Description of real-time Ada software implementation of a power system monitor for the Space Station Freedom PMAD DC testbed

The Ada language software development to perform the electrical system monitoring functions for the NASA Lewis Research Center's Power Management and Distribution (PMAD) DC testbed is described. The results of the effort to implement this monitor are presented. The PMAD DC testbed is a reduced-scale prototype of the electrical power system to be used in the Space Station Freedom. The power is controlled by smart switches known as power control components (or switchgear). The power control components are currently coordinated by five Compaq 382/20e computers connected through an 802.4 local area network. One of these computers is designated as the control node with the other four acting as subsidiary controllers. The subsidiary controllers are connected to the power control components with a Mil-Std-1553 network. An operator interface is supplied by adding a sixth computer. The power system monitor algorithm is comprised of several functions including: periodic data acquisition, data smoothing, system performance analysis, and status reporting. Data is collected from the switchgear sensors every 100 milliseconds, then passed through a 2 Hz digital filter. System performance analysis includes power interruption and overcurrent detection. The reporting mechanism notifies an operator of any abnormalities in the system. Once per second, the system monitor provides data to the control node for further processing, such as state estimation. The system monitor required a hardware time interrupt to activate the data acquisition function. The execution time of the code was optimized using an assembly language routine. The routine allows direct vectoring of the processor to Ada language procedures that perform periodic control activities. A summary of the advantages and side effects of this technique are discussed

Description of the SSF PMAD DC testbed control system data acquisition function

The NASA LeRC in Cleveland, Ohio has completed the development and integration of a Power Management and Distribution (PMAD) DC Testbed. This testbed is a reduced scale representation of the end to end, sources to loads, Space Station Freedom Electrical Power System (SSF EPS). This unique facility is being used to demonstrate DC power generation and distribution, power management and control, and system operation techniques considered to be prime candidates for the Space Station Freedom. A key capability of the testbed is its ability to be configured to address system level issues in support of critical SSF program design milestones. Electrical power system control and operation issues like source control, source regulation, system fault protection, end-to-end system stability, health monitoring, resource allocation, and resource management are being evaluated in the testbed. The SSF EPS control functional allocation between on-board computers and ground based systems is evolving. Initially, ground based systems will perform the bulk of power system control and operation. The EPS control system is required to continuously monitor and determine the current state of the power system. The DC Testbed Control System consists of standard controllers arranged in a hierarchical and distributed architecture. These controllers provide all the monitoring and control functions for the DC Testbed Electrical Power System. Higher level controllers include the Power Management Controller, Load Management Controller, Operator Interface System, and a network of computer systems that perform some of the SSF Ground based Control Center Operation. The lower level controllers include Main Bus Switch Controllers and Photovoltaic Controllers. Power system status information is periodically provided to the higher level controllers to perform system control and operation. The data acquisition function of the control system is distributed among the various levels of the hierarchy. Data requirements are dictated by the control system algorithms being implemented at each level. A functional description of the various levels of the testbed control system architecture, the data acquisition function, and the status of its implementationis presented

Advanced Extravehicular Mobility Unit Informatics Software Design

This is a description of the software design for the 2013 edition of the Advanced Extravehicular Mobility Unit (AEMU) Informatics computer assembly. The Informatics system is an optional part of the space suit assembly. It adds a graphical interface for displaying suit status, timelines, procedures, and caution and warning information. In the future it will display maps with GPS position data, and video and still images captured by the astronaut

A Raster Based Approach To Solar Pressure Modeling

The impact of photons upon a spacecraft introduces small forces and moments. The magnitude and direction of the forces depend on the material properties of the spacecraft components being illuminated. Which components are being lit depends on the orientation of the craft with respect to the Sun as well as the gimbal angles for any significant moving external parts (solar arrays, typically). Some components may shield others from the Sun.To determine solar pressure in the presence overlapping components, a 3D model can be used to determine which components are illuminated. A view (image) of the model as seen from the Sun shows the only contributors to solar pressure. This image can be decomposed into pixels, each of which can be treated as a non-overlapping flat plate as far as solar pressure calculations are concerned. The sums of the pressures and moments on these plates approximate the solar pressure and moments on the entire vehicle.The image rasterization technique can also be used to compute other spacecraft attributes that are dependent on attitude and geometry, including solar array power generation capability and free molecular flow drag

Authors\u27 reply to discussant\u27s response: An investigation of a measurement based approach to the evaluation of audit evidence

https://egrove.olemiss.edu/dl_proceedings/1129/thumbnail.jp

Auditor evidential planning judgments

https://egrove.olemiss.edu/dl_proceedings/1028/thumbnail.jp

Investigation of a measurement based approach to the evaluation of audit evidence

https://egrove.olemiss.edu/dl_proceedings/1127/thumbnail.jp

Investigation of adaptability in evidential planning

https://egrove.olemiss.edu/dl_proceedings/1053/thumbnail.jp

The Framing and Evaluation of Multiple Hypotheses

This is the author's final draft. The publisher's official version is available electronically from: .This study provides exploratory evidence on auditors’ framing and evaluation of hypotheses, identifies implications for improving audit decision-making and facilitates the interpretation of prior research. Prior studies usually assume hypotheses to be framed as mutually exclusive and exhaustive. However, both verbal protocol evidence and probability assessments reveal that in a realistic case most auditors frame the hypotheses as a non-mutually exclusive and exhaustive set of causes. Further, auditor probability assessments tend to reflect multiple causes. Finally, exploratory analyses indicate auditors have difficulty in updating assessments consistent with the perceived interrelationships between hypotheses

The art of recovery: outcomes from participatory arts activities for people using mental health services

Background: There is a growing evidence base for the use of participatory arts for the purposes of health promotion. In recent years, recovery approaches in mental healthcare have become commonplace in English speaking countries amongst others. There are few studies that bring together these two fields of practice. Aims: The two aims of this study were (a) to investigate the validity of the CHIME framework (Leamy et al, 2011) for characterising the experience of Participatory Arts and (b) to use the CHIME framework to investigate the relationship between participatory arts and mental health recovery. Method: The study employed a two-phase methodology: a rapid review of relevant literature followed by secondary analysis of qualitative data collected from 38 people who use mental health service who took part in participatory arts activities designed to improve mental health. Results: Each of the recovery processes identified by CHIME are present in the qualitative research literature as well as in the data of the secondary analysis. Conclusions: Participatory arts activities produce outcomes which support recovery, specifically including enhancing connectedness and improving hope. They can be recommended to people living with mental health problems