JP4419109B2 - Vehicle steering control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is based on the operation of a power steering device that assists steering by transmitting a driving force from a steering actuator that is driven and controlled in accordance with a steering torque to a steering mechanism, and an operation means such as a steering wheel. The present invention relates to a control device applied to a vehicle steering device or the like configured to drive a steering mechanism having no mechanical coupling with means by a steering actuator.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a power steering device that assists steering by transmitting a driving force from an electric motor to a steering mechanism via a gear or a hydraulic device is mounted on a vehicle and used. For example, the electric motor is feedback-controlled based on a target current value set in accordance with a steering torque applied to the steering wheel, whereby a steering assist force (target current corresponding to the steering torque) is set. Force corresponding to the value) is applied to the steering mechanism. The target current value is set to be larger as the steering torque is larger, whereby a steering assist force corresponding to the magnitude of the steering torque is given to the steering mechanism.
[0003]
On the other hand, the mechanical coupling between the steering wheel and the steering mechanism for steering the steering wheel is eliminated, the operation direction and the operation amount of the steering wheel are detected, and an electric motor or the like is added to the steering mechanism based on the detection result. There has been proposed a vehicle steering apparatus that applies a driving force from the actuator (see, for example, JP-A-9-142330). Such a vehicle steering apparatus is hereinafter referred to as a “steer-by-wire system”.
[0004]
In the steer-by-wire system, the relationship between steering wheel operation and steering mechanism operation can be freely changed by electrical control, which is expected to dramatically improve the driving performance of the vehicle. ing.
For example, by obtaining a target yaw rate or target lateral acceleration corresponding to the steering wheel operating torque or steering angle, and controlling the operation of the steering mechanism based on the target yaw rate or the target lateral acceleration, the attitude control of the vehicle can be performed. The motion characteristics can be optimized.
[0005]
[Problems to be solved by the invention]
FIG. 9 is a diagram illustrating an example of a locus of a vehicle position, that is, a line drawing when the vehicle travels in a corner. FIG. 9A shows a trajectory of the vehicle position in the case of a driver who takes a line that is faithful to the curvature of the corner. FIG. 9 (b) shows a driver's line-drawing that tries to pass the corner along a straight line as much as possible.
In the case of a driver who takes a faithful line as shown in FIG. 9A, the steering angle when operating the steering wheel increases, and the steering angular velocity and the yaw rate of the vehicle also increase. On the other hand, in the case of a driver who tends to make a line as shown in FIG. 9B, the steering angle, the steering angular velocity, and the yaw rate all tend to be small.
[0006]
Regardless of whether the vehicle is equipped with a power steering device or a steer-by-wire system, the driver shown in FIG. Compared to a driver who takes a straight line as shown in FIG. This is because, in the power steering apparatus, the assist characteristic that is the characteristic of the steering assist force with respect to the steering torque does not reflect the driver's tendency to line. Further, in the steer-by-wire system, the gear ratio, which is the relationship between the steering angle of the tire with respect to the steering angle of the steering wheel, is set regardless of the driver's tendency to line up.
[0007]
Accordingly, an object of the present invention is to solve the above-mentioned technical problem and to give an appropriate driving force to the steering mechanism according to the steering tendency of each driver during cornering, thereby improving the steering feeling. An object of the present invention is to provide a vehicle steering control device that can do this.
[0008]
[Means for Solving the Problems and Effects of the Invention]
  In order to achieve the above object, according to the first aspect of the present invention, the steering actuator (50; 2) for generating the driving force to be applied to the steering mechanism (33; 3) is used to operate the operating means (31; 1). A vehicle steering control device that controls the actuator according to a predetermined control characteristic, and an actuator control means (41; 20) for controlling the steering actuator and a steering angle of the operation means.,Steering angular speedDegreeOr the yaw rate of the vehicleHistogram creation means for creating a histogram and outputting an absolute value of a peak corresponding value which is a value of the steering angle, the steering angular velocity or the yaw rate corresponding to the peak of the histogram(44, S1, S2; 20, S11, S12And thisOutput of histogram creation meansControl characteristic changing means (43, S3 to S6; 20, S13 to S16) for changing the control characteristic in the actuator control means based onThe control characteristic changing means has means for comparing the absolute value of the peak corresponding value with a predetermined reference value. When the absolute value of the peak corresponding value is less than the reference value, the control characteristic is changed. When the absolute value of the peak-corresponding value is equal to or higher than a reference value, the control characteristic is a burden reducing characteristic that reduces the driver's steering burden more than the normal characteristic.1 is a vehicle steering control device. In addition, the alphanumeric characters in parentheses represent corresponding components in the embodiments described later. The same applies hereinafter.
