Search Results

Deep-hole drilling is among the most critical precision machining processes for production of high-performance discrete components. The effects of drilling with superimposed, controlled low-frequency modulation - Modulation-Assisted Machining (MAM) - on the surface textures created in deep-hole drilling (ie, gun-drilling) are discussed. In MAM, the oscillation of the drill tool creates unique surface textures by altering the burnishing action typical in conventional drilling. The effects of modulation frequency and amplitude are investigated using a modulation device for single-flute gun-drilling on a computer-controlled lathe. The experimental results for the gun-drilling of titanium alloy with modulation are compared and contrasted with conventional gun-drilling. The chip morphology and surface textures are characterized over a range of modulation conditions, and a model for predicting the surface texture is presented. Implications for production gun-drilling are discussed.

This paper presents a simulation model for the analysis of internal gear ring pumps. The model follows a multi domain simulation approach comprising sub-models for parametric geometry generation, fluid dynamic simulation, numerical calculation of characteristic geometry data and CAD/FEM integration. The sub-models are interacting in different domains and relevant design and simulation parameters are accessible in a central, easy to handle graphical user interface. The potentials of the described tool are represented by simulation results for both steady state and transient pump operating conditions and by their correlation with measured data. Although the presented approach is suitable to all applications of gear ring pumps, a particular focus is given to hydraulic actuation systems used in automotive drivetrain applications.

Excessive vibration and poor controllability occur in many mobile fluid power applications, with negative consequences as concerns operators' health and comfort as well as machine safety and productivity. This paper addresses the problem of reducing oscillations in fluid power machines presenting a novel control technique of general applicability. Strong nonlinearities of hydraulic systems and the unpredictable operating conditions of the specific application (e.g. uneven ground, varying loads, etc.) are the main challenges to the development of satisfactory general vibration damping methods. The state of the art methods are typically designed as a function of the specific application, and in many cases they introduce energy dissipation and/or system slowdown. This paper contributes to this research by introducing an energy efficient active damping method based on feedback signals from pressure sensors mounted on the flow control valve block.

In long-duration, closed human habitats in space that include crop growth, one challenge that is faced while designing a candidate waste processor is the composition of solid-waste loads, which include human waste, packaging and food-processing materials, crop spoilage, and plant residues. In this work, a new modeling tool is developed to characterize crop residues and food wastes based on diet in order to support the design of solid-waste technologies for closed systems. The model predicts amounts of crop residues and food wastes due to food processing, crop harvests, and edible spoilage. To support the design of solid-waste technologies, the generation of crop residues and food wastes was characterized for a 600-day mission to Mars using integrated menu, crop, and waste models. The three sources of plant residues and food waste are identified to be food processors, crop harvests, and edible spoilage.

Dynamics of machine tool components play a critical role in the outcome of machining processes. This paper addresses several important issues on machine tool and machining dynamics. It illustrates the dynamic behavior of structural components under operating conditions and presents an improved technique for modeling structural non-linearity. It also describes spindle modeling capability that has been developed to predict dynamic and thermal characteristics of spindle systems. Finally, the paper discusses the impact of non-linear dynamics on machining stability.

This paper presents in-process monitoring and control based on a novel ultrasonic sensing technique. The developed ultrasonic system provides non-contact measurement of surface roughness, which is applicable to wet machining environments. The utility and robustness of the technique are demonstrated through applications to different processes and materials. In-process surface roughness monitoring capability of the system is also shown along with its potential to monitor flank wear conditions. The result of in-process surface roughness control implementation based on the developed technique shows the control scheme is able to maintain consistent surface roughness values regardless of the tool wear state.

Audio playbacks are mechanisms which read data from a storage medium and produce commands and signals which an audio system turns into music. Playbacks are constantly changed to meet market demands, requiring that the control software be updated quickly and efficiently. This paper reviews a 12 month project using the MATLAB/Simulink/Stateflow environment for model-based development, system simulation, autocode generation, and hardware-in-the-loop (HIL) verification for playbacks which read music CDs or MP3 disks. Our team began with a “clean slate” approach to playback architecture, and demonstrated working units running production-ready code. This modular, layered architecture enables rapid development and verification of new playback mechanisms, thereby reducing the time needed to evaluate playback mechanisms and integrate into a complete infotainment system.

