基于三坐标测量机的机器人位姿精度检测方法

针对医疗场合导航引导下的手术机器人定位精度检测问题,提出了基于三坐标测量机的机器人位姿距离精度测量方法。该方法通过放置在一个平面上的三个标准球来实现三坐标测量机对姿态精度的测量,并参照机器人辅助外科手术系统的定位原理构建基于三坐标测量机的机器人位姿检测平台。在此基础上,依据国家标准规定的机器人性能检测方法和过程,完成机器人位姿距离精度的测量。通过该方法对研发的骨科手术定位机器人进行测量的结果表明,所设计机器人位置距离准确度和重复性分别在[10-1]mm和[10-2]mm级别,姿态距离准确度和重复性分别在[10-1]度和[10-2]度级别。最后将该机器人应用于前交叉韧带重建手术实验,结果表明通过这种方法检测的机器人能够满足手术场合要求。     

An Analytical Method for Decoupled Local Smoothing of Linear Paths in Industrial Robots

The linear-format path is widely adopted to approximate the continuous contour in robot controllers. The tangential discontinuity of the linear paths usually causes the discontinuity of the joint velocity. To comply with the joint kinematics limits, the robots have to stop at each corner point, resulting in a great loss of efficiency. To achieve a smooth motion, this paper presents an analytical decoupled C³ continuous local path smoothing method for industrial robots. The tool position path is smoothed in the reference frame while the tool orientation is smoothed in the rotation parametric space based on the exponential coordinates of rotations. The quintic B-splines are inserted at the corners of the linear segments to achieve the G³ continuity of the tool position path and tool orientation path. The orientation smoothing error is constrained analytically. By reparameterization of the remaining linear segments using specially constructed B-splines, the C³ continuity of the tool position path and tool orientation path is achieved. Then, the synchronization of the tool orientation path and tool position path can be guaranteed by sharing the same curve parameter. Besides, to improve the smoothness of the angular motion on the remaining linear segments during parameter synchronization, the transition lengths of the inserted B-splines are optimized. The proposed local smoothing method guarantees that the generated smooth orientation path in the rotation space is invariant with the selection of the reference frame and the orientation of the tool frame, and ensures the jerk-continuous motion with a smoother angular motion on the remaining linear segments, which could improve the motion smoothness of the tool path and tracking accuracy. The effectiveness of the proposed method is validated through simulation and experiments.     

Reconstruction of medical images under different image acquisition angles

Compared to object-based registration, feature-based registration is much less complex. However, in order for feature-based registration to work, the two image stacks under consideration must have the same acquisition tilt angle and the same anatomical location - two requirements that are not always fulfilled. In this paper, we propose a technique that reconstructs two sets of medical images acquired with different acquisition angles and anatomical cross sections into one set of images of identical scanning orientation and positions. The space correlation information among the two image stacks is first extracted and is used to correct the tilt angle and anatomical position differences in the image stacks. Satisfactory reconstruction results were presented to prove our points.     

Design and implementation of a PC-based image-guided surgical system

In interactive, image-guided surgery, current physical space position in the operating room is displayed on various sets of medical images used for surgical navigation. We have developed a PC-based surgical guidance system (ORION) which synchronously displays surgical position on up to four image sets and updates them in real time. There are three essential components which must be developed for this system: (1) accurately tracked instruments; (2) accurate registration techniques to map physical space to image space; and (3) methods to display and update the image sets on a computer monitor. For each of these components, we have developed a set of dynamic link libraries in MS Visual C++ 6.0 supporting various hardware tools and software techniques. Surgical instruments are tracked in physical space using an active optical tracking system. Several of the different registration algorithms were developed with a library of robust math kernel functions, and the accuracy of all registration techniques was thoroughly investigated. Our display was developed using the Win32 API for windows management and tomographic visualization, a frame grabber for live video capture, and OpenGL for visualization of surface renderings. We have begun to use this current implementation of our system for several surgical procedures, including open and minimally invasive liver surgery.     

