Method and apparatus for providing time source for autonomous driving
A method and an apparatus for providing a time source for autonomous driving are provided, which may be applied to autonomous driving of a vehicle in the field of artificial intelligence. The method includes: providing a first time source for a first subsystem of an autonomous driving system by using a first crystal oscillator, and providing a second time source for a second subsystem of the autonomous driving system based on a received satellite time signal. According to embodiments of the present disclosure, a stable and reliable global time source reference can be provided for the autonomous driving system, to ensure secure operation of the autonomous driving system, and meet a requirement of the system for coordinated universal time.
1. An apparatus for providing a time source for an autonomous driving system in a vehicle, and comprising a first processor and a first crystal oscillator connected to the first processor, wherein
the first processor is configured to provide a first time source for a first subsystem of the autonomous driving system by using the first crystal oscillator, and provide a second time source for a second subsystem of the autonomous driving system based on a received satellite time signal, the first subsystem is configured to process driving service-related data of the vehicle, and the second subsystem is configured to process management-related data of the vehicle.
2. The apparatus according to claim 1 , wherein the first processor is further configured to:
when the satellite time signal is not received, provide the second time source for the second subsystem by using the first crystal oscillator.
3. The apparatus according to claim 2 , wherein the apparatus further comprises a signal receiving module connected to the first processor; wherein the signal receiving module is configured to: when the satellite time signal is received, provide a reference frequency for the second time source based on the satellite time signal; and
the first processor is further configured to:
generate the second time source based on the reference frequency, and provide the second time source for the second subsystem.
4. The apparatus according to claim 3 , wherein the apparatus further comprises a first clock module connected to the first processor; and
the first clock module is configured to synchronize a third time source based on the second time source and a preset adjustment periodicity, wherein the third time source is a time source provided by the first clock module.
5. The apparatus according to claim 4 , wherein the first processor is further configured to:
determine frequency ratios of the first time source, the second time source and the third time source, wherein the frequency ratios of the first time source, the second time source and the third time source comprise a first frequency ratio of the first time source to the second time source, a second frequency ratio of the first time source to the third time source, and a third frequency ratio of the second time source to the third time source;
determine a frequency ratio difference of any two of the first time source, the second time source and the third time source based on the frequency ratios of the first time source, the second time source and the third time source and a historical frequency ratio corresponding to any two of the first time source, the second time source and the third time source, wherein the frequency ratio differences of the first time source, the second time source and the third time source comprise a first frequency ratio difference between the first frequency ratio and a historical first frequency ratio, a second frequency ratio difference between the second frequency ratio and a historical second frequency ratio, and a third frequency ratio difference between the third frequency ratio and a historical third frequency ratio; and
determine, based on the first frequency ratio difference, the second frequency ratio difference, and the third frequency ratio difference, that a frequency of a crystal oscillator corresponding to a target time source in the first time source, the second time source, or the third time source offsets from a preset frequency range.
6. The apparatus according to claim 5 , wherein the first processor is configured to:
determine the first frequency ratio FR1, the second frequency ratio FR2, and the third frequency ratio FR3 according to the following formulas:
FR
1
=
OS_CLK
Frequency
GNSS_CLK
Frequency
FR
2
=
OS_CLK
Frequency
RTC_CLK
Frequency
FR
3
=
GNSS_CLK
Frequency
RTC_CLK
Frequency
,
wherein
OS_CLK Frequency is a clock frequency of the first time source, GNSS_CLK Frequency is a clock frequency of the second time source, and RTC_CLK Frequency is a clock frequency of the third time source.
7. The apparatus according to claim 6 , wherein the first processor is configured to:
determine the first frequency ratio difference ΔFR1, the second frequency ratio difference ΔFR2, and the third frequency ratio difference ΔFR3 according to the following formulas:
Δ
FR
1
=
abs
(
FR
1
-
FR
1
AVG
)
Δ
FR
2
=
abs
(
FR
2
-
FR
2
AVG
)
Δ
FR
3
=
abs
(
FR
3
-
FR
3
AVG
)
,
wherein
abs(FR1−FR1 AVG ) is an absolute value of a difference between the first frequency ratio and the historical first frequency ratio, abs (FR2−FR2 AVG ) is an absolute value of a difference between the second frequency ratio and the historical second frequency ratio, and abs(FR3−FR3 AVG ) is an absolute value of a difference between the third frequency ratio and the historical third frequency ratio.
