Patent Description:
In recent years, automated driving has been actively studied, and its actual use has been desired (for example, refer to Patent Literature <NUM>). To achieve automated driving, it is imperative to grasp the surrounding environment of the vehicle with high accuracy, such as a road structure. The road structure and so forth can be acquired from map data in which data about the shape of the road, the lane width, the shape of a road shoulder, and so forth are made into detail.

<CIT> discloses a sensing device for detecting a vehicle's skid, an attitude and a speed with lane markers. The sensing device allows sensors mounted on the vehicle to detect lane markers arranged on the lane center along a road. The lane markers are detected in a magnetic, electric, or optical manner. Based on outputs of the sensors, a movement of the vehicle is measured. Two sensors each are provided on front and rear of the vehicle. Four outputs from the respective sensors are calculated based on given equations so that a skid amount of the vehicle from the lane center, the attitude and the speed of the vehicle can be found.

<CIT> discloses a method for determining a position deviation of an object with respect to a magnetic marker. The method senses at least two axial field strength components of the magnetic field emitted from the magnetic marker with each of at least two magnetic field sensors mounted on the object. For each axial direction, the method computes a difference in the axial field strength components sensed by the two sensors. The method then determines the position deviation of the object from the magnetic marker as a function of the two differences. The method can be used by an intelligent lateral control system to provide lateral deviation of a mobile object, such as a vehicle, from a desired path, and the intelligent lateral control determines and applies the desired steering control to the mobile object so as to guide it along a desired path automatically.

<CIT> discloses an automatically driven motor vehicle that is controlled to travel automatically along a predetermined running path on a road while successively detecting magnetic sources positioned along the running path with a sensor on the motor vehicle. A position of the motor vehicle on the running path is recognized based on detection of the magnetic sources with the magnetic sensor while the motor vehicle is running along the running path. A present position of the motor vehicle on the running path is estimated based on map information of the running path, which is stored on the motor vehicle, and positional information of the motor vehicle produced upon the detection of the magnetic sources before the sensor becomes unable to detect the magnetic sources, when the motor vehicle deviates from the running path and the sensor is unable to detect the magnetic sources. A steering control quantity for the motor vehicle is corrected based on a positional relationship between the present position and the running path, for thereby automatically returning the motor vehicle to the running path.

<CIT> discloses a position deviation detection device comprising magnetic sensors respectively disposed in front part and rear part center positions of an automated guided vehicle, having the large number of the magnetic detection elements in a right-and-left direction perpendicular to a direction of the travel route, two magnetic markers parallel along the travel route, respectively disposed front and rear positions capable of being simultaneously detected by both magnetic sensors of the automated guided vehicle along the travel route, and a controller calculating the lateral displacement amount between the travel route and the center position of the front magnetic sensor, and the lateral displacement amount between the travel route and the center position of the rear magnetic sensor by detection data of the two magnetic markers respectively detected by the magnetic detection elements of the front and rear magnetic sensors.

<CIT> discloses a vehicular steering control device, which executes steering control to run a vehicle along a course set on a road, provided with a travelling position detection means for detecting the travelling position, a location detection means for detecting the locations on the course, a course estimation means for estimating a course for the vehicle to travel on the basis of a plurality of course points detected by the location detection means, and a steering control amount calculation means for calculating a steering control amount, which is estimated on the basis of the travelling position detected by the travelling position detection means and of the course estimated by the estimation means, for the vehicle to travel along the estimated course. The device executes a steering control of the vehicle by using the steering control amount obtained by the steering control amount calculation means.

However, there is a problem in which, for example, a direction of a course to be traveled cannot be determined with high accuracy unless the traveling direction of the vehicle can be accurately grasped even if the surrounding environment of the own vehicle such as the road structure can be grasped.

The present invention was made in view of the conventional problem described above, and is to provide a vehicular system and course estimation method for estimating a traveling direction of a vehicle, for example, whether the vehicle is traveling along or crossing a traveling road.

The present invention provides a vehicular system according to claim <NUM>, and a course estimation method according to claim <NUM>. Further embodiments of the present invention are disclosed in the dependent claims.

One aspect of the present invention resides in a vehicular system according to claim <NUM>.

One aspect of the present invention resides in a course estimation method according to claim <NUM>.

The vehicular system of the one aspect measures the lateral shift amount with respect to each of the two magnetic markers and, by using a difference therebetween, estimates a deviation in the traveling direction of the vehicle with respect to the line segment direction connecting the positions of the two magnetic markers. The line segment direction is a direction defined by the two magnetic markers, and can serve as a reference direction. By identifying the deviation with respect to this line segment direction, the traveling direction of the vehicle can be estimated with high accuracy.

Also, according to the course estimation method of the one aspect, with the use of two magnetic markers disposed along the route direction of the traveling road, a deviation in the traveling direction of the vehicle with respect to the route direction can be estimated.

In the vehicular system of the present invention, it is preferable that the lateral shift amount measurement parts are arranged at at least two positions separated in a longitudinal direction of the vehicle with a space equal to the space between the two magnetic markers, and
the course estimation part estimates the deviation in the traveling direction by using a difference between a lateral shift amount measured by a front-side lateral shift amount measurement part of two lateral shift amount measurement parts separated with the space equal to the space between the two magnetic markers with one magnetic marker positioned on a vehicle forwarding side of the two magnetic markers and a lateral shift amount measured by a rear-side lateral shift amount measurement part with another magnetic marker.

