In this paper, a new method for the estimation of orientation repeatability index is proposed for industrial manipulator robots. First, we compute orientation repeatability in different locations of the workspace using the experimental covariance matrix and the stochastic ellipsoid modeling. Then we display experimental results about the direct measurement of orientation repeatability for an industrial Samsung robot in different workspace locations and with different loads. The two proposed procedures are compared. We analyze the incidence of workspace location on orientation repeatability and bring additional results to the existing literature.

The paper proposes a new procedure to compare the repeatability of serial and parallel robots based on the stochastic ellipsoid theory. The ISO9283 position repeatability index is estimated but also other performance criteria built upon the stochastic ellipsoid geometrical characteristics. The choice of the best comparison criterion is investigated and different solutions are proposed, associated with the task specificity. For each criterion, maps are built to determine the set of workspace points where the serial robot is better than the parallel robot. The ratio of the workspace surface where one robot is better than the other is computed and the results are analysed. Contrary to the common opinion that parallel robots are more accurate than serial robots, we prove here that the repeatability performance depends mainly on the chosen performance criterion. Another result found is that the considered R̲RRRR̲ parallel robot keeps the same repeatability in all its workspace.

In this paper, we display experimental results about the measurement of repeatability of an industrial Kuka robot. We first study the distributions of the angular positions and show that these distributions can be considered as Gaussian. We compute repeatability in different locations of the workspace using the experimental angular covariance matrix and the stochastic ellipsoid modeling. We measure repeatability and observe a high variability. We explain the phenomenon by drawing the distribution of the 30 sample repeatability index. We then compare the computed andmeasured repeatability and conclude that our modeling gives good results. We analyse the incidence of weight and workspace location on repeatability and bring additional results to the existing literature.

This article is about the design and simulation of hybrid dynamic systems modelled by Petri nets without conflict. For this purpose, a fuzzy multi-model is developed that combines a discrete event description and a continuous approximation of the transitions firing. The transitions are characterised by local clocks, firing rates, and starting orders that are described as fuzzy variables. The definition of the fuzzy sets is related to balance parameters that are suitable to represent the discrete and continuous parts of the hybrid Petri nets. In fact, the fuzzy multi-model has two limit behaviours that correspond to T-timed Petri nets and continuous Petri nets with variable speeds when the balance parameters tend either to zero or to infinity. Thus, the spatial distribution of the balance parameters is useful to design and simulate hybrid systems with a unique model.