JP6493140B2 - Orientation estimation device - Google Patents

Description

  The present invention relates to an azimuth estimation apparatus that estimates the azimuth of a host vehicle.

  As the above-described azimuth estimation device, one having the following configuration is known. That is, first, an azimuth angle detection accuracy based on a change in the position of the host vehicle based on the satellite information is obtained. And when this azimuth angle detection accuracy is high, this azimuth angle is adopted as the azimuth angle of the host vehicle, and when this azimuth angle detection accuracy is low, the azimuth angle obtained by the sensor that detects the azimuth angle Is adopted as the azimuth angle of the host vehicle (see, for example, Patent Document 1).

JP 2012-098185 A

  By the way, in said azimuth | direction estimation apparatus, there exists a request | requirement about detecting the azimuth | direction of the own vehicle with high precision in consideration of vehicle motion and vehicle environment. Therefore, an object of the present invention is to make it possible to detect the azimuth of the host vehicle with higher accuracy in an azimuth estimation apparatus that estimates the azimuth of the host vehicle.

  In the azimuth angle estimation device according to one aspect of the present invention, the absolute azimuth obtaining unit obtains an absolute azimuth representing the absolute azimuth of the own vehicle based on a change in the position of the own vehicle, and the relative azimuth obtaining unit is configured to A relative bearing representing a relative bearing of the host vehicle based on the yaw rate integration is acquired. Then, the frequency characteristic acquisition unit acquires the frequency characteristic regarding the turning of the host vehicle, and the adoption setting unit employs at least one of the absolute direction and the relative direction as the direction of the host vehicle according to the frequency characteristic.

  According to such an azimuth estimation device, at least one of the absolute azimuth and the relative azimuth is adopted as the azimuth of the own vehicle according to the frequency characteristics of the turn of the own vehicle that changes according to the vehicle motion and the vehicle environment. Therefore, the direction of the host vehicle can be detected with higher accuracy.

  In addition, description of each claim can be arbitrarily combined as much as possible. At this time, a part of the configuration may be excluded.

It is a block diagram which shows schematic structure of the azimuth angle estimation apparatus 1 to which this invention was applied. It is a flowchart which shows the absolute azimuth angle estimation process which the control part 10 performs. It is a flowchart which shows the relative azimuth angle estimation process which the control part 10 performs. 4 is a flowchart showing an azimuth angle integration process executed by the control unit 10. It is a flowchart which shows the cutoff frequency setting process in an azimuth integration process. It is a graph which shows an example of the relationship between a steering system movement frequency and the response characteristic (PSD of a yaw rate) of a vehicle. It is a graph which shows an example of the relationship between a steering system movement frequency and the characteristic (PSD of a yaw rate) according to the road shape. It is a map which shows an example of the relationship between a steering system movement frequency and the utilization rate of each azimuth. It is a graph which shows the magnitude | size of the error of the azimuth according to a cutoff frequency in a snowy road.

Embodiments according to the present invention will be described below with reference to the drawings.
[Configuration of this embodiment]
An azimuth angle estimation apparatus 1 to which the present invention is applied is mounted on a vehicle such as a passenger car (hereinafter referred to as the own vehicle), and is an apparatus that estimates the direction (particularly the azimuth angle) of the own vehicle. Specifically, as shown in FIG. 1, the azimuth estimation device 1 includes a control unit 10, a satellite information receiver 21, a vehicle speed sensor 22, a yaw rate sensor 23, a map database (DB) 24, and a steering angle. A sensor 25 and an output target device 31 are provided.

  The satellite information receiver 21 is configured as a well-known satellite information receiver that detects the position of the host vehicle by receiving radio waves transmitted from a plurality of satellites. For example, the satellite information receiver 21 detects the position of the host vehicle at a cycle of about 1000 ms, and sends satellite information indicating the position of the host vehicle to the control unit 10.

The vehicle speed sensor 22 is configured as a known vehicle speed sensor that detects the traveling speed of the host vehicle. The vehicle speed sensor 22 sends the obtained speed information to the control unit 10.
The yaw rate sensor 23 is configured as a known yaw rate sensor that detects the turning angular velocity of the host vehicle. The yaw rate sensor 23 detects the angular velocity at a cycle shorter than the detection cycle of the position of the host vehicle by the satellite information receiver 21 (for example, a cycle of about 20 ms), and sends the obtained angular velocity to the control unit 10.