By using a difference between the lateral shift amounts measured with each of the two magnetic markers with the space equal to the space between the two lateral shift amount measurement parts, a deviation of the vehicle in the traveling direction with respect to the line segment direction connecting the positions of the two magnetic markers can be estimated with high accuracy.

In the vehicular system of the present invention, the two magnetic markers are preferably disposed along a route direction of a traveling road where the vehicle travels.

In this case, the line segment direction connecting the positions of the two magnetic markers coincides with the route direction of the traveling road, and thus a deviation of the vehicle in the traveling direction with respect to the route direction of the traveling road can be estimated.

The course estimation part preferably changes the space between the two magnetic markers for use in estimation of the deviation in accordance with a vehicle velocity.

In a low vehicle velocity zone, the steering angle of the steering wheel of the vehicle is large, and the traveling direction of the vehicle changes at a relatively short distance. On the other hand, in a high vehicle velocity zone, the steering angle is small, and there is a tendency to require a relatively long distance for the traveling direction of the vehicle to change. Therefore, a distance in which the traveling direction of the vehicle is regarded as constant tends to be shorter as the vehicle velocity is lower, and tends to be longer as the vehicle velocity is higher.

Therefore, the space between two magnetic markers for use in estimating the deviation is preferably longer as the velocity of the vehicle is higher and is shorter as the velocity of the vehicle is lower. For example, the space with which the magnetic markers are arranged may be varied between an expressway in a high vehicle velocity zone and an urban road in a low vehicle velocity zone. Alternatively, the magnetic markers may be arranged with a relatively short space that can correspond to a low vehicle velocity and a combination (space) of the two magnetic markers may be changed in accordance with the vehicle velocity.

The magnetic markers may be disposed along a lane that is a region of the vehicle to travel, and
the system may include a prediction part that predicts at least one of a time and a distance until the vehicle departs from the lane by using the lateral shift amount, the deviation, and the vehicle velocity and a warning device which issues warning in accordance with the time or distance predicted by the prediction part.

By using the deviation, a time or a distance until the vehicle departs from the lane can be predicted with high accuracy. Using this time or distance allows departure warning with high accuracy. Furthermore, a combination of the lateral shift amount and the deviation allows departure warning with higher accuracy.

The magnetic markers may be disposed along a lane that is a region of the vehicle to travel, and
the system may include a road structure estimation part that estimates a three-dimensional road structure with reference to the own vehicle by using the lateral shift amount and the deviation.

For example, when the traveling direction of the vehicle coincides with the direction of the lane and the deviation is almost zero, the possibility of the vehicle traveling along the lane is high. In this case, for example, it can be estimated that the course of the vehicle predicted from the steering angle of the vehicle coincides with the lane. With reference to this lane, a road side where guardrails, signs, and so forth are present and a road structure such as an opposing lane can be estimated.

The course estimation part may acquire information that can identify a deviation in the line segment direction with respect to a route direction of the traveling road where the vehicle travels, and may estimate the deviation of the vehicle in the traveling direction with respect to the route direction of the traveling road based on a deviation in the line segment direction with respect to the route direction identified by using this information and a deviation in the traveling direction of the vehicle with respect to the line segment direction.

If there is an error at the position of the magnetic marker, there is a possibility of increasing the deviation in the line segment direction with reference to the route direction of the traveling road, and it is difficult to determine whether the vehicle is traveling along the traveling road based on the deviation of the vehicle in the traveling direction with respect to the line segment direction. If the deviation in the line segment direction with respect to the route direction can be identified on a vehicle side, the deviation of the vehicle in the traveling direction with respect to the route direction of the traveling road can be estimated with high accuracy irrespective of a positional error of the magnetic marker.

The system may identify an absolute position of the vehicle at a time point when the deviation in the traveling direction of the vehicle is estimated by acquiring an absolute position of the magnetic marker.

Embodiments of the present invention are specifically described by using the following examples.

The present example is an example regarding a vehicular system <NUM> for estimating a traveling direction of a vehicle <NUM> by using magnetic markers <NUM> laid in a road. Details about this are described by using <FIG>.

The vehicular system <NUM> is configured to include, as in <FIG>, a combination of a sensor unit <NUM> including magnetic sensors Cn (n is an integer from <NUM> to <NUM>) and a control unit <NUM>. In the following, after the magnetic markers <NUM> are generally described, the sensor unit <NUM>, the control unit <NUM>, and so forth configuring the vehicular system <NUM> are described.

The magnetic markers <NUM> are, as in <FIG> and <FIG>, road markers laid in a road surface <NUM> of a lane <NUM> as a traveling road for the vehicle <NUM>. The magnetic markers <NUM> are arranged every <NUM> (marker span S=<NUM>) along the center of the lane <NUM> in a vehicle width direction. Note that the present example assumes that the lane <NUM> of a road in a relatively high speed zone such as an expressway.

