Dynamic Model of a Conjugate-Surface Flexure Hinge Considering Impacts between Cylinders

A dynamic model of a Conjugate-Surface Flexure Hinge (CSFH) has been proposed as a component for MEMS/NEMS Technology-based devices with lumped compliance. However, impacts between the conjugate surfaces have not been studied yet and, therefore, this paper attempts to fill this gap by proposing a detailed multibody system (MBS) model that includes not only rigid-body dynamics but also elastic forces, friction, and impacts. Two models based on the Lankarani-Nikravesh constitutive law are first recalled and a new model based on the contact of cylinders is proposed. All three models are complemented by the friction model proposed by Ambrosio. Then, the non-smooth Moreau time-stepping scheme with Coulomb friction is described. The four models are compared in different scenarios and the results confirm that the proposed model outcomes comply with the most reliable models

Equation Section 1Proceedings of IDETC/CIE 2005: Fifth ASME International Conference on Multibody Systems, Nonlinear Dynamics and Control DYNAMICS OF A TWO-DOF PARALLEL POINTING MECHANISM

ABSTRACT This paper presents kinematic and dynamic analyses of a two-degree-of-freedom pointing parallel mechanism. The mechanism consists of a moving platform, connected to a fixed platform by two legs of type PUS (prismatic-universalspherical). At first a simplified kinematic model of the pointing mechanism is introduced. Based on this proposed model, the dynamics equations of the system using the Natural Orthogonal Complement method are developed. Numerical examples of the inverse dynamics results are presented by numerical simulation

Kinetostatic and Inertial Conditioning of the McGill Schönflies-Motion Generator

This paper focuses on the optimization of the McGill Schönflies Motion Generator. Recent trends on optimum design of parallel robots led us to investigate the advantages and disadvantages derived from an optimization based on performance indices. Particularly, we optimize here two different indices: the kinematic conditioning and the inertial conditioning, pertaining to the condition number of the Jacobian matrix and to that of the generalized inertia matrix of the robot, respectively. The problem of finding the characteristic length for the robot is first investigated by means of a constrained optimization problem; then plots of the kinetostatic and the inertial conditioning indices are provided for a particular trajectory to be tracked by the moving platform of the SMG. Deep connections appear between the two indices, reflecting a correlation between kinematics and dynamics

Tie-System Calibration for the Experimental Setup of Large Deployable Reflectors

The trade-off between the design phase and the experimental setup is crucial in satisfying the accuracy requirements of large deployable reflectors. Manufacturing errors and tolerances change the root mean square (RMS) of the reflecting surface and require careful calibration of the tie-rod system to be able to fit into the initial design specifications. To give a possible solution to this problem, two calibration methods—for rigid and flexible ring truss supports, respectively—are described in this study. Starting from the acquired experimental data on the net nodal co-ordinates, the initial problem of satisfying the static equilibrium with the measured configuration is described. Then, two constrained optimization problems (for rigid or flexible ring truss supports) are defined to meet the desired RMS accuracy of the reflecting surface by modifying the tie lengths. Finally, a case study to demonstrate the validity of the proposed methods is presented

Direct Kinetostatic Analysis of a Gripper with Curved Flexures

Micro-electro-mechanical-systems (MEMS) extensively employed planar mechanisms with elastic curved beams. However, using a curved circular beam as a flexure hinge, in most cases, needs a more sophisticated kinetostatic model than the conventional planar flexures. An elastic curved beam generally allows its outer sections to experience full plane mobility with three degrees of freedom, making complex non-linear models necessary to predict their behavior. This paper describes the direct kinetostatic analysis of a planar gripper with an elastic curved beam is described and then solved by calculating the tangent stiffness matrix in closed form. Two simplified models and different contributions to derive their tangent stiffness matrices are considered. Then, the Newton–Raphson iterative method solves the non-linear direct kinetostatic problem. The technique, which appears particularly useful for real-time applications, is finally applied to a case study consisting of a four-bar linkage gripper with elastic curved beam joints that can be used in real-time grasping operations at the microscale