Autonomous Braking Research Articles

Volvo Drivers’ Experiences With Advanced Crash Avoidance and Related Technologies

Objective: Crash avoidance technologies can potentially prevent or mitigate many crashes, but their success depends in part on driver acceptance. Owners of 2010–2012 model Volvo vehicles with several technologies were interviewed about their experiences. Methods: Interviews were conducted in summer 2012 with 155 owners of vehicles with City Safety as a standard feature; 145 owners with an optional technology package that included adaptive cruise control, distance alert, collision warning with full auto brake (and pedestrian detection on certain models), driver alert control, and lane departure warning; and 172 owners with both City Safety and the technology package. The survey response rates were 21 percent for owners with City Safety, 30 percent for owners with the technology package, and 27 percent for owners with both. Ten percent of owners opted out before the telephone survey began, and 18 percent declined to participate when called. Results: Despite some annoyance, most respondents always leave the systems on, although fewer do so for lane departure warning (59%). For each of the systems, at least 80 percent of respondents with the system would want it on their next vehicle. Many respondents reported safer driving habits with the systems (e.g., following less closely with adaptive cruise control, using turn signals more often with lane departure warning). Fewer respondents reported potentially unsafe behavior, such as allowing the vehicle to brake for them at least some of the time. About one third of respondents experienced autonomous braking when they believed they were at risk of crashing, and about one fifth of respondents thought it had prevented a crash. About one fifth of respondents with the technology package reported that they were confused or misunderstood which safety system had activated in their vehicle. Conclusions: Consistent with the results for early adopters in the previous survey of Volvo and Infiniti owners, the present survey found that driver acceptance of the technologies remains high, although less so for lane departure warning. This study is the first to report drivers’ experiences with City Safety, a collision avoidance system provided as standard equipment on certain Volvo 2010–2012 models, and driver acceptance of this system was high, although not to the same extent as the optional forward collision avoidance system. Future research should continue to monitor drivers’ experiences with these technologies as they become available in more vehicles.

Influences of pre-crash braking induced dummy – Forward displacements on dummy behaviour during EuroNCAP frontal crashtest

Combination of active and passive safety systems is a future key to further improvement in vehicle safety. Autonomous braking systems are able to reduce collision speeds, and therefore severity levels significantly. Passengers change their position due to pre-impact vehicle motion, a fact, which has not yet been considered in common crash tests. For this paper, finite elements simulations of crash tests were performed to show that forward displacements due to pre-crash braking do not necessarily increase dummy load levels. So the influence of different pre-crash scenarios, all leading to equal closing speeds in the crash phase, are considered in terms of vehicle motion (pitching, deceleration) and restraint system configurations (belt load limiter, pretensioner). The influence is evaluated by dummy loads as well as contact risk between the dummy and the interior.

Evaluation of an Autonomous Braking System in Real-World PTW Crashes

Objectives: Powered 2-wheelers (PTWs) are becoming increasingly popular in Europe. They have the ability to get around traffic queues, thus lowering fuel consumption and increasing mobility. The risk of rider injury in a traffic crash is however much higher than that associated with car users. The European project, Powered Two Wheeler Integrated Safety (PISa), identified an autonomous braking system (AB) as a priority to reduce the injury consequences of a PTW crash. The aim of this study was to assess the potential effectiveness of the AB system developed in PISa, taking into account the specific system characteristics that emerged during the design, development and testing phases. Methods: Fifty-eight PTW cases representing European crash configurations were examined, in which 43 percent of riders sustained a Maximum Abbreviated Injury Scale (MAIS) 2+ injury. Two of the most common crash types were a PTW impacting a stationary object (car following scenario) 16% and an object pulling across the PTW path (crossing scenario) 54%. An expert team analysed the in-depth material of the sample crashes and determined a posteriori to what extent the AB would have affected the crash. For those cases where the AB was evaluated as applicable, a further quantitative evaluation of the benefits was conducted by considering a set of different possible rider reactions in addition to that exhibited in the actual crash. Results: In 67 percent of cases, the application of AB could have mitigated the crash outcome. Analysis of those real crash cases showed the potential for an expert rider to avoid the collision. An early reaction of the rider, associated with a correct application of the brakes would have avoided 18 of the 37 car following/crossing scenarios. Conversely, according to the analysis, an expert rider would not have been able to avoid 19 of the 37 cases. In 14 of those 19 cases, the AB would have contributed to mitigating the crash outcome. Conclusions: This study demonstrated significant potential for application of the autonomous braking system in car following and crossing scenarios. In addition, the theoretical benefit curves for the AB globally, were able to provide good quantitative indications of its benefits in real cases where the AB was considered applicable. Further analysis with larger databases is suggested in order to confirm the magnitude of benefits in the PTW crash population. Supplemental materials are available for this article. Go to the publisher's online edition of Traffic Injury Prevention to view the supplemental file.

