Design and Experimental Validation of Reorientation Manoeuvres for a Free Falling Robot Inspired From the Cat Righting Reflex

Abstract

This paper presents two distinct manoeuvres allowing an articulated robot in free fall to change its orientation using closed paths in the joint space. It is shown through dynamics simulations that the magnitude of the net rotation is dependent upon the amplitude of the angular displacement of the joints. With realistic joint limitations, the robot, which includes rotary actuators only, can perform a 180-degree reorientation about its longitudinal axis, similar to the cat righting reflex. The second manoeuvre allows the robot to accomplish rotations of smaller magnitude about a different axis. A physical prototype and a VICON motion tracking system are used to experimentally validate the simulation results. Finally, it is shown that the two manoeuvres, which yield rotations about fixed axes, can be repeated and alternated to enable the robot to reach any arbitrary 3D orientation.

Reorientation of Free-Falling Legged Robots

“…Another approach that can be used to describe the kinematic and dynamic behavior of free-floating robots is similar to the one presented in Ref. [25]. In this approach, the forward kinematic and Fig.…”

“…The architecture of these appendages is inspired from the robot presented in Ref. [25], with, referring to the configuration shown at the top of Fig. 2, the first DoF allowing a rotation of the appendage about the y-axis (joints R5-R8) and the second DoF allowing rotations of the end piece about the x-axis (joints R9-R12).…”

“…The second maneuver (fine maneuver), inspired by Garant and Gosselin [25] and shown on the right-hand side of Fig. 3, is more elaborate, but more flexible than the first one.…”

“…However, in the case of the cat-inspired maneuvers, which are generally more elaborate and complex than the tail-based maneuvers, there is no physical limitation as to why the resulting reorientation should be limited to one axis of movement. Garant and Gosselin [25] address this by developing a three DoF articulated robot capable of completing two separate, closed-loop maneuvers which allow for reorientation about the roll and the pitch axes during free fall. Given that any given rotation in three-dimensional space can be described as a linear combination of rotations about any two distinct axes [26,27], Garant et al's robot is thus capable of producing any desired reorientation provided that the fall lasts long enough.…”

“…Notably, this architecture builds upon the work presented in Ref. [25] in order to obtain high-amplitude reorientation maneuvers about both horizontal axes ideal for controlling its landing configuration. Furthermore, the presented architecture, built as a generalized four-legged robot, illustrates the cat-inspired maneuvers in a conceptually functional context and demonstrates the minimal articular requirements to achieve these maneuvers.…”