Selection of systems to perform extravehicular activities, man and manipulator. Volume 2 - Final report

Technologies for EVA and remote manipulation systems - handbook for systems designer

Kinematic variability in repetitive occupational tasks as an individual trait from different motor control perspectives

Recent ergonomic research suggests that individuals with low motor variability (repeaters) are at higher risk of developing work-related musculoskeletal disorders than individuals with high motor variability (replacers) when performing repetitive tasks. Importantly, the repeaters-replacers hypothesis is dependent on the fundamental condition that motor variability is genuinely an individual trait, which is currently unknown. Therefore, this dissertation aimed to examine several measures of whole-body kinematic variability under different task constraints during lifting, during fatigue development in lifting and in different occupational tasks to evaluate kinematic variability as an individual trait. Healthy females and males were recruited from the student population for two experimental sessions to perform self-paced repetitive lifting, carrying and simulated sawing tasks. The lifting task was performed four times under different task constraints of foot movement (restricted by instruction versus no restriction) and load weight (low versus high). For these six tasks, the total number of repetitions of each task was limited to 105 repetitions to avoid inducing excessive fatigue. The unrestricted high load lifting task was repeated in a prolonged protocol until volitional fatigue or up to a maximum of 1 hour. Whole-body joint angles and crate trajectories were obtained using optoelectronic motion capture. Kinematic variability was quantified using three different measures, a linear measure of joint angle mean point-by-point standard deviation, nonlinear continuous relative phase (CRP) variability of joint angle couplings, and nonlinear task-relevant and task-irrelevant variability derived from joint angles and crate trajectories. In addition, rate of perceived exertion was assessed as an indicator of fatigue. In repetitive lifting under different constraints, individual variability demonstrated strong consistency independent of variability measures. However, across individuals, variability increased in response to removing the foot movement restriction when assessed using linear and nonlinear measures while task-relevant and task-irrelevant variability did not show any differences. When individuals were ranked on variability, strong consistency across measures was also demonstrated although CRP measures appeared to capture a slightly different construct than the other measures. In different repetitive tasks of lifting, carrying and simulated sawing, only moderate consistency was found in linear individual variability. Across individuals, linear variability was affected by task type where the order from highest to lowest variability was carrying, lifting and sawing, respectively. When unrestricted high load lifting was compared to three phases during prolonged unrestricted high load lifting, individual variability demonstrated strong consistency independent of (non)linear measures. In addition, across individuals no changes in variability were observed with different fatigue states. Variability during unrestricted high load lifting was associated with some indicators of fatigue. This work reveals strong evidence for kinematic variability as an individual trait across investigated task constraints, variability measures, and fatigue development in lifting; however, variability could be task specific. Based on the effects of foot movement and task type on kinematic variability, variability increased when more degrees of freedom were allowed. Also, during lifting kinematic variability showed different responses to task constraint depending on variability measure. However, kinematic variability was related to some fatigue measures. The findings of this dissertation provide insight into kinematic variability as an individual trait in repetitive occupational tasks and therefore contribute to an essential aspect of the repeaters-replacers hypothesis. If kinematic variability can be related to risk of work-related musculoskeletal disorders, risk of injury could be prevented or lowered by altering individuals’ variability through training or workplace interventions assuming it is possible to convert a repeater into a replacer

Intelligent Machining Systems

Machining is one of the most widespread manufacturing processes and plays a critical role in industries. As a matter of fact, machine tools are often called mother machines as they are used to produce other machines and production plants. The continuous development of innovative materials and the increasing competitiveness are two of the challenges that nowadays manufacturing industries have to cope with. The increasing attention to environmental issues and the rising costs of raw materials drive the development of machining systems able to continuously monitor the ongoing process, identify eventual arising problems and adopt appropriate countermeasures to resolve or prevent these issues, leading to an overall optimization of the process. This work presents the development of intelligent machining systems based on in-process monitoring which can be implemented on production machines in order to enhance their performances. Therefore, some cases of monitoring systems developed in different fields, and for different applications, are presented in order to demonstrate the functions which can be enabled by the adoption of these systems. Design and realization of an advanced experimental machining testbed is presented in order to give an example of a machine tool retrofit aimed to enable advanced monitoring and control solutions. Finally, the implementation of a data-driven simulation of the machining process is presented. The modelling and simulation phases are presented and discussed. So, the model is applied to data collected during an experimental campaign in order to tune it. The opportunities enabled by integrating monitoring systems with simulation are presented with preliminary studies on the development of two virtual sensors for the material conformance and cutting parameter estimation during machining processes

Arc-Liberation of Intermolecular Bond Energy for Marine Propulsion

While modern electronics technology has facilitated the development of small, low-power Unmanned Surface Vessels, common propeller-driven marine propulsion systems are not optimized for such crafts. The goal of the Electrodynamic Water Arc Propulsion (EWAP) project is to develop a solid-state water arc explosion propulsion engine and implement it on a USV. When a high voltage arc is struck through water it has an explosive effect, causing a high pressure, and expelling the water from its chamber. In order to apply this phenomenon to marine propulsion, the EWAP team developed several explosion chambers, and evaluated each design through comprehensive analyses. The team’s research culminated in the development of the final EWAP USV, called the Water-Arc Explosion Vessel – I, or WAEV-I

Small business innovation research. Abstracts of completed 1987 phase 1 projects

Non-proprietary summaries of Phase 1 Small Business Innovation Research (SBIR) projects supported by NASA in the 1987 program year are given. Work in the areas of aeronautical propulsion, aerodynamics, acoustics, aircraft systems, materials and structures, teleoperators and robotics, computer sciences, information systems, spacecraft systems, spacecraft power supplies, spacecraft propulsion, bioastronautics, satellite communication, and space processing are covered

Single- and dual-carrier microwave noise abatement in the deep space network

The NASA/JPL Deep Space Network (DSN) microwave ground antenna systems are presented which simultaneously uplink very high power S-band signals while receiving very low level S- and X-band downlinks. Tertiary mechanisms associated with elements give rise to self-interference in the forms of broadband noise burst and coherent intermodulation products. A long-term program to reduce or eliminate both forms of interference is described in detail. Two DSN antennas were subjected to extensive interference testing and practical cleanup program; the initial performance, modification details, and final performance achieved at several planned stages are discussed. Test equipment and field procedures found useful in locating interference sources are discussed. Practices deemed necessary for interference-free operations in the DSN are described. Much of the specific information given is expected to be easily generalized for application in a variety of similar installations. Recommendations for future investigations and individual element design are given