Shape Sensing for Soft Robotic Manipulators

2009 ◽  
Author(s):  
Deepak Trivedi ◽  
Christopher D. Rahn
Keyword(s):  
Degrees Of Freedom ◽  
Soft Materials ◽  
Robotic Manipulators ◽  
Sensors And Actuators ◽  
Backbone Curve ◽  
Continuum Robots ◽  
Soft Robots ◽  
Load Cells ◽  
Simulation Results ◽  
Shape Sensing

Soft robotic manipulators are continuum robots made of soft materials that undergo continuous elastic deformation and produce motion with a smooth backbone curve. These manipulators offer significant advantages over traditional manipulators due to their ability to conform to their surroundings, move with dexterity and manipulate objects of widely varying size using whole arm manipulation. Theoretically, soft robots have infinite degrees of freedom (dof), but the number of sensors and actuators are limited. Many dofs of soft robots are not directly observable and/or controllable, complicating shape sensing and controlling. In this paper, we present two methods of shape sensing for soft robotic manipulators based on a geometrically exact mechanical model. The first method use s load cells mounted at the base of the manipulator and the second method makes use of cable encoders running through the length of the manipulator. Simulation results show an endpoint localization error of less than 3% of manipulator length.

Model-Based Shape Estimation for Soft Robotic Manipulators: The Planar Case

2014 ◽  
Vol 6 (2) ◽  
Author(s):  
Deepak Trivedi ◽  
Christopher D. Rahn
Keyword(s):  
Degrees Of Freedom ◽  
Soft Materials ◽  
Robotic Manipulators ◽  
Shape Estimation ◽  
Sensors And Actuators ◽  
Backbone Curve ◽  
Planar Case ◽  
Soft Robots ◽  
Estimation And Control ◽  
Shape Sensing

Soft robotic manipulators are continuum robots made of soft materials that undergo continuous elastic deformation and produce motion with a smooth backbone curve. In many applications, these manipulators offer significant advantages over traditional manipulators due to their ability to conform to their surroundings, and manipulate objects of widely varying size using whole arm manipulation. Theoretically, soft robots have infinite degrees of freedom (DOF), but the number of sensors and actuators are limited. Many DOFs of soft robots are not directly observable and/or controllable, complicating shape estimation and control. In this paper, we present three methods of shape sensing for soft robotic manipulators based on a geometrically exact mechanical model. The first method uses load cells mounted at the base of the manipulator, the second method makes use of cable encoders running through the length of the manipulator, and the third method uses inclinometers mounted at the end of each section of the manipulator. Simulation results show an endpoint localization error of less than 3% of manipulator length with typical sensors. The methods are validated experimentally on the OctArm VI manipulator.

Dexterity and Workspace Analysis of Two Soft Robotic Manipulators

2010 ◽  
Author(s):  
Deepak Trivedi ◽  
Daniel Lesutis ◽  
Christopher D. Rahn
Keyword(s):  
Elastic Deformation ◽  
Cost Effective ◽  
Soft Materials ◽  
Robotic Manipulators ◽  
Backbone Curve ◽  
Continuum Robots ◽  
Workspace Analysis ◽  
Air Muscle ◽  
Distal Section ◽  
Effective Design

Soft robotic manipulators are continuum robots made of soft materials that undergo continuous elastic deformation and produce motion with a smooth backbone curve. These manipulators offer significant advantages over traditional manipulators due to their ability to conform to their surroundings, move with dexterity and manipulate objects of widely varying size using whole arm manipulation. Soft robotic manipulators are complex and difficult to design, model and fabricate. In this paper, we present a cost effective design for a pneumatic air muscle based soft robotic manipulator in which the actuators for the distal section extend from the base to the tip of the arm, thereby simplifying the pneumatic design and eliminating the need for endplates. We compare the workspace and dexterity of continuous tube (CT) design with a previously developed OctArm type manipulator and conclude that although the two designs have comparable workspace area, the OctArm workspace has better dexterity characteristics.

