JP4434095B2 - Steering device - Google Patents

Description

  The present invention relates to a steering device that applies a steering torque to a steering mechanism so that a vehicle travels along a predetermined position on a travel path based on a captured image of the travel path.

As a steering device, there is a lane keeping device that recognizes a lane from a captured image of a traveling road ahead of the vehicle and applies a steering torque to the steering mechanism so that the vehicle travels along the center of the lane. In the lane keeping device, the curve radius (curvature) of the road, the yaw angle of the vehicle with respect to the lane, the vehicle offset from the lane center, etc. are obtained from the relationship between the recognized lane and the vehicle, and the additional steering torque is based on these parameters. Set. Some steering devices add a correction steering torque for canceling the disturbance to the steering mechanism when a disturbance (such as a crosswind) that affects the vehicle behavior occurs (see Patent Document 1). In this steering device, in order to set the disturbance influence value based on the lateral acceleration, the yaw rate, the steering angle, and the steering torque, or to remove the steady-state deviation due to the disturbance, the second-order integration value of the lateral acceleration (the vehicle lateral direction) The disturbance influence value is set as a positive correlation value of the integrated value of the vehicle behavior due to the disturbance obtained from the position change amount) and the first-order time integral value (yaw angle) of the yaw rate. In this way, the control using the integral value includes a lane keeping device that sets the additional steering torque in consideration of the time integral value of the vehicle offset from the center of the lane.
JP 2001-1923 A

  In consideration of drainage and the direction of the curve, the road is provided with a cross slope inclined in either direction of the road. Therefore, a gravity component acts on the vehicle toward the right or left of the road due to the influence of the cross gradient. In a conventional lane keeping device that also uses an integrated value of an offset, an additional steering torque that is applied in a direction opposite to the direction in which the gravity component acts is set based on the integrated value of the offset.

  However, if the vehicle enters the curve and the direction of the cross gradient suddenly changes according to the direction of the curve, the direction of the gravity component acting on the vehicle also changes. As a result, the direction of the steering torque applied before entering the curve is the same as the direction in which the gravity component after entering the curve acts. Therefore, the steering torque further acts in the direction in which the gravity component acts on the vehicle, and the vehicle is separated from the lane center. In other words, an appropriate steering torque according to the crossing gradient is not applied.

  Then, this invention makes it a subject to provide the steering device which can provide the appropriate steering torque according to a cross gradient.

  A steering apparatus according to the present invention is a steering apparatus that images a travel path by an imaging unit and applies a steering torque to a steering mechanism so that the vehicle travels along a predetermined position on the travel path. A first integrating means for integrating the deviation of the position to obtain an integral value for the right side with respect to the predetermined position on the road; and integrating the deviation of the vehicle position with respect to the predetermined position on the road to integrate the left side with respect to the predetermined position on the road Second integration means for obtaining a value, switching means for switching between the first integrating means and the second integrating means based on a deviation of the vehicle position with respect to a predetermined position on the traveling road and a predetermined distance from the predetermined position on the traveling road, and switching means Steering torque setting means for setting a steering torque to be applied to the steering mechanism based on the integrated value of the integration means switched in step (5), when the curvature of the traveling road is large than when the curvature of the traveling road is small. The switching of the integrating means and second integration means, characterized in that hardly performed.

  In this steering apparatus, the deviation of the vehicle position with respect to the predetermined position on the traveling road is obtained from the captured image of the traveling road, the integral value for the right side with respect to the predetermined position on the traveling road is obtained by the first integrating means, and the traveling by the second integrating means. The integral value for the left side of the predetermined position on the road is obtained. In the steering apparatus, the switching means switches between the first integrating means and the second integrating means in accordance with the deviation from the predetermined position with reference to the predetermined distance from the predetermined position on the travel path. Further, in the steering device, the steering torque applied to the steering mechanism based on the integrated value obtained by the integrating means switched by the steering torque setting means so that the integrated value of the deviation does not increase (that is, approaches the predetermined position). And the set steering torque is applied to the steering mechanism. When the direction of the transverse gradient changes and the direction of the gravity component acting on the vehicle changes, the deviation of the changed gravity component toward the direction increases due to the influence of the gravity component. Therefore, in the steering device, even when the steering torque is applied based on the integration value of the other-side integration means, it can be switched to the integration means on the side where the deviation increases, and the integration value of the deviation increases. Therefore, the steering torque can be applied based on the integrated value of the switched integration means. As a result, the steering torque acts in a direction opposite to the direction in which the gravity component acts on the vehicle, and the vehicle approaches a predetermined position on the travel path. Further, in the steering device, when the curvature of the traveling road is large (the curve radius is small), switching between the first integrating means and the second integrating means is less likely to be performed than when the curvature of the traveling road is small (the curve radius is large). . As a result, it is possible to suppress switching of the integration means during curve driving than when driving on a straight line or a road that is close to a straight line, and large vehicle fluctuations during curve driving and reaction force fluctuations via the steering wheel for the driver Can be suppressed. Thus, in this steering apparatus, it is possible to apply an appropriate steering torque according to the crossing gradient, and it is possible to improve the accuracy of traveling the vehicle along the predetermined position.

