Collision Avoidance Mode Research Articles

Event-triggered error-constrained switching guidance-based marine surface vessel path-following control and collision avoidance

For marine surface vessel with input saturation, model uncertainties, and unknown disturbances, this article proposes a path-following control and collision avoidance method based on error-constrained event-triggered switching line-of-sight guidance. This method can autonomously switch between path-following and collision avoidance modes, constrain the position and heading errors to satisfy safe navigation in confined waters, and reduce the computational frequency of the controller and the mechanical wear of the actuator. In the path-following mode, we construct an asymmetric modified barrier Lyapunov function to constrain the position errors and use the relative threshold event-triggered mechanism to reduce the update frequency of the guidance heading angle. In the collision avoidance mode, static or dynamic obstacles are avoided through the response of collision avoidance radius. In the heading and velocity control design, asymmetric modified barrier Lyapunov function and event-triggered mechanism are also applied, so that the marine surface vessel can track the guided heading angle and meet the heading error-constrained while reducing the update frequency of the controller. The adaptive auxiliary systems are used to compensate for the input saturation, and radial basis function neural networks and adaptive laws are used to approximate the model uncertainties and composite disturbances. According to the Lyapunov stability theory, all signals are semi-globally uniformly ultimately bounded and the Zeno phenomenon is avoided. Finally, the comparative experiment shows the superiority of the designed control strategy.

Decision-making of active collision avoidance system based on comprehensive evaluation method of dangerous scenarios

Dangerous scenario modeling is of great significance for the development of automatic driving functions, and the active collision avoidance system directly affects the safety of vehicles and the intelligence level of vehicles. However, the current existing collision risk evaluation methods are difficult to comprehensively evaluate different dangerous scenarios, the evaluation methods are complicated and there is no normalized description form. In addition, the traditional decision-making method of active collision avoidance system based on collision time distance will lead to the problems of inconsistent risk evaluation scale and single way of collision avoidance. To solve the above problems, the mechanism analysis of the longitudinal, lateral, and parallel collision risks is carried out respectively, and then the model based on kinematics and dynamics is established. After that, the corresponding expression form of collision risks is derived. Finally, the comprehensive evaluation method of dangerous collision scenarios is proposed. Secondly, based on the comprehensive evaluation method of collision risk, considering longitudinal constraints, lateral constraints, parallel constraints, and road regulations, an active collision avoidance decision-making method that used the cooperative collision avoidance mode of breaking and steering is designed. Thirdly, different simulation experiments are designed based on PanoSim/Simulink. The results show the comprehensive evaluation method can effectively model the collision risk of vehicles in the motion process. At the same time, the decision-making method of the active collision avoidance system achieves the expected working effect, thus improving driving stability and safety.

COLREGs-Constrained Adaptive Fuzzy Event-Triggered Control for Underactuated Surface Vessels With the Actuator Failures

This article investigates the adaptive fuzzy event-triggered control for the underactuated surface vessels (USVs), considering constraints of the International Regulations for Preventing Collisions at Sea (COLREGs) and the actuator failures. The proposed scheme can be divided into the guidance module and the control module. An improved logic virtual ship guidance principle, considering the ship-to-ship collision avoidance, is developed to generate the real-time reference signal for USVs. The main characteristic of the guidance principle is to ensure USVs sailing in the path following mode and collision avoidance mode. Especially for the collision avoidance mode, the collision avoidance guidance is targetedly designed for three sailing situations (the head-on situation, the overtaking situation, and the crossing situation), which is consistent with the COLREGs. Furthermore, an adaptive fuzzy event-triggered law is designed to control the USVs to converge to the desired path. The model unknown terms and the basic fault of the actuator are identified by the fuzzy logic system, and the fuzzy logic state observer is designed to estimate the unmeasured states of the USVs. Unlike the existing results, the communication burden from the controller to the actuators is reduced for the merits of the input event-triggered rule. Through the Lyapunov theory, it is proved that all the signals of the closed-loop control system are the semiglobal uniform ultimate bounded. Finally, the simulated examples are provided to illustrate the validity of the proposed control approach.

