CN111537995B - Time delay obtaining method and device and electronic equipment - Google Patents
Time delay obtaining method and device and electronic equipment Download PDFInfo
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- CN111537995B CN111537995B CN202010424922.0A CN202010424922A CN111537995B CN 111537995 B CN111537995 B CN 111537995B CN 202010424922 A CN202010424922 A CN 202010424922A CN 111537995 B CN111537995 B CN 111537995B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/86—Combinations of radar systems with non-radar systems, e.g. sonar, direction finder
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
- G01C21/10—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration
- G01C21/12—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning
- G01C21/16—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation
- G01C21/165—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation combined with non-inertial navigation instruments
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Abstract
The application discloses a time delay obtaining method, a time delay obtaining device and electronic equipment, wherein the method comprises the following steps: obtaining a first curve of the change of the angular speed of the radar on at least one target degree of freedom along with time; obtaining a second curve of the angular velocity of an inertial measurement unit IMU in the target degree of freedom over time, wherein the IMU and the radar belong to the same electronic device; performing curve fitting on the first curve and the second curve so that the first curve and the second curve subjected to curve fitting correspond to curve values at any time of the same curve; and obtaining a curve time delay between the first curve and the second curve according to the curve value, wherein the curve time delay represents the transmission time delay between the radar and the IMU.
Description
Technical Field
The present application relates to the field of positioning technologies, and in particular, to a time delay obtaining method and apparatus, and an electronic device.
Background
Positioning and mapping are important algorithms that extend through the fields of autopilot, robot, augmented reality ar (augmented reality)/virtual reality vr (virtual reality), unmanned aerial vehicles, etc., while lidar and inertial measurement units imu (inertial measurement unit) are the most commonly used sensors for such algorithms. When positioning is performed by coupling the two sensors, it is usually required that the timestamps carried by the raw data of the two sensors come from the same clock in order to improve the accuracy, i.e. the data transmission is synchronized in real time. The actual transmission of the data of the two is usually different by a time delay dt, subject to hardware conditions. Therefore, how to obtain this time delay becomes the key to improve the positioning and mapping accuracy.
In the current scheme of obtaining the time delay, the current scheme usually depends on an external tool and an external environment, so that the obtaining process is complex, and the problem of low efficiency exists.
Disclosure of Invention
In view of this, the present application provides a method, an apparatus, and an electronic device for obtaining a time delay, which includes:
a time delay acquisition method comprises the following steps:
obtaining a first curve of the change of the angular speed of the radar on at least one target degree of freedom along with time;
obtaining a second curve of the angular velocity of an inertial measurement unit IMU in the target degree of freedom over time, wherein the IMU and the radar belong to the same electronic device;
performing curve fitting on the first curve and the second curve so that the first curve and the second curve subjected to curve fitting correspond to curve values at any time of the same curve;
and obtaining a curve time delay between the first curve and the second curve according to the curve value, wherein the curve time delay represents the transmission time delay between the radar and the IMU.
Preferably, the obtaining a curve delay between the first curve and the second curve according to the curve value includes:
respectively calculating root mean square errors corresponding to the first curve and the second curve on each reference time delay according to each reference time delay in a preset time delay set;
and selecting the reference time delay corresponding to the minimum value in the root mean square error as the curve time delay between the first curve and the second curve.
Preferably, the method for calculating a root mean square error of the first curve and a root mean square error of the second curve on each reference delay according to each reference delay in a preset delay set includes:
respectively acquiring curve values corresponding to at least part of curve moments on the first curve and the second curve according to a preset sampling frequency;
and according to each reference time delay in a preset time delay set, calculating the root mean square error corresponding to each reference time delay of the first curve and the second curve according to the curve value.
The above method, preferably, obtaining a first curve of the angular velocity of the radar in at least one target degree of freedom over time, comprises:
acquiring point cloud data of a radar;
generating an initial curve of the motion track of the radar on at least one degree of freedom along with time according to the point cloud data;
and generating a first curve of the change of the angular speed of the radar on the target degree of freedom along with time according to the initial curve corresponding to the target degree of freedom selected from the at least one degree of freedom.
Preferably, before generating a first curve of the change of the angular velocity of the radar with time according to the initial curve corresponding to the target degree of freedom selected from the at least one degree of freedom, the method further includes:
and updating the track of the initial curve according to the curve frequency corresponding to the initial curve.
