scholarly journals Nut Unfastening by Robotic Surface Exploration

Robotics ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 107
Author(s):  
Alireza Rastegarpanah ◽  
Rohit Ner ◽  
Rustam Stolkin ◽  
Naresh Marturi
Keyword(s):  
Degrees Of Freedom ◽  
Iterative Closest Point ◽  
Task Space ◽  
Shape Estimation ◽  
Active Compliance ◽  
Visually Impaired People ◽  
Surface Exploration ◽  
Compliant Robot ◽  
Novel Concept ◽  
Mechanical Tool

In this paper, we present a novel concept and primary investigations regarding automated unfastening of hexagonal nuts by means of surface exploration with a compliant robot. In contrast to the conventional industrial approaches that rely on custom-designed motorised tools and mechanical tool changers, we propose to use robot fingers to position, grasp and unfasten unknown random-sized hexagonal nuts, which are arbitrarily positioned in the robot’s task space. Inspired by how visually impaired people handle unknown objects, in this work, we use information observed from surface exploration to devise the unfastening strategy. It combines torque monitoring with active compliance for the robot fingers to smoothly explore the object’s surface. We implement a shape estimation technique combining scaled iterative closest point and hypotrochoid approximation to estimate the location as well as contour profile of the hexagonal nut so as to accurately position the gripper fingers. We demonstrate this work in the context of dismantling an electrically driven vehicle battery pack. The experiments are conducted using a seven degrees of freedom (DoF)–compliant robot fitted with a two-finger gripper to unfasten four different sized randomly positioned hexagonal nuts. The obtained results suggest an overall exploration and unfastening success rate of 95% over an average of ten trials for each nut.

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.

Generating real-time trajectories for a planar biped robot crossing a wide ditch with landing uncertainties

Robotica ◽  
2018 ◽  
Vol 37 (1) ◽  
pp. 109-140 ◽  
Author(s):  
V. Janardhan ◽  
R. Prasanth Kumar
Keyword(s):  
Real Time ◽  
Degrees Of Freedom ◽  
Dynamic Balance ◽  
Surface Friction ◽  
Biped Robot ◽  
Net Energy ◽  
Leg Length ◽  
Uncertain Environments ◽  
Novel Concept ◽  
Time Planning

SUMMARYDitch crossing is one of the essential capabilities required for a biped robot in disaster management and search and rescue operations. Present work focuses on crossing a wide ditch with landing uncertainties by an under-actuated planar biped robot with five degrees of freedom. We consider a ditch as wide for a robot when the ankle to ankle stretch required to cross it is at least equal to the leg length of the robot. Since locomotion in uncertain environments requires real-time planning, in this paper, we present a new approach for generating real-time joint trajectories using control constraints not explicitly dependent on time, considering impact, dynamic balance, and friction. As part of the approach, we introduce a novel concept called the point of feasibility for bringing the biped robot to complete rest at the end of ditch crossing. We present a study on the influence of initial posture on landing impact and net energy consumption. Through simulations, we found the best initial postures to efficiently cross a wide ditch of width 1.05 m, with less impact and without singularities. Finally, we demonstrate the advantage of the proposed approach to cross a wide ditch when the surface friction is not same on both sides of the ditch.

Optimal configuration of dual-arm cam-lock robot based on task-space manipulability

Robotica ◽  
2009 ◽  
Vol 27 (1) ◽  
pp. 13-18 ◽  
Author(s):  
Kambiz Ghaemi Osgouie ◽  
Ali Meghdari ◽  
Saeed Sohrabpour
Keyword(s):  
Degrees Of Freedom ◽  
Optimal Configuration ◽  
Task Space ◽  
Specific Point ◽  
Optimum Configuration ◽  
Geometrical Constraints ◽  
Dual Arm

SUMMARYIn this paper obtaining the optimal configuration of the dual-arm cam-lock (DACL) robot at a specific point is addressed. The objective is to optimize the applicable task-space force in a desired direction. The DACL robot is a reconfigurable manipulator formed by two parallel cooperative arms. The arms normally operate redundantly but when needed, they can lock into each other in certain joints in order to achieve a higher stiffness, while losing some degrees of freedom. Furthermore, the dynamics of the DACL robot is discussed and parametrically formulated. Considering the geometrical constraints at a given point in the robot's workspace, the optimum configuration for maximizing the cooperatively applicable force by dual arms is determined.