Analysis of the minimum swerving distance for the development of a motorcycle autonomous braking system

In the recent years the autonomous emergency brake (AEB) was introduced in the automotive field to mitigate the injury severity in case of unavoidable collisions. A crucial element for the activation of the AEB is to establish when the obstacle is no longer avoidable by lateral evasive maneuvers (swerving). In the present paper a model to compute the minimum swerving distance needed by a powered two-wheeler (PTW) to avoid the collision against a fixed obstacle, named last-second swerving model (Lsw), is proposed. The effectiveness of the model was investigated by an experimental campaign involving 12 volunteers riding a scooter equipped with a prototype autonomous emergency braking, named motorcycle autonomous emergency braking system (MAEB). The tests showed the performance of the model in evasive trajectory computation for different riding styles and fixed obstacles.

Assessing the Potential Benefits of the Motorcycle Autonomous Emergency Braking Using Detailed Crash Reconstructions

Objective: The aim of this study was to assess the feasibility and quantitative potential benefits of a motorcycle autonomous emergency braking (MAEB) system in fatal rear-end crashes. A further aim was to identify possible criticalities of this safety system in the field of powered 2-wheelers (PTWs; e.g., any additional risk introduced by the system itself). Methods: Seven relevant cases from the Swedish national in-depth fatal crash database were selected. All crashes involved car-following in which a non-anti-lock braking system (ABS)-equipped motorcycle was the bullet vehicle. Those crashes were reconstructed in a virtual environment with Prescan, simulating the road scenario, the vehicles involved, their precrash trajectories, ABS, and, alternatively, MAEB. The MAEB chosen as reference for the investigation was developed within the European Commission–funded Powered Two-Wheeler Integrated Safety (PISa) project and further detailed in later studies, with the addition of the ABS functionality. The boundary conditions of each simulation varied within a range compatible with the uncertainty of the in-depth data and also included a range of possible rider behaviors including the actual one. The benefits of the MAEB were evaluated by comparing the simulated impact speed in each configuration (no ABS/MAEB, ABS only, MAEB). Results: The MAEB proved to be beneficial in a large number of cases. When applicable, the benefits of the system were in line with the expected values. When not applicable, there was no clear evidence of an increased risk for the rider due to the system. Discussion and Limitations: MAEB represents an innovative safety device in the field of PTWs, and the feasibility of such a system was investigated with promising results. Nevertheless, this technology is not mature yet for PTW application. Research in the field of passenger cars does not directly apply to PTWs because the activation logic of a braking system is more challenging on PTWs. The deployment of an autonomous deceleration would affect the vehicle dynamics, thus requesting an additional control action of the rider to keep the vehicle stable. In addition, the potential effectiveness of the MAEB should be investigated on a wider set of crash scenarios in order also to avoid false triggering of the autonomous braking. Supplemental materials are available for this article. Go to the publisher's online edition of Traffic Injury Prevention to view the supplemental file.

