Duperret, Jeffrey M.
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Publication Technical Report on: Towards Reactive Control of Simplified Legged Robotics Maneuvers(2017-10-24) Duperret, Jeff; Koditschek, Daniel EThis technical report provides proofs and calculations for the paper "Towards Reactive Control of Simplified Legged Robotics Maneuvers," as well as implementation notes and a discussion on robustness.Publication An Empirical Investigation of Legged Transitional Maneuvers Leveraging Raibert’s Scissor Algorithm(2015-12-01) Duperret, Jeff; Koditschek, Daniel EWe empirically investigate the implications of applying Raibert’s Scissor algorithm to the Spring Loaded Inverted Pendulum (SLIP) model in combination with other controllers to achieve transitional maneuvers. Specifically, we are interested in how the conjectured neutral stability of Raibert’s algorithm allows combined controllers to push the system’s operating point around the state space without needing to expend limited control affordance in overcoming its stability or compensating for its instability. We demonstrate 2 cases where this facilitates the construction of interesting transitional controllers on a physical robot. In the first we use the motors in stance to maximize the rate of change of the body energy; in the second we take advantage of the local environmental energy landscape to push the robot’s operating point to a higher or lower energy level without expending valuable motor affordance. We present data bearing on the energetic performance of these approaches in executing an accelerate-and-leap maneuver on a monopedal hopping robot affixed to a boom in comparison to the cost of anchoring the robot to the SLIP template. For more information: Kod*labPublication Free-Standing Leaping Experiments with a Power-Autonomous, Elastic-Spined Quadruped(2013-04-01) Duperret, Jeffrey M.; Pusey, Jason L.; Haynes, G. Clark; Koditschek, Daniel E; Knopf, RyanWe document initial experiments with Canid, a freestanding, power-autonomous quadrupedal robot equipped with a parallel actuated elastic spine. Research into robotic bounding and galloping platforms holds scientific and engineering interest because it can both probe biological hypotheses regarding bounding and galloping mammals and also provide the engineering community with a new class of agile, efficient and rapidly-locomoting legged robots. We detail the design features of Canid that promote our goals of agile operation in a relatively cheap, conventionally prototyped, commercial off-the-shelf actuated platform. We introduce new measurement methodology aimed at capturing our robot’s “body energy” during real time operation as a means of quantifying its potential for agile behavior. Finally, we present joint motor, inertial and motion capture data taken from Canid’s initial leaps into highly energetic regimes exhibiting large accelerations that illustrate the use of this measure and suggest its future potential as a platform for developing efficient, stable, hence useful bounding gaits. For more information: Kod*LabPublication Empirical validation of a spined sagittal-plane quadrupedal model(2017-06-01) Duperret, Jeff; Koditschek, Daniel EWe document empirically stable bounding using an actively powered spine on the Inu quadrupedal robot, and propose a reduced-order model to capture the dynamics associated with this additional, actuated spine degree of freedom. This model is sufficiently accurate as to roughly describe the robots mass center trajectory during a bounding limit cycle, thus making it a potential option for low dimensional representations of spine actuation in steady-state legged locomotion.Publication Core Actuation Promotes Self-Manipulability on a Direct-Drive Quadrupedal Robot(2016-10-20) Duperret, Jeff; Kramer, Benjamin; Koditschek, Daniel EFor direct-drive legged robots operating in unstructured environments, workspace volume and force generation are competing, scarce resources. In this paper we demonstrate that introducing geared core actuation (i.e., proximal to rather than distal from the mass center) increases workspace volume and can provide a disproportionate amount of work-producing force to the mass center without affecting leg linkage transparency. These effects are analytically quantifiable up to modest assumptions, and are demonstrated empirically on a spined quadruped performing a leap both on level ground and from an isolated foothold (an archetypal feature of unstructured terrain).Publication Towards a Comparative Measure for Legged Agility(2014-06-01) Duperret, Jeffrey; Kenneally, Gavin; Koditschek, Daniel E; Pusey, JasonWe introduce an agility measure enabling the comparison of two very different leaping-from-rest