A Co-operative Transferring Task by Mobile Manipulators

2000 ◽  
Vol 12 (6) ◽  
pp. 712-717
Author(s):  
Kazuya Yasui ◽  
◽  
Toshiyuki Murakami ◽  
Kouhei Ohnishi
Keyword(s):  
Trajectory Planning ◽  
Null Space ◽  
Internal Force ◽  
Mobile Manipulator ◽  
Mobile Manipulators ◽  
Positioning Errors ◽  
Force Relation ◽  
End Effectors ◽  
Computational Analyses ◽  
Complicated Task

In this paper, a method of grasping and transferring a large object by cooperative motion of multiple manipulators is introduced. To implement the task with mobile manipulators, the compliance of the grasping system between the object and end-effectors is needed. It enables us to avoid excessive internal force due to mutual positioning errors. However, the simple way of trajectory planning of the system is also required. Because the trajectory planning used to be given to each manipulator, it has been very complicated task to design the desired trajectories for each mobile manipulator. Thus this paper adopt the control algorithm with respect to objects to reduce the amount of planning tasks. The static relation between the object and end-effectors is introduced to solve the issues above. It combines the force reference of end-effectors and that of an object with static analysis of force. With this algorithm, the motion of an object is distributed to each end-effector. Then the grasping is projected to the null space of this static force relation. For confirmation of the proposed method, computational analyses are implemented and shown.

Manipulability-based configuration evaluation of cooperative payload transport by mobile manipulator collectives

Robotica ◽  
2006 ◽  
Vol 25 (1) ◽  
pp. 29-42 ◽  
Author(s):  
Chin Pei Tang ◽  
Venkat N. Krovi
Keyword(s):  
Kinematic Model ◽  
Nonholonomic Constraints ◽  
System Level ◽  
Mobile Manipulator ◽  
Mobile Manipulators ◽  
Cooperative System ◽  
Relative Configuration ◽  
Positioning Errors ◽  
Kinematic Loops ◽  
End Effectors

In this paper, we focus on the development of a quantitative performance analysis framework for a cooperative system of multiple wheeled mobile manipulators physically transporting a common payload. Each mobile manipulator module consists of a differentially driven wheeled mobile robot (WMR) with a mounted planar three-degree-of-freedom (DOF) revolute-jointed manipulator. A composite cooperative system is formed when a payload is placed at the end-effectors of many such modules. The system possesses the ability to change its relative configuration as well as to accommodate relative positioning errors of the wheeled agents. However, the combination of nonholonomic constraints due to the mobile bases, holonomic constraints due to the closed kinematic loops, and the different joint-actuation schema (active/passive/locked) within the system requires careful quantitative evaluation to efficiently realize the payload manipulation task. Hence, in this paper, we extend the differential kinematic model for treatment of constrained articulated mechanical systems to formulate a framework to include both the mixture effect of holonomic/nonholonomic constraints and the different possible joint-actuation schema in our system. The system-level performance is then examined quantitatively by the manipulability measure in terms of isotropy index with representative case studies.

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.

Trajectory planning of mobile manipulators using dynamic programming approach

Robotica ◽  
2012 ◽  
Vol 31 (4) ◽  
pp. 643-656 ◽  
Author(s):  
M. H. Korayem ◽  
M. Irani ◽  
A. Charesaz ◽  
A. H. Korayem ◽  
A. Hashemi
Keyword(s):  
Dynamic Programming ◽  
Trajectory Planning ◽  
Optimal Trajectory ◽  
Vision System ◽  
Optimal Path ◽  
Optimization Method ◽  
Mobile Manipulator ◽  
Programming Approach ◽  
Planning Problem ◽  
Mobile Manipulators

SUMMARYThis paper presents a solution for optimal trajectory planning problem of robotic manipulators with complicated dynamic equations. The main goal is to find the optimal path with maximum dynamic load carrying capacity (DLCC). Proposed method can be implemented to problems of both motion along a specified path and point-to-point motion. Dynamic Programming (DP) approach is applied to solve optimization problem and find the positions and velocities that minimize a pre-defined performance index. Unlike previous attempts, proposed method increases the speed of convergence by using the sequential quadratic programming (SQP) formulation. This formulation is used for solving problems with nonlinear constraints. Also, this paper proposes a new algorithm to design optimal trajectory with maximum DLCC for both fixed and mobile base mechanical manipulators. Algorithms for DLCC calculations in previous works were based on indirect optimization method or linear programming approach. The proposed trajectory planning method is applied to a linear tracked Puma and the mobile manipulator named Scout. Application of this algorithm is confirmed and simulation results are compared with experimental results for Scout robot. In experimental test, results are obtained using a new stereo vision system to determine the position of the robot end-effector.

scholarly journals Point-to-Point Collision-Free Trajectory Planning for Mobile Manipulators

