JP6811658B2 - Vehicle steering system - Google Patents

Description

The present invention relates to a steering device for a vehicle that controls a steering angle adjusting device (EPS motor, torque vectoring mechanism, etc.) so as to reduce an error between a target steering angle and a detected steering angle.

It is an object of Patent Document 1 to provide a steering device for a vehicle capable of traveling on a course according to a driver's intention regardless of a change in loading conditions and a change in tire pressure or the like. ([0008], summary).

In order to achieve the object, the vehicle steering device of Patent Document 1 (summary) includes a steering angle detecting means 11, a vehicle speed detecting means 12, a yaw rate detecting means 13, a steering wheel angle detecting means 14, and a target steering. The steering wheel angle generating means 40 and the steering wheel angle controlling means 15 are provided. The target steering wheel angle generating means 40 determines the steering angle, vehicle speed, yaw rate, and actual steering wheel angle detected by the steering angle detecting means 11, the vehicle speed detecting means 12, the yaw rate detecting means 13, and the steering wheel angle detecting means 14. Based on this, the target steering wheel angle is generated. The steering wheel angle control means 15 controls the steering wheel angle of the vehicle based on the target steering wheel angle generated by the target steering wheel angle generating means 40. The target steering wheel angle generating means 40 uses the actual stability factor, which is a value equivalent to the actual turning radius generated in the vehicle, and the standard stability factor, which is a value equivalent to the standard turning radius predetermined by the vehicle, to steer the target. Generate a radius.

In Embodiment 1 of Patent Document 1 (FIGS. 3, 4, [0023], [0030] and [0031]), the stability factor error is calculated based on the normative stability factor signal and the actual stability factor signal. , Stability factor Outputs an error signal. In addition, the steering angle ratio correction amount is calculated based on the stability factor error signal, and the steering angle ratio correction amount signal is output. Further, the target steering angle ratio is calculated based on the basic steering angle ratio signal and the steering angle ratio correction amount signal, and the target steering angle ratio signal is output. Furthermore, the target steering angle ratio signal and the steering angle signal are multiplied to generate a target steering wheel angle signal. The same applies to the second embodiment of Patent Document 1 (FIGS. 5, 6 and [0049] to [0051]).

JP-A-2009-119921

As described above, in Patent Document 1, when calculating the target steering wheel angle (target steering angle), the error between the normative stability factor and the actual stability factor is obtained. Then, the target steering angle ratio is calculated by reflecting the steering angle ratio correction amount based on this error in the basic steering angle ratio. Further, the target steering wheel angle is calculated by multiplying the target steering angle ratio and the steering angle. Based on the above, Patent Document 1 is premised on a configuration in which the steering angle ratio is variable (so-called steer-by-wire configuration) (see [0002] to [0007] and FIG. 2).

In paragraph [0062] of Patent Document 1, there is a description that the steering wheel and the steering wheel mechanism are not mechanically connected to each other, but there is no specific disclosure regarding other configurations. Therefore, in Patent Document 1, there is room for improvement in terms of application to vehicles having a fixed steering angle ratio.

The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a steering device for a vehicle capable of improving steering performance regardless of whether or not the steering angle ratio is variable. ..

The vehicle steering device according to the present invention is
A rudder angle adjustment device that adjusts the rudder angle of the own vehicle,
A detection steering angle acquisition means for acquiring the detection steering angle of the own vehicle, and
Lane information acquisition means to acquire information on own vehicle lane,
The vehicle speed acquisition means for acquiring the vehicle speed of the own vehicle and
The detection yaw rate acquisition means for acquiring the detection yaw rate of the own vehicle and
A control device that executes steering control that controls the steering angle adjusting device using the target steering angle, and
With
In the steering control, the control device
A reference yaw rate is calculated based on the detected steering angle or the target steering angle and the vehicle speed.
The normative stability factor is calculated based on the deviation between the detected yaw rate and the normative yaw rate.
A new target steering angle is calculated based on the information of the own vehicle lane, the vehicle speed, and the normative stability factor.
It is characterized in that the steering angle adjusting device is controlled so as to reduce an error between the target steering angle and the detected steering angle.

According to the present invention, the normative stability factor calculated based on the deviation between the normative yaw rate and the detected yaw rate is reflected in the target steering angle. Therefore, the target steering angle can be calculated regardless of whether or not the steering angle ratio is used. Therefore, regardless of whether the steering angle ratio is variable or not, steering control can be performed in consideration of changes in the normative stability factor. Therefore, steering performance can be improved by realizing steering control in consideration of the wheel condition (aging, pressure change, etc.), the number and position of occupants, the load condition of luggage, and the like.

The control device may update the normative stability factor only when the steering angular velocity is below the speed threshold. When the rudder angular velocity exceeds the speed threshold value, there is a high possibility of erroneous learning such as the phase shift between the normative yaw rate and the detected yaw rate, or the normative stability factor fluctuates due to the high rudder angular velocity. In the present invention, the normative stability factor is not updated when the steering angular velocity exceeds the speed threshold value. Therefore, it is possible to suppress the above-mentioned erroneous learning, and it is possible to execute steering control without a sense of discomfort.

