Measuring apparatus, control method for measuring apparatus, control program for measuring apparatus, and computer-readable recording medium storing computer program

Abstract

To estimate an expected arrival time at which a measuring apparatus relatively reaches a measurement target, without requiring acquisition of speed information of the measurement target from outside.SOLUTION: The measuring apparatus includes: a projector for emitting light; a photodetector for receiving light which was emitted from the projector, was reflected from a measurement target, and returned to the photodetector; and a controller. The controller acquires the distance to the measurement target and the speed of the measurement target on the basis of light receiving timing of the reflected light in the photodetector, and estimates the expected arrival time at which the measuring apparatus relatively reaches the measurement target on the basis of the distance to the measurement target and the speed of the measurement target.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a measurement device. [Background technology]

[0002] With the advancement of AD (Autonomous Driving) and ADAS (Advanced Driver-Assistance Systems), research and development of LiDAR (Light Detection and Ranging) is underway as one of the measurement devices used to grasp the surrounding environment and estimate the vehicle's own position while driving. LiDAR is equipped with a reflective sensor. The reflective sensor projects (irradiates) a laser beam onto a measurement target and receives the reflected light that is reflected back from the measurement target. LiDAR outputs information about the measurement target by measuring the distance to the measurement target based on the time difference between the time when the reflective sensor projects the laser beam and the time when it receives the reflected light (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 115260 Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors have studied a technology for estimating a predicted arrival time relative to a measurement target, for example, when a measurement device installed on a moving object that moves relative to the measurement target arrives at the measurement target. For example, a measurement device installed on a vehicle can estimate the predicted arrival time using the traveling speed provided by the vehicle. However, traveling speed is generally calculated based on the number of rotations of the wheels and the diameter of the wheels. Therefore, if a deviation occurs in the correlation between the number of rotations of the wheels, the diameter, and the traveling distance due to, for example, variations in the wheel diameter caused by tire wear or tire slippage, the predicted arrival time may not be accurately estimated based on the traveling speed.

[0005] This specification discloses a technique that can solve the above-mentioned problems. [Means for solving the problem]

[0006] The technology disclosed in this specification can be realized, for example, in the following forms.

[0007] (1) A measurement device disclosed in this specification includes a light projector that emits light, a light receiver that receives reflected light that is returned from a measurement target after the light projector is reflected, and a controller. The controller acquires the distance to the measurement target and the speed of the measurement target based on the timing at which the light receiver receives the reflected light, and estimates an estimated time of arrival of the measurement device relative to the measurement target based on the distance to the measurement target and the speed of the measurement target. This measurement device can estimate the estimated time of arrival of the measurement device relative to the measurement target without needing to obtain speed information of the measurement target from an external source.

[0008] (2) In the above measurement device, the controller may further acquire the acceleration of the measurement object based on the timing of reception of the reflected light by the optical receiver, and estimate the estimated time of arrival based on the distance to the measurement object, the speed of the measurement object, and the acceleration of the measurement object. This measurement device can prevent a decrease in the accuracy of estimating the estimated time of arrival due to changes in the speed of the measurement object.

[0009] (3) In the above-described measuring device, the measuring device may be configured to use an FMCW method, and the controller may be configured to acquire the acceleration of the object to be measured based on a difference in the velocity of the object to be measured between multiple frames. According to this measuring device, the measuring device uses an FMCW method and can acquire the velocity of the object to be measured from each frame, thereby efficiently and accurately acquiring the acceleration of the object to be measured and preventing a decrease in the accuracy of the estimated estimated time of arrival.

[0010] The technology disclosed in this specification can be realized in various forms, such as a measurement device, a measurement method, a control program for the measurement device, and a computer-readable recording medium on which a computer program is recorded. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram showing the configuration of a measurement device 1 according to an embodiment. [Figure 2] An explanatory diagram showing the relative positional relationship between the measurement object and the measurement device. [Figure 3] Flowchart showing estimation processing DETAILED DESCRIPTION OF THE INVENTION

[0012] A. Implementation: A-1. Configuration of measuring device 1: FIG. 1 is a block diagram showing the configuration of a measurement device 1 according to this embodiment. The measurement device 1 is a device that measures the distance to an object 90. The measurement device 1 has a function as a LiDAR. The measurement device 1 measures the distance to the object 90 using the FMCW (Frequency Modulated Continuous Wave) method. That is, the measurement device 1 irradiates the object 90 with frequency-modulated measurement light (irradiation light L1), causes reflected light L2 from the object 90 to interfere with measurement light (reference light L4), and measures the distance to the object 90 based on the frequency (beat frequency) of a beat signal Sb, which is the detection result of the interference light L5. The measurement device 1 can measure not only the distance to the object 90 but also the relative speed of the object 90.

