Profile: Mark Tilden

Mark Tilden is a roboticist recently recruited by Wowwee Toys; Wowwee shortly thereafter released the Robosapien and the Roboraptor, with which Mark Tilden was clearly involved. Prior to working in the toy business, however, Mark led quite a different life: as a physicist at the Defense Department's Los Alamos National Laboratories, he was responsible for building autonomous, distributed and parallel-processing robots. Mark also worked at NASA, where he seems to have been intimately involved in the design of the Mars rovers.

A dominant theme in Mark Tilden's robotics research is embodiment. Many of his robots don't possess a central microprocessor - instead, they rely entirely on the non-linear coupled oscillations of electrical activity between as few as 12 transistors, connected in parallel. These patterns drive activity in the sensor and motor layers, and are "constantly attempting phase lock synchronization among variable pulse trains," according to Tilden's 2003 article in Robotics and Autonomous Systems. [Sound familiar?]

There are several major advantages to this approach, all of which contribute to what Mark calls a high "performance to silicon" ratio. First, Mark's robots are inexpensive. Many of the parts necessary to build an autonomous, foraging ant-like robot can be found inside a Sony Walkman. Second, much less building time (and no programming, at least in the traditional sense) is required: Mark claims to have built more than 500 autonomous robots, at less than 40 hours each (40 or 50 of these robots currently function as Mark Tilden's full-time housecleaners).

Finally, his robots are adaptive; because their behavior emerges from a sub-symbolic, non-linear, bi-directional interaction between a "nervous net" and its environment, the patterns of electrical activity driving all behavior are extremely plastic to changing situations. As a result, some of Mark's "biobugs" are still capable of movement after their legs have been sharply bent (a change that would surely foil any traditional symbolic mobility system), and are in some cases resilient to damage to 80% of their parts. Mark writes that "the loads generated by the motors directly modified the oscillator processes so that each motor [becomes] its own inertia-damped sensor ... This reduces robot control electronics to almost nothing, and as Nv systems are automatically self-optimizing, no programming is required either."

Mark refers to this architecture as biomorphic, and clearly takes many cues from nature. For example, in this interview Mark talks about the problem of motivation: without an internal drive for food (or power, more generally speaking) his robots have little need to move. But once he implements an appropriate "survival gradient," such as phototaxis, relatively organized behavior emerges. Here are some videos of these paradoxically simple machines.

Perhaps the most interesting, and yet most cryptic aspect of Tilden's work is the role of memory. His biorobots do not have memory per se; instead, their architecture can cultivate multiple attractor states. In other words, the creatures can show multiple patterns of behavior, as though they had been memorized.

It's still a matter of debate whether "biorobotics" actually has anything to teach biology. In fact, this article is dedicated to this far-from-resolved debate. Approaches like Tilden's are valuable even if it's only for their imaginative quality. However, the ultimate contribution of physical non-linear computation, like Tilden's, is likely to be much greater.

Interviews with Mark Tilden:
About his Los Alamos biorobots
About the Robosapien, from November 2004
About his DARPA work, including nanoscale MEMS
An upcoming documentary on Mark Tilden

Related Posts:
Binding through Synchrony: Proof from Developmental Robotics
Military Robotics: The State of the Art of War
Emotional Robotics
Imitation vs Self-Awareness: The Mirror Test
Neurorobotics
Giving the Ghost a Machine
A Mind of Its Own: Wakamaru