  The traveling road is, for example, a traveling lane or a traveling road when there is no lane. The predetermined position of the travel path is, for example, the center of the travel path (lane). The predetermined distance from the predetermined position on the travel path is a reference distance for switching between the first integrating means and the second integrating means.

  The steering apparatus according to the present invention may be configured such that a predetermined distance from a predetermined position on the travel path is determined based on the curvature of the travel path.

  In this steering apparatus, a predetermined distance from a predetermined position on the travel path serving as a reference for switching is determined based on the curvature of the travel path (the reciprocal of the curve radius). Thus, in the steering device, when the curvature of the traveling road is large, the traveling road is curved, straight, or curved so that the switching between the first integrating means and the second integrating means is less likely to be performed than when the curvature of the traveling road is small. The condition for switching the integration means can be changed by changing the value of the predetermined distance in accordance with (the reciprocal of the curve radius).

  In the above steering device of the present invention, the predetermined distance from the predetermined position on the travel path may be configured to increase as the curvature of the travel path increases.

  In this steering apparatus, the predetermined distance from the predetermined position on the travel path is increased as the curvature of the travel path increases (that is, the curve radius decreases). As described above, the smaller the curve radius is, the more difficult the switching of the integration means is made by the curve by increasing the switching reference of the integration means. Therefore, it is possible to stabilize the vehicle behavior during the curve traveling and to suppress the steering reaction force fluctuation with respect to the driver.

  The steering apparatus according to the present invention is a steering apparatus that images a travel path by an image means and applies a steering torque to a steering mechanism so that the vehicle travels along a predetermined position on the travel path. A first integrating means for integrating the deviation of the position to obtain an integral value for the right side with respect to the predetermined position on the road; and integrating the deviation of the vehicle position with respect to the predetermined position on the road to integrate the left side with respect to the predetermined position on the road Second integration means for obtaining a value, switching means for switching between the first integrating means and the second integrating means based on a deviation of the vehicle position with respect to a predetermined position on the traveling road and a predetermined distance from the predetermined position on the traveling road, and switching means And a steering torque setting means for setting a steering torque to be applied to the steering mechanism based on the integrated value of the integrating means switched in step 1, wherein the switching means is either the first integrating means or the second integrating means. When the deviation of the vehicle position with respect to the predetermined position of the traveling road on the other side of the switched one of the integrating means is not more than the absolute value of the predetermined distance from the predetermined position of the traveling road in a state where the integral means is switched, When the integration value of one of the switched integration means is 0 or close to 0, the other integration means is switched.

  In this steering apparatus, the deviation of the vehicle position with respect to the predetermined position on the traveling road is obtained from the captured image of the traveling road, the integral value for the right side with respect to the predetermined position on the traveling road is obtained by the first integrating means, and the traveling by the second integrating means. The integral value for the left side of the predetermined position on the road is obtained. In the steering apparatus, the switching means switches between the first integrating means and the second integrating means in accordance with the deviation from the predetermined position with reference to the predetermined distance from the predetermined position on the travel path. Further, the steering device sets the steering torque to be applied to the steering mechanism based on the integral value obtained by the integrating means switched by the steering torque setting means, and applies the set steering torque to the steering mechanism. In particular, in the steering apparatus, even when the deviation on the other side of the vehicle is equal to or smaller than the absolute value of the predetermined distance from the predetermined position on the travel path by the switching means while being switched to one of the two integrating means, When it is determined that the integration value of one of the integration means is 0 or close to 0, the one integration means is switched to the other integration means. In this way, even if the deviation on the other side is less than the reference for switching and switching from one integrating means to the other integrating means is not possible, the integral value being selected becomes very small and the influence of the integral value being selected is eliminated. When it is, the integration means being selected can be switched to the other integration means, and the steering torque can be applied based on the integration value on the other side. For example, when the curve changes from a straight line or when the direction of the curve changes with an S-curve, the crossing gradient changes. Therefore, when the integration means on the side where the gravity component does not act is selected after entering the curve, the gravity component acts. It is possible to switch to an appropriate integration means on the side to be performed. In other words, when an appropriate integration means corresponding to the cross gradient is not selected, it is possible to quickly switch to the integration means corresponding to the cross gradient. Thus, in the steering device, an appropriate steering torque can be applied in accordance with the crossing gradient, and the accuracy with which the vehicle travels along the predetermined position can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the appropriate steering torque according to a crossing gradient can be provided, and a vehicle can be drive | worked with high precision along the predetermined position of a driving path.

