scholarly journals Variable Curvature Modelling Method of Continuum Robots with Contraints

2021 ◽  
Author(s):  
Peng Chen ◽  
Yi Yu ◽  
Yuwang Liu
Keyword(s):  
Degrees Of Freedom ◽  
Human Robot Interaction ◽  
Great Promise ◽  
Complex Deformation ◽  
Continuum Robots ◽  
Mechanics Model ◽  
Variable Curvature ◽  
Main Challenge ◽  
High Flexibility ◽  
External Forces

Abstract The inherent compliance of continuum robots holds great promise in the fields of soft manipulation and safe human-robot interaction. This compliance reduces the risk of damage to the manipulated object and the surroundings. However, continuum robots have theoretically infinite degrees of freedom, and this high flexibility usually leads to complex deformations with external forces and positional constraints. How to describe this complex deformation is the main challenge for modelling continuum robots. In this study, we investigated a novel variable curvature modeling method for continuum robots, considering external forces and positional constraints. The robot configuration curve is described by the developed mechanics model, and then the robot is fitted to the curve. To validate the model, a 10-section continuum robot prototype with a length of 1 m was developed. The ability of the robot to reach the target points and track complex trajectories with load verified the feasibility and accuracy of the model. The ratio of the average position error of the robot endpoint to the robot length was less than 2.38%. This work may serve a new perspective for design analysis and motion control of continuum robots.

Model Validation of an Octopus Inspired Continuum Robotic Arm for Use in Underwater Environments

2013 ◽  
Vol 5 (2) ◽  
Author(s):  
Tianjiang Zheng ◽  
David T. Branson ◽  
Emanuele Guglielmino ◽  
Rongjie Kang ◽  
Gustavo A. Medrano Cerda ◽  
...  
Keyword(s):  
Dynamic Model ◽  
Model Validation ◽  
Degrees Of Freedom ◽  
Robotic Arm ◽  
Octopus Vulgaris ◽  
Light Weight ◽  
Continuum Robots ◽  
Continuum Structure ◽  
External Forces ◽  
Good Agreement

Octopuses are an example of dexterous animals found in nature. Their arms are flexible, can vary in stiffness, grasp objects, apply high forces with respect to their relatively light weight, and bend in all directions. Robotic structures inspired by octopus arms have to undertake the challenges of a high number of degrees of freedom (DOF), coupled with highly flexible continuum structure. This paper presents a kinematic and dynamic model for underwater continuum robots inspired by Octopus vulgaris. Mass, damping, stiffness, and external forces such as gravity, buoyancy, and hydrodynamic forces are considered in the dynamic model. A continuum arm prototype was built utilizing longitudinal and radial actuators, and comparisons between the simulated and experimental results show good agreement.

Kinematics of Continuum Robots With Constant Curvature Bending and Extension Capabilities

2018 ◽  
Vol 11 (1) ◽  
Author(s):  
Arnau Garriga-Casanovas ◽  
Ferdinando Rodriguez y Baena
Keyword(s):  
Closed Form ◽  
Inverse Kinematics ◽  
Degrees Of Freedom ◽  
Rapid Development ◽  
Closed Form Expression ◽  
Great Promise ◽  
Continuum Robots ◽  
Cluttered Environments ◽  
Closed Form Solutions ◽  
Significant Attention

Continuum robots are becoming increasingly popular due to the capabilities they offer, especially when operating in cluttered environments, where their dexterity, maneuverability, and compliance represent a significant advantage. The subset of continuum robots that also belong to the soft robots category has seen rapid development in recent years, showing great promise. However, despite the significant attention received by these devices, various aspects of their kinematics remain unresolved, limiting their adoption and obscuring their potential. In this paper, the kinematics of continuum robots with the ability to bend and extend are studied, and analytical, closed-form solutions to both the direct and inverse kinematics are presented. The results obtained expose the redundancies of these devices, which are subsequently explored. The solution to the inverse kinematics derived here is shown to provide an analytical, closed-form expression describing the curve associated with these redundancies, which is also presented and analyzed. A condition on the reachable end-effector poses for robots with six actuation degrees-of-freedom (DOFs) is then distilled. The kinematics of robot layouts with over six actuation DOFs are subsequently considered. Finally, simulated results of the inverse kinematics are provided, verifying the study.

