多轴分布式驱动无人车辆极限操纵状态整车集成控制方法

doi:10.12382/bgxb.2023.0775

摘要/Abstract

摘要：

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。

关键词: 无人车辆, 多轴分布式驱动, 车辆操纵极限, 包络线控制方法, 轨迹跟踪

Abstract:

Envelope control originated in the aerospace industry, which provides the safety guarantees and movement limit and brings a better performance in aircraft control. A vehicle dynamics controller, which pushes the vehicle in handling limit, is proposed based on 8×8 distributed driving unmanned ground vehicle and the core idea of envelope method. Firstly, a novel method is proposed to evaluate the driving force status of vehicle by establishing a tire slip circle. The tire slip status and “g-g” diagram are combined to achieve approaching the vehicle handling limit under autonomous driving, and to perform the vehicle’s mobility and maneuverability. On the other hand, the controller is used to insure the tracking accuracy during trajectory tracking which can complete tasks more accurately and efficiently. Subsequently, in considering the impact of external environmental uncertainties on the stability of vehicles in extreme states, the stability phase planes under different conditions are obtained based on the analysis of stability characteristics of vehicle lateral dynamics model, and the mathematical expressions of them are summarized according to change mechanism. A stability maintaining controller with yaw moment output is proposed by analyzing the stability phase plane. Finally, based on the output of the upper-level controller, a lower-level torque distribution control strategy is designed to achieve full performance through the optimal allocation of actuators. The integrated control strategy is deployed on an 8×8 prototype vehicle and was tested with multiple subjects under the condition of off-road. The test results show that the vehicle has better dynamic performance and safety in trajectory tracking under high-speed condition.

Key words: unmanned ground vehicle, multi-axle distributed driving, handling limit of vehicle, envelope control, trajectory tracking

中图分类号:

TP13

潘博, 李胜飞, 汪洋, 谭森起, 张乃斯, 罗天, 崔星. 多轴分布式驱动无人车辆极限操纵状态整车集成控制方法[J]. 兵工学报, 2023, 44(11): 3279-3294.

PAN Bo, LI Shengfei, WANG Yang, TAN Senqi, ZHANG Naisi, LUO Tian, CUI Xing. Integrated Control Method of Multi-axle Distributed Driving Unmanned Ground Vehicle in Handling Limit[J]. Acta Armamentarii, 2023, 44(11): 3279-3294.

图/表 17

图1 无人驾驶方程式赛车

Fig.1 Autonomous formula race car

图2 8×8车辆与轮胎动力学简化模型

Fig.2 Simplified dynamics models of 8×8 vehicle and tire

表1 动力学模型参数含义注释

Table 1 Signification of symbols in vehicle model equation

参数	含义
F_x_w_ij,F_y_w_ij,F_z_w_ij	轮胎坐标系下每个轮胎的纵、横、垂向力
F_xij,F_yij	大地坐标系下每个轮胎的纵、横向力
v_x, v_y, v_z, ω_x, ω_y, ω_z	车辆质心x轴、y轴、z轴方向的速度与角速度
m,a_x, a_y, m_c, l₁, l₂	整车质量、车辆纵向加速度、车辆横向加速度、车身质量、侧倾中心与质心之间高度、俯仰中心与质心之间高度
F_s_ij, F_ss_ij, F_sd_ij	悬架力、静态悬架力、动态悬架力
δ_ij, B, L_i	转向角、轮距、车轴与质心之间距离
I_x, I_y, I_z	车身x轴、y轴、z轴方向的转动惯量
β, θ, ϕ	车身质心的侧偏角、侧倾角、横摆角
α_s, C_D, A, ρ, f	路面坡度、风阻系数、迎风面积、空气密度、轮胎滚动阻力系数
J_e, T_ij, R_e, ω_ij	滚动力矩、驱动力矩、轮胎半径、轮胎转速
z_s, z_w	悬架变形量(位移)、轮胎垂向位移

图3 8×8车辆动力极限表述——“g-g”图

Fig.3 Dynamic limit description of 8×8 vehicle: “g-g” diagram

图4 轮胎力学典型非线性特征曲线

Fig.4 Typical nonlinear characteristic curve of tire mechanics

图5 轮胎滑移圆

Fig.5 Slip circle of tire

图6 不同状态下的车辆稳定域相图

Fig.6 Stability phase plane diagrams of vehicle in different conditions

图7 整车集成控制器架构示意图

Fig.7 Framework of vehicle integrated controller

图8 8×8车辆轨迹跟踪横向误差模型

Fig.8 Lateral error model of trajectory tracking for 8×8 vehicle

表2 仿真与外场试验测试主要参数

Table 2 Main parameters for simulation and experiment

参数	含义	数值
C_D	整车空气阻力系数	0.45
f	轮胎地面阻力系数	0.4
k_u	纵向速度误差反馈系数	4000
k_κ	纵向滑移误差反馈系数	6150
k_α	纵向侧偏误差反馈系数	4230
k_no-slip	纵向非滑移误差反馈系数	2500
k_e	横向误差系数	1390
k_Δ_ψ	航向误差系数	545
K_qd	稳定性反馈系数	1320
q	稳定性权重矩阵系数	0.3
r_fd	稳定性反馈控制权重系数	0.355

图9 试验测试场地图

Fig.9 Experiment site

图10 双移线场景仿真测试结果

Fig.10 Results of double line change test in simulation

图11 加速性能测试结果

Fig.11 Results of acceleration test

图12 试验测试的轨迹定位信息

Fig.12 Trajectory positioning information in test

图13 综合性能测试结果

Fig.13 Results of comprehensive performance test

图14 稳定性能测试结果对比

Fig.14 Comparison of stability performance test results

图15 分布式电机驱动力矩分配效果对比

Fig.15 Comparison of distributed driving motor torque allocation effects

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