Vehicle Safety. Airbag Sensing

Vehicle Safety with focus on Airbag Sensing Prof. Dr. Stefan Dominico Seite 1

Content 1. Introduction to Vehicle Safety 2. Restraint Systems 3. Introduction to Airbag Sensing 4. Airbag Sensing (Calibration) Development 5. Future Trends 6. Lessons Learned (for real life) Page 2

1 1. Introduction to Vehicle Safety Page 3

1 Statistics Worldwide Road Deaths by Region (2010) Page 4

1 Statistics People killed in road accidents (Europe) source: IRTAD Page 5

Number of people 1 Statistics (2) People killed in road accidents (Germany) (1953 2013) 19193 max. speed on highways: 100 kph max. blood alcohol level: 0,8 helmet by law belt by law max. blood alcohol level: 0,5 ESC by law ABS for < 2,5t 3340 source: Wikipedia Year Page 6

1 Vehicle Safety Overview Occupant Protection Robust Crash Structure Buckle Pretensioner Multi Stage Airbag Occupant / Child Seat Detection Belt Force Limiter CDC Continuous Damping Control Under Steer Control IDS PLUS Traction Control ESP PLUS Child Protection Thorax-Pelvis Side Airbag Pedal Release System Head (Curtain) Side Airbag Brake Assist Cornering Brake Control Pedestrian Protection AFL Adaptive Forward Lighting Page 7

Occupant Protection Systems 1 Vehicle Safety Overview (2) Vehicle Safety Active Safety Accident Avoidance Passive Safety Improve Crashworthiness Driver Assist Systems: ABS, ESP, Speed Control Distance Control Brake Assist Collision Warning Lane Departure Warning Blind Spot Detection Adaptive Forward Lighting AFL Car-to-Car Communication Structural Design e.g. Stiff Occupant Compartment Interior Design e.g. Foamed Covers Others e.g. Seat Belt Reminder Restraint Systems e.g. Airbags, Belt Pretensioners Page 8

1 Vehicle Safety Overview (3) The development of the vehicle safety performance is a big part during the development of a new car Main objective of passive vehicle safety performance development is: Protect occupants from injuries in case of an accident! Protection is mainly achieved by design of vehicle structure and by restraint systems (airbags & belts) How good a restraint system works depends on the design of the airbags & belts and on the sensing system which is responsible for deploying the restraint systems Page 9

1 Vehicle Safety Overview (4) A little historic background on crash testing 1929 Frontal Impact 1930 Rollover Crash Testing in the past (1) Crash Testing in the past (2) 1983 Rollover Sled Test Unbelted Frontal Impact Today Page 10

1 Vehicle Safety Performance Development The vehicle safety performance development includes the following aspects: fulfillment of legal safety requirements for type approval good insurance rating good consumer rating Page 11

1 Legal (Safety) Requirements Type approval for a new car is based on UN regulations which cover vehicle safety, environmental protection, energy efficiency and theft-resistance (created by WP.29 of UNECE). This includes among many other things the following regulations regarding crashworthiness: R11 R13-H R13 R14 R16 R17 R27 R42 R43 R94 R95 R116 door latches and door retention components braking (passenger cars) braking (trucks and busses) safety belt anchorages safety belts and restraint systems seats, seat anchorages, head restraints advance-warning triangles front and rear protective devices (bumpers, etc.) safety glazing materials and their installation on vehicles protection of the occupants in the event of a frontal collision protection of the occupants in the event of a lateral collision protection of motor vehicles against unauthorized use Page 12

1 Legal (Safety) Requirements (2) R94 protection of the occupants in the event of a frontal collision R95 protection of the occupants in the event of a lateral collision Frontal Impact ODB R94 Lateral Impact MDB R95 56 kph ODB = Offset deformable barrier 50 kph MDB = Moving deformable barrier Page 13

1 Legal (Safety) Requirements (3) worldwide Examples of front and side impact regulations in use: Page 14

1 Insurance Rating AZT/RCAR/IIHS Goal: Minimize repair costs from low speed and parking accidents. The initial insurance rating for a new car program is based on special crash tests solely. Override-/Underride Test RCAR 10 Rigid Wall/Barrier Test 15 kph 10 kph + both load cases also conducted for rear impact Page 15

1 Consumer Rating EuroNCAP Adult Occupant Protection Child Occupant Protection Pedestrian Protection Safety Assist ESC = Electronic Stability Control SBR = Seatbelt Reminder SAS = Speed Assistance Systems Page 16

