Microbots for Large-Scale Planetary Surface and Subsurface Exploration

This project studies a new mission concept for planetary exploration, based on the deployment of a large number of small spherical mobile robots (“microbots”) over vast areas of a planet’s surface and subsurface, including structures such as caves and near-surface crevasses. This would allow extremely large-scale in situ analysis of terrain composition and history. This approach represents an alternative to rover and lander-based planetary exploration, which is limited to studying small areas of a planet’s surface at a small number of sites. The proposed approach is also distinct from balloon or aerial vehicle-based missions, in that it would allow direct in situ measurement.

In the proposed mission, a large number (i.e. hundreds or thousands) of cm-scale, sub-kilogram microbots would be distributed over a planet’s surface by an orbital craft and would employ hopping, bouncing and rolling as a locomotion mode to reach scientifically interesting artifacts in very rugged terrain. They would be powered by high energy-density polymer “muscle” actuators, and equipped with a suite of miniaturized imagers, spectrometers, sampling devices, and chemical detection sensors to conduct in situ measurements of terrain and rock composition, structure, etc. Multiple microbots would coordinate to share information, cooperatively analyze large portions of a planet’s surface or subsurface, and provide context for scientific measurements.

The goal of this research project is to assess the feasibility of space exploration based on microbots in a time frame of 10-40 years. This is done by addressing the following objectives:

(*) Developed a detailed mission scenario for specific scientific objectifs on the Moon and Mars;
(*) Survey enabling technologies for actuation, power, sensing and communication;
(*) Conduct fundamental research on “muscle” actuators and microbot mobility mechanisms;
(*) Develop algorithms for efficient coordination of large microbot “teams;”
(*) Propose preliminary microbot physical design concepts;
(*) Assess the feasibility of the concept within the context of selected representative missions.

A microbot is a self-contained spherical robot equipped with power and communication systems, a mobility system that enables it to move via hopping, rolling, and bouncing, and a suite of miniaturized sensors such as imagers, spectrometers, and sensors for chemical analysis. With advanced power, locomotion, sensing, and computation technology, we expect that microbots would be on the order of 10 cm in diameter and approximately 100 g or less in 10 to 40 years. The key technical challenge to enable microbots are discussed bellow:

Mobility -- The mobility system uses Dielectric Elastomer Actuators (DEAs) for their large strains, lightweight, low cost, and inherently simplicity. Proof-of-concepts experiments have shown that DEAs can be used for hopping when used in conjunction with bistable devices to store and release hopping energy, see the Mechatronics Webpage These deformation-based actuators are fundamentally simple and are ideal to be used in large numbers in microbots missions. DEAs are also used to orient microbots before hopping.

Power -- Power plays a critical role in any mobile robots for long duration missions. The proposed power generation concept for microbots uses miniature fuel cells using Printed Circuit Board technology. The use of bi-stable mechanisms with Dielectric Elastomer Actuators lowers the peak power consumption necessary for hopping, which in turn enables the use of high efficiency/low power devices such as fuel cells. The fuel cell power system combined with dielectric elastomer actuators provide significant weight reduction over a comparable lithium based battery systems for long range missions (> 100 hops).

Communications -- The main communications challenge is to establish reliable communication from subsurface to surface. Due to radio wave absorption by rock and/or debris, high power and very low frequency is required to communicate directly from subsurface to surface. A very large antenna would be needed for low frequencies, which makes this solution impractical. At high frequencies the distance for reliable non-line-of-sight communication is small, preventing direct subsurface-to-surface communications via the cave entrance. A solution to this problem is to use the microbot units as communications network to relay information back to a central unit on the surface via the cave entrance.

Electronics and Sensors -- Each microbot would contain miniature electronic components for data processing enabling online decision making. Miniature sensors would provide navigation information and scientific measurements such as macro and micro images and chemical substance identification.