JP6374308B2 - Vehicle control apparatus and vehicle control method - Google Patents

Description

  The present invention relates to a vehicle control device and a vehicle control method.

  Recently, a vehicle that generates a yaw rate different from that of a steering wheel steering system by torque vectoring control in which a rear wheel is independently driven by a motor is known. A vehicle that performs lane tracking control and cornering assist control for causing the vehicle to follow a lane detected by a camera or the like using such a yaw rate generation mechanism is known. In such a vehicle, a desired yaw rate can be obtained regardless of the steering operation of the driver.

  Patent Document 1 below describes that the braking force of each wheel is controlled as a mechanism for generating a yaw rate different from that of the steering wheel steering system. It is described that the assist force is reduced. Patent Document 1 discloses an apparatus that calculates an ideal steering angle from a yaw rate detected by a yaw rate sensor, a vehicle body speed (vehicle speed), and a vehicle slip angle, and reduces the assist force in accordance with a deviation from the actual steering angle. Has been.

  Further, in Patent Document 2 below, in a vehicle equipped with an automatic steering control device capable of changing the vehicle state quantity independently of the driver's steering, the automatic steering control is changed to driver steering corresponding to the driver's steering. It is described that when switching, the first state quantity (first yaw rate) generated by the automatic steering control and the second state quantity (second yaw rate) to be generated with respect to the detected steering wheel angle are controlled to coincide with each other. Has been.

Japanese Patent Application Laid-Open No. 09-039762 JP 2012-232676 A

  When generation of yaw rate different from that of the steering wheel steering system is generated by torque vectoring control for independently driving the rear wheels by a motor, self-steering due to generation of the yaw rate occurs, and this self-steering may interfere with the steering wheel steering system. Since such self-steering can normally be pushed back by the reaction force of the power steering mechanism, it is not transmitted directly to the driver steering the steering wheel. For this reason, there is a problem that it is difficult for the driver to recognize that the yaw rate control by the yaw rate generation mechanism different from the steering system is being performed.

  In the technique described in Patent Document 1, when the driver performs correction steering in a direction in which the deviation between the actual steering angle and the theoretical steering angle is reduced during execution of the braking force control, the assist force gradually increases. When the driver performs corrective steering in a direction in which the deviation between the actual steering angle and the theoretical steering angle increases, the assist force gradually decreases and the corrective steering is continued. For this purpose, a large steering torque is required. However, in the technique described in Patent Document 1, the steering angle is unnecessarily increased or decreased by the driver during the execution of the braking force control, and as a result, the vehicle can stably turn. Torque that causes the actual steering angle to be excessive or insufficient with respect to the ideal steering angle originally required for the vehicle, and to cause the vehicle to follow the lane detected by a camera or the like. It is not intended for vectoring control. For this reason, in the technique described in Patent Document 1, it is difficult to optimally adjust the steering force when performing torque vectoring control for causing the vehicle to follow the lane.

  In addition, when performing lane tracking control that changes the vehicle state quantity independently of the driver's steering, the driver may steer the steering wheel to suspend the lane tracking control due to correction of the traveling path (hereinafter referred to as `` following control ''). Such an operation is also referred to as an override). When the force for pushing back the self-steer described above is set as the control override condition, there is a problem that the condition is satisfied by steering with a light force by the driver and the lane tracking control is easily interrupted.

  Furthermore, when the lane tracking control is interrupted, the steering is switched to the steering operation by the driver, but the yaw rate corresponding to the steering angle of steering does not match the yaw rate generated by the vehicle at the time of switching. A sudden yaw change may occur and the steering feeling may become uncomfortable.

  In this regard, in the technique described in Patent Document 2, when the automatic steering control is switched to the control corresponding to the driver's steering, the first yaw rate generated by the automatic steering control and the detected steering angle are determined. Although control is performed so that the second yaw rate to be generated matches, the steering input by the intention of the driver does not correspond to the actual behavior of the vehicle until the two match. For this reason, when switching from automatic steering control to control according to the driver's steering, the driver feels uncomfortable with the steering feeling. It is difficult to avoid the problem of uncomfortable feeling when switching from automatic steering control to steering by a driver.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to perform steering when performing control to generate a yaw rate independently of a steering system based on an estimated traveling path. It is an object of the present invention to provide a new and improved vehicle control apparatus and vehicle control method capable of optimally adjusting the steering force of the vehicle.

  In order to solve the above-described problems, according to an aspect of the present invention, a lane tracking yaw rate calculation unit that calculates a lane tracking yaw rate based on an estimated traveling road, and a tire obtained by multiplying a steering wheel steering angle by a conversion gain A vehicle reference yaw rate calculation unit that calculates a vehicle reference yaw rate from a vehicle model based on a steering angle, and a steering wheel based on the detected yaw rate of the vehicle when lane tracking control based on the lane tracking yaw rate is performed. A conversion gain calculation unit that calculates a virtual conversion gain for converting from a steering angle to a tire steering angle from a vehicle model, an initial value of a conversion gain from a steering wheel steering angle to a tire steering angle when the lane tracking control is not performed, and the When the virtual conversion gain is larger than the initial value, the virtual conversion gain is compared with the virtual conversion gain. Control apparatus for a vehicle comprising an assist force control unit that reduces the assist force of the power steering, the Te is provided.

  An assist gain calculation unit that calculates an assist gain of a power steering based on the virtual conversion gain may be provided, and the assist force control unit may reduce the assist force based on the assist gain.

  The assist force control unit may reduce the assist force as the virtual conversion gain is larger than the initial value based on the assist gain.