The magnetic marker <NUM> is formed in a columnar shape having a diameter of <NUM> and a height of <NUM>, and can be accommodated in a hole provided to the road surface <NUM>. A magnet forming the magnetic marker <NUM> is an isotropic ferrite plastic magnet formed by dispersing a magnetic powder of iron oxide as a magnetic material in a polymer material as a base material, and has a characteristic of a maximum energy product (BHmax) =<NUM>. <NUM> kJ/m<NUM>. This magnetic marker <NUM> is laid in a state of being accommodated in the hole bored in the road surface <NUM>.

Specifications of the magnetic marker <NUM> of the present example are partially described in Table <NUM>.

This magnetic marker <NUM> can act with magnetism having a magnetic flux density of <NUM>µT (<NUM>×<NUM>-<NUM> T, T: tesla) at a height of <NUM>, which is an upper limit of a range from <NUM> to <NUM>, assumed as an attachment height of the magnetic sensors Cn.

Next, the sensor unit <NUM> and the control unit <NUM> configuring the vehicular system <NUM> are described.

The sensor unit <NUM> is a unit attached to a vehicle body floor <NUM> corresponding to a bottom surface of the vehicle <NUM>, as depicted in <FIG>. The sensor unit <NUM> is attached, for example, near the inside of a front bumper. For example, in the case of the vehicle <NUM> of a sedan type, the attachment height with reference to the road surface <NUM> is approximately <NUM>.

The sensor unit <NUM> includes, as in <FIG>, fifteen magnetic sensors Cn arrayed on a straight line along a vehicle width direction and a detection processing circuit <NUM> having a CPU not depicted and so forth incorporated therein.

The detection processing circuit <NUM> is an arithmetic circuit which performs various computation processes such as a marker detection process for detecting the magnetic marker <NUM>. This detection processing circuit <NUM> is configured of a CPU (central processing unit) which performs various computations, and also by using elements such as memory elements including a ROM (read only memory) and a RAM (random access memory).

The detection processing circuit <NUM> performs marker detection process and so forth by acquiring a sensor signal outputted from each magnetic sensor Cn. The results of detection of the magnetic marker <NUM> computed by the detection processing circuit <NUM> including a measured lateral shift amount are all inputted to the control unit <NUM>. Note that the sensor unit <NUM> can perform marker detection process in a period of <NUM>.

Here, the configuration of the magnetic sensor Cn is described. In the present example, as in <FIG>, a one-chip MI sensor having an MI element <NUM> and a driving circuit integrated therein is adopted as the magnetic sensor Cn. The MI element <NUM> is an element including an amorphous wire <NUM> made of a CoFeSiB-based alloy with approximately zero magnetostriction and a pickup coil <NUM> wound around this amorphous wire <NUM>. The magnetic sensor Cn detects magnetism acting on the amorphous wire <NUM> by measuring a voltage occurring at the pickup coil <NUM> when a pulse current is applied to the amorphous wire <NUM>. The MI element <NUM> has detection sensitivity in an axial direction of the amorphous wire <NUM> as a magneto-sensitive body. In each magnetic sensor Cn of the sensor unit <NUM> of the present example, the amorphous wire <NUM> is disposed along a vertical direction.

The driving circuit is an electronic circuit including a pulse circuit <NUM> which supplies a pulse current to the amorphous wire <NUM> and a signal processing circuit <NUM> which samples and outputs a voltage occurring at the pickup coil <NUM> at a predetermined timing. The pulse circuit <NUM> is a circuit including a pulse generator <NUM> that generates a pulse signal which is a base signal of a pulse current. The signal processing circuit <NUM> is a circuit which takes out an induced voltage of the pickup coil <NUM> via a synchronous detection <NUM> which is opened and closed in conjunction with a pulse signal, and amplifies the voltage by an amplifier <NUM> at a predetermined amplification factor. A signal amplified by this signal processing circuit <NUM> is externally outputted as a sensor signal.

The magnetic sensor Cn is a high-sensitivity sensor having a measurement range of a magnetic flux density of ±<NUM> mT and a magnetic flux resolution of <NUM>µT within the measurement range. This high sensitivity is achieved by the MI element <NUM> using the MI effect in which the impedance of the amorphous wire <NUM> sensitively changes in accordance with the external magnetic field. Furthermore, this magnetic sensor Cn can perform high-speed sampling in a period of <NUM> and supports high-speed vehicle traveling. In the present example, the period of magnetic measurement by the sensor unit <NUM> is set at <NUM>. The sensor unit <NUM> inputs the detection result to the control unit <NUM> every time magnetic measurement is performed.

Specifications of the magnetic sensor Cn are partially described in Table <NUM>.

As described above, the magnetic marker <NUM> can act with magnetism having a magnetic flux density equal to or larger than <NUM>µT (<NUM>×<NUM>-<NUM> T) in a range of <NUM> to <NUM> assumed as an attachment height of the magnetic sensors Cn. The magnetic marker <NUM> acting with magnetism having a magnetic flux density equal to or larger than <NUM>µT is detectable with high reliability by using the magnetic sensor Cn having a magnetic flux resolution of <NUM>µT.

Next, the control unit <NUM> (<FIG>) is a unit which controls the sensor unit <NUM> and estimates a traveling direction of the vehicle <NUM> by using the detection result of the sensor unit <NUM>. The estimation result of the traveling direction of the vehicle <NUM> by the control unit <NUM> is inputted to a vehicle ECU not depicted, and is used for various vehicle controls for enhancing traveling safety, such as throttle control, brake control, and torque control of each wheel.

