Virtual Model Control An Intuitive Approach for Bipedal….pdfVIP

Virtual Model Control: An Intuitive Approach for Bipedal Locomotion Jerry Pratt, Chee-Meng Chew, Ann Torres, Peter Dilworth, Gill Pratt MIT Leg Laboratory, Cambridge, MA 02139 /projects/leglab/ Abstract The transformation from high level task specification to low level motion control is a fundamental issue in sensorimotor control in animals and robots. This paper describes a control scheme called Virtual Model Control that addresses this issue. Virtual Model Control is a motion control language that uses simulations of imagined mechan- ical components to create forces, which are applied through real joint torques, thereby creating the illusion that the virtual components are connected to the robot. Due to the intuitive nature of this technique, designing a Virtual Model Controller requires the same skills as designing the mechanism itself. A high level control system can be cascaded with the low level Virtual Model Controller to modulate the parameters of the virtual mechanisms. Discrete commands from the high level controller would then result in fluid motion. Virtual Model Control has been applied to a physical bipedal walking robot. A simple algo- 1 rithm utilizing a simple set of virtual components has successfully compelled the robot to walk continuously over level terrain. We also describe how an algorithm based on Virtual Model Control can be applied to dynamic walking over sloped terrain without knowing the slope gradients and transition locations. The algorithm is augmented from the level terrain algorithm based on geometric considerations. The overall algorithm is very simple and does not require the biped to have an extensive sensory system for walk