  A determination unit that determines that the lane tracking control based on the lane tracking yaw rate is interrupted; and if the lane tracking control is performed, the lane tracking yaw rate is selected as a target yaw rate, and the determination unit A target yaw rate selection unit that selects, as a target yaw rate, the vehicle reference yaw rate calculated by the vehicle reference yaw rate calculation unit when it is determined that lane tracking control is interrupted; a steering wheel steering system based on the target yaw rate; And a control unit that independently controls the yaw rate of the vehicle, and when it is determined by the determination unit that the lane tracking control is interrupted, the vehicle reference yaw rate calculation unit includes the virtual conversion gain. The vehicle standard yaw rate may be calculated using the conversion gain as the conversion gain.

  In addition, the assist force control unit, based on a value obtained by gradually reducing the virtual conversion gain to the initial value when the lane tracking control is interrupted after the lane tracking control is interrupted. The assist force may be reduced.

  Further, the vehicle reference yaw rate calculation unit, when the lane tracking control is interrupted after the lane tracking control is interrupted, the value obtained by gradually decreasing the virtual conversion gain to the initial value, The vehicle reference yaw rate may be calculated as a conversion gain.

  The determination unit may determine whether or not the lane tracking control is interrupted based on a comparison between the steering wheel torque and the steering reaction torque by the driver.

  Further, the lane following yaw rate calculating unit may calculate the lane following yaw rate based on an estimated traveling path obtained from an image captured by a camera.

  In order to solve the above problem, according to another aspect of the present invention, a step of calculating a lane following yaw rate based on an estimated traveling road, and a tire rudder obtained by multiplying a steering wheel steering angle by a conversion gain. Calculating the vehicle reference yaw rate from the vehicle model based on the angle, and the lane tracking control based on the detected lane tracking yaw rate when the lane tracking control based on the lane tracking yaw rate is performed. A step of calculating a virtual conversion gain to be converted into a corner from a vehicle model is compared with an initial value of a conversion gain from a steering wheel steering angle to a tire steering angle when the lane tracking control is not performed and the virtual conversion gain. , When the virtual conversion gain is larger than the initial value, the assist force of the power steering based on the virtual conversion gain The vehicle control method comprising the steps of lowering, is provided.

  As described above, according to the present invention, it is possible to optimally adjust the steering force of the steering when the control for generating the yaw rate is performed independently of the steering system.

It is a mimetic diagram showing the composition of the vehicles concerning one embodiment of the present invention. It is a mimetic diagram showing composition of a control device of vehicles concerning one embodiment of the present invention. It is a schematic diagram for demonstrating the calculation method of the lane follow-up yaw rate Ytg1 by the lane follow-up yaw rate calculation part. It is a schematic diagram which shows the state which the vehicle is drive | working along the presumed traveling path obtained by a camera system based on lane tracking yaw rate Ytg1. FIG. 6 is a characteristic diagram showing a state in which different yaw rates are generated even when the driver sets the same steering angle θh when torque vectoring control is performed. FIG. 6 is a characteristic diagram showing a state in which different yaw rates are generated even when the driver sets the same steering angle θh when torque vectoring control is performed. It is a characteristic view showing a map for the assist gain calculation unit to calculate the assist gain Gps. It is a schematic diagram which shows the structure of a power steering motor control part. It is a characteristic view showing a map for gradually reducing the conversion gain Gh after the occurrence of an override. It is a flowchart which shows the process in the control apparatus of the vehicle which concerns on this embodiment. It is a flowchart which shows the process which calculates virtual conversion gain Gh according to the presence or absence of an override. It is a flowchart showing a process of determining whether torque vectoring control is being performed based on the drive torque difference between the left and right wheels and reducing the assist gain of the power steering when torque vectoring control is being performed. .

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  First, with reference to FIG. 1, the structure of the vehicle 1000 which concerns on one Embodiment of this invention is demonstrated. FIG. 1 is a schematic diagram showing a vehicle 1000 according to the present embodiment. As shown in FIG. 1, a vehicle 1000 includes front wheels 100 and 102, rear wheels 104 and 106, motors 110 and 112 for driving the rear wheels 104 and 106, a power steering mechanism (P / S) 120, a steering angle sensor 130, The system includes a steering 132, inverters 140 and 142, a battery 150, a yaw rate sensor 160, a vehicle speed sensor 170, a camera system 180, and a control unit (ECU) 200.

  The vehicle 1000 according to the present embodiment is provided with motors 110 and 112 for driving the rear wheels 104 and 106, respectively. For this reason, the driving torque can be controlled for each of the rear wheels 104 and 106. Therefore, the yaw rate can be generated by the torque vectoring control by driving each of the rear wheels 104 and 106 independently of the yaw rate generation by the steering of the front wheels 100 and 102. The driving torque of the rear wheels 104 and 106 is controlled by controlling the inverters 140 and 142 corresponding to the rear wheels 104 and 106 based on a command from the control device 200. Electric power is supplied from the battery 150 to each of the inverters 140 and 142.

  The power steering mechanism 120 controls the steering angle of the front wheels 100 and 102 by torque control or angle control. The steering angle sensor 130 detects the steering angle θh input by the driver operating the steering 132. The yaw rate sensor 160 detects the yaw rate Yaw of the vehicle 1000. The vehicle speed sensor 170 detects the vehicle speed V of the vehicle 1000.

