# Momentum Control of Humanoid Robots with Series Elastic Actuators

## TL;DR

This paper introduces a control framework for humanoid robots with series elastic actuators, enabling stable momentum control by managing motor velocities, which enhances compliance and safety.

## Contribution

It extends momentum-based control methods to robots with series elastic actuators by using motor velocities as an intermediate control input.

## Key findings

- Simulation results verify the effectiveness of the proposed control approach.
- The method improves stability and compliance in humanoid robot control.
- The framework is applicable to robots with joint elasticity.

## Abstract

Humanoid robots may require a degree of compliance at the joint level for improving efficiency, shock tolerance, and safe interaction with humans. The presence of joint elasticity, however, complexifies the design of balancing and walking controllers. This paper proposes a control framework for extending momentum based controllers developed for stiff actuators to the case of series elastic actuators. The key point is to consider the motor velocities as an intermediate control input, and then apply high-gain control to stabilise the desired motor velocities achieving momentum control. Simulations carried out on a model of the robot iCub verify the soundness of the proposed approach.