The control device may acquire the contact margin time between the vehicle in front and the own vehicle. Further, the control device may stop updating the normative stability factor when the contact margin time is less than the time threshold value. If the contact margin time between the vehicle in front and the vehicle in front is relatively short, it is highly probable that the vehicle has started accelerating in order to overtake the vehicle in front. When the own vehicle tries to overtake, the behavior of the own vehicle is likely to change suddenly, and it can be considered that it is not suitable for updating the normative stability factor. In the present invention, it is possible to improve the accuracy of the normative stability factor by stopping the update of the normative stability factor in a state where the possibility of overtaking is high.

According to the present invention, steering performance can be improved regardless of whether or not the steering angle ratio is variable.

It is a schematic block diagram of the vehicle which has the steering device for a vehicle which concerns on one Embodiment of this invention. It is a flowchart which switches between basic assist control and LKAS control in the said vehicle of the said embodiment. It is a figure which shows the functional structure of the arithmetic unit of the electronic control device (ECU) in the said embodiment. It is a figure which shows the specific functional structure of the target steering angle setting part of the said embodiment. It is a flowchart of the norm stability factor (SF) update control executed by the norm stability factor update part of the said embodiment. It is a flowchart of the norm stability factor (SF) update control which concerns on a modification.

A. One Embodiment <A-1. Explanation of the overall configuration>
[A-1-1. Overview]
FIG. 1 is a schematic configuration diagram of a vehicle 10 having a vehicle steering device 12 according to an embodiment of the present invention. The steering device 12 of the present embodiment also serves as an electric power steering device 14 (hereinafter referred to as "EPS device 14") and a lane keep assist system 16 (hereinafter referred to as "LKAS 16").

[A-1-2. EPS device 14]
(A-1-2-1. Outline of EPS device 14)
Among the steering devices 12, the EPS device 14 includes a steering wheel 20, a steering column 22, an intermediate joint 24, a steering gearbox 26, and a motor 28 for driving the EPS device (hereinafter, also referred to as “EPS motor 28”). , Inverter 30 (hereinafter also referred to as "EPS inverter 30"), vehicle speed sensor 32, current sensor 34, yaw rate sensor 36, electronic control device 38 (hereinafter referred to as "ECU 38"), and low voltage battery 40 (hereinafter referred to as "ECU 38"). Hereinafter, it is also referred to as “battery 40”).

The steering column 22 includes a housing 50, a steering shaft 52 supported by bearings 54, 56, and 58 inside the housing 50, a torque sensor 60, and a steering angle sensor 62.

The intermediate joint 24 has two universal joints 70a and 70b and a shaft portion 72 arranged between them.

The steering gearbox 26 includes a housing 80, a pinion shaft 82 provided with a pinion 84 of a rack and pinion mechanism and supported by bearings 86 and 88, and a rack shaft 90 provided with rack teeth 92 of the rack and pinion mechanism. , With a tie rod 94.

(A-1-2-2. Manual steering system)
One end of the steering shaft 52 is fixed to the steering wheel 20, and the other end is connected to the universal joint 70a. The universal joint 70a connects one end of the steering shaft 52 and one end of the shaft portion 72. The universal joint 70b connects the other end of the shaft portion 72 and one end of the pinion shaft 82. The pinion 84 of the pinion shaft 82 and the rack teeth 92 of the rack shaft 90 that can reciprocate in the vehicle width direction mesh with each other. Both ends of the rack shaft 90 are connected to the left and right front wheels 96 (steering wheels) via tie rods 94, respectively.

Therefore, the steering torque Tstr (rotational force) generated by the driver operating the steering wheel 20 is transmitted to the pinion shaft 82 via the steering shaft 52 and the intermediate joint 24. Then, the steering torque Tstr is converted into thrust by the pinion 84 of the pinion shaft 82 and the rack teeth 92 of the rack shaft 90, and the rack shaft 90 is displaced in the vehicle width direction. The tie rod 94 steers the front wheels 96 with the displacement of the rack shaft 90, so that the direction of the vehicle 10 can be changed.

The steering shaft 52, the intermediate joint 24, the pinion shaft 82, the rack shaft 90, and the tie rod 94 constitute a manual steering system that directly transmits the steering operation of the driver with respect to the steering wheel 20 to the front wheels 96.

(A-1-2-3. Steering assist system)
(A-1-2-3-1. Assist drive system)
The EPS motor 28 (steering angle adjusting device) is connected to the steering shaft 52 via the worm gear 100 and the worm wheel gear 102. That is, the output shaft of the EPS motor 28 is connected to the worm gear 100. Further, the worm wheel gear 102 that meshes with the worm gear 100 is integrally formed with the steering shaft 52 itself.

