On-line multi-criteria based collision-free posture generation of redundant manipulator in constrained workspace

Robotica ◽  
2002 ◽  
Vol 20 (6) ◽  
pp. 625-636 ◽  
Author(s):  
Jin-Liang Chen ◽  
Jing-Sin Liu ◽  
Wan-Chi Lee ◽  
Tzu-Chen Liang
Keyword(s):  
Null Space ◽  
Large Degree ◽  
Redundancy Resolution ◽  
Secondary Tasks ◽  
End Effector ◽  
Robotic Arms ◽  
Tracking Motion ◽  
On Line ◽  
Joint Limits ◽  
Joint Velocity

The manipulator with a large degree of redundancy is useful for realizing multiple tasks such as maneuvering the robotic arms in the constrained workspace, e.g. the task of maneuvering the end-effector of the manipulator along a pre-specified path into a window. This paper presents an on-line technique based on a posture generation rule to compute a null-space joint velocity vector in a singularity-robust redundancy resolution method. This rule suggests that the end of each link has to track an implicit trajectory that is indirectly resulted from the constraint imposed on tracking motion of the end-effector. A proper posture can be determined by sequentially optimizing an objective function integrating multiple criteria of the orientation of each link from the end-effector toward the base link as the secondary task for redundancy resolution, by assuming one end of the link is clamped. The criteria flexibly incorporate obstacle avoidance, joint limits, preference of posture in tracking, and connection of posture to realize a compromise between the primary and secondary tasks. Furthermore, computational demanding of the posture is reduced due to the sequential link-by-link computation feature. Simulations show the effectiveness and flexibility of the proposed method in generating proper postures for the collision avoidance and the joint limits as a singularity-robust null-space projection vector in maneuvering redundant robots within constrained workspaces.

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.

Resolution of redundant manipulators via distance optimization

2000 ◽  
Vol 214 (8) ◽  
pp. 1037-1047 ◽  
Author(s):  
M Z Ding ◽  
C J Ong ◽  
A N Poo
Keyword(s):  
Three Dimensional ◽  
Redundant Manipulators ◽  
Joint Position ◽  
Redundancy Resolution ◽  
End Effector ◽  
Numerical Examples ◽  
The Past ◽  
Shortest Distance ◽  
Joint Velocity ◽  
Velocity Level

Redundant manipulators are useful in practice as they have freedom in addition to that needed for a specific end-effector position. This additional freedom has to be properly resolved, and such redundancy resolution problems have been actively studied over the past decade. The most common scheme for redundancy resolution is achieved at the joint velocity level and does not take into account the presence of obstacles. This work presents a new scheme for redundancy resolution based on maximizing the shortest distance to obstacles. The aim is to resolve the redundancy by reconfiguring the robot to be at the safest pose or furthest from obstacles. The proposed scheme resolves the redundancy at the joint position level and, hence, has the advantage of ensuring collision-free motion. Several numerical examples in two- and three-dimensional spaces demonstrate the effectiveness of the proposed scheme.

Enhancing the Autonomy of Teleoperated Redundant Manipulators Through Fusion of Intelligent Control Modules

2002 ◽  
Vol 14 (3) ◽  
pp. 278-289 ◽  
Author(s):  
D. P. Thrishantha Nanayakkara ◽  
◽  
Kazuo Kiguchi ◽  
Tsukasa Murakami ◽  
Keigo Watanabe ◽  
...  
Keyword(s):  
Force Control ◽  
Degrees Of Freedom ◽  
Null Space ◽  
Redundancy Resolution ◽  
Control Task ◽  
Industrial Manipulator ◽  
Moving Obstacles ◽  
Vision Sensors ◽  
Fuzzy Neural ◽  
On Line

