Screw theory based method to formulate local Jacobian’ magnitude estimator contours for 6 DoF robots

2020 ◽  
pp. 095440622096253
Author(s):  
Rajesh Kumar ◽  
Jitendra Prasad Khatait
Keyword(s):  
Control Algorithm ◽  
Screw Theory ◽  
Robotic Manipulators ◽  
Mathematical Entity ◽  
End Effector ◽  
Joint Torques ◽  
Online Computation ◽  
The Matrix ◽  
Six Dof ◽  
And Performance

Singularity prediction of Jacobian is inherently related to the design of any manipulator. Optimization of Jacobian is known to improve the joint rates and joint torques for the same set of end-effector twists and wrenches. Any mathematical entity which is an estimator of Jacobian can be used as a manifestation of the stated two schemes. It is required that online computation of Jacobian be implemented so that singular poses can be avoided and performance is maximized. We present an algorithm that relates to the determinant of the Jacobian for robotic manipulators. The algorithm developed is quicker to compute, and a strategy is developed to synthesize the local estimator contour. The contours change dynamically, henceforth optimal motor torques (in case of presence of interaction fields or system requiring force control) and optimal joint rates can be defined, depending on the control algorithm. The algorithm developed is independent of the structure of the matrix and is generalized to any six DoF manipulator structure used.

Obstacle avoidance control for redundant manipulators using collidability measure

Robotica ◽  
2000 ◽  
Vol 18 (2) ◽  
pp. 143-151 ◽  
Author(s):  
Su Il Choi ◽  
Byung Kook Kim
Keyword(s):  
Obstacle Avoidance ◽  
Control Algorithm ◽  
Null Space ◽  
Control Law ◽  
Redundant Manipulators ◽  
Redundancy Resolution ◽  
End Effector ◽  
Joint Torques ◽  
Avoidance Control ◽  
Joint Acceleration

We present an efficient obstacle avoidance control algorithm for redundant manipulators using a new measure called collidability measure. Considering moving directions of manipulator links, the collidability measure is defined as the sum of inverse of predicted collision distances between links and obstacles: This measure is suitable for obstacle avoidance since directions of moving links are as important as distances to obstacles. For kinematic or dynamic redundancy resolution, null space control is utilized to avoid obstacles by minimizing the collidability measure: We present a velocity-bounded kinematic control law which allows reasonably large gains to improve the system performance. Also, by clarifying decomposition in the joint acceleration level, we present a simple dynamic control law with bounded joint torques which guarantees tracking of a given end-effector trajectory and improves a kinematic cost function such as collidability measure. Simulation results are presented to illustrate the effectiveness of the proposed algorithm.

scholarly journals Bio-inspired kinematical control of redundant robotic manipulators

2016 ◽  
Vol 36 (2) ◽  
pp. 200-215 ◽  
Author(s):  
Ali Leylavi Shoushtari ◽  
Stefano Mazzoleni ◽  
Paolo Dario
Keyword(s):  
Control Algorithm ◽  
Design Methodology ◽  
Three Dimensional ◽  
Robotic Manipulators ◽  
Robotic Arm ◽  
Kinematic Redundancy ◽  
End Effector ◽  
Content Type ◽  
Tracking Tasks ◽  
Two Degree Of Freedom

Purpose This paper aims to propose an innovative kinematic control algorithm for redundant robotic manipulators. The algorithm takes advantage of a bio-inspired approach. Design/methodology/approach A simplified two-degree-of-freedom model is presented to handle kinematic redundancy in the x-y plane; an extension to three-dimensional tracking tasks is presented as well. A set of sample trajectories was used to evaluate the performances of the proposed algorithm. Findings The results from the simulations confirm the continuity and accuracy of generated joint profiles for given end-effector trajectories as well as algorithm robustness, singularity and self-collision avoidance. Originality/value This paper shows how to control a redundant robotic arm by applying human upper arm-inspired concept of inter-joint dependency.

scholarly journals Force-Free Control for Direct Teaching of a Surgical Assistant Robot End Effector with Wire-Driven Bidirectional Telescopic Mechanism

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3498
Author(s):  
Youqiang Zhang ◽  
Cheol-Su Jeong ◽  
Minhyo Kim ◽  
Sangrok Jin
Keyword(s):  
Control Algorithm ◽  
Position Control ◽  
Friction Model ◽  
Surgical Instruments ◽  
Control Input ◽  
End Effector ◽  
Motor Current ◽  
Direct Teaching ◽  
End Effectors ◽  
Teaching Operation

This paper shows the design and modeling of an end effector with a bidirectional telescopic mechanism to allow a surgical assistant robot to hold and handle surgical instruments. It also presents a force-free control algorithm for the direct teaching of end effectors. The bidirectional telescopic mechanism can actively transmit force both upwards and downwards by staggering the wires on both sides. In order to estimate and control torque via motor current without a force/torque sensor, the gravity model and friction model of the device are derived through repeated experiments. The LuGre model is applied to the friction model, and the static and dynamic parameters are obtained using a curve fitting function and a genetic algorithm. Direct teaching control is designed using a force-free control algorithm that compensates for the estimated torque from the motor current for gravity and friction, and then converts it into a position control input. Direct teaching operation sensitivity is verified through hand-guiding experiments.

scholarly journals Optimization of Dynamic Task Location within a Manipulator’s Workspace for the Utilization of the Minimum Required Joint Torques

Electronics ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 288
Author(s):  
Adam Wolniakowski ◽  
Charalampos Valsamos ◽  
Kanstantsin Miatliuk ◽  
Vassilis Moulianitis ◽  
Nikos Aspragathos
Keyword(s):  
High Performance ◽  
Human Robot Interaction ◽  
Optimal Position ◽  
End Effector ◽  
Joint Torques ◽  
Dynamic Task ◽  
Arbitrary Position ◽  
Simulation Results ◽  
Set Up ◽  
Task Placement

