Acceleration Of Leading Vehicle Research Articles

A local traffic characteristic based dynamic gains tuning algorithm for cooperative adaptive cruise control considering wireless communication delay

Due to the inevitable existence of wireless communication delay, the string stability of cooperative adaptive cruise control (CACC) platoon systems may not be guaranteed if the controller gains are not tuned in time. Most relevant studies discussed how to determine the stable region of controller gains under different communication delays, but seldom told us how to select the optimal gains. Some simulation-based approaches just gave out the feasible gains to meet CACC string stability conditions under different communication delays by using standard input signal (e.g. Sine wave, step function) as the leading vehicle acceleration curve. Unfortunately, as the above approaches did not consider the local traffic characteristics, these feasible gains were not robust enough and even failed when tackling a realistic environment. To this end, this paper proposes a dynamic controller gains tuning algorithm to ensure CACC string stability. First, a synthesized leading vehicle acceleration curve is obtained by performing an inverse fast Fourier transform (IFFT) on the average frequency spectra of 230 vehicles’ acceleration from the next-generation simulation (NGSIM) dataset, which is highly related to the local traffic flow characteristics of the specified road. Then, the ratio of the ∞-norm of the spacing error between the ego vehicle and the preceding vehicle is set as the objective function, and with the synthesized curve as the input of the vehicle platoon, we apply an improved particle swarm optimization (PSO) algorithm to dynamically tune the gains of the CACC controller when the wireless communication delay changes. Hereby, the improved PSO utilizes the nonlinear decreasing inertia weight to accelerate the convergence speed of the algorithm. Finally, three groups of detailed simulation experiments are conducted to verify the effectiveness and performance of the dynamic optimal gains generated by the synthesized curve on string stability and assess the convergence speed of the improved PSO. The experimental results reveal that the proposed algorithm outperforms the traditional methods and can significantly suppress the disturbance along the direction upstream of the platoon.

High-resolution simulation-based analysis of leading vehicle acceleration profiles at signalized intersections for emission modeling

The acceleration profile of leading vehicles at intersections is critical for emission estimation and microlevel queue simulation. Data obtained from experiments using a high-resolution driving simulator can deliver useful insights into microscale acceleration behaviors at signalized intersections. Acceleration data of the leading vehicles in queues are collected by the simulator. The observed accelerations are found to be stochastic. The acceleration characteristics are also significantly diversified among participants. Hence, a Markov chain is implemented to simulate the acceleration behaviors. The acceleration data are classified into varied operation states. And the Markov chain reconstructs the acceleration profiles of leading vehicles and reproduces the randomness of acceleration behaviors. Among numerous candidate profiles, a speed profile is selected by a proposed criterion that represents the typical acceleration behaviors at signalized intersections.

Dynamics of a long platoon of cooperative adaptive cruise control vehicles

The dynamics of long platoons of adaptive cruise control vehicles with Vehicle-to-Vehicle communications are analyzed. The effects of feedback of the position, velocity and acceleration from the platoon’s lead vehicle are evaluated with numerical simulations. An alternative derivation of the equations pertaining to small deviations about equilibrium and a linear extrapolation for a general control law are given. Under a constant headway time range policy the upstream vehicles of platoons with lead velocity feedback reach a velocity plateau as the lead vehicle accelerates. The headway remains constant at the equilibrium value until the end of the plateau. Simulations show that velocity feedback produces improvements, especially reductions of platoon acceleration. Adding position feedback smooths the response to lead vehicle acceleration. Unlike the case of constant headway range policy where acceleration feedback is essential, only minor effects are found for acceleration feedback for the constant headway time policy. Simulations show that typical communication interruptions (treated simply as delays) do not have significant effects. However, if simulations take into account the discrete nature of occasional failures of information transmissions (packet drops), oscillations are induced in platoon vehicle acceleration. Simulations demonstrate that replacing feedback from the lead vehicle with feedback from a few immediately preceding vehicles can be effective.

