The Robotics Institute

RI | Seminar | April 22

Robotics Institute Seminar, April 22
Time and Place | Seminar Abstract | Speaker Biography | Speaker Appointments

Scaling Issues in Robotics:
Strength, Range, and Communication Limits on Big and Small Robots

Mel Siegel

Associate Research Professor

Carnegie Mellon University



Time and Place

Mauldin Auditorium (NSH 1305)
Refreshments 3:15 pm
Talk 3:30 pm



Over the last two or three years I have been developing this talk and presenting it to a wide range of audiences. The first

time or two I worried that its content and conclusions might be too trivial to be worth taking up even 20 minutes as a

contributed paper at a conference. But to my growing amazement, every time I give it I get more invitations – now at the

level of hour-long keynote addresses at international conferences – and more requests from people who want to draw on it in

upcoming courses and books. So I figured the time has come to expose it to the light of day here at home, and to hear if my

colleagues think this topic and my approach are actually worth the interest they are attracting far away.


I will start by discussing the fundamental strength and consequent design issues that arise as robotics moves in the

directions of machines and systems that are much larger and much smaller than human scale, and to the inevitable new issues

of energy storage capacity and communication efficiency. Some of the most interesting systems we envision manifest

simultaneously the difficulties of being very large and very small, e.g., spatially and numerically large networks of small

robotic sensor nodes. In these complex systems, deployment is limited globally by the fundamental problems of transporting

and controlling large systems, and locally because node function is hampered by the problems of small-scale devices, i.e.,

operating time limited by the small size of on-board energy reservoirs, and inter-node communication efficiency limited by

the small sizes of the antennas that can be deployed whilst continuing to call the whole “small”. Interesting possibilities arise

when we imagine individual devices that have different scales in different dimensions, e.g., decameter-length filaments of



Regarding strength and energy, two generalities counterintuitive to the non-technical population are well-known to

scientists and engineers: (1) big is weak, small is strong, i.e., it is large structures that collapse under their own weight and

large animals that break their legs when they stumble, whereas small structures and small animals are practically oblivious to

gravity, and (2) horses “eat like birds” and birds “eat like horses”, i.e., a large animal or machine stores relatively larger

quantities of energy and dissipates relatively smaller quantities of energy than a small animal or machine. The critical

consequence of (2) is that the smaller the robot the smaller its range and its operating time between refuelings. Applying

simple scaling models to contemplated small robots, the conclusion is quickly reached that robots at currently contemplated

small scales will be never be able to carry enough energy to complete any sensible mission. They will rather have to forage

for fuel in the environment, just as microorganisms have to forage for their nutrients in the energy-rich liquid environments –

the soup! – to which their lives are mostly constrained. I will show that in any model scenario in which the lion’s share of

the onboard fuel is used to overcome frictional drag a mobile robot’s range is a scale-independent constant multiple of its

length, and its running time is the same scale-independent constant multiple of the time it takes to traverse its own length. I

will discuss the corresponding relationships for several other energy consumption rate scenarios, e.g., where the lion’s share

of the on-board energy is expended climbing hills.


If time permits I will outline how large and small scale issues come into play simultaneously when considering systems

composed of large numbers of small devices spread over large areas or dispersed through large volumes. The fundamental

issues hinge on the universal fact that antennas are efficient only for wavelengths around their own size. Small devices are

thus good antennas only for small wavelengths, i.e., high frequencies, i.e. high energy per photon, making naive approaches

to communication unacceptably high energy-cost propositions for devices whose energy storage capacities are limited by

their small scale.



Speaker Biography


Mel Siegel received a B.A. in Physics from Cornell University 1962, and M.S. and Ph.D. degrees in Physics from the University of Colorado (Boulder) in 1967 and 1970, respectively.  His Ph.D. research, on the structure of molecular negative ions of interest in the upper atmosphere, was conducted at the Joint Institute for Laboratory Astrophysics, a collaborative facility of the University of Colorado and the National Institute of Standards and Technology.  From 1962 to 1964 he taught physics and math as a member of the Peace Corps in Ghana.  From 1970 to 1972, he was a post-doc, then a research faculty member, in the Department of Aerospace Engineering and Engineering Physics, University of Virginia (Charlottesville).  From 1972 to 1974 he was a faculty member in the Department of Physics and Astrophysics at the State University of New York (Buffalo).  From 1974 to 1982 he was a research scientist, then director of research, development, and applications, at Extranuclear Laboratories, now the Extrel Division of ABB (Pittsburgh), a designer and manufacturer of mass spectrometer systems for laboratory, process, forensic, and space applications.  In 1982 he joined the faculty and became the founding director of the Sensors, Measurement, and Control Laboratory at the Robotics Institute, now a department of the School of Computer Science, Carnegie Mellon University.  He and his graduate students are involved in research on sensor networks and sensor fusion for context aware computing, sensors and systems for rehabilitation engineering, stereoscopic image capture and display systems for teleoperation, issues in confidence fusion, and scaling issues in robotics.  He is also active in teaching, having developed the core course “Sensing and Sensors” designed for Robotics PhD students, which he currently teaches, and the required undergraduate course “Electromechanical Systems for Mechanical Engineering Department junior-year students.  He has served as the lead faculty person in the Carnegie Mellon University RoboCamp-West program, a college-level hands-on summer course for high school students between their junior and senior years, and is the coordinator and lead faculty person for the Master of Science in Information Technology / Robotic Technology program with SSN School of Advanced Software Engineering in Chennai, India.  His resume includes approximately 250 publications in archival journals, professional magazine articles, book chapters, and conference and workshop proceedings, including seven issued and two pending patents in areas of analytical sensing and instrumentation, teleoperated mobile robot systems, and stereoscopic video and graphics systems.  He has been a consultant to companies involved in scientific instrumentation, scientific software, data storage, stereoscopy, and several manufacturing areas.  He is a Fellow of the IEEE, and a member of the administrative committee, and currently the treasurer, of the IEEE Instrumentation and Measurements Society, and an associate editor of the IEEE Transactions on Instrumentation and Measurements.  He regularly reviews research proposals for funding agencies including the US, Canadian, Austrian, Netherlands, and Italian governments.



Speaker Appointments

For appointments, please contact Mel Siegel (

The Robotics Institute is part of the School of Computer Science, Carnegie Mellon University.