JP2010132221A - Steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering device for a vehicle capable of traveling on a curved road without making a driver have the feeling of discomfort of the delay in turning steering wheel. <P>SOLUTION: The steering device for the vehicle is equipped with a steering angle sensor 3 for detecting a steering angle θh of the steering wheel, and an angular velocity calculation part 23 for calculating a steering angular velocity dθh/dt of the steering wheel, sets a target turning angle θf based on the steering angle θh and the steering angular velocity dθh/dt, and turns the turning wheel so that the turning angle of the turning wheel of the vehicle becomes the target turning angle θf. The steering device for the vehicle detects the radius R of the curve of the center line of the vehicle road where the vehicle currently travels, sets a steering angular velocity gain K1 so as to increase when the radius R of the curve becomes small, and sets the target turning angle θf based on the sum of the product K0×θh of the steering angle θh and the steering angle gain K0, and the product K1×dθh/dt of the steering angular velocity dθh/dt and the steering angular velocity gain K1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle steering apparatus that sets a target turning angle based on a steering angle and a steering angular velocity of a steering wheel, and performs turning so that a turning angle of a turning wheel of the vehicle becomes the target turning angle.

Conventionally, active front steering (AFS) and steer-by-wire (SBW), which can change the turning angle of the steering wheel of the vehicle relative to the steering angle of the steering wheel by the driver, have been proposed. (For example, refer to Patent Document 1). In such a steering device, the target turning angle of the steered wheels is determined according to the operation amount of the steering wheel and the vehicle speed, and the steered wheels are steered according to the target steered angle.
JP 2008-189200 A

  Not only in vehicles equipped with active front wheel steering and steer-by-wire, but in general vehicles, when the vehicle enters a curve, the vehicle becomes understeer, and the driver thinks that the steering wheel is delayed There was a case of feeling uncomfortable.

  Accordingly, an object of the present invention is to provide a vehicle steering apparatus that allows a driver to travel a curve without feeling uncomfortable that the steering wheel is delayed.

The present invention comprises a steering angle detection means for detecting a steering angle of a steering wheel and a steering angular speed calculation means for calculating a steering angular speed of the steering wheel, and a target turning angle is determined based on the steering angle and the steering angular speed. In the vehicle steering apparatus that sets and steers the steered wheels so that the steered angle of the steered wheels of the vehicle becomes the target steered angle,
Detecting the curve radius of the centerline of the roadway on which the vehicle is currently traveling;
Set the steering angular velocity gain to increase as the curve radius decreases,
The target turning angle is set based on a sum of a product of the steering angle and a steering angle gain and a product of the steering angular velocity and the steering angular velocity gain.

  The smaller the curve radius of the center line of the roadway on which the vehicle is currently traveling, the larger the steered angle of the steered wheels of the vehicle, and accordingly, the steered wheel must also be steered. According to the present invention, when the curve radius is small, a large steering angular velocity gain can be set, and further, the target turning angle can be set based on the product of the large steering angular velocity gain and the steering angular velocity. Even if the angle is small, the target turning angle can be increased. For this reason, understeer on the curve is unlikely to occur, and it is possible to suppress the uncomfortable feeling of delay in cutting that the steering wheel held by the driver cannot be cut as expected. In addition, since the target turning angle can be set based on the product of the steering angular velocity gain and the steering angular velocity, if the driver wants to turn the steering wheel quickly and steer quickly, the steering angular velocity increases. The steering angle can also be increased, and the response of the steering angle when turning can be improved. This also can suppress the uncomfortable feeling that the steering wheel held by the driver cannot be cut as expected.

  In the detection of the curve radius of the present invention, it is preferable that the curve radius is detected based on map information of the roadway acquired from a navigation system. The navigation system has map information of the vicinity including the roadway on which the vehicle is currently traveling during traveling. From this map information, if the road information of the roadway on which the vehicle along the planned route of the vehicle is currently traveling is obtained, the curve radius of the center line of the roadway (road information) is obtained from the road information by image processing. Can be easily detected.

