JP7284011B2 - moving body - Google Patents

Description

The present invention relates to mobile objects.

2. Description of the Related Art Conventionally, so-called guideless autonomous guided vehicles have been known that autonomously travel and transport objects in factories and the like without requiring lines or the like to mark their travel. Such transport vehicles are equipped with sensors that measure the distance to objects in order to sense the surrounding environment. , to identify the position of the vehicle itself.

When the sensor is mounted on the carriage of the carrier, the position and orientation of the sensor with respect to the carriage may deviate from design values. If the transport vehicle is driven while the position and posture of the sensor are deviated, there is a risk that the accuracy of autonomous driving will be degraded. Therefore, in order to calibrate such a deviation, for example, Patent Document 1 below discloses a method of measuring a reference member provided on the vehicle body with a sensor and calibrating the angular deviation of the sensor based on the measurement result. .

JP 2011-221957 A

A sensor that measures the distance to an object measures the distance based on, for example, the time from when the laser beam is irradiated to when it is reflected by the object and returns. At this time, various factors such as the shape of the object and the material of the surface may cause an error in the distance measurement, or an abnormal value greatly deviating from the ideal value. However, in Patent Document 1, the existence of such sensor errors and abnormal values is not taken into consideration, so there is a risk that abnormal values may be included in the estimation of the position of the object, and the accuracy of estimating the position of the reference member is deteriorated. Angular deviation of the sensor cannot be calibrated with high accuracy.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a moving body capable of accurately calibrating the displacement of the sensor with respect to the carriage.

A moving body according to one aspect of the present invention includes a carriage capable of autonomous travel, a sensor provided on the carriage capable of measuring a distance to an object existing in the surroundings, and a relative positional relationship between the carriage and the carriage. A measurement that is included in the effective area, which is the area within a predetermined range from the known reference position of the reference member, among the measured values obtained by measuring the distance to the reference member and the sensor. An estimating unit that extracts values to estimate the position of the reference member, and a calibration unit that calibrates the displacement of the sensor with respect to the truck based on the reference position of the reference member and the estimated position of the reference member.

According to this aspect, since the position of the reference member can be estimated by excluding measured values greatly deviating from the reference member, the accuracy of estimating the position of the reference member is improved, which in turn improves the accuracy of calibration of the sensor displacement. improves.

In the above aspect, the reference member includes a first flat plate and a second flat plate extending respectively along first and second directions different from each other, the first flat plate and the second flat plate being joined at the joint, and effective The region includes a first region and a second region corresponding to the first flat plate and the second flat plate, respectively, the first region does not include a predetermined range along the first direction from the joint, and the second region is The predetermined range along the second direction from the joint may not be included.

According to this aspect, the position of the reference member can be estimated by excluding the measured value near the joint between the flat plates, where the measurement accuracy of the sensor is relatively low, so that the estimation accuracy of the position of the reference member is further improved. do.

In the above aspect, the length of the first region in the first direction is shorter than the length of the first flat plate in the first direction, and the length of the second region in the second direction is shorter than the length of the second flat plate in the second direction. It can be short.

According to this aspect, the position of the reference member can be estimated by excluding the measured values near the edge of the flat plate where the measurement accuracy of the sensor is relatively low, so the accuracy of estimating the position of the reference member is further improved.

In the above aspect, the calibrator calibrates the positional deviation of the sensor with respect to the carriage by comparing the coordinates of the joint that are known and the coordinates of the joint that are estimated. By comparing the angle to the bisector of the angle formed by and the angle to the bisector of the angle formed by the first and second plates estimated from the reference axis, the deviation of the sensor's attitude with respect to the truck can be determined. may be calibrated.

According to this aspect, it is possible to calibrate the deviation of the position and attitude of the sensor with respect to the truck.

ADVANTAGE OF THE INVENTION According to this invention, the mobile body which can calibrate the deviation|shift of the sensor with respect to a trolley with high precision can be provided.

1 is a top view of a transport vehicle according to one embodiment of the present invention; FIG. 1 is a side view of a transport vehicle according to one embodiment of the present invention; FIG. It is a figure which shows the functional structure of the conveyance vehicle which concerns on one Embodiment of this invention. 4 is a flow chart showing a calibration method in a transport vehicle according to an embodiment of the present invention; It is a figure which shows the position and attitude|position of a jig|tool which are known. FIG. 5 is a diagram showing the estimated position and orientation of a jig;

Embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that, in each figure, the same reference numerals have the same or similar configurations.

