SAFETY ENHANCED INNOVATIONS FOR OLDER ROAD USERS. EUROPEAN COMMISSION EIGHTH FRAMEWORK PROGRAMME HORIZON 2020 GA No

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1 SAFETY ENHANCED INNOVATIONS FOR OLDER ROAD USERS EUROPEAN COMMISSION EIGHTH FRAMEWORK PROGRAMME HORIZON 2020 GA No Deliverable No. 2.3 Deliverable Title Kinematic comparison between the THOR dummy, older volunteers and older PMHS in low-speed non-injurious frontal impacts Dissemination level Public 21/04/2017 Written by Francisco J. Lopez-Valdes UNIZAR Checked by Hynd, David TRL 26/04/2017 Approved by Wisch, Marcus BASt 28/04/2017 Issue date 28/04/2017 The research leading to the results of this work has received funding from the European Community's Eighth Framework Program (Horizon2020) under grant agreement n

2 EXECUTIVE SUMMARY This report discusses the similarities and differences observed in 41 sled tests that simulated a 9 km/h impact (non-injurious) on three different types of surrogates: young and elderly volunteers, Post Mortem Human Subjects and the THOR M dummy. The tests detailed here were performed by the Impact Laboratory (I3A) of the University of Zaragoza (Spain) under the subcontract established with the Ludwig-Maximilian-University of Munich (LMU). The report describes the test fixture used in the tests and provides information about the analysis methods. The generic test fixture was designed to facilitate FE modelling of these experiments in other parts of the SENIORS project, as well as to be able to replicate the equipment at other laboratories so that future tests can add to the dataset produced here. The report also contains information about the occupant surrogates that were exposed to the non-injurious impacts, and their responses to these tests in the form of response corridors that can be used in the FE modelling activities. This deliverable describes and discusses the main similarities and differences found in the kinematics of volunteers, the THOR M dummy and PMHS. The main findings of this comparison are the following: - The head of the volunteers moved forward parallel to the x axis before undergoing slight flexion, while the head of the THOR M dummy and specially the head of the PMHS underwent flexion from the beginning of the deceleration. - The THOR M and the PMHS moved forward as a whole at the beginning of the deceleration. The motion of the volunteers was limited to the upper spine and head. These difference can be attributed to volunteers bracing, although the hypothesis needs to be confirmed in future analysis of the collected data. - Differences in magnitude and phasing were observed in the z local axis acceleration of the center of gravity of the head between the volunteers and the THOR M and PMHS tests. - The greatest differences were identified for the y local angular rate sensor due to the more significant head rotation observed in the THOR M and PMHS tests. - Seat belt forces peak values and timing were similar for all the surrogates. Page 2 out of 52

3 CONTENTS Executive summary Introduction The EU Project SENIORS Background for this Deliverable Objectives of this Deliverable Structure of this Deliverable Method Test matrix Test fixture A safe test pulse Seat belt and other test fixture geometry adjustments Surrogate characteristics Instrumentation Vicon Analysis Occupant seating procedure and initial positioning Data processing Ethical approval Results Kinematics in the sagittal plane Head acceleration and angular rate sensors Head acceleration (local x) Head acceleration (local y) Head acceleration (local z) Head angular rate (local x) Head angular rate (local y) Head angular rate (local z) Seat belt forces Upper shoulder seat belt forces Lower shoulder seat belt forces Lap seat belt forces (outer) Lap seat belt forces (inner) Head trajectory in the sagittal plane Conclusions Page 3 out of 52

4 5 References Acknowledgments Disclaimer Appendix 1 Ethical approval from CEICA Page 4 out of 52

5 1 INTRODUCTION 1.1 THE EU PROJECT SENIORS Because society is aging demographically and obesity is becoming more prevalent, the SENIORS (Safety ENhanced Innovations for Older Road users) project aims to improve the safe mobility of the elderly, and overweight/obese persons, using an integrated approach that covers the main modes of transport as well as the specific requirements of this vulnerable road user group. This project primarily investigates and assesses the injury reduction in road traffic crashes that can be achieved through innovative and suitable tools, test and assessment procedures, as well as safety systems in the area of the passive vehicle safety. The goal is to reduce, in near future, the numbers of fatally and seriously injured older road users for both major groups: car occupants and external road users (pedestrians, cyclists). Implemented in a project structure, the SENIORS project consists of four technical Work Packages (WP1 WP4) which interact and will provide the substantial knowledge needed throughout the project. These WPs are: WP1: Accidentology and behaviour of elderly in road traffic WP2: Biomechanics WP3: Test tool development WP4: Current protection and impact of new safety systems In addition, there is one Work Package assigned for the Dissemination and Exploitation (WP5) as well as one Work Package for the Project Management (WP6). The overall scope for the SENIORS project is shown in the flowchart below. Page 5 out of 52

