JP2007168660A - Steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering device capable of performing suitable steering control when inclination in a road lateral direction exists on a traveling road. <P>SOLUTION: The steering device 1 for detecting the traveling road of a vehicle by a traveling road detection means and controlling a steering mechanism such that the vehicle travels along a predetermined position of the traveling road is provided with an inclination detection means 12 for detecting the inclination in the road lateral direction; and steering control direction detection means 20, 21, 30 for detecting a steering control direction. When the inclination in the road lateral direction detected by the inclination detection means 12 during traveling on a curve road is low at an inner side of the curve, reduction control of an output for controlling the steering mechanism is performed when the steering control direction detected by the steering control direction detection means 20, 21, 30 is in an inward direction of the curve. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a steering apparatus that controls a steering mechanism so as to travel along a predetermined position on a traveling path.

As a steering device, there is a lane keeping device that recognizes a lane from a captured image of a traveling road ahead of the vehicle and applies torque to the steering mechanism so that the vehicle travels along the center of the lane (see Patent Document 1). In the lane keeping device, the curve radius (road curvature) of the travel path from the recognized lane and the vehicle, the yaw angle of the vehicle with respect to the lane, the offset of the vehicle from the lane center, and the like are obtained. In the lane keeping device, the feedforward output is obtained based on the road curvature, the feedback output is obtained based on the yaw angle and the offset, and the output torque to be added to the steering mechanism is set from these outputs. Further, some lane keeping devices integrate an offset, and a feedback output based on the integral term also takes into account the output torque.
JP 2001-10518 A

  The road is provided with a road surface cant (transverse gradient) inclined in either the left or right direction of the road in consideration of the direction of drainage or the curve. For example, in the case of a curved road, an inclined road surface cant is usually provided on the inside of the curve. Therefore, even if the same lane keeping torque is applied to the vehicle in the left-right direction, the direction of the torque is the same as the inclination direction of the road surface cant with respect to the lateral acceleration (target lateral acceleration) acting on the vehicle due to the torque. In this case, the lateral acceleration acting on the vehicle is increased (excessive lateral acceleration), and when the torque direction is opposite to the inclination direction of the road surface cant, the lateral acceleration acting on the vehicle is reduced (insufficient lateral acceleration). In particular, when the slope of the road surface cant is steep, a lateral acceleration that is larger than the target lateral acceleration acts, which may cause a lane departure of the vehicle. Further, when the slope of the road surface cant is gentle, the lateral acceleration caused by the road surface cant can be resisted to some extent by the torque generated by the lane keep, so that the vehicle moves toward the inclination direction of the road surface cant while staggering. Therefore, in order to improve the lane following performance by lane keeping, it is necessary to set the output torque of the lane keeping in consideration of the presence / absence of the road surface cant and the inclination direction.

  Therefore, an object of the present invention is to provide a steering device that can perform appropriate steering control when the road is inclined in the lateral direction of the road.

  A steering device according to the present invention detects a road of a vehicle by a road detection unit, and controls a steering mechanism so that the vehicle travels along a predetermined position of the road. And a steering control direction detecting means for detecting a steering control direction. When the road lateral inclination detected by the inclination detecting means during traveling on a curved road is low inside the curve, the steering control direction is detected. When the steering control direction detected by the means is an inner direction of the curve, output reduction control for controlling the steering mechanism is performed.

  In this steering apparatus, the travel path of the vehicle is detected by the travel path detection means. Then, the steering device obtains a steering output for controlling the steering mechanism so that the vehicle travels along a predetermined position on the traveling path, and controls the steering mechanism based on the steering output. Further, in the steering apparatus, the inclination detecting means detects the inclination in the lateral direction of the road, and the steering control direction detecting means detects the direction (steering control direction) in which the steering output is applied. In the steering device, when the vehicle is traveling on a curved road, if the slope in the lateral direction of the road is low on the inside of the curve, the steering output is reduced compared to the normal control when the steering control direction is the inside of the curve. To control the steering mechanism. In other words, when there is a low road lateral inclination inside the curve on the curved road, the lateral acceleration in the curve inner direction acts on the vehicle due to the inclination, so when the steering control direction is the same as the direction of the inclination ( When the steering output during normal control is applied to the vehicle at the time of further increase, the lateral acceleration acting on the vehicle becomes larger than when there is no low inclination inside the curve, and the vehicle approaches the inside of the curve. Therefore, in this case, in the steering device, the lateral output acting on the vehicle is prevented from increasing by controlling the steering output to be lower than that during normal control. As a result, no curb entrainment occurs and the vehicle travels along a predetermined position on the travel path. Thus, in the steering device, when there is a low road lateral direction inclination inside the curve on the curved road, it is possible to compensate for the influence of the inclination and perform appropriate steering control.

  In the above steering apparatus of the present invention, when the road lateral inclination detected by the inclination detecting means during traveling on a curved road is low on the inside of the curve, the steering control direction detected by the steering control direction detecting means is on the outside of the curve. It is good also as a structure which does not perform the increase control of the output for controlling a steering mechanism.

  This steering device controls the steering mechanism without increasing the steering output compared with the normal control when the steering control direction is the curve outward direction when the road lateral inclination is a low slope inside the curve while traveling on a curved road. . In other words, when there is a low road lateral inclination inside the curve on the curved road, the lateral acceleration in the curve inner direction acts on the vehicle due to the inclination, so when the steering control direction is opposite to the inclination direction ( If the steering output during normal control is applied to the vehicle at the time of switching back, the lateral acceleration acting on the vehicle becomes smaller than when there is no low inclination inside the curve. In this case, it is conceivable that the lateral acceleration acting on the vehicle is not reduced by increasing the steering output from the normal control. However, it is very rare that the steering control direction becomes the curve outer direction, and there is a high possibility of erroneous detection when detecting the travel path. Since it is not desirable to perform special control in such a situation where there is a high possibility of erroneous detection, the steering control device does not perform increase control on the steering output.

