This article identifies the space of spatial impedance behaviors that can be achieved by a grasp of a multifinger hand in which each fingertip makes hard-point contact with the held object. The dimension of the space of realizable impedances for a given number of fingers is determined analytically. A set of necessary and sufficient conditions on impedance matrices that can be realized by a given grasp is developed and the physical significance of these conditions is identified. The space of impedances that can be achieved by a hard point grasp is a hyperplane in the space of all possible impedance behaviors. A process to achieve an arbitrary full-rank impedance in the hyperplane with a grasp having the minimum number of fingers is developed. With this process, any spatial impedance behavior in the hyperplane can be attained with a three-finger grasp by properly selecting: first, the locations where fingertips contact the held object, and second, the translational impedance provided by a finger at each of these locations.

P4 (Programming Protocol-independent Packet Processors) language provides target-independent programming regardless of the SDN data plane's underlying architecture. However, manufacturers have adapted P4 for their architectures, imposing more restrictions for the standard P4. Consequently, the intention of building a target-independent data plane has been diluted. Accordingly, this paper summarizes three categories of restrictions (branch, state, and primitive) and their differences in the standard P4 and programmable switch. We devised the P4 Transformer to remove the barrier to running standard P4 on a commodity switch, making a step towards unified high- level programming for the SDN data plane. Besides, the P4 Transformer enables originally invalid programs on the switch, thus making the switch more powerful.

Flow measurement is a fundamental problem in various network domains. As network bandwidth develops, the available memory space becomes too scarce to enable full-accurate flow measurement. Thus, counter and sketch algorithms are used to leverage approximation techniques so as to create a trade-off between memory usage and measurement accuracy. However, a single algorithm may not be able to measure Top-ks and small flows simultaneously. Accordingly, this paper proposes the Counter-Sketch-Hybrid (CSH) algorithm, which combines the counter and sketch algorithms to facilitate more accurate flow measurement under memory space constraints. We tune the relative proportion of memory allocated to the counter and sketch part to obtain the global optimal accuracy in CSH. Results show that CSH outperforms a single counter algorithm in terms of both frequency estimation and the Top-k problem, under all values of identical memory space. CSH reduces ARE by 27% and MSE by 35% on average for frequency estimation. CSH also improves F1 score by 1.9% in the Top-k problem.

Network measurement is essential to many network applications. The trend of ever-increasing network traffic calls for contemporary network measurement approaches to have three key characteristics: accuracy, timeliness, and memory efficiency. The sketch algorithm offers a suitable trade-off between accuracy and memory consumption; however, its interval method is not as accurate and rapid as the sliding window method in Heavy Hitter detection. However, the sliding window method is believed to be highly memory-consuming. Accordingly, this paper proposes ARMHH: Accurate, Rapid, and Memory-efficient Heavy Hitter detection, which combines the sliding window and sketch algorithm approaches. Compared with the interval method, our experiments show that ARMHH improves the accuracy by 121.8x, 2.8x, and 3.5x on average for CM, CU, and Hashpipe, respectively, by consuming additional memory overhead for the sliding window. ARMHH also compresses the sliding window memory by at most 60%.

This paper identifies conditions for designing the appropriate spatial admittance to achieve reliable force-guided assembly of polyhedral parts for cases in which a single frictional contact occurs between the two parts. This work is an extension of previous work in which frictionless contact was considered. This paper presents a way to characterize friction without solving a set of complicated non-linear equations. We show that, by modifying the error reduction function and evaluating the function bounds associated with friction, the procedures developed for frictionless contact apply to the frictional cases. Thus, for bounded misalignments, if an admittance satisfies the misalignment-reducing conditions at a finite number of contact configurations, then the admittance will also satisfy the conditions at all intermediate configurations for any value of friction less than the specified upper bound.

In recent years, the research on malware variant classification has attracted much more attention. However, there are still many challenges, including the low accuracy of classification of samples of similar malware families, high time, and resource consumption. This paper proposes a new method of malware classification based on multiple visual features of malware and deep learning algorithms. In prior research, visualization techniques and entropy demonstrated exemplary performance in many areas. This paper extracts numerous visual features from the raw bytes and entropy sequence of the malware, which makes it more sensitive to malware samples of similar families and endows it the ability to classify malware variants more accurately. To evaluate the proposed method, this paper conducted a series of experiments on two malware datasets with a total of more than 20,000 samples provided by the Malware Research Lab and Microsoft Research. Through experiments, the method showed its superiority compared with some leading malware visual classification methods, achieving good performance on the accuracy with at least 1% improvement. The accuracy of the method even could reach 99.73% and 99.54%, respectively, on the two datasets.

