A nonlinear feedback controller for aerial self-righting by a tailed robot

Abstract

Ahstract-In this work, we propose a control scheme for attitude control of a falling, two link active tailed robot with only two degrees of freedom of actuation. We derive a simplified expression for the robot's angular momentum and invert this expression to solve for the shape velocities that drive the body's angular momentum to a desired value. By choosing a body angular velocity vector parallel to the axis of error rotation, the controller steers the robot towards its desired orientation. The proposed scheme is accomplished through feedback laws as opposed to feed forward trajectory generation, is fairly robust to model uncertainties, and is simple enough to implement on a miniature microcontroller. We verify our approach by implementing the controller on a small (175 g) robot platform, enabling rapid maneuvers approaching the spectacular capability of animals.

A spider-inspired dragline enables aerial pitch righting in a mobile robot

“…Terrestrial animals, lacking dedicated structures for aerial control, often achieve this by zero-angular-momentum methods including back twisting, most associated with cats [1] [2], or the rapid rotation of a tail exhibited by many reptiles [1] [3][4] [5]. Robots inspired by cats [2] and lizards [3] [4] [5] have demonstrated that these methods are not only effective when applied to robots, but actually compare favourably to traditional alternatives such as reaction wheels [3].…”

From Rousettus aegyptiacus (bat) landing to robotic landing: Regulation of CG-CP distance using a nonlinear closed-loop feedback

“…Utilizing contact forces and zero angular momentum condition, the lizard-inspired robot uses a Proportional-Derivative (PD) controller for self-righting in a free fall. The attitude controller for the robot with 2-DOF tail has been presented in [14].…”

Orienting in mid-air through configuration changes to achieve a rolling landing for reducing impact after a fall

“…Optimal control has been proposed to solve for trajectories that minimize joint path length for a given orientation [8], [9], [7]. Also, recent work by the Full group has generated controllers for orienting when angular momentum is not initially zero [10], [11], [12]. Inspired by Hatton and Choset [13], [14], our work exploits the underlying geometry of the nonholonomic constraint of conserved angular momentum to solve for trajectories that allow orienting even when angular momentum is zero.…”

“…The dead drop was performed with orientations of q 0 = [10,20,30,40,50,60,70,80] • and two cases were tested: one with the absorbing impact control on and another with the joints locked. The falling experiment used an initial orientation of q 0 = 45…”