The EPS motor 28 of the present embodiment is, for example, a three-phase AC brushless type, but may be another motor such as a three-phase AC brush type, a single-phase AC type, or a DC type. The EPS motor 28 is supplied with electric power from the low-voltage battery 40 via the EPS inverter 30 controlled by the ECU 38. Then, a drive torque Tm (hereinafter, also referred to as "motor torque Tm" or "torque Tm") corresponding to the electric power is generated. The motor torque Tm (or thrust based on the motor torque Tm) is transmitted to the rack shaft 90 via the output shaft of the EPS motor 28, the worm gear 100, the steering shaft 52 (worm wheel gear 102), the intermediate joint 24, and the pinion shaft 82. The EPS motor 28, the worm gear 100, and the steering shaft 52 (worm wheel gear 102) form an assist drive system that generates a driving force (motor torque Tm) for steering.

The torque Tm in this embodiment is used as the steering assist torque Tasi. The steering assist torque Tasi includes a basic assist torque Tb and a LKAS torque Tlkas.

The basic assist torque Tb is a driving force that works in the same direction as the driver's input torque (steering torque Tstr) with respect to the steering wheel 20 to assist the driver in steering. The LKAS torque Tlkas is a torque for steering the vehicle 10 so as to continuously travel in the traveling lane (not shown). The steering assist torque Tasi can also be acted in the direction opposite to the steering torque Tstr as a reaction force for notifying the driver of preferable steering.

(A-1-2-3-2. Assist control system)
The EPS inverter 30, the vehicle speed sensor 32, the current sensor 34, the yaw rate sensor 36, the ECU 38, the torque sensor 60, and the steering angle sensor 62 constitute an assist control system that controls the assist drive system. Hereinafter, the assist drive system, the assist control system, and the low-voltage battery 40 are collectively referred to as a steering assist system. In this embodiment, the output of the EPS motor 28 is controlled by so-called vector control using the d-axis and the q-axis.

(A) Feedforward sensors The torque sensor 60 detects the steering torque Tstr applied to the steering shaft 52 and outputs it to the ECU 38. The vehicle speed sensor 32 (vehicle speed acquisition means) detects the vehicle speed V [km / h] and outputs it to the ECU 38. The yaw rate sensor 36 (detection yaw rate acquisition means) detects the yaw rate Y generated in the vehicle 10 and outputs it to the ECU 38. The steering angle sensor 62 (detection steering angle acquisition means) detects the steering angle θstr (detected steering angle θstr) [degrees] indicating the steering amount of the steering wheel 20 and outputs the steering angle to the ECU 38. The steering torque Tstr, vehicle speed V, yaw rate Y, and steering angle θstr are used for feedforward control in the ECU 38.

Hereinafter, the yaw rate Y detected by the yaw rate sensor 36 is also referred to as a detected yaw rate Ydet or an actual yaw rate Ydet. Further, the rudder angle θstr detected by the rudder angle sensor 62 is also referred to as a detected rudder angle θstrdet.

(B) EPS inverter 30
The EPS inverter 30 has a three-phase bridge type configuration, performs DC / AC conversion, converts the DC from the low-voltage battery 40 into a three-phase AC, and supplies it to the EPS motor 28.

(C) Feedback system sensors The current sensor 34 detects a q-axis current (hereinafter referred to as “motor current Im”) which is a torque current component in the vector control. The motor current Im in the present embodiment is set to a positive value when the rotation direction of the motor 28 is the first direction (for example, the direction for rotating the vehicle 10 to the right), and the second direction (for example, the vehicle 10 is rotated to the left). It is a negative value when it is in the direction of making it. However, if the first direction and the second direction can be determined, the motor current Im may be controlled only by a positive value.

The current sensor 34 is a current sensor (not shown) that detects the current of at least two phases of the U phase, V phase, and W phase in the winding (not shown) of the EPS motor 28, and the EPS motor 28 (not shown). A resolver (not shown) that detects the electric angle θ that is the rotation angle of the output shaft or the outer rotor, and the q-axis that calculates the q-axis current (motor current Im) based on the current and electric angle θ of at least two phases. Includes a current calculation unit. The function of the q-axis current calculation unit can also be performed by the ECU 38.

(D) ECU 38
As shown in FIG. 1, the ECU 38 has an input / output unit 110, a calculation unit 112, and a storage unit 114 as a hardware configuration. The ECU 38 controls the output of the EPS motor 28 via the EPS inverter 30 based on the output value from each sensor. The input / output unit 110 inputs / outputs between the ECU 38 and an external device (for example, a vehicle speed sensor 32 and a steering angle sensor 62).

The calculation unit 112 includes a central processing unit (CPU), and controls the steering device 12 (EPS device 14 and LKAS 16) using the programs and data stored in the storage unit 114. The calculation unit 112 includes a basic assist control unit 130 and a LKAS control unit 132. The basic assist control unit 130 and the LKAS control unit 132 both form a part of the EPS device 14. The LKAS control unit 132 also constitutes a part of the LKAS 16. Details of the ECU 38 will be described later with reference to FIG. 3 and the like.

The storage unit 114 stores programs and data used by the arithmetic unit 112, and includes a random access memory (hereinafter referred to as “RAM”). As the RAM, a volatile memory such as a register and a non-volatile memory such as a flash memory can be used. Further, the storage unit 114 may have a read-only memory (hereinafter referred to as “ROM”) in addition to the RAM.