8. The apparatus according to claim 7 , wherein the first processor is further configured to:
determine a k th first frequency ratio, a k th second frequency ratio, and a k th third frequency ratio based on a preset measurement periodicity, until N first frequency ratios, N second frequency ratios, and N third frequency ratios are determined, wherein 0<k≤N, and k is an integer; and
determine, based on the N first frequency ratios, the N second frequency ratios, and the N third frequency ratios, historical frequency ratios corresponding to the three groups of frequency ratios, wherein the historical frequency ratios corresponding to the three groups of frequency ratios comprise the historical first frequency ratio corresponding to the first frequency ratio, the historical second frequency ratio corresponding to the second frequency ratio, and the historical third frequency ratio corresponding to the third frequency ratio.
9. The apparatus according to claim 8 , wherein the first processor is configured to:
determine the historical first frequency ratio FR1 AVG , the historical second frequency ratio FR2 AVG , and the historical third frequency ratio FR3 AVG according to the following formulas:
FR
1
AVG
=
fr
1
1
+
fr
1
2
+
fr
1
3
+
…
+
fr
1
N
N
FR
2
AVG
=
fr
2
1
+
fr
2
2
+
fr
2
3
+
…
+
fr
2
N
N
FR
3
AVG
=
fr
3
1
+
fr
3
2
+
fr
3
3
+
…
+
fr
3
N
N
,
wherein
fr1 1 , fr1 2 , fr1 3 , . . . , and fr1 N are respectively a 1 st first frequency ratio, a 2 nd first frequency ratio, a 3 rd first frequency ratio, . . . , and an N th first frequency ratio, fr2 1 , fr2 2 , fr2 3 , . . . , and fr2 N are respectively a 1 st second frequency ratio, a 2 nd second frequency ratio, a 3 rd second frequency ratio, . . . , and an N th second frequency ratio, and fr3 1 , fr3 2 , fr3 3 , . . . , and fr3 N are respectively a 1 st third frequency ratio, a 2 nd third frequency ratio, a 3 rd third frequency ratio, . . . , and an N th third frequency ratio.
10. The apparatus according to claim 9 , wherein the apparatus further comprises a second processor connected to the first processor, wherein
the second processor is a backup processor of the first processor, and
the second processor is further connected to a second crystal oscillator and a second clock module, the second crystal oscillator is a backup crystal oscillator of the first crystal oscillator, and the second clock module is a backup module of the first clock module.
11. The apparatus according to claim 10 , wherein the first crystal oscillator is a temperature compensated crystal oscillator.
12. A method for providing a time source for autonomous driving, in an autonomous driving system of a vehicle, wherein the method comprises:
providing a first time source for a first subsystem of the autonomous driving system by using a first crystal oscillator, and providing a second time source for a second subsystem of the autonomous driving system based on a received satellite time signal, wherein the first subsystem is configured to process driving service-related data of the vehicle, and the second subsystem is configured to process management-related data of the vehicle.
13. The method according to claim 12 , wherein the method further comprises:
when the satellite time signal is not received, providing the second time source for the second subsystem by using the first crystal oscillator.
14. The method according to claim 13 , wherein the providing a second time source for a second subsystem of the autonomous driving system based on a received satellite time signal comprises:
generating the second time source by using the satellite time signal as a reference frequency of the second time source, wherein the satellite time signal is received by using a signal receiving module; and
providing the second time source for the second subsystem.
15. The method according to claim 14 , wherein the method further comprises:
synchronizing a third time source based on the second time source and a preset adjustment periodicity, wherein the third time source is a time source provided by a first clock module.
16. The method according to claim 15 , wherein the method further comprises:
determining frequency ratios of the first time source, the second time source and the third time source, wherein the frequency ratios of the first time source, the second time source and the third time source comprise a first frequency ratio of the first time source to the second time source, a second frequency ratio of the first time source to the third time source, and a third frequency ratio of the second time source to the third time source;
determining a frequency ratio difference of any two of the first time source, the second time source and the third time source based on the frequency ratios of the three time sources and a historical frequency ratio corresponding to any two of the first time source, the second time source and the third time source, wherein the frequency ratio differences of the three time sources comprise a first frequency ratio difference between the first frequency ratio and a historical first frequency ratio, a second frequency ratio difference between the second frequency ratio and a historical second frequency ratio, and a third frequency ratio difference between the third frequency ratio and a historical third frequency ratio; and
determining, based on the first frequency ratio difference, the second frequency ratio difference, and the third frequency ratio difference, that a frequency of a crystal oscillator corresponding to a target time source in the first time source, the second time source, or the third time source offsets from a preset frequency range.