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

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

  A lane keeping device 1 according to the present embodiment will be described with reference to FIGS. FIG. 1 is a configuration diagram of a lane keeping device according to the present embodiment. FIG. 2 is a control block diagram of the lane keeping device according to the present embodiment. FIG. 3 is an explanatory diagram of the process of switching the value of the offset threshold 1, where (a) is a straight line and (b) is a curve. FIG. 4 is an explanatory diagram of an erroneous selection integration correction process.

  The lane keeping device 1 sets a target steering torque necessary for assisting traveling in the center of the lane, and applies the target steering torque by the electric power steering device. At that time, the lane keeping device 1 sets the target steering torque based on the curve curvature, the vehicle direction (yaw angle) with respect to the white line, the deviation (offset) of the vehicle position with respect to the lane center, and the time integral value of the offset. In particular, in the lane keeping device 1, the integral value of the offset for the right side and the integral value of the offset for the left side with respect to the lane center are separately obtained as the integral value of the lane, and one integration is performed by switching the right integration and the left integration. A target steering torque is set based on the value. The lane keeping device 1 includes a white line recognition sensor 2 and a lane keeping ECU [Electronic Control Unit] 3, and uses an electric power steering device 10. The white line recognition sensor 2 includes a camera 2a as an imaging unit and a white line recognition ECU 2b. Since the curve curvature is the reciprocal of the curve radius, the curve curvature can be substituted with the reciprocal of the curve radius.

  The electric power steering device 10 controls the EPS motor 10b by an EPS [Electronic Power Steering] ECU 10a, and assists the steering by the driver with the driving torque of the EPS motor 10b. As shown in FIG. 2, the EPS ECU 10a sets an assist torque based on the steering torque generated by the driver's steering, and drives and controls the EPS motor 10b according to the assist torque. In particular, when the EPSECU 10a receives the steering torque signal TS from the lane keep ECU 3, the EPS ECU 10a multiplies the target steering torque indicated by the steering torque signal TS by a predetermined coefficient, and adds the multiplied value (additional torque) to the assist torque. The EPS motor 10b is driven and controlled according to the assist torque + addition torque. Driving torque by the EPS motor 10b is added to the steering mechanism, and torque by the EPS motor 10b is applied to the steering mechanism in addition to the steering torque by the driver. The additional torque is a relatively small torque that assists the steering torque by the driver.

  The camera 2a is, for example, a CCD [Charge Coupled Device] camera, and is attached to the front of the vehicle on which the lane keeping device 1 is mounted. At this time, the camera 2a is attached so that the optical axis direction thereof coincides with the traveling direction of the vehicle. The camera 2a captures a road ahead of the vehicle and acquires a captured color image (for example, an image of RGB [RedGreen Blue]). The camera 2a transmits the captured image data to the white line recognition ECU 2b as an imaging signal PS. The camera 2a has a wide imaging range in the left-right direction, and can sufficiently capture the white lines on both the left and right sides (a pair) indicating the traveling lane. Although the camera 2a is colored, it may be a black and white camera as long as it can acquire an image that can recognize a white line on the road.

  The white line recognition ECU 2b includes a CPU [Central Processing Unit], a ROM [Read Only Memory], a RAM [Random Access Memory], and the like. The white line recognition ECU 2b takes in the imaging signal PS and recognizes a pair of white lines indicating the lane in which the vehicle is traveling from the captured image data of the imaging signal PS. Then, the white line recognition ECU 2b calculates a lane width and a line passing through the center of the pair of white lines (that is, the center of the lane) from the recognized pair of white lines. Further, the white line recognition ECU 2b calculates the radius of the lane center (curve radius R), and calculates the curve curvature γ (= 1 / R) from the curve radius R. Further, the white line recognition ECU 2b calculates the vehicle direction (yaw angle θ) with respect to the white line and the position of the vehicle center (offset D) with respect to the center of the lane. Then, the white line recognition ECU 2b transmits the information of the recognized pair of white lines and the calculated information to the lane keep ECU 3 as an image signal GS. In the present embodiment, the curve radius R, the curvature γ, the yaw angle θ, and the offset D are expressed as positive values on the right side with respect to the right turn direction or the lane center, and the left turn direction or the lane center. On the other hand, it is assumed that the value on the left side is expressed as a negative value.

  The lane keep ECU 3 includes a CPU, a ROM, a RAM, and the like. The lane keep ECU 3 takes in the image signal GS from the white line recognition sensor 2 at regular intervals. Then, in the lane keeping ECU 3, when the lane keeping device 1 is activated by an operation by the driver, various information (curve curvature γ, yaw angle θ) indicated by the image signal GS so that the vehicle travels near the center of the lane. The target steering torque is set based on the offset D), and a steering torque signal TS indicating the target steering torque is transmitted to the electric power steering apparatus 10 (EPS ECU 10a). The lane keep ECU 3 executes various processing (right integration processing, left integration processing, integration switching processing, target steering torque setting processing, etc.) by executing an application program (software) for lane keeping processing. The processing corresponds to first integration means, second integration means, switching means, and steering torque setting means described in the claims.