  FIG. 2 is a schematic diagram illustrating a configuration of a vehicle control device according to an embodiment of the present invention. As shown in FIG. 2, the vehicle control apparatus according to the present embodiment includes a camera system 180, a lane following yaw rate calculation unit 204, a vehicle reference yaw rate calculation unit 206, an override determination unit 208, a conversion gain calculation unit 210, and a target yaw rate selection. 212, a torque vectoring motor control unit 214, a conversion gain multiplication unit 216, an assist gain calculation unit 218, and a power steering motor control unit 220. In the configuration illustrated in FIG. 2, the configuration other than the camera system 180 is configured by the control device 200.

  In the configuration shown in FIG. 2, the lane tracking yaw rate calculation unit 204 calculates the lane tracking yaw rate Ytg1 based on the estimated traveling path information acquired from the camera system 180 and the vehicle speed V. The vehicle reference yaw rate calculation unit 206 calculates a vehicle reference yaw rate Ytg2 based on the vehicle speed V and the tire steering angle. The control device 200 performs the torque vectoring control so that the vehicle 1000 travels along the estimated traveling path acquired from the camera system 180 by performing the control based on the lane tracking yaw rate Ytg1, and thus along the estimated traveling path. Lane tracking control can be performed.

  The override determination unit 208 determines whether the driver (driver) has overridden the lane tracking control based on a comparison between the steering wheel torque Tq_h by the driver (driver) and the steering reaction torque. More specifically, the override determination unit 208 determines that the override has been performed when the steering wheel steering torque Tq_h is greater than the steering reaction torque. The steering wheel torque Tq_h can be detected by a sensor included in the power steering mechanism 120. Further, the steering reaction torque can be obtained from a map that defines the steering reaction torque according to the steering angle θh and the vehicle speed V.

  Further, the override determination unit 208 compares the direction of the steering angle θh by the steering operation of the driver with the direction of the lateral deviation ε obtained from the camera system 180 and a traveling path described later, and the directions of both coincide with each other. If not, it may be determined that an override has been performed.

  The conversion gain calculation unit 210 calculates a conversion gain Gh for converting the steering wheel steering angle θh to the tire steering angle δ based on the steering wheel steering angle θh, the generated yaw rate Yaw, and the vehicle speed V.

  The target yaw rate selection unit 212 receives the lane following yaw rate Ytg1 and the vehicle standard yaw rate Ytg2. The target yaw rate selection unit 212 selects the vehicle reference yaw rate Ytg2 as the target yaw rate Ytg when the lane tracking control is not performed. Further, the target yaw rate selecting unit 212 selects the lane following yaw rate Ytg1 as the target yaw rate Ytg when the lane following control is performed. Therefore, the target yaw rate selection unit 212 receives the determination flag indicating the determination result of the override from the override determination unit 208, and when the lane tracking control is overridden based on the determination flag, the target yaw rate Ytg2 is set as the target yaw rate. Select as Ytg. Further, the target yaw rate selection unit 212 selects the lane tracking yaw rate Ytg1 as the target yaw rate Ytg when the lane tracking control is not overridden. The target yaw rate selection unit 212 outputs the target yaw rate Ytg obtained by the selection to the torque vectoring control unit 214. The torque vectoring motor control unit 214 performs torque vectoring control of the motors 110 and 112 based on the input target yaw rate Ytg, and controls the vehicle yaw rate Yaw to be the target yaw rate Ytg.

  The vehicle reference yaw rate Ytg2 can be calculated by the vehicle reference yaw rate calculation unit 206 from the following equation (1) that represents a general vehicle model (planar two-wheel model). The vehicle reference yaw rate Ytg2 corresponds to the vehicle yaw rate γ in the equation (1) of the plane two-wheel model.

In the expressions (1) to (3), variables and constants are as follows.
<Variable>
γ: vehicle yaw rate V: vehicle speed δ: tire steering angle θh: steering wheel steering angle Gh: conversion gain from steering wheel steering angle to tire steering angle <constant>
l: Vehicle wheel base l _f : Distance from vehicle center of gravity to front wheel center l _r : Distance from vehicle center of gravity to front wheel center m: Vehicle weight k _f : Cornering power constant (front)
k _r : Cornering power constant (rear)
G_h0: Initial value of conversion gain from steering wheel steering angle to tire steering angle (steering gear ratio)

  The vehicle reference yaw rate Ytg2 (= γ) is calculated from the equation (1) using the vehicle speed V and the tire steering angle δ as variables. Since the tire steering angle δ in the equation (1) cannot be directly sensed, it is calculated from the equation (2) by multiplying the steering wheel steering angle θh by the conversion gain Gh. In normal times, an initial value (steering gear ratio) G_h0 is used as the conversion gain Gh. The steering gear ratio G_h0 is a value of about 1/15, for example. Further, the constant A in the expression (1) is a constant representing the characteristics of the vehicle, and is obtained from the expression (3).

  FIG. 3 is a schematic diagram for explaining a method of calculating the lane following yaw rate Ytg1 by the lane following yaw rate calculating unit 204. The camera system 180 includes a pair of left and right cameras having image sensors such as a CCD sensor and a CMOS sensor, images the external environment outside the vehicle, and uses the white line W of the lane in which the host vehicle travels as image information. Can be recognized. In addition, the camera system 180 can generate and acquire distance information to a target object based on the principle of triangulation from the corresponding positional deviation amount for a pair of captured left and right stereo images. In addition, the camera system 180 performs a well-known grouping process on the distance information generated based on the principle of triangulation, and compares the grouping process distance information with preset three-dimensional solid object data or the like. Thus, three-dimensional object data, white line data, and the like are detected. Thereby, the camera system 180 can also recognize a stop sign, a stop line, an ETC gate, and the like in addition to the white line W indicating the preceding vehicle and the traveling lane.

