A robot was developed for the purpose of research into legged locomotion. Legged robots are complex mechanisms, and their development can be greatly aided by insights into the mechanisms—both physical and control—by which animals locomote.
This text presents the design methodology used for the development of the fifth such biologically inspired robot at Case: Robot V. The robot is based on the deathhead cockroach, Blaberus discoidalis. It has twenty-four degrees of freedom (DOF) distributed amongst task oriented legs; five DOF in the front legs, four DOF in the middle, and three DOF in the rear.
Previous research has shown that this joint configuration can closely approximate that of the cockroach, while not being too complex from and engineering standpoint. Actuation is by braided pneumatic actuators, and coupled with a valve system that allows air to be trapped within the actuators, numerous beneficial muscle-like properties were produced. Most importantly, this system enabled rapid response to perturbation, much like “preflexes” exhibited by animals, affording the system a level of passive stability.
The robot is controlled by a hierarchical control system, and the operation of the interleg coordination mechanism, a variant of the distributed network of the responsible for stick insect interleg coordination proposed by Cruse, is discussed in detail. The robot has demonstrated open loop passive stability and locomotion.
With the addition of joint angle and actuator pressure sensors, the robot has been able to perform “air walking” motions while suspended from a gantry as well as walking on a treadmill while its weight is partially supported. Closed loop walking has been accomplished, but further development of its locomotion controllers is called for.
Source: Stanford University
Author: Daniel A. Kingsley