UAV autonomous collision avoidance approach

ABSTRACTThe conventional sense-and-avoid collision avoidance mode of UAV (unmaned aerial vehicle) lacks applicability and timeliness in a multi-threat environment. In this paper, a new efficient collision avoidance approach for uncertain threat environments derived from the idea of autonomous mental development is proposed. The proposed collision avoidance pattern consists of a sensory layer, a logic layer and a development layer. The threat information is sensed using the sensory layer, and the path planning approach in the logical layer is applied to the output configuration of UAV. In the development phase, the developmental networks approach is used for online learning, training and updating the logical layer so as to form the sense–action mapping, which is stored as the “basic experience” for UAV executing the avoidance manoeuvre. In the implementation phase, the command is executed by matching the sensing information and action base. The simulation results show that the proposed approach has better timeliness compared to the conventional approaches.

Spectrum sharing optimization with QoS guarantee in cognitive radio networks

In this paper, we propose an optimized spectrum sharing scheme based on the Hungarian Algorithm to guarantee the quality of service (QoS) for individual cognitive radio (CR) users belonging to different CR cells. The proposed scheme is most favorable for overlapping cells where the users are demanding channels for heterogeneous applications such as chatting, web browsing, or voice and video streaming. The spectrum sharing optimization with the QoS guarantee (SSO-QG) is an optimal scheme that can operate in throughput enhancement mode, high reliability mode and collision avoidance mode based on the weight assigned to the corresponding QoS parameters in accordance with the demands of different applications. Simulation results show that the proposed scheme outperforms the existing schemes in terms of forming the optimal sharing pattern and meeting the stringent QoS requirements fairly enough according to the demands of the cell. Moreover, it reduces collisions with primary users.

輻輳海域シミュレーションシステムによる海域評価

"Marine Traffic Simulation System" has been developed by the first author and others for long years. It has three simulation modes. First mode is normal navigation mode. It reproduces realistic traffic flows according to the predefined planed route. Second mode is collision avoidance mode. It has the feature of automatic collision avoidance for all ships besides the normal navigation mode. Third mode is external data mode. It reproduces traffic flow according to the data given by such as AIS. With collision avoidance mode, more realistic traffic flow can be reproduced. However, the validation of the simulation result is not yet done, because it was difficult to get the real traffic flow data before AIS data acquisition system established. This is one of the main purposes of this paper. The system is applied for southward area from Tokyo Bay. Assuming external mode as a real traffic flow, other two modes are evaluated. Normal navigation mode overestimates the navigational risk, while collision avoidance mode reproduces it fairly well in terms of several indices to represent the risk of the area. Three indices; number of occurrence of CR≧0.9, near-miss, and collision respectively, are proposed to assess the navigational risk and discussed. The normalization of these indices, traffic density and gaming area is also proposed and verified including the simulation results of two other areas.

Obstacle Awareness and Collision Avoidance Radar Sensor System for Smart UAV

In this paper, the critical requirement for obstacle awareness and avoidance is assessed with the compliance of the equivalent level of safety regulation, and then the collision avoidance sensor system is presented with the key design parameters for the requirement of the smart unmanned aerial vehicle in low-altitude flight. Based on the assessment of various sensors, small-sized radar sensor is selected for the suitable candidate due to the real-time range and range-rate acquisition capability of the stationary and moving aircraft even under all-weather environments. Through the performance analysis for the system requirement, the conceptual design result of radar sensor model is proposed with the range detection probability and collision avoidance mode is established based on the time-to-collision, which is analyzed by collision scenario.

Collision Avoiding Navigation of Marine Vehicles Using Fuzzy Logic

A fuzzy logic for collision avoiding navigation of marine vehicles is proposed in this paper. VFF(Virtual Force Field) method, which is used widely in the field of mobile robots, is modifiel to apply to marine vehicles. The method is named MVFF (Modified Virtual Force Field) mothod. The MVFF consists of the determination of the heading angles far track-keeping mode ()and collision avoidance mode (). The operator can choose the pattern of the track-keeping mode in the proposed algorithm. The collision avoidance algorithm can handle static and/or moving obstacles. These functons are implemented using fuzzy logic. Various simulation results verify the proposed alogorithm.