FIG. 1 is a top view of a transport vehicle according to one embodiment of the present invention. FIG. 2 is a side view of a carrier according to one embodiment of the present invention. The side view shown in FIG. 2 is a view seen from the direction of the white arrow shown in FIG. The transport vehicle 10 according to the present embodiment transports articles and the like by moving autonomously in, for example, factories, offices, hospitals, commercial facilities, and the like. It should be noted that moving autonomously may mean that the guided vehicle 10 moves to a destination based on its own judgment, instead of moving according to instructions received from a user or the like. In this specification, a trolley-type transport vehicle 10 will be described as a specific example of a moving body, but the moving body is not limited to a transport vehicle, and may be, for example, a moving robot, capable of other autonomous traveling. It may be a variety of moving bodies.

As shown in FIGS. 1 and 2, the carrier 10 includes a carriage 20, two laser scanners 30a and 30b, two fixing holes 40a and 40b, and a jig 50. As shown in FIGS.

The carriage 20 constitutes the vehicle body of the transport vehicle 10 and transports articles and the like. As shown in FIG. 1, the truck 20 has a center R _C in a plan view (hereinafter also referred to as a “top view”) of the main surface of the truck 20 parallel to the floor on which the truck 20 travels. A local coordinate system is set up that is composed of orthogonal X and Y axes. Although illustration is omitted, the carriage 20 has, for example, four wheels, and realizes movement such as forward movement, backward movement, and turning of the transport vehicle 10 . Since a well-known configuration can be applied to the moving mechanism provided in the transport vehicle 10, detailed description thereof will be omitted.

The two laser scanners 30 a and 30 b are specific examples of sensors that measure the distance to objects existing around the transport vehicle 10 . Since the same laser scanners 30a and 30b can be applied, the two laser scanners will also be collectively referred to as the "laser scanner 30" when there is no particular need to distinguish them in the following description.

The laser scanner 30 irradiates a laser beam, for example, so as to be substantially parallel to the main surface of the carriage 20, and performs distance measurement based on the time from the irradiation until the laser beam is reflected by the object and returned. The laser scanner 30 has a measurement range of, for example, a predetermined radius (for example, about 10 m), and emits laser light at a predetermined degree pitch (for example, about 0.2 to 0.5 degrees) at a predetermined viewing angle (for example, 270 degrees). Several hundreds to thousands of measurement values are acquired per scan while scanning over an area of about 100 mm. The radial arrows shown in FIG. 1 schematically indicate the laser beams emitted from the laser scanners 30a and 30b.

The two laser scanners 30a and 30b are mounted on both ends of the diagonal line of the carriage 20 when viewed from above so as to face the outside of the carrier 10, respectively. As a result, when data obtained from the two laser scanners 30a and 30b are combined, distance measurement in all directions as viewed from the carriage 20 becomes possible. By measuring the surrounding environment using the laser scanner 30, the transport vehicle 10 creates an environmental map of the surrounding environment, and estimates the self-position of the transport vehicle 10 by collating it with map information stored in advance. , to move to a destination while planning a route and avoiding obstacles.

When the laser scanner 30 is mounted on the truck 20, the position and posture of the laser scanner 30 with respect to the truck 20 may deviate from design values. If the transport vehicle is caused to travel while the position or posture of the laser scanner 30 is deviated, the accuracy of autonomous travel may deteriorate. Therefore, in order to calibrate such a deviation, calibration of the deviation of the laser scanner 30 is performed after the laser scanner 30 is mounted. Details of the calibration will be described later.

Note that the laser scanner 30 is a specific example of a sensor that senses the surrounding environment of the transport vehicle. Such sensors are not limited to laser scanners, and may be sensors capable of measuring the distance to an object, such as ultrasonic sensors, distance sensors using microwaves, distance sensors using stereo images captured by a stereo camera, etc. Just do it.

Further, in the present embodiment, the transport vehicle 10 includes two laser scanners 30a and 30b, but the number of sensors included in the transport vehicle may be one, or three or more. For example, the transport vehicle may be equipped with one sensor that can measure in all directions.

The two fixing holes 40a and 40b are provided on a diagonal line of the truck 20 when viewed from above. It is assumed that the positions of the fixing holes 40a and 40b with respect to the carriage 20 are known.

The jig 50 is a specific example of a reference member whose distance is to be measured by the laser scanner 30 . By measuring the distance from the laser scanner 30 to the jig 50, the degree of deviation of the position and orientation of the laser scanner 30 from the design values can be measured. As shown in FIGS. 1 and 2, the jig 50 includes a first flat plate 51a and a second flat plate extending along the Y-axis negative direction (first direction) and the X-axis negative direction (second direction), which are different from each other. 51 b and a shaft 52 that fixes these two flat plates to the carriage 20 .

