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2 Bulletin of the Polish Academy of Sciences. Technical Sciences

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A global path-planning algorithm based on critical point diffusion binary tree for a planar mobile robot

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Yang Z. , Wang L. , Cao Z. , Zhang Z. , Xu Z.

tom Vol. 72, nr 2

art. no. e148834

A global path-planning algorithm for robots is proposed based on the critical-node diffusion binary tree (CDBT), which solves the problems of large memory consumption, long computing time, and many path inflection points of the traditional methods. First of all, the concept of Quad-connected, Tri-connected, Bi-connected nodes, and critical nodes are defined, and the mathematical models of diverse types of nodes are established. Second, the CDBT algorithm is proposed, in which different planning directions are determined due to the critical node as the diffusion object. Furthermore, the optimization indices of several types of nodes are evaluated in real-time. Third, a path optimization algorithm based on reverse searching is designed, in which the redundant nodes are eliminated, and the constraints of the robot are considered to provide the final optimized path. Finally, on one hand, the proposed algorithm is compared with the A* and RRT methods in the ROS system, in which four types of indicators in the eight maps are analysed. On the other hand, an experiment with an actual robot is conducted based on the proposed algorithm. The simulation and experiment verify that the new method can reduce the number of nodes in the path and the planning time and is suitable for the motion constraints of an actual robot.

Analysis and control of nonlinear vibration of autonomous vehicle passing through hybrid consecutive speed control humps

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Yang Z. , Wang L. , Yu Y. , Mou Z. , Ou M.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2022

tom Vol. 70, nr 6

art. no. e143643

In order to improve the safety and comfort of autonomous vehicles passing through the expressway, relevant departments of expressway construction often design and lay consecutive speed control humps (SCHs) with cross-sections of different shapes according to different road conditions, such as the combination of trapezoidal and sinusoidal SCHs. In this paper, we conduct a study about the nonlinear dynamic characteristics of the autonomous vehicle passing through hybrid SCHs. Firstly, a four-degree-of-freedom (4-DOF) nonlinear model of the vehicle suspension and the speed coupling excitation model under hybrid SCHs are established. Then the fourth-fifth order Runge–Kutta method is used to simulate the nonlinear system, and its nonlinear dynamic characteristics are analyzed. The results show that chaotic motion occurs when the vehicle passes through hybrid SCHs, and the speed range of chaotic motion is obtained. Then, a direct variable feedback control method is used to suppress the chaotic vibration of semi-active suspension vehicles, and the effect is verified by simulation experiments. Finally, this paper presents a multi-objective optimization model based on a genetic algorithm (GA) for active suspension vehicles. The optimization model selects the vertical displacement and pitching angle of the vehicle body as the objective function. The research results of this paper can provide information on the ride comfort’s optimization for autonomous vehicles passing through hybrid SCHs and on the design of vehicle suspension system.