Optimal Robust Safety-Critical Control for Legged Locomotion

Legged Research

Legged Research

Our research is advancing Lyapunov-funciton based controllers that offer formal guarantees on stability along the three axis of constraints, model uncertainty, and safety-critical constrains. This enables taking a feedback controller that stabilize periodic orbits and enable the following features: - Enforce input constraints such as torque saturation; - Enforce input and state constraints such as unilateral ground contact force constraints and friction constraints; - Enforce safety-critical constraints such as precise footstep placements for walking dynamically on stepping stones or UAV flight while avoiding collisions; and - Do all of the above while also being subject to significant model uncertainty.

Publications - Robust Stability and Safety (Robust CLFs / CBFs)

  1. Optimal Robust Control for Constrained Nonlinear Hybrid Systems with Application to Bipedal Locomotion. Quan Nguyen and Koushil Sreenath. American Control Conference (ACC), pages 4807--4813, Boston, MA, July 2016. pdf Video
    @conference{ ACC2016_Robust_CBFCLF,
    author={ Quan Nguyen and Koushil Sreenath },
    title={ Optimal Robust Control for Constrained Nonlinear Hybrid Systems with Application to Bipedal Locomotion },
    booktitle={ American Control Conference (ACC) },
    pages={ 4807--4813 },
    month={ July },
    year={ 2016 },
    address={ Boston, MA },
    }
  2. Optimal Robust Time-Varying Safety-Critical Control with Application to Dynamic Walking on Moving Stepping Stones. Quan Nguyen and Koushil Sreenath. ASME Dynamics Systems and Control Conference (DSCC), Minneapolis, MN, October 2016. pdf Video
    @conference{ DSCC2016_Robust_TimeVarying_SteppingStones,
    author={ Quan Nguyen and Koushil Sreenath },
    title={ Optimal Robust Time-Varying Safety-Critical Control with Application to Dynamic Walking on Moving Stepping Stones },
    booktitle={ ASME Dynamics Systems and Control Conference (DSCC) },
    pages={ },
    month={ October },
    year={ 2016 },
    address={ Minneapolis, MN },
    }
  3. Optimal Robust Safety-Critical Control for Dynamic Robotics. Quan Nguyen and Koushil Sreenath. International Journal of Robotics Research (IJRR), in review, 2016. pdf Video
    @article{ IJRR2016_RobustCBF,
    author={ Quan Nguyen and Koushil Sreenath },
    title={ Optimal Robust Safety-Critical Control for Dynamic Robotics },
    journal={ International Journal of Robotics Research (IJRR) },
    volume={ },
    number={ },
    pages={ },
    month={ },
    year={ in review, 2016 },
    }

Publications - Safety-Critical Constraints (CBFs)

  1. Safety-Critical and Constrained Geometric Control Synthesis using Control Lyapunov and Control Barrier Functions for Systems Evolving on Manifolds. Guofan Wu and Koushil Sreenath. American Control Conference (ACC), pages 2038--2044, Chicago, IL, July 2015. pdf
    @conference{ ACC2015_Geometric_CBFCLF,
    author={ Guofan Wu and Koushil Sreenath },
    title={ Safety-Critical and Constrained Geometric Control Synthesis using Control Lyapunov and Control Barrier Functions for Systems Evolving on Manifolds },
    booktitle={ American Control Conference (ACC) },
    pages={ 2038--2044 },
    month={ July },
    year={ 2015 },
    address={ Chicago, IL },
    }
  2. Safety-Critical Control for Dynamical Bipedal Walking with Precise Footstep Placement. Quan Nguyen and Koushil Sreenath. IFAC Analysis and Design of Hybrid Systems (ADHS), Atlanta, GA, October 2015. pdf Video
    @conference{ ADHS2015_FootstepCBF,
    author={ Quan Nguyen and Koushil Sreenath },
    title={ Safety-Critical Control for Dynamical Bipedal Walking with Precise Footstep Placement },
    booktitle={ IFAC Analysis and Design of Hybrid Systems (ADHS) },
    pages={ },
    month={ October },
    year={ 2015 },
    address={ Atlanta, GA },
    }
  3. Safety-Critical Control of a Planar Quadrotor. Guofan Wu and Koushil Sreenath. American Control Conference (ACC), pages 2252--2258, Boston, MA, July 2016. pdf Video
    @conference{ ACC2016_Safety_Control_Planar_Quadrotor,
    author={ Guofan Wu and Koushil Sreenath },
    title={ Safety-Critical Control of a Planar Quadrotor },
    booktitle={ American Control Conference (ACC) },
    pages={ 2252--2258 },
    month={ July },
    year={ 2016 },
    address={ Boston, MA },
    }
  4. 3D Dynamic Walking on Stepping Stones with Control Barrier Functions. Quan Nguyen, Ayonga Hereid, J. W. Grizzle, Aaron D. Ames, and Koushil Sreenath. IEEE International Conference on Decision and Control (CDC), pages 827--834, Las Vegas, NV, December 2016. pdf Video
    @conference{ CDC2016_3DWalking_SteppingStones,
    author={ Quan Nguyen and Ayonga Hereid and J. W. Grizzle and Aaron D. Ames and Koushil Sreenath },
    title={ 3D Dynamic Walking on Stepping Stones with Control Barrier Functions },
    booktitle={ IEEE International Conference on Decision and Control (CDC) },
    pages={ 827--834 },
    month={ December },
    year={ 2016 },
    address={ Las Vegas, NV },
    }
  5. Safety-Critical Control of a 3D Quadrotor with Range-Limited Sensing. Guofan Wu and Koushil Sreenath. ASME Dynamics Systems and Control Conference (DSCC), Minneapolis, MN, October 2016. pdf Video
    @conference{ DSCC2016_Safety_Control_3D_Quadrotor,
    author={ Guofan Wu and Koushil Sreenath },
    title={ Safety-Critical Control of a 3D Quadrotor with Range-Limited Sensing },
    booktitle={ ASME Dynamics Systems and Control Conference (DSCC) },
    pages={ },
    month={ October },
    year={ 2016 },
    address={ Minneapolis, MN },
    }
  6. Dynamic Walking on Stepping Stones with Gait Library and Control Barrier. Quan Nguyen, Xingye Da, J. W. Grizzle, and Koushil Sreenath. Workshop on Algorithimic Foundations of Robotics (WAFR), 2016. pdf Video
    @conference{ WAFR2016_GaitLibrary_SteppingStones,
    author={ Quan Nguyen and Xingye Da and J. W. Grizzle and Koushil Sreenath },
    title={ Dynamic Walking on Stepping Stones with Gait Library and Control Barrier },
    booktitle={ Workshop on Algorithimic Foundations of Robotics (WAFR) },
    pages={ },
    month={ },
    year={ 2016 },
    address={ },
    }
  7. Safety-Critical Geometric Control for Systems on Manifolds Subject to Time-Varying Constraints. Guofan Wu and Koushil Sreenath. IEEE Transactions on Automatic Control (TAC), in review, 2016. pdf Video
    @article{ TAC2016_Geometric_TimeVarying_CBF,
    author={ Guofan Wu and Koushil Sreenath },
    title={ Safety-Critical Geometric Control for Systems on Manifolds Subject to Time-Varying Constraints },
    journal={ IEEE Transactions on Automatic Control (TAC) },
    volume={ },
    number={ },
    pages={ },
    month={ },
    year={ in review, 2016 },
    }

