JP5301877B2 - Vehicle steering control device - Google Patents

Description

  The present invention relates to a vehicle steering control device, and more specifically, when performing lane keeping control for controlling the behavior of a host vehicle so as to travel along a lane (travel lane), the reaction force of the steering wheel is optimally applied. It is related with the apparatus made to do.

  As an example of the lane keeping control for controlling the traveling of the host vehicle so as to travel along the lane, a technique described in Patent Document 1 proposed by the present applicant is known.

  In the technique described in Patent Document 1, a curvature is obtained by obtaining a center line of a traveling road from an image obtained by imaging a traveling road ahead of the host vehicle, and a lateral deviation indicating a deviation in distance from the center line. Calculate the deflection angle indicating the amount and angle deviation, and calculate the basic assist torque to balance the cornering force of the vehicle from the curvature, while traveling along the center line of the road from the lateral deviation amount and deflection angle The correction assist torque is calculated, and the steering assist torque calculated by detecting the steering torque of the occupant is added to them to determine the operation amount to the electric motor.

Further, in the technique described in Patent Document 2, a steering reaction force control device that suppresses the steering wheel behavior that is caused by the difference between the driving force or braking force of the left and right front wheels and that can be removed from the steering wheel is provided. Disclose.
JP 2006-264405 A JP 2002-370657 A

  In the technique described in Patent Document 1, for example, if the lane keeping control is stopped while turning a curve with a large curvature, the steering wheel may suddenly return to the neutral position due to self-aligning torque, which may cause the passenger to feel uncomfortable. It was.

  In addition, although the technique of patent document 2 is comprised so that the suppression amount of a steering reaction force may increase as a curvature becomes large in order to suppress such a steering behavior, the structure beyond it is disclosed. It wasn't.

  Accordingly, an object of the present invention is to provide a vehicle steering control device that solves the above-described problems and suppresses the return of the steering wheel to a sharp neutral position due to self-aligning torque even when the lane keeping control is interrupted. It is to provide.

In order to solve the above object, according to claim 1, an actuator for turning a steering wheel of the host vehicle, a steering torque detecting means for detecting a steering torque input by a passenger via the steering wheel, Steering assist control means for performing steering assist control for assisting occupant steering according to a predetermined characteristic according to the detected steering torque, and a reaction force is applied to the steering wheel according to the steering speed of the steering wheel. Steering reaction force control means, imaging means for imaging the traveling direction of the host vehicle at predetermined time intervals, and travel capable of recognizing the travelable area of the traveling direction of the host vehicle based on the image captured by the imaging means Area recognition means, target point setting means for setting a target point ahead of the vehicle within a travelable area by a predetermined distance, and the set eyes Based on the travel control means for controlling the travel of the vehicle so that the vehicle passes through the point, the operation amount of the steering assist control means, the operation amount of the steering reaction force control means, and the operation amount of the travel control means In the vehicle steering control device including an operation amount calculation unit that calculates an operation amount to be supplied to the actuator, the vehicle reaches the target point set in the travelable region in the image captured by the imaging unit. A movement parameter calculation means for calculating a movement parameter of the own vehicle, which is an output of the travel control means, and an operation amount of the steering reaction force control means so as to increase as the calculated movement parameter increases. A steering reaction force correcting means for correcting is provided.

  In the vehicle steering control apparatus according to a second aspect, the steering reaction force correction means is configured to decrease a correction amount for correcting the steering reaction force operation amount as the steering torque increases.

According to the first aspect, the reaction force applied to the steering wheel according to the operation amount of the steering assist control means for assisting the steering of the occupant according to the predetermined characteristic according to the detected steering torque and the steering speed of the steering wheel. The operation amount to be supplied to the actuator is calculated on the basis of the operation amount of the steering reaction force control means for applying the driving force and the operation amount of the travel control means for controlling the travel of the host vehicle so as to pass the target point of the travel path. In the vehicle steering control device, the motion parameter of the host vehicle, which is the output of the travel control means necessary to reach the target point set in the travelable area in the image captured by the image capturing means , is calculated and calculated. Since the operation amount of the steering reaction force control means is corrected so as to increase as the motion parameter increases, it is set forward in the travelable area. It is possible to suppress the return of the steering wheel to a sharp neutral position due to the self-aligning torque even when the travel control for controlling the travel of the host vehicle so as to pass the mark point, that is, the lane keeping control is interrupted. Therefore, it does not give the passenger a sense of incongruity.