[0009]
  According to this configuration, the steering angle or steering angular velocity of the operating means such as the steering wheel or the distribution of the yaw rate of the vehicle(histogram)Is required. Steering angle or steering angular velocity or vehicle yaw rate distribution(histogram)Corresponds to the driver's steering tendency during cornering, that is, line taking. Specifically, in the case of a driver who takes a line that is faithful to the curvature of the corner, the steering angle, steering angular velocity, or vehicle yaw ratehistogramTakes a peak in the value of a relatively large steering angle, steering angular velocity or vehicle yaw rate. On the other hand, in the case of a driver who tries to pass a corner with a straight line as much as possible, the steering angle, steering angular velocity or vehicle yaw ratehistogramThe peak at appears at a position corresponding to a relatively small value.
[0010]
  Therefore, the steering angle, steering angular velocity or vehicle yaw ratePeak position in the histogramTherefore, if the control characteristic of the steering actuator is changed, a driving force adapted to the steering tendency of the driver can be given to the steering mechanism. In addition, a good steering feeling can be obtained.
  In the present invention, the histogram creating means creates a histogram of the steering angle, the steering angular velocity or the yaw rate, and the peak corresponding value which is the value of the steering angle, the steering angular velocity or the yaw rate corresponding to the peak of the histogram. Output the absolute value. AndThe control characteristic changing means isAbsolute value of the corresponding peak valueHas means (S5; S15) for comparing the size of the value with a predetermined reference valueRu. That is, the aboveAbsolute value of peak correspondenceBased on whether the value is larger or smaller than the reference value, or a driver who tends to take a line that is faithful to the curvature of the corner, or a driver who tends to pass the corner with a straight line as much as possible It can be judged whether there is.Therefore, the control characteristic changing means is,the abovePeak correspondence value andChange the control characteristics of the steering actuator based on the comparison result with the reference valueTo do. ThisEspecially, in the case of a driver who takes a line faithful to a corner, the steering burden can be reduced.
[0011]
The vehicle steering control device of the present invention is configured to transmit the driving force generated by the steering actuator to the steering mechanism directly or via an appropriate driving force transmission mechanism such as a gear mechanism or a hydraulic device. The present invention can be applied to a vehicle steering device. Such a vehicle steering device may be a power steering device that applies steering assist force to the steering mechanism in a configuration that mechanically transmits the operating force of the operating means to the steering mechanism. In the vehicle steering apparatus, the operation means and the steering mechanism do not have a mechanical coupling, the operation of the operation means is electrically detected, and the steering actuator is driven and controlled based on the detection result. The steering mechanism may be driven by a so-called steer-by-wire system.
[0012]
  Also, aboveHistogram creationThe means samples, for example, an output signal of a steering angle sensor (36; 11) provided in association with the operation means at a constant sampling period, and counts the frequency for each value of the sampled steering angle. It may be a means for repeatedly creating a histogram at regular intervals. Also,Histogram creationThe means may calculate the steering angular velocity from the output of the steering angle sensor, obtain the frequency for each value of the calculated steering angular velocity, and repeatedly create a histogram for each fixed time of the steering angular velocity. Moreover,Histogram creationThe means may sample the output of the yaw rate detection means (16) and repeatedly create a yaw rate histogram for each fixed time.The invention according to claim 2 is the vehicle steering apparatus according to claim 1, wherein the burden reducing characteristic is a burden reducing assist characteristic that generates a larger driving force than when the steering actuator has the normal characteristic. .