This paper addresses the realization of spatial elastic behavior with a parallel or a serial manipulator. Necessary and sufficient conditions for a manipulator (either parallel or serial) to realize a specific elastic behavior are presented and interpreted in terms of the manipulator geometry. These conditions completely decouple the requirements on component elastic properties from the requirements on mechanism kinematics. New construction-based synthesis procedures for spatial elastic behaviors are developed. With these synthesis procedures, one can select each elastic component of a parallel (or serial) mechanism based on the geometry of a restricted space of allowable candidates. With each elastic component selected, the space of allowable candidates is further restricted. For each stage of the selection process, the geometry of the remaining allowable space is described.

A significant amount of research has been directed toward developing a more intuitive appreciation of spatial elastic behavior. Results of these analyses have been described in terms of behaviordecompositionsand in terms of behaviorcenters. In a recent paper entitled “The Principal Axes Decomposition of Spatial Stiffness Matrices” by Chenet al.(IEEE Trans. Robot., vol. 31, no. 1, pp. 191–207), a decomposition of spatial stiffness was presented, and centers of stiffness and compliance were identified. The results presented in the paper have substantial overlap with previously published results and redefine previously used terms. The objective of this communication is to clarify the contributions of prior work and to standardize the terminology used in describing spatial elastic behavior.

The admittance of a manipulator can be used to improve robotic assembly. If properly selected, the admittance will regulate a contact force and use it to guide the parts to proper positioning. In previous work, procedures for selecting the appropriate admittance for single principal contact (PC) cases were identified. This paper extends this research for some of the two PC cases-those for which each contact occurs at a single point. The conditions obtained ensure that the motion that results from frictionless contact always instantaneously reduces part misalignment. We show that, for bounded misalignments, if an admittance satisfies the misalignment-reducing conditions at a finite number of contact configurations, then the admittance will also satisfy the conditions at all intermediate configurations.

By judiciously selecting the admittance of a manipulator, the forces of contact that occur during assembly can be used to guide the parts to proper positioning. This paper identifies conditions for selecting the appropriate spatial admittance to achieve reliable force-guided assembly of polyhedral parts for cases in which a single feature (vertex, edge, or face) of one part contacts a single feature of the other, i.e., all single principal contact cases. These conditions ensure that the motion that results from frictionless contact always instantaneously reduces part misalignment. We show that, for bounded misalignments, if an admittance satisfies the misalignment-reducing conditions at a finite number of contact configurations, then the admittance will also satisfy the conditions at all intermediate configurations.

The selection of the proper admittance is important in achieving force-guided assembly. This paper identifies procedures for selecting the appropriate spatial admittance to achieve reliable force-guided assembly of polyhedral parts for single-point frictionless contact cases. Sets of conditions that are imposed on the admittance matrix for different types of single-point contact are presented. These conditions ensure that the motion that results from contact reduces part misalignment in the selected contact state. We show that, for bounded misalignments, if an admittance satisfies the misalignment-reduction conditions at a finite number of contact configurations, then the admittance also satisfy the conditions at all intermediate configurations.

An important issue in the development of force guidance assembly strategies is the specification of an appropriate admittance control law. This paper identifies conditions to be satisfied when selecting the appropriate admittance to achieve force-guided assembly of polygonal parts for multipoint contact with friction. These conditions restrict the admittance behavior for each of the various one-point and two-point contact cases and ensure that the motion that results from contact reduces part misalignment for each case. We show that, for bounded friction and part misalignments, if the identified conditions are satisfied for a finite number of contact configurations and friction coefficients, the conditions ensure that force guidance is achieved for all configurations and values of friction within the specified bounds.

This paper identifies procedures for selecting the appropriate admittance to achieve reliable planar force-guided assembly for single-point frictional contact cases. A set of conditions that are imposed on the admittance matrix is presented. These conditions ensure that the motion that results from contact reduces part misalignment. We show that, for bounded misalignments, if an admittance satisfies the misalignment-reduction conditions at a finite number of contact configurations and a given coefficient of friction /spl mu//sub M/) then the admittance will also ensure that the conditions are satisfied at all intermediate configurations for all coefficients less than /spl mu//sub M/.

An important issue in the development of force guidance assembly strategies is the specification of an appropriate admittance control law. This paper identifies procedures for selecting the appropriate admittance to achieve reliable planar force-guided assembly for multi-point contact cases. Conditions that restrict the admittance behavior for each of the various types of two-point contact are presented. These conditions ensure that the motion that results from contact reduces part misalignment for each case. We show that, for bounded misalignments, if the conditions are satisfied for a finite number of contact configurations, the conditions ensure that force guidance is achieved for all configurations within the specified bounds.

