In-Vehicle Global Synchronization

Transcription

1 In-Vehicle Global ronization In-Vehicle Global ronization IEEE Plenary Meeting - Geneva Aboubacar Diarra Robert Bosch GmbH 1 IEEE Plenary Meeting - Geneva

2 In-Vehicle Global ronization Outline Global ronization Goal Global ronization Use-Cases and Scenarios Global ronization Basics Global ronization Mechanisms Next Steps? 2 IEEE Plenary Meeting - Geneva

3 In-Vehicle Global ronization Global ronization Goal Goal? Define a Common Global Time Reference for all In-Vehicle Networks What is the Purpose of that? Make all automotive Time Sensitive Systems work on a same Time Base when exchanging data between each other, even though they belong to different domains with different Communication Bus Systems (CAN, FlexRay, Ethernet, etc... ) Make all automotive Time Sensitive Systems have a complete & correct view of Time 3 IEEE Plenary Meeting - Geneva

4 In-Vehicle Global ronization Outline Global ronization Goal Global ronization Use-Cases and Scenarios Global ronization Basics Global ronization Mechanisms Next Steps? 4 IEEE Plenary Meeting - Geneva

5 In-Vehicle Global ronization Global ronization Use Cases and Scenarios Improvements on Sophisticated Automotive Advanced Drivers Assistance Systems like: Adaptive Cruise Control Lane Departure Assist Blind Spot Assist Brake Assist These Systems need support of different Sensors and ECUs for Cameras, Radars,, Brakes etc From Sensors Data Fusion to the Control of Brakes, Steering Systems, etc..., Data are exchanged between different Sub-Networks which should be time-correlated In addition, for ADAS Recording, Event Data Recording, System Analysis Recording, an Absolute or Universal Time Perspective needs to be added to ronization Perspective, on top of Working or Relative Time Apprehension This trend leads to high ronization Demands 5 IEEE Plenary Meeting - Geneva

6 In-Vehicle Global ronization Outline Global ronization Goal Global ronization Use-Cases and Scenarios Global ronization Basics Global ronization Mechanisms Next Steps? 6 IEEE Plenary Meeting - Geneva

7 In-Vehicle Global ronization Global ronization Basics (GW E/E A) 2 Time Scales for an effective view of time 2 Time Scales for an effective view of time 2 Time Scales for an effective view of time On Time Master for each Time Scale Absolute or Universal Time e.g.: at 09hrs, 30min, 50sec Relative or Working Time e.g.: 40 min, 15.3 sec Absolute (Universal) Time Master Head Unit (Access to GPS) Relative (Working) Time Master (2 Possibilities) Central Gateway for a GW based E/E Architecture One of the DCUs* for a Backbone E/E Architecture Remark: These 2 Time Masters play the roles of Global Time Masters 2 Time Scales for an effective view of time Concept of Local Time Masters Role: Forward Time Information (Absolute or Relative) in Sub-Network Central Gateway as Local Time Master in each Sub-Network Each DCU is a Local Time Master in its corresponding Sub-Network * DCU: Domain Control Unit Problematic How will the coexistence of 2 Time Scales be handled in in-vehicle networks? How can different ECUs based on different Communication Systems have the same view of Absolute Time and Relative Time? Alternative: Introduction of PTP Mechanisms on CAN & FlexRay Support for 2 Time Scales on TSN 7 IEEE Plenary Meeting - Geneva

8 In-vehicle Global ronization Global ronization Basics (GW E/E A) Global Time Master 1 Central Gateway Global Time Master 2 CAN SSDTM FlexRay Switch SDTM GPS LIN High speed CAN Ethernet SSD SD1 SD2 SD3 SD4 SDi: ronization Domain i SDTM: ronization Domain Time Master SSD: ronization Sub-Domain SSDTM: ronization Sub-Domain Time Master Remarks: - The Central Gateway is the Relative Time Master. - The Switch linked to the GPS can provide the Absolute Time. It is then the Absolute Time Master. 8 IEEE Plenary Meeting - Geneva

9 In-vehicle Global ronization Global ronization Basics (Backbone E/E A) SD5 CAN DCU1 DCU2 DCU3 DCU4 SDTM1 SDTM2 SDTM3 SDTM4 SSDTM LIN FlexRay High speed CAN Switch Global Time Master 2 Ethernet GPS SDi: ronization Domain i SDTMi: ronization Domain Time Master i SSD: ronization Sub-Domain SSDTM: ronization Sub-Domain Time Master SSD SD1 SD2 SD3 SD4 Remarks: - One DCU is the first Global Time Master. It is also the Relative Time Master. The other DCUs are synchronized to it. - Each DCU is the Local Time Master in its ronization Domain excepted the SD5 where one DCU is the Time Master (The first Global Time Master ) - The Switch linked to the GPS can provide the Absolute Time. It is then the Absolute Time Master. The other DCUs are synchronized to it. 9 IEEE Plenary Meeting - Geneva

