It has been 15 years since the first generation of adaptive cruise control (ACC)-equipped vehicles was available on the market and 7 years since the ISO standard for the first generation of ACC systems was produced. Since the next generation of ACC systems and more advanced driver-assistant systems are at the verge of complete introduction and deployment, it is necessary to summarise the development and research achievements of the first generation of ACC systems in order to provide more useful experiential guidance for the new deployment. From multidimensional perspectives, this paper looks into the related development and research achievements to objectively and comprehensively introduce an ACC system to researchers, automakers, governments and consumers. It attempts to simply explain what an ACC system is and how it operates from a systematic perspective. Then, it clearly draws a broad historical picture of ACC development by splitting the entire history into three different phases. Finally, the most significant research findings-related ACC systems have been reviewed and summarised from the human, traffic and social perspectives respectively.

A Comprehensive Review of the Development of Adaptive Cruise Control Systems

An adaptive control scheme for emergency braking of vehicles is designed based on a LuGre dynamic model for the tire-road friction. The wheel angular speed and longitudinal vehicle acceleration information are used to design a fast convergence observer to estimate the vehicle velocity and the internal state of the friction model. The unknown parameters of the dynamic friction model are estimated through a parameter adaptation law. A Lyapunov-based state estimator and a stabilizing braking controller are designed to achieve near to maximum braking capability of the vehicle. Underestimation of the maximum friction coefficient, a very desirable feature from the perspective of safety, is guaranteed by a proper choice of adaptation gains and initial values of the estimated friction parameters. fDOI: 10.1115/1.1870036g

Dynamic Friction Model-Based Tire-Road Friction Estimation and Emergency Braking Control

A cellular automata model is proposed to simulate microscopic traffic flow. In this type of models, based on methods from statistical physics, vehicles follow a reduced set of rules that can be applied in parallel. This allows simulation of large traffic networks with a reasonable computational effort. A cellular automata model is applied to a single-lane highway with a ring topology. Simulation results show the ability of this modeling paradigm to capture the most important features of the traffic flow phenomena.

Cellular automata for one-lane traffic flow modeling

Falsification aims to disprove the safety of systems by providing counter-examples that lead to a violation of safety properties. In this work, we present two novel falsification methods to reveal safety flaws in adaptive cruise control (ACC) systems of automated vehicles. Our methods use rapidly-exploring random trees to generate motions for a leading vehicle such that the ACC under test causes a rear-end collision. By considering unsafe states and searching backward in time, we are able to drastically improve computation times and falsify even sophisticated ACC systems. The obtained collision scenarios reveal safety flaws of the ACC under test and can be directly used to improve the system’s design. We demonstrate the benefits of our methods by successfully falsifying the safety of state-of-the-art ACC systems and comparing the results to that of existing approaches.

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Computationally Efficient Safety Falsification of Adaptive Cruise Control Systems

This paper is concerned with the realization of semi-autonomous vehicle arrangements as the natural transition towards fully automated traffic In particular, we are interested in road trains or platoons, which involve a group of vehicles at close following distances This is known to reduce fuel -- or energy -- consumption due to reduced aerodynamic forces acting on them Currently, available techniques and technologies allow for inter-vehicle distances close to 5 meters with suboptimal fuel/energy savings To obtain the most savings from a platoon formation (with even less consumption for the lead vehicle), it has been shown that the inter-vehicle distance needs to be reduced to 25 meters or less making braking maneuvers even more dangerous In this paper, we present the design and analysis of a brake-by-wire system for the above case, whose operation is characterized by the law of the weakest That is, the system automatically adapts braking forces at different platoon members -- taking vehicles' load condition, etc into account -- to equalize that of the weakest one, ie, the one braking at the slowest rate in the platoon We present simulation results based on an automotive hardware-in-the-loop (HiL) setup with realistic car models Our experiments shows that the proposed system is safe, enabling for collision-free emergency braking at intervehicle distances of 25 meters and, hence, paving the way for highly efficient platoons

