无人动力伞带跟踪微分器的高度控制方法

为全面改善无人动力伞飞行高度控制性能,提出一种带跟踪微分器的积分先行控制(TD-IPD)方法。以线性二次型最优控制引出的积分先行控制器为基础,考虑到微分环节的干扰问题,引入跟踪微分器将信号从干扰中分离出来,并用最速控制综合函数fsun(·)减小达到稳态时所用步数;由于积分环节易饱和,采用饱和补偿方法对积分环节结构进行修改,从而提高积分环节抗饱和能力;以某动力伞的高度控制为对象,通过Matlab仿真验证了所提方法的有效性。     

Second-order optical differentiator using mechanically-induced LPFG with a single π-shift

An all-optical second-order temporal differentiator using a mechanically-induced long-period fiber grating (MI-LPFG) with a single π-shift was demonstrated.The MI-LPFG was created by pressing a fiber b...     

High-order tracking differentiator based adaptive neural control of a flexible air-breathing hypersonic vehicle subject to actuators constraints

In this paper, an adaptive neural controller is exploited for a constrained flexible air-breathing hypersonic vehicle (FAHV) based on high-order tracking differentiator (HTD). By utilizing functional decomposition methodology, the dynamic model is reasonably decomposed into the respective velocity subsystem and altitude subsystem. For the velocity subsystem, a dynamic inversion based neural controller is constructed. By introducing the HTD to adaptively estimate the newly defined states generated in the process of model transformation, a novel neural based altitude controller that is quite simpler than the ones derived from back-stepping is addressed based on the normal output-feedback form instead of the strict-feedback formulation. Based on minimal-learning parameter scheme, only two neural networks with two adaptive parameters are needed for neural approximation. Especially, a novel auxiliary system is explored to deal with the problem of control inputs constraints. Finally, simulation results are presented to test the effectiveness of the proposed control strategy in the presence of system uncertainties and actuators constraints.     

Sensor fault detection and isolation for aircraft control systems by kinematic relations

This paper presents a new approach to Fault Detection and Isolation (FDI) for sensors of aircraft. In the most general case, fault detection of these sensors on modern aircraft is performed by a logic that selects one of, or combines, the three redundant measurements. Such a method is compliant with current airworthiness regulations. However, in the framework of the global aircraft optimization for future and upcoming aircraft, it could be required, e.g., to extend the availability of sensor measurements. Introducing a form of analytical redundancy of these measurements can increase the fault detection performance and result in a weight saving of the aircraft. This can be achieved by exploiting the knowledge of the kinematic relations between the measured variables. These relations are exactly known giving the advantage that no model-mismatches need to be accounted for. Furthermore these relations are valid over the whole flight envelope and general for any type of aircraft. Two example applications will be presented, showing the applicability of the method for the FDI of air data sensors and measurements of the inertial reference unit.     

Virtual sensing of load forces in hydraulic actuators using second- and higher-order sliding modes

External load forces are challenging for sensing or estimating in the hydraulic actuators. Once it is due to inconvenient instrumentation of the force sensors, especially on an open-end mechanical interface. The other way, the complex nonlinear system behavior aggravates reconstructing the system states in a robust and real-time suitable manner. This paper proposes a sensorless estimation of external load forces in standard hydraulic actuators by using a well-established equivalent output injection of the second-order sliding mode and also higher-order sliding mode differentiator. Only the basic inertial and frictional parameters are assumed to be known from an initial identification without external load. Afterwards, the robust exact differentiators are used in order to reconstruct the system states. Noisy signals of the cylinder chamber pressures and piston stroke are the single quantities available from the measurement. An experimental case study, accomplished on the setup of two hydraulic cylinders arranged and operated in antagonistic way, is provided. The force-cell on the rigid interface between both cylinders is used for reference measurements and evaluation of the estimation algorithms. Two estimation approaches, one of the 2nd and another of the 4th order, are assessed in performance and compared to each other along with discussion.     

