Distance measuring device

Abstract

To provide a distance measuring device that can appropriately detect an abnormality in the operating state of a scanning unit.SOLUTION: A distance measuring device 1 comprises a scanning unit 20, an encoder 40, and a control unit 50. The scanning unit 20 has a mirror 21 that reflects a transmitted wave, and an oscillation motor 30 that drives to oscillate the mirror 21 so that the transmitted wave scans a scanning range. The encoder 40 outputs an angle signal according to the rotation of the mirror 21. The control unit 50 has a position calculation unit 51, a drive control unit 53, and an abnormality diagnosis unit 55. The position calculation unit 51 calculates the position of an object that has reflected a scanned light beam. The drive control unit 53 controls the drive of the oscillation motor 30. The abnormality diagnosis unit 55 performs abnormality diagnosis related to the operating state of the scanning unit 20 based on a signal output from the encoder 40.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a distance measuring device. [Background technology]

[0002] Distance measuring devices are known that detect the distance to an object by emitting a transmission wave and detecting the reflected wave from the object. Distance measuring devices are equipped with a scanning unit that changes the direction of emission of the transmission wave. For example, in Patent Document 1, a mirror that is driven to oscillate is used in the scanning unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-81419 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the rotational position of the mirror is controlled by detecting the position with an incremental encoder. However, Patent Document 1 does not mention details of abnormality detection in the scan unit.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has as its object to provide a distance measuring device capable of appropriately detecting an abnormality in the operating state of a scan unit. [Means for solving the problem]

[0006] The distance measuring device of the present invention includes a scanning unit (20), an encoder (40), and a control unit (50). The scanning unit (20) has a mirror (21) that reflects a transmission wave, and an actuator (30) that drives the mirror to swing so that the transmission wave scans a scanning range. The encoder outputs an angle signal according to the rotational position of the mirror.

[0007] The control unit has a position calculation unit (51), a drive control unit (53), and an abnormality diagnosis unit (55). The position calculation unit calculates the position of an object that reflects the scanned transmission wave. The drive control unit controls the drive of the actuator. The abnormality diagnosis unit performs abnormality diagnosis related to the operating state of the scan unit based on the signal output from the encoder. This makes it possible to properly detect abnormalities in the operating state of the scan unit. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram showing a configuration of a distance measuring device according to an embodiment; [Diagram 2] 1 is a schematic diagram showing a distance measuring device according to an embodiment as viewed from above; [Diagram 3] FIG. 2 is a perspective view showing a measurement unit according to one embodiment. [Figure 4] 1 is a schematic diagram corresponding to a cross section of a swing motor according to an embodiment taken along a plane perpendicular to a swing shaft; [Diagram 5] FIG. 2 is an exploded perspective view of an encoder according to one embodiment; [Figure 6] 5A-5C are schematic diagrams illustrating the operation of a mirror according to one embodiment. [Figure 7] FIG. 4 is a diagram illustrating an A-phase signal, a B-phase signal, and a Z-phase signal according to one embodiment. [Figure 8] 11 is a flowchart illustrating a scanning control according to an embodiment. [Figure 9] 4 is a time chart illustrating scanning control according to an embodiment. [Figure 10] 4 is a time chart illustrating an amplitude anomaly according to an embodiment. [Figure 11] 11 is a flowchart illustrating an amplitude abnormality diagnosis process according to an embodiment. [Figure 12] 4 is a time chart illustrating an angular velocity abnormality according to an embodiment. [Figure 13] 10 is a flowchart illustrating an angular velocity abnormality diagnosis process according to an embodiment. [Figure 14]4 is a time chart illustrating an angle signal abnormality according to an embodiment. [Figure 15] 4 is a flowchart illustrating an angle signal abnormality diagnosis process according to an embodiment. [Figure 16] 4 is a time chart illustrating a reference signal abnormality according to an embodiment. [Figure 17] 10 is a flowchart illustrating a reference signal abnormality diagnosis process according to an embodiment. [Figure 18] 13A is a time chart showing the mirror angle and angular velocity when the distance measurement period is relatively long, and FIG. 13B is a time chart showing the mirror angle and angular velocity when the distance measurement period is relatively short. [Figure 19] 13A is a time chart showing an angle signal when the distance measurement period is relatively long, and FIG. 13B is a time chart showing an angle signal when the distance measurement period is relatively short. [Figure 20] 13A is a time chart showing the mirror angle when the distance measurement range is relatively wide, and FIG. 13B is a time chart showing the mirror angle when the distance measurement range is relatively narrow. [Figure 21] 13A is a time chart showing the angular velocity when the distance measurement range is relatively wide, and FIG. 13B is a time chart showing the angular velocity when the distance measurement range is relatively narrow. [Figure 22] 13A is a time chart showing an angle signal when the distance measurement range is relatively wide, and FIG. 13B is a time chart showing an angle signal when the distance measurement range is relatively narrow. [Diagram 23] 13A is a time chart showing the mirror angle and angular velocity when measuring distance during forward rotation, and FIG. 13B is a time chart showing the mirror angle and angular velocity when measuring distance during reverse rotation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (One embodiment) A distance measuring device according to the present invention will be described below with reference to the drawings. One embodiment is shown in Figs. 1 to 23. As shown in Figs. 1 and 2, the distance measuring device 1 is a LiDAR (Light Detection and Ranging) device that measures the distance to an object by irradiating light and detecting reflected light from the object onto which the light is irradiated. The distance measuring device 1 is mounted on, for example, a vehicle and used to detect an object present in front of the vehicle.

