scholarly journals A Novel Calibration Algorithm for Cable-Driven Parallel Robots with Application to Rehabilitation

2019 ◽  
Vol 9 (11) ◽  
pp. 2182 ◽  
Author(s):  
Han Yuan ◽  
Xianghui You ◽  
Yongqing Zhang ◽  
Wenjing Zhang ◽  
Wenfu Xu
Keyword(s):  
Calibration Method ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Human Robot Interaction ◽  
Automatic Calibration ◽  
Unknown Parameters ◽  
Robot Interaction ◽  
Geometric Calibration ◽  
Rehabilitation Robots ◽  
Calibration Algorithm

Cable-driven parallel robots are suitable candidates for rehabilitation due to their intrinsic flexibility and adaptability, especially considering the safety of human–robot interaction. However, there are still some challenges to apply cable-driven parallel robots to rehabilitation, one of which is the geometric calibration. This paper proposes a new automatic calibration method that is applicable for cable-driven parallel rehabilitation robots. The key point of this method is to establish the mapping between the unknown parameters to be calibrated and the parameters that could be measured by the inner sensors and then use least squares algorithm to find the solutions. Specifically, the unknown parameters herein are the coordinates of the attachment points, and the measured parameters are the lengths of the redundant cables. Simulations are performed on a 3-DOF parallel robot driven by four cables for validation. Results show that the proposed calibration method could precisely find the real coordinate values of the attachment points, with errors less than 10 − 12 mm. Trajectory simulations also indicate that the positioning accuracy of the cable-driven parallel robot (CDPR) could be greatly improved after calibration using the proposed method.

Human–Robot Interaction Control of Rehabilitation Robots With Series Elastic Actuators

2015 ◽  
Vol 31 (5) ◽  
pp. 1089-1100 ◽  
Author(s):  
Haoyong Yu ◽  
Sunan Huang ◽  
Gong Chen ◽  
Yongping Pan ◽  
Zhao Guo
Keyword(s):  
Human Robot Interaction ◽  
Robot Interaction ◽  
Interaction Control ◽  
Rehabilitation Robots ◽  
Series Elastic Actuators ◽  
Series Elastic

Parallel Robot Calibration Utilizing Adaptronic Joints

2008 ◽  
Author(s):  
Philipp Last ◽  
Annika Raatz ◽  
Ju¨rgen Hesselbach ◽  
Nenad Pavlovic ◽  
Ralf Keimer
Keyword(s):  
Parallel Robot ◽  
Parallel Robots ◽  
Machine Component ◽  
Robot Calibration ◽  
Geometric Calibration ◽  
Self Calibration ◽  
Mechanical Constraints ◽  
Special Machine ◽  
Calibration Methods ◽  
Calibration Techniques

Model based geometric calibration is well known to be an efficient way to enhance absolute accuracy of robotic systems. Generally its application requires redundant measurements, which are achieved by external metrology equipment in most traditional calibration techniques. However, these methods are usually time-consuming, expensive and inconvenient. Thus, so-called self-calibration methods have achieved attention from researchers, which either use internal sensors or rely on mechanical constraints instead. In this paper a new self-calibration technique is presented for parallel robots which is motivated by the idea of constrained calibration. The new approach utilizes a special machine component called the adaptronic swivel joint in order to achieve the required redundant information. Compared to similar approaches it offers several advantages. The new calibration scheme is described and verified in simulation studies using a RRRRR-structure as an example.

scholarly journals Holographic Micromirror Array with Diffuse Areas for Accurate Calibration of 3D Light-Field Display

2020 ◽  
Vol 10 (20) ◽  
pp. 7188
Author(s):  
Lode Jorissen ◽  
Ryutaro Oi ◽  
Koki Wakunami ◽  
Yasuyuki Ichihashi ◽  
Gauthier Lafruit ◽  
...  
Keyword(s):  
Light Field ◽  
3D Visualization ◽  
Calibration Method ◽  
Automatic Calibration ◽  
Display System ◽  
Extrinsic Parameters ◽  
Calibration Algorithm ◽  
Fully Automatic ◽  
Intrinsic And Extrinsic Parameters ◽  
Micromirror Array

