欠驱动两足步行机器人研究现状

针对欠驱动两足步行机器人的研究现状与发展趋势进行了探讨。首先,总结了被动行走和踝关节欠驱动两足机器人的研究现状,介绍了欠驱动两足步行机器人的基本研究方法,包括问题描述、步态规划、运动控制和稳定性判定等,并对欠驱动两足机器人需要进一步研究的问题和发展方向进行深入研究,最终目标是将欠驱动控制策略应用于两足步行机器人的行走过程控制,以提高其运动性能。     

A Differentially Flat Open-Chain Space Robot with Arbitrarily Oriented Joint Axes and Two Momentum Wheels at the Base

The motion of a free-floating space robot is characterized by the principle of conservation of angular momentum. It is well known that these angular momentum equations are nonholonomic, i.e., are nonintegrable rate equations. If the base of the free-floating robot is partially actuated, it is difficult to determine joint trajectories that will result in point-to-point motion of the entire robot system in its configuration space. However, if the drift-less system associated with the angular momentum conservation equations is differentially flat, point-to-point maneuvers of the free-floating robot in its configuration space can be constructed by properly choosing trajectories in the differentially flat space. The primary advantages of this approach is that it avoids the use of nonlinear programming (NLP) to solve the nonintegrable rate equations, which at best can provide only approximate solutions. A currently open research problem is how to design a differentially flat space robot with under-actuated base. The contributions of this technical note are as follows: i) study systematically the structure of the nonholonomic rate constraint equations of a free-floating open-chain space robot with two momentum wheels at the base and arbitrarily oriented joint axes; ii) identify a set of sufficient conditions on the inertia distribution under which the system exhibits differential flatness; iii) exploit these design conditions for point-to-point trajectory planning and control of the space robot.     

基于遗传算法的欠驱动机器人运动规划

研究了平面欠驱动机器人的非完整运动规划问题,建立欠驱动机器人系统动力学模型,提出了一种利用遗传算法(GA)解决欠驱动机器人运动规划的方法。引入部分稳定控制器的思想,提出基于能量最优的评价函数,利用遗传算法对评价函数进行离线优化,得到有关部分稳定控制器的切换规则。此方法可以推广到任意平面欠驱动机器人的规划问题上,以平面3R欠驱动机器人为研究对象进行了数值仿真,仿真结果验证了该方法的有效性。     

Translational Planar Cable-Direct-Driven Robots

A planar cable-direct-driven robot (CDDR) architecture is introduced with only translational freedoms. The motivation behind this work is to improve the serious cable interference problem with existing CDDRs and to avoid configurations where negative cable tensions are required to exert general forces on the environment and during dynamic motions. These problems generally arise for rotational CDDR motions. Thus, we propose a class of purely translational CDDRs; of course, these are not general but may only perform tasks where no rotational motion or resistance of moments is required at the end-effector. This article includes kinematics and statics modeling, determination of the statics workspace (the space wherein all possible Cartesian forces may be exerted with only positive cable tensions), plus a dynamics model and simulated control for planar translational CDDRs. Examples are presented to demonstrate simulated control including feedback linearization of the 4-cable CDDR (with two degrees of actuation redundancy) performing a Cartesian task. We introduce an on-line dynamic minimum torque estimation algorithm to ensure all cable tensions remain positive for all motion; otherwise slack cables result from the CDDR dynamics and control is lost.     

欠驱动多指节机器人手的仿真实现

欠驱动多指节机器人手具有较复杂的非线性运动方程组以及运动过程的阶段性,公用Ｓｉｍｕｌｉｎｋ仿真系统一般很难实现这种机器人手的动态仿真为此提出用Ｍａｔｌａｂ语言编写的Ｍ－文件与Ｓｉｍｕｌｉｎｋ的仿真系统之间的合理组合,实现多指节手的动态仿真过程。文中用于欠驱动多指节机器人手的动态仿真模型能够发映手指操作的起初过程,并能简化仿真系统的复杂性,这为多指节手的运动、受力分析以及机构、控制设计等提供了有效工     

