Cognitive Arthropods

Insects are nature’s engineering marvels. They can perform marvellous feats such as jumping many times their own body length, lifting many times their own body weight, moving around even with multiple missing limbs and doing all this with amazing efficiency. It is little wonder then that roboticists have been attempting to replicate nature’s design feat in robots. The primary thrust in the area of arthropod robotics has been locomotion. Various insect-like robots directly inspired by biology have been built using knowledge discovered about insect locomotion. As the literature in the area is vast and is much beyond the scope of this article, a brief review focussed on a critical analysis of a few hexapod robots is presented here. The robots discussed here include the series of cockroach-like robots built at Case Western Reserve University, the RHex program [Saranli01] at the University of Michigan and the joint work done by Stanford University and the University of California, Berkeley [Clark01]. It is not a mere coincidence that all these robots have the cockroach as their biological basis (as does the example scenario given in the workshop prospectus). Cockroaches, in addition to being extremely hardy and agile, are also easy to study, as the vast literature on cockroach locomotion shows. Hence, these omnipresent pests are ideal models for roboticists. So as to increase performance as much as possible, bioroboticists (as they are known) try to incorporate the mechanics of a single species throughout the design of the robot. The study of cockroach gait has revealed that the legs of the cockroach essentially act as inverted pendulums on which the body swings. The cockroach has a tripod gait where only three legs are in contact with the ground at any given instant. Each leg passes through a stance and a swing phase in one motion cycle, where the stance phase involves the part where the leg touches the ground and provides reaction force for movement and the swing part involves the forward motion of the leg. The cockroach robot series at Case Western Reserve consists of a series of roach-robots of different sophistication levels. Robot I [Beer92] and II [Quinn93] are basic in design and demonstrate simple walking behaviors. Robot III [Ritzmann00] is described in greater detail here. The robot legs in Robot III are designed to closely match the design of cockroach legs. The hind legs of a cockroach provide maximum thrust for locomotion while the front legs are solely to provide deceleration. The legs of Robot III follow this trend in that the hind legs are more powerful than the