[0010] The distance measuring device 1 includes a measurement unit 5 and a control unit 50. The measurement unit 5 includes a light emitting unit 10, a light receiving unit 15, a scanning unit 20, and an encoder 40. As shown in FIG. 2, the measurement unit 5 is housed in a housing 6. The housing 6 is a rectangular parallelepiped made of, for example, resin, and has an opening on one side. A transparent optical window 7 that transmits light is provided in the opening so as to cover the entire opening.

[0011] The light emitting unit 10 is accommodated on the upper side and the light receiving unit 15 is accommodated on the lower side within the housing 6. The light emitting unit 10 intermittently outputs a light beam B. The light receiving unit 15 receives reflected light R from an object irradiated with the light beam B and converts it into an electrical signal.

[0012] The scanning unit 20 includes a mirror 21 that is driven to oscillate, and a oscillating motor 30 (see FIG. 3) that oscillates the mirror 21. The scanning unit 20 reflects the light beam B output from the light emitting unit 10 by the mirror 21, and emits the light beam B from the optical window 7 to the outside in a direction according to the rotational position of the mirror 21, thereby scanning the light beam B within a preset scanning range.

[0013] 3, the mirror 21 is a flat member having a reflective surface that reflects light, and is attached to the oscillating shaft 22 so as to move integrally with the oscillating shaft 22. The oscillating shaft 22 is formed to extend in the vertical direction, and the mirror 21 is fixed to the oscillating shaft 22 on the surface opposite to the reflective surface so that the oscillating shaft 22 is aligned along the vertical center line of the surface.

[0014] The swing motor 30 is disposed vertically below the mirror 21, and drives the swing shaft 22 to swing the mirror 21 about the swing shaft 22. This causes the light beam B output from the light-emitting unit 10 to scan a predetermined scanning range.

[0015] As shown in Fig. 4, the oscillating motor 30 has a rotary magnet 31, a pair of fixed magnets 32, an electromagnetic coil 33, and a rotary shaft 35, and is housed in a case 38. The rotary magnet 31 is a disk-shaped magnet with an axial hole at the center. The rotary shaft 35 is fixed in the axial hole of the rotary magnet 31 by press-fitting or the like. The rotary shaft 35 is rotatably supported by the case 38. The rotary magnet 31 is disposed so that the direction in which both poles are arranged is perpendicular to the axial direction.

[0016] The pair of fixed magnets 32 are fixed to case 38 so that the direction in which the poles are arranged is perpendicular to the axial direction of rotation shaft 35 (i.e., the vertical direction in the plane of FIG. 4). In the example of FIG. 4, fixed magnet 32 ​​is arranged so that the upper side of the plane of the paper is the S pole and the lower side is the N pole.

[0017] The magnetic field of the rotating magnet 31 and the magnetic field of the pair of fixed magnets 32 interact with each other, causing the rotating magnet 31 to stop at a stationary position where its magnetic poles are in the opposite direction to the magnetic poles of the fixed magnets 32. Fig. 4 shows the rotating magnet 31 at a stationary position, and in the example of Fig. 4, the upper side of the page of the rotating magnet 31 is the north pole, and the lower side is the south pole. In other words, the rotating magnet 31 can be considered to be urged by the magnetic force of the fixed magnets 32 to return to the stationary position.

[0018] 4, and when energized, generates magnetic field lines having a perpendicular component to the magnetic field lines generated between the rotating magnet 31 and the fixed magnet 32. The electromagnetic coil 33 is connected to an AC power supply or a pulse oscillation power supply.