According to a third aspect of the present invention, the steering actuator steers a steering wheel of a vehicle, and the control characteristic is a gear that is a relationship of a steering angle of the steering wheel with respect to an operation angle of the operation means. The vehicle steering apparatus according to claim 1, wherein the load reduction characteristic is a load reduction gear ratio characteristic that is steeper than when the turning angle accompanying an increase in the operation angle is the normal characteristic. is there.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram showing an electrical configuration of the power steering apparatus according to the first embodiment of the present invention. The steering torque applied to the steering wheel 31 as the operation means is transmitted to the steering mechanism 33 via the steering shaft 32. A driving force generated from an electric motor 50 as a steering actuator is transmitted to the steering mechanism 33 as a steering assist force through a driving force transmission mechanism such as a gear mechanism or a ball screw mechanism. .
[0014]
The steering shaft 32 is divided into an input shaft 32A coupled to the steering wheel 31 side and an output shaft 32B coupled to the steering mechanism 33 side. The input shaft 32A and the output shaft 32B are connected to a torsion bar 34. Are connected to each other. The torsion bar 34 is twisted according to the steering torque T, and the direction and amount of the twist are detected by the torque sensor 35. The output signal of the torque sensor 35 is input to the controller 40 (ECU).
[0015]
The controller 40 applies a drive current corresponding to the steering torque T detected by the torque sensor 35 to the electric motor 50, and drives the electric motor 50 so that a steering assist force corresponding to the steering torque T is applied to the steering mechanism 33. Control. In addition to the output signal of the torque sensor 35, the controller 40 includes a steering angle sensor 36 that detects a steering angle θ as a rotation angle of the steering wheel 31, and a vehicle speed V of a vehicle on which the electric power steering device is mounted. Each output signal with the vehicle speed sensor 37 for detecting is also input.
[0016]
The controller 40 includes an assist control unit 41 that sets a target current value I corresponding to the steering torque T and the vehicle speed V by program processing using a microcomputer provided therein, and the target current value I set by the assist control unit 41. The motor control unit 42 that feedback-controls the electric motor 50 based on the above, the assist characteristic changing unit 43 for changing the assist characteristic that is the steering torque versus target current value characteristic in the assist control unit 41, and the distribution of the steering angle θ are represented. Each function of the histogram creation unit 44 that creates a histogram is realized.
[0017]
The histogram creation unit 44 takes in the steering angle θ output from the steering angle sensor 36 at regular sampling intervals, and counts the frequency for each value. Based on this, a histogram representing the distribution of the steering angle θ within a certain time (for example, 5 seconds) is repeatedly created.
An example of this histogram is shown in FIG. FIG. 2A shows a histogram of the steering angle θ in the case of a driver who takes a line faithful to a corner as shown in FIG. On the other hand, FIG. 2B shows a histogram of the steering angle θ in the case of a driver who takes a straight line as shown in FIG. 9B.
[0018]
  As understood from the comparison between FIGS. 2 (a) and 2 (b), in the case of a driver who takes a line faithfully in a corner, a relatively large value of the absolute value of the steering angle θ in the histogram of the steering angle θ. A peak appears at a position corresponding to. On the other hand, in the case of a driver who tries to pass through a corner by taking a straight line, a peak appears in the histogram at a position corresponding to a relatively small absolute value of the steering angle.
  Therefore, the histogram creation unit 44 determines the steering angle θ corresponding to the peak in the histogram of the steering angle θ.(Peak correspondence value)Are output (hereinafter referred to as “peak steering angle”) θ1, θ2 (where θ1, θ2> 0, collectively referred to as “θp”). The peak steering angle θp is given to the assist characteristic changing unit 43.
[0019]
The assist characteristic changing unit 43 compares the peak steering angle θp given from the histogram creating unit 44 with a predetermined reference value θref (θref> 0). This reference value θref is set so as to correspond to the peak of the histogram in the case of passing through the corner with an intermediate line drawing between the two line drawing shown in FIGS. 9 (a) and 9 (b). Therefore, the peak steering angle θ1 when the line is faithful to the corner takes a value equal to or larger than the reference value θref. On the other hand, the peak steering angle θ2 when the vehicle passes through the corner by linear line taking takes a value smaller than the reference value θref. That is, the comparison result between the peak steering angle θp and the reference value θref in the histogram represents the steering tendency of the driver passing through the corner.
