基于预瞄距离的地下矿用铰接车路径跟踪预测控制
Path following control of underground mining articulated vehicle based on the preview control method
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摘要: 矿用车辆无人驾驶是实现矿山无人化开采的关键技术, 而路径跟踪控制是无人驾驶系统的核心技术之一.路径跟踪控制系统是多变量、多约束系统, 采用传统方法在多约束条件下存在执行器饱和等问题.针对上述问题, 本文引入模型预测控制方法, 通过考虑车辆的姿态与位置之间的关系, 以跟踪路径的横向偏差最小化和车辆的航向角偏差最小化为目标对预测控制的目标函数进行优化, 以获得车辆速度和铰接角度的最优控制量, 实现对多变量、多约束系统的求解.针对模型预测控制算法不能提前判断道路曲率突变而导致跟踪超调的问题, 提出基于预瞄距离的控制方法, 通过提前判断道路突变信息, 提高车辆路径跟踪精确性和稳定性.使用Matlab/Adams仿真软件进行对比仿真试验, 结果表明: 使用模型预测跟踪控制器能够解决多变量、多约束系统控制问题, 有效防止执行器饱和; 而使用基于预瞄距离的模型预测跟踪控制器能够使车辆的横向位置偏差保持在±0.04 m, 航向角偏差保持在±1.8°范围内, 相较于改进前的控制器, 其横向位置偏差减少了80.9%, 航向角偏差减少了59.1%, 证明改进后的控制器具有更好的横向稳定性和精确性.Abstract: Due to the narrow roadway and poor working environment, underground mines pose a threat to the safety of vehicle drivers. The realization of automatic driving of underground mine vehicles can improve mining automation and intelligence and ensure safety of workers, and it can significantly increase mining and exploitation efficiency. Automatic driving of underground mining vehicles requires the technologies of location, communication, navigation, and path following control. Automatic driving of mining vehicles is the ultimate approach of autonomous navigation and auto driving, while path following control system is one of the core technologies of the autopilot system. The path following control system is a multi-variable, multi-constraint system. There are optimization problems under multiple constraints as well as challenges such as actuator saturation during the control process. To solve the above problems, a model predictive control method was introduced in this paper. By considering the relationship between the position and situation of the vehicle, the objective function of the predictive control was optimized by minimizing the lateral deviation of the following path and the heading angle deviation of the vehicle. Therefore, the optimal controls of vehicle speed and articulation angle were obtained, and the problem of multi-variable and multi-constraint system was solved. For the tracking overshoot problem caused by the inability of determining sudden changes of road curvature in the model predictive control strategy, a control method based on preview distance was proposed; thus, the vehicle path following control accuracy and stability was improved through the advance judgment of road mutation information. Matlab/Adams simulation software was used to perform a comparison simulation test. The results show that the model predictive following controller is capable of solving the control problem in multi-variable, multi-constrained system and effectively prevent the actuator saturation. Moreover, the model predictive following control strategy based on the preview distance keeps the horizontal deviation of the vehicle within ±0.04 m and the heading angle deviation within ±1.8°. Compared with the controller before improvement, the lateral position deviation is reduced by 80.9%, and the heading angle deviation is reduced by 59.1%; this proves that the improved controller has better lateral stability and accuracy.