JP2020082881A - Steering assist device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apply an appropriate steering reaction force to a driver in consideration of a degree of fatigue of the driver at the start of driving and a change in the driving ability and / or perceptual ability of the driver after the start of driving. SOLUTION: A steering support device is a driver after the start of operation based on an initial degree of fatigue (D_start), an elapsed time (t) from the start of operation, and steering feature amounts (RCS, SCS, FBFS). Fatigue degree (D (t)) is calculated. The steering support device includes a specific reaction torque (Ta), a gain (G) obtained from the specific reaction torque and the initial fatigue degree, and a driver fatigue degree (D (t)) after the start of operation. Based on, the corrected cooperative reaction torque (Fadteam), which is the corrected value of the cooperative reaction torque (Fteam), is calculated. [Selection diagram] Fig. 2

Description

The present invention relates to a steering assist device that applies a steering reaction force to a steering device of a vehicle.

Conventionally, there is known a steering assist device that assists a driver's steering operation while coordinating a target steering amount calculated by a predetermined system (for example, a driving assist control system) and a driver's steering amount. (For example, refer to Patent Document 1).

JP, 2017-065323, A

However, the steering assist device described in Patent Document 1 does not support the steering operation of the driver in consideration of the degree of fatigue of the driver. The degree of fatigue of the driver at the start of driving varies depending on the situation at that time. Furthermore, when a certain amount of time has passed after the start of driving, fatigue tends to reduce the driving ability and/or the perception ability of the driver.

The present invention has been made to solve the above problems. That is, one of the objects of the present invention is appropriate for the driver in consideration of the degree of fatigue of the driver at the start of driving and the change in the driving ability and/or the perceptual ability of the driver after starting driving. It is an object of the present invention to provide a steering assist device that can apply various steering reaction forces.

The steering assist device of the present invention (hereinafter, also referred to as “the present device” in some cases) is
A steering device including a steering handle (SW) that is steered by a driver;
Steering angle detection means (11) for detecting the rotation angle of the steering wheel as a steering angle (θ),
Steering reaction force application means (10, 40,) configured to apply a steering reaction force torque to the steering device to return the steering wheel to the neutral position when the driver rotates the steering wheel. 41),
Lane information acquisition means (13, 52) for acquiring lane information of the lane in which the vehicle is traveling,
A target steering amount calculation unit (202, step 730) that calculates a target steering angle (θ target) for the vehicle to maintain traveling in the lane based on the lane information;
Means (10, 50, 53, 204, step 720) for acquiring an initial fatigue degree (D_start), which is the degree of fatigue of the driver at the start of driving;
Means (10, 50, 53, 204, step 720) for obtaining a correction value (Mu) for the basic cooperation torque (Tbase) obtained from the relationship between the deviation of the target steering angle and the steering angle and the reaction torque. When,
A specific reaction force torque (Ta) is obtained based on the basic cooperation torque (Tbase) and the correction value (Mu) (step 735), and the specific reaction force torque (Ta) and the initial fatigue degree (D_start) are also obtained. A gain calculation unit (204, step 740) for calculating a gain (G) based on
A basic reaction force calculation unit that calculates a basic reaction force torque (Fbase) for returning the steering wheel to a neutral position when the driver rotationally operates the steering wheel based on a value related to the steering angle ( 201, step 725),
A cooperative reaction force calculation unit (203, step 745) that calculates a cooperative reaction force torque (Fteam) based on the deviation between the target steering angle and the steering angle,
A steering characteristic amount calculation unit (204, step 750) that calculates a steering characteristic amount (RCS, SCS, FBFS) that is a characteristic amount for evaluating the steering operation of the driver based on at least the value related to the steering angle. )When,
Based on the initial fatigue level (D_start), the elapsed time (t) from the start of driving, and the steering characteristic amount (RCS, SCS, FBFS), the driver's fatigue level (D(t) after the start of driving. )) for calculating the degree of fatigue (204, step 755),
A value obtained by correcting the cooperative reaction torque (Fteam) based on the specific reaction torque (Ta), the gain (G), and the degree of fatigue (D(t)) of the driver after the start of driving. A cooperative reaction force correction unit (204, step 760) for calculating a corrected cooperative reaction force torque (Fadteam);
Based on the basic reaction force torque and the corrected cooperative reaction force torque, a target steering reaction force torque that is a target value of the steering reaction force torque is calculated, and the steering reaction force torque applied to the steering device is A steering assist unit (205, 205a, step 765, step 770) configured to control the steering reaction force applying means so as to match the target steering reaction force torque;
Equipped with.

The device of the present invention having such a configuration acquires the initial degree of fatigue of the driver and the correction value (e.g., magnification) for the basic cooperative torque at the start of driving. The device of the present invention obtains the specific reaction torque based on the basic cooperative torque and the correction value. The device of the present invention calculates the gain based on the initial degree of fatigue and the specific reaction force torque. This gain is a value that reflects both the degree of fatigue at the start of driving and the cooperative reaction torque (specific reaction torque) that the driver likes. By using this gain, it is possible to calculate the cooperative reaction torque that considers both the driver's fatigue level and his/her preference.