[0020]
When the peak steering angle θp given from the histogram creation unit 44 is smaller than the reference value θref, the assist characteristic changing unit 43 outputs a command signal indicating that the electric motor 50 should be controlled according to the normal assist characteristic. 41. On the other hand, when the peak steering angle θp given from the histogram creating unit 44 is equal to or larger than the reference value θref, the assist control unit 41 generates assist assist force (hereinafter, “ A command signal indicating that the electric motor 50 should be controlled is given in accordance with “load reduction assist characteristics”.
[0021]
FIG. 4 is a diagram illustrating assist characteristics in the assist control unit 41. In FIG. 4, a curve L0 indicates a normal assist characteristic, and a curve L1 indicates a burden reduction assist characteristic. The assist control unit 41 determines a target current value I of the electric motor 50 according to the magnitude of the steering torque T according to any assist characteristic represented by the curve L0 or L1. When the target current value I is given to the motor control unit 42, the electric motor 50 gives an appropriate steering assist force corresponding to the steering torque T to the steering mechanism 33.
[0022]
When the steering torque T takes a value near zero, a large steering assist force is not necessary, so the target current value I takes a very small value close to zero. In the normal assist characteristic according to the curve L0, the target current value I increases relatively gradually as the steering torque T increases. On the other hand, the load reduction assist characteristic according to the curve L1 is set such that the target current value I rises relatively steeply as the steering torque T increases. As a result, when the assist control unit 41 employs the burden reduction assist characteristic according to the curve L1, a steering assist force larger than that in a normal case is applied to the steering mechanism 33, and the steering burden on the driver is reduced.
[0023]
In this embodiment, when the peak steering angle θp of the histogram created by the histogram creation unit 44 is greater than or equal to the reference value θref, that is, as shown in FIG. In this case, the burden reduction assist characteristic according to the curve L1 is employed. As a result, the steering burden on the driver who takes a line faithful to the curvature of the corner is reduced.
The histogram creation unit 44 may create a histogram of the steering angular velocity θ ′, which is a differential value of the steering angle θ, instead of creating a histogram of the steering angle θ. Examples of the histogram of the steering angular velocity θ ′ are shown in FIGS. 3 (a) and 3 (b). FIG. 3A shows a histogram of the steering angular velocity θ ′ obtained in the case of a driver who takes a line faithful to the corner as shown in FIG. 9A. On the other hand, FIG. 3B shows a histogram of the steering angular velocity θ ′ obtained in the case of a driver who takes a straight line as shown in FIG. 9B.
[0024]
As understood from the comparison of FIGS. 3A and 3B, in the case of a driver who takes a line faithfully in the corner, the steering wheel 31 has to be operated largely, and accordingly the steering angular velocity θ The absolute value of ′ also increases. Therefore, in the steering angular velocity θ ′ histogram, a peak appears at a relatively large absolute value of the steering angular velocity θ ′. On the other hand, in the case of a driver who takes a straight line, since the amount of operation of the steering wheel 31 is small, the absolute value of the steering angular velocity θ ′ tends to decrease accordingly. Therefore, a peak in the histogram of the steering angular velocity θ ′ appears at the position of the steering angular velocity θ ′ having a relatively small absolute value.
[0025]
  Therefore, the steering angle velocity corresponding to the peak of the histogram of the steering angular velocity θ ′ is determined by the histogram creation unit 44.(Peak correspondence value)(Hereinafter referred to as “peak steering angular velocity”) θ′1, θ′2 (however, θ′1, θ′2> 0, hereinafter referred to as “θ′p”). In this case, the assist characteristic changing unit 43 compares the peak steering angular velocity θ′p with the corresponding reference value θ′ref (θ′ref> 0), and outputs a command signal corresponding to the comparison result. What is necessary is just to give to the assist control part 41. The reference value θ′ref in this case is the same as that in the case of creating a histogram of the steering angle θ in the case of a driver who passes through a corner with an intermediate line drawing of both line drawing in FIGS. 9 (a) and 9 (b). A value corresponding to a peak in the histogram of the steering angular velocity θ ′ may be used.