[0019] When no current is applied, the rotating magnet 31 remains stationary at the stationary position shown in Fig. 4. When current is applied to the electromagnetic coil 33, magnetic field lines having a perpendicular component to the magnetic field lines generated between the rotating magnet 31 and the fixed magnet 32 ​​are generated, and the rotating magnet 31 oscillates around the stationary position.

[0020] The oscillation is a motion in which the rotational motion is periodically repeated between forward and reverse rotation within a predetermined angle range less than 360°. The rotary magnet 31 rotates forward from the rest position to a predetermined angle, then switches to reverse rotation, returns to the rest position, and then rotates reversely from the rest position to a predetermined angle. It then switches to forward rotation again, returns to the rest position, and repeats the above operation. In this embodiment, the angle range of forward rotation from the rest position is equal to the angle range of reverse rotation, but the angle range of the forward rotation direction and the angle range of the reverse rotation direction may be different. When the power supply to the electromagnetic coil 33 is cut off, the rotary magnet 31 returns to the rest position and stops.

[0021] The further away from the stationary position, the stronger the repulsive force between the rotary magnet 31 and the fixed magnet 32. Therefore, in order to hold it in a fixed position, the greater the rotation angle from the stationary position, the more torque is required to overcome the repulsive force.

[0022] In this embodiment, clockwise rotation in Fig. 4 is defined as forward rotation, and counterclockwise rotation is defined as reverse rotation. Note that the rotation direction in Fig. 4 corresponds to the rotation direction when the distance measuring device 1 is mounted on a vehicle and viewed from above in the vertical direction.

[0023] The oscillating shaft 22 is provided so as to move integrally with the rotary magnet 31. That is, the oscillating shaft 22 stops at a stationary position when the oscillating motor 30 is not energized, and oscillates around the stationary position when energized.

[0024] The mirror 21 is attached to the oscillation shaft 22 so that, when the oscillation shaft 22 is at a rest position, the mirror 21 is at a reference position where the light beam B can be reflected toward approximately the center of the scanning range. The mirror 21 oscillates within a predetermined angle range including the reference position as the oscillation shaft 22 rotates. When the power supply to the oscillation motor 30 is cut off, the oscillation shaft returns to the rest position, and the mirror 21 returns to the reference position and becomes stationary. That is, the mirror 21 is biased in a direction returning to the reference position by the magnetic force of the fixed magnet 32.

[0025] 5, the encoder 40 detects the rotation angle of the mirror 21, and in this embodiment is a three-phase output type incremental encoder. The encoder 40 has a rotating disk 41, a fixed slit 42, a light-emitting element 43, and a light-receiving element 44.

[0026] The rotating disk 41 is formed in a disk shape. The rotating disk 41 has a plurality of outer peripheral slits 411 formed on the outer periphery, and an origin slit 413 indicating an origin position formed on the inner periphery side of the outer peripheral slits 411. A rotating shaft 415 of the rotating disk 41 is fixed to the oscillating shaft 22. As a result, the rotating disk 41 rotates integrally with the oscillating shaft 22 as indicated by the arrow E.

[0027] In order to make the output signal have multiple phases, three types of slits, namely, A-phase slits 421, B-phase slits 422, and Z-phase slits 423, are formed in fixed slits 42. A-phase slits 421 and B-phase slits 422 are formed at positions facing outer peripheral slits 411 of rotating disk 41 so that the phase difference between the A-phase output signal and the B-phase output signal is 90°. Z-phase slit 423 is formed at a position facing origin slit 413.

[0028] The light-emitting element 43 is, for example, a light-emitting diode, and emits light toward the rotating disk 41. The light-emitting element 43 and the light-receiving element 44 are provided to face each other with the rotating disk 41 and the fixed slit 42 in between. The light-receiving element 44 is, for example, a phototransistor, and receives light that has passed through the slits of the rotating disk 41 and the fixed slit 42, and outputs A-phase, B-phase, and Z-phase pulse signals. The encoder 40 detects edges of the A-phase and B-phase signals, and accumulates a counter. Also, when a rising edge of the Z-phase is detected, the counter is reset.

[0029] Fig. 6 is a schematic diagram showing a cross section of mirror 21 cut by a plane perpendicular to oscillation axis 22. Fig. 6 shows a state in which mirror 21 is in a reference position in the center of the page, with the state in which mirror 21 moves from the left to the right on the page corresponding to forward rotation, and the state in which mirror 21 moves from the right to the left on the page corresponding to reverse rotation.