A low-cost hydrostatic absorption dynamometer has been developed for small to medium sized engines. The dynamometer was designed and built by students to support student projects and educational activities. The availability of such a dynamometer permits engine break-in cycles, performance testing, and laboratory instruction in the areas of engines, fuels, sensors, and data acquisition. The dynamometer, capable of loading engines up to 60kW at 155Nm and 3600rpm, incorporates a two-section gear pump and an electronically operated proportional pressure control valve to develop and control the load. A bypass valve permits the use of only one pump section, allowing increased fidelity of load control at lower torque levels. Torque is measured directly on the drive shaft with a strain gage. Torque and speed signals are transmitted by an inductively-powered collar mounted to the dynamometer drive shaft. Pressure transducers at the pump inlet and pump outlet allow secondary load measurement.

This paper presents hydraulic topographies using a network of valves to achieve better energy efficiency, reliability, and performance. The Topography with Integrated Energy Recovery (TIER) system allows the valves and actuators to reconfigure so that flow from assistive loads on actuators can be used to move actuators with resistive loads. Many variations are possible, including using multiple valves with either a single pump/motor or with multiple pump/motors. When multiple pump/motors are used, units of different displacements can be chosen such that units are controlled to minimize time operating at low displacement, thus increasing overall system efficiency. Other variations include configurations allowing open loop or closed loop pump/motors to be used, the use of fixed displacement pump/motors, or the ability to store energy in an accumulator. This paper gives a system level overview and summarizes the hydraulic systems using the TIER approach.

This paper describes the numerical modeling of the hydraulic circuit of a self-moving boom lift. Boom lifts consist of several hydraulic actuators, each of them performs a specific movement. Hydraulic systems for lifting applications must ensure consistent performance no matter what the load and how many users are in operation at the same time. Common solutions comprise a fixed or a variable displacement pump with load-sensing control strategy. Instead, the hydraulic circuit studied in this paper includes a fixed displacement pump and an innovative (patented) proportional valve assembly. Each proportional valve (one for each user) permits a flow regulation for all typical load conditions and movement simultaneously. The study of the hydraulic system required a detailed modeling of some components such as: the overcenter valves, for the control of the assistive loads; the proportional valve, which keeps a constant flow independently of pressure drop across itself.

A digital electrohydraulic control system for emergency braking is designed, simulated, built, and tested. First, a dynamic model of the system was developed with Matlab Simulink. The parameters are obtained experimentally. Feedback gains are obtained by tuning the model. Then, the digital controller is implemented on an industrial personal computer programmed in Turbo C++. The control strategy is an improved digital version of the PID control. The key element in the control of the brake was an electro-hydraulic proportional pressure valve. Experiments show that the control system successfully realizes constant-deceleration emergency brake within mine safety rules. The same hardware can be reprogrammed for various hoists, different load conditions, and different control objectives. Although the test was conducted on a mine hoist brake, the control system can be applied to most vehicles.

Mobile Earth Moving Machinery like Skid-steer loaders have tight turning radius in limited spaces due to a short wheelbase which prevents the use of suspensions in these vehicles. The absence of a suspension system exposes the vehicle to ground vibrations of high magnitude and low frequency. Vibrations reduce operator comfort, productivity and life of components. Along with vibrations, the machine productivity is also hampered by material spillage which is caused by the tilting of the bucket due to the extension of the boom. The first part of the paper focuses on vibration damping. The chassis’ vibrations are reduced by the use of an active suspension element which is the hydraulic boom cylinder which is equivalent to a spring-damper. With this objective, a linear model for the skid steer loader is developed and a state feedback control law is implemented.

Typically, earthmoving machines do not have wheel suspensions. This lack of components often causes uncomfortable driving, and in some cases reduces machine productivity and safety. Several solutions to this problem have been proposed in the last decades, and particularly successful is the passive solution based on the introduction of accumulators in the hydraulic circuit connecting the machine boom. The extra capacitance effect created by the accumulator causes a magnification of the boom oscillations, in such a way that these oscillations counter-react the machine oscillation caused by the driving on uneven ground. This principle of counter-reacting machine oscillations through the boom motion can be achieved also with electro-hydraulic solutions, properly actuating the flow supply to the boom actuators on the basis of a feedback sensors and a proper control strategy.

The On-line Project Information System (OPIS) is a LAMP-based (Linux, Apache, MySQL, PHP) system being developed at NASA Ames Research Center to improve Agency information transfer and data availability, largely for improvement of system analysis and engineering. The tool will enable users to investigate NASA technology development efforts, connect with experts, and access technology development data. OPIS is currently being developed for NASA's Exploration Life Support (ELS) Project. Within OPIS, NASA ELS Managers assign projects to Principal Investigators (PI), track responsible individuals and institutions, and designate reporting assignments. Each PI populates a “Project Page” with a project overview, team member information, files, citations, and images. PI's may also delegate on-line report viewing and editing privileges to specific team members. Users can browse or search for project and member information.