  In the above steering device of the present invention, the output characteristics for controlling the steering mechanism are set by the output at the time of increase with hysteresis and the output at the time of return, and at the time of increase when the reduction control is performed. The output may be set to a value smaller than that during normal control.

  This steering device is provided with a steering output characteristic comprising a steering output at the time of increase with hysteresis and a steering output at the time of return. This hysteresis is, for example, for compensating for friction in the steering mechanism, and increases the steering output to compensate for the friction when the switch is increased, and decreases the steering output to compensate for the friction when switching back. Accordingly, when the steering output at the time of switching is switched from the steering output at the time of switching back, the steering output decreases. In the steering device, when the steering control direction is the curve inner side direction, the steering output at the time of increase is set to a value smaller than that at the time of normal control, thereby reducing the steering output from that at the time of normal control.

  In the steering apparatus according to the present invention, in the steering apparatus that detects the travel path of the vehicle by the travel path detection unit and controls the steering mechanism so that the vehicle travels along the predetermined position of the travel path, the inclination in the lateral direction of the road is determined. An inclination detecting means for detecting and a steering control direction detecting means for detecting a steering control direction, and the steering control direction with respect to the direction in which the inclination in the lateral direction of the road detected by the inclination detecting means decreases during traveling on a straight road. It is characterized by suppressing output reduction control for controlling the steering mechanism when the steering control direction detected by the detecting means shifts from the reverse direction to the same direction.

  In this steering apparatus, as described above, the travel path is detected, and the steering mechanism is controlled so that the vehicle travels along a predetermined position on the travel path. In the steering device, the inclination detection means detects the inclination in the lateral direction of the road, and the steering control direction detection means detects the steering control direction. And in the steering device, during the straight road traveling, when the steering control direction shifts from the reverse direction to the same direction with respect to the direction in which the lateral inclination of the road becomes low, the reduction control during the normal control of the steering output is suppressed, The steering mechanism is controlled by the steering output that suppresses the reduction. If there is a road lateral inclination on a straight road, a lateral acceleration in the low direction acts on the vehicle due to the inclination. Therefore, the steering device applies a steering output in a direction opposite to the lateral acceleration due to the inclination. And resists the lateral inclination of the road. Further, in the case of normal control, in the case of normal control, when switching from the additional direction to the return direction, the steering output is reduced in order to compensate for the friction in the steering mechanism, and the steering mechanism is controlled by the reduced steering output. To do. Therefore, when the steering output is applied in the opposite direction to the lateral acceleration due to the lateral inclination of the road, when the steering output is switched from the increasing direction to the returning direction, and the steering output is reduced, the resistance to the lateral inclination of the road is reduced. The vehicle is approaching the side with a low slope in the lateral direction of the road. Therefore, in this case, in the steering device, when switching from the increasing direction to the returning direction (when the steering control direction shifts from the reverse direction to the same direction with respect to the direction in which the inclination in the lateral direction of the road becomes lower), it is normal. By suppressing the reduction of the steering output from the time of control, it is possible to suppress a decrease in resistance to the lateral inclination of the road. As a result, the vehicle does not approach the low inclination side, and the vehicle travels along a predetermined position on the travel path. Thus, in the steering device, when there is a slope in the lateral direction of the road on the straight road, it is possible to compensate for the influence of the slope and perform appropriate steering control.

  In the above steering device of the present invention, the output characteristics for controlling the steering mechanism are set by the output at the time of switching with hysteresis and the output at the time of switching back, and switching back when the reduction control is suppressed. The output at the time may be set to an intermediate value between the output at the time of increase during normal control and the output at the time of return.

  Similar to the above, this steering device has a steering output characteristic composed of a steering output at the time of increase with hysteresis and a steering output at the time of return. In the steering device, when the steering control direction shifts from the reverse direction to the same direction with respect to the direction in which the inclination in the lateral direction of the road becomes low, the steering output at the time of switching back and the steering output at the time of increasing at the time of normal control are switched back. The steering output reduction control is suppressed by setting an intermediate value of the steering output at the time (that is, the steering output at the time of switching back to a value larger than that during the normal control).

  The traveling road is, for example, a traveling lane or a traveling road when there is no lane. The predetermined position of the travel path is, for example, the center of the travel path (lane). The output for controlling the steering mechanism may be any output that can change the steering state such as the steering torque and the steering angle. As the travel path detection means, for example, when detecting based on a captured image captured by the imaging means, when detecting based on processing by the navigation system and map information, when detecting using various sensors, road-to-vehicle communication, etc. Information may be obtained from outside the vehicle using. As the inclination detecting means, for example, when detecting by detecting means such as road inclination with respect to a horizontal plane or lateral acceleration acting on the vehicle, when acquiring from map information including road crossing gradient information, the road lateral inclination is determined from the vehicle behavior. May guess. The steering control direction is a direction in which a steering torque, a steering angle, or the like acts as an output in the steering device, and is a right direction and a left direction.

  The present invention can correct the output for controlling the steering mechanism as necessary when the road has a slope in the lateral direction of the road, and perform appropriate steering control.

  Hereinafter, embodiments of a steering apparatus according to the present invention will be described with reference to the drawings.

  In the present embodiment, the steering device according to the present invention is applied to a lane keeping device. The lane keeping device according to the present embodiment recognizes a white line from an image captured by the camera and assists steering by the driver, and assists steering torque toward the center of the left and right white lines (lanes) that are the traveling road. Is added.

  A lane keeping device 1 according to the present embodiment will be described with reference to FIGS. FIG. 1 is a configuration diagram of a lane keeping device according to the present embodiment. FIG. 2 is a control block diagram of the lane keeping device of FIG. FIG. 3 is a map of output torque with respect to the target lateral acceleration when normal control is performed in the lane keeping device of FIG. 1 and correction is performed in consideration of a road surface cant on a curved road. FIG. 4 is a map of the output torque with respect to the target lateral acceleration when the lane keeping device of FIG. 1 is corrected in consideration of the normal control and the straight road surface cant.

