Analysis and Control of Contact Centers of Pressure and Internal Forces in Humanoid Robots Using the Virtual Linkage Model

Dr. Luis Sentis, Stanford University

Abstract

Since Waseda University unveiled the humanoid robot Wabot-1 in 1973, humanoids have evolved from a showcase device to a promising service machine. An important problem in humanoids is their ability to manipulate and move in their environments through whole-body multicontact interactions. This ability is an important skill towards enabling humanoids to operate efficiently in human environments. In this talk I will present a methodology for the analysis and control of internal forces produced during multicontact interactions between humanoid robots and their environment. The approach is based on the virtual linkage model which provides a physical representation of the internal forces and moments acting between the various contacts. The forces acting at the contacts are decomposed into internal and resulting forces and the latter are represented at the robot's center of mass. A grasp/contact matrix describing the complex interactions between contact forces and center of mass movements is developed and proposed as a tool to analyze the stability of multicontact behaviors. A new approach for the control of internal forces is suggested and illustrated on the Asimo humanoid robot. The new controller is integrated into the framework for whole-body prioritized multitasking enabling the unifed control of operational tasks, postures, and internal forces.