  As shown in FIG. 2, the lane keep ECU 3 performs the right integration process and the left integration process using the offset D at regular intervals to obtain the right integration value RI and the left integration value LI. The lane keep ECU 3 switches between the right integral value RI and the left integral value LI by the integral switching process at regular intervals, and selects the integral value used in the target steering torque setting process. Further, the rake keep ECU 3 multiplies the curve curvature γ by the gain G1, multiplies the yaw angle θ by the gain G2, and multiplies the offset D by the gain G3 by a target steering torque setting process at a fixed time interval. The value is multiplied by the gain G4, and the target steering torque is set based on the curve curvature γ, the yaw angle θ, the offset D, and the integrated value of the offset multiplied by the gains G1 to G4. Here, for the curve curvature γ, the vehicle follows the road curve, for the yaw angle θ, the yaw angle converges to 0, for the offset D, the offset D converges to 0, and for the offset integral value, the integral value is set. A target steering torque that saturates is set. The right integration process and the left integration process, and the integration switching process between the right integration and the left integration will be described in detail below.

  The right integration process and the left integration process will be described. The lane keep ECU 3 performs time integration (right integration processing) on the right side of the lane center and time integration (left integration processing) on the left side with respect to the offset D input at regular intervals. As described above, the offset D is expressed as a positive value when the vehicle position is on the right side with respect to the lane center, and as a negative value when the vehicle position is on the left side. In this case, in the right integration process, the offset D is time-integrated. If the integral value is larger than 0, the integral value is output as it is, and if the integral value is 0 or less, 0 is output. Therefore, the right integration output value (right integration value) increases when the offset D is greater than 0, does not change when the offset D is 0, and lowers 0 when the offset D is less than 0. As it decreases. In the left integration process, the offset D is time integrated, and if the integral value is smaller than 0, the integral value is output as it is, and if the integral value is 0 or more, 0 is output. Accordingly, the output value (left integral value) of the left integration decreases (the absolute value increases) when the offset D is smaller than 0, does not change when the offset D is 0, and the offset D is larger than 0. In this case, the value increases with 0 as the upper limit (the absolute value decreases with 0 as the lower limit). When the offset D is expressed as a negative value when the vehicle position is on the right side with respect to the lane center and as a positive value when the vehicle position is on the left side, there is a relationship between positive and negative in the right integration and left integration. The reverse of the above.

The integration switching process will be described. First, the lane keep ECU 3 determines whether or not the absolute value of the curve radius R is larger than the curve determination threshold value _R0 . The curve determination threshold value R ₀ is a threshold value for determining whether the curve is a straight line (including almost a straight line) or a curve, and is a large value.

The absolute value of the curve radius R (in the case of a straight line) when it is determined that the curve is greater than the determination threshold value R _0, the lane keeping ECU 3, sets the offset D ₀ as offset threshold 1. The offset D ₀ is a threshold value for determining whether or not it is necessary to switch to an integral value on the side where the offset D becomes large because the absolute value of the offset D of the vehicle becomes large due to the influence of the crossing gradient or the like. Is a threshold value used in. FIG. 3A shows the white lines WL, WL on both sides and the center line CL of the lane. In the case of a straight line, an offset threshold 1 of offset D ₀ is set on each side of the center line CL.

The absolute value of the curve radius R (in the case of the curve) when: the curve judgment threshold R _0, the lane keeping ECU 3, sets the offset D ₁ as the offset threshold 1. The offset D ₁ is set to a value larger than the offset D ₀ and is a threshold value for suppressing the switching of the integral value during the curve traveling, and is a threshold value used in the curve. Incidentally, when the absolute value of the offset D of the vehicle is greater than the offset D _1, the vehicle since the corresponding deviation from the lane center, it is necessary to switch to the integral value of the side of the offset D is large even in the curve. In FIG. 3B, in the case of a curve, an offset threshold value 1 for an offset D ₁ greater than the offset D ₀ is set on both sides from the center line CL.

  When the currently selected integral is the left integral, the lane keep ECU 3 determines whether or not the right offset (the absolute value of the plus value of the offset D) is larger than the absolute value of the offset threshold value 1. When the right offset is larger than the absolute value of the offset threshold 1, the lane keep ECU 3 switches from left integration to right integration. In this case, since the deviation from the lane center to the right side is increased due to the influence of the crossing gradient, the steering torque is applied from the right side to the left side by switching to the right integral value.