1 Consumer Rating EuroNCAP (2) Adult Occupant Protection Frontal Impact ODB Lateral Impact MDB Lateral Impact Pole 64 kph ODB = Offset deformable barrier 50 kph MDB = Moving deformable barrier 29 kph Page 17

1 Consumer Rating NCAP worldwide Page 18

1 Consumer Rating US-NCAP special load cases Rollover Small Overlap (25%) Page 19

1 Focus on frontal impact vehicle deformation zones structural deformation zone (front rails) for high speed crash (occupant protection) special deformation zone (crash box) for low speed crash (insurance rating) soft zone (fascia + foam) for pedestrian protection Page 20

2 2. Restraint Systems Page 21

2 Airbags Overview standard equipment: optional equipment: Page 22 - front airbags (driver + passenger) - side airbags (thorax bags) (driver + passenger) - curtain airbags (head bags) (left side + right side) - side airbags (rear passengers, 2 nd row) - knee airbags

2 Airbags Example: Frontal Airbags cover gas generator airbag (folded) with straps and ventholes Page 23

2 Airbags How do they work? Driver Airbag Timeline Codriver Airbag Page 24

2 Question: How long does it take to inflate a typical driver frontal airbag to full size? Answer: Page 25

2 Airbags How do they work? Page 26

2 Question: How long is the relevant crash time, during which the main occupant injuries happen? Answer: Page 27

2 We are too late he suffocated Question: Is a scenario like this possible? Answer: Page 28

2 Seat-Belt Pretensioner In the event of certain collisions, seat-belt pretensioners are designed to tighten the seat-belts pulling the driver and occupants more snugly into their seats in anticipation of an impact to help to reduce the likelihood of injury. anchor buckle retractor Page 29

2 Seat-Belt Pretensioner + Seat-Belt Force Limiter Seat-Belt Pretensioner: Removes slack ( Gurtlose ) Belt Force Limiter: Limits the max. force on pelvis, ribs and shoulder Page 30

2 Question: Did the developers do something wrong or why are there airbags outside the occupant compartment? Answer: source: [2] Page 31

3 3. Introduction to Airbag Sensing Page 32

3 Airbag Sensing What does it do? Events High Speed Impact (Crash) Low Speed Impact (e.g. in Parking Lot) Other (normal Driving and Misuse) Sensing System Parameters Vehicle Structure Sensors Algorithm Restraint Systems Airbag fire Airbag fire Airbag no-fire Airbag no-fire Airbag no-fire Page 33

3 Airbag Sensing How does it work in a nutshell? Event Crash Sensors Calibration Control Unit Restraint Systems Page 34

3 Crash Sensing System Sensors and Control Unit The crash sensing system consists of crash sensors that detect a crash and an airbag module that decides if and when restraint systems have to be deployed to protect the occupants from injury. Crash Sensors Acceleration [g = m/s²] Pressure [mbar] Airbag Module (SDM) connected to structural parts of the vehicle located e.g. in door cavity SDM = Sensing Diagnostic Module Page 35

3 Question: What do you think: How many crash sensors are available in a typical vehicle? Answer: Page 36

3 Sensor Locations Maximum Sensor Configuration SIS right (p) SIS right (g) B-Pillar SIS right (g) C-Pillar EFS (g) right EFS (g) center EFS (g) left Roll SDM (g) SIS left (p) SIS left (g) B-Pillar SIS left (g) C-Pillar EFS = Electronic Front Sensor SIS = Side Impact Sensor SDM = Sensing Diagnostic Module Page 37

3 Question: How much does an acceleration crash sensor cost (including mounting, cable, connector, )? Answer: Page 38

3 Sensor Locations EU standard sensor configuration SIS right (g) B-Pillar EFS (g) center SDM (g) SIS left (g) B-Pillar EFS = Electronic Front Sensor SIS = Side Impact Sensor SDM = Sensing Diagnostic Module Page 39

3 Sensor Locations US standard sensor configuration SIS right (g) B-Pillar SIS right (g) C-Pillar EFS (g) right SDM (g) EFS (g) left Roll SIS left (g) B-Pillar SIS left (g) C-Pillar EFS = Electronic Front Sensor SIS = Side Impact Sensor SDM = Sensing Diagnostic Module Page 40

3 What signals can be derived from acceleration sensors? acceleration (raw, filtered, mean, ) integral of acceleration (velocity, velocity change) sliding mean of acceleration double integral of acceleration (displacement) differences and sums of signals (e.g. relative velocity or relative displacement between two signals) derivative of acceleration ( jerk ) sum of absolute values of acceleration (energy) frequency content of acceleration signal (e.g. wavelet analysis) an infinite pool of ideas, but always the same (limited) base acceleration signal available Page 41