Admittance control approaches show significant promise in providing reliable force-guided assembly. An important issue in the development of these approaches is the specification of an appropriate admittance control law. This paper identifies procedures for selecting the appropriate admittance to achieve reliable force-guided assembly of planar polyhedral parts for single-point contact cases. A set of conditions that are imposed on the admittance matrix is presented. These conditions ensure that the motion that results from contact reduces part misalignment. We show that, for bounded misalignments, if an admittance satisfies the misalignment-reduction conditions at a finite number of contact configurations, then the admittance will also satisfy the conditions at all intermediate configurations.

Admittance control approaches show significant promise in providing reliable force-guided assembly. An important issue in the development of these approaches is the specification of an appropriate admittance control law. This paper identifies procedures for selecting the appropriate admittance to achieve reliable planar force-guided assembly for single-point contact cases. A set of conditions that are imposed on the admittance matrix is presented. These conditions ensure that the motion that results from contact reduces part misalignment. We show that for bounded misalignment, if the conditions are satisfied for a finite number of contact configurations, the system ensures that force guidance is achieved for all intermediate configurations.

We address the spatial elastic behavior that can be achieved through the use of a serial chain of revolute and prismatic elastic joints. We show that, regardless of the number of joints or the configuration of the links, there exists a subspace within the 21-dimensional compliance matrix space that cannot be reached by a simple serial elastic mechanism. This restriction is shown to be dual to the restriction on the stiffness matrices associated with simple parallel mechanisms. Although analogous to each other, the two restrictions correspond to different elastic behaviors. A procedure to synthesize any realizable compliance matrix with a simple serial mechanism is provided. The dualities and differences between the parallel and serial cases are discussed.

We address the spatial elastic behavior that can be achieved through the use of a serial chain of revolute and prismatic elastic joints. We show that, regardless of the number of joints or the configuration of the links, there exists a subspace within the 21-dimensional compliance matrix space that cannot be reached by a simple serial elastic mechanism. This restriction is shown to be dual to the restriction on the stiffness matrices associated with simple parallel mechanisms. Although analogous to each other, the two restrictions correspond to different elastic behaviors. A procedure to synthesize any realizable compliance matrix with a simple serial mechanism is provided. The dualities and differences between the parallel and serial cases are discussed.

A manipulator system is modeled as a kinematically unconstrained rigid body suspended by elastic devices. The structure of spatial stiffness is investigated by evaluating the stiffness matrix "primitives"-the rank-1 matrices that compose a spatial stiffness matrix. Although the decomposition of a rank-2 or higher stiffness matrix into the sum of rank-1 matrices is not unique, one property of the set of matrices is conserved. This property, defined as the stiffness-coupling index, identifies how the translational and rotational components of the stiffness are related. Here, we investigate the stiffness-coupling index of the rank-1 matrices that compose a spatial stiffness matrix. We develop a matrix decomposition that yields a set of rank-1 stiffness matrices that identifies the bounds on the stiffness-coupling index for any decomposition. This decomposition, referred to as the eigenscrew decomposition, is shown to be invariant in coordinate transformation. With this decomposition, we provide some physical insight into the behavior associated with a general spatial stiffness matrix.

In this paper, the structure and extremal properties of spatial stiffness matrices are investigated. From this work a better understanding of the spatial compliant behavior important in robot interaction tasks is attained. We develop a rank-1 decomposition of a spatial stiffness matrix which is independent of the coordinate frame used to describe the elastic behavior. We also identify the extremal properties associated with this decomposition. To attain better physical insight, analogies are drawn between this unique spatial stiffness matrix decomposition and the conventional eigenvalues decomposition of a translational stiffness matrix.

We identify the space of spatial compliant behavior that can be achieved through the use of simple springs connected in parallel to a single rigid body. Here, the expression "simple spring" refers to the set of compliant relations associated with passive translational springs and rotational springs. The restriction on the stiffness matrices is derived using the screw theory by investigating the compliant behavior of individual simple springs. We show that the restriction results from the fact that simple springs can only provide either a pure force or a pure torque to the suspended body. We show that the 20-dimensional subspace of "realizable" spatial stiffness matrices achieved with parallel simple springs is defined by a linear necessary and sufficient condition on the positive semidefinite stiffness matrix. A procedure to synthesize an arbitrary full-rank stiffness matrix within this realizable subspace is provided. This procedure requires no more than seven simple springs.