When the right offset is less than or equal to the absolute value of the offset threshold 1, the lane keep ECU 3 determines whether or not the left integrated value is 0 (that is, whether or not the influence of the left integration has been eliminated). When the left integrated value is 0, the lane keep ECU 3 determines whether or not the right offset is larger than the absolute value of the offset threshold value 2. The offset threshold value 2 is set to a value smaller than the offset threshold value 1 (= offset D ₁ ) in order to enable switching of an integration value that is erroneously selected during curve traveling. The offset threshold 2 are set offset _{D 2} is the offset _{D 2} is the value of the same or _{D 0} near the offset _{D 0.} 4 shows, on each side from the center line CL, offset threshold 2 offset D ₂ minutes is set in the vicinity of the offset D _0. When the right offset is larger than the absolute value of the offset threshold 2, the lane keep ECU 3 switches from left integration to right integration. In this case, since the left integration is selected even though the vehicle enters the curve in the right direction, the steering torque is applied from the right side to the left side by switching to the right integration. Here, when the left integral value becomes 0 and the influence of the left integral value is eliminated, the right integral is switched. Furthermore, by setting an offset threshold 2 smaller than the offset threshold 1, switching can be performed in consideration of the vehicle position.

  When the currently selected integration is a right integration, the lane keep ECU 3 determines whether the left offset (the absolute value of the minus value of the offset D) is larger than the absolute value of the offset threshold value 1. When the left offset is larger than the absolute value of the offset threshold 1, the lane keep ECU 3 switches from right integration to left integration. In this case, since the deviation from the lane center to the left side is increased due to the influence of the crossing gradient, the steering torque is applied from the left side to the right side by switching to the left integrated value.

  When the left offset is equal to or smaller than the absolute value of the offset threshold 1, the lane keep ECU 3 determines whether the right integral value is 0 (that is, whether the influence of the right integration has been eliminated). When the right integral value is 0, the lane keep ECU 3 determines whether the left offset is larger than the absolute value of the offset threshold value 2. When the left offset is larger than the absolute value of the offset threshold 2, the lane keep ECU 3 switches from right integration to left integration. In this case, since right integration is selected even though the vehicle has entered the curve in the left direction, switching to left integration is performed so that steering torque from the left side to the right side is added. Here, when the right integration value is 0 and the influence of the right integration value is eliminated, the left integration value is switched. Furthermore, by setting an offset threshold 2 smaller than the offset threshold 1, switching can be performed in consideration of the vehicle position.

  A curve usually has a cross slope with a high outside and a low inside, and the direction of the cross slope does not change during the curve. Therefore, it is desirable to always select an integral value inside the curve and apply a steering torque from the inside to the outside of the curve in order to counter the gravitational component acting on the vehicle due to the crossing gradient while driving on the curve. . In addition, if the integral value inside the curve is switched to the integral value outside the curve while driving on the curve, a steering torque directed from the outside to the inside of the curve, which is the same direction as the direction of the gravity component, is added. Fluctuates inward and the steering reaction force against the driver also increases. Therefore, in the case of a curve, the lane keep ECU 3 increases the offset threshold 1 so that the left integration and the right integration are not switched.

In the example of FIG. 3B, the direction of the crossing gradient is a direction where the left side of the road is higher and the right side is lower than when it is a straight line, and it does not change even when entering a curve. Therefore, since the straight line before entering the curve, the right integral value has been selected, and steering torque from the right side to the left side of the road has been added. Therefore, after entering the curve, the locus RL of the offset D of the vehicle is from the right side to the left side across the lane center line CL. When the offset threshold 1 is the offset D ₀ , the left offset exceeds the offset D ₀ , and the left integrated value is switched, and a steering torque from the left to the right is added. Then, the direction in which the steering torque is applied is the same as the direction of the gravity component due to the cross gradient, the vehicle suddenly changes to the right side of the road, and the locus RL ′ of the vehicle offset D also changes abruptly. However, the lane-keep ECU 3, since the offset threshold 1 and large offset D _1, never left offset exceeds the offset D _1, the selection of the right integrated value is maintained, the additional steering torque directed from right to left Continue to be. In this case, since the direction in which the steering torque is applied and the direction of the gravity component due to the cross gradient are opposite, the vehicle is less fluctuating and the locus RL of the offset D of the vehicle is also near the center line CL. .

As described above, the lane keep ECU 3 increases the offset threshold 1 (= offset D ₁ ) in the case of a curve so that the left integration and the right integration are not switched. However, when changing from an S-shaped curve or a straight line to the curve (hereinafter referred to as the current curve), the direction of the transverse gradient may change suddenly, and the direction of the gravity component acting on the vehicle changes. In this case, before entering the current curve, steering torque is applied from the outside to the inside of the current curve due to the influence of the cross gradient in the direction opposite to the cross gradient of the current curve. The steering torque directed from the outside to the inside of the current curve is in the same direction as the gravity component acting on the vehicle when entering the current curve. Therefore, when entering the current curve, it is necessary to switch from the integral value outside the current curve to the integral value inside to add the steering torque from the inside to the outside of the current curve to counter the gravity component. There is. However, since the offset threshold value 1 is large in the curve, it takes time until the offset inside the current curve exceeds the offset threshold value 1, and the vehicle position also deviates greatly from the lane center. Therefore, even if the offset inside the current curve is less than or equal to the absolute value of the offset threshold 1, the integral value outside the current curve becomes 0 (that is, the influence of the integral value disappears), and the offset inside the current curve becomes the offset threshold value. When the offset threshold value is smaller than 1, the integral value outside the current curve can be switched to the integral value inside.

