Electromechanical actuation for thrust vector control applications

At present, actuation systems for the Thrust Vector Control (TVC) for launch vehicles are hydraulic systems. The Advanced Launch System (ALS), a joint initiative between NASA and the Air Force, is a launch vehicle that is designed to be cost effective, highly reliable and operationally efficient with a goal of reducing the cost per pound to orbit. As part of this initiative, an electromechanical actuation system is being developed as an attractive alternative to the hydraulic systems used today. NASA-Lewis is developing and demonstrating an Induction Motor Controller Actuation System with a 40 hp peak rating. The controller will integrate 20 kHz resonant link Power Management and Distribution (PMAD) technology and Pulse Population Modulation (PPM) techniques to implement Field Oriented Vector Control (FOVC) of a new advanced induction motor. Through PPM, multiphase variable frequency, variable voltage waveforms can be synthesized from the 20 kHz source. FOVC shows that varying both the voltage and frequency and their ratio (V/F), permits independent control of both torque and speed while operating at maximum efficiency at any point on the torque-speed curve. The driver and the FOVC will be microprocessor controlled. For increased system reliability, a Built-in Test (BITE) capability will be included. This involves introducing testability into the design of a system such that testing is calibrated and exercised during the design, manufacturing, maintenance and prelaunch activities. An actuator will be integrated with the motor controller for performance testing of the EMA TVC system. The design and fabrication of the motor controller is being done by General Dynamics Space Systems Division. The University of Wisconsin-Madison will assist in the design of the advanced induction motor and in the implementation of the FOVC theory. A 75 hp electronically controlled dynamometer will be used to test the motor controller in all four quadrants of operation using flight type control algorithms. Integrated testing of the controller and actuator will be conducted at a facility yet to be named. The EMA system described above is discussed in detail

Resonant mode controllers for launch vehicle applications

Electro-mechanical actuator (EMA) systems are currently being investigated for the National Launch System (NLS) as a replacement for hydraulic actuators due to the large amount of manpower and support hardware required to maintain the hydraulic systems. EMA systems in weight sensitive applications, such as launch vehicles, have been limited to around 5 hp due to system size, controller efficiency, thermal management, and battery size. Presented here are design and test data for an EMA system that competes favorably in weight and is superior in maintainability to the hydraulic system. An EMA system uses dc power provided by a high energy density bipolar lithium thionyl chloride battery, with power conversion performed by low loss resonant topologies, and a high efficiency induction motor controlled with a high performance field oriented controller to drive a linear actuator

A Multimodal Approach for Counseling Rural Women: Models and Case Studies

THE PROBLEM The purpose of this study was to develop a counseling model which would provide time-efficient and effective counseling services to meet the needs of rural women. Criteria were established for selected of a model and for evaluation of outcomes. PROCEDURES Research on previously-tested methods of counseling women as well as that on other counseling models was examined. Models were evaluated on the basis of established criteria. Discussion of use of the model selected was presented with three case studies illustrating its application. Evaluation of outcomes at the conclusion of therapy and on a follow-up basis concludes each case. On the basis of evaluation of subject\u27s counseling gains, the following conclusions may be drawn: The Wholistic Model is a time-efficient and effective means of providing counseling services to rural women. Clients met counseling goals in less than six months and reported maintenance of gains at follow-up intervals of six and twelve months. RECOMMENDATIONS This study is limited in scope to twenty rural women. However, the writer believes that the results warrant further investigation. Therefore, the following recommendations are offered: Further study with a larger, randomly selected, sample with pre- and post-testing of counseling gains on bases other than client self-report and counselor judgment should be implemented. The potential of the Wholistic Model for use with other populations and in group counseling should be examined. Exploration of the use of the Wholistic Model by counselors, therapists, and other helping persons in self-assessment and self-renewal to avoid professional burn-out should be initiated. Counselor educators should acquaint counselors and counselor trainees, through preservice and inservice experiences, with use of the Wholistic Model to structure their varied counseling techniques into a usable package

Field oriented control of induction motors

Induction motors have always been known for their simple rugged construction, but until lately were not suitable for variable speed or servo drives due to the inherent complexity of the controls. With the advent of field oriented control (FOC), however, the induction motor has become an attractive option for these types of drive systems. An FOC system which utilizes the pulse population modulation method to synthesize the motor drive frequencies is examined. This system allows for a variable voltage to frequency ratio and enables the user to have independent control of both the speed and torque of an induction motor. A second generation of the control boards were developed and tested with the next point of focus being the minimization of the size and complexity of these controls. Many options were considered with the best approach being the use of a digital signal processor (DSP) due to its inherent ability to quickly evaluate control algorithms. The present test results of the system and the status of the optimization process using a DSP are discussed

