Autonomous vehicle has been one of the most active study with the potential to enhance safety and convenience. As one of the safety-critical tasks that must be executed by autonomous vehicle, the motion planning is generally divided into path planning and velocity planning. The main purpose of velocity planning is to determine a safe and comfortable velocity change mode for autonomous vehicle, which is a crucial task. A velocity planning method based on pre-set model is proposed in this paper. The exponential function model with undetermined parameters is constructed as the velocity planning model in this method. We take comfort and time-effectiveness as evaluation indexes and construct model functions respectively, and the objective function is constructed in the form of weighted sum to determine the optimal parameters of the velocity planning model in each scenario. The exponential model is suitable for most application scenes, and its closed form expression form is easy to implement in real-time applications. By analysis with actual data, the model is proved to be reasonable.
The current autonomous driving vehicles cannot collaborate with each other due to the disconnection of sensors between vehicles, which leads to poor performance in traffic efficiency and safety. Recently, with the development of wireless intelligent sensors, vehicular sensor network (VSN) is emerging to provide information sharing between vehicles, so that cooperative autonomous driving (CAD) can be enabled. This paper especially investigates the VSN-assisted straight-going CAD at urban intersections under the rule of traffic signals. First, the function of VSN is presented, and the information sharing mechanism is designed. Then distributed stop-and-go strategies with maintaining the optimal safety spacing between adjacent vehicles are proposed for multiple traffic cases. With the proposed strategies, every vehicle can get an exact time to decelerate or accelerate at signalized intersections. Finally, we use the model predictive control (MPC) scheme to actuate our strategies, and it is demonstrated that vehicles perform well in both passage safety and efficiency as expected.
Butterworth-type and Bessel function-type two ways are used for design of Bandpass filter for receiver,and with the help of EDA simulation tools,the bold plot and the group delay characteristics of the filters designed are compared.Bessel function design simulation results show the small pass-band ups,stop-band attenuation,in the pass-band with a better group delay characteristics,which can meet the design requirements.
Automatic parking system has been widely equipped on manual driving vehicles for decades. Due to the limited environment sensing ability and not-accurate-enough positioning system, however, it usually requires a very large redundant space for a car to accomplish one successful parking maneuver. There would be two differences in the coming era of automatic driving: (1) sufficiently accurate perception and positioning systems can be expected to be available, and (2) the number of parking trials could be large when parking without passengers on the vehicle. Under such circumstances, it is quite important for the vehicle to know exactly whether the external and internal spaces are large enough for parking and how the minimum number of trials will be required. This paper presents closed-form solutions of minimum internal and external space required for automatic parallel parking and the corresponding trials if the parking is based on circular arcs. On the other hand, it is also very useful for the vehicle to know the required minimum space if only one trial is allowed, for which the solutions are presented both for circular arcs and continuous-curvature curves based parking, respectively. To the best of our knowledge, there is no so far systematic analysis and research on the issue addressed in this paper.
Currently the research and development of autonomous driving vehicles (ADVs) mainly consider the situation whereby manual driving vehicles and ADVs run simultaneously on lanes. In order to acquire the information of the vehicle itself and the environment necessary for decision-making and controlling, the ADVs that are under development now are normally equipped with a lot of sensing units, for example, high precision global positioning systems, various types of radar, and video processing systems. Obviously, the current advanced driver assistance systems (ADAS) or ADVs still have some problems concerning high reliability of driving safety, as well as the vehicle’s cost and price. It is certain, however, that in the future there will be some roads, areas or cities where all the vehicles are ADVs, i.e., without any human driving vehicles in traffic. For such scenarios, the methods of environment sensing, traffic instruction indicating, and vehicle controlling should be different from that of the situation mentioned above if the reliability of driving safety and the production cost expectation is to be improved significantly. With the anticipation that a more sophisticated vehicle ad hoc network (VANET) should be an essential transportation infrastructure for future ADV scenarios, the problem of vehicle turning control based on vehicle to everything (V2X) communication at road intersections is studied. The turning control at intersections mainly deals with three basic issues, i.e., target lane selection, trajectory planning and calculation, and vehicle controlling and tracking. In this paper, control strategy, model and algorithms are proposed for the three basic problems. A model predictive control (MPC) paradigm is used as the vehicle upper layer controller. Simulation is conducted on the CarSim-Simulink platform with typical intersection scenes.
Based on the software Systemview,direct sequence spread spectrum(DSSS) communication is simulated and analyzed.The simulation result shows that the anti-jamming capability of the DSSS communication system is better than that of common binary digital systems,that with the increasing of the spread spectrum(SS) gain,the probability of error bits decreases,and that the system's capability depends greatly on the characteristic of spread spectral sequences.
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