Automatic Steering and Avoidance Time Analysis of a Front Steered Electric Vehicle Using Active Traction and Braking Control with Kingpin-Offset

A vehicle driver's operating performance is limited in emergency conditions. For this reason, the importance of vehicle safety technology geared to collision avoidance increases. This study discusses a collision avoidance technology designed to improve the safety of small or micro-sized vehicles. In this paper, autonomous steering experiment by the automatic steering system by micro electric automobile (ATS Vehicle) which steered the front tire by right and left driving force difference and kingpin offset is carried out. Autonomous steering utilizing ‘Active Torque Steered’ (ATS) vehicle is proposed and evaluated performance of collision avoidance using simulation of critical avoidance time compared with autonomous braking of this vehicle.

Autonomous Braking Control System for Pedestrian Collision Avoidance by Using Potential Field

Pedestrian collision avoidance in urban environments is an important active safety technology to protect vulnerable road users and realize zero-traffic-accident society. This paper focuses on the intersection right turn driving situation which drivers need to negotiate pedestrians near crosswalk region. This paper describes an autonomous collision avoidance by electric braking torque of electric vehicle. The intensity of braking maneuver is determined by the application of Potential Fields theory with considering potential hazard due to occlusions in intersection. Finally, the effectiveness of the autonomous collision avoidance system is verified by the computer simulation and driving experiments using the micro-scale electric vehicle.

Safety Benefits of Forward Collision Warning, Brake Assist, and Autonomous Braking Systems in Rear-End Collisions

This paper examines the potential effectiveness of the following three precollision system (PCS) algorithms: 1) forward collision warning only; 2) forward collision warning and precrash brake assist; and 3) forward collision warning, precrash brake assist, and autonomous precrash brake. Real-world rear-end crashes were extracted from a nationally representative sample of collisions in the United States. A sample of 1396 collisions, corresponding to 1.1 million crashes, were computationally simulated as if they occurred, with the driver operating a precollision-system-equipped vehicle. A probability-based framework was developed to account for the variable driver reaction to the warning system. As more components were added to the algorithms, greater benefits were realized. The results indicate that the exemplar PCS investigated in this paper could reduce the severity (i.e., ΔV) of the collision between 14% and 34%. The number of moderately to fatally injured drivers who wore their seat belts could have been reduced by 29% to 50%. These collision-mitigating algorithms could have prevented 3.2% to 7.7% of rear-end collisions. This paper shows the dramatic reductions in serious and fatal injuries that a PCS, which is one of the first intelligent vehicle technologies to be deployed in production cars, can bring to highway safety when available throughout the fleet. This paper also presents the framework of an innovative safety benefits methodology that, when adapted to other emerging active safety technologies, can be employed to estimate potential reductions in the frequency and severity of highway crashes.

Pedestrian Headform Testing: Inferring Performance at Impact Speeds and for Headform Masses Not Tested, and Estimating Average Performance in a Range of Real-World Conditions

Objective: Tests are routinely conducted where instrumented headforms are projected at the fronts of cars to assess pedestrian safety. Better information would be obtained by accounting for performance over the range of expected impact conditions in the field. Moreover, methods will be required to integrate the assessment of secondary safety performance with primary safety systems that reduce the speeds of impacts. Thus, we discuss how to estimate performance over a range of impact conditions from performance in one test and how this information can be combined with information on the probability of different impact speeds to provide a balanced assessment of pedestrian safety. Method: Theoretical consideration is given to 2 distinct aspects to impact safety performance: the test impact severity (measured by the head injury criterion, HIC) at a speed at which a structure does not bottom out and the speed at which bottoming out occurs. Further considerations are given to an injury risk function, the distribution of impact speeds likely in the field, and the effect of primary safety systems on impact speeds. These are used to calculate curves that estimate injuriousness for combinations of test HIC, bottoming out speed, and alternative distributions of impact speeds. Results: The injuriousness of a structure that may be struck by the head of a pedestrian depends not only on the result of the impact test but also the bottoming out speed and the distribution of impact speeds. Example calculations indicate that the relationship between the test HIC and injuriousness extends over a larger range than is presently used by the European New Car Assessment Programme (Euro NCAP), that bottoming out at speeds only slightly higher than the test speed can significantly increase the injuriousness of an impact location and that effective primary safety systems that reduce impact speeds significantly modify the relationship between the test HIC and injuriousness. Conclusions: Present testing regimes do not take fully into account the relationship between impact severity and variations in impact conditions. Instead, they assess injury risk at a single impact speed. Hence, they may fail to differentiate risks due to the effects of bottoming out under different impact conditions. Because the level of injuriousness changes across a wide range of HIC values, even slight improvements to very stiff structures need to be encouraged through testing. Indications are that the potential of autonomous braking systems is substantial and needs to be weighted highly in vehicle safety assessments.

