The Stability of Heavy Objects with Multiple Contacts

In both robot grasping and robot locomotion, we wish to hold objects stably in the presence of gravity. We present a derivation of second-order stability conditions for a supported heavy object, employing the tool of Stratified Morse theory. We then apply these general results to the case of objects in the plane

Overview of the Systems Special Investigation Group investigation

The Long Duration Exposure Facility (LDEF) carried a remarkable variety of electrical, mechanical, thermal, and optical systems, subsystems, and components. Nineteen of the fifty-seven experiments flown on LDEF contained functional systems that were active on-orbit. Almost all of the other experiments possessed at least a few specific components of interest to the Systems Special Investigation Group (Systems SIG), such as adhesives, seals, fasteners, optical components, and thermal blankets. Almost all top level functional testing of the active LDEF and experiment systems has been completed. Failure analysis of both LDEF hardware and individual experiments that failed to perform as designed has also been completed. Testing of system components and experimenter hardware of interest to the Systems SIG is ongoing. All available testing and analysis results were collected and integrated by the Systems SIG. An overview of our findings is provided. An LDEF Optical Experiment Database containing information for all 29 optical related experiments is also discussed

Experiments in carangiform robotic fish locomotion

This paper studies a form of robotic fish movement that is analogous to the carangiform style of swimming seen in nature. We propose a simple quasi-steady fluid flow model for predicting the thrust generated by the flapping tail. We then describe an experimental system, consisting of a three-link robot, that has been constructed in order to study carangiform-like swimming. Experimental results obtained with this system suggest that the simplified propulsion model is reasonably accurate. The input parameters that realize optimum thrust are experimentally determined. Finally, we consider some issues in maneuvering

Trajectory planning using reachable-state density functions

Presents a trajectory planning algorithm for mobile robots which may be subject to kinodynamic constraints. Using computational methods from noncommutative harmonic analysis, the algorithm efficiently constructs an approximation to the robot's reachable-state density function. Based on a multiscale approach, the density function is then used to plan a path. One variation of the algorithm exhibits time complexity that is logarithmic in the number of steps. Simulations illustrate the method

Cultural Resource Survey Of Proposed Expansion Areas For The Kerrville City Landfill And Limited Testing Of Site 41KR501, Kerrville, Kerr County, Texas

In April of 2015, AmaTerra Environmental, Inc. staff conducted intensive cultural resource investigations of approximately 78 acres of proposed expansions to the City of Kerrville’s existing Kerrville Landfill in Kerr County, Texas. Working on behalf of the City of Kerrville (the land owner and project sponsor) and their design consultant LNV, Inc., AmaTerra investigated portions of the Landfill’s proposed Western Expansion Area (36.5 acres) and the Big Hill Expansion Area (41.5 acres) for compliance with Section 106 of the National Historic Preservation Act of 1966 (as amended) and the Antiquities Code of Texas (Antiquities Permit 7238). Within undisturbed and previously-unsurveyed portions of the Big Hill Expansion Area, archeologists conducted intensive area survey and excavated 17 subsurface shovel tests, finding the expansion area composed of shallow, deflated, upland soils. Previously recorded Site 41KR673, a diffuse prehistoric surface scatter of non-diagnostic tools and lithic debris was expanded to encompass approximately 15 acres of the Big Hill Expansion Area. The proposed Western Expansion Area was surveyed previously, hence, archeologists focused on intensive survey and limited NRHP/SAL-eligibility testing of a previously recorded prehistoric site, Site 41KR501. Nine backhoe trenches were excavated within the site area. These yielded seven flakes and three burned rock fragments in three of the trenches. All of the artifacts were found within secondary, high-energy, flood-related contexts (or subsurface disturbance) ranging from 70 to 210 centimeters below the surface. A small surface scatter of burned rock was also observed near the site’s southern boundary. No evidence of intact features was observed. Given the lack of temporal diagnostics, very minimal artifacts, and the resulting poor level of research potential, Sites 41KR501 and 41KR673 are recommended as not eligible for listing in the National Register of Historic Places or as a State Antiquities Landmarks. Accordingly, AmaTerra recommends that the project proceed with no adverse effects to Historic Properties and/or State Antiquities Landmarks and no further work necessary. No artifacts were collected during the survey but all field-generated notes, forms, and photographs will be permanently curated at the Texas Archeological Research Laboratory in Austin

Stable Poses of 3-Dimensional Objects

This paper considers the gravitational stability of a frictionless 3-dimensional object in contact with immovable objects. Arbitrarily curved objects are considered. This paper also shows how to determine the region over which the object's center of mass can move while the object maintains a given set of contacts and remains in stable equilibrium. We present symbolic solutions for up to three contacts and discuss numerical solutions for larger numbers of contacts. This analysis has application in planning the motions of quasi-statically walking robots over uneven terrain and the manipulation of heavy objects

Modelling and experimental investigation of carangiform locomotion for control

We propose a model for planar carangiform swimming based on conservative equations for the interaction of a rigid body and an incompressible fluid. We account for the generation of thrust due to vortex shedding through controlled coupling terms. We investigate the correct form of this coupling experimentally with a robotic propulsor, comparing its observed behavior to that predicted by unsteady hydrodynamics. Our analysis of thrust generation by an oscillating hydrofoil allows us to characterize and evaluate certain families of gaits. Our final swimming model takes the form of a control-affine nonlinear system

Chronic and Residual Effects of a Two-Week Foam Rolling Intervention on Ankle Flexibility and Dynamic Balance

Background Foam rolling has been shown to acutely improve joint range of motion (ROM). However, limited knowledge exists on the chronic and residual effects. The primary purpose of this study was to examine the chronic and residual effects of a 2-week roller–massager intervention on ankle dorsiflexion ROM and dynamic balance. Methods Forty-two participants (24.3 ± 2.5 years, 33 males, 9 females) were randomly assigned to either roller-massage (RM) or control group (= no intervention). Ankle ROM was assessed with the weight-bearing lunge test (WBLT) and dynamic balance with the Y-Balance test for both limbs. The RM group was instructed to roll their calf muscles for three sets of 60 s per leg on 6 days a week over 2 weeks. Acute effects were measured during baseline testing for dorsiflexion ROM and dynamic balance immediately after foam rolling. Chronic and residual effects were measured 1 day and 7 days after the intervention period. Multivariate ANOVA was performed for post-hoc comparisons to determine acute, chronic, and residual effects. Results Significant acute and chronic foam rolling effects ( p <0.05) were found for ankle dorsiflexion ROM. The chronic increase in ROM slightly decreased 7 days post-intervention but remained significantly above baseline ( p < 0.05). Regarding dynamic balance, there were no acute but chronic ( p < 0.05) and residual ( p < 0.05) effects. Conclusion Using a roller–massager for a 2-week period chronically increases ROM and dynamic balance. These increases are still significant 7 days post-intervention emphasizing the sustainability of foam rolling effects