Technical Report: A New Hopping Controller for Highly Dynamical Bipeds

TL;DR

This paper introduces a novel angle of attack control strategy for a biped robot, enabling stable, high-speed hopping by managing velocity and momentum, with analytical predictions matching empirical results.

Contribution

The paper presents a new control method for bipeds that improves stability and speed, supported by analytical models and experimental validation.

Findings

Stable hopping at speeds up to 2.5 m/s

Analytical model accurately predicts steady-state performance

Avoids traction issues common in hip-actuated SLIP

Abstract

We present angle of attack control, a novel control strategy for a hip energized Penn Jerboa. The energetic losses from damping are counteracted by aligning most of the velocity at touchdown in the radial direction and the fore-aft velocity is controlled by using the hip torque to control to a target angular momentum. The control strategy results in highly asymmetric leg angle trajectories, thus avoiding the traction issues that plague hip actuated SLIP. Using a series of assumptions we find an analytical expression for the fixed points of an approximation to the hopping return map relating the design parameters to steady state gait performance. The hardware robot demonstrates stable locomotion with speeds ranging from 0.4 m/s to 2.5 m/s (2 leg lengths/s to 12.5 leg lengths/s) and heights ranging from 0.21 m to 0.27 m (1.05 leg lengths to 1.35 leg lengths). The performance of the empirical trials is well approximated by the analytical predictions.