CN112654893A

CN112654893A - Motor rotating speed control method and device of scanning module and distance measuring device

Info

Publication number: CN112654893A
Application number: CN201980031290.7A
Authority: CN
Inventors: 陈亚林; 董帅; 洪小平
Original assignee: SZ DJI Technology Co Ltd
Current assignee: SZ DJI Technology Co Ltd
Priority date: 2019-08-13
Filing date: 2019-08-13
Publication date: 2021-04-13
Also published as: WO2021026766A1

Abstract

A motor rotation speed control method, device and distance measuring device (200) of a scanning module (202), the scanning module (202) comprising a first optical element (214) and a first motor (216) connected with the first optical element (214), the first motor (216) being used for driving the first optical element (214) to rotate, and a second optical element (215) and a second motor (217) connected with the second optical element (215), the second motor (217) being used for driving the second optical element (215) to rotate, the control method comprising: controlling a rotational speed of the first motor (216) to change to a first target speed (S301); controlling the rotation speed of the second motor (217) to change to a second target speed according to the first target speed (S302), wherein the first target speed and the second target speed meet a predetermined functional relationship. The method and the device can effectively control the maximum gap of the point cloud within a small range, improve the distribution uniformity of the point cloud points and further improve the scanning density of a scanning view field.

Description

Motor rotating speed control method and device of scanning module and distance measuring device

Description

Technical Field

The present invention generally relates to the field of distance measuring devices, and more particularly, to a method and a device for controlling a motor rotation speed of a scanning module, and a distance measuring device.

Background

For example, a distance measuring device of a mechanical rotation type laser radar generally comprises a scanning module, wherein the scanning module is used for changing the direction of light emitted by a light source to be initial, the scanning module generally comprises two double prisms, the two double prisms are respectively driven by two rotating motors to rotate, so that the propagation direction of the light is changed, the rotating speeds of the two motors fluctuate in practical application, and the change of a point cloud gap output by the distance measuring device can be caused, so that the distribution uniformity of point cloud points is poor, and part of the point cloud gap exceeds a tolerance range, so that the accuracy of the distance measuring device in measuring a detected object is influenced.

Therefore, in view of the above problems, the present invention provides a motor rotation speed control method and apparatus for a scan module, and a distance measuring apparatus.

Disclosure of Invention

The present invention has been made to solve at least one of the above problems. Specifically, one aspect of the present invention provides a motor rotation speed control method for a scanning module, the scanning module including a first optical element and a first motor connected to the first optical element, the first motor being configured to drive the first optical element to rotate, and a second optical element and a second motor connected to the second optical element, the second motor being configured to drive the second optical element to rotate, the control method including:

controlling the rotating speed of the first motor to change to a first target speed;

and controlling the rotating speed of the second motor to change to a second target speed according to the first target speed, wherein the first target speed and the second target speed meet a preset functional relation.

In one example, the control method further includes:

and when the first target speed fluctuates within a first target speed threshold interval, controlling the second target speed to change along with the first target speed according to the preset functional relation so as to enable the maximum gap of the point cloud pattern to be within a threshold range.

In one example, the predetermined functional relationship comprises a linear functional relationship.

In one example, the linear functional relationship satisfies the following relationship:

the second target speed is substantially the speed of the product of the first target speed and the scaling factor, which is then added to the constant factor.

In one example, the scaling factor is negative, wherein the scaling factor comprises a negative number greater than-1, and/or,

the constant factor ranges from 180rpm to 210 rpm.

In one example, the scaling factor includes-2/3.

In one example, the scanning module is configured to sequentially change light beams emitted by a light source to different propagation directions for emission, so as to form a scanning field of view, where the maximum gap includes a gap in a point cloud pattern projected on an imaging plane, and the imaging plane is a plane perpendicular to an optical axis of the light source and spaced apart from the light source by a predetermined distance.

Another aspect of the present invention provides a motor rotation speed control apparatus of a scanning module, the scanning module including a first optical element and a first motor connected to the first optical element, the first motor being configured to drive the first optical element to rotate, and a second optical element and a second motor connected to the second optical element, the second motor being configured to drive the second optical element to rotate, the motor rotation speed control apparatus including a control module configured to:

Still another aspect of the present invention provides a ranging apparatus, including:

a light source for emitting a light beam;

the scanning module is used for sequentially changing light beams emitted by the light source to different propagation directions to be emitted to form a scanning field of view, wherein the scanning module comprises a first optical element and a first motor connected with the first optical element, the first motor is used for driving the first optical element to rotate, and a second optical element and a second motor connected with the second optical element are used for driving the second optical element to rotate;

the detector is used for receiving at least part of the light beam emitted by the light source and reflected back by the object and acquiring the distance between the distance detection device and the object according to the received light beam;

a control module to:

According to the control method, the control device and the distance measuring device provided by the embodiment of the invention, the rotating speed of the first motor is controlled to be at the first target speed with the change value, the rotating speed of the second electrode is controlled to follow the first target speed with the change value to be at the second target speed, and the adjustment of the second target speed always keeps the first target speed and the second target speed to meet the preset functional relation, so that the maximum gap of point cloud is effectively controlled in a smaller range, the distribution uniformity of point cloud points is improved, the scanning density of a scanning view field is improved, and the accuracy of the distance measuring device in measuring a detected object is improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive labor.

