Application of Wrench-Based Feasibility Analysis to the Online Trajectory Optimization of Legged Robots

Romeo Orsolino, Michele Focchi, Carlos Mastalli, Hongkai Dai, Darwin G. Caldwell, Claudio Semini

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Motion planning in multicontact scenarios has recently gathered interest within the legged robotics community, however actuator force/torque limits are rarely considered. We believe that these limits gain paramount importance when the complexity of the terrains to be traversed increases. We build on previous research from the field of robotic grasping to propose two new six-dimensional bounded polytopes named the Actuation Wrench Polytope (AWP) and the Feasible Wrench Polytope (FWP). We define the AWP as the set of all the wrenches that a robot can generate while considering its actuation limits. This considers the admissible contact forces that the robot can generate given its current configuration and actuation capabilities. The Contact Wrench Cone (CWC) instead includes features of the environment such as the contact normal or the friction coefficient. The intersection of the AWP and of the CWC results in a convex polytope, the FWP, which turns out to be more descriptive of the real robot capabilities than existing simplified models, while maintaining the same compact representation. We explain how to efficiently compute the vertex-description of the FWP that is then used to evaluate a feasibility factor that we adapted from the field of robotic grasping. This allows us to optimize for robustness to external disturbance wrenches. Based on this, we present an implementation of a motion planner for our quadruped robot HyQ that provides online Center of Mass trajectories that are guaranteed to be statically stable and actuation-consistent.
Original languageEnglish
Pages (from-to)3363-3370
Number of pages8
JournalIEEE Robotics and Automation Letters
Issue number4
Publication statusPublished - 15 May 2018

Keywords / Materials (for Non-textual outputs)

  • actuators
  • end effectors
  • friction
  • legged locomotion
  • path planning
  • online trajectory optimization
  • legged robots
  • motion planning
  • robotic grasping
  • six-dimensional bounded polytopes
  • AWP
  • FWP
  • actuation limits
  • admissible contact forces
  • contact normal
  • convex polytope
  • motion planner
  • quadruped robot HyQ
  • force limits
  • CWC
  • actuation wrench polytope
  • feasible wrench polytope
  • contact wrench cone
  • wrench-based feasibility analysis
  • friction coefficient
  • online center of mass trajectories
  • torque limits
  • Legged locomotion
  • Friction
  • Force
  • Planning
  • Trajectory
  • Grasping
  • Legged robots
  • motion and path planning
  • manipulation planning
  • humanoid and bipedal locomotion


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