6 Quantification of needs Literature (injury, behaviour, ) Accident studies Initial benefit assessment Achievable injury prevention Analysis of risks Derivation of safety strategies IDENTIFICATION OF NEEDS / PRIORITIES FOR OLDER ROAD USERS Prioritise Future project activities Biomechanical testing Dummies / impactors Numerical models Injury criteria IMPROVED TOOLS Injury risk curves Test procedures Assessment procedures * To be confirmed from the accident analysis CAR OCCUPANT Better older thorax IRC * Obese occupant Active HBM PEDESTRIAN/CYCLIST Flex-PLI with UBM Head-neck Pedestrian thorax Head-neck and pedestrian thorax will be early-stage research Safety of older road users Effectiveness of new tools and advantages of new procedures Applied to current and advanced new safety systems Passive Active BENEFIT AND IMPACT ASSESSMENTS Integrated benefit analysis 1.2 BACKGROUND FOR THIS DELIVERABLE This report titled Kinematic comparison between the THOR dummy, older volunteers and older PMHS in low-speed non-injurious frontal impacts has been produced within the Task 2.2: Elderly people muscular reaction in virtual and real environment within the Work Package 2 Biomechanics of the SENIORS project. The goal was to characterize the influence of muscular activity in the kinematics of elderly occupants in low-speed non-injurious manouvers. To that end, the SENIORS project designed an ambitious test matrix that combined sled tests performed with volunteers (divided in two groups: elderly and young), with the THOR M dummy and with elderly Post Mortem Human Subjects (PMHS). The PMHS tests served as controls to understand the role of passive muscle mechanics in the kinematics of the occupant. The THOR M dummy has been designed incorporating features that were identified in volunteer tests and therefore it was supposed to provide an intermediate response between that of the PMHS and that of the volunteers at this very low speed. Last, the sled tests with the younger and older volunteer groups allowed to investigate whether age plays a major role in the low-speed non-injurious experiments performed within the SENIORS project. The kinematic and dynamic differences between Anthropometric Test Devices (ATD) and PMHS in sled tests have been extensively reported in the literature (Kent et al., 2003; Lopez-Valdes et al., 2009; Lopez-Valdes et al., 2010a; Lopez-Valdes et al., 2010b; Seacrist et al., 2012; Seacrist et al., 2010; Shaw et al., 2000) and will not be further discussed here. Page 6 out of 52

7 However, when it comes to compare the response between ATD and volunteers, the number of studies drop significantly. A comparison between the Hybrid III 50 th percentile and adult PMHS showed substantially different kinematics and dynamics between the dummy and the cadavers in simulated low-speed frontal impacts. These differences were observed in the sagittal trajectories of the head and spine and consequently in the forces and moments calculated at the atlanto-occipital joint in the PMHS and measured at the upper neck load cell in the ATD (Lopez-Valdes et al., 2010b). A similar study compared the performance of pediatric dummies (Hybrid III 6-yearold, Q6) with the kinematic and dynamic response of pediatric volunteers exposed to a crash test pulse similar to the one that was used in the tests reported within this deliverable (Seacrist et al., 2012; Seacrist et al., 2010). Again the ATD were not able to capture the mechanics exhibited by the pediatric volunteers. In a previous study, the response of the same group of pediatric volunteers was compared to that of a young adult group that were restrained in the same conditions and exposed to the same deceleration. The study found that when the response of all the volunteers was normalized by seated height to control for the effects of the height of the occupants in the trajectories, pediatric volunteers exhibited longer forward excursions than those exhibited by the young adult volunteers (Arbogast et al., 2009). The authors suggested the potential influence of neck and thoracic musculature in the frontal response of the adult volunteers as the cause for these differences. 1.3 OBJECTIVES OF THIS DELIVERABLE To the knowledge of the author of this report the existing literature was missing the following: - The kinematic and dynamic comparison of the THOR M dummy to volunteers (including trajectories and accelerations of selected landmarks, seat belt forces and test fixture reaction forces). - The comparison of the response of young adult volunteers to elderly volunteers in frontal impacts. So that the experiments performed within the SENIORS project could expand the available data already published, the low-speed, non-injurious deceleration pulse was selected to match that used in the study involving pediatric and young volunteers aforementioned (Arbogast et al., 2009). Thus, the results presented in this report complement and expand previous research by including data from elderly volunteers. It also includes data from PMHS test that could serve to understand the differences between ATD that were designed bases on cadaveric tests and human volunteers. 1.4 STRUCTURE OF THIS DELIVERABLE Section 2 details the method used in this test series, including definition of the test fixture and instrumentation. The test fixture used was selected with the goal of facilitating the modelling of the experiments. With the exception of the seat belt, all Page 7 out of 52

8 materials were selected to be rigid. Instead of using a commercial retractor, the seat belt was attached rigidly to the test fixture to avoid the potential uncertainties associated to modelling the interaction between the seat belt webbing and the spool of the retractor. In addition, the forces and moments developed between the occupants and the test fixture were measured using 6-degree-of-freedom load cells. Section 3 shows the main parameters required to compare the kinematics of the three different types of surrogates included in the study. It focuses mainly on the kinematics of the head and spine (both accelerations and displacements in the sagittal plane). In addition the seat belt forces that restrained the occupants are also presented and discussed. To facilitate the comparison between the different types of occupant surrogates, the results are presented in the form of corridors that include the average response of a group of tests and a shaded area that corresponds to the plus/minus one standard deviation region around the average response. The main findings and conclusions of this study are summarised in Section 4. In a later stage of the SENIORS project, the presented results will be complemented by the results of further three PMHS tests. Page 8 out of 52

9 2 METHOD 2.1 TEST MATRIX Three different types of occupant surrogates (volunteers, PMHS and the THOR M dummy) were exposed to a low-speed crash test pulse with a nominal change of velocity of 9 km/h (see Section 2.2.1) in a specifically designed test fixture. A total of 41 sled tests were completed as indicated in Table 1. Table 1 Test matrix Occupant type Speed (km/h) Tests Comments Young volunteers Elderly volunteers PMHS THOR M trials per each subject, except for volunteer VOL 05 that received only 3 trials 3 trials per subject, except for volunteer VOL 08 that received only 2 trials 2.2 TEST FIXTURE The test fixture used in this study (Eggers et al., 2017) was designed to represent the seating posture of a passenger car occupant in a simplified manner (Figure 1). In particular, all fixture components were designed to be easily reproducible at any mechanical shop and to facilitate the development of finite element (FE) computer models. The fixture consisted of a rigid seat that was specifically designed so that the interaction of the occupant with the seat was comparable to that of an occupant in a production vehicle seat. The design procedure has been described in the literature (Pipkorn et al., 2016). In addition to the seat, the fixture is composed also of a rigid footrest and a rigid framework that provides support to the D-ring and to a wire back support. All the remaining seat belt anchors were connected to the sled platform using steel plates. The position of the different components was documented using a 3D coordinate measurement device (FARO arm) and are included in Table 2. Page 9 out of 52

