scholarly journals Planning to Flip Heavy Objects Considering Soft-Finger Contacts

2021 ◽  
Vol 15 (2) ◽  
pp. 158-167
Author(s):  
Mohamed Raessa ◽  
◽  
Weiwei Wan ◽  
Keisuke Koyama ◽  
Kensuke Harada
Keyword(s):  
Rotation Angle ◽  
Relaxation Method ◽  
Friction Torque ◽  
Robot Arm ◽  
Constrained Motion ◽  
Planning Time ◽  
End Effector ◽  
Constraint Relaxation ◽  
Critical Rotation ◽  
Soft Finger

In this study, we implemented a constrained motion planner that enables robot manipulators to flip large and heavy objects without slippage while continuously holding them. Based on the soft-finger maximum friction torque, we developed a constraint relaxation method to estimate the critical rotation angle that a robot end effector can rotate while avoiding in-hand slippage. The critical rotation angle was used in a motion planner to sample safe configurations and generate slippage-free motion. The proposed planner was implemented using a 6-degree-of-freedom robot arm and a 2-finger robotic gripper with rubber pads attached to the fingertips. Experiments were performed with several objects to examine and demonstrate the performance of the planner. The results indicated satisfying planning time and the elimination of object slippage.

Three-Degree-of-Freedom Parallel Robot Arm

2006 ◽  
Author(s):  
Martin Hosek ◽  
Michael Valasek ◽  
Jairo Moura
Keyword(s):  
Parallel Robot ◽  
Degree Of Freedom ◽  
Motion Path ◽  
Angular Orientation ◽  
Robot Arm ◽  
Flat Panel Display ◽  
End Effector ◽  
Cluster Tools ◽  
Manufacturing Applications ◽  
Three Degree Of Freedom

This paper presents single- and dual-end-effector configurations of a planar three-degree of freedom parallel robot arm designed for automated pick-place operations in vacuum cluster tools for semiconductor and flat-panel-display manufacturing applications. The basic single end-effector configuration of the arm consists of a pivoting base platform, two elbow platforms and a wrist platform, which are connected through two symmetric pairs of parallelogram mechanisms. The wrist platform carries an end-effector, the position and angular orientation of which can be controlled independently by three motors located at the base of the robot. The joints and links of the mechanism are arranged in a unique geometric configuration which provides a sufficient range of motion for typical vacuum cluster tools. The geometric properties of the mechanism are further optimized for a given motion path of the robot. In addition to the basic symmetric single end-effector configuration, an asymmetric costeffective version of the mechanism is derived, and two dual-end-effector alternatives for improved throughput performance are described. In contrast to prior attempts to control angular orientation of the end-effector(s) of the conventional arms employed currently in vacuum cluster tools, all of the motors that drive the arm can be located at the stationary base of the robot with no need for joint actuators carried by the arm or complicated belt arrangements running through the arm. As a result, the motors do not contribute to the mass and inertia properties of the moving parts of the arm, no power and signal wires through the arm are necessary, the reliability and maintenance aspects of operation are improved, and the level of undesirable particle generation is reduced. This is particularly beneficial for high-throughput applications in vacuum and particlesensitive environments.

Cooperation and Null-Space Control of Networked Omni-Directional Mobile Manipulators

2020 ◽  
Author(s):  
Michael John Chua ◽  
Yen-Chen Liu
Keyword(s):  
Degrees Of Freedom ◽  
Null Space ◽  
Kinematic Model ◽  
Mobile Manipulator ◽  
Main Task ◽  
Mobile Manipulators ◽  
Robot Arm ◽  
Task Space ◽  
End Effector ◽  
Mobile Base