  The lane keeping device 1 sets an output torque necessary for traveling in the center of the lane, and uses the electric power steering device to add the output torque to the steering mechanism. At that time, the lane keeping device 1 is based on the road curvature γ (curve radius R), the direction of the vehicle with respect to the lane (yaw angle θ), the displacement of the vehicle position with respect to the lane center (offset D), and the integral term of the offset. A target lateral acceleration is set, and an output torque is obtained from the target lateral acceleration. In particular, the lane keeping device 1 corrects the output torque as necessary in consideration of the presence / absence of the road surface cant and its inclination direction in order to add an appropriate output torque even when the road surface has a road cant. The lane keeping device 1 includes a steering torque sensor 10, a vehicle speed sensor 11, a road surface cant sensor 12, a CCD [Charge Coupled Device] camera 20, an image processing unit 21, and an ECU [Electronic Control Unit] 30, and an electric power steering device. Use 40. In the present embodiment, the road surface cant sensor 12 corresponds to the inclination detecting means described in the claims.

  In a steering mechanism in a vehicle, steered wheels (left and right front wheels FR, FL) are steered in accordance with an operation on the steering wheel 2 by a driver. The steering wheel 2 is fixed to one end of the steering shaft 3. The steering shaft 3 rotates as the steering wheel 2 rotates. A rack bar 5 is connected to the other end of the steering shaft 3 via a steering gear box 4. The steering gear box 4 has a function of converting the rotational movement of the steering shaft 3 into the linear movement of the rack bar 5 in the axial direction. Both ends of the rack bar 5 are connected to the hub carriers of the wheels FL and FR via the knuckle arm 6. Thus, the wheels FL and FR are steered via the steering shaft 3 and the steering gear box 4 (rack bar 5) when the steering wheel 2 is rotated.

  The electric power steering device 40 drives and controls a motor 42 by an EPS [Electric Power Steering] ECU 41, and assists steering by the driver by a driving torque by the motor 42. The EPS ECU 41 sets an assist torque based on the steering torque generated by the driver's steering, and drives and controls the motor 42 in order to generate the assist torque by the motor driver. In particular, EPSECU 41, when receiving the output torque signal from ECU 30, multiplies the output torque indicated by the output torque signal by a predetermined coefficient, adds the multiplied value (additional torque) to the assist torque, and outputs the assist torque + In order to generate the additional torque, the motor 42 is driven and controlled. The driving torque by the motor 42 is added to the steering mechanism, and the torque by the motor 42 is applied to the steering mechanism in addition to the steering torque by the driver. Note that the steering torque, assist torque, and output torque (additional torque) are represented by plus / minus values, and the sign indicates the direction. For each torque, a positive value indicates torque in the right direction, and a negative value indicates torque in the left direction.

  A ball screw groove is formed on a part of the outer peripheral surface of the rack bar 5, and a ball nut having a ball screw groove corresponding to the ball screw groove on the inner peripheral surface is fixed to the rotor of the motor 42. A plurality of bearing balls are accommodated between the pair of ball screw grooves. When the motor 42 is driven, the rotor can be rotated and moved in the axial direction of the rack bar 5 (that is, assisting the steering). be able to). At this time, the motor 42 applies to the rack bar 5 a torque corresponding to the drive current supplied from the motor driver of the EPSECU 41.

  The steering torque sensor 10 is a sensor that detects the steering torque input from the steering wheel 2. The steering torque sensor 10 transmits the detected steering torque to the ECU 30 as a steering torque signal. The vehicle speed sensor 11 is a sensor that detects the speed of the vehicle. The vehicle speed sensor 11 transmits the detected vehicle speed to the ECU 30 as a vehicle speed signal. The road surface cant sensor 12 is a sensor that detects the road surface cant of the traveling road. For example, a sensor that detects the inclination of the road with respect to the horizontal plane and a sensor that detects the lateral acceleration acting on the vehicle are used. The road surface cant sensor 12 transmits the detected road surface cant to the ECU 30 as a road surface cant signal. The road surface cant sensor 12 only needs to be able to detect information indicating at least the presence / absence of a road surface cant and the inclination direction (lowering direction) when there is a road surface cant.

  The CCD camera 20 is attached in front of a vehicle on which the lane keeping device 1 is mounted (for example, built in a rearview mirror). At this time, the CCD camera 20 is mounted such that its optical axis direction coincides with the traveling direction of the vehicle. The CCD camera 20 images a road ahead of the vehicle and acquires a captured color image (for example, an image by RGB [Red Green Blue]). The CCD camera 20 transmits the captured image data to the image processing unit 21 as an imaging signal. The CCD camera 20 has a wide imaging range in the left-right direction, and can sufficiently image the left and right (a pair of) white lines indicating the traveling lane. Although the CCD camera 20 is color, it may be a black and white camera as long as it can acquire an image that can recognize a white line on the road.

  The image processing unit 21 takes an image signal from the CCD camera 20 and recognizes a pair of white lines (road lane lines) indicating the lane in which the vehicle is traveling from the image data of the image signal. In the captured image, the brightness difference between the road surface and the white line drawn on it is large, so the white line that divides the lane is relatively easy to detect by edge detection etc., which is convenient for detecting the lane ahead of the vehicle. Good.

  Then, the image processing unit 21 calculates a lane width and a line passing through the center of the pair of white lines (that is, the center of the lane) from the recognized pair of white lines. Further, the image processing unit 21 calculates the radius of the center of the lane (curve radius R), and calculates the road curvature γ (= 1 / R) from the curve radius R. Further, the image processing unit 21 calculates an angle (yaw angle θ) formed between the center line of the lane and the center axis in the front-rear direction of the vehicle and a lateral shift amount (offset D) of the vehicle center of gravity with respect to the center line of the lane. To do. Then, the image processing unit 21 transmits the recognized pair of white line information and each calculated information to the ECU 30 as image signals.

