scholarly journals Singularity Analysis of Redundant Space Robot with the Structure of Canadarm2

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Gang Chen ◽  
Long Zhang ◽  
Qingxuan Jia ◽  
Hanxu Sun
Keyword(s):  
Reference Point ◽  
Reference System ◽  
Jacobian Matrix ◽  
Singularity Analysis ◽  
Space Robot ◽  
Analysis Method ◽  
Singularity Problem ◽  
End Effector ◽  
Novel Method

A novel method of singularity analysis for redundant space robot with the structure of Canadarm2 is proposed in this paper. This kind of structure has the characteristics of three consecutive parallel axes. First, the “virtual manipulator” method is employed to transfer the singularity problem of a space robot to that of a ground one. By choosing an appropriate reference system and a reference point of the end-effector, Jacobian matrix is greatly simplified and then it is reconstructed according to a new standard. On this basis, the Jacobian matrix can be partitioned into four submatrixes whose degradation conditions are put forward; thereafter, the singularity conditions and singular directions of the redundant space robot are obtained. The effectiveness of the proposed singularity analysis method is verified through simulation.

scholarly journals Singularity analysis of the H4 robot using Grassmann–Cayley algebra

Robotica ◽  
2012 ◽  
Vol 30 (7) ◽  
pp. 1109-1118 ◽  
Author(s):  
Semaan Amine ◽  
Stéphane Caro ◽  
Philippe Wenger ◽  
Daniel Kanaan
Keyword(s):  
Jacobian Matrix ◽  
Screw Theory ◽  
Parallel Manipulators ◽  
Singularity Analysis ◽  
Analysis Method ◽  
Rank Deficiency ◽  
Constraint Analysis ◽  
Cayley Algebra ◽  
Lower Mobility ◽  
Grassmann Cayley Algebra

SUMMARYThis paper extends a recently proposed singularity analysis method to lower-mobility parallel manipulators having an articulated nacelle. Using screw theory, a twist graph is introduced in order to simplify the constraint analysis of such manipulators. Then, a wrench graph is obtained in order to represent some points at infinity on the Plücker lines of the Jacobian matrix. Using Grassmann–Cayley algebra, the rank deficiency of the Jacobian matrix amounts to the vanishing condition of the superbracket. Accordingly, the parallel singularities are expressed in three different forms involving superbrackets, meet and join operators, and vector cross and dot products, respectively. The approach is explained through the singularity analysis of the H4 robot. All the parallel singularity conditions of this robot are enumerated and the motions associated with these singularities are characterized.

scholarly journals Geometric Parameter Identification of a 6-DOF Space Robot Using a Laser-Ranger

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Yu Liu ◽  
Zainan Jiang ◽  
Hong Liu ◽  
Wenfu Xu
Keyword(s):  
Parameter Identification ◽  
Geometric Parameter ◽  
Jacobian Matrix ◽  
Geometric Parameters ◽  
Space Robot ◽  
Orientation Error ◽  
End Effector ◽  
Identification Method ◽  
Observability Index ◽  
Position And Orientation

The geometric parameters of a space robot change with the terrible temperature change in orbit, which will cause the end-effector pose (position and orientation) error of a space robot, and so weakens its operability. With this in consideration, a new geometric parameter identification method is presented based on a laser-ranger attached to the end-effector. Then, independence of the geometric parameters is analyzed, and their identification equations are derived. With the derived identification Jacobian matrix, the optimal identification configurations are chosen according to the observability indexO3. Subsequently, through simulation the geometric parameter identification of a 6-DOF space robot is implemented for these identification configurations, and the identified parameters are verified in a set of independent reference configurations. The result shows that in spite of distance measurement alone, pose accuracy of the space robot still has a greater improvement, so the identification method is practical and valid.

Compliant Grasp Strategy for Three-fingered Space Robot End-effector

ROBOT ◽  
2011 ◽  
Vol 33 (4) ◽  
pp. 427-433 ◽  
Author(s):  
Qingli ZHANG ◽  
Fenglei NI ◽  
Yingyuan ZHU ◽  
Jin DANG ◽  
Hong LIU
Keyword(s):  
Space Robot ◽  
End Effector

scholarly journals Imitation learning-based framework for learning 6-D linear compliant motions

2021 ◽  
Author(s):  
Markku Suomalainen ◽  
Fares J. Abu-dakka ◽  
Ville Kyrki
Keyword(s):  
Contact Force ◽  
Free Space ◽  
Prior Information ◽  
Goal Area ◽  
Imitation Learning ◽  
Learning From Demonstration ◽  
End Effector ◽  
Localization Accuracy ◽  
Novel Method ◽  
Contact Tasks

AbstractWe present a novel method for learning from demonstration 6-D tasks that can be modeled as a sequence of linear motions and compliances. The focus of this paper is the learning of a single linear primitive, many of which can be sequenced to perform more complex tasks. The presented method learns from demonstrations how to take advantage of mechanical gradients in in-contact tasks, such as assembly, both for translations and rotations, without any prior information. The method assumes there exists a desired linear direction in 6-D which, if followed by the manipulator, leads the robot’s end-effector to the goal area shown in the demonstration, either in free space or by leveraging contact through compliance. First, demonstrations are gathered where the teacher explicitly shows the robot how the mechanical gradients can be used as guidance towards the goal. From the demonstrations, a set of directions is computed which would result in the observed motion at each timestep during a demonstration of a single primitive. By observing which direction is included in all these sets, we find a single desired direction which can reproduce the demonstrated motion. Finding the number of compliant axes and their directions in both rotation and translation is based on the assumption that in the presence of a desired direction of motion, all other observed motion is caused by the contact force of the environment, signalling the need for compliance. We evaluate the method on a KUKA LWR4+ robot with test setups imitating typical tasks where a human would use compliance to cope with positional uncertainty. Results show that the method can successfully learn and reproduce compliant motions by taking advantage of the geometry of the task, therefore reducing the need for localization accuracy.

