Deﬁning and Evaluating New Load Cases in Autonomous Cars
Examensarbete för masterexamen
Biomedical engineering (MPBME), MSc
Autonomous vehicles (AVs) are the focus for many research projects right now and are widely regarded as the most important next step for the automotive industry. AVs are anticipated to result in safer roads and with fully automated vehicles the driver does not need to be involved in the driving. This new situation opens up the possibility for new spatial orientations within the vehicle, which might be a challenge for today’s passive safety systems. This master thesis is done in collaboration with Autoliv and aims to deﬁne new potential load cases in fully automated cars and to evaluate how today’s passive safety systems handle these new load cases. A literature review were complemented with a qualitative study to understand what activities occupants expect they will be engaged in when no one needs to focus on the driving, and how they will be seated. The qualitative study was performed at a local exhibition called V˚arg˚ardam¨assan with a method called ”Setting the Stage”, developed speciﬁcally to explore user expectations. To evaluate the passive safety system, twelve sled tests with the THOR dummy were run in three of the newly deﬁned load cases. A position representing the extended living room, with the front seats rearward-facing, and a relaxing position, with the seatback reclined, were the most popular new seating positions both in the literature and in the qualitative study. These positions together with a conversation position, with the fronts seats rotated 30°inboard, were run in sled tests. The test matrix included rear-end impact, frontal impact and three diﬀerent speeds (24 kph Euro NCAP rear-end pulse, 40 kph and 56 kph FMVSS 208 full frontal barrier pulse). The restraint parameters diﬀered for each test and consisted of a driver airbag, an extra belt, an simulated knee airbag, a PRC (Pelvis Restraint Cushion), load limiting, pretensioning and modiﬁcations of belt geometry and seat adjustments. The rearward-facing living room position generally performed well in frontal impact (rear-end impact for the dummy), with low injury risk values for HIC, BrIC and femur. The challenge for this position is to absorb the energy in the seat construction. The relaxing position was more challenging and got more focus in frontal impact; a beneﬁcial kinematic for keeping the dummy in position, without high spinal loads, was an immediate forward motion or rotation of the upper body. The extra belt was the most important restraint system for the conversation position in frontal impact, but new solutions might be found that could handle this position. Only a few tests were performed for this load case, but much can be learned from small overlap/NHTSA oblique testing that resemble the test carried out in the conversation position. The method ”Setting the Stage”, used in the qualitative study, resulted in detailed and realistic reﬂections from potential occupants and ﬁve new load cases were deﬁned in total in the ﬁrst part of the thesis. Some load cases were evaluated using sled tests, which limited the test matrix due to simpliﬁcations in the setup and limitations of the ATD; still, useful information was gained. Beneﬁcial kinematics were identiﬁed and future potential challenges addressed for the two most popular load cases: the relaxing position and the living room position. This thesis was a ﬁrst exploratory attempt to understand potential challenges within passive safety in autonomous vehicles, but more research and testing is needed to complete the results.
Transport , Farkostteknik , Transport , Vehicle Engineering