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Twisting Spine or Rigid Torso: Exploring Quadrupedal Morphology via Trajectory Optimization
Full text linkModern legged robot morphologies assign most of their actuated degrees of freedom (DoF’s) to the limbs and designs continue to converge to twelve DoF quadrupeds with three actuators per leg and a rigid torso often modeled as a Single Rigid Body (SRB). This is in contrast to the animal kingdom, which provides tantalizing hints that core actuation of a jointed torso confers substantial benefit for efficient agility. Unfortunately, the limited specific power of available actuators continues to hamper roboticists’ efforts to capitalize on this bio-inspiration. This paper presents the initial steps in a comparative study of the costs and benefits associated with a traditionally neglected torso degree of freedom: a twisting spine. We use trajectory optimization to explore how a one-DoF, axially twisting spine might help or hinder a set of axially-active (twisting) behaviors: trots, sudden turns while bounding, and parkour-style wall jumps. By optimizing for minimum electrical energy or average power, intuitive cost functions for robots, we avoid hand-tuning the behaviors and explore the activation of the spine. Initial evidence suggests that for lower energy behaviors the spine increases the electrical energy required when compared to the rigid torso, but for higher energy runs the spine trends toward having no effect or reducing the electrical work. These results support future, more bio-inspired versions of the spine with inherent stiffness or dampening built into their mechanical design.For more information: Kod*la
Penn Library\u27s Ms. Codex 1662 - Chemical characters from several authors. (Video Orientation)
No full texthttps://repository.upenn.edu/sims_video/1213/thumbnail.jp
Penn Library\u27s LJS 481 - [Ḥaṭṭ al-niqāb ʻan wujūh aʻmāl al-ḥisāb]. (Video Orientation)
No full texthttps://repository.upenn.edu/sims_video/1220/thumbnail.jp
Extended Version of Stability of a Groucho-Style Bounding Run in the Sagittal Plane
Full text linkThis 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\u27s 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
Penn Library\u27s Library\u27s LJS 487 - [Treatises on astronomical instruments].(Video Orientation)
No full texthttps://repository.upenn.edu/sims_video/1225/thumbnail.jp
Collation Model for Ms. Codex 218: [Four English devotional works].
Full text linkFour works written in Middle English, with passages in Latin. Texts included are Scale of perfection or Scala perfectionis, Bk. 1, ch. 19-93, and Bk. 2, ch. 1-46, by Walter Hilton; Stimulus amoris, or Prickyng of love, translated by Walter Hilton , attributed to St. Bonaventure; Amor die or Love of God; The Prick of conscience by Richard Rolle.https://repository.upenn.edu/sims_models/1160/thumbnail.jp
Penn Library\u27s Library\u27s LJS 490 - [Astronomical compendium]. (Video Orientation)
No full texthttps://repository.upenn.edu/sims_video/1228/thumbnail.jp
The Importance of Financial Literacy: Opening a New Field
Full text linkWe undertake an assessment of our two decades of research on financial literacy, building on our empirical research and theoretical work casting financial knowledge as a form of investment in human capital. We also draw on recent data to determine who is the most – and least – financially savvy in the United States, and we highlight the similarity of our results in other countries. A number of convincing studies is now available, from which we draw conclusions about the effects and consequences of financial illiteracy, and what can be done to fill these gaps. We conclude by offering our thoughts on implications for teaching, financial literacy programs, and future research
Shorthand Crosses the Atlantic: An Overview and Preliminary Census of Shorthand Manuscripts in Early American Archives
Full text linkForms of short and fast writing have existed since antiquity, but interest in them rapidly took off during the early modern period. Dozens of different manuals andmethods appeared, all promising to teach the trendiest manuscript technologies of the day. Despite the widespread early modern interest in stenography and ciphers, relatively little research has been conducted on these scribal arts. Some scholars have focused on the famed diary of Samuel Pepys, but few have considered the scores of early modern journalists, ministers, students, diplomats, and merchants, among many others, who also actively employed fast writing in their daily lives. This article provides a historical overview of early modern shorthand, as well as an original bibliographic account of shorthand\u27s presence and prevalence in colonial American archives
Penn Library\u27s LJS 478 - [Kitāb fī istīʻāb al-wujūh al-mumkinah fī ...] (Video Orientation)
No full texthttps://repository.upenn.edu/sims_video/1217/thumbnail.jp