Safety and comfort analysis of a 3-D vehicle model with optimal non-linear active seat suspension

A generalized nonlinear model is formulated for the dynamic analysis of suspension seats with passive, semi-active and active dampers. The model incorporates coulomb friction due to suspension linkages and bushings, forces arising from interactions with the elastic limit stops, a linear suspension spring and nonlinear damping force for passive, semi-active and active dampers, while the contribution due to biodynamics of the human operator is considered to be negligible. The semi-active and active dampers are characterized by force generators in accordance with the control laws based upon suspension mass velocity. Two different suspension seats are experimentally assessed in the laboratory under sinusoidal and random excitations arising from an urban bus, and the measured data is used to demonstrate the validity of the proposed generalized model. The results showed reasonably good agreement between the model results and the measured data. Optimal model parameters are selected using the sequential unconstrained minimization technique with an objective to minimize the acceleration due to vibration transmitted to the occupant mass. The comfort and safety performance characteristics of the optimal suspension seat with semi-active and active dampers are evaluated under both the sinusoidal and random excitations based on the guidelines provided by ISO-2631. From these results, it is concluded that the comfort performance of a suspension seat with semi-active and active dampers can be considerably enhanced by 20–30%.     

An instrumented vehicle for offroad dynamics testing

The paper presents an instrumented vehicle that was equipped with measuring systems to perform complete dynamics tests, especially in off-road conditions. The equipment consists of four wheel dynamometers, a steering robot, and a differential GPS system together with an inertial platform, a non-contact vehicle speed sensor, and an on-board computer with software to control the devices and collect experimental data. The four wheel dynamometers measure six elements; based on strain gage force transducers, it measures three orthogonal forces and three moments. The steering robot can control the steering wheel of the vehicle at a variety of excitation modes; it can carry out typical vehicle dynamics tests (ISO 7401, ISO 4138, ISO/TR3888, etc.) as well as custom engineered tests at a wide range of setting parameters (steer angle rate up to 1600 deg/s). The differential GPS system gives true time vehicle kinematics data (velocities, accelerations, angles, etc.) at 10-ns sample rate and 20-mm accuracy. The base vehicle, a Suzuki Vitara 4 × 4, required no special modifications or changes to install the measuring equipment. The paper also describes typical tests performed with the use of the instrumented vehicle together with sample results.     

The effect of velocity on rigid wheel performance

A simulation model to predict the effect of velocity on rigid-wheel performance for off-road terrain was examined. The soil–wheel simulation model is based on determining the forces acting on a wheel in steady state conditions. The stress distribution at the interface was analyzed from the instantaneous equilibrium between wheel and soil elements. The soil was presented by its reaction to penetration and shear. The simulation model describes the effect of wheel velocity on the soil–wheel interaction performances such as: wheel sinkage, wheel slip, net tractive ratio, gross traction ratio, tractive efficiency and motion resistance ratio. Simulation results from several soil-wheel configurations corroborate that the effect of velocity should be considered. It was found that wheel performance such as net tractive ratio and tractive efficiency, increases with increasing velocity. Both, relative wheel sinkage and relative free rolling wheel force ratio, decrease as velocity increases. The suggested model improves the performance prediction of off-road operating vehicles and can be used for applications such as controlling and improving off-road vehicle performance.     

两栖UAV滑跳动力学特性仿真研究

基于空气动力学、势流理论和二元平面滑行理论,建立了两栖UAV入水滑跳动力学模型,重点对两栖UAV入水滑跳动力学特性进行了分析,并研究了多种入水条件对滑跳状态的影响.结果显示:(1)两栖UAV触水瞬间,姿态出现明显变化,UAV出现瞬时剧烈抬头趋势;(2)两栖UAV入水攻角增大,会造成UAV较大的沾湿深度和较短的滑水时间;...     

A hybrid feedback control strategy for autonomous waypoint transitioning and loitering of unmanned aerial vehicles

We consider the problem of autonomously controlling a fixed-wing aerial vehicle to visit a neighborhood of a pre-defined waypoint, and when nearby it, loiter around it. To solve this problem, we propose a hybrid feedback control strategy that unites two state-feedback controllers: a transit controller capable of steering or transitioning the vehicle to nearby the waypoint and a loiter controller capable of steering the vehicle about a loitering radius. The aerial vehicle is modeled on a level flight plane with system performance characterized in terms of the aerodynamic, propulsion, and mass properties. Thrust and bank angle are the control inputs. Asymptotic stability properties of the individual control algorithms, which are designed using backstepping, as well as of the closed-loop system, which includes a hybrid algorithm uniting the two controllers, are established. In particular, for this application of hybrid feedback control, Lyapunov functions and hybrid systems theory are employed to establish stability properties of the set of points defining loitering. The analytical results are confirmed numerically by simulations.     