10 In addition to provide an environment that could be mimicked in later studies, the test fixture allowed direct visual access to the occupant during the deceleration. This characteristic was essential to facilitate the use of a 3D motion capture system that recorded the displacement of the occupant at every millisecond during the impact. This motion capture system will be described in a subsequent section. Figure 1 General view of the test fixture (top) and details of the D-ring arrangement (bottom left) and generic seat and seat belt buckle (bottom right) The seat belt webbing and seat belt buckle tongue were replaced for each of the occupants (but not in between trials with the same subject). All other seat belt components were not considered susceptible of being overloaded or modified in the tests. Page 10 out of 52

11 2.2.1 A safe test pulse The crash test pulse was selected to ensure a safe environment to the volunteers. The magnitude and the time history of the sled deceleration were chosen based on previous studies published in the literature (Arbogast et al., 2009; Lopez-Valdes et al., 2010b). These previous studies had exposed volunteers to a triangular pulse with a peak of 3.5 g and a duration of 100 ms and had reported that no volunteer had experienced pain or discomfort. The selection of this pulse had been based in a field study in which peak accelerations in a bumper car attraction of an amusement park had been measured and scaled down by 20% to ensure a safety test deceleration. The selected test pulse for this study is shown in Figure 2. Figure 2 Sled deceleration pulse Seat belt and other test fixture geometry adjustments The initial seat belt anchoring positions were selected based on previous tests that were available in the scientific literature (Lopez-Valdes et al., 2014). To ensure that the seat belt loading conditions were comparable across subjects of different anthropometries, it was decided to adapt the position of the seat belt D-ring to the specific dimensions of each of the subjects. To do so, after the subject was seated aligned with the center line of the seat and checking that either the H-point or the greater trochanter (bilaterally) were aligned with the defined H-point of the seat, the following procedure was followed: a) The vertical position of the D-ring was adjusted so that the height of the D-ring matched the height (Z position) of the right External Auditory Meatus (EAM) of the occupant. b) The inboard position of the D-ring was adjusted so that the distance between the right acromion and the D-ring (Y position) was approximately 100 mm. Page 11 out of 52

12 In addition to adapting the position of the seat belt anchoring points, additional measurements of the position of the seat belt on the torso of the occupants were taken as shown in Table 6 and Table 7. Table 2 Coordinates of relevant parts of the test fixture. Coordinates * (mm) Point x y z Origin ** Seat, front left corner Seat, front right corner Foot rest, bottom left lateral Foot rest, bottom left medial Foot rest, bottom right lateral Foot rest, bottom rigth medial D-ring bolt D-ring belt Lower anchor bolt Lower anchor belt Buckle bolt Buckle attachment (12) * Coordinates measures with the Hybrid III 50 th percentile dummy seated as occupant ** Origin: the intersection of the mid seat line in the X direction and the line connecting the two H-point seat marks in the Y direction. 2.3 SURROGATE CHARACTERISTICS Three different types of test occupants were involved in this study: human volunteers, post mortem human surrogates (PMHS) and the THOR M dummy. Volunteers were split into two age groups: the younger group consisted of five volunteers younger than 25 years old and the older group that was formed by four subjects older than 65 years old. Other requirements were that the volunteers should not have any health condition susceptible of being aggravated because of the tests and to be close in height and weight to the 50th male percentile (175 cm; 78 kg). The main anthropometric characteristics of the volunteers are summarized in Table 3. Vol 01 through Vol 04 were exposed to five sled runs. It was observed that exposing the volunteers to five runs was not needed to ensure the repeatibility of the tests and, in parallel, caused discomfort to the volunteers. While this situation was bereable in Page 12 out of 52

13 the case of the younger group, the researchers judged that it would not be appropriate with the volunteers in the elderly group. Thus, Vol 05 through Vol 09 were exposed to just three runs, with the exception of Vol 08 that required to stop the trials after the second run due to discomfort. None of the volunteers experienced any pain or non-bearable discomfort during the experiments. PMHS were selected from the Donor Program established in the Impact Laboratory (I3A) of the University of Zaragoza. Advanced age was the primary target in the selection of the surrogates and this reason explains why PMHS 3 was included in the study despite his weight and height. The possibility of including a 94 year old subject in the study weighted more that the anthropometric differences with respect to the other two PMHS. The main characteristics of the three PMHS are shown in Table 4. Last, the THOR M (Test-device for Human Occupant Restraint Metric) dummy was also used in the comparison. The THOR M dummy is defined as the THOR NT dummy including the Modification Kit and the SD3 shoulder. Note: this dummy configuration will likely be used in both the US NCAP and in the Euro NCAP testing protocols in the near future. Table 3 Anthropometry and main characteristics of the volunteers Subject ID Age (years) Stature (cm) Weight (kg) Vol Vol Vol Vol Vol Vol Vol Vol Vol Table 4 Anthropometry and main characteristics of the PMHS Subject Age Stature (cm) Weight (kg) Sitting height (cm) Cause of death PMHS Hepatic intoxication PMHS Liver infection, sepsis PMHS Prostatic cancer, anemia Page 13 out of 52