  In the detection of the curve radius of the present invention, it is preferable that the curve radius is detected based on image information of the roadway photographed by a camera. From the image information of the roadway on which the vehicle photographed by the camera mounted on the vehicle is currently traveling, the curve radius of the centerline of the roadway can be easily detected by image processing.

  In the present invention, there is provided a differential gear that changes a transmission ratio of the steering angle with respect to the steering angle, and the differential gear is configured so that the steering angle becomes the target turning angle. It is preferable to change the transmission ratio according to the angle. According to this, the vehicle steering apparatus according to the present invention can be provided in active front wheel steering.

  In the present invention, it is preferable to have a turning actuator that drives the steered wheels to be steered without transmitting generated torque to the steering wheel. According to this, the vehicle steering apparatus according to the present invention can be provided in steer-by-wire.

  According to the present invention, it is possible to provide a vehicle steering apparatus that allows a driver to travel a curve without feeling uncomfortable that the steering wheel is delayed.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.

FIG. 1 shows a configuration diagram of a vehicle steering apparatus 1 according to an embodiment of the present invention.
The vehicle steering apparatus 1 includes a steering wheel 2 that can be steered by a driver, a steering angle sensor (steering angle detection means) 3 that detects a steering angle θh by the steering, and a torque sensor 4 that detects a steering torque by the steering. The transmission ratio variable mechanism 5 that varies the magnitude of the transmission ratio K2 that is the ratio of the turning angle of the vehicle turning wheel 11 to the steering angle θh, and the steering angle θh (steering force) of the steering wheel 2 is changed to the turning wheel 11. A rack and pinion type gear box 6 that converts the steering angle into a steering angle (steering force) and a steering angle sensor 7 that detects the steering angle.

  The steering wheel 2 is connected to the steering shaft 2 a, and the steering angle θh (steering force) is transmitted to the transmission variable mechanism 5 when the steering shaft 2 a rotates with the steering wheel 2. The steering angle sensor (steering angle detection means) 3 and the torque sensor 4 are provided in the vicinity of the steering shaft 2a. The detected steering angle θh and steering torque are transmitted to the control means 8. The steering angle θh is defined as a positive value with the neutral position θh = 0. Here, the neutral position of the steering wheel 2 corresponds to the position of the steering wheel 2 that is controlled so that the steered wheels 11 are in a straight traveling state.

  The transmission ratio variable mechanism 5 includes a differential gear 5b connected to each of the steering shaft 2a and the rack and pinion type gear box 6, and a differential gear motor that rotates the differential gear 5b to change the transmission ratio K2. 5a and drive means 5c for receiving a transmission ratio K2 from the control means 8 and supplying a drive current for driving the differential gear motor 5a so as to obtain the received transmission ratio K2.

  The rack and pinion type gear box 6 converts the rotational motion of the substantially rod-shaped rack shaft 6d that moves in the axial direction and steers the steered wheels 11 and the steering wheel 2 into linear motion in the axial direction of the rack shaft 6d. A rack and pinion 6a; an EPS motor 6b that applies a steering force assisting force to the rack shaft 6d; and a drive unit 6c that supplies a driving current for generating an assisting force by PWM driving the EPS motor 6b. ing.

The steered wheels 11 are connected to both ends of the rack shaft 6d through a steering rod 14, a tie rod 13, and a knuckle arm 12, respectively. The steering rod 14 linearly moves by the turning force transmitted to the rack shaft 6d, and the steered wheels 11 change the turning angle through the tie rod 13 and the knuckle arm 12.

The turning angle sensor 7 is provided on the rack shaft 6d. The steered angle sensor 7 has a potentiometer that detects the amount of movement of the steering rod 14.

