Jørgen Asbøl Kepler

Dynamic modeling and design optimization of a 3-DOF spherical parallel manipulator

This paper deals with the dynamic modeling and design optimization of a three Degree-of-Freedom spherical parallel manipulator. Using the method of Lagrange multipliers, the equations of motion of the manipulator are derived by considering its motion characteristics, namely, all the components rotating about the center of rotation. Using the derived dynamic model, a multiobjective optimization problem is formulated to optimize the structural and geometric parameters of the spherical parallel manipulator. The proposed approach is illustrated with the design optimization of an unlimited-roll spherical parallel manipulator with a main objective to minimize the mechanism mass in order to enhance both kinematic and dynamic performances.

Error Modeling and Experimental Validation of a Planar 3-PPR Parallel Manipulator With Joint Clearances

This paper deals with the error modelling and analysis of a 3-\underline{P}PR planar parallel manipulator with joint clearances. The kinematics and the Cartesian workspace of the manipulator are analyzed. An error model is established with considerations of both configuration errors and joint clearances. Using this model, the upper bounds and distributions of the pose errors for this manipulator are established. The results are compared with experimental measurements and show the effectiveness of the error prediction model.

Stiffness characterization of a 3-PPR planar parallel manipulator with actuation compliance

This paper investigates the stiffness of a compliant planar parallel manipulator. Instead of establishing stiffness matrix directly for planar mechanisms, we adopt the modeling approach for spatial mechanisms, which allows us to derive two decoupled homogeneous matrices, corresponding to the translational and rotational stiffness. This is achieved by resorting to the generalized eigenvalue problem, through which the eigenscrew decomposition is implemented to yield six screw springs. The principal stiffnesses and their directions are then identified from the eigenvalue problem of the two separated submatrices. In addition, the influence of the nonlinear actuation compliance to the manipulator stiffness is investigated, and the established stiffness model is experimentally verified.

Stiffness Analysis and Comparison of 3-PPR Planar Parallel Manipulators With Actuation Compliance

In this paper, the stiffness of 3-PPR planar parallel manipulator (PPM) is analyzed with the consideration of nonlinear actuation compliance. The characteristics of the stiffness matrix pertaining to the planar parallel manipulators are analyzed and discussed. Graphic representation of the stiffness characteristics by means of translational and rotational stiffness mapping is developed. The developed method is illustrated with an unsymmetrical 3-PPR PPM, being compared with its structure-symmetrical counterpart.Copyright

Error modelling and experimental validation for a planar 3-PPR parallel manipulator

In this paper, the positioning error of a 3-PPR planar parallel manipulator is studied with an error model and experimental validation. First, the displacement and workspace are analyzed. An error model considering both configuration errors and joint clearance errors is established. Using this model, the maximum positioning error was estimated for a U-shape PPR planar manipulator, the results being compared with the experimental measurements. It is found that the error distributions from the simulation is approximate to that of the measurements.

Ballistic impact facility - considerations and experiences

A facility for testing of ballistic impact has been designed and developed. The goal was to develop a facility which was relatively easy to use and modify, as the requirements for the testing equipment changed with different research projects, e.g. students projects [1]. The setup consisted of a compressed air gun with an exchangeable barrel, a speed trap for measuring the incident velocity and a kinetic pendulum which both served as a means to measure the residual energy of the projectile and to catch the projectile from further travel. The aim of this paper was to cover some of the experiences encountered during the design and development high velocity impact test equipment.