FIG. 1 is a schematic diagram of a ranging apparatus according to an embodiment of the present invention;

FIG. 2 shows a schematic view of a distance measuring device in one embodiment of the invention;

FIG. 3 shows a schematic flow chart of a method of motor speed control of a scan module in an embodiment of the invention;

FIG. 4 is a schematic diagram illustrating the distribution of the maximum gap of the point cloud scanned by different motor combinations in the scanning module according to an embodiment of the present invention;

FIG. 5 illustrates a cloud of points obtained when a first target speed fluctuates randomly while a second target speed follows in one embodiment of the invention;

fig. 6 shows a point cloud obtained when the first target rotational speed fluctuates randomly and the second target rotational speed fluctuates randomly in one embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, exemplary embodiments according to the present invention will be described in detail below with reference to the accompanying drawings. It is to be understood that the described embodiments are merely a subset of embodiments of the invention and not all embodiments of the invention, with the understanding that the invention is not limited to the example embodiments described herein. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the invention described herein without inventive step, shall fall within the scope of protection of the invention.

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the invention.

It is to be understood that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of the associated listed items.

In order to provide a thorough understanding of the present invention, a detailed structure will be set forth in the following description in order to explain the present invention. Alternative embodiments of the invention are described in detail below, however, the invention may be practiced in other embodiments that depart from these specific details.

A ranging device, such as a laser ranging system, is a sensing system that uses laser light for scanning and distance measurement to obtain three-dimensional information in a surrounding scene. The basic principle is that laser pulses are actively transmitted to a detected object, laser echo signals are captured, and the distance of the detected object is calculated according to the time difference between the transmission and the reception of the laser; obtaining angle information of the measured object based on the known emission direction of the laser; by high-frequency transmission and reception, massive distance and angle information of the detection points can be acquired, and the information is called point cloud. Three-dimensional information of the surrounding scene can be reconstructed based on the point cloud.

In the following, the structure of a distance measuring device in the embodiments of the present invention, which includes a laser radar, is exemplarily described in more detail with reference to fig. 1 and 2, and the distance measuring device is merely an example, and other suitable distance measuring devices may be applied to the present application.

The scheme provided by each embodiment of the invention can be applied to a distance measuring device, and the distance measuring device can be electronic equipment such as a laser radar, laser distance measuring equipment and the like. In one embodiment, the ranging device is used to sense external environmental information, such as distance information, orientation information, reflected intensity information, velocity information, etc. of environmental targets. In one implementation, the ranging device may detect the distance of the probe to the ranging device by measuring the Time of Flight (TOF), which is the Time-of-Flight Time, of light traveling between the ranging device and the probe. Alternatively, the distance measuring device may detect the distance from the probe to the distance measuring device by other techniques, such as a distance measuring method based on phase shift (phase shift) measurement or a distance measuring method based on frequency shift (frequency shift) measurement, which is not limited herein.

For ease of understanding, the following describes an example of the ranging operation with reference to the ranging apparatus 100 shown in fig. 1.

Illustratively, the distance measuring device may include a transmitting module, a receiving module and a temperature control system, wherein the transmitting module is used for emitting light pulses; the receiving module is used for receiving at least part of the light pulse reflected back by the object and determining the distance of the object relative to the distance measuring device according to the received at least part of the light pulse.

Specifically, as shown in fig. 1, the transmitting module includes a transmitting circuit 110; the receiving module includes a receiving circuit 120, a sampling circuit 130, and an arithmetic circuit 140.

The transmit circuit 110 may emit a train of light pulses (e.g., a train of laser pulses). The receiving circuit 120 may receive the optical pulse train reflected by the detected object, perform photoelectric conversion on the optical pulse train to obtain an electrical signal, process the electrical signal, and output the electrical signal to the sampling circuit 130. The sampling circuit 130 may sample the electrical signal to obtain a sampling result. The arithmetic circuit 140 may determine the distance between the distance measuring device 100 and the detected object based on the sampling result of the sampling circuit 130.

Optionally, the distance measuring apparatus 100 may further include a control circuit 150, and the control circuit 150 may implement control of other circuits, for example, may control an operating time of each circuit and/or perform parameter setting on each circuit, and the like.

It should be understood that, although the distance measuring device shown in fig. 1 includes a transmitting circuit, a receiving circuit, a sampling circuit and an arithmetic circuit for emitting a light beam to detect, the embodiments of the present application are not limited thereto, and the number of any one of the transmitting circuit, the receiving circuit, the sampling circuit and the arithmetic circuit may be at least two, and the at least two light beams are emitted in the same direction or in different directions respectively; the at least two light paths may be emitted simultaneously or at different times. In one example, the light emitting chips in the at least two transmitting circuits are packaged in the same module. For example, each transmitting circuit comprises a laser emitting chip, and die of the laser emitting chips in the at least two transmitting circuits are packaged together and accommodated in the same packaging space.

In some implementations, in addition to the circuit shown in fig. 1, the distance measuring apparatus 100 may further include a scanning module, configured to change a propagation direction of at least one light pulse sequence (e.g., a laser pulse sequence) emitted by the emitting circuit to emit light, so as to scan the field of view. Illustratively, the scan area of the scan module within the field of view of the ranging device increases over time.

