Time and freestyle piling: a subjective approach to 3D printing

This paper considers the influence of 3D printers on the temporality and subjectivity of making by looking at current 3D printing processes through the concept of ‘duration’ that was theorized by the philosopher Henri Bergson. The discussion is contextualized within technological developments at the turn of the twentieth century—specifically, European railways—that changed our perception of time. The foundational ideas of duration are introduced as a response to these developments. The contemporary technological concept of ‘real-time computing’ is presented to contrast with duration and set up an in-depth explanation of the delays inherent to the 3D printing process. These delays are discussed within the discourse of 3D printing and technological innovation, in general. Current maker-3D printer interactions are then critiqued. Finally, an alternative method of 3D printing concrete that is founded on working with its inherent delays is introduced, along with its implications for digital making and the act of making time.     

Vision-based Control of a Delta Parallel Robot via Linear Camera-Space Manipulation

One of the open problems to control a parallel robot in real-time is the larger number of parameters to be incorporated in the control model when compared to serial robots. This paper presents an innovative vision-based method to control a delta-type parallel robot based on Linear Camera-Space Manipulation. The proposed method is a simple and robust technique capable of achieving real-time control of robots without relying on the calibration of either the robot or the environment parameters. To document the robustness of this technique, a sensitivity analysis was performed in simulation where the effect of two sources of error on the end-point positioning are considered. Such sources are the variability of each link’s parameters, and the uncertainty of the visual measurements. Experimental results on a Clavel’s delta parallel robot show that end-point positioning errors obtained with Linear Camera-Space Manipulation are less than 1.5 mm, demonstrating a low sensitivity to parameter uncertainty in qualitative agreement with the simulation results. The results show that the developed approach is advantageous to control parallel robots for industrial applications in real-time and can obviate to a number of open problems common with the control of parallel robots.     

打印参数可变模式下3D打印批调度问题研究

研究打印参数可变模式下3D打印批调度问题,旨在对打印任务随机到达的3D打印服务系统进行优化建模.考虑到工作台尺寸的限制以及打印参数层高对打印质量的影响,论文以各个任务队列长度作为系统联合状态,以任务组合以及打印参数层高作为系统的联合控制变量,以提高生产率、减少打印质量损失、节约电能为综合目标,将优化问题描述为半马尔科夫决策过程(SMDP),以便采用策略迭代算法、Q学习等算法求解系统最优调度策略.仿真结果表明,与层高参数固定模式以及先到先服务(FCFS)模式相比,本文求解的批调度策略能够有效提高生产性能.     

基于层次化联结CPG模型的蛇形机器人3维步态控制

联结CPG(connectionist central pattern generator,CCPG)模型适于控制机器人生成步态,但是传统的CCPG模型无法很好地生成3维步态.为此,本文根据生物学原理,提出了一个改进的神经元模型和一个改进的层次化CCPG(hierarchical CCPG,HCCPG)模型.HCCPG模型能够生成相位协调的多自由度运动控制信号,从而解决了传统CCPG模型的步态生成问题.基于该模型,提出了一个统一方法来生成机器人的2维、3维步态.对转弯步态的特性进行了系统化深入分析,以便更好地利用该步态来适应狭窄的弯道环境.本文提出的HCCPG模型以及得到的步态特性,有助于提高机器人的环境适应能力.     

一种具有三维运动能力的蛇形机器人的研究

分析了生物蛇的3种典型运动模式,介绍了研制出的具有三维运动能力的蛇形机器人,实现了生物蛇的3种典型运动模式．     

基于三维线性倒立摆的双足机器人步态规划

双足机器人的步态控制策略是保证双足稳定行走的重要条件之一.提出一种基于三维线性倒立摆模型的双足机器人步态规划的算法.首先简化了三维倒立摆模型,并且假设了步行周期起始状态的ZMP位置,然后通过运动方程推导出含参数的质心与时间的函数,再将机器人的步态规划简化到每个步行周期,通过每个周期的初始条件获得函数的相关参数,最后将此方法推广到带转向的步态规划中,并应用于实际Robocup3D比赛中.实验结果表明该方法具有可行性和有效性.     

