Parallel Transmission Aware Co-Design: Enhancing Manipulator Performance Through Actuation-Space Optimization

TL;DR

This paper introduces a co-design method for parallel robotic manipulators that optimizes transmission ratios and actuation trajectories simultaneously, significantly improving payload capacity over traditional tree-model approaches.

Contribution

It presents a novel co-design framework explicitly modeling parallel coupling constraints, enabling joint optimization of transmission ratios and trajectories for enhanced performance.

Findings

Increased dynamic payload capacity compared to conventional methods

Effective integration of parallel mechanisms into co-design process

Improved utilization of the manipulator's dynamic range

Abstract

In robotics, structural design and behavior optimization have long been considered separate processes, resulting in the development of systems with limited capabilities. Recently, co-design methods have gained popularity, where bi-level formulations are used to simultaneously optimize the robot design and behavior for specific tasks. However, most implementations assume a serial or tree-type model of the robot, overlooking the fact that many robot platforms incorporate parallel mechanisms. In this paper, we present a novel co-design approach that explicitly incorporates parallel coupling constraints into the dynamic model of the robot. In this framework, an outer optimization loop focuses on the design parameters, in our case the transmission ratios of a parallel belt-driven manipulator, which map the desired torques from the joint space to the actuation space. An inner loop performs trajectory optimization in the actuation space, thus exploiting the entire dynamic range of the manipulator. We compare the proposed method with a conventional co-design approach based on a simplified tree-type model. By taking advantage of the actuation space representation, our approach leads to a significant increase in dynamic payload capacity compared to the conventional co-design implementation.