Soft magnetic skin for super-resolution tactile sensing with force self-decoupling

2021 ◽  
Vol 6 (51) ◽  
pp. eabc8801
Author(s):  
Youcan Yan ◽  
Zhe Hu ◽  
Zhengbao Yang ◽  
Wenzhen Yuan ◽  
Chaoyang Song ◽  
...  
Keyword(s):  
External Disturbance ◽  
Super Resolution ◽  
Tactile Sensor ◽  
Human Robot Interaction ◽  
Tactile Sensors ◽  
Dexterous Manipulation ◽  
Robot Interaction ◽  
Flexible Film ◽  
Challenging Tasks ◽  
External Forces

Human skin can sense subtle changes of both normal and shear forces (i.e., self-decoupled) and perceive stimuli with finer resolution than the average spacing between mechanoreceptors (i.e., super-resolved). By contrast, existing tactile sensors for robotic applications are inferior, lacking accurate force decoupling and proper spatial resolution at the same time. Here, we present a soft tactile sensor with self-decoupling and super-resolution abilities by designing a sinusoidally magnetized flexible film (with the thickness ~0.5 millimeters), whose deformation can be detected by a Hall sensor according to the change of magnetic flux densities under external forces. The sensor can accurately measure the normal force and the shear force (demonstrated in one dimension) with a single unit and achieve a 60-fold super-resolved accuracy enhanced by deep learning. By mounting our sensor at the fingertip of a robotic gripper, we show that robots can accomplish challenging tasks such as stably grasping fragile objects under external disturbance and threading a needle via teleoperation. This research provides new insight into tactile sensor design and could be beneficial to various applications in robotics field, such as adaptive grasping, dexterous manipulation, and human-robot interaction.

Stiffness Control of Parallel Continuum Robots

2018 ◽  
Author(s):  
Vincent Aloi ◽  
Caroline Black ◽  
Caleb Rucker
Keyword(s):  
Position Control ◽  
Target Position ◽  
Human Robot Interaction ◽  
Force Measurements ◽  
Modeling Framework ◽  
Continuum Robots ◽  
Integral Control ◽  
Control Approach ◽  
Cosserat Rods ◽  
Stiffness Control

Parallel continuum robots can provide compact, compliant manipulation of tools in robotic surgery and larger-scale human robot interaction. In this paper we address stiffness control of parallel continuum robots using a general nonlinear kinetostatic modeling framework based on Cosserat rods. We use a model formulation that estimates the applied end-effector force and pose using actuator force measurements. An integral control approach then modifies the commanded target position based on the desired stiffness behavior and the estimated force and position. We then use low-level position control of the actuators to achieve the modified target position. Experimental results show that after calibration of a single model parameter, the proposed approach achieves accurate stiffness control in various directions and poses.

scholarly journals Human-Robot Interaction with Robust Prediction of Movement Intention Surpasses Manual Control

2020 ◽  
Author(s):  
Sebastijan Veselic ◽  
Claudio Zito ◽  
Dario Farina
Keyword(s):  
Degrees Of Freedom ◽  
Linear Time ◽  
Open Loop ◽  
Human Robot Interaction ◽  
Manual Control ◽  
Reach To Grasp ◽  
Robot Interaction ◽  
Loop Control ◽  
User Awareness ◽  
Improving Accuracy

