基于Delaunay剖分的心内膜表面动态三维重建算法

心内膜表面三维重建技术在三维标测系统起着手术导航和靶点定位的作用。针对心内科手术中实时采集的散乱心内膜点云,提出了一种基于Delaunay剖分的表面动态三维重建算法。以CGAL非递归方式实现的逐点插入计算Delaunay剖分算法为基础,在剖分过程中,用关联采样点的伞局部替换原来表面中不满足Gabriel准则表面面片的集合,心内膜表面结构随着点云Delaunay剖分的变化而进行动态地更新。同时为了有效地表达心内膜表面及其点云的Delaunay剖分,并能够快速地索引四面体网格和表面三角面片,提出了一种以vtkDataArray为基础的几何数据结构。最后,实验表明该方法在重建结果和重建时间上可以满足心内科手术中的临床应用。     

Optimal 3D trajectory generation in delivering missions under urban constraints for a flying robot

Interest in applying flying robots especially quadcopters for civil applications, in particular for delivering purposes, has dramatically grown in the recent years. In fact, since quadcopters are capable of vertical takeoff and landing, they can be widely employed for nearly any aerial task where a human presence is hazardous or response time is critical. In this regard, quadcopters come to be very beneficial in delivering packages; accordingly, generating an optimal flight trajectory plays a preponderant role for meeting this vision. This paper is concerned with generation of a time-optimal 3D path for a quadcopter under municipal restrictions in delivering tasks. To this end, the flying robot’s dynamics is first modeled through Newton–Euler method. Subsequently, the problem is formulated as a time-optimal control problem such that the urban constraints, which are safe-margins of high-rise buildings located throughout the course, are first modeled and then imposed to the trajectory optimization problem as inequality constraints. After discretizing the trajectory by means of Hermit–Simpson method, the optimal control problem is transformed into a nonlinear programming problem and finally is solved by the direct collocation technique. Extensive simulations demonstrate the efficacy of the proposed method and correspondingly verify the effectiveness of the suggested method in generation of optimum 3D routes while all constraints and mission requirements are satisfied.     

一种用于机器人三维表面扫描系统的手眼标定算法

将线结构光测头安装在机器人末端,构成自由曲面非接触测量系统,利用齐次坐标变换理论建立测量系统的数学模型,针对该模型中的手眼标定问题,使用平面作为参考物,控制机器人以特定的位姿测量该平面,建立关于手眼关系的约束方程,并给出手眼参数的封闭解.通过对实际系统进行标定实验,验证了算法的有效性.     

A new trajectory control of a flexible-link robot based on a distributed-parameter dynamic model

The objective of this study is to develop a new trajectory-tracking control method, free from the so-called spillover instability, for a flexible-link robot. Based on a distributed-parameter dynamic model (a partial differential equation), a new moment-feedback trajectory-tracking control scheme is designed for a one-link flexible robot having a payload at the free end, in which zero geometric boundary conditions at the hub end and non-zero dynamic boundary conditions at the free end are taken into account. The proposed control is then extended to an adaptive scheme to cope with parametric uncertainties. The proposed control is stable for trajectory-tracking control and asymptotically stable at desired goal positions, which is proven by using the Lyapunov stability theorem. In addition, the proposed trajectory-tracking control, based on a distributed-parameter dynamic model, does not have the spillover problem. Furthermore, the control performance is guaranteed regardless of the magnitude of desired angle of rotation, which does not require any additional actuators such as piezoelectric actuators on the link and boundary force or moment actuators at the free end. The effectiveness of the proposed control has been shown by experiments.     

Automatic surface roughing with 3D machine vision and cooperative robot control

This paper presents an innovative and practical strategy for automated leather surface roughing, using structured light 3D machine vision for object profile perception, and NURBS interpolation for accurate and smooth trajectory generation. As high pressure grit blasting is used for roughing, considering the spacial constraints in the blasting chamber, an additional degree of freedom is introduced using a rotary table, which supports the workpiece. Cooperative control is implemented between a 6-DOF robot and the rotary table to minimize robot movements, while satisfying the requirements of variable velocity control, accurate trajectory tracking and orientation control. Experimental results of consistent roughing performance have shown the efficiency of the proposed method.     