基于累积绝对差图像与交叉熵分割的运动目标检测与定位

提出了一种新的运动目标检测与定位方法。针对位移变化较小的运动目标，先对运动序列中所有相邻两帧图像作绝对值差分运算，然后再将绝对值差分结果进行累加，从而得到累积绝对差图像。利用交叉熵分割法对累积绝对差图像二值化，并结合形态学方法去除噪声，求取出目标的运动区域。对运动序列的首帧和尾帧进行差分运算并二值化．为了去噪，将首尾帧差图像与累积绝对差图像进行逻辑与运算，确定出目标在首尾图像中的位置。实验结果表明了本方法的有效性和鲁棒性。     

On the optical-mechanical analogy in general relativity

The existence of a new optical-mechanical analogy is revealed between the equation of rotational motion of a body in the mechanics of general relativity (GR) and the first pair of the Maxwell equations. It is also shown that the equations of rotational motion are a consequence of the equations of translational motion in GR mechanics.     

Multivariate vector autoregressive prognosis-based model following control method for robot-assisted beating heart surgery

Robotics tool enables the surgeon to conduct the operation on the beating heart during the off-pump coronary artery graft bypass surgery. The robotic tool actively cancels the relative motion between the point of intersect (POI) on the surface of the heart and surgical tool, which allows the surgeon to operate as if the heart is stationary. The nonlinear nature of the beating heart motion disables the conventional feedback controller and pose difficulty to the robot tool. We apply Granger causality to analyze simultaneously measured electrocardiography (ECG) and 3D heart motion data. The extracted interdependency between the different sets of time series reveals the feasiblity for the improved prediction of the heart motion. In this paper, we propose an adaptive multivariate vector autoregressive (MVAR) prognosis-based model following (MF) control algorithm. Using this method, the prediction part takes advantage of the ECG signal, which contains the nonstationary heart rate dynamics significantly correlated with the heart motion. In addition, the control part automatically incorporates the feedforward path to enhance the tracking of the abrupt change and occasional abnormality in heart motion. The comparative experiment results for evaluating the proposed algorithm are reported by using the vivo collected data. The results indicate that MVAR-based MF improves the control accuracy by 0.2?mm and achieves better tracking performance by capturing more nonlinear characteristics of the heart motion, and following the heart motion better with sufficient details.     

Machine models and tool motions for simulating five-axis machining

This paper presents a method of determining the tool motion of a five-axis machine. The method is motivated by the imprint point method, where points on the machined surface are computed based on the tool position and tool motion. While simple linear motion can be used as a coarse approximation to this motion, this paper looks at more accurate models of tool motion based on machine kinematics that can be generalized and applied to any CNC machine with one tool head. A kinematic chain is created by decomposing the linear motion of a machine’s translational and rotational axes into parameterized affine transformations, and a hierarchical model of the machine combines the transformations to provide an accurate model of machine motion.     

一种新的指纹节点匹配方法

指纹匹配是指纹识别中的一个重要问题,在指纹识别系统中常用一组节点来表示一个指纹。目前的指纹识别系统主要采用基于节点的匹配方法。文章提出了一种新的指纹节点匹配方法,在抽取节点特征时不但提取其坐标和方向,而且还提取每个节点沿着其方向和反方向的一定距离内的局部方向,在匹配两个节点时匹配这些方向信息,并将节点按方向信息排序,以加速查找。匹配时首先确定最佳参考节点,然后根据最佳参考节点下匹配节点对的位置和方向差异再次旋转和平移输入指纹,最后在直角坐标下再次匹配两个指纹。实验表明,该方法能有效地提高系统的识别性能。     

Asynchronous reflections: theory and practice in the design of multimedia mirror systems

In this paper, we present a theoretical framing of the functions of a mirror by breaking the synchrony between the state of a reference object and its reflection. This framing provides a new conceptualization of the uses of reflections for various applications. We describe the fundamental technical components of such systems and illustrate the technical challenges in two different forms of electronic mirror systems for apparel shopping. The first example, the Responsive Mirror, is an intelligent video capture and access system for clothes shopping in physical stores that provides personalized asynchronous reflections of clothing items through an implicitly controlled human–computer interface. The Responsive Mirror employs computer vision and machine learning techniques to interpret the visual cues of the shopper’s behavior from cameras to then display two different reflections of the shopper on digital displays: (1) the shopper in previously worn clothing with matching pose and orientation and (2) other people in similar and dissimilar shirts with matching pose and orientation. The second example system is a Countertop Responsive Mirror that differs from the first in that the images do not respond to the real-time movement of the shopper but to frames in a recorded video so that the motion of the shopper in the different recordings are matched non-sequentially. These instantiations of the mirror systems in fitting room and jewelry shopping scenarios are described, focusing on the system architecture and the intelligent computer vision components. The effectiveness of Responsive Mirror is demonstrated by the user study. The paper contributes a conceptualization of reflection and examples of systems illustrating new applications in multimedia systems that break traditional reflective synchronies.     

