On compliant underactuated robotic fingers

Abstract

SummaryDriven by societal trends, such as aging, and by a desire to drive economic growth and enhance commercial competitiveness, researchers have tried to move robots from structured manufacturing tasks to unstructured professional and personal service applications.As announced in the Falcon project, an example of a possible unstructured professional service task for future robots is found in package-handling tasks in warehouses (distribution centers). The Falcon project aimed to design a new system architecture for a fully automated distribution center and to define, within this architecture, specific critical robotic components, which were then targeted to be researched. The author observed some inherent challenges in following such an application driven research approach. Chapter 2 presents the author's reflections on the tensions between top-down systems engineering approaches and the classical bottom-up approach for doing research.Rather than targeting one specific robotic service application, several general technological challenges were identified that require resolution to let robots move from structured to unstructured applications. One such general technological challenge is to develop versatile robotic end-effectors which are able to execute a diverse set of unstructured human-like service tasks, either being professional or personal tasks. Various approaches can be taken to develop these versatile end-effectors. This thesis focuses on contributing in the development of human-like dexterous robotic hands. The thesis presents a study on a novel robotic finger concept (aimed to be used in dexterous robotic hands), the control thereof and an accompanying theoretic treaty on natural pseudo-inverses.Inspired by human hand studies, Chapter 3 describes the desired functions for a dexterous robotic hand, being dexterous grasping, dexterous manipulation, free motion and interactive motion. Following a brief review of the current status of dexterous robotic hand technology, Chapter 3 formulates design considerations and a research direction for further developments and innovations in dexterous robotic hand technology. Variable mechanical compliance and underactuated actuation methods are marked as important design features to support robust, reliable, low weight, human dimensional and affordable technologies for dexterous robotic hands. Benefits of using actuation methods with variable compliance for grasping are presented separately in Chapter 4. Several simple grasp scenarios are used to show that different scenarios have different preferred compliance settings, which highlights the advantages of using variable compliance.Chapter 5 gives insights on natural space decompositions for the pseudo-inverse of physical maps in models of physical systems, such as the actuation Jacobian (also called transmission matrix) in a kinematic model of a drive-train of an underactuated robotic finger. Multiple mathematical view-points are used to explain the importance of choosing proper metrics on vector spaces, especially w...