Roberts, Sonia F
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Publication Mitigating energy loss in a robot hopping on a physically emulated dissipative substrate(2019-05-01) Roberts, Sonia F.; Koditschek, Daniel EWe work with geoscientists studying erosion and desertification to improve the spatial and temporal resolution of their data collection over long transects in difficult realworld environments such as deserts. The Minitaur robot, which can run quickly over uneven terrain and use a single leg to measure relevant ground properties such as stiffness, is an attractive scout robot candidate for inclusion in a heterogeneous team in collaboration with a heavily geared, sensor-laden RHex. However, Minitaur is challenged by long-distance locomotion on sand dunes. Previous simulation results suggested that the energetic cost of transport can be mitigated by programming a virtual damping force to slow the intrusion of a Minitaur foot into simulated granular media following a bulk-behavior force law. In this paper, we present a ground emulator that can be used to test such locomotion hypotheses with a physical single-legged hopper jumping on emulated ground programmed to exhibit any compliance and damping characteristics of interest. The new emulator allows us to corroborate the conclusions of our previous simulation with physical hopping experiments. Programming the substrate emulator to exhibit the mechanics of a simplified bulk-behavior model of granular media characterized by linear stiffness and quadratic damping, we achieve a consistent energy savings of 20% in comparison with a nominal controller, with savings of up to 50% under specific conditions. For more information, see https://kodlab.seas.upenn.edu.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 Ground robotic measurement of aeolian processes(2017-08-01) Qian, Feifei; Jerolmack, Douglas J; Lancaster, Nicholas; Nikolich, George; Reverdy, Paul B; Roberts, Sonia F; Shipley, Thomas F; Van pelt, Robert Scott; Zobeck, Ted M; Koditschek, Daniel EModels of aeolian processes rely on accurate measurements of the rates of sediment transport by wind, and careful evaluation of the environmental controls of these processes. Existing field approaches typically require intensive, event-based experiments involving dense arrays of instruments. These devices are often cumbersome and logistically difficult to set up and maintain, especially near steep or vegetated dune surfaces. Significant advances in instrumentation are needed to provide the datasets that are required to validate and improve mechanistic models of aeolian sediment transport. Recent advances in robotics show great promise for assisting and amplifying scientists’ efforts to increase the spatial and temporal resolution of many environmental measurements governing sediment transport. The emergence of cheap, agile, human-scale robotic platforms endowed with increasingly sophisticated sensor and motor suites opens up the prospect of deploying programmable, reactive sensor payloads across complex terrain in the service of aeolian science. This paper surveys the need and assesses the opportunities and challenges for amassing novel, highly resolved spatiotemporal datasets for aeolian research using partially-automated ground mobility. We review the limitations of existing measurement approaches for aeolian processes, and discuss how they may be transformed by ground-based robotic platforms, using examples from our initial field experiments. We then review how the need to traverse challenging aeolian terrains and simultaneously make high-resolution measurements of critical variables requires enhanced robotic capability. Finally, we conclude with a look to the future, in which robotic platforms may operate with increasing autonomy in harsh conditions. Besides expanding the completeness of terrestrial datasets, bringing ground-based robots to the aeolian research community may lead to unexpected discoveries that generate new hypotheses to expand the science itself. For more information: Kod*lab (http://kodlab.seas.upenn.edu/)Publication RHex Slips on Granular Media(2016-01-01) Roberts, Sonia F.; Koditschek, Dan E.RHex is one of very few legged robots being used for realworld rough-terrain locomotion applications. From its early days, RHex has been shown to locomote successfully over obstacles higher than its own hip height [1], and more recently, on sand [2] and sand dunes [3], [4] (see Figure 1). The commercial version of RHex made by Boston Dynamics has been demonstrated in a variety of difficult, natural terrains such as branches, culverts, and rocks, and has been shipped to Afghanistan, ostensibly for use in mine clearing in sandy environments [5]. Here, we discuss recent qualitative observations of an updated research version of RHex [6] slipping at the toes on two main types of difficult terrain: sand dunes and rubble piles. No lumped parameter (finite dimensional) formal model nor even a satisfactory computational model of RHexs locomotion on sand dunes or rubble piles currently exists. We briefly review the extent to which available physical theories describe legged locomotion on flat granular media and possible extensions to locomotion on sand dunes.