An analytical C3 continuous tool path corner smoothing algorithm for 6R robot manipulator

Tool path smoothness is important to guarantee good dynamic and tracking performance of robot manipulators. An analytical C³ continuous tool path corner smoothing algorithm is proposed for robot manipulators with 6 rotational (6R) joints. The tool tip position is smoothed directly in the workpiece coordinate system (WCS). The tool orientation is smoothed after transferring the tool orientation matrix as three rotary angles. Micro-splines of the tool tip position and tool orientation are constructed under the constraints of the maximum deviation error tolerances in the WCS. Then the tool orientation and tool tip position are synchronized to the tool tip displacement with C³ continuity by replacing the remaining linear segments using specially constructed B-splines. Control points of the locally inserted micro-splines are all evaluated analytically without any iterative calculations. Simulation and experimental results show that the proposed algorithm satisfies constraints of the preset tool tip position and the tool orientation tolerances. The proposed corner smoothing algorithm achieves smoother and lower jerks than C² continuous corner smoothing algorithm. Experimental results show that the tracking errors associated to the execution of the C³ continuous tool path are up to 10% smaller than C² continuous path errors.     

Dexterous manipulation of an object by means of multi‐DOF robotic fingers with soft tips

This article analyzes the dynamics of motion of various setups of two multiple degree‐of‐freedom (DOF) fingers that have soft tips, in fine manipulation of an object, and shows performances of their motions via computer simulation. A mathematical model of these dynamics is described as a system of nonlinear differential equations expressing motion of the overall fingers‐object system together with algebraic constraints due to tight area contacts between the finger‐tips and surfaces of the object. First, problems of (1) dynamic, stable grasping and (2) regulation of the object rotational angle by means of a setup of dual two‐DOF fingers, are treated. Second, the problem of regulating the position of the object mass center by means of a pair of two‐DOF and three‐DOF fingers is considered. Third, a set of dual three‐DOF fingers is treated, in order to let it perform a sophisticated task, which is specified by a periodic pattern of the object posture and a constant internal force. In any case, there exist sensory‐motor coordinations, which are described by analytic feedback connections from sensing to actions at finger joints. In the cases of setpoint control problems, convergences of motion to secure grasping together with the specified object rotational angle and/or the specified object mass center position, are proved theoretically. A constraint stabilization method (CSM) is used for solving numerically the differential algebraic equations to show performances of the proposed sensory‐feedback schemes. © 2002 Wiley Periodicals, Inc.     

Dynamic Manipulation Inspired by the Handling of a Pizza Peel

This paper discusses dynamic manipulation inspired by the handling mechanism of a pizza chef. The chef handles a tool called “pizza peel,” where a plate is attached at the tip of a bar, and he remotely manipulates a pizza on the plate. We found that he aggressively utilizes only two degrees of freedom (DOFs) from the remote handling location during manipulation: translation along the bar and rotation about the bar. From the viewpoint of a dynamic system, the inertial loads for these specific DOFs are never affected by the length of the bar. This is important for the production of quick plate motions so that the object on the plate can be dynamically and remotely manipulated. Applying this handling mechanism to a robot system, we first reveal how to make the object's motion for three DOFs by using two DOFs of plate motion. We then show that it is guaranteed to achieve an arbitrary desired set of position and orientation of the object by the proposed manipulation scheme. The proposed method has good manipulability because the translational motion of the object can be fully decoupled from the rotational motion (though not vice versa). Finally, we show a couple of experiments that confirm the basic idea.      

Pose and motion recovery from feature correspondences and a digital terrain map

A novel algorithm for pose and motion estimation using corresponding features and a digital terrain map is proposed. Using a digital terrain (or digital elevation) map (DTM/DEM) as a global reference enables the elimination of the ambiguity present in vision-based algorithms for motion recovery. As a consequence, the absolute position and orientation of a camera can be recovered with respect to the external reference frame. In order to do this, the DTM is used to formulate a constraint between corresponding features in two consecutive frames. Explicit reconstruction of the 3D world is not required. When considering a number of feature points, the resulting constraints can be solved using nonlinear optimization in terms of position, orientation, and motion. Such a procedure requires an initial guess of these parameters, which can be obtained from dead-reckoning or any other source. The feasibility of the algorithm is established through extensive experimentation. Performance is compared with a state-of-the-art alternative algorithm, which intermediately reconstructs the 3D structure and then registers it to the DTM. A clear advantage for the novel algorithm is demonstrated in variety of scenarios.     