基于VTK的三维点云曲面重建研究

针对三维点云数据重建效率低、不能实时交互等问题,利用鲁棒性强的Power Crust算法和三维可视化类库Visualization Toolkit (VTK)的良好并行机制与强大的图像处理能力,实现了三维点云数据曲面快速重建.该算法使用Power Crust对三维点云进行曲面重建,接着对得到的网格进行线性调整、简化和平滑,最后引入VTK进行渲染、绘制、显示,并实时交互.实验结果表明,该算法可以加快散乱点云数据的重建速度,较好地保持了点云数据的拓扑结构,提高了曲面重建的精确性和鲁棒性,且交互性强,适合实时处理.     

基于节能考虑的全向移动机器人鲁棒补偿轨迹跟踪控制

针对全向移动机器人在跟踪目标的过程中存在跟踪误差以及产生能量损耗的问题,首先构建一种新型机器人能耗模型,该模型能够有效预测机器人运行过程中各种能量消耗;其次,基于该能耗模型设置兼顾轨迹跟踪误差和能耗最小的性能指标函数,在其约束下,提出一种基于干扰鲁棒补偿的反馈节能控制器;然后,引入不确定性及干扰估计观测法,构建鲁棒补偿项,在满足能耗最优的前提下实现对外界干扰的有效抑制;最后,基于Lyapunov稳定性理论证明所提出的节能干扰鲁棒补偿控制系统是渐近稳定的.通过将所提出的控制器与比例微分控制器、$H_infty$控制以及节能补偿控制进行比较,仿真结果表明,所提出的控制方法其控制精度更高、能量损耗更低、具有更强的鲁棒性.     

基于轮廓线的旋转曲面三维重建

根据旋转曲面的几何特性,提出了一种基于单幅图像,采用轮廓线进行旋转曲面重建的方法.该方法通过获取旋转体的对称轴,并结合旋转体的边缘曲线及其特征点信息,实现了旋转曲面的三雏重建.实验结果表明,通过使用该方法可以根据旋转体的二维图像方便的重建出其三维形状.该方法在文物保护、考古、工业测量等领域具有很高的实用价值.     

轮式移动机器人固定时间轨迹跟踪控制

针对存在外部干扰的轮式移动机器人轨迹跟踪控制问题,提出一种固定时间轨迹跟踪控制方案.首先,对于轮式移动机器人的运动学误差模型,基于一种新颖的积分滑模面设计固定时间运动学速度控制器,使跟踪误差在固定时间收敛到原点所在的邻域内;其次,对于轮式移动机器人的动力学模型,设计固定时间干扰观测器对外部干扰信息进行估计,提出一种固定时间轨迹跟踪控制器,以确保动力学系统的固定时间稳定性,实现轮式移动机器人的高精度轨迹跟踪控制;最后,通过仿真结果验证所设计的轨迹跟踪控制方案的有效性.     

机器人末端臂轨迹跟踪自适应控制设计

本文提出了新颖的机器人末端臂轨迹跟踪自适应控制方法。该方法与已有的神经网络模型不同之处在于数据首先利用运动学反解求出机器人各关节旋转的角度,然后应用径向基函数自组织进行神经网络学习生成模糊规则,利用监督学习算法(SLA)、最小二乘法(LMS)、反向传播算法(BP)和聚类分析的方法在线优化控制规则以及隶属函数的参数。仿真结果表明,该方法不但规则生成的时间少,有效的防止了规则数爆炸,而且在机器人轨迹跟踪控制的应用中效果好。     

Linearized dynamic models for trajectory control of robot manipulators

To make an appropriate choice of linear model for the development of real-time control of robot manipulators, four direct linearization schemes have been studied here on the basis of computation and accuracy. Accuracy is assured in the state linearization method, whereas the rate linearization method leads to a satisfactory trade-off between computational effort and accuracy. In the case of high-velocity motions, a combination of state and rate linearization is proposed.     