Analytic Formulation for Kinematics, Statics, and Shape Restoration of Multibackbone Continuum Robots Via Elliptic Integrals

2009 ◽  
Vol 2 (1) ◽  
Author(s):  
Kai Xu ◽  
Nabil Simaan
Keyword(s):  
Degrees Of Freedom ◽  
Elliptic Integrals ◽  
Continuum Robots ◽  
Actuation Redundancy ◽  
Circular Shape ◽  
Shape Restoration ◽  
Simulation Results ◽  
Tip Position ◽  
Geometric Compatibility ◽  
External Loads

This paper presents a novel and unified analytic formulation for kinematics, statics, and shape restoration of multiple-backbone continuum robots. These robots achieve actuation redundancy by independently pulling and pushing three backbones to carry out a bending motion of two-degrees-of-freedom (DoF). A solution framework based on constraints of geometric compatibility and static equilibrium is derived using elliptic integrals. This framework allows the investigation of the effects of different external loads and actuation redundancy resolutions on the shape variations in these continuum robots. The simulation and experimental validation results show that these continuum robots bend into an exact circular shape for one particular actuation resolution. This provides a proof to the ubiquitously accepted circular-shape assumption in deriving kinematics for continuum robots. The shape variations due to various actuation redundancy resolutions are also investigated. The simulation results show that these continuum robots have the ability to redistribute loads among their backbones without introducing significant shape variations. A strategy for partially restoring the shape of the externally loaded continuum robots is proposed. The simulation results show that either the tip orientation or the tip position can be successfully restored.

scholarly journals Stretchable optical fibre sensor for soft surgical robot shape reconstruction

2021 ◽  
Vol 51 (4) ◽  
Author(s):  
Yanlin He ◽  
Likun Gao ◽  
Yuchen Bai ◽  
Hangwei Zhu ◽  
Guangkai Sun ◽  
...  
Keyword(s):  
Optical Fibre ◽  
Soft Materials ◽  
Maximum Error ◽  
Shape Reconstruction ◽  
Fibre Bragg Grating ◽  
Soft Robot ◽  
Soft Robots ◽  
Optical Fibre Sensor ◽  
Fibre Sensor ◽  
Shape Sensing

Soft robotics presents several advantages in the field of minimally invasive surgery. However, existing methods have not fully addressed problems related to soft robot shape sensing due to the complex motion of soft robots and the stretchable nature of the soft materials employed. This study demonstrates the shape sensing of a soft robot with a helically embedded stretchable fibre Bragg grating (FBG)-based optical fibre sensor. Unlike straight FBG embedding configurations, this unique helical configuration prevents sensor dislocation, supports material stretchability, and facilitates shape detection for various soft-robot movements. The proposed soft-robot design principle and FBG sensor are analysed and their fabrication process, which includes an FBG-written optical fibre sensor, is described. Bending experiments are conducted with the soft robot, the wavelengths of FBG sensors at different bending and telescopic movement states are obtained, and the soft-robot shape is reconstructed. Experimental results demonstrate that the maximum error between FBG sensing and the actual bending state is less than 2.5%, validating the feasibility and effectiveness of the proposed helical stretchable FBG sensing method for the shape measurement of soft robots. These results indicate the potential and applicability of this shape-sensing approach in biomedical research.

Kinematics and Statics for Soft Continuum Manipulators With Heterogeneous Soft Materials

2016 ◽  
Author(s):  
Fei Jiang ◽  
Haijie Zhang ◽  
Jianguo Zhao
Keyword(s):  
Degrees Of Freedom ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Soft Materials ◽  
Initial Study ◽  
Cylindrical Shape ◽  
Continuum Manipulators ◽  
Static Modeling ◽  
Simulation Results ◽  
Three Dimensional Space

