JP5445485B2 - Vehicle travel control device - Google Patents

Description

  The present invention relates to a vehicle equipped with various steering mechanisms such as EPS (Electric Power Steering) and VGRS (Variable Gear Ratio Steering), for example, LKA (Lane Keeping Assist: Lane Maintenance). The present invention relates to a technical field of a travel control device for a vehicle that performs travel.

  As this type of device, for example, when the vehicle is in the lane keeping mode, the electric power steering and the braking pressure of each wheel are controlled to achieve the target rudder angle, and the lateral position deviation or yaw angle of the vehicle with respect to the travel path is controlled. An apparatus for controlling the steering gear ratio variable device has been proposed in order to reduce the deviation (see Patent Document 1).

  In addition, when performing vehicle trajectory control by steering control, a device is also proposed that outputs a control amount corresponding to the target rudder angle of the trajectory control, one of EPS and VGRS, and the other outputs a control amount corresponding to one output. (For example, refer to Patent Document 2).

  When steering control of the vehicle is performed by controlling the steering angle of the rear wheel of the vehicle, if a driver's conscious steering operation is detected, it depends on the steering operation state and steering operation direction. There has also been proposed a device for reducing and correcting the control amount of steering control (see Patent Document 3).

JP 2007-160998 A JP 2008-06651 A Japanese Patent Laid-Open No. 11-245832

  However, in the device described in Patent Document 1 described above, the vehicle trajectory control direction caused by the lane keep and the vehicle driver steering direction coincide with or does not coincide with the steering amount of the vehicle. Since the responsiveness is different, there is a technical problem that the driver may feel uncomfortable.

  Further, in the apparatus described in Patent Document 2 described above, a malfunction caused by trajectory control by one device using two types of steering control devices, EPS and VGRS, is compensated by the other device. Similarly, there is a technical problem that the driver feels uncomfortable due to the responsiveness of the vehicle to the steering amount.

  In the device described in Patent Document 3 described above, the control amount is changed depending on whether or not the direction of the trajectory control matches the steering direction, but the driver feels uncomfortable due to the responsiveness of the vehicle. There is a technical problem that there is a possibility of memorizing.

  Here, in particular, in mitigating the uncomfortable feeling caused by the interference between the trajectory tracking control and the driver steering, it is conceivable to reduce the responsiveness of the trajectory tracking control. In other words, the sense of incongruity is reduced by suppressing the interference of the trajectory tracking control with respect to the driver override.

  However, such control is based on the premise that information related to the driver's steering input (for example, information such as the steering angle and the steering speed) has been accurately acquired. For this reason, when the sensor output values of various sensors that detect information related to the steering input cannot be read for some reason, the driver's steering input cannot be accurately grasped, resulting in responsiveness. Due to the reduced trajectory tracking control, a new problem that the tracking performance related to the trajectory tracking control cannot be sufficiently secured may occur.

  The present invention has been made in view of such a new problem, and it is preferable to follow a trajectory even in the case of a malfunction of a device that detects steering input information while alleviating a sense of incongruity due to interference with driver steering. It is an object of the present invention to provide a travel control device for a vehicle that can ensure safety.

  In order to solve the above-described problem, the vehicle travel control apparatus according to the present invention can change the relationship between the steering angle that is the rotation angle of the steering input shaft and the steering angle that is the rotation angle of the steering wheel. A travel control device for a vehicle including a rudder angle varying unit, a trajectory control unit for controlling the rudder angle varying unit so that the trajectory of the vehicle approaches a target road, and a driver of the vehicle via a handle An acquisition unit that acquires steering input information related to a steering input given to the steering input shaft, and a response of the trajectory control by the trajectory control unit is changed according to the acquired steering input information, and the steering input information is And responsiveness changing means for improving the responsiveness of the trajectory control when it cannot be acquired.

  The vehicle according to the present invention includes at least a rudder angle varying unit. The steering angle variable means can change the relationship between the steering angle, which is the rotation angle of the steering input shaft, and the steering angle, which is the rotation angle of the steered wheels. The steering angle varying means is a concept including various physical, mechanical, electrical, or magnetic devices that can vary the relationship between the steering angle and the steering angle stepwise or continuously.