Here, a module including the transmission circuit 110, the reception circuit 120, the sampling circuit 130, and the operation circuit 140, or a module including the transmission circuit 110, the reception circuit 120, the sampling circuit 130, the operation circuit 140, and the control circuit 150 may be referred to as a ranging module, which may be independent of other modules, for example, a scanning module.

The distance measuring device can adopt a coaxial light path, namely the light beam emitted by the distance measuring device and the reflected light beam share at least part of the light path in the distance measuring device. For example, at least one path of laser pulse sequence emitted by the emitting circuit is emitted by the scanning module after the propagation direction is changed, and the laser pulse sequence reflected by the detector is emitted to the receiving circuit after passing through the scanning module. Alternatively, the distance measuring device may also adopt an off-axis optical path, that is, the light beam emitted by the distance measuring device and the reflected light beam are transmitted along different optical paths in the distance measuring device. FIG. 2 is a schematic diagram of one embodiment of the distance measuring device of the present invention using coaxial optical paths.

The ranging apparatus 200 comprises a ranging module 210, the ranging module 210 comprising a light source, i.e. a transmitter 203 (which may comprise the transmitting circuitry described above), a collimating element 204, a detector 205 (which may comprise the receiving circuitry, sampling circuitry and arithmetic circuitry described above) and a path-altering element 206. The distance measuring module 210 is configured to emit a light beam, receive return light, and convert the return light into an electrical signal. Wherein the emitter 203 may be configured to emit a sequence of light pulses. In one embodiment, the transmitter 203 may emit a sequence of laser pulses. Optionally, the laser beam emitted by the emitter 203 is a narrow bandwidth beam having a wavelength outside the visible range. The collimating element 204 is disposed on an emitting light path of the emitter, and is configured to collimate the light beam emitted from the emitter 203, and collimate the light beam emitted from the emitter 203 into parallel light to be emitted to the scanning module. The collimating element is also for converging at least a portion of the return light reflected by the detector. The collimating element 204 may be a collimating lens or other element capable of collimating a light beam.

In the embodiment shown in fig. 2, the transmit and receive optical paths within the distance measuring device are combined by the optical path altering element 206 before the collimating element 204, so that the transmit and receive optical paths may share the same collimating element, making the optical path more compact. In other implementations, the emitter 203 and the detector 205 may use respective collimating elements, and the optical path changing element 206 may be disposed in the optical path after the collimating elements.

In the embodiment shown in fig. 2, since the beam aperture of the light beam emitted from the emitter 203 is small and the beam aperture of the return light received by the distance measuring device is large, the optical path changing element can adopt a small-area mirror to combine the emission optical path and the reception optical path. In other implementations, the optical path changing element may also be a mirror with a through hole, wherein the through hole is used for transmitting the outgoing light from the emitter 203, and the mirror is used for reflecting the return light to the detector 205. Therefore, the shielding of the bracket of the small reflector to the return light can be reduced in the case of adopting the small reflector.

In the embodiment shown in fig. 2, the optical path altering element is offset from the optical axis of the collimating element 204. In other implementations, the optical path altering element may also be located on the optical axis of the collimating element 204.

The distance measuring device 200 further comprises a scanning module 202, configured to change the light beams emitted by the light sources to different propagation directions in sequence and emit the light beams, so as to form a scanning field of view. The scanning module 202 is disposed on the emitting light path of the distance measuring module 210, and the scanning module 202 is configured to change the transmission direction of the collimated light beam 219 emitted by the collimating element 204, project the collimated light beam to the external environment, and project the return light to the collimating element 204. The return light is converged by the collimating element 204 onto the detector 205.

In one embodiment, the scanning module 202 may include at least one optical element for changing the propagation path of the light beam, wherein the optical element may change the propagation path of the light beam by reflecting, refracting, diffracting, etc. the optical element includes at least one light refracting element having non-parallel exit and entrance faces, for example. For example, the scanning module 202 includes a lens, mirror, prism, galvanometer, grating, liquid crystal, Optical Phased Array (Optical Phased Array), or any combination thereof. In one example, at least a portion of the optical element is moved, for example, by a driving module, and the moved optical element can reflect, refract, or diffract the light beam to different directions at different times. In some embodiments, multiple optical elements of the scanning module 202 may rotate or oscillate about a common axis 209, with each rotating or oscillating optical element serving to constantly change the direction of propagation of an incident beam. In one embodiment, the multiple optical elements of the scanning module 202 may rotate at different rotational speeds or oscillate at different speeds. In another embodiment, at least some of the optical elements of the scanning module 202 may rotate at substantially the same rotational speed. In some embodiments, the multiple optical elements of the scanning module may also be rotated about different axes. In some embodiments, the multiple optical elements of the scanning module may also rotate in the same direction, or in different directions; or in the same direction, or in different directions, without limitation.

