Push Recovery of a Position-Controlled Humanoid Robot Based on Capture Point Feedback Control

TL;DR

This paper presents a practical push recovery method for position-controlled humanoid robots using capture point feedback, combining ankle and hip strategies without requiring torque sensors, verified on SURENA-Mini.

Contribution

It introduces a novel feedback control scheme enabling push recovery on position-controlled robots by emulating ankle and hip strategies without torque sensors.

Findings

Effective push recovery demonstrated on SURENA-Mini

Method works under severe pushes

No torque sensors needed for implementation

Abstract

In this paper, a combination of ankle and hip strategy is used for push recovery of a position-controlled humanoid robot. Ankle strategy and hip strategy are equivalent to Center of Pressure (CoP) and Centroidal Moment Pivot (CMP) regulation respectively. For controlling the CMP and CoP we need a torque-controlled robot, however most of the conventional humanoid robots are position controlled. In this regard, we present an efficient way for implementation of the hip and ankle strategies on a position controlled humanoid robot. We employ a feedback controller to compensate the capture point error. Using our scheme, a simple and practical push recovery controller is designed which can be implemented on the most of the conventional humanoid robots without the need for torque sensors. The effectiveness of the proposed approach is verified through push recovery experiments on SURENA-Mini humanoid robot under severe pushes.