17. The method according to claim 16 , wherein the determining frequency ratios of three time sources comprises:
determining the first frequency ratio FR1, the second frequency ratio FR2, and the third frequency ratio FR3 according to the following formulas:
FR
1
=
OS_CLK
Frequency
GNSS_CLK
Frequency
FR
2
=
OS_CLK
Frequency
RTC_CLK
Frequency
FR
3
=
GNSS_CLK
Frequency
RTC_CLK
Frequency
,
wherein
OS_CLK Frequency is a clock frequency of the first time source, GNSS_CLK Frequency is a clock frequency of the second time source, and RTC_CLK Frequency is a clock frequency of the third time source.
18. The method according to claim 17 , wherein the determining a frequency ratio difference of any two of the three time sources based on the frequency ratios of the three time sources and a historical frequency ratio corresponding to any two of the three time sources comprises:
determining the first frequency ratio difference ΔFR1, the second frequency ratio difference ΔFR2, and the third frequency ratio difference ΔFR3 according to the following formulas:
Δ
FR
1
=
abs
(
FR
1
-
FR
1
AVG
)
Δ
FR
2
=
abs
(
FR
2
-
FR
2
AVG
)
Δ
FR
3
=
abs
(
FR
3
-
FR
3
AVG
)
,
wherein
abs(FR1−FR1 AVG ) is an absolute value of a difference between the first frequency ratio and the historical first frequency ratio, abs(FR2−FR2 AVG ) is an absolute value of a difference between the second frequency ratio and the historical second frequency ratio, and abs(FR3−FR3 AVG ) is an absolute value of a difference between the third frequency ratio and the historical third frequency ratio.
19. The method according to claim 18 , wherein the method further comprises:
determining a k th first frequency ratio, a k th second frequency ratio, and a k th third frequency ratio based on a preset measurement periodicity, until N first frequency ratios, N second frequency ratios, and N third frequency ratios are determined, wherein 0<k≤N, and k is an integer; and
determining, based on the N first frequency ratios, the N second frequency ratios, and the N third frequency ratios, historical frequency ratios corresponding to the three groups of frequency ratios, wherein the historical frequency ratios corresponding to the three groups of frequency ratios comprise the historical first frequency ratio corresponding to the first frequency ratio, the historical second frequency ratio corresponding to the second frequency ratio, and the historical third frequency ratio corresponding to the third frequency ratio.
20. The method according to claim 19 , wherein the determining, based on the N first frequency ratios, the N second frequency ratios, and the N third frequency ratios, historical frequency ratios corresponding to the three groups of frequency ratios comprises:
determining the historical first frequency ratio FR1 AVG , the historical second frequency ratio FR2 AVG , and the historical third frequency ratio FR3 AVG according to the following formulas:
FR
1
AVG
=
fr
1
1
+
fr
1
2
+
fr
1
3
+
…
+
fr
1
N
N
FR
2
AVG
=
fr
2
1
+
fr
2
2
+
fr
2
3
+
…
+
fr
2
N
N
R
3
AVG
=
fr
3
1
+
fr
3
2
+
fr
3
3
+
…
+
fr
3
N
N
,
wherein
fr1 1 , fr1 2 , fr1 3 , . . . , and fr1 N are respectively a 1 st first frequency ratio, a 2 nd first frequency ratio, a 3 rd first frequency ratio, . . . , and an N th first frequency ratio, fr2 1 , fr2 2 , fr2 3 , . . . , and fr2 N are respectively a 1 st second frequency ratio, a 2 nd second frequency ratio, a 3 rd second frequency ratio, . . . , and an N th second frequency ratio, and fr3 1 , fr3 2 , fr3 3 , . . . , and fr3 N are respectively a 1 st third frequency ratio, a 2 nd third frequency ratio, a 3 rd third frequency ratio, . . . , and an N th third frequency ratio.
21. The method according to claim 12 , wherein the first crystal oscillator is a temperature compensated crystal oscillator.