(A-1-2-3-3. Low voltage battery 40)
The low voltage battery 40 is a power storage device capable of outputting a low voltage (12 volts in this embodiment), and for example, a secondary battery such as a lead storage battery can be used.

[A-1--3. LKAS16]
Of the steering devices 12, the LKAS 16 has a front camera 140 (hereinafter, also referred to as “camera 140”) and a LKAS switch 142 in addition to the EPS motor 28, ECU 38, and the like described above.

The camera 140 (lane information acquisition means) is attached to the inside of the front windshield in front of the rearview mirror, and when the LKAS switch 142 is turned on, the lanes on both sides on the front road surface (traveling lane). Mark LM (not shown) is captured as an image. The LKAS switch 142 outputs a signal Slkas according to the user's operation to switch the LKAS 16 on and off.

The ECU 38 (particularly the LKAS control unit 132) executes the LKAS control (lane maintenance control). The lane marks LM (white line or boundary line) on both sides of the vehicle 10 are detected from the front image If acquired by the camera 140. Then, the vehicle 10 controls the EPS motor 28 so as to travel in the center of both lane marks LM, for example. In the LKAS control of the present embodiment, the vehicle speed V is executed in the range of, for example, 65 to 100 [km / h].

<A-2. Output control of EPS motor 28>
[A2-1. Overview]
As described above, in the present embodiment, the basic assist control and the LKAS control are executed. The basic assist control is a control that assists according to the steering of the driver. In the basic assist control, the basic assist torque Tb is used. The basic assist torque Tb is a torque for amplifying the steering torque Tstr.

The LKAS control controls the EPS motor 28 so that the own vehicle 10 continuously travels in the traveling lane. More specifically, the EPS so that the reference position Prefv of the vehicle 10 (hereinafter, also referred to as “vehicle reference position Prefv”) coincides with the reference position Prefl of the traveling lane (hereinafter, also referred to as “lane reference position Prefl”). Controls the motor 28. The vehicle reference position Prefv is set, for example, in the center of the vehicle 10 in the vehicle width direction. The lane reference position Prefl is set, for example, in the center of the traveling lane in the vehicle width direction.

In the LKAS control, the LKAS torque Tlkas is used. The LKAS torque Tlkas is a torque for reducing the deviation between the vehicle reference position Prefv and the lane reference position Prefl.

[A-2-2. Switching between basic assist control and LKAS control]
FIG. 2 is a flowchart for switching between basic assist control and LKAS control in the vehicle 10 of the present embodiment. Here, it will be described as the movement of the entire vehicle 10 rather than the processing of a specific ECU or the like. The vehicle 10 repeats the switching of FIG. 2 at predetermined intervals. When the LKAS 16 is on (operating) (S11: TRUE), in step S12, the vehicle 10 executes the LKAS control. In this case, the EPS motor 28 outputs the basic assist torque Tb and the LKAS torque Tlkas.

When the LKAS 16 is off (stopped) (S11: FALSE), in step S13, the vehicle 10 executes the basic assist control. In this case, the EPS motor 28 outputs only the basic assist torque Tb.

[A-2-3. Functional configuration of the calculation unit 112 of the ECU 38]
(A-2-3-1. Overview)
FIG. 3 is a diagram showing a functional configuration of the calculation unit 112 of the ECU 38 in the present embodiment. As shown in FIG. 3, the calculation unit 112 includes a basic assist current calculation unit 200, a LKAS current calculation unit 202, an adder 204, and a drive signal output unit 206.

The calculation unit 112 realizes each of the above units by executing the program stored in the storage unit 114. However, it is also possible to realize some functions of each part by hardware (electric circuit or the like).

(A-2-3-2. Basic assist current calculation unit 200)
The basic assist current calculation unit 200 (hereinafter, also referred to as “calculation unit 200”) is based on the steering torque Tstr from the torque sensor 60, the steering angle θstr from the steering angle sensor 62, and the vehicle speed V from the vehicle speed sensor 32. The basic assist current Ibase is calculated. The basic assist current Ibase is a current corresponding to the basic assist torque Tb. In the present embodiment, the storage unit 114 stores a map in which the combination of the steering torque Tstr, the steering angular velocity Vθstr, and the vehicle speed V and the basic assist current Ibase are associated with each other. The calculation unit 200 calculates the steering angular velocity Vθstr [deg / s] based on the steering angle θstr [deg], and then specifies the basic assist current Ibase corresponding to the combination of the steering torque Tstr, the steering angular velocity Vθstr, and the vehicle speed V. ..

(A-2-3-3. LKAS current calculation unit 202)
(A-2-3-3-1. Outline of LKAS current calculation unit 202)
The LKAS current calculation unit 202 (hereinafter, also referred to as “calculation unit 202”) is a front image If from the camera 140, a vehicle speed V from the vehicle speed sensor 32, a yaw rate Y from the yaw rate sensor 36, and a steering angle sensor 62. The LKAS current Ilkas is calculated based on the rudder angle θstr of. The LKAS current Ilkas is a current corresponding to the LKAS torque Tlkas. As shown in FIG. 3, the calculation unit 202 includes a camera information processing unit 210, a reference steering angle current calculation unit 212, a lateral deviation amount correction current calculation unit 214, and an adder 216.