In one embodiment, the scanning module 202 includes a first optical element 214 and a driver 216, such as a first motor, coupled to the first optical element 214, the driver 216 for driving the first optical element 214 to rotate about the rotation axis 209, causing the first optical element 214 to change the direction of the collimated light beam 219. The first optical element 214 projects the collimated beam 219 into different directions. In one embodiment, the angle between the direction of the collimated beam 219 after it is altered by the first optical element and the axis of rotation 209 changes as the first optical element 214 is rotated. In one embodiment, the first optical element 214 includes a pair of opposing non-parallel surfaces through which the collimated light beam 219 passes. In one embodiment, the first optical element 214 includes a prism having a thickness that varies along at least one radial direction. In one embodiment, the first optical element 214 comprises a wedge angle prism that refracts the collimated beam 219.

In one embodiment, the scanning module 202 further comprises a second optical element 215, the second optical element 215 rotating around a rotation axis 209, the rotation speed of the second optical element 215 being different from the rotation speed of the first optical element 214. The second optical element 215 is used to change the direction of the light beam projected by the first optical element 214. In one embodiment, second optical element 215 is coupled to another driver 217 (e.g., a second motor), and driver 217 rotates second optical element 215. The first optical element 214 and the second optical element 215 may be driven by the same or different drivers, such that the first optical element 214 and the second optical element 215 rotate at different speeds and/or turns, thereby projecting the collimated light beam 219 into different directions in the ambient space, which may scan a larger spatial range. In one embodiment, the controller 218 controls the

drivers

216 and 217 to drive the first optical element 214 and the second optical element 215, respectively. The rotation speed of the first optical element 214 and the second optical element 215 can be determined according to the region and the pattern expected to be scanned in the actual application. The

drives

216 and 217 may include motors or other drives.

In one example, the driver 216 and the driver 217 may have opposite rotation directions to respectively drive the first optical element 214 and the second optical element 215 to rotate in opposite rotation directions, or the driver 216 and the driver 217 may have the same rotation direction to respectively drive the first optical element 214 and the second optical element 215 to rotate in the same rotation direction, which is set according to practical requirements.

In one embodiment, second optical element 215 includes a pair of opposing non-parallel surfaces through which the light beam passes. In one embodiment, second optical element 215 includes a prism having a thickness that varies along at least one radial direction. In one embodiment, second optical element 215 comprises a wedge angle prism.

In one embodiment, the scan module 202 further comprises a third optical element (not shown) and a driver for driving the third optical element to move. Optionally, the third optical element comprises a pair of opposed non-parallel surfaces through which the light beam passes. In one embodiment, the third optical element comprises a prism having a thickness that varies along at least one radial direction. In one embodiment, the third optical element comprises a wedge angle prism. At least two of the first, second and third optical elements rotate at different rotational speeds and/or rotational directions.

In one embodiment, the scanning module comprises 2 or 3 photorefractive elements arranged in sequence on an outgoing light path of the optical pulse sequence. Optionally, at least 2 of the photorefractive elements in the scanning module rotate during scanning to change the direction of the sequence of light pulses.

The scanning module has different scanning paths at least partially different times, and the rotation of each optical element in the scanning module 202 may project light in different directions, such as the direction of the projected light 211 and the direction 213, so as to scan the space around the distance measuring device 200. When the light 211 projected by the scanning module 202 hits the detection object 201, a part of the light is reflected by the detection object 201 to the distance measuring device 200 in the opposite direction to the projected light 211. The return light 212 reflected by the object 201 passes through the scanning module 202 and then enters the collimating element 204.

The detector 205 is placed on the same side of the collimating element 204 as the emitter 203, and the detector 205 is used to convert at least part of the return light passing through the collimating element 204 into an electrical signal.

In one embodiment, each optical element is coated with an antireflection coating. Optionally, the thickness of the antireflection film is equal to or close to the wavelength of the light beam emitted by the emitter 203, which can increase the intensity of the transmitted light beam.

In one embodiment, a filter layer is coated on a surface of a component in the distance measuring device, which is located on the light beam propagation path, or a filter is arranged on the light beam propagation path, and is used for transmitting at least a wave band in which the light beam emitted by the emitter is located and reflecting other wave bands, so as to reduce noise brought to the receiver by ambient light.

In some embodiments, the transmitter 203 may include a laser diode through which laser pulses in the order of nanoseconds are emitted. Further, the laser pulse reception time may be determined, for example, by detecting the rising edge time and/or the falling edge time of the electrical signal pulse. In this manner, the ranging apparatus 200 may calculate TOF using the pulse reception time information and the pulse emission time information, thereby determining the distance of the probe 201 to the ranging apparatus 200. The distance and orientation detected by ranging device 200 may be used for remote sensing, obstacle avoidance, mapping, modeling, navigation, and the like.

Based on the application scenario, in practical application, because the rotating speeds of the two motors fluctuate, the gap of the point cloud output by the distance measuring device changes, the distribution uniformity of the point cloud is poor, and part of the gap of the point cloud exceeds a tolerance range, so that the accuracy of the distance measuring device in measuring a detected object is affected. Controlling the rotating speed of the first motor to change to a first target speed; and controlling the rotating speed of the second motor to change to a second target speed according to the first target speed, wherein the first target speed and the second target speed meet a preset functional relation. According to the control method provided by the embodiment of the invention, the rotating speed of the first motor is controlled to be at the first target speed with the change value, the rotating speed of the second electrode is controlled to follow the first target speed with the change value to be at the second target speed, and the adjustment of the second target speed always keeps the first target speed and the second target speed to meet the preset functional relationship, so that the maximum gap of the point cloud is effectively controlled in a smaller range, the point cloud distribution uniformity of points is improved, the scanning density of a scanning visual field is improved, and the accuracy of the distance measuring device in measuring the detected object is improved.