The determination of the optimal position of a robotic task within a manipulator’s workspace is crucial for the manipulator to achieve high performance regarding selected aspects of its operation. In this paper, a method for determining the optimal task placement for a serial manipulator is presented, so that the required joint torques are minimized. The task considered comprises the exercise of a given force in a given direction along a 3D path followed by the end effector. Given that many such tasks are usually conducted by human workers and as such the utilized trajectories are quite complex to model, a Human Robot Interaction (HRI) approach was chosen to define the task, where the robot is taught the task trajectory by a human operator. Furthermore, the presented method considers the singular free paths of the manipulator’s end-effector motion in the configuration space. Simulation results are utilized to set up a physical execution of the task in the optimal derived position within a UR-3 manipulator’s workspace. For reference the task is also placed at an arbitrary “bad” location in order to validate the simulation results. Experimental results verify that the positioning of the task at the optimal location derived by the presented method allows for the task execution with minimum joint torques as opposed to the arbitrary position.

scholarly journals Stiffness Modeling of Robotic-Manipulators Under Auxiliary Loadings

2012 ◽  
Author(s):  
Alexandr Klimchik ◽  
Anatol Pashkevich ◽  
Stéphane Caro ◽  
Damien Chablat
Keyword(s):  
Robotic Manipulators ◽  
Computationally Efficient ◽  
End Effector ◽  
Efficient Procedure ◽  
Stiffness Modeling ◽  
Cartesian Stiffness Matrix ◽  
Different Types ◽  
Mapping Equation ◽  
Linear Force ◽  
Cartesian Stiffness

The paper focuses on the extension of the virtual-joint-based stiffness modeling technique for the case of different types of loadings applied both to the robot end-effector and to manipulator intermediate points (auxiliary loading). It is assumed that the manipulator can be presented as a set of compliant links separated by passive or active joints. It proposes a computationally efficient procedure that is able to obtain a non-linear force-deflection relation taking into account the internal and external loadings. It also produces the Cartesian stiffness matrix. This allows to extend the classical stiffness mapping equation for the case of manipulators with auxiliary loading. The results are illustrated by numerical examples.

Diamond tool wear monitoring by sensory analysis in milling of absolute black granite

2021 ◽  
pp. 095440542110406
Author(s):  
Sandro Turchetta ◽  
Luca Sorrentino ◽  
Gianluca Parodo
Keyword(s):  
Tool Wear ◽  
Cutting Tools ◽  
Depth Of Cut ◽  
Surface Machining ◽  
Diamond Tools ◽  
The Matrix ◽  
Cutting Force Components ◽  
Force Components ◽  
Natural Stones ◽  
And Performance

Diamond tools suitable for machining operations of natural stones can be divided into two groups: cutting tools, including blades, the circular blades and the wires, and the surface machining ones, involving mills and grinders, that can be of different shapes. For the stone sawing process, the most adopted tool type is the diamond mill, whose duration and performance are influenced by various elements such as: the mineralogical characteristics of the material to be machined; the working conditions such as the depth of cut, the feed rate and the spindle speed; the production process of the diamond segment and the characteristics of both the matrix and the diamond, such as the size, the type and the concentration of the diamonds and the metal bond formulation hardness. This work allows to indirectly assess the wear of sintered diamond tools by signal analysis (in time and frequency domain) of the cutting force components acquired in the process. The results obtained represent a fundamental step for the development of a sensory supervision system capable of assessing the tool wear and hence to modify the process parameters in process, in order to optimize cutting performance and tool life.

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.

scholarly journals Rocess Design of Fiber Reinforced Magnesium Matrix Composites

2018 ◽  
Vol 1 (1) ◽  
Author(s):  
Ding Hualun
Keyword(s):  
Composite Materials ◽  
Matrix Composites ◽  
Deposition Method ◽  
Fiber Reinforced ◽  
Casting Method ◽  
Magnesium Matrix ◽  
Preparation Methods ◽  
Magnesium Matrix Composites ◽  
The Matrix ◽  
And Performance

This paper chooses magnesium as the matrix of composite materials, selects carbon fi ber as reinforcement, anddesigns the composite scheme according to the structure and performance of Mg-based composites. The performancecharacteristics and application prospect of fiber-reinforced magnesium matrix composites are introduced. Wait. Inthis paper, the process of preparing carbon fi ber magnesium matrix composites by compression casting method andspray deposition method is designed. The process fl ow chart of these two design schemes is determined by analyzingthe principle of these two kinds of preparation methods, and the specifi c problems of the process are analyzed andsummarized.

Research on Process Optimization and Abrasion Resistance of Plasma Spraying Al2O3-13wt%TiO2 Coating

2013 ◽  
Vol 341-342 ◽  
pp. 92-95
Author(s):  
Li Jun Wang ◽  
Jian Jun Hao ◽  
Yue Jin Ma ◽  
Jian Guo Zhao ◽  
Jian Chang Li
Keyword(s):  
Wear Resistance ◽  
Plasma Spraying ◽  
Friction And Wear ◽  
Performance Test ◽  
Sample Surface ◽  
Coating Performance ◽  
The Matrix ◽  
Average Wear ◽  
And Performance ◽  
Spraying Process

Using plasma spraying equipment to prepare Al2O3-13wt%TiO2 coating on Q235 substrate. Study of its organization and performance, test the performance of coating microhardness and the resistance of friction and wear resistance then optimize the spraying process parameters. The surface of the coating performance was studied by SEM. The results show that, Coating microhardness can be as high as 1132HV, Far more than the matrix microhardness. The minimum average wear weightlessness of Sample surface is 0.95mg. Greatly improve the wear resistance

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