Electric Resistive Heat Curing of the Fiber-Matrix Interphase in Graphite/Epoxy Composites

1991 ◽  
Author(s):  
Erol Sancaktar ◽  
Weijian Ma ◽  
Steven W. Yurgartis
Keyword(s):  
Carbon Fiber ◽  
Heat Conduction Problem ◽  
Electric Heating ◽  
Single Fiber ◽  
Analysis Method ◽  
Fracture Properties ◽  
Temperature Distributions ◽  
Heat Curing ◽  
Convective Thermal ◽  
Novel Method

Abstract A novel method for tailoring the interphase of carbon fiber-polymer composites by resistive electric heating is presented. The single fiber-epoxy resin tensile test is used to investigate the adhesion and fracture properties of the interphase. Electric resistive heating is shown to increase adhesion and toughness at the interphase region. In analyzing the results, the strength and fracture energy of the interphase are related to the thermal postcure conditions created by resistive electric heating. For this purpose, difference analysis method is used to obtain numerical solution for heat conduction problem in the single fiber test specimen and the temperature distributions are plotted. Improvements obtained using resistive electric heating via carbon fiber are compared with those obtained by postcuring of the whole sample via convective thermal postcuring. The results obtained using these two different postcure methods seem to be similar with electric heating procedure producing superior benefits in both increased toughness and adhesion.

scholarly journals A Novel Kinematically Redundant Planar Parallel Robot Manipulator With Full Rotatability

2018 ◽  
Vol 11 (1) ◽  
Author(s):  
Nicholas Baron ◽  
Andrew Philippides ◽  
Nicolas Rojas
Keyword(s):  
Potential Application ◽  
Robot Manipulator ◽  
Video Recording ◽  
Parallel Robot ◽  
Singularity Analysis ◽  
Geometric Method ◽  
Forward Kinematics ◽  
Online Video ◽  
End Effector ◽  
Moving Platform

This paper presents a novel kinematically redundant planar parallel robot manipulator, which has full rotatability. The proposed robot manipulator has an architecture that corresponds to a fundamental truss, meaning that it does not contain internal rigid structures when the actuators are locked. This also implies that its rigidity is not inherited from more general architectures or resulting from the combination of other fundamental structures. The introduced topology is a departure from the standard 3-RPR (or 3-RRR) mechanism on which most kinematically redundant planar parallel robot manipulators are based. The robot manipulator consists of a moving platform that is connected to the base via two RRR legs and connected to a ternary link, which is joined to the base by a passive revolute joint, via two other RRR legs. The resulting robot mechanism is kinematically redundant, being able to avoid the production of singularities and having unlimited rotational capability. The inverse and forward kinematics analyses of this novel robot manipulator are derived using distance-based techniques, and the singularity analysis is performed using a geometric method based on the properties of instantaneous centers of rotation. An example robot mechanism is analyzed numerically and physically tested; and a test trajectory where the end effector completes a full cycle rotation is reported. A link to an online video recording of such a capability, along with the avoidance of singularities and a potential application, is also provided.

scholarly journals Amplitude domain analysis of strong range and Doppler spread radar echos

2008 ◽  
Vol 26 (8) ◽  
pp. 2419-2426 ◽  
Author(s):  
J. Vierinen ◽  
M. S. Lehtinen ◽  
I. I. Virtanen
Keyword(s):  
Domain Analysis ◽  
Doppler Spread ◽  
Estimation Methods ◽  
Radar Target ◽  
Analysis Method ◽  
Novel Method ◽  
Head Echo

Abstract. We present a novel method for analyzing range and Doppler spread targets in the amplitude domain using linear statistical inversion. The result of the analysis is an estimate of the range dependent amplitude behaviour of the target backscatter during the time that the transmission passes the target. A meteor head echo and strong backscatter from artificially heated regions of the ionosphere are used to demonstrate this novel analysis method. Plans to apply amplitude-domain radar target estimation methods to more complicated noisy underdetermined targets are also briefly discussed.

scholarly journals Low Order Harmonics Control in Stair Case Waveform by a Novel Estimation based Technique

2018 ◽  
Author(s):  
Salman Ahmad ◽  
Atif Iqbal ◽  
Imtiaz Ashraf ◽  
Sanjeevikumar Padmanaban ◽  
Mohammed Meraj
Keyword(s):  
Pulse Width Modulation ◽  
Jacobian Matrix ◽  
Initial Guess ◽  
Singularity Problem ◽  
Linear Set ◽  
Medium Voltage ◽  
Switching Losses ◽  
Voltage Application ◽  
Simulation Results ◽  
Subsequent Iteration

Few switching transitions in high power and medium voltage application of Power converters are desirable. The selective harmonics elimination (SHE) pulse width modulation offers a better quality waveform with lower switching transitions and hence lower switching losses. The SHE is a pre-programmed modulation technique where certain amounts of lower order harmonics are removed and fundamental voltage is controlled. After Fourier analysis of output waveform, a set of nonlinear transcendental equations is obtained which exhibits, multiple, unique or no solution in different range of modulation index (MI). In this paper, an iterative method based on the Jacobian estimate is proposed to solve a highly non-linear set of SHE equations. The proposed technique is easy in implementation and can solve a large number of such equations as computation of the Jacobian matrix in the subsequent iteration is estimated from the previous values.  Moreover, the proposed method also removes the singularity problem, especially for large SHE equations. High accuracy in the initial guess is also not essential for this method and can converge to the solution with any random initial guess. The computational and simulation results are given to validate the concept. The hardware result is provided to confirm the computational and simulation results.

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