Miniature Wheel-Leg Mobile Robots

These robots can run and can climb obstacles with cockroach-like motions.

Mini-Whegs™ are small mobile robots, designed according to abstracted cockroach locomotion principles, that can run and can climb obstacles taller than themselves. Mini-Whegs are derived from larger mobile robots denoted Whegs™, with modifications to reduce size, reduce the number of mechanisms, and increase relative mobility. The name “Whegs” originated as a contraction of “wheel-legs,” referring to three-spoke appendages by means of which these robots move, as described below.

Figure 1. Several Stages in the Motion of a pair of front wheel-legs approaching and climbing an obstacle illustrate important principles of design and operation. A far (black) wheel-leg makes contact first and then, by virtue of passive torsional compliance in the drive train, a near (grey) wheel-leg rotates into phase with the far wheel-leg. Once in phase, the two wheel-legs can propel the front of the robot over the obstacle. Atop the obstacle, the two wheel-legs spring back to their nominal 60° rotational separation.

Each axle contains a passive, compliant mechanism that enables the two attached wheel-legs to rotate by as much as 60° from their nominal phase difference of 60°. This feature is a key element of both mobility and relative simplicity of design in that it enables a robot to adapt its motion to changing terrain in a manner similar to that of a cockroach, without need for an active adaptation control subsystem. In particular, as illustrated by the example of Figure 1, this feature can cause the wheel-legs in each pair to become aligned as needed for climbing an obstacle and then spring back to the normal 60° phase difference once the obstacle has been surmounted.