14 2.4 INSTRUMENTATION The test fixture was instrumented so that the interaction between the occupant and the fixture could be completely characterized at all times. A 6-degree-of-freedom (dof) load cell was placed under the seat and two 6-dof were used in the footrest. Four tension seat belt load cells were placed between the occupant s shoulder and the ring, at an arbitrary location in the lower shoulder seat belt area and bilaterally on the lap seat belt. Two accelerometers were used to measure the deceleration of the sled during the simulated collision. Test surrogates were instrumented with a head mount that included a tridimensional accelerometer cube and a tridimensional angular rate sensor (ARS). The head mount was attached to an elastic adjustable headband in the case of the volunteers as shown in Figure 3 that permitted a good fit to the head of the volunteer. The location of the head mount was the center of gravity of the head form in the case of the THOR M dummy. Last, head acceleration and angular speed were also measured in the PMHS tests via a head mount that was rigidly attached to the cranial aspect of the skull of the PMHS as shown in Figure 4. All sensor data were recorded at 10,000 Hz using an external data acquisition system (PCI-6254, National Instruments; Austin, TX). Sensor data were filtered using a low pass filter (CFC 60 or CFC 100). In addition to the above detailed sensors, retro-reflective spherical markers were attached to selected locations on the head, torso and extremities of the test surrogates. In the case of the THOR M dummy and the PMHS, marker clusters were attached using low-weight aluminum plates to selected structures (T1 and T12 load cell locations in the THOR M dummy; head, T1, T8, L2 and pelvis in the PMHS tests). The marker clusters were rigidly attached to internal structures to create a rigid body and so that the translation and the rotation of these rigid bodies could be described with respect to a Global Coordinate System (GCS) that was fixed to the lab using a motion capture system that is described in a subsequent section of this document. The procedure for attaching these marker clusters to the anatomical structures of the PMHS have been explained in detail elsewhere (Shaw et al., 2009). Two high-speed video cameras recorded the motion of the occupant in the sagittal and frontal anatomical planes at 1,000 Hz. Page 14 out of 52

15 Figure 3 Instrumentation used in the volunteer tests including test fixture sensors, reflective markers and a 6-dof head mount. Figure 4 Marker clusters locations and installation details in the spine (left) and head (right) of one PMHS subject. Page 15 out of 52

16 2.5 VICON ANALYSIS Kinematic data were collected at 1,000 Hz using an optoelectric stereophotogrammetric system consisting of 10 cameras (Vicon, TS series, Oxford, UK). The system captured the position of the aforementioned retro-reflective spherical markers within a calibrated 3D volume. A calibration procedure, performed prior to testing, estimated the optical characteristics of each camera and established its position and orientation in a reference coordinate system. The trajectory of each marker was recorded and smoothed through a rigidity constraint using the least squares pose (LSP) estimator (Cappozzo et al., 2005; Chiari et al., 2005; Della Croce et al., 2005; Leardini et al., 2005). A global coordinate system (GCS) was defined at a laboratory fix location. A local coordinate system (LCS) moving with the test buck was defined with origin at the front right corner of the seat following SAE J211 indications (Society of Automotive Engineers, 1998). Local x axis pointed forward and it was coincident initially with the frontal anatomical axis of the occupant. The vertical z axis pointed upwards (opposite to ground) and the y axis was defined to form a right-hand oriented coordinate system. Unless otherwise indicated, displacement data are expressed with respect to this LCS. A photogrammetric algorithm within the Vicon Nexus software package (Nexus 1.8.5, Vicon, Oxford, UK) reconstructed the 3D position of each target for each video sample increment from the multiple 2D camera images. 2.6 OCCUPANT SEATING PROCEDURE AND INITIAL POSITIONING Regardless of the type of occupant surrogate involved in the experiments the seating procedure was consistently repeated in each test. It consisted of the following steps: 1) Position the occupant pelvis on the midline of the seat. 2) Ensure that the H-point or greater trochanter of the occupant was aligned with the H-point defined in the seat. 3) Adjust the position of the foot rest so that the femur angle was around 11 degrees and the tibia angle was around 50 degrees. 4) Adjust the position and tension of the seat back wires so that the occupant torso angle measured over the sternum (or corresponding location in the THOR M dummy) was about 60 degrees. In the case of the THOR dummy further positioning was carried out to ensure the spine of the dummy was straight in the frontal plane and that the tilt angles of the different spine joints were consistent in the repeats (as given by the commercially available software TiltView). These measurements are included in Table 5. Additional measurements were taken to ensure that the seat belt position on the torso of the dummy was comparable across the different trials (see Table 6). In the case of the volunteers no further positioning was performed to avoid causing them discomfort. However, the analysis of the reflective markers allowed to quantify the differences in the initial position of the volunteers in the different trials (intrasubject) and between the volunteers (inter-subjects). As for the PMHS, several further measurements were taken as shown in Table 7 to ensure that the initial position of the subject and the seat belt position on the subject s torso were consistent across tests. Page 16 out of 52

17 A visual comparison of the initial position of the surrogates is provided in Figure 5. Table 5 Head, spine and pelvis angles used to position the THOR M dummy Test Head (deg) Upper Thoracic Spine (deg) Mid Thoracic Spine (deg) Lower Thoracic Spine (deg) Pelvis (deg) x y x y x y Table 6 Other occupant and seat belt adjustment parameters. THOR M dummy tests. C D D F A H I A: Sternum angle (deg) D : Sternal notch to bottom edge of belt (mm) I: Tibia angle (deg) C: Belt Angle at shoulder (deg) F: Belt angle at sternum (deg) K: distance from plate on thighs to lower belt edge (mm) D: Sternal notch to top edge of belt (mm) H: Femur angle (deg) Test H-point H-point A C D D F H I L R L R L R Page 17 out of 52

