Towards Task-Specific Modular Gripper Fingers Automatic Production of Fingertip Mechanics Johannes Ringwald Samuel Schneider Lingyun Chen Dennis Knobbe Lars Johannsmeier

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Towards Task-Specific Modular Gripper Fingers: Automatic Production
of Fingertip Mechanics
Johannes Ringwald, Samuel Schneider, Lingyun Chen, Dennis Knobbe, Lars Johannsmeier,
Abdalla Swikir and Sami Haddadin
Abstract The number of sequential tasks a single gripper
can perform is significantly limited by its design. In many cases,
changing the gripper fingers is required to successfully conduct
multiple consecutive tasks. For this reason, several robotic tool
change systems have been introduced that allow an automatic
changing of the entire end-effector. However, many situations
require only the modification or the change of the fingertip,
making the exchange of the entire gripper uneconomic. In
this paper, we introduce a paradigm for automatic task-specific
fingertip production. The setup used in the proposed framework
consists of a production and task execution unit, containing
a robotic manipulator, and two 3D printers - autonomously
producing the gripper fingers. It also consists of a second
manipulator that uses a quick-exchange mechanism to pick
up the printed fingertips and evaluates gripping performance.
The setup is experimentally validated by conducting automatic
production of three different fingertips and executing grasp-
stability tests as well as multiple pick- and insertion tasks,
with and without position offsets - using these fingertips. The
proposed paradigm, indeed, goes beyond fingertip production
and serves as a foundation for a fully automatic fingertip design,
production and application pipeline - potentially improving
manufacturing flexibility and representing a new production
paradigm: tactile 3D manufacturing.
I. INTRODUCTION
Most conditions of manipulation tasks in industrial pro-
duction setups can be precisely controlled, like initial posi-
tions and orientations of manipulation objects which should
be processed. Despite these controllable conditions, per-
forming tasks with multi-degree of freedom (DoF) hands is
still a complex assignment and a subject of basic research.
Moreover, the performance of soft grippers depends on the
scenario considered. For example, robustness problems can
arise if objects with sharp edges must be grasped with
high grasping forces. Accordingly, most industrial assembly
This work was funded by the German Research Foundation (DFG,
Deutsche Forschungsgemeinschaft) as part of Germany’s Excellence Strat-
egy – EXC 2050/1 – Project ID 390696704 – Cluster of Excellence
“Centre for Tactile Internet with Human-in-the-Loop” (CeTI) of Technische
Universit¨
at Dresden. The authors gratefully acknowledge the funding of the
Lighthouse Initiative KI.FABRIK Bayern by StMWi Bayern (KI.FABRIK
Bayern Phase 1: Aufbau Infrastruktur and KI.Fabrik Bayern Forschungs-
und Entwicklungsprojekt, grant no. DIK0249). We also gratefully acknowl-
edge the funding of the Lighthouse Initiative Geriatronics by LongLeif
GaPa gGmbH (Project Y).The authors are with the Chair of Robotics and
Systems Intelligence and Munich Institute of Robotics and Machine Intel-
ligence, Technical University Munich (TUM), D-80797 Munich, Germany
e-mail: {firstname.surname}@tum.de
?Please note that S. Haddadin has a potential conflict of interest as a
shareholder of Franka Emika GmbH.
?This work has been submitted to the IEEE for possible publication.
Copyright may be transferred without notice, after which this version may
no longer be accessible.
Fig. 1. Automatic fingertip production and task execution based on a
given fingertip design and finger base set - using two robot-arms and two
3D printers.
tasks are still performed by two- or three-finger parallel
grippers. To enable robust grasping and manipulation of
defined objects, the fingers of these grippers must be man-
ually designed, produced, tested and iterated until reaching
a satisfactory performance. This adaptation process is not
only very laborious and time-consuming, but also requires a
high level of design experience in this field [1]. Therefore,
the number of assembly objects and manipulation scenarios
that can be handled is limited by the time a designer needs
to adapt a finger to a specific application. This makes the
assembly line setup in-flexible, since any changes, like tool-
changing, finger adaption etc. are very time consuming
and therefore costly. Accordingly, assembly or production
lines are usually setup for a few product types, which are
produced in masses over a longer time period (month/years).
All integrated robots conduct only one specific task with
one specialized tool or finger design, which increases the
required number of robots for a designated assembly scenario
significantly.
A flexible production of smaller batch sizes requires a
smaller adaption time of the setup to a new product (min-
utes/hours). Therefore, a significantly shorter - ideally fully
automatized - gripper finger design, production and iteration
process would be needed.
Several automatic approaches for robot finger design adap-
