Systems and methods for time synchronization of multiple sensors in a vehicle
A method for time synchronization in a vehicle may include transmitting, by a satellite navigation device to a controller and at least one LiDAR device, a UTC and a PPS signal. The satellite navigation device may have a first clock. The method may include synchronizing, by the controller, a second clock of the controller with the first clock of the satellite navigation device based on the PPS signal and the UTC. The method may include synchronizing, by the at least one LiDAR device, a third clock of the at least one LiDAR device with the first clock of the satellite navigation device based on the PPS signal and the UTC. The method may include synchronizing, by at least one camera, a fourth clock of the at least one camera with the second clock of the controller.
1. A method for time synchronization in a vehicle, the vehicle including a satellite navigation device, at least one light detection and ranging (LiDAR) device, at least one camera, and a controller, the method comprising:
transmitting, by the satellite navigation device to the controller and the at least one LIDAR device, a coordinated universal time (UTC) and a pulse per second (PPS) signal, the PPS signal incorporating integer second information of the UTC, the satellite navigation device having a first clock;
synchronizing, by the controller, a second clock of the controller with the first clock of the satellite navigation device based on the PPS signal and the UTC;
synchronizing, by the at least one LiDAR device, a third clock of the at least one LIDAR device with the first clock of the satellite navigation device based on the PPS signal and the UTC;
transmitting, by the at least one camera, an initial data package to the controller, the initial data package including a first timestamp according to a fourth clock of the at least one camera, the first timestamp indicating a time when the at least one camera transmits the initial data package;
transmitting, by the controller after receiving the initial data package, a modified data package to the at least one camera, the modified data package including a second timestamp indicating a time when the controller receives the initial data package and a third timestamp indicating a time when the controller transmits the modified data package according to the second clock;
recording, by the at least one camera after receiving the modified data package, a fourth timestamp according to the fourth clock of the at least one camera, indicating a time when the at least one camera receives the modified data package from the controller;
determining, by the at least one camera, an offset between the second clock and the fourth clock based on the first timestamp, the second timestamp, the third timestamp, and the fourth timestamp; and
synchronizing, by the at least one camera, the fourth clock of the at least one camera with the second clock of the controller based on the offset.
2. The method of claim 1 , wherein determining, by the at least one camera, the offset between the second clock and the fourth clock based on the first timestamp, the second timestamp, the third timestamp, and the fourth timestamp includes:
determining, by the at least one camera, a delay of the initial data package or the modified data package of a single trip between the controller and the at least one camera based on the first timestamp, the second timestamp, the third timestamp, and the fourth timestamp; and
determining, by the at least one camera, the offset based on the delay.
3. The method of claim 1 , further comprising:
receiving, by the satellite navigation device from one or more satellites, navigation signals; and
determining, by the satellite navigation device, the PPS signal and the UTC based on the navigation signals.
4. The method of claim 1 , wherein the PPS signals and the UTC are transmitted to the controller or the at least one LiDAR device at the same time.
5. The method of claim 1 , wherein the UTC are transmitted to the controller or the at least one LiDAR device after a period of time when the PPS signal is transmitted to the controller or the at least one LiDAR device.
6. The method of claim 1 , wherein the vehicle further includes an inertial navigation system (INS);
the method further comprising:
receiving, by the INS, the PPS signal and the UTC from the satellite navigation device; and
synchronizing, by the INS, a fifth clock of the INS with the first clock of the satellite navigation device based on the PPS signal and the UTC.
7. The method of claim 1 , wherein the PPS signal is processed by performing amplification or optoelectronic isolation when the PPS signal is transmitted to the controller or the at least one LiDAR.
8. The method of claim 1 , wherein the PPS signal is processed by filtering high-frequency noise in the PPS signal when the PPS signal is transmitted to the controller or the at least one LiDAR.
9. The method of claim 8 , wherein the high-frequency noise in the PPS signal is filtered using a magnet ring.
10. A system for time synchronization in a vehicle, comprising:
a satellite navigation device having a first clock, configured to transmit a pulse per second (PPS) signal and a coordinated universal time (UTC), the PPS signal incorporating integer second information of the UTC;
a controller, configured to
receive the PPS signal and the UTC from the satellite navigation device; and
synchronize a second clock of the controller with the first clock of the satellite navigation device based on the PPS signal and the UTC;
at least one LiDAR device, configured to
receive the PPS signal and the UTC from the satellite navigation device; and
synchronize a third clock of the at least one LiDAR device with the first clock of the satellite navigation device based on the PPS signal and the UTC; and
at least one camera, configured to
transmit, by the at least one camera, an initial data package to the controller, the initial data package including a first timestamp according to a fourth clock of the at least one camera, the first timestamp indicating a time when the at least one camera transmits the initial data package;
transmit, by the controller after receiving the initial data package, a modified data package to the at least one camera, the modified data package including a second timestamp indicating a time when the controller receives the initial data package and a third timestamp indicating a time when the controller transmits the modified data package according to the second clock;
record, by the at least one camera after receiving the modified data package, a fourth timestamp according to the fourth clock of the at least one camera, indicating a time when the at least one camera receives the modified data package from the controller;
determine, by the at least one camera, an offset between the second clock and the fourth clock based on the first timestamp, the second timestamp, the third timestamp, and the fourth timestamp; and
synchronize the fourth clock of the at least one camera with the second clock of the controller based on the offset.
11. The system of claim 10 , wherein determining, by the at least one camera, the offset between the second clock and the fourth clock based on the first timestamp, the second timestamp, the third timestamp, and the fourth timestamp includes:
determining, by the at least one camera, a delay of the initial data package or the modified data package of a single trip between the controller and the at least one camera based on the first timestamp, the second timestamp, the third timestamp, and the fourth timestamp; and
determining, by the at least one camera, the offset based on the delay.
12. The system of claim 10 , wherein the satellite navigation device is further configured to
receive navigation signals from one or more satellites; and
determine the PPS signal and the UTC based on the navigation signals.
13. The system of claim 10 , wherein the PPS signals and the UTC are transmitted to the controller or the at least one LiDAR device at the same time.
14. The system of claim 10 , wherein the UTC are transmitted to the controller or the at least one LiDAR device after a period of time when the PPS signal is transmitted to the controller or the at least one LiDAR device.
15. The system of claim 10 , further comprising an inertial navigation system (INS) configured to
receive the PPS signal and the UTC from the satellite navigation device; and
synchronize a fifth clock of the INS with the first clock of the satellite navigation device based on the PPS signal and the UTC.
16. The system of claim 10 , wherein the PPS signal is processed by performing amplification or optoelectronic isolation when the PPS signal is transmitted to the controller or the at least one LiDAR.
17. The system of claim 10 , wherein the PPS signal is processed by filtering high-frequency noise in the PPS signal when the PPS signal is transmitted to the controller or the at least one LiDAR.
18. The system of claim 17 , wherein the high-frequency noise in the PPS signal is filtered using a magnet ring.