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Honeywell Engines and Systems (E&S) Environmental Control Systems (ECS) division has been developing a 50 kW proton exchange membrane (PEM) fuel cell brassboard system for automotive application as part of a U.S. Department of Energy (DOE) program. A primary issue in the development of the brassboard is the automatic control of the system. A preferred DOE requirement is dynamic load following from idle to peak power. Since the PEM stacks require precise inlet condition control for both the air and fuel to achieve high efficiency, the control system must provide good dynamic tracking and low steady-state error over the entire operating range. In addition, the controller must provide automatic system start-up and shutdown, built-in-test (BIT) to monitor key system parameters, and take corrective action if those parameters reach an unsafe condition. The purpose of this paper is to present the control system design approach taken by the authors to achieve those goals.

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.

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.

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.