Designing robotic assistance devices for manipulation tasks is challenging. This work aims at improving accuracy and usability of physical human-robot interaction (pHRI) where a user interacts with a physical robotic device (e.g., a human operated manipulator or exoskeleton) by transmitting signals which need to be interpreted by the machine. Typically these signals are used as an open-loop control, but this approach has several limitations such as low take-up and high cognitive burden for the user. In contrast, a control framework is proposed that can respond robustly and efficiently to intentions of a user by reacting proactively to their commands. The key insight is to include context- and user-awareness in the controller, improving decision making on how to assist the user. Context-awareness is achieved by creating a set of candidate grasp targets and reach-to grasp trajectories in a cluttered scene. User-awareness is implemented as a linear time-variant feedback controller (TV-LQR) over the generated trajectories to facilitate the motion towards the most likely intention of a user. The system also dynamically recovers from incorrect predictions. Experimental results in a virtual environment of two degrees of freedom control show the capability of this approach to outperform manual control. By robustly predicting the user’s intention, the proposed controller allows the subject to achieve superhuman performance in terms of accuracy and thereby usability.

scholarly journals Contribution to Speeding-Up the Solving of Nonlinear Ordinary Differential Equations on Parallel/Multi-Core Platforms for Sensing Systems

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6130
Author(s):  
Vahid Tavakkoli ◽  
Kabeh Mohsenzadegan ◽  
Jean Chamberlain Chedjou ◽  
Kyandoghere Kyamakya
Keyword(s):  
Differential Equations ◽  
Ordinary Differential Equations ◽  
Heterogeneous Computing ◽  
Sensor Nodes ◽  
Calibration Model ◽  
Real Time Processing ◽  
Sensing Systems ◽  
Processing Power ◽  
Main Challenge ◽  
High Flexibility

Solving ordinary differential equations (ODE) on heterogenous or multi-core/parallel embedded systems does significantly increase the operational capacity of many sensing systems in view of processing tasks such as self-calibration, model-based measurement and self-diagnostics. The main challenge is usually related to the complexity of the processing task at hand which costs/requires too much processing power, which may not be available, to ensure a real-time processing. Therefore, a distributed solving involving multiple cores or nodes is a good/precious option. Also, speeding-up the processing does also result in significant energy consumption or sensor nodes involved. There exist several methods for solving differential equations on single processors. But most of them are not suitable for an implementation on parallel (i.e., multi-core) systems due to the increasing communication related network delays between computing nodes, which become a main and serious bottleneck to solve such problems in a parallel computing context. Most of the problems faced relate to the very nature of differential equations. Normally, one should first complete calculations of a previous step in order to use it in the next/following step. Hereby, it appears also that increasing performance (e.g., through increasing step sizes) may possibly result in decreasing the accuracy of calculations on parallel/multi-core systems like GPUs. In this paper, we do create a new adaptive algorithm based on the Adams–Moulton and Parareal method (we call it PAMCL) and we do compare this novel method with other most relevant implementations/schemes such as the so-called DOPRI5, PAM, etc. Our algorithm (PAMCL) is showing very good performance (i.e., speed-up) while compared to related competing algorithms, while thereby ensuring a reasonable accuracy. For a better usage of computing units/resources, the OpenCL platform is selected and ODE solver algorithms are optimized to work on both GPUs and CPUs. This platform does ensure/enable a high flexibility in the use of heterogeneous computing resources and does result in a very efficient utilization of available resources when compared to other comparable/competing algorithm/schemes implementations.

Fake Empathy and Human-Robot Interaction (HRI)

2020 ◽  
pp. 1556-1572
Author(s):  
Jordi Vallverdú ◽  
Toyoaki Nishida ◽  
Yoshisama Ohmoto ◽  
Stuart Moran ◽  
Sarah Lázare
Keyword(s):  
Social Relationships ◽  
Human Robot Interaction ◽  
Basic Emotion ◽  
Human Beings ◽  
Robot Interaction ◽  
Video Recordings ◽  
Main Challenge ◽  
Positive Results ◽  
Different Levels

Empathy is a basic emotion trigger for human beings, especially while regulating social relationships and behaviour. The main challenge of this paper is study whether people's empathic reactions towards robots change depending on previous information given to human about the robot before the interaction. The use of false data about robot skills creates different levels of what we call ‘fake empathy'. This study performs an experiment in WOZ environment in which different subjects (n=17) interacting with the same robot while they believe that the robot is a different robot, up to three versions. Each robot scenario provides a different ‘humanoid' description, and out hypothesis is that the more human-like looks the robot, the more empathically can be the human responses. Results were obtained from questionnaires and multi- angle video recordings. Positive results reinforce the strength of our hypothesis, although we recommend a new and bigger and then more robust experiment.