Abstract This paper presents cooperation and null-space control for networked mobile manipulators with high degrees of freedom (DOFs). First, kinematic model and Euler-Lagrange dynamic model of the mobile manipulator, which has an articulated robot arm mounted on a mobile base with omni-directional wheels, have been presented. Then, the dynamic decoupling has been considered so that the task-space and the null-space can be controlled separately to accomplish different missions. The motion of the end-effector is controlled in the task-space, and the force control is implemented to make sure the cooperation of the mobile manipulators, as well as the transportation tasks. Also, the null-space control for the manipulator has been combined into the decoupling control. For the mobile base, it is controlled in the null-space to track the velocity of the end-effector, avoid other agents, avoid the obstacles, and move in a defined range based on the length of the manipulator without affecting the main task. Numerical simulations have been addressed to demonstrate the proposed methods.

scholarly journals Detachable Robotic Grippers for Human-Robot Collaboration

2021 ◽  
Vol 8 ◽  
Author(s):  
Zubair Iqbal ◽  
Maria Pozzi ◽  
Domenico Prattichizzo ◽  
Gionata Salvietti
Keyword(s):  
Degrees Of Freedom ◽  
Tactile Feedback ◽  
Industrial Robots ◽  
Physical Interaction ◽  
Robot Arm ◽  
Robotic Hands ◽  
End Effector ◽  
External Power ◽  
Self Powered ◽  
Automatic Tool

Collaborative robots promise to add flexibility to production cells thanks to the fact that they can work not only close to humans but also with humans. The possibility of a direct physical interaction between humans and robots allows to perform operations that were inconceivable with industrial robots. Collaborative soft grippers have been recently introduced to extend this possibility beyond the robot end-effector, making humans able to directly act on robotic hands. In this work, we propose to exploit collaborative grippers in a novel paradigm in which these devices can be easily attached and detached from the robot arm and used also independently from it. This is possible only with self-powered hands, that are still quite uncommon in the market. In the presented paradigm not only hands can be attached/detached to/from the robot end-effector as if they were simple tools, but they can also remain active and fully functional after detachment. This ensures all the advantages brought in by tool changers, that allow for quick and possibly automatic tool exchange at the robot end-effector, but also gives the possibility of using the hand capabilities and degrees of freedom without the need of an arm or of external power supplies. In this paper, the concept of detachable robotic grippers is introduced and demonstrated through two illustrative tasks conducted with a new tool changer designed for collaborative grippers. The novel tool changer embeds electromagnets that are used to add safety during attach/detach operations. The activation of the electromagnets is controlled through a wearable interface capable of providing tactile feedback. The usability of the system is confirmed by the evaluations of 12 users.

Finite element method stiffness analysis of a novel telemanipulator for minimally invasive surgery

SIMULATION ◽  
2019 ◽  
Vol 95 (11) ◽  
pp. 1015-1025 ◽  
Author(s):  
Roman Trochimczuk ◽  
Andrzej Łukaszewicz ◽  
Tadeusz Mikołajczyk ◽  
Francesco Aggogeri ◽  
Alberto Borboni
Keyword(s):  
Minimally Invasive Surgery ◽  
Minimally Invasive ◽  
Invasive Surgery ◽  
Numerical Study ◽  
Kinematic Chain ◽  
Robot Arm ◽  
End Effector ◽  
Stiffness Analysis ◽  
Position Accuracy ◽  
Main Factors

This paper presents the concept of a novel telemanipulator for minimally invasive surgery, along with numerical analysis to validate the main system performance. The proposed kinematic structure consists of a passive and an active module. The passive module is similar to the Selective Compliance Assembly Robot Arm - SCARA robot. The active module is based on a parallelogram mechanism. The results of the numerical study are discussed, focusing on the influence of geometry parameters of the kinematic chain on the displacement accuracy of the end-effector. In particular, the paper deals with the identification of the main factors that impact the position accuracy of the robot.