Classification of Compliant Mechanisms and Determination of the Degrees of Freedom Using the Concepts of Compliance Number and Pseudo-Rigid-Body Model

2019 ◽  
Author(s):  
Pratheek Bagivalu Prasanna ◽  
Ashok Midha ◽  
Sushrut G. Bapat
Keyword(s):  
Rigid Body ◽  
Degrees Of Freedom ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Body Model ◽  
Active Compliance ◽  
Kinematic Behavior ◽  
Rigid Body Model

Abstract Understanding the kinematic properties of a compliant mechanism has always proved to be a challenge. A concept of compliance number offered earlier emphasized the development of terminology that aided in its determination. A method to evaluate the elastic degrees of freedom associated with the flexible segments/links of a compliant mechanism using the pseudo-rigid-body model (PRBM) concept is provided. In this process, two distinct classes of compliant mechanisms are developed involving: (i) Active Compliance and (ii) Passive Compliance. Furthermore, these also aid in a better characterization of the kinematic behavior of a compliant mechanism. A more lucid interpretation of the significance of compliance number is provided. Applications of this method to both active and passive compliant mechanisms are exemplified. Finally, an experimental procedure that aids in visualizing the degrees of freedom as calculated is presented.

A Hierarchical Distributed Path Planning for Redundant Manipulators Based on Virtual Arm

1992 ◽  
Vol 4 (3) ◽  
pp. 210-217
Author(s):  
Toshio Tsuji ◽  
◽  
Koji Ito ◽  
Keyword(s):  
Path Planning ◽  
Degrees Of Freedom ◽  
Local Level ◽  
Intermediate Level ◽  
Global Level ◽  
Task Space ◽  
End Point ◽  
Planning Algorithm ◽  
Global Representation ◽  
Path Planning Algorithm

This paper proposes a collision-free path planning algorithm in the task space based on virtual arms. The virtual arm has the same kinematic structure as the actual arm except that its end-point is located at the joint or link of the actual arm. Therefore, the configuration of the actual arm can be represented as a set of end-points of the virtual arms, and the path planning for multi-joint manipulators can be performed only in the task space. Our method adopts a hierarchical strategy which consists of the global level, the intermediate level, and the local level. The global level plans the collision-free endpoint trajectory of the actual arm based on the global representation of the task space. The intermediate level generates the subgoals for the actual and virtual endpoints based on the current positions and the actual endpoint trajectory specified by the global level. The local level moves each end-point to the corresponding subgoal, avoiding the close obstacles based on the local informations of the task space. The effectiveness of the method is verified by computer simulations using a planar manipulator with redundant joint degrees of freedom.

Optimal Configuration of a 4-DOF Dual-Arm Cam-Lock Manipulator

2007 ◽  
Author(s):  
Kambiz Ghaemi Osgouie ◽  
Ali Meghdari ◽  
Saeed Sohrabpour ◽  
Mehdi Salmani Jelodar
Keyword(s):  
Degrees Of Freedom ◽  
Robot Manipulators ◽  
The Other ◽  
Initial Population ◽  
Structural Stiffness ◽  
Task Space ◽  
Specific Point ◽  
Geometrical Constraints ◽  
Dual Arm ◽  
Cooperative Manipulators

The Dual-Arm Cam-Lock (DACL) robot manipulators are reconfigurable arms formed by two parallel cooperative manipulators. Some of their joints may lock into each other. Therefore, the arms normally operate redundantly. However, when higher structural stiffness is needed these two arms can lock into each other in specific joints and loose some degrees of freedom. In this paper, the dynamics of the DACL robot is discussed and parametrically formulated. On the other hand, the criteria and implementation of genetic algorithm (GA) to optimize the configuration of DACL robot manipulators at a specific point with the objective to maximize the cooperatively applicable task-space force in a desired direction are addressed. To obtain a more efficient process, an initial population is generated satisfying the geometrical constraints of the planar arms.

