基于智能优化算法的Pendubot轨迹规划与控制方法设计

以垂直Pendubot为研究对象,提出一种基于智能优化算法的轨迹规划与控制方法,以解决Pendubot控制过程中难以从摇起区过渡至平衡区的问题.为Pendubot的驱动连杆规划一条从初始角度到中间角度的正向轨迹和一条从中间角度到目标角度的反向轨迹.欠驱动连杆在系统耦合关系作用下进行运动,对应的Pendubot末端点也运动至相应位置.通过遗传算法优化轨迹参数,将正向和反向轨迹拼合为一条由初始角度到目标角度的驱动连杆轨迹的同时,对应的Pendubot末端点轨迹拼合为一条由垂直向下平衡位置到垂直向上平衡位置的完整轨迹,然后设计跟踪控制器跟踪优化后的驱动连杆轨迹至目标角度,由于耦合关系的存在,Pendubot末端点也运动至垂直向上平衡位置.由于Pendubot受重力作用,其末端点很难长时间稳定在垂直向上平衡位置,故设计镇定控制器,实现Pendubot末端点在垂直向上平衡位置的镇定控制.最后通过仿真实验验证所提出方法的有效性,并通过对比说明所提出方法在奇异点规避、控制器设计和控制效果方面的优势.     

Acrobot控制器设计与全局稳定性分析

提出一种基于非光滑 Lyapunov 函数的 Acrobot 控制器设计和全局稳定性分析方法. 基于三个 Lyapunov 函数分别设计了三种控制规律, 用来增加 Acrobot 的能量和保持合适的姿态, 使 Acrobot 摇起并稳定在垂直向上的不稳定平衡点. 应用 LaSalle 不变原理和非光滑 Lyapunov 函数理论, 保证了 Acrobot 在整个运动空间的全局稳定性. 仿真结果证明了该方法的有效性.     

基于能量的Acrobot动态伺服控制

研究了Acrobot垂直平面欠驱动机械臂的动态伺服控制问题.动态伺服控制不同于定点控制和轨迹跟踪控制,而是利用欠驱动系统中存在的周期轨道特性,实现对轨迹的动态跟踪.首先通过对比单摆运动规律寻找到周期轨道所满足的条件;然后利用Lyapunov稳定性理论设计反馈控制律,并给出控制律存在的一系列条件;最后分析了系统中存在的奇点及其对收敛性的影响.仿真实验表明了所设计的控制器是有效的.     

基于能量的 Acrobot动态伺服控制

研究了 Acrobot 垂直平面欠驱动机械臂的动态伺服控制问题. 动态伺服控制不同于定点控制和轨迹跟踪控制,而是利用欠驱动系统中存在的周期轨道特性,实现对轨迹的动态跟踪 .首先通过对比单摆运动规律寻找到周期轨道所满足的条件;然后利用 Lyapunov稳定性理论设计反馈控制律,并给出控制律存在的一系列条件;最后分析了系统中存在的奇点及其对收敛性的影响.仿真实验表明了所设计的控制器是有效的.

     

Acrobot动态伺服控制及其对称虚约束方法研究

研究了Acrobot这一垂直平面欠驱动机械臂的动态伺服控制问题. 该问题期望驱动Acrobot到达构形空间中任意目标位置. 由于Acrobot不能稳定在除平衡点外的位置, 因此考虑将系统镇定到经过目标点的周期轨道上. 利用虚约束来描述这样的轨道, 进而给出了在所选虚约束作用下系统的零动态和积分曲线. 接着设计了级联形式的控制器, 内环控制器基于改进的反馈线性化方法, 引入了一个使内环呈现二阶系统特性的虚拟输入, 在该虚拟输入的基础上, 设计了基于Lyapunov稳定性理论的外环控制器. 最后通过数字仿真证明所提出的方法合理有效, 并且获得比基于能量的动态伺服方法更优的结果.     

基于线性矩阵不等式的Acrobot鲁棒镇定控制

针对欠驱动机器人Acrobot,提出一种基于线性矩阵不等式的鲁棒镇定控制方法。通过将Acrobot在垂直向上不稳定平衡点附近的第一杆角速度看作一种不确定性,得到Acrobot的不确定模型,在此基础上设计一种基于线性矩阵不等式的鲁棒镇定状态反馈控制律,实现Acrobot较大范围的平衡控制。仿真和对比结果验证了方法的有效性和优越性。     

基于T-S模型的体操机器人系统模糊变结构控制

针对体操机器人（Acrobot）这类非线性系统，给出一种基于T—S模型的模糊变结构控制律设计．首先采用T—S模型建模,得到Acrobot的全局模糊模型;然后基于Lyapunov理论设计出保证Acrobot全局渐近稳定的模糊变结构平衡控制器．仿真结果表明，所设计的模糊变结构控制器与普通变结构控制器相比．可使Acrobot系统在垂直向上平衡点附近具有更大的吸引域和更强的鲁棒性．     

针对串联弹性驱动器抖动抑制的轨迹规划和跟踪控制

针对串联弹性驱动器（Series elastic actuator,SEA）的位置控制问题,本文提出了一种"规划+控制"的策略.首先根据连杆端运动学约束方程,基于数字滤波器对电机位置进行轨迹规划;为了使电机能够准确跟踪期望轨迹,根据电机端的动力学模型设计位置跟踪控制器.理论分析证明了规划的抖动抑制作用和跟踪控制系统的稳定性,随后的实验结果也表明了这种"规划+控制"方法在使连杆到达期望位置的前提下,能够有效地抑制残余抖动.     