(A-2-3-3-2. Camera Information Processing Unit 210)
The camera information processing unit 210 (hereinafter, also referred to as “processing unit 210”) outputs image information Ii (radius of curvature R and lateral deviation amount ΔDlat described later) based on the front image If from the camera 140. As shown in FIG. 3, the processing unit 210 includes a radius of curvature calculation unit 220 and a lateral deviation amount calculation unit 222. The radius of curvature calculation unit 220 calculates the radius of curvature R [m] of the traveling lane based on the forward image If. The lateral displacement amount calculation unit 222 calculates the lateral displacement amount ΔDlat of the vehicle 10. The lateral displacement amount ΔDlat indicates the deviation [m] between the vehicle reference position Prefv and the lane reference position Prefl. As described above, the vehicle reference position Prefv is set, for example, in the center of the vehicle 10 in the vehicle width direction, and the lane reference position Prefl is set, for example, in the center of the traveling lane in the vehicle width direction.

(A-2-3-3-3. Reference rudder angle current calculation unit 212)
(A-2-3-3-3-1. Outline of reference rudder angle current calculation unit 212)
The reference steering angle current calculation unit 212 (hereinafter, also referred to as “calculation unit 212”) calculates the reference steering angle current Iθ corresponding to a part of the LKAS torque Tlkas. As shown in FIG. 3, the calculation unit 212 includes a target steering angle setting unit 230, a subtractor 232, and a current calculation unit 234.

The target rudder angle setting unit 230 (hereinafter, also referred to as “setting unit 230”) is based on a rudder angle θstr (detected rudder angle θstrdet), a vehicle speed V, a yaw rate Y (detected yaw rate Ydet), and a radius of curvature R. The target rudder angle θstratar is set (details will be described later with reference to FIG. 4). The subtractor 232 determines the deviation between the target rudder angle θstrtar set by the target rudder angle setting unit 230 and the rudder angle θstr (detected rudder angle θstrdet) from the rudder angle sensor 62 (hereinafter referred to as “rudder angle deviation Δθstr”). Calculate (Δθstr = θstrtar−θstr). The current calculation unit 234 calculates the reference steering angle current Iθ based on the steering angle deviation Δθstr.

Specifically, the current calculation unit 234 calculates the reference steering angle current Iθ so that the steering angle deviation Δθstr becomes zero. The storage unit 114 stores a map (reference steering angle current map) in which the steering angle deviation Δθstr and the reference steering angle current Iθ are associated with each other. The current calculation unit 234 reads out the reference steering angle current Iθ corresponding to the steering angle deviation Δθstr from the reference steering angle current map and outputs it.

(A-2-3-3-3-2. Target steering angle setting unit 230)
(A-2-3-3-3-2-1. Outline of target rudder angle setting unit 230)
FIG. 4 is a diagram showing a specific functional configuration of the target steering angle setting unit 230 of the present embodiment. As described above, the setting unit 230 sets the target steering angle θstrtar based on the steering angle θstr (detected steering angle θstrdet), the vehicle speed V, the yaw rate Y (detected yaw rate Ydet), and the radius of curvature R. As shown in FIG. 4, the setting unit 230 includes a norm yaw rate calculation unit 250, a subtractor 252, a norm stability factor update unit 254, and a target steering angle calculation unit 256.

(A-2-3-3-3-2-2. Normative yaw rate calculation unit 250)
The standard yaw rate calculation unit 250 (hereinafter, also referred to as “calculation unit 250”) includes a steering angle θstr from the steering angle sensor 62, a vehicle speed V from the vehicle speed sensor 32, and a standard stability factor A from the SF update unit 254. The normative yaw rate Yref is calculated based on. Specifically, the calculation unit 250 calculates the normative yaw rate Yref using the following equation (1).

In equation (1), A is the normative stability factor, V is the vehicle speed, L is the wheelbase (fixed value) of the vehicle 10, Ks is the steering ratio (fixed value), and θstr. Is the steering angle (detected steering angle θstrdet).

(A-2-3-3-3-2-3. Subtractor 252)
The subtractor 252 calculates the deviation between the yaw rate Y (detected yaw rate Ydet) from the yaw rate sensor 36 and the norm yaw rate Yref from the norm yaw rate calculation unit 250 (hereinafter referred to as “yaw rate deviation ΔY”) (ΔY = Y−Yref). ).

(A-2-3-3-3-2-4. Norm Stability Factor Update Department 254)
The norm stability factor update unit 254 (hereinafter, also referred to as "norm SF update unit 254", "SF update unit 254", or "update unit 254") is also referred to as "norm stability factor update control" (hereinafter, "norm SF update control"). ) Is executed. The norm SF update control is a control for updating the norm stability factor A (hereinafter, also referred to as “norm SF A”) of the vehicle 10.

FIG. 5 is a flowchart of the norm SF update control executed by the norm stability factor update unit 254 of the present embodiment. In step S21, the SF update unit 254 calculates the steering angular velocity Vθstr based on the steering angle θstr (detected steering angle θstrdet) from the steering angle sensor 62.

