Flexible Splicing of Upper‐Body Motion Spaces on Locomotion

This paper presents an efficient technique for synthesizing motions by stitching, or splicing, an upper‐body motion retrieved from a motion space on top of an existing lower‐body locomotion of another motion. Compared to the standard motion splicing problem, motion space splicing imposes new challenges as both the upper and lower body motions might not be known in advance. Our technique is the first motion (space) splicing technique that propagates temporal and spatial properties of the lower‐body locomotion to the newly generated upper‐body motion and vice versa. Whereas existing techniques only adapt the upper‐body motion to fit the lower‐body motion, our technique also adapts the lower‐body locomotion based on the upper body task for a more coherent full‐body motion. In this paper, we will show that our decoupled approach is able to generate high‐fidelity full‐body motion for interactive applications such as games.     

Describing Upper-Body Motions Based on Labanotation for Learning-from-Observation Robots

We have been developing a paradigm that we call learning-from-observation for a robot to automatically acquire a robot program to conduct a series of operations, or for a robot to understand what to do, through observing humans performing the same operations. Since a simple mimicking method to repeat exact joint angles or exact end-effector trajectories does not work well because of the kinematic and dynamic differences between a human and a robot, the proposed method employs intermediate symbolic representations, tasks, for conceptually representing what-to-do through observation. These tasks are subsequently mapped to appropriate robot operations depending on the robot hardware. In the present work, task models for upper-body operations of humanoid robots are presented, which are designed on the basis of Labanotation. Given a series of human operations, we first analyze the upper-body motions and extract certain fixed poses from key frames. These key poses are translated into tasks represented by Labanotation symbols. Then, a robot performs the operations corresponding to those task models. Because tasks based on Labanotation are independent of robot hardware, different robots can share the same observation module, and only different task-mapping modules specific to robot hardware are required. The system was implemented and demonstrated that three different robots can automatically mimic human upper-body operations with a satisfactory level of resemblance.     

Learning Biped Locomotion

We propose a model-based reinforcement learning (RL) algorithm for biped walking in which the robot learns to appropriately modulate an observed walking pattern. Via-points are detected from the observed walking trajectories using the minimum jerk criterion. The learning algorithm controls the via-points based on a learned model of the Poincare map of the periodic walking pattern. The model maps from a state in the single support phase and the controlled via-points to a state in the next single support phase. We applied this approach to both a simulated robot model and an actual biped robot. We show that successful walking policies were acquired.     

Locomotion with articulated legs in pipes or ducts

Different implementations of remote controlled robots exist that can inspect and repair the interior of a pipe or duct. For this purpose they have video cameras and tools like a welding set or a grinder on board. This paper describes an approach with articulated legs that are pushed against the walls to obtain a grip. In contrast to wheels, for instance, legs overcome problems of common pipe inspection robots, like branches or obstacles in the pipe. The robot has a hierarchical control architecture with reflexive behaviour in the lower layers. In a two-dimensional simulation environment the robot performed successfully in several shapes of pipes. The results show that simple reflexive behaviour is sufficient to overcome even complex shapes. In the tested environment, reflexive behaviour prevented deadlock and ensured the robot's safe operation.     

Texture Splicing

We propose a new texture editing operation called texture splicing. For this operation, we regard a texture as having repetitive elements (textons) seamlessly distributed in a particular pattern. Taking two textures as input, texture splicing generates a new texture by selecting the texton appearance from one texture and distribution from the other. Texture splicing involves self‐similarity search to extract the distribution, distribution warping, context‐dependent warping, and finally, texture refinement to preserve overall appearance. We show a variety of results to illustrate this operation.     

Locomotion versatility through self-reconfiguration

We discuss a robotic module called a Molecule. Molecules can be the basis for building self-reconfiguring robots. They support multiple modalities of locomotion and manipulation. We describe the design, functionality, and control of the Molecule. We show how a set of Molecules can aggregate as active three-dimensional structures that can move and change shape. Finally, we discuss global motion algorithms for Molecular structures.     

Modal Locomotion: Animating Virtual Characters with Natural Vibrations

We present a general method to intuitively create a wide range of locomotion controllers for 3D legged characters. The key of our approach is the assumption that efficient locomotion can exploit the natural vibration modes of the body, where these modes are related to morphological parameters such as the shape, size, mass, and joint stiffness. The vibration modes are computed for a mechanical model of any 3D character with rigid bones, elastic joints, and additional constraints as desired. A small number of vibration modes can be selected with respect to their relevance to locomotion patterns and combined into a compact controller driven by very few parameters. We show that these controllers can be used in dynamic simulations of simple creatures, and for kinematic animations of more complex creatures of a variety of shapes and sizes.     