  The torque sensor 4 is provided between the steering wheel 2 and the differential gear 5b so that the steering torque applied to the steering wheel 2 can be directly detected. The steering torque measured by the torque sensor 4 is transmitted to the control means 8. The control means 8 determines the magnitude of the auxiliary force based on the steering torque, and transmits a control signal to the drive means 6c so as to output a drive current corresponding to the auxiliary force to the EPS motor 6b. The EPS motor 6b generates an assisting force to reduce the steering force that the driver acts on the steering wheel 2, and reduces or increases the turning angle corresponding to the steering angle θh. There is basically no change. On the other hand, the transmission ratio variable mechanism 5 can change the turning angle (transmission ratio K2) corresponding to the steering angle θh to be small or large. When the transmission ratio K2 is set to a predetermined value, the steering wheel 2 to the steered wheel 11 are substantially mechanically coupled, and the EPS motor 6b alone cannot basically move the rack shaft 6d. .

From this, the (target) steered angle θf can be obtained by Equation 1. Here, K0 is a steering angle gain. The transmission ratio K2 changes with the curve radius R of the center line of the roadway on which the vehicle is currently traveling, but the steering angle gain K0 is a value that does not change with the curve radius R.

θf = K2 × K0 × θh Equation 1

  The control means 8 is connected to at least one of the navigation system 9a and the camera 9b. The control means 8 detects the curve radius R based on the map information of the roadway on which the vehicle is currently traveling obtained from the navigation system 9a. The control means 8 detects the curve radius R based on image information of the roadway on which the vehicle photographed by the camera 9b is currently traveling.

  FIG. 2 shows a block diagram of the control means 8. The control means 8 includes a steering angle gain setting unit 21, a multiplication unit 22, an angular velocity calculation unit 23, an R detection unit 24, a steering angular velocity gain setting unit 25, a multiplication unit 26, an addition unit 27, and a transmission. A ratio calculation unit 28;

  The R detector 24 is connected to at least one of the navigation system 9a and the camera 9b. When the navigation system 9 a is connected, map information 31 around the roadway on which the vehicle is currently traveling as shown in FIG. 3 is transmitted from the navigation system 9 a to the R detection unit 24. The map information 31 includes road information 32 that indicates the shape of the roadway on which the vehicle is currently traveling, that is, where and how the vehicle is turning. The R detection unit 24 extracts road information 32 from the map information 31. Based on the extracted road information 32, the R detection unit 24 creates a center line 33 of the roadway on which the vehicle is currently traveling. The center line 33 is created before and after the vehicle position 35 indicating the current position of the vehicle. Instead of the center line 33, a planned route created by the navigation system 9a and selected for the vehicle to go to the destination may be used. Next, the R detector 24 detects the radius of the circle 34 fitted to the center line 33 before and after the vehicle position 35 as the curve radius R.

  When the camera 9b is connected to the R detection unit 24, image information 36 obtained by photographing the roadway on which the vehicle is currently traveling as shown in FIG. 4 with the camera 9b is transferred from the camera 9b to the R detection unit 24. Sent to. The R detection unit 24 extracts the curbstone 37 and the center separation 38 that are both ends of the roadway based on the image information 36. The R detection unit 24 creates a center line 39 of the roadway on which the vehicle is currently traveling at the center between the curbstone 37 and the center separation 38. Next, the R detector 24 detects the radius of the arc 40 fitted to the center line 39 as the curve radius R.

  Then, the detected curve radius R is transmitted from the R detection unit 24 to the steering angular velocity gain setting unit 25.

  FIG. 5 shows the relationship between the curve radius R input by the steering angular velocity gain setting unit 25 and the steering angular velocity gain K1 set (output) with respect to the curve radius R. As shown in FIG. 5, the steering angular velocity gain K1 output from the steering angular velocity gain setting unit 25 is set to increase as the curve radius R input to the steering angular velocity gain setting unit 25 decreases. Such a setting can be realized by storing the relationship between the curve radius R and the steering angular velocity gain K1 in the database, and reading out and outputting the corresponding steering angular velocity gain K1 according to the input curve radius R. .

  Further, as shown in FIG. 2, in the control means 8, the multiplier 22, the angular velocity calculator 23, and the transmission ratio calculator 28 receive the steering angle θh received from the steering angle sensor 3.

