Handwriting-Assistant

Pen-based handwriting has become one of the major human-computer interaction methods. Traditional approaches either require writing on the specific supporting device like the touch screen, or limit the way of using the pen to pure rotation or translation. In this paper, we propose Handwriting-Assistant, to capture the free handwriting of ordinary pens on regular planes with mm-level accuracy. By attaching the inertial measurement unit (IMU) to the pen tail, we can infer the handwriting on the notebook, blackboard or other planes. Particularly, we build a generalized writing model to correlate the rotation and translation of IMU with the tip displacement comprehensively, thereby we can infer the tip trace accurately. Further, to display the effective handwriting during the continuous writing process, we leverage the principal component analysis (PCA) based method to detect the candidate writing plane, and then exploit the distance variation of each segment relative to the plane to distinguish on-plane strokes. Moreover, our solution can apply to other rigid bodies, enabling smart devices embedded with IMUs to act as handwriting tools. Experiment results show that our approach can capture the handwriting with high accuracy, e.g., the average tracking error is 1.84mm for letters with the size of about 2cmx1cm, and the average character recognition rate of recovered single letters achieves 98.2% accuracy of the ground-truth recorded by touch screen.

Development of Wrist Interface Based on Fully Actuated Coaxial Spherical Parallel Mechanism for Force Interaction

To develop a wrist robotic exoskeleton-type interface (REI) for force interaction, it should have a suitable range of motion similar to human wrist activities of daily living, large torque output performance, and low moving parts inertia for dynamic motion response to cover the human behavior frequency. In this paper, a wrist REI based on a fully actuated coaxial spherical parallel mechanism (CSPM) is proposed to satisfy the aforementioned features. The fully actuated CSPM-based wrist REI (FC-WREI) has the characteristics of pure rotation similar to the human wrist, high torque output by parallel torque synthesis, and low moving parts inertia due to the base arrangement of the actuators. Due to the mechanical advantages and design optimization, the FC-WREI maximally provides torque as much as 56.49–130.43% of the maximum isometric torque of the human wrist, while providing a consistent range of motion to the human wrist without interference problem. Moreover, it is confirmed that the inertia of the FC-WREI is up to 5.35 times lower than similar devices. These advantages of the FC-WREI mean that the device is applicable to various fields of REIs for force interaction.

Spatial Variation in Temperature and Density in the IC 63 PDR from H2 Spectroscopy

We have measured the gas temperature in the IC 63 photodissociation region (PDR) using the S(1) and S(5) pure rotation lines of molecular hydrogen with SOFIA/EXES. We divide the PDR into three regions for analysis based on the illumination from γ Cas: sunny, ridge, and shady. Constructing rotation diagrams for the different regions, we obtain temperatures of T ex = 562 − 43 + 52 K toward the ridge and T ex = 495 − 25 + 28 K in the shady side. The H2 emission was not detected on the sunny side of the ridge, likely due to the photodissociation of H2 in this gas. Our temperature values are lower than the value of T ex = 685 ± 68 K using the S(1), S(3), and S(5) pure rotation lines, derived by Thi et al. using lower spatial resolution ISO-SWS data at a different location of the IC 63 PDR. This difference indicates that the PDR is inhomogeneous and illustrates the need for high-resolution mapping of such regions to fully understand their physics. The detection of a temperature gradient correlated with the extinction into the cloud, points to the ability of using H2 pure rotational line spectroscopy to map the gas temperature on small scales. We used a PDR model to estimate the FUV radiation and corresponding gas densities in IC 63. Our results shows the capability of SOFIA/EXES to resolve and provide detailed information on the temperature in such regions.

Exact equilibrium distributions in statistical quantum field theory with rotation and acceleration: Dirac field

We derive the general exact forms of the Wigner function, of mean values of conserved currents, of the spin density matrix, of the spin polarization vector and of the distribution function of massless particles for the free Dirac field at global thermodynamic equilibrium with rotation and acceleration, extending our previous results obtained for the scalar field. The solutions are obtained by means of an iterative method and analytic continuation, which lead to formal series in thermal vorticity. In order to obtain finite values, we extend to the fermionic case the method of analytic distillation introduced for bosonic series. The obtained mean values of the stress-energy tensor, vector and axial currents for the massless Dirac field are in agreement with known analytic results in the special cases of pure acceleration and pure rotation. By using this approach, we obtain new expressions of the currents for the more general case of combined rotation and acceleration and, in the pure acceleration case, we demonstrate that they must vanish at the Unruh temperature.

