403 research outputs found
Approximate Piecewise Constant Curvature Equivalent Model and Their Application to Continuum Robot Configuration Estimation
The continuum robot has attracted more attention for its flexibility.
Continuum robot kinematics models are the basis for further perception,
planning, and control. The design and research of continuum robots are usually
based on the assumption of piecewise constant curvature (PCC). However, due to
the influence of friction, etc., the actual motion of the continuum robot is
approximate piecewise constant curvature (APCC). To address this, we present a
kinematic equivalent model for continuum robots, i.e. APCC 2L-5R. Using
classical rigid linkages to replace the original model in kinematic, the APCC
2L-5R model effectively reduces complexity and improves numerical stability.
Furthermore, based on the model, the configuration self-estimation of the
continuum robot is realized by monocular cameras installed at the end of each
approximate constant curvature segment. The potential of APCC 2L-5R in
perception, planning, and control of continuum robots remains to be explored
Dynamic Modeling of Soft-Material Actuators Combining Constant Curvature Kinematics and Floating-Base Approach
Soft robotic manipulators are on the verge to their first real applications. In most cases they are actuated by fluidic pressure or tendons and molded of highly elastic material, which performs large deformation if put under stress. Performing tasks e.g. in inspection of narrow machines or endoscopy requires the actuator to be tactile and controllable. Due to their highly nonlinear behavior, model-based approaches are investigated to combine and utilize sensor information to estimate the system states of the manipulator. In this paper, equations of motion (EoM) for the well-known piecewise constant curvature (PCC) approach are extended by a floating base as it is often used in kinematic chains for legged robots and their contact with the ground. Base reaction forces and moments, which are easily measurable quantities, become visible in the EoM, if the six spatial degrees of freedom at the base of the manipulator are considered. Thereby, additional information on the system's states is obtained and used in the proposed identification scheme. Essentially, the floating base, a center-of-gravity approach and a state-of-the-art parametrization of the PCC kinematics are combined to derive and validate a Lagrangian dynamics model. On a best-case set of validation step responses, the identified inverse dynamics model performs with an accuracy of 5% to 7.6% of max. actuation torque.© 2022 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
A review on model-based and model-free approaches to control soft actuators and their potentials in colonoscopy
Colorectal cancer (CRC) is the third most common cancer worldwide and responsible for approximately 1 million deaths annually. Early screening is essential to increase the chances of survival, and it can also reduce the cost of treatments for healthcare centres. Colonoscopy is the gold standard for CRC screening and treatment, but it has several drawbacks, including difficulty in manoeuvring the device, patient discomfort, and high cost. Soft endorobots, small and compliant devices thatcan reduce the force exerted on the colonic wall, offer a potential solution to these issues. However, controlling these soft robots is challenging due to their deformable materials and the limitations of mathematical models. In this Review, we discuss model-free and model-based approaches for controlling soft robots that can potentially be applied to endorobots for colonoscopy. We highlight the importance of selecting appropriate control methods based on various parameters, such as sensor and actuator solutions. This review aims to contribute to the development of smart control strategies for soft endorobots that can enhance the effectiveness and safety of robotics in colonoscopy. These strategies can be defined based on the available information about the robot and surrounding environment, control demands, mechanical design impact and characterization data based on calibration.<br/
ViSE: Vision-Based 3D Online Shape Estimation of Continuously Deformable Robots
The precise control of soft and continuum robots requires knowledge of their
shape. The shape of these robots has, in contrast to classical rigid robots,
infinite degrees of freedom. To partially reconstruct the shape, proprioceptive
techniques use built-in sensors resulting in inaccurate results and increased
fabrication complexity. Exteroceptive methods so far rely on placing reflective
markers on all tracked components and triangulating their position using
multiple motion-tracking cameras. Tracking systems are expensive and infeasible
for deformable robots interacting with the environment due to marker occlusion
and damage. Here, we present a regression approach for 3D shape estimation
using a convolutional neural network. The proposed approach takes advantage of
data-driven supervised learning and is capable of real-time marker-less shape
estimation during inference. Two images of a robotic system are taken
simultaneously at 25 Hz from two different perspectives, and are fed to the
network, which returns for each pair the parameterized shape. The proposed
approach outperforms marker-less state-of-the-art methods by a maximum of 4.4%
in estimation accuracy while at the same time being more robust and requiring
no prior knowledge of the shape. The approach can be easily implemented due to
only requiring two color cameras without depth and not needing an explicit
calibration of the extrinsic parameters. Evaluations on two types of soft
robotic arms and a soft robotic fish demonstrate our method's accuracy and
versatility on highly deformable systems in real-time. The robust performance
of the approach against different scene modifications (camera alignment and
brightness) suggests its generalizability to a wider range of experimental
setups, which will benefit downstream tasks such as robotic grasping and
manipulation
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
Bioinspired Soft Robotics: state of the art, challenges, and future directions
Purpose of Review: This review provides an overview of the state of the art
in bioinspired soft robotics with by examining advancements in actuation,
functionality, modeling, and control. Recent Findings: Recent research into
actuation methods, such as artificial muscles, have expanded the functionality
and potential use of bioinspired soft robots. Additionally, the application of
finite dimensional models has improved computational efficiency for modeling
soft continuum systems, and garnered interest as a basis for controller
formulation. Summary: Bioinspiration in the field of soft robotics has led to
diverse approaches to problems in a range of task spaces. In particular, new
capabilities in system simplification, miniaturization, and untethering have
each contributed to the field's growth. There is still significant room for
improvement in the streamlining of design and manufacturing for these systems,
as well as in their control
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