  In the vehicle steering control device according to the second aspect, since the correction amount for correcting the steering reaction force operation amount is decreased as the steering torque increases, in addition to the effects described above, Interference can be prevented.

  The best mode for carrying out a vehicle steering control apparatus according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic view generally showing a vehicle steering control apparatus according to an embodiment of the present invention.

  In the following, the steering wheel 14 disposed in the driver's seat 12 in the own vehicle (vehicle) 10 is connected to the steering shaft 16. The steering shaft 16 is connected to the connecting shaft 22 via universal joints 18 and 20.

  The connecting shaft 22 is connected to a pinion 26 of a rack and pinion type steering gear 24. The pinion 26 meshes with the rack 28, so that the rotational motion input from the steering wheel 14 is converted into the reciprocating motion of the rack 28 via the pinion 26, and tie rods (steering rods) 30 disposed at both ends of the front axle. The two front wheels (steering wheels) 32 are steered in a desired direction via a kingpin (not shown).

  An EPS motor (electric motor or actuator) 38 and a ball screw mechanism 40 are coaxially disposed on the rack 28, and the motor output is converted into a reciprocating motion of the rack 28 via the ball screw mechanism 40, and is transmitted via the steering wheel 14. The rack 28 is driven in a direction to decrease the input steering force (steering torque).

  A torque sensor 42 is provided in the vicinity of the steering gear 24 and outputs a signal corresponding to the direction and magnitude of the steering force (steering torque) input by the occupant. A steering angle sensor 44 including a rotary encoder is provided in the vicinity of the steering shaft 16 and outputs a signal corresponding to the direction and magnitude of the steering angle (steering angle, more specifically, the front wheel steering angle) input by the occupant. To do.

  In the vicinity of the two front wheels 32, wheel speed sensors 46 such as electromagnetic pickups are arranged to output a signal for each rotation of the front wheel, and the same kind of structure is also provided in the vicinity of the two rear wheels (not shown). These wheel speed sensors are arranged to output a signal for each rotation of the rear wheel. In the host vehicle 10, an internal combustion engine (not shown) is disposed on the front wheel side, so the front wheel 32 is a driving wheel and the rear wheel is a driven wheel.

  A CCD camera 54 is mounted near the roof (not shown) of the driver's seat 12. The CCD camera 54 images the traveling direction of the host vehicle 10 and outputs an image signal at a predetermined time interval (for example, 100 msec). The output of the CCD camera 54 is sent to an image processing ECU 56 composed of a microcomputer, and a dividing line (white line) of a lane (travel lane) on the travel path is extracted.

  A laser radar 58 is provided at an appropriate position near the front bumper of the host vehicle 10. The laser radar 58 transmits laser light (electromagnetic wave (carrier wave)) at a predetermined interval in the traveling direction of the host vehicle 10 and reflects the laser beam to an object such as a vehicle (another vehicle) in front of the host vehicle 10. An object is detected by receiving the obtained reflected wave.

  The output of the laser radar 58 is sent to a radar output processing ECU (electronic control unit) 60 comprising a microcomputer. The radar output processing ECU 60 calculates the relative distance (relative position) to the object by measuring the time from when the laser light is emitted until the reflected light is received, and further differentiates the relative distance so that the relative to the object is obtained. Find the speed.

  The vehicle steering control device according to this application is similarly provided with an LKAS control unit (Electronic Control Unit) 64 composed of a microcomputer, and the output of the image processing ECU 56 and the torque sensor 42 described above is the LKAS control unit. 64.

  The apparatus also includes an EPS control unit 66 comprising a similar electronic control unit. The outputs of the torque sensor 42 and the wheel speed sensor 46 described above are also input to the EPS control unit 66.

  The LKAS control unit 64 and the EPS control unit 66 are connected via a signal line 68 so that they can communicate with each other. The LKAS control unit 64 calculates a steering assist torque for maintaining the lane (for lane keeping) and transmits it to the EPS control unit 66 as will be described later.

  As will be described later, the EPS control unit 66 calculates the steering assist torque when the steering torque input by the occupant is detected, and generates the steering assist torque in order to apply the steering reaction force to the steering wheel 14. The current command value to be supplied to the EPS motor 38 is determined by calculating and adding / subtracting them to / from the steering assist torque for maintaining the lane.

  A motor drive circuit 70 is connected to the EPS control unit 66. The motor drive circuit 70 includes a known bridge circuit (not shown) composed of four power FET switching elements, and the EPS motor 38 is rotated forward or reverse by turning on / off the FET switching elements.

