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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. HUBO KAIST. PETMAN Boston Dynamics.
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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 HUBO KAIST PETMAN Boston Dynamics
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
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
Overview user interaction animation engine tracking control forward dynamics simulation data-driven control
Data-Driven Control • Continuous modulation of reference motion • Spatial deviation • SIMBICON-style feedback balance control • Temporal deviation • Synchronization reference to simulation
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
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
Tracking Control • Compute torques that attempts to follow reference trajectory (ex. PD control) • We use floating-base hybrid inverse dynamics external forces desired joint accelerations inverse dynamics joint torques
Why does this simple approach work? • Human locomotion is inherently robust • Mimicking human behavior • Distinctive gait serves as a reference trajectory • We do modulate the reference trajectory
Discussion • We do not need optimization, optimal control, machine learning, or any precomputation • Physically feasible reference motion data • Future work • Wider spectrum of human motions
Acknowledgements • Thank • All the members of SNU Movement Research Laboratory • Anonymous reviewers • Support • MKE & MCST of Korea