10 In-Vehicle Global ronization Global ronization Example on ACC System (1) Ethernet Global Time Master 1 Central Gateway CAN FlexRay or CAN Global Time Master 2 Head Unit Universal Time GPS ECU Radar Master Radar Slave Camera ESP ECU Hydraulic Modulator To Sensors Remark: This Use-Case highlights a ronization Process on the Relative Time. The Central Gateway is in this case, the Global Time Master Sensor To the Brakes 10 IEEE Plenary Meeting - Geneva

11 In-Vehicle Global ronization Global ronization Example on ACC System (2) Ethernet Global Time Master 1 Central Gateway CAN FlexRay or CAN Global Time Master 2 Head Unit Universal Time GPS ECU Radar Master Radar Slave Camera ESP ECU Hydraulic Modulator To Sensors Remark: This Use-Case highlights a ronization Process on the Absolute Time. The Head Unit is in this case, the Global Time Master Sensor To the Brakes 11

12 In-Vehicle Global ronization Global ronization Example on ACC System (3) Global Time Master 2 Ethernet Global Time Master 1 Central Gateway CAN Ethernet FlexRay or CAN Radar Master FlexRay or CAN Head Unit Universal Time GPS ECU Radar Slave Camera ESP ECU Hydraulic Modulator To Sensors Remark: This Use-Case highlights a ronization Process on the Relative Time. The Central Gateway is in this case, the Global Time Master Sensor To the Brakes 12 IEEE Plenary Meeting - Geneva

13 In-Vehicle Global ronization Global ronization Example on ACC System (4) Global Time Master 2 Ethernet Global Time Master 1 Central Gateway CAN Ethernet FlexRay or CAN Radar Master FlexRay or CAN Head Unit Universal Time GPS ECU Radar Slave Camera ESP ECU Hydraulic Modulator To Sensors Remark: This Use-Case highlights a ronization Process on the Absolute Time. The Head Unit is in this case, the Global Time Master Sensor To the Brakes 13 IEEE Plenary Meeting - Geneva

14 In-Vehicle Global ronization Global ronization Example on ACC System (7) DCU1 DCU2 DCU3 DCU4 Global Time Master 2 Ethernet Head Unit Universal Time GPS Remark: This Use-Case highlights a ronization Process on the Relative Time. The DCU2 is in this case, the Global Time Master CAN Global Time Master 1 ECU Sensor Ethernet Radar Master Radar Slave Camera FlexRay or CAN ESP ECU Hydraulic Modulator To the Brakes To Sensors 14 IEEE Plenary Meeting - Geneva

15 In-Vehicle Global ronization Global ronization Example on ACC System (8) DCU1 DCU2 DCU3 DCU4 Global Time Master 2 Ethernet Head Unit GPS Universal Time CAN ECU Ethernet Global Time Master 1 Radar Master Radar Slave Camera FlexRay or CAN ESP ECU Hydraulic Modulator To Sensors Remark: This Use-Case highlights a ronization Process on the Absolute Time. The Head Unit is in this case, the Global Time Master Sensor To the Brakes 15 IEEE Plenary Meeting - Geneva

16 In-Vehicle Global ronization Outline Global ronization Goal Global ronization Use-Cases and Scenarios Global ronization Basics Global ronization Mechanisms Next Steps? 16 IEEE Plenary Meeting - Geneva

17 In-Vehicle Global ronization CAN Global ronization PTP Mechanisms (Proposed in AUTOSAR ) CAN Timemaster CAN Timeslave Capture relative time (t0r) and put second portion in CAN message t0r, t0 t1r Capture actual time of transmission (t1r) through Transmit Confirmation mechanism t2r Capture actual time of reception (t2r) through Receive Indication mechanism Transmit t4r = t1r-s(t0r) in FUP message t3r Compute new, relative time at old time t3r Computed rel. time = (t3r-t2r)+s(t0r)+t4r Transmit offset t5o between relative time and absolute time at t0 (or at current point in time) s(t) = second portion of time t ns(t) = nanosecond portion of time t Computed absolute time = actual relative time + t5o 17 IEEE Plenary Meeting - Geneva