The Occupant Response to Autonomous Braking: A Modeling Approach That Accounts for Active Musculature

Objective: The aim of this study is to model occupant kinematics in an autonomous braking event by using a finite element (FE) human body model (HBM) with active muscles as a step toward HBMs that can be used for injury prediction in integrated precrash and crash simulations. Methods: Trunk and neck musculature was added to an existing FE HBM. Active muscle responses were achieved using a simplified implementation of 3 feedback controllers for head angle, neck angle, and angle of the lumbar spine. The HBM was compared with volunteer responses in sled tests with 10 ms−2 deceleration over 0.2 s and in 1.4-s autonomous braking interventions with a peak deceleration of 6.7 ms−2. Results: The HBM captures the characteristics of the kinematics of volunteers in sled tests. Peak forward displacements have the same timing as for the volunteers, and lumbar muscle activation timing matches data from one of the volunteers. The responses of volunteers in autonomous braking interventions are mainly small head rotations and translational motions. This is captured by the HBM controller objective, which is to maintain the initial angular positions. The HBM response with active muscles is within ±1 standard deviation of the average volunteer response with respect to head displacements and angular rotation. Conclusions: With the implementation of feedback control of active musculature in an FE HBM it is possible to model the occupant response to autonomous braking interventions. The lumbar controller is important for the simulations of lap belt–restrained occupants; it is less important for the kinematics of occupants with a modern 3-point seat belt. Increasing head and neck controller gains provides a better correlation for head rotation, whereas it reduces the vertical head displacement and introduces oscillations.

Driving With a Partially Autonomous Forward Collision Warning System

The effects of a forward collision warning (FCW) and braking system (FCW+) were examined in a driving simulator study analyzing driving and gaze behavior and the engagement in a secondary task. In-depth accident analyses indicate that a lack of appropriate expectations for possible critical situations and visual distraction may be the major causes of rear-end crashes. Studies with FCW systems have shown that a warning alone was not enough for a driver to be able to avoid the accident. Thus,an additional braking intervention by such systems could be necessary. In a driving simulator experiment, 30 drivers took part in a car-following scenario in an urban area. It was assumed that different lead car behaviors and environmental aspects would lead to different drivers' expectations of the future traffic situation. Driving with and without FCW+ was introduced as a between-subjects factor. Driving with FCW+ resulted in significantly fewer accidents in critical situations. This result was achieved by the system's earlier reaction time as compared with that of drivers. The analysis of the gaze behavior showed that driving with the system did not lead to a stronger involvement in secondary tasks. The study supports the hypotheses about the importance of missing expectations for the occurrence of accidents. These accidents can be prevented by an FCW+ that brakes autonomously. The results indicate that an autonomous braking intervention should be implemented in FCW systems to increase the effectiveness of these assistance systems.

Decision logic of an active braking system for powered two wheelers

Powered two-wheeler (PTW) users are exposed to a high risk of accidents leading to severe injuries and fatalities. The trend of PTW accidents has pointed out the need for an intervention on PTW safety with new and effective solutions. One of the possible answers came from the EC-funded Powered two wheeler Integrated Safety (PISa) project which identified the autonomous braking of the vehicle as one of the most promising safety functions for PTWs. The aim of this paper is to report on the design of the decision logic for deploying a PTW autonomous braking system in case of an imminent collision. Rationales and limitations for this pioneering application are given. The feasibility of the autonomous deceleration is demonstrated by an experimental study conducted with the PISa test bike implementing a prototype of the autonomous braking system, named the Active Braking (AB) system.