Algorithmic path planning of static robots in three dimensions using configuration space metrics

Robotica ◽  
2010 ◽  
Vol 29 (2) ◽  
pp. 295-315 ◽  
Author(s):  
Debanik Roy
Keyword(s):  
Path Planning ◽  
Configuration Space ◽  
Heuristic Algorithm ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Industrial Applications ◽  
Three Dimensions ◽  
Task Space ◽  
Articulated Robot

SUMMARYCollision-free path planning for static robots is a demanding manifold of contemporary robotics research, vastly due to the growing industrial applications. In this paper, a novel ‘visibility map’-based heuristic algorithm is used to generate near-optimal safe path for a three-dimensional congested robot workspace. The final path is obtainable in terms of joint configurations, by considering the Configuration Space of the task space. The developed algorithm has been verified initially by considering representative 2D workspaces, cluttered with different obstacles with regular geometries and then after with the spatial endeavour. A case study reveals the effectiveness of the developed modules of the configuration space mapping, pertaining to a five degrees-of-freedom low payload articulated robot.

scholarly journals Augmenting Maneuverability of UUVs with Cycloidal Propellers

2020 ◽  
Author(s):  
Manavendra Desai ◽  
Ruddhi Gokhale ◽  
Atanu Halder ◽  
Moble Benedict ◽  
Yin Lu Young
Keyword(s):  
Degrees Of Freedom ◽  
Underwater Vehicle ◽  
Underwater Vehicles ◽  
Low Speed ◽  
Six Degrees Of Freedom ◽  
Hydrodynamic Motion ◽  
Screw Propeller ◽  
Heave Motion ◽  
Novel Concept ◽  
And Control

This paper investigates the novel concept of augmenting the maneuverability of underwater vehicles with cycloidal propellers. Cycloidal propellers have the potential of providing agile manoeuvring capabilities to an underwater vehicle such as enabling pure heave motion and spot turns. They will also enable the vehicle to surge in forward and backward directions with equal ease. Such manoeuvres are not possible with the more conventional screw propeller and control fin combinations. Moreover, cycloidal propellers can enable precise dynamic positioning in low speed applications like station-keeping, underwater surveying and maintenance, minesweeping and teaming activities. In this paper, manoeuvring capabilities of an underwater vehicle with conventional screw propeller and control fins only are compared with one augmented with cycloidal propellers. The cases considered include a turning circle manoeuvre, a low speed 180o turn and a low speed heave manoeuvre. A six degrees-of-freedom non-linear hydrodynamic motion prediction model was developed and validated. Simulation results demonstrated that compared to conventional propulsion systems, cycloidal propeller augmented underwater vehicles can be more swift and compact in low speed manoeuvres, making a case for further investigation into this concept.

scholarly journals Design, analysis & testing of an enhanced radial-axial hybrid compliant deburring tool

2021 ◽  
Author(s):  
Jeremy Kroeker
Keyword(s):  
Finite Element Method ◽  
Gas Turbine ◽  
Degrees Of Freedom ◽  
Material Model ◽  
Gas Turbine Engine ◽  
Plane Model ◽  
Turbine Engine ◽  
Active Compliance ◽  
Engine Components ◽  
Three Degrees Of Freedom

This thesis will discuss the development of a radial actuator incorporated into a deburring tool. Gas turbine engine deburring is complex; this requires the tooltip to maintain active compliance in three degrees of freedom. This can be achieved through the use of a rotating action plane so that only radial and axial actuation is required. A proposed enhanced radial actuator has been made that utilizes the action plane model and fulfill the requirements for precision deburring of gas turbine engine components. The enhanced radial actuator was designed using four silicone rubber pneumatic diaphragms. The diaphragms were modelled using a finite element method and applying an Arruda-Boyce material model to the mesh. The stiffness behaviour was analyzed and compared to data from previous research completed on radial actuation within an action plane. The stiffness behaviour was determined to be superior and significantly improved as it could be reliably predicted.

Unified Virtual Guides Framework for Path Tracking Tasks

Robotica ◽  
2019 ◽  
Vol 38 (10) ◽  
pp. 1807-1823 ◽  
Author(s):  
Leon Žlajpah ◽  
Tadej Petrič
Keyword(s):  
Control Algorithm ◽  
Degrees Of Freedom ◽  
Path Tracking ◽  
Human Robot Interaction ◽  
Task Space ◽  
Admittance Control ◽  
Unified Framework ◽  
Robot Interaction ◽  
Tracking Tasks ◽  
Selection Of

SUMMARYIn this paper, we propose a novel unified framework for virtual guides. The human–robot interaction is based on a virtual robot, which is controlled by the admittance control. The unified framework combines virtual guides, control of the dynamic behavior, and path tracking. Different virtual guides and active constraints can be realized by using dead-zones in the position part of the admittance controller. The proposed algorithm can act in a changing task space and allows selection of the tasks-space and redundant degrees-of-freedom during the task execution. The admittance control algorithm can be implemented either on a velocity or on acceleration level. The proposed framework has been validated by an experiment on a KUKA LWR robot performing the Buzz-Wire task.

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