  The EPS control unit 66 determines the motor control current by the duty ratio (duty ratio by PWM) and outputs it to the motor drive circuit 70. More specifically, the EPS control unit 66 controls the drive current of the EPS motor 38 by controlling the motor energization current by controlling the duty ratio of the FET switching element.

  A yaw rate sensor 72 is disposed near the center of gravity of the host vehicle 10 and outputs a signal corresponding to the yaw rate (rotational angular velocity) about the vertical (gravity) axis of the center of gravity of the vehicle. A brake sensor 74 is provided on a brake pedal (not shown) on the floor of the driver's seat 12 and outputs a signal corresponding to the depression of the brake pedal of the occupant.

  2 is a block diagram showing the operation of the apparatus shown in FIG. 1, and FIG. 3 is a relative view with the position of the vehicle 10 superimposed on an absolute coordinate system (not shown) generated in the memory of the image processing ECU 56 as the origin. It is explanatory drawing which shows a coordinate system. In FIG. 2, a portion surrounded by a broken line indicates the operation of the LKAS control unit 64, and the remainder indicates the operation of the EPS control unit 66.

  As shown in FIG. 3, the LKAS control unit 64 detects a predetermined time Tm (for example, 2 sec) and a vehicle speed V from the dividing line (white line) of the lane (lane) of the travel path detected by the image processing ECU 56. And a forward gazing point Cm is set on the lane center line yc at the location where the distance Lm is obtained by multiplying the, and the curvature of the travel route to the forward gazing point Cm set along the lane center line yc is calculated. The lateral shift amount yd from the lane center line yc is calculated.

  Next, the LKAS control unit 64 calculates a basic assist torque by multiplying the calculated curvature by a predetermined feedforward gain Kf, and corrects the assist torque using a feedback control law so that the lateral deviation amount yd is reduced in the FB controller 64a. Is calculated.

  The calculated basic assist torque and the corrected assist torque are added in the addition stage 64b, and then converted into a current command value to the EPS motor 38. This current command value is a current command value for lane (running lane) maintenance control, and the current command value is determined in the travelable area recognized in the traveling direction of the host vehicle 10 based on the images captured by the CCD camera 54 and the image processing ECU 56. A forward gazing point (target point) Cm is set in front of a predetermined distance Lm from the vehicle, and the operation amount of the traveling control means for controlling the traveling of the vehicle 10 so that the vehicle 10 passes through the set forward gazing point Cm. Equivalent to.

  The EPS control unit 66 searches the assist map 66a with the steering torque detected by the torque sensor 42, calculates the steering assist torque, and converts the calculated value into a motor current command value indicating the steering assist current.

  This motor current command value performs steering assist control for assisting the occupant's steering in accordance with a predetermined characteristic (characteristic shown in the assist map 66a) in accordance with the steering torque input by the occupant through the steering wheel 14. This corresponds to the operation amount of the control means. The converted steering assist current command value is added to the current command value of the lane keeping control in the addition stage 66b.

  The added current command value is supplied to the EPS motor 38 via the addition stage 66c and the motor drive circuit 70 (not shown in FIG. 2), and rotates the EPS motor 38. The rotation of the EPS motor 38 is transmitted to the host vehicle (vehicle) 10 through the EPS gear box (screw mechanism 40 and rack 28) (the steering wheel 14 is rotated).

  Further, the rotation angle of the EPS motor 38 is detected through a rotation speed sensor (not shown in FIGS. 1 and 2), and as shown in the upper part of FIG. The rotational speed of the wheel 14) is calculated.

  The EPS control unit 66 multiplies the calculated motor rotation speed by a damping gain Kdmp and converts the product thus obtained into a current command value, more specifically, a damping current command value, and from the motor current command value in the addition / subtraction stage 66c. Subtract. That is, the EPS control unit 66 supplies the motor current command value obtained by subtracting the damping current command value to the EPS motor 38. Thus, the EPS control unit 66 calculates the operation amount to be supplied to the EPS motor 38 based on the operation amount of the steering assist control means, the operation amount of the steering reaction force control means, and the operation amount of the travel control means.

  This damping current command value corresponds to the operation amount of the steering reaction force control means for applying a reaction force to the steering wheel 14 in accordance with the steering speed of the steering wheel 14. This control is for stabilizing the behavior of the host vehicle 10 as an operation amount (viscosity term) proportional to the rotation speed of the steering wheel 14 when the lane keeping control is performed.

  What is characteristic in this embodiment is that the above-described damping current command value is calculated (corrected), and the return of the steering wheel 14 to the steep neutral position due to the self-aligning torque is suppressed even when the lane keeping control is interrupted. There is in doing so.

