Adaptive saturated tracking control for solid launch vehicles in ascending based on differential inclusion stabilization

The large-range uncertainties of specific impulse,mass flow per second,aerodynamic coefficients and atmospheric density during rapid turning in solid launch vehicles(SLVs) ascending leads to the deviation of the actual trajectory from the reference one.One of the traditional trajectory tracking methods is to observe the uncertainties by Extended State Observer(ESO) and then modify the control commands.However,ESO cannot accurately estimate the uncertainties when the uncertainty ranges are large,which reduces the guidance accuracy.This paper introduces differential inclusion(DI) and designs a controller to solve the large-range parameter uncertainties problem.When above uncertainties have large ranges,it can be combined with the ascent dynamic equation and described as a DI system in the mathematical form of a set.If the DI system is stabilized,all the subsets are stabilized.Different from the traditional controllers,the parameters of the designed controller are calculated by the uncertain boundaries.Therefore,the controller can solve the problem of large-range parameter uncertainties of in ascending.Firstly,the ascent deviation system is obtained by linearization along the reference trajectory.The trajectory tracking system with engine parameters and aerodynamic uncertainties is described as an ascent DI system with respect to state deviation,which is called DI system.A DI adaptive saturation tracking controller(DIAST) is proposed to stabilize the DI system.Secondly,an improved barrier Lyapunov function(named time-varying tangent-log barrier Lyapunov function) is proposed to constrain the state deviations.Compared with traditional barrier Lyapunov function,it can dynamically adjust the boundary of deviation convergence,which improve the convergence rate and accuracy of altitude,velocity and LTIA deviation.In addition,the correction amplitudes of angle of attack(AOA) and angle of sideslip(AOS) need to be limited in order to guarantee that the overload constraint is not violated during actual flight.In this paper,a fixed time adaptive saturation compensation auxiliary system is designed to shorten the saturation time and accelerate the convergence rate,which eliminates the adverse effects caused by the saturation.Finally,it is proved that the state deviations are ultimately uniformly bounded under the action of DIAST controller.Simulation results show that the DI ascent tracking system is stabilized within the given uncertainty boundary values.The feasible bounds of uncertainty is broadened compared with Integrated Guidance and Control algorithm.Compared with Robust Gain-Scheduling Control method,the robustness to the engine parameters are greatly improved and the control variable is smoother.

DESIGN AND ANALYSIS FOR NEW DISCRETE TRACKING-DIFFERENTIATORS

In this paper,some kinds of linear and nonlinear tracking-differentiators are designed by using suitable exponent functions instead of switch functions,and the stability of these tracking-differentiators is proved.From the result of simulations,it is manifest that the tracking speeds of these kinds of linear and nonlinear tracking-differentiators are very high,and their design procedures are simple.

Stable Transition of Quadruped Rhythmic Motion Using the Tracking Differentiator

Since the quadruped robot possesses predominant environmental adaptability,it is expected to be employed in nature environments. In some situations,such as ice surface and tight space,the quadruped robot is required to lower the height of center of gravity( COG) to enhance the stability and maneuverability. To properly handle these situations,a quadruped controller based on the central pattern generator( CPG) model,the discrete tracking differentiator( TD) and proportional-derivative( PD) sub-controllers is presented. The CPG is used to generate basic rhythmic motion for the quadruped robot. The discrete TD is not only creatively employed to implement the transition between two different rhythmic medium values of the CPG which results in the adjustment of the height of COG of the quadruped robot,but also modified to control the transition duration which enables the quadruped robot to achieve the stable transition. Additionally,two specific PD sub-controllers are constructed to adjust the oscillation amplitude of the CPG,so as to avoid the severe deviation in the transverse direction during transition locomotion. Finally,the controller is validated on a quadruped model. A tunnel with variable height is built for the quadruped model to travel through. The simulation demonstrates the severe deviation without the PD sub-controllers,and the reduced deviation with the PD sub-controllers.

Design of a Modified Tracking Differentiator

A modified tracking differentiator is proposed. Firstly, a nonlinear odd exponent continuous function is adopted which is only stable at one equilibrium point and proved the global asymptotic stability of the modified tracking differentiator by select a Lyapunov function. Through combining of the nonlinear and linear function properly, it can be sure that the state converges to the equilibrium point with high speed automatically no matter that the state was far away from the equilibrium point or near to it, and it can prevent the chattering.?Simulation results show that the modified tracking differentiator tracking results?are?superior to the classical nonlinear tracking differentiator, and the response?of state variables tracking differentiator estimated?is?almost coincide with the real state of the variables of the given system.