Further, the device of the present invention calculates a steering characteristic amount which is a characteristic amount for evaluating the steering operation of the driver. The device of the present invention detects a change in the driving ability and/or the perceptual ability of the driver after the start of driving from the steering characteristic amount, and thereby can evaluate how much the fatigue of the driver has changed after the start of driving. .. The device of the present invention calculates the degree of fatigue of the driver after the start of driving based on the initial degree of fatigue, the elapsed time from the start of driving, and the steering characteristic amount. Then, the present embodiment calculates the corrected cooperative reaction torque by correcting the cooperative reaction torque based on the specific reaction torque, the gain, and the degree of fatigue of the driver after the start of driving. As described above, the device of the present invention calculates the final cooperative reaction force torque (corrected cooperative reaction force torque) in consideration of how much the driver's fatigue changes from the initial degree of fatigue. Therefore, the device of the present invention can give an appropriate steering reaction force torque to the driver in consideration of the degree of fatigue.

In the above description, in order to help understanding of the present invention, the names and/or reference numerals used in the embodiments are added in parentheses to the configurations of the invention corresponding to the embodiments described later. However, each component of the present invention is not limited to the embodiment defined by the name and/or code.

It is a schematic block diagram of the steering assistance apparatus which concerns on embodiment of this invention. FIG. 2 is a functional block diagram of a steering assist ECU shown in FIG. 1. 6 is a graph for explaining a basic cooperation torque Tbase defined by a relationship between a deviation θdef between a steering angle (actual steering angle) and a target steering angle and a reaction force torque [Nm]. It is a figure for demonstrating Rough Control Score (RCS) which is one of the steering feature-values, and is a graph which has a horizontal axis as time and a vertical axis as steering error. It is a figure for demonstrating Stop Control Score (SCS) which is one of the steering feature-values, and is a graph which has a horizontal axis as time and a vertical axis as steering angular velocity. It is a figure for demonstrating Feed Back Frequency component Score(FBFS) which is one of the steering feature-values, and is a graph which set the horizontal axis to the frequency and the vertical axis to the one-sided amplitude spectrum. 4 is a flowchart showing a “cooperative reaction force control routine” executed by the steering assist ECU according to the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

<Structure>
The steering assist device according to the embodiment of the present invention (hereinafter sometimes referred to as “the present embodiment”) is applied to a vehicle. As shown in FIG. 1, the present embodiment includes a steering assist ECU 10, an engine ECU 20, a brake ECU 30, an electric power steering ECU (hereinafter referred to as “EPS/ECU”) 40, and a navigation ECU 50. ..

These ECUs are electric control units (Electric Control Units) that mainly include a microcomputer, and are connected to each other via a CAN (Controller Area Network) (not shown) so that information can be transmitted and received mutually. In this specification, the microcomputer includes a CPU, a RAM, a ROM, a non-volatile memory, an interface (I/F), and the like. For example, the steering assist ECU 10 includes a microcomputer including a CPU 10a, a RAM 10b, a ROM 10c, a non-volatile memory 10d, an interface (I/F) 10e, and the like. The CPU 10a is adapted to realize various functions by executing instructions (programs, routines) stored in the ROM 10c.

The steering assist ECU 10 is connected to the sensors listed below and receives detection signals or output signals from these sensors. Note that each sensor may be connected to an ECU other than the steering assist ECU 10.

The steering angle sensor 11 detects the rotation angle of the steering shaft US rotated by the operation of the steering wheel SW as a steering angle, and outputs a signal indicating the steering angle θ. The steering assist ECU 10 is configured to calculate the steering angular velocity (θ′) from the steering angle θ received from the steering angle sensor 11. Further, the steering assist ECU 10 is configured to calculate the steering angular acceleration (θ″) from the steering angle θ received from the steering angle sensor 11.
The steering torque sensor 12 detects the steering torque applied to the steering shaft US of the own vehicle by operating the steering handle SW and outputs a signal representing the steering torque Tra.
The steering angle sensor 11 and the steering torque sensor 12 are adapted to detect the steering angle and the steering torque, respectively, with positive steering of the vehicle in the left turning direction.

The surroundings sensor 13 is configured to acquire information about roads around the own vehicle (for example, a traveling lane in which the own vehicle is traveling) and information about three-dimensional objects existing on those roads. The three-dimensional object represents, for example, a moving object such as an automobile, a pedestrian and a bicycle, and a fixed object such as a guardrail and a fence. Hereinafter, these three-dimensional objects may be referred to as “targets”. The ambient sensor 13 includes a radar sensor 13a and a camera sensor 13b.

The radar sensor 13a radiates, for example, a millimeter-wave band radio wave (hereinafter, referred to as "millimeter wave") to a surrounding area of the own vehicle including at least a front area of the own vehicle, and the target existing within the radiation range. The millimeter wave (that is, the reflected wave) reflected by is received. Further, the radar sensor 13a determines the presence or absence of the target and indicates the relative relationship between the own vehicle and the target (that is, the position of the target with respect to the own vehicle, the distance between the own vehicle and the target, and , The relative speed between the vehicle and the target, etc.) is calculated and output.