When high-intensity discharge (HID) electric lamps are used for plant growth, system inefficiencies occur due to an inability to effectively target light to all photosynthetic tissues of a growing crop stand, especially when it is closed with respect to light penetration. To maintain acceptable crop productivity, light levels typically are increased thus increasing heat loads on the plants. Evapotranspiration (ET) or transparent thermal barrier systems are subsequently required to maintain thermal balance, and power-intensive condensers are used to recover the evaporated water for reuse in closed systems. By accurately targeting light to plant tissues, electric lamps can be operated at lower power settings and produce less heat. With lower power and heat loads, less energy is used for plant growth, and possibly less water is evapotranspired. By combining these effects, a considerable energy savings is possible.

The ALS/NSCORT Education and Outreach provides an avenue to engage and educate higher education students and K-12 educators/students in the center's investigations of the synergistic concepts and principles required for regenerative life-support in extended-duration space exploration. The following K-12 Education programs will be addressed: 1) Key Learning Community Project provides exposure, mentoring and research opportunities for 9-12th grade students at Key Learning Community This program was expanded in 2004 to include an “Explore Mars” 3-day camp experience for 150 Key students. The overall goal of the collaborative project is to motivate students to pursue careers in science, technology, and engineering; 2) Mission to Mars Program introduces 5th-8th grade students to the complex issues involved with living on Mars, stressing the interdisciplinary fundamentals of science, technology and engineering that underlie Advanced Life Support research.

Wheat is a candidate crop for the Advanced Life Support (ALS) system, and cereal grains and their products will be included on long-term space missions beyond low earth orbit. While the exact supply scenario has yet to be determined, some type of post-processing of these grains must occur if they are shipped as bulk ingredients or grown on site for use in foods. Understanding the requirements for processing grains in space is essential for incorporating the process into the ALS food system. The ESM metric developed by NASA describes and compares individual system impact on a closed system in terms of a single parameter, mass. The objective of this study was to compare the impact of grain mill type on the ESM of producing yeast and flat breads. Hard red spring wheat berries were ground using a Brabender Quadrumat Jr. or the Kitchen-Aid grain mill attachment (both are proposed post-harvest technologies for the ALS system) to produce white and whole wheat flour, respectively.

One of the challenges NASA faces today is developing an Advanced Life Support (ALS) system that will enable long duration space missions beyond low earth orbit (LEO). This ALS system must include a food processing subsystem capable of producing a variety of nutritious, acceptable, and safe edible ingredients and food products from pre-packaged and re-supply foods as well as salad crops grown on the transit vehicle or other crops grown on planetary surfaces. However, designing, building, developing, and maintaining such a subsystem is bound to many constraints and restrictions. The limited power supply, storage locations, variety of crops, crew time, need to minimize waste, and other ESM parameters influence the selection of processing equipment and techniques.

Modern on-road vehicles have been making steady strides when it comes to employing technological advances featuring active safety systems. However, off-highway machines are lagging in this area and are in dire need for modernization. One chassis system that has been receiving much attention in the automotive field is the steering system, where several electric and electrohydraulic steering architectures have been implemented and steer-by-wire technologies are under current research and development activities. On the other hand, off-highway articulated steering vehicles have not adequately evolved to meet the needs of Original Equipment Manufacturers (OEM) as well as their end customers. Present-day hydrostatic steering systems are plagued with poor energy efficiency due to valve throttling losses and are considered passive systems relative to safety, adjustability, and comfort.

Current gasoline-gas vapor recovery system is incomplete, for it cannot adjust the vapor-liquid ratio automatically due to the change of working temperature. To solve this problem, this paper intends to design a new system and optimize its parameters. In this research, variables control method is used for tests while linear regression is used for data processing. This new system moves proportion valve away and adds a DSP control module, a frequency conversion device, and a temperature sensor. With this research, it is clearly reviewed that the vapor-liquid ratio should remains 1.0 from 0 °C to 20 °C as its working temperature, be changed into 1.1 from 20 °C to 25 °C, be changed into 1.2 from 25 °C to 30 °C, and be changed into 1.3 when the working temperature is above 30 °C.