18 Table 7 Other occupant and seat belt adjustment parameters. PMHS tests. Legend as shown in Table 6 Test H- point H- point A C D D F H I K L R L R L R PMHS 2 had right leg substantially shorter than left one, which affected the position of the lower extremities in the test fixture. Page 18 out of 52

19 Figure 5 Comparison of the initial position of the THOR M dummy (top), a young volunteer (middle) and a PMHS (bottom). 2.7 DATA PROCESSING The sensor data included in this report have been filtered using CFC100 or CFC60 filters as defined in SAE J211 (Society of Automotive Engineers, 1998). To facilitate the presentation and compaisone of the data from 36 sled tests, data from similar occupant types were combined in the form of corridors. These corridors have been developed for: - Each of the trials performed on a single volunteer (blue corridors); - The combination of the three tests performed on the THOR dummy (red corridors); and - The combination of the three PMHS tests (green corridors). To compare the kinematics between the different surrogates and given the influence of the anthropometry on the kinematics of the subjects, all the results were massscaled to the size and weight of a 50th percentile male (Eppinger et al., 1984). The corridors were developed considering the inter-trial variability both in the x and z direction in case of the reported trajectories (Lessley et al., 2004). 2.8 ETHICAL APPROVAL All procedures related to the recruitment, informed consent procurement and methods related to the volunteer tests were reviewed and approved by the Ethical Commission for Clinical Research of Aragon (CEICA), which is the official body responsible for assessing all research projects involving human subjects in the region of Aragon. CEICA also supervised the procurement and handling of the human donors according to the established procedures of the Impact Laboratory (I3A) of the University of Zaragoza. The approval certificate was submitted to the European Commission on December 16th, 2015 as part of the initial ethics assessment of the project. The letter of approvement (in Spanish) is included as Appendix 1 of this document. Page 19 out of 52

20 3 RESULTS 3.1 KINEMATICS IN THE SAGITTAL PLANE This subsection shows the kinematics of the different types of surrogates in the sagittal plane. Selected video frames (at 0 ms, 80 ms, 160 ms and 240 ms) are included in the following figures showing matched comparisons between the surrogates. These video captures illustrate qualitatively the differences and serve to introduce the quantitative results of the following result subsections. Note that the motion capture system requires low light to work properly and therefore there is a trade-off between the light in the high-speed videos and the optimal conditions for an optimal tracking of the occupants trajectories. Figure 6 shows the comparison between the motion of one of the younger subjects and one of the elderly ones. It can be seen that while the head of the elderly volunteer is already moving forward at t=80 ms, the one of the younger subject has barely moved. The younger volunteer s head lagged the older volunteer s one as shown at t=160 ms and t=240 ms, instant in which the head of the younger volunteer was reaching its maximum head forward excursion while the head of the older subject was already in the rebound phase. Another difference to be pointed out is the neck elongation shown by the younger subject that was not found in the motion of the elderly volunteer. The comparison of the kinematics of a younger volunteer with one of the PMHS in Figure 7 illustrates important differences. The earlier head motion start that had been observed for the elderly volunteer was even more relevant in the case of the PMHS as shown in the comparison of the video frames at t=80 ms. At least in the case of the PMHS test, this earlier motion of the head can be likely attributed to the lack of neck muscle activity. In addition, the neck elongation observed in the volunteer was replaced by a flexion motion of the head of the PMHS with no observable neck elongation. Again, this effect can be probably attributed to the absence of muscle reactions. The above paragraphs suggest that the elderly volunteer s kinematics would occupy a place between those of the younger subjects and the PMHS. Figure 8 confirms this hypothesis, even if the head of the elderly volunteer is far from reaching the flexion motion undergone by the head of the PMHS as shown in the video frame capture at t=240 ms. Page 20 out of 52

21 t(ms) Test 1693 Test Figure 6 Comparison of the kinematics of one young volunteer (left) and one elderly volunteer (right) at selected times during the deceleration. Page 21 out of 52

22 t(ms) Test 1693 Test Figure 7 Comparison of the kinematics of one young volunteer (left) and one PMHS (right) at selected times during the deceleration. Page 22 out of 52

23 t(ms) Test 1780 Test Figure 8 Comparison of the kinematics of one elderly volunteer (left) and one PMHS (right) at selected times during the deceleration. Page 23 out of 52

24 As for the comparisons between the THOR M dummy and the other surrogates, Figure 9 and Figure 10 show that globally the dummy moves further than the other occupant types. Even at t=80 ms, it is possible to identify that the dummy has moved forward while the human volunteer are still loading back rest in a very similar way than they did initially. When the seatbelt arrested the forward motion of the dummy, the neck started to undergo a flexion motion. This is illustrated in the video frame captured at t=160 ms. It is at this time that the younger volunteer in Figure 10 exhibitis a clear elongation of the neck (that is much more difficult to appreciate in the case of the elderly volunteer as above mentioned). This comparison suggests that while the human volunteers managed to keep the torso and pelvis from moving forward with the neck undergoing the described elongation deformation, the dummy moved as a whole initially and once its motion was arrested the neck started to move in flexion. There can be two potential explanations for these differences. The first one can be attributed to the potential bracing of the volunteers against the footrest and the tension of abdominal and back muscles that could have contributed to restrain the motion of the body. A detailed analysis of the muscle activity of the volunteers will contribute to ellucidate the validity of this hypothesis. The second contributing factor to the observed differences between the THOR M and the volunteers could have been the more coupled structure of the dummy vs the more compliant body of the volunteers. The last comparison is included in Figure 11 and shows the kinematics of the THOR M dummy and one PMHS. In this case, it can be seen that also the PMHS moved forward as a whole in the early instants of the deceleration (see t=80 ms). The motion of the PMHS supports the hypothesis of the volunteers bracing and therefore limiting their forward motion. As above, once the seat belt arrested the motion of the trunk, the head of the dummy and the head of the PMHS started to undergo flexion although this motion was limited in the case of the THOR dummy and it was very extensive in the case of the PMHS test. Since the design of the neck of the THOR M dummy included volunteer tests, it would be expected to find differences in the kinematic behavior of the neck as the ones identified in the comparison included here. However, as the volunteer experiments that informed the design of the THOR dummy were limited by the need of not being harmful to the volunteers (as it is the case with the tests included in this report), it is not clear if the effect of muscle tension would be as influential at higher impact speeds. In fact, the own mechanics of the muscles that require a critical time to activate and recruit muscle fibres before the muscle force builds up may limit its influence at higher energy levels. In short, it is possible that these differences between volunteers and PMHS are not that significant at higher speeds and therefore the THOR M dummy kinematics could approximate closer the actual kinematics of the living at those speeds. Page 24 out of 52