In the following, a motor rotation speed control method of a scan module according to an embodiment of the present invention is described in detail with reference to the accompanying drawings, and features of the embodiments and implementations herein may be combined with each other without conflict.

As shown in fig. 3, the method for controlling the rotational speed of a motor according to the embodiment of the present invention includes the following steps:

first, in step S301, the rotation speed of the first motor is controlled to be changed to a first target speed. The first target speed can be set reasonably according to the user's needs, for example, the first target speed V1 can be set between [7054rpm,7534rpm ], or other suitable target rotation speed.

Next, in step S302, the rotation speed of the second motor is controlled to change to a second target speed according to the first target speed, wherein a predetermined functional relationship is satisfied between the first target speed and the second target speed. That is, according to the predetermined functional relationship, the rotation speed of the second motor is adjusted to be changed to the second target speed V2, so that the predetermined functional relationship is always maintained between the first target speed V1 and the second target speed, and the maximum gap of the point cloud is effectively controlled within a small range.

The predetermined functional relationship may be any suitable functional relationship that enables the maximum clearance of the point cloud to be controlled within a reasonable threshold range, for example, the predetermined functional relationship includes a linear functional relationship, i.e., the first target speed V1 and the second target speed V2 satisfy the linear functional relationship.

The first target rotating speed of the rotating speeds of the first motor is set as V1, the second target rotating speed is set as V2, and the maximum gaps of the point clouds scanned by different motor rotating speed combinations are different. For example, as shown in fig. 4, the abscissa indicates V1, the ordinate indicates V2, the frame time (frame time) is approximately 1.3s, the sizes of the gaps indicated by different colors in the figure are different, the color gradually increases from deep to light cloud gaps, and for example, V1 is set at [7054rpm,7534rpm ], and V2 is set at [ -4904rpm, -4424rpm ], it can be seen that the motor rotation speed satisfies a linear function relationship, so that the cloud gaps are the same in size.

For example, the first motor and the second motor have opposite directions of rotation, one rotates counterclockwise and the other rotates clockwise, for example, the first target speed V1 is 7123rpm, the rotational speed of the second motor is controlled to change to a second target speed V2, for example, V2 is-4550 rpm, "-" indicates that the second motor and the first motor have opposite directions of rotation, at which the maximum clearance of the point cloud is substantially 0.6845m, or the first target speed V1 is 7123rpm, the rotational speed of the second motor is controlled to change to a second target speed V2, for example, V2 is-4559 rpm, at which the maximum clearance of the point cloud is substantially 0.6991m, or the first target speed V1 is 7141rpm, the rotational speed of the second motor is controlled to change to a second target speed V2, for example, V2 is-4559 rpm, at which the maximum clearance of the point cloud is substantially 0.6998 m; or when the first target speed V1 is 7294rpm, the rotation speed of the second motor is controlled to change to a second target speed V2, for example, V2 is-4664 rpm, and the maximum gap of the point cloud is substantially 0.6764 m; or, when the first target speed V1 is 7333rpm, the rotation speed of the second motor is controlled to change to a second target speed V2, for example, V2 is-4682 rpm, and the maximum gap of the point cloud is substantially 0.6955 m; alternatively, when the first target speed V1 is 7315rpm, the rotation speed of the second motor is controlled to change to a second target speed V2, for example, V2 is-4682 rpm, and the maximum gap of the point cloud is substantially 0.6889 m. It can be seen that the first target speed and the second target speed satisfy a linear function relationship, and the maximum clearance of the point cloud can be within a reasonable threshold range, wherein the reasonable threshold range of the maximum clearance can be reasonably set according to the actual combination of the rotating speeds, for example, as the first target rotating speed V1 and/or the second target rotating speed V2 increases, the threshold range of the maximum clearance of the point cloud may also increase, for example, as V1 is set at [7054rpm,7534rpm ], and V2 is set at [ -4904rpm, -4424rpm ], and the threshold range of the maximum clearance may be substantially between [0.65m,1m ].

In one example, the linear functional relationship satisfies the following relationship: the second target speed is substantially the speed of the product of the first target speed and the scaling factor, which is then added to the constant factor. Optionally, the scaling factor is a negative number or an integer, for example, the scaling factor includes a negative number greater than-1, and the range of the constant factor may be reasonably set according to practical situations, for example, the range of the constant factor may be 180rpm to 210 rpm.

Taking the white line indicated by the arrow in fig. 4 as an example, it can be calculated that the following linear relationship is satisfied between the first target speed V1 and the second target speed V2: v2 ═ 2/3 × (V1-1) +198, i.e. the proportionality coefficient is-2/3, with a constant factor of roughly 198.7. It is worth mentioning that this linear relationship is only an example, and the relationship of V1 and V2 is not limited to these numerical ranges and relations.