Integrated pedestrian countermeasures – Potential of head injury reduction combining passive and active countermeasures

A rapid development of both pedestrian passive and active safety, such as pedestrian bonnets/airbags and autonomous braking, is in progress. The aim of this study was to investigate the potential pedestrian head injury reduction from hypothetical passive and active countermeasures compared to an integrated system. The German In-Depth Accident Study (GIDAS) database was queried from 1999 to 2008 for severely (AIS3+) head injured pedestrians when struck by car or van fronts. This, resulted in 54 cases where information was sufficient. The passive countermeasure was designed to mitigate head injuries caused by the bonnet area, A-pillars, and the remaining windscreen area up to 2.1 m wrap around distance (WAD). The active countermeasure was an autonomous braking system, which was activated one second prior to impact if the pedestrian was visible to a forward-looking sensor. The integrated system was a direct combination of the passive and active countermeasures. Case by case the effect from each of the active, passive and integrated systems was estimated. For the integrated system, the influence of the active system on the passive system performance was explicitly modeled in each case. The integrated system resulted in 50% (95% confidence interval: 30–70%) greater effectiveness than the active countermeasure in reducing the number of pedestrians sustaining severe (AIS3+) head injuries, and 90% (95% CI: 50–150%) greater effectiveness than the passive countermeasure. Integrated systems of passive and active pedestrian countermeasures offer a considerably increased potential for head injury reduction compared to either of the two systems alone.

Analysis of the stability of PTW riders in autonomous braking scenarios

While fatalities of car occupants in the EU decreased remarkably over the last decade, Powered Two Wheelers (PTWs) fatalities still increase following the increase of PTW ownership. Autonomous braking systems have been implemented in several types of vehicles and are presently addressed by research in the field of PTWs. A major concern in this context is the rider stability. Experiments with volunteers were performed in order to find out whether autonomous braking for PTWs will produce a greater instability of the rider in comparison to manual braking. The PTW's braking conditions were simulated in a laboratory with a motorcycle mock-up mounted on a sled, which was accelerated with an average of 0.35g. The motion of the rider was captured in autonomous braking scenarios with and without pre-warning as well as in manual braking scenarios. No significant differences between the scenarios were found with respect to maximum forward displacement of the volunteer's torso and head (p<0.05). By performing clustering analysis on two kinematic parameters, two different strategies of the volunteers were identified. They were not related to the braking scenarios. A relation of the clusters with the initial posture represented by the elbow angle was revealed (p<0.05). It is concluded that autonomous braking at low deceleration will not cause significant instabilities of the rider in comparison to manual braking in idealized laboratory conditions. Based on this, further research into the development and implementation of autonomous braking systems for PTWs, e.g. by extensive riding tests, seems valuable.

Potential of Pedestrian Protection Systems—A Parameter Study Using Finite Element Models of Pedestrian Dummy and Generic Passenger Vehicles

Objective: To study the potential of active, passive, and integrated (combined active and passive) safety systems in reducing pedestrian upper body loading in typical impact configurations. Methods: Finite element simulations using models of generic sedan car fronts and the Polar II pedestrian dummy were performed for 3 impact configurations at 2 impact speeds. Chest contact force, head injury criterion (HIC15), head angular acceleration, and the cumulative strain damage measure (CSDM0.25) were employed as injury parameters. Further, 3 countermeasures were modeled: an active autonomous braking system, a passive deployable countermeasure, and an integrated system combining the active and passive systems. The auto-brake system was modeled by reducing impact speed by 10 km/h (equivalent to ideal full braking over 0.3 s) and introducing a pitch of 1 degree and in-crash deceleration of 1 g. The deployable system consisted of a deployable hood, lifting 100 mm in the rear, and a lower windshield air bag. Results: All 3 countermeasures showed benefit in a majority of impact configurations in terms of injury prevention. The auto-brake system reduced chest force in a majority of the configurations and decreased HIC15, head angular acceleration, and CSDM in all configurations. Averaging all impact configurations, the auto-brake system showed reductions of injury predictors from 20 percent (chest force) to 82 percent (HIC). The passive deployable countermeasure reduced chest force and HIC15 in a majority of configurations and head angular acceleration and CSDM in all configurations, although the CSDM decrease in 2 configurations was minimal. On average a reduction from 20 percent (CSDM) to 58 percent (HIC) was recorded in the passive deployable countermeasures. Finally, the integrated system evaluated in this study reduced all injury assessment parameters in all configurations compared to the reference situations. The average reductions achieved by the integrated system ranged from 56 percent (CSDM) to 85 percent (HIC). Conclusions: Both the active (autonomous braking) and passive deployable system studied had a potential to decrease pedestrian upper body loading. An integrated pedestrian safety system combining the active and passive systems increased the potential of the individual systems in reducing pedestrian head and chest loading.