3 The Big 5 Airbag (Algorithm) Suppliers Page 42

4 4. Airbag Sensing (Calibration) Development Page 43

no wake-up 4 How is a deploy decision being made? Car drives around Crash sensors measure signal SDM Airbags/pretensioners deploy Signal above certain algorithm threshold? wake-up no Algorithm falls asleep again Sensor signals are evaluated (filtered, integrated ) SDM Critical Crash Event? yes SDM sends deploy signal to the relevant airbags/pretensioners Page 44

Δ Velocity [m/s] Acceleration [m/s²] 4 How does Sensing Calibration work? Time [sec] Normal Driving Crash Threshold Airbag Deploy Decision Time [sec] v( t) t 0 a( t) dt Page 45

4 Deploy Decision Which devices will be deployed? The acceleration crash sensors supply information about the crash direction (front, side, rear, rollover). Depending on the crash direction and on the severity of the crash, different restraint systems can be deployed. Front Crash: Pretensioners, Front Airbags (both sides) Side Crash: Pretensioners (both sides) Thorax-Bag, Curtain Bag (only on impacted side) Rear Crash: Pretensioners (both sides) Rollover: Pretensioners (both sides) Curtain Bags (both sides) special rollover curtain bags are necessary which last for approximately 5 sec! Page 46

4 Sensing System Sensing Calibration Development Objective: Develop a sensing system, based on a limited number auf laboratory tests ( load cases ), which works in real life for all possible events that could occur. fire events crash tests x x x deploy threshold deploy zone x x x x x x x x x x x non-deploy zone x no-fire events no-fire crash tests misuse tests normal driving Page 47

4 Load Cases Input for Sensing Calibration Frontal Impact (ECE-R94/EuroNCAP) Frontal Impact (Insurance) Lateral Impact (ECE-R95/EuroNCAP) Misuse Sensing Calibration Lateral Impact (Insurance) Rollover US only Rear Impact (Insurance) Rear Impact (Crash) Page 48

4 Load Cases Crash Test Input for Sensing Calibration Frontal Crash Lateral Crash Rear Crash v 30 ~ 20 Load Cases ~ 15 Load Cases ~ 10 Load Cases Page 49

4 Load Cases Example: Frontal Impact low speed no deploy mid speed deploy high speed fast deploy Page 50

4 Load Cases Misuse Misuse investigation includes events that can occur during the lifetime of a car and that are not critical for the occupant s health The deploy of restraint systems in such cases is not needed and not wanted (e.g. in order to prevent high repair costs) Misuse load cases are e.g. Wild boar impact Curb impact (longitudinal + lateral) Potholes Ramps Bicycle impact Door slam and many many more Page 51

4 Sensing System Steps during Development Generating Sensing Data acceleration sensor data is recorded performing different vehicle tests (crash, misuse, ) Calibrate Sensing System define requirements (fire vs. no-fire events, deploy target times, ) calibrate sensing system based on generated data Validate Sensing System acceleration sensor data is recorded performing different vehicle tests (crash, ) check functionality and robustness of sensing system (e.g. are there any unwanted deploys, are the deploy target times met, ) Page 52

4 Deploy Decision Sensor Combinations Example: Frontal Crash In the early days of crash sensing the deploy decision was based only on a SDM sensor Today an EFS sensor is included in the deploy decision EFS (g) center SDM (g) Why? SDM = Sensing Diagnostic Module EFS = Electronic Front Sensor Page 53

Δ Velocity [m/s] Δ Velocity [m/s] 4 Deploy Decision Sensor Combinations (2) 1. It is always better to have more than one input for a deploy decision ( confirmation concept ) if in case of a single sensor this sensor is faulty, it might cause an unwanted deploy 2. The crash regulations and especially the EuroNCAP ratings require very fast deploy times for e.g. the ODB load case SDM ODB RCAR EFS Threshold Threshold Airbag Deploy Decision needed for ODB Time [sec] Airbag Deploy Decision needed for ODB Time [sec] Page 54

Δ Velocity [m/s] Δ Velocity [m/s] 4 Deploy Decision Sensor Combinations (3) Usually there is more than one threshold per sensor signal Example: 3 thresholds each low, medium, high SDM SDM high EFS EFS high SDM mid EFS mid SDM low EFS low ODB RCAR Time [sec] Time [sec] Combination of threshold to deploy restraint systems: SDM low + EFS high (ODB: deploy, RCAR: no deploy) SDM mid + EFS mid (ODB: deploy, RCAR: no deploy) SDM high + EFS low (ODB: deploy, RCAR: no deploy) Page 55