The control unit <NUM> includes an electronic board (omitted in the drawings) having implemented thereon memory elements such as a ROM and RAM, and so forth, in addition to a CPU which performs various computations. The control unit <NUM> controls the operation of the sensor unit <NUM> and estimates the traveling direction of the vehicle <NUM> by using a change of a lateral shift amount of the vehicle <NUM> with respect to the magnetic markers <NUM> laid along the lane <NUM>.

The control unit <NUM> includes each of the following functions.

Next, description is made to each of the following: (<NUM>) a marker detection process for each sensor unit <NUM> to detect the magnetic marker <NUM>, (<NUM>) a flow of entire operation of the vehicular system <NUM>, and (<NUM>) a course estimation process.

The sensor unit <NUM> performs marker detection process in a period of <NUM> by the control of the control unit <NUM>. The sensor unit <NUM> performs sampling on magnetic measurement values indicated by sensor signals from fifteen magnetic sensors Cn for each of periods (p1 to p7) of performing a marker detection process to acquire a magnetic distribution in the vehicle width direction (refer to <FIG>). A peak value of this magnetic distribution in the vehicle width direction becomes maximum at a timing of passage over the magnetic marker <NUM> as depicted in the drawing (in the period of p4 in <FIG>).

When the vehicle <NUM> travels along the lane <NUM> (<FIG>) where the magnetic markers <NUM> are laid, the peak value of the magnetic distribution in the vehicle width direction described above increases every time the vehicle passes over the magnetic marker <NUM> as in <FIG>. In the marker detection process, a threshold determination regarding this peak value is performed, and it is determined that the magnetic marker <NUM> has been detected when the peak value is equal to or larger than a predetermined threshold value.

When detecting the magnetic marker <NUM>, the sensor unit (lateral shift amount measurement part) <NUM> identifies the position of the peak value in the vehicle width direction of the magnetic distribution in the vehicle width direction, which is a distribution of magnetic measurement values of the magnetic sensors Cn. By using the position of this peak value in the vehicle width direction, a lateral shift amount of the vehicle <NUM> with respect to the magnetic marker <NUM> can be computed. In the vehicle <NUM>, the sensor unit <NUM> is attached so that the central magnetic sensor C8 is positioned on the center line of the vehicle <NUM>. Thus, a deviation in the position of the above-described peak value in the vehicle width direction with respect to the magnetic sensor C8 indicates the lateral shift amount of the vehicle <NUM> with respect to the magnetic marker <NUM>. Note that positives and negatives of the lateral shift amounts are preferably different depending on which of left and right sides the peak value is positioned with respect to the position of the magnetic sensor C8.

In particular, as in <FIG>, the sensor unit <NUM> of the present example performs curve approximation (quadratic approximation) on the magnetic distribution in the vehicle width direction, which is a distribution of magnetic measurement values of the magnetic sensors Cn, to identify the position of the peak value of an approximation curve in the vehicle width direction. Using the approximation curve can identify the position of the peak value with accuracy finer than a space between the fifteen magnetic sensors, and can measure the lateral shift amount of the vehicle <NUM> with respect to the magnetic marker <NUM> with high accuracy.

The entire operation of the vehicular system <NUM> is described by using a flow diagram of <FIG>, with the control unit <NUM> mainly as a subject.

The control unit <NUM> causes the sensor unit <NUM> to repeatedly perform the marker detection process described above until any magnetic marker <NUM> is detected (S101, a first detection step→S102: NO). When receiving from the sensor unit <NUM> an input indicating that the magnetic marker <NUM> has been detected (S102: YES), the control unit <NUM> sets a detection duration, which is a temporal duration in which the sensor unit <NUM> is caused to perform a new marker detection process (S103, a duration setting step).

Specifically, as in <FIG>, the control unit <NUM> first adds a required time δta acquired by dividing the marker span S (refer to <FIG>, a laying space between the magnetic markers <NUM>, <NUM> in the present example) by a vehicle velocity (velocity of the vehicle) V (m/second) measured by a vehicle velocity sensor to a time t1, which is a time point of detection of the first magnetic marker <NUM> by the sensor unit <NUM>. With this addition of the required time δta to the time t1, it is possible to predict a time t2 as a time point when the sensor unit <NUM> can detect the new magnetic marker <NUM>. The control unit <NUM> then sets, as a detection duration, a temporal section having a time (t2-δtb) acquired by subtracting a section time δtb acquired by dividing a reference distance (for example, <NUM> (m)) by the vehicle velocity V (m/second) from a time t2 as a start time and a time (t2+δtb) acquired by adding the section time δtb to the time t2 as an end time. Note that the reference distance can be changed as appropriate in consideration of the detection range and so forth of the sensor unit <NUM>.

The control unit <NUM> causes the sensor unit <NUM> to repeatedly perform the marker detection process in the detection duration (<FIG>) set at the above-described step S103 (S104: NO→S114, a second detection step). Details about this marker detection process is the same as the marker detection process for the first magnetic marker <NUM> at step S101.