Evaluation of a Multi-kw, High Frequency Transformer for Space Applications

Various NASA studies have shown that high power (multi-kW and higher) electrical systems for various aerospace applications favor high frequency distribution systems, due to the improved safety and weight factors associated with those systems. Other favorable characteristics include low EMI, minimal wiring and ease of system parameter sensing and control of a single phase system. In aerospace power systems, as in terrestrial AC distribution systems, transformers are needed to provide voltage changes, isolation and the resetting of ground. Under NASA contract NAS3-21948 a multi-kW high frequency transformer was designed, fabricated and tested by Thermal Technology Lab, Inc. of Buffalo, New York. 'The goals of this program included the determination of the relationships between transformer weight, efficiency and operating frequency; low internal temperatures and reduced specific weight; and the validation of these new design concepts through experimentation and the fabrication and testing of transformers and their insulation systems.' The transformer was delivered to NASA-Lewis, where an evaluation program was conducted in Lewis' High Power High Frequency Component Test Facility. The transformer was tested in both atmosphere and under vacuum conditions. This paper will discuss the design of the transformer, the evaluation program and test results, the failures experienced and conclusions

Birth Weight as a Risk Factor for Breast Cancer: a Meta-Analysis of 18 Epidemiologic Studies

Background: Birth weight has been identified as a birth-related factor associated with the risk of breast cancer. However, the evidence is inconsistent. Methods: To investigate the association between birth weight and breast cancer, we conducted a meta-analysis of published studies between 1996 and 2008. Eighteen studies encompassing 16,424 breast cancer cases were included in the meta-analysis. Data were combined using a fixed-effect or random-effect model depending on the heterogeneity across studies. Results: Women with their own birth weight \u3e4000 g or 8.5 lb had a higher risk for developing breast cancer than those with birth weight(OR¼1.20, 95% CI 1.08, 1.34). Findings were also consistent with a dose-response pattern effect. The summary effect estimate for breast cancer risk per 1 kg increase in birth weight was statistically significant (random effects OR¼1.07, 95% CI 1.02, 1.12). Conclusions: Although these results provided no evidence indicating whether birth weight is more strongly related to early-onset than to later-onset breast cancer, our findings suggest an association between birth weight and breast cancer. The underlying biological mechanism relating to this phenomenon needs additional study

Functional assessment in spinal cord injury: a comparison of the Modified Barthel Index and the 'adapted' Functional Independence Measure

The Modified Barthel Index (MBI) and the Functional Independence Measure (FIM) have been used to provide objective measures of functional status and change of spinal cord injured (SCI) patients. To compare rating scores on the MBI and FIM, the functional abilities of 41 SCI patients were rated by one trained nurse-clinician using both scales at admission to initial rehabilitation (ADM), discharge from rehabilitation (DC) and at follow-up (FU) 12 months after rehabilitation. An 'adapted' FIM score was used, and total MBI and FIM scores were divided into self-care and mobility subscores. Comparisons were made between each MBI score and each FIM score at each point in time (ADM, DC, FU) using simple linear regression, which was also used to compare changes in the MBI and FIM scores from ADM to DC and from DC to FU. Excellent correlations ( p<0.0005) were found between MBI and FIM scores at all points in time and between changes in MBI scores and changes in FIM scores over each time interval.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66557/2/10.1177_026921559000400405.pd

Autonomous power expert system

The Autonomous Power Expert (APEX) system was designed to monitor and diagnose fault conditions that occur within the Space Station Freedom Electrical Power System (SSF/EPS) Testbed. APEX is designed to interface with SSF/EPS testbed power management controllers to provide enhanced autonomous operation and control capability. The APEX architecture consists of three components: (1) a rule-based expert system, (2) a testbed data acquisition interface, and (3) a power scheduler interface. Fault detection, fault isolation, justification of probable causes, recommended actions, and incipient fault analysis are the main functions of the expert system component. The data acquisition component requests and receives pertinent parametric values from the EPS testbed and asserts the values into a knowledge base. Power load profile information is obtained from a remote scheduler through the power scheduler interface component. The current APEX design and development work is discussed. Operation and use of APEX by way of the user interface screens is also covered