Vision-based Stabilization of Nonholonomic Mobile Robots by Integrating Sliding-mode Control and Adaptive Approach

Vision-based pose stabilization of nonholonomic mobile robots has received extensive attention. At present, most of the solutions of the problem do not take the robot dynamics into account in the controller design, so that these controllers are difficult to realize satisfactory control in practical application. Besides, many of the approaches suffer from the initial speed and torque jump which are not practical in the real world. Considering the kinematics and dynamics, a two-stage visual controller for solving the stabilization problem of a mobile robot is presented, applying the integration of adaptive control, sliding-mode control, and neural dynamics. In the first stage, an adaptive kinematic stabilization controller utilized to generate the command of velocity is developed based on Lyapunov theory. In the second stage, adopting the sliding-mode control approach, a dynamic controller with a variable speed function used to reduce the chattering is designed, which is utilized to generate the command of torque to make the actual velocity of the mobile robot asymptotically reach the desired velocity. Furthermore, to handle the speed and torque jump problems, the neural dynamics model is integrated into the above mentioned controllers. The stability of the proposed control system is analyzed by using Lyapunov theory. Finally, the simulation of the control law is implemented in perturbed case, and the results show that the control scheme can solve the stabilization problem effectively. The proposed control law can solve the speed and torque jump problems, overcome external disturbances, and provide a new solution for the vision-based stabilization of the mobile robot.

Fixed-Time Sliding Mode Control With Varying Exponent Coefficient for Modular Reconfigurable Flight Arrays

The modular system can change its physical structure by self-assembly and self-disassembly between modules to dynamically adapt to task and environmental requirements. Recognizing the adaptive capability of modular systems, we introduce a modular reconfigurable flight array(MRFA) to pursue a multifunction aircraft fitting for diverse tasks and requirements,and investigate the attitude control and the control allocation problem by using the modular reconfigurable flight array as a platform. First, considering the variable and irregular topological configuration of the modular array, a center-of-mass-independent flight array dynamics model is proposed to allow control allocation under over-actuated situations. Secondly, in order to meet the stable, fast and accurate attitude tracking performance of the MRFA, a fixed-time convergent sliding mode controller with state-dependent variable exponent coefficients is proposed to ensure fast convergence rate both away from and near the system equilibrium point without encountering the singularity. It is shown that the controller also has fixed-time convergent characteristics even in the presence of external disturbances. Finally,simulation results are provided to demonstrate the effectiveness of the proposed modeling and control strategies.

基于终端滑模的F-16固定翼飞行器有限时间编队控制

以F-16固定翼飞行器为研究对象,采用终端滑模控制方法,实现了六自由度固定翼飞行器的有限时间编队控制。首先,根据奇异摄动理论,将固定翼飞行器十二阶微分运动方程按照响应速度快慢分为外环位置编队控制系统和内环姿态跟踪控制系统。外环应用有限时间稳定性理论和非线性滑模控制方法设计了分布式控制器,实现多固定翼飞行器系统的有限时间编队控制。然后,将外环分布式控制器产生的控制信号转换为内环单架固定翼飞行器的姿态跟踪参考信号,内环应用非线性动态逆(nonlinear dynamic inversion,NDI)控制和增量非线性动态逆(incremental nonlinear dynamic inversion,INDI)控制在可能存在执行器故障的情况下实现单架固定翼飞行器姿态的跟踪控制。最后,通过仿真实例验证了该控制方法的有效性。

大攻角条件下制导弹滚转稳定控制方法

制导弹跨域飞行过程中,伴随着大攻角下的涡流非对称以及跨音速气动转捩,这些干扰将引起控制失稳,进一步增大脱靶量。针对以上问题,考虑气动模型强非线性、强参数不确定性及强外界干扰,建立制导弹滚转通道动力学模型,进而提出一种基于滑模观测器与非奇异终端滑模的滚转姿态组合控制方法。以此为基础框架,结合微分跟踪器设计一种反步控制方法,以补偿执行机构动力学。利用Lyapunov稳定性理论证明了闭环系统稳定性及有限时间收敛特性。通过仿真实验验证了所设计控制方法的优越性及普适性。