航空相机镜筒全程快速无超调位置控制

为消除航空相机镜筒在位置控制过程中的超调,本文提出采用跟踪微分器对阶跃输入信号进行处理,通过合理设计过渡过程来实现镜筒位置控制的快速无超调响应.首先,阐述了跟踪微分器理论,分析其工作特性.然后,以90°位置阶跃响应为例,进行了过渡过程设计,并与无过渡过程设计的控制效果进行了比较.实验结果表明,合理设计过渡过程能完全消除镜筒位置响应的超调,同时减小调节时间.在90°阶跃输入时,超调量由24.1％减小为零,同时调节时间缩短28.8％.此外,采用最小二乘法拟合阶跃输入量与过渡过程快速因子的函数关系,控制过程中根据阶跃输入量计算最优过渡过程参数,实现了镜筒位置的全程快速无超调控制.该方法已经在航空相机镜筒中进行了实际应用,取得了良好的效果,有效改善了系统的动态性能.     

基于自抗扰控制的PMSM转速调节系统

经典PI调节的永磁同步电动机转速控制,存在快速性与超调量之间的矛盾.将自抗扰控制技术应用于永磁同步电动机转速控制中,设计跟踪微分器对输入安排过渡过程,使系统有良好的转速适应性;扩张状态观测器通过对综合扰动项的观测和实时补偿,增强了系统的鲁棒性.仿真实验结果表明,基于ADRC的PMSM转速调节系统,可实现对输入信号的快速无超调跟踪.     

Novel adaptive method based on the Taylor series to compensate channel-mismatches of TIADC

Static-gain and timing-skew mismatches among channels of TIADC significantly limit the Signal-to-Noise plus Distortion Ratio (SNDR) and the Spurious Free Dynamic Range (SFDR) of system. In this paper, an adaptive structure based on the Taylor series theory is proposed to compensate these mismatches. The novel structure is composed of differentiators and external reference channel. Controlled by the clock, sub-channels and reference channel sample simultaneously at some times. Comparing the output of reference channel with those of differentiators of sub-channels, the parameters of mismatches can be estimated, and then compensations can be carried out. The whole structure is implemented in the digital domain, and has the advantage of stability. Due to the special clock divider, all sub-channels share the same reference channel, which simplifies the system. Experimental results demonstrate that the SNDR and the SFDR of the output can be raised around 50dB, and the effective number of bits(ENOB) of the system can reaches about 12bits when the ADCs outputs are quantized to 14bits, which proves the validity of the proposed method.     

Model-free fractional order differentiator based on fractional order Jacobi orthonormal functions

The aim of this paper is to design an algebraic and robust fractional order differentiator to estimate both the Riemann–Liouville and the Caputo fractional derivatives with an arbitrary order of an unknown signal in noisy environment, without knowing the model defining the signal. For this purpose, a new class of fractional order Jacobi orthonormal functions is firstly introduced. Secondly, the truncated fractional order Jacobi orthonormal series expansion is applied to filter the noisy signal, whose fractional derivative is used to estimate the desired one. Thus, the obtained differentiator is exactly given by an integral formula which depends on a set of design parameters. Thirdly, by applying the generalized Taylor's formula, some error analysis is provided. In particular, error bounds are given, which permit to study the design parameters' influence. Fourthly, a digital fractional order differentiator is deduced in discrete noisy case. Finally, by comparing with two existing fractional order differentiators, numerical results are given to illustrate the accuracy and the robustness of the proposed fractional order differentiator.     

Discrete Lanczos derivatives of noisy data

Finite differences are frequently used to differentiate empirical functions, but standard differences tend to amplify the random error that is present in almost all empirical data. This paper uses higher-order Lanczos derivatives and discretized Legendre polynomials to generate minimum variance finite differences to approximate ordinary derivatives of all orders for a fixed discretization error magnitude. The resulting differences can be implemented as finite impulse response filters and are therefore very fast on a computer.