In the example of FIG. 4, when the direction of the cross slope is a straight line, the left side of the road is low and the right side is high. When the curve is a curve, the left side of the road is high and the right side is low. Therefore, the left integrated value is selected on the straight line before entering the curve, and the steering torque from the left side to the right side of the road is added. When entering the curve in this state, a gravity component from the left side to the right side of the road in the same direction as the applied steering torque acts on the vehicle. As a result, the vehicle suddenly moves to the right side of the road. At this time, since became curve, it has offset threshold 1 is a large offset D _1. When performing the switching judgment at this offset threshold 1, the right offset does not easily exceed the offset D _1, not switched from left integral value to the right the integral value, it continues to be added steering torque directed from left to right. Therefore, since the direction in which the steering torque is applied and the direction of the gravity component due to the cross gradient are the same direction, the vehicle continues to fluctuate to the right side of the road, and the locus RL ′ of the offset D of the vehicle also increases abruptly. To change. This state continues until the right offset exceeds the offset D _1. However, the lane keep ECU 3 determines whether or not the left integral value has become 0, and when the left integral has become 0, the left integral value is switched to the right integral value, and the steering torque from the right side to the left side is determined. Start adding. At this time, the lane keep ECU 3 also performs determination with an offset threshold 2 (= offset D ₂ ) smaller than the offset threshold 1 in order to perform switching in consideration of the vehicle position. In this way, when the influence of the left integrated value is eliminated, switching to the right integrated value so as to add the steering torque from the right side to the left side, the direction in which this steering torque is applied and the gravity due to the cross gradient Since the direction of the component is opposite, there is little fluctuation of the vehicle, and the locus RL of the offset D of the vehicle is also near the center line CL.

  The operation of the lane keeping device 1 will be described with reference to FIGS. 1 and 2. In particular, the integration switching process in the lane keep ECU 3 will be described with reference to the flowchart of FIG. FIG. 5 is a flowchart showing the flow of integral switching processing in the lane keeping ECU of FIG. Here, a case where the lane keeping device 1 is activated by the driver will be described.

  The camera 2a captures an image of a road ahead of the vehicle and transmits data of the captured image to the white line recognition ECU 2b as an image signal PS. The white line recognition ECU 2b recognizes a pair of white lines that divide the lane from the captured image. Then, the white line recognition ECU 2b calculates the lane width, the lane center, the curve radius R and curvature γ, the yaw angle θ, and the vehicle offset D from the lane center from the pair of white lines. Further, the white line recognition ECU 2b transmits the information of the pair of white lines and each calculated information to the lane keep ECU 3 as an image signal GS at regular time intervals.

The lane keep ECU 3 receives the image signal GS at regular intervals. Then, the lane keep ECU 3 obtains the curve radius R, the curvature γ, the yaw angle θ, and the offset D from the image signal GS (S1, S2). The lane keep ECU 3 calculates the right integration value by the right integration process and calculates the left integration value by the left integration process every time the offset D is acquired. Further, the lane keep ECU 3 determines whether or not the absolute value of the curve radius R is larger than the curve determination threshold value _R0 (S3). If the absolute value of the curve radius R in S3 is determined to be larger than the curve determination threshold _{R 0} (if linear), the lane keeping ECU 3, sets the offset _{D 0} to offset threshold 1 (S4). Therefore, in the case of a straight line, the offset threshold 1 is small, and when the vehicle is offset from the lane center, the right integration and the left integration are easily switched. If the absolute value of the curve radius R in S3 is determined as follows curve determination threshold _{R 0} (if the curve), the lane keeping ECU 3, sets the offset _D 1 (> offset _{D 0)} to offset threshold 1 (S5) . Therefore, in the case of a curve, the offset threshold value 1 is large, and it is difficult to switch between right integration and left integration. Further, the lane keep ECU 3 determines whether or not the left integration is being selected (S6).

  When it is determined in S6 that the left integration is being selected, the lane keep ECU 3 determines whether or not the right offset with respect to the lane center is larger than the absolute value of the offset threshold 1 (S7). When it is determined in S7 that the absolute value of the offset threshold value 1 is larger than the absolute value, the lane keep ECU 3 switches from the left integration to the right integration (S8). This switching is performed mainly in the case of a straight line with a small offset threshold value 1.

On the other hand, if it is determined in S7 that the absolute value of the offset threshold 1 is not more than the value, the lane keep ECU 3 determines whether or not the integral value of the left integral is 0 (S9). When it is determined in S9 that the integral value of the left integral is 0, the lane keep ECU 3 determines whether or not the right offset is larger than the absolute value of the offset threshold 2 (S10). In this case, although the left integration is selected, the left integration value is 0, so it is estimated that the left integration is selected regardless of the right curve. Therefore, it is determined whether the right offset is greater than the absolute value of the offset D ₁ is smaller than the offset threshold 2. If it is determined in S10 that the absolute value of the offset threshold value 2 is larger, the lane keep ECU 3 switches from left integration to right integration (S11). This switching is performed when left integration is selected for the right curve. If it is determined in S9 that the integration value of the left integration is not 0, or if it is determined in S10 that it is equal to or less than the absolute value of the offset threshold 2, the lane keep ECU 3 continues to select the left integration.