The first flat plate 51a and the second flat plate 51b are joined orthogonally so as to form an L shape when the carriage 20 is viewed from above. A first flat plate 51 a and a second flat plate 52 b are fixed to one end of the shaft 52 , and the other end is detachably attached to two fixing holes 40 a and 40 b of the carriage 20 . By attaching the shafts 52 to two or more locations on the carriage 20 whose positions are known, the jig 50 can be fixed at the designed position with high accuracy. That is, the jig 50 has a known relative positional relationship with the carriage 20, and the position of the jig 50 in the local coordinate system shown in FIG. 1 can be calculated in advance.

FIG. 3 is a diagram showing the functional configuration of the carrier according to one embodiment of the present invention. As shown in the figure, the transport vehicle 10 includes an estimation unit 100, a calibration unit 110, and a storage unit 120 as functional units. It should be noted that illustration of functional units related to the driving of the carriage 20 is omitted.

The estimation unit 100 measures the distance to the jig 50 using the laser scanner 30 . The estimating section 100 extracts the measured values included in the effective area from the measured values obtained by the measurement, and estimates the position of the jig 50 using the extracted measured values. Effective areas will be described later.

The calibration unit 110 calibrates at least one of positional deviation and attitude deviation of the laser scanner 30 with respect to the carriage 20 based on the known reference position of the jig 50 and the estimated position of the jig 50 . do.

The storage unit 120 stores, for example, the position of the jig 50 in the local coordinate system, and information on the position and posture deviation of the laser scanner 30 calculated by the calibration unit 110 . The storage unit 120 also stores, for example, a map of the surrounding environment in which the transport vehicle 10 travels.

Next, with reference to FIGS. 4 to 6, the details of the method for calibrating the position and posture of the laser scanner 30 will be described.

FIG. 4 is a flow chart illustrating a calibration method in a vehicle according to one embodiment of the invention. FIG. 5 is a diagram showing known positions and orientations of jigs. FIG. 6 is a diagram showing the estimated position and orientation of the jig. In FIGS. 5 and 6, the case of calibrating the deviation of one laser scanner 30a is shown as an example, but the same method can be used when calibrating the deviation of the other laser scanner 30b. can be applied.

First, the jig 50 is attached to the carriage 20 so as to be placed within the field of view of the laser scanner 30 (step S10). As described above, the position of the jig 50 relative to the carriage 20 is determined by fixing the jig 50 to the two fixing holes 40 a and 40 b provided in the carriage 20 . That is, it becomes possible to calculate the position of the jig 50 in the local coordinate system.

FIG. 5 is a diagram schematically showing the jig 50 and one laser scanner 30a in top view of the carriage 20. As shown in FIG. Let P _C (X _C , Y _C ) be the X and Y coordinates in the local coordinate system of the joint portion P _C where the first flat plate 51a and the second flat plate 51b of the jig 50 are joined. Since the relative positional relationship between the carriage 20 and the jig 50 is known, and the shape and size of the jig 50 are known, the coordinates P _C (X _C , Y _C ) of the joint P _C can be calculated. be.

An axis parallel to the X-axis with the junction P _C as a base point is a reference axis X _RO . Let θ _C be the angle between the reference axis X _RO and the bisector of the larger angle (ie, 270 degrees) between the first flat plate 51 a and the second flat plate 51 b of the jig 50 .

In addition, with the joint P _C as a base point, it is moved by a length K ₁ from the joint P _C in a direction obtained by rotating the reference axis X _RO clockwise by θ ₁ degree (that is, a direction along the Y-axis). Let the point be the end point P _E1 . A line segment P _C P _E1 corresponds to the first flat plate 51a. Similarly, with the joint P _C as the base point, it is moved by a length K ₂ from the joint P _C in the direction obtained by rotating the reference axis X _RO clockwise by θ ₂ degrees (that is, the direction along the X-axis). The point obtained is defined as the end point P _E2 . A line segment P _C P _E2 corresponds to the second flat plate 51b. Here, θ ₁ <θ ₂ and θ ₂ −θ ₁ =90 degrees. The lengths K ₁ and K ₂ may be the lengths of the first flat plate 51a and the second flat plate 51b in the Y-axis direction and the X-axis direction, respectively. The line segment _{PCP E1} and the line segment _{PCP E2} obtained in this way are the reference positions of the first flat plate 51a and the second flat plate 51b of the jig 50, respectively.