In the method, preferably, the target degree of freedom is a target degree of freedom selected from three degrees of freedom corresponding to a fixed axis in the at least one degree of freedom, and the fixed axis is an axis around which the device on which the radar is located moves.
The above method, preferably, before generating an initial curve of the motion trajectory of the radar in multiple degrees of freedom with time according to the point cloud data, further includes:
and denoising the point cloud data by using a noise point filtering algorithm.
A latency acquisition apparatus, comprising:
a first curve obtaining unit for obtaining a first curve of the angular velocity of the radar in at least one target degree of freedom over time;
a second curve obtaining unit, configured to obtain a second curve of a change over time of an angular velocity of an IMU in the target degree of freedom, where the IMU and the radar belong to the same electronic device;
a curve fitting unit, configured to perform curve fitting on the first curve and the second curve, so that the first curve and the second curve subjected to curve fitting both correspond to curve values at any time of the same curve;
and the time delay obtaining unit is used for obtaining the curve time delay between the first curve and the second curve according to the curve value, and the curve time delay represents the transmission time delay between the radar and the IMU.
Preferably, in the apparatus, the delay obtaining unit is specifically configured to: respectively calculating the root mean square error of the first curve and the second curve corresponding to each reference time delay according to each reference time delay in a preset time delay set; and selecting the reference time delay corresponding to the minimum value in the root mean square error as the curve time delay between the first curve and the second curve.
An electronic device, comprising:
a radar;
IMU；
a processor for obtaining a first curve of angular velocity of the radar in at least one target degree of freedom over time; obtaining a second curve of the IMU over time of angular velocity in the target degree of freedom, the IMU and the radar belonging to the same electronic device; performing curve fitting on the first curve and the second curve so that the first curve and the second curve subjected to curve fitting correspond to curve values at any time of the same curve; and obtaining a curve time delay between the first curve and the second curve according to the curve value, wherein the curve time delay represents the transmission time delay between the radar and the IMU.
According to the technical scheme, the time delay obtaining method, the time delay obtaining device and the electronic equipment disclosed by the application have the advantages that the curves of the radar and the IMU, which change along with time, in the angular speed of the target degree of freedom are obtained, the curves are fitted, so that the two curves correspond to curve values in any same curve time, then the curve time delay between the two curves is obtained according to the fitted curve values on the two curves, and the curve time delay is the transmission time delay between the radar and the IMU. Therefore, in the application, by fitting the curves of the radar and the IMU, which change along with the time, of the angular velocities of the radar and the IMU in the target degree of freedom, the curve time delay between the two curves can be obtained through the curve values of the fitted curves, and then the transmission time delay between the radar and the IMU can be obtained.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a flowchart of a delay obtaining method according to an embodiment of the present application;
FIGS. 2-5 are partial flow charts of a first embodiment of the present application;
fig. 6 is a schematic structural diagram of a delay obtaining apparatus according to a second embodiment of the present application;
fig. 7 is a schematic structural diagram of an electronic device according to a third embodiment of the present application;
fig. 8 is a schematic structural diagram of an electronic device according to a fourth embodiment of the present application;
fig. 9-13 are schematic diagrams illustrating practical applications of the embodiments of the present application, respectively.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Referring to fig. 1, an implementation flowchart of a time delay obtaining method provided in an embodiment of the present disclosure is shown, where the method may be applied to an electronic device with a radar and an IMU, such as a robot, an unmanned aerial vehicle, an AR or a VR device, or the method in this embodiment may also be applied to a device connected to an electronic device with a radar and an IMU, such as a computer or a server. The technical scheme in the embodiment is mainly used for acquiring the transmission delay between the radar and the IMU so as to improve the positioning and mapping accuracy of the electronic equipment.
Specifically, the method in this embodiment may include the following steps:
step 101: a first curve of angular velocity of the radar in at least one target degree of freedom over time is obtained.
The degree of freedom refers to the degree of freedom of the radar moving in space along with the electronic equipment where the radar is located, such as the degree of freedom of movement along the directions of three orthogonal coordinate axes x, y and z and the degree of freedom of rotation around the three coordinate axes. The target degree of freedom in this embodiment refers to one or more of the 6 degrees of freedom, and the present embodiment may select the target degree of freedom from the 6 degrees of freedom according to a specific rule or according to a specific condition.
