# Control of A High Performance Bipedal Robot using Viscoelastic Liquid Cooled Actuators

## TL;DR

This paper presents the design, control, and evaluation of a high-performance bipedal robot with innovative liquid-cooled viscoelastic actuators, emphasizing energy efficiency, compactness, and dynamic walking capabilities.

## Contribution

It introduces a new system design with RFSEA and FSEA actuators, and evaluates advanced control algorithms for stable, dynamic bipedal walking.

## Key findings

- Successful implementation of a compact, energy-efficient actuation system.
- Effective control algorithms enabling stable dynamic walking.
- Enhanced torque density and impact resistance in the robot.

## Abstract

This paper describes the control, and evaluation of a new human-scaled biped robot with liquid cooled viscoelastic actuators (VLCA). Based on the lessons learned from previous work from our team on VLCA [1], we present a new system design embodying a Reaction Force Sensing Series Elastic Actuator (RFSEA) and a Force Sensing Series Elastic Actuator (FSEA). These designs are aimed at reducing the size and weight of the robot's actuation system while inheriting the advantages of our designs such as energy efficiency, torque density, impact resistance and position/force controllability. The system design takes into consideration human-inspired kinematics and range-of-motion (ROM), while relying on foot placement to balance. In terms of actuator control, we perform a stability analysis on a Disturbance Observer (DOB) designed for force control. We then evaluate various position control algorithms both in the time and frequency domains for our VLCA actuators. Having the low level baseline established, we first perform a controller evaluation on the legs using Operational Space Control (OSC) [2]. Finally, we move on to evaluating the full bipedal robot by accomplishing unsupported dynamic walking by means of the algorithms to appear in [3].