欠驱动两关节平面机械手的控制

欠驱动平面机械手是带有非完整约束的高度非线性系统,对其进行有效的控制仍然是个难点热点问题。针对最具代表性的两关节情形,给出了欠驱动两关节平面机械手的动力学方程,据此分析了该系统的可积性、线性化、稳定性、可控性和可反馈镇定性。根据控制目标的不同,将控制任务分为镇定到流形、镇定到单个平衡点和跟踪时变信号3种。针对这3种控制任务,分别回顾了各种已有的控制方式,仔细分析了它们的优点和有待改进的地方。最后探索了欠驱动平面机械手的研究中需要解决的几个关键问题,指出未来的可能研究方向。     

Universal Practical Tracking Control of a Planar Underactuated Vehicle

In this article, a universal controller is proposed for a planar underactuated vehicle to track arbitrary trajectories including feasible/non‐feasible ones and fixed points. The controller design relies on several coordinate/input transformations, auxiliary trajectory design and the back‐stepping technique. The stability analysis shows that the position and orientation tracking errors are uniformly globally practically asymptotically convergent (UGPAC), and the velocity tracking errors are uniformly globally asymptotically convergent (UGAC) to a ball of origin. Moreover, if the tracked target is in uniform rectilinear motion or motionless, the whole closed‐loop tracking error system is uniformly globally practically asymptotically stable (UGPAS). The effectiveness of proposed control law is verified by simulation examples.     

Planar Cable-Direct-Driven Robots: Design for Wrench Exertion

Cable-direct-driven robots and haptic interfaces are appealing because of their structural simplicity, high stiffness, and high exerted wrench-to-weight ratio. A major drawback is that cables can only exert tension. Therefore, actuation redundancy is required to apply general wrenches (force/moment vectors). Even with actuation redundancy, not all desired wrenches can be applied in some configurations due to one or more negative cable forces required. In addition, cable interference can be a serious problem for these devices. The objective of this article is to present the best design for planar cable-direct-driven robots and/or haptic interfaces with one degree of actuation redundancy, with regard to general wrench exertion and cable interference. Results indicate that the cable interference constraint dominates which suggests the need for future design work to alleviate this interference.     

Hybrid Force and Vision-Based Contour Following of Planar Robots

Manipulators interacted with uncalibrated environments have limited dexterity due to constraints imposed by unknown environments. However, to perform science or industrial operations, it is necessary to be able to position and orient these manipulators on targets in order to accomplish required control tasks. This article describes how one might enhance manipulator dexterity for planar contour following tasks using hybrid force and vision-based control. The proposed control approach can guarantee task precision employing only a single-axis force sensor and an imprecisely calibrated CCD camera whose optical axis is perpendicular to the planar workspace. The goal of the autonomous task is to drive an instrument mounted on the end-effector of a planar robotic manipulator to follow a visually determined planar contour and continue tracking the contour in desired pose, contact force, and speed, all demanding time-varying, with precision. The proposed control architecture is suitable for applications that require simultaneous force and pose control in unknown environments. Our approach is successfully validated in a real task environment by performing experiments with an industrial robotic manipulator.     

基于模型降阶的平面三连杆欠驱动机械系统位置控制

针对第一关节为被动的平面三连杆欠驱动机械系统,提出一种基于模型降阶的位置控制方法. 首先,建立平面三连杆欠驱动系统数学模型,并分析其积分特性;其次,将部分可积的三连杆系统分段降阶为两个完全可积的两连杆子系统,并基于两子系统获得系统驱动杆与欠驱动杆之间的状态约束关系;然后,利用粒子群优化算法,根据系统末端点目标位置计算驱动杆目标角度;最后,分别设计两连杆子系统控制器,实现系统从任意初始位置到任意目标位置的控制目标. 仿真结果验证所提控制策略的有效性.     