动态事件触发机制下的无人艇无模型控制

针对复杂海洋环境下无人艇的轨迹跟踪控制问题,本文结合滑模变结构控制与自适应控制,设计了无模型控制器,基于此提出了动态事件触发机制,利用Lyapunov稳定性判据证明了闭环系统一致最终有界,且不存在Zeno现象。仿真试验结果表明:在模型参数未知情况下,所提控制器具有良好的控制性能,可有效降低执行机构和能源消耗,为无人艇轨迹控制的实际应用提供了有效基础。

串联机械臂分布式电液伺服运动系统稳定性控制方法研究

串联机械臂分布式电液伺服系统是部件高度耦合的复杂控制系统,针对其高负荷大功率状态下运动稳定性能下降的问题,在串联机械臂分布式电液伺服系统结构和动力学分析基础上,构建了分布式电液伺服系统的运动控制模型,利用扩展劳斯稳定性判据构造了串联机械臂的运动稳定性判据,进而充分地分析了串联机械臂运动失稳的影响因素,采用滑模控制策略优化串联机械臂分布式电液伺服系统的运动稳定性能,在模块化实验环境中验证了控制方法的可靠性和有效性,通过对实验结果的分析,所设计的滑模控制方法能够快速有效提升串联机械臂分布式电液伺服系统运动稳定性能。

An impact angle constraint integral sliding mode guidance law for maneuvering targets interception

An integral sliding mode guidance law(ISMGL)combined with the advantages of the integral sliding mode control(SMC)method is designed to address maneuvering target interception problems with impact angle constraints.The relative motion equation of the missile and the target considering the impact angle constraint is established in the longitudinal plane,and an integral sliding mode surface is constructed.The proposed guidance law resolves the existence of a steady-state error problem in the traditional SMC.Such a guidance law ensures that the missile hits the target with an ideal impact angle in finite time and the missile is kept highly robust throughout the interception process.By adopting the dynamic surface control method,the ISMGL is designed considering the impact angle constraints and the autopilot dynamic characteristics.According to the Lyapunov stability theorem,all states of the closed-loop system are finally proven to be uniformly bounded.Simulation results are compared with the general sliding mode guidance law and the trajectory shaping guidance law,and the findings verify the effectiveness and superiority of the ISMGL.

Research on the attitude regulation of 3-DOF hover system

Quadrotor helicopter is emerging as a popular platform for unmanned aerial vehicle re- search, due to its simplicity of structure and maintenance as well as the capability of hovering and vertical take-off and landing. The attitude controller is an important feature of quadrotor helicopter since it allows the vehicle to keep balance and perform the desired maneuver. In this paper, nonlin- ear control strategies including active disturbance rejection control （ADRC）, sliding mode control （SMC） and backstepping method are studied and implemented to stabilize the attitude of a 3-DOF hover system. ADRC is an error-driven control law, with extended state observer （ESO） estimating the unmodeled inner dynamics and external disturbance to dynamically compensate their impacts. Meanwhile; both backstepping technique and SMC are developed based on the mathematical model, whose stability is ensured by Lyapunov global stability theorem. Furthermore, the performance of each control algorithm is evaluated by experiments. The results validate effectiveness of the strate- gies for attitude regulation. Finally, the respective characteristics of the three controllers are high- lighted by-comparison, and conclusions are drawn on the basis of the theoretical and experimental a- nalysis.

