A paper describes a modular design for new controllers for infrared heating during cruise stage solar thermal vacuum test of the Mars Science Laboratory. The controllers had to be easy to use and maintain, used with a wide variety of different control schemes, and made using commercial off-the-shelf (COTS) components wherever possible.
A new controller was designed and built using COTS components that could be operated manually, or automatically in a temperature control mode through the use of programmable PID (proportional–integral–derivative) controllers. Another option is through computer control to implement control schemes involving average over a number of sensors, with no sensor above or below the temperature set point or use of non-thermocouple sensors such as PRTs (platinum resistance thermometer), calorimeters, etc. The system incorporates a thermal failsafe to guard against high-temperature overruns of the test item, ground fault circuit interrupters for personal protection, and has provision for an external shutdown signal for other conditions such as a vacuum system entering the corona region with the addition of a proper alarm system.
This controller was designed and built as a versatile general-purpose controller. Its modular design will make upgrades or modifications simple to implement. Previous controllers used at JPL were purpose-built for the project that required them, and difficult to upgrade or modify.
This work was done by Michael R. McKee, Isaac M. Brown, Seth L. Chazanoff, and Bruce Woodward of Caltech for NASA’s Jet Propulsion Laboratory. NPO-47402
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