Specifically, in this embodiment, after the target degree of freedom is selected, a first curve of the change of the angular velocity with time when the radar moves on the target degree of freedom is obtained, the first curve includes a plurality of curve moments, each curve moment corresponds to a curve value of the angular velocity, the abscissa represents the curve moment, and the ordinate represents the curve value of the angular velocity at the corresponding curve moment.
It should be noted that the first curve may be a curve generated by acquiring data as the radar starts to move as the device where the radar is located starts to be triggered when the transmission delay acquisition is performed, and a starting curve time of the first curve corresponds to a specific target time, such as 2 points and 10 minutes.
Step 102: a second plot of angular velocity of the IMU in the target degree of freedom over time is obtained.
The execution sequence of step 102 and step 101 is not limited by the execution sequence in the drawings, and the technical solutions formed by different execution sequences belong to the same inventive concept and are within the protection scope of the present application.
Specifically, the second curve includes a plurality of curve times, each curve time corresponds to a curve value of angular velocity, where an abscissa represents the curve time and an ordinate represents the curve value of angular velocity at the corresponding curve time.
It should be noted that, in this embodiment, the second curve may be a curve obtained by acquiring data as the IMU starts to move as the device where the IMU is located starts to be triggered when the transmission delay is acquired, that is, the second curve and the first curve are curves in which angular velocities of the IMU and the radar on the target degree of freedom respectively change with time at the same time segment, where an initial curve time of the second curve is theoretically consistent with an initial curve time of the first curve, but there is a curve delay between the first curve and the second curve due to a transmission delay between the radar and the IMU, and at this time, there is a deviation of the curve delay between the initial curve time of the second curve and the initial curve time of the first curve.
Step 103: and performing curve fitting on the first curve and the second curve, so that the curve-fitted first curve and the curve-fitted second curve correspond to curve values at any same curve time.
The frequency of the curves of the radar and the IMU, which are respectively the angular velocity changes with time in the target degree of freedom, is different due to the difference of the data acquisition frequencies of the radar and the IMU, for example, the frequency of the first curve of the radar is usually 10Hz, the frequency of the second curve of the IMU is usually 200Hz, and there may be a case where the curve moments corresponding to the curve values of the first curve and the second curve respectively have are inconsistent, for example, the first curve may have the curve values of the angular velocity in the 5 th millisecond and the 20 th millisecond, and the second curve may have the curve values of the angular velocity in the 1 st millisecond, the 11 th millisecond and the 21 st millisecond.
Based on this, in this embodiment, a curve fitting algorithm, such as a B-spline difference algorithm, may be used to perform curve fitting on the first curve and the second curve, so that the curve frequencies of the first curve and the second curve are consistent, that is, the curve values correspond to any same curve time, for example, after the curve fitting, the curve frequencies of the first curve and the second curve are both curve frequency values of 200Hz or more, and the first curve and the second curve have the curve values of the angular velocity at 1 millisecond, 5 millisecond, 11 millisecond, 20 millisecond, and 21 millisecond, respectively, although the curve values of the angular velocity also exist at other corresponding curve times at the curve frequency after the fitting.
Step 104: and obtaining the curve time delay between the first curve and the second curve according to the curve value, wherein the curve time delay represents the transmission time delay between the radar and the IMU.
The radar and the IMU belong to the same electronic device, so that the change trends of the curve values between the first curve and the second curve of the radar and the IMU in the target degree of freedom are the same or similar, but a certain curve delay exists at the moment of the curve, and the curve delay can be understood as: if the first curve or the second curve is moved to the left or right along the abscissa by the distance of the curve delay, the first curve and the second curve are approximately coincident, and based on this, the curve delay between the first curve and the second curve can be obtained according to the curve value in this embodiment, and the curve delay at this time is the transmission delay between the radar and the IMU.
According to the above scheme, in the time delay obtaining method provided in the embodiment of the present application, curves of angular velocities of the radar and the IMU in the target degree of freedom respectively changing with time are obtained, and then after the curves are fitted, the two curves are corresponding to curve values at any same curve time, and then the curve time delay between the two curves is obtained according to the curve values on the two fitted curves, where the curve time delay is the transmission time delay between the radar and the IMU. It can be seen that, in this embodiment, by fitting the curves of the radar and the IMU, which are respectively in the target degree of freedom and change in angular velocity with time, the curve time delay between the two curves can be obtained through the curve value of the fitted curve, and then the transmission time delay between the radar and the IMU can be obtained.
