Modeling of robots in contact with a dynamic environment

A control-oriented modeling approach for describing kinematics and dynamics of robots in contact with a dynamic environment is presented. In many robotic tasks the manipulator in contact cannot be simply modeled as a kinematically constrained system. Conversely, modeling of robot-environment interactions through dynamic impedance may not fit the task layout. A suitable model structure is proposed in this note that handles the more general case in which purely kinematic constraints on the robot end-effector live together with dynamic interactions. Feasible end-effector configurations are parameterized from the environment point of view, using a minimal set of coordinates. Accordingly, a description is obtained also for admissible velocities and contact forces. In particular, a force parameterization is chosen so as to separate static reaction forces from active forces responsible for energy transfer between robot and environment. The overall dynamics of the coupled robot-environment system is obtained in a single framework. The introduced modeling technique naturally leads to the design of new hybrid control laws