Waypoint Following for Differentially Driven Wheeled Robots with Limited Velocity Perturbations

In this paper a unified motion control strategy dedicated for the waypoint following task realized by a differentially driven robot is presented. It is assumed that the vehicle moves with limited velocities and accelerations in order to reduce excessive slip and skid effects. In order to include operational constraints, a motion planner is combined with a universal stabilizer taking advantage of transverse functions. To improve tracking precision translated transverse functions are deployed and a new adaptive technique for the controller tuning is proposed. During the motion planning stage an auxiliary trajectory connecting points in the configuration space and satisfying assumed phase constraints is generated. The resulting motion execution system has been implemented on a laboratory-scale skid-steering mobile robot, which served as platform for experimental validation of presented algorithms.     

Flat Dry Elastomer Adhesives as Attachment Materials for Climbing Robots

In this paper, flat elastomers are proposed as an attachment material for climbing robots on less than a few micrometer-scale rough surfaces due to their energy-efficient, quiet, and residue-free characteristics. The proper elastomer is chosen by the use of the current adhesion, friction, and peeling elastomer-contact-mechanics models. Then, adhesion and friction properties of the chosen dry flat-elastomer thick films (Vytaflex-10) are characterized on acrylic and smooth and rough glass surfaces for variations in preloads, speeds, contact times, and elastomer thicknesses. A climbing robot with four-bar-based legged-body kinematics is designed and fabricated as simple and lightweight as possible to demonstrate the feasibility of the elastomers as attachment materials on relatively smooth surfaces. The robot utilizes a passive alignment system to make the footpads parallel to the surface on light contact, a peeling mechanism to minimize the detachment vibration, and a passive tail to minimize the pitch-back moment. Experimental results showed that the robot can climb stably on vertical, smooth surfaces in any direction and can walk inverted for a limited amount of time.      

Planar Translational Cable‐Direct‐Driven Robots

We present the simulated dynamics and control of a planar, translational cable‐directdriven robot (CDDR). The motivation behind this work is to improve the serious cable interference problem with existing CDDRs and to avoid configurations where negative cable tensions are required to exert general forces and moments on the environment and during dynamic motions. Generally for CDDRs the commanded rotations are more demanding than commanded translations in terms of slack cable conditions. Therefore we propose a translational CDDR whose end‐effector may be fitted with a traditional serial wrist mechanism to provide rotational freedom (assuming proper design to resist the moments). Only the translational CDDR is considered in this article, including kinematics and statics modeling, statics workspace (wherein all possible Cartesian forces and moments may be exerted with only positive cable tensions), plus a dynamics model and simulated control for planar CDDRs. Here we focus only on planar CDDRs, to clearly demonstrate our dynamics and control work; we will extend this work to spatial CDDRs in the future. Examples are presented to demonstrate simulated control including feedback linearization of the four‐cable CDDR (with one degree of actuation redundancy) performing a Cartesian task. An on‐line dynamic minimum torque estimation algorithm is introduced to ensure all cable tensions remain positive for all motion; otherwise slack cables can result from CDDR dynamics and control is lost. © 2003 Wiley Periodicals, Inc.     

Virtual Model Reduction-based Control Strategy of Planar Three-link Underactuated Manipulator with Middle Passive Joint

This paper presents a position control strategy for a planar active-passive-active (APA) underactuated manipulator with second-order nonholonomic characteristics. According to the structural characteristics of the planar APA system, we divide the system into two parts: a planar virtual Pendubot (PVP) and a planar virtual Acrobot (PVA). For the PVP, we mainly fulfill the target angle of the first link, which is calculated through the geometry method, and make the system stable. In this stage, via keeping the states of the third link being zero, the system is reduced to the PVP. Meanwhile, we design an open-loop control law based on the nilpotent approximation (NA) model of the PVP to make the second link stable and the first link stabilize at its target angle. Then, the planar APA system is reduced to a PVA with all links’ angular velocities being zero. For the PVA, we mainly realize the other two links’ target angles obtained via the particle swarm optimization (PSO) algorithm. Thus, the control objective of the planar APA system is achieved. Finally, above control strategy is verified by simulation results.