In one implementation, the delay in obtaining the curve in step 104 may be implemented by the following steps, as shown in fig. 2:
step 201: and respectively calculating the root mean square error corresponding to the first curve and the second curve on each reference time delay according to each reference time delay in a preset time delay set.
In this embodiment, the root mean square error corresponding to each reference delay of the first curve and the second curve is calculated respectively, specifically as follows:
firstly, moving a first curve or a second curve leftwards or rightwards by a time distance corresponding to a reference time delay, then calculating the root mean square error of the first curve and the second curve according to curve values corresponding to the curve times on the first curve and the second curve, wherein the root mean square error represents the coincidence degree of the first curve and the second curve, the larger the root mean square error is, the smaller the coincidence degree of the first curve and the second curve is represented, the smaller the root mean square error is, the larger the coincidence degree of the first curve and the second curve is represented, and the more similar the first curve and the second curve is.
In a specific implementation, in order to improve accuracy, in this embodiment, curve values corresponding to all curve times in the first curve and the second curve may be selected, for example, the curve values corresponding to all curve times of the first curve and the second curve in 1 st millisecond to 100 th millisecond are selected, and according to the curve values and each reference time delay in a preset time delay set, root mean square errors corresponding to each reference time delay of the first curve and the second curve are respectively calculated; or, in order to reduce the amount of calculation and speed up the acquisition efficiency of the time delay, in this embodiment, curve values corresponding to part of the curve times may be obtained on the first curve and the second curve respectively according to a preset sampling frequency, for example, only curve values corresponding to the curve times of 1 st millisecond, 5 th millisecond, 11 th millisecond, 20 th millisecond, 21 st millisecond, and the like are selected from the first curve and the second curve respectively, and then, according to the selected curve values corresponding to part of the curve times, a root mean square error corresponding to each reference time delay of the first curve and the second curve in each reference time delay is calculated according to each reference time delay in the time delay set.
The sampling frequency may be a frequency lower than the curve frequency of the fitted first curve and second curve, for example, the sampling frequency may be a frequency value between 10Hz and 200Hz, such as 100Hz or 50Hz which is lower than the curve frequency of 200 Hz.
Step 202: and selecting the reference time delay corresponding to the minimum value in the root mean square error as the curve time delay between the first curve and the second curve.
The minimum value of the root mean square errors is the root mean square error representing the maximum coincidence degree of the first curve and the second curve, at this time, the reference time delay corresponding to the root mean square error is the curve time delay between the first curve and the second curve, that is, the first curve and the second curve are in the maximum coincidence state when the first curve or the second curve is moved leftwards or rightwards along the abscissa by the time delay of the curve. Therefore, the curve delay at this time is the transmission delay of the radar and the IMU.
In one implementation, step 101, in obtaining a first curve of the angular velocity of the radar in at least one target degree of freedom over time, may be implemented by:
step 301: and acquiring point cloud data of the radar.
The point cloud data is the original data collected by the radar. Specifically, in this embodiment, a bus connection with the radar may be established to read point cloud data collected by the radar.
Step 302: and generating an initial curve of the motion trail of the radar on at least one degree of freedom along with time according to the point cloud data.
Wherein, the curve frequency of the initial curve at this time is consistent with the data acquisition frequency of the radar, such as 10 Hz.
For example, in the present embodiment, initial curves of motion trajectories of the radar in 6 degrees of freedom respectively changing with time are generated by using a loam algorithm according to point cloud data.
Step 303: and generating a first curve of the change of the angular speed of the radar on the target degree of freedom along with time according to the initial curve corresponding to the target degree of freedom selected from the at least one degree of freedom.
In this embodiment, when transmission delay is acquired, the device where the radar is located may be triggered to rotate around a specific fixed axis, such as around an X axis, and the like, at this time, point cloud data of the radar is collected and an initial curve corresponding to 6 degrees of freedom is generated, and since the device where the radar is located only moves around a fixed axis, one or more target degrees of freedom may be selected from the three degrees of freedom corresponding to the fixed axis, and then a first curve of angular velocity of the radar on the target degree of freedom, which varies with time, may be generated according to the initial curve corresponding to the target degree of freedom.
