201 research outputs found
Towards a Modular Framework for Visco-Hyperelastic Simulations of Soft Material Manipulators with Well-Parameterised Material
Controller design for continuum robots maintains to be a difficult task. Testing controllers requires dedicated work in manufacturing and investment into hardware as well as software, to acquire a test bench capable of performing dynamic control tasks. Typically, proprietary software for practical controller design such as Matlab/Simulink is used but lacks specific implementations of soft material robots. This intermediate work presents the results of a toolchain to derive well-identified rod simulations. State-of-the-art methods to simulate the dynamics of continuum robots are integrated into an object-oriented implementation and wrapped into the Simulink framework. The generated S-function is capable of handling arbitrary, user-defined input such as pressure actuation or external tip forces as demonstrated in numerical examples. With application to a soft pneumatic actuator, stiffness parameters of a nonlinear hyperelastic material law are identified via finite element simulation and paired with heuristically identified damping parameters to perform dynamic simulation. To prove the general functionality of the simulation, a numerical example as well as a benchmark from literature is implemented and shown. A soft pneumatic actuator is used to generate validation data, which is in good accordance with the respective simulation output. The tool is provided as an open-source project. Code is available under https://gitlab.com/soft_material_robotics/cosserat-rod-simulink-sfunction.© 2023 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other work
Dynamics Modeling of a Continuum Robotic Arm with a Contact Point in Planar Grasp
Grasping objects by continuum arms or fingers is a new field of interest in robotics. Continuum manipulators have the advantages of high adaptation and compatibility with respect to the object shape. However, due to their extremely nonlinear behavior and infinite degrees of freedom, continuum arms cannot be easily modeled. In fact, dynamics modeling of continuum robotic manipulators is state-of-the-art. Using the exact modeling approaches, such as theory of Cosserat rod, the resulting models are either too much time-taking for computation or numerically unstable. Thus, such models are not suitable for applications such as real-time control. However, based on realistic assumptions and using some approximations, these systems can be modeled with reasonable computational efforts. In this paper, a planar continuum robotic arm is modeled, considering its backbone as two circular arcs. In order to simulate finger grasping, the continuum arm experiences a point-force along its body. Finally, the results are validated using obtained experimental data
Dynamic modelling and visco-elastic parameter identification of a fibre-reinforced soft fluidic elastomer manipulator
A dynamic model of a soft fibre-reinforced fluidic elastomer is presented and experimentally verified, which
can be used for model-based controller design. Due to the
inherent visco-(hyper)elastic characteristics and nonlinear timedependent behaviour of soft fluidic elastomer robots, analytic
dynamic modelling is challenging. The fibre reinforced noninflatable soft fluidic elastomer robot used in this paper can produce both planar and spatial movements. Dynamic equations
are developed for both cases. Parameters, related to the viscoelastic behaviour of the robot during elongation and bending
motion, are identified experimentally and incorporated into
our model. The modified dynamic model is then validated in
experiments comparing the time responses of the physical robot
with the corresponding outputs of the simulation model. The
results validate the accuracy of the proposed dynamic model
Model Based Control of Soft Robots: A Survey of the State of the Art and Open Challenges
Continuum soft robots are mechanical systems entirely made of continuously
deformable elements. This design solution aims to bring robots closer to
invertebrate animals and soft appendices of vertebrate animals (e.g., an
elephant's trunk, a monkey's tail). This work aims to introduce the control
theorist perspective to this novel development in robotics. We aim to remove
the barriers to entry into this field by presenting existing results and future
challenges using a unified language and within a coherent framework. Indeed,
the main difficulty in entering this field is the wide variability of
terminology and scientific backgrounds, making it quite hard to acquire a
comprehensive view on the topic. Another limiting factor is that it is not
