| 1. |
- Gorospe, Joseba, et al.
(author)
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Analyzing Inter-Vehicle Collision Predictions during Emergency Braking with Automated Vehicles
- 2023
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In: International Conference on Wireless and Mobile Computing, Networking and Communications. - : IEEE Computer Society. - 9798350336672 ; , s. 411-418
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Conference paper (peer-reviewed)abstract
- Automated Vehicles (AVs) require sensing and perception to integrate data from multiple sources, such as cameras, lidars, and radars, to operate safely and efficiently. Collaborative sensing through wireless vehicular communications can enhance this process. However, failures in sensors and communication systems may require the vehicle to perform a safe stop or emergency braking when encountering hazards. By identifying the conditions for being able to perform emergency braking without collisions, better automation models that also consider communications need to be developed. Hence, we propose to employ Machine Learning (ML) to predict inter-vehicle collisions during emergency braking by utilizing a comprehensive dataset that has been prepared through rigorous simulations. Using simulations and data-driven modeling has several advantages over physics-based models in this case, as it, e.g., enables us to provide a dataset with varying vehicle kinematic parameters, traffic density, network load, vehicle automation controller parameters, and more. To further establish the conditions for inter-vehicle collisions, we analyze the predictions made through interpretable ML models and rank the features that contribute to collisions. We also extract human-interpretable rules that can establish the conditions leading to collisions between AVs during emergency braking. Finally, we plot the decision boundaries between different input features to separate the collision and non-collision classes and demonstrate the safe region of emergency braking.
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| 2. |
- Hasan, Shahriar, 1991-, et al.
(author)
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A fault-tolerant controller manager for platooning simulation
- 2019
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In: 2019 8th IEEE International Conference on Connected Vehicles and Expo, ICCVE 2019 - Proceedings. - : Institute of Electrical and Electronics Engineers Inc.. - 9781728101422
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Conference paper (peer-reviewed)abstract
- Recent development in wireless technology enabling communication between vehicles led to introduction of the concept of Cooperative Adaptive Cruise Control (CACC), which uses wireless vehicle-to-vehicle communication and aims at string stable behavior in a platoon of vehicles. Degradation cascades have been proposed as a way to maintain a certain level of the system functionality in presence of failures. Such degradation behaviour is usually controlled by a runtime/state manager that performs fault detection and transitions the system into states where it will remain acceptably safe. In this paper, we propose a dynamic controller manager that focuses on both safety and performance of the system. In particular, it monitors the channel quality within the platoon and reacts by degrading platoon performance in presence of communication failures, or upgrading the performance when the communication quality is high enough. The reaction can include, e.g., adjusting the inter-vehicle distance or switching to another suitable platoon controller to prevent collisions. We focus on the functional and operational safety and evaluate the performance of the dynamic controller manager under different scenarios and settings in simulation experiments to demonstrate that it can avoid rear-end collisions in a platoon, continue platooning operation even in dense traffic scenarios where the state-of-the-art controllers fail to do so.
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| 3. |
- Hasan, Shahriar, 1991-, et al.
(author)
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Characterization of Transient Communication Outages Into States to Enable Autonomous Fault Tolerance in Vehicle Platooning
- 2023
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In: IEEE Open Journal of Intelligent Transportation Systems. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2687-7813. ; 4, s. 101-129
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Journal article (peer-reviewed)abstract
- The benefits of platooning, e.g., fuel efficiency, road throughput enhancement, driver offload, etc., have sparked an interest in a more connected, intelligent, and sustainable transportation ecosystem. However, efficient platooning is realized through wireless communications, characterized by transient connectivity, which is caused by occasional packet losses. Being a safety-critical system of systems, a platoon must be fail-operational even during transient connectivity. Moreover, a platoon should be capable of transitioning into a fail-safe state upon encountering a hazard. To this end, we propose a strategy for classifying the transient communication outages incurred by platooning vehicles into states. Furthermore, a state machine using these states to enable safe automated platooning is proposed that also defines the transitions between the states based on the nature and levels of transient connectivity and hazards. To achieve this, a graceful degradation and upgradation method is proposed, such that the platoon can remain fail-operational by adjusting, e.g., the automated controller and/or the inter-vehicle gaps based on the current communication quality. An emergency braking strategy is also proposed to enable a fast transition into a fail-safe state, should the platoon encounter a hazard. Rigorous simulation studies show that the proposed strategies enable fault-tolerant automated platooning also during transient connectivity.
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| 4. |
- Hasan, Shahriar, 1991-, et al.