[0013] The measurement device 1 includes a generating device 10, an optical device 20, a detecting device 30, and a signal processing device 40. The optical device 20 is an example of a light projector and a light receiver.

[0014] The generating device 10 is a device that generates frequency-modulated light (frequency-modulated light L3). The generating device 10 outputs the frequency-modulated light L3 to the optical device 20. A part of the frequency-modulated light L3 (measurement light) output by the generating device 10 becomes the illumination light L1 that is irradiated onto the object 90, and another part becomes the reference light L4 that is made to interfere with the reflected light L2. The generating device 10 has a signal generator 11, a current source 12, a laser light source 13, and a temperature controller 14.

[0015] The signal generator 11 generates a voltage signal for controlling the current source 12. The signal generator 11 is, for example, a waveform generator, and generates, for example, a triangular wave voltage signal and outputs it to the current source 12. The current source 12 generates a current signal for controlling the laser light source 13. The current source 12 generates a current signal corresponding to the voltage signal of the signal generator 11. For example, the current source 12 generates a triangular wave current signal corresponding to the triangular wave voltage signal and outputs it to the laser light source 13.

[0016] The laser light source 13 emits light whose frequency is modulated (frequency-modulated light L3). For example, the laser light source 13 is configured using a distributed feedback (DFB) laser element. The laser light source 13 generates laser light whose frequency corresponds to the current signal of the current source 12. The laser light generated is frequency-modulated in the range of 193.4024 to 193.4266 THz (λ=1549.903 to 1550.097 nm). For example, the laser light source 13 generates laser light (frequency-modulated light L3) whose frequency gradually increases or decreases according to a triangular wave current signal. The laser light source 13 outputs the laser light to the optical device 20.

[0017] The temperature regulator 14 adjusts the temperature of the laser light source 13 (particularly the laser element) to a predetermined temperature. The temperature regulator 14 has, for example, a temperature sensor 14A and a thermoelectric element (for example, a Peltier element), and measures the temperature of the laser light source 13 with the temperature sensor 14A and adjusts the laser light source 13 to a predetermined temperature by feedback-controlling the thermoelectric element based on the measurement result of the temperature sensor 14A.

[0018] The optical device 20 is a device that irradiates the object 90 with frequency-modulated light (irradiation light L1) and causes reflected light L2 from the object 90 to interfere with reference light L4 (measurement light). The optical device 20 uses part of the measurement light (frequency-modulated light L3) input from the generation device 10 as irradiation light L1 to irradiate the object 90, and part of the measurement light input from the generation device 10 as reference light L4, and causes the reflected light L2 from the object 90 to interfere with the reference light L4 to generate interference light L5 (interference wave). The optical device 20 outputs the interference light L5 (interference wave) caused by interference between the reflected light L2 and the reference light L4 to the detection device 30.

[0019] The optical device 20 includes a branching device 21, a circulator 22, an optical system 23, an optical waveguide 24, and a coupler 25. The branching device 21 branches the frequency-modulated light L3 from the generation device 10. The branching device 21 is configured, for example, by an optical coupler. One of the branched light beams (frequency-modulated light L3) is output to the circulator 22 and becomes the illumination light L1 that is irradiated onto the object 90. The other branched light beam (frequency-modulated light L3) is output to the optical waveguide 24 and becomes the reference light L4 that interferes with the reflected light L2. The circulator 22 guides the light from the branching device 21 (illumination light L1) to the optical system 23, and guides the light from the optical system 23 (reflected light L2) to the coupler 25.

[0020] The optical system 23 irradiates light (irradiation light L1) toward the object 90 and collects and outputs reflected light L2. The optical system 23 is composed of optical elements such as lenses, mirrors, and prisms. The optical system 23 has, for example, a light-projecting optical system that irradiates the irradiation light L1 toward the object, and a light-receiving optical system that collects the reflected light L2. The optical system 23 may also have a function of scanning the irradiation light L1. The optical system 23 outputs the collected reflected light L2 to the circulator 22. The reflected light L2 is input to the coupler 25 via the circulator 22.