The camera sensor 13b includes a stereo camera and an image processing unit, captures a landscape of a left side region and a right side region in front of the vehicle, and acquires a pair of left and right image data. The camera sensor 13b determines the presence/absence of a target based on the imaged pair of left and right image data, calculates a parameter indicating the relative relationship between the own vehicle and the target, and outputs the determination result and the calculation result. It is supposed to do. In this case, the steering assist ECU 10 includes a parameter indicating the relative relationship between the own vehicle and the target obtained by the radar sensor 13a, and a parameter indicating the relative relationship between the own vehicle and the target obtained by the camera sensor 13b. The parameters indicating the relative relationship between the host vehicle and the target are determined by synthesizing.

Further, the camera sensor 13b recognizes the left and right lane markings of the road (the traveling lane in which the vehicle is traveling) based on the paired left and right image data, and determines the shape of the road (for example, the road). Curvature) and the positional relationship between the road and the host vehicle (for example, the distance from the left end or the right end of the lane in which the host vehicle is traveling to the center position of the host vehicle in the vehicle width direction) are calculated. Note that the demarcation line includes a white line, a yellow line, and the like, but in the following description, it is assumed that the demarcation line is a white line.

Information about the lane including the shape of the road and the positional relationship between the road and the host vehicle is called “lane information”. Further, the information about the target acquired by the surrounding sensor 13 (including the parameter indicating the relative relationship between the own vehicle and the target) is referred to as “target information”. The ambient sensor 13 repeatedly transmits the target information and the lane information to the steering assist ECU 10 each time a predetermined sampling time elapses. The steering assist ECU 10 acquires, as "vehicle peripheral information", information about the vehicle surroundings including "target information and lane information".

The ambient sensor 13 does not necessarily have to include both the radar sensor and the camera sensor, and may include only the camera sensor, for example. The ambient sensor 13 may be referred to as an “information acquisition unit (information acquisition unit) that acquires vehicle surrounding information”.

The engine ECU 20 is connected to the engine actuator 21. The engine actuator 21 includes a throttle valve actuator that changes the opening degree of the throttle valve of the internal combustion engine 22. The engine ECU 20 can change the torque generated by the internal combustion engine 22 by driving the engine actuator 21. Therefore, the engine ECU 20 can control the driving force of the host vehicle by controlling the engine actuator 21. When the vehicle is a hybrid vehicle, engine ECU 20 can control the driving force of the own vehicle generated by one or both of the "internal combustion engine and the electric motor" as the vehicle drive source. Further, when the vehicle is an electric vehicle, the engine ECU 20 can control the driving force of the own vehicle generated by the electric motor as the vehicle drive source.

The brake ECU 30 is connected to the brake actuator 31. The brake actuator 31 adjusts the hydraulic pressure supplied to the wheel cylinder incorporated in the brake caliper 32b according to an instruction from the brake ECU 30, and presses the brake pad against the brake disc 32a by the hydraulic pressure to generate a friction braking force. Therefore, the brake ECU 30 can control the braking force of the host vehicle by controlling the brake actuator 31.

The EPS/ECU 40 is connected to an electric power steering device (hereinafter referred to as “EPS”) 41. The EPS 41 is incorporated in a "steering mechanism 60 including a steering wheel SW, a steering shaft US, a steering gear mechanism (not shown), and the like" of the vehicle. The EPS/ECU 40 can apply torque to the steering mechanism 60 by controlling the torque generated by the EPS 41.

In addition, when the EPS/ECU 40 receives the steering reaction force command from the steering support ECU 10 during execution of the steering support control described below, the actual steering reaction force torque is the target specified by the steering reaction force command. The EPS 41 is controlled so as to match the steering reaction force torque. The steering reaction force torque is a torque applied to return the steering wheel SW to the neutral position when the driver steers the steering wheel SW. The neutral position is a reference position where the steering angle θ is zero, and is the position of the steering wheel SW when the vehicle travels straight.

The navigation ECU 50 receives a GPS signal for detecting the “latitude and longitude” of the place where the vehicle is located, a map database 52 storing map information, and a touch panel (touch panel display) 53. Is equipped with. The map information stored in the map database 52 includes road information. For example, in the road information, the radius of curvature of the road, the width of the road, the slope of the road, and the like are associated with each of the road sections. The navigation ECU 50 performs various arithmetic processes based on the latitude and longitude of the place where the vehicle is located, the map information, etc., and displays the position of the vehicle on the map on the touch panel 53.

<Steering support control (cooperative reaction force control)>
The steering assist ECU 10 assists the driver's steering operation by applying a steering reaction torque to the steering wheel SW by the EPS 41. Hereinafter, such steering assist control may be referred to as “cooperative reaction force control”.

As shown in FIG. 2, the steering assist ECU 10, when viewed functionally, includes a basic reaction force calculation unit 201, a target steering amount calculation unit 202, a cooperative reaction force calculation unit 203, a cooperative reaction force correction unit 204, and The steering assist unit 205 is provided.

