Electrical and Computer Engineering
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PublicationDesert RHex Technical Report: Jornada and White Sands Trip(2014-11-01) Roberts, Sonia; Duperret, Jeff; Roberts, Sonia; Duperret, Jeff; Johnson, Aaron M.; Koditschek, Daniel E; Zobeck, Ted; Lancaster, Nick; Koditschek, Daniel EResearchers 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*Lab PublicationMechanical and virtual compliance for robot locomotion in a compliant world(2019-05-23) Roberts, Sonia F.; Koditschek, Daniel E.; 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. PublicationReactive Velocity Control Reduces Energetic Cost of Jumping with a Virtual Leg Spring on Simulated Granular Media(2018-11-05) Roberts, Sonia F.; 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.edu PublicationTowards a method for obstacle porosity classification(2014-01-01) Roberts, Sonia F; Roberts, Sonia F PublicationGround 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 E; 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/) PublicationDesert RHex Technical Report: Tengger Desert Trip(2014-11-01) Roberts, Sonia F; Duperret, Jeffrey M; Roberts, Sonia F; Duperret, Jeffrey M; Li, Xinwan; Wang, Hesheng; Koditschek, D. E.Desertification 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. PublicationNomadic Monument for Women in Robotics(2018-04-21) Krieger, Diedra; Alfaro, Gaby; Hartmann-Dow, Joey; Roberts, Sonia F.; Krieger, Diedra; Alfaro, Gaby; Hartmann-Dow, Joey; Roberts, Sonia F.We describe the Nomadic Monument for Women in Robotis (NMWR), a project celebrating women pioneers in robotics. NMWR is a 13’ semi-transparent geodesic dome with illustrations and descriptions of the women and their research on the inside faces of the triangles. Visitors can see rough outlines of the illustrations from the outside, but must enter the dome to learn about the women. As an immersive environment, the dome provides visitors not only a place to learn about inspiring women but also a space to feel that they are a member of this inspiring community. The geodesic dome was introduced by Buckminster Fuller in the mid-20th century as a new form for human shelter that would be more environmentally friendly and affordable, made possible by new building materials and the innovative use of tension to hold a built structure together. Simple facts and diagrams about dome geometry are included on dome. Fuller’s domes have also had a lasting influence on artists, including Krieger. Her 11-year ongoing project Plastic Fantastic engages community members in building a geodesic dome out of 6000 post-consumer water bottles, with notable installations at the Anchorage Museum in 2014 and Philadelphia’s inaugural Art in the Open in 2010. The NMWR dome will be constructed out of PVC piping and light blue, red, and purple panels of acrylic. A range of living women roboticists, many with a connection to Philadelphia, are featured in the dome. They work on a variety of problems in modern robotics, including helping give robots a sense of touch (Katherine Kuchenbecker, formerly at Penn); programming groups of robots to work together (Daniela Rus, MIT); sensing devices with medical applications (Ruzena Bajcsky, founder of the GRASP Lab at Penn); designing robots to move around in and collect information about harsh environments like Mars and Antarctica (Ayanna Howard, Georgia Tech); developing technologies (including robots) to assist in caring for children or the elderly (Maja Mataric, University of Southern California), and many more. The portraits and descriptions of these women challenge stereotypes about who can be an engineer, and the presentation of Hartmann-Dow’s near life-sized portraits at eye level around the inside of the dome creates a space for visitors to enter the community of women roboticists. Stereotype challenge and the sense of belonging to a community have both been shown to influence interest in engineering by women and girls (for a review, see ). NMWR will be presented at the 2018 Philadelphia Science Festival and will be on view at three events throughout the festival: At the Screening of Top Secret Rosies on Friday, April 20; at the Be a Pennovator event on Sunday, April 22; and at the Science Carnival on Saturday, April 28. The first two events will be at the Pennovation Center, and the last will be on the Parkway.  Cheryan, Sapna, Sianna A. Ziegler, Amanda K. Montoya, and Lily Jiang. “Why Are Some STEM Fields More Gender Balanced than Others?” Psychological Bulletin 143, no. 1 (2017): 1. For more information: Kod*lab. PublicationRHex Slips on Granular Media(2016-01-01) Roberts, Sonia F.; Koditschek, Dan E.; 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 , and more recently, on sand  and sand dunes ,  (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 . Here, we discuss recent qualitative observations of an updated research version of RHex  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. PublicationUsing the art practice of play to communicate legged robotics research concepts(2018-01-04) Krieger, Diedra; Roberts, Sonia F.; 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. PublicationTechnical Report: Control and Design of an Open-Source Two-Degree-of-Freedom Hopping Robot(2020-09-01) Tang, Weiyi; Roberts, Sonia F.; Tang, Weiyi; Roberts, Sonia F.; Koditschek, Daniel EUsing mechanical design inspired by the Ghost Minitaur and the open-source motor controller hardware from the Stanford Doggo, we built an open-source two-degree-of-freedom hopping robot. The robot hops using a Raibert-inspired reactive controller on the leg length and velocity. This technical report documents the project and provides a guide to others interested in building similar research robots.