  According to the rudder angle varying means, the relationship between the steering angle and the rudder angle is not uniquely defined. For example, the ratio of the steering angle to the rudder angle can be changed, or the rudder can be steered regardless of the steering angle. The angle can be changed.

  According to the vehicle travel control apparatus of the present invention, for example, a trajectory control means that can be appropriately provided with a memory and a processor controls the steering angle varying means so that the trajectory of the vehicle approaches the target path (target trajectory) of the vehicle. .

  Specifically, for example, based on the image of the target road imaged by an in-vehicle camera or the like, the curvature of the target road, the white line that defines the target road, etc., the position deviation of the vehicle and the yaw angle deviation (an example) Based on the calculated or estimated target lateral acceleration after the calculated or estimated target lateral acceleration (an example) is calculated or estimated based on them. Thus, for example, the control amount is determined so that the target lateral acceleration is obtained due to the change of the steering angle by the steering angle variable means, and the steering angle variable means is controlled based on the determined control amount. The

  Further, according to the vehicle travel control apparatus of the present invention, the steering input information is acquired by an acquisition unit that can take an aspect such as a sensor or a processor.

  Steering input information is information relating to steering input given to a steering input shaft by a driver via a steering wheel (steering wheel), and specifically means information such as a steering angle and a steering speed (steering angular velocity). To do. The acquisition unit that acquires the steering input information may be, for example, a detection unit such as a steering angle sensor, but may be a processor that acquires the detection result of the detection target from these detection units as an electrical signal or the like. Further, it may be a means for calculating the steering input information through a numerical calculation process based on the acquired detection result.

  On the other hand, according to the research of the present inventor, the following matters have been found. That is, in a vehicle equipped with trajectory control means, when there is an artificial steering input that is input to the steering input shaft by the driver via an input means such as a steering wheel (so-called overriding), steering by the driver is performed. And the trajectory control by the trajectory control means may interfere with each other, and the driver may feel uncomfortable.

  In particular, the trajectory control by the trajectory control means has a relatively gradual vehicle behavior due to a fail-sale viewpoint and, for example, the recognition time of the in-vehicle camera. The steering by the driver and the trajectory control by the trajectory control means are not linked. For this reason, due to the follow-up delay of the trajectory control by the trajectory control means, a deviation occurs between the driver's intention and the trajectory control target by the trajectory control means, and the driver may feel uncomfortable. Or stabilization of a vehicle behavior may be prevented.

  Therefore, in the vehicle travel control apparatus according to the present invention, for example, when the steering input is provided to the steering input shaft by the vehicle driver via the steering wheel by the responsiveness changing means including a memory, a processor, etc. (that is, override) ), The responsiveness of the trajectory control by the trajectory control means is changed.

  Here, “responsiveness” is calculated based on, for example, the response time until the imaging result of the road surface by the vehicle-mounted camera or the like is reflected in the actual change in the steering angle, the response frequency as the reciprocal of the response time, or the like. This means a property defined by the degree of time response of the trajectory control, such as various index values, and responsiveness is good (bad) or high (low), for example, that the response time is short (long). means.

  Specifically, for example, the responsiveness changing means lowers the response frequency of the trajectory control by the trajectory control means with respect to the reference value when there is an override, for example, according to the acquired steering input information. If the responsiveness is reduced in this way, the time delay until the vehicle deflection due to the driver override is reflected in the trajectory control is increased, so that the situation where the trajectory control interferes with the driver override is prevented. It can be suppressed that the driver feels uncomfortable due to the responsiveness of the vehicle.

  Note that when the response frequency of the trajectory control is lowered, it is possible to alleviate a sense of incongruity when an override is generated by the driver, but there is a concern that the followability to the target path in the trajectory control may be reduced. In order to compensate for such a problem, the responsiveness changing means predicts the vehicle behavior from the steering angular velocity as part of the responsiveness change according to the steering input information, and determines the control amount of the basic trajectory control. You may correct | amend suitably according to the vehicle behavior made. In this case, since the followability to the target path in the trajectory control can be suitably ensured, only the discomfort mitigating effect by reducing the response frequency of the trajectory control can be enjoyed.