When the driver operates the steering wheel SW at the steering angle (actual steering angle) θ, the basic reaction force calculation unit 201 determines the basic reaction force torque Fbase according to the steering angle θ. Specifically, the basic reaction force calculation unit 201 receives the steering angle (actual steering angle) θ from the steering angle sensor 11 and also calculates the steering angular velocity (θ′) and the steering angular acceleration (θ″) from the steering angle θ. Calculate The basic reaction force calculation unit 201 determines the basic reaction force torque Fbase by the method shown in the following equation (1). Hereinafter, “the steering angle θ, the steering angular velocity θ′, and the steering angular acceleration θ″” may be collectively referred to as a “value related to the steering angle θ”. The basic reaction force calculation unit 201 outputs the basic reaction force torque Fbase to the steering assist unit 205.

ここで、Ｍは慣性項の係数であり、Ｃは粘性項の係数であり、Ｋは弾性項の係数であり、Ｆは摩擦項である。これらの値（Ｍ，Ｃ，Ｋ，Ｆ）は何れも正の値である。なお、基本反力トルクＦbaseを求める上述の式は一例であり、これに限定されない。

Here, M is the coefficient of the inertial term, C is the coefficient of the viscous term, K is the coefficient of the elastic term, and F is the friction term. All of these values (M, C, K, F) are positive values. The above formula for obtaining the basic reaction force torque Fbase is an example, and the present invention is not limited to this.

The steering assist ECU 10 may store a predetermined look-up table Map(θ, θ′) in advance. The basic reaction force calculation unit 201 may obtain the basic reaction force torque Fbase by applying the steering angle θ and the steering angular velocity θ′ to the lookup table Map (that is, Fbase=Map(θ, θ′)). ..

The target steering amount calculation unit 202 receives the lane information from the camera sensor 13b. The target steering amount calculation unit 202 calculates a target steering angle θtarget for the vehicle to travel while maintaining the center position of the traveling lane based on the lane information. A method of calculating the target steering angle θ target based on the lane information is known (see, for example, Japanese Patent Application Laid-Open Nos. 2002-046640 and 2015-217737). Therefore, a brief description will be given below.

The target steering amount calculation unit 202 acquires information about the “left white line and right white line” of the traveling lane in which the vehicle is traveling, based on the lane information. The target steering amount calculation unit 202 sets a line connecting the obtained left white line and the right white line at the center position in the road width direction as a target travel line. The target steering amount calculation unit 202 determines a distance in the road width direction between the center position of the vehicle in the vehicle width direction and the target travel line, and a deviation angle between the direction of the target travel line (tangential direction) and the traveling direction of the vehicle. The target steering angle θtarget is calculated based on the (yaw angle) and the like. The target steering amount calculation unit 202 outputs the target steering angle θtarget to the cooperative reaction force calculation unit 203 and the cooperative reaction force correction unit 204.

The target steering amount calculation unit 202 sets the traveling locus of the preceding vehicle (another vehicle traveling immediately before the own vehicle) detected based on the target information as the target traveling line, and the target steering angle θtarget May be calculated.

The cooperative reaction force calculation unit 203 receives the steering angle (actual steering angle) θ from the steering angle sensor 11 and the target steering angle θ target from the target steering amount calculation unit 202. The cooperative reaction force calculation unit 203 calculates a deviation θdef between the steering angle (actual steering angle) θ and the target steering angle θtarget. Hereinafter, the deviation θdef between the steering angle (actual steering angle) θ and the target steering angle θtarget will be referred to as “steering angle deviation θdef”. The cooperative reaction force calculation unit 203 calculates the cooperative reaction force torque Fteam by multiplying the steering angle deviation θdef by a predetermined gain. Note that a method for obtaining the cooperative reaction force torque (assist torque) from the steering angle deviation θdef in this way is known (see, for example, Patent Document 1). Then, the cooperative reaction force calculation unit 203 outputs the cooperative reaction force torque Fteam to the cooperative reaction force correction unit 204.

The cooperative reaction force correction unit 204 receives the steering angle (actual steering angle) θ from the steering angle sensor 11, receives the target steering angle θ target from the target steering amount calculation unit 202, and calculates the cooperative reaction force torque Fteam as the cooperative reaction force calculation unit 203. Receive from Then, the cooperative reaction force correction unit 204 calculates the corrected cooperative reaction force torque Fadteam as described below.

When the ignition (IG) switch (not shown) is changed from OFF to ON, the cooperative reaction force correction unit 204 displays a screen (hereinafter referred to as “first screen”) for causing the driver to input the degree of fatigue D_start[%]. Is displayed on the touch panel 53. In this example, the fatigue degree D_start is defined in the range of 1 to 100%. "100%" indicates that the driver is not tired. The smaller this value, the greater the degree of fatigue of the driver. When the driver inputs the degree of fatigue D_start on the first screen, the cooperative reaction force correction unit 204 receives the degree of fatigue D_start via the navigation ECU 50.

The cooperative reaction force correction unit 204 may divide the degree of fatigue into a plurality of options and display them on the first screen so that the driver can select one from the plurality of options. For example, four types of no fatigue (=100%), low fatigue level (=80%), medium fatigue level (=50%), and high fatigue level (=20%) are displayed on the first screen, and One may be selected from the above.