25 t(ms) Test 1740 Test Figure 9 Comparison of the kinematics of the THOR dummy (left) and one elderly volunteer (right) at selected times during the deceleration. Page 25 out of 52

26 t(ms) Test 1740 Test Figure 10 Comparison of the kinematics of the THOR dummy (left) and one young volunteer (right) at selected times during the deceleration. Page 26 out of 52

27 t(ms) Test 1740 Test Figure 11 Comparison of the kinematics of the THOR dummy (left) and one PMHS (right) at selected times during the deceleration. Page 27 out of 52

28 3.2 HEAD ACCELERATION AND ANGULAR RATE SENSORS The following subsections include some of the most relevant sensor data measured in the tests. As indicated in Section 2.6, it has been preferred to develop corridors to facilitate the comparison between the different types of surrogates. Although the color code is indicated in the caption of the figures, blue corridors correspond to the volunteers, green corridors to the PMHS tests and the red corridors are the ones corresponding to the THOR M sled tests. It should be noted that the sensor data included here have not been transformed to the head center of gravity and therefore are local to the position of the head in which the head mount was attached. In addition, the magnitudes are reported with respect to a local coordinate system that was initially aligned with the Global Coordinate System (GCS) but that moves with the head of the occupant. It could be observed that the width of the corridors from Vol 05 onwards is smaller than the width of Vol 01 to Vol 04. This is probably due to the lower number of trials per subject done on Vol 05 and following subjects. Despite this fact, it can be seen that the intra-subject variability of the different trials was not significant and that the volunteers behaved in a similar manner throughout the trials. The maximum variability was observed in the PMHS tests and especially during the last part of the deceleration, in which the head is undergoing the flexion motion described in the previous section. Despite the variability observed in the motion of the head, the peak value and the general shape of the corridor were in good agreement with those measured with the THOR M dummy and observed in the volunteer tests. Peak head decelerations in the x local direction were limited to 8 g consistently in the three surrogates as shown in Figure 12 and Figure 13. The head acceleration values in the lateral directions were negligible. Last, the head acceleration measured in the volunteer tests in the local z direction was different in nature to that observed in the PMHS and THOR M tests. This difference is probably associated to the lack of rotation of the head of the volunteers compared to the PMHS and dummy head. See Figure 16 and Figure 17. The more important flexion of the PMHS head is clearly reflected in Figure 21 (right) in which the peak rotation value was almost twice the peak value measured in most of the volunteer tests (Figure 20) and almost 25% higher the peak value observed in the THOR M tests (Figure 21, left). The oscillations seen in the response of the THOR M dummy were consequence of the large dynamic range of the sensors used in the dummy. As this dummy is intended to be used at higher impact velocities the dynamic range of the sensors installed in the dummy was not the most appropriate for the current task. Despite these oscillations that appeared when there was no clear mechanical input, the reading of the THOR sensors were considered to be reliable during the motion of the occupant. Page 28 out of 52

29 3.2.1 Head acceleration (local x) Figure 12 Time history corridors of head acceleration in the local x axis. Volunteer tests. From top to bottom and from left to right: Volunteer 01 up to Volunteer 09. Corridors correspond to the average response ± standard deviation of the total of trials with each volunteer. Figure 13 Time history corridors of head acceleration in the local x-axis. Left: THOR M dummy. Right: PMHS. Corridors include average response ± standard deviation. Page 29 out of 52

30 3.2.2 Head acceleration (local y) Figure 14 Time history corridors of head acceleration in the local y axis. Volunteer tests. From top to bottom and from left to right: Volunteer 01 up to Volunteer 09. Corridors correspond to the average response ± standard deviation of the total of trials with each volunteer. Page 30 out of 52

31 Figure 15 Time history corridors of head acceleration in the local y-axis. Left: THOR M dummy. Right: PMHS. Corridors include average response ± standard deviation. Page 31 out of 52

32 3.2.3 Head acceleration (local z) Figure 16 Time history corridors of head acceleration in the local z axis. Volunteer tests. From top to bottom and from left to right: Volunteer 01 up to Volunteer 09. Corridors correspond to the average response ± standard deviation of the total of trials with each volunteer. Page 32 out of 52

33 Figure 17 Time history corridors of head acceleration in the local z-axis. Left: THOR M dummy. Right: PMHS. Corridors include average response ± standard deviation. Page 33 out of 52

34 3.2.4 Head angular rate (local x) Figure 18 Time history corridors of head angular rate in the local x axis. Volunteer tests. From top to bottom and from left to right: Volunteer 01 up to Volunteer 09. Corridors correspond to the average response ± standard deviation of the total of trials with each volunteer. Page 34 out of 52