  By the way, the measure for changing the response of the trajectory control related to the response changing means is based on the assumption that the steering input information is obtained accurately. Therefore, in the situation where the steering input information cannot be obtained accurately, if there is no control guideline for the response control of the trajectory control, the followability to the target road by the trajectory control is reduced, or the vehicle behavior is sufficiently stable. It becomes difficult to achieve.

  Therefore, the responsiveness changing means according to the present invention is configured to improve the responsiveness related to the trajectory control when the steering input information cannot be acquired. Improving the response of the trajectory control means, for example, returning the response frequency of the trajectory control to a reference value or increasing the response frequency to a higher frequency side than the reference value.

  As described above, according to the vehicle travel control device of the present invention, when the steering input information cannot be obtained accurately, the trajectory tracking response of the trajectory control can be given priority and the response of the trajectory control can be improved. . Therefore, even when the steering input information cannot be acquired, the trajectory control can be preferably continued.

  In one aspect of the vehicle travel control apparatus according to the present invention, the responsiveness changing means changes the responsiveness according to a steering speed.

  According to this aspect, the responsiveness changing means changes the responsiveness according to the steering speed (in short, the rotational angular speed of the steering wheel) as the steering input information.

  According to this aspect, for example, when the steering speed is relatively fast, it is predicted that the fluctuation of the vehicle behavior is relatively large. Therefore, the responsiveness changing unit is responsive to the trajectory control by the trajectory control unit (for example, the response frequency). ). If comprised in this way, it can suppress that the control amount which concerns on the locus | trajectory control by a locus | trajectory control means changes comparatively large, for example. Alternatively, the trajectory control by the trajectory control means cannot follow the driver's steering and can be prevented from stopping the control.

  On the other hand, when the steering speed is relatively slow, the fluctuation in vehicle behavior is predicted to be relatively small, so the responsiveness changing means decreases the responsiveness (for example, response frequency) of the trajectory control by the trajectory control means. If comprised in this way, it can suppress that a driver | operator's steering and locus | trajectory control by locus | trajectory control means mutually interfere. As a result, the driver can be prevented from feeling uncomfortable due to the responsiveness of the vehicle.

  In another aspect of the vehicle travel control apparatus according to the present invention, the responsiveness changing means corrects the increase amount related to the improvement of the responsiveness in accordance with a travel condition of the vehicle.

  According to this aspect, the degree of improvement in responsiveness when the steering input information cannot be acquired is corrected according to the traveling condition of the vehicle.

  Here, the “vehicle running condition” means a condition accompanied by an element that relatively lowers the stability of the trajectory tracking control. For example, even if the control logic for trajectory tracking control is the same and the tracking performance for a certain virtual target road is the same, the latter is more stable when the driving path is narrow or not. It can be said that it is driving. Similarly, it can be said that the vehicle is running stably in the latter case when the road is a bad road and when the road is not.

  The improvement in the response of the track following control is related to the stability of the track following control. When the response of the track following control is increased, the steering feeling in the driver is deteriorated. As a result, on the other hand, the followability to the target road is ensured, but the vehicle behavior tends to be ugly as a whole. For this reason, depending on the driving conditions of the vehicle, it is easy to cause a driver's anxiety.

  According to this aspect, the degree of improvement in responsiveness is corrected in consideration of the traveling condition of the vehicle in such a meaning. In short, the responsiveness is corrected to the decreasing side as appropriate. As a result, appropriate stability according to the vehicle driving conditions is ensured, and when the steering input information cannot be acquired, more robust trajectory followability can be ensured with respect to the vehicle driving conditions.

In this aspect, the travel condition may be a condition related to the state of the travel path.
As described above, the state of the traveling road, for example, the road width, the degree of road surface roughness, the presence or absence of a level difference, etc., tends to make the vehicle behavior worse if the responsiveness of the trajectory tracking control is excessively increased. Accordingly, by setting the responsiveness in consideration of these, a suitable failsafe when the steering input information cannot be obtained is realized.