Publications - Uncertainty (Robust / Adaptive CLFs)

  1. L1 Adaptive Control for Bipedal Robots with Control Lyapunov Function based Quadratic Programs. Quan Nguyen and Koushil Sreenath. American Control Conference (ACC), pages 862--867, Chicago, IL, July 2015. pdf Video
    @conference{ ACC2015_L1_CLF,
    author={ Quan Nguyen and Koushil Sreenath },
    title={ L1 Adaptive Control for Bipedal Robots with Control Lyapunov Function based Quadratic Programs },
    booktitle={ American Control Conference (ACC) },
    pages={ 862--867 },
    month={ July },
    year={ 2015 },
    address={ Chicago, IL },
    }
  2. Optimal Robust Control for Bipedal Robots through Control Lyapunov Function based Quadratic Programs. Quan Nguyen and Koushil Sreenath. Robotics: Science and Systems (RSS), Rome, Italy, July 2015. pdf Supplementary Material
    @conference{ RSS2015_RobustCLF,
    author={ Quan Nguyen and Koushil Sreenath },
    title={ Optimal Robust Control for Bipedal Robots through Control Lyapunov Function based Quadratic Programs },
    booktitle={ Robotics: Science and Systems (RSS) },
    pages={ },
    month={ July },
    year={ 2015 },
    address={ Rome, Italy },
    }

Publications - Constraints (CLF-QP)

  1. Torque Saturation in Bipedal Robotic Walking through Control Lyapunov Function Based Quadratic Programs. Kevin Galloway, Koushil Sreenath, Aaron D. Ames, and Jessy W. Grizzle. IEEE Access, 3:323--332, April 2015. pdf Video
    @article{ Access2015_CLFQP,
    author={ Kevin Galloway and Koushil Sreenath and Aaron D. Ames and Jessy W. Grizzle },
    title={ Torque Saturation in Bipedal Robotic Walking through Control Lyapunov Function Based Quadratic Programs },
    journal={ IEEE Access },
    volume={ 3 },
    number={ },
    pages={ 323--332 },
    month={ April },
    year={ 2015 },
    }

Publications - Stability

  1. Torque Saturation in Bipedal Robotic Walking through Control Lyapunov Function Based Quadratic Programs. Kevin Galloway, Koushil Sreenath, Aaron D. Ames, and Jessy W. Grizzle. IEEE Access, 3:323--332, April 2015. pdf Video
    @article{ Access2015_CLFQP,
    author={ Kevin Galloway and Koushil Sreenath and Aaron D. Ames and Jessy W. Grizzle },
    title={ Torque Saturation in Bipedal Robotic Walking through Control Lyapunov Function Based Quadratic Programs },
    journal={ IEEE Access },
    volume={ 3 },
    number={ },
    pages={ 323--332 },
    month={ April },
    year={ 2015 },
    }