  In other words, if the lane keeping control is stopped while turning a curve with a large curvature, the steering wheel 14 may suddenly return to the neutral position due to the self-aligning torque, which may cause the passenger to feel uncomfortable. I made it. The “self-aligning torque” means a lateral force generated on the road surface and the wheel when the steering wheel 14 is steered to produce a turning angle (force to return the wheel to the neutral position when turning). .

  Therefore, in this embodiment, the damping current command value of the steering wheel 14 is calculated so that the steering wheel 14 returns according to the lateral acceleration (or yaw rate) obtained from the traveling locus to the forward gazing point Cm. I did it.

  FIG. 4 is a flowchart showing the processing.

  In the following description, an image output from the image processing ECU 56 is acquired in S10, vehicle information such as the vehicle speed V of the host vehicle 10 is acquired in S12, the process proceeds to S14, and the forward gazing point Cm is set as described above. The process so far is the same as the process of the travel control means for performing the lane keeping control.

  Next, in S16, a motion parameter for reaching the front gazing point Cm, specifically, a lateral acceleration is calculated. The calculation formula is shown on the left side of FIG. That is, the lateral acceleration acting on the host vehicle 10 when the host vehicle 10 turns, more specifically the target acceleration, is calculated from the positions Yl and Lm obtained from the positional relationship between the forward gazing point Cm and the host vehicle 10.

  Returning to the description of FIG. 4, the process then proceeds to S18, where the table 66d (FIG. 2) is searched from the calculated target lateral acceleration to calculate the damping gain Kdrr. FIG. 5 shows the characteristics of the table 66d.

  Next, in S20, the table 66e (FIG. 2) is searched from the steering torque detected by the torque sensor 42 to calculate the coefficient ratio, and the calculated gain ratio is multiplied by the damping gain Kdrr in the multiplication stage 66f (FIG. 2). To correct the damping gain Kdrr. This is to prevent the occupant from feeling uncomfortable by setting the calculated damping current command value larger than the steering assist current. FIG. 6 shows the characteristics of the table 66e.

  Next, in S22, a damping current command value is calculated according to the equation shown. That is, the damping current command value is finally calculated (or corrected) by multiplying the product obtained by multiplying the motor rotation speed by the damping gain Kdmp and a new damping gain Kdrr.

  If the above is applied, if excessive understeer or oversteer has not occurred, a self-aligning torque proportional to the lateral acceleration is generated in the own vehicle 10, so that the current self-aligning torque is calculated by calculating the lateral acceleration. Can be estimated.

  Therefore, the damping current command value can be calculated according to the self-aligning torque by calculating the damping gain Kdrr accordingly and multiplying the product of the motor rotational speed and the damping gain Kdmp. When the lane keeping control is interrupted during traveling, it is possible to suppress the steering wheel 14 from suddenly returning to neutral, and to prevent the occupant from feeling uncomfortable.

  Even when the lane keeping control is not executed, even if the occupant inadvertently weakens the steering force during turning by setting the damping gain Kdrr corresponding to the turning behavior of the host vehicle 10, the steering wheel The return of 14 can be a slow movement with respect to the steering assist torque, and similarly, the passenger can be prevented from feeling uncomfortable.

  Thus, in this embodiment, the target lateral acceleration (motion parameter) of the host vehicle 10 necessary to reach the forward gazing point (target point) Cm is calculated, and increases as the calculated motion parameter increases. Thus, the operation amount of the steering reaction force control means is corrected so that the return of the steering wheel 14 to the steep neutral position due to the self-aligning torque can be suppressed even when the lane keeping control is interrupted. Therefore, it does not give the passenger a sense of incongruity.

  Further, as shown in FIG. 6, since the ratio ratio is decreased as the steering torque is increased, and the correction amount for correcting the steering reaction force operation amount, that is, the damping gain Kdrr is decreased, in addition to the above-described effects, Interference with the operation of the occupant can be prevented.

  The technique described in Patent Document 2 is configured so that the amount of suppression of the steering reaction force increases as the curvature increases in order to suppress such steering behavior, but it does not assume lane keeping control. No further configuration is disclosed.