(author)
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Cooperative Automated Emergency Braking for CAVs under Time-Varying Communication Delays
- 2023
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In: IAVVC 2023 - IEEE International Automated Vehicle Validation Conference, Proceedings. - : Institute of Electrical and Electronics Engineers Inc.. - 9798350322538
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Conference paper (peer-reviewed)abstract
- Connected and Automated Vehicles (CAVs) have the potential to significantly improve road safety, fuel efficiency, and traffic flow by forming platoons with short inter-vehicle gaps, enabled by vehicle-to-vehicle communications and onboard sensors. However, wireless connectivity for CAVs is subject to time-varying delays, which can significantly impact platoon safety during emergency braking. To this end, this paper evaluates the communication delays incurred by platoon vehicles during emergency braking under various data and traffic densities. Additionally, an emergency braking strategy named adaptive emergency braking is proposed and compared with five other strategies based on their ability to meet the functional requirements of collision avoidance and minimizing the stopping distance of the platoon lead vehicle, which are crucial for transitioning a platoon to a fail-safe state. Moreover, the emergency braking strategies are evaluated through rigorous simulations, considering non-functional criteria such as required inter-vehicle gaps, maximum allowable deceleration rates, and their robustness under time-varying communication delays.
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| 5. |
- Hasan, Shahriar, 1991-
(author)
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Fail-Operational and Fail-Safe Vehicle Platooningin the Presence of Transient Communication Errors
- 2022
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Reports (other academic/artistic)abstract
- Recent advances in wireless technology facilitating Vehicle-to-Vehicle (V2V)communication has paved the way towards a more connected and Cooperative-Intelligent Transportation System (C-ITS). It has unveiled the possibility of many services which are anticipated to make the road transport eco system safer, cleaner, and more sustainable. Platooning is one such application that is expected to soon appear on the roads. In platooning, a group of connected and highly automated vehicles follow a lead vehicle with short inter-vehicle distances. They adapt their speed, acceleration, steering angle, etc., with the help of on-board sensors and inter-vehicle communications. Due to the highly automated driving and the very short inter-vehicle distances required to achieve fuel-efficiency, platooning is a complex and safety-critical system of systems. As a result, the consequences of component or system failure can endanger human life, cause damage to property, or the environment. Given that V2V communication is subject to packet losses due to interference, path loss, fading and shadowing, it is usually desirable to maintain a sufficient level of platooning functionality without compromising safety also during periods of transient errors. Moreover, a platoon can experience different sensor failures, permanent hardware/software failures, or a suddenly appearing road hazard,e.g., a moose. The platoon should, therefore, also be capable of dissolving and transitioning into a fail-safe state by performing emergency braking, safestop, or manual handover without causing any harm to the equipment, people, or to the environment. This research work focuses on incorporating fail-operational mechanisms in platooning in a fuel-efficient and safe way, even inthe presence of transient errors and enable transition into a fail-safe state inthe event of an emergency. To this end, a platoon runtime manager is proposed, which monitors the channel quality and keeps the platoon operational in cases of temporal failures by degrading the platoon performance to the level at which it will remain acceptably safe. Simulation results demonstrate that the runtime manager can avoid collisions in the platoon and still maintain fair performance in terms of fuel-efficiency by either adjusting the inter-vehicle distances or switching to a different controller during runtime. Furthermore, two emergency braking strategies, namely Synchronized Braking and Adaptive Emergency Braking, are proposed to address the emergency events that can arise while platooning. These braking strategies are compared to several state-of-the-art braking strategies in terms of their ability to avoid collisions, and the distance traversed by the lead vehicle. Simulation results show that Synchronized Braking and Adaptive Emergency Braking strategies can ensure fail-safe platooning while the other braking strategies fail to do so. Moreover, a simulation tool named PlatoonSAFE has been developed to facilitate the evaluation of fail-operational and fail-safe mechanisms in platooning under realistic traffic, vehicle dynamics, and communication scenarios.
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| 6. |
- Hasan, Shahriar, 1991-
(author)
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On Transient Communication Outages among Collaborating Connected and Automated Vehicles
- 2023
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Doctoral thesis (other academic/artistic)abstract
- Recent advances in wireless technology facilitating Vehicle-to-Vehicle (V2V) communication have paved the way towards connected and more cooperative Intelligent Transportation Systems (ITSs), enhancing road safety and sustainability. Connected and Automated Vehicles (CAVs) can exchange information with one another and their surrounding infrastructure, thereby enabling cooperative automated maneuvering such as vehicle platooning. In platooning, a group of CAVs follows the longitudinal and lateral movements of a Lead Vehicle (LV) through V2V communication and onboard sensors to form a close-knit vehicle train. Collaborating CAVs hold the potential to revolutionize transportation by enabling, e.g., enhanced safety, fuel efficiency, road efficiency, and overall mobility. However, wireless communication, a key enabling technology for collaborating CAVs, is often subject to transient outages due to irregular packet losses, which are caused by factors such as attenuation, fading and interference. An automated platoon of CAVs must remain fail-operational during such transient communication outages to stay as safe as before the outage, even if the inter-vehicle distances are short. Furthermore, a platoon may encounter road hazards, requiring emergency braking to transition into a fail-safe state. Traditionally, communication outages have been treated as permanent faults or failures, which is a worst-case scenario that has little practical value. More recent attempts to model wireless communication as either on or off as a function of time are still too pessimistic and may lead to safety distances which are unnecessarily long. To this end, this thesis proposes to characterize the nature of transient wireless communication outages into finer granularities so that, e.g., the vehicles in a platoon can adapt to the currently available information, prioritize safety, and still remain as efficient as possible. Such characterization also enables formulating a state machine in which the states represent various fail-operational, emergency braking, and fail-safe states as a function of the instantaneous communication quality. An approach involving changing states by switching controllers and adjusting inter-vehicle gaps is developed to keep a platoon fail-operational during runtime. In addition, several emergency braking strategies are proposed to minimize the LV's stopping distance while avoiding inter-vehicle collisions when transitioning the platoon into a fail-safe state. The thesis also employs Machine Learning (ML) for real-time prediction of communication outages and collision risks during emergency braking, enabling proactive collision avoidance measures. A simulation tool named PlatoonSAFE, using realistic traffic mobility models, has been developed to evaluate the proposed algorithms. Rigorous simulation studies demonstrate that the characterization of communication outages into finer granularities enables fault tolerance and provides a more balanced trade-off between fuel efficiency, string stability, and LV tracking compared to the traditional way of modeling communication outages. Finally, the ML tool and the outage model enable fuel-efficient platooning at high speed while still being able to respond to road hazards by enabling fast emergency braking.