  When it is determined in S6 that the right integration is being selected, the lane keep ECU 3 determines whether or not the left offset relative to the lane center is larger than the absolute value of the offset threshold 1 (S12). If it is determined in S12 that the absolute value of the offset threshold value 1 is larger, the lane keep ECU 3 switches from right integration to left integration (S13). This switching is performed mainly in the case of a straight line with a small offset threshold value 1.

On the other hand, if it is determined in S12 that the absolute value of the offset threshold value 1 or less, the lane keep ECU 3 determines whether or not the integration value of the right integration is 0 (S14). If it is determined in S14 that the right integration value is 0, the lane keep ECU 3 determines whether the left offset is larger than the absolute value of the offset threshold 2 (S15). In this case, since the right integration value is 0 even though the right integration is selected, it is estimated that the right integration is selected regardless of the left curve. Therefore, it is determined whether the left offset is greater than the absolute value of the offset D ₁ is smaller than the offset threshold 2. If it is determined in S15 that the offset threshold value is greater than 2, the lane keep ECU 3 switches from right integration to left integration (S16). This switching is performed when right integration is selected for the left curve. If it is determined in S14 that the integration value of the right integration is not 0, or if it is determined in S15 that it is equal to or less than the absolute value of the offset threshold 2, the lane keep ECU 3 continues to select the right integration.

  The lane keep ECU 3 multiplies the curve curvature γ, the yaw angle θ, the offset D, and the selected integral value by the gains G1, G2, G3, and G4, respectively, and calculates the target steering torque based on each multiplication value. Set. The lane keep ECU 3 transmits a steering torque signal TS indicating the set target steering torque to the EPS ECU 10a.

  The EPS ECU 10a receives the steering torque signal TS, and multiplies the target steering torque indicated by the steering torque signal TS by a predetermined coefficient. Then, the EPS ECU 10a adds the multiplication value (additional torque) to the assist torque, and drives and controls the EPS motor 10b according to the assist torque + addition torque. The EPS motor 10b generates a predetermined torque under the control of the ECPECU 10a, and adds the torque to the steering mechanism. Then, an assist torque corresponding to the steering torque by the driver is applied to the steering mechanism, and an auxiliary additional torque for causing the vehicle to travel along the vehicle center is applied.

  According to this lane keeping device 1, by switching the value of the offset threshold value 1 between the straight line and the curve, the straight line can be switched to the integral on the appropriate side according to the vehicle offset, and the integral switching is switched on the curve. Suppress. Therefore, it is possible to add a steering torque in an appropriate direction according to the crossing gradient in the straight line, and to continue adding a steering torque in a certain direction according to the crossing gradient in the curve. Furthermore, the vehicle behavior can be stabilized during the curve, and the fluctuation of the steering reaction force against the driver can be suppressed.

  Further, according to the lane keeping device 1, even when the integral is erroneously selected in the curve and the offset is equal to or smaller than the absolute value of the offset threshold 1, it is determined whether the integral value is 0 or not, so that the cross slope can be obtained even in the curve. It is possible to switch to an appropriate integration according to. Further, the lane keeping device 1 can perform the switching with high accuracy in consideration of the vehicle position by performing the determination based on the offset threshold 2 smaller than the offset threshold 1. Therefore, it is possible to apply a steering torque so that the vehicle does not greatly deviate from the center of the lane during the curve, and the vehicle follows the center of the lane.

  Thus, according to the lane keeping device 1, it is possible to apply an appropriate steering torque according to the crossing gradient, and it is possible to improve the accuracy of traveling the vehicle along the lane center.

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

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

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

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

  Further, in the present embodiment, the determination of whether it is a straight line or a curve is made based on the curve radius, but other means may be used for determining the road shape, for example, a road that is running from a car navigation system It is also possible to acquire information on the road shape and determine from the information.

  In this embodiment, the curve radius is determined to be a straight line or a curve, and a two-stage offset threshold is set. However, the offset threshold is set in a plurality of stages according to the radius (curvature) of the curve. Alternatively, a larger offset threshold may be set stepwise as the curve radius decreases. By setting in this way, more accurate control according to the curve radius can be performed.

Further, in the present embodiment, the offset D ₁ larger than the offset D ₀ is set as the offset threshold 1 in the curve so that the switching between the right integration and the left integration is difficult to be performed in the curve. However, in the curve, the offset threshold 1 is set. Infinite may be set as, and the curve may not be switched between right integration and left integration.

