Patent ID: 12228649

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described below with reference to the drawings. Note that identical or corresponding portions in the drawings are denoted by identical reference characters. A description of an identical or corresponding portion will be appropriately omitted or simplified in the description of the embodiments.

Embodiment 1

***Description of Configuration***

FIG.1is a diagram showing detection positions when distance measurement of a moving body is performed.FIG.2is a diagram representing, as pieces of data for an identical time, pieces of data for one frame.

InFIG.1, distance measurement is performed for respective directions over a time period from a time t1to a time t6in order to acquire pieces of data for one frame by a sensor1.FIG.2is a diagram representing, as pieces of data for an identical time, a result of the distance measurement.

As shown inFIG.2, data adjacent to a distance measurement result for a direction obtained at the time t1is a distance measurement result obtained at the time t6. Use of the distance measurement results without change makes the size or shape of a body incorrect, as shown inFIG.2. Such a phenomenon may occur similarly in a case where a sensor itself moves.

The present embodiment will describe an aspect which extracts a region of a moving body using a distance measurement result for one frame acquired on a current occasion and a distance measurement result for a previous frame acquired on a previous occasion, calculates distance measurement results for all directions for an identical time, and detects the shape and size of the body.

FIG.3is a configuration diagram of a distance measurement correction system500according to the present embodiment.

The distance measurement correction system500according to the present embodiment includes a distance measurement correction device10and the sensor1. Specifically, the sensor1is a laser sensor, such as a LiDAR.

The distance measurement correction device10is a computer. The distance measurement correction device10is a car-mounted computer in the present embodiment. The distance measurement correction device10, however, may be a server computer, such as a cloud server, which is installed at a distant site. The sensor1, such as a LiDAR, is mounted on a vehicle on which the distance measurement correction device10is mounted. The distance measurement correction device10is connected to the sensor1by wire or wirelessly.

The distance measurement correction system500is also called a LiDAR detection result correction device.

The distance measurement correction device10includes a processor11and also includes other pieces of hardware, such as a memory12and an I/O interface13. The processor11is connected to the other pieces of hardware via a signal line14and controls the other pieces of hardware.

The distance measurement correction device10includes, as functional elements, an extraction unit200and a correction unit300. The extraction unit200includes an acquisition unit201, a movement calculation unit202, and a correction direction extraction unit203. The correction unit300includes a distance measurement information correction unit301and a detection unit302. Functions of the extraction unit200and the correction unit300are implemented by software. Specifically, the functions of the extraction unit200and the correction unit300are implemented by a distance measurement correction program. The distance measurement correction program is a program for causing a computer to execute processing to be performed by the extraction unit200and the correction unit300as an acquisition process, a movement calculation process, a correction direction extraction process, a distance measurement information correction process, and a detection process. A distance measurement correction method is a method to be performed through execution of the distance measurement correction program by the distance measurement correction system500. The distance measurement correction program may be provided recorded on a computer-readable medium, be provided stored in a recording medium or a storage medium, or be provided as a program product.

The processor11is an IC (Integrated Circuit) which performs arithmetic processing. A specific example of the processor11is a CPU, a DSP, or a GPU. The processor11is a device which executes the distance measurement correction program. “CPU” stands for Central Processing Unit. “DSP” stands for Digital Signal Processor. “GPU” stands for Graphics Processing Unit.

The memory12is a device which stores in advance or temporarily stores the distance measurement correction program. A specific example of the memory12is a RAM, a flash memory, or a combination thereof “RAM” stands for Random Access Memory.

The I/O interface13includes a receiver which receives data to be input to the distance measurement correction program and a transmitter which transmits data output from the distance measurement correction program. The I/O interface13is a circuit which acquires data from the sensor1in accordance with an instruction from the processor11. A specific example of the I/O interface13is a communication chip or a NIC. “NIC” stands for Network Interface Card.

The distance measurement correction device10may further include, as pieces of hardware, an input instrument and a display. The input instrument is an instrument which is manipulated by a user to input data to the distance measurement correction program. A specific example of the input instrument is a mouse, a keyboard, a touch panel, or a combination of some or all thereof. The display is an instrument which displays data output from the distance measurement correction program on a screen. A specific example of the display is an LCD. “LCD” stands for Liquid Crystal Display.

The distance measurement correction program is read from the memory12into the processor11and is executed by the processor11. Not only the distance measurement correction program but also an OS is stored in the memory12. “OS” stands for Operating System. The processor11executes the distance measurement correction program while executing the OS. Note that a part or the whole of the distance measurement correction program may be incorporated in the OS.