Slice coherence in a query-based architecture for 3D heterogeneous printing

We report on 3D printing of artifacts with a structured, inhomogeneous interior. The interior is decomposed into cells defined by a 3D Voronoi diagram and their sites. When printing such objects, most slices the printer deposits are topologically the same and change only locally in the interior. The slicing algorithm capitalizes on this coherence and minimizes print head moves that do not deposit material. This approach has been implemented on a client/server architecture that computes the slices on the geometry side. The slices are printed by fused deposition, and are communicated upon demand.     

A visual simulation technique for 3D printing

Rapid prototyping technologies can create the physical part directly from the digital model by accumulating layers of a given material. Providing a tremendous flexibility of a part geometry that they can fabricate, these technologies present an opportunity for the creation of new products that cannot be made with existing technologies. One of its capabilities is to fabricate surface texture, which denotes a set of tiny repetitive geometric features on an object surface. In this paper we propose a visual simulation technique involving development of an intermediate geometric model of the surface texture design prior to fabricating the physical model. Careful examination of the visually simulated model before the actual fabrication can help minimize unwanted design iterations. The proposed technique demonstrated visualization capability by comparing the virtual model with the physical model for several test cases.     

基于激光扫描的移动机器人3D室外环境实时建模

针对室外非结构化3D环境,研究了基于激光扫描的移动机器人实时地形建模问题.考虑了建模过程中可能存在的多源不确定性误差,将其建模为零均值高斯噪声,由此建立多级坐标变换矩阵将激光扫描数据转化为全局坐标系中的概率化高程估计,并根据置信区间将得到的高程估计关联至多个地形网格,在此基础上对关联网格内分配的高程估计进行概率融合,实现了局部高程地图的更新.此外,采用局部窗口检测方法对地形遮挡问题进行了处理,并同时解决了室外环境下移动机器人的3D定位问题.实验结果表明了该算法的实时性和有效性.     

An optimal approach for random signals classification

A method is proposed which solves the problem of the Bayes classification of ARMA (autoregressive moving average) signals when the models of classes and samples are not exactly known but only estimated from finite-length data sequences. Justified approximations and the hypothesis lead to decision rules including the variances of the estimations. The results obtained on a large set of simulated data show that this approach is superior to the best classical methods (cepstral distance or Kullback divergence), particularly in the common case where the hypothesis of those methods is not verified (short samples. small training sets. random classes)     

一种高效的开放式关节型机器人3D仿真环境构建方法

提出了一种高效地构建开放式的机器人3D仿真环境的方法.该方法以Matlab软件为平台,充分结合Pro/E等3D实体设计软件、Matlab机器人工具箱和Matlab 3D动画技术建立可视化程度高、细节显示逼真的机器人3D仿真研究平台.以应用广泛的VA1400弧焊机器人为例,详细介绍了机器人3D仿真模型的建立、仿真实体的数据导入和仿真系统的3D动画演示等步骤,最终得到一个系统软件开放程度高、可视化效果逼真的机器人3D仿真环境.给出了仿真系统的部分显示效果,验证了本方法的有效性.     

An algebraic approach for morphological operations on 2D and 3D images

This paper describes an algebraic approach to morphological operations on 2D and 3D images. For 2D images, a matching algorithm based on mathematical morphology is given. For 3D images represented by voxels, algorithms are developed for the shape decomposition and thinning. The possible advantages of the algebraic approach are indicated by showing that a considerable speedup takes place (for large-sized templates) if the Fast Fourier Transform (FFT) is used to compute the convolutions.     

