Co-design Optimization and Actuator Optimization for Legged Robots

Co-design Optimization and Actuator Optimization for Legged Robots



Introduction

Legged robots—such as quadrupeds and humanoids—require actuators that are not only high in torque and efficiency but also lightweight and responsive. Multiple actuator architectures exist for meeting joint-level performance requirements, including single-stage, two-stage, and compound planetary gearboxes, cycloidal drives, and strain-wave gearboxes. However, most actuator designs in the field today rely heavily on heuristics or designer intuition, with limited use of rigorous optimization-based design techniques. While some studies have employed optimization methods for actuator design, they often fail to account for key real-world parameters like mass and efficiency. Even when such factors are considered, the underlying models tend to be overly simplistic, limiting their applicability in practical robotic systems.

Recent approaches in robot design use co-design optimization, where mechanical design and control strategies are optimized simultaneously. Although these methods optimize parameters such as link lengths, gear ratios, compliance, and actuator scaling, they often overlook the critical choice of gearbox architecture itself. Moreover, their actuator models lack detailed representation of mass and efficiency, which are essential for realistic, high-performance designs.

Our research aims to bridge this gap by addressing two core questions:

Applications

This research has two primary applications:



Methodology


drawing

The optimization framework (left) optimizes gearbox parameters for a given motor and performance requirements, passing them to the design automation block. This generates a parametric template model, which a human designer uses to create the manufacturable CAD of the actuator.

Current Work Status

Currently, we have developed a comprehensive optimization framework for two widely used single-stage planetary gearbox architectures: the Internal Single-Stage Planetary Gearbox (ISSPG) and the External Single-Stage Planetary Gearbox (ESSPG). Given a specific motor and joint performance requirements, this framework computes the optimal design parameters for both gearbox architectures. In addition, we have developed an automated actuator design framework that utilizes these optimized parameters to generate a template CAD model. This CAD generation process is fully automated and provides a baseline design that captures the essential mechanical features needed for manufacturability. Using the generated template, designers can efficiently finalize and detail the actuator for fabrication.



Actuator Designs

Gearbox Type Gear Ratio (a, b) Design for Manufacturing; (c, d) Template Designs
ESSPG 7.2:1 ESSPG Actuator
ISSPG 6:1 ISSPG Actuator



Future Work

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People

Aman Singh
Design and Control Co-Optimization
Aastha Mishra
Aastha Mishra
Design and Control Co-Optimization
Shishir Kolathaya
Assistant Professor, CSA & CPS, IISc
Last updated: 2025-02-28