The distance measurement correction program and the OS may be stored in an auxiliary storage device. A specific example of the auxiliary storage device is an HDD, a flash memory, or a combination thereof “HDD” stands for Hard Disk Drive. If the distance measurement correction program and the OS are stored in the auxiliary storage device, the distance measurement correction program and the OS are loaded into the memory12and are executed by the processor11.

The distance measurement correction device10may include a plurality of processors which substitute for the processor11. The plurality of processors share execution of the distance measurement correction program. A specific example of each processor is a CPU.

Data, information, a signal value, and a variable value to be used, processed, or output by the distance measurement correction program are stored in the memory12, the auxiliary storage device, or a register or a cache memory in the processor11. In particular, data which can be acquired by the I/O interface13, a calculation result from the distance measurement correction program, direction and time information15, and body velocity information16are stored in the memory12. The direction and time information15includes information on a direction of distance measurement by the sensor1, the order of distance measurement, and time information for each distance measurement. The body velocity information16includes a threshold velocity161corresponding to a body3. Specifically, the threshold velocity161is a maximum velocity at which the body3as an object to be measured by the sensor1can move. Data and information stored in the memory12are input and output in accordance with a request from the processor11.

***Description of Operation***

Operation of the distance measurement correction system500according to the present embodiment will be described with reference toFIG.4.

A distance measurement correction process by the distance measurement correction system500according to the present embodiment is implemented by combination of operation of the distance measurement correction device10and operation of the sensor1.

The distance measurement correction device10corrects pieces of distance measurement information31obtained by measuring, through one cycle, a space between the sensor1and the body3, at least one of which moves, by the sensor1, the pieces of distance measurement information31being respective distances from the sensor1to the body3in a plurality of directions.

Specifically, the sensor1is a laser sensor, such as a LiDAR.

FIG.5is a chart showing distance measurement by the sensor1according to the present embodiment.

The sensor1applies lasers in the plurality of directions, receives light beams reflected from the body3, and calculates distances to the body. The sensor1measures a distance m to an obstacle at each angle (θ,ω) about the sensor1, as shown inFIG.5.

In step S101, the acquisition unit201acquires, via the I/O interface13, distance information from the sensor1to the body3which is obtained by the sensor1. The distance information is a distance from the sensor1to the body3in each direction. The acquisition unit201acquires, as pieces of distance measurement information31, pieces of distance information measured through one cycle by the sensor1. That is, the pieces of distance measurement information31are pieces of distance information for one frame.

The acquisition unit201acquires the pieces of distance measurement information31for one frame measured on a current occasion and pieces of distance measurement information for a previous frame measured on a previous occasion. Note that the pieces of distance measurement information31acquired by the acquisition unit201are stored in the memory12. The acquisition unit201acquires the pieces of distance measurement information for the previous frame measured on the previous occasion from the memory12.

In step S102, the movement calculation unit202calculates, as pieces of movement information32, respective movement distances of the body3with respect to the sensor1in a plurality of directions on the basis of a difference between the pieces of distance measurement information31measured on the current occasion by the sensor1and the pieces of distance measurement information measured on the previous occasion by the sensor1.

Specifically, the movement calculation unit202obtains, as movement distances, a difference between pieces of distance information for each direction of the most recent frame, using data of the previous frame and data of a most recent frame, that is, the frame acquired on the current occasion by the sensor1. The movement calculation unit202calculates, as the pieces of movement information32, the movement distances for the respective directions of the most recent frame. Note that, if a measurement direction of data of the most recent frame and a measurement direction of data of the previous frame are not identical, data of the previous frame which is identical in direction to the most recent frame is created using data for a closest direction of the previous frame, and pieces of movement information32for the respective directions of the most recent frame are calculated.

In step S103, the correction direction extraction unit203calculates, as body movement velocities, movement velocities of the body3using the respective pieces of movement information32for the plurality of directions. The correction direction extraction unit203extracts, as a correction direction33, a direction, for which the distance measurement information31is to be corrected, from among the plurality of directions, on the basis of the body movement velocities. The correction direction extraction unit203extracts, as the correction direction33, each of the plurality of directions if the body movement velocity in the direction of the plurality of directions is equal to or less than a threshold which is calculated on the basis of the threshold velocity161. Extraction of the correction directions33corresponds to extraction of a region, for which the pieces of distance measurement information31are to be corrected.