  The map DB 24 is a well-known database that stores map data associated with latitude and longitude information. Data in the map DB 24 is read by the control unit 10 as necessary.

  The steering angle sensor 25 is a well-known steering angle sensor that detects the steering angle operated by the driver of the host vehicle. The steering angle sensor 25 detects the steering angle at a cycle shorter than the detection cycle of the position of the host vehicle by the satellite information receiver 21 (for example, a cycle of about 50 ms), and sends the obtained steering angle to the control unit 10. send.

  The control unit 10 is configured as a computer including a CPU 11 and a memory 12 such as a ROM and a RAM. The CPU 11 estimates the azimuth angle of the host vehicle (the azimuth angle toward which the front direction of the host vehicle is directed) according to the program stored in the memory 12, and outputs the azimuth angle to the output target device 31.

  The output target device 31 obtains the azimuth angle of the host vehicle estimated by the control unit 10 and performs driving support of the host vehicle. For example, the output target device 31 accurately guides the host vehicle to the destination by accurately recognizing the traveling direction of the host vehicle based on the azimuth angle of the host vehicle. Further, for example, the output target device 31 recognizes a skew with respect to the direction in which the road on which the host vehicle travels extends based on the azimuth angle of the host vehicle, and issues a warning or the like.

[Process of this embodiment]
In the azimuth angle estimating apparatus 1 configured as described above, the control unit 10 performs various processes shown in FIG. As one of various processes, the absolute azimuth angle estimation process shown in FIG. 2 is performed. The absolute azimuth angle estimation process is a process of estimating the azimuth angle (absolute azimuth angle) that the host vehicle is facing from the change in position using the positions of a plurality of host vehicles.

  In this way, since the error is not accumulated in the method for obtaining the absolute azimuth angle, the error does not increase with the passage of time, and the vehicle is traveling stably on a straight road (described later). In the case where the steering system motion frequency is low). However, in the method for obtaining the absolute azimuth angle, the accuracy of the situation in which the steering angle of the host vehicle changes frequently (when the steering system motion frequency described later is high), such as when the host vehicle travels on a curved road such as a mountain road, etc. There is a feature that decreases.

  The absolute azimuth angle estimation process is a process that is started when a power source (such as an ignition or an accessory) of the host vehicle is turned on, and is then repeatedly performed at regular intervals (for example, about every 1000 ms). In the absolute azimuth estimation process, as shown in FIG. 2, first, the latest satellite information obtained this time is acquired from the satellite information receiver 21, and the previous satellite information stored in the memory 12 is acquired (S110). . At this time, the latest satellite information is recorded in the memory 12.

  Subsequently, the speed vector of the host vehicle is calculated based on the acquired satellite information (S120). The velocity vector is obtained by dividing the position difference by the time difference. Subsequently, an angle with respect to the meridian about the velocity vector is obtained, and an azimuth angle is obtained according to this angle (S130). This azimuth angle is recorded in the memory 12 as an absolute azimuth angle [A].

  Subsequently, the azimuth angle is estimated by performing mapping on the map obtained from the map DB 24 based on sensor values obtained by various sensors (vehicle speed sensor 22, yaw rate sensor 23, steering angle sensor 25, etc.) (S140). That is, the position (current location) on the map of the host vehicle is specified based on the sensor value.

  And the angle with respect to the meridian in the direction on the traveling direction side of the host vehicle among the directions in which the road at this position extends is obtained, and the azimuth is obtained according to this angle. This azimuth angle is recorded in the memory 12 as an absolute azimuth angle [B].

  Subsequently, the absolute azimuth [C] is obtained by arbitrarily combining the absolute azimuth [A] and the absolute azimuth [B] (S150). When combining the absolute azimuth, for example, the accuracy of the absolute azimuth [A] and the absolute azimuth [B] is determined according to the accuracy of the map data, the number of captured satellites, and the like. Any one of the absolute azimuth angle [A] and the absolute azimuth angle [B] may be employed.