[0030] The encoder 40 is installed on the oscillating motor 30 so that a Z-phase signal is output when the mirror 21 is at the reference position. That is, the rotating shaft 415 of the rotating disk 41 is fixed to the oscillating shaft 22 so that a Z-phase signal is output when the oscillating shaft 22 is at a stationary position. If the angle between the mirror 21 and the light beam B output from the light emitting unit 10 at the reference position is X° (45° in this embodiment), then the Z-phase signal is output at X°.

[0031] 7, when the mirror 21 rotates forward, the B-phase signal is output with a delay of 90° from the A-phase signal. When the mirror 21 rotates backward, the A-phase signal is output with a delay of 90° from the B-phase signal. This allows the encoder 40 to detect the mirror angle θ, which is the rotation angle of the mirror 21 with respect to the reference position, based on the waveforms of the A-phase signal and the B-phase signal after the Z-phase signal is detected.

[0032] 1, the control unit 50 is mainly composed of a microcomputer and includes a CPU, ROM, RAM, I / O, and bus lines connecting these components (all not shown). Each process in the control unit 50 may be software processing in which the CPU executes a program stored in advance in a substantial memory device (i.e., a readable non-transitory tangible recording medium) such as a ROM, or may be hardware processing in which a dedicated electronic circuit is used.

[0033] The control unit 50 has a position calculation unit 51, a drive control unit 53, and an abnormality diagnosis unit 55 as functional blocks. The position calculation unit 51 calculates the distance to the object that reflected the light beam B. Specifically, the position calculation unit 51 identifies the timing of receiving the reflected light based on the waveform of the electrical signal output from the light receiving unit 15, and calculates the distance to the object from the difference with the timing of outputting the light beam. The position calculation unit 51 can also calculate position information such as the orientation of the object that reflected the light beam. The drive control unit 53 controls the drive of the swing motor 30 that drives the mirror 21. The abnormality diagnosis unit 55 judges whether the scan unit 20 is abnormal. When an abnormality in the scan unit 20 is detected, for example, the distance measurement is stopped.

[0034] The drive control unit 53 performs alignment control prior to scanning control. In alignment control, the oscillating motor 30 is driven at a predetermined voltage value by open loop control that does not use the detection value of the encoder 40. An origin search is performed by alignment control, and the position where the Z-phase signal is detected is set as the mirror angle θ=0°. In addition, the angle difference with the mirror position when no current is applied is stored as a correction value. Note that since the oscillating motor 30 is biased in the direction returning to the reference position, the oscillation range in alignment control does not need to be the same as that in scanning control, and a relatively narrow range is sufficient.

[0035] After the alignment control, the drive control unit 53 performs scanning control to drive the swing motor 30 so as to swing the mirror 21 within a predetermined angle range from the reference position to perform scanning with the light beam. The scanning control is a feedback control based on the detection value of the encoder 40.

[0036] The scanning control of this embodiment will be described with reference to the flowchart of Fig. 8. This process is executed at a predetermined cycle by the control unit 50 after the alignment control. Hereinafter, the "step" such as step S101 will be omitted and simply denoted by the symbol "S".

[0037] In S101, the control unit 50 acquires the current mirror angle θ and angular velocity ω based on the detection value of the encoder 40. In S102, the drive control unit 53 acquires the target mirror angle θ based on the elapsed time from the start of scanning control. * In this embodiment, the target mirror angle θ is calculated according to time so that the mirror 21 is oscillated at a constant period. * is set.

[0038] In S103, the drive control unit 53 sets the target mirror angle θ * From the difference Δθ between the current mirror angle θ and the target angular velocity ω * In S104, the drive control unit 53 calculates the target angular velocity ω * The target duty ratio D in PWM control is calculated from the difference Δω between the current angular velocity ω and * In S105, the drive control unit 53 calculates the target duty ratio D * Then, the oscillation motor 30 is energized.

[0039] The scanning control of this embodiment will be described based on the time chart of Fig. 9. In Fig. 9, the horizontal axis represents a common time axis, and from the top, the mirror angle θ, the angular velocity ω, the motor current, the A-phase signal, the B-phase signal, and the Z-phase signal are shown.

[0040] The mirror angle θ is calculated by detecting the edges of the A-phase signal and the B-phase signal and integrating the counter, with 0° being the angle when the mirror 21 is at the reference position. Detection deviations and the like can be reset by resetting the counter upon detection of an edge of the Z-phase signal. The angular velocity ω is calculated by the time differentiation of the mirror angle θ. One cycle of scanning control is defined as the period from when a Z-phase pulse is detected during reverse rotation to when a Z-phase pulse is next detected during reverse rotation. One cycle of scanning control is also referred to as the "distance measurement cycle" as appropriate.