In step S22, the SF update unit 254 determines whether or not the steering angular velocity Vθstr is lower than the speed threshold THvθstr (hereinafter, also referred to as “threshold THvθstr”). The threshold value THvθstr is a threshold value for determining whether or not the correlation between the steering angle θstr (detected steering angle θstrdet) and the detected yaw rate Ydet is sufficiently secured. This is because if the rudder angle θstr changes too quickly, the detected yaw rate Ydet cannot follow due to inertia, and the learning value tends to include an error. When the rudder angular velocity Vθstr is lower than the threshold value THvθstr (S22: TRUE), in step S23, the SF update unit 254 updates the norm SF A. Specifically, the update unit 254 calculates a new norm SF A using the following equation (2).

In equation (2), _An is the previous value of the normative stability factor, _{An + 1} is the current value of the normative stability factor, m (or 2 m) is the update gain, and Y is the yaw rate ( The detected yaw rate Ydet), and Yref is the normative yaw rate. The update gain m is set between 0 and a predetermined positive value. In step S23, the update gain m can be set to a fixed value. Alternatively, m may be reduced as the steering angular velocity Vθstr becomes higher.

In the equation (2), the value obtained by adding the second term on the right side to the previous value A _n is set as the current value A _{n + 1} . The second term on the right side includes the deviation ΔY between the yaw rate Y (detected yaw rate Ydet) and the normative yaw rate Yref. Therefore, the norm SF _{An + 1} changes according to the yaw rate deviation ΔY. Further, the second term on the right side, comprises a value obtained by partially differentiating the reference yaw rate Yref normative SF A _n.

When the steering angular velocity Vθstr does not fall below the threshold value THvθstr (S22: FALSE), the ECU 38 does not update (stop) the normative stability factor A in step S24. The ECU 38 can cancel the update by, for example, setting the update gain m of the equation (2) to zero.

(A-2-3-3-3-2-5. Target steering angle calculation unit 256)
The target steering angle calculation unit 256 (hereinafter, also referred to as “calculation unit 256”) is derived from the reference SF A from the update unit 254, the vehicle speed V from the vehicle speed sensor 32, and the curvature radius calculation unit 220 of the camera information processing unit 210. The target rudder angle θstrtar is calculated based on the radius of curvature R of. Specifically, the calculation unit 256 calculates the target rudder angle θstrtar using the following equation (3).

In equation (3), Ks is the steering ratio, L is the wheelbase, A is the normative stability factor, V is the vehicle speed, and R is the radius of curvature.

(A-2-3-3-4. Lateral displacement correction current calculation unit 214)
The lateral displacement amount correction current calculation unit 214 (hereinafter, also referred to as “calculation unit 214”) in FIG. 3 is also referred to as a lateral displacement amount correction current Id (hereinafter, also referred to as “correction current Id”) for correcting the lateral displacement amount ΔDlat. ) Is calculated. The calculation unit 214 of the present embodiment has a map in the storage unit 114 that stores a combination of the lateral displacement amount ΔDlat and the correction current Id for each vehicle speed V. For example, as the vehicle speed V increases, the correction current Id corresponding to the lateral displacement amount ΔDlat is reduced. Therefore, the calculation unit 214 calculates the correction current Id based on the lateral displacement amount ΔDlat and the vehicle speed V.

(A-2-3-3-5. Adder 216)
The adder 216 adds the reference steering angle current Iθ from the reference steering angle current calculation unit 212 and the correction current Id from the correction current calculation unit 214 to calculate the LKAS current Ilkas (Ilkas = Iθ + Id).

(A-2-3-4. Adder 204)
The adder 204 adds the basic assist current Ibase from the basic assist current calculation unit 200 and the LKAS current Ilkas from the LKAS current calculation unit 202, and outputs the assist current Iasi (Iasi = Ibase + Ilkas).

(A-2-3-5. Drive signal output unit 206)
The drive signal output unit 206 (hereinafter, also referred to as “output unit 206”) generates a drive signal Sd for the inverter 30 so that the deviation between the assist current Iasi and the motor current Im from the adder 204 becomes zero. That is, when the motor current Im is smaller than the assist current Iasi, the drive duty ratio DUT of the switching element (not shown) of the inverter 30 is increased. When the motor current Im is larger than the assist current Isi, the drive duty ratio DUT is reduced. When the motor current Im is equal to the assist current Isi, the current drive duty ratio DUT is maintained.

<A-3. Effect of this embodiment>
As described above, according to the present embodiment, the normative stability factor A calculated based on the deviation ΔY between the normative yaw rate Yref and the yaw rate Y (detected yaw rate Ydet) is reflected in the target steering angle θstra (FIG. 4). .. Therefore, the target steering angle θstrtar can be calculated regardless of whether or not the steering angle ratio is used. Therefore, regardless of whether the steering angle ratio is variable or not, steering control can be performed in consideration of the change in the normative stability factor A. Therefore, steering performance can be improved by realizing steering control in consideration of the state of the wheels (front wheels 96, etc.) (aging, pressure change, etc.), the number and position of occupants, the load state of luggage, and the like.