  The multiplier 22 multiplies the steering angle θh and the steering angle gain K0 and outputs the product K0 · θh. As described above, since the steering angle gain K0 is a value that does not change depending on the curve radius R, a predetermined steering angle gain K0 is preset and stored in the steering angle gain setting unit 21, and can be read out as necessary. That's fine.

  The angular velocity calculation unit (steering angular velocity calculation means) 23 calculates a steering angular velocity dθh / dt, which is a time derivative of the steering angle θh, using the received steering angle θh, and transmits it to the multiplication unit 26.

  The multiplication unit 26 multiplies the steering angular velocity dθh / dt and the steering angular velocity gain K1 and outputs the product K1 · dθh / dt.

  The summation unit 27 sums the product K0 · θh and the product K1 · dθh / dt, and outputs the sum (K0 × θh + K1 × dθh / dt) as the target turning angle θf. The target turning angle θf is a target value that the control means 8 attempts to closely match the turning angles of the steered wheels of the vehicle. That is, the control means 8 sets the sum to the target turning angle θf (θf = K0 × θh + K1 × dθh / dt).

  Based on the target turning angle θf received from the summation unit 27, the transmission ratio calculation unit 28 calculates the transmission ratio K2 using Equation 1 above. The calculated transmission ratio K2 is transmitted to the drive means 5c (see FIG. 1). In the transmission ratio variable mechanism 5 (see FIG. 1), the transmission ratio K2 is such that the turning angle matches the target turning angle θf. Will be realized. Further, the control means 8 receives the turning angle measured by the turning angle sensor 7, and performs feedback control so that the received turning angle matches the target turning angle θf. Can be increased.

  FIG. 6 shows the change over time of the target turning angle θf when the steering wheel is steered. Since the target turning angle θf is the sum of the steering angle dependent component (K0 · θh) and the steering angular velocity dependent component (K1 · dθh / dt), the steering angular velocity dependent component (K0 · θh) FIG. 6 shows a state where K1 · dθh / dt) is added and stacked. Further, the “large R” of the solid line is a case where the curve radius R is large as shown in FIG. 5, and the “small R” of the broken line is a case where the curve radius R is small.

  Therefore, the smaller the curve radius R, the larger the target turning angle θf, even if the steering angle is the same, the understeer in the curve is unlikely to occur, and the steering wheel 2 held by the driver is not cut as expected. The uncomfortable feeling of cutting delay can be suppressed. In addition, when the curve radius R is smaller, the time from the start of steering until the target turning angle θf reaches the peak is shorter, so the response of the steering angle at the time of the curve becomes higher, and the steering wheel 2 held by the driver is thought. It is possible to suppress a sense of incongruity of the cutting delay that cannot be cut.

  In FIG. 7, the block diagram of the steering device 1 for vehicles which concerns on the modification of embodiment of this invention is shown. Although the vehicle steering apparatus 1 according to the embodiment of FIG. 1 is based on active front wheel steering, the vehicle steering apparatus 1 according to a modification of the embodiment of FIG. 7 is based on steer-by-wire. The modification differs from the embodiment in that the torque sensor 4 and the transmission ratio variable mechanism 5 are omitted, and a reaction force motor 15 and a reaction force motor driving means 15a are provided. Further, the rack and pinion 6a, the EPS motor 6b, and the driving means 6c are omitted, and the turning actuator 16 and the turning actuator driving means 16a are provided. In particular, since the transmission ratio variable mechanism 5 and the rack and pinion 6a are omitted, the steering wheel 2 and the rack shaft 6d are not mechanically connected to each other. Further, since the transmission ratio variable mechanism 5 is omitted, the control means 8 need only output the target turning angle θf without outputting the transmission ratio K2, so the transmission ratio calculation unit 28 in FIG. 2 is omitted. be able to.