  The effect | action and other gain of this invention are clarified from the form for implementing demonstrated below.

1 is a schematic configuration diagram conceptually showing the configuration of a vehicle according to a first embodiment. 2 is a flowchart of LKA control executed by an ECU in the vehicle of FIG. FIG. 3 is a diagram illustrating a relationship between a yaw angle deviation φ and an LKA basic target angle δ1 in the LKA control of FIG. 2. It is a conceptual diagram which concerns on the response frequency change of LKA control. It is a conceptual diagram which illustrates the relationship between the driving | running | working conditions of a vehicle and vehicle stability concerning 2nd Embodiment.

  Embodiments of a vehicle travel control device according to the present invention will be described below with reference to the drawings.

<First Embodiment>
1st Embodiment of the vehicle travel control apparatus which concerns on this invention is described with reference to FIG.1 and FIG.2.

  First, the configuration of the vehicle 1 according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic configuration diagram conceptually showing the configuration of the vehicle 1.

  In FIG. 1, a vehicle 1 includes a pair of left and right front wheels FL and FR as steering wheels, and is configured to be able to travel in a desired direction by turning these front wheels. The vehicle 1 includes an ECU (Electronic Control Unit) 100, a VGRS actuator 200, a VGRS driving device 300, an EPS actuator 400, and an EPS driving device 500.

  The ECU 100 is an electronic control unit that includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory) (not shown) and is configured to be able to control the entire operation of the vehicle 1. This is an example of a “vehicle travel control device”.

  The ECU 100 is configured to be able to execute LKA control described later in accordance with a control program stored in the ROM. The LKA control is control for causing the vehicle 1 to follow the target road (lane), and is an example of vehicle trajectory control by the “trajectory control means” according to the present invention.

  In the vehicle 1, a steering input given by a driver via a handle 11 is connected to the handle 11 so as to be coaxially rotatable, and is transmitted to an upper steering shaft 12 that is a shaft body that can rotate in the same direction as the handle 11. The upper steering shaft 12 is an example of the “steering input shaft” according to the present invention. The upper steering shaft 12 is connected to the VGRS actuator 200 at its downstream end.

  The VGRS actuator 200 is an example of the “steering angle varying means” according to the present invention, which includes a housing 201, a VGRS motor 202, and a speed reduction mechanism 203.

  The housing 201 is a housing of the VGRS actuator 200 that houses the VGRS motor 202 and the speed reduction mechanism 203. The downstream end of the above-described upper steering shaft 12 is fixed to the housing 201, and the housing 201 can rotate integrally with the upper steering shaft 12.

  The VGRS motor 202 is a DC brushless motor having a rotor 202a serving as a rotor, a stator 202b serving as a stator, and a rotating shaft 202c serving as an output shaft for driving force. The stator 202b is fixed inside the housing 201, and the rotor 202a is rotatably held inside the housing 201. The rotating shaft 202c is fixed so as to be coaxially rotatable with the rotor 202a, and its downstream end is connected to the speed reduction mechanism 203.

  The speed reduction mechanism 203 is a planetary gear mechanism having a plurality of rotational elements (sun gear, carrier, and ring gear) that can be differentially rotated. Among the plurality of rotating elements, the sun gear is connected to the rotating shaft 202 c of the VGRS motor 202, and the carrier is connected to the housing 201. A ring gear is connected to the lower steering shaft 13.

  According to the speed reduction mechanism 203 having such a configuration, the rotational speed of the upper steering shaft 12 (that is, the rotational speed of the housing 201 connected to the carrier) corresponding to the operation amount of the handle 11 and the rotational speed of the VGRS motor 202 (That is, the rotational speed of the rotary shaft 202c connected to the sun gear) uniquely determines the rotational speed of the lower steering shaft 13 connected to the ring gear that is the remaining one rotational element. At this time, the rotational speed of the lower steering shaft 13 can be controlled to increase / decrease by controlling the rotational speed of the VGRS motor 202 to increase / decrease by the differential action between the rotating elements. That is, the upper steering shaft 12 and the lower steering shaft 13 can be rotated relative to each other by the action of the VGRS motor 202 and the speed reduction mechanism 203. Further, due to the configuration of each rotary element in the speed reduction mechanism 203, the rotation speed of the VGRS motor 202 is transmitted to the lower steering shaft 13 in a state where the speed is reduced according to a predetermined reduction ratio determined according to the gear ratio between the respective rotary elements. The