[0026]
FIG. 5 is a flowchart for explaining the operation of the controller 40. First, in the histogram creation unit 44, the steering angle θ (or steering angular velocity θ ′) is sampled at a constant sampling period, and the frequency of each value is counted over a fixed time (for example, 5 seconds). Thereby, a histogram of the steering angle θ (or steering angular velocity θ ′) is created (step S1). When this histogram is completed, the histogram creation unit 44 detects a peak position (that is, peak steering angle θp (or peak steering angular velocity θ′p)) in the created histogram (step S2).
[0027]
Depending on the curvature of the corner and the line removal, there may be no peak in the histogram. In this case, a signal indicating that no peak exists (for example, a signal indicating θp = 0 (or θ′p = 0)). ) To the assist characteristic changing unit 43.
The assist characteristic changing unit 43 first determines the presence or absence of a peak in the histogram (step S3), and if there is no peak, a command indicating that the target current I should be set according to the normal assist characteristic (curve L0 in FIG. 4). A signal is given to the assist control unit 41 (step S4).
[0028]
On the other hand, when a significant value (for example, a value other than zero) of the peak steering angle θp (or peak steering angular velocity θ′p) is given from the histogram creation unit 44 (YES in step S3), the reference value θref corresponding thereto. (Or θ′ref) is compared (step S5). When the peak steering angle θp (or peak steering angular velocity θ′p) is equal to or larger than the reference value θref (or θ′ref), a command signal indicating that the burden reduction assist characteristic indicated by the curve L1 in FIG. It gives to the assist control part 41 (step S6). On the other hand, when the peak steering angle θref (or peak steering angular velocity θ′p) is less than the reference value θref (or θ′ref), the normal assist characteristic indicated by the curve L0 in FIG. 4 should be selected. A command signal indicating that is given to the assist control unit 41 (step S4).
[0029]
When the assist characteristic to be followed by the assist control unit 41 is determined in this way, the assist control unit 41 determines the target current value I based on the steering torque T and the vehicle speed V (step S7). Based on the target current value I thus determined, the motor control unit 42 performs feedback control of the electric motor 50 (step S8).
The assist control unit 41 has a plurality of tables of target current values I with respect to the steering torque T, corresponding to a plurality of vehicle speed ranges, for example. Thus, the steering assist force is reduced during high-speed travel, and a large steering assist force can be generated from the electric motor 50 during low-speed travel or when stopped. However, in FIG. 4, only the assist characteristic in one vehicle speed range is shown.
[0030]
As described above, according to this embodiment, the steering tendency of the driver during cornering is determined based on the peak position of the histogram of the steering angle θ (or steering angular velocity θ ′). Based on the determination result, in the case of a driver who takes a line faithful to a corner, the steering assist force is increased to reduce the driver's steering burden. Further, in the case of a driver who passes through a corner by taking a straight line, a normal assist characteristic is adopted so that excessive steering assistance is not performed. In this way, an appropriate steering assist force can be applied to the steering mechanism 33 in a good manner corresponding to the steering tendency of each driver. As a result, a driver having any steering tendency can obtain a good steering feeling.
[0031]
FIG. 6 is a conceptual diagram for explaining a basic configuration of a vehicle steering system according to a second embodiment of the present invention. In this vehicle steering device, the operation of the steering actuator 2 driven in accordance with the rotational operation of the steering wheel (operation means) 1 is converted by the steering gear 3 into the turning motion of the front left and right wheels 4 (steering wheels). Thus, the steer-by-wire system achieves steering without mechanically connecting the steering wheel 1 and the steering gear 3. In this case, a steering mechanism is constituted by the steering actuator 2, the steering gear 3, and the like.