  The curve radius R, the road curvature γ, the yaw angle θ, and the offset D are represented by plus / minus values, and the sign indicates the direction. As for the curve radius R and the road curvature γ, a positive value indicates the right direction and a negative value indicates the left direction. Therefore, the direction of the curve road can be determined from the curve radius R and the road curvature γ. When the curve radius R and the road curvature γ are positive values, the curve road is a right turn, and when the curve radius is negative, the curve road is a left turn. It is. The yaw angle θ has a positive value in the left direction and a negative value in the right direction. The offset D (integrated value of the offset D) has a positive value on the left side of the lane and a negative value on the right side of the lane. In the present embodiment, the CCD camera 20 and the image processing unit 21 correspond to the travel path detection means described in the claims.

  The ECU 30 includes a CPU [Central Processing Unit], a ROM [Read Only Memory], a RAM [Random Access Memory], and the like, and comprehensively controls the lane keeping device 1. The ECU 30 takes in the image signals from the image processing unit 21 and takes in the detection signals from the sensors 10, 11, 12 at regular intervals. Then, in the ECU 30, when the lane keeping device 1 is activated by an operation by the driver, various information (road curvature γ, yaw angle θ, offset D) shown in the image signal so that the vehicle travels near the center of the lane. ) And the vehicle speed V, an output torque (target lateral acceleration) is set, and an output torque signal indicating the output torque is transmitted to the electric power steering device 40 (EPS ECU 41).

  With reference to FIG. 2, a basic process for obtaining the output torque in the ECU 30 will be described.

In ECU 30, multiplied by the gain K _gamma to the multiplication value of the road curvature gamma and vehicle speed V in the F / F controller 31 calculates the yaw rate omega _gamma. The yaw rate ω _γ is a yaw rate that generates a target lateral acceleration necessary for the vehicle to travel along the curve, and is 0 on a straight road. The yaw rate ω _γ is a feedforward output of lane keeping. An upper limit is set for the feedforward output.

The ECU 30 calculates a deviation ΔD = (D ₀ −D) between the offset D and the target offset D ₀ (for example, 0). Then, the ECU 30 integrates the deviation ΔD with time in the integrator 32 to calculate the integrated value ID of the offset. Further, the ECU 30, multiplied by the gain _{K D} the deviation ΔD with multiplying the gain _{K ID} to the integral value ID, and calculates a yaw rate omega _D by adding the two multiplied values. The yaw rate ω _D is a yaw rate that generates a target lateral acceleration necessary for converging the offset (integral value).

The ECU 30 calculates a deviation Δθ = (θ ₀ −θ) between the yaw angle θ and the target yaw angle θ ₀ (for example, 0). Then, the ECU 30, multiplied by the gain K _theta the deviation [Delta] [theta], and calculates the yaw rate omega _theta. The yaw rate ω _θ is a yaw rate that generates a target lateral acceleration necessary for converging the yaw angle. Yaw rate ω _D and the yaw rate _ω θ is a feedback output of the lane keep.

The ECU 30 calculates the target yaw rate ω by adding the three calculated yaw rates ω _γ , ω _D , and ω _θ . In the ECU 30, the target lateral acceleration calculator 33 multiplies the target yaw rate ω by the vehicle speed V to calculate the target lateral acceleration G. The target lateral acceleration G is represented by a plus value / minus value, and the sign indicates the direction. For the target lateral acceleration G, a positive value indicates a lateral acceleration in the right direction, and a negative value indicates a lateral acceleration in the left direction. The direction of the output torque applied to the steering mechanism by lane keeping (lane keeping steering direction) is determined by the change in the target lateral acceleration G. For example, output torque is added in the right direction when the target lateral acceleration increases by a predetermined amount or more, and output torque is added in the left direction when the target lateral acceleration decreases by a predetermined amount or more. Therefore, in the present embodiment, the processes in the CCD camera 20, the image processing unit 21, and the ECU 30 correspond to the steering control direction detecting means described in the claims.

  In the ECU 30, an output torque T corresponding to the target lateral acceleration G is obtained by the output torque calculator 34. The output torque calculator 34 holds the output torque map shown in FIG. 3, and the output torque T corresponding to the target lateral acceleration G is obtained from the output torque map with reference to the output torque map. As the output torque map, a map TI at the time of increasing and a map TR at the time of switching back are set, and hysteresis is provided between the two maps TI and TR. This hysteresis is for compensating for friction in the steering mechanism, and increases the output torque when increasing the cut and decreases the output torque when switching back. In the output torque map, the direction in which the output torque T (target lateral acceleration G) increases to the plus side is the lane keeping steering direction to the right, and the output torque T (target lateral acceleration G) increases to the minus side. The steering direction of the lane keep is the left direction. The output torque calculator 34 selects either the map TI at the time of increase or the map TR at the time of return according to the sign of the lane keep steering direction and the target lateral acceleration G. Then, the output torque calculator 34 extracts the output torque T corresponding to the value of the target lateral acceleration G from the selected map. Then, the ECU 30 transmits an output torque signal indicating the output torque T to the EPS ECU 41.

  In particular, the ECU 30 considers the presence or absence of a road surface cant on the traveling road and the inclination direction thereof, and corrects the output torque as necessary. Correct. Therefore, the ECU 30 performs a curve turning map correction process and a straight running map correction process in the output torque calculator 34 at regular intervals. Here, an outline of the process for correcting the map in the ECU 30 will be described, and details of each process described above will be described when the operation of the lane keeping device 1 is described.

  The ECU 30 uses four flags: a right curve cant presence / absence flag, a left curve cant presence / absence flag, a straight line right cant presence / absence flag, and a straight line left cant presence / absence flag.

