Constraint-based identification of a dynamic model

Dynamic simulation is potentially a powerful tool for studying complex contact interactions between robots and their environments. One of the main problems of such a simulation is the determination of the model parameters which provide realistic behavior for objects. This paper describes how to identify such parameters for a masses/springs based system (the Robot Phi system [JL97]). This identification process is composed of two main steps: the first step consists in distributing the total mass of the object between the different particles while respecting the inertial properties of the object; the second one consists in finding the values of the physical parameters of the model such as elasticity, viscosity, plasticity, etc. A numerical solution of the first step will be described, while a genetic algorithm base approach will be proposed for the second step. This approach allows us to find the values of the parameters which provide a consistent behavior under a set of given constraints (position, velocity, volume, etc.). It also allows us to minimize the computation time and to attach priorities with these constraints.