[0032]
The steering actuator 2 can be constituted by an electric motor such as a known brushless motor. The steering gear 3 has a motion conversion mechanism (such as a ball screw mechanism) that converts the rotational motion of the output shaft of the steering actuator 2 into a linear motion in the axial direction (vehicle width direction) of the steering rod 7. The movement of the steering rod 7 is transmitted to the knuckle arm 9 via the tie rod 8 and causes the knuckle arm 9 to rotate. Thereby, steering of the wheel 4 supported by the knuckle arm 9 is achieved.
[0033]
The steering wheel 1 is connected to a rotary shaft 10 that is rotatably supported with respect to the vehicle body. The rotary shaft 10 is provided with a reaction force actuator 19 for applying a steering reaction force to the steering wheel 1. Specifically, the reaction force actuator 19 can be configured by an electric motor such as a brushless motor having an output shaft integrated with the rotary shaft 10.
An elastic member 30 made of a spiral spring or the like is coupled to the end of the rotating shaft 10 on the opposite side of the steering wheel 1 from the vehicle body. The elastic member 30 returns the steering wheel 1 to the straight steering position by the elastic force when the reaction force actuator 19 is not applying torque to the steering wheel 1.
[0034]
In order to detect an operation input value of the steering wheel 1, a steering angle sensor 11 for detecting a steering angle δh corresponding to the rotation angle of the rotary shaft 10 is provided. The rotating shaft 10 is provided with a torque sensor 12 for detecting a steering torque T applied to the steering wheel 1.
On the other hand, as an output value sensor for detecting the output value of the steering actuator 2, a turning angle sensor 13 for detecting the turning angle δ of the wheel 4 is provided. The steered angle sensor 13 can be configured by a potentiometer or the like that detects the operation amount of the steering rod 7 by the steering actuator 2.
[0035]
The steering angle sensor 11, the torque sensor 12, and the turning angle sensor 13 are connected to a steering system control device 20 (steering control means) including a computer. The control device 20 is further connected with a lateral acceleration sensor 15 for detecting the lateral acceleration Gy of the vehicle, a yaw rate sensor 16 for detecting the yaw rate γ of the vehicle, and a speed sensor 14 for detecting the vehicle speed V. Yes. In addition to the steering angle δh and the vehicle speed V, as a variable correlated with the lateral acceleration Gy and the yaw rate γ, for example, a sensor that detects a wheel speed may be connected to the control device 20.
[0036]
The control device 20 controls the steering actuator 2 and the reaction force actuator 19 via the drive circuits 22 and 23.
More specifically, the control device 20 performs steering control for controlling the steering actuator 2 so that the turning angle δ corresponding to the steering angle δh detected by the steering angle sensor 11 is achieved. Furthermore, the control device 20 performs, for example, attitude control for stabilizing the behavior of the vehicle based on the yaw rate γ and the lateral acceleration Gy of the vehicle detected by the yaw rate sensor 16 and the lateral acceleration sensor 15 respectively, and the steering actuator. It may be realized by steering control by driving of No. 2. That is, for example, when the vehicle is about to spin, the vehicle attitude may be reestablished by promptly leading to the counter-steer state by controlling the steering actuator 2.
[0037]
The control device 20 can arbitrarily set a gear ratio that is a relationship of the turning angle δ with respect to the steering angle δh. FIG. 7 is a diagram for explaining a setting example of such a gear ratio. For example, the control device 20 can set a constant gear ratio such that the steering angle δh and the turning angle δ are proportional (curve L10). On the other hand, the control device 20 changes the gear ratio for a relatively large steering angle δh as necessary, as indicated by a curve L11, and turns the steering angle as the steering angle δh increases. It is also possible to set a gear ratio characteristic (burden reduction gear ratio characteristic) such that δ rises relatively steeply.
[0038]
In this embodiment, in the case of a driver who takes a line that is faithful to the curvature of the corner as shown in FIG. 9A, the load reduction gear ratio characteristic shown in the curve L11 is automatically selected. In the case of a driver who takes a straight line as shown in (b), a normal gear ratio characteristic as shown by a curve L10 is automatically selected.