If the position and posture of the laser scanner 30 with respect to the carriage 20 deviate from the design values, the distance to the jig 50 measured by the laser scanner 30 also deviates from the design values. On the other hand, when the laser scanner 30 measures the distance to an object, errors and abnormal values may occur depending on the shape and material of the object. Therefore, in the present embodiment, in estimating the position of the jig 50, the measurement values measured by the laser scanner 30 are adjusted so as to include a certain range from the known reference position of the jig 50 and not include abnormal values. Extract measurements that fall within the valid range. This effective range will be explained in more detail.

The effective range in the present embodiment includes a rectangular first region R ₁ and second rectangular region R ₂ when viewed from the top of the truck 20 (see hatched region in FIG. 5). The first region R ₁ corresponds to the first flat plate 51a, and the second region R2 corresponds to the second flat plate 51b.

The first region R ₁ has a width W ₁ extending in a predetermined range from the reference position of the first flat plate 51a to the front and back of the first flat plate 51a when viewed from the laser scanner 30a in the direction of the measurement radius of the laser scanner 30a. The first region R ₁ does not include the margin _{M 1} within a predetermined range from the joint P _C toward the end point P _E1 along the Y-axis negative direction in the scanning direction of the laser scanner 30a, and A predetermined range of margin M ₂ is not included toward the joint P _C side along the positive direction of the Y-axis. That is, the first region R ₁ has a length L ₁ of L ₁ =K ₁ -(M ₁ +M ₂ ). That is, the length L ₁ of the first region R ₁ in the Y-axis direction is shorter than the length K ₁ of the first flat plate 51a in the Y-axis direction.

Similarly, the second region R ₂ also has a width W ₂ that spreads over a predetermined range from the reference position of the second flat plate 51b to the front and back of the second flat plate 51b as viewed from the laser scanner 30a in the direction of the measurement radius of the laser scanner 30a. The second region R ₂ does not include the margin _{M 3} in a predetermined range from the junction P _C toward the end point P _E2 along the X-axis negative direction in the scanning direction of the laser scanner 30a, and A predetermined range of margin _M4 is not included toward the joint P _C side along the positive direction of the X-axis. That is, the second region R ₂ has a length L ₂ of L ₂ =K ₂ -(M ₃ +M ₄ ). That is, the length L ₂ of the second region R ₂ in the X-axis direction is shorter than the length K ₂ of the second flat plate 51b in the X-axis direction.

The vicinity of the joint P _C between the first flat plate 51a and the second flat plate 51b, the end P _E1 of the first flat plate, and the end P _E2 of the second flat plate are appropriately irradiated with the laser beam emitted from the laser scanner. Or it is not reflected, which tends to increase the measurement error. In the present embodiment, the first region _R1 does not include the margins _M1 and _M2 , and the second region _R2 does not include the margins _M3 and _M4 . The position of the reference member can be estimated by excluding measurements near P _C and near the ends P _E1 , P _E2 . Therefore, the estimation accuracy of the position of the jig 50 is improved.

The lengths of the margins M ₁ to M ₄ may all be the same, or part or all of them may be different.

Returning to FIG. 4, the estimation unit 100 measures the distances to the first flat plate 51a and the second flat plate 51b of the jig 50 using the laser scanner 30a (step S20). Here, measurements of areas not included in the valid area are also obtained.

Subsequently, the estimating unit 100 extracts the measured values included in the first region R ₁ and the second region R ₂ from the acquired measured values, and uses the extracted measured values to generate the first flat plate 51a. And the position of the second flat plate 51b is estimated (step S30). The positions of the first flat plate 51a and the second flat plate 51b may be estimated, for example, by obtaining an approximate curve from the measured values included in each region in each of the first region _R1 and the second region _R2 . . Although the method of calculating the approximate curve is not particularly limited, the regression line may be calculated by, for example, the least squares method.

As shown in FIG. 6, the point of intersection of the calculated straight lines Q ₁ and Q ₂ is assumed to be the joint point _PCM , and the coordinates of the joint point _PCM in the local coordinate system _{are PCM} ( _XCM , YCM ₎ . ). Let θ _1M be the angle formed by the estimated straight line Q ₁ and the reference axis X _RO parallel to the X axis with the estimated joint P _CM as a base point. Let θ _2M be the angle between the reference axis X _RO and the estimated straight line Q ₂ . Let θ _CM be the angle between the reference axis X _RO and the bisector of the larger angle between the straight lines Q ₁ and Q ₂ (that is, the rotation angle of the jig 50). The rotation angle θ _CM is obtained by θ _CM =0.5×(θ _1M +θ _2M )−180.