  As shown in FIG. 3, the stereo camera system 180 detects a white line W of a travel lane in which the vehicle 1000 travels, and an intersection of the straight line L1 and the white line W that is separated from the camera system 180 by a front viewpoint distance L toward the front. White line coordinates are obtained at P1 and P2. Then, the traveling path coordinates are obtained at the midpoint P3 of the intersection points P1 and P2. Further, the coordinates of the intersection P4 (front gazing point) between the front direction of the camera system 180 and the straight line L1 are obtained.

In FIG. 3, the deviation ε ′ from the traveling path can be approximated by the lateral deviation ε (distance between P3 and P4) from the traveling path, so that ε ′ → ε. Then, a parameter (= turning support angle α [rad]) corresponding to the steering amount is calculated from the lateral deviation ε from the traveling path detected in advance by the camera system 180 and the forward gaze distance L. The turning support angle α can be calculated from the following equation (4).
α = 2 × sin ⁻¹ (ε / 2L) (4)

  When the amount of steering by the steering 132 is insufficient at the time of entering a corner, traveling at a corner, etc., rear torque vectoring control (preview cornering assist control) based on the turning support angle α is performed. The lane following yaw rate Ytg1 can be obtained by substituting the turning support angle α into δ in the equation (1) of the plane two-wheel model. That is, the lane tracking yaw rate Ytg1 can be calculated from the following equation (5).

  In the present embodiment, the lane following yaw rate is calculated based on the estimated traveling road obtained from the image captured by the camera system 180, but the estimated traveling road is acquired from other information to calculate the lane following yaw rate Ytg1. Also good.

  The target yaw rate selection unit 212 compares the input lane follow-up yaw rate Ytg1 and the vehicle reference yaw rate Ytg2, and selects either one according to whether or not lane follow-up control is performed (result of override determination).

  FIG. 4 is a schematic diagram showing a state where the vehicle 1000 is traveling along the estimated traveling path obtained by the camera system 180 based on the lane tracking yaw rate Ytg1. As described with reference to FIG. 3, the camera system 180 detects the white line W indicating the travel lane, and the turning support angle α is obtained. Then, the lane tracking yaw rate Ytg1 is calculated from the vehicle speed V and the turning support angle α. As described above, the vehicle 1000 according to the present embodiment includes a yaw rate generation mechanism that is different from the steering wheel operation system, and drives the rear wheels 104 and 106 by independent motors 110 and 112, respectively. Torque vectoring control based on Ytg1 can be performed. In this case, a desired yaw rate can be obtained regardless of the steering angle θh by the driver's operation.

  5 and 6 are characteristic diagrams showing a state in which different yaw rates are generated even when the driver sets the same steering wheel steering angle θh when torque vectoring control is performed. 5 and 6, the vertical axis represents the steering angle and the vehicle yaw rate, and the horizontal axis represents time. Here, FIG. 5 shows a case where lane tracking control is not performed. In the period T1 shown in FIG. 5, the steering wheel steering angle is about −15 [deg], and the vehicle yaw rate detected by the yaw sensor is 0.075 [rad / sec].

  On the other hand, FIG. 6 shows a case where lane tracking control is performed. In the period T2 shown in FIG. 6, the vehicle yaw rate is about 0.075 [rad / sec], which is the same as the period T1 in FIG. 5, but the steering wheel steering angle is about −6 [deg], which is smaller than FIG. Yes. Therefore, it can be seen that the steering angle is different between the case where the lane tracking control is not performed (FIG. 5) and the case where the lane tracking control is performed (FIG. 6), even though the vehicle yaw rate is the same.

  In other words, in the period T1 shown in FIG. 5 and the period T2 shown in FIG. 6, since the vehicle yaw rate is the same, the vehicle travels on the same radius curve, but the steering angle of the steering wheel is smaller in FIG. ing. This is because when the lane tracking control is performed, the corner can be turned with a smaller steering angle by the torque vectoring control of the rear wheels.

  When the vehicle 1000 shown in FIG. 4 travels in the direction of the arrow A1, lane tracking control corresponding to the estimated travel path is performed according to the white line W by torque vectoring control of the rear wheels. That is, in this case, control based on the lane tracking yaw rate Ytg1 is performed. Therefore, when traveling in the direction of the arrow A1, the vehicle 1000 travels without causing the driver to feel uncomfortable.

  On the other hand, when the driver tries to steer the vehicle 1000 in the direction of the arrow A2, the steering by the lane tracking control is overridden, and the control is switched to the control by the steering wheel. That is, the lane tracking control according to the estimated travel path based on the white line W is finished, and control by steering the driver's own steering wheel is performed. At this time, the override determination unit 208 determines that the lane tracking control has been overridden by the driver (driver). When the target yaw rate selection unit 212 receives a determination flag indicating that the override has been performed from the override determination unit 208, the target yaw rate selection unit 212 switches the target yaw rate from Ytg1 to Ytg2. Thereby, control based on the vehicle standard yaw rate Ytg2 is performed.