[0041] In the scanning control, the mirror 21 is swung by alternately performing a forward rotation period in which the mirror 21 is driven at a constant speed from one side to the other side of the reference position and a reverse rotation period that is relatively shorter than the forward rotation period in which the mirror 21 is driven back from the other side to the one side. In addition, when the mirror 21 is rotating at a constant speed during the forward rotation period, distance measurement is performed by the LiDAR.

[0042] However, if there is an abnormality in the angular velocity ω or the detection value of the encoder 40, the accuracy of the distance measurement to the object decreases, or normal distance measurement becomes impossible. Therefore, in this embodiment, the abnormality diagnosis unit 55 performs an abnormality determination based on the signal output from the encoder 40.

[0043] The amplitude abnormality diagnosis of this embodiment will be described with reference to Fig. 10 and Fig. 11. Fig. 10 is a simplified time chart, and reference lines and the like are omitted as appropriate. Moreover, behavior during abnormality is indicated by a circle with a dashed dotted line. The same applies to the time charts explaining various abnormality diagnoses described later, such as Fig. 12.

[0044] As shown in Figure 10, when no amplitude abnormality occurs, the rotation direction is reversed when the mirror angle θ is within the normal range. On the other hand, when an amplitude abnormality occurs, as shown by the dashed-dotted circle, the rotation direction is reversed before reaching the normal range, and the amplitude of the mirror angle θ is narrower than normal. The amplitude of the mirror angle θ corresponds to the LiDAR field of view, and when the amplitude of the mirror angle θ is small, it can be said that the field of view in scanning control is narrow. When a defect occurs in the LiDAR field of view, there is a possibility that obstacles, etc. will be overlooked, so it is judged to be an abnormality.

[0045] The amplitude abnormality diagnosis process will be described with reference to the flowchart of Fig. 11. In S201, the abnormality diagnosis unit 55 judges whether the distance measurement control is stable or not. For example, if the origin position or correction value is reset at the start of operation, control to the targeted angle is not possible, so abnormality diagnosis is not performed. Here, if the origin has been searched for and correction processing using the correction value can be performed, a positive judgment is made. If it is judged that the distance measurement control is not stable (S201: NO), the process from S202 onwards is skipped.

[0046] In S202, the abnormality diagnosis unit 55 judges whether one cycle of the scan control has been completed. If it is judged that one cycle has not been completed (S202: NO), this judgment process is repeated. If it is judged that one cycle has been completed (S202: YES), the process proceeds to S203, where the maximum value θmax and the minimum value θmin of the mirror angle θ during one cycle are obtained.

[0047] In S204, the abnormality diagnosis unit 55 judges whether or not at least one of the maximum value θmax and the minimum value θmin is outside the normal range. If it is judged that the maximum value θmax and the minimum value θmin are within the normal range (S204: NO), the process from S205 onwards is skipped. If it is judged that at least one of the maximum value θmax and the minimum value θmin is outside the normal range (S204: YES), the process proceeds to S205.

[0048] In S205, the abnormality diagnosis unit 55 judges whether or not at least one of the maximum value θmax and the minimum value θmin is out of the normal range for n consecutive periods. n can be set to any natural number (e.g., n=2). The same applies to the embodiments described below. If it is judged that at least one of the maximum value θmax and the minimum value θmin is out of the normal range for less than n consecutive periods (S205: NO), the process of S206 is skipped. If it is judged that at least one of the maximum value θmax and the minimum value θmin is out of the normal range for n consecutive periods (S205: YES), the process proceeds to S206 and detects it as an amplitude abnormality.

[0049] The angular velocity anomaly diagnosis of this embodiment will be described with reference to Fig. 12 and Fig. 13. Fig. 12 shows, from the top, the mirror angle θ, the angular velocity ω, and the angular velocity anomaly counter Cω, with the horizontal axis representing a common time axis.

[0050] As shown in Fig. 12, during normal rotation, feedback control is performed to keep the angular velocity ω constant for LiDAR measurement. If an angular velocity anomaly occurs that causes the angular velocity ω during normal rotation to fall outside the normal range, the angle accuracy of the LiDAR decreases. The upper limit of the normal range is determined by the CPU's computing power, and the lower limit is determined by the LiDAR measurement cycle. If the angular velocity ω falls outside the normal range, visual field loss and cycle delays occur due to excessive processing power, making accurate position detection impossible, and it is determined to be an anomaly.