35 Figure 19 Time history corridors of head angular rate in the local x-axis. Left: THOR M dummy. Right: PMHS. Corridors include average response ± standard deviation. Page 35 out of 52

36 3.2.5 Head angular rate (local y) Figure 20 Time history corridors of head angular rate in the local y axis. Volunteer tests. From top to bottom and from left to right: Volunteer 01 up to Volunteer 09. Corridors correspond to the average response ± standard deviation of the total of trials with each volunteer. Page 36 out of 52

37 Figure 21 Time history corridors of head angular rate in the local y-axis. Left: THOR M dummy. Right: PMHS. Corridors include average response ± standard deviation. Page 37 out of 52

38 3.2.6 Head angular rate (local z) Figure 22 Time history corridors of head angular rate in the local z axis. Volunteer tests. From top to bottom and from left to right: Volunteer 01 up to Volunteer 09. Corridors correspond to the average response ± standard deviation of the total of trials with each volunteer. Page 38 out of 52

39 Figure 23 Time history corridors of head angular rate in the local z-axis. Left: THOR M dummy. Right: PMHS. Corridors include average response ± standard deviation. Page 39 out of 52

40 3.3 SEAT BELT FORCES As in the previous section, corridors were developed to ease the comparison between the different surrogates. There was good agreement between the peak values observed at the upper shoulder seat belt location once the data from the different surrogates were scaled with peak values between 1000 N and 1200 N (Figure 24 and Figure 25). The THOR M dummy and the PMHS started to load the seatbelt slightly earlier than some of the volunteers although it is difficult to observe a clear trend on this aspect within the volunteer group. The same general comments can be made about the measured seat belt forces at the other three locations (Figure 26 to Figure 31): in general the three different types of surrogates experienced comparable seat belt forces and for about the same time. The seat belt load cell located at the lower shoulder belt failed during the tests ran with Vol 06 and was not replaced to avoid keeping the volunteer seated on the sled for a longer period of time. The lap belt force could not be measured at the inner side in the PMHS tests due to the interference of the seat belt load cell with the buckle of the seatbelt. Page 40 out of 52

41 3.3.1 Upper shoulder seat belt forces Figure 24 Time history corridors of upper shoulder belt force. Volunteer tests. From top to bottom and from left to right: Volunteer 01 up to Volunteer 09. Corridors correspond to the average response ± standard deviation of the total of trials with each volunteer. Figure 25 Time history corridors of upper shoulder belt force. Left: THOR M dummy. Right: PMHS. Corridors include average response ± standard deviation. Page 41 out of 52

42 3.3.2 Lower shoulder seat belt forces -- Figure 26 Time history corridors of lower shoulder belt force. Volunteer tests. Similar to Figure 24. Seat belt gauge failed in the tests corresponding to Volunteer 06 (no data available). Figure 27 Time history corridors of lower shoulder belt force. Left: THOR M dummy. Right: PMHS. Corridors include average response ± standard deviation. Page 42 out of 52

43 3.3.3 Lap seat belt forces (outer) Figure 28 Time history corridors of outer lap belt force. Volunteer tests. Similar to Figure 24. Figure 29 Time history corridors of outer lap belt force. Left: THOR M dummy. Right: PMHS. Corridors include average response ± standard deviation. Page 43 out of 52

44 3.3.4 Lap seat belt forces (inner) Figure 30 Time history corridors of inner lap belt force. Volunteer tests. Similar to Figure Figure 31 Time history corridors of inner lap belt force (THOR M dummy). PMHS data could not be collected due to interference of the belt gauge with the buckle. Page 44 out of 52

45 3.4 HEAD TRAJECTORY IN THE SAGITTAL PLANE This subsection includes the trajectory of the head center of gravity (nominal) in the sagittal plane (Figure 32 to Figure 33). To approximate the location of the center of gravity of the head, the mid point between the bilateral external auditori meatii was calculated and used as proxy for the center of gravity. Again the trajectories have been mass-scaled to the size of a 50th percentile male and are presented in the form of corridors for the different types of surrogates. Interestingly, both the THOR M dummy and the PMHS were the surrogates showing the largest variability (Figure 34). As indicated in the comparison of the video frames, the volunteers exhibited initially a rectilinear trajectory almost parallel to the global X axis that ended up in a circulinear motion (coinciding with the flexion of the neck), while both the THOR M dummy and the PMHS exhibited a curvilinear trajectory in the sagittal plane from the beginning of the deceleration. This curvilinear trajectory was especially significant in the case of the PMHS tests. Page 45 out of 52

46 Figure 32 Head center of gravity trajectory in the sagittal plane. Younger volunteers. Left column: Vol 01 to Vol 03 (top to bottom); right column: Vol 04 (top) and Vol 05 (bottom). Page 46 out of 52

47 Figure 33 Head center of gravity trajectory in the sagittal plane. Elderly volunteers. Left column: Vol 06 (top) and Vol 07 (bottom); right column: Vol 08 (top) and Vol 09 (bottom). Page 47 out of 52

48 Figure 34 Head center of gravity trajectory in the sagittal plane. Left column: THOR M dummy. Right column: PMHS. Page 48 out of 52