In the present embodiment, the ECU 38 (control device) updates the normative stability factor A only when the steering angular velocity Vθstr is lower than the velocity threshold THvθstr (S22: TRUE → S23 in FIG. 5). When the rudder angular velocity Vθstr exceeds the speed threshold THvθstr, erroneous learning occurs, such as the phase shift between the normative yaw rate Yref and the yaw rate Y (detected yaw rate Ydet), or the normative stability factor A fluctuates due to the high rudder angular velocity Vθstr. The possibility is high. In the present embodiment, when the steering angular velocity Vθstr exceeds the velocity threshold THvθstr (S22: FALSE in FIG. 5), the normative stability factor A is not updated (S24). Therefore, it is possible to suppress the above-mentioned erroneous learning, and it is possible to execute steering control without a sense of discomfort.

B. Modifications The present invention is not limited to the above-described embodiment, and it goes without saying that various configurations can be adopted based on the contents described in the present specification. For example, the following configuration can be adopted.

<B-1. Applicable target>
In the above embodiment, it is assumed that the vehicle 10 equipped with the steering device 12 is a four-wheeled vehicle (FIG. 1). However, it is not limited to this, for example, from the viewpoint of calculating the target rudder angle θstrtar using the normative stability factor A calculated based on the deviation ΔY between the detected yaw rate Ydet and the normative yaw rate Yref. For example, the vehicle 10 may be a motorcycle, a tricycle, a six-wheeled vehicle, or the like.

In the above embodiment, the present invention is applied to a configuration in which LKAS control is performed to assist the driver's steering (FIG. 1). However, it is not limited to this, for example, from the viewpoint of calculating the target rudder angle θstrtar using the normative stability factor A calculated based on the deviation ΔY between the detected yaw rate Ydet and the normative yaw rate Yref. For example, it is also possible to apply the present invention to automatic driving in which acceleration and deceleration can be performed without a driver's operation in addition to steering.

<B-2. EPS device 14>
[B-2-1. Overall configuration of EPS device 14]
The EPS device 14 of the above embodiment has a configuration in which the EPS motor 28 transmits the motor torque Tm to the steering shaft 52 (so-called column assist type EPS device). However, the configuration of the EPS device 14 is not limited to this as long as it generates a motor torque Tm. For example, it may be any one of a pinion assist type EPS device, a dual pinion assist type EPS device, a rack assist type EPS device, and an electro-hydraulic power steering device. In the electro-hydraulic power steering device, an electric pump creates a flood control, and the hydraulic pressure is used to generate a motor torque Tm.

In the above embodiment, the steering torque by the driver is directly transmitted to the front wheels 96 (hereinafter, also referred to as “direct transmission method”), but it can also be applied to a steer-by-wire type electric power steering device.

In the above embodiment, the traveling direction of the vehicle 10 is controlled by the EPS device 14 (particularly the EPS motor 28) (FIG. 1), but the present invention is not limited to this. For example, in addition to or in place of the EPS device 14, the traveling direction of the vehicle 10 may be controlled by a so-called torque vectoring mechanism. In that case, the detection of the steering angle θstr can be detected as, for example, the difference in transmission torque (or the difference in rotational speed) between the left and right wheels.

[B-2-2. EPS motor 28]
In the above embodiment, the EPS motor 28 is a three-phase AC brushless type, but the present invention is not limited to this. For example, the motor 28 may be a three-phase AC brush type, a single-phase AC type, or a DC type.

In the above embodiment, the motor 28 is powered by the low voltage battery 40 (FIG. 1). In addition to or instead of this, the motor 28 may be powered by an alternator, a fuel cell or a high voltage battery.

[B-2-3. ECU38]
In the above embodiment, the ECU 38 has been described with the vehicle mounted in mind (FIG. 1). However, for example, the ECU 38 may be configured by providing a part of the ECU 38 on the mobile terminal and connecting the mobile terminal to the network of the vehicle 10.

In the above embodiment, one ECU 38 controls both the EPS device 14 and the LKAS 16 (FIG. 1). However, it is also possible to separately provide the EPS device 14 and the LKAS 16 separately.

<B-3. LKAS16>
In the above embodiment, the radius of curvature R is calculated based on the forward image If from the camera 140 (FIG. 3). However, in addition to or instead of this, the radius of curvature R may be determined using map information and current position information from a navigation device (not shown).

In the above embodiment, the radius of curvature R is used as the information of the own vehicle lane (FIG. 3). However, it is not limited to this, for example, from the viewpoint of calculating the target steering angle θ strtar. For example, the curvature of the own vehicle lane can be used instead of the radius of curvature R.

In the above embodiment, the normative yaw rate Yref is calculated using the rudder angle θstr (detection rudder angle θstrdet), the vehicle speed V, and the normative stability factor A. However, for example, from the viewpoint of calculating the normative yaw rate Yref as a reference value of yaw rate Y, the present invention is not limited to this. For example, it is also possible to use the previous value of the target steering angle θstrtar instead of the steering angle θstr (detection steering angle θstrdet).