Alternatively, a weighted average value or an average value may be adopted. Subsequently, the absolute azimuth [C] is recorded (output) in the memory 12 (S160), and the absolute azimuth estimation process is terminated.
By the way, the control part 10 implements the relative azimuth angle estimation process shown in FIG. 3 as one of various processes. In the relative azimuth angle estimation process, the sensor value from the yaw rate sensor 23 is used to detect a change in the direction of the host vehicle relative to the previously detected azimuth angle of the host vehicle. This is a process for estimating the angle.

  Thus, the method for obtaining the relative azimuth angle has a feature that the azimuth angle of the host vehicle can be accurately estimated in a situation where the steering angle of the host vehicle frequently changes (when the steering system motion frequency described later is high). However, since this is a method of integrating changes from azimuth angles detected in the past, there is a feature that errors are accumulated and errors increase with time. For this reason, when the host vehicle is traveling stably on a straight road (when the steering system motion frequency described later is low), there is a high possibility that the above-mentioned absolute azimuth will be more accurate as a result. .

  The relative azimuth angle estimation process is a process that is started when, for example, a power supply (ignition, accessory, or the like) of the host vehicle is turned on, and thereafter is a process that is repeatedly performed at regular intervals (for example, approximately every 20 ms). Further, this process is executed independently of other processes. In the relative azimuth angle estimation process, as shown in FIG. 3, first, the latest azimuth angle (integrated azimuth angle) obtained in an azimuth angle integration process described later is acquired (S210).

  Subsequently, the yaw rate is acquired from the yaw rate sensor 23 (S220), and yaw rate integration is performed (S230). The yaw rate integration indicates that one or a plurality of yaw rates obtained after the time when the latest azimuth angle is obtained are integrated. The amount of change in azimuth after the latest azimuth is obtained by yaw rate integration.

  Subsequently, the relative azimuth angle is estimated (S240). In this process, a relative azimuth is obtained by adding (or subtracting) the integrated value obtained by yaw rate integration to the latest azimuth. This azimuth is recorded (output) in the memory 12 as a relative azimuth [D] (S250).

When such processing ends, the relative azimuth angle estimation processing ends.
Moreover, the control part 10 implements the azimuth integration process shown in FIG. 4 as one of various processes. The azimuth integration processing is processing for estimating the most probable azimuth using the absolute azimuth [C] and the relative azimuth [D].

  The azimuth integration processing is processing that is started when, for example, the power of the host vehicle (ignition, accessory, or the like) is turned on, and is then repeatedly executed at regular intervals (for example, about every 50 ms). Further, this process is executed independently of other processes. In the azimuth integration process, as shown in FIG. 4, first, a cut-off frequency setting process is performed (S310).

  The cut-off frequency setting process is a process for setting a cut-off frequency (boundary frequency) to be used when determining at what ratio the absolute azimuth angle [C] and the relative azimuth angle [D] are used. The cut-off frequency is a value set in the steering system motion frequency.

  Here, the steering system motion frequency (frequency characteristics regarding the turning of the host vehicle) indicates a frequency when a parameter related to steering (for example, a sensor value by the steering angle sensor 25 or the yaw rate sensor 23) changes. That is, it can be said that the steering system motion frequency becomes high in a situation where there is a lot of vibration, such as when traveling on a road having a rough road surface, or in a situation such as a mountain road where steering is finely operated. Further, it can be said that the steering system motion frequency is low in a situation where there is little vibration, such as when traveling on a road having a smooth road surface, or a situation such as a straight road where steering is hardly operated.

  In the cutoff frequency setting process, as shown in FIG. 5, first, the response characteristic of the vehicle is acquired (S410). The vehicle response characteristics can be obtained by using, for example, PSD (power spectrum function) of the yaw rate with respect to the steering system motion frequency, as shown in FIG. That is, it is determined by how much the vehicle motion (turning of the vehicle) is reflected when there is an input related to steering (steering operation or the like). The followability of the vehicle motion with respect to the input relating to the steering varies depending on, for example, the slipperiness of the road surface, the response of the steering system of the host vehicle, and the like, and is obtained as a characteristic specific to the vehicle (vehicle type).