If the sensor unit <NUM> was able to detect the second magnetic marker <NUM> in the detection duration (<FIG>) (S104: YES→S105: YES), the control unit <NUM> performs (<NUM>) a course estimation process for estimating the traveling direction of the vehicle <NUM> (S106). On the other hand, if the sensor unit <NUM> was able to detect the first magnetic marker <NUM> (S102: YES) but was not able to detect the second magnetic marker <NUM> in the above-described detection duration (<FIG>) (S104: YES→S105: NO), the control unit <NUM> returns to the marker detection process (S101) for detecting the first magnetic marker <NUM> to repeatedly perform the above-described series of processes.

The course estimation process (step S106 in <FIG>) to be performed by the control unit <NUM> is a process including, as in <FIG>, a step of computing a difference between lateral shift amounts measured by the sensor unit <NUM> when passing over two magnetic markers <NUM> (S201) and a step of computing a course deviation angle Rf, which is a deviation in a traveling direction with respect to a line segment direction connecting the positions of the two magnetic markers <NUM> (S202). The two magnetic markers <NUM> are laid at the center of the lane <NUM> so as to be along the lane direction, which is a route direction of the lane <NUM>, and thus the above-described line segment direction represents a lane direction.

At step S201, as in <FIG>, when the vehicle <NUM> passes over the magnetic markers <NUM> twice, a difference Ofd between a lateral shift amount Of1 measured with the first magnetic marker <NUM> and a lateral shift amount Of2 measured with the second magnetic marker <NUM> is computed by the following equation. Note that in the case of the drawing, positives and negatives are different between Of1 and Of2, and thus the absolute value of Ofd is a value acquired by adding absolute values of Of1 and Of2 together, in accordance with the difference.

At step S202, as in <FIG>, the course deviation angle Rf (deviation of an angle in a turning direction) is computed, which is a formed angle between a traveling direction Dir of the vehicle <NUM> and a line segment direction Mx (coinciding with the lane direction) connecting the positions of the two magnetic markers <NUM>. This course deviation angle Rf is calculated by the following equation including the difference Ofd between the lateral shift amounts and the marker span S.

For example, when the vehicle <NUM> is traveling along the lane (<FIG>), the course deviation angle Rf, which is a formed angle between the traveling direction Dir of the vehicle <NUM> and the line segment direction Mx connecting the positions of the two magnetic markers, becomes zero. On the other hand, when the vehicle diagonally travels the lane (<FIG>), the traveling direction Dir of the vehicle <NUM> with respect to the line segment direction Mx is shifted to increase the course deviation angle Rf. Also, when the vehicle <NUM> is traveling along a curved road (<FIG>), the line segment direction Mx connecting the positions of the two magnetic markers coincides with a tangent direction of the lane as the curved road, and the course deviation angle Rf, which is a "formed angle" between the traveling direction Dir of the vehicle <NUM> and the line segment direction Mx, becomes zero. On the other hand, when the vehicle diagonally travels the lane as a curved road (<FIG>), a shift of the vehicle <NUM> in the traveling direction Dir with respect to the tangent direction of the lane as the curved road is increased and the course deviation angle Rf becomes larger.

As described above, the vehicular system <NUM> of the present example estimates the traveling direction of the vehicle <NUM> by using a difference between the lateral shift amounts with respect to two magnetic markers <NUM>. The course deviation angle Rf, which is a traveling direction of the vehicle <NUM> to be estimated by this vehicular system <NUM> is not an absolute azimuth but is a "formed angle" with respect to the line segment direction Mx connecting the positions of the two magnetic markers <NUM>. The line segment direction Mx is a direction that can serve as a reference defined by two magnetic markers <NUM> fixed in the road surface <NUM>, and thus an angular deviation in the traveling direction of the vehicle with respect to this line segment direction Mx can serve as an index indicating the traveling direction of the vehicle <NUM> with high accuracy.

In the vehicular system <NUM>, the difference Ofd between the lateral shift amounts with respect to the two magnetic markers <NUM> is used to obtain the computed course deviation angle Rf as a deviation. In place of or in addition to this, a distance shift amount in a lateral direction with respect to the above-described line segment direction Mx predicted when the vehicle travels a predetermined distance, for example, <NUM> ahead or <NUM> ahead, may be obtained as a deviation.

Note that in the present example, the latest two adjacent magnetic markers <NUM> among the magnetic markers <NUM> laid every <NUM> are used to estimate the traveling direction Dir of the vehicle <NUM>. For example, a distance traveled per second by the vehicle at a velocity of <NUM> per hour is <NUM>, and thus a passage time for <NUM> is <NUM> seconds, which is less than <NUM> seconds. In consideration of a reaction time of steering operation, the passage time may be <NUM> to <NUM> seconds. In this case, the traveling direction Dir may be estimated by using a combination of two adjacent magnetic markers <NUM> with a space of <NUM> with one magnetic marker interposed therebetween or with a space of <NUM> with two magnetic markers interposed therebetween. For example, as for the magnetic markers <NUM> arranged with a relatively dense space, such as a space of <NUM> or a space of <NUM>, a combination of two magnetic markers <NUM> with a wider space may be used as the velocity is higher, and a combination of two magnetic markers <NUM> with a narrower space may be used as the velocity is lower. Alternatively, the space between the magnetic markers <NUM> may be set to be relatively wide on a road such as an expressway, and the space between the magnetic markers <NUM> may be set to be relatively narrow on an ordinary road. Furthermore, in the present example, the magnetic markers <NUM> are arranged at a space of <NUM>, and estimation of the traveling direction can be made for all magnetic markers <NUM>. In place of this, for example, on a road where the magnetic markers <NUM> are arranged at a space of <NUM> to <NUM> for lane departure or automated driving, as for specific magnetic markers <NUM> with two or one magnetic marker interposed therebetween, a magnetic marker <NUM> for estimation of the traveling direction may be additionally arranged adjacently.