  The right curve cant presence / absence flag is a flag indicating whether or not the road surface cant is low on the inside of the curve (right side of the lane) on the right curve road, and when the road surface cant is low on the inside of the curve on the right curve road If it is ON and not applicable, it is OFF. The left curve cant flag is a flag indicating whether the road surface cant has a low slope inside the curve (left side of the lane) on the left curve road. If the road surface cant has a low slope inside the curve on the left curve road, If it is ON and not applicable, it is OFF.

  The straight right cant presence flag is a flag indicating whether the road surface cant has a low slope on the right side of the lane on a straight road, and is ON when the road surface cant has a low slope on the right side of the lane. If not, it is OFF. The straight line left cant flag indicates whether the road surface cant has a low slope on the left side of the lane on a straight road, and is ON when the road surface cant has a low slope on the left side of the lane. If not, it is OFF.

  The ECU 30 determines whether the road is a curved road or a straight road based on the curve radius R or the road curvature γ, and further determines the direction of the curve in the case of a curved road. In the case of a curved road, the ECU 30 determines whether or not the road surface cant has a low slope inside the curve when there is a road surface cant and the presence of the road surface cant, based on the detected road surface cant information. Set the right curve cant presence flag and left curve cant presence flag. Further, in the case of a straight road, the ECU 30 determines the presence or absence of a road surface cant and, if there is a road surface cant, whether the road surface cant has a low slope on the right side or a low slope on the left side based on the detected road surface cant. Then, a straight right / left cant presence / absence flag and a straight / left cant presence / absence flag are set.

  The ECU 30 corrects the output torque by separating the curved road and the straight road. In general, on a curved road, the inclination direction of the road surface cant is inside the curve. However, on a straight road, the inclination direction of the road surface cant is arbitrary.

  In the case of a curved road, the road surface cant generally has a low slope inside the curve. Therefore, lateral acceleration in the curve inner direction acts on the vehicle by the road surface cant. Therefore, when the direction of the target lateral acceleration G is the inside of the curve (when increased by lane keeping), if an output torque corresponding to the target lateral acceleration G is added to the vehicle as in normal control, the lateral acceleration acting on the vehicle Becomes larger and the vehicle approaches the inside of the curve. In view of this, the ECU 30 reduces the output torque when the target lateral acceleration G is increased toward the inside of the curve, compared with the normal control. For this purpose, the ECU 30 corrects the map TI at the time of increase in the normal control to a map in which a small value is associated with the target lateral acceleration as the magnitude of the output torque (see FIG. 3). As a correction method for this map, the initial value (K, −K) of the output torque side map intercept in the map TI at the time of rounding is made smaller by the cant compensation torque Δk, and the correction map TI ′ at the time of rounding is set. . That is, the positive output torque side map intercept is (K−Δk), the positive output torque is reduced by Δk, and the negative output torque side map intercept is (−K + Δk), and the negative output torque is Is increased by Δk. As a result, the correction map TI ′ at the time of increase is shifted from the map TI at the time of increase to the map TR side at the time of return. The cant compensation torque Δk is set in advance based on the average inclination angle of the road surface cant on a curved road.

  Further, when the direction of the target lateral acceleration G on the curved road is the curve outward direction (when switching back by lane keeping), the ECU 30 performs normal control without correcting the output torque. This is because the direction of the target lateral acceleration G is the direction outside the curve because each parameter for obtaining the target lateral acceleration G is obtained from the lane recognized from the captured image, and is affected by camera noise. This is because the possibility of misrecognition is extremely high. The direction of the target lateral acceleration based on the feedforward output for traveling along the curve is always inward of the curve, and this feedforward output is usually a larger value than the feedback output. However, since the feedback output is larger than the feedforward output when the direction of the target lateral acceleration G is the direction outside the curve, such a state is considered to be a misrecognition due to camera noise. It is reasonable. Therefore, normal control is performed in order not to overreact with such erroneous recognition.

  In the case of a straight road, when the direction of the target lateral acceleration G is opposite to the inclination direction of the road surface cant, the vehicle is subjected to a lateral acceleration in a low inclination direction by the road surface cant. It is necessary to resist the road surface cant by the torque (escape from the road surface cant). In view of this, the ECU 30 uses the map TI at the time of increasing when the output is increased when the direction of the target lateral acceleration G is opposite to the inclination direction of the road surface cant. Perform normal control. However, when switching from increased to switched back, in normal control, the map is switched to the map TR at the time of switching back, so that the output torque is greatly reduced for the same target lateral acceleration G. Therefore, when the direction of the target lateral acceleration G is opposite to the inclination direction of the road surface cant, the ECU 30 suppresses the reduction of the output torque when switching to switching back. For this purpose, the ECU 30 corrects the map TR at the time of switching back during normal control to a map in which a small value is associated with the output torque as the magnitude of the target lateral acceleration (see FIG. 4). As a correction method for this map, the initial value (G, -G) of the lateral acceleration side map intercept in the map TR at the time of switching back is set to a value that is smaller by the Kant compensated lateral acceleration Δg, and the correction map TR 'at the time of switching back is set. To do. That is, the positive lateral acceleration side map intercept is set to (G−Δg), the positive lateral target lateral acceleration is reduced by Δg, and the negative lateral acceleration side map intercept is set to (−G + Δg) to obtain the negative target The lateral acceleration is increased by Δg. As a result, the correction map TR 'at the time of switching back is shifted from the map TR at the time of switching back to the map TI side at the time of increasing, thereby increasing the output torque on the plus side and increasing the output torque on the minus side. The cant-compensated lateral acceleration Δg is set in advance based on the average inclination angle of the road surface cant on a straight road.