A Newly Developed Differential Steering Rubber-tracked Agriculture Tractor

This paper introduces a newly developed ag tractor.The differential steering system and rubber tracks are described in detail.

Convergence Track Based Adaptive Differential Evolution Algorithm(CTbADE)

One of the challenging problems with evolutionary computing algorithms is to maintain the balance between exploration and exploitation capability in order to search global optima.A novel convergence track based adaptive differential evolution(CTbADE)algorithm is presented in this research paper.The crossover rate and mutation probability parameters in a differential evolution algorithm have a significant role in searching global optima.A more diverse population improves the global searching capability and helps to escape from the local optima problem.Tracking the convergence path over time helps enhance the searching speed of a differential evolution algorithm for varying problems.An adaptive powerful parameter-controlled sequences utilized learning period-based memory and following convergence track over time are introduced in this paper.The proposed algorithm will be helpful in maintaining the equilibrium between an algorithm’s exploration and exploitation capability.A comprehensive test suite of standard benchmark problems with different natures,i.e.,unimodal/multimodal and separable/non-separable,was used to test the convergence power of the proposed CTbADE algorithm.Experimental results show the significant performance of the CTbADE algorithm in terms of average fitness,solution quality,and convergence speed when compared with standard differential evolution algorithms and a few other commonly used state-of-the-art algorithms,such as jDE,CoDE,and EPSDE algorithms.This algorithm will prove to be a significant addition to the literature in order to solve real time problems and to optimize computationalmodels with a high number of parameters to adjust during the problem-solving process.

On a novel tracking differentiator design based on iterative learning in a moving window

Differential signals are key in control engineering as they anticipate future behavior of process variables and therefore are critical in formulating control laws such as proportional-integral-derivative(PID).The practical challenge,however,is to extract such signals from noisy measurements and this difficulty is addressed first by J.Han in the form of linear and nonlinear tracking differentiator(TD).While improvements were made,TD did not completely resolve the conflict between the noise sensitivity and the accuracy and timeliness of the differentiation.The two approaches proposed in this paper start with the basic linear TD,but apply iterative learning mechanism to the historical data in a moving window(MW),to form two new iterative learning tracking differentiators(IL-TD):one is a parallel IL-TD using an iterative ladder network structure which is implementable in analog circuits;the other a serial IL-TD which is implementable digitally on any computer platform.Both algorithms are validated in simulations which show that the proposed two IL-TDs have better tracking differentiation and de-noise performance compared to the existing linear TD.

Fast and Simple Motion Tracking Unit with Motion Estimation

Surveillance system using active tracking camera has no distance limitation of surveillance range compared to supersonic or sound sensors.However,complex motion tracking algorithm requires huge amount of computation,and it often requires expensive DSPs or embedded processors.This paper proposes a novel motion tracking unit based on different image for fast and simple motion tracking.It uses configuration factor to avoid noise and inaccuracy.It reduces the required computation significantly,so as to be implemented on Field Programmable Gate Array(FPGAs)instead of expensive Digital Signal Processing(DSPs).It also performs calculation for motion estimation in video compression,so it can be easily combined with surveillance system with video recording functionality based on video compression.The proposed motion tracking system implemented on Xilinx Vertex-4 FPGA can process 48 frames per second,and operating frequency of motion tracking unit is 100 MHz.

Fuzzy Modeling, Tracking Control and Synchronization of the Rossler's Chaotic System

In this paper, a novel method to model, track control and synchronize the Rossler’s chaotic system is proposed. The fuzzy logical system is used so that the fuzzy inference rule is transferred into a type of variable coefficient nonlinear ordinary differential equation. Consequently the model of the chaotic system is obtained. Then a fuzzy tracking control and a fuzzy synchronization for chaotic systems is proposed as well. First, a known tracking control for the Rossler’s system is used in this paper. We represent the Rossler’s chaotic and control systems into fuzzy inference rules. Then the variable coefficient nonlinear ordinary differential equation is also got. Simulation results show that such an approach is effective and has a high precision.

Application of linear active disturbance rejection control for photoelectric tracking system

Dynamic characteristics and tracking precision are studied in the photoelectric tracking system and a linear active disturbance rejection control( LADRC) scheme is proposed for position loop. A current and speed controller is designed by a transfer function model,which is obtained by adaptive differential evolution. Model error,friction and nonlinear factor existing in position loop are treated as ‘disturbance',which is estimated and compensated by generalized proportional integral( GPI)observer. Comparative results are provided to demonstrate the remarkable performance of the proposed method. It turns out that the proposed scheme is successful and has superior features,such as quick dynamic response,low overshoot and high tracking precision. Furthermore,with the proposed method,friction is suppressed effectively.