Position Control of Flexible Joint Carts Using Adaptive Generalized Dynamics Inversion

This paper presents the design and implementation of Adaptive Generalized Dynamic Inversion(AGDI)to track the position of a Linear Flexible Joint Cart(LFJC)system along with vibration suppression of the flexible joint.The proposed AGDI control law will be comprised of two control elements.The baseline(continuous)control law is based on principle of conventional GDI approach and is established by prescribing the constraint dynamics of controlled state variables that reflect the control objectives.The control law is realized by inverting the prescribed dynamics using dynamically scaledMoore-Penrose generalized inversion.To boost the robust attributes against system nonlinearities,parametric uncertainties and external perturbations,a discontinuous control law will be augmented which is based on the concept of sliding mode principle.In discontinuous control law,the sliding mode gain is made adaptive in order to achieve improved tracking performance and chattering reduction.The closed-loop stability of resultant control law is established by introducing a positive define Lyapunov candidate function such that semi-global asymptotic attitude tracking of LFJC system is guaranteed.Rigorous computer simulations followed by experimental investigation will be performed on Quanser’s LFJC system to authenticate the feasibility of proposed control approach for its application to real world problems.

Robust backstepping global integral terminal sliding mode controller to enhance dynamic stability of hybrid AC/DC microgrids

In this paper,a Backstepping Global Integral Terminal Sliding Mode Controller(BGITSMC)with the view to enhancing the dynamic stability of a hybrid AC/DC microgrid has been presented.The proposed approach controls the switch-ing signals of the inverter,interlinking the DC-bus with the AC-bus in an AC/DC microgrid for a seamless interface and regulation of the output power of renewable energy sources(Solar Photovoltaic unit,PMSG-based wind farm),and Battery Energy Storage System.The proposed control approach guarantees the dynamic stability of a hybrid AC/DC microgrid by regulating the associated states of the microgrid system to their intended values.The dynamic stabil-ity of the microgrid system with the proposed control law has been proved using the Control Lyapunov Function.A simulation analysis was performed on a test hybrid AC/DC microgrid system to demonstrate the performance of the proposed control strategy in terms of maintaining power balance while the system’s operating point changed.Furthermore,the superiority of the proposed approach has been demonstrated by comparing its performance with the existing Sliding Mode Control(SMC)approach for a hybrid AC/DC microgrid.

移动机器人编队的神经网络滑模控制

针对非完整移动机器人编队控制问题,基于领航者-跟随者l-ψ控制结构,提出了一种运动学控制器与自适应神经滑模控制器相结合的新型控制策略。采用径向基神经网络(radial basis function neural network,RBFNN)对跟随者及领航者动力学非线性不确定部分进行在线估计,并通过自适应鲁棒控制器对神经网络建模误差进行补偿。实验结果表明所提方法不但解决了移动机器人编队控制的参数与非参数不确定性问题,还确保了机器人编队在期望队形下对指定轨迹的跟踪;基于Lyapunov方法的设计过程,保证了控制系统的稳定。

基于滑模观测器的孤岛风柴混合电力系统SVC滑模补偿控制器设计

针对独立风柴混合电力系统中风能和无功负荷变化所引起的电压波动问题,提出了利用静止无功补偿器(static var compensator,SVC)稳定电压的控制策略。实际SVC存在模型参数不确定及状态变量不完全可测的问题,故利用滑模控制算法,设计基于鲁棒观测器的SVC附加滑模电压控制器。为此,首先建立孤岛情况下包含SVC的风柴混合电力系统的数学模型;然后选择适当的比例切换面和趋近律到达条件,并基于观测器估计值来构造SVC鲁棒电压控制器;最后基于Matlab仿真平台搭建算例模型,对所设计SVC滑模电压控制器的鲁棒性进行验证。仿真结果表明,所设计的SVC滑模电压控制器与传统的SVC控制策略相比,可有效抑制电压波动。

基于滑模位置控制的机器人灵巧手模糊自适应阻抗控制

提出一种基于滑模位置控制的模糊自适应阻抗控制策略。该控制方案通过模糊控制器实时地调整阻抗参数 ,不但可使系统稳定 ,而且具有良好的动态品质 ;同时内环的滑模位置控制器可增强系统的鲁棒性。最后以机器人灵巧手单关节为对象进行仿真研究 。