Continuum manipulators are continuously bending robots with unlimited number of kinematic degrees of freedom. Most existing continuum manipulators have a central strut made of a single elastic material, and multiple cables placed around the strut are employed to actuate the manipulator. The kinematics for such robots has been extensively studied by assuming the manipulator has a circular shape. In this paper, we aim to investigate the kinematic and static modeling for novel soft continuum manipulators fabricated by multi-material 3D printing with heterogeneous soft materials. We model cylindrical shape manipulators consisting of three sections with three different materials, and they are actuated by three independent cables placed symmetrically. By pulling the cables with different displacements, the manipulators can be bent in three-dimensional space. As our initial study, we employ a single cable for all prototypes. Experimental results are compared with the simulation results to validate the proposed modeling method.

scholarly journals Task space adaptation via the learning of gait controllers of magnetic soft millirobots

2021 ◽  
pp. 027836492110218
Author(s):  
Sinan O. Demir ◽  
Utku Culha ◽  
Alp C. Karacakol ◽  
Abdon Pena-Francesch ◽  
Sebastian Trimpe ◽  
...  
Keyword(s):  
Human Body ◽  
Degrees Of Freedom ◽  
Bayesian Optimization ◽  
Small Scale ◽  
Soft Robots ◽  
Modeling And Control ◽  
Walking Gait ◽  
Physical Experiments ◽  
Efficient Learning ◽  
Task Environments

Untethered small-scale soft robots have promising applications in minimally invasive surgery, targeted drug delivery, and bioengineering applications as they can directly and non-invasively access confined and hard-to-reach spaces in the human body. For such potential biomedical applications, the adaptivity of the robot control is essential to ensure the continuity of the operations, as task environment conditions show dynamic variations that can alter the robot’s motion and task performance. The applicability of the conventional modeling and control methods is further limited for soft robots at the small-scale owing to their kinematics with virtually infinite degrees of freedom, inherent stochastic variability during fabrication, and changing dynamics during real-world interactions. To address the controller adaptation challenge to dynamically changing task environments, we propose using a probabilistic learning approach for a millimeter-scale magnetic walking soft robot using Bayesian optimization (BO) and Gaussian processes (GPs). Our approach provides a data-efficient learning scheme by finding the gait controller parameters while optimizing the stride length of the walking soft millirobot using a small number of physical experiments. To demonstrate the controller adaptation, we test the walking gait of the robot in task environments with different surface adhesion and roughness, and medium viscosity, which aims to represent the possible conditions for future robotic tasks inside the human body. We further utilize the transfer of the learned GP parameters among different task spaces and robots and compare their efficacy on the improvement of data-efficient controller learning.

scholarly journals Design and Calibration of Robot Base Force/Torque Sensors and Their Application to Non-Collocated Admittance Control for Automated Tool Changing

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 2895
Author(s):  
Hubert Gattringer ◽  
Andreas Müller ◽  
Philip Hoermandinger
Keyword(s):  
Steel Plate ◽  
Robotic Manipulators ◽  
Indirect Measurement ◽  
Local Deformation ◽  
Contact Forces ◽  
The Novel ◽  
Admittance Control ◽  
Load Cells ◽  
Series Elastic Actuators ◽  
Automated Tool

Robotic manipulators physically interacting with their environment must be able to measure contact forces/torques. The standard approach to this end is attaching force/torque sensors directly at the end-effector (EE). This provides accurate measurements, but at a significant cost. Indirect measurement of the EE-loads by means of torque sensors at the actuated joint of a robot is an alternative, in particular for series-elastic actuators, but requires dedicated robot designs and significantly increases costs. In this paper, two alternative sensor concept for indirect measurement of EE-loads are presented. Both sensors are located at the robot base. The first sensor design involves three load cells on which the robot is mounted. The second concept consists of a steel plate with four spokes, at which it is suspended. At each spoke, strain gauges are attached to measure the local deformation, which is related to the load at the sensor plate (resembling the main principle of a force/torque sensor). Inferring the EE-load from the so determined base wrench necessitates a dynamic model of the robot, which accounts for the static as well as dynamic loads. A prototype implementation of both concepts is reported. Special attention is given to the model-based calibration, which is crucial for these indirect measurement concepts. Experimental results are shown when the novel sensors are employed for a tool changing task, which to some extend resembles the well-known peg-in-the-hole problem.