49 4 CONCLUSIONS This report discusses the similarities and differences observed in 41 sled tests (using the generic crash sled test set-up developed in SENIORS) that simulated a 9 km/h impact (non-injurious) on three different types of surrogates: young and elderly volunteers, Post Mortem Human Subjects and the THOR M dummy. The main findings of this comparison are the following: - The head of the volunteers moved forward parallel to the X axis before undergoing slight flexion, while the head of the THOR M dummy and specially the head of the PMHS underwent flexion from the beginning of the deceleration. - The THOR M and the PMHS moved forward as a whole at the beginning of the deceleration. The motion of the volunteers was limited to the upper spine and head. These difference can be attributed to volunteers bracing, although the hypothesis needs to be confirmed in future analysis of the collected data. - Differences in magnitude and phasing were observed in the z local axis acceleration of the center of gravity of the head between the volunteers and the THOR M and PMHS tests. - The greatest differences were identified for the y local angular rate sensor due to the more significant head rotation observed in the THOR M and PMHS tests. - Seat belt forces peak values and timing were similar for all the surrogates. Further analysis of the differences between younger and older subjects has been performed within the project and are going to be published at the AAAM 2017 conference (Lopez-Valdes et al., 2017). Page 49 out of 52

50 5 REFERENCES Arbogast, K. B., Balasubramanian, S., Seacrist, T., Maltese, M. R., Garcia-Espana, J. F., Hopely, T., Constans, E., Lopez-Valdes, F. J., Kent, R. W., Tanji, H., Higuchi, K., Comparison of kinematic responses of the head and spine for children and adults in low-speed frontal sled tests. Stapp Car Crash Journal 53, Eggers, A., Ott, J., Pipkorn, B., Bråse, D., Mroz, K., López Valdés, F., Hynd, D., A generic sled test set-up for frontal occupant evaluation developed within the EU project SENIORS. Proceedings of the 25th Enhanced Safety of Vehicles (ESV) Conference, 5-8 June, Detroit, USA Eppinger, R. H., Marcus, J. H., Morgan, R. M., Development of dummy and injury index for NHTSA's thoracic side impact protection research program. Society of Automotive Engineers. Kent, R., Shaw, G., Lessley, D., Crandall, J., Kallieris, D., Svensson, M., Comparison of Belted Hybrid III, THOR, and Cadaver Thoracic Responses in Oblique Frontal and Full Frontal Tests. In SAE Paper no Lessley, D., Crandall, J., Shaw, G., Kent, R., A normalization technique for developing corridors from individual subject responses. Society of Automotive Engineers. Lopez-Valdes, F. J., Forman, J., Bostrom, O., Kent, R., 2010a. The frontal-impact response of a booster-seated child-size PMHS. Traffic Injury Prevention 11, Lopez-Valdes, F. J., Forman, J., Kent, R., Bostrom, O., Segui-Gomez, M., A comparison between a child-size PMHS and the Hybrid III 6 YO in a sled frontal impact. Annual Proceedings / Association for the Advancement of Automotive Medicine.Association for the Advancement of Automotive Medicine 53, Lopez-Valdes, F. J., Juste, O., Pipkorn, B., Garcia-Munoz, I., Sunnevang, C., Dahlgren, M., Alba, J. J., A comparison of the performance of two advanced restraint systems in frontal impacts. Traffic Injury Prevention 15 Suppl 1, S Lopez-Valdes, F. J., Lau, A., Lamp, J., Riley, P., Lessley, D. J., Damon, A., Kindig, M., Kent, R., Balasubramanian, S., Seacrist, T., Maltese, M. R., Arbogast, K. B., Higuchi, K., Tanji, H., 2010b. Analysis of spinal motion and loads during frontal impacts. Comparison between PMHS and ATD. Ann Adv Automot Med. 54, Lopez-Valdes, F., Juste-Lorente, O., Lorente A., Piqueras, A., Danauskienė, A., Muehlbauer, J.; Schick, S., Symeonidis, I., Maza-Frechin, M., Peldschus S., Kinematics and dynamic responses of young and elderly occupants in low-speed frontal tests. Annual Proceedings / Association for the Advancement of Automotive Medicine (Under Review). Page 50 out of 52

51 Pipkorn, B., Sunnevang, C., Juste-Lorente, O., Maza, M., Lopez-Valdes FJ., Exploratory study of the kinematics of the THOR dummy in nearside oblique impacts. In Proceedings of the 2016 IRCOBI Conference (Under Review). Seacrist, T., Arbogast, K. B., Maltese, M. R., Garcia-Espana, J. F., Lopez-Valdes, F. J., Kent, R. W., Tanji, H., Higuchi, K., Balasubramanian, S., Kinetics of the cervical spine in pediatric and adult volunteers during low speed frontal impacts. Journal of Biomechanics 45, Seacrist, T., Balasubramanian, S., Garcia-Espana, J. F., Maltese, M. R., Arbogast, K. B., Lopez-Valdes, F. J., Kent, R. W., Tanji, H., Higuchi, K., Kinematic Comparison of Pediatric Human Volunteers and the Hybrid III 6-Year-Old Anthropomorphic Test Device. Annals of Advances in Automotive Medicine / Annual Scientific Conference. Association for the Advancement of Automotive Medicine. Scientific Conference 54, Shaw, G., Crandall, J., Butcher, J., Biofidelity Evaluation of the Thor Advanced Frontal Crash Test Dummy. In IRCOBI Conference on the Biomechanics of Impact. Shaw, G., Parent, D., Purtsezov, S., Lessley, D., Crandall, J., Kent, R., Guillemot, H., Ridella, S. A., Takhounts, R., Martin, P., Impact Response of Restrained PMHS in Frontal Sled Tests: Skeletal Deformation Patterns Under Seat Belt Loading. Stapp Car Crash Journal 53, Society of Automotive Engineers, SAE J211/1 Instrumentation for Impact Test- Part1- Electronic Instrumentation. ACKNOWLEDGMENTS This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No DISCLAIMER This publication has been produced by the SENIORS project, which is funded under the Horizon 2020 Programme of the European Commission. The present document is a draft and has not been approved. The content of this report does not reflect the official opinion of the European Union. Responsibility for the information and views expressed therein lies entirely with the authors. Page 51 out of 52