In the present example, a detection duration is set in which the first magnetic marker <NUM> is detected and then detection of the second magnetic marker <NUM> is tried. This detection duration is not a necessary configuration, and may be omitted. Alternatively, in case the detection duration is not set, it is preferable to always try the detection of the magnetic marker <NUM>. In this case, reliability determination may be made in a manner such that there is a possibility of erroneous detection if the time point when the second magnetic marker <NUM> is detected is not included in a duration corresponding to the above-described detection duration with reference to the time point of detection of the first magnetic marker <NUM>.

Note that the lateral shift amount Rf may be computed for every two adjacent magnetic markers <NUM> among three or more magnetic markers <NUM> and an average value of the plurality of lateral shift amounts Rf may be calculated. In this manner, a configuration may be adopted in which three or more magnetic markers <NUM> are used in estimating a deviation of the vehicle in the traveling direction.

Note that in the sensor unit <NUM>, common noise acts on each magnetic sensor Cn, which is almost uniform magnetic noise derived from, in addition to geomagnetism, a large-sized magnetism generation source such as, for example, an iron bridge or another vehicle. This common noise has a high possibility of almost uniformly acting on each magnetic sensor Cn of the sensor unit <NUM>. Thus, the magnetic marker <NUM> may be detected by using a differential value between the magnetic measurement values of the respective magnetic sensors Cn arrayed in the vehicle width direction. In this differential value indicating a magnetic gradient in the vehicle width direction, the common noise almost uniformly acting on each magnetic sensor Cn is effectively reduced.

In the present example, while the magnetic sensors Cn having sensitivity in the vertical direction are adopted, magnetic sensors having sensitivity in the traveling direction or magnetic sensors having sensitivity in the vehicle width direction may be adopted. Furthermore, for example, magnetic sensors having sensitivity in two axial directions of the vehicle width direction and the traveling direction, two axial directions of the vehicle width direction and the vertical direction, or two axial directions of the traveling direction and the vertical direction may be adopted. For example, a magnetic sensor having sensitivity in three axial directions of the vehicle width direction, the traveling direction, and the vertical direction may be adopted. Using a magnetic sensor having sensitivity in a plurality of axial directions can measure a magnetism acting direction together with the magnitude of magnetism and can generate magnetic vectors. By using a difference between the magnetic vectors and a change rate of the difference in the traveling direction, a distinction between magnetism of the magnetic markers <NUM> and disturbance magnetism can be made. Note that while the magnetic marker made of a ferrite plastic magnet is exemplarily described in the present example, a magnetic marker made of a ferrite rubber magnet may be adopted.

The present example is an example in which the course deviation angle Rf is computed by using the sensor units <NUM> provided in the front and rear of the vehicle <NUM> based on the vehicular system <NUM> of the first embodiment. Details about this are described with reference to <FIG>.

In the vehicle <NUM>, the sensor units <NUM> are arranged with a space of <NUM> provided therebetween. On the other hand, as with the first embodiment, the magnetic markers <NUM> are arranged with the marker span S=<NUM>. <NUM> as a space between the front and rear sensor units <NUM> coincides with the space of <NUM> (taken as a marker span S1) between two magnetic markers <NUM> with one marker interposed therebetween. According to the sensor units <NUM> arranged with the space of <NUM>, two adjacent magnetic markers <NUM> with one magnetic marker <NUM> interposed therebetween can be detected approximately at the same timing.

As in <FIG>, when a lateral shift amount measured by the front-side sensor unit <NUM> is taken as Of1, a lateral shift amount measured by the rear-side sensor unit <NUM> is taken as Of2, and a difference therebetween is taken as Ofd, a lateral deviation angle Rf can be computed by the following equation.

Note that the sensor unit <NUM> may be additionally arranged at the center between the front and rear sensor unit <NUM> with a space of <NUM>. In this case, with at least either one of a combination of the front-side sensor unit <NUM> and the central sensor unit <NUM> and a combination of the rear-side sensor unit <NUM> and the central sensor unit <NUM>, the magnetic markers <NUM> adjacent with a space of <NUM> can be detected at the same timing to allow measurement of a lateral shift amount. Depending on the velocity, switching may be made between two magnetic markers <NUM> with a space of <NUM> or two magnetic markers <NUM> with a space of <NUM>.

Note that other configurations and operations and effects are the same as to those in the first embodiment.

The present example is an example in which a function of estimating a road structure is added based on the vehicular system <NUM> of the first embodiment. Details about this are described with reference to <FIG>.

The present example is an example in which a two-dimensional road structure is estimated by using a course deviation angle Rf in an image <NUM> taken by an onboard camera installed so that the optical axis matches the center axis of the vehicle <NUM>.

For example, when the vehicle <NUM> travels along a straight road, in the road structure in the taken image <NUM> acquired by the onboard camera, as in <FIG>, a vanishing point Vp where a lane, a road, left and right lane marks, guardrails, and so forth vanish in the distance is positioned at the center of the screen.