It should be noted that, in this embodiment, one or more target degrees of freedom may be provided, and when there are a plurality of target degrees of freedom, a plurality of curve delays may be finally obtained in this embodiment, and further, one or an average value or a specific maximum value of the plurality of curve delays may be arbitrarily taken from the plurality of curve delays as the transmission delay between the radar and the IMU.
Based on this, in order to improve the accuracy of the first curve in this embodiment, the following steps may be performed before step 303, as shown in fig. 4:
step 304: and updating the track of the initial curve according to the curve frequency corresponding to the initial curve.
Specifically, in this embodiment, the slam algorithm, for example, a high-precision trajectory update algorithm according to a curve frequency of the initial curve, for example, 10Hz, may be used to optimize trajectory update of the initial curve of the motion trajectory changing with time, and after trajectory integration, the high-precision initial curve may be obtained.
In addition, in order to improve the accuracy, in the present embodiment, before step 302, the following steps may be performed, as shown in fig. 5:
step 305: and denoising the point cloud data by using a noise point filtering algorithm.
Specifically, in this embodiment, the plane data with an area larger than the threshold in the point cloud data may be selected, the remaining point cloud data except the plane data may be clustered according to spatial distribution, and then the point cloud clusters with jitter abnormal data, absolute distance larger than a distance threshold, shape rule not satisfied by the point cloud shape, and number smaller than a number threshold are deleted.
Referring to fig. 6, a schematic structural diagram of a time delay obtaining apparatus provided in the second embodiment of the present disclosure is shown, where the apparatus may be configured in an electronic device having a radar and an IMU, such as a robot, an unmanned aerial vehicle, an AR or a VR device, or the apparatus in this embodiment may also be configured in a device connected to the electronic device having a radar and an IMU, such as a computer or a server. The technical scheme in the embodiment is mainly used for acquiring the transmission delay between the radar and the IMU so as to improve the positioning and mapping accuracy of the electronic equipment.
Specifically, the apparatus in this embodiment may include the following units:
a first curve obtaining unit 601, configured to obtain a first curve of a change over time of an angular velocity of the radar in at least one target degree of freedom;
a second curve obtaining unit 602, configured to obtain a second curve of a change over time of an angular velocity of an IMU in the target degree of freedom, where the IMU and the radar belong to the same electronic device;
a curve fitting unit 603, configured to perform curve fitting on the first curve and the second curve, so that the first curve and the second curve subjected to curve fitting both correspond to curve values at any time of the same curve;
a time delay obtaining unit 604, configured to obtain a curve time delay between the first curve and the second curve according to the curve value, where the curve time delay represents a transmission time delay between the radar and the IMU.
According to the above scheme, the time delay obtaining device provided in the second embodiment of the present application obtains the curves of the radar and the IMU, which are respectively in the target degree of freedom and change in angular velocity with time, so that the two curves correspond to curve values at any same curve time after the curves are fitted, and then obtains the curve time delay between the two curves according to the fitted curve values on the two curves, where the curve time delay is the transmission time delay between the radar and the IMU. It can be seen that, in this embodiment, by fitting the curves of the radar and the IMU, which change with time in angular velocity in the target degree of freedom, the curve time delay between the two curves can be obtained through the curve value of the fitted curve, and then the transmission time delay between the radar and the IMU can be obtained, and this implementation process does not need to rely on external tools or external environments, and thus the time delay obtaining process can be simplified, and the purpose of improving the time delay obtaining efficiency is achieved.
In an implementation manner, the delay obtaining unit 604 is specifically configured to: respectively calculating a root mean square error corresponding to each reference delay of the first curve and the second curve according to each reference delay in a preset delay set, for example, respectively obtaining curve values corresponding to at least part of curve moments on the first curve and the second curve according to a preset sampling frequency, and calculating a root mean square error corresponding to each reference delay of the first curve and the second curve according to each reference delay in a preset delay set and the curve values; and then selecting the reference time delay corresponding to the minimum value in the root mean square error as the curve time delay between the first curve and the second curve.