Although the rotating speed of the first motor is adjusted to the second target speed according to the predetermined functional relationship after the rotating speed of the first motor is changed to the first target speed, since the rotating speed of the first motor may fluctuate near the first target speed in practical applications, if the second target speed is still maintained, the maximum gap of the point cloud may be too large to exceed a reasonable threshold range, and therefore, the control method of the embodiment of the present invention further includes the following steps: when the first target speed fluctuates within a first target speed threshold interval, the second target speed is controlled to vary with the first target speed according to the predetermined functional relationship so that the maximum gap of the point cloud pattern is within a threshold range, for example, the first target speed V1 is set to be substantially 7141rpm, and the corresponding second target speed V2 is-4559 rpm, but for some reasons the first target speed V1 fluctuates, for example, within the first target speed threshold interval, for example, within ± 10rpm, ± 20rpm, ± 30rpm, etc., the second target speed is controlled to vary with the first target speed according to the aforementioned predetermined functional relationship (for example, a linear functional relationship) so that the maximum gap of the point cloud pattern is within the threshold range.

It is worth mentioning that, herein, the maximum void includes a void between point clouds in a point cloud pattern projected on an imaging plane, which is a plane perpendicular to an optical axis of the light source and spaced apart from the light source by a predetermined distance.

In one specific example, the first target rotation speed V1 of the first motor fluctuates randomly, while the second target rotation speed V2 of the second motor fluctuates following V1 according to a predetermined functional relationship, so that the following relationship is satisfied between V2 and V1: when V2 is-2/3 × (V1-1) +198, a cloud point image when the integration time is 1s is shown in fig. 5, the predetermined separation distance between the imaging plane on which the cloud point image is located and the light source is substantially 100m, and the maximum gap at 100m in the cloud point image is substantially 0.8727 m.

In other examples, when the first target rotational speed V1 fluctuates randomly and the second target rotational speed V2 also fluctuates randomly, a point cloud chart obtained when the integration time is also 1s is shown in fig. 6, the predetermined separation distance between the imaging plane and the light source is substantially 100m, and the maximum gap at 100m in the point cloud chart is substantially 1.5708m, which is significantly larger than the maximum gap shown in fig. 5.

Therefore, as can be seen from the comparative analysis of fig. 5 and 6, by controlling the rotation speed of the second motor to fluctuate along with the rotation speed of the first motor, the maximum gap of the point cloud can be effectively controlled within a small range, the uniformity of the scanning density of the scanning module and the coverage rate of the scanning module on a detected object are ensured, and the detection accuracy is improved.

In summary, in the control method according to the embodiment of the present invention, the rotation speed of the first motor is controlled to be at the first target speed with the variation value, and the rotation speed of the second electrode is controlled to follow the second target speed with the variation value of the first target speed, and the adjustment of the second target speed always keeps the first target speed and the second target speed to satisfy the predetermined functional relationship, so that the maximum gap of the point cloud is effectively controlled to be in a smaller range, the distribution uniformity of the point cloud is improved, the scanning density of the scanning field of view is improved, and the accuracy of the distance measuring device in measuring the detected object is improved.

In another embodiment, the present invention further provides a motor rotation speed control apparatus of a scanning module, based on which the control method described above can be implemented, where the scanning module includes a first optical element and a first motor connected to the first optical element, the first motor is used to drive the first optical element to rotate, and a second optical element and a second motor connected to the second optical element, the second motor is used to drive the second optical element to rotate, and the description of the scanning module may refer to the description in the foregoing, and is not repeated herein.

Further, the motor speed control device comprises a control module for: controlling the rotating speed of the first motor to change to a first target speed; and controlling the rotating speed of the second motor to change to a second target speed according to the first target speed, wherein the first target speed and the second target speed meet a preset functional relation. According to the motor rotating speed control device provided by the embodiment of the invention, the rotating speed of the first motor is controlled to be in the first target speed with the change value, the rotating speed of the second electrode is controlled to follow the first target speed with the change value to be in the second target speed, and the adjustment of the second target speed always keeps the first target speed and the second target speed to meet the preset functional relation, so that the maximum gap of point cloud is effectively controlled in a smaller range, the distribution uniformity of point cloud points is improved, the scanning density of a scanning visual field is improved, and the accuracy of the distance measuring device in measuring a detected object is improved.

Alternatively, the control module may be implemented by the controller 218 shown in fig. 2, or may also be implemented by other control circuits having control functions, which are not specifically limited herein.

In one example, the control module is further configured to: and when the first target speed fluctuates within a first target speed threshold interval, controlling the second target speed to change along with the first target speed according to the preset functional relation so as to enable the maximum gap of the point cloud pattern to be within a threshold range.

In one example, the predetermined functional relationship comprises a linear functional relationship. Optionally, the linear functional relationship satisfies the following relationship: the second target speed is substantially the speed of the product of the first target speed and the scaling factor, which is then added to the constant factor. The scaling factor may be negative, wherein the scaling factor comprises a negative number greater than-1, optionally the scaling factor comprises-2/3.

In one example, the constant factor ranges from 180rpm to 210 rpm.

In summary, the control device of the embodiment of the present invention includes a control module, the control module controls the rotation speed of the first motor to be at a first target speed with a variation value, and controls the rotation speed of the second electrode to follow a second target speed with the variation value of the first target speed, and the adjustment of the second target speed always keeps the first target speed and the second target speed to satisfy a predetermined functional relationship, so as to effectively control the maximum gap of the point cloud to be within a smaller range, improve the distribution uniformity of the point cloud, thereby improving the scanning density of the scanning field of view, and further improving the accuracy of the distance measuring device in measuring the detected object.