Specifically, the correction direction extraction unit203obtains a region, for which the pieces of distance measurement information31are to be corrected, using the pieces of movement information for the respective directions. In the case of a stationary body, since there is little distance measurement variation within a micro time period within one frame, correction processing is not performed. On the other hand, in a case where distance measurement of an obstacle is performed for a most recent frame and another distant body is measured for a previous frame, a difference in distance information is large. The same applies to a case where the most recent frame and the previous frame are reversed. In this case, even if distance measurement information for an arbitrary time period is created using data of the most recent frame and data of the previous frame, the distance measurement information is not correct information. For this reason, a body movement velocity which is conceivable for a usage condition is used as a threshold, and a direction which has a variation and whose variation is equal to or less than the threshold is extracted. Note that the threshold is calculated using the body velocity information16and using a movement velocity of the sensor1and the threshold velocity161, that is, a maximum velocity for the body3which is conceivable in a space where the sensor1is present. The threshold velocity161that is a maximum velocity which the body3can take is stored in the body velocity information16.

FIG.6is a chart showing correction of distance measurement information by the distance measurement information correction unit301according to the present embodiment.

In step S104, the distance measurement information correction unit301calculates, for each of the correction directions33, a distance A from the sensor1to the body at a correction time point t between a time point ta0of measurement on the previous occasion by the sensor1and a time point ta1of measurement on the current occasion by the sensor1. The distance measurement information correction unit301sets the distance A as post-correction distance measurement information34.

Specifically, the distance measurement information correction unit301obtains, for the correction directions among the plurality of directions, that is, the region extracted by the extraction unit200, pieces of distance information from the sensor1for the respective directions at the correction time point t that is an arbitrary time. As shown inFIG.6, let a0and a1be distance measurement results for an identical direction for the previous frame and the most recent frame. Also, let ta0and ta1be respective distance measurement times. In this case, the post-correction distance A at the time t can be calculated by Expression 1 below.
A=a0+(a1−a0)*(t−t−0)/(ta1−ta0)  (Expression 1)

In step S105, the detection unit302detects a state of the body3using the pieces of post-correction distance measurement information34. The state of the body3refers to information, such as the size and shape of a body. Specifically, the detection unit302may develop a movement velocity in a two-dimensional array using an angle (θ,ω) which is information acquired from a distance measurement information sensor and group similar regions with adjacent values as one body, as for a body size. Alternatively, the detection unit302may make a plot in a three-dimensional space on the basis of corrected distance measurement information and directions and regard a group of points present at short distances as one group to create a body. The detection unit302then obtains shape information, such as the size and flatness or a curvature of a body, from grouped pieces of data.

Description of Advantageous Effects of Present Embodiment

A distance measurement correction device according to the present embodiment is a device which handles distance measurement information output by a sensor. An extraction unit compares pieces of distance measurement information from the sensor to an obstacle for respective directions with pieces of distance measurement information of a previous frame to calculate an amount of change and extracts a region for which pieces of distance measurement information are to be corrected. A correction unit calculates pieces of distance measurement information for respective directions at an identical time for the extracted region to obtain the shape and size of a body. The extraction unit has a function of setting a threshold for determining that a body is moving, using maximum velocity information for a body serving as an object of distance measurement.

As described above, a distance measurement correction system according to the present embodiment extracts a body movement region from amounts of change in distance information in respective directions, using data of a most recent frame and data of a previous frame which are acquired by a sensor. The distance measurement correction system according to the present embodiment performs distance measurement information correction on the movement region. Thus, the distance measurement correction system according to the present embodiment is capable of executing distance measurement information correction with high accuracy and of detecting, with high accuracy, a state of a body, such as the size and shape of the body.

Other Configurations

Modification 1

In the present embodiment, the functions of the extraction unit200and the correction unit300are implemented by software. As a modification, functions of the extraction unit200and the correction unit300may be implemented by hardware. Specifically, the distance measurement correction device10includes an electronic circuit instead of the processor11.

The electronic circuit is a dedicated electronic circuit which implements the functions of the extraction unit200and the correction unit300.

Specifically, the electronic circuit is a single circuit, a composite circuit, a programmed processor, a parallel-programmed processor, a logic IC, a GA, an ASIC, or an FPGA. “GA” stands for Gate Array. “ASIC” stands for Application Specific Integrated Circuit. “FPGA” stands for Field-Programmable Gate Array.

The functions of the extraction unit200and the correction unit300may be implemented by one electronic circuit or may be distributed to and implemented by a plurality of electronic circuits.

As another modification, some of the functions of the extraction unit200and the correction unit300may be implemented by an electronic circuit, and the others may be implemented by software. Alternatively, some or all of the functions of the extraction unit200and the correction unit300may be implemented by firmware.

Each of a processor and an electronic circuit is also called processing circuitry. That is, in the distance measurement correction device10, the functions of the extraction unit200and the correction unit300are implemented by processing circuitry.