In one implementation, the first curve obtaining unit 601 is specifically configured to: acquiring point cloud data of a radar; generating an initial curve of the motion track of the radar on at least one degree of freedom along with time according to the point cloud data; and generating a first curve of the change of the angular speed of the radar on the target degree of freedom along with time according to the initial curve corresponding to the target degree of freedom selected from the at least one degree of freedom.
Optionally, the first curve obtaining unit 601, before generating an initial curve of the motion trajectory of the radar in at least one degree of freedom with time according to the point cloud data, is further configured to: denoising the point cloud data by using a noise point filtering algorithm;
optionally, before generating the first curve of the change of the angular velocity of the radar with time according to the initial curve corresponding to the target degree of freedom selected from the at least one degree of freedom, the first curve obtaining unit 601 is further configured to: and updating the track of the initial curve according to the curve frequency corresponding to the initial curve.
The target degree of freedom is selected from three degrees of freedom corresponding to the fixed shaft in the at least one degree of freedom, and the fixed shaft is a shaft around which the equipment where the radar is located moves.
Referring to fig. 7, a schematic structural diagram of an electronic device provided in the third embodiment of the present application is shown, where the electronic device may be an electronic device with a radar and an IMU, such as a robot, an unmanned aerial vehicle, an AR or a VR device, and the like. The technical scheme in the embodiment is mainly used for acquiring the transmission delay between the radar and the IMU so as to improve the positioning and mapping accuracy of the electronic equipment.
Specifically, the electronic device in this embodiment may include the following structure:
a radar 701;
IMU702；
a processor 703 for obtaining a first curve of angular velocity of the radar 701 in at least one target degree of freedom over time; obtaining a second curve of angular velocity over time of the IMU702 in the target degree of freedom, the IMU and the radar belonging to the same electronic device; performing curve fitting on the first curve and the second curve so that the first curve and the second curve subjected to curve fitting correspond to curve values at any time of the same curve; and obtaining a curve delay between the first curve and the second curve according to the curve value, wherein the curve delay represents the transmission delay between the radar 701 and the IMU 702.
According to the scheme, the electronic device provided by the third embodiment of the application obtains the curves of the radar and the IMU, which change with time, of the angular velocities of the radar and the IMU in the target degree of freedom respectively, so that the two curves correspond to curve values at any same curve time, and then obtains the curve time delay between the two curves according to the curve values on the two fitted curves, wherein the curve time delay is the transmission time delay between the radar and the IMU. It can be seen that, in this embodiment, by fitting the curves of the radar and the IMU, which are respectively in the target degree of freedom and change in angular velocity with time, the curve time delay between the two curves can be obtained through the curve value of the fitted curve, and then the transmission time delay between the radar and the IMU can be obtained.
Referring to fig. 8, a schematic structural diagram of an electronic device according to a fourth embodiment of the present disclosure is provided, where the electronic device may be a device connected to an electronic device having a radar and an IMU, such as a computer or a server. The technical scheme in the embodiment is mainly used for acquiring the transmission delay between the radar and the IMU so as to improve the positioning and mapping accuracy of the electronic equipment.
Specifically, the electronic device in this embodiment may include the following structure:
a memory 801 for storing applications and data generated by the application operations;
a processor 802 for executing an application to implement: obtaining a first curve of angular velocity of the radar in at least one target degree of freedom over time; obtaining a second curve of the IMU in the target degree of freedom in angular velocity change with time, wherein the IMU and the radar belong to the same electronic device; performing curve fitting on the first curve and the second curve so that the first curve and the second curve subjected to curve fitting correspond to curve values at any time of the same curve; and obtaining a curve time delay between the first curve and the second curve according to the curve value, wherein the curve time delay represents the transmission time delay between the radar and the IMU.
According to the scheme, the electronic device provided by the fourth embodiment of the application obtains the curves of the radar and the IMU, which change with time, of the angular velocities of the radar and the IMU in the target degree of freedom respectively, so that the two curves correspond to curve values at any same curve time, and then obtains the curve time delay between the two curves according to the curve values on the two fitted curves, wherein the curve time delay is the transmission time delay between the radar and the IMU. It can be seen that, in this embodiment, by fitting the curves of the radar and the IMU, which are respectively in the target degree of freedom and change in angular velocity with time, the curve time delay between the two curves can be obtained through the curve value of the fitted curve, and then the transmission time delay between the radar and the IMU can be obtained.