In a further embodiment of the present invention, the distance measuring device 200 shown in fig. 2 may further include the motor speed control device described above, and the related steps in the motor speed control method described above may be implemented based on the distance measuring device 200.

In particular, the specific structure of the distance measuring device 200 may refer to the description of the embodiment of fig. 2, which may include a light source for emitting a light beam, for example, implemented as the emitter 203 in fig. 2.

Further, as shown in fig. 2, the distance measuring device 200 further includes a scanning module 202 for sequentially changing the light beams emitted by the light sources to different propagation directions to exit, so as to form a scanning field of view, wherein the scanning module includes a first optical element 214 and a driver 216, such as a first motor, connected to the first optical element 214, the first motor being used for driving the first optical element 214 to rotate, and a second optical element 215 and another driver 217, such as a second motor, connected to the second optical element 215, the second motor being used for driving the second optical element 215 to rotate.

Further, as shown in fig. 2, the distance measuring device 200 further includes a detector 205 for receiving at least a portion of the light beam emitted by the light source reflected by the object, and obtaining the distance between the distance measuring device and the object according to the received light beam.

Further, as shown in fig. 2, the control module is configured to: controlling the rotating speed of the first motor to change to a first target speed; and controlling the rotating speed of the second motor to change to a second target speed according to the first target speed, wherein the first target speed and the second target speed meet a preset functional relation. The control module may include a controller 218 or other control circuitry that enables separate control of the first and second motors.

In one example, the control module is further configured to: when the first target speed fluctuates within a first target speed threshold interval, the second target speed is controlled to change along with the first target speed according to the preset functional relation, so that the maximum gap of the point cloud pattern is within a threshold range.

In one example, the predetermined functional relationship comprises a linear functional relationship. Optionally, the linear functional relationship satisfies the following relationship: the second target speed is substantially the speed of the product of the first target speed and the scaling factor, which is then added to the constant factor. Optionally, the scaling factor comprises a negative number greater than-1, the scaling factor is a negative number, e.g., the scaling factor comprises-2/3, and/or the constant factor ranges from 180rpm to 210 rpm.

In one example, the maximum void includes a void in a point cloud pattern projected on an imaging plane, the imaging plane being a plane perpendicular to an optical axis of the light source and spaced apart from the light source by a predetermined distance.

In summary, the distance measuring device according to the embodiment of the present invention includes the foregoing control device and can be used to implement the foregoing control method, and therefore, the distance measuring device has the advantages of the foregoing control device and control method.

In one embodiment, the distance measuring device of the embodiment of the invention can be applied to a mobile platform, and the distance measuring device can be installed on a platform body of the mobile platform. The mobile platform with the distance measuring device can measure the external environment, for example, the distance between the mobile platform and an obstacle is measured for the purpose of avoiding the obstacle, and the external environment is mapped in two dimensions or three dimensions. In certain embodiments, the mobile platform comprises at least one of an unmanned aerial vehicle, an automobile, a remote control car, a robot, a boat, a camera. When the distance measuring device is applied to the unmanned aerial vehicle, the platform body is a fuselage of the unmanned aerial vehicle. When the distance measuring device is applied to an automobile, the platform body is the automobile body of the automobile. The vehicle may be an autonomous vehicle or a semi-autonomous vehicle, without limitation. When the distance measuring device is applied to the remote control car, the platform body is the car body of the remote control car. When the distance measuring device is applied to a robot, the platform body is the robot. When the distance measuring device is applied to a camera, the platform body is the camera itself.

Although the illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the foregoing illustrative embodiments are merely exemplary and are not intended to limit the scope of the invention thereto. Various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the scope or spirit of the present invention. All such changes and modifications are intended to be included within the scope of the present invention as set forth in the appended claims.

Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described device embodiments are merely illustrative, and for example, the division of the units is only one logical functional division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another device, or some features may be omitted, or not executed.

In the description provided herein, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Similarly, it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the invention and aiding in the understanding of one or more of the various inventive aspects. However, the method of the present invention should not be construed to reflect the intent: that the invention as claimed requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

It will be understood by those skilled in the art that all of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and all of the processes or elements of any method or apparatus so disclosed, may be combined in any combination, except combinations where such features are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.

Furthermore, those skilled in the art will appreciate that while some embodiments described herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments may be used in any combination.

The various component embodiments of the invention may be implemented in hardware, or in software modules running on one or more processors, or in a combination thereof. Those skilled in the art will appreciate that a microprocessor or Digital Signal Processor (DSP) may be used in practice to implement some or all of the functionality of some of the modules according to embodiments of the present invention. The present invention may also be embodied as apparatus programs (e.g., computer programs and computer program products) for performing a portion or all of the methods described herein. Such programs implementing the present invention may be stored on computer-readable media or may be in the form of one or more signals. Such a signal may be downloaded from an internet website or provided on a carrier signal or in any other form.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The usage of the words first, second and third, etcetera do not indicate any ordering. These words may be interpreted as names.