tation have been introduced to solve the aforementioned
problems [2]–[9]. One aspect of this adaptation process
concerns the finger surface design which majorly affects the
ability to robustly perform stable grasps and manipulation
tasks. Different approaches have been introduced to optimize
the gripper finger morphology and geometry based on a
given set of objects [1], [10]–[16]. Despite all the efforts to
automate the gripper finger design, the set of tasks a robot
manipulator can perform is still limited to its mounted fin-
gers. Therefore, different tool-changing systems for robotic
applications have been developed [17]–[32]. While most of
arXiv:2210.10015v1 [cs.RO] 18 Oct 2022
Fig. 2. Presented testbed divided into a production and a task-execution unit. The production unit conducts the extension of 3D printed standard finger-bases
with custom fingertip elements by: 1. extraction of two finger-bases from corresponding finger-base magazines by a robot-arm. 2. Insertion and locking of
these finger-bases to finger-holder frames, stationary placed on the build-plate of two 3D printers. 3. Printing of custom fingertips on top of pre-produced
finger-bases. 4. The extended finger is picked up by the robot-arm and inserted into the magazines of the quick-finger-exchange system. 5. Using the QFE
system, the gripper fingers are picked up by the task execution unit. To conduct the finger testing tasks an IoT-Box is used, which provides pick and place
tasks for three different objects: key, Ethernet-cable, battery.
these systems focus on exchanging the entire end-effector,
some of them focus specifically on replacing single fingers
[17], [20], [31], or modifying the finger configuration [32].
Unfortunately, none of the aforementioned work provides
a fully automated process for the gripper finger production
and exchange. In other words, the fingers must be replaced
manually during an ongoing manipulation process.
Motivated by the above limitations, we introduce a fully
automated setup for gripper finger production and exchange.
In particular, by integrating a collaborative robot - the Panda
arm - with two 3D printers, it was possible to automate the
production of a predefined set of fingertips. Furthermore, we
introduce a passive quick-finger-exchange system that allows
the robot to automatically change the used finger-pair during
a manipulation task. By combining the automatic fingertip
production and the quick-finger-exchange system, the time
required to adapt to a new assembly task dramatically
decreases. E.g., the automatic production of new fingertips
using a standard finger base reduces the production time of
new gripper fingers significantly (minutes instead of hour).
The number of assembly steps a single robot can perform
during a new production/assembly task increases, since one
robot can select and change its gripper-finger automatically
during the entire assembly process. Accordingly our ap-
proach makes it possible to realize an efficient and flexible
small batch production/assembly process, while minimizing
the required time, labor and infrastructure required for the
assembly - like the number of robots needed for the task.
Fig.1 illustrates this automatic process. Moreover, the pro-
posed approach will serve as a first step and foundation for a
fully automated task-specific finger design, production, and
application pipeline, which will enable a robot to identify its
own fingertips and, potentially, provide the base for a novel
production paradigm: tactile 3D manufacturing.
The paper is organized as follows. In Sec. II, we describe
the production processes as well as the quick-finger-exchange
mechanism. Then, in Sec. III, we demonstrate the appli-
cation and effectiveness of the proposed approach through
experiments. Finally, we discuss our results and provide a
conclusion in Sec. IV.
II. PRODUCTION AND TASK EXECUTION UNIT
The proposed setup is divided into a production unit and a
task execution unit, see Fig.2. The production unit performs
all the required steps to automatically build a task-specific
parallel gripper fingertip design onto a pre-defined finger-
base. The task execution unit uses these fingers to conduct
a defined set of tasks. Those fingers can be automatically
changed during the robot operation using a quick-exchange
system. Accordingly, the fingers the production unit provides
can be collected to a finger library and used multiple times
by the task-execution unit - depending on the currently
needed fingertip geometry. This allows the same robots of
an assembly line/setup to change their fingers automatically
in seconds and adapt to a new product quickly.
Therefor, our specifically designed 3D-printing based pro-
duction setup has the following advantages compared to a
摘要:

TowardsTask-SpecicModularGripperFingers:AutomaticProductionofFingertipMechanicsJohannesRingwald,SamuelSchneider,LingyunChen,DennisKnobbe,LarsJohannsmeier,AbdallaSwikirandSamiHaddadinAbstract—Thenumberofsequentialtasksasinglegrippercanperformissignicantlylimitedbyitsdesign.Inmanycases,changingthegr...

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