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What biomechanics teaches us about biped control design

What biomechanics teaches us about biped control design. Hugh Herr Biomechatronics Group Media Lab , MIT Workshop: Learning for Locomotion June 11, 2005 . The MIT Biomechatronics Group . Organismal Biomechanics & Control. Muscle Biomechanics & Control.

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What biomechanics teaches us about biped control design

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  1. What biomechanics teaches us about biped control design Hugh Herr Biomechatronics Group Media Lab , MIT Workshop: Learning for Locomotion June 11, 2005

  2. The MIT Biomechatronics Group Organismal Biomechanics & Control Muscle Biomechanics & Control Human Rehabilitation & Amplification

  3. Why Study Human Biomechanics? • An understanding of human biomechanics may motivate improved methodologies for the evaluation and treatment of motor pathology. • Biomechanical investigations may elucidate underlying, reduced order models that explain human CM, ZMP and body rotational dynamics. • That knowledge may prove valuable for biomimetic hardware designs and for the development of human-like control systems for rehabilitation (restoring function) and amplification technologies (advancing function).

  4. R CONTACT FLIGHT PHASE CONTACT y R APEX vX TOUCH- DOWN TAKE-OFF yAPEX 0 x Are Swing Phase Limb Rotations Critical to Running Stability? Seyfarth, A., Geyer, H., Herr, H. (2003) Swing-leg retraction: a simple control model for stable running. Journal of Experimental Biology 206, 2547-2555 2547.

  5. Normalized Spin Angular Momentum Whole body Effective Angle Whole body effective angular velocity is Recipe: Integrate angular velocity to get whole body effective angle. Spin angular momentum highly regulated in walking (Popovic et al. 2004) Zero spin as global control objective (Popovic et al.2002)

  6. CM ZMP Zero-Moment Body Mechanics

  7. Results: Walking

  8. Centroidal Moment Pivot (CMP) Point (Popovic et al. 2005)

  9. Virtual Center of Mass (VCM)

  10. Spin Regulation: Rapid generation of CMP and VCM trajectories (Popovic et al. 2004)

  11. Is Spin Always Regulated? NO! (Popovic and Herr 2005)

  12. The Limits of Zero-Moment Balancing (ZMP Control) • Since the ZMP is bounded by the support polygon, there exists a limit on CM force magnitudes for the zero-moment case • What if the zero-moment force is not enough? What if more horizontal force is required, but the feet can not be repositioned?

  13. Would Controlling Both ZMP and CMP Enhance Legged Stability? Zero-Moment Moment (Popovic et al. 2005)

  14. Moment Balance Strategy Critical for Human-Like Balancing

  15. Would Controlling Both ZMP and CMP Enhance Legged Stability? CMP (red) ZMP (blue) Hofmann A., Popovic M., Massaquoi S., Herr H. A Sliding Controller for Bipedal Balancing Using Integrated Movement of Non-Contact Limbs. IEEE/RSJ International Conference on Intelligent Robots and Systems; 2004 October; Sendai, Japan; pp. 1952-1959.

  16. Trip Recovery through prediction and global force field adjustment

  17. Who We Are

  18. Key Conclusions • Assuming zero CM moment, we derive a nonlinear relationship between ground reaction force, center of mass position, and ZMP location, or • For human walking, these zero-moment forces closely match experimental forces (R2x = 0.94; R2y =0.91), indicating a high degree of angular momentum regulation. • The zero-moment condition allows for a simple mapping from CM trajectory to a predicted ZMP trajectory (CMP), or from a ZMP trajectory to a predicted CM trajectory (VCM). • For movements where spin is not regulated, bipedal balance is greatly improved through the application of Zero-Moment and Moment Balance Strategies (ZMP and CMP control)

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