Claims

A motor speed control method for a scan module, the scan module including a first optical element and a first motor coupled to the first optical element, the first motor being configured to drive the first optical element to rotate, and a second optical element and a second motor coupled to the second optical element, the second motor being configured to drive the second optical element to rotate, the control method comprising:

controlling the rotating speed of the first motor to change to a first target speed;

and controlling the rotating speed of the second motor to change to a second target speed according to the first target speed, wherein the first target speed and the second target speed meet a preset functional relation.
A motor speed control method as claimed in claim 1, characterized by further comprising:

and when the first target speed fluctuates within a first target speed threshold interval, controlling the second target speed to change along with the first target speed according to the preset functional relation so as to enable the maximum gap of the point cloud pattern to be within a threshold range.
A method of controlling the speed of a motor as claimed in claim 1 or claim 2, wherein the predetermined functional relationship comprises a linear functional relationship.
A method of controlling the speed of a motor as claimed in claim 3, wherein said linear function satisfies the following relationship:

the second target speed is substantially the speed of the product of the first target speed and the scaling factor, which is then added to the constant factor.
The motor speed control method according to claim 4,

the scaling factor is negative, wherein the scaling factor comprises a negative number greater than-1, and/or,

the constant factor ranges from 180rpm to 210 rpm.
The motor speed control method of claim 4 wherein the scaling factor comprises-2/3.
The method of claim 2, wherein the scanning module is configured to sequentially change the light beams emitted from the light source to different directions of propagation for emission to form a scanning field of view, and wherein the maximum gap comprises a gap in the point cloud pattern projected on an imaging plane, and the imaging plane is perpendicular to the optical axis of the light source and spaced apart from the light source by a predetermined distance.
A motor speed control apparatus of a scan module, wherein the scan module comprises a first optical element and a first motor connected to the first optical element, the first motor being configured to drive the first optical element to rotate, and a second optical element and a second motor connected to the second optical element, the second motor being configured to drive the second optical element to rotate, the motor speed control apparatus comprising a control module configured to:

controlling the rotating speed of the first motor to change to a first target speed;

and controlling the rotating speed of the second motor to change to a second target speed according to the first target speed, wherein the first target speed and the second target speed meet a preset functional relation.
A motor speed control apparatus as claimed in claim 8, wherein the control module is further configured to:

and when the first target speed fluctuates within a first target speed threshold interval, controlling the second target speed to change along with the first target speed according to the preset functional relation so as to enable the maximum gap of the point cloud pattern to be within a threshold range.
A motor speed control apparatus as claimed in claim 8 or 9, wherein the predetermined functional relationship comprises a linear functional relationship.
A motor speed control apparatus as claimed in claim 10, wherein the linear function relationship satisfies the following relationship:

the second target speed is substantially the speed of the product of the first target speed and the scaling factor, which is then added to the constant factor.
The motor speed control apparatus according to claim 11,

the scaling factor is negative, wherein the scaling factor comprises a negative number greater than-1, and/or,

the constant factor ranges from 180rpm to 210 rpm.
A motor speed control apparatus as claimed in claim 11 wherein said scaling factor comprises-2/3.
The apparatus of claim 9, wherein the scanning module is configured to sequentially change the light beams emitted from the light source to different directions of propagation for emission to form a scanning field of view, and wherein the maximum gap comprises a gap in the point cloud pattern projected on an imaging plane, and the imaging plane is perpendicular to the optical axis of the light source and spaced apart from the light source by a predetermined distance.
A ranging apparatus, comprising:

a light source for emitting a light beam;

the scanning module is used for sequentially changing light beams emitted by the light source to different propagation directions to be emitted to form a scanning field of view, wherein the scanning module comprises a first optical element and a first motor connected with the first optical element, the first motor is used for driving the first optical element to rotate, and a second optical element and a second motor connected with the second optical element are used for driving the second optical element to rotate;

the detector is used for receiving at least part of the light beam emitted by the light source and reflected back by the object and acquiring the distance between the distance detection device and the object according to the received light beam;

a control module to:

controlling the rotating speed of the first motor to change to a first target speed;

and controlling the rotating speed of the second motor to change to a second target speed according to the first target speed, wherein the first target speed and the second target speed meet a preset functional relation.
The ranging apparatus of claim 15, wherein the control module is further configured to:

and when the first target speed fluctuates within a first target speed threshold interval, controlling the second target speed to change along with the first target speed according to the preset functional relation so as to enable the maximum gap of the point cloud pattern to be within a threshold range.
A ranging apparatus as claimed in claim 15 or 16 wherein said predetermined functional relationship comprises a linear functional relationship.
The ranging apparatus of claim 17 wherein said linear functional relationship satisfies the following relationship:

the second target speed is substantially the speed of the product of the first target speed and the scaling factor, which is then added to the constant factor.
The ranging apparatus of claim 18,

the scaling factor is negative, wherein the scaling factor comprises a negative number greater than-1, and/or,

the constant factor ranges from 180rpm to 210 rpm.
The ranging apparatus of claim 18 wherein said scaling factor comprises-2/3.
The ranging apparatus as claimed in claim 15, wherein the maximum space comprises a space in the point cloud pattern projected on an imaging plane, the imaging plane being a plane perpendicular to an optical axis of the light source and spaced apart from the light source by a predetermined distance.