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.

Development of a Multi-Cable-Driven Continuum Robot Controlled by Parallel Platforms

2020 ◽  
pp. 1-11 ◽  
Author(s):  
Xinbo Chen ◽  
Jiantao Yao ◽  
Tong Li ◽  
Haili Li ◽  
Pan Zhou ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Load Capacity ◽  
Continuum Robots ◽  
Position Accuracy ◽  
Continuum Robot ◽  
In Series ◽  
Kinematic Models ◽  
Parallel Platform ◽  
Tube Structure ◽  
The Continuum

Abstract Cable-driven continuum robots exhibit excellent capabilities in the unstructured environment due to their inherent compliance and dexterity. To improve the reliability and load capacity of continuum robots, increasing the number of cables is often used in the control of continuum robots. However, the number of actuators will increase with the cables. To tackle this challenge, this work proposes a method for increasing the number of cables without increasing actuators in a continuum robot through parallel platforms. The parallel platforms are used to control all the cables in the continuum robot, and can be separated from the continuum robot to enable the remote drive of a manipulation arm by using the cable-tube structure. The manipulation arm is composed of several independent bending modules in series, which can be configured freely according to the demand of degrees of freedom. Further, each bending module is controlled independently by a parallel platform, which can avoid the mutual interference between the cables of one bending module and another one, improve the position accuracy and simplify the control difficulty of the manipulation arm. To evaluate the proposed method, this work develops a prototype of six-cable-driven continuum robot controlled by 3RPS parallel platforms, and presents some basic kinematic models to describe its function, and then an experimental work characterizing its performance. Experimental results illustrated the importance of increasing the number of cables, the rationality of kinematic models of the continuum robot, and the feasibility of controlling multiple cables by a parallel platform.

Ferromagnetic soft continuum robots

2019 ◽  
Vol 4 (33) ◽  
pp. eaax7329 ◽  
Author(s):  
Yoonho Kim ◽  
German A. Parada ◽  
Shengduo Liu ◽  
Xuanhe Zhao
Keyword(s):  
Great Promise ◽  
Small Scale ◽  
Magnetic Actuation ◽  
Continuum Robots ◽  
Active Steering ◽  
Ferromagnetic Domains ◽  
Continuum Robot ◽  
Constrained Environments ◽  
Soft Polymer ◽  
Minimally Invasive Robotic Surgery

Small-scale soft continuum robots capable of active steering and navigation in a remotely controllable manner hold great promise in diverse areas, particularly in medical applications. Existing continuum robots, however, are often limited to millimeter or centimeter scales due to miniaturization challenges inherent in conventional actuation mechanisms, such as pulling mechanical wires, inflating pneumatic or hydraulic chambers, or embedding rigid magnets for manipulation. In addition, the friction experienced by the continuum robots during navigation poses another challenge for their applications. Here, we present a submillimeter-scale, self-lubricating soft continuum robot with omnidirectional steering and navigating capabilities based on magnetic actuation, which are enabled by programming ferromagnetic domains in its soft body while growing hydrogel skin on its surface. The robot’s body, composed of a homogeneous continuum of a soft polymer matrix with uniformly dispersed ferromagnetic microparticles, can be miniaturized below a few hundreds of micrometers in diameter, and the hydrogel skin reduces the friction by more than 10 times. We demonstrate the capability of navigating through complex and constrained environments, such as a tortuous cerebrovascular phantom with multiple aneurysms. We further demonstrate additional functionalities, such as steerable laser delivery through a functional core incorporated in the robot’s body. Given their compact, self-contained actuation and intuitive manipulation, our ferromagnetic soft continuum robots may open avenues to minimally invasive robotic surgery for previously inaccessible lesions, thereby addressing challenges and unmet needs in healthcare.

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