Trajectory tracking of tail-sitter aircraft by L_(1)adaptive fault tolerant control

This paper proposes an L_(1)adaptive fault tolerant control method for trajectory tracking of tail-sitter aircraft in the state of motor loss fault.The tail-sitter model considers the uncertainties produced by the features of nonlinearities and couplings which cause difficulties in control.An L_(1)adaptive controller is designed to reduce the position and attitude error when actuators have faults.A reference trajectory containing large maneuver flight transitions is designed,which makes it even harder for the L_(1)controller to track accurately.Compensators are designed to assist L_(1)adaptive controller tracking of the reference trajectory.The stability of the L_(1)adaptive controller including compensators is proved.Finally,the simulation results are used to analyse the effectiveness of the proposed controller.Compared to the H∞controller,the L_(1)adaptive controller with compensators has better performance in position control and attitude control under fault tolerance state even when the aircraft conducts large maneuver.Besides,as the L_(1)adaptive control method separates feedback control and adaptive law design,the response speed of the whole system is improved.

基于L_(1)自适应控制律的无人机滚转控制

在飞行器参数变化时,L_(1)自适应控制相对于传统比例积分微分(proportional integral derivative,PID)控制方法具有理想的控制效果。针对某型存在参数不确定性的无人机,建立了无人机横侧向动力学模型,在对L_(1)自适应控制理论进行研究的基础上,分别设计了L_(1)自适应控制律和比例微分(proportional derivative,PD)控制律,通过算例仿真,对比分析了这两种控制律对无人机滚转角的控制效果。结果表明,L_(1)自适应控制律具有良好的抗飞行器参数变化能力,鲁棒性强,对无人机飞行控制系统设计具有重要的参考价值。

Nonlinear L_(1) adaptive control of stagnation pressure in a cryogenic wind tunnel

Cryogenic wind tunnel is a sophisticated aerodynamics ground test faility,which operates in cryogenic temperature with injection of liquid nitrogen.The multi-variable,nonlinear and coupled dynamics existing between the temperature,pressure and Mach number in the tunnel,poses great challenges for the effective control of the tunnel.L_(1) adaptive control is a new control methodology developed in recent years with good robustness properties,which has good potentials to address these challenges.But this control method does not provide full adaptive feedforward control in its generic structure.In the paper,adaptive feedforward control action is introduced into the standard L_(1) adaptive control architecture for nonlinear systems in the presence of matched un-modeled dynamics.This new control structure is applied to the stagnation pressure control in a cryogenic wind tunnel,which could also be used for the control of temperature and Mach number in the tunnel.This new method could effectively compensate known disturbances with linear gain uncertainty,which occur in the nonlinear systems,while retaining the closed-loop control performance of L_(1) adaptive control.After the proof and discussions on the stability of this method,simulations of the stagnation pressure control in the wind tunnel are presented.The results and analysis demonstrate the effectiveness of the proposed control architecture.

永磁直线电机自适应区间二型模糊滑模控制

针对永磁直线同步电机伺服系统受到系统参数变化、负载扰动而降低其性能的问题,考虑端部效应以及摩擦力的存在,提出一种自适应区间二型模糊滑模控制方法.采用自适应区间二型模糊系统逼近滑模控制等效控制部分,把传统的一型模糊系统扩展到区间二型模糊系统,提高系统面临参数变化、不确定性扰动时的处理能力.基于Lyapunov函数设计切换项增益调整的自适应律,保证系统的稳定性.仿真结果表明,该方法提高了系统的鲁棒性,有效地削弱了系统的抖振.

基于虚拟领航者的无人机一致性编队控制

针对二阶一致性理论的无人机编队控制问题,以固定翼无人机为研究对象,提出了一种改进二阶一致性算法的无人机编队控制策略。通过引入虚拟领航者构建能够直观描述编队队形的相对运动坐标系,从水平与纵向相解耦的无人机运动学模型出发,同时考虑无人机系统的性能约束条件,对一致性算法进行了改进。针对无人机在不同飞行场景下的队形变换,基于KM算法设计了编队变换时编队成员位置的再分配策略,并采用改进L_(1)制导律作为虚拟领航者的航迹跟踪方法。最后通过仿真验证了本文所设计控制方法的可行性和有效性,仿真结果表明该方法可以在满足无人机系统性能约束的前提下形成稳定编队,同时在多种飞行场景中快速进行队形变换及拓扑切换并消除位置误差。

考虑执行机构饱和的迎角跟踪控制

为了进一步改善控制系统的鲁棒性,在非线性动态逆控制器设计的基础上,设计L_(1)自适应控制环节补偿逆误差及外部干扰的影响。为了保证系统稳定性,针对执行机构饱和约束,引入伪控制保护补偿信号,调整参考输入,使得执行机构在任何时刻均不会进入饱和状态。最后,以迎角指令跟踪控制为例进行仿真验证,表明具有伪控制保护的L_(1)自适应补偿策略对迎角跟踪控制保持良好的指令跟踪性能。