  Thus, in the vehicle 1, the upper steering shaft 12 and the lower steering shaft 13 can rotate relative to each other, so that the steering angle MA that is the amount of rotation of the upper steering shaft 12 and the amount of rotation of the lower steering shaft 13 are determined. The steering transmission ratio, which is uniquely determined (which also relates to the gear ratio of the rack and pinion mechanism described later) and the steering angle of the front wheel, which is the steering wheel, is continuously variable within a predetermined range.

  The speed reduction mechanism 204 is not limited to the planetary gear mechanism illustrated here, but is connected to other modes (for example, gears having different numbers of teeth are connected to the upper steering shaft 12 and the lower steering shaft 13, respectively, and partially contact each gear. An aspect in which a flexible gear is installed and the upper steering shaft 12 and the lower steering shaft 13 are rotated relative to each other by rotating the flexible gear with a motor torque transmitted via a wave generator. The planetary gear mechanism may have a physical, mechanical, or mechanical aspect different from the above.

  The VGRS driving device 300 is an electric driving circuit including a PWM circuit, a transistor circuit, an inverter, and the like that are configured to be energized to the stator 202b of the VGRS motor 202. The VGRS driving device 300 is electrically connected to a battery (not shown), and is configured to be able to supply a driving voltage to the VGRS motor 202 with electric power supplied from the battery. Further, the VGRS driving device 300 is electrically connected to the ECU 100, and its operation is controlled by the ECU 100. The VGRS driving device 300, together with the VGRS actuator 200, constitutes an example of “steering angle varying means” according to the present invention.

  The rotation of the lower steering shaft 13 is transmitted to the rack and pinion mechanism. The rack and pinion mechanism is a steering force transmission mechanism including a pinion gear 14 connected to a downstream end portion of the lower steering shaft 13 and a rack bar 15 formed with gear teeth that mesh with gear teeth of the pinion gear. The rotation of the pinion gear 14 is converted into the horizontal movement of the rack bar 15 in the drawing, so that the steering force is applied to each steered wheel via a tie rod and a knuckle (not shown) connected to both ends of the rack bar 15. It is configured to be transmitted. That is, the vehicle 1 realizes a so-called rack and pinion type steering system.

  The EPS actuator 400 includes an EPS motor as a DC brushless motor including a rotor (not shown) as a rotor to which a permanent magnet is attached, and a stator as a stator surrounding the rotor. This EPS motor is configured to be capable of generating an assist torque TA in the rotation direction when the rotor is rotated by the action of a rotating magnetic field formed in the EPS motor by energizing the stator via the EPS driving device 500. ing.

  On the other hand, a reduction gear (not shown) is fixed to the motor shaft that is the rotation shaft of the EPS motor, and this reduction gear is also meshed with the pinion gear 14. For this reason, the assist torque TA generated from the EPS motor functions as an assist torque that assists the rotation of the pinion gear 14. The pinion gear 14 is connected to the lower steering shaft 13 as described above, and the lower steering shaft 13 is connected to the upper steering shaft 12 via the VGRS actuator 200. Accordingly, the driver steering torque MT applied to the upper steering shaft 12 is transmitted to the rack bar 15 in a form that is appropriately assisted by the assist torque TA, so that the driver's steering burden is reduced.

  The EPS drive device 500 is an electric drive circuit including a PWM circuit, a transistor circuit, an inverter, and the like that are configured to be energized to the stator of the EPS motor. The EPS driving device 500 is electrically connected to a battery (not shown), and is configured to be able to supply a driving voltage to the EPS motor with electric power supplied from the battery. Further, the EPS driving device 500 is electrically connected to the ECU 100, and its operation is controlled by the ECU 100.