18 In-Vehicle Global ronization CAN Global ronization PTP Mechanisms (Proposed in AUTOSAR ) CAN Timemaster CAN Timeslave t0r = s t0abs = , 15:30:20.8 t1r = s t2r = 20s 0,001s t3r = s tsr = = s t OFS = , 15:30:20-0:01:40 t OFNS = 0,8-0,05 tsa = 100, , 15:28:40,75 = , 15:30:20,81 18 IEEE Plenary Meeting - Geneva

19 In-Vehicle Global ronization FlexRay Global ronization PTP Mechanisms (Proposed in AUTOSAR) Cycle Start of Cycle 0 FR Timemaster t0r, t0 FR Timeslave t1r Cycle Start of Cycle 0 Computation of t0r Transmit t0r somewhen in current FR cycle Receive and save t0r t2r Compute new, relative time at old time t2r Computed relative time = (t2r-t1r)+t0r Transmit offset t3o = t0 t0r between relative time and absolute time at t0 Computed absolute time = actual relative time + t3o 19

20 In-Vehicle Global ronization FlexRay Global ronization PTP Mechanisms (Proposed in AUTOSAR) FR Timemaster FR Timeslave Cycle start t0r, t0 t1r Cycle start -Relative time at macrotick 71 is s -t0r at cycle start = *macrotickduration -For macrotickduration = µs t0r = * µs = s Transmission in Slot 7 - t0 = , 15:30: (t0-t0r) = , 15:30: s t2r Save t0r -t2r = 20.58s -Current macrotick = t1r at cycle start = 20.58s 282* µs - t1r = s - relative time =(20.58s s) s relative time = s tsa = , 15:30: s s tsa = , 15:31: s 20 IEEE Plenary Meeting - Geneva

21 In-Vehicle Global ronization Ethernet Global ronization PTP Mechanisms (1) Tlink Central Gateway t1r Head Unit trel_hu : Computed Relative Time on Head Unit tabs_hu : Absolute Time on Head Unit trel_cgw: Relative Time on Central Gateway tabs_hu : Computed Absolute Time on Central Gateway t2r trel_hu = t1r + Residence Time + Tlink t5r t3r t4r t6r Residence Time offset = tabs_hu - trel_hu tabs_cgw = trel_cgw + offset trel_cgw, tabs_cgw trel_hu, tabs_hu t7r Time Master Switchover : Head Unit becomes the Time Master! Add-on: The Follow_up contains Absolute Time on top of Relative Time 21 IEEE Plenary Meeting - Geneva

22 In-Vehicle Global ronization Ethernet Global ronization PTP Mechanisms (2) Central Gateway Head Unit t1r = s t5r = s t2r = 20s t3r = s t4r = s Tlink = 0.5 * [( s s) - ( s-20s)] = 1.5ms Residence Time = 8.3ms Offset = , 15:40: s = , 15:38: t6r = s trel_hu = s + 8.3ms +1.5ms = s tabs_hu = , 15:40:25.8 t7r trel_cgw = s tabs_cgw = , 15:38: s tabs_cgw = , 15:40: IEEE Plenary Meeting - Geneva

23 In-Vehicle Global ronization Ethernet Global ronization PTP Mechanisms (3) Tlink tabs_cgw, t1r Central Gateway ECU tabs_cgw : Absolute Time on Central Gateway trel_ecu : Computed Relative Time on ECU tabs_ecu : Computed Absolute Time on ECU t2r t3r t5r t4r t6r trel_ecu, tabs_ecu Residence Time trel_ecu = t1r + Residence Time + Tlink offset = tabs_cgw t1r tabs_ecu = trel_ecu + offset 23 IEEE Plenary Meeting - Geneva

24 In-Vehicle Global ronization Outline Global ronization Goal Global ronization Use-Cases and Scenarios Global ronization Basics Global ronization Mechanisms Next Steps? 24 IEEE Plenary Meeting - Geneva

25 In-Vehicle Global ronization Next Steps? Requirements Analysis on: ronization Accuracy for Absolute Time & Relative Time ronization Intervals for Absolute Time & Relative Time Clock Difference between 2 Nodes on 2 different Sub-Networks (e.g.: Clock Difference between a node based on CAN and Another one based on Ethernet) Time Master Switchover Handling Time Scale Switchover Handling Absolute and Relative Clock Availability Redundant ronization Paths and Grand Masters necessity Etc... ronization Frames Formats Definition (e.g.: Need of a field to indicate the Time Scale in which a Info is transmitted) 25 IEEE Plenary Meeting - Geneva

26 In-Vehicle Global ronization Thank You for your Attention Any Questions? AE-BE/EKE 1/23/2013 Robert Bosch GmbH All rights reserved, also regarding any disposal, exploitation, reproduction, editing, 26 IEEE Plenary Meeting - Geneva