Biped Controller for Character Animation

Abstract

In this chapter, we first overview the common methods for building biped con-trollers in physics-based character animation. Then we explain in detail two closely related biped controllers: SIMBICON and GENBICON. The simple biped loco-motion control (SIMBICON) strategy adopts a simple linear feedback strategy for foot placement to maintain balance during locomotion. The generalized biped walking control (GENBICON) strategy improves the balance control using an inverted pendulum model for foot placement, in conjunction with Jacobian-transpose control for velocity fine-tuning and gravity compensation for all limb movement. Both SIMBICON and GENBICON use proportional-derivative joint servos to track a desired motion style, which can be interactively edited by users. The major advantages of such biped controllers include simplicity, robustness, and directable styles. Finally, we discuss our ongoing efforts toward building more versatile and robust controllers with minimal prior knowledge.