Next, the cooperative reaction force correction unit 204 displays, on the touch panel 53, a screen (hereinafter referred to as “second screen”) for allowing the driver to input the preference of the size of the cooperative reaction force torque. Different people have different preferences for the magnitude of cooperative reaction torque. For example, a driver with a high driving skill prefers to apply a relatively small cooperative reaction torque because the steering operation is stable. On the other hand, a driver with low driving skill prefers to give a relatively large cooperative reaction torque because the steering operation is not stable. Therefore, the cooperative reaction force correction unit 204 displays, on the touch panel 53, the second screen for allowing the driver to input the magnification Mu to the basic cooperative torque Tbase described later. The magnification Mu can be selected from a value between “a predetermined lower limit value less than 1” and “a predetermined upper limit value greater than 1”. When the driver inputs the magnification Mu on the second screen, the cooperative reaction force correction unit 204 receives the magnification Mu via the navigation ECU 50. The information input to the driver on the second screen is not limited to the magnification Mu and may be any correction value that reflects the driver's preference. For example, it may be an addition value or a subtraction value of the torque with respect to the basic cooperative torque Tbase.

The cooperative reaction force correction unit 204 stores information on a preset basic cooperative torque Tbase. The basic cooperative torque Tbase is, for example, data of a cooperative reaction torque set for a driver with an average driving skill. Specifically, as shown in FIG. 3, the cooperative reaction force correction unit 204 stores a look-up table (map) that predefines the relationship between the steering angle deviation θdef and the reaction force torque [Nm]. The basic cooperation torque Tbase is defined by the product of the spring constant and the steering angle deviation θdef as shown in the following equation (2). Here, K1 to K5 are predetermined spring constants, respectively.

It should be noted that in the formula (2), the steering angle deviation θdef is divided into five sections and a function for obtaining the basic cooperation torque Tbase is defined for each section, but the function is not limited to this. The steering angle deviation θdef may be divided into more than five sections and a function for obtaining the basic cooperation torque Tbase may be defined for each section. Furthermore, the function for obtaining the basic cooperation torque Tbase is not limited to the above-mentioned linear function, and may be defined by another function.

The cooperative reaction force correction unit 204 calculates the reaction force torque Ta according to the following equation (3). The reaction force torque Ta obtained by adjusting the basic cooperative torque Tbase by the magnification Mu in this way is referred to as “specific reaction force torque Ta” in order to distinguish it from other torques.

As shown in FIG. 3, for example, when the driver inputs “magnification Mu1 larger than 1” on the second screen, the specific reaction force torque Ta becomes larger than the basic cooperative torque Tbase. On the other hand, when the driver inputs the “magnification Mu2 smaller than 1” on the second screen, the specific reaction force torque Ta becomes smaller than the basic cooperation torque Tbase. Thus, the driver can select the magnitude of the reaction torque according to his/her preference by inputting the magnification Mu to the basic cooperative torque Tbase at the start of driving.

The cooperative reaction force correction unit 204 may display a plurality of options corresponding to the plurality of magnifications Mu on the second screen and allow the driver to select one from a plurality of degrees. For example, three (strong (magnification = 1.2), medium (magnification = 1), and weak (magnification = 0.8) are displayed on the 2nd screen, and even if the driver selects one of these, Good.

The cooperative reaction force correction unit 204 calculates the gain G according to the following equation (4) based on the fatigue degree D_start and the specific reaction force torque Ta.

Further, the cooperative reaction force correction unit 204 calculates the degree of fatigue of the driver after starting the driving based on the feature amount described later. It is known that the driver's fatigue level increases as the driving time becomes longer, and the driver's performance (driving ability and/or perceptual ability) decreases. Therefore, in the present embodiment, the cooperative reaction force correction unit 204 evaluates the driving ability and/or the perceptual ability of the driver based on the following three feature amounts (RCS, SCS, FBFS), thereby driving the vehicle. The degree of fatigue of the driver after the start is calculated.

1. Rough Control Score (RCS)
RCS is a feature amount for evaluating the stability of the steering operation by the driver. A larger value of RCS indicates that the driver's steering operation is rough, and a smaller value of RCS indicates that the driver's steering operation is smoother (stable).

更に、協調反力補正部２０４は、下記（６）式に従って誤差ｅ（ｘ_ｎ）を演算する。

The cooperative reaction force correction unit 204 acquires the data of the steering angle θ at a predetermined sampling cycle. The steering angle θ at a certain time point x _n is y(x _n ). A predicted value yp( _xn ) of the steering angle θ at a certain time point _xn is calculated according to the following equation (5).

Further, the cooperative reaction force correction unit 204 calculates the error e( _xn ) according to the following equation (6).

The cooperative reaction force correction unit 204 counts the number of times that the absolute value |e( _xn )| of the error e( _xn ) exceeds a predetermined threshold Th1. In the example shown in FIG. 4, the absolute value |e(x _n )| of the error e(x _n ) exceeds the predetermined threshold Th1 at T1, T2, and T3. Therefore, the cooperative reaction force correction unit 204 calculates “3” as the value of RCS.

