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Previous sweat modeling attempts have produced several models of the human sweat regulation mechanism. To effectively use the models for control purposes, the sensitivity of the models to their parameters must be quantified. The characteristics of several meaningful sweat models are discussed. The parameters of each model are ranked in order to identify which parameters are the most important to the models. An objective of the study is to quantify the uncertainties in such models, to the extent possible. The sensitivity needed to measure the evaporative heat loss is calculated for a subject in the calorimeter being developed at University of Missouri-Columbia. This study is part of a larger effort at the University to develop reliable human thermal models for space suit thermal modeling studies.

Automatic thermal comfort control for the minimum consumables PLSS is undertaken using several control approaches. Accuracy and performance of the strategies using feedforward, feedback, and gain scheduling are evaluated through simulation, highlighting their advantages and limitations. Implementation issues, consumable usage, and the provision for the extension of these control strategies to the cryogenic PLSS are addressed.

A transient model of the Minimum Consumables Portable Life Support System (MPLSS) Advanced Space Suit design has been developed and implemented using MAT-LAB/Simulink. The purpose of the model is to help with sizing and evaluation of the MPLSS design and aid development of an automatic thermal comfort control strategy. The MPLSS model is described, a basic thermal comfort control strategy implemented, and the thermal characteristics of the MPLSS Advanced Space Suit are investigated.

The NASA JSC Shuttle EMU computer model (SINDA EMU) is presently used to analyze the thermal behavior of the Space Shuttle EMU. This paper uses the SINDA EMU model along with EMU experimental and flight data to investigate and define several performance characteristics of the Space Shuttle EMU related to thermal comfort control.

The prospect of using automatic control for astronaut thermal comfort regulation during extravehicular activity (EVA) requires an investigation of issues concerning the current state of the art of human thermal models. The analysis presented includes, but is not limited to, the discussion of assumptions and the accuracy, range and relative significance of parameters (e.g., thermal properties, physical dimensions, etc.) of transient human thermal models. The Wissler 1D model attracts primary consideration; however, there exists the appropriate inclusion of the 41-Node Man model for reflection and study.

This paper discusses several issues related to the PLSS thermal model requirements for a planned generalized EVA Simulation Test Bed. The existing models of the extravehicular mobility unit (EMU) are briefly discussed and then the paper focuses specifically on the NASA JSC Shuttle EMU model (referred to as SINDA EMU). After the SINDA EMU model review, the PLSS thermal model requirements for the EVA Simulation Test Bed are discussed in detail.

NASA is funding a research project at the University of Missouri - Columbia as part of a more general effort to learn about the human physiological response to the types of exercise that astronauts perform on EVA missions. The authors created a dynamic state-space mathematical model representing the thermal behavior of the NASA environmental chamber located at the Ames Research Center. This model predicts chamber performance from which the authors identify modifications to the system which will improve its accuracy and usefulness. Simulation results closely match expected values for chamber performance. Recommendations are presented to improve chamber performance and instrumentation measurement accuracy.

A detailed comparison has begun of the structure and function of two human thermal models, the 41-Node Man model and the Wissler model, being considered for use in a proposed simulation test bed to model the fully transient extravehicular activity (EVA) automatic thermal control problem. The evaluation is directed toward demonstrating the current state of the art in human thermal modeling methodology and performance. Internal formulative differences between the models is the primary focus.

A transient thermal model of the portable life support system (PLSS) is being developed for use in thermal control studies. The transient thermal PLSS (TTPLSS) model has been developed and implemented using SIMULINK in conjunction with MATLAB. The TTPLSS has been developed with modularity and flexibility in mind so that alternative PLSS designs and configurations can easily be implemented and evaluated. The basic structure and functionality of the TTPLSS SIMULINK model is described and demonstrated. The various thermal dynamics issues associated with the PLSS such as time delays and the dynamics of individual components are discussed and considered.

Modeling the sweat regulation mechanism is important for reliable simulation of the human thermoregulatory processes. The complexity of the mechanism makes it very difficult to model using traditional techniques. An engineering or systems overview of the human thermoregulatory system is reported. An extensive review of previous attempts to model the human sweat rate forms an important part of this paper. In addition, this study investigates the applicability of neural networks to the problem of modeling the complex nonlinearities of the sweat regulatory mechanism. It is believed that neural networks provide better generalization capabilities for all the cited dependencies resulting in better sweat prediction models. The network is thus in a position to generalize based on the different operating conditions and provide more reliable outputs over an entire range of environments and metabolic profiles.

Long-duration, frequent extravehicular activity (EVA) will require automatic thermal control and improved thermo-mechanical design of portable life support system (PLSS) packs and suits. This paper addresses the control problem in EVA, previous attempts to develop automatic control, and relevant issues in human thermoregulation and is directed toward the development of a generalized computer simulation test bed for the investigation of alternative PLSS control strategies and designs.