快速终端滑模控制在并联机器人中的应用

针对二自由度冗余驱动并联机器人,提出了并联机器人的快速终端滑模控制(FTSMC)以实现其鲁棒控制,并利用Lyapunov函数证明了该控制系统的稳定性。仿真结果表明,该控制系统跟踪效果好,系统误差小,可以满足并联机器人控制的要求。与采用普通滑模控制相比,该控制系统具有状态响应速度快,系统状态在有限时间内收敛到零的特点。仿真实验证实了该控制策略的正确性和有效性。     

考虑打滑干扰的解耦式主动脚轮全向移动机器人跟踪控制

基于解耦式主动脚轮的全向移动机器人系统，提出了一种考虑未知脚轮打滑的轨迹跟踪控制方法。建立了包含脚轮打滑情况的全向移动机器人运动学模型，利用附加传感器获得的冗余信息对滑动参数进行估计；根据反步法设计轨迹跟踪控制器，利用Lyapunov定理证明闭环系统的稳定性，并依据极点配置的方法实现控制参数的整定。仿真与实验结果表明：该控制方法能够使全向移动机器人在复杂室内地面稳定地跟踪设定轨迹。     

Learning from adaptive neural network output feedback control of a unicycle-type mobile robot

This paper studies learning from adaptive neural network (NN) output feedback control of nonholonomic unicycle-type mobile robots. The major difficulties are caused by the unknown robot system dynamics and the unmeasurable states. To overcome these difficulties, a new adaptive control scheme is proposed including designing a new adaptive NN output feedback controller and two high-gain observers. It is shown that the stability of the closed-loop robot system and the convergence of tracking errors are guaranteed. The unknown robot system dynamics can be approximated by radial basis function NNs. When repeating same or similar control tasks, the learned knowledge can be recalled and reused to achieve guaranteed stability and better control performance, thereby avoiding the tremendous repeated training process of NNs.     

Control design for one-sided Lipschitz nonlinear differential inclusions

This paper considers stabilization and signal tracking control for one-sided Lipschitz nonlinear differential inclusions (NDIs). Sufficient conditions for exponential stabilization for the closed-loop system are given based on linear matrix inequality theory. Further, the design method is extended to signal tracking control for one-sided Lipschitz NDIs. A control law is designed such that the state of the closed-loop system asymptotically tracks the reference signal. Finally, two numerical examples are given to illustrate the effectiveness of the proposed design technique.     

Sliding mode based trajectory linearization control for hypersonic reentry vehicle via extended disturbance observer

This paper proposes a novel hybrid control framework by combing observer-based sliding mode control (SMC) with trajectory linearization control (TLC) for hypersonic reentry vehicle (HRV) attitude tracking problem. First, fewer control consumption is achieved using nonlinear tracking differentiator (TD) in the attitude loop. Second, a novel SMC that employs extended disturbance observer (EDO) to counteract the effect of uncertainties using a new sliding surface which includes the estimation error is integrated to address the tracking error stabilization issues in the attitude and angular rate loop, respectively. In addition, new results associated with EDO are examined in terms of dynamic response and noise-tolerant performance, as well as estimation accuracy. The key feature of the proposed compound control approach is that chattering free tracking performance with high accuracy can be ensured for HRV in the presence of multiple uncertainties under control constraints. Based on finite time convergence stability theory, the stability of the resulting closed-loop system is well established. Also, comparisons and extensive simulation results are presented to demonstrate the effectiveness of the control strategy.     

Trajectory tracking for two-degree of freedom helicopter system using a controller-disturbance observer integrated design

Trajectory tracking control for helicopters, which are widely used in severe situations such as military and rescue missions, is a challenging field of research. In helicopter system, the stability problem and predefined trajectories tracking are main challenges, especially in the presence of external disturbances and dynamic model uncertainties. Hence, a robust control design is needed for tracking the desired references. There has been a lot of motivation for solving these problems with simpler methods and also reducing the couplings in the helicopter system to achieve better performance, as the presented paper attempts to fill these gaps. This paper focuses on designing control laws for two-degree of freedom helicopter system while assuring the closed-loop stability. A nonlinear disturbance observer-based control (NDOBC) is designed for attenuating the effects of exogenous disturbances. Trajectory tracking controller and nonlinear disturbance observer are formulated in the form of two linear matrix inequality (LMI) problems. The closed-loop system stability, including controller and observer, is investigated by Lyapunov theorem. The effectiveness of the proposed design for tracking the trajectories (vertical flight and pitch angle rotor blade) and disturbance estimation is verified by simulation results.     