[0051] The angular velocity abnormality diagnosis process will be described with reference to the flowchart of Fig. 13. In S301, the abnormality diagnosis unit 55 judges whether the distance measurement control is stable and is operating in the forward rotation direction. If it is judged that the distance measurement control is not stable or is operating in the reverse rotation direction (S301: NO), the process from S302 onwards is skipped. If it is judged that the distance measurement control is stable and is operating in the forward rotation direction (S301: YES), an angular velocity abnormality diagnosis is performed. In S302, which is entered after a positive judgment in S301, the current angular velocity ω is obtained.

[0052] In S303, the abnormality diagnosis unit 55 judges whether the angular velocity ω is outside the normal range. If it is judged that the angular velocity ω is within the normal range (S303: NO), the process of S304 and thereafter is skipped. If it is judged that the angular velocity ω is outside the normal range (S303: YES), the process proceeds to S304, and the angular velocity abnormality counter Cω is incremented. Note that the angular velocity abnormality counter Cω is reset at the end of one period.

[0053] In S305, the abnormality diagnosis unit 55 judges whether the angular velocity abnormality counter Cω is greater than the abnormality determination threshold THω. If it is judged that the angular velocity abnormality counter Cω is equal to or less than the abnormality determination threshold THω (S305: NO), the process of S306 and thereafter is skipped. If it is judged that the angular velocity abnormality counter Cω is greater than the abnormality determination threshold THω (S305: YES), the process proceeds to S306.

[0054] In S306, the abnormality diagnosis unit 55 judges whether the state in which the angular velocity abnormality counter Cω is greater than the abnormality determination threshold THω has continued for n consecutive periods. If it is judged that the state in which the angular velocity abnormality counter Cω is greater than the abnormality determination threshold THω has continued for less than n periods (S306: NO), the process of S307 is skipped. If it is judged that the state in which the angular velocity abnormality counter Cω is greater than the abnormality determination threshold THω has continued for n consecutive periods (S306: YES), the process proceeds to S307 and an angular velocity abnormality is detected. Note that the number of periods related to abnormality detection may be the same value or may be different values ​​depending on the abnormality to be detected.

[0055] Angle signal abnormality diagnosis will be explained with reference to Figs. 14 and 15. Fig. 14 has a common time axis as the horizontal axis, and from the top, shows the mirror angle, the A-phase signal, the B-phase signal, and the pulse interval. In Fig. 14, the A-phase signal and the B-phase signal are collectively described as "AB phase." The same applies to Figs. 19 and 22 described below. The pulse interval is the interval between edges, and is the time counted from when an edge is detected until the next edge is detected. When an edge is detected, the time count is reset and counting begins again.

[0056] As shown in FIG. 14, as described above, during forward rotation, the angular velocity ω is controlled to be constant for LiDAR measurement. Therefore, during forward rotation, the pulse detection intervals of the A-phase signal and B-phase signal, which are angle signals, are approximately constant under normal circumstances. On the other hand, if the number of pulses increases due to pulse loss or noise, the pulse detection intervals become unstable. If the pulse intervals become unstable, the calculated angle differs from the actual mirror position, making it impossible to detect the position accurately, and therefore an abnormality is determined.

[0057] The angle signal abnormality diagnosis process will be described with reference to the flowchart of Fig. 15. The process of S401 is similar to the process of S301 in Fig. 13. If a positive determination is made in S401, an angle signal abnormality diagnosis is performed. In S402, the abnormality diagnosis unit 55 detects the rising and falling edges of the A-phase signal and the B-phase signal, and obtains a pulse interval from the time interval between the edges.

[0058] In S403, the abnormality diagnosis unit 55 judges whether the pulse interval is outside the normal range. If it is judged that the pulse interval is within the normal range (S403: NO), the process of S404 is skipped. If it is judged that the pulse interval is outside the normal range (S403: YES), the process proceeds to S404 and the angle signal is detected as abnormal.

[0059] The reference signal abnormality diagnosis will be explained with reference to Fig. 16 and Fig. 17. Fig. 16 has a common time axis as the horizontal axis, and from the top, it shows the mirror angle θ, the Z-phase signal, and the number of edge detections. As shown in Fig. 16, when distance measurement control is being performed, the origin is crossed twice in one period, so that under normal circumstances, the Z-phase signal detects four edges, including rising and falling edges. On the other hand, if the number of pulses increases due to pulse loss or noise, the number of edge detections will be other than four. If the Z-phase signal is abnormal, the reference position will shift and accurate position detection will no longer be possible, so it is determined to be abnormal.