On the other hand, when the vehicle <NUM> travels so as to diagonally deviate from the straight road to right, the vanishing point Vp where the lane and so forth vanish is positioned as being shifted to the left side of the screen as in <FIG>. The shift amount of the vanishing point Vp at this time is determined by the ratio of the course deviation angle Rf with respect to the angle of view of the onboard camera. For example, if the ratio of the course deviation angle Rf with respect to the angle of view of the onboard camera in a horizontal direction is <NUM>/<NUM>, the shift amount of the vanishing point Vp is a half of the screen width. For example, if the above-described ratio of the course deviation angle Rf is <NUM>/<NUM> when the position of the vanishing point Vp with the course deviation angle Rf=<NUM> is at the center of the screen as in <FIG>, the vanishing point Vp is shifted from the center by <NUM>/<NUM> of the screen width, and is positioned at an edge of the screen. Also, if the ratio of the course deviation angle Rf with respect to the angle of view of the onboard camera in the horizontal direction is <NUM>/<NUM>, the shift amount of the vanishing point Vp from the center of the screen is <NUM>/<NUM> of the screen width.

As described above, if the traveling direction of the vehicle such as the course deviation angle Rf can be estimated, the position of the vanishing point Vp in the taken image <NUM> can be estimated, and the road structure in the taken image <NUM> can be grasped. If the position of the vanishing point Vp where the lane and so forth vanish is known, the region of the lane, the region on a road side, and so forth in the taken image <NUM> can be estimated. If this region estimation is possible, image recognition can be efficiently performed. For example, if the region of the lane can be estimated, a process for recognizing a lane mark which sections the lane can be efficiently performed, thereby allowing reduction in erroneous detection and an improvement in recognition rate. Also, for example, if the region on the road side can be estimated, a recognition rate of a sign, a signal light, and so forth installed on the road side can be improved.

Also, a three-dimensional road structure may be estimated. For example, when the vehicle <NUM> includes a sensor which measures a steering angle, a course Es of the vehicle <NUM> can be predicted by using the steering angle as in <FIG>. Here, when the course deviation angle Rf is zero, a region A along the predicted course Es can be estimated as a region of a lane. Furthermore, if map information indicating that the road is for two-way traveling with each side having one lane can be acquired from map database or the like, for example, in the case of left-hand traffic, a region B on the right side of the region A can be estimated as a region of a counter traffic, and a region C on the left side of the region A can be estimated as a region on a road side. For example, when an object on the road side such as a sign or guardrail is recognized by image recognition by an onboard camera, an active sensor such as a laser radar, or the like, the process is performed by taking the region C as a main subject, thereby allowing decrease in processing load and an improvement in efficiency. Also, for example, in a system which automatically switches to a low beam when passing an oncoming vehicle, the oncoming vehicle is captured by taking the region B as a main subject, thereby reducing malfunctions beforehand due to light from a street light or the like.

Also, for example, if map information indicating that the road has four lanes with each side having two lanes is acquired from map database or the like and information indicating that the lane being travelled is a center-side lane can be acquired from an infrastructure side, the region C can be estimated as a region of a parallel travel lane. As a method of providing information from the infrastructure side, for example, there is a method of providing information about lanes, with the polarity of the magnetic markers <NUM> being varied for each lane.

The present example is an example in which a function of lane departure warning is added to the vehicular system <NUM> of the first embodiment.

Details about this are described with reference to <FIG>.

<FIG> exemplarily depicts a traveling situation in which the lane width is Wr and the vehicle <NUM> (vehicle width Wc) on the lane <NUM> where the magnetic markers <NUM> are arrayed along the center diagonally travels the lane <NUM> with the velocity V (m/second) and the course deviation angle Rf. Note that the drawing is a drawing of taking a bird's-eye view of a plane where the vehicle <NUM> travels and the horizontal direction in the drawing corresponds to the vehicle width direction and the vertical direction in the drawing corresponds to a forward direction. Also in the drawing, only the second magnetic marker <NUM> is depicted in the drawing, and depiction of the magnetic markers <NUM> including the first one is omitted.

Departure warning when the lateral shift amount measured with the magnetic marker <NUM> which the vehicle passes secondly is Of2 and the course deviation angle estimated at this time is Rf is described. This departure warning is a warning by a control part including functions as a prediction part which predicts a departure time described below and a warning device which issues departure warning.

With reference to the following equations <NUM> to <NUM>, description is made to a procedure of computing a departure time, which is a time until the vehicle <NUM> departs from the lane <NUM> when the vehicle <NUM> is diagonally traveling the lane <NUM> with the course deviation angle Rf.

First, in <FIG>, a distance D1 from the center of the lane <NUM> indicated by a one-dot-chain line to a side end of the vehicle <NUM> can be computed by the following equation.

Then, a distance D2 between a lane boundary (for example, a lane mark) 100E which is located in the forwarding direction of the diagonally traveling vehicle and a side of the vehicle <NUM> is as in the following equation.

On the other hand, of a velocity V (m/second) of the vehicle <NUM>, a velocity component Vx (m/second) in the vehicle width direction is as in the following equation.