obvious where to draw a clear line between the limitations imposed by the
technology not being mature yet and the challenges intrinsic to this class of
robots. In this work, we argue that the intrinsic effects are the continuum or
multi-body dynamics, the presence of a non-negligible elastic potential field,
and the variability in sensing and actuation strategies.Comment: 69 pages, 13 figure
Geared rod-driven continuum robot with woodpecker-inspired extension mechanism and IMU-based force sensing
Continuum robot arms that can access confined spaces are useful in many applications, such as invasive surgery, search and rescue, and inspection. However, their reach is often limited because their extension mechanism relies on elastic deformation or folding structures. To address this challenge, we propose a continuum robot with a novel extension mechanism inspired by the impressive ability of woodpeckers to extend and bend their long tongues to catch insects in tree holes. The proposed mechanism can change the effective length of the robot from almost zero to any length by moving the robot's body back and forth. Our prototype robot demonstrated a maximum extension of 450 mm and a minimum bending radius of 125 mm. In addition, we developed a Gaussian process regression model to predict an external force applied to the robot's tip using inertial measurement units. This enabled us to determine the magnitude and direction of the force with an error rate of 4.8 percent and 11.1 percent, even when the robot's length was varied between the training and test data. The unrestricted extension capability of the proposed approach has the potential to increase the application prospects of continuum robots
A continuum robotic platform for endoscopic non-contact laser surgery: design, control, and preclinical evaluation
The application of laser technologies in surgical interventions has been accepted in the clinical
domain due to their atraumatic properties. In addition to manual application of fibre-guided
lasers with tissue contact, non-contact transoral laser microsurgery (TLM) of laryngeal tumours
has been prevailed in ENT surgery. However, TLM requires many years of surgical training
for tumour resection in order to preserve the function of adjacent organs and thus preserve the
patient’s quality of life. The positioning of the microscopic laser applicator outside the patient
can also impede a direct line-of-sight to the target area due to anatomical variability and limit
the working space. Further clinical challenges include positioning the laser focus on the tissue
surface, imaging, planning and performing laser ablation, and motion of the target area during
surgery. This dissertation aims to address the limitations of TLM through robotic approaches and
intraoperative assistance. Although a trend towards minimally invasive surgery is apparent, no
highly integrated platform for endoscopic delivery of focused laser radiation is available to date.
Likewise, there are no known devices that incorporate scene information from endoscopic imaging
into ablation planning and execution. For focusing of the laser beam close to the target tissue, this
work first presents miniaturised focusing optics that can be integrated into endoscopic systems.
Experimental trials characterise the optical properties and the ablation performance. A robotic
platform is realised for manipulation of the focusing optics. This is based on a variable-length
continuum manipulator. The latter enables movements of the endoscopic end effector in five
degrees of freedom with a mechatronic actuation unit. The kinematic modelling and control of the
robot are integrated into a modular framework that is evaluated experimentally. The manipulation
of focused laser radiation also requires precise adjustment of the focal position on the tissue. For
this purpose, visual, haptic and visual-haptic assistance functions are presented. These support
the operator during teleoperation to set an optimal working distance. Advantages of visual-haptic
assistance are demonstrated in a user study. The system performance and usability of the overall
robotic system are assessed in an additional user study. Analogous to a clinical scenario, the
subjects follow predefined target patterns with a laser spot. The mean positioning accuracy of the
spot is 0.5 mm. Finally, methods of image-guided robot control are introduced to automate laser
ablation. Experiments confirm a positive effect of proposed automation concepts on non-contact
laser surgery.Die Anwendung von Lasertechnologien in chirurgischen Interventionen hat sich aufgrund der atraumatischen Eigenschaften in der Klinik etabliert. Neben manueller Applikation von fasergefĂĽhrten