4 Calibration Example EFS Acc. time dependent thresholds EFS Vel. wake-up of EFS @ 20 ms ODB Test 1 Deploy: 25 ms ODB Test 2 Deploy: 41 ms SDM Acc. SDM Vel. wake-up of SDM @ 10 ms Page 56

wall 4 Deploy Decision Unwanted Deploy An unwanted deploy means a deploy of the restraint systems in case of an event in which it is not necessary for the protection of the occupants to deploy airbags or pretensioners. Why should this be avoided? 1. High repair costs (new pretensioners and airbags; new dash board) 2. The driver might loose control over the vehicle 3. The occupants loose protection Think about the following scenario: curb Page 57

4 Deploy Time Rule of Thumb for high speed crashes (useful for sensing simulation) The driver frontal airbag has to be fully inflated at the time when the relative displacement of the free flying driver head and the vehicle reaches 125 mm Example: 125 mm are reached after 70 ms latest deploy time should be: Page 58

4 Simplified deploy evaluation for high speed crashes (rule of thumb for estimating expected deploy times) Frontal Impact Velocity Thresholds EFS > m/s & SDM > m/s Lateral Impact Velocity Thresholds SIS > m/s & SDM > m/s Page 59

4 Sensing Calibration how to improve the performance Frontal Impact using vehicle speed information Idea: Issues: If the car drives with a speed faster than a certain velocity (e.g. 40 kph), the sensing thresholds are reduced to deploy airbags faster for high speed crashes Lateral Impact using LVE (lateral velocity estimation) Idea: Issue: If the car slides laterally with a speed faster than a certain velocity (e.g. 20 kph), the sensing thresholds are reduced deploy airbags faster for high speed crashes Page 60

4 Question: Is it likely to deploy airbags when you slam on the brakes with full force? Answer: Page 61

4 Question: From which impact speed is it likely to deploy airbags when you hit a rigid wall (frontal impact)? Answer: Page 62

4 Question: From which impact speed is it likely to deploy airbags in a frontal ODB crash? Answer: Page 63

4 Question: How fast after the time of the first contact between vehicle and barrier is a deploy decision needed for the EuroNCAP ODB (64 kph)? Answer: Page 64

4 Design for Sensing Conflicting Design Targets soft front structure soft and stiff front structure stiff front structure Page 65

4 Design for Sensing Conflicting Design Targets (2) The front structure has to be soft enough to see enough deformation at the sensor position early enough during a high speed crash in order to deploy the airbags in time (if needed) The front structure has to be stiff enough not to see too much deformation at the sensor position during a low speed crash in order to not deploy the airbags (if not needed) soft and stiff front structure The front structure has to be stiff enough to prevent vibrations during normal driving situations which could create signal at the sensor (issue: sensor wake-up) Page 66

4 Design for Sensing Possible Frontal Sensor Positions Mounted on the upper tiebar Mounted on the bumper beam Mounted on the front rail(s) Usually the upper tiebar is the best sensor position Page 67

4 Design for Sensing Additional Design Aspects protect the sensor during the crash select position of sensor behind structural parts (e.g. upper tiebar) if position in front of structural parts is only possible position, protect sensor by special design additional bracket prevent vibrating parts of the vehicle (e.g. engine) to have contact with sensor 10-20 mm gap required Page 68

4 Crash Testing vs. CAE Crash Simulation Crash Testing: First prototypes are available approximately 18 month before SOP Prototypes are very expensive Limited number of vehicles and crash tests during development (~50 vehicles, 100-150 crash tests) CAE Crash Simulation: CAE model is available early during development (more than 3 years before SOP) Almost no limitation in number of simulation runs Simulation results give insight in what really happens below the vehicle outer skin Page 69

4 CAE Crash Simulation Example Opel Insignia Page 70

4 CAE Crash Simulation BIW + Doors Front & Rear Axle Bumper Beam Engine Engine Package Hood Fascia Dummies Belts Size of finite elements: 4-7 mm Number of finite elements: 2.000.000 Simulation time on 32 CPUs: 1-2 days Page 71

