Abstract
A cylindrical rolling robot is developed that generates roll torque by changing the shape of its flexible, elliptical outer surface whenever one of four elliptical axes rotates past an inclination called trigger angle. The robot is equipped with a sensing/control system by which it measures angular position and angular velocity, and computes error with respect to a desired step angular velocity profile. When shape change is triggered, the newly assumed shape of the outer surface is determined according to the computed error. A series of trial rolls is conducted using various trigger angles, and energy consumed by the actuation motor per unit roll distance is measured. Results show that, for each of three desired velocity profiles investigated, there exists a range of trigger angles that results in relatively low energy consumption per unit roll distance, and when the robot operates within this optimal trigger angle range, it undergoes minimal actuation burdening and inadvertent braking, both of which are inherent to the mechanics of rolling robots that use shape change to generate roll torque. A mathematical model of motion is developed and applied in a simulation program that can be used to predict and further understand behavior of the robot.
Highlights
Ground based robots typically move from place to place using wheels, legs, or by changing shape in a biomimetic fashion, as with peristaltic or slithering locomotion [1,2,3]
Each of the simulated rolls has a set of initial conditions and control constants that are identical to a trial roll conducted in the experiment
When θt is decreased relative to this range, so that actuation is triggered with less tilt of the triggering axis with respect to the vertical, energy economy of robot locomotion is observed to decrease; and when θt is increased relative to this range, so that actuation is triggered with more tilt of the triggering axis, energy economy of robot locomotion is again observed to decrease
Summary
Ground based robots typically move from place to place using wheels, legs, or by changing shape in a biomimetic fashion, as with peristaltic or slithering locomotion [1,2,3]. The study investigates locomotion of an autonomous rolling robot, developed at the Unmanned Systems Laboratory at Oklahoma State University (OSU) and pictured, which generates torque by means of changing its outer surface. In addition to being shape changing and partially gravity powered, locomotion of the OSU Roller, as it is entitled, is categorized as dynamic [5], meaning it has a natural rocking tendency and exhibits inertial motion. Non-dynamic rollers, such as crawling rolling robots [6,7], move slowly in comparison and do not exhibit dramatic inertial effects after motion input has ceased.
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