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| 7. |
- Hasan, Shahriar, 1991-, et al.
(author)
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PlatoonSAFE : An Integrated Simulation Tool for Evaluating Platoon Safety
- 2023
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In: IEEE Open Journal of Intelligent Transportation Systems. - : Institute of Electrical and Electronics Engineers Inc.. - 2687-7813. ; 4, s. 325-347
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Journal article (peer-reviewed)abstract
- Platooning is highly tractable for enabling fuel savings for autonomous and semi-autonomous cars and trucks. Safety concerns are one of the main impediments that need to be overcome before vehicle platoons can be deployed on ordinary roads despite their readily available technical feasibility. Simulation studies remain vital for evaluating platoon safety applications primarily due to the high cost of field tests. To this end, we present PlatoonSAFE, an open-source simulation tool that promotes the simulation studies of fault tolerance in platooning by enabling the monitoring of transient communication outages during runtime and assigning an appropriate performance level as a function of the instantaneous communication quality. In addition, PlatoonSAFE facilitates the simulation of several emergency braking strategies to evaluate their efficacy in transitioning a platoon to a fail-safe state. Furthermore, two Machine Learning (ML) models are integrated into PlatoonSAFE that can be employed as an onboard prediction tool in the platooning vehicles to facilitate online training of ML models and real-time prediction of communication, network, and traffic parameters. In this paper, we present the PlatoonSAFE structure, its features and implementation details, configuration parameters, and evaluation metrics required to evaluate the fault tolerance of platoon safety applications.
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| 8. |
- Hasan, Shahriar, 1991-, et al.
(author)
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Prediction of Communication Delays in Connected Vehicles and Platoons
- 2023
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In: 2023 IEEE 97TH VEHICULAR TECHNOLOGY CONFERENCE, VTC2023-SPRING. - : IEEE. - 9798350311143
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Conference paper (peer-reviewed)abstract
- Automated vehicles connected through vehicle-tovehicle communications can use onboard sensor information from adjacent vehicles to provide higher traffic safety or passenger comfort. In particular, automated vehicles forming a platoon can enhance traffic safety by communicating before braking hard. It can also improve fuel efficiency by enabling reduced aerodynamic drag through short gaps. However, packet losses may increase the delay between periodic beacons, especially for the rear vehicles in a platoon. If the connected vehicles can forecast link quality, they can assign different performance levels in terms of intervehicle distances and also facilitate the designing of safer braking strategies. This paper proposes a strategy for incorporating machine learning algorithms into, e.g., the lead vehicle of a platoon to enable online training and real-time prediction of communication delays incurred by connected vehicles during runtime. The prediction accuracy and its suitability for making safety-critical decisions during, e.g., emergency braking have been evaluated through rigorous simulations.
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| 9. |
- Hasan, Shahriar, 1991-, et al.
(author)
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Towards emergency braking as a fail-safe state in platooning : A simulative approach
- 2019
-
In: IEEE Vehicular Technology Conference. - : Institute of Electrical and Electronics Engineers Inc.. - 9781728112206
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Conference paper (peer-reviewed)abstract
- Platooning is anticipated to facilitate automated driving even with semi-automated vehicles, by forming road trains using breadcrumb tracing and Cooperative Adaptive Cruise Control (CACC). With CACC, the vehicles coordinate and adapt their speed based on wireless communications. To keep the platoon fuel-efficient, the inter-vehicle distances need to be quite short, which requires automated emergency braking capabilities. In this paper, we propose synchronized braking, which can be used together with existing CACC controllers. In synchronized braking, the leading vehicle in the platoon does not brake immediately, but instead communicates its intentions and then, slightly later, the whole platoon brakes simultaneously. We show that synchronized braking can avoid rear-end collisions even at a very high deceleration rate and with short inter- vehicle distances. Also, the extra distance travelled during the delay before braking can be compensated by enabling a higher deceleration, through coordinated synchronized braking.
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