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 Towards a method for obstacle porosity classification(2014-01-01) Roberts, Sonia FPublication Mechanical and virtual compliance for robot locomotion in a compliant world(2019-05-23) Roberts, Sonia F.; Koditschek, Daniel E.This abstract was accepted to the Robot Design and Customization workshop at ICRA 2019. For more information: Kod*lab.Publication Systematizing Gibsonian affordances in robotics: an empirical, generative approach derived from case studies in legged locomotion(2019-05-25) Roberts, Sonia F.; Miracchi, Lisa J.; Koditschek, Daniel E.A Gibsonian theory of affordances commits to direct perception and the mutuality of the agent-environment system. We argue that there already exists a research program in robotics which incorporates Gibsonian affordances. Controllers under this research program use information perceived directly from the environment with little or no further processing, and implicitly respect the indivisibility of the agentenvironment system. Research investigating the relationships between environmental and robot properties can be used to design reactive controllers that provably allow robots to take advantage of these affordances. We lay out key features of our empirical, generative Gibsonian approach and both show how it illuminates existing practice and suggest that it could be adopted to facilitate the systematic development of autonomous robots. We limit the scope of projects discussed here to legged robot systems but expect that applications can be found in other fields of robotics research. This paper was presented at the 2nd International Workshop on Computational Models of Affordances at ICRA 2019. For more information, see: Kod*labPublication Reactive Velocity Control Reduces Energetic Cost of Jumping with a Virtual Leg Spring on Simulated Granular Media(2018-11-05) Roberts, Sonia F.; Koditschek, Daniel ERobots capable of dynamic locomotion behaviors and high-bandwidth sensing with their limbs have a high cost of transport, especially when locomoting over highly dissipative substrates such as sand. We formulate the problem of reducing the energetic cost of locomotion by a Minitaur robot on sand, reacting to robot state variables in the inertial world frame without modeling the ground online. Using a bulk-behavior model of high-velocity intrusions into dry granular media, we simulated single jumps by a one-legged hopper using a Raibert-style compression-extension virtual leg spring. We compose this controller with a controller that added damping to the leg spring in proportion to the intrusion velocity of the robot's foot into the simulated sand while the robot is pushing off in the second half of stance. This has the effect of both reducing the torque exerted by the motors because the added virtual "active damping" force acts in opposition to the virtual leg spring force, and reducing the transfer of energy from the robot to the sand by slowing the intrusion velocity of the foot. Varying the simulated robot's initial conditions and the simulated ground parameters, we gained a consistent 20% energy savings by adding active damping with no cost in apex height. For more information, see the Kod*lab website: kodlab.seas.upenn.eduPublication Using the art practice of play to communicate legged robotics research concepts(2018-01-04) Krieger, Diedra; Roberts, Sonia F.The art practice of play uses spontaneity and surprise to communicate meaningful content and inspire critical thinking (1-3). We describe three engineering education outreach efforts that use play to communicate legged robotics research concepts. In the first workshop, Penn engineering students were motivated to learn how to program a legged robot using the narrative of a “dance competition,” with the winning dances to be showcased at the Philadelphia Science Festival. In the second workshop, Philadelphia School District high school students used a poseably programmable legged robot to tell a story by performing a series of behaviors in a set of their own design and documenting the story as a video artwork. Here, there were two narratives: One created by the workshop directors, communicating concepts about complex multi-legged behaviors and gaits, and the other created by the students using the robots to express their ideas. In the final workshop, middle school students created locomoting robots using motors, post-consumer materials, and basic art supplies. The concepts of energy and physical programming were demonstrated using working Trashbots and practiced during an introductory exercise making a vibrating motor from a spinning one. Participants then created a robot of their own design using iterative experimentation. We conclude from these three workshops that play can be used as a vehicle for scientific communication. (1) David Getsy, ed. From diversion to subversion: Games, play, and twentieth-century art, Vol. 16 (Penn State Press, 2011). (2) Nato Thompson and Gregory Scholette, eds. The interventionists: Users' manual for the creative disruption of everyday life (MIT Press, 2004). (3) Diedra Krieger, ‘Plastic Fantastic,’ Gyre Exhibition, Anchorage Museum, Alaska, 2014. For more information: Kod*lab.