挠性航天器预设性能自适应姿态跟踪控制

摘要

为研究存在外界干扰及未建模动态的挠性航天器姿态跟踪问题,提出了一种基于预设性能方法的自适应姿态跟踪控制策略.预设性能方法利用性能函数和一种误差变换方式,将系统的跟踪误差限制在预先设定的约束范围内,以保证系统响应具有期望的超调、收敛速度以及稳态误差.采用径向基函数(RBF)神经网络来处理由干扰和附件挠性振荡产生的模型未知动态.考虑到存在未知的神经网络逼近误差,为减小控制参数选取的保守性,进一步对逼近误差的上界进行自适应估计.结合权值和逼近误差上界的自适应律,设计了预设性能自适应姿态跟踪控制器.仿真结果表明,使用本方法可以有效补偿干扰及挠性振动所产生的影响,同时使姿态控制系统获得快速平稳的动态过程和给定的稳态跟踪精度.与未采用预设性能的方法相比,所提出的方法在收敛速度、跟踪精度与振荡抑制效果等方面均具有较明显的优势,并且对控制器参数选取的依赖性更低.%A kind of prescribed performance based adaptive attitude tracking control scheme is discussed for flexible spacecraft attitude tracking problem with external disturbances and unmodeled dynamics. The prescribed performance method utilizes performance functions and error transformation for constraining the system tracking error within prespecified bounds to ensure desired overshoot, convergence rate, and steady-state error. Radial basis function (RBF)neural network is used to deal with the unknown dynamics caused by disturbances and flexible vibration. When considering the existence of the unknown neural network approximation error, the upper bound of the approximation error is further estimated to reduce the conservativeness in parameter selection. By using the designed adaptive laws,the prescribed performance adaptive attitude tracking control law is constructed.A simulation study on a flexible spacecraft system shows that the proposed method can compensate the influence of disturbances and flexible appendages while obtaining a fast transient process and expected attitude tracking accuracy. Compared with the method without using prescribed performance, the proposed method has obvious advantages in the convergence, tracking accuracy,and vibration suppression with lower dependence on control parameters.