  By the way, when performing lane tracking control, a method of performing control superimposed on steering wheel steering (for example, steering by a power steering motor) directly interferes with steering of a driver because steering by lane tracking control directly interferes with steering of the driver. Gets worse. On the other hand, when performing torque vectoring control based on the lane tracking yaw rate Ytg1, there is no interference with the steering of the driver. However, when torque vectoring control based on the lane following yaw rate Ytg1 is performed, the yaw rate is generated by a yaw rate generating mechanism different from the steering system, so that interference from the road surface via the front wheels 100 and 102 occurs as self-steer. Occur. Normally, such self-steering can be pushed back by a driver's light steering force using the power steering mechanism 120. For this reason, regardless of whether the lane tracking control is valid or invalid, the driver feels a certain steering feeling, and it becomes difficult to discriminate the intervention situation by the torque vectoring control. Moreover, when the force for pushing back such self-steer is used as the condition for the override determination, it is assumed that the override condition is satisfied by the light steering force by the driver, and torque vectoring control is easily interrupted. The

  Therefore, in the present embodiment, when the lane tracking control along the estimated traveling path is performed, the driver's lane tracking control is performed by reducing the assist force by the power steering mechanism 120. Recognize it reliably, and prevent frequent overrides that are not intended by the driver.

  Specifically, the conversion gain calculation unit 210 generates a virtual conversion gain Gh from the steering wheel steering angle θh to the tire steering angle δ based on the current steering wheel steering angle θh, the generated yaw rate Yaw, and the vehicle speed V. Is calculated by inverse calculation from the vehicle model. As described above, when the lane tracking control is performed, the corner can be turned with a smaller steering angle θh by the torque vectoring control of the rear wheels 104 and 106. Therefore, when the obtained virtual conversion gain Gh is larger than the conversion gain initial value Gh_0 (corresponding to a mechanical steering gear ratio), it is determined that the lane tracking control by torque vectoring is being performed. it can. Here, the virtual conversion gain Gh is calculated based on a virtual tire steering angle estimated from the traveling direction of the vehicle 1000 when the lane tracking control is being performed, and is a virtual conversion gain Gh with respect to the steering wheel steering angle θh. This is the ratio of the tire rudder angle. The virtual tire steering angle estimated from the traveling direction of the vehicle 1000 is determined by turning by the steering wheel steering angle and turning by torque vectoring of the rear wheels.

  And while the lane following control by torque vectoring is performed, the assist force by the power steering mechanism 120 is reduced to increase the steering operation. Thus, the driver can easily recognize that the torque vectoring control is performed based on the weight of the steering operation. In addition, since the steering operation becomes heavy, it is possible to reliably prevent frequent override determination unintended by the driver.

  The calculation method of the virtual conversion gain Gh is as follows. First, the tire steering angle δ is obtained by detecting the vehicle yaw rate Yaw from the yaw rate sensor 160 and substituting it into γ in equation (1) and substituting the vehicle speed V into equation (1). Then, by substituting the obtained tire steering angle δ and the steering angle θh detected by the steering angle sensor 130 into the equation (2), a virtual conversion gain Gh is obtained. When the calculated virtual conversion gain Gh matches the conversion gain initial value Gh_0, lane tracking control by torque vectoring is not performed. When the virtual conversion gain Gh is larger than the conversion gain initial value Gh_0, lane tracking control by torque vectoring is performed.

  For example, when the lane tracking control is not performed, the initial value of the conversion gain from the steering wheel steering angle to the tire steering angle (steering gear ratio G_h0) is 1/15. In FIG. 4, when the vehicle 1000 is traveling in the direction of arrow A1 by lane tracking control, the virtual conversion gain from the steering wheel steering angle to the tire steering angle Gh is assumed to be 1/10. In this embodiment, the virtual conversion gain Gh (= 1/10) at the time of performing lane tracking control is back-calculated from Formula (1) and Formula (2) as needed, and lane tracking control is not performed. The conversion gain initial value (= 1/15) is compared. In this example, since the virtual conversion gain Gh is larger than the conversion gain initial value G_h0, it is determined that the lane following control by the torque vectoring of the rear wheels 104 and 106 is performed, and the assist force of the power steering mechanism 120 is determined. Reduce.

  In FIG. 2, the assist gain calculation unit 218 calculates an assist gain Gps that defines the assist force of the power steering mechanism 120 based on the virtual conversion gain Gh calculated by the conversion gain calculation unit 210. The assist gain Gps is input to the power steering motor control unit 220. Based on the assist gain Gps, the power steering motor control unit 220 controls the motor of the power steering mechanism 120 so that the assist force by the power steering mechanism 120 decreases as the assist gain decreases.

  FIG. 7 is a characteristic diagram showing a map for the assist gain calculation unit 218 to calculate the assist gain Gps. In FIG. 7, the vertical axis represents the assist gain Gps, and the horizontal axis represents the virtual conversion gain Gh. As shown in FIG. 7, when the virtual conversion gain Gh is equal to or less than the conversion gain initial value G_h0, the value of the assist gain Gps is 1.0. On the other hand, when the virtual conversion gain Gh is larger than the conversion gain initial value G_h0, the value of the assist gain Gps decreases as the conversion gain Gh increases.

  Further, when the virtual conversion gain Gh becomes larger than the predetermined value Gh_1, the assist gain Gps becomes a constant value. Thereby, the steering force by the driver can be prevented from becoming excessively heavy.

  Therefore, the larger the value of the virtual conversion gain Gh, that is, the larger the control amount by torque vectoring of the rear wheels 104 and 106, the smaller the assist gain Gps, and the steer operation becomes heavier. As a result, it becomes possible to give the driver appropriate steering reaction force, and to make the driver recognize that the lane tracking control by the rear wheel torque vectoring is performed, and to improve the steering feeling. .

  In addition, by giving an appropriate steering reaction force to the driver, it is possible to reliably prevent an unintended override from being performed by the driver, and it is possible to optimally perform the override determination.

