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.

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.

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 On path following control of nonholonomic mobile manipulators

2009 ◽  
Vol 19 (4) ◽  
pp. 561-574 ◽  
Author(s):  
Alicja Mazur ◽  
Dawid Szakiel
Keyword(s):  
Control Algorithm ◽  
Dynamic Control ◽  
Path Following ◽  
Mobile Manipulator ◽  
Mobile Manipulators ◽  
Control Laws ◽  
Kinematic Control ◽  
Motion Constraints ◽  
Path Following Control ◽  
Cascade Structure

On path following control of nonholonomic mobile manipulatorsThis paper describes the problem of designing control laws for path following robots, including two types of nonholonomic mobile manipulators. Due to a cascade structure of the motion equation, a backstepping procedure is used to achieve motion along a desired path. The control algorithm consists of two simultaneously working controllers: the kinematic controller, solving motion constraints, and the dynamic controller, preserving an appropriate coordination between both subsystems of a mobile manipulator, i.e. the mobile platform and the manipulating arm. A description of the nonholonomic subsystem relative to the desired path using the Frenet parametrization is the basis for formulating the path following problem and designing a kinematic control algorithm. In turn, the dynamic control algorithm is a modification of a passivity-based controller. Theoretical deliberations are illustrated with simulations.

scholarly journals A Fuzzy Backstepping Control of a Mobile Manipulator with Torque Limits Avoidance

1970 ◽  
Vol 5 (2) ◽  
pp. 127-133
Author(s):  
Mohamed Boukattaya ◽  
Tarak Damak ◽  
Mohamed Jallouli
Keyword(s):  
Control Algorithm ◽  
Null Space ◽  
Joint Torque ◽  
Mobile Manipulator ◽  
Redundancy Resolution ◽  
Task Space ◽  
End Effector ◽  
Simulation Results ◽  
Pseudo Inverse ◽  
Selection Of

In this paper, we present a dynamic redundancy resolution technique for mobile manipulator subject to joint torque limits. First, the dynamic model of the mobile manipulator in feasible motion space is given. Next, a control algorithm is proposed which completely decouples the motion of the system into the end-effector motion in the task space and an internal motion in the null space and controls them in prioritized basis with priority given to the primary task space and enables the selection of characteristics in both subspaces separately. A special attention is given to the joints torque limits avoidance where a new weighted pseudo-inverse of the Jacobian that accounts for both inertia and torque limits is proposed to solve problems inherent to torque limits of the system. Simulation results are given to illustrate the coordination of two subsystems in executing the desired trajectory without violating the joint torque limits.

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.

Mission Design of Mobile Manipulators in Cluttered Environments for Service Applications

2020 ◽  
pp. 1358-1376
Author(s):  
Elias K. Xidias ◽  
Philip N. Azariadis ◽  
Nikos A. Aspragathos
Keyword(s):  
Inverse Image ◽  
Mission Design ◽  
Mobile Manipulator ◽  
Indoor Environments ◽  
Mobile Manipulators ◽  
Higher Dimension ◽  
End Effector ◽  
Cluttered Environments ◽  
Cost Simulation ◽  
The Given

The purpose of this paper is to present a mission design approach for a service mobile manipulator which is moving and manipulating objects in partly known indoor environments. The mobile manipulator is requested to pick up and place objects on predefined places (stations). The proposed approach is based on the Bump-Surface concept to represent robot's environment through a single mathematical entity. The solution of the mission design problem is searched on a higher dimension Bump-Surface in such a way that its inverse image into the actual robot environment satisfies the given objectives and constraints. The problem's objectives consist of determining the best feasible paths for both the mobile platform and for the manipulator's end-effector so that all the stations are served at the lowest possible cost. Simulation examples are presented to show the effectiveness of the presented approach.

scholarly journals Planning of Collision-Free Trajectory for Mobile Manipulators

2013 ◽  
Vol 18 (2) ◽  
pp. 475-489
Author(s):  
G. Pająk
Keyword(s):  
Mobile Manipulator ◽  
Reference Trajectory ◽  
Mobile Manipulators ◽  
Redundancy Resolution ◽  
Task Space ◽  
End Effector ◽  
Acceleration Level ◽  
Manipulability Measure ◽  
And Control ◽  
Penalty Function Approach

A method of planning sub-optimal trajectory for a mobile manipulator working in the environment including obstacles is presented. The path of the end-effector is defined as a curve that can be parameterized by any scaling parameter, the reference trajectory of a mobile platform is not needed. Constraints connected with the existence of mechanical limits for a given manipulator configuration, collision avoidance conditions and control constraints are considered. The motion of the mobile manipulator is planned in order to maximize the manipulability measure, thus to avoid manipulator singularities. The method is based on a penalty function approach and a redundancy resolution at the acceleration level. A computer example involving a mobile manipulator consisting of a nonholonomic platform and a SCARA type holonomic manipulator operating in a two-dimensional task space is also presented.

Sub-optimal trajectory planning for mobile manipulators

Robotica ◽  
2014 ◽  
Vol 33 (6) ◽  
pp. 1181-1200 ◽  
Author(s):  
Grzegorz Pajak ◽  
Iwona Pajak
Keyword(s):  
Optimal Trajectory ◽  
Control Algorithm ◽  
Nonholonomic Constraints ◽  
Mobile Manipulator ◽  
Reference Trajectory ◽  
Mobile Manipulators ◽  
Control Constraints ◽  
Manipulability Measure ◽  
And Control ◽  
Optimal Trajectory Planning

SUMMARYThis paper presents a method of planning a sub-optimal trajectory for a mobile manipulator subject to mechanical and control constraints. The path of the end-effector is defined as a curve that can be parameterised by any scaling parameter—the reference trajectory of a mobile platform is not needed. Constraints connected with the existence of mechanical limits for a given manipulator configuration, collision avoidance conditions and control constraints are considered. Nonholonomic constraints in a Pfaffian form are explicitly incorporated to the control algorithm. To avoid manipulator singularities, the motion of the robot is planned in order to maximise the manipulability measure.

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 Position-force control of mobile manipulator – nonadaptive and adaptive case

2017 ◽  
Vol 27 (4) ◽  
pp. 487-503 ◽  
Author(s):  
Mirela Kaczmarek ◽  
Wojciech Domski ◽  
Alicja Mazur
Keyword(s):  
Force Control ◽  
Control Algorithm ◽  
Parametric Uncertainty ◽  
Mobile Manipulator ◽  
Control Law ◽  
Mobile Manipulators ◽  
Constrained Dynamics ◽  
Holonomic Constraint ◽  
System A ◽  
Theoretical Considerations

AbstractThis article presents a control algorithm for nonholonomic mobile manipulators with a simple, geometric holonomic constraint imposed on the robot’s arm. A mathematical model in generalized, auxiliary and linearized coordinates is presented, as well as the constrained dynamics of the robotic system. A position-force control law is proposed, both for the fully known robot’s model, as well as for the model with parametric uncertainty in the dynamics. Theoretical considerations are supported by the results of computer simulations.

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