Singular Perturbation Model of Robots with Elastic Joints and Elastic Links Constrained by Rigid Environment

A robot with distributed flexibility in the links and lumped flexibility in the joints is considered in this paper. First the model of the system in free motion is formulated as a set of ordinary differential equations, adopting a finite number of modes of the link deformation. Then algebraic constraint equations on the generalized coordinates of the system are added, to account for the loss of degrees of freedom due to the contact with rigid environment. A reduced order model, expressed in the residual degrees of freedom is then derived, based on a coordinate partitioning procedure. The singularly perturbed model of the system is finally computed, and the expression of the fast subsystem is given. The special cases of a robot with rigid joints or rigid links are also addressed.     

基于神经网络与粒子滤波的柔性臂控制方法研究

基于奇异摄动法将单连杆柔性臂系统分解为慢变、快变子系统,采用混合控制方法;设计了基于粒子滤波的神经网络控制器来线性化慢子系统,使其跟踪期望轨迹;采用粒子滤波训练神经网络克服了BP算法收敛速度慢、易陷入局部极小值的缺陷,及扩展卡尔曼滤波方法带来的模型线性化损失;对于快变系统采用最优控制方法;仿真结果表明:在神经网络训练误差收敛速度及精度方面,粒子滤波要比BP及卡尔曼滤波要好;组合控制方法能有效地抑制柔性臂弹性振动,轨迹跟踪迅速准确,精度方面也是前者最优。     

Contact Conditions for Cylindrical,Prismatic, and Screw Joints in Flexible Multibody Systems

This paper focuses on the modeling of the contact conditionsassociated with cylindrical, prismatic, and screw joints in flexiblemultibody systems. In the classical formulation these joints aredeveloped for rigid bodies, and kinematic constraints are enforcedbetween the kinematic variables of the two bodies. These constraintsexpress the conditions for relative translation and rotation of the twobodies along and about a body-fixed axis, and imply the relative slidingand rotation of the two bodies which remain in constant contact witheach other. However, these kinematic constraints no longer implyrelative sliding with contact when one of the bodies is flexible. Toremedy this situation, a sliding joint and a sliding screwjoint are proposed that involves kinematic constraints at theinstantaneous point of contact between the sliding bodies. For slidingscrew joints, additional constraints are added on the relative rotationof the contacting bodies. Various numerical examples are presented thatdemonstrate the dramatically different behavior of cylindrical,prismatic, or screw joints and of the proposed sliding and sliding screwjoints in the presence of elastic bodies, and the usefulness of theseconstraint elements in the modeling of complex mechanical systems.     

考虑关节柔性的模块机器人动力学参数辨识

提出了一种基于3维运动测量系统Optotrak3020的柔性关节模块机器人动力学模型参数辨识方法.首先将机器人的动力学模型参数化为不包括刚度力矩的线性形式,避免了参数矩阵的标定问题.激励轨迹基于有限的傅里叶级数函数,采用自适应遗传算法得出了优化的傅里叶级数系数.机器人每一关节单独跟随优化激励轨迹进行运动,同时电机位置、...     

A Geometric Calibration Methodology for Single-Head Cone-Beam X-Ray Systems

During X-ray based quality inspection, accurate reconstruction of a 3D object model from a set of its 2D X-ray projections requires efficient geometric calibration, i.e., accurate estimation of the geometric parameters of the setup. We present a calibration methodology for the estimation of the geometric parameters of single-head cone-beam X-ray radiography systems. Our method is related to known approaches regarding camera calibration and geometric calibration of tomography/radiography systems, but performs better in terms of computational efficiency.     

激光线扫式形貌测量机器人的标定研究

为能够高效、高精度的获取大型自由曲面物体的形貌,研究了基于通用工业机器人和激光线扫描传感器的测量方法.论述了激光线扫式形貌测量系统的原理与结构,利用标准球及优化算法实现了机器人和激光扫描传感器位姿关系的精确解算,并针对机器人运动学误差对系统测量影响较大,通过对机器人运动学参数的修正有效减小了机器人的绝对定位误差.实验和分析结果表明,经标定和运动学参数校正后的测量系统对标准球的测量能达到较高精度,为采集高精度三维点云提供了保证.     