2. Stop Control Score (SCS)
The SCS is a feature amount for evaluating the awkwardness of the driver's steering operation. A larger value of SCS indicates that the driver's steering operation is intermittent, and a smaller value of SCS indicates that the driver's steering operation is continuous (smooth).

The cooperative reaction force correction unit 204 acquires the data of the steering angle θ at a predetermined sampling cycle and calculates the data of the steering angular velocity θ′. The cooperative reaction force correction unit 204 counts the places where both the following conditions A and B are satisfied in the absolute value data of the steering angular velocity θ′.
(Condition A) The absolute value of the steering angular velocity θ'exceeds a predetermined first threshold Tha.
(Condition B) Within a predetermined time Tm1 from the time when the absolute value of the steering angular velocity θ′ exceeds a predetermined first threshold Tha, the absolute value of the steering angular velocity θ′ is equal to or less than a predetermined second threshold Thb (<Tha). It changed to the value of.

In the example shown in FIG. 5, at time T1, the absolute value of the steering angular velocity θ′ exceeds the predetermined first threshold Tha. After that, at a time T2 that is a time within a predetermined time Tm1 from the time T1, the absolute value of the steering angular velocity θ'changes to a value equal to or smaller than a predetermined second threshold Thb. If there is such a portion, the cooperative reaction force correction unit 204 counts as the value of SCS because both the condition A and the condition B are satisfied.

3. Feed Back Frequency component Score (FBFS)
FBFS is a feature amount for evaluating the correction operation component of the driver's steering operation. The larger the value of FBFS, the larger the frequency component of the correction operation (that is, the larger the number of corrections in the steering operation), and the smaller the value of FBFS, the smaller the frequency component of the correction operation.

The cooperative reaction force correction unit 204 acquires the data of the steering angle θ at a predetermined sampling cycle. The cooperative reaction force correction unit 204 decomposes the steering angle θ data into a frequency domain by FFT (Fast Fourier Transform). Thereby, as shown in FIG. 6, the cooperative reaction force correction unit 204 causes the values P1 ₁ , P1 ₂ , P1 ₃ ,..., Of the one-sided amplitude spectrum in the predetermined frequency band (0.5 Hz to 1.0 Hz). Get P1 _N. The cooperative reaction force correction unit 204 calculates FBFS according to the following equation (7). Here, fspan represents the difference in frequency between adjacent P1 components.

Note that, hereinafter, the above-mentioned "RCS, SCS and FBFS" may be collectively referred to as "steering feature amount". Note that, in the present embodiment, an example in which all of “RCS, SCS and FBFS” are adopted as the steering characteristic amount will be described, but the present invention is not limited to this, and at least one of “RCS, SCS and FBFS” is used. It may be adopted.

Ｆ（ｔ、ＳＣＳ、ＲＣＳ、ＦＢＦＳ）は、下記（９）式によって求められる。ここで、Ａ１、Ａ２、Ａ３及びＡ４は、それぞれ、所定の係数である。

The cooperative reaction force correction unit 204 calculates the driver's fatigue degree D(t) at a certain time point after the start of driving according to the following equation (8). In addition, "t" in the following formulas represents the elapsed time from the start of operation (at the time when the IG switch is turned on).

F(t, SCS, RCS, FBFS) is calculated by the following equation (9). Here, A1, A2, A3, and A4 are predetermined coefficients.

The value of F(t, SCS, RCS, FBFS) increases as t, SCS, RCS, and FBFS increase (as time elapses and the performance of the steering operation by the driver decreases). Therefore, by subtracting the value of F(t, SCS, RCS, FBFS) from the degree of fatigue D_start at the start of driving, the degree of fatigue of the driver at a certain time t after the start of driving can be obtained.

Note that F(t, SCS, RCS, FBFS) is not limited to the above linear function, and may be defined by another function.

The cooperative reaction force correction unit 204 uses the specific reaction force torque Ta, the gain G, and the fatigue degree D(t) at a certain time point t after the start of driving, according to the following equation (10), and cooperates at the time point t. The reaction force torque Fteam(t) is corrected, and the corrected cooperative reaction force torque Fadteam(t) at the time point t is calculated. The cooperative reaction force correction unit 204 outputs the corrected cooperative reaction force torque Fadteam(t) to the steering assist unit 205.

The steering assist unit 205 is configured to execute cooperative reaction force control. Specifically, the steering assist unit 205 includes a steering reaction force torque calculation unit 205a. The steering reaction force torque calculation unit 205a receives the basic reaction force torque Fbase from the basic reaction force calculation unit 201 and the corrected cooperative reaction force torque Fadteam from the cooperative reaction force correction unit 204. The steering reaction force torque calculation unit 205a determines the final target steering reaction force torque Fr by adding the basic reaction force torque Fbase and the corrected cooperative reaction force torque Fadteam.

