Stably Extending Two-Dimensional Bipedal Walking to Three Dimensions

In this paper we develop a feedback control law that results in stable walking gaits on flat ground for a three-dimensional bipedal robotic walker given stable walking gaits for a two-dimensional bipedal robotic walker. This is achieved by combining disparate techniques that have been employed in the bipedal robotic community: controlled symmetries, geometric reduction and hybrid zero dynamics. Controlled symmetries are utilized to obtain stable walking gaits for a two-dimensional bipedal robot walking on flat ground. These are related to walking gaits for a three-dimensional (hipless) bipedal robot through the use of geometric reduction. Finally, these walking gaits in three dimensions are made stable through the use of hybrid zero dynamics

A review of California sea otter, Enhydra lutris, surveys

Recent surveys (1977 to 1983) of the sea otter, Enhydra lutris, in California were summarized and compared to past surveys, to evaluate the adequacy of current survey design and to-make inferences about current population status. Ground counts within selected index areas provided the best indicator of population trends. These data suggest a rather remarkable stability in the long-term occupied range. Rangewide aerial surveys with ground truth stations provided the best available data for estimating total population size. The most recent (1979) survey yielded a population estimate of approximately 1500 sea otters. Comparisons with past surveys suggest there have been no demonstrable changes in population size since at least 1976. (34pp.

A geometric approach to three-dimensional hipped bipedal robotic walking

This paper presents a control law that results in stable walking for a three-dimensional bipedal robot with a hip. To obtain this control law, we utilize techniques from geometric reduction, and specifically a variant of Routhian reduction termed functional Routhian reduction, to effectively decouple the dynamics of the three-dimensional biped into its sagittal and lateral components. Motivated by the decoupling afforded by functional Routhian reduction, the control law we present is obtained by combining three separate control laws: the first shapes the potential energy of the sagittal dynamics of the biped to obtain stable walking gaits when it is constrained to the sagittal plane, the second shapes the total energy of the walker so that functional Routhian reduction can be applied to decoupling the dynamics of the walker for certain initial conditions, and the third utilizes an output zeroing controller to stabilize to the surface defining these initial conditions. We numerically verify that this method results in stable walking, and we discuss certain attributes of this walking gait

A simulated translocation of sea otters, Enhydra lutris, with a review of capture, transport and holding techniques

A number of techniques and pieces of equipment judged necessary for the translocation of sea otters were field tested. Captures were accomplished with either a scuba diver operated capture device (Wilson trap), a surface set tangle net or a dip net. A portable floating pen proved very satisfactory for simultaneously holding at least ten otters for several days. Commercially available pet transport kennels, with the capability of holding water, were adequate for maintaining the otter's pelage in good condition during a transport of approximately five hours duration. Subsequent observations indicated no apparent stress related dispersal. (17pp.

Preferences of pupils in sixteen high school biology classes

Thesis (M.A.)--Boston University, 1948. This item was digitized by the Internet Archive

Movement Response Times Associated with Blocking in Football from the Three- and Four-Point Center Stances

The purposes of this study were: (1) to determine the significance in variability between right, left, forward and backward movement times resulting from assuming the three-point and the four-point center stances, for junior high, senior high, junior college and college football players without previous experience at the center position; and (2) to determine the significance of difference between means of right, left, forward and backward movement of the three-point and four-point stances for each of the groups, viz., junior high, senior high, junior college and college

Politicians in Uniform

African and African American StudiesGovernmen

An assessment of the accidental take of sea otters, Enhydra lutris, in gill and trammel nets

The sea otter, Enhydra 1utris, is fully protected in California by both state and federal law. Despite this protection the population has not grown appreciably since at least 1976. Research efforts directed at identifying the reasons for the lack of population growth have concentrated on sources of mortality and their contribution to total mortality. The accidental drowning of sea otters in gill and trammel nets used to take California halibut, Para1ichthys ca1ifornicus, was identified as a source of mortality which has probably increased as the sea otter population expanded into areas of intense fishing. As a result, an existing gill and trammel net fishery observation program in Monterey Bay was expanded to assess the extent and significance of the accidental drownings of sea otters in the areas near Morro Bay and Port San Luis. Three different estimates of the number of sea otters drowned annually in gill and trammel nets were generated using comparable data bases. The average of these estimates was approximately 80 sea otters per year for the level of fishing effort expended during the June 1982 through June 1984 study period. Back calculations of the annual take of sea otters by the gill and trammel net fishery for California halibut were made for each year from 1973 through 1983. These calculations suggest that the level of accidental take of sea otters during the last decade may have been high enough to be a significant factor in the lack of sea otter population growth. (31pp.