A robust trajectory tracking control of a polishing robot system based on CAM data

Polishing a die that has free-form surfaces is a time-consuming and tedious job, and requires a considerable amount of high-precision skill. In order to reduce the polishing time and cope with the shortage of skilled workers, a user-friendly automatic polishing system was developed in this research. The polishing system is composed of two subsystems, a three-axis machining center and a two-axis polishing robot. The developed polishing system with five degrees of freedom is able to keep the polishing tool normal to the die surface during operation. A sliding mode control algorithm with velocity compensation is proposed to reduce tracking errors. Trajectory tracking experiments showed that the effect of reducing the tracking error by the proposed sliding mode control is superior to that by the proportional derivative control. The polishing data is generated from computer-aided design (CAD) data or from teaching data by PolyCAM, a computer-aided manufacturing (CAM) system consisting of 4 modules: a geometric modeller, a CAD data exchange module, a polishing data generation module, and a graphic simulator. To evaluate the performance of the polishing robot system, some polishing experiments on a shadow-mask die were performed.     

基于边界检测的三维散乱点快速曲面重建算法

针对Power Crust算法提出一种带边界检测的不均匀降采样算法。曲面重建前先通过该算法减少参与运算的采样点,表面特征丰富的区域削减的采样点数远小于特征不丰富的区域,再进行曲面重建。通过实例表明该算法大大加快了散乱点数据的重建速度,而且很好地保持了模型表面的特征,能够较为真实地重建出曲面模型。     

四轮移动机器人智能预瞄轨迹跟踪控制

针对后轮驱动四轮移动机器人存在非完整约束、模型复杂等特点,提出一种基于多预瞄点的轨迹跟踪混合控制算法。该算法设计从仿人驾车的角度出发,根据不同路况通过模糊控制在线调节机器人的速度、预瞄点个数和预瞄距离。采用免疫控制方法在线整定PID控制器的参数。从控制稳定性角度出发提出轨迹偏离度评价指标。仿真结果表明该控制器的有效性。     

基于模糊CMAC的移动机器人轨迹跟踪控制

针对受非完整约束的移动机器人的轨迹跟踪问题,提出了一种基于模糊CMAC的轨迹跟踪控制策略。该策略利用模糊CMAC神经网络逼近移动机器人动力学模型的非线性和不确定,同时与速度误差结合起来构成力矩控制器,并用滑模项来补偿不确定性扰动对系统的影响。李亚普诺夫稳定性定理保证了系统的稳定性和跟踪误差的渐近收敛,仿真结果进一步验证了所提方法的有效性。     

Inversion techniques for trajectory control of flexible robot arms

A general framework is given for computing the torques that are needed for moving a flexible arm exactly along a given trajectory. This torque computation requires a dynamic generator system, as opposed to the rigid case, and can be accomplished both in an open- or in a closed-loop fashion. In the open-loop case, the dynamic generator is the full or reduced order inverse system associated to the arm dynamics and outputs. In order to successfully invert the arm dynamics, the torque generator should be a stable system. The stability properties depend on the chosen system output, that is on the robot variables (e.g., joint or end-effector) to be controlled. The same inversion technique can be applied for closed-loop trajectory control of flexible robots. A simple but meaningful nonlinear dynamic model of a one-link flexible arm is used to illustrate different feasible control strategies. Simulation results are reported that display the effects of the system output choice on the closed-loop stability and on the overall tracking performance.     

A robot hand-eye calibration method of line laser sensor based on 3D reconstruction

In the robotic eye-in-hand measurement system, a hand-eye calibration method is essential. From the perspective of 3D reconstruction, this paper first analyzes the influence of the line laser sensor hand-eye calibration error on the 3D reconstructed point clouds error. Based on this, considering the influence of line laser sensor measurement errors and the need for high efficiency and convenience in robotic manufacturing systems, this paper proposes a 3D reconstruction-based robot line laser hand-eye calibration method. In this method, combined with the point cloud registration technique, the newly defined error-index more intuitively reflects the calibration result than traditional methods. To raise the performance of the calibration algorithm, a Particle Swarm Optimization - Gaussian Process (PSO-GP) method is adopted to improve the efficiency of the calibration. The experiments show that the Root Mean Square Error (RMSE) of the reconstructed point cloud can reach 0.1256 mm when using the proposed method, and the reprojection error is superior to those using traditional hand-eye calibration methods.