This paper presents a method for redundancy resolution of an industrial manipulator in a teleoperated force control task. A seven degree-of-freedom (DOF) industrial manipulator manufactured by the Mitsubishi Heavy Industries Ltd. is used for experiments. The task involves obeying a force command sent from a remote computer while autonomously adapting the posture to avoid unexpected obstacles moving toward the manipulator. Redundancy resolution is employed for autonomous adaptation of the configuration to avoid the obstacle while continuing the force control task. This self-adaptive skill on the slave manipulator side is very important because teleoperation is often performed in dangerous or partially unknown environments where unexpected changes such as moving obstacles can well be expected. In such situations, the control ability of the master side is very limited due to the practical limitations of vision sensors to capture a comprehensive view of the environment and the limitations of the degrees of freedom on the master manipulator. The proposed method relies on two modules of an intelligent controller on the slave side. The first is an on-line fuzzy neural network (FNN) for intelligent force control, and the second is a configuration controller that works in harmony with the first to exploit redundancy to react to avoid moving obstacles such that the latter does not inhibit the progress of the former. The second controller generates joint velocity commands in null space of the hand Jacobian, so that its activation does not affect the force controller. Here we show that the proposed method can skillfully avoid a moving obstacle without stopping the force control task. This skillful adaptation ability can significantly improve the efficiency and safety of teleoperated force control tasks with less burden on the master side. This paper presents some promising experimental results to demonstrate the effectiveness of the proposed method.

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.

Task-space dynamics and motion/force control of fixed-base manipulators under reaction null-space-based redundancy resolution

Robotica ◽  
2015 ◽  
Vol 34 (12) ◽  
pp. 2860-2877 ◽  
Author(s):  
Dragomir Nenchev ◽  
Ryohei Okawa ◽  
Hiroki Sone
Keyword(s):  
Null Space ◽  
Joint Space ◽  
Force Balance ◽  
Redundancy Resolution ◽  
Task Space ◽  
End Effector ◽  
Floating Base ◽  
Fixed Base ◽  
Space Dynamics ◽  
Reaction Null Space

SUMMARYThis paper introduces a task-space dynamics formulation for fixed-base serial-link kinematically redundant manipulators and a motion/force controller based on it. The aim is to alleviate joint-space instability problems that have been observed with other motion/force controllers. The dynamics are represented in floating-base coordinates, wherein the end effector is regarded as the floating base. This representation gives rise to a momentum-conserving redundancy resolution scheme based on the reaction null-space (RNS) method used in past studies on free-floating and flexible-base space robots. A generalized inverse is obtained that is shown to satisfy the conditions for dynamic consistency in the sense of the operational space (OS) formulation, but may lead to the joint-space instabilities observed earlier. The proposed controller is based on the pseudoinverse of the coupling inertia matrix and ensures reactionless link motion that does not disturb the force balance at the end effector. The performance of the RNS motion/force controller is examined by comparison to that with an OS motion/force controller. It is shown that while the performance in task-space of both controllers is satisfactory, the joint-space performance of the proposed controller is superior.

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.

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.

Pseudoinverse-type bi-criteria minimization scheme for redundancy resolution of robot manipulators

Robotica ◽  
2014 ◽  
Vol 33 (10) ◽  
pp. 2100-2113 ◽  
Author(s):  
Bolin Liao ◽  
Weijun Liu
Keyword(s):  
Robot Manipulator ◽  
Robot Manipulators ◽  
Weighting Factor ◽  
Redundancy Resolution ◽  
Type Solution ◽  
Revolute Joints ◽  
Joint Velocity ◽  
Joint Acceleration ◽  
Minimum Velocity ◽  
Minimization Scheme

SUMMARYIn this paper, a pseudoinverse-type bi-criteria minimization scheme is proposed and investigated for the redundancy resolution of robot manipulators at the joint-acceleration level. Such a bi-criteria minimization scheme combines the weighted minimum acceleration norm solution and the minimum velocity norm solution via a weighting factor. The resultant bi-criteria minimization scheme, formulated as the pseudoinverse-type solution, not only avoids the high joint-velocity and joint-acceleration phenomena but also causes the joint velocity to be near zero at the end of motion. Computer simulation results based on a 4-Degree-of-Freedom planar robot manipulator comprising revolute joints further verify the efficacy and flexibility of the proposed bi-criteria minimization scheme on robotic redundancy resolution.

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