Scaling issues in robot-based sensing missions

Scaling analysis provides a systematic way to translate the performance of a system from one size domain, operating environment, etc., to another. In this paper, we identify scaling issues and present some simple results in the domain of individual mobile robots, as well as teams, swarms, etc., deployed on sensing missions. Since most robot-based sensing missions anticipate mini-, micro-, and nano-scale robots, our explicit examples focus on scaling-down of existing human-scale robot design and concepts. However the principles articulated apply equally to scaling-up situations. The topic is introduced via a simple example that shows why scaling-down of mobile robots that carry their own energy source will generally prove impractical: to obtain reasonable operating times it will rather be necessary to develop small robots into which energy can be beamed, or which can forage for energy sources in the environment. From this concrete illustrative example, the paper moves on to a higher level discussion of robot architecture and the applicability of scaling principles, to varying degrees, to all the modules, i.e., it is not exclusively a mobility issue. There follows a short discussion of how changes of scale are not inherently problematic, but to the contrary, in many cases suitable scale change provides the key to solving a difficult engineering problem. The final section is a quantitative example in which design and operating parameters of the robotic nodes of a sensor network are considered from the perspective of operating time limited by the energy cost of node-to-node communication. This example powerfully illustrates a system in which fairly modest changes contemplated range of engineering parameters result in enormous changes in the anticipated operating time of the system.