Novel Cooperative Collision Avoidance Model for Connected Vehicles

Connected vehicle technology exchanges real-time vehicle and traffic information through vehicle-to-vehicle and vehicle-to-infrastructure communication. The technology has the potential to improve traffic safety applications such as collision avoidance. In this paper, a novel cooperative collision avoidance (CCA) model that could improve the effectiveness of the collision avoidance system of connected vehicles was developed. Unlike traditional collision avoidance models, which relied mainly on emergency braking, the proposed CCA approach avoided collision through a combination of following vehicle deceleration and leading vehicle acceleration. Through spacing policy theory and nonlinear optimization, the model calculated the desired deceleration rate for the following vehicle and the acceleration rate for the leading vehicle, respectively, at each time interval. The CCA approach was then tested on a scaled platform with hardware-in-the-loop simulation embedded with MATLAB/Simulink and a car simulator package, CarSim. Results show that the proposed model can effectively avoid rear-end collisions in a three-vehicle platoon.

Nonlinear platoon control of Arduino cars with range-limited sensors

This paper investigates the problem of platoon control with sensor range limitation. A nonlinear vehicular platoon model is established, in which the sensing range constraint described by a piecewise nonlinear function is involved. Then a robust nonlinear control design method is proposed based on a disturbance observer and the backstepping technique. The results are obtained in the context of both individual vehicle stability and platoon string stability analysis, which can lead to substantially enhanced platoon control performance with a guaranteed level of attenuation of the disturbance caused by lead vehicle acceleration and wind gust. The effectiveness of the method has been shown by numerical simulations and experiments carried out with Arduino cars.

Hierarchical platoon control with heterogeneous information feedback

The problem of autonomous platoon control via wireless communication network is studied in this study. Firstly, a novel hybrid model is established for the platoon's longitudinal movement, where disturbances of lead vehicle acceleration and wind gust, parameter uncertainties and intermediate uncertainties induced by communication network (e.g. time delay, quantisation and packet dropout) are given full considerations and involved in the model for the first time. Then, the authors establish a hierarchical platoon controller design framework comprising a feedback linearisation controller at the first layer and a guaranteed cost H ∞ controller at the second layer. By reducing the non-linear system to a linear model using the top layer feedback linearisation controller, a robust H ∞ controller, the kernel controller, is designed utilising novel techniques in robust control of time-delay systems. For the general objective of disturbance attenuation, string stability and robust platoon control to be achieved simultaneously, the robust H ∞ controller is complemented by additional conditions established for guaranteeing string stability and zero steady-state spacing errors. Simulations are given to show the efficiency of the proposed results.

Decentralized Spacing Control of a String of Multiple Vehicles Over Lossy Datalinks

In spacing control of multiple vehicles as in aircraft, spacecraft formation flying and highway vehicle platooning, previous research has shown that the lead vehicle state is required by all following vehicles in order to achieve leader-to-formation stability. Following vehicles can estimate the lead vehicle's state during losses by assuming that the lead vehicle maintains its speed. In this paper, it is determined that, for bursty links, leader-to-formation stability can be retained if the lead vehicle indeed maintains its speed and if not, the spacing error will not exceed some bound which is some finite factor of the peak value of the lead vehicle's acceleration.

Drivers' Use of Deceleration and Acceleration Information in Car-Following Process

Understanding driver behavior is important for the development of many applications such as microscopic traffic simulation models and advanced driver assistance systems. The car-following process is an important phase of driving behavior and takes place when a driver follows a lead vehicle and tries to maintain distance and relative speed within an acceptable range. A key to improving knowledge of driver behavior during this process is determining the information perceived by drivers that could influence their decisions. It has been believed for some time that the main kinematic parameters that affect driver judgment in car following are the relative speed, the distance separation, and the absolute speed. The research described investigated whether drivers are also able to use information on the lead vehicle's deceleration or acceleration during the car-following process through experimental validation of current car-following hypotheses. For this research, an instrumented vehicle was used to collect a large database of car-following time sequences, the analysis of which showed strong evidence that drivers are able to perceive information such as the deceleration or acceleration of the vehicle being followed, although no empirical relationship was determined. An example demonstrating the importance of such perception shows that modeling a driver trying to avoid a collision with a lead vehicle would lose 20% of its fit accuracy if the lead-vehicle acceleration state were not considered.

Note on detection of vehicle velocity changes.

Simple expressions are derived for the time required by an observer in a moving vehicle to detect accelerations and decelerations of a leading vehicle. The expressions, which are derived by the use of dimensional analysis, are in agreement with the experimental results of Braunstein and Laughery. Latency time is shown to vary as the square root of separation distance and as the inverse square root of lead vehicle acceleration.