Subsequently, a cutoff frequency (f1) according to the response characteristic of the vehicle is set (S420).
In the example shown in FIG. 6, the response characteristics of the vehicle when the host vehicle travels on a dry road surface and the response characteristics of the vehicle when the host vehicle travels on a snowy road are shown in a graph. The PSD peak on the dry road surface has a higher frequency than the PSD peak on the snowy road. That is, it can be said that the output from the yaw rate sensor 23 should be used on a dry road surface at a higher frequency than that on a snowy road. Therefore, in the process of S420, when the host vehicle is traveling on a snowy road, a relatively low cutoff frequency is set, and when the host vehicle is traveling on a dry road surface, Set a higher cutoff frequency.

  Specifically, in this process, the vehicle response characteristics (PSD peak, etc.) are obtained by monitoring the PSD of the yaw rate with respect to the steering system motion frequency (for example, the sensor value by the steering angle sensor 25), and cut according to the response characteristics. An off frequency may be set. Alternatively, a road surface condition (dry, wet, snowy road, etc.) may be recognized by a camera or the like, and a preset cutoff frequency may be set according to the road surface condition.

  Subsequently, a cutoff frequency (f2) is set based on the road shape (S430). In this process, for example, the response characteristic of the vehicle is estimated on the assumption that the road shape is a clothoidoid curve that is frequently used for an actual road. The road shape is a trajectory drawn when it is assumed that an arbitrary position in the width direction orthogonal to the extending direction (for example, the center or the left and right end portions) in which the road extends extends along the extending direction. Indicates.

  When the above equation [1] is used, the yaw rate in the host vehicle can be obtained as follows.

  At this time, the relationship between the steering system motion frequency and the PSD of the yaw rate can be expressed as shown in FIG. That is, the characteristic that the PSD of the yaw rate monotonously decreases as the steering system motion frequency increases is obtained. In such a relationship, for example, the steering system motion frequency at the point where the PSD of the yaw rate becomes 0 is obtained as the cutoff frequency (f2). The cut-off frequency (f2) varies depending on the setting of the clothoid parameter C0.

  Subsequently, a cutoff frequency (fc) used for setting is obtained by combining the cutoff frequencies f1 and f2 (S440). In this process, for example, the cutoff frequency is synthesized using the following equation.

  In the above equation [3], α is an arbitrary constant and can be changed dynamically. For example, when the cut-off frequency (f2) obtained from the road shape in the near future is expected to be smaller than the cut-off frequency (f1) obtained from the vehicle response characteristics, the value of α is gradually reduced. And so on.

  When such processing is finished, the cutoff frequency setting processing is finished and the processing returns to FIG. Subsequently, the steering system motion frequency is acquired from various sensors (for example, the yaw rate sensor 23 or the steering angle sensor 25) (S320). Then, the absolute azimuth [C] and the relative azimuth [D] are acquired from the memory 12 (S330).

  Subsequently, a cutoff frequency (fc) is set in a map prepared in advance (S340), and an integrated azimuth angle is calculated based on this map (S350). Here, for example, as shown in FIG. 8, the map is a map in which the utilization ratios of the respective azimuth angles are associated with each other according to the steering system motion frequency. The integrated azimuth indicates the azimuth of the host vehicle that is finally estimated in this process.

  In this map, as shown in FIG. 8, when β is an arbitrary value and the steering system motion frequency is less than fc−β, the absolute azimuth [C] is set as the integrated azimuth as it is. When the steering system motion frequency is fc + β or more, the relative azimuth [D] is set as the integrated azimuth as it is.

  In addition, when the steering system motion frequency is within the range of fc−β to fc + β, the crossover region where both the absolute azimuth angle [C] and the relative azimuth angle [D] are used. In the crossover region, the usage rate of the absolute azimuth angle [C] decreases as the steering system motion frequency approaches fc + β from fc−β, and the usage rate of the relative azimuth angle [D] is the usage rate of the absolute azimuth angle [C]. Increases by the amount of the decrease. When the steering system motion frequency coincides with the cutoff frequency fc, the utilization ratios of the absolute azimuth angle [C] and the relative azimuth angle [D] are both set to 50%.