  On the other hand, the vehicle 1 includes various sensors including a steering torque sensor 16, a steering angle sensor 17, and a rotation sensor 18.

  The steering torque sensor 16 is a sensor configured to be able to detect a driver steering torque MT given from the driver via the handle 11.

  More specifically, the upper steering shaft 12 is divided into an upstream portion and a downstream portion, and has a configuration in which they are connected to each other by a torsion bar (not shown). Rings for detecting a rotational phase difference are fixed to both upstream and downstream ends of the torsion bar. This torsion bar is twisted in the rotational direction in accordance with the steering torque (ie, driver steering torque MT) transmitted through the upstream portion of the upper steering shaft 12 when the driver of the vehicle 1 operates the handle 11. The steering torque can be transmitted to the downstream portion while causing such a twist. Therefore, when the steering torque is transmitted, a rotational phase difference is generated between the above-described rings for detecting the rotational phase difference. The steering torque sensor 16 is configured to detect the rotational phase difference and to convert the rotational phase difference into a steering torque and output it as an electrical signal corresponding to the steering torque MT.

  Further, the steering torque sensor 16 is electrically connected to the ECU 100, and the detected steering torque MT is referred to by the ECU 100 at a constant or indefinite period.

  The steering angle sensor 17 is an angle sensor configured to be able to detect a steering angle MA that represents the amount of rotation of the upper steering shaft 12. The steering angle sensor 17 is electrically connected to the ECU 100, and the detected steering angle MA is referred to by the ECU 100 at a constant or indefinite period.

  The rotation sensor 18 is a rotary encoder configured to detect a rotational phase difference between the housing 201 (that is, equivalent to the upper steering shaft 12 in terms of the rotation angle) and the lower steering shaft 13 in the VGRS actuator 200. . The rotation sensor 18 is electrically connected to the ECU 100, and the detected rotation phase difference is referred to by the ECU 100 at a constant or indefinite period.

  The vehicle speed sensor 19 is a sensor configured to be able to detect the vehicle speed V that is the speed of the vehicle 1. The vehicle speed sensor 19 is electrically connected to the ECU 100, and the detected vehicle speed V is referred to by the ECU 100 at a constant or indefinite period.

  The in-vehicle camera 20 is an imaging device that is installed on the front nose of the vehicle 1 and configured to be able to image a predetermined area in front of the vehicle 1. The in-vehicle camera 20 is electrically connected to the ECU 100, and the captured front area is sent to the ECU 100 as image data at a constant or indefinite period. The ECU 100 can analyze the image data and acquire various data necessary for LKA control.

  Next, the LKA control executed by the ECU 100 will be described with reference to FIG. FIG. 2 is a flowchart of LKA control executed by the ECU according to the present embodiment.

  In FIG. 2, the ECU 100 reads various signals including operation signals of various switches provided in the vehicle 1, various flags and sensor signals related to the various sensors (step S <b> 101), and is installed in the vehicle 1 in advance. It is determined whether or not the LKA mode is selected as a result of the operation button for activating the LKA control being operated by the driver (step S102). When the LKA mode is not selected (step S102: NO), the ECU 100 returns the process to step S101.

  When the LKA mode is selected (step S102: YES), the ECU 100 defines a white line (target road (here, lane)) that defines the LKA target path based on the image data sent from the in-vehicle camera 20. It is determined whether or not a road surface structure or road surface display object is detected (step S103) If a white line is not detected (step S103: NO), a virtual target road cannot be set. ECU 100 returns the process to step S101. On the other hand, when the white line is detected (step S103: YES), the ECU 100 calculates road surface information necessary for causing the vehicle 1 to follow the target road (step S104).

  In step S104, the lane offset Y, which is the lateral deviation between the white line and the vehicle 1, or the yaw angle deviation φ between the white line and the vehicle 1 is calculated. Based on the lane offset Y or yaw angle deviation φ, the ECU 100 determines the LKA basic target angle δ1 that is the amount of change in the front wheel steering angle that is necessary for the vehicle 1 to follow the target road (step S105).