The steering assist unit 205 transmits a steering reaction force command representing the determined target steering reaction force torque Fr to the EPS/ECU 40. The EPS/ECU 40 controls the EPS 41 by feedback control so that the actual steering reaction force torque matches the target steering reaction force torque Fr. As a result, the steering reaction force torque is applied to the steering wheel SW.

<Specific operation>
Next, a specific operation when the steering assist ECU 10 executes the cooperative reaction force control will be described with reference to FIG. 7. The CPU 10a (hereinafter, simply referred to as "CPU") of the steering assist ECU 10 is adapted to execute the "cooperative reaction force control routine" shown by the flowchart of FIG. 7 every time a predetermined time elapses. Further, as described above, the CPU obtains the steering angle θ from the steering angle sensor 11 and the lane information from the camera sensor 13b by executing a routine (not shown).

Therefore, at a predetermined timing, the CPU starts the process from step 700 in FIG. 7 and proceeds to step 705 to determine whether or not the value of the flag F is “0”. The flag F indicates that the IG switch is in the ON state (that is, is in operation) when the value is "1", and the IG switch is in the OFF state when the value is "0" (ie, the IG switch is in the OFF state). , Not in operation).

Assuming that the value of the flag F is “0”, the CPU makes a “Yes” determination at step 705 to proceed to step 710, at which point the current time is “immediately after the IG switch is turned on”. Determine if there is. Hereinafter, the "time point when the IG switch is turned on" may be simply referred to as "ON time point". When the present time is not the “ON time”, the CPU makes a “No” determination at step 710 to directly proceed to step 795 to end the present routine tentatively.

On the other hand, when the current time is the “ON time”, the CPU determines “Yes” in step 710, and sequentially performs the processes of steps 715 to 770 described below. After that, the CPU proceeds to step 795 to end the present routine tentatively.

Step 715: The CPU sets the value of the flag F to “1”.
Step 720: The CPU displays the first screen on the touch panel 53 and prompts the driver to input the fatigue degree D_start at the start of driving. As a result, the CPU acquires the fatigue degree D_start. The CPU displays the second screen on the touch panel 53 and prompts the driver to input the magnification Mu with respect to the basic cooperative torque Tbase. As a result, the CPU acquires the magnification Mu.

Step 725: As described above, the CPU calculates the basic reaction force torque Fbase according to the equation (1).
Step 730: As described above, the CPU calculates the target steering angle θtarget based on the lane information.
Step 735: As described above, the CPU obtains the basic cooperative torque Tbase from the steering angle deviation θdef and calculates the specific reaction force torque Ta according to the equation (3).
Step 740: The CPU calculates the gain G according to the equation (4) as described above.

Step 745: As described above, the CPU calculates the cooperative reaction force torque Fteam by multiplying the steering angle deviation θdef by a predetermined gain.
Step 750: The CPU calculates the three steering characteristic amounts (RCS, SCS and FBFS) as described above.
Step 755: As described above, the CPU calculates the driver's fatigue level D(t) at the present time (t) according to the equation (8).
Step 760: The CPU calculates the corrected cooperative reaction torque Fadteam(t) according to the equation (10) as described above.

Step 765: As described above, the CPU calculates the final target steering reaction force torque Fr based on the basic reaction force torque Fbase and the corrected cooperative reaction force torque Fadteam(t).
Step 770: The CPU executes cooperative reaction force control. That is, the CPU transmits a steering reaction force command indicating the target steering reaction force torque Fr to the EPS/ECU 40. The EPS/ECU 40 controls the EPS 41 by feedback control so that the actual steering reaction force torque matches the target steering reaction force torque Fr.

When the value of the flag F is not “0” (that is, the operation is in progress) at the time when the CPU proceeds to step 705, the CPU makes a “No” determination at step 705 and proceeds to step 775. move on. In step 775, the CPU determines whether the IG switch has been changed from ON to OFF. When the IG switch is in the ON state, the CPU determines “No” in step 775, and sequentially executes the processes of steps 725 to 770 as described above. That is, the CPU continues the cooperative reaction force control. After that, the CPU proceeds to step 795 to end the present routine tentatively.

On the other hand, in step 775, when the present time is the time when the IG switch is changed from ON to OFF, the CPU determines “Yes” in step 775, proceeds to step 780, and sets the flag F to ON. Set the value to "0". After that, the CPU proceeds to step 795 to end the present routine tentatively.

The apparatus of the present embodiment described above causes the driver to input the fatigue degree D_start at the start of driving. Further, the present embodiment causes the driver to input the magnification Mu with respect to the basic cooperative torque Tbase. Accordingly, the present embodiment calculates the specific reaction force torque Ta by multiplying the basic cooperation torque Tbase by the magnification Mu. The present embodiment calculates the gain G based on the degree of fatigue D_start at the start of operation and the specific reaction force torque Ta. The gain G is a value that reflects both the degree of fatigue at the start of driving and the cooperative reaction torque desired by the driver. By using this gain G, the cooperative reaction torque can be calculated in consideration of both the driver's fatigue level and his/her preference.

