedback axial force T _FB reversed. Thus, for example, without correcting the feedback axial force T _FB, in the method of simply calculating the final axial force by distributing the feedback axial force T _FB without correcting the feedforward axial force T _FF, feedforward axial force T _FF When the magnitude relationship between the feedback axial force T _FB and the feedback axial force T _FB fluctuates, there is a possibility that the sign of the final axial force is switched. Therefore, there is a possibility that the steering reaction force is switched between positive and negative, and the steering reaction force vibrates.

On the other hand, the steering control device of the present embodiment replaces the feedback axial force T _FB with the feed forward axial force T _FF when it is determined that the vehicle A is traveling backward, thereby providing the feed forward axial force T _FF Is the final axial force. Therefore, the steering control apparatus of the present embodiment, for example, when the vehicle A is subjected to turning in reverse travel, the feedforward axial force T _FF is steering reaction force based on the steering angle [delta], the tire lateral force Fd Even if the positive / negative of the feedback axial force T _FB that is the steering rack axial force based on the state quantity of the vehicle A (steering current, lateral acceleration Gy, yaw rate γ) fluctuating by Does not switch. Therefore, switching of the driving direction of the reaction force motor 9A can be suppressed, and vibration of the steering reaction force can be suppressed.

Further, the steering control device of the present embodiment can apply a steering reaction force that returns the steering wheel 1 to the neutral position by using the feedforward axial force _TFF as the final axial force. Therefore, the steering control device of the present embodiment can provide a steering reaction force that is more suitable for a general driving feeling.
For example, in the method of using the feedback axial force _TFB as the final axial force, the steering reaction force is applied in a direction that causes the steering rack to deviate from the neutral position. Therefore, there is a possibility of giving the driver a feeling that the steering wheel 1 is taken in the steering direction.
Further, the steering control device of the present embodiment determines that the vehicle A is traveling backward when it is detected that the shift lever is in the R range (reverse traveling position). Therefore, the steering control device of the present embodiment can relatively easily determine whether the vehicle A is traveling backward.

  In this embodiment, the steering wheel 1 of FIG. 1 comprises a steering wheel. Similarly, the steered motor 8A in FIG. 1 constitutes a steered actuator, and the steered motor drive unit 8C constitutes a steered actuator. Moreover, the steering angle sensor 3 of FIG. 1 comprises a steering angle detection part. Further, the feedforward axial force calculation unit 11Ba of FIG. 1 constitutes a feedforward axial force calculation unit. Further, the lateral G sensor 6, the yaw rate sensor 7, and the steering current detection unit 8B in FIG. Further, the feedback axial force calculation unit 11Bb in FIG. 3 and the feedback axial force calculation execution unit 11Bbe in FIG. 11 constitute a feedback axial force calculation unit. Further, the feedback axial force correction unit 11Bf in FIG. 2 and the final axial force calculation unit 11Bc in FIG. 3 constitute a final axial force setting unit. Further, the reaction force motor 9A, the reaction force motor drive unit 9C in FIG. 1, and the target reaction force current calculation unit 11B in FIG. 2 constitute a reaction force actuator. 1 constitutes a shift lever position detector.

(Effect of this embodiment)
This embodiment has the following effects.
(1) The control calculation unit 11 calculates the steering reaction force based on the steering angle δ as the feedforward axial force _TFF . Subsequently, the control calculation unit 11 calculates the steering rack axial force based on the state quantity of the vehicle A that varies with the tire lateral force Fd acting on the steered wheels 2 as the feedback axial force _TFB . Subsequently, the control calculation unit 11 distributes the calculated feedforward axial force _TFF and feedback axial force _TFB to set the final axial force. Subsequently, the control calculation unit 11 applies a steering reaction force based on the set final axial force. At that time, when the control calculation unit 11 determines that the vehicle A is traveling backward, the feedforward axial force _TFF is set as the final axial force.
According to such a configuration, when it is determined that the vehicle A is traveling backward, the feedforward axial force _TFF is set as the final axial force. Thus, for example, when the vehicle A is subjected to turning in reverse travel, the feedforward axial force T _FF is steering reaction force based on the steering angle [delta], the state quantity of the vehicle A which varies in the tire lateral force Fd Even if the positive and negative of the feedback axial force T _FB that is the steering rack axial force based on it is reversed, the positive and negative of the final axial force is not switched. Therefore, switching of the driving direction of the reaction force motor 9A can be suppressed, and vibration of the steering reaction force can be suppressed.

(2) When the control calculation unit 11 detects that the shift lever is in the R range (reverse travel position), it determines that the vehicle A is traveling backward.
According to such a configuration, it can be relatively easily determined whether the vehicle A is traveling backward.
As described above, the entire contents of Japanese Patent Application No. 2013-3878 (filed on January 11, 2013) to which the present application claims priority form part of the present disclosure by reference.
Although the present invention has been described with reference to a limited number of embodiments, the scope of rights is not limited thereto, and modifications of each embodiment based on the above disclosure are obvious to those skilled in the art.

1 Steering wheel (steering wheel)
3 Steering angle sensor (steering angle detector)
5 Vehicle speed sensor (vehicle speed detector)
6 Horizontal G sensor (state quantity detector)
7 Yaw rate sensor (state quantity detector)
8A Steering motor (steering actuator)
8B Steering current detector (state quantity detector)
8C Steering motor drive (steering actuator)
9A reaction force motor (reaction force actuator)
9C Reaction force motor drive (Reaction force actuator)
11B Target reaction force current calculation part (Reaction force actuator)
11Ba Feedforward axial force calculation unit (feedforward axial force calculation unit)
11Bb Feedback axial force calculation unit (feedback axial force calculation unit)
11Bbe Feedback axial force calculation execution unit (feedback axial force calculation unit)
11Bc Final axial force calculation unit (final axial force setting unit)
11Bf Feedback axial force correction unit (final axial force setting unit)
12 Shift sensor (shift lever position detector)

Claims (2)

A steering wheel mechanically separated from the steering wheel;
A steering angle detector for detecting a steering angle of the steering wheel;
A steering actuator that steers the steered wheels according to the steering angle detected by the steering angle detector;
Based on the steering angle detected by the steering angle detector, a feedforward axial force that is a force generated in the steering system in a direction to return the steering wheel to a neutral position as an axial force that gives a steering reaction force according to the steering angle. A feedforward axial force calculation unit for calculating
A state quantity detection unit for detecting a state quantity of the vehicle that varies with a tire lateral force acting on the steering wheel;
Based on the state quantity of the vehicle detected by the state quantity detection unit, in a direction to return the steering wheel to the neutral position when moving forward as an axial force that returns a steering reaction force to the driver from the road surface input to the steering wheel. A feedback axial force calculation unit that calculates a feedback axial force that is a force generated in the steering system and is a force generated in the steering system in a direction that causes the steering wheel to deviate from a neutral position when reversing;
A final axial force that is an axial force obtained by distributing the feedforward axial force calculated by the feedforward axial force calculating unit and the feedback axial force calculated by the feedback axial force calculating unit at a certain distribution ratio is set. The final axial force setting section,
A reaction force actuator for applying an operation reaction force based on the final axial force set by the final axial force setting unit,
When it is determined that the vehicle is traveling backward, the final axial force setting unit sets the feedforward axial force calculated by the feedforward axial force calculation unit as the final axial force. A steering control device. A shift lever position detector for detecting the position of the shift lever of the transmission;
The final axial force setting unit determines that the vehicle is traveling backward when the shift lever position detecting unit detects that the shift lever is in a backward traveling position. The steering control device according to 1.

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