  Here, the LKA basic target angle δ1 will be described with reference to FIG. FIG. 3 is a diagram illustrating the relationship between the LKA basic target angle δ1 and the yaw angle deviation φ.

  In FIG. 3, the LKA basic target angle δ1 is relatively steep only in the vicinity of the zero point with respect to the yaw angle deviation φ, and thereafter increases gradually with increasing absolute value of the yaw angle deviation φ. It becomes a function.

  Returning to FIG. 2, when the LKA basic target angle δ1 is determined, the ECU 100 determines the presence or absence of steering input information (step S106). In the present embodiment, the steering input information means the steering angle MA and a steering angular velocity MA ′ that is a time differential value of the steering angle MA (that is, an example of “steering velocity” according to the present invention). Here, the description will be continued assuming that the steering input information is obtained.

  When the steering input information is obtained (step S106: YES), that is, when there is no occurrence such as the steering angle sensor 17 outputting an abnormal signal or the steering angle sensor 17 not responding, the ECU 100 Then, it is determined whether or not there is a steering input, that is, whether or not the steering angle MA by the driver steering is not zero (step S107). If there is no steering input (step S107: NO), the process proceeds to step S110. Step S110 will be described later.

  When there is a steering input (step S107: YES), the ECU 100 first reduces the response frequency fLKA of the LKA control with respect to the reference value (step S108).

  Here, the higher the response frequency fLKA, the higher the speed of image processing and calculation processing, and the higher the steering angle control frequency of the steering target wheel (here, the front wheel). As a result, the followability to the target road is good, but the degree of interference with driver steering is increased. Therefore, when the steering input of the driver is generated, the ECU 100 reduces the response frequency fLKA of the LKA control to a low frequency region where such interference can be sufficiently mitigated from a practical viewpoint.

  On the other hand, if the response frequency of the LKA control is lowered in this way, the followability to the target path in the LKA control is lowered. Therefore, ECU 100 further calculates normal angle δ2 and locus correction angle δ3 (step S109).

  Here, the normal angle δ2 is obtained by multiplying the steering angle MA by a predetermined steady gain corresponding to the vehicle speed V and the steering angular speed MA ′ by a predetermined differential gain corresponding to the vehicle speed V. This is an addition value with the second angle element, and means a normal steering angle change amount that the VGRS actuator 200 should realize in accordance with the steering input of the driver.

  Separately, the trajectory correction angle δ3 is an angle obtained by processing the trajectory correction amount set with respect to the steering angular velocity MA ′ with a predetermined filter frequency corresponding to the vehicle speed V. Prior to being reflected in the LKA control according to the control response frequency fLKA, it means a correction amount for reflecting the driver steering in the final target angle δLKA of the LKA control.

  The ECU 100 finally calculates the LKA final angle δLKA by adding the LKA basic target angle δ1, the normal angle δ2, and the trajectory correction angle δ3 (step S110). When there is no driver steering input in step S107, the LKA basic target angle δ1 becomes the LKA final angle δLKA.

  When the LKA final angle δLKA is calculated, the VGRS actuator 200 is driven and controlled to realize the LKA final angle δLKA, and the process returns to step S101.

  According to such LKA control, the trajectory of the vehicle 1 follows the target road, and the degree of interference between the steering angle change corresponding to the driver steering and the steering angle change related to the tracking to the target road is reduced. The driver feels uncomfortable.

  On the other hand, such an effect is limited to the case where the steering input information is normally obtained. For example, when some abnormality occurs in the steering angle sensor 17 temporarily or permanently, the steering angle MA and the steering angular velocity MA ′ are not normally input. It becomes invalid. As a result, only the response frequency reduction measure of the LKA control according to step S108 becomes effective, and a decrease in the followability to the target road is likely to be manifested.

  Therefore, when there is no steering input information (step S106: NO), the ECU 100 returns the response frequency fLKA of the LKA control to the reference value, or a frequency higher than the reference value in order to ensure followability to the target road. (Step S111).

  As a result, even in a situation where the steering input information cannot be obtained for some reason, the tracking to the target road based on the LKA basic target angle δ1 that does not depend on the steering angle MA and the steering angular velocity MA ′ is preferably realized.