Light field 3D displays require a precise alignment between the display source and the micromirror-array screen for error free 3D visualization. Hence, calibrating the system using an external camera becomes necessary, before displaying any 3D contents. The inter-dependency of the intrinsic and extrinsic parameters of display-source, calibration-camera, and micromirror-array screen, makes the calibration process very complex and error-prone. Thus, several assumptions are made with regard to the display setup, in order to simplify the calibration. A fully automatic calibration method based on several such assumptions was reported by us earlier. Here, in this paper, we report a method that uses no such assumptions, but yields a better calibration. The proposed method adapts an optical solution where the micromirror-array screen is fabricated as a computer generated hologram with a tiny diffuser engraved at one corner of each elemental micromirror in the array. The calibration algorithm uses these diffusing areas as markers to determine the relation between the pixels of display source and the mirrors in the micromirror-array screen. Calibration results show that virtually reconstructed 3D scenes align well with the real world contents, and are free from any distortion. This method also eliminates the position dependency of display source, calibration-camera, and mirror-array screen during calibration, which enables easy setup of the display system.

Pose Calibration Method of 6-D.O.F. Cable Driven Parallel Robot Using Hybrid Recurrent Neural Network

2018 ◽  
Author(s):  
Sung-Hyun Choi ◽  
Kyoung-Su Park ◽  
Jun-Mu Heo ◽  
Hue Ha
Keyword(s):  
Neural Network ◽  
Recurrent Neural Network ◽  
Calibration Method ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Cable Model ◽  
Repetitive Motion

Cable driven parallel robots (CDPRs) have been widely used in precision Industries. However, an error occurs in repetitive motion of the CDPR because of the elongation and recovery of cable. Also, it is difficult to apply the numerical cable model because of its complexity. In this paper, we use the frequency based H-RNN method for accurate kinematics. H-RNN predicted more accurately compared with LSTM and RNN algorithms.

scholarly journals Vision-Based Hybrid Controller to Release a 4-DOF Parallel Robot from a Type II Singularity

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4080
Author(s):  
José L. Pulloquinga ◽  
Rafael J. Escarabajal ◽  
Jesús Ferrándiz ◽  
Marina Vallés ◽  
Vicente Mata ◽  
...  
Keyword(s):  
Vision System ◽  
Dynamic Performance ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Human Robot Interaction ◽  
Type Ii ◽  
Hybrid Controller ◽  
Knee Rehabilitation ◽  
System Data ◽  
Singular Configuration

The high accuracy and dynamic performance of parallel robots (PRs) make them suitable to ensure safe operation in human–robot interaction. However, these advantages come at the expense of a reduced workspace and the possible appearance of type II singularities. The latter is due to the loss of control of the PR and requires further analysis to keep the stiffness of the PR even after a singular configuration is reached. All or a subset of the limbs could be responsible for a type II singularity, and they can be detected by using the angle between two output twist screws (OTSs). However, this angle has not been applied in control because it requires an accurate measure of the pose of the PR. This paper proposes a new hybrid controller to release a 4-DOF PR from a type II singularity based on a real time vision system. The vision system data are used to automatically readapt the configuration of the PR by moving the limbs identified by the angle between two OTSs. This controller is intended for a knee rehabilitation PR, and the results show how this release is accomplished with smooth controlled movements where the patient’s safety is not compromised.

scholarly journals Exoskeleton transparency: feed-forward compensation vs. disturbance observer

2018 ◽  
Vol 66 (12) ◽  
pp. 1014-1026 ◽  
Author(s):  
Fabian Just ◽  
Özhan Özen ◽  
Philipp Bösch ◽  
Hanna Bobrovsky ◽  
Verena Klamroth-Marganska ◽  
...  
Keyword(s):  
Disturbance Observer ◽  
Human Robot Interaction ◽  
Forward Model ◽  
Training Effectiveness ◽  
Robot Interaction ◽  
Systematic Analysis ◽  
Feed Forward ◽  
Model Based ◽  
Rehabilitation Robots ◽  
Feed Forward Model

Abstract Undesired forces during human-robot interaction limit training effectiveness with rehabilitation robots. Thus, avoiding such undesired forces by improved mechanics, sensorics, kinematics, and controllers are the way to increase exoskeleton transparency. In this paper, the arm therapy exoskeleton ARMin IV+ was used to compare the differences in transparency offered by using the previous feed-forward model-based controller, with a disturbance observer in a study. Systematic analysis of velocity-dependent effects of controller transparency in single- and multi-joint scenarios performed in this study highlight the advantage of using disturbance observers for obtaining consistent transparency behavior at different velocities in single-joint and multi-joint movements. As the main result, the concept of the disturbance observer sets a new benchmark for ARMin transparency.

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