  FIG. 8 is a schematic diagram showing the configuration of the power steering motor control unit 220. As shown in FIG. 8, the power steering motor control unit 220 includes a base current calculation unit 220a, an assist gain multiplication unit 220b, a target current determination unit 220c, and a drive circuit 220d. have. The base current calculation unit 220 a calculates the base current of the motor 240 of the power steering mechanism 120 based on the steering wheel steering torque Tq_h detected by the torque sensor 230 and the vehicle speed V detected by the vehicle speed sensor 170. The assist gain multiplication unit 220b multiplies the base current by the assist gain Gps. The target current determination unit 220d determines the target current based on the base current multiplied by the assist gain Gps. The drive circuit 220d drives the motor 240 of the power steering mechanism 120 based on the target current.

  Next, control after steering by lane tracking control is overridden will be described. In FIG. 4, when the lane tracking control is performed, the vehicle 1000 is moved in the direction of the arrow A1 with a smaller steering angle than the case where the lane tracking control is not performed by the torque vectoring control of the rear wheels 104 and 106. It can be run. On the other hand, when the steering by the lane tracking control is overridden, the torque vectoring control of the rear wheels 104 and 106 is terminated. Therefore, when the driver runs the vehicle 1000 at the steering angle before the override in the lane tracking control, the rear wheel The turning radius is increased by the amount of turning due to torque vectoring 104 and 106, and the vehicle 1000 travels outward (in a more straight forward direction). That is, after the override, the steering wheel cannot be advanced in the same direction as before the override at the same steering angle as that before the override. As a result, the driver feels uncomfortable with the behavior of the vehicle 1000.

  For this reason, the vehicle control apparatus according to the present embodiment switches from control based on the lane tracking yaw rate Ytg1 to control based on the vehicle reference yaw rate Ytg2 when an override is performed from the lane tracking control to the tracking control based on steering wheel steering. Then, control is performed to maintain the conversion gain Gh from the steering wheel steering angle to the tire steering angle at the conversion gain at the timing when the override occurs.

  As described above, when switching from the control based on the lane following yaw rate Ytg1 to the control based on the vehicle standard yaw rate Ytg2 while traveling on the curve shown in FIG. 4, the tire steering angle becomes smaller than the driver's assumption, The vehicle 1000 tries to go outside the intended direction. In the present embodiment, after the override occurs, a virtual tire steering angle is calculated based on the virtual conversion gain Gh.

  For example, as in the above example, when lane tracking control is not performed, the conversion gain (steering gear ratio G_h0) from the steering wheel steering angle to the tire steering angle is 1/15, and when lane tracking control is performed, It is assumed that a virtual conversion gain from the steering wheel steering angle to the tire steering angle is 1/10. In this case, in the present embodiment, when the override is performed, the vehicle reference yaw rate Ytg2 is calculated based on the virtual conversion gain Gh (= 1/10) calculated backward when the override is started, and the steering control is performed. Thereby, the conversion from the steering wheel steering angle θh to the tire steering angle δ is performed with a virtual conversion gain Gh that is larger than the steering gear ratio G_h0. Therefore, the traveling direction of the vehicle 1000 determined by the steering wheel steering angle θh is And after the override, it is possible to reliably prevent the vehicle 1000 from feeling uncomfortable at the start of the override.

  After switching to the control based on the vehicle standard yaw rate Ytg2, the vehicle standard yaw rate Ytg2 (= γ) is obtained from the equations (1) and (2) based on the virtual conversion gain Gh, and the obtained vehicle The torque vectoring motor control unit 114 performs control based on the standard yaw rate Ytg2. As a result, steering control is performed based on the virtual conversion gain θh obtained at the start of the override, and therefore, when switching from control based on the lane tracking yaw rate Ytg1 to control based on the vehicle reference yaw rate Ytg2 is performed. Thus, the conversion gain from the steering wheel steering angle θh to the tire steering angle δ is optimally adjusted, and a vehicle behavior corresponding to the steering wheel input of the driver can be obtained. Thereby, even when the steering wheel steering angle θh is smaller than the yaw rate Yaw generated by the vehicle 1000 at the time of override, the conversion gain from the steering wheel steering angle θh to the tire steering angle δ is optimally adjusted. Thus, it is possible to suppress changes in vehicle behavior and reliably prevent the vehicle behavior from feeling uncomfortable. Therefore, the driver can obtain the vehicle behavior corresponding to the steering wheel steering input.

  Since the virtual conversion gain Gh is inversely calculated from the vehicle yaw rate Yaw obtained from the yaw rate sensor 160, the vehicle reference yaw rate Ytg2 becomes equal to the vehicle yaw rate Yaw when the override is started. During the subsequent override, the vehicle reference yaw rate Ytg2 is calculated based on the virtual conversion gain Gh in accordance with the driver's steering operation. Therefore, it is possible to ensure the continuity of the target vehicle standard yaw rate Ytg2.

  In the method described in Patent Document 2 described above, for example, when switching from automatic steering control to control corresponding to driver steering while traveling on a curve, the first yaw rate generated by automatic steering control and the detected steering wheel angle Since the control is performed so that the second yaw rate to be generated coincides with the vehicle, the yaw rate of the vehicle changes every moment even if the steering angle of the steering wheel is constant, and the driver feels uncomfortable. On the other hand, according to the present embodiment, since the virtual conversion gain Gh is obtained at the start of overriding, the vehicle reference yaw rate Ytg2 is uniquely obtained from the steering wheel steering angle θh at the start of overriding, and thereafter the virtual conversion gain Gh is obtained. Based on this, the vehicle standard yaw rate Ytg2 is calculated. Therefore, a transitional period in which the vehicle behavior does not coincide with the steering angle of the steering wheel does not occur, and the vehicle yaw rate continues to be generated according to the steering angle of the steering wheel if the driver turns the steering wheel. Thereby, it is possible to reliably prevent the vehicle behavior from feeling uncomfortable.