With reference to the flow shown in fig. 9, the technical solution of the present application is described by taking the transmission delay of the radar and the IMU in the unmanned aerial vehicle or the robot as an example to be calibrated:
firstly, triggering a sensor module comprising a radar and an IMU to rotate back and forth in situ for a plurality of seconds (rotate around a fixed shaft);
in the rotating process, data of the IMU and the radar are collected, the data of the motion trail of the radar on 6 degrees of freedom changing along with time are calculated by utilizing an improved open source laser instant positioning and mapping slam (simultaneous Localization and mapping) algorithm and a leam algorithm in the embodiment, the data (a first curve) of the angular speed of the radar rotating around a fixed shaft changing along with time are taken out, and meanwhile, the data (a second curve) of the angular speed of the IMU rotating around the fixed shaft changing along with time are obtained.
Then, curve fitting is carried out on curves of IMU and radar which change along with time around a certain fixed rotation angular velocity by using a B-spline interpolation algorithm, delay time is preset to be dt (reference time delay), a radar angular velocity value corresponding to each IMU timestamp under dt delay is calculated, a difference is made between the radar angular velocity value and the angular velocity value of the IMU to calculate a root Mean square error RMSE (root Mean Squared error), then the dt size is changed in a range corresponding to dt, a new RMSE is calculated, and finally dt corresponding to the RMSE minimum is taken as the real time delay of the curve.
Based on the above implementation, in this embodiment, the implementation process of curve acquisition for the loam algorithm is improved, and as shown in fig. 10, in this embodiment, a noise filtering algorithm is added at the front end of the algorithm to filter out noise of the point clouds, and a specific method is to preferentially detect a large-area plane, cluster the remaining point clouds after detecting the plane according to spatial distribution, delete point cloud clusters with abnormal inter-visibility, too long absolute distance, too irregular shape, and too small number, and perform subsequent angular velocity calculation using the remaining point clouds and the plane. And the map optimization part which runs the laser slam each time is updated with a high-precision track to ensure the curve precision of the obtained motion track along with the change of time. Meanwhile, as the robot only moves around one fixed shaft, the robot can only optimize three degrees of freedom with large change: tx, ty, yaw (or one or both of them) to prevent the over-degree-of-freedom problem.
That is, in the present embodiment, after the time-dependent change curve of the trajectory in 6 degrees of freedom is obtained, only the target degree of freedom in which the trajectory rotates around the fixed axis is taken, and the angular velocity is calculated, thereby obtaining the time-dependent change curve of the angular velocity of the radar in the target degree of freedom. Therefore, the front end and the back end of the loam algorithm are changed in the embodiment, so that the algorithm precision is higher.
As shown in fig. 9, the time delay dt is set to obtain the curve of the rotational angular velocity of the IMU and the radar as a function of time in the present embodiment, and the procedure of calculating RMSE is as follows:
wherein the lidar _ velocity _ times and IMU _ velocity _ times are the angular velocity versus time curves of the radar and IMU, as shown in fig. 11 and 12; in this embodiment, a RMSE change curve with dt is calculated through the above algorithm process, as shown in fig. 13, based on which dt corresponding to the RMSE minimum is solved through the curve in this embodiment, that is, a calibrated time delay, that is, a transmission delay between the radar and the IMU.
It should be noted that, since the attitude pos times of the radar and the IMU are not strictly corresponding, in order to accurately calculate the time delay, the corresponding position relationship between the radar and the IMU under the same timestamp must be calculated. Therefore, in this embodiment, the radar angular velocity curve needs to be interpolated at several IMU time stamps. For example, this embodiment is implemented by using B-spline interpolation with higher accuracy.
Therefore, the technical scheme of the application does not depend on an external tool and an external environment, and can be directly used for complete machine calibration without disassembling a machine, so that the operation is quick and convenient, the calibration by professional personnel is not needed, the precision is reliable and guaranteed, and the millisecond-level measurement error can be achieved. Meanwhile, the method can measure the change curve of the delay along with time and motion, and is a reliable high-precision positioning method for off-line calculation of the radar pose on the premise that the time is a constant.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. 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 application.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A method for obtaining delay, comprising:
obtaining a first curve value of the change of the angular speed of the laser radar on at least one target degree of freedom along with time;
obtaining a second curve value of the angular velocity of an inertial measurement unit IMU on the target degree of freedom changing along with time, wherein the IMU and the laser radar belong to the same electronic device;
performing curve fitting on the first curve value and the second curve value, so that the first curve subjected to curve fitting and the second curve subjected to curve fitting both correspond to curve values at any same curve time;
and calculating a root mean square error corresponding to the reference time delay according to the curve value to obtain a curve time delay between the first curve and the second curve, wherein the curve time delay represents the transmission time delay between the laser radar and the IMU.