纸片拼接技术

计算机辅助二维碎片自动拼接是模式识别领域中的一个典型问题,它在司法鉴定、文物修复等领域有着广泛的应用.本文对这种二维图像碎片的自动拼接问题展开研究.对于仅纵切的碎片,比较任意两张图片拼接后边界处的相似度来判断碎片之间是否左右相邻;对于纵切加横切的碎片,在纵切模型的基础上考虑了碎片文字所在行的几何特征信息,解决了判断碎片上下相邻的问题;对于双面的碎片,处理方法与纵切加横切类似,仅在对行的几何特征按照相似度进行分组时需要考虑正反面的情况.实验结果验证了方案的有效性.另外,对于文字特点不同于中文的英文碎片建立了改进模型.     

Passivity-Based Control of Bipedal Locomotion

In this article, we have shown how to design energy-based and passivity-based control laws that exploit the existence of passive walking gaits to achieve walking on different ground slopes, to increase the size of the basin of attraction and robustness properties of stable limit cycles, and to regulate walking speed. Many of the results presented in this are the compass gait are equally applicable to bipeds with knees and a torso. Practical considerations such as actuator saturation, ground reaction forces, and ground friction need to be addressed. The problem of foot rotation introduces an underactuated phase into the walking gait, which greatly challenges the application of energy shaping ideas. For walking in 3D, finding purely passive limit cycles, which is the first step in applying our energy control results, may be difficult. It was shown how ideas of geometric reduction can be used to generate 3D stable gaits given only 2D passive limit cycles.     

带主动腰关节的四足机器人平稳运动控制

针对四足机器人在对角小跑运动时出现的后腿“拖地”、机体振荡的现象,提出了一种基于偏航方向上主动腰关节摆动的解决方法。通过D-H法对机器人各关节进行运动学建模,获得其运动学方程,并采用Kuramoto振荡器模型作为扩展的CPG耦合网络振子,实现对腰、腿关节的统一控制。仿真实验表明,经过腰关节控制优化后的机器人在对角小跑时,相对于刚体躯干的机器人,姿态角变化幅度显著减小,抬腿高度明显增加,有效地提高了机器人的运动稳定性,证明了方法的可行性。     

Locomotion Skills for Insects with Sample‐based Controller

Natural‐looking insect animation is very difficult to simulate. The fast movement and small scale of insects often challenge the standard motion capture techniques. As for the manual key‐framing or physics‐driven methods, significant amounts of time and efforts are necessary due to the delicate structure of the insect, which prevents practical applications. In this paper, we address this challenge by presenting a two‐level control framework to efficiently automate the modeling and authoring of insects’ locomotion. On the top level, we design a Triangle Placement Engine to automatically determine the location and orientation of insects’ foot contacts, given the user‐defined trajectory and settings, including speed, load, path and terrain etc. On the low‐level, we relate the Central Pattern Generator to the triangle profiles with the assistance of a Controller Look‐Up Table to fast simulate the physically‐based movement of insects. With our approach, animators can directly author insects’ behavior among a wide range of locomotion repertoire, including walking along a specified path or on an uneven terrain, dynamically adjusting to external perturbations and collectively transporting prey back to the nest.     

Skill Memory in Biped Locomotion

Robots must be able to adapt their motor behavior to unexpected situations in order to safely move among humans. A necessary step is to be able to predict failures, which result in behavior abnormalities and may cause irrecoverable damage to the robot and its surroundings, i.e. humans. In this paper we build a predictive model of sensor traces that enables early failure detection by means of a skill memory. Specifically, we propose an architecture based on a biped locomotion solution with improved robustness due to sensory feedback, and extend the concept of Associative Skill Memories (ASM) to periodic movements by introducing several mechanisms into the training workflow, such as linear interpolation and regression into a Dynamical Motion Primitive (DMP) system such that representation becomes time invariant and easily parameterizable. The failure detection mechanism applies statistical tests to determine the optimal operating conditions. Both training and failure testing were conducted on a DARwIn-OP inside a simulation environment to assess and validate the failure detection system proposed. Results show that the system performance in terms of the compromise between sensitivity and specificity is similar with and without the proposed mechanism, while achieving a significant data size reduction due to the periodic approach taken.     