Validating a GIS-based multi-criteria method for potential road identification

This paper investigated the validation of a multi-criteria method for identifying potential roads, and demonstrated the capability of analyzing GPS vehicle tracking data for identifying vehicle movement patterns and potential roads. The multi-criteria method was evaluated by comparing the predictions to the site visit results on 34 selected road segments meeting different criteria levels. Results show that locations meeting higher criteria levels have higher possibilities to be roads: an approximately 91% possibility of road existence for the locations meeting all five criteria; 55% for the locations meeting four criteria; and 14% for those meeting criteria level two or three. This approach provides an opportunity for land managers to update existing GIS roads map, or identify newly formed roads that may need either rehabilitation or inclusion into the roads maintenance program.     

Power allocation for enhancing energy efficiency in unmanned aerial vehicle networks

The non-orthogonal multiple access (NOMA) wireless networks are a robust multi-access mechanism that serves multiple clients accessing the same resource block simultaneously. The fifth-generation wireless networks offer huge efficiency in spectrum utilization, which can be exploited to deploy NOMA for LOS communication of unmanned aerial vehicles (UAVs). Previous research has extensively analyzed various aspects of NOMA-UAV communication systems, including user access fairness, coverage, maximizing system capacity, and total energy efficiency. However, only a few researchers have focused on maximizing the EE of NOMA-UAV wireless networks with user quality of service (QoS) constraints. This paper proposes a fuzzy logic-based crossover-based coati optimization algorithm for maximizing the energy efficiency of NOMA-UAV, along with user scheduling. The main objective of this model is to offer a solution to the joint energy efficiency and user QoS scheduling problem. The fuzzy decision-making strategy optimizes the energy efficiency (EE) of NOMA-UAV by selecting appropriate power and time resources. Additionally, the crossover-based coati optimization algorithm transforms the subchannel allocation problem into a two-sided matching procedure. The efficiency of the proposed algorithm is evaluated concerning overall residual energy, number of remaining nodes, and time consumption. The experimental outcomes demonstrate the capability of the proposed model in optimizing the energy efficiency of the NOMA-UAV network by identifying the optimal resource set in terms of time and power while satisfying the clients' QoS.     

基于强化学习的能量受限无人机通信感知轨迹规划方法

针对能量受限下无人机（Unmanned Aerial Vehicle,UAV）辅助通信感知中的无人机轨迹规划问题,采用激光无线充电的方式为无人机额外提供能量,同时考虑了无人机动力学和感知通信速率等约束,以对移动目标感知互信息量最大化为目标,建立了移动目标感知通信轨迹规划问题。为了求解建立的包含大量复杂约束的优化问题,将原优化问题建立为马尔可夫决策过程,把无人机运动、能量变化、目标感知、基站通信等过程建模为环境空间,无人机电机转速设计为动作空间,并采用深度强化学习方法进行训练,实现无人机的轨迹规划。由于考虑了无人机动力学,规划得到的轨迹更符合无人机运动特性,并且训练得到的最优控制序列可以直接作用于无人机电机转速,降低了无人机控制难度。在设计的实验场景下,相较于传统最优控制方法,所提方法对移动目标感知互信息量提升了约3倍。     

基于搜索规则和交叉熵优化的无人机路径规划方法

针对快速扩展随机树(RRP)算法计算效率低、不具备渐进最优性等问题,该文提出一种基于搜索规则和交叉熵优化的改进RRT(IRRT)算法。在路径搜索过程中根据当前节点位置及搜索规则,调整搜索步长及搜索方向,实现高效、快速的初始路径规划。然后,利用交叉熵理论优化初始路径,使得路径具备渐进最优性。仿真实验1结果表明所提方法的有效性和收敛性,仿真实验2将该文所提算法与多种变体RRT算法进行比较,结果表明所提算法能够保证计算效率,同时使得路径具备渐进最优性。     

无人机辅助的非正交多址反向散射通信系统max-min速率优化算法

无人机(UAV)、非正交多址(NOMA)和反向散射通信(BC)相结合,可以满足热点地区高容量需求,提高通信质量。该文提出一种无人机辅助的NOMA反向散射通信系统最小速率最大化资源分配算法。考虑无人机发射功率、能量收集、反射系数、传输速率以及连续干扰消除(SIC)解码顺序约束,建立基于系统最小速率最大化的资源分配模型。首先利用块坐标下降将原问题分解为无人机发射功率优化、反射系数优化和无人机位置与SIC解码顺序联合优化3个子问题,然后使用反证法给出无人机最优发射功率,再用变量替换法和连续凸逼近将剩余子问题进一步转化为凸优化问题进行求解。仿真结果表明,所提算法在系统和速率与用户公平性之间具有较好折中。