Standing self-manipulation for a legged robot

Abstract

Follow this and additional works at: http://repository.upenn.edu/ese_papers Part of the Electrical and Computer Engineering Commons, and the Systems Engineering Commons BibTeX entry @inproceedings{paper:johnson-iros-2012, author = {Aaron M. Johnson and G Clark Haynes and D E Koditschek}, title = {Standing Self-Manipulation for a Legged Robot}, booktitle = {Proceedings of the IEEE/RSJ Intl. Conference on Intelligent Robots and Systems}, month = {October}, year = {2012}, address = {Algarve, Portugal}, pages = {272--279} } AbstractOn challenging, uneven terrain a legged robot's open loop posture will almost inevitably be inefficient, due to uncoordinated support of gravitational loads with coupled internal torques. By reasoning about certain structural properties governing the infinitesimal kinematics of the closed chains arising from a typical stance, we have developed a computationally trivial self-manipulation behavior that can minimize both internal and external torques absent any terrain information. The key to this behavior is a change of basis in torque space that approximates the partially decoupled nature of the two types of disturbances. The new coordinates reveal how to use actuator current measurements as proprioceptive sensors for the approximate gradients of both the internal and external task potential fields, without recourse to further modeling. The behavior is derived using a manipulation framework informed by the dual relationship between a legged robot and a multifingered hand. We implement the reactive posture controller resulting from simple online descent along these proprioceptively sensed gradients on the X-RHex robot to document the significant savings in standing power. For more information: Kod*Lab Disciplines Electrical and Computer Engineering | Engineering | Systems EngineeringComments BibTeX entry @inproceedings{paper:johnson-iros-2012, author = {Aaron M. Johnson and G Clark Haynes and D E Koditschek}, title = {Standing Self-Manipulation for a Legged Robot}, booktitle = {Proceedings of the IEEE/ RSJ Intl. Conference on Intelligent Robots and Systems}, month = {October}, year = {2012}, address = {Algarve, Portugal}, pages = {272--279} } Abstract-On challenging, uneven terrain a legged robot's open loop posture will almost inevitably be inefficient, due to uncoordinated support of gravitational loads with coupled internal torques. By reasoning about certain structural properties governing the infinitesimal kinematics of the closed chains arising from a typical stance, we have developed a computationally trivial self-manipulation behavior that can minimize both internal and external torques absent any terrain information. The key to this behavior is a change of basis in torque space that approximates the partially decoupled nature of the two types of disturbances. The new coordinates reveal how to use actuator current measurements as proprioceptive sensors for the approximate gradients of both the internal and external task potential fields, without recourse to further modeling. The beha...

Kinematics and methods for combined quasi-static stance/reach planning in multi-limbed robots

“…Many authors [4], [9], [16]- [18] have previously noted these similarities. One of the contributions of this paper is to make these analogies explicit.…”

Toward a vocabulary of legged leaping

“…We will assume that the actuators can deliver the greatest amount of work to the body when they are individually doing the most work they can on their individual motor shafts. The infinitesimal kinematics of rigid closed kinematic chains generically accord unequally weighted contribution to the net body wrench (see [24] for one example). However, none of the closed chains relevant to leaps against the simple level substrate encounter sign changes in these weights, so actuators might "waste" energy generating internal forces but will not impart negative work 3 Though compliance can easily be added back, as in [23] and others.…”

“…Given present space constraints, we defer to [32] our preferred method of populating (by formal symbolic manipulation) the exact terms in appropriate local coordinates arising in each of the 16 different Lagrangian dynamical systems describing the distinctly different contact mechanics associated with each GRC cell 6 . We simply exhibit here the formal abstract expression from which each specific instance can be systematically derived.…”

“…Take for example the case where both legs are on the ground (following [24]). The holonomic constraints a : Q → R 4 that induce forces Γ ∈ T * Q that act on the body give rise to the takeoff condition, The constraint force magnitudes at contact, λ ∈ R 4 , and the friction matrix F ∈ R 4x2 will give the guard condition.…”

“…For example, several high kinetic energy RHex gaits have relatively small basins which can be very effectively "prepared" [50] by selecting the apex state from rest via a leap [32]. However, here, we focus on compound jumps across bigger obstacles than any single leap can afford.…”