Exposing Region Splicing Forgeries with Blind Local Noise Estimation

Region splicing is a simple and common digital image tampering operation, where a chosen region from one image is composited into another image with the aim to modify the original image’s content. In this paper, we describe an effective method to expose region splicing by revealing inconsistencies in local noise levels, based on the fact that images of different origins may have different noise characteristics introduced by the sensors or post-processing steps. The basis of our region splicing detection method is a new blind noise estimation algorithm, which exploits a particular regular property of the kurtosis of nature images in band-pass domains and the relationship between noise characteristics and kurtosis. The estimation of noise statistics is formulated as an optimization problem with closed-form solution, and is further extended to an efficient estimation method of local noise statistics. We demonstrate the efficacy of our blind global and local noise estimation methods on natural images, and evaluate the performances and robustness of the region splicing detection method on forged images.     

结合游程长度与共生矩阵的图像拼接篡改检测方法

针对拼接图像篡改鉴别问题,研究了运用游程长度和灰度共生矩阵等统计特征进行图像盲检测的算法。该算法将拼接篡改检测问题转换为二分类模式识别问题,在图像的色度通道Cb和Cr中提取游程长度特征,并将其与灰度共生矩阵特征相结合,然后以结合后的新的特征向量训练LibSVM作为最后的分类器,确定所给图像是否被拼接篡改。实验结果显示,在彩色图像测试库CASIA v2.0上,利用融合后的特征检测图像使识别率得到较大提高,同时该算法在复制粘贴篡改方面也有较好的识别性能。     

Splicing systems and regularity

A direct and constructive proof is given that every regular language is the homomorphic image of a splicing language as defined by Head. The class of splicing languages involved have a particularly simple presentation and are regular. Also presented are some examples which demonstrate the relation of the class of splicing languages to that of regular languages and an example of a regular language which is not a splicing language.     

Splicing on tree-like structures

In this paper, we provide a method to increase the power of splicing systems. We introduce the splicing systems on trees to be built as partially annealed single strands, which is a quite similar notion and a natural extension of splicing systems on strings. Trees are a common and useful data structure in computer science and have a biological counterpart such as molecular sequences with secondary structures, which are typical structures in RNA sequences. Splicing on trees involves (1) complete subtrees as axioms, (2) restriction operated on the annealed subsequences, (3) rules to substitute a complete subtree with another. We show that splicing systems on trees with finite sets of axioms and finite sets of rules can generate the class of context-free languages without the need of imposing multiplicity constraints.     

Locomotion and depth control of robotic fish with modular undulating fins

This paper presents an environmental-friendly robotic system mimicking the undulating fins of a fish. To mimic the actual flexible fin of real fish, a fin-like mechanism with a series of connecting linkages is modeled and attached to the robotic fish, by virtue of a specially designed strip. Each link is able to turn and slide with respect to the adjacent link. These driving linkages are then used to form a mechanical fin consisting of several fin segments, which are able to produce undulations, similar to those produced by the actual fish fins. Owing to the modular and re-configurable design of the mechanical fin, we are able to construct biomimetic robotic fish with various swimming modes by fin undulations. Some qualitative and workspace observations by experiments of the robotic fish are shown and discussed.     

微小气动机器人的移动控制

根据仿生尺蠖运动机理研制了一种用于人体腔道微创诊查的气动微机器人系统。该机器人系统由前支撑单元、后支撑单元和具有3个气室的橡胶驱动器三部分组成。设计了控制机器人移动的计算机电-气控制系统,通过控制该电-气系统的继电器和高速开关电磁阀来控制机器人系统的钳位气囊和驱动器气室内的气压。通过分析一个运动周期内机器人的运动状态,给出了机器人移动的控制算法,使机器人前、后支撑单元的气囊和驱动器的气室实现有规律的充气、保持及放气3种状态,从而实现有规律的运动。研究结果表明所设计的机器人具有仿生尺蠖移动机理的柔性结构,通过所设计的电-气控制系统可实现机器人的自动移动。     

Recurrent Motion Refiner for Locomotion Stitching

Stitching different character motions is one of the most commonly used techniques as it allows the user to make new animations that fit one's purpose from pieces of motion. However, current motion stitching methods often produce unnatural motion with foot sliding artefacts, depending on the performance of the interpolation. In this paper, we propose a novel motion stitching technique based on a recurrent motion refiner (RMR) that connects discontinuous locomotions into a single natural locomotion. Our model receives different locomotions as input, in which the root of the last pose of the previous motion and that of the first pose of the next motion are aligned. During runtime, the model slides through the sequence, editing frames window by window to output a smoothly connected animation. Our model consists of a two-layer recurrent network that comes between a simple encoder and decoder. To train this network, we created a sufficient number of paired data with a newly designed data generation. This process employs a K-nearest neighbour search that explores a predefined motion database to create the corresponding input to the ground truth. Once trained, the suggested model can connect various lengths of locomotion sequences into a single natural locomotion.