[0021] The optical waveguide 24 forms an optical path of a predetermined length from the splitter 21 to the coupler 25. The optical waveguide 24 guides the reference light from the splitter 21 to the coupler 25 over a predetermined optical path length. The optical waveguide 24 is made up of, for example, an optical fiber. The coupler 25 combines the reflected light L2 from the circulator 22 with the reference light L4 from the optical waveguide 24. The coupler 25 is made up of, for example, an optical coupler. The coupler 25 functions as an interferometer that causes interference between the reflected light L2 and the reference light L4, and generates interference light L5 (interference wave) by causing interference between the reflected light L2 and the reference light L4. The coupler 25 outputs the interference light L5 to the detection device 30.

[0022] The detection device 30 detects interference light L5 between the reflected light L2 and the reference light L4 and outputs a beat signal Sb. The detection device 30 has a photoelectric converter 31 and an amplifier 32. The photoelectric converter 31 outputs an electrical signal (current signal) corresponding to the intensity of the detected optical signal (here, interference light L5). The photoelectric converter 31 is, for example, a photodiode. The interference light L5 detected by the photoelectric converter 31 is a wave whose amplitude changes periodically due to interference between the reflected light L2 and the reference light L4, which have different frequencies.

[0023] The amplifier 32 converts the current signal of the photoelectric converter 31 into a voltage signal and outputs it. The amplifier 32 is configured, for example, by a transimpedance amplifier. The beat signal Sb output from the amplifier 32 is a signal that indicates the difference in frequency between the reflected light L2 and the reference light L4. The beat frequency of the beat signal Sb corresponds to the frequency of the beat component of the interference light L5. The beat frequency of the beat signal Sb also corresponds to the difference in frequency between the reflected light L2 and the reference light L4.

[0024] The signal processing device 40 is a device that calculates the distance to the object 90 based on the beat signal Sb. The signal processing device 40 has an A / D converter, an arithmetic unit, a storage device, etc. (not shown). The arithmetic unit is composed of an arithmetic processing device such as a CPU, a GPU, or an MPU. The storage device is composed of a main storage device and an auxiliary storage device, and is a device that stores programs and data. The arithmetic unit executes the programs stored in the storage device, thereby performing various processes for measuring the distance to the object 90. In FIG. 1, the various processes performed by the signal processing device 40 are shown as functional blocks. The signal processing device 40 is an example of a controller.

[0025] The signal processing device 40 has a signal acquiring unit 41, an analyzing unit 42, and an output unit 43. The signal acquiring unit 41 acquires the beat signal Sb of the detection device 30 as a digital signal. The signal acquiring unit 41 is configured by, for example, an A / D converter (such as an A / D conversion board). The analyzing unit 42 calculates the distance to the object 90 based on the beat signal Sb. The output unit 43 outputs the analysis result of the analyzing unit 42 to the outside. For example, the output unit 43 outputs distance data indicating the distance to the object 90 and speed data indicating the relative speed of the object 90 to a vehicle ECU, which is an external device.

[0026] A-2. Estimation process: FIG. 2 is an explanatory diagram showing the relative positional relationship between the measurement object and the measurement device, and FIG. 3 is a flowchart showing the estimation process. The estimation process is a process of detecting unevenness on the road surface R and estimating the estimated arrival time relative to the unevenness detected by the measurement device 1. In FIG. 2, a convex portion R1 is shown as an example of the unevenness on the road surface R. The object 90 is assumed to be traveling toward the convex portion R1 at a speed v with an acceleration α. ​​The unevenness on the road surface R (convex portion R1) is an example of the measurement object.

[0027] When the signal processing device 40 receives an instruction to start measurement from, for example, an external device, it executes the estimation process shown in Fig. 3. The signal processing device 40 determines whether the measurement timing has arrived (S110). The measurement timing is the timing that triggers the start of the measurement process of the measurement device 1 in units of one frame (the process of performing a light emission and reception operation, described below, once to obtain a measurement result (point cloud data)). If the signal processing device 40 determines that the measurement timing has not arrived (S110: NO), it waits.

[0028] When the signal processing device 40 determines that the measurement timing has arrived (S110: YES), it causes the optical device 20 to perform a light projecting and receiving operation (S120). The light projecting and receiving operation is an operation in which irradiation light L1 is directed toward a plurality of different locations on the measurement object (such as the convex portion R1) and reflected light L2 from each of the locations is received. In this way, the signal processing device 40 acquires one frame of point cloud data. The point cloud data is data on a plurality of measurement points corresponding to each of a plurality of different locations on the measurement object.

