Genetic Optimization of a Manipulator: Comparison between Straight, Rounded, and Curved Mechanism Links

Robert Pastor,Daniel Huczala,Stefan Grushko,Zdenko Bobovský

doi:10.3390/app11062471

Abstract

There are several ubiquitous kinematic structures that are used in industrial robots, with the most prominent being a six-axis angular structure. However, researchers are experimenting with task-based mechanism synthesis that could provide higher efficiency with custom optimized manipulators. Many studies have focused on finding the most efficient optimization algorithm for task-based robot manipulators. These manipulators, however, are usually optimized from simple modular joints and links, without exploring more elaborate modules. Here, we show that link modules defined by small numbers of parameters have better performance than more complicated ones. We compare four different manipulator link types, namely basic predefined links with fixed dimensions, straight links that can be optimized for different lengths, rounded links, and links with a curvature defined by a Hermite spline. Manipulators are then built from these modules using a genetic algorithm and are optimized for three different tasks. The results demonstrate that manipulators built from simple links not only converge faster, which is expected given the fewer optimized parameters, but also converge on lower cost values.

Highlights

There are several ubiquitous kinematic structures that are used in industrial robots, with the most prominent being a six-axis angular structure
Custom manipulator designs can overcome this problem, as best shown in the work by Brandstoetter [1], where he presented a robotic manipulator with a task-desired kinematic structure
We used a genetic algorithm (GA) implemented in .NET C# combined with a simulation implemented in CoppeliaSim [24], whereby the GA takes care of the optimization and the simulation provides a way to evaluate the individuals proposed by the GA and calculates their cost value

Summary

Introduction

There are several ubiquitous kinematic structures that are used in industrial robots, with the most prominent being a six-axis angular structure. Many studies have focused on finding the most efficient optimization algorithm for task-based robot manipulators. These manipulators, are usually optimized from simple modular joints and links, without exploring more elaborate modules. The most common serial manipulator design in the industry benefits from its so-called angular structure with 6 degrees of freedom, which can reach the surrounding areas and achieve multiple different poses. This universal kinematic structure has a disadvantage in that when such robots are deployed in densely built workplaces, they can collide either with obstacles or themselves. Hornby [8] was one of the first that demonstrated the possible application

Objectives

Methods

Results

Conclusion