基于速度控制的机器人轨迹摩擦补偿控制算法

目前机器人已在工业生产制造中得到广泛的应用,但由于机器人系统中关节摩擦等因素的影响,机器人的轨迹跟踪精度难以满足高精度生产的需求。为减少机械结构中非线性摩擦因素和系统中未建模干扰等因素对机器人运行稳定性和加工精度的影响,文中提出了一种速度模式下的摩擦补偿控制算法。首先,基于傅里叶级数和5次多项式混合的方式设计最优激励轨迹,通过最小二乘法完成动力学参数的预辨识,并利用Levenberg-Marquardt法对预辨识结果进行迭代寻优,从而建立更为精确的机器人动力学模型;然后,基于李雅普诺夫方法设计机器人轨迹跟踪控制算法,将最速离散跟踪微分器中采集的关节角度输入所设计的轨迹跟踪控制算法中,得到实时的关节速度补偿值,将补偿值实时输入机器人中实现摩擦补偿控制;最后,以六自由度串联机器人为实验对象,对所设计的摩擦补偿控制算法进行实验验证。结果表明,相对于摩擦补偿前,机器人的末端轨迹跟踪精度提升约35%,从而验证了文中所提算法在机器人摩擦补偿领域的有效性。

基于微分平坦的板球系统反步滑模控制

为改善板球系统轨迹跟踪控制误差大,控制精度低的问题,提出了一种基于微分平坦的板球系统反步滑模控制方法。首先基于欧拉-拉格朗日方程建立板球系统的运动学模型,通过合理简化得到解耦线性状态空间模型。以X轴方向控制器设计为例,利用微分平坦技术获得系统的目标状态量以及前馈控制量,建立误差系统,进而采用反步法实现对误差系统的滑模控制,利用李雅普诺夫稳定性理论证明了闭环系统的稳定性。算法中使用双曲正切函数抑制滑模的抖动,实现了对板球系统的轨迹高精度跟踪控制。仿真实验结果表明,该方法控制精度高,具有良好的控制效果。

基于联邦学习的中心化差分隐私保护算法研究

近年来,联邦学习以独特的训练方式打破了数据“孤岛”,因此受到越来越多的关注。然而在训练全局模型时,联邦学习易受到推理攻击,可能会泄露参与训练成员的一些信息,产生严重的安全隐患。针对联邦训练过程中半诚实/恶意客户端造成的差分攻击,文章提出了基于中心化的差分隐私联邦学习算法DP-FEDAC。首先,优化联邦加速随机梯度下降算法,改进服务器的聚合方式,计算参数更新差值后采用梯度聚合方式更新全局模型,以提升稳定收敛;然后,通过对聚合参数添加中心化差分高斯噪声隐藏参与训练的成员贡献,达到保护参与方隐私信息的目的,同时还引入时刻会计(MA)计算隐私损失,进一步平衡模型收敛和隐私损失之间的关系;最后,与Fed AC、分布式MB-SGD、分布式MB-AC-SGD等算法做对比实验,评估DP-FEDAC的综合性能。实验结果表明,在通信不频繁的情况下,DP-FEDAC算法的线性加速最接近Fed AC,远优于另外两种算法,拥有较好的健壮性;此外DP-FEDAC算法在保护隐私的前提下能够达到与Fed AC算法相同的模型精度,体现了算法的优越性和可用性。

低附着路况条件下车辆横向稳定性控制

针对在冰雪环境下车辆横向稳定控制,为解决在低附着、分布不均的路面情况下车辆对参考轨迹的稳定跟踪问题,设计了基于神经网络调节的模糊PID(Proportional-Integral-Differential)制器,以及基于线性化车辆模型的模型预测控制(MPC:Model Predictive Controll)。以路面附着系数及车辆速度作为输入构建BP(Back-Propagation)神经网络,输出调节系数优化模糊PID控制器控制性能;设计了十自由度模型表征车辆在冰雪环境下的动力学特性,使用MPC实现车辆横向稳定控制。使用CarSim/Simulink进行联合仿真实验,结果表明该控制器能显著提高车辆轨迹跟踪性能。

