Optimal Braking Patterns and Forces in Autonomous Safety-Critical Maneuvers

Optimal Braking Patterns and Forces in Autonomous Safety-Critical Maneuvers
Author: Victor Fors
Publisher: Linköping University Electronic Press
Total Pages: 19
Release: 2019-05-02
Genre:
ISBN: 9176853012

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The trend of more advanced driver-assistance features and the development toward autonomous vehicles enable new possibilities in the area of active safety. With more information available in the vehicle about the surrounding traffic and the road ahead, there is the possibility of improved active-safety systems that make use of this information for stability control in safety-critical maneuvers. Such a system could adaptively make a trade-off between controlling the longitudinal, lateral, and rotational dynamics of the vehicle in such a way that the risk of collision is minimized. To support this development, the main aim of this licentiate thesis is to provide new insights into the optimal behavior for autonomous vehicles in safety-critical situations. The knowledge gained have the potential to be used in future vehicle control systems, which can perform maneuvers at-the-limit of vehicle capabilities. Stability control of a vehicle in autonomous safety-critical at-the-limit maneuvers is analyzed by the use of optimal control. Since analytical solutions of the studied optimal control problems are intractable, they are discretized and solved numerically. A formulation of an optimization criterion depending on a single interpolation parameter is introduced, which results in a continuous family of optimal coordinated steering and braking patterns. This formulation provides several new insights into the relation between different braking patterns for vehicles in at-the-limit maneuvers. The braking patterns bridge the gap between optimal lane-keeping control and optimal yaw control, and have the potential to be used for future active-safety systems that can adapt the level of braking to the situation at hand. A new illustration named attainable force volumes is introduced, which effectively shows how the trajectory of a vehicle maneuver relates to the attainable forces over the duration of the maneuver. It is shown that the optimal behavior develops on the boundary surface of the attainable force volume. Applied to lane-keeping control, this indicates a set of control principles similar to those analytically obtained for friction-limited particle models in earlier research, but is shown to result in vehicle behavior close to the globally optimal solution also for more complex models and scenarios.

Autonomous Vehicle Maneuvering at the Limit of Friction

Autonomous Vehicle Maneuvering at the Limit of Friction
Author: Victor Fors
Publisher: Linköping University Electronic Press
Total Pages: 60
Release: 2020-10-23
Genre: Electronic books
ISBN: 9179297706

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Without a driver to fall back on, a fully self-driving car needs to be able to handle any situation it can encounter. With the perspective of future safety systems, this research studies autonomous maneuvering at the tire-road friction limit. In these situations, the dynamics is highly nonlinear, and the tire-road parameters are uncertain. To gain insights into the optimal behavior of autonomous safety-critical maneuvers, they are analyzed using optimal control. Since analytical solutions of the studied optimal control problems are intractable, they are solved numerically. An optimization formulation reveals how the optimal behavior is influenced by the total amount of braking. By studying how the optimal trajectory relates to the attainable forces throughout a maneuver, it is found that maximizing the force in a certain direction is important. This is like the analytical solutions obtained for friction-limited particle models in earlier research, and it is shown to result in vehicle behavior close to the optimal also for a more complex model. Based on the insights gained from the optimal behavior, controllers for autonomous safety maneuvers are developed. These controllers are based on using acceleration-vector references obtained from friction-limited particle models. Exploiting that the individual tire forces tend to be close to their friction limits, the desired tire slip angles are determined for a given acceleration-vector reference. This results in controllers capable of operating at the limit of friction at a low computational cost and reduces the number of vehicle parameters used. For straight-line braking, ABS can intervene to reduce the braking distance without prior information about the road friction. Inspired by this, a controller that uses the available actuation according to the least friction necessary to avoid a collision is developed, resulting in autonomous collision avoidance without any estimation of the tire–road friction. Investigating time-optimal lane changes, it is found that a simple friction-limited particle model is insufficient to determine the desired acceleration vector, but including a jerk limit to account for the yaw dynamics is sufficient. To enable a tradeoff between braking and avoidance with a more general obstacle representation, the acceleration-vector reference is computed in a receding-horizon framework. The controllers developed in this thesis show great promise with low computational cost and performance not far from that obtained offline by using numerical optimization when evaluated in high-fidelity simulation.