机器人柔性视觉检测系统现场标定技术

针对江淮车身厂的轿车车身提出了一种基于工业机器人的柔性视觉检测系统．通过控制机器人在空间的位姿变换,立体视觉传感器能够依次到达空间指定测量位置采集空间特征点的图像信息,并通过计算图像数据获得该点的三维坐标数据．利用双经纬仪和精密靶标对机器人视觉测量系统进行整体标定,同时完成了测试试验数据的采集及计算,取得了较好的测量效果．该系统柔性好、测量无死角,能适应生产线多车型检测的需要．     

On the Robust Nonlinear Motion Position and Force Control of Flexible Joints Robot Manipulators

The design of a robust nonlinear position and force controller for a flexible joints robot manipulator interacting with a rigid environment is presented. The controller is designed using the concept of feedback linearization, sliding mode techniques, and LQE estimation methodologies. It is shown that the nonlinear robot manipulator model is feedback linearizable. A robust performance of the proposed control approach is achieved by accounting for the system parameters uncertainties in the derivation of the nonlinear control law. An upper bound of the error introduced by parametric uncertainties in the system is computed. Then, the feedback linearizing control law is modified by adding a switching action to compensate the errors and to guarantee the achievement of the desired tracking performance. The relationship between the minimum achievable boundary layer thickness and the parametric uncertainties is derived. The proposed controller is tested using an experimental flexible joints robot manipulator, and the results demonstrate its potential benefits in reducing the number of sensors required and the complexity of the design. This is achieved by eliminating the need for nonlinear observers. A robust performance is obtained with minimum control effort by taking into account the effect of system parameter uncertainties and measurement noise.     

轴不对准角在挠性陀螺组合静态误差标定中的应用

陀螺组合的安装误差会引起陀螺漂移,从而对惯导系统产生影响。从挠性陀螺组合安装误差模型入手,推导出存在轴不对准角情况下的挠性陀螺组合静态误差标定模型,并给出静态误差标定的位置试验方案。提出的标定方案可以有效标定陀螺组合静态误差系数,从而减少陀螺漂移。     

一种基于点对的相机几何标定方法

提出了一种基于点对的几何标定方法,用于标定相机外部参数．该方法考虑点对而不是单个点与相机的几何关系．首先根据三个标定点对计算旋转矩阵且不需要任何点对的精确三维信息．然后根据相机和一个点对的几何关系计算平移且只需这个点对的相对位置是已知的．整个标定过程不需要任何点对的绝对位置信息．试验结果表明了该方法的有效性．     

Observer-Based Optimal Control of Flexible Stewart Parallel Robots

The design and simulation of two optimal control schemes for a parallel flexible link manipulator of the Stewart type is presented. The first control scheme combines a nonlinear rigid model of the flexible manipulator with a linear rigid observer, whereas the second scheme uses a nonlinear flexible manipulator model with a linear flexible observer. The majority of the results available in the literature do not address the optimal control problem through the use of observers, as it is done in this paper, for the control of parallel robots. The simulation results have shown in both cases that indeed optimal state-obscrver-based control is a good candidate for controlling parallel-link manipulators in practice. As expected, the second scheme (flexible model plus flexible observer) gives better results than the first one, achieving faster trajectory tracking. The effects of white noises, applied forces, and zero gravity environment were taken under consideration.     

Active Vibration Control of Flexible Robots Using Virtual Spring-damper Systems

When using robots for heavy loads and huge operating ranges, elastic deformations of the links have to be taken into account during modeling and controller design. Whereas for conventional rigid multilink industrial robots modeling can schematically be done by standard techniques, it is a massive problem to obtain an accurate analytic model for multilink flexible robots. But an accurate analytic model is essential for most modern controller design techniques, and modeling errors can lead to instability of the controlled system due to spillover since the eigenvalues of the system are only slightly damped. A new approach to active damping control for flexible robots is presented in this paper where the actuators act like virtual spring-damper-systems. As the spring-damper-element is a passive energy dissipative device, it will never destabilize the system and thus the control concept will be very insensitive to modeling errors. Basically, the two parameters, spring stiffness and damping constant of this system, are arbitrary and model independent. To satisfy performance requirements they are adjusted using knowledge of the system model. The more it is known about the system model, the better these parameters may be adjusted. The new input of the controlled system is a virtual variation of the spring base. The paper illustrates this technique with the help of a simple and easy to model one link flexible robot which is also available as a real laboratory testbed.     