Returning to FIG. 4, the calibration unit 110 compares the joint coordinates P _C (X _C , Y _C ) stored in the storage unit 120 with the estimated joint coordinates P _CM (X _CM , Y _CM ). From the comparison, the positional deviation of the laser scanner 30a with respect to the carriage 20 is calibrated (step S40). That is, the difference between the coordinates P _C (X _C , Y _C ) of the joint P _C and the estimated coordinates P _CM (X _CM , Y _CM ) of the joint P _CM corresponds to the error in the installation position of the laser scanner 30a. do.

Further, the calibration unit 110 compares the rotation angle θ _C of the jig 50 stored in the storage unit 120 with the estimated rotation angle θ _CM of the jig 50 to determine the displacement of the laser scanner 30 a with respect to the carriage 20 . is calibrated (step S40). That is, the difference between the rotation angle θ _C of the jig 50 and the estimated rotation angle θ _CM of the jig 50 corresponds to the error in the installation posture of the laser scanner 30a. The calibration unit 110 calibrates the design values of the installation position and installation attitude of the laser scanner 30a stored in advance in the storage unit 120 by reflecting the error.

With the above configuration, in the transport vehicle 10 according to the present embodiment, the first region R ₁ and the second region R ₂ that are effective regions are set, and by extracting the measurement values included in the effective regions, the jig 50 It is possible to estimate the position of the jig 50 by excluding abnormal values that deviate greatly from the position where . As a result, the accuracy of estimating the position of the jig 50 is improved, and the deviation of the laser scanners 30a and 30b can be calibrated with high accuracy.

Also, the first region R ₁ and the second region R ₂ do not include the vicinity of the joint P _C and the vicinity of the ends P _E1 and P _E2 of the first flat plate 51a and the second flat plate 51b. As a result, the position of the jig 50 can be estimated by excluding the measured values of the portions where the measurement accuracy of the laser scanners 30a and 30b is relatively poor, so the estimation accuracy of the position of the jig 50 is further improved. In addition, since the measured values of the flat portions of the first flat plate 51a and the second flat plate 51b are used, the accuracy of calibration is improved compared to a configuration in which calibration is performed using, for example, corners of the jig as feature points.

Note that when the laser scanners 30a and 30b measure the same part of the object a plurality of times, a certain amount of error may occur and the measured values may vary. Therefore, the measurements by the laser scanners 30a and 30b are performed multiple times (for example, about 10 times), and from the results of the multiple measurements, the average value, the median value, or both of the points are obtained, and the error is leveled. The position of the jig 50 may be estimated later. This further improves calibration accuracy compared to using measurements in a single scan.

The embodiments described above are for facilitating understanding of the present invention, and are not intended to limit and interpret the present invention. Each element included in the embodiment and its arrangement, materials, conditions, shape, size, etc. are not limited to those illustrated and can be changed as appropriate. Also, it is possible to partially replace or combine the configurations shown in different embodiments.

DESCRIPTION OF SYMBOLS 10... Conveyance vehicle (moving body), 20... Carriage, 30a, 30b... Laser scanner (sensor), 40a, 40b... Fixing hole, 50... Jig (reference member), 51a... First flat plate, 51b... Second flat plate , 52... axis, 100... estimation unit, 110... calibration unit, 120... storage unit

Claims (3)

A trolley capable of autonomous travel,
a sensor provided on the trolley and capable of measuring a distance to an object existing in the surroundings;
a reference member having a known relative positional relationship with the carriage;
The distance to the reference member is measured by the sensor, and among the measured values obtained by the measurement, the measurement value included in the effective region, which is the region within a predetermined range from the known reference position of the reference member. an estimation unit that extracts and estimates the position of the reference member;
a calibration unit that calibrates the displacement of the sensor with respect to the carriage based on the reference position of the reference member and the estimated position of the reference member;
with
the reference member includes a first flat plate and a second flat plate extending along first and second directions different from each other;
The first flat plate and the second flat plate are joined at a joint,
The calibration unit
calibrating the displacement of the sensor relative to the carriage from a comparison of the known joint coordinates and the estimated joint coordinates;
The angle from the reference axis to the bisector of the angle formed by the first plate and the second plate, and the bisector of the angle formed by the first plate and the second plate estimated from the reference axis calibrate the orientation deviation of the sensor with respect to the carriage from a comparison with the angle of
Mobile. the effective area includes a first area and a second area corresponding to the first flat plate and the second flat plate, respectively;
The first region does not include a predetermined range along the first direction from the joint,
The second region does not include a predetermined range along the second direction from the joint,
The moving object according to claim 1. The length of the first region in the first direction is shorter than the length of the first flat plate in the first direction, and the length of the second region in the second direction is shorter than the length of the second flat plate in the second direction. less than the length of the direction,
The moving object according to claim 2.

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