Design and Control of Hybrid Brake-by-Wire System for Autonomous Vehicle

Design and Control of Hybrid Brake-by-Wire System for Autonomous Vehicle
Author: Donghai Hu
Publisher: Springer Nature
Total Pages: 155
Release: 2022-01-22
Genre: Technology & Engineering
ISBN: 9811689466

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This book establishes the models of the electric motor, the hydraulic compound brake system, and the electromagnetic and friction integrated brake system. Considering the two principles on safety and energy saving, it proposes a hybrid brake-by-wire system optimization design method and proposes the optimization method of braking force distribution in different braking modes. The methodology of the book is by using the common Lyapunov function to analyze the stability of the braking mode switching process and designs the braking mode switching controller of the hybrid braking system. The selection of materials provides readers with some guidance in the future design and control of hybrid drive-by-wire systems for autonomous vehicles

Autonomous Vehicle Technology

Autonomous Vehicle Technology
Author: James M. Anderson
Publisher: Rand Corporation
Total Pages: 215
Release: 2014-01-10
Genre: Transportation
ISBN: 0833084372

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The automotive industry appears close to substantial change engendered by “self-driving” technologies. This technology offers the possibility of significant benefits to social welfare—saving lives; reducing crashes, congestion, fuel consumption, and pollution; increasing mobility for the disabled; and ultimately improving land use. This report is intended as a guide for state and federal policymakers on the many issues that this technology raises.

Brakes, Brake Control and Driver Assistance Systems

Brakes, Brake Control and Driver Assistance Systems
Author: Konrad Reif
Publisher: Springer
Total Pages: 284
Release: 2014-07-18
Genre: Technology & Engineering
ISBN: 3658039787

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Braking systems have been continuously developed and improved throughout the last years. Major milestones were the introduction of antilock braking system (ABS) and electronic stability program. This reference book provides a detailed description of braking components and how they interact in electronic braking systems.

Vehicle Dynamics

Vehicle Dynamics
Author: Reza N. Jazar
Publisher: Springer Science & Business Media
Total Pages: 1074
Release: 2013-11-19
Genre: Technology & Engineering
ISBN: 1461485444

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This textbook is appropriate for senior undergraduate and first year graduate students in mechanical and automotive engineering. The contents in this book are presented at a theoretical-practical level. It explains vehicle dynamics concepts in detail, concentrating on their practical use. Related theorems and formal proofs are provided, as are real-life applications. Students, researchers and practicing engineers alike will appreciate the user-friendly presentation of a wealth of topics, most notably steering, handling, ride, and related components. This book also: Illustrates all key concepts with examples Includes exercises for each chapter Covers front, rear, and four wheel steering systems, as well as the advantages and disadvantages of different steering schemes Includes an emphasis on design throughout the text, which provides a practical, hands-on approach

Brake Design and Safety

Brake Design and Safety
Author: Rudolf Limpert
Publisher: SAE International
Total Pages: 542
Release: 1999-07-16
Genre: Technology & Engineering
ISBN: 0768027101

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This book was written to help engineers to design safer brakes that can be operated and maintained easily. All the necessary analytical tools to study and determine the involvement of brakes in accident causation are included as well as all essential concepts, guidelines, and design checks.

Vehicle Dynamics

Vehicle Dynamics
Author: Dieter Schramm
Publisher: Springer
Total Pages: 450
Release: 2017-07-03
Genre: Technology & Engineering
ISBN: 3662544830

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The authors examine in detail the fundamentals and mathematical descriptions of the dynamics of automobiles. In this context, different levels of complexity are presented, starting with basic single-track models up to complex three-dimensional multi-body models. A particular focus is on the process of establishing mathematical models based on real cars and the validation of simulation results. The methods presented are explained in detail by means of selected application scenarios. In addition to some corrections, further application examples for standard driving maneuvers have been added for the present second edition. To take account of the increased use of driving simulators, both in research, and in industrial applications, a new section on the conception, implementation and application of driving simulators has been added.

Vehicle Propulsion Systems

Vehicle Propulsion Systems
Author: Lino Guzzella
Publisher: Springer Science & Business Media
Total Pages: 345
Release: 2007-09-21
Genre: Technology & Engineering
ISBN: 3540746927

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The authors of this text have written a comprehensive introduction to the modeling and optimization problems encountered when designing new propulsion systems for passenger cars. It is intended for persons interested in the analysis and optimization of vehicle propulsion systems. Its focus is on the control-oriented mathematical description of the physical processes and on the model-based optimization of the system structure and of the supervisory control algorithms.

Handbook of Driver Assistance Systems

Handbook of Driver Assistance Systems
Author: Hermann Winner
Publisher: Springer
Total Pages: 0
Release: 2015-10-15
Genre: Technology & Engineering
ISBN: 9783319123516

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This fundamental work explains in detail systems for active safety and driver assistance, considering both their structure and their function. These include the well-known standard systems such as Anti-lock braking system (ABS), Electronic Stability Control (ESC) or Adaptive Cruise Control (ACC). But it includes also new systems for protecting collisions protection, for changing the lane, or for convenient parking. The book aims at giving a complete picture focusing on the entire system. First, it describes the components which are necessary for assistance systems, such as sensors, actuators, mechatronic subsystems, and control elements. Then, it explains key features for the user-friendly design of human-machine interfaces between driver and assistance system. Finally, important characteristic features of driver assistance systems for particular vehicles are presented: Systems for commercial vehicles and motorcycles.