In the above embodiment, the lateral displacement amount ΔDlat was calculated based on the forward image If from the camera 140 (FIG. 3). However, in addition to or instead of this, it is also possible to calculate the lateral displacement amount ΔDlat by using the map information and the current position information from the navigation device (not shown).

In the norm SF update control of the above embodiment, the necessity of updating the norm stability factor A is determined based on whether or not the rudder angular velocity Vθstr is lower than the velocity threshold THvθstr (FIG. 5). However, it is not limited to this, for example, from the viewpoint of calculating the target rudder angle θstrtar using the normative stability factor A calculated based on the deviation ΔY between the detected yaw rate Ydet and the normative yaw rate Yref. For example, it is possible to omit the determination of whether or not the steering angular velocity Vθstr is lower than the velocity threshold THvθstr.

FIG. 6 is a flowchart of the norm stability factor update control according to the modified example. In step S31, the ECU 38 calculates the TTC (Time to Collision) with the vehicle in front (not shown) of the own vehicle 10. In step S32, the ECU 38 determines whether or not the TTC exceeds the TTC threshold THttc. When the TTC exceeds the TTC threshold THttc (S32: TRUE), in step S33, the ECU 38 updates the normative stability factor A. If the TTC does not exceed the TTC threshold THttc (S32: FALSE), in step S34, the ECU 38 does not update (stop) the normative stability factor A.

According to the modification of FIG. 6, the ECU 38 (control device) acquires the TTC (contact margin time) between the vehicle ahead and the own vehicle 10 (S31). When the TTC is lower than the TTC threshold THttc (time threshold) (S32: FALSE), the ECU 38 stops updating the normative stability factor A (S34). When the TTC between the vehicle in front and the vehicle 10 is relatively short, it is highly probable that the vehicle 10 has started accelerating in order to overtake the vehicle in front. When the own vehicle 10 tries to overtake, the behavior of the own vehicle 10 is likely to change suddenly, and it can be considered that it is not suitable for updating the normative stability factor A. In this modification, it is possible to improve the accuracy of the norm stability factor A by stopping the update of the norm stability factor A in a state where the possibility of overtaking is high.

For example, in order to determine that the own vehicle 10 has started accelerating in order to overtake the vehicle in front, an index other than TTC may be used. As such an index, for example, whether or not the operation amount of the accelerator pedal (not shown) exceeds the operation amount threshold value can be used. Alternatively, it may be used whether or not the operation speed of the accelerator pedal (time derivative value of the operation amount) exceeds the operation speed threshold value.

<B-4. Others>
In the above embodiment, there are cases where the equal sign is included and cases where the equal sign is not included in the comparison of numerical values (S22 and the like in FIG. 5). However, for example, unless there is a special meaning to include or remove the equal sign (in other words, when the effect of the present invention can be obtained), it is optional to include or not include the equal sign in the numerical comparison. Can be set to.

In that sense, for example, the determination of whether or not the steering angular velocity Vθstr is lower than the threshold value THvθstr in step S22 of FIG. ) Can be replaced.

10 ... Vehicle (own vehicle) 28 ... EPS motor (rudder angle adjustment device)
32 ... Vehicle speed sensor (vehicle speed acquisition means)
36 ... Yaw rate sensor (detection yaw rate acquisition means)
38 ... ECU (control device) 62 ... Rudder angle sensor (detection rudder angle acquisition means)
140 ... Camera (lane information acquisition means) A ... Standard stability factor THttc ... TTC threshold (time threshold) THvθstr ... Speed threshold V ... Vehicle speed Vθstr ... Steering angular velocity Y ... Yaw rate Ydet ... Detection yaw rate Yref ... Normative yaw rate θstr ... … Detected rudder angle θstrtar… Target rudder angle ΔY… Yaw rate deviation (deviation between detected yaw rate and normative yaw rate)
Δθstr… Rudder angle deviation (error between target rudder angle and detected rudder angle)

Claims (2)

A rudder angle adjustment device that adjusts the rudder angle of the own vehicle,
A detection steering angle acquisition means for acquiring the detection steering angle of the own vehicle, and
Lane information acquisition means to acquire information on own vehicle lane,
The vehicle speed acquisition means for acquiring the vehicle speed of the own vehicle and
The detection yaw rate acquisition means for acquiring the detection yaw rate of the own vehicle and
A control device that executes steering control that controls the steering angle adjusting device using the target steering angle, and
With
In the steering control, the control device
A reference yaw rate is calculated based on the detected steering angle or the target steering angle and the vehicle speed.
A normative stability factor is calculated based on the deviation between the detected yaw rate and the normative yaw rate.
A new target steering angle is calculated based on the information of the own vehicle lane, the vehicle speed, and the normative stability factor.
The steering angle adjusting device is controlled so as to reduce the error between the target steering angle and the detected steering angle .
Obtain the contact margin time between the vehicle in front and the own vehicle,
A vehicle steering device that stops updating the normative stability factor when the contact margin time falls below the time threshold value . In the steering device according to claim 1,
Wherein the control device, only when the steering angular velocity is below the velocity threshold, cormorants row updating of the norms stability factor, the vehicle steering system.

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