Optimal control of a two-wheeled mobile robot: Simulation for selecting of the motors

This paper presents how a novel simulation package for optimal control based on dynamic programming can be used for selecting the drives once the constraints are known: range of speeds, trajectory (minimum radius for turns), load that will be carried by the mobile robot and its position on the platform (inertia! properties of the mobile robot with the load). We calculate the necessary driving torques at the wheels of the mobile robot for various trajectories having a shape of the figure eight within a given time. The simulation uses fully customized dynamic model of the mobile robot that is propelled by two independent wheels and has third non-powered wheel that freely rotates around the vertical shaft to ensure three degrees of freedom. Dynamic programming and the discrete mathematic model allow simulation of the non-holonomic system. We presented in this paper only one possible application, that is, the analysis of three different loads carried along the same trajectory. The simulation clearly shows the relation between the tracking error and required diving torque; thereby, allow selection of the adequate driving motors for a given load and vice versa.

Modélisation et Traitement Informatique de la Synonymie

This paper deals with automatic structuring of semantic values in a dictionary of synonyms. The data we used were first extracted from seven French published dictionnaries of synonyms and then merged to obtain the files we worked on. We explain here why a discrete mathematic representation of synonymic relation is not sufficient to produce a semantic structure (that represents the different meanings of a term but also their overlapping). Then we propose a continuous representation (using data analysis) that ables the machine to produce for each term its semantic values. The system also labels these values with prototypic synonyms and detects synonyms that share different semantic "axes" with the headword. It should be noted that these semantic spaces are obtained automatically for each headword from a homogeneous list of synonyms.