双连杆刚柔机械臂无残余振动位置控制

针对双连杆刚柔机械臂,提出一种基于轨迹规划的无残余振动位置控制方法,在将机械臂的末端执行器从任意初始位置移动到目标位置的同时,确保系统没有残余振动产生.首先,建立系统的动力学模型,并通过分析该模型得到系统的状态约束方程.其次,基于状态约束方程,运用双向轨迹规划方法规划一条系统前向轨迹和一条系统反向轨迹.然后,利用时间倒转方法及基于遗传算法的轨迹优化方法对两条轨迹进行拼合,得到一条从系统初始状态到目标状态的期望轨迹.最后,设计轨迹跟踪控制器使系统沿期望轨迹到达目标状态,实现系统的无残余振动位置控制目标.仿真结果验证了本文所提方法的有效性.     

基于三步法的机械臂轨迹跟踪控制

考虑机械臂末端轨迹跟踪控制问题,以跟踪逆运动学求解出的末端期望轨迹对应的各关节期望角度为控制目标.设计了一种基于三步法的控制器,该控制器由类稳态控制、可变参考前馈控制和误差反馈控制3部分组成.证明了该控制器可以通过控制机械臂的各关节力矩实现各关节实际角度对期望角度的状态跟踪,进而使得末端轨迹渐近跟踪期望轨迹,并且跟踪误差是输入到状态稳定的.仿真表明基于三步法控制器的空间机械臂末端可以渐近跟踪期望轨迹,并且该算法可以克服系统的末端负载质量变化等不确定性的影响.     

Motion planning and tracking control for an acrobot based on a rewinding approach

This paper concerns motion planning and tracking control for an acrobot. We first introduce an artificial friction torque in order to construct a downward trajectory, and rewind it to make an upward trajectory. Then, we combine the upward trajectory with a stabilizing trajectory to make a complete trajectory. Finally, we use the pole assignment method to design a tracking controller that makes the acrobot exponentially track the whole trajectory. This enables the acrobot to be swung up from the straight-down position and stabilized at the straight-up position. Unlike the most commonly used switching stabilization control methods, the strategy presented here features a single controller for motion control in the whole motion space. It is simple and efficient. Simulation results demonstrate the validity of the method.     

Advanced LMI based analysis and design for Acrobot walking

This article aims to further improve previously developed design for Acrobot walking based on partial exact feedback linearisation of order 3. Namely, such an exact system transformation leads to an almost linear system where error dynamics along trajectory to be tracked is a 4-dimensional linear time-varying system having three time-varying entries only, the remaining entries being either zero or one. In such a way, exponentially stable tracking can be obtained by quadratically stabilising a linear system with polytopic uncertainty. The current improvement is based on applying linear matrix inequalities (LMI) methods to solve this problem numerically. This careful analysis significantly improves previously known approaches. Numerical simulations of Acrobot walking based on the above-mentioned LMI design are demonstrated as well.     

Aggressive Longitudinal Aircraft Path Tracking Using Nonlinear Control

We study the problem of converting a trajectory tracking controller to a path tracking controller for a nonlinear non-minimum phase longitudinal aircraft model. The solution of the trajectory tracking problem is based on the requirement that the aircraft follows a given time parameterized trajectory in inertial frame. In this paper we introduce an alternative nonlinear control design approach called path tracking control. The path tracking approach is based on designing a nonlinear state feedback controller that maintains a desired speed along a desired path with closed loop stability. This design approach is different from the trajectory tracking approach where aircraft speed and position are regulated along the desired path. The path tracking controller regulates the position errors transverse to the desired path but it does not regulate the position error along the desired path. First, a trajectory tracking controller, consisting of feedforward and static state feedback, is designed to guarantee uniform asymptotic trajectory tracking. The feedforward is determined by solving a stable noncausal inversion problem. Constant feedback gains are determined based on LQR with singular perturbation approach. A path tracking controller is then obtained from the trajectory tracking controller by introducing a suitable state projection.     