The output shaft of the reaction force motor 15 is coupled to the steering shaft 2a, whereby the reaction force acting in the direction of returning the steering wheel 2 to the neutral position (θh = 0) and the neutral position (θh = It is possible to generate a return resistance force that acts in a direction opposite to the direction of returning to 0). The control means 8 outputs a control signal based on the steering angle θh to the reaction force motor drive means 15a. The reaction force motor driving means 15a drives the reaction force motor 15 based on the control signal, and reacts against the steering wheel 2 according to the traveling state of the vehicle and the operation state by the driver, or the return resistance force. Is granted.

  The turning actuator 16 applies turning power to the rack shaft 6d, moves the rack shaft 6d in the axial direction, and turns the steered wheels 11. The turning actuator driving means 16 a receives the target turning angle θf from the control means 8. The steered actuator driving means 16a drives the steered actuator 16 and moves the rack shaft 6d so that the steered angle approaches and coincides with the target steered angle θf.

It is a lineblock diagram of the steering device for vehicles concerning the embodiment of the present invention. It is a block diagram of a control means. It is an example of the map information acquired from the navigation system, and shows a method for detecting a curve radius. It is an example of the image information acquired from the camera, and shows a method for detecting the curve radius. 6 is a graph showing a relationship between an input curve radius R and a steering angular velocity gain K1 set (output) with respect to the curve radius R by a steering angular velocity gain setting unit. It is a graph which shows the time change of the target turning angle (theta) f at the time of steering a steering wheel, and the steering angle dependence component (K1 * d (theta) h when a curve radius R is large and small is included in a steering angle dependence component (K0 * thetah). / Dt) is added. It is a block diagram of the steering apparatus for vehicles which concerns on the modification of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle steering device 2 Steering wheel 2a Steering shaft 3 Steering angle sensor (steering angle detection means)
4 Torque sensor 5 Transmission ratio variable mechanism 5a Differential gear motor 5b Differential gear (planetary gear)
5c Driving means 6 Rack & pinion type gear box 6a Rack & pinion 6b EPS motor 6c Driving means 6d Rack shaft 7 Steering angle sensor 8 Control means 9a Navigation system 9b Camera 11 Steering wheel 12 Knuckle arm 13 Tie rod 14 Steering rod 15 Reaction force Motor 15a Reaction force motor drive means 16 Steering actuator 16a Steering actuator drive means 21 Steering angle gain setting unit 22 Multiplying unit 23 Angular velocity calculation unit 24 R detection unit 25 Steering angular velocity gain setting unit 26 Multiplying unit 27 Summing unit 28 Transmission ratio Calculation unit 31 Map information 32 Road information 33 Center line 34 Fitted circle 35 Vehicle position 36 Image information 37 Curb 38 Center separation 39 Center line 40 Fitted arc

Claims (5)

A steering angle detecting means for detecting a steering angle of the steering wheel; and a steering angular speed calculating means for calculating a steering angular speed of the steering wheel, wherein a target turning angle is set based on the steering angle and the steering angular speed, In the vehicle steering apparatus that steers the steered wheels so that the steered angle of the steered wheels becomes the target steered angle,
Detecting the curve radius of the centerline of the roadway on which the vehicle is currently traveling;
Set the steering angular velocity gain to increase as the curve radius decreases,
The vehicle steering apparatus, wherein the target turning angle is set based on a sum of a product of the steering angle and a steering angle gain and a product of the steering angular velocity and the steering angular velocity gain.   2. The vehicle steering apparatus according to claim 1, wherein in detecting the curve radius, the curve radius is detected based on map information of the roadway acquired from a navigation system. 3.   2. The vehicle steering apparatus according to claim 1, wherein the curve radius is detected based on image information of the roadway photographed by a camera. 3. A differential gear that changes a transmission ratio of the steering angle to the steering angle;
4. The differential gear according to claim 1, wherein the differential gear changes the transmission ratio according to the steering angle so that the turning angle becomes the target turning angle. 5. The vehicle steering device according to claim 1.   The vehicle according to any one of claims 1 to 3, further comprising a steering actuator that drives the steered wheels to steer without transmitting generated torque to the steering wheel. Steering device.

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