Design and Analysis of a Flipping Controller for RHex

Abstract

We report on the design and analysis of a controller that can achieve dynamical self-righting of our hexapedal robot, RHex. We present an empirically tuned controller that works reasonably well on indoor surfaces, using a hybrid energy pumping strategy to overcome torque limitations of its actuators. Subsequent modeling and analysis yields a new controller with a much wider domain of success as well as a preliminary understanding of the hybrid control strategy. Simulation results demonstrate the superiority of the improved control strategy relative to the first generation empirically designed controller. * Supported in part by DARPA/ONR Grant N00014-98-1-0747 Report Documentation PageForm Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

Multi-Point Contact Models for Dynamic Self-Righting of a Hexapod

“…As a consequence, the leg must "lift off" before it reaches its vertical configuration, at an angle which is a function of both the pitch angle and the pitch velocity. Detailed discussions of the algorithms necessary to uniquely identify contact states for this model and the derivation of its dynamics can be found in [13].…”

“…In this paper, we report on efforts to extend RHex's present capabilities with a self-righting controller. Based on our earlier work in this domain [13,14], we introduce a multi-point contact model based on Coulomb friction so as to derive the maximum benefit of our robot's limited power budget. In designing a model-based feedback controller, we highlight fundamental singularity problems in handling multiple intermittent contacts under external actuation and illustrate a particular solution for our application domain.…”

Kinetostatic backflip strategy for self-recovery of quadruped robots with the selected rotation axis

“…For legged robots, work has been presented on six-legged robots. A hexapod robot named the RHex [29] achieved the self-recovery ability, which was further improved by a specially designed controller [30]. Utilizing the inertia with a dynamic process and extra boosters or multiple legs to gain more support points, a solution was proposed by Peng [31] for a hexapod robot to plan the self-recovery motion.…”