一种基于Multi-Egocentric视频运动轨迹重建的多目标跟踪算法

Egocentric视频具有目标运动剧烈、遮挡频繁、目标尺度差异明显及视角时变性强的特点，给目标跟踪任务造成了极大的困难。本文从重建不同视角Egocentric视频中各目标的运动轨迹出发，提出一种基于Multi-Egocentric视频运动轨迹重建的多目标跟踪算法，该方法基于多视角同步帧之间的单应性约束解决目标遮挡和丢失问题，然后根据多视角目标空间位置约束关系通过轨迹重建进一步优化目标定位，并采用卡尔曼滤波构建目标运动模型优化目标运动轨迹，在BJMOT、EPLF-campus4数据集上的对比实验验证了本文算法在解决Multi-Egocentric视频多目标跟踪轨迹不连续问题的有效性。     

Transverse function control with prescribed performance guarantees for underactuated marine surface vehicles

This paper studies the problem of stabilizing reference trajectories (also called as the trajectory tracking problem) for underactuated marine vehicles under predefined tracking error constraints. The boundary functions of the predefined constraints are asymmetric and time‐varying. The time‐varying boundary functions allow us to quantify prescribed performance of tracking errors on both transient and steady‐state stages. To overcome difficulties raised by underactuation and nonzero off‐diagonal terms in the system matrices, we develop a novel transverse function control approach to introduce an additional control input in backstepping procedure. This approach provides practical stabilization of any smooth reference trajectory, whether this trajectory is feasible or not. By practical stabilization, we mean that the tracking errors of vehicle position and orientation converge to a small neighborhood of zero. With the introduction of an error transformation function, we construct an inverse‐hyperbolic‐tangent‐like barrier Lyapunov function to show practical stability of the closed‐loop systems with prescribed transient and steady‐state performances. To deal with unmodeled dynamic uncertainties and external disturbances, we employ neural network (NN) approximators to estimate uncertain dynamics and present disturbance observers to estimate unknown disturbances. Subsequently, we develop adaptive control, based on NN approximators and disturbance estimates, that guarantees the prescribed performance of tracking errors during the transient stage of on‐line NN weight adaptations and disturbance estimates. Simulation results show the performance of the proposed tracking control.     

Analysis of the energy‐based swing‐up control of the Acrobot

This paper addresses the energy‐based swing‐up control problem for the Acrobot, a two‐link underactuated robot with a single actuator at the joint of the two links. In line with the energy‐based control approach, this paper presents a necessary and sufficient condition for non‐existence of any singular point in the derived control law, and provides a complete analysis of the convergence of the energy and the motion of the Acrobot. Specifically, for any initial state of the Acrobot, this paper shows clearly how to choose control parameters such that the Acrobot will eventually either be swung up to any arbitrarily small neighbourhood of the upright equilibrium point, or remain in a set containing a finite number of equilibrium points. Moreover, this paper shows that these equilibrium points are unstable. Furthermore, imposing a stronger condition on a control parameter yields that the equilibrium set contains only the downward equilibrium point, which is shown to be hyperbolic and unstable. This proves that the Acrobot will eventually enter the basin of attraction of any stabilizing controller for all initial conditions with the exception of a set of Lebesgue measure zero. Copyright © 2007 John Wiley & Sons, Ltd.     

Design of motion trajectory and tracking control for underactuated cart‐pendulum system

A cart‐pendulum system is a nonlinear underactuated mechanical system with two degrees of freedom. This paper addresses the motion trajectory design and tracking control problems for this underactuated system. First, a friction‐like control law is designed for the system. Then, the characteristics of the closed‐loop control system are analyzed. Second, a new method of constructing an optimal trajectory for the system is developed. Then, a tracking control law is designed to quickly track the constructed trajectory. It guarantees that the motion control of the cart‐pendulum system is achieved along a reference trajectory. Finally, a numerical example is presented to demonstrate the effectiveness of the theoretical results. This study constructs an optimal trajectory for the cart‐pendulum system in its whole motion space and solves the motion control objective by tracking the constructed trajectory. It has many advantages compared with other motion control methods, eg, the optimal motion control objective of the system is achieved by a single control law; and the motion process and transient characteristics (eg, the settling time) of the control system can be accurately predicted.     

The posture control of a two-link free flying acrobot with initial angular momentum

This note studies the posture control problem of a two-link free flying Acrobot with nonzero initial angular momentum, where the control objective is to design an acceleration based control law such that the robot can pass through a desired posture at a given time. Based on the previous results, this posture control problem can be tackled by solving the problem of stabilizing the origin of a system obtained via an appropriate coordinate transformation. The main contribution of this note is to provide a control scheme which globally asymptotically stabilizes the origin of the system. The numerical simulations are given to validate the provided theoretical results.     

Tracking control for an object in pushing operation

In this paper, we consider the problem of making a manipulator push an object on a flat floor with a point of contact to a desired position. A manipulator control method for the object to follow a planned trajectory is proposed. First, using the given distribution of frictional forces between the object and the floor, we find a particular point, named pseudo center, on which the motion of the pushed object can be approximated by the motion of a wheeled mobile robot on its center. Then, a control rule for the pushing operation is derived by applying a tracking control rule for a nonholonomic mobile robot at the pseudo center. This method makes it possible for the robot to perform the tracking control in the pushing operation. A simulation result shows the effectiveness of the proposed method. Finally, we present an approach for using a mobile manipulator to realize the pushing operation. Experimental verification of the proposed method was performed and the result is described. ©1997 John Wiley & Sons, Inc.