  Further, in the present embodiment, after the override determination is performed, control is performed to gradually decrease the virtual conversion gain Gh and gradually decrease to Gh_0 while the override is continued. FIG. 9 is a characteristic diagram showing a map for gradually decreasing the conversion gain Gh after occurrence of an override. As shown in FIG. 9, after the occurrence of the override, the virtual conversion gain Gh is gradually decreased with the passage of time t, and the virtual conversion gain Gh finally reaches Gh_0. As an example, T is a time constant when the virtual conversion gain Gh is gradually decreased. The gradual decrease of the conversion gain Gh based on the map of FIG. 9 is performed every control cycle, and the virtual conversion gain Gh calculated in the current control cycle is the virtual conversion gain Gh ′ calculated in the previous control cycle. Is a value obtained by gradually decreasing the decrease in the time T of the control cycle. As a result, after the override determination, the virtual conversion gain Gh can be made asymptotic to a value Gh_0 corresponding to the steering gear ratio as time elapses. Therefore, after the override determination, the assist gain Gps of the power steering mechanism 120 gradually increases as the virtual conversion gain Gh decreases, and it is possible to prevent the driver's steering operation from being suddenly lightened. . In addition, after the override determination, until the virtual conversion gain Gh reaches Gh_0, it is possible to ensure the continuity of the vehicle standard yaw rate Ytg2 calculated based on the virtual conversion gain Gh. It can prevent giving a sense of incongruity.

  In the present embodiment, the vehicle 1000 that performs lane tracking control using torque vectoring by independent driving of the rear wheels 104 and 106 is illustrated. However, the vehicle control device according to the present embodiment includes a driver's steering wheel operation. Can be widely applied to configurations having an independent yaw rate generating mechanism. As the yaw rate generation mechanism independent of the driver's steering operation, the rear wheel 104, 106 is driven independently as in this embodiment, the torque vectoring differential, the rear wheel steering mechanism (4WS) , Friction brakes, and the like.

  FIG. 10 is a flowchart showing processing in the vehicle control apparatus according to the present embodiment. First, in step S10, a virtual conversion gain Gh from the steering wheel steering angle to the tire steering angle is calculated. As described above, the calculation of the virtual conversion gain Gh differs depending on whether or not the override is performed while the rear wheel torque vectoring control is being performed. FIG. 11 is a flowchart showing the process of step S10 of FIG. 10, that is, a process of calculating a virtual conversion gain Gh according to whether or not there is an override. In step S20 of FIG. 11, it is determined whether or not an override has been performed while the rear wheel torque vectoring control is being performed. If the override has not been performed, the process proceeds to step S22. In step S22, a virtual conversion gain Gh is calculated from equations (1) and (2).

  If it is determined in step S20 in FIG. 11 that the override has been performed, the process proceeds to step S24. In step S24, when the override occurs, the value calculated from the equations (1) and (2) is set as a virtual conversion gain Gh. After the override occurs, based on the elapsed time t from the occurrence of the override, FIG. The conversion gain Gh is calculated from the map. Thereby, a virtual conversion gain Gh obtained by gradually decreasing the virtual conversion gain Gh ′ calculated in the previous control cycle is calculated. After steps S22 and S24, the process ends, and the process proceeds to step S12 in FIG.

  In step S12 of FIG. 10, the virtual conversion gain Gh calculated in step S10 is compared with the conversion gain initial value Gh_0 to determine whether or not Gh> Gh_0. If Gh> Gh_0, the process proceeds to step S14. In step S14, the assist gain Gps of the power steering mechanism 120 is calculated from the virtual conversion gain Gh using the map of FIG.

  On the other hand, if Gh> Gh_0 is not satisfied in step S12, the process proceeds to step S16. In step S16, the assist gain Gps is set to 1.0 based on the map of FIG.

  After steps S14 and S16, the process proceeds to step S18. In step S18, processing for changing the driving force of the motor of the power steering mechanism 120 is executed based on the assist gain Gps calculated in steps S14 and S16. Thereby, the assist of the steering force by the power steering mechanism 120 is performed based on the assist gain Gps. After step S18, the process ends.

  The processes of FIGS. 10 and 11 are performed for each control cycle. Therefore, after the override occurs, the virtual conversion gain Gh calculated in step S24 of FIG. 11 decreases for each control cycle, and the assist gain Gps calculated in step S14 of FIG. 10 is the virtual conversion gain. Decreases with decreasing Gh. Therefore, after the override occurs, the assist force of the power steering mechanism 120 gradually increases as the virtual conversion gain Gh decreases until the virtual conversion gain Gh reaches the conversion gain initial value Gh_0. However, the steering operation by the driver becomes lighter with time.

  In the above-described embodiment, based on the comparison between the virtual conversion gain Gh and the conversion gain initial value Gh_0, when Gh> Gh_0, the value of the assist gain Gps is set according to the value of the virtual conversion gain Gh. By setting, the steering operation is made heavy when torque vectoring control is performed. On the other hand, it may be determined whether torque vectoring control is performed by another method, and the steering operation may be made heavy when torque vectoring control is performed.

