Creating controllers for physics-based characters is a long-standing open problem in animation and robotics. Such controllers would have numerous applications while potentially yielding insight into human motion. Creating controllers remains difficult: current approaches are either constrained to track motion capture data, are not robust, or provide limited control over style.;This thesis presents an approach to control of physics-based characters based on high-level features of human movement, such as center-of-mass, angular momentum, and end-effector motion. Objective terms are used to control each feature, and are combined via optimization. We show how locomotion can be expressed in terms of a small number of features that control balance and end-effectors. This approach is used to build controllers for biped balancing, jumping, walking, and jogging.;These controllers provide numerous benefits: human-like qualities such as arm-swing, heel-off, and hip-shoulder counter-rotation emerge automatically during walking; controllers are robust to changes in body parameters; control parameters apply to intuitive properties; and controller may be mapped onto entirely new bipeds with different topology and mass distribution, without controller modifications. Transitions between multiple types of gaits, including walking, jumping, and jogging, emerge automatically. Controllers can traverse challenging terrain while following high-level user commands at interactive rates. This approach uses no motion capture or off-line optimization process.;Although we focus on the challenging case of bipedal locomotion, many other types of controllers stand to benefit from our approach.
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