     

Chaos-PSO-based Motion Planning and Accurate Tracking for Position-posture Control of a Planar Underactuated Manipulator with Disturbance

Unlike a fully-actuated manipulator, the position-posture control of a planar underactuated manipulator (PUM) is more difficult, but the research on it is significant due to the wide practical applications. The existing control methods consider no external disturbance and are involved in the staged control idea, bringing the problems of nonsmooth control torque and time-consuming. A novel one-stage control approach is proposed in this paper for the position-posture control of a three-link PUM with the first free joint under the external disturbance. By analyzing the coupling relationship between its active joints and free joint, the position-posture control is transformed into the trajectory tracking control. Unlike the general trajectory planning, the trajectories of the active joints are planned to include several parameters. Meanwhile, the parameters are solved using a chaos particle swarm optimization algorithm to guarantee that all joint angles can reach to their desired angles. Then, to obtain the high trajectory tracking accuracy at every moment under the external disturbance, the nonlinear disturbance observer is constructed and a nonlinear fast terminal sliding mode tracking controller is designed. Finally, the feasibility and superiority of this strategy are verified via two simulations.

     

Coverage of a Planar Point Set With Multiple Robots Subject to Geometric Constraints

This paper focuses on the assignment of N discrete points among K geometrically constrained robots and determination of the order in which the points should be processed by the robots. This path planning problem is directly motivated by an industrial laser drilling system with two robots that are constrained to translate along a common line while satisfying collision avoidance constraints. The points lie on a planar base plate that translates normal to the axis of motion of the robots. The geometric constraints on the motions of the robots lead to constraints on points that can be processed simultaneously.We use a two step approach to solve the path planning problem: (1) Splitting Problem: Assign the points to the K robots, subject to geometric constraints, to maximize parallel processing of the points. (2) Ordering Problem: Find an order of processing the split points by formulating and solving a multidimensional Traveling Salesman Problem (TSP) in the if-tuple space with an appropriately defined metric to minimize the total travel cost. For K = 2, we solve the splitting problem optimally in O(N³) time by converting it to a maximum cardinality matching problem. Since this is too slow for large datasets, we also provide a greedy O(N log N) algorithm. We provide computational results showing that the greedy algorithm solution is very close to the optimal solution for large datasets. For the ordering problem we present local search based heuristics to improve the multidimensional TSP tour. We give computational results for the ordering problem and for the overall performance gain obtained (over a single robot system) by using our algorithm. Finally, we extend our approach to a K-robot system and give computational results for K = 4.     

公路设计中平、纵、横联合视图的编程及应用

针对常用公路 CAD 软件中路线平、纵、横成果只能独立显示，无法联合查询的问题，提出了实现平、纵、横成果联合显示、查询的编程思路，并介绍了该程序在设计中的应用，以期为提高设计工作效率提供更好的解决方案。     

微型ICP激发源微电路组件的参数设计

本文简要介绍了一种采用微结构平面螺旋线圈的新的ICP(电感耦合等离子体)光谱激发源.作者设计加工出的基于PCB(印刷电路板)镀金工艺的微型ICP激发源在13.56MHz下成功启燃,并给出了ICP火炬照片.详细介绍了作者研制的微型ICP激发源的平面螺旋电感和交指电容的参数设计方法,给出了设计版图和实物照片,微结构线条宽度和间隙在数百微米量级.展望了平面螺旋电感和交指电容在微型ICP激发源的中的应用前景.     

Dynamic Feedback Control of XYnR̄ Planar Robots with n Rotational Passive Joints

We consider the problem of trajectory planning and control for an XYnR? Planar robot with the first two joints (rotational or prismatic) actuated and n rotational passive joints, moving both in the presence and the absence of gravity. Under the assumption that each passive link is attached at the center of percussion of the previous passive link, dynamics of the system can be expressed through the behavior of n special points of the plane. These points are called link‐related acceleration points (LRAP) since their instantaneous acceleration is oriented as the axis of the related passive links. Moreover, LRAP dynamics present a backward recursive form which can be exploited to recursively design a dynamic feedback that completely linearizes the system equations. We use this approach to solve trajectory planning and tracking problems and report simulation results obtained for an RR2R? robot having the first two rotational joints actuated. © 2003 Wiley Periodicals, Inc.