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Two degree-of-freedom (DOF) manipulators have been widely applied in pointing devices. Besides the commonly used gimbal platforms, two different kinds of parallel platforms base on parallel manipulators are presented as real applications in this paper. In a situation, a pointing device acquires and tracks a remote target via optical sensors amounted on the device. As the authors’ recent research, there are image distortions caused by deflected camera axis while the pointing device changing its attitudes. The paper refers the phenomena to the self-motion characteristics as the 2-DOF platforms rotate around the fixed platform axis. Basic image distortion principles of the three platforms are illustrated and discussed. Relationship between the self-motion and revolution are analyzed via the graphic approach and simulated on the software. Results indicate that these different phenomena are due to the different inherent characters of the platform’s freedom lines and freedom disks. Conclusions revealed in this paper would help the engineers with the type selections and applications, especially for the remote virtual reality devices which can provide realistic images for the human eyes. This work will facilitate the image processing and improve the measuring accuracy for the pointing devices.

In this work, a family of two degrees of freedom (2-DOF) rotational parallel manipulators (RPMs) with an equal-diameter spherical pure rotation (ESPR) is presented and discussed systematically. The theoretical models of both kinematics and constraints inherited in the manipulators are analyzed through a graphical approach. Based on the established constraint model, these 2-DOF ESPR RPMs are classified into three types according to their compositions of constraint spaces and several novel parallel manipulators are illustrated correspondingly. Finally, two common necessary geometric conditions satisfied for these manipulators are discussed in details with examples. The two conditions will be helpful for engineers with designing ESPR RPMs. Moreover, as one characteristic existing in the ESPR RPMs, two cases of self-rotations accompanying revolutions around fixed axes are revealed. As a result, the corresponding loci of points in the moving platform are proved to be compositions of two subrotations, which are spatial curves and surfaces rather than spherical curves and surfaces. [DOI: 10.1115/1.4025860]

Two-degree-of-freedom (2-DOF) rotational parallel manipulators (RPMs) have been widely used in pointing devices and robot wrists. This paper focuses on a class of 2-DOF RPMs achieving an equal-diameter spherical pure rolling motion (ESPRM) around the base. At first, a theoretical model of spherical pure rolling motion is analyzed and the characteristic of the associated constraint space is derived. Taking the Omni-Wrist III as a typical 2-DOF RPMs with an equal-diameter spherical pure rolling motion, mappings between the geometry and the motion are established and eight useful constraint conditions are derived which will be instructive for the type synthesis. Then, with focus on symmetrical structures, nine classes of 2-DOF RPMs with equal-diameter spherical pure rolling motion are synthesized based on the graphic method. Most of these RPMs have already been used in practice. Unlike the conventional type synthesis of lower-mobility parallel manipulators in literatures, some geometrical parameters of links, in addition to the distributions of joints and limbs, are taken into consideration in the type synthesis in this paper. This proposed research may help produce novel architectures.Copyright © 2013 by ASME

A leaf-type isosceles-trapezoidal flexural pivot can be of great practical use for designing compliant mechanisms. The analysis of load-deflection behavior for such a pivot is essential to the study of the mechanisms that are comprised of them. Based on the analysis of a single special loaded leaf segment, a pseudo-rigid-body four-bar model is proposed. The four-bar model is further simplified to a pin-joint model for some simple applications. The accuracy of both models is demonstrated by comparing results to those of nonlinear finite element analysis. At last, the two models are applied to analyze the cartwheel hinge as an example.

An isosceles-trapezoidal flexural pivot can be of great use for practical designs, especially in the cases that a pure rotation about a virtual pivot is required. The analysis of rotational precision for such a structure is important for the mechanical design in precise-required applications. For this purpose, a rigid isosceles-trapezoidal linkage model is first proposed to provide an accurate analytical result for its notch-type flexural counterpart. The influence of dimensional parameters on the center shift is discussed. In order to disclose the equivalence between leaf-type flexure structure and its pseudo-rigid-body model, a transitional model is introduced, from which an equivalent pseudo-rigid-body model for leaf-type isosceles-trapezoidal flexure structure is then derived. The results of both simulation and experiment verify that the equivalent rigid model is also accurate enough in the case of a larger deflection.

A novel dexterous 6DOF manipulator serially connected by two compliant parallel stages is presented in this paper. The upper stage is a 3-RPS mechanism and the lower one is a 3-RRR mechanism. In virtue of the method of the physical model of the solution space, optimal design of the lower stage has been accomplished. Then, the calibration of the lower stage is undergoing by means of an ultra-precision vision system. The experiment shows that the lower stage possesses workspace of 120 mum times 130 mum times 18mrad with the resolution of 50 nm, 50 nm, 18 arcsec, respectively. This manipulator is to be used as a fiber optics aligner

With respect to the great ratio of the length to the thickness of right-angle-notch flexure hinge, the necessity of the study on the buckling characteristics of the right-angle-notch flexure universal hinges and the compliant parallel mechanism composed of them, was presented. The mathematical model, for calculating the buckling critical force of the right-angle-notch flexure universal hinge, was established on the approximate differential equation of deflection curve of the material bending theory. With this, the conception of equivalent section inertial moment was put forward. Finally, based on the former theoretical research on the compliant parallel multi-bar mechanism composed of the right-angle-notch flexure hinges, the mathematical formula for calculating the buckling critical force of the compliant parallel mechanism was proposed. The buckling critical force of the sample has been measured by experiment and by FEA (finite element analysis) with the commercial software ANSYS 8.0. The values from the mathematical model, from experiment and from FEA separately all met well, which indicated the correctness of the mathematical model. In summary, the mathematical model proposed above can be used in the optimization of the design of the right-angle-notch flexure hinge and it's compliant parallel mechanism in buckling characteristic.

In this paper, the fluorescence detection of microarray is analyzed. The guidelines for optical system of microarray scanner based on CCD is proposed. A novel CCD-based microarray scanner system is developed in terms of the guidelines. The control subsystem and software for scanner are studied in details. Finally, some preliminary experiment results are presented.

A new dexterous 6-DOF two-stage serial-parallel micromanipulator is described. The kinematics of this mechanism are analyzed with the method of vector analysis, and some advantages are also discussed. Inertia forces, moments of inertia and elastic potential energy are also analyzed. The dynamics of the SP mechanism has been modeled using a Lagrangian approach.

The 6 DOF serial-parallel micromotion manipulator discussed in this paper comprises two 3 DOF parallel mechanisms connected in series with one another. Manufacturing tolerances, actuation errors, link offsets, and connection errors of two stages cause deviations with respect to the nominal structural parameters of the manipulator. If the nominal values of these parameters are used within the control software of the manipulator, the resulting pose of the end-effector will be inaccurate. In order to evaluate the effects of the above factors upon the pose accuracy, a vector arithmetic method is applied to establish the relations between the pose accuracy and manufacturing tolerances, actuation errors, and connection errors of two parallel mechanisms. Some results which are very useful to the design and manufacture of the micromotion manipulator are derived. The analysis method can also be used on the accuracy analysis of other type parallel or serial-parallel mechanisms.