Development of a geometric slip flat model when turning a vehicle with two steering axles

Introduction (problem statement and relevance). One of the main stages in the design ofspecial purpose vehicles is the calculation of the steering control. At that, engineers are guided by anumber of regulatory documents that lack one of the most important requirements, which is to minimize tire lateral deviation. The author notes the lack of scientific research in the field of geometric slip, which is caused by the non-compliance between the actual angles of wheels rotation and the calculated values for pure rolling and is an inherent property of any traditional steering linkage.The purpose of the study was to develop a mathematical model of the steering drive of a special-purpose vehicle with two steering axles to assess the geometric and power slip.Methodology and research methods. There is a known method for calculating the steering drive using trigonometric expressions, in particular the cosine theorem. The author proposed to use the coordinateiterative method developed by him and based on the equation of the sphere, with the steering wheel rotation angle in the kinematic calculation of the steering drive as a differentiation step. The choice of the steering drive parameters according to the conditions of symmetry and minimization of slip was carried out by the method of multivariable optimization.Results. In the course of the research, it was found that the choice of the characteristic of geometric noncompliance was a multi-parameter task, and changing one parameter led to the necessity of adjusting the others. If it was not possible to achieve zero geometric slip for all steered wheels, the task of optimizing the steering drive parameters wasreduced to minimizing geometric or total slip. The value of the slip essentially depended on the selected differentiation step. When choosing the characteristic of geometric slip, it was necessary to observe the condition of the steering linkage symmetry when turning left and right. When the wheels were turned from the neutral position to the periphery, the power and geometric slip compensated each other, which led to the decrease of the total slip and tire wear.The scientific novelty of the work lies in the development of a geometric slip model for a vehicle with two steerable axles, including a spatial model of the steering drive which allows to evaluate the influence of the geometric slip on the turn kinematics, as well as the mutual influence of geometric and power slip in order to select the steering drive optimal parameters of the multi-axle vehicle from the viewpoint of minimizing tire wear during curvilinear motion.Practical significance. The research results must be taken into account in the development of steering drive and turning control systems for multi-axle special-purpose vehicles, including them in the educational process as well.

Intersection Vehicle Turning Control for Fully Autonomous Driving Scenarios

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.

Row End Detection and Headland Turning Control for an Autonomous Banana-Picking Robot

A row-following system based on machine vision for a picking robot was designed in our previous study. However, the visual perception could not provide reliable information during headland turning according to the test results. A complete navigation system for a picking robot working in an orchard needs to support accurate row following and headland turning. To fill this gap, a headland turning method for an autonomous picking robot was developed in this paper. Three steps were executed during headland turning. First, row end was detected based on machine vision. Second, the deviation was further reduced before turning using the designed fast posture adjustment algorithm based on satellite information. Third, a curve path tracking controller was developed for turning control. During the MATLAB simulation and experimental test, different controllers were developed and compared with the designed method. The results show that the designed turning method enabled the robot to converge to the path more quickly and remain on the path with lower radial errors, which eventually led to reductions in time, space, and deviation during headland turning.