Scenario advisor tool for requirements engineering

This study investigates the usefulness of a scenario advisor tool which was built to help requirements engineers to generate sufficient sets of scenarios in the domain of socio-technical systems. The tool provides traceability between scenario models and requirements and helps to generate new scenarios and scenario variations. Through two series of evaluation sessions, we found that the scenario advisor tool helped users to write more sound scenarios without any domain knowledge, and to generate more variations on existing scenarios by providing specific scenario-generation hints for each scenario component. The tool should improve the reliability of requirements elicitation and validation.     

A Series-elastic Robot for Back-pain Rehabilitation

This paper addresses the robot-assisted rehabilitation of back pain, an epidemic health problem affecting a large portion of the population. The design is composed of two springs in series connected to an end-effector via a pair of antagonistic cables. The spring and cable arrangement forms an elastic coupling from the actuator to the output shaft. An input-output torque model of the series-elastic mechanism is established and studied numerically. The study also illustrates the variation of the mechanism’s effective stiffness by changing the springs’ position. In addition, we built a prototype of the robotic mechanism and design experiments with a robotic manipulator to experimentally investigate its dynamic characteristics. The experimental results confirm the predicted elasticity between the input motion and the output torque at the end-effector. We also observe an agreement between the data generated by the torque model and data collected from the experiments. An experiment with a full-scale robot and a human subject is carried out to investigate the human-robot interaction and the mechanism behavior.

     

General construction of time-domain filters for orientation data

Capturing live motion has gained considerable attention in computer animation as an important motion generation technique. Canned motion data are comprised of both position and orientation components. Although a great number of signal processing methods are available for manipulating position data, the majority of these methods cannot be generalized easily to orientation data due to the inherent nonlinearity of the orientation space. In this paper, we present a new scheme that enables us to apply a filter mask (or a convolution filter) to orientation data. The key idea is to transform the orientation data into their analogues in a vector space, to apply a filter mask on them, and then to transform the results back to the orientation space. This scheme gives time-domain filters for orientation data that are computationally efficient and satisfy such important properties as coordinate invariance, time invariance and symmetry. Experimental results indicate that our scheme is useful for various purposes, including smoothing and sharpening     

Primitive Object Grasping for Finger Motion Synthesis

We developed a new framework to generate hand and finger grasping motions. The proposed framework provides online adaptation to the position and orientation of objects and can generate grasping motions even when the object shape differs from that used during motion capture. This is achieved by using a mesh model, which we call primitive object grasping (POG), to represent the object grasping motion. The POG model uses a mesh deformation algorithm that keeps the original shape of the mesh while adapting to varying constraints. These characteristics are beneficial for finger grasping motion synthesis that satisfies constraints for mimicking the motion capture sequence and the grasping points reflecting the shape of the object. We verify the adaptability of the proposed motion synthesizer according to its position/orientation and shape variations of different objects by using motion capture sequences for grasping primitive objects, namely, a sphere, a cylinder, and a box. In addition, a different grasp strategy called a three‐finger grasp is synthesized to validate the generality of the POG‐based synthesis framework.     

一种基于多因素的告警关联方法

入侵检测系统作为保护网络安全的重要工具已被广泛使用,其通常产生大量冗余度高、误报率高的告警。告警关联分析通过对底层告警进行综合分析与处理,揭示出其中包含的多步攻击行为。许多告警关联方法通过在历史告警中挖掘频繁模式来构建攻击场景,方法容易受冗余告警、误报影响,挖掘出的多步攻击链在某些情况下不能反映出真实的多步攻击行为。为此,提出一种基于多因素的多步攻击关联方法。通过聚合原始告警以得到超级告警,降低冗余告警带来的影响;将超级告警构造成超级告警时间关系图,同时结合超级告警间的多因素关联度评价函数从时间关系图中挖掘出多步攻击场景。实验结果表明,该方法能克服冗余告警及大部分误报带来的负面影响、有效地挖掘出多步攻击链。