  Further, when the direction of the target lateral acceleration G on the straight road is the inclination direction of the road surface cant, the ECU 30 performs normal control without correcting the output torque. This is because, on a straight road with a road surface cant, the target lateral acceleration based on the integral value of the offset D should be opposite to the inclination direction of the road surface cant, so the direction of the target lateral acceleration G is the inclination direction of the road surface cant. This is because it is considered a special situation. In a situation where the direction of the target lateral acceleration G on the straight road is the inclination direction of the road surface cant, the vehicle yaw angle θ increases in the opposite direction to the inclination direction of the road surface cant, or the vehicle offset D is inclined beyond the lane center. The situation where it becomes large on the higher side can be considered. In this case, since there is a possibility that the vehicle has greatly overshooted on the high inclination side, the output torque should not be further reduced, and therefore normal control is performed. In addition, as a situation where the direction of the target lateral acceleration G is the inclination direction of the road surface cant on a straight road, erroneous recognition due to camera noise can be considered as described above. In order not to overreact to such erroneous recognition, normal control is performed.

  The operation of the lane keeping device 1 will be described with reference to FIGS. In particular, the curve turning map correction process in the ECU 30 will be described with reference to the flowchart of FIG. 5, and the straight running map correction process will be described with reference to the flowchart of FIG. FIG. 5 is a flowchart showing a curve turning map correction process in the ECU of the lane keeping device of FIG. FIG. 6 is a flowchart showing the flow of map correction processing during straight running in the ECU of the lane keeping device of FIG.

  The steering torque sensor 10 detects the steering torque input from the steering wheel 2 and transmits a steering torque signal indicating the steering torque to the ECU 30. The vehicle speed sensor 11 detects the vehicle speed and transmits a vehicle speed signal indicating the vehicle speed to the ECU 30. The road surface cant sensor 12 detects a road surface cant and transmits a road surface cant signal indicating the road surface cant to the ECU 30.

  The CCD camera 20 captures the front of the vehicle and transmits data of the captured image to the image processing unit 21 as an imaging signal. The image processing unit 21 recognizes a pair of white lines that divide the lane from the captured image. Then, the image processing unit 21 calculates the lane width, the lane center line, the lane center curve radius R, the road curvature γ, the yaw angle θ, and the vehicle offset D from the pair of white lines. Further, the image processing unit 21 transmits the information on the pair of white lines and the calculated information to the ECU 30 as image signals.

  The ECU 30 receives a steering torque signal, a vehicle speed signal, a road surface cant signal, and an image signal at regular intervals. Then, the ECU 30 acquires the curve radius R, road curvature γ, yaw angle θ, and offset D from the steering torque, vehicle speed, road surface cant and image signal, and filters each of these input data. The ECU 30 determines the direction of the curve in the case of a curved road or a straight road and a curved road based on the calculated curve radius R (road curvature γ). Further, the ECU 30 determines the presence / absence of a road surface cant and the inclination direction when there is a road surface cant based on the detected road surface cant, and a right curve cant presence / absence flag, a left curve cant presence / absence flag, a straight line right cant Set presence / absence flag and straight left / right cant presence / absence flag.

The F / F controller 31 of the ECU 30 calculates a yaw rate ω _γ by multiplying a multiplication value of the road curvature γ and the vehicle speed V by a gain K _γ at regular time intervals.

Further, the ECU 30 calculates a deviation Δθ = (θ ₀ −θ) between the yaw angle θ and the target yaw angle θ _0, and calculates the yaw rate ω _θ by multiplying the deviation Δθ by the gain K _θ .

Further, the ECU 30 calculates a deviation ΔD = (D ₀ −D) between the offset D and the target offset D ₀ . Then, the integrator 32 of the ECU 30 time-integrates the deviation ΔD to calculate the offset integral value ID. Further, the ECU 30, multiplied by the gain _{K D} the deviation ΔD with multiplying the gain _{K ID} to the integral value ID, and calculates a yaw rate omega _D by adding the two multiplied values.

The ECU 30 calculates the target yaw rate ω by adding the three calculated yaw rates ω _γ , ω _D , and ω _θ . Then, the target lateral acceleration calculator 33 of the ECU 30 multiplies the target yaw rate ω by the vehicle speed V to calculate the target lateral acceleration G. Further, the ECU 30 determines the lane keeping steering direction from the change in the target lateral acceleration G.

  When it is determined from the curve radius R that the traveling road is a curved road, the ECU 30 determines whether or not the target lateral acceleration G is 0 or more and the right curve cant presence flag is ON at certain time intervals (that is, the inside of the curve on the right curved road). (S10 in FIG. 5) is determined. When the determination condition of S10 is satisfied, the ECU 30 sets Δk as the cant compensation torque (S13 in FIG. 5).

  If the determination condition of S10 is not satisfied, the ECU 30 determines whether or not the target lateral acceleration G is 0 or less and the left curve cant presence / absence flag is ON (that is, there is a road surface cant with a low slope inside the curve on the left curve road, It is determined whether or not the direction of the lateral acceleration G is the curve inner side direction (S11 in FIG. 5). When the determination condition of S11 is satisfied, the ECU 30 sets Δk as the cant compensation torque (S13 in FIG. 5). When the determination condition of S11 is not satisfied, the ECU 30 sets 0 as the cant compensation torque (S12 in FIG. 5).

  Then, the ECU 30 subtracts the cant compensation torque from the output torque side map intercept initial value (K), sets the subtracted value as the positive output torque side map intercept (S14 in FIG. 5), and outputs the output torque side map intercept. The cant compensation torque is added to the initial value (-K), and the added value is used as the negative output torque side map intercept (S15 in FIG. 5). Here, when Δk is set as the cant compensation torque, the output torque side map intercept in the map at the time of increase is changed. In this case, the ECU 30 corrects the map TI at the time of increase based on the changed output torque side map intercept to obtain a correction map TI ′ at the time of increase. When the correction map TI ′ at the time of increase is used, the magnitude of the output torque T corresponding to the target lateral acceleration G is smaller than when the map TI at the time of increase is used.