基于领航-跟随法的多机器人编队控制

编队控制是多机器人系统研究的核心问题之一,具有广泛的研究价值。针对编队问题,通过对轮式差分驱动机器人运动模型进行分析,并设计相应的控制器。在传统的领航-跟随模型上,引入“虚拟机器人”,将跟随者机器人对领航者机器人的轨迹跟踪转换为跟随者对“虚拟领航者”的轨迹跟踪。首先,预设定实际领航者机器人的行进路径,由实际领航者引导运动方向的运动轨迹被视为主轨迹,虚拟机器人通过数据产生参考点从而生成参考轨迹,跟随者机器人通过对参考轨迹的跟踪与“虚拟领航者”构成轨迹误差跟踪系统。然后通过Lyapunov的控制理论验证控制器的理论可行性,最后在MATLAB/Simulink仿真平台进行实验,通过改变控制参数来使机器人形成相应的期望队形,在较短的时间内,跟随机器人对参考轨迹的跟踪误差趋向于0且速度收敛,验证了编队系统的可行性。

小曲率路面车辆差动转向与横摆稳定性集成控制研究

为减小车辆在前轮转向系统失效的负面影响,保证转向系统的瞬态控制性能,本文提出差动转向控制与横向稳定性控制相结合的控制方法,通过调节左右轮毂电机转矩形成横摆力矩,实现对系统完全失效车辆的转向控制与横向稳定性控制。首先设计基于LQR差动转向控制器跟踪参考前轮转角与参考横摆角速度,保证车辆轨迹跟踪能力,然后设计基于模糊PID横向稳定性控制器跟踪参考质心侧偏角,保证车辆横摆稳定性,两者构成双闭环控制系统将控制量最终转化为横摆力矩,实现车辆的集成控制。最后通过Simulink-Carsim联合仿真验证,仿真结果表明差动转向系统能够在前轮转向系统失效情况下实现车辆转向控制,并在横向稳定性控制系统的作用下有效地提高了车辆瞬态控制性能。

基于双预瞄纯追踪算法的丘陵山区农机差分导航系统研究

针对丘陵山区农业机械因体积小、种类多,难以无人作业改造的问题,搭建基于双预瞄纯追踪算法的丘陵山区农机差分导航系统,完成导航系统结构、路径规划策略和追踪控制器的设计。使用Ntrip DTU和北斗定位板卡完成差分定位。采用平滑转向方式,提出适用于丘陵山区的全局路径规划策略,可有效适配不同转弯半径的农机,减少地头区域。设计双预瞄纯追踪模糊控制器,开展与纯追踪控制器的对比仿真试验,并搭建试验样机完成测试。实际测试结果显示:控制器在追踪直线时,在s=2.9 m处收敛,在之后的直线追踪中平均绝对误差保持在0.01 m;在追踪曲线时,两段弯道最大误差分别为0.08 m和0.75 m,平均绝对误差0.04 m。

基于并联差速机构的通信天线及指向建模和跟踪方法

随着卫星星座互联网的发展及通信装备实战化升级换代,通信天线性能指标的要求越来越高。设计了一种基于并联差速机构的通信天线,介绍了通信天线的结构,分析了并联差速机构的原理,并进行通信天线指向建模和跟踪方法研究。在研究中,定义了运动数学模型,推导了解析式,进而得到跟踪方法。相较于传统采用串联驱动结构的通信天线,基于并联差速机构的通信天线具有刚度大、体积小、指向精度高等特点,在民品通信和军用通信领域具有良好的适用性。

多传感器协同区域搜索与目标跟踪的调度方法

为解决区域搜索和目标跟踪2种任务协同时对传感器资源的竞争问题,提出了一种多传感器调度方法。针对双任务协同背景,将传感器调度转换为多目标优化问题,以搜索性能和跟踪性能为优化目标建立了目标函数;建立了区域搜索模型,考虑目标的新生、消亡和转移,将未被发现目标的更新过程建立为非齐次泊松过程,提出以漏警损失量化区域搜索性能;建立了目标跟踪模型,引入后验克拉美罗下界(PCRLB)量化未来时刻的跟踪性能;针对最优调度方案求解,在传统多目标差分进化算法的基础上,引入混沌映射理论和双种群协同方法,提出了混沌映射-多目标协同差分进化算法(CM-MOCDEA)以提高寻优能力。仿真实验验证了所提优化算法能够兼顾收敛性和多样性,具有较强的全局搜索能力;所提方法能够有效分配传感器资源完成区域搜索和目标跟踪任务,从而获得较高的作战收益。

预设时间性能约束下高超声速飞行器的自适应容错控制

考虑输出误差约束、不确定和执行器故障影响下的高超声速飞行器的跟踪控制问题,提出自适应容错反步控制策略。首先,设计指数型预设时间性能函数,保证输出误差在预设时间内满足约束要求。其次,通过自适应律解决不确定项和升降舵故障。利用跟踪微分器解决“计算爆炸”问题,避免反步控制中对虚拟控制输入的高阶求导。最后,基于Lyapunov理论证明闭环系统的稳定性,并通过仿真验证所提控制策略的有效性。