FIG. 8 is a flowchart for explaining processing related to selection of the gear ratio characteristic in the control device 20. The control device 20 takes in the steering angle δh at a constant sampling period, counts the frequency for each value over a fixed time (for example, 5 seconds), and repeatedly creates a histogram (step S11). Instead of this, the control device 20 may create a histogram of the steering angular velocity δh ′, which is a differential value of the steering angle δh. In the case of the steering angle δh, the histogram created in this case is similar to the histogram for the steering angle θ shown in FIGS. When a histogram of the steering angular velocity δh ′ is created, this histogram is similar to the distribution shown in FIGS. 3 (a) and 3 (b).
[0039]
  Next, the control apparatus 20 detects the peak of the created histogram (step S12). That is, the steering angle δh corresponding to the peak of the histogram(Peak correspondence value)Absolute value P (where P> 0 or less, referred to as “peak steering angle P”) or steering angular velocity δh ′ corresponding to the peak.(Peak correspondence value)The absolute value P ′ (where P ′> 0; hereinafter referred to as “peak steering angular velocity P ′”) is detected. The peak may not appear in the histogram depending on the shape of the corner through which the vehicle passes and the line drawing. If no peak appears in the histogram (NO in step S13), the normal gear ratio characteristic indicated by the curve L10 in FIG. 7 is adopted (step S14).
[0040]
On the other hand, if a peak appears in the histogram (YES in step S13), the peak steering angle P (or peak steering angular velocity P ′) and the corresponding reference value Pref (> 0)) (or P′ref ( > 0)) is compared (step S15). When the peak steering angle P (or peak steering angular velocity P ′) is greater than or equal to the reference value Pref (or P′ref) (YES in step S15), the burden reducing gear ratio characteristic indicated by the curve L11 in FIG. 7 is employed. (Step S16). That is, when the steering angle δh is increased by turning the steering wheel 1 relatively large, the wheels 4 are quickly steered, thereby reducing the driver's steering burden.
[0041]
If the peak steering angle P (or peak steering angular velocity P ′) in the histogram is smaller than the reference value Pref (or P′ref) (NO in step S15), the normal gear ratio characteristic indicated by the curve L10 in FIG. Since it is adopted (step S14), the turning angle δ of the wheel 4 will not be excessively increased.
The reference value Pref or P′ref is set to a value similar to the reference value θref or θ′ref in the first embodiment described above. That is, the reference value Pref or P′ref is a value corresponding to the steering tendency of the driver passing through the corner with an intermediate line drawing between the two line drawing in FIGS. 9 (a) and 9 (b). Therefore, in the case of a driver who takes a line that is faithful to the corner, the steering angle δh can be quickly increased with respect to the relatively large steering angle δh, thereby reducing the driver's steering burden. be able to. On the other hand, for a driver who passes a corner with a straight line, the turning angle δ does not increase rapidly even for a large steering angle δh, which is contrary to the driver's intention. Thus, the wheel 4 is not steered greatly.
[0042]
As described above, according to this embodiment, in the steer-by-wire system, an appropriate gear ratio characteristic adapted to the steering tendency of the driver is set. In addition, a good steering feeling can be obtained.
As mentioned above, although two embodiment of this invention was described, this invention can also be implemented with another form. For example, in the first embodiment described above, two types of assist characteristics are selectively used based on the peak position of the histogram of the steering angle θ or the steering angular velocity θ ′. Three or more types of assist characteristics may be selected by comparing the corresponding peak steering angle θp or peak steering angular velocity θ′p with two or more reference values. As a result, the steering tendency of the driver can be analyzed in more detail, so that the steering feeling can be further improved.
[0043]
  The same modification can be made for the second embodiment described above, and the peak position (that is, the peak steering angle P or the peak steering angular velocity P ′) in the histogram of the steering angle δh or the steering angular velocity δh ′ is two or more references. Compared with the value, the driver's steering tendency may be analyzed in more detail, and the gear ratio characteristic may be changed to two or more types.
[0044]
  In the above-described first embodiment, the configuration in which the driving force generated by the electric motor 50 is transmitted to the steering mechanism 33 via the mechanical driving force transmission mechanism has been described. A configuration may be adopted in which the hydraulic pump is driven and the force from the power cylinder driven by the hydraulic oil pumped by the hydraulic pump is transmitted to the steering mechanism 33.