基于几何方法的摄像机内外参数求解

根据摄像机透视投影模型的几何意义,从几何角度推导了由投影矩阵求解摄像机内外参数的过程以及任意矩阵能够成为透视投影变换描述的约束条件。     

一般7R串联机器人标定的仿真与实验

为了标定一般7R冗余度串联机器人的所有几何参数,提出了一种实效的算法．首先,使用D-H矩阵对机器人建立了运动学模型和几何参数识别模型,对雅可比矩阵进行奇异值分解并对分解后的正交阵的最后5行进行初等行变换,以确定需要补偿的几何参数．通过机器人关节角和末端手爪位置的测量数据,计算雅可比矩阵以及手爪位置理论值和实测值的误差,采用最小二乘法对机器人的尺寸参数进行补偿量的计算．仿真过程表明,在有测量扰动的情况下,算法是稳定的和可靠的．最后,对机器人进行了实际的测量和标定,取得了满意的结果．     

Modelling and Model Fitting of Flexible Robots – a Multibody System Toolkit Approach

During the last decade robots with flexible links became a popular research object for control engineers. This is because of their sophisticated properties referring to feedback control, e.g., non-minimum phase behaviour in end-effector control. Massive problems already occur trying to obtain an accurate analytic model for multilink flexible robots. This paper presents an effective way for numerical modelling of multilink flexible robots using the multibody system toolkit MBILE. The experimental model fitting to a laboratory test bed of a two-link flexible robot is documented.     

基于单幅透视图像确定相机参数的几何方法

提出一种求解相机内、外参数的几何方法．在不考虑相机镜头变形的前提下，首先根据空间平面上的单个矩形，从该矩形的两灭点透视图中，根据灭点间的几何关系，补出另外一个灭点的坐标；然后根据透视投影的灭点理论，计算出相机的相对位置；若已知矩形边的实际长度，可以恢复出相机在三维空间中的实际位置和矩形顶点的空间坐标；最后根据透视投影关系计算出相机的有效焦距．大量的模拟和真实实验表明，该方法简单、易于操作，具有标定精度高、鲁棒性强的优点．     

单向ad-hoc移动网络优化路由协议OUAOR

ad-hoc移动网络是一种完全由移动主机构成的网络,该文基于作者设计的单向ad-hoc移动网络路由协议UAOR,提出了优化受限查找,双向链路感知和按需维护的单向路由协议OUAOR。和UAOR相比,OUAOR具有路由查找和维护控制开销小,网络扩展性高,路由查找的初始延迟低等特点。该文证明了OUAOR协议的正确性,并给出了模拟实验分析数据。     

关节臂式坐标测量机标定系统的设计

关节臂式坐标测量机是一种新型的多自由度非笛卡尔式坐标测量系统,提出了一种基于反转法的标定方法,该方法避免了其他参数误差对于标定结果的影响。研制了相应的标定装置,装置的控制系统采用上位机加下位机结构,由单片机完成标定装置的控制并将测量数据通过串口通讯上传到PC机;PC机程序由虚拟仪器开发平台LabVIEW完成,实现与单片机间的通信和指令处理。实验表明,该系统能够很好地完成关节臂式测量机的标定任务,运动精度高,测量结构具有较好的重复性。     

瞬态表面温度传感器动态校准及误差补偿研究

测量瞬态高温时,由于传感器自身的热惯性,测量结果与真实结果之间存在很大的动态误差。动态补偿对于改善测温系统动态特性,减小动态误差有重要意义。该文首先熟悉现有的瞬态表面温度传感器动态校准系统;然后,利用系统所测得输人输出数据,采用系统辨识方法建立了测温系统的动态数学模型,并利用交叉检验法验证该模型的正确性;最后,利用反滤波动态补偿方法实现对瞬态表面温度传感器测温系统的动态补偿。经检验该方法可以达到理想的补偿效果,减小了动态误差,改善了系统的动态特性。     

Identical Projective Geometric Properties of Central Catadioptric Line Images and Sphere Images with Applications to Calibration

Central catadioptric cameras are imaging devices that use mirrors to enhance the field of view while preserving a single effective viewpoint. Lines and spheres in space are all projected into conics in the central catadioptric image planes, and such conics are called line images and sphere images, respectively. We discovered that there exists an imaginary conic in the central catadioptric image planes, defined as the modified image of the absolute conic (MIAC), and by utilizing the MIAC, the novel identical projective geometric properties of line images and sphere images may be exploited: Each line image or each sphere image is double-contact with the MIAC, which is an analogy of the discovery in pinhole camera that the image of the absolute conic (IAC) is double-contact with sphere images. Note that the IAC also exists in the central catadioptric image plane, but it does not have the double-contact properties with line images or sphere images. This is the main reason to propose the MIAC. From these geometric properties with the MIAC, two linear calibration methods for central catadioptric cameras using sphere images as well as using line images are proposed in the same framework. Note that there are many linear approaches to central catadioptric camera calibration using line images. It seems that to use the properties that line images are tangent to the MIAC only leads to an alternative geometric construction for calibration. However, for sphere images, there are only some nonlinear calibration methods in literature. Therefore, to propose linear methods for sphere images may be the main contribution of this paper. Our new algorithms have been tested in extensive experiments with respect to noise sensitivity.