A Real-time Implementation of an Intersection Collision Avoidance System

AbstractThis paper presents a real-time implementation of a collision avoidance (CA) system that uses autonomous braking and model predictive control to assist drivers in avoiding collisions with other road users. To the authors knowledge, this is the first CA system that targets general vehicle collisions that has been implemented in a car. The system is based on a recently published decision-making algorithm which is described in [1]. To validate the CA system in various collision scenarios without endangering the driver of the vehicle, a novel test platform has been developed. The test platform consist of a soft crashable obstacle which is movable in speeds up to 70 km/h and safe to collide with in any angle in relative speeds up to 100 km/h. In the current implementation, estimates of the motion of the obstacle are obtained through a reference sensor fusion system that is based on a combination of in-vehicle sensors and a differential global positioning system. Results from both intersection and rear-end collision situations are presented. The results show that the proposed CA system can be implemented in a real-time environment and that the predictive brake control algorithm accurately accounts for delays and ramp-up times in the brake system of the vehicle.

Pedestrian injury mitigation by autonomous braking

The objective of this study was to calculate the potential effectiveness of a pedestrian injury mitigation system that autonomously brakes the car prior to impact. The effectiveness was measured by the reduction of fatally and severely injured pedestrians. The database from the German In-Depth Accident Study (GIDAS) was queried for pedestrians hit by the front of cars from 1999 to 2007. Case by case information on vehicle and pedestrian velocities and trajectories were analysed to estimate the field of view needed for a vehicle-based sensor to detect the pedestrians one second prior to the crash. The pre-impact braking system was assumed to activate the brakes one second prior to crash and to provide a braking deceleration up to the limit of the road surface conditions, but never to exceed 0.6 g. New impact speeds were then calculated for pedestrians that would have been detected by the sensor. These calculations assumed that all pedestrians who were within a given field of view but not obstructed by surrounding objects would be detected. The changes in fatality and severe injury risks were quantified using risk curves derived by logistic regression of the accident data. Summing the risks for all pedestrians, relationships between mitigation effectiveness, sensor field of view, braking initiation time, and deceleration were established. The study documents that the effectiveness at reducing fatally (severely) injured pedestrians in frontal collisions with cars reached 40% (27%) at a field of view of 40°. Increasing the field of view further led to only marginal improvements in effectiveness.

A PROBABILISTIC APPROACH TO COLLISION RISK ESTIMATION FOR PASSENGER VEHICLES

Active safety and collision avoidance (CA) is a growing field within the automotive industry. The aim of CA systems is to prevent or mitigate collisions by active interventions i.e. warning, braking and steering. For many reasons, such as driver acceptance of the system and legal requirement that the system itself must not cause hazards, the decision making is a crucial part of the system. This paper presents a method for risk estimation on which to base the decision making. We will show how one can form criterions for decision making in terms of probability of collision. This criterion handles the noisy sensor data and process noise (driver behavior) in a natural way, using existing tracking theory. The method is illustrated by simulation results as well as test result from a prototype vehicle. Simulations and tests are examples of a system which performs autonomous braking actuation at imminent collision.