Dynamic Modeling of a High-Dynamic Flight Simulator

2014 ◽  
Vol 687-691 ◽  
pp. 610-615 ◽  
Author(s):  
Hui Liu ◽  
Li Wen Guan
Keyword(s):  
Dynamic Modeling ◽  
Degrees Of Freedom ◽  
Flight Simulator ◽  
Inverse Dynamic ◽  
Dynamic Formulation ◽  
Time Histories ◽  
Rotational Degrees Of Freedom ◽  
High Dynamic ◽  
Euler Approach ◽  
Simulation Results

High-dynamic flight simulator (HDFS), using a centrifuge as its motion base, is a machine utilized for simulating the acceleration environment associated with modern advanced tactical aircrafts. This paper models the HDFS as a robotic system with three rotational degrees of freedom. The forward and inverse dynamic formulations are carried out by the recursive Newton-Euler approach. The driving torques acting on the joints are determined on the basis of the inverse dynamic formulation. The formulation has been implemented in two numerical simulation examples, which are used for calculating the maximum torques of actuators and simulating the time-histories of kinematic and dynamic parameters of pure trapezoid Gz-load command profiles, respectively. The simulation results can be applied to the design of the control system. The dynamic modeling approach presented in this paper can also be generalized to some similar devices.

New repetitive motion planning scheme with cube end-effector planning precision for redundant robotic manipulators

Robotica ◽  
2021 ◽  
pp. 1-22
Author(s):  
Limin Shen ◽  
Yuanmei Wen
Keyword(s):  
Theoretical Analysis ◽  
Motion Planning ◽  
Robotic Manipulators ◽  
Robotic Manipulator ◽  
Repetitive Motion ◽  
End Effector ◽  
Difference Formula ◽  
Planning Scheme ◽  
Simulation Results ◽  
The Difference

Abstract Repetitive motion planning (RMP) is important in operating redundant robotic manipulators. In this paper, a new RMP scheme that is based on the pseudoinverse formulation is proposed for redundant robotic manipulators. Such a scheme is derived from the discretization of an existing RMP scheme by utilizing the difference formula. Then, theoretical analysis and results are presented to show the characteristic of the proposed RMP scheme. That is, this scheme possesses the characteristic of cube pattern in the end-effector planning precision. The proposed RMP scheme is further extended and studied for redundant robotic manipulators under joint constraint. Based on a four-link robotic manipulator, simulation results substantiate the effectiveness and superiority of the proposed RMP scheme and its extended one.

Behavior of a smart one-way micro-valve considering fluid–structure interaction

2018 ◽  
Vol 29 (20) ◽  
pp. 3960-3971 ◽  
Author(s):  
H Mazaheri ◽  
AH Namdar ◽  
A Amiri
Keyword(s):  
Interaction Effect ◽  
Fluid Structure Interaction ◽  
Pressure Head ◽  
Soft Materials ◽  
Crosslinking Density ◽  
Operational Parameters ◽  
Sensors And Actuators ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Different Temperatures

Smart hydrogels are soft materials which can be applied in sensors and actuators especially in microfluidics in which the fluid–structure interaction is important. In this work, first, the behavior of a one-way hydrogel micro-valve is investigated by considering the fluid–structure interaction effect for a specified geometry of the micro-valve. Second, both the fluid–structure interaction and non-fluid–structure interaction simulations are conducted to study the fluid flow effect on the operational parameters of the micro-valve. The obtained results show that the fluid–structure interaction effects are important and have a considerable influence on the micro-valve parameters especially on its closing temperature. Thereafter, a precise study on the micro-valve is executed by considering the micro-valve operational parameters such as inlet pressure, head size, crosslinking density, and breaking pressure at different temperatures. The results show the importance of considering the fluid–structure interaction effect in the design of these devices.

Sign in / Sign up

Export Citation Format

Share Document