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Data-Driven Biped Control. Yoonsang Lee Sungeun Kim Jehee Lee Seoul National University. Biped Control. Human. Biped character. ?. Biped Control is Difficult. Balance, Robustness, Looking natural Various stylistic gaits. ASIMO Honda. Issues in Biped Control. Naturalness.
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Data-Driven Biped Control Yoonsang Lee Sungeun Kim Jehee Lee Seoul National University
Biped Control Human Biped character ?
Biped Control is Difficult • Balance, Robustness, Looking natural • Various stylistic gaits ASIMO Honda
Issues in Biped Control Naturalness human-like natural result Robustness maintaining balance Richness variety of motor skills Interactivity interactive control via user interface
Goal Naturalness As realistic as motion capture data Robust under various conditions Equipped with a variety of motor skills Controlled interactively Robustness Richness Interactivity
Related Work • Manually designed controller • [Hodgins et al. 1995] [Yin et al. 2007] • Non-linear optimization • [Sok 2007] [da Silva 2008] [Yin 2008] [Muico 2009] [Wang 2009] [Lasa 2010] [Wang 2010] [Wu 2010] • Advanced control methodologies • [da Silva 2008] [Muico 2009] [Ye 2010] [Coros 2010] [Mordatch 2010] • Data-driven approach • [Sok 2007] [da Silva 2008] [Muico 2009] [Tsai 2010] [Ye 2010] [Liu 2010]
Our Approach • Control methods have been main focus • Machine learning, optimization, LQR/NQR • We focus on reference data • Tracking control while modulatingreference data
Our Approach • Modulation of reference data • Balancing behavior of human • Importance of ground contact timings
Advantages • Do not require • Non-linear optimization solver • Derivatives of equations of motion • Optimal control • Precomputation Easy to implement & Computationally efficient
Advantages • Reference trajectory generated on-the-fly can be used Any existing data-driven techniques can be used to actuate physically simulated bipeds
Overview user interaction animation engine tracking control forward dynamics simulation data-driven control
Overview user interaction animation engine tracking control forward dynamics simulation data-driven control
PD (Proportional Derivative) Control • Compute joint torques directly generated torque desired pose current pose
Hybrid Dynamics Tracking Control • Compute desired tracking acceleration • Forward Dynamics : force -> acceleration • Inverse Dynamics : acceleration -> force • Hybrid Dynamics • floating root joint : force -> acceleration • internal joints : acceleration -> force external forces desired joint accelerations hybrid dynamics joint torques
Overview user interaction animation engine tracking control forward dynamics simulation data-driven control
Data-Driven Control • Continuous modulation of reference motion • Spatial deviation • Simple feedback balance control (Balancing behavior) • Temporal deviation • Synchronization reference to simulation (Importance of ground contact timings)
Balancing frame n frame n+1 frame n+2 reference motion ... ... ... simulation
Balancing frame n frame n+1 frame n+2 reference motion ... ... target pose ... simulation
Balancing frame n frame n+1 frame n+2 reference motion ... ... tracking ... simulation
Balancing frame n frame n+1 frame n+2 reference motion ... ... tracking ... simulation
Balance Feedback • Near-passive knees in human walking • Three-step feedback • stance hip • swing hip & stance ankle • swing foot height
Balance Feedback • Biped is leaning backward ? reference motion at current frame reference motion at next frame simulation
Balance Feedback • Stance Hip simulation target pose at next frame reference frame
Balance Feedback • Swing Hip & Stance Ankle simulation target pose at next frame reference frame
Balance Feedback • Swing Foot Height simulation target pose at next frame reference frame
Feedback Equations Stance hip Swing hip Stance ankle Swing foot height target pose reference frame
Feedback Equations Stance hip Swing hip Stance ankle Swing foot height desired states current states
Feedback Equations Stance hip Swing hip Stance ankle Swing foot height transition function parameters
Synchronization reference motion swing foot contacts the ground
Synchronization reference motion simulation current time
Early Landing reference motion contact occurs! simulation
Early Landing reference motion dequed simulation
Early Landing reference motion simulation
Early Landing reference motion warped simulation
Motion Warping motion1 motion2
Motion Warping motion1 motion2 d
Early Landing reference motion simulation
Delayed Landing reference motion not contact yet! simulation
Delayed Landing reference motion expand by integration simulation
Delayed Landing reference motion expand by integration contact occurs! simulation
Delayed Landing reference motion warped simulation
Delayed Landing reference motion simulation
Overview user interaction animation engine tracking control forward dynamics simulation data-driven control
Animation Engine • High-level control through user interfaces • Generate a stream of movement patterns user interaction query motion DB pattern generator motion fragments stream of movement patterns
Motion Database motion capture data motion fragments Collection of half-cycle motion fragments Maintain fragments in a directed graph