Design and implementation of series elastic actuation in a biomorphic robot leg

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (leaf 21).Fluid, efficient, robust bipedal locomotion is hard by some approaches. Today's most advanced bipedal robots require flat and level floors, but are still prone to trips and falls. They have trouble interacting with objects in their surroundings, and adapting to them. We think that new approaches may make bipedal control easier. The following work details the design of the BOB (Bag of Bones) biomorphic robot leg that is a continuation of an effort to achieve a better understanding of the sensorimotor neurocontrol of locomotion, particularly in humans. Such an understanding will not only lead to robots that move as well or better than people while being easier to control, but will also enable powerful therapies for ataxia patients. One of the main design requirements for BOB was to incorporate series elastic actuation, but with hobby servo motors as the power source. The use of hobby servos was intended to keep costs low, as was the extensive use of off the shelf parts whenever possible. With the recent advances in hobby servo motors, it was expected that reasonable if not high performance would be possible. The specific contribution of this work includes the entire series elastic actuation system powered by servo motors.(Cont.) The elements of the actuation system include circular servo horns, wire rope used in loops, turnbuckles, and series elastic elements that use compression springs in extension. It was found that the knee joint can flex from 0 to 90 degrees and back in about 0.7 seconds. Similarly, the ankle cycled from approximately 20 degrees of extension to approximately 35 degrees of flexion in about 0.7 seconds. These performance figures indicate that the gearing ratios at the knee and ankle are appropriate and that the current design is sufficiently powered for walking.by Nathaniel K. Chan.S.B

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field