Further, the present embodiment calculates a steering characteristic amount (RCS, SCS, FBFS) which is a characteristic amount for evaluating the steering operation of the driver. The present embodiment, based on the initial fatigue level (D_start), the elapsed time (t) from the start of driving, and the steering characteristic amount (RCS, SCS, FBFS), the driver's fatigue level after the start of driving ( D(t)) is calculated. Then, the present embodiment device corrects the cooperative reaction torque Fteam based on the specific reaction torque Ta, the gain G, and the degree of fatigue (D(t)) of the driver after the start of the operation. Calculate the reaction torque Fadteam. As described above, the present embodiment calculates the final cooperative reaction torque (corrected cooperative reaction torque Fadteam) in consideration of how much the driver's fatigue changes from the initial fatigue degree (D_start). be able to. Therefore, an appropriate steering reaction torque can be applied to the driver.

The present invention is not limited to the above embodiment, and various modifications can be adopted within the scope of the present invention.

(Modification 1)
The cooperative reaction force correction unit 204 may allow the driver to input the operation range of the steering reaction force torque when the second screen is displayed. This operating range is defined as the range of the value of the steering angle deviation θdef. The cooperative reaction force correction unit 204 determines whether or not the steering angle deviation θdef is within the above-mentioned working range. When the steering angle deviation θdef is within the above-mentioned working range, the cooperative reaction force correction unit 204 calculates the corrected cooperative reaction force torque Fadteam(t) as described above. On the other hand, the cooperative reaction force correction unit 204 may set the specific reaction force torque Ta to “0” when the steering angle deviation θdef is outside the above-described working range. Furthermore, the cooperative reaction force correction unit 204 may set the cooperative reaction force torque Fteam to “0” when the steering angle deviation θdef is outside the above-described working range. Therefore, in this case, the corrected cooperative reaction torque Fadteam(t) becomes “0”, and the support by the cooperative reaction torque is not performed. In this way, the cooperative reaction force control may be executed only within a specific range of the steering angle deviation θdef.

(Modification 2)
The steering assist ECU 10 may acquire lane information from other than the surrounding sensor 13. For example, the steering assist ECU 10 may acquire the radius of curvature for each section of the road from the road information included in the map DB 52 and calculate the target steering angle θtarget from the radius of curvature.

(Modification 3)
The cooperative reaction force control of the present invention is applied to a steering system (a so-called steer-by-wire system) in which the steering wheel SW and the steering mechanism for steering the steered wheels of the vehicle are not mechanically connected. Good. In this case, the steering wheel SW is provided with a steering reaction force motor that applies a steering reaction torque to return the steering wheel SW to the neutral position when the driver operates the steering wheel SW. The steering assist ECU 10 controls the steering reaction force motor by feedback control so that the actual steering reaction force torque applied to the steering wheel SW matches the target steering reaction force torque Fr.

10... Steering assist ECU, 20... Engine ECU, 30... Brake ECU, 40... EPS-ECU, 41... Electric power steering device (EPS), 50... Navigation ECU, 60... Steering mechanism, 11... Steering angle sensor, 12... Steering torque, 13... Ambient sensor.

Claims (1)

A steering device including a steering wheel that is steered by a driver;
A steering angle detection unit that detects the rotation angle of the steering wheel as a steering angle;
Steering reaction force imparting means configured to impart to the steering device a steering reaction force torque for returning the steering wheel to a neutral position when the driver rotationally operates the steering wheel,
A lane information acquisition unit that acquires lane information of the lane in which the vehicle is traveling,
A target steering amount calculation unit that calculates a target steering angle for the vehicle to maintain traveling in the lane based on the lane information;
A means for acquiring an initial degree of fatigue, which is the degree of fatigue of the driver at the start of driving,
A deviation between the target steering angle and the steering angle, and means for obtaining a correction value for the basic cooperative torque defined by the relationship between the reaction torque and
A gain calculation unit that calculates a specific reaction force torque based on the basic cooperative torque and the correction value, and calculates a gain based on the specific reaction force torque and the initial fatigue degree,
A basic reaction force calculation unit that calculates a basic reaction force torque for returning the steering wheel to a neutral position when the driver rotationally operates the steering wheel based on a value related to the steering angle;
A cooperative reaction force calculation unit that calculates a cooperative reaction force torque based on the deviation between the target steering angle and the steering angle,
A steering characteristic amount calculation unit that calculates a steering characteristic amount that is a characteristic amount for evaluating the steering operation of the driver based on at least the value related to the steering angle;
The initial degree of fatigue, the elapsed time from the start of driving, based on the steering feature amount, a degree-of-fatigue calculating unit that calculates the degree of fatigue of the driver after the start of driving,
A cooperative reaction force correction unit that calculates a corrected cooperative reaction torque, which is a value obtained by correcting the cooperative reaction torque based on the specific reaction torque, the gain, and the degree of fatigue of the driver after the start of driving. ,
Based on the basic reaction force torque and the corrected cooperative reaction force torque, a target steering reaction force torque that is a target value of the steering reaction force torque is calculated, and the steering reaction force torque applied to the steering device is calculated as follows. A steering assist unit configured to control the steering reaction force applying means so as to match the target steering reaction force torque;
Steering assist device.

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