Cooperative Control of a 3D Dual-Flexible-Arm Robot

This paper discusses cooperative control of a dual-flexible-arm robot to handle a rigid object in three-dimensional space. The proposed control scheme integrates hybrid position/force control and vibration suppression control. To derive the control scheme, kinematics and dynamics of the robot when it forms a closed kinematic chain is discussed. Kinematics is described using workspace force, velocity and position vectors, and hybrid position/force control is extended from that on dual-rigid-arm robots. Dynamics is derived from constraint conditions and the lumped-mass-spring model of the flexible robots and an object. The vibration suppression control is calculated from the deflections of the flexible links and the dynamics. Experiments on cooperative control are performed. The absolute positions/orientations and internal forces/moments are controlled using the robot, each arm of which has two flexible links, seven joints and a force/torque sensor. The results illustrate that the robot handled the rigid object damping links' vibration successfully in three-dimensional space.     

An approximate and efficient method for optimal rotation alignment of 3D models

In many shape analysis applications, the ability to find the best rotation that aligns two models is an essential first step in the analysis process. In the past, methods for model alignment have either used normalization techniques, such as PCA alignment, or have performed an exhaustive search over the space of rotation to find the best optimal alignment. While normalization techniques have the advantage of efficiency, providing a quick method for registering two shapes, they are often imprecise and can give rise to poor alignments. Conversely, exhaustive search is guaranteed to provide the correct answer, but, even using efficient signal processing techniques, this type of approach can be prohibitively slow. In this paper, we present a new method for aligning two 3D shapes. We show that the method is markedly faster than existing approaches based on efficient signal processing and we provide registration results demonstrating that the alignments obtained using our method have a high degree of precision and are markedly better than those obtained using normalization.     

An optimal control approach for ultrasound induced heating

The absorbed energy of ultrasound and microwaves is changed into heat in a dissipative medium. This wave field induced heating has numerous applications in industry and medicine. In these applications the ability to control the resulting heat distribution is essential. In this paper we design a controller for quadratic cost criteria in the ultrasound induced heating problem in inhomogeneous media. In this approach the time-harmonic pressure fields are computed from individual wave sources by solving the Helmholtz equation with the ultra-weak variational formulation. The equations that define the controller are derived from the Hamiltonian form of the system, which results in a large dimension non-linear control problem. As an example we study a numerical simulation that resembles an ultrasound therapy problem in 2D. The simulation shows that feasible solutions can be obtained with this approach.     

An Autonomous Navigation Methodology for a Pioneer 3DX Robot

Autonomous navigation is a complex challenge that involves the interpretation and analysis of information about the scenario to facilitate the cognitive processes of a robot to perform free trajectories in dynamic environments. To solve this, the paper introduces a Case-Based Reasoning methodology to endow robots with an efficient decision structure aiming of selecting the best maneuver to avoid collisions. In particular, Manhattan Distance was implemented to perform the retrieval process in CBR method. Four scenarios were depicted to run a set of experiments in order to validate the functionality of the implemented work. Finally, conclusions emphasize the advantages of CBR methodology to perform autonomous navigation in unknown and uncertain environments.     

Robot calibration using a 3D vision-based measurement system with a single camera

One of the problems that slows the development of off-line programming is the low static and dynamic positioning accuracy of robots. Robot calibration improves the positioning accuracy and can also be used as a diagnostic tool in robot production and maintenance. This work presents techniques for modeling and performing robot calibration processes with off-line programming using a 3D vision-based measurement system. The measurement system is portable, accurate and low cost, consisting of a single CCD camera mounted on the robot tool flange to measure the robot end-effector pose relative to a world coordinate system. Radial lens distortion is included in the photogrammetric model. Scale factors and image centers are obtained with innovative techniques, making use of a multiview approach. Results show that the achieved average accuracy using a common off-the-shelf CCD camera varies from 0.2 to 0.4 mm, at distances from 600 to 1000 mm from the target, respectively, with different camera orientations. Experimentation is performed on two industrial robots to test their position accuracy improvement using the calibration system proposed: an ABB IRB-2400 and a PUMA-500. The robots were calibrated at different regions and volumes within their workspace achieving accuracy from three to six times better when comparing errors before and after calibration, if measured locally. The proposed off-line robot calibration system is fast, accurate and easy to set up.