In the present embodiment, two offsets D ₀ and D ₁ are used, and in the straight line, the right integration and the left integration are switched by the offset D _{0 in the} straight line, and in the curve, the right integration and the left integration are switched by the offset D ₁ . By switching the offset threshold value between the straight line and the curve, it is difficult to switch the right integration and the left integration in the curve compared to the straight line, so that the variation in the travel position of the vehicle during the curve travel can be suppressed small. As another method for making it difficult to switch between right integration and left integration in a curve as compared with a straight line, the switching condition may be changed using only one offset threshold value instead of changing the offset threshold value. For example, the time when the vehicle offset exceeds the absolute value of the offset threshold 1 is measured, the right integration and the left integration are switched by comparing the measurement time with the time threshold 1 in the straight line, and the measurement time and the time threshold 2 (> in the curve) The right integration and the left integration may be switched by comparison with the time threshold 1), or the number of times that the vehicle offset exceeds the absolute value of the offset threshold 1 is counted. The right integration and the left integration may be switched by comparing with the left and the right integration and the left integration may be switched by comparing the number of counts with the number threshold 2 (> threshold 1). In this way, by using one offset threshold value and switching the threshold value such as the time and number of times exceeding the absolute value of the offset threshold value between the curve and the straight line, it is more difficult for the curve to switch between the right integration and the left integration than the straight line. Therefore, it is possible to suppress the fluctuation of the traveling position of the vehicle during the curve traveling.

  Further, in the present embodiment, there is provided both a control for switching the value of the offset threshold 1 depending on whether or not it is a curve and a control for switching to the other-side integration when the one-side integration value becomes 0 as a countermeasure against erroneous selection. However, it may be configured to have only one of the controls.

  Further, in the present embodiment, as a countermeasure for erroneous selection, the determination is made based on the offset threshold 2 when the integrated value becomes 0. However, when the determination of the offset threshold 2 is eliminated and the integrated value becomes 0, It is good also as a structure which switches integration.

It is a block diagram of the lane keeping apparatus which concerns on this Embodiment. It is a control block diagram of the lane keeping device according to the present embodiment. It is explanatory drawing of the switching process of the value of the offset threshold value 1, (a) is a straight line, (b) is a curve. It is explanatory drawing of the correction process of the mistaken integration. It is a flowchart which shows the flow of the integral switching process in lane keep ECU of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Lane keeping device, 2 ... White line recognition sensor, 2a ... Camera, 2b ... White line recognition ECU, 3 ... Lane keep ECU, 10 ... Electric power steering device, 10a ... EPSECU, 10b ... EPS motor

Claims (4)

In a steering apparatus that images a travel path by an imaging unit and applies a steering torque to a steering mechanism so that the vehicle travels along a predetermined position of the travel path.
A first integrating means for integrating a deviation of the vehicle position with respect to a predetermined position on the travel path and obtaining an integral value of the right side with respect to the predetermined position on the travel path;
A second integrating means for integrating the deviation of the vehicle position with respect to the predetermined position of the travel path and obtaining an integral value of the left side with respect to the predetermined position of the travel path;
Switching means for switching between the first integrating means and the second integrating means based on a deviation of the vehicle position with respect to a predetermined position on the traveling path and a predetermined distance from the predetermined position on the traveling path;
Steering torque setting means for setting a steering torque to be applied to the steering mechanism based on the integration value of the integration means switched by the switching means;
A steering apparatus characterized in that the switching between the first integrating means and the second integrating means is less likely to be performed when the curvature of the traveling road is large than when the curvature of the traveling road is small.   The steering apparatus according to claim 1, wherein a predetermined distance from a predetermined position on the travel path is determined based on a curvature of the travel path.   The steering apparatus according to claim 1 or 2, wherein a predetermined distance from a predetermined position on the travel path is increased as the curvature of the travel path increases. In a steering apparatus that images a travel path by an imaging unit and applies a steering torque to a steering mechanism so that the vehicle travels along a predetermined position of the travel path.
A first integrating means for integrating a deviation of the vehicle position with respect to a predetermined position on the travel path and obtaining an integral value of the right side with respect to the predetermined position on the travel path;
A second integrating means for integrating the deviation of the vehicle position with respect to the predetermined position of the travel path and obtaining an integral value of the left side with respect to the predetermined position of the travel path;
Switching means for switching between the first integrating means and the second integrating means based on a deviation of the vehicle position with respect to a predetermined position on the traveling path and a predetermined distance from the predetermined position on the traveling path;
Steering torque setting means for setting a steering torque to be applied to the steering mechanism based on the integration value of the integration means switched by the switching means;
In the state where the switching means is switched to one of the first integrating means or the second integrating means, the switching means is for a predetermined position on the travel path on the other side of the switched one integrating means. When the deviation of the vehicle position is equal to or smaller than the absolute value of the predetermined distance from the predetermined position on the travel path, the switching is switched to the other integrating means when the integrated value of one of the switched integrating means is 0 or near zero. Steering device.

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