transitions by two comparably powered but morphologically different legged robots. We use the measure to show that a flexible spine outperforms a rigid back in the leaping- from-rest task. The agility measure also sheds light on the source of this benefit: core actuation through a sufficiently powerful parallel elastic actuated spine outperforms a similar power budget applied either only to preload the spine or only to actuate the spine during the leap, as well as a rigid backed configuration of the identical machine.Publication Towards Reactive Control of Transitional Legged Robot Maneuvers(2017-12-14) Duperret, JeffWe propose the idea of a discrete navigation problem – consisting of controlling the state of a discrete-time control system to reach a goal set while in the interim avoiding a set of obstacle states – to approximate a simplified class of transitional legged robotic tasks such as leaping which have no well established mathematical description that lends itself to synthesis. The control relation given in Theorem 1 is (assuming a task solution exists) necessary and sufficient to solve a discrete navigation problem in a minimum number of steps, and is well suited to computation when a legged system’s continuous-time within-stride controller anchors sufficiently simple stance mechanics. We demonstrate the efficacy of this control technique on a physical hopping robot affixed to a boom to reactively leap over an obstacle with a running start, controlling in continuous time during stance to exhibit a linear stance map.Publication Desert RHex Technical Report: Tengger Desert Trip(2014-11-01) Roberts, Sonia F; Duperret, Jeffrey M; Li, Xinwan; Wang, Hesheng; Koditschek, Daniel EDesertification is a long-standing issue in China, but research on the processes of desertification is limited by availability of personnel and technical equipment. This suggests a perfect application and further testing ground for the mobile desert sensing technology described in a previous technical report. We describe here the first of two trips to the Tengger Desert as part of a collaborative effort to bring Desert RHexes to China, with the goal of this trip being to discover and address potential locomotor challenges. Our robots were able to ascend 20-degree slopes with an 8.5kg payload, indicating that they could indeed be used for this novel mobile desert sensor application. We achieved locomotion on up to 30-degree slopes unreliably and on up to 27-degree slopes using morphological and behavioral adaptations inspired by our last desert trip.Publication Desert RHex Technical Report: Jornada and White Sands Trip(2014-11-01) Roberts, Sonia; Duperret, Jeff; Johnson, Aaron M.; van Pelt, Scott; Koditschek, Daniel E; Zobeck, Ted; Lancaster, NickResearchers in a variety of fields, including aeolian science, biology, and environmental science, have already made use of stationary and mobile remote sensing equipment to increase their variety of data collection opportunities. However, due to mobility challenges, remote sensing opportunities relevant to desert environments and in particular dune fields have been limited to stationary equipment. We describe here an investigative trip to two well-studied experimental deserts in New Mexico with D-RHex, a mobile remote sensing platform oriented towards desert research. D-RHex is the latest iteration of the RHex family of robots, which are six-legged, biologically inspired, small (10kg) platforms with good mobility in a variety of rough terrains, including on inclines and over obstacles of higher than robot hip height. For more information: Kod*LabPublication Extended Version of Stability of a Groucho-Style Bounding Run in the Sagittal Plane(2023-01-12) Duperret, Jeff; Koditschek, Daniel EThis paper develops a three degree-of-freedom sagittal-plane hybrid dynamical systems model of a Groucho-style bounding quadrupedal run. Simple within-stance controls using a modular architecture yield a closed form expression for a family of hybrid limit cycles that represent bounding behavior over a range of user-selected fore-aft speeds as a function of the model's kinematic and dynamical parameters. Controls acting on the hybrid transitions are structured so as to achieve a cascade composition of in-place bounding driving the fore-aft degree of freedom, thereby decoupling the linearized dynamics of an approximation to the stride map. Careful selection of the feedback channels used to implement these controls affords infinitesimal deadbeat stability which is relatively robust against parameter mismatch. Experiments with a physical quadruped reasonably closely match the bounding behavior predicted by the hybrid limit cycle and its stable linearized approximation.