Lasern mit Gewebekontakt hat sich die kontaktfreie transorale Lasermikrochirurgie (TLM) von
Tumoren des Larynx in der HNO-Chirurgie durchgesetzt. Die TLM erfordert zur Tumorresektion
jedoch ein langjähriges chirurgisches Training, um die Funktion der angrenzenden Organe zu
sichern und damit die Lebensqualität der Patienten zu erhalten. Die Positionierung des mikroskopis chen Laserapplikators außerhalb des Patienten kann zudem die direkte Sicht auf das Zielgebiet
durch anatomische Variabilität erschweren und den Arbeitsraum einschränken. Weitere klinische
Herausforderungen betreffen die Positionierung des Laserfokus auf der Gewebeoberfläche, die
Bildgebung, die Planung und AusfĂĽhrung der Laserablation sowie intraoperative Bewegungen
des Zielgebietes. Die vorliegende Dissertation zielt darauf ab, die Limitierungen der TLM durch
robotische Ansätze und intraoperative Assistenz zu adressieren. Obwohl ein Trend zur minimal
invasiven Chirurgie besteht, sind bislang keine hochintegrierten Plattformen fĂĽr die endoskopische
Applikation fokussierter Laserstrahlung verfĂĽgbar. Ebenfalls sind keine Systeme bekannt, die
Szeneninformationen aus der endoskopischen Bildgebung in die Ablationsplanung und -ausfĂĽhrung
einbeziehen. Für eine situsnahe Fokussierung des Laserstrahls wird in dieser Arbeit zunächst
eine miniaturisierte Fokussieroptik zur Integration in endoskopische Systeme vorgestellt. Experimentelle Versuche charakterisieren die optischen Eigenschaften und das Ablationsverhalten. Zur
Manipulation der Fokussieroptik wird eine robotische Plattform realisiert. Diese basiert auf einem
längenveränderlichen Kontinuumsmanipulator. Letzterer ermöglicht in Kombination mit einer
mechatronischen Aktuierungseinheit Bewegungen des Endoskopkopfes in fĂĽnf Freiheitsgraden.
Die kinematische Modellierung und Regelung des Systems werden in ein modulares Framework
eingebunden und evaluiert. Die Manipulation fokussierter Laserstrahlung erfordert zudem eine
präzise Anpassung der Fokuslage auf das Gewebe. Dafür werden visuelle, haptische und visuell haptische Assistenzfunktionen eingeführt. Diese unterstützen den Anwender bei Teleoperation
zur Einstellung eines optimalen Arbeitsabstandes. In einer Anwenderstudie werden Vorteile der
visuell-haptischen Assistenz nachgewiesen. Die Systemperformanz und Gebrauchstauglichkeit
des robotischen Gesamtsystems werden in einer weiteren Anwenderstudie untersucht. Analog zu
einem klinischen Einsatz verfolgen die Probanden mit einem Laserspot vorgegebene Sollpfade. Die
mittlere Positioniergenauigkeit des Spots beträgt dabei 0,5 mm. Zur Automatisierung der Ablation
werden abschließend Methoden der bildgestützten Regelung vorgestellt. Experimente bestätigen
einen positiven Effekt der Automationskonzepte fĂĽr die kontaktfreie Laserchirurgie
Open-loop position control in collaborative, modular Variable-Stiffness-Link (VSL) robots
— Collaborative robots (cobots) open up new avenues
in the fields of industrial robotics and physical Human-Robot
Interaction (pHRI) as they are suitable to work in close approximation and in collaboration with humans. The integration
and control of variable stiffness elements allow inherently safe
interaction. Apart from notable work on Variable Stiffness
Actuators, the concept of Variable-Stiffness-Link (VSL) manipulators promises safety improvements in cases of unintentional
physical collisions. However, position control of these type of
robotic manipulators is challenging for critical task-oriented
motions (e.g., pick and place). Hence, the study of open-loop
position control for VSL robots is crucial to achieve high
levels of safety, accuracy and hardware cost-efficiency in pHRI
applications. In this paper, we propose a hybrid, learning based
kinematic modelling approach to improve the performance
of traditional open-loop position controllers for a modular,
collaborative VSL robot. We show that our approach improves
the performance of traditional open-loop position controllers
for robots with VSL and compensates for position errors, in
particular, for lower stiffness values inside the links: Using
our upgraded and modular robot, two experiments have been
carried out to evaluate the behaviour of the robot during taskoriented motions. Results show that traditional model-based
kinematics are not able to accurately control the position
of the end-effector: the position error increases with higher
loads and lower pressures inside the VSLs. On the other
hand, we demonstrate that, using our approach, the VSL robot
can outperform the position control compared to a robotic
manipulator with 3D printed rigid links
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