2016 ◽  
Vol 85 (3-4) ◽  
pp. 523-538 ◽  
Author(s):  
Grzegorz Pajak ◽  
Iwona Pajak
Keyword(s):  
Collision Avoidance ◽  
Trajectory Planning ◽  
Three Dimensional ◽  
Nonholonomic Constraints ◽  
Inequality Constraints ◽  
Mobile Manipulator ◽  
Local Perturbation ◽  
Mobile Manipulators ◽  
State Variables ◽  
Mechanical Constraints

AbstractThe collision-free trajectory planning method subject to control constraints for mobile manipulators is presented. The robot task is to move from the current configuration to a given final position in the workspace. The motions are planned in order to maximise an instantaneous manipulability measure to avoid manipulator singularities. Inequality constraints on state variables i.e. collision avoidance conditions and mechanical constraints are taken into consideration. The collision avoidance is accomplished by local perturbation of the mobile manipulator motion in the obstacles neighbourhood. The fulfilment of mechanical constraints is ensured by using a penalty function approach. The proposed method guarantees satisfying control limitations resulting from capabilities of robot actuators by applying the trajectory scaling approach. Nonholonomic constraints in a Pfaffian form are explicitly incorporated into the control algorithm. A computer example involving a mobile manipulator consisting of nonholonomic platform (2,0) class and 3DOF RPR type holonomic manipulator operating in a three-dimensional task space is also presented.

Decentralized Dynamic Control of a Nonholonomic Mobile Manipulator Collective: A Simulation Study

2008 ◽  
Author(s):  
Hao Su ◽  
Venkat Krovi
Keyword(s):  
Control Algorithm ◽  
Null Space ◽  
Dynamic Control ◽  
Mobile Manipulator ◽  
Mobile Manipulators ◽  
Level Control ◽  
Individual Agent ◽  
End Effector ◽  
High Level ◽  
Task Accomplishment

In this paper, we present a decentralized dynamic control algorithm for a robot collective consisting of multiple nonholonomic wheeled mobile manipulators (NH-WMMs) capable of cooperatively transporting a common payload. In this algorithm, the high level controller deals with motion/force control of the payload, at the same time distributes the motion/force task into individual agents by grasp description matrix. In each individual agent, the low level controller decomposes the system dynamics into decoupled task space (end-effector motions/forces) and a dynamically-consistent null-space (internal motions/forces) component. The agent level control algorithm facilitates the prioritized operational task accomplishment with the end-effector impedance-mode controller and secondary null-space control. The scalability and modularity is guaranteed upon the decentralized control architecture. Numerical simulations are performed for a 2-NH-WMM system carrying a payload (with/without uncertainty) to validate this approach.

Decentralized Kinematic Control of a Cooperating System of Mobile Manipulators

2002 ◽  
Author(s):  
Michel Abou-Samah ◽  
Venkat Krovi
Keyword(s):  
Degree Of Freedom ◽  
Modular System ◽  
Mobile Manipulator ◽  
Mobile Manipulators ◽  
Relative Positioning ◽  
Mobile Platforms ◽  
Relative Configuration ◽  
Kinematic Control ◽  
Common Object ◽  
Positioning Errors

In this paper, we examine the development of a decentralized control framework for a modular system of wheeled mobile manipulators that can team up to cooperatively transport a large common object. Each individually autonomous mobile manipulator consists of a differentially-driven wheeled mobile robot (WMR) with a passive, two-degree-of-freedom, planar, revolute-jointed arm mounted in the plane parallel to the base of the WMR. The composite multi-degree-of-freedom vehicle, formed by placing a common object on the end-effector of two (or more) such mobile manipulator systems, possesses the ability to accommodate relative positioning errors of the mobile bases as well as change its relative configuration. Particular attention is paid for the development of kinematic control schemes for mobile manipulators, which take into account the non-holonomic constraints of the base and the presence of passive joints in the manipulator system. The control scheme developed for the individual mobile manipulators is then adapted for the decentralized kinematic control of two mobile manipulators carrying a common object along a desired trajectory. Experimental evaluation of the performance of the resulting approach and the ability of the overall collaborating system to accommodate, detect and correct for relative positioning errors between the mobile platforms is also presented.

scholarly journals An Exponential Varying-Parameter Neural Network for Repetitive Tracking of Mobile Manipulators

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Ying Kong ◽  
Qingqing Tang ◽  
Jingsheng Lei ◽  
Ruiyang Zhang
Keyword(s):  
Neural Network ◽  
Trajectory Planning ◽  
Matrix Equation ◽  
Mobile Manipulator ◽  
Mobile Manipulators ◽  
Time Varying ◽  
Repetitive Motion ◽  
End Effector ◽  
The Matrix ◽  
Simulation Results

A novel exponential varying-parameter neural network (EVPNN) is presented and investigated to solve the inverse redundancy scheme of the mobile manipulators via quadratic programming (QP). To suspend the phenomenon of drifting free joints and guarantee high convergent precision of the end effector, the EVPNN model is applied to trajectory planning of mobile manipulators. Firstly, the repetitive motion scheme for mobile manipulators is formulated into a QP index. Secondly, the QP index is transformed into a time-varying matrix equation. Finally, the proposed EVPNN method is used to solve the QP index via the matrix equation. Theoretical analysis and simulations illustrate that the EVPNN solver has an exponential convergent speed and strong robustness in mobile manipulator applications. Comparative simulation results demonstrate that the EVPNN possesses a superior convergent rate and accuracy than the traditional ZNN solver in repetitive trajectory planning with a mobile manipulator.