复杂环境下磁弹性微型游泳机器人的路径规划与识别跟踪

磁弹性材料设计的毫米级微型游泳机器人可通过外部均匀磁场实现连续形变来完成游泳动作,通过视觉反馈能提高机器人的路径跟随精度,但在复杂背景下机器人的视觉闭环控制易发生识别错误、跟踪失败等现象。针对上述问题,首先获取复杂环境下的障碍物信息,提出改进RRT*算法(IIC-RRT*)进行路径规划,同时基于环形平滑标签的YOLOv5识别跟踪算法(CSL-YOLOv5),在复杂背景下对微型游泳机器人的中心位置与旋转角度进行实时更新。在此基础上进行微型游泳机器人在障碍物复杂背景下的位置与角度的双闭环伺服控制,试验结果表明,提出的路径规划算法改善了路径生成的效率与平滑性,识别跟踪算法提高了微型游泳机器人的识别稳定性与精确性,为磁控微型游泳机器人在复杂背景下的精确控制提供了新思路。     

面向不平地面的双足欠驱动步行稳定控制

为实现双足机器人在不平地面上的欠驱动步行,提出一种基于质心运动状态的稳定步行控制策略。考虑地面柔性,使用柔性接触模型描述“机器人足部地面”柔性接触,并通过解耦建模的方式建立了“机器人地面”前向与侧向耦合动力学模型。根据人类变速步行特征,提出基于机器人质心速度控制的步行控制策略,将三维步行解耦为前向和侧向的主从控制,通过控制质心位移实现质心速度控制,进而实现稳定步行。搭建三维欠驱动双足步行机器人样机,在地面高度变化不大于0.032 m的不平地面上成功实现了平均步行速度0.216 m/s、步幅为0.31倍腿长的欠驱动步行。试验结果表明,所提控制策略可通过质心速度控制来实现不平地面上的欠驱动稳定步行。     

轮式移动机器人路径跟踪控制方法研究

针对轮式移动机器人的路径跟踪问题,提出了一种基于动态预瞄的移动机器人路径跟踪控制方法。根据差速轮式移动机器人运动学模型和实时位置信息,建立路径跟踪偏差模型,并采用构建虚拟运动路径的方式设计移动机器人路径跟踪控制方法,结合路径跟踪偏差模型,实时调整移动机器人的运动状态,不断缩小运动过程中的偏差,最终实现路径跟踪。实验结果表明,所设计的移动机器人路径跟踪控制方法能够实现高精度的路径跟踪控制,同时具有良好的可靠性,平稳性。     

机械臂任务空间鲁棒Terminal滑模控制

不确定性和外部干扰是制约机器人控制精度的主要因素,传统Terminal滑模控制方法未能考虑机械臂运动学不确定性。提出一种新的机械臂任务空间鲁棒连续非奇异Terminal滑模跟踪控制方法。该方法具有较强的鲁棒性,能够有效克服运动学不确定性、动力学不确定性和外部干扰,保证机械臂任务空间跟踪误差有限时间稳定,将现有机械臂Terminal滑模控制方法从关节空间扩展到任务空间。通过模型转换,同时考虑机械臂运动学不确定性和动力学模型不确定性。使用矢量和矩阵范数定义,给出系统不确定性的界定方法。运用Lyapunov再设计方法和有界稳定理论,分析系统稳定性,明确给出系统调节时间和跟踪误差剩余集的估计方法。仿真中,通过与现有机械臂关节空间Terminal滑模跟踪控制方法比较,验证了所提方法的有效性。     

Robust observer-based absolute stabilization for Lur’e singularly perturbed systems with state delay

This paper is concerned with the problem of robust observer-based absolute stabilization for Lur’e singularly perturbed time-delay systems. The aim is to design a suitable observer-based feedback control law such that the resulting closed-loop system is absolutely stable. First, a full-order state observer is constructed. Based on the linear matrix inequality (LMI) technique, a delay-dependent sufficient condition is presented such that the observer error system is absolutely stable. Then, for observer-based feedback control, by introducing some slack matrices, a sufficient condition for input-to-state stability (ISS) of the closed-loop system with regard to the observer error is presented. Thus, the absolute stabilization of the closed-loop system can be guaranteed based on the ISS property. In addition, the criteria presented are both independent of the small parameter and the upper bound for the absolute stability can be obtained in a workable algorithm. Finally, two numerical examples are provided to illustrate the effectiveness of the developed methods.     

Recurrent fuzzy neural network backstepping control for the prescribed output tracking performance of nonlinear dynamic systems

This paper proposes a backstepping control system that uses a tracking error constraint and recurrent fuzzy neural networks (RFNNs) to achieve a prescribed tracking performance for a strict-feedback nonlinear dynamic system. A new constraint variable was defined to generate the virtual control that forces the tracking error to fall within prescribed boundaries. An adaptive RFNN was also used to obtain the required improvement on the approximation performances in order to avoid calculating the explosive number of terms generated by the recursive steps of traditional backstepping control. The boundedness and convergence of the closed-loop system was confirmed based on the Lyapunov stability theory. The prescribed performance of the proposed control scheme was validated by using it to control the prescribed error of a nonlinear system and a robot manipulator.     