Therefore, when the vehicle <NUM> travels at the velocity V (m/second) while keeping the course deviation angle Rf, a time Tr in the following equation required for reaching the boundary 100E of the lane <NUM> may be calculated as a departure time.

By using this departure time Tr, departure warning can be performed with high accuracy. For example, it may be such that no warning is issued if the departure time Tr is equal to or more than <NUM> seconds, moderate warning is issued when the departure time Tr is from <NUM> seconds to <NUM> seconds, and warning for calling attention or emergency warning is issued when the departure time Tr is equal to or less than <NUM> seconds. Note that a threshold of the departure time can be changed as appropriate. An example of moderate warning is a chime sound such as "ding dong". An example of emergency warning is a repeated buzzer sound such as "beep, beep, beep".

Note that in place of the departure time, a departure distance, which is a predicted distance to be traveled until the vehicle departs from the lane, may be computed, and departure warning may be issued in accordance with the magnitude of this departure distance. The departure distance can be calculated by multiplying the departure time Tr by a velocity component in the lane direction (V×cosRf).

The present example is an example in which it is configured that a deviation of the vehicle in the traveling direction with respect to the route direction of the traveling road of the vehicle can be estimated based on the vehicular system of the first embodiment.

The laying positions of the magnetic markers in the traveling road have errors, and the line segment direction connecting the positions of adjacent magnetic markers does not necessarily coincide with the route direction of the traveling road. To enhance accuracy of this coincidence, cost for laying the magnetic markers may be increased. Thus, a technique is desired in which a deviation of the vehicle in the traveling direction with respect to the route direction of the traveling road is estimated with high accuracy while permitting errors in the laying positions of the magnetic markers to some extent.

The vehicular system of the present example is an example in which the above-described technique is achieved by configuring the system so that the system can acquire information that can identify the above-described deviation in the line segment direction with respect to the route direction of the traveling road.

In the first embodiment, the lateral deviation angle Rf indicating a first deviation of the vehicle in the traveling direction with respect to the above-described line segment direction is estimated. In this example, a second deviation in the line segment direction with respect to the route direction of the traveling road is identified and, based on this second deviation and the above-described first deviation, estimation of a third deviation of the vehicle in the traveling direction with respect to the route direction of the traveling road can be performed.

The following configurations are examples of a configuration for identifying a deviation (second deviation) in the line segment direction with respect to the route direction of the traveling road.

Note that in either of the configurations described above, the map database may be stored in a storage medium equipped in the vehicle, or may be stored in a storage medium of a server device connectable via the Internet or the like.

A wireless communication RF-ID tag capable of operating upon reception of external power supply and wirelessly outputting information may be annexed to the magnetic marker, and a reception device which receives information about the above-described shift transmitted from the RF-ID tag may be provided on the vehicle side. Information about the absolute position of the center of the traveling road and information about the absolute position of the magnetic marker may also be transmitted from the RF-ID tag.

Other configurations and operations and effects are the same as to those in the first embodiment.

The present example is an example in which the absolute position of the vehicle when the deviation in the traveling direction of the vehicle is estimated can be identified based on the vehicular system of the first embodiment.

In the vehicular system of the present example, information indicating the absolute positions of the magnetic markers can be acquired from the map database, and the absolute position of the vehicle can be identified from the absolute positions of the detected magnetic markers. The map database may be stored in a storage medium equipped in the vehicle, or may be stored in a storage medium of a server device connectable via the Internet or the like.

If the absolute position of the vehicle can be identified, for example, with reference to the database storing the map information which can identify the route direction of the traveling road, the shape and so forth of the forward traveling road of the vehicle can be grasped. And, by comparing the shape of the forward traveling road and the estimated deviation of the traveling direction of the vehicle, a degree of danger and so forth as to the estimated traveling direction of the vehicle can be estimated. For example, when the vehicle traveling on the right-side lane reaches the position before a left curve and the deviation in the traveling direction of the vehicle is toward the right, it can be estimated that the degree of danger is high.

Claim 1:
A vehicular system (<NUM>) comprising:
a lateral shift amount measurement part (<NUM>) that measures a lateral shift amount, that is a positional deviation of a vehicle (<NUM>) in a vehicle width direction with respect to a magnetic marker (<NUM>);
a course estimation part (<NUM>) that uses a difference between the lateral shift amounts with respect to two magnetic markers (<NUM>) disposed with a space provided therebetween in a road surface where the vehicle travels and estimates a deviation of the vehicle in a traveling direction (Dir) with respect to a line segment direction (Mx) connecting the positions of the two magnetic markers (<NUM>);
a vehicle velocity sensor which measures velocity of the vehicle (<NUM>); and
a unit (<NUM>) which sets, when the lateral shift amount measurement part (<NUM>) detects a first magnetic marker (<NUM>), a temporal duration including a time point of when the lateral shift amount measurement part (<NUM>) is predicted to detect a second magnetic marker (<NUM>) as a detection duration for the lateral shift amount measurement part (<NUM>) to detect the second magnetic marker (<NUM>),
wherein the temporal duration is set based on the space between the magnetic markers (<NUM>) and the velocity of the vehicle (<NUM>), and
wherein the lateral shift amount measurement part (<NUM>) repeatedly performs a marker detection process in the detection duration to detect the second magnetic marker (<NUM>) .