Design and Validation of A Novel Planar 2R1T Remote Center-of-motion Mechanism Composing of Dual-Triangular and Straight-Line Linkages

Benefiting from small incision and fast recovery, minimally invasive surgeries (MIS) exhibit great advantages in clinical operations. In such kind of surgeries, the remote center-of-motion (RCM) mechanisms play an important role owing to their special motion characteristics. This paper presents the design of a novel planar RCM mechanism of two rotational and one translational degrees-of-freedom. In the proposed design, the mobility of RCM mechanisms is decomposed into one-DOF pure rotation and translation with a remote stationary point. The dual-triangular linkage and the Peaucellier-Lipkin straight-line linkage are introduced to achieve the remote rotation and translation, respectively. Inspired by the concept of virtual screw, a dual-helical differential-motion joint is particularly designed to generate the coaxial rotation and translation. A preliminary prototype is developed to validate the feasibility of the designed RCM mechanism. The experimental results show that the developed prototype is easy to control and of acceptable positioning accuracy, which manifests potential application in MIS.

CONSTRAINT-BASED ANALYSIS OF PARALLEL KINEMATIC ARTICULATED WRIST MECHANISM

This paper presents a systematic constraint-based analysis of the performance attributes of eight parallel kinematic articulated wrist mechanisms from the existing literature. These performance attributes include the number, nature (i.e. pure rotation, or translation, or a combination), and location of a mechanism's Degrees of Freedom (DoFs) in the nominal and displaced configurations, load transmission capability along these DoFs, and load bearing capability along the constraint directions. This systematic analysis reveals performance tradeoffs between these performance attributes for a given mechanism, as well as design tradeoffs across these mechanisms. This analysis also helps inform the suitability of a given mechanism for specific applications.

3D Model for Active Vibration Control of Rotating Machines Mounted on Active Machine Foot Mounts Using Vibration Mode Coupling by Asymmetry

Purpose In this work, active vibration control of rotating machines mounted on active machine foot mounts is investigated. Methods Therefore, a simplified 3D model is derived and the mathematical coherences are described. Different mathematical solutions are presented for special boundary conditions and a method called “vibration mode coupling by asymmetry” is derived. Results It could be shown that a symmetrical system with a machine design, where the center of gravity lies symmetrically between the machine feet with a vertical distance, and where all actuators are identical, represents a system, where all vibration shapes but one can be influenced by the controllers, when the gyroscopic effect can be neglected. In this case, a special vibration shape occurs—where the machine is only rotating at its vertical axis—which cannot be influenced by the controllers. When the stiffness and/or damping in axial and/or horizontal direction of only one actuator will be changed—which will lead to an asymmetrical system—the vibration shape with pure rotation at the vertical axis will not exist anymore. Now, the vibration shapes will become more coupled and they all can be influenced by the controllers, which is here called “vibration mode coupling by asymmetry”. Conclusions With the here presented method of “vibration mode coupling by asymmetry”, all vibrations mode shapes can now be active controlled.

Constraint-Based Analysis of Parallel Kinematic Articulated Wrist Mechanisms

This paper presents a systematic constraint-based analysis of the motion attributes of six parallel kinematic articulated wrist mechanisms from the existing literature. These motion attributes include the number, nature (i.e. pure rotation, or translation, or a combination), and location of mechanism’s Degrees of Freedom (DoFs) in the nominal and displaced configurations, range of operation along these DoFs, load transmission capability along these DoFs, and load bearing capability along the constraint directions. This systematic analysis reveals performance tradeoffs between these motion attributes for a given mechanism, as well as design tradeoffs across these multiple mechanisms with respect to these motion attributes. This analysis should help inform the suitability of a given mechanism for specific applications.

Metric-Affine Geometries with Spherical Symmetry

We provide a comprehensive overview of metric-affine geometries with spherical symmetry, which may be used in order to solve the field equations for generic gravity theories which employ these geometries as their field variables. We discuss the most general class of such geometries, which we display both in the metric-Palatini formulation and in the tetrad/spin connection formulation, and show its characteristic properties: torsion, curvature and nonmetricity. We then use these properties to derive a classification of all possible subclasses of spherically symmetric metric-affine geometries, depending on which of the aforementioned quantities are vanishing or non-vanishing. We discuss both the cases of the pure rotation group SO ( 3 ) , which has been previously studied in the literature, and extend these previous results to the full orthogonal group O ( 3 ) , which also includes reflections. As an example for a potential physical application of the results we present here, we study circular orbits arising from autoparallel motion. Finally, we mention how these results can be extended to cosmological symmetry.