【作者】 刘震；

【导师】 胡德文；

【作者基本信息】 国防科学技术大学 ， 控制科学与工程， 2007， 博士

【摘要】 主动悬挂凭借其巨大的技术优势、广阔的应用前景,从诞生之初就倍受青睐,被称为代表未来车辆悬挂趋势的技术。特别是近些年来,它更是成为汽车工业领域的研究热点。同时,主动悬挂技术本身面临着巨大的技术挑战,在动力学、控制与应用方面有很多问题等待研究。本文针对车辆液压主动悬挂的建模与控制的相关问题进行了较为系统和深入的研究,包括液压主动悬挂的模型建立、最优控制与Backstepping方法相结合的级联控制、悬挂系统不确定性的自适应控制以及引入乘客-座椅模块后的悬挂系统分析。主要研究成果如下:1、车辆液压主动悬挂系统的非线性模型的建立。本文在深入研究液压作动器动力学的基础上,为了全面分析主动悬挂性能,从简单到复杂依次建立了详尽的二自由度1/4车辆悬挂模型、四自由度半车(1/2车)俯仰悬挂模型、七自由度全车悬挂模型以及考虑了乘客-座椅的六自由度半车俯仰悬挂模型。2、根据悬挂系统的结构特点,将系统分为外环和内环两个部分。在线性的外环,利用最优控制来实现对车体垂直振动加速度、悬挂行程以及轮胎动载荷的多目标控制需求;在内环则利用Backstepping方法对液压作动器所带来的非线性项进行补偿。从而提出了最优控制与Backstepping方法相结合的级联控制策略,并通过在所建立的主动悬挂模型上进行的仿真验证了其有效性。3、考虑到建模误差是不可避免的,对模型参数不确定性带来的影响进行了研究。并以作动器时间常数作为未知参数,在系统的内环采用自适应Backstepping方法设计了新的控制律以及参数更新律,有效的解决了非线性和参数不确定同时存在的问题,文中的理论证明和仿真结果都很好的验证了这一点。4、采用自适应增益调度控制策略设计了路面输入自适应控制器。该策略利用系统加速度的变化来估计路面输入,从而选择预先离线计算的相应路面输入的控制增益。仿真结果表明,它可以很好的满足变化的路面状况要求,进一步改善了悬挂性能。5、分析了乘客-座椅模块带来的影响,首先利用前面所提出的级联控制策略进行了控制设计与仿真,并在其基础上对轴距预见控制进行了研究。结果表明:在系统中引入乘客-座椅动力学使得模型更贴近实际的车辆,在控制设计中可以直接用乘客的运动响应来体现乘坐舒适性,性能评价指标更加明确;利用轴距预见控制则可以进一步提升主动悬挂性能,特别是对后悬挂作用明显。总之,本文以理论分析与仿真计算相结合的方式,对车辆液压主动悬挂的动力学、模型建立与控制设计进行了有益的研究和探讨,提出了若干解决液压主动悬挂控制与实际问题的方法,对于其它类型主动悬挂的相关研究也具有借鉴意义,希望能为主动悬挂技术的理论研究和实际应用提供一定的技术参考。更多还原

【Abstract】 For its advantages in technology and vast field of application, active suspension has been a hot point since it appeared and is called as a kind of technology representing the developing trend of vehicle suspensions. At the same time, there are a lot of challenges in dynamics, control and application of the active suspension systems.This dissertation systematically discusses some issues related to the modeling and control of the vehicle hydraulic active suspensions. These issues include the modeling of active suapension systems based on considering hydraulic actuator dynamics, combining control of the optimal control and the backstepping method, and adaptive control on the problems of uncertainties. What’s more, there is a discussion on the passenger-seat dynamics included in active suspension system. The main contributions are as follows:1. The nonlinear models of the vehicle hydraulic active suspension system are built based on hydraulic actuator dynamics analysis. For better evaluating the performance of the active suspension system, we choose two degrees-of-freedom quarter-car model of active suspension, four degrees-of-freedom half-car model of active suspension, seven degrees-of-freedom whole-car model of active suspension, and six degrees-of-freedom half-car model of active suspension including passenger-seat dynamics in the dissertation.2. The control strategy using a combination of the optimal control and the nonlinear backstepping technique is provided for the active suspension system, which is divided into two parts: the linear part (outer loop) and the nonlinear part caused by hydraulic actuator (inner loop). The detailed procedure is also divided into two steps: firstly the linear quadratic optimal controller is designed based on the performance requirements in the outer loop, and then the nonlinear terms are dealt with the backstepping method in the inner loop. Simulation results show the effectiveness of the proposed strategy.3. Considering the variations in the parameters of the active suspension, we study the sensitivity of the control strategy proposed in the third chapter. Aiming at the uncertainty of the time constant, the control law and parameter update law are designed in the inner loop using adaptive backstepping method in this dissertation. The verifying in theory and simulation results demonstrate that the uncertainty can be dealt effectively.4. In order to realize the full potential of active suspensions the controller should have the capability of adapting to changing road environments. We present a gain scheduling control strategy for vehicle suspension design. The control gains of the optimal controller in the outer loop are adapted to the changes of the road input by acceleration feedback. Thus, optimal suspension performance can be obtained in different conditions. Simulations show that the control strategy provides superior passenger comfort over the whole range of road conditions.5. An analytical investigation of the nonlinear half-car model including passenger-seat dynamics is examined. The simulation results demonstrate that the control strategy based on the combination of the optimal control and the backstepping technique, when including passenger acceleration in the performance index, retains both excellent ride comfort and road handling characteristics. Furthermore, the potential improvements through wheelbase preview control are investigated.In conclusion, by analyzing and simulating, it mainly studies the problems in dynamics, modeling and control of the vehicle hydraulic active suspension in the dissertation and proposes some methods on the control design and the practical problems, which can provide ideas for the study of the active suspension in other kinds, and be of some help to the development of active suspensions.更多还原