[0060] The reference signal abnormality diagnosis process will be described with reference to the flowchart of Fig. 17. The processes of S501 and S502 are similar to the processes of S201 and S202 in Fig. 11. Note that the period of one cycle may be different from that of Fig. 9, for example, as shown in Fig. 16, one cycle is defined as from the start of reverse rotation to the end of forward rotation, so as to facilitate edge detection of the Z-phase signal.

[0061] In S503, abnormality diagnosis unit 55 acquires the number of pulse edges of the Z phase signal in one period. In S504, abnormality diagnosis unit 55 determines whether the number of pulse edges of the Z phase signal is outside the normal range. If it is determined that the number of pulse edges of the Z phase signal is within the normal range (S504: NO), that is, if the number of pulse edges of the Z phase signal is four, the processing from S505 onwards is skipped. If it is determined that the number of pulse edges of the Z phase signal is outside the normal range (S504: YES), that is, if the number of pulse edges of the Z phase signal is other than four, the processing proceeds to S505.

[0062] In S505, the abnormality diagnosis unit 55 determines whether the number of pulse edges of the Z-phase signal is out of the normal range for n consecutive periods. If it is determined that the number of pulse edges of the Z-phase signal is out of the normal range for less than n consecutive periods (S505: NO), the process of S506 is skipped. If it is determined that the number of pulse edges of the Z-phase signal is out of the normal range for n consecutive periods (S506: YES), the process proceeds to S506 and detects the reference signal as abnormal.

[0063] Here, the operation method of the distance measuring device 1 may be changed depending on the mobility to be applied. In this embodiment, by changing the normal range, it is possible to determine an abnormality depending on the mobility to be applied.

[0064] Fig. 18(a) shows the case where the distance measurement cycle is relatively long, and Fig. 18(b) shows the case where the distance measurement cycle is relatively short. When the distance measurement cycle is short, the angular velocity ω is larger than when the distance measurement cycle is relatively long. In such a case, it is possible to determine an abnormality by shifting the normal range.

[0065] Fig. 19(a) shows a case where the distance measurement cycle is relatively long, and Fig. 19(b) shows a case where the distance measurement cycle is relatively short. When the distance measurement cycle is short, the pulse intervals of the A-phase signal and the B-phase signal become smaller than when the distance measurement cycle is long. In such a case, it is possible to determine an abnormality by shifting the normal range.

[0066] Fig. 20(a) shows a case where the distance measurement range is relatively wide, and Fig. 20(b) shows a case where the distance measurement range is relatively narrow. When the distance measurement range is narrow, the amplitude of the mirror angle θ is smaller than when the distance measurement range is wide. In such a case, it is possible to determine whether there is an abnormality by shifting the normal range.

[0067] 21(a) shows a case where the distance measurement range is relatively wide, and FIG. 21(b) shows a case where the distance measurement range is relatively narrow, and the distance measurement cycles are the same. When the distance measurement cycles are the same and the distance measurement range is narrow, the angular velocity ω becomes smaller. In such a case, it is possible to determine an abnormality by shifting the normal range.

[0068] Fig. 22(a) shows a case where the distance measurement range is relatively wide, and Fig. 22(b) shows a case where the distance measurement range is relatively narrow, and the distance measurement cycles are equal. As explained in Fig. 21(a) and Fig. 21(b), when the distance measurement cycles are equal and the distance measurement range is narrow, the angular velocity ω becomes small, and the pulse intervals of the A-phase signal and the B-phase signal become large. In such a case, it is possible to determine an abnormality by shifting the normal range.

[0069] FIG. 23(a) shows the case where distance measurement is performed during forward rotation, and FIG. 23(b) shows the case where distance measurement is performed during reverse rotation. When distance measurement is performed during reverse rotation, abnormality diagnosis is performed during reverse rotation, and the angular velocity ω during diagnosis is a negative value. In such a case, abnormality can be determined by shifting the normal range. Note that if the period and amplitude are the same, the sign of the normal range in FIG. 23(a) can be changed from positive to negative.

[0070] As described above, the distance measuring device 1 of this embodiment includes the scanning unit 20, the encoder 40, and the control unit 50. The scanning unit 20 has a mirror 21 and an oscillating motor 30. The mirror 21 reflects a light beam, which is a transmission wave output from the light emitting unit 10. The oscillating motor 30 drives the mirror 21 to oscillate so that the light beam scans a scanning range. The encoder 40 outputs an angle signal according to the rotation of the mirror 21.