4 Top View CAE Crash Simulation Load Case Front ODB Inital Velocity: 64 kph 40% Side View 72

dt(m/s²) 4 Example: Elephant Foot How Modifications influence Sensing Signal s_zn9bl021.mat s_zn9bl254_fascia.mat s_zn9bl767.mat file-1: s_zn9bl021.mat comment : Simulation 3700, s_zn9bl021.mat 68km/h Frontal impact ODB s_zn9bl254_fascia.mat 0 left 40% 68 km/h 0 L MM08, w ithout fascia, grill, h...w ; 400.0 Hz ; Ord:4 ; filter ) s_zn9bl021.mat file-2: s_zn9bl254_fascia.mat comment : Simulation 3700, 68km/h Frontal impact ODB 0 left 40% 68 km/h 0 L MM10, fascia+lamps+foam...w ; 400.0 Hz ; Ord:4 ; filter ) file-1: s_zn9bl021.mat comment : Simulation 3700, 68km/h Frontal impact ODB 0 left 40% 68 km/h 0 L MM08, w ithout fascia, grill, h...w ; 400.0 Hz ; Ord:4 ; filter ) file-3: s_zn9bl767.mat file-1: s_zn9bl021.mat comment : channels: Simulation 13 3700, samples: 65km/h 1026 Frontal sample impact frequency:10000.20 ODB 0 left 40% 65 Hz km/h time 0 step:1.00e-004 L upper tiebar: s frontal measurement part 1.2...w time: ; 400.0 0.10 Hz s ; Ord:4 ; filter ) file-2: s_zn9bl254_fascia.mat comment : Simulation 3700, 68km/h Frontal impact ODB 0 left 40% 68 km/h 0 L MM10, fascia+lamps+foam...w ; 400.0 Hz ; Ord:4 ; filter ) comment : Simulation 3700, 68km/h Frontal impact ODB 0 left 40% 68 km/h 0 L MM08, w ithout fascia, grill, headlamps ( Filter: butte...w ; 400.0 Hz ; Ord:4 ; filter ) ECU-X in "m/s" 18 Sensor Velocity Change EFS center X in "m/s" Vehicle Safety Vehicle Safety Vehicle Safety 16 14 12 10 8 6 Threshold 4 2 0 0.03 0.04 0.05 0.06 0.07 0.08 time [s] -2 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 time [s] 73 GME Sensing Performance GME Sensing - 14.03.11-g:\20_data\simulation\epsilon\3700\front\daten_3_matmodify\s_zn9bl021.mat-11844771-DO2 Performance GME Sensing - 14.03.11-s_zn9bl021.mat Performance - 14.03.11-s_zn9bl021.mat s_zn9bl254_fascia.mat s_zn9bl254_fascia.mat-11844771-do2 s_zn9bl767.mat-11844771-do2

4 GME 18 Example: Elephant Foot s_zn9bl021.mat s_zn9bl254_fascia.mat s_zn9bl767.mat file-1: s_zn9bl021.mat comment : Simulation 3700, 68km/h Frontal impact ODB 0 left 40% 68 km/h 0 L MM08, w ithout fascia, grill, h...w ; 400.0 Hz ; Ord:4 ; filter ) file-2: s_zn9bl254_fascia.mat comment : Simulation 3700, 68km/h Frontal impact ODB 0 left 40% 68 km/h 0 L MM10, fascia+lamps+foam...w ; 400.0 Hz ; Ord:4 ; filter ) Deformation during Crash file-3: s_zn9bl767.mat comment : Simulation 3700, 65km/h Frontal impact ODB 0 left 40% 65 km/h 0 L upper tiebar: frontal part 1.2...w ; 400.0 Hz ; Ord:4 ; filter ) ECU-X in "m/s" EFS center X in "m/s" 18 Vehicle Safety 16 16 14 12 10 8 20 ms 14 12 10 8 6 6 4 4 2 2 0 0-2 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 time [s] -2 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 time [s] GME Sensing Performance - 14.03.11-s_zn9bl021.mat s_zn9bl254_fascia.mat s_zn9bl767.mat-11844771-do2 74

4 Other safety features triggered by the SDM - Pop-Up Bars for Convertibles - Door Unlock - Active Head Rest - Fuel Pump Shut-Off - Battery Cut-Off - Page 78

5 5. Future Trends Page 79

5 The future of airbag sensing integration of camera information Opel integration of radar information Opel Bosch Page 80

5 The future of airbag sensing (2) integration of car2car communication integration of car2x communication autonomous driving Will we still need airbags and sensing in the future? Page 81

6 6. Lessons Learned (for real life) Page 82

6 Lessons learned Always buckle up also in the rear seats! People from the rear seats can kill people in the front row! And don t do this: Page 83

Thank you for your attention! Any questions? Page 84