Control of a Flexible Robot Arm: Experimental and Theoretical Results

1987 ◽  
Vol 109 (4) ◽  
pp. 299-309 ◽  
Author(s):  
N. G. Chalhoub ◽  
A. G. Ulsoy
Keyword(s):  
Partial Evaluation ◽  
Digital Simulation ◽  
Robot Arm ◽  
Flexible Robot ◽  
Motion Controller ◽  
Positional Accuracy ◽  
Spherical Coordinate ◽  
End Effector ◽  
Theoretical Results ◽  
Observation Spillover

The operation of high precision robots is severely limited by. their manipulator dynamic deflection, which persists for a period of time after a move is completed. These unwanted vibrations deteriorate the end effector positional accuracy and reduce significantly the robot arm production rate. A “rigid and flexible motion controller” is derived to introduce additional damping into the flexible motion. This is done by using additional sensors to measure the compliant link vibrations and feed them back to the controller. The existing actuators at the robot joints are used (i.e., no additional actuators are introduced). The performance of the controller is tested on a dynamic model, developed in previous work, for a spherical coordinate robot arm whose last link only is considered to be flexible. The simulation results show a significant reduction in the vibratory motion. The important issue of control and observation spillover is examined and found to present no significant practical problems. Partial evaluation of this approach is performed experimentally by testing two controllers, a “rigid body controller” and a “rigid and flexible motion controller,” on a single joint of a spherical coordinate, laboratory robot arm. The experimental results show a significant reduction in the end effector dynamic deflection; thus partially validating the results of the digital simulation studies.

Rotatability of the Floating Link on Multi-Loop Planar Linkages

2020 ◽  
Vol 12 (6) ◽  
Author(s):  
Cody Leeheng Chan ◽  
Kwun-Lon Ting
Keyword(s):  
Rotation Angle ◽  
Parallel Manipulators ◽  
Orientation Error ◽  
Joint Rotation ◽  
Position Uncertainty ◽  
End Effector ◽  
Uncertainty Model ◽  
Branch Formation ◽  
Joint Clearances ◽  
Planar Linkages

Abstract This paper proposes a method to deal with the orientation uncertainty problem affected by joint clearances. To solve this problem, it is necessary to establish the theory of mobility of the floating link of multi-loop linkages. Since the theory of the mobility of floating link is yet complete, this paper provides a simple treatment to determine the rotatability between any two links, adjoined or not, in planar multi-loop linkages. The rotation angle of the floating link with respect to the reference link is defined so that there is no ambiguity in analyzing the rotation range of the floating link. Based on the joint rotation space (JRS) method, one may identify not only the branch formation but also the rotatability between any two links on each of the branches. It is a visualized method that reveals the rotation characteristic of multi-loop linkages. This paper demonstrates the rotation range of the floating link with respect to the reference link on six-bar Stephenson linkages, 2-degree-of-freedom (DOF). 7-bar linkages, and 3-DOF. Eight-bar parallel manipulators. This might be the first paper to deal with the rotatability of 3-DOF planar multi-loop linkages. This paper uses the method to predict the clearance-induced angle uncertainty of the 8-bar parallel manipulators, which determines the worst orientation error of the end-effector and fills up the void of the joint clearance uncertainty model proposed by Ting et al. (2017, “Clearance-Induced Position Uncertainty of Planar Linkages and Parallel Manipulators,” J. Mech. Rob., 9, p. 061001).

Application of redundant robots to constrained-motion tasks

Robotica ◽  
1992 ◽  
Vol 10 (5) ◽  
pp. 397-407 ◽  
Author(s):  
Veljko Potkonjak
Keyword(s):  
Free Motion ◽  
Constrained Motion ◽  
End Effector ◽  
Redundant Robot ◽  
Redundant Robots ◽  
Passive Compliance ◽  
Two Phases ◽  
The Impact

SUMMARYThe problem of the constrained motion of robot end-effector is discussed. The redundant robot is considered, redundancy being added in order to improve robot working characteristics. In the phase of free motion towards the constraint the errors of basic non-redundant configuration are corrected by means of redundancy. During the constrained motion redundancy plays the role either of active or passive compliance. Between these two phases, the collision with the constraint occurs, and the impact can be absorbed by using redundancy.

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