非协调移动机器人的变结构跟踪控制

研究非协调移动机器人系统的跟踪问题。根据反演设计的方法 ,针对双后轮驱动移动机器人的运动学模型 ,设计变结构跟踪控制方案 ,使闭环跟踪系统渐近稳定。对双后轮驱动机器人的仿真证实了控制器的鲁棒跟踪能力     

自由浮动冗余度空间机器人的姿态稳定控制

研究了自由浮动冗余度空间机器人的姿态稳定控制问题。针对自由浮动空间机器人姿态稳定控制的主要特点,通过分析自由浮动冗余度空间机械臂惯性矩阵的伪逆和零空间特性,结合空间机器人的运动学方程推导出了基于本体姿态稳定的广义雅可比矩阵。采用基于该矩阵的分解运动速度控制方法,保证机械臂末端执行器在跟踪期望轨迹的同时不对本体姿态产生干扰。最后,对平面三自由度空间机器人进行了仿真实验,实验结果表明了该方法的有效性。     

Multi-channel control system design for a robot manipulator based on the time-scale method

The problem of controller design for nonlinear multi-channel dynamical plants is discussed. Trajectory motion tracking control for a multilink manipulator is treated as an example of the proposed design methodology. A distinctive feature of the discussed approach to calculate controller parameters is that two-time-scale motions are artificially forced in a closed-loop system where stability of the fast mode is provided by selection of the controller parameters while the induced slow mode correspond to the reference model of desired nonlinear plant behavior. Simulation results for a two-link manipulator robot manipulator tracking control system are presented..     

Vibration suppression of speed-controlled robots with nonlinear control

In this paper, a simple nonlinear control strategy for the simultaneous position tracking and vibration damping of robots is presented. The control is developed for devices actuated by speed-controlled servo drives. The conditions for the asymptotic stability of the closed-loop system are derived by ensuring its passivity. The capability of achieving improved trajectory tracking and vibration suppression is shown through experimental tests conducted on a three-axis Cartesian robot. The control is aimed to be compatible with most industrial applications given the simplicity of implementation, the reduced computational requirements, and the use of joint position as the only measured signal.     

Model-based feedforward precompensation and VS-type robust nonlinear postcompensation for uncertain robotic systems with/without knowledge of uncertainty bounds (II)

In this paper, the robust nonlinear controller for an uncertain robot system is developed and characterized with a unified method. Based on deterministic approach, the control structure consists of two parts: In the first part, the primary control law is synthesized to precompensate for the nominal system; and in the second part the adaptive version of robust controllers are utilized to postcompensate for the system uncertainties. The uncertainties assumed in this papar are bounded by higher-order polynomials in the Euclidean norms of system states without knowledge of bounding coefficients. Using the Lyapunov stability theory, we can guarantee that all possible responses of the closed-loop system are at least uniformly and ultimately bounded. The tracking properties of the control algorithms are verified through numerical simulations, and the results show that the proposed controllers are proven to be robust enough for any higher-order system uncertainty.     

非时间参考的类车机器人定点跟踪控制

针对移动机器人控制研究中的小车速度与加速度饱和限制现象,提出了非时间参考的定点跟踪控制方法。选择随时间单调递增的非时间变量为转向控制律变量,摆脱了移动机器人速度与加速度对控制律的时域限制。在Simulink中建立控制逻辑并进行了单目标点与多目标点连续跟踪仿真。单目标点跟踪仿真结果表明,对于任意初始状态机器人,提出的定点跟踪控制方法均能使小车到达目标状态。多目标点连续跟踪结果表明,可将定点跟踪控制策略应用于类车机器人的路径跟踪控制。     

Super-twisting sliding mode differentiation for improving PD controllers performance of second order systems

Designing a proportional derivative (PD) controller has as main problem, to obtain the derivative of the output error signal when it is contaminated with high frequency noises. To overcome this disadvantage, the supertwisting algorithm (STA) is applied in closed-loop with a PD structure for multi-input multi-output (MIMO) second order nonlinear systems. The stability conditions were analyzed in terms of a strict non-smooth Lyapunov function and the solution of Riccati equations. A set of numerical test was designed to show the advantages of implementing PD controllers that used STA as a robust exact differentiator. The first numerical example showed the stabilization of an inverted pendulum. The second example was designed to solve the tracking problem of a two-link robot manipulator.     

输入受限无人帆船自适应航向跟踪控制

针对带有输入受限且存在未知控制系数约束情形下,考虑了具有未知模型和风、浪等外界干扰的无人船航向跟踪控制问题,提出一种受限控制输入约束下的跟踪控制方法。该方法运用RBF神经网络对未知模型进行在线逼近,利用Nussbaum自适应增益技术解决未知控制系数问题。根据滑模控制理论,设计具有指数趋近律的鲁棒控制项,保证所得误差闭环系统快速响应且最终趋向0。为弱化传统滑模控制产生的抖振问题,将符号函数替换成饱和函数使控制输入变得平滑。引入一种误差辅助系统,构建了帮助误差闭环系统输入退出饱和机制。通过李雅普诺夫稳定性理论,给出了跟踪控制方法的稳定性数学分析过程,证明误差闭环跟踪控制系统的所有信号最终一致有界性。最后通过仿真结果验证了所得理论的有效性。