2. The method of claim 1, wherein calculating a root mean square error corresponding to a reference delay from the curve values to obtain a curve delay between the first curve and the second curve comprises:
respectively calculating the root mean square error of the first curve and the second curve corresponding to each reference time delay according to each reference time delay in a preset time delay set;
and selecting the reference time delay corresponding to the minimum value in the root mean square error as the curve time delay between the first curve and the second curve.
3. The method of claim 2, wherein calculating a root mean square error of the first curve and the second curve respectively at each reference delay in a preset delay set comprises:
respectively acquiring curve values corresponding to at least part of curve moments on the first curve and the second curve according to a preset sampling frequency;
and according to each reference time delay in a preset time delay set, calculating the root mean square error corresponding to each reference time delay of the first curve and the second curve according to the curve value.
4. The method of claim 1 or 2, wherein obtaining a first curve value of the lidar for angular velocity in at least one target degree of freedom over time comprises:
acquiring point cloud data of the laser radar;
generating an initial curve value of the movement track of the laser radar on at least one degree of freedom along with time change according to the point cloud data;
and generating a first curve value of the laser radar with the angular speed of the target degree of freedom changing along with time according to the initial curve value corresponding to the target degree of freedom selected from the at least one degree of freedom.
5. The method of claim 4, wherein prior to generating a first curve value of angular velocity of the lidar over time based on the initial curve value for a selected target degree of freedom of the at least one degree of freedom, the method further comprises:
and updating the track of the initial curve value according to the curve value frequency corresponding to the initial curve value.
6. The method of claim 4, wherein the target degree of freedom is a selected target degree of freedom of three degrees of freedom corresponding to a fixed axis of the at least one degree of freedom, the fixed axis being an axis about which the lidar is moved.
7. The method of claim 4, wherein prior to generating an initial curve of the lidar motion trajectory in multiple degrees of freedom over time from the point cloud data, the method further comprises:
and denoising the point cloud data by using a noise point filtering algorithm.
8. A delay time acquisition apparatus, comprising:
a first curve obtaining unit, configured to obtain a first curve value of a change with time of an angular velocity of the laser radar in at least one target degree of freedom;
a second curve obtaining unit, configured to obtain a second curve value of a temporal change in an angular velocity of the IMU in the target degree of freedom, where the IMU and the lidar belong to the same electronic device;
a curve fitting unit, configured to perform curve fitting on the first curve value and the second curve value, so that the first curve subjected to curve fitting and the second curve subjected to curve fitting both correspond to curve values at any same curve time;
and the time delay obtaining unit is used for calculating a root mean square error corresponding to the reference time delay according to the curve value to obtain a curve time delay between the first curve and the second curve, and the curve time delay represents the transmission time delay between the laser radar and the IMU.
9. The apparatus according to claim 8, wherein the delay obtaining unit is specifically configured to: respectively calculating the root mean square error of the first curve and the second curve corresponding to each reference time delay according to each reference time delay in a preset time delay set; and selecting the reference time delay corresponding to the minimum value in the root mean square error as the curve time delay between the first curve and the second curve.
10. An electronic device, comprising:
a laser radar;
IMU；
a processor for obtaining a first curve of angular velocity of the lidar in at least one target degree of freedom over time; obtaining a second curve of the IMU in angular velocity variation with time in the target degree of freedom, wherein the IMU and the lidar belong to the same electronic device; performing curve fitting on the first curve and the second curve so that the first curve subjected to curve fitting and the second curve subjected to curve fitting both correspond to curve values at any time of the same curve; and calculating a root mean square error corresponding to the reference time delay according to the curve value to obtain a curve time delay between the first curve and the second curve, wherein the curve time delay represents the transmission time delay between the laser radar and the IMU.
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