[0029] Next, the signal processing device 40 determines whether or not there is a measurement target based on the timing of receiving reflected light L2 from multiple locations (point cloud data) (S130). The measurement target here refers to an object, background, etc. measured by the measurement device 1 that satisfies the execution conditions for estimating the estimated arrival time. In this embodiment, for example, this refers to unevenness in the road surface R that has a height difference equal to or greater than a predetermined reference value. If the signal processing device 40 determines that there is no measurement target (S130: NO), it returns to S110 and waits until the next measurement timing.

[0030] When it is determined that a measurement object is present (S130: YES), the signal processing device 40 acquires the distance D from the measuring device 1 to the measurement object (protrusion R1) based on the point cloud data (S140).

[0031] Next, the signal processing device 40 acquires velocity data indicating the relative velocity of the measuring device 1 with respect to the measurement target (hereinafter simply referred to as "velocity v") (S150). As described above, the measuring device 1 of this embodiment employs the FMCW method, and therefore can acquire velocity v based on one frame of point cloud data.

[0032] Next, the signal processing device 40 acquires acceleration data indicating the relative acceleration of the measuring device 1 with respect to the measurement target (hereinafter simply referred to as "acceleration α") (S160). For example, the signal processing device 40 acquires the acceleration data for each measurement point of the point cloud data based on changes in velocity v between multiple different frames. Specifically, for each measurement point, the signal processing device 40 calculates the acceleration α from the difference between velocity v0 in the frame at the previous measurement timing and velocity v1 in the frame at the current measurement timing.

[0033] The signal processing device 40 can correct the relative positional relationship in the measurement results of the multiple locations based on multiple light receiving timings (point cloud data) corresponding to the multiple locations and the acceleration α. ​​Specifically, the signal processing device 40 calculates the measurement position Y1 of each measurement point based on the following equation 1, and converts it into the corrected position Y of the measurement point. 1h Correct to. Y 1h =Y1-[(1 / 2)×(v1-v0)×Δt 2 ]-(v1×Δt)·Equation 1 Δt: Time difference between the previous measurement and the current measurement

[0034] Next, the signal processing device 40 estimates the estimated arrival time (S170). Here, the estimated arrival time is a predicted time from the measurement timing at which the measurement target (protrusion R1) is detected until the measuring device 1 (object 90) reaches the measurement target. The signal processing device 40 estimates the estimated arrival time based on the distance D to the measurement target (protrusion R1), the speed v of the measurement target, and the acceleration α of the measurement target. By considering not only the speed v of the measurement target but also the acceleration α of the measurement target, the signal processing device 40 can grasp the speed fluctuations until the measuring device 1 (object 90) reaches the measurement target, and can therefore accurately estimate the estimated arrival time.

[0035] Next, the signal processing device 40 outputs the estimated estimated arrival time to an external device (such as the vehicle body) (S180). Based on the estimated estimated arrival time, the vehicle body may, for example, reduce the vehicle's elevation fluctuation caused by the unevenness of the road surface R by changing the strength of the vehicle's suspension, or may slow down or stop the vehicle.

[0036] Thereafter, the signal processing device 40 returns to S110. Note that the signal processing device 40 may return to S110 and execute the next light projection and reception operation before completing the processes of S130 to S180. In other words, the processes of S130 to S180 for one frame and the light projection and reception operation for the next frame may be executed simultaneously in parallel.

[0037] A-3. Advantages of this embodiment: As described above, in the measuring device 1 according to this embodiment, the signal processing device 40 estimates the estimated time of arrival based on the distance D to the measurement target (protrusion R1) and the speed v of the measurement target (S14, 150, S170 in FIG. 3). As a result, according to this embodiment, it is possible to estimate the estimated time of arrival of the measuring device 1 relative to the measurement target without needing to obtain speed information (traveling speed, etc.) of the measurement target from an external source.

[0038] In this embodiment, the signal processing device 40 estimates the estimated arrival time based on the acceleration α of the measurement target (S160 in FIG. 3). This makes it possible to prevent a decrease in the accuracy of estimating the estimated arrival time due to fluctuations in the speed of the measurement device 1 when the measurement device 1 (target 90) accelerates or decelerates.

