The distributed drive electric platform is extensively utilized in special-purpose unmanned ground vehicles due to exceptional maneuverability and obstacle navigation capabilities in off-road environments. This paper comes up with an energy-saving torque allocation strategy to enhance path-tracking precision and energy utilization efficiency. For mitigating the conflict between path tracking and energy management in torque distribution, a hierarchical control framework is proposed for total demanding torque control, inter-axle torque distribution, and inter-wheel torque allocation. The inter-axle torque distribution is determined by considering the total motors efficiency region reflection to enhance energy conversion efficiency. This approach ensures that torque is allocated to maximize energy conversion efficiency. Besides, the inter-wheel torque allocation is optimized using quadratic programming, considering factors such as tire vertical load distribution and path tracking error. By decoupling these control aspects, the proposed framework ensures optimal performance in both path tracking and energy management. In contrast, a traditional torque allocation method is also presented. Finally, the simulation experiments are conducted in MATLAB/Simulink and TruckSim with specialized off-road working cycles. The numerical experiment results demonstrate that the presented strategy considerably ensures an optimal torque allocation for path tracking while simultaneously enhances the overall efficiency of the distributed drive system compared with the conventional approach.

包络线控制起源于航空航天工业,它提供了飞行状态的安全保障和机动边界,为飞行器控制带来了良好效果.基于8×8多轴分布式驱动无人车辆和包络线方法核心思想,提出一种将车辆推向极限的整车动力学控制器.通过建立轮胎滑移圆提出一种新的方法以用于评估车辆驱动力状态,并将轮胎滑移状态与车辆"g-g"图相结合,用来实现无人驾驶状态下逼近车辆操纵能力极限,发挥车辆动力性能与灵活性能,同时确保在轨迹跟踪时的跟踪精度,精准高效地完成平台任务.考虑外界环境不确定扰动与因素变化对极限状态下车辆稳定性影响,基于车辆横向动力学模型的稳定特性分析,获得不同条件下稳定域相平面,并探索其变化机理、归纳数学描述表达式.通过对车辆稳定相平面的分析,提出以车辆横摆力矩为输出的稳定保持控制器.针对上层控制器驱动力与横摆力矩的输出,设计下层转矩分配控制策略,通过冗余执行器的最优分配实现整车性能发挥.整车集成控制策略部署于一辆8×8原型试验车辆,在越野路面上进行多项科目测试,试验结果表明:在高速条件下,无人车在轨迹跟踪中具有更好的动力性能和安全性能.

分布式电驱动平台以其优越的越障能力和机动能力受到国内外国防军事领域的广泛关注.为提高8×8独立驱动无人平台越野机动的行驶控制稳定性,提出一种分布式独立驱动无人平台的驱动扭矩优化分配控制框架.首先,建立了面向控制的整车动力学模型并提出一种分层控制框架.在该控制框架内,上层控制器用于快速求解无约束条件下的需求驱动力矩和横摆力矩,下层控制器以轮胎垂直载荷利用率以及路径跟踪控制精度为目标,采用二次规划算法对各轮胎扭矩分配进行优化求解,获取最优驱动力分配方案.其次,利用TruckSim和MATLAB搭建了越野机动仿真环境,对所提出的分层控制框架进行能效验证.联合仿真实验结果表明,该控制方法能合理分配车轮转矩,提高车辆的行驶稳定性,从而提升平台的越野自主机动能力.

Unstructured off-road environments with complex terrain obstacles and pavement properties bring obvious challenges for special purpose autonomous vehicle control. A cascade direct yaw moment control strategy (CDYC), which contains a main loop and a servo loop, is proposed to enhance the accuracy and stability of an independent eight in-wheel motor-driven autonomous vehicle with rear-wheel steering (8WD/RWS). In the main loop, double PID controllers are designed to generate the desired drive moment and yaw rate. In the servo loop, the quadratic programming (QP) algorithm with the tire force boundaries optimally allocates the demanded yaw moment to individual wheel torques. The 8WD/RWS prototype is virtually established using TruckSim and serves as the control object for co-simulation. The proposed cascade controller is verified by simulations in customized off-road driving scenarios. The simulation results show that the proposed control architecture can effectively enhance the path-tracking ability and handling stability of the 8WD/RWS, as to ensure the maneuverability and control stability under extreme off-road conditions.

In-wheel motor driving is regarded as an important development direction of vehicles. In-wheel motors design simplifies the chassis structure, but the increase in the number of actuators brings challenges to vehicle safety. Considering the faults of one or more actuators during path tracking working mode, a hierarchical fault-tolerant controller strategy for an eight in-wheel-driving autonomous vehicle with rear-wheel-steering (SWD-RWS) is proposed in this paper. The controller can be divided into two layers. The upper controller mainly includes the path tracking module and velocity planning control module, which receives desired path and then converts it into the longitudinal traction force and the yaw moment, receives maximum velocity and then generates velocity distribution among waypoints, respectively. The lower controller optimizes the allocation of vehicle-level forces and moments to the available in-wheel motors to achieve fault tolerance. A nonlinear vehicle dynamics model with 21 degrees of freedom (DOF) is established and simulated in Matlab/Simulink. Simulation results show that the proposed fault-tolerant control strategy can realize wheel torque redistribution when the in-wheel motor faults. Vehicle motion path tracking is not greatly affected, and the stability can be guaranteed.

Multi-axle unmanned distributed drive vehicle involves the coordinated control of multiple actuators for stable and safe motion. Aiming at the controlling problem under complicated conditions, this paper proposes an optimal hierarchical torque distribution strategy. A control-oriented dynamic model for an 8× 8 vehicle with rear-wheel-steering is established firstly, then a hierarchical controller combined with linear quadratic regulator and quadratic programming algorithm is presented. Simulation results show that the proposed strategy can realize desired motion tracking control and improve the vehicle's handling stability.