  Note that the value of β in the map is set to a value of 30 to 50% of the cutoff frequency, for example. Subsequently, the integrated azimuth angle set in this way is output to the output target device 31 (S360), and the azimuth angle integration processing is terminated.

[Effects of this embodiment]
In the azimuth angle estimation device 1 described above, the control unit 10 obtains an absolute azimuth representing the absolute azimuth of the host vehicle based on a change in the position of the host vehicle, and calculates the relative position of the host vehicle based on integration of the yaw rate of the host vehicle. Get the relative orientation that represents the orientation. And the control part 10 acquires the frequency characteristic about the turn of the own vehicle, and employ | adopts at least one of an absolute azimuth | direction and a relative azimuth | direction as an azimuth | direction of the own vehicle according to a frequency characteristic.

  According to such an azimuth estimation device 1, at least one of the absolute azimuth and the relative azimuth is set as the azimuth of the host vehicle in accordance with the frequency characteristics of the turn of the host vehicle that changes according to the vehicle motion and the vehicle environment. Since it is adopted, the direction of the host vehicle can be detected with higher accuracy.

  Note that the direction of the host vehicle indicates a direction (an angle with respect to a certain reference direction) in which an arbitrary part such as a front portion of the host vehicle is directed. However, in the above embodiment, an azimuth angle (an angle with respect to the meridian) of the azimuth is estimated. As the frequency characteristics, for example, the frequency when the steering angle or the steering angle changes, the vibration frequency of the vehicle, or the like is monitored and this value may be adopted.

  In addition, the absolute azimuth indicates an azimuth that is obtained without taking the azimuth obtained in the past into consideration. On the other hand, the relative direction of the host vehicle indicates the direction obtained by integrating the displacement according to the sensor value such as the yaw rate with respect to the direction obtained in the past.

  When the frequency characteristic is equal to or higher than a preset boundary frequency (cut-off frequency) in the azimuth angle estimation device 1 described above, the control unit 10 sets the relative azimuth weighting relative to the absolute azimuth to be larger than the boundary frequency. The weight of the relative direction with respect to the absolute direction is set small.

According to such an azimuth angle estimating apparatus 1, it is possible to estimate the azimuth by using a technique that increases the accuracy of obtaining the azimuth when the frequency characteristics of the turn of the host vehicle change.
In the azimuth angle estimation device 1 described above, the control unit 10 sets a boundary frequency according to the environment or the running state of the host vehicle, and sets weighting using the set boundary frequency.

  According to such an azimuth estimation device 1, since the boundary frequency is appropriately set according to the environment or the driving state of the host vehicle, the characteristic that the response performance of the vehicle changes according to the environment or the driving state of the host vehicle. An appropriate boundary frequency can be set by using this.

In the azimuth estimation device 1 described above, the control unit 10 sets the boundary frequency in consideration of the slipperiness of the road on which the host vehicle is traveling.
According to such an azimuth estimation device 1, it is possible to set an appropriate boundary frequency using the characteristic that the response performance of the vehicle changes according to the slipperiness of the road on which the host vehicle is traveling.

  For example, FIG. 9 shows a case where the vehicle travels on a snowy road, when the cut-off frequency fc is set appropriately by the above method (fc = 0.05 Hz), and a dry cut-off regardless of the snowy road. The relationship between the magnitude of the azimuth angle error when the azimuth angle of the host vehicle changes with the passage of time when the frequency (fc = 3.0 Hz) is set is shown.

  When the cut-off frequency for snowy roads is set by the above method, the magnitude of the error changes as the azimuth angle of the host vehicle changes, but it can be seen that the magnitude of the error is generally less than 3 degrees. On the other hand, when the dry cut-off frequency is set, the error amplitude is large and the value thereof is relatively large. In other words, it can be seen that a stable azimuth with a small error can be obtained by using the above method.

In the azimuth angle estimation apparatus 1 described above, the control unit 10 sets the boundary frequency in consideration of the road shape assumed on the road on which the host vehicle travels.
According to such an azimuth estimation device 1, it is possible to set an appropriate boundary frequency using the characteristic that the response performance of the vehicle changes according to the shape of the road on which the host vehicle travels.