液压马达式汽车主动稳定杆系统建模与控制

以液压马达式主动稳定杆系统为研究对象,推导得到了液压马达式主动稳定杆的非线性动力学模型。利用线性化反馈的滑模控制方法设计了其控制器,并利用Lyapunov理论对控制系统的稳定性进行了证明。通过CarSim和MATLAB/Simulink对主动稳定杆系统进行了联合仿真,得出安装液压马达式主动稳定杆系统的车辆在双移线工况下运行的响应曲线。为了验证设计的控制方法,进行了实车试验。结果表明,与被动稳定杆相比,主动稳定杆系统具有较好的抗侧倾特性以及乘坐舒适性。

一种球形机器人的非线性滑模运动控制

基于非线性滑模控制方法,对一种欠驱动的球形机器人的运动控制问题进行了研究.球形机器人的输入由两个相互正交的力矩组成.在非完整约束的条件下,分别建立球形机器人的运动学和动力学模型,并通过输入变换将动力学模型变换为一个两输入的二阶系统.基于非线性滑模控制方法分别设计了横向姿态控制器和纵向速度控制器,可以保证被控的运动状态收敛到期望的邻域内.仿真和实验结果验证了所建立的动力学模型和控制方法的有效性.

车辆动力学稳定性系统变结构滑模控制研究

探讨了转弯车辆行驶在极限运动工况下时 ,依靠施加各车轮不同纵向制动力从而产生辅助横摆力矩来提高车辆动力学稳定性的基本原理。推导了两自由度车辆横向动力学方程 ,提出了车辆侧滑速度的 3种实时估计方案(积分法、代数法和 Luenberger观察器法 ) ,视实际车辆前后轮胎侧偏刚度为有界不确定性参数 ,为跟踪线性两自由度理想车辆模型的稳态输出响应 ,设计了车辆动力学稳定性变结构控制策略 。

基于控制分配的过驱动系统稳定性设计方法综述

过驱动系统是一类控制输入数多于输出数的系统,冗余控制为控制器的设计提供更大自由度的同时也提出挑战。控制分配是处理冗余控制的一种常用方法,同时对驱动器故障具有一定的容错能力。但是控制分配可能会导致系统不稳定,所以设计控制器时必须考虑这种不稳定因素的影响。基于控制分配的稳定性设计方法正是针对这种情况而提出。根据不同原理,这些方法可以概括为零动态方法,优化方法,内动态方法,滑模方法,模型预测方法和智能方法等。概括了这些方法的基本思路,并指出其不足之处,进一步提出新的研究方向。

基于滑模PID的飞行机械臂稳定性控制

机械臂与旋翼飞行器之间的耦合运动、系统自身的欠驱动特性以及外界的不确定干扰,都会影响旋翼飞行器的稳定性控制。为提高整个系统的飞行稳定性,考虑到波动输入信号和外界扰动的影响,该文建立了飞行机械臂的动力学模型,设计了一种基于滑模PID控制方法的指数趋近率控制器。与传统的PID控制方法相比,该方法不仅能够减弱外界不确定干扰的影响,准确快速地对飞行器进行姿态稳定,而且缩短了调节时间,增强了飞行器的自身稳定性和鲁棒性。

独立轮电驱动车辆主动操纵稳定控制研究

提出了采用变增益参考模型的滑模跟踪控制策略,以横摆角速度和侧滑速度为控制对象,独立控制左右轮驱动力产生直接横摆力矩,提高了车辆在极限工况下的操纵稳定性,并改善了车辆固有的转向特性。改进的滑模控制算法减小了系统抖振并具有较强的鲁棒性。

用滑动模态实现一类非完整动力学系统的指数镇定

对于基变量具有对称性的一类确定非完整动力学系统 ,直接基于该系统模型 ,利用滑动模态的方法设计了指数镇定控制器 ,得到了状态空间中的一个区域 .当系统初始状态位于该区域内时 ,系统状态是指数收敛的 ,而当初始状态不在该区域内时 ,可用非零的开环常值控制使系统状态在有限时间内进入这一区域 .因此 ,它是一种简洁的全局镇定律 .最后 。