  Then, the ECU 30 selects the correction map TI ′ at the time of increase when the determination condition of S10 is satisfied or the determination condition of S11 is satisfied, and otherwise, the steering direction of the lane keep and the target lateral acceleration G are selected. The map TI at the time of increase or the map TR at the time of return is selected by the sign of, and the output torque T corresponding to the value of the target lateral acceleration G is extracted with reference to the selected map. Then, the ECU 30 transmits an output torque signal indicating the output torque T to the EPS ECU 41.

  On the other hand, when it is determined from the curve radius R that the traveling road is a straight road, the ECU 30 determines whether the target lateral acceleration G is 0 or less and the right cant presence / absence flag for straight lines is ON at certain time intervals (that is, the lane on the straight road) It is determined whether there is a low road surface cant on the right side and the direction of the target lateral acceleration G is the left side of the lane (S20 in FIG. 6). When the determination condition of S20 is satisfied, the ECU 30 sets Δg as a cant compensated lateral acceleration (S23 in FIG. 6).

  If the determination condition of S20 is not satisfied, the ECU 30 determines whether or not the target lateral acceleration G is 0 or more and the straight left cant presence flag is ON (that is, there is a low slope road surface cant on the left side of the lane on a straight road, It is determined whether or not the direction of the acceleration G is the right lane direction (S21 in FIG. 6). When the determination condition of S21 is satisfied, the ECU 30 sets Δg as a cant compensated lateral acceleration (S23 in FIG. 6). When the determination condition of S21 is not satisfied, the ECU 30 sets 0 as the cant compensated lateral acceleration (S22 in FIG. 6).

  The ECU 30 subtracts the Kant compensated lateral acceleration from the lateral acceleration side map intercept initial value (G) and sets the subtracted value as the positive lateral acceleration side map intercept (S24 in FIG. 6). The cant compensated lateral acceleration is added to the initial intercept value (-G), and the added value is used as the negative lateral acceleration side map intercept (S25 in FIG. 6). Here, when Δg is set as the cant compensated lateral acceleration, the lateral acceleration side map intercept in the map at the time of switching back is changed. In this case, the ECU 30 corrects the map TR at the time of switching back based on the changed lateral acceleration side map intercept, and sets it as a correction map TR 'at the time of switching back. When switching from increasing to switching back, if the correction map TR ′ at switching back is used, the magnitude of the output torque T corresponding to the target lateral acceleration G is reduced compared to when using the map TR at switching back. The amount is reduced.

  Then, when the ECU 30 satisfies the determination condition of S20 or satisfies the determination condition of S21, the correction at the time of switching is performed when the steering direction of the lane keep and the sign of the target lateral acceleration G are switched from the increasing direction to the returning direction. Select the map TR ', otherwise select the map TI when increasing or the map TR when returning according to the sign of the steering direction of the lane keep and the target lateral acceleration G, and refer to the selected map Thus, the output torque T corresponding to the value of the target lateral acceleration G is extracted. Then, the ECU 30 transmits an output torque signal indicating the output torque T to the EPS ECU 41.

  The EPS ECU 41 receives the output torque signal, and multiplies the output torque indicated by the output torque signal by a predetermined coefficient. Then, the EPS ECU 41 adds the multiplication value (additional torque) to the assist torque, and drives and controls the motor 42 according to the assist torque + additional torque. The motor 42 generates a predetermined torque under the control of the EPS ECU 41 and adds the torque to the steering mechanism. Then, an assist torque corresponding to the steering torque by the driver is applied to the steering mechanism, and an auxiliary additional torque for causing the vehicle to travel along the vehicle center is applied.

  FIG. 7 shows the vehicle travel trajectories ML1 and ML1 'when the road surface cant turns on a left curved road with a low slope on the left side. The travel locus ML1 is corrected in consideration of the road surface cant with a low slope inside the curve when the direction of the target lateral acceleration G is the same as the inside direction of the curve (and thus the output torque of the lane keep). In this case, the output torque is reduced as compared with the normal control when turning up, so that the vehicle has a locus along the center line of the lane. On the other hand, the travel locus ML1 'is a case where the output torque of the lane keep is not corrected, and the output torque is not reduced when the lane keep is increased.

  FIG. 20 shows vehicle trajectories ML2 and ML2 'when the road surface cant travels on a straight road with a low slope on the left side. The travel trajectory ML2 takes into account a low slope road surface cant on the left side of the lane of the map at the time of switching back (when the output torque of the lane keep) when the direction of the target lateral acceleration G is opposite to the inclination direction of the road surface cant. In this case, the output torque is not reduced compared with the normal control when switching to the switch back, so that the vehicle has a locus along the center line of the lane. On the other hand, the travel locus ML2 ′ is a case where the output torque of the lane keep is not corrected, and the output torque is greatly reduced when switching back to the switch back. It has become.

  According to this lane keeping device 1, by correcting the output torque in consideration of the presence / absence of the road surface cant and its inclination direction, an appropriate output torque can be applied to the vehicle even when there is a road surface cant. The accuracy of running along the lane center can be improved.

  In particular, in the lane keeping device 1, since the output torque is controlled to be reduced when the direction of the target lateral acceleration G is the inside of the curve on a curved road having a low-inclined road surface cant on the inside of the curve, the influence of the road surface cant on the curved road. Appropriate output torque correction can be performed only when it is necessary to consider the above. In the lane keeping device 1, on a straight road with a road surface cant, when the direction of the target lateral acceleration G is opposite to the inclination direction of the road surface cant, the reduction in output torque is suppressed when switching from increase to return. Since control is performed, appropriate output torque correction can be performed only when it is necessary to consider the influence of the road surface cant.

  As mentioned above, although embodiment which concerns on this invention was described, this invention is implemented in various forms, without being limited to the said embodiment.

  For example, although the present embodiment is applied to the lane keeping device, it can also be applied to other devices, for example, an automatic steering device.

  In this embodiment, the steering torque is applied by using the electric power steering device. However, the lane keeping device may be provided with an actuator that assists the rack and pinion. Therefore, the present invention can be applied to a vehicle that does not include a power steering device. Further, the present invention can be applied not only to an electric power steering device but also to a hydraulic power steering device, and may be configured to add steering torque by controlling an actuator that adjusts hydraulic pressure.