  When setting the boundary frequency considering both the slipperiness of the road on which the host vehicle is traveling and the road shape assumed on the road on which the host vehicle is traveling, set a more appropriate boundary frequency. Can do.

[Other Embodiments]
The present invention is not construed as being limited by the above embodiment. Further, the reference numerals used in the description of the above embodiments are also used in the claims as appropriate, but they are used for the purpose of facilitating the understanding of the invention according to each claim, and the invention according to each claim. It is not intended to limit the technical scope of The functions of one component in the above embodiment may be distributed as a plurality of components, or the functions of a plurality of components may be integrated into one component. Further, at least a part of the configuration of the above embodiment may be replaced with a known configuration having the same function. Moreover, you may abbreviate | omit a part of structure of the said embodiment as long as a subject can be solved. In addition, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified only by the wording described in the claim are embodiment of this invention.

  In addition to the azimuth angle estimation apparatus 1 described above, a system including the azimuth angle estimation apparatus 1 as a constituent element, a program for causing a computer to function as the azimuth angle estimation apparatus 1, a medium storing the program, an azimuth angle estimation method, and the like The present invention can also be realized in various forms.

For example, in the above embodiment, the azimuth angle is estimated, but a configuration in which the azimuth is simply estimated may be employed.
[Correspondence between Configuration of Embodiment and Means of Present Invention]
Of the processes executed by the control unit 10 in the above embodiment, the processes of S110 to S160 and S330 correspond to the absolute direction acquisition means in the present invention, and in the above embodiment, the processes of S210 to S250 and S330 are referred to in the present invention. It corresponds to a relative orientation acquisition means. In the above embodiment, the processes of S310 and S340 correspond to the boundary frequency setting means in the present invention, and the process of S320 in the above embodiment corresponds to the frequency characteristic acquisition means in the present invention. In the above embodiment, the process of S350 corresponds to the adoption setting means in the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Azimuth angle estimation apparatus, 10 ... Control part, 11 ... CPU, 12 ... Memory, 21 ... Satellite information receiver, 22 ... Vehicle speed sensor, 23 ... Yaw rate sensor, 24 ... Map DB, 25 ... Steer angle sensor, 31 ... Output target device.

Claims (4)

A direction estimation device (1) for estimating a direction of a host vehicle,
Absolute azimuth obtaining means (S330: S110 to S160) for obtaining an absolute azimuth representing the absolute azimuth of the own vehicle based on a change in the position of the own vehicle;
Relative bearing acquisition means (S330: S210 to S250) for obtaining a relative bearing indicating the relative bearing of the host vehicle based on the yaw rate of the host vehicle;
Frequency characteristic acquisition means (S320) for acquiring a steering system motion frequency that is a frequency that changes according to the frequency at which the steering angle or yaw rate of the host vehicle changes ;
Employment setting means (S350) that employs at least one of the absolute azimuth and the relative azimuth as the azimuth of the host vehicle in accordance with the steering system motion frequency ;
Equipped with a,
When the steering system motion frequency is equal to or higher than a preset boundary frequency, the adoption setting means sets the relative azimuth weighting with respect to the absolute azimuth to be large, and when the steering system motion frequency is less than the boundary frequency, Set a smaller relative orientation weight
An azimuth estimation apparatus characterized by that. In the azimuth estimation device according to claim 1 ,
Boundary frequency setting means (S310, S340) for setting the boundary frequency according to the environment or traveling state of the host vehicle,
The azimuth estimation apparatus characterized in that the adoption setting means sets the weight using the boundary frequency set by the boundary frequency setting means. In the azimuth estimation apparatus according to claim 2 ,
The azimuth estimation apparatus according to claim 1, wherein the boundary frequency setting means sets the boundary frequency in consideration of slipperiness of a road on which the host vehicle is traveling. In the azimuth estimation apparatus according to claim 2 or claim 3 ,
The azimuth estimation apparatus characterized in that the boundary frequency setting means sets the boundary frequency in consideration of a road shape assumed in a road on which the host vehicle travels.