[0071] The control unit 50 has a position calculation unit 51, a drive control unit 53, and an abnormality diagnosis unit 55. The position calculation unit 51 calculates the position of an object that reflects the scanned light beam. The drive control unit 53 controls the driving of the oscillating motor 30. The abnormality diagnosis unit 55 performs abnormality diagnosis regarding the operating state of the scan unit 20 based on the signal output from the encoder 40. This makes it possible to appropriately detect an operational abnormality of the scan unit 20 based on the signal from the encoder 40.

[0072] The abnormality diagnosis unit 55 determines that the oscillation amplitude is abnormal if at least one of the maximum and minimum values ​​of the mirror angle θ calculated based on the angle signal is outside the normal range during one cycle of scanning control. This makes it possible to properly detect the amplitude abnormality, and to detect a loss of the distance measurement range due to, for example, a failure of the oscillation motor 30 or a lack of amplitude due to an increase in load.

[0073] When the angular velocity ω of the mirror 21 calculated based on the angle signal is outside the normal range in the distance measurement possible range, the abnormality diagnosis unit 55 determines that the angular velocity is abnormal. In this embodiment, the normal rotation mainly corresponds to the "distance measurement possible range" and abnormality diagnosis related to the angular velocity ω is performed, but for example, a range excluding a predetermined range before and after the reversal of the rotation direction may be set as the "distance measurement possible range" and abnormality diagnosis may be performed in that range. Note that, in FIG. 23(b), the reverse rotation corresponds to the "distance measurement possible range" and similarly, for example, a range excluding a predetermined range before and after the reversal of the rotation direction may be set as the "distance measurement possible range". The same applies to the abnormality diagnosis of the angle signal. This makes it possible to detect a decrease in distance measurement accuracy due to an angular velocity abnormality.

[0074] The encoder 40 outputs an A-phase signal and a B-phase signal, which are multiple pulse signals, as angle signals. The abnormality diagnosis unit 55 determines that the output of the angle signal is abnormal when the edge interval of the A-phase signal and the B-phase signal in the distance measurement executable range is outside the normal range. This makes it possible to detect that the calculated mirror angle θ differs from the actual angle due to an output abnormality of the encoder 40.

[0075] The encoder 40 outputs a Z-phase signal, which is a pulse signal, as a reference signal in addition to the angle signal. If the number of edge detections of the reference signal in one cycle of scanning control is outside the normal range, the abnormality diagnosis unit 55 determines that the reference signal is abnormal. This makes it possible to detect that the reference position of the mirror 21 cannot be recognized.

[0076] If an abnormality occurs in the A-phase signal, B-phase signal, or Z-phase signal, which is the reference signal, of the encoder 40, the oscillation of the mirror 21 cannot be appropriately controlled, so diagnosing the A-phase signal, B-phase signal, and Z-phase signal for abnormalities is considered to be included in the concept of "diagnosis of abnormalities related to the operating state." In the embodiment, the oscillation motor 30 corresponds to the "actuator."

[0077] (Other embodiments) In the above embodiment, the mirror is biased to return to the reference position by a magnetic force. In other embodiments, the mirror may be biased to return to the reference position by an elastic member such as a spring. Also, the configuration of the scanning unit and the details of the distance measurement control may be different from those of the above embodiment.

[0078] In the above embodiment, the encoder outputs two-phase signals, an A-phase signal and a B-phase signal, as the angle signal. In other embodiments, the encoder may output three or more phase signals as the angle signal. Also, the reference signal may be omitted.

[0079] The control unit and the method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control unit and the method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described in the present disclosure may be realized by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. In addition, the computer program may be stored in a computer-readable non-transient tangible recording medium as instructions executed by a computer. As described above, the present invention is not limited to the above embodiment, and can be implemented in various forms within the scope of the invention. [Explanation of symbols]

[0080] 1... Distance measuring device 5. Measurement section 20. Scanning section 21. Mirror 30.... Swing motor (actuator) 40 Encoder 50...Control section 51...Position calculation section 53 Drive control unit 55 Abnormality diagnosis section

Claims

[Claim 1] a scanning unit (20) having a mirror (21) that reflects a transmission wave and an actuator (30) that drives the mirror to swing so that the transmission wave scans a scanning range; an encoder (40) that outputs an angle signal according to the rotation of the mirror; a control unit (50) having a position calculation unit (51) that calculates the position of an object that reflects the scanned transmission wave, a drive control unit (53) that controls the drive of the actuator, and an abnormality diagnosis unit (55) that performs abnormality diagnosis regarding the operating state of the scan unit based on a signal output from the encoder; Equipped with The abnormality diagnosis unit determines that the angular velocity is abnormal when the angular velocity of the mirror calculated based on the angle signal is outside a normal range within a distance measurement feasible range.

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