This paper presents a systematic procedure for the elastodynamic modeling of industrial robots that is applicable to either serial or parallel manipulators. This procedure is based on a 3-D space generalization of the equivalent rigid link system (ERLS) description, the finite-element method (FEM), and the Lagrange principle. It considers flexible links and joints, and leads to generic equations of motion expressed according to the angles of the actuated joints and the independent elastic degrees of freedom. An efficient identification process through modal analysis is detailed, and the description of damping and joint behavior according to the model application is discussed. The method is applied to a 3-D delta-like parallel structure and successfully validated through an experimental impact testing-based modal analysis.

This paper presents the design optimization of a Delta-like robot manipulator with respect to multiple global stiffness objectives. For this purpose, a systematic elasto-geometrical modeling method is used to derive the analytical manipulator stiffness models by taking into account their link and joint compliances. The models are then involved within a statistically sensitivity analysis of the influence of the geometric parameters on four global indices that describe the structure stiffness over the workspace. Multi-Objective Genetic Algorithm, i.e. Pareto-optimization, is taken as the appropriate framework for the definition and the solution of the addressed multi-objective optimization problem. Our approach is original in the sense that it is systematic and it can be applied to any serial and parallel manipulators for which stiffness is a critical issue.

This paper presents the elasto-geometrical modelling of an industrial robot manipulator whose structure includes a closed-loop mechanism. This modelling is done for sensitivity studies and calibration purposes since the robot is involved in machining operations that require a high level of quasi static positioning accuracy. The kinematics of the machine is described first then the systematic approach that is proposed to calculate the elastic modelling of its architecture is presented. Simulations and experiments are presented next in order to evaluate the limitations and benefits of the proposed modelling approach.

The purpose of this work is to propose a new approach for the calculation of PKM stiffness matrix by using an analytical method based on matrix structural analysis. This method has as the main advantage to be systematic and it also can be applied to hyper-static PKM stiffness analysis. The implementation of the proposed method is fast and convenient and it can easily be involved during PKM design optimization. Moreover, as the stiffness matrix is obtained in a close form, it can be implemented directly on the robot controller. In other words, the proposed method could be used to reduce the gap existing between actual PKM and those that have to meet the high accuracy specifications required for machining applications. At first this paper presents the proposed analytical method that is applied to calculate the stiffness matrix of a delta parallel structure. Then the experimental results that have been done to evaluate and validate its efficiency are presented

This paper presents an improved method for the geometrical calibration of parallel robots for which the structure is based upon some parallelogram mechanisms. Its originality is to identify the complete geometry of the mechanism's parallelograms, and to compensate the positioning error of the TCP (tool centre point), due to the infinitesimal rotation of the traveling plate, induced by the parallelogram geometrical errors. The main difficulties are: (i) to derive the calibration model relative to all geometrical parameters, and (ii) to reuse the identified errors in a control model in order to compensate the positioning errors. In fact, the position relationship taking into account the full geometry of the parallelograms is difficult, not to say impossible, to derive in a close form; therefore a linear approximation of the model is proposed. The formulas necessary to run the method on a Delta robot are given. Then a simple mechanism is used to illustrate the benefits of this method compared to classical ones

The increasing applications of parallel robots in domains such as medical or machine-tools require a high accuracy. As a result, the geometrical calibration of these mechanisms becomes a major step to reach the expected accuracy. An effective and simple calibration method based on 1D and 3D measurements of a new low cost artifact is presented and then validated on the Surgiscope/spl reg/, a structure based on a delta parallel robot used in neurosurgery.

A new geometrical self-calibration method for delta parallel robots with compensation of the non-geometrical gravity effects is proposed. It allows a quick and easy enhancement of the robot positioning accuracy through the implementation of redundant sensors on its structure. After the theoretical aspects of the method, simulations are presented and compared to the experimental results.

A two stage calibration method for the parallel robot Delta 4 is presented. It allows one to identify the offsets on the three first joints and the absolute location of the robot base. It involves a cheap displacement sensor and dedicated targets which can be easily moved on the work area. Intensive simulations show the robustness of the protocol and experimental results validate this procedure.