Braking in Close Following Platoons: The Law of the Weakest

In this paper, we consider the problem of estimating three safety parameters, namely, the probability of an intervehicular collision, expected number of such collisions and expected relative velocity at impact, for assessing the safety benefits of coordination. We consider an emergency braking scenario, in which the lead vehicle brakes at its maximum capability and the following vehicles obey a vehicle following control law. It is assumed that the maximum braking capability of all vehicles are independent and identically distributed random variable. The fact, that coordination renders effective braking of a vehicle different from its maximum braking capability, leads us to a natural way of analyzing the problem: the first step is that of determining how the coordination of vehicles alters the probability distribution of "effective" braking; this has been done in an earlier paper by the authors. The second step is that of determining how one can compute the probability of a collision, the expected number of primary collisions and relative velocity at impact in a platoon of n vehicles, from the knowledge of the probability distribution of "effective" braking and from the braking differential that guarantees a collision/no-collision between successive vehicles; this is the focus of this paper. We have conducted Monte Carlo simulation to demonstrate the safety benefits of coordination during emergency braking and the viability of our analytical approach to estimate them.

Assessing the safety benefits due to coordination amongst vehicles during an emergency braking maneuver

We present a methodology for assessing the benefits of coordination on the safety of a platoon during emergency braking. When every following vehicle brakes at its maximum possible deceleration in response to hard braking by the lead vehicle in the platoon, it is referred to as uncoordinated braking. A braking strategy B is referred to be more beneficial than a strategy A, if strategy B leads to a larger reduction in the probability of a collision, the expected number of collisions, and the expected relative velocity at impact as compared to strategy A. The sequence of maximum deceleration of vehicles in the platoon is assumed to be a sequence of independent and identically distributed random variables; this distribution is assumed to be discrete and known. Due to coordination, the "effective" deceleration of a following vehicle may not necessarily be its maximum value. The problem of assessing the benefits of coordination can be initiated by dealing with determining the probability distribution of the "effective" deceleration of following vehicles during emergency braking. It is intuitive that the smaller the variance of this distribution, the greater the safety benefits are. We present a coordination strategy, which offers distinct safety benefits in the asymptotic cases.

Assessing the benefits of coordination in automatically controlled vehicles

Author(s): Choi, Woosuk; Swaroop, Darbha | Abstract: In this report, we present a methodology for assessing the benefits of different vehicle coordination strategies on the safety of a platoon during emergency braking One can say that a coordinated braking strategy B is more beneficial than a strategy, if strategy B leads to a larger reduction in the probability of a collision, the expected number of collisions, and the expected relative velocity at impact as compared to strategy We consider an emergency braking scenario, in which the lead vehicle brakes at its maximum capability and the following vehicles brake while obeying a vehicle following control law The sequence of maximum deceleration of vehicles in the platoon is assumed to be a sequence of independent and identically distributed random variables; this distribution is assumed to be discrete and known Due to coordination, however, the "executive "deceleration of a following vehicle may not necessarily be its maximum value The problem of assessing the benefits of coordination can be formulated as three subproblems: the first subproblem deals with determining the probability distribution of the "executive" deceleration of following vehicles during emergency braking It is intuitive that the smaller the variance of this distribution, the greater the safety benefits are The second subproblem deals with determining the probability of an intervehicular collision, the expected number of collisions and the expected relative velocity at impact as a function of the difference in the braking capabilities of successive vehicles in a platoon The probability of an intervehicular collision and the expected number of primary collisions are computed via a Markov chain Here, the asymptotic behavior (as the size of the string increases indefinitely) of the probability of an intervehicular collision and the expected number of primary collisions is computed The third subproblem deals with conducting Monte Carlo simulation to demonstrate the safety benefits of coordination during emergency braking and the viability of our analytical approach to estimate them

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Woosuk Choi

Papers

Assessing the safety benefits due to coordination amongst vehicles during an emergency braking maneuver

Assessing the benefits of coordination in automatically controlled vehicles

Assessing Benefits of Coordination on Safety in Automated Highway Systems

Assessing the safety benefits amongst vehicles during an due to coordination emergency braking maneuver