As described above, in this embodiment, the steering (the EPS motor) 38 that steers the steering wheel 32 of the host vehicle (vehicle) 10 and the steering torque that is input by the occupant via the steering wheel 14 are detected. Torque detection means (torque sensor 42) and steering assist control means (EPS control unit 66) for performing steering assist control for assisting occupant steering in accordance with a predetermined characteristic (assist map 66a) in accordance with the detected steering torque. ), Steering reaction force control means (EPS control unit 66) for applying a reaction force to the steering wheel 14 in accordance with the steering speed of the steering wheel 14, and imaging for imaging the traveling direction of the vehicle at predetermined time intervals Means (CCD camera 54, image processing ECU 56) and the image pickup means. A travelable area recognition means (LKAS control unit 64) for recognizing a travelable area in the traveling direction of the host vehicle 10 based on the image, and a target point (frontward) ahead of the host vehicle 10 by a predetermined distance Lm within the travelable area. Gaze point) Target point setting means (LKAS control unit 64) for setting Cm, and travel control means (LKAS control unit 64) for controlling the travel of the host vehicle 10 so that the host vehicle 10 passes through the set target point. ), An operation amount calculating means (EPS control) for calculating an operation amount to be supplied to the actuator based on the operation amount of the steering assist control means, the operation amount of the steering reaction force control means, and the operation amount of the travel control means. the vehicular steering control apparatus provided with a unit 66) and, to reach the target point set in the travelable area in the image captured by the imaging means Vehicle motion parameters (lateral acceleration, a target lateral acceleration is more specifically) which is the output of the running control means necessary in order a motion parameter calculating means for calculating a (S16 from EPS control unit 66, S10), wherein The operation amount of the steering reaction force control means is corrected so as to increase as the calculated motion parameter increases, and more specifically, multiplied by a damping gain Kdrr set so as to increase as the motion parameter increases. Steering reaction force correction means (EPS control unit 66, S18 to S22) for correcting the operation amount of the steering reaction force control means is provided.

  The steering reaction force correcting means corrects the steering reaction force manipulated variable as the steering torque increases, and more specifically, sets a coefficient ratio set to decrease as the steering torque increases as a damping gain Kdrr. The correction amount for correcting the steering reaction force operation amount is reduced by multiplying by (EPS control unit 66, S20).

  In the above description, the lateral acceleration is shown as the motion parameter, but it may be a yaw rate.

  Further, although the damping gain Kdrr is shown as a multiplication term, it may be an addition / subtraction term.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram illustrating an overall vehicle steering control apparatus according to an embodiment of the present invention. It is a block diagram which shows operation | movement of the apparatus shown in FIG. It is explanatory drawing which shows the relative coordinate system which makes the origin the position of the own vehicle superimposed on an absolute coordinate system produced | generated in the memory of image processing ECU of FIG. 3 is a flowchart showing a calculation process of a damping current in the block diagram of FIG. 4 is an explanatory graph showing the characteristics of the damping gain used in the processing of the flow chart. 4 is an explanatory graph showing the characteristics of the correction term of the damping gain used in the processing of the flow chart.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Own vehicle (vehicle), 14 Steering wheel, 32 Front wheel (steering wheel), 38 EPS motor (electric motor, actuator), 44 Steering angle sensor, 46 Wheel speed sensor, 54 CCD camera, 56 Image processing ECU, 64 LKAS control Unit, 66 EPS control unit, 72 Yaw rate sensor

Claims (2)

An actuator that steers the steering wheel of the host vehicle, steering torque detection means that detects steering torque input by the occupant via the steering wheel, and steering of the occupant according to predetermined characteristics in accordance with the detected steering torque Steering assist control means for performing steering assist control for assisting, steering reaction force control means for applying a reaction force to the steering wheel in accordance with the steering speed of the steering wheel, and the traveling direction of the vehicle at predetermined time intervals Imaging means for imaging the vehicle, travelable area recognition means for recognizing the travelable area in the traveling direction of the host vehicle based on the image captured by the imaging means, and a predetermined distance forward from the host vehicle within the travelable area Target point setting means for setting a target point to the vehicle, and driving for controlling the traveling of the host vehicle so that the host vehicle passes the set target point. Control means; and an operation amount calculation means for calculating an operation amount to be supplied to the actuator based on an operation amount of the steering assist control means, an operation amount of the steering reaction force control means, and an operation amount of the travel control means. In the vehicle steering control apparatus provided, the movement parameter of the own vehicle which is an output of the travel control means required to reach the target point set in the travelable area in the image captured by the image capturing means And a steering reaction force correcting means for correcting an operation amount of the steering reaction force control means so as to increase as the calculated movement parameter increases. Steering control device.   The vehicle steering control device according to claim 1, wherein the steering reaction force correction unit decreases a correction amount for correcting the steering reaction force operation amount as the steering torque increases.

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