  In this embodiment, the lane keep control is performed by adding torque to the steering mechanism. However, the lane keep control may be performed by another parameter that can change the steering state such as the steering angle. Good.

  In the present embodiment, the lane is detected by recognizing a pair of white lines. However, the lane may be detected by recognizing other lines such as a yellow line other than the white line, or a road shoulder. Alternatively, the lane may be detected by another method such as detecting the lane by recognizing a block that partitions the lane and the sidewalk. Further, although the present embodiment is applied to a road having a lane, the present invention can also be applied to a road having no lane. In this case, it is necessary to detect the shoulder of the road.

  In the present embodiment, a lane (traveling road) is recognized based on an image captured by a camera, and a curve radius (road curvature), a vehicle yaw angle, and a vehicle offset are calculated based on the recognized lane. However, the road and these parameters may be obtained by other methods, for example, when detecting based on processing in the navigation system and map information, when detecting using various sensors, road-to-vehicle communication, etc. In some cases, information is obtained from outside the vehicle.

  In this embodiment, the road surface cant sensor is used to detect the road surface cant. However, the road surface cant may be detected by other methods, for example, road information such as navigation including road surface cant information. When there is road information, the road surface cant may be estimated from the vehicle behavior.

  Further, in the present embodiment, the output torque is corrected by correcting the map at the time of increase and return, but the output torque may be corrected by other methods, for example, extracted from each map The output torque itself corresponding to the target lateral acceleration may be corrected based on the presence / absence of the road surface cant and the inclination direction.

  In this embodiment, the cant compensation torque Δk and the cant compensation lateral acceleration Δg are fixed values, but may be variable values. For example, when the inclination angle of the road surface cant can be detected, Δk or The value of Δg may be changed.

  In this embodiment, the normal lateral control is performed when the direction of the target lateral acceleration is on the outside of the curve on the curved road. However, the recognition accuracy using the camera for each parameter for obtaining the target lateral acceleration is improved. When it is high or when each parameter can be detected by other high-accuracy sensors other than the camera (when high-accuracy target lateral acceleration can be obtained at all times), the direction of the target lateral acceleration on the curve road is the direction outside the curve. In this case, output torque increase control may be performed.

It is a block diagram of the lane keeping apparatus which concerns on this Embodiment. FIG. 2 is a control block diagram of the lane keeping device of FIG. 1. FIG. 2 is a map of output torque with respect to a target lateral acceleration when normal control is performed in the lane keeping device of FIG. FIG. 2 is a map of output torque with respect to a target lateral acceleration when normal control is performed in the lane keeping device of FIG. 1 and correction is performed in consideration of a road surface cant of a straight road. It is a flowchart which shows the flow of the map correction process at the time of the curve turning in ECU of the lane keeping apparatus of FIG. It is a flowchart which shows the flow of the map correction process at the time of the straight running in ECU of the lane keeping apparatus of FIG. FIG. 5 is an example of a traveling locus when the road surface cant turns on a left curved road with a low slope to the left and when the lane keep output torque is corrected in consideration of the road surface cant and when the traveling locus is not corrected. It is an example of a travel locus when the road surface cant travels on a straight road with a low slope on the left side when the lane keep output torque is corrected in consideration of the road surface cant and when it is not corrected.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Lane keeping device, 2 ... Steering wheel, 3 ... Steering shaft, 4 ... Steering gear box, 5 ... Rack bar, 6 ... Knuckle arm, 10 ... Steering torque sensor, 11 ... Vehicle speed sensor, 12 ... Road surface cant sensor, 20 DESCRIPTION OF SYMBOLS ... CCD camera, 21 ... Image processing part, 30 ... ECU, 31 ... F / F controller, 32 ... Integrator, 33 ... Target lateral acceleration calculator, 34 ... Output torque calculator, 40 ... Electric power steering device, 41 ... EPSECU, 42 ... motor

Claims (5)

In a steering device that detects a travel path of a vehicle by a travel path detection unit and controls a steering mechanism so that the vehicle travels along a predetermined position of the travel path.
An inclination detecting means for detecting the inclination in the lateral direction of the road;
Steering control direction detection means for detecting the steering control direction,
When the road lateral inclination detected by the inclination detection means is low on the inside of the curve while traveling on a curved road, the steering mechanism is controlled when the steering control direction detected by the steering control direction detection means is in the curve. A steering apparatus characterized by performing reduction control of the output of the engine.   When the road lateral inclination detected by the inclination detecting means during running on a curved road is low inside the curve, the steering mechanism is controlled when the steering control direction detected by the steering control direction detecting means is the direction outside the curve. The steering apparatus according to claim 1, wherein the output increase control is not performed. The output characteristics for controlling the steering mechanism are set by the output at the time of increase with hysteresis and the output at the time of return,
The steering apparatus according to claim 1 or 2, wherein an output at the time of addition when performing the reduction control is set to a value smaller than that during normal control. In a steering device that detects a travel path of a vehicle by a travel path detection unit and controls a steering mechanism so that the vehicle travels along a predetermined position of the travel path.
An inclination detecting means for detecting the inclination in the lateral direction of the road;
Steering control direction detection means for detecting the steering control direction,
Steering when the steering control direction detected by the steering control direction detecting means shifts from the reverse direction to the same direction with respect to the direction in which the road lateral inclination detected by the inclination detecting means decreases during traveling on a straight road. A steering apparatus characterized by suppressing output reduction control for controlling a mechanism. The output characteristics for controlling the steering mechanism are set by the output at the time of increase with hysteresis and the output at the time of return,
The steering apparatus according to claim 4, wherein the output at the time of switching back when the reduction control is suppressed is set to an intermediate value between the output at the time of switching back at the normal control and the output at the time of switching back. .

Images