[0039] B. Variations: The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified into various forms without departing from the spirit thereof, for example, the following modifications are also possible.

[0040] The configuration of the measuring device 1 in the above embodiment is merely an example and can be modified in various ways. For example, the measuring device 1 is of a flash type, but is not limited to this, and may be of a scanning type equipped with a scanner. The measuring device 1 may be fixed at a predetermined position, and the measurement target may move relative to the measuring device 1. Both the measuring device 1 and the measurement target may move relative to each other. The measurement target is not limited to the unevenness of the road surface R, but may also be, for example, an object on the road surface R (such as an obstacle or sign) or an object outside the road surface R (such as an obstacle or sign).

[0041] In the above embodiment, the measurement device 1 employs the FMCW method. However, a measurement device other than the FMCW method may also be used. Such a measurement device can calculate the velocity of the measurement object based on the positional deviation of each measurement point between multiple frames and the light projection period. Then, the velocity between frames at different timings is acquired, and the acceleration of the measurement object can be acquired based on the difference between these velocities. For example, for a certain measurement point, a first velocity is calculated based on the positional deviation between the position in a first frame and the position in a subsequent second frame and the light projection period. Next, a second velocity is calculated based on the positional deviation between the position in the second frame and the position in a subsequent third frame and the light projection period. The acceleration of the measurement object is acquired from the difference between the first velocity and the second velocity.

[0042] In the estimation process of the above embodiment, the signal processing device 40 may always execute the processes from S140 onwards without executing the determination of S130. Also, in the estimation process, the signal processing device 40 may estimate the estimated time of arrival based on the distance D to the measurement target and the speed v of the measurement target without executing the process of S150. [Explanation of symbols]

[0043] 1: Measuring device 10: Generating device 11: Signal generator 12: Current source 13: Laser light source 14: Temperature controller 14A: Temperature sensor 20: Optical device 21: Branching device 22: Circulator 23: Optical system 24: Optical waveguide 25: Coupler 30: Detecting device 31: Photoelectric converter 32: Amplifier 40: Signal processing device 41: Signal acquisition unit 42: Analysis unit 43: Output unit 90: Object L1: Irradiated light L2: Reflected light R1: Convex portion R: Road surface

Claims

1. A floodlight that emits light; a light receiver that receives reflected light that is emitted by the light projector and reflected back from the object to be measured; a controller, The controller acquiring a distance to the measurement object and a speed of the measurement object based on a timing of receiving the reflected light at the light receiver; A measurement device that estimates an estimated time of arrival of the measurement device relative to the measurement target based on the distance to the measurement target and the speed of the measurement target.

2. 2. The measuring device according to claim 1, The controller further acquiring an acceleration of the measurement object based on a timing of receiving the reflected light at the light receiver; A measuring device that estimates the estimated time of arrival based on the distance to the object to be measured, the speed of the object to be measured, and the acceleration of the object to be measured.

3. 3. The measuring device according to claim 2, The measuring device is an FMCW type, The controller A measurement device that acquires acceleration of the measurement object based on a difference in velocity of the measurement object between multiple frames.

4. A floodlight that emits light; a light receiver that receives reflected light that is emitted by the light projector and reflected back from the object to be measured; A control method for a measurement device comprising: acquiring a distance to the measurement object and a speed of the measurement object based on a timing of receiving the reflected light at the light receiver; A method for controlling a measuring device, comprising: estimating an estimated time of arrival of the measuring device relative to the object to be measured based on the distance to the object to be measured and the speed of the object to be measured.

5. A floodlight that emits light; a light receiver that receives reflected light that is emitted by the light projector and reflected back from the object to be measured; a computer included in the measurement device, acquiring a distance to the measurement object and a speed of the measurement object based on a timing of receiving the reflected light at the light receiver; A control program for a measuring device that causes the measuring device to estimate an estimated time of arrival relative to the measurement target based on the distance to the measurement target and the speed of the measurement target.

6. A floodlight that emits light; a light receiver that receives reflected light that is emitted by the light projector and reflected back from the object to be measured; A computer-readable recording medium having a computer program recorded thereon for controlling a measurement device including a controller, acquiring a distance to the measurement object and a speed of the measurement object based on a timing of receiving the reflected light at the light receiver; A computer-readable recording medium having a computer program recorded thereon, which causes the measuring device to estimate an estimated time of arrival relative to the object to be measured, based on the distance to the object to be measured and the speed of the object to be measured.

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