  Here, the response frequency of the LKA control will be described with reference to FIG. FIG. 4 is a diagram illustrating the relationship between the response frequency fLKA and the vehicle speed V.

  In FIG. 4, the characteristic of the reference value of the response frequency fLKA is shown as an illustrated PRF_A (see solid line). Further, the characteristic of the response frequency set by the response frequency reduction measure in step S108 in the LKA control is shown as illustrated PRF_C (see the chain line). Further, the characteristic of the response frequency set by the response frequency increase measure according to step S111 in the LKA control is shown as illustrated PRF_B (see the broken line).

  The response frequency fLKA is a decreasing function that gradually decreases as the vehicle speed increases. This is because the higher the vehicle speed, the greater the influence of the change in the steering angle on the vehicle behavior, and the relative instability of the LKA control is reduced to prevent the vehicle behavior from becoming unstable. .

Second Embodiment
Next, with reference to FIG. 5, problems that may occur in the operation of the LKA control according to the first embodiment will be described. Here, FIG. 5 is a conceptual diagram illustrating the relationship between the traveling road condition of the vehicle and the stability of the vehicle. In the figure, the same reference numerals are given to the same portions as those in FIG. 1, and the description thereof will be omitted as appropriate.

  5A, FIG. 5A shows a state in which the vehicle 1 is traveling on a curved road 2A having a road width W1 in accordance with LKA control, and FIG. 5B shows a road width W2 (W2 <W1). The state which is drive | working the curved path 2B similarly is shown.

  Here, in step S111 in the LKA control, when the response frequency fLKA of the LKA control is increased, particularly when the response frequency fLKA is increased above the reference value, the vehicle 1 follows the target road (chain line), but the vehicle behavior is generally (See the broken line trajectory).

  For this reason, the vehicle behavior becomes relatively unstable depending on the travel conditions of the vehicle 1, particularly the conditions of the travel path. In order to overcome such problems, in the LKA control according to the second embodiment, the ECU 100 acquires information on the travel path, and based on the travel path information, the response frequency fLKA of the LKA control is appropriately reduced. to correct.

  As the information on the traveling road, image recognition processing based on the imaging result of the traveling road by the in-vehicle camera 20, or more simply, when the vehicle 1 includes a car navigation processing device, various road-to-vehicle communication devices, etc. Necessary information may be acquired from.

  In addition, although the road width of the traveling road is shown here as an example, the road surface state of the traveling road can greatly affect the stability of the vehicle. In view of this point, the ECU 100 may lower the response frequency based on the road surface condition (friction coefficient, presence / absence of a step, etc.) instead of or in addition to the above-described road width of the road.

  In this way, by correcting and decreasing the response frequency fLKA based on the information on the road, it is possible to follow the target road according to the state of the road and to stabilize the vehicle behavior regardless of the state of the road. It becomes possible to make it equal.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. The apparatus is also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 11 ... Handle, 12 ... Upper steering shaft, 100 ... ECU, 200 ... VGRS actuator, 300 ... VGRS drive device

Claims (4)

A travel control device in a vehicle including a steering angle variable means capable of changing a relationship between a steering angle that is a rotation angle of a steering input shaft and a steering angle that is a rotation angle of a steering wheel,
Trajectory control means for controlling the rudder angle varying means so that the trajectory of the vehicle approaches a target road;
Obtaining means for obtaining steering input information related to a steering input given to the steering input shaft via a steering wheel by a driver of the vehicle;
Responsiveness change means for changing the responsiveness of the trajectory control by the trajectory control means according to the acquired steering input information, and improving the responsiveness of the trajectory control when the steering input information cannot be obtained;
A vehicle travel control device comprising: The vehicle travel control apparatus according to claim 1, wherein the responsiveness changing unit changes the responsiveness according to a steering speed. 3. The vehicle travel control device according to claim 1, wherein the responsiveness changing unit corrects an increase amount related to the improvement of the responsiveness according to a travel condition of the vehicle. The vehicle travel control device according to claim 3, wherein the travel condition is a condition related to a state of a travel path.

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