Embodiment 2

The present embodiment will mainly describe differences from Embodiment 1. Note that the same components as those in Embodiment 1 are denoted by identical reference characters and that a description thereof will be omitted.

In Embodiment 1, a threshold is defined on the basis of the body velocity information16at the time of extraction of a region for which distance measurement information is to be corrected. In the present embodiment, a threshold is defined using body velocity information16and movement information of a sensor1.

***Description of Configuration***

FIG.7is a configuration diagram of a distance measurement correction system500aaccording to the present embodiment.

The distance measurement correction system500aaccording to the present embodiment includes a sensor information storage device2in addition to the components of the distance measurement correction system500according to Embodiment 1. The sensor information storage device2is connected to a distance measurement correction device10via an I/O interface13.

The sensor information storage device2stores sensor movement information21which includes a movement velocity of the sensor1and a movement direction of the sensor1.

***Description of Operation***

Operation of the distance measurement correction system500aaccording to the present embodiment will be described with reference toFIG.8.

Processes in steps S101and S102are the same as in Embodiment 1.

In step S103a, a correction direction extraction unit203aextracts a correction direction33from among a plurality of directions on the basis of respective body movement velocities in the plurality of directions and the sensor movement information21including the sensor movement velocity and the sensor movement direction. Information on a position where the sensor1is present may be included in the sensor movement information21.

FIG.9is a chart showing an example of use of the sensor movement information21according to the present embodiment.

The correction direction extraction unit203aadjusts a threshold which is used to obtain a correction direction, for which distance measurement information31is to be corrected, in accordance with the sensor movement information21and the position where the sensor1is present. The sensor movement information21includes the movement direction of the sensor1and the movement velocity of the sensor1.

Specifically, if the sensor1is moving at a velocity v and an angle ρ, as shown inFIG.9, the correction direction extraction unit203asubtracts v*cos(ρ−ω) from the threshold.

Specifically, the information on the position where the sensor1is present is information as to whether the sensor1is present on a general road or the sensor1is present on an expressway. Specifically, if the sensor1is present on a general road, a threshold velocity161for a body3is set to 80 km/h. If the sensor is present on an expressway, the threshold velocity161is set to 100 km/h. As described above, the information on the position where the sensor1is present is used to switch the threshold velocity161, that is, a maximum velocity for the body3.

Processes in steps S104and S105are the same as in Embodiment 1.

Description of Advantageous Effects of Present Embodiment

In a distance measurement correction device according to the present embodiment, an extraction unit has a function of extracting a region, for which pieces of distance measurement information are to be corrected, using movement information and position information of a sensor. A correction unit calculates pieces of distance measurement information for respective directions at an identical time for the extracted region to obtain a state of a body, such as the shape and size of the body. The distance measurement correction device according to the present embodiment is capable of adjusting a threshold which is used to extract a region, for which pieces of distance measurement information are to be corrected, in accordance with the movement information of the sensor or a position where the sensor is present. The distance measurement correction device according to the present embodiment is thus capable of correcting distance measurement information with higher accuracy.

Embodiments 1 and 2 above each have described, as independent functional blocks, units of a distance measurement correction device. A configuration of a distance measurement correction device, however, may not be like those of the above-described embodiments. Functional blocks of the distance measurement correction device may be configured in any manner as long as the functions described in the above embodiments can be implemented. The distance measurement correction device may be a system which is composed not of one device but of a plurality of devices.

A plurality of portions of Embodiments 1 and 2 may be combined and carried out. Alternatively, one portion of the embodiments may be carried out. The embodiments may be combined and carried out in any manner, in whole or in part.

That is, as for Embodiments 1 and 2, the embodiments can be freely combined, any constituent element in each embodiment can be modified, or any constituent element can be omitted in each embodiment.

Note that the embodiments described above are merely preferred examples in nature and are not intended to limit the scope of the present invention, applications of the present invention, and use of the present invention. Various changes can be made to the above-described embodiments as needed.

REFERENCE SIGNS LIST

1: sensor;2: sensor information storage device;3: body;10: distance measurement correction device;11: processor;12: memory;13: I/O interface;14: signal line;15: direction and time information;16: body velocity information;21: sensor movement information;31: distance measurement information;32: movement information;33: correction direction;34: post-correction distance measurement information;161: threshold velocity;200: extraction unit;201: acquisition unit;202: movement calculation unit;203,203a: correction direction extraction unit;300: correction unit;301: distance measurement information correction unit;302: detection unit;500,500a: distance measurement correction system