Experimental Capabilities and Achievements of the Space Environment Dynamometer (SED)

The Space Environment Dynamometer (SED) chamber was designed to conduct research in cryobotics; an area of
study that focuses on robotic systems and rotating machinery
operating in extreme cold environments including Earth, low
Earth orbit, Mars, Moon, asteroids, Solar orbit, planetary orbit,
or those encountered during travel among these destinations.
The test chamber incorporates a modular dynamometer, consisting of a variety of brakes, torque sensors and motors to
be easily interchanged between tests. Each test employs a
unique test profile that incorporates different setpoints of applied torques and velocities for a given period or number of rev-
olutions. The modularity of the dynamometer setup allows for
any combination of motor, gearbox to be tested. This chamber
is one of a kind and resides at the Swamp Works facility within
the Granular Mechanics and Regolith Operations laboratory
(GMRO) at NASA Kennedy Space Center. Other cold chambers
exist, however they are project specific and do not simultaneously output real time torque, temperature and efficiency data.
The modularity of this extreme cold environment test chamber,
coupled with the custom software and instrumentation, makes it
one of a kind.

The chamber is capable of stabilizing cryogenic temperatures
and pressures to commensurate moon environments. Tests
have successfully been conducted on motors and gearboxes for
various cryogenic temperature set points, torques, and angular
velocities. Relevant internal temperatures of the test article and
chamber were recorded using a variety of temperature sensors.
The temperature setpoints, on the motors and gearboxes tested,
were stabilized by using PID gain scheduling of the PWM
signal for the various heaters. The heat removal for the motor
was provided by creating a thermally conductive path from a
cryohead directly to the test article using copper straps.

A variety of strainwave gears (SWGs), also known as Harmonic
drives, planetary gear systems and DC motor actuator configurations have been tested in the chamber. The experiments
performed were for various projects including Bulk Metallic
Glass Gears (BMGG), Volatiles Investigating Polar Exploration
Rover (VIPER), In-Situ Resource Utilization Pilot Excavator
(IPEX) . Various upgrades have been made to the extreme cold
environment test chamber for the use of cryobotic research.

These upgrades greatly increased the autonomous capabilities of
the test set up by providing redundancies in the hardware and
software. The redundancies were primarily added to protect
the integrity of the cryohead. A new strapping and insulation
method was performed to create the thermal conductive path
from the actuators to the cryohead. The software was upgraded
to include temperature setpoint control, further increasing the
autonomous capabilities of the test. This paper goes into detail
regarding the upgrades made to the extreme cold environment
test chamber, as well as highlights the results from a COLDArm
acceptance test.