四轮线控转向叉车动力学建模及控制仿真研究

发布时间：2018-10-15 14:48

【摘要】：随着叉车工业技术的快速发展及其在物流系统的广泛应用,叉车操纵稳定性问题日益受到人们的关注。四轮转向是一种有效提高车辆行驶安全和操纵稳定性的主动控制技术,能够减小车辆的转弯半径,使其转向更加灵活。装配线控转向系统的车辆通过电信号传递转向控制信息,不仅节能环保,而且提高了车辆设计的灵活性,同时也使得跟踪车辆转向的期望状态成为可能。本文以四轮线控转向叉车为研究对象,并结合预瞄最优曲率驾驶员模型,对四轮转向叉车控制策略进行深入研究。首先基于魔术公式引入了叉车非线性轮胎模型,并在此基础上基于车辆标准坐标系推导出非线性三自由度四轮转向叉车动力学模型,同时根据叉车特点引入驾驶员模型和双移线道路模型的闭环系统模型,为后文的控制器研究设计提供一个良好的仿真模型平台。其次考虑到实时准确地获取叉车行驶中的关键状态变量是实现四轮转向控制系统设计的前提,针对质心侧偏角不易测量的特点,分别基于扩展卡尔曼滤波和无迹卡尔曼滤波理论建立了非线性二自由度质心侧偏角估计模型,并通过仿真验证了所设计的无迹卡尔曼质心侧偏角估计模型在开环和闭环系统中的有效性。最后针对叉车系统参数摄动和外部干扰等不确定因素影响,基于线控转向技术,采用滑模变结构理论设计了四轮转向滑模控制器主动控制叉车前后轮转角,并在开环和闭环系统下进行仿真分析。仿真结果表明基于滑模控制的四轮转向叉车有效减小了质心侧偏角,同时横摆角速度能够很好的跟踪期望值,并有效抑制了系统内部参数摄动和外部干扰,提高了叉车的操纵稳定性。
[Abstract]:With the rapid development of forklift industry and its wide application in logistics system, people pay more and more attention to the stability of forklift handling. Four-wheel steering is a kind of active control technology which can effectively improve the driving safety and control stability of vehicles. It can reduce the turning radius of vehicles and make their steering more flexible. The vehicle of assembly line control steering system transmits steering control information by electric signal, which not only saves energy and environmental protection, but also improves the flexibility of vehicle design, and makes it possible to track the expected state of vehicle steering. In this paper, the control strategy of four-wheel steering forklift truck is deeply studied by combining with the preview optimal curvature driver model and the four-wheel steering forklift truck as the research object. Firstly, the nonlinear tire model of forklift truck is introduced based on magic formula, and the nonlinear dynamic model of four-wheel steering forklift truck with three degrees of freedom is derived based on the vehicle standard coordinate system. At the same time, according to the characteristics of forklift truck, the closed-loop system model of driver model and double-shift road model is introduced, which provides a good simulation model platform for the later research and design of controller. Secondly, considering that the key state variables in forklift running in real time and accurately are the premise of the design of four-wheel steering control system, aiming at the characteristics that the side deflection angle of mass center is not easy to be measured, Based on the extended Kalman filter and the unscented Kalman filter theory, the nonlinear two-degree-of-freedom (2-DOF) centroid side deflection estimation models are established, respectively. The effectiveness of the unscented Kalman centroid side deflection estimation model in open loop and closed loop systems is verified by simulation. Finally, aiming at the influence of uncertain factors such as parameter perturbation and external disturbance of forklift system, based on wire steering technology and sliding mode variable structure theory, a four wheel steering sliding mode controller is designed to control forklift front and rear wheel rotation angle actively. And under the open-loop and closed-loop system simulation analysis. The simulation results show that the four-wheel steering forklift based on sliding mode control can effectively reduce the side deflection angle of mass center, at the same time, the yaw angular velocity can track the expected value well, and effectively restrain the internal parameter perturbation and external interference. The handling stability of forklift truck is improved.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH242

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