Decoupled Task- and Null-Space Dynamic Control of a Redundant Nonholonomic Mobile Manipulator

2006 ◽  
Author(s):  
Glenn D. White ◽  
Venkat N. Krovi
Keyword(s):  
Null Space ◽  
Dynamic Control ◽  
Mobile Manipulator ◽  
Mobile Manipulators ◽  
Redundancy Resolution ◽  
Task Space ◽  
Dynamic Interactions ◽  
End Effector ◽  
Internal Motions ◽  
Mobile Base

Our overall goal is to develop semi-autonomous and decentralized task performance capabilities during cooperative payload transport by a fleet of wheeled mobile manipulators (WMM). Each nonholonomic WMM consists of a planar two-link manipulator mounted on top of a differentially-driven wheeled mobile base. The nonholonomic base and the significant inherent redundancy create challenges for control of end-effector motion/force outputs. Nevertheless, realizing this capability is a critical precursor to decentralized payload manipulation operations. To this end, a dynamic redundancy resolution strategy is critical in order to control the dynamic interactions. The system dynamics are decomposed into a task space component (consisting of end-effector motions/forces) and a decoupled dynamically-consistent null-space part (of internal-motions/forces). A task-space controller is developed that allows each WMM module to be able to control its end-effector (motions/forces) interactions with respect to the payload. The surplus of actuation is then used to independently control internal-motions (of the mobile base) as long as they do not conflict with the primary goal. A variety of numerical simulations are then performed to test this capability of the end-effector and mobile base to independently track complex motion/force trajectories.

Dynamic redundancy resolution in a nonholonomic wheeled mobile manipulator

Robotica ◽  
2007 ◽  
Vol 25 (2) ◽  
pp. 147-156 ◽  
Author(s):  
Glenn D. White ◽  
Rajankumar M. Bhatt ◽  
Venkat N. Krovi
Keyword(s):  
Null Space ◽  
Subsequent Development ◽  
Nonholonomic Constraints ◽  
Mobile Manipulator ◽  
Mobile Manipulators ◽  
Redundancy Resolution ◽  
Task Space ◽  
End Effector ◽  
Internal Motions ◽  
Fixed Base

SUMMARYWheeled Mobile Manipulators (WMM) possess many advantages over fixed-base counterparts in terms of improved workspace, mobility and robustness. However, the combination of the nonholonomic constraints with the inherent redundancy limits effective exploitation of end-effector payload manipulation capabilities. The dynamic-level redundancy-resolution scheme presented in this paper decomposes the system dynamics into decoupled task-space (end-effector motions/forces) and a dynamically consistent null-space (internal motions/forces) component. This simplifies the subsequent development of a prioritized task-space control (of end-effector interactions) and a decoupled but secondary null-space control (of internal motions) in a hierarchical WMM controller. Various aspects of the ensuing novel capabilities are illustrated using a series of simulation results.

Virtual-mechanism-based analysis of cooperative manipulation

2005 ◽  
Vol 219 (3) ◽  
pp. 315-323
Author(s):  
H Liu ◽  
J S Dai ◽  
H Y Xu ◽  
H Li
Keyword(s):  
Trajectory Planning ◽  
Manipulation Planning ◽  
End Points ◽  
New Approach ◽  
Cooperative Manipulation ◽  
Hypothetical Mechanism ◽  
End Effectors ◽  
Cooperative Manipulators ◽  
Mechanism Theory

This paper proposes a new approach for analysing cooperative manipulation in which cooperative manipulators form a mechanism closure that allows a virtual-mechanism-based analysis to take place. The method is based on the geometry of manipulators during manipulation and converts the cooperative manipulation problem into the analysis of a hypothetical mechanism so that the mechanism theory can be used for the manipulation. This mechanism is hence generated by the fact that the end points (or geometric centres of respective grippers) of cooperative manipulators coincide with a virtual joint during cooperative manipulation. The analysis not only generates positions and orientations of the end effectors of cooperative manipulators but also produces corresponding link configurations that can be used for manipulation planning. The approach is further used for the orientation-based trajectory planning with two different cases. Simulations and discussions are made with respect to cooperative manipulations using two 2R manipulators and one 2R manipulators and one 3R manipulator.

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