  FIG. 12 determines whether torque vectoring control is being performed based on the drive torque difference between the left and right wheels. If torque vectoring control is being performed, a process for reducing the assist gain of the power steering is performed. It is a flowchart to show. First, in step S30, an absolute value | Tq_l−Tq_r | of the driving torque difference between the left and right wheels is calculated, and it is determined whether or not the absolute value | Tq_l−Tq_r | is greater than a predetermined threshold value d. Here, Tq_l is the driving torque of the left rear wheel 104, and Tq_r is the driving torque of the right rear wheel 106.

  When the absolute value | Tq_l−Tq_r | is larger than the threshold value d, the torque vectoring control is performed by the driving force difference between the rear wheels 104 and 106, and thus the process proceeds to step S32 and the assist gain Gps is set. 0.7. Thereby, when torque vectoring control is performed, the assist force of the power steering mechanism 120 can be reduced and the steering operation can be increased. Therefore, when torque vectoring control is performed, it is possible to apply an appropriate steering reaction force to the driver, and to improve the steering feeling.

  On the other hand, if the absolute value | Tq_l−Tq_r | is equal to or less than the threshold value d, it is determined that the torque vectoring control based on the driving force difference between the rear wheels 104 and 106 is not performed, and the process proceeds to step S34. In step S34, the assist gain is set to 1.0. Thereby, the assist force by the power steering mechanism 120 is maximized, and the steering operation can be lightened when the torque vectoring control is not performed.

  As described above, according to the present embodiment, when the torque vectoring control of the rear wheels 104 and 106 is performed, the magnitude relationship between the virtual conversion gain Gh and the conversion gain initial value Gh_0 is compared. The assist of the power steering mechanism 120 is reduced when> Gh_0. As a result, the steering operation becomes heavy during the torque vectoring control, so that an appropriate steering reaction force can be given to the driver during cornering, and the steering feeling can be improved. In addition, by applying an appropriate steering reaction force to the driver during cornering, it is possible to prevent frequent overriding unintended by the driver.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

180 camera system 200 control unit 204 lane following yaw rate calculation unit 206 vehicle reference yaw rate calculation unit 208 override determination unit 210 conversion gain calculation unit 212 target yaw rate selection unit 214 torque vectoring motor control unit 218 assist gain calculation unit 220 power steering motor control unit

Claims (9)

A lane follow-up yaw rate calculator that calculates a lane follow-up yaw rate based on the estimated travel path;
A vehicle reference yaw rate calculation unit that calculates a vehicle reference yaw rate from a vehicle model based on a tire steering angle obtained by multiplying a steering wheel steering angle by a conversion gain;
Conversion gain calculation for calculating, from the vehicle model, a virtual conversion gain for converting the steering wheel steering angle to the tire steering angle based on the detected yaw rate of the vehicle when the lane tracking control based on the lane tracking yaw rate is performed. And
The initial value of the conversion gain from the steering wheel steering angle to the tire steering angle when the lane tracking control is not performed is compared with the virtual conversion gain, and when the virtual conversion gain is larger than the initial value, An assist force control unit that reduces the assist force of the power steering based on a virtual conversion gain;
A vehicle control device comprising: An assist gain calculator that calculates an assist gain of a power steering based on the virtual conversion gain;
2. The vehicle control device according to claim 1, wherein the assist force control unit reduces the assist force based on the assist gain.   3. The vehicle control device according to claim 2, wherein the assist force control unit reduces the assist force based on the assist gain as the virtual conversion gain is larger than the initial value. 4. A determination unit that determines that the lane tracking control based on the lane tracking yaw rate is interrupted;
When the lane tracking control is performed, the lane tracking yaw rate is selected as a target yaw rate, and the vehicle reference yaw rate calculation unit calculates the lane tracking control when the determination unit determines that the lane tracking control is interrupted A target yaw rate selection unit that selects the vehicle reference yaw rate as a target yaw rate;
A control unit for controlling the yaw rate of the vehicle independently of the steering system based on the target yaw rate,
When the determination unit determines that the lane tracking control is interrupted, the vehicle reference yaw rate calculation unit calculates the vehicle reference yaw rate using the virtual conversion gain as the conversion gain. The vehicle control device according to claim 1.   When the lane tracking control is interrupted after the lane tracking control is interrupted, the assist force control unit is configured to perform the assist based on a value obtained by gradually decreasing the virtual conversion gain to the initial value. The vehicle control device according to claim 4, wherein the force is reduced.   When the lane tracking control is interrupted after the lane tracking control is interrupted, the vehicle reference yaw rate calculation unit calculates a value obtained by gradually decreasing the virtual conversion gain to the initial value. The vehicle control device according to claim 4, wherein the vehicle reference yaw rate is calculated as follows.   The said determination part determines whether the said lane tracking control was interrupted based on the comparison with the steering wheel steering torque and steering reaction force torque by a driver | operator, The any one of Claims 4-6 characterized by the above-mentioned. The vehicle control device described.   The vehicle control according to any one of claims 1 to 7, wherein the lane following yaw rate calculating unit calculates the lane following yaw rate based on an estimated traveling path obtained from an image captured by a camera. apparatus. Calculating a lane following yaw rate based on the estimated travel path;
Calculating a vehicle reference yaw rate from a vehicle model based on a tire steering angle obtained by multiplying a steering angle by a conversion gain;
When a lane tracking control based on the lane tracking yaw rate is performed, a virtual conversion gain for converting from a steering wheel steering angle to a tire steering angle is calculated from a vehicle model based on the detected yaw rate of the vehicle;
The initial value of the conversion gain from the steering wheel steering angle to the tire steering angle when the lane tracking control is not performed is compared with the virtual conversion gain, and when the virtual conversion gain is larger than the initial value, Reducing the assist power of the power steering based on the virtual conversion gain;
A vehicle control method comprising:

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