Most of the time, the construction of
legged robots is made in an empirical way and the
optimization of the mechanical structure is seldom taken into account.
In order to avoid spending time and money on the
construction of many prototypes to test their performance, a CAD
tool and a methodology seem to be necessary. In this
way it will be possible to optimize on one hand
the kinematic structure of the legs, on the other hand
the gaits which will be used by the future robot.
Thus, we have developed a methodology to design walking structures
such as quadrupeds and bipeds, to simulate their dynamic behavior
and analyse their performances. The feet/ground interaction is one of
the major problem in the context of dynamic simulation for
walking devices. Thus, we focus here about the phenomenon of
contact. This paper describes a general model for dynamic simulation
of contacts between a walking robot and ground. This model
considers a force distribution and uses an analytical form for
each force depending only on the known state of the
robot system. The simulation includes all phenomena that may occur
during the locomotion cycle: impact, transition from impact to contact,
contact during support with static friction, transition from static to
sliding friction, sliding friction and transition from sliding to static
friction. Some examples are presented to show the use of
this contact model for the simulation of the foot-ground interaction
during a walking gait.
DYNAMIC SIMULATION OF LEGGED ROBOTS USING A PHYSICS ENGINE