  In the above-described embodiment, the histogram of the steering angle or the steering angular velocity is obtained, but the yaw rate of the vehicle also has a distribution corresponding to the steering tendency of the driver. Therefore, an assist characteristic or a gear ratio characteristic corresponding to the driver's steering tendency may be set by creating a histogram for the yaw rate and analyzing the histogram. More specifically, for example, in the configuration of the second embodiment described above, the output of the yaw rate sensor 16 is sampled over a certain period of time, a histogram thereof is created, and the gear ratio characteristic is based on the peak position in the histogram. Can be changed. In this case, in the case of a driver who takes a line that is faithful to the curvature of the corner, a peak appears at a position corresponding to a large absolute value of the yaw rate in the histogram of the yaw rate, and the line that passes straight through the corner. In the case of a driver who tends to remove, a peak appears at a position corresponding to a small value of the absolute value of the yaw rate. Therefore, the yaw rate corresponding to this peak position(Peak correspondence value)The steering tendency of the driver can be analyzed by comparing the absolute value of the value with an appropriate reference value.
[0045]
In addition, various design changes can be made within the scope of technical matters described in the claims.
[Brief description of the drawings]
FIG. 1 is a block diagram for explaining an electrical configuration of an electric power steering apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram showing an example of a histogram of steering angles.
FIG. 3 is a diagram showing an example of a histogram of steering angular velocities.
FIG. 4 is a diagram illustrating an example of assist characteristics.
FIG. 5 is a flowchart for explaining processing related to control of the electric motor.
FIG. 6 is a conceptual diagram for explaining a configuration of a steer-by-wire system according to a second embodiment of the present invention.
FIG. 7 is a diagram for explaining a setting example of gear ratio characteristics;
FIG. 8 is a flowchart for explaining processing for setting gear ratio characteristics;
FIG. 9 is a diagram illustrating an example of a driver's steering tendency when passing through a corner;
[Explanation of symbols]
31 Steering wheel
33 Steering mechanism
34 Torsion bar
35 Torque sensor
36 Rudder angle sensor
37 Vehicle speed sensor
40 controller
41 Assist control unit
42 Motor controller
43 Assist characteristic change section
44 Histogram generator
50 Electric motor
1 Steering wheel
2 Steering actuator
3 Steering gear
11 Steering angle sensor
12 Torque sensor
13 Steering angle sensor
16 Yaw rate sensor
20 Steering system controller
22 Drive circuit

Claims (3)

A vehicle steering control device for controlling a steering actuator for generating a driving force to be applied to a steering mechanism in accordance with an operation of an operating means,
Actuator control means for controlling the steering actuator according to predetermined control characteristics;
Steering angle of the operation means, the steering angle speed Doma other creates a histogram of the yaw rate of the vehicle, the steering angle corresponding to the peak of the histogram, the steering angular velocity or the absolute value of the peak corresponding value is the value of the yaw rate Histogram generating means for outputting
Based on the output of the histogram creating means, seen including a control characteristics changing means for changing a control characteristic of the actuator control means,
The control characteristic changing means has means for comparing the absolute value of the peak corresponding value with a predetermined reference value. When the absolute value of the peak corresponding value is less than the reference value, the control characteristic is changed to a normal characteristic. When the absolute value of the peak-corresponding value is greater than or equal to a reference value, the vehicle steering control device is configured such that the control characteristic is a burden reducing characteristic that reduces a driver's steering burden more than the normal characteristic. .   The vehicle steering device according to claim 1, wherein the burden reducing characteristic is a burden reducing assist characteristic that generates a larger driving force than when the steering actuator has the normal characteristic.   The steering actuator is for turning a steering wheel of a vehicle.
  The control characteristic is a gear ratio characteristic that is a relationship of a steering angle of the steering wheel with respect to an operation angle of the operation means,
  The vehicle steering device according to claim 1, wherein the load reduction characteristic is a load reduction gear ratio characteristic that is steeper than when the turning angle accompanying the increase in the operation angle is the normal characteristic.

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