Complementary projector for null-space stiffness control of redundant assembly robot arm

2019 ◽  
Vol 39 (4) ◽  
pp. 696-714
Author(s):  
Nikola Lukic ◽  
Petar B. Petrovic
Keyword(s):  
Control System ◽  
Null Space ◽  
Open Architecture ◽  
Robot Arm ◽  
Task Space ◽  
Simulation Experiments ◽  
Redundant Robot ◽  
Content Type ◽  
Physical Experiments ◽  
Stiffness Control

Purpose Stiffness control of redundant robot arm, aimed at using extra degrees of freedom (DoF) to shape the robot tool center point (TCP) elastomechanical behavior to be consistent with the essential requirements needed for a successful part mating process, i.e., to mimic part supporting mechanism with selective quasi-isotropic compliance (Remote Center of Compliance – RCC), with additional properties of inherent flexibility. Design/methodology/approach Theoretical analysis and synthesis of the complementary projector for null-space stiffness control of kinematically redundant robot arm. Practical feasibility of the proposed approach was proven by extensive computer simulations and physical experiments, based on commercially available 7 DoF SIA 10 F Yaskawa articulated robot arm, equipped with the open-architecture control system, system for generating excitation force, dedicated sensory system for displacement measurement and a system for real-time acquisition of sensory data. Findings Simulation experiments demonstrated convergence and stability of the proposed complementary projector. Physical experiments demonstrated that the proposed complementary projector can be implemented on the commercially available anthropomorphic redundant arm upgraded with open-architecture control system and that this projector has the capacity to efficiently affect the task-space TCP stiffness of the robot arm, with a satisfactory degree of consistency with the behavior obtained in the simulation experiments. Originality/value A novel complementary projector was synthesized based on the adopted objective function. Practical verification was conducted using computer simulations and physical experiments. For the needs of physical experiments, an adequate open-architecture control system was developed and upgraded through the implementation of the proposed complementary projector and an adequate system for generating excitation and measuring displacement of the robot TCP. Experiments demonstrated that the proposed complementary projector for null-space stiffness control is capable of producing the task-space TCP stiffness, which can satisfy the essential requirements needed for a successful part-mating process, thus allowing the redundant robot arm to mimic the RCC supporting mechanism behavior in a programmable manner.

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 Compliant behaviour of redundant robot arm - experiments with null-space

2015 ◽  
Vol 12 (1) ◽  
pp. 81-98
Author(s):  
Petar Petrovic ◽  
Nikola Lukic ◽  
Ivan Danilov
Keyword(s):  
Stiffness Matrix ◽  
Jacobian Matrix ◽  
Null Space ◽  
Joint Space ◽  
Robot Arm ◽  
Kinematic Redundancy ◽  
Redundant Robot ◽  
Redundant Robots ◽  
Compliant Behavior ◽  
Congruent Transformation

This paper presents theoretical and experimental aspects of Jacobian nullspace use in kinematically redundant robots for achieving kinetostatically consistent control of their compliant behavior. When the stiffness of the robot endpoint is dominantly influenced by the compliance of the robot joints, generalized stiffness matrix can be mapped into joint space using appropriate congruent transformation. Actuation stiffness matrix achieved by this transformation is generally nondiagonal. Off-diagonal elements of the actuation matrix can be generated by redundant actuation only (polyarticular actuators), but such kind of actuation is very difficult to realize practically in technical systems. The approach of solving this problem which is proposed in this paper is based on the use of kinematic redundancy and nullspace of the Jacobian matrix. Evaluation of the developed analytical model was done numerically by a minimal redundant robot with one redundant d.o.f. and experimentally by a 7 d.o.f. Yaskawa SIA 10F robot arm.

Adaptive control of redundant robot manipulators with null-space compliance

2018 ◽  
Vol 38 (5) ◽  
pp. 615-624 ◽  
Author(s):  
Qing Xu ◽  
Shuzhi Sam Ge
Keyword(s):  
Adaptive Control ◽  
Null Space ◽  
Robot Manipulator ◽  
Impedance Control ◽  
Robot Manipulators ◽  
Design Procedure ◽  
Space Velocity ◽  
Redundant Robot ◽  
Content Type ◽  
Reference Velocity

Purpose The purpose of this paper is to propose an adaptive control for a redundant robot manipulator interacting physically with the environment, especially with the existence of humans, on its body. Design/methodology/approach The redundant properties of the robot manipulator are used and a reference velocity variable is introduced to unify the operation-space tracking control and the null-space impedance control under one common framework. Neural networks are constructed to deal with unstructured and unmodeled dynamic nonlinearities. Lyapunov function is used during the course of control design and simulation studies are carried out to further illustrate the effectiveness of the proposed strategies. Findings Satisfying tracking performance in the operation-space and compliance behavior in the null-space of the redundant robot manipulator are ensured simultaneously. Originality/value The design procedure of redundant robot manipulators control can be greatly simplified, and the framework of multi-priority control can be transformed into a joint-space velocity tracking problem via the introducing of a reference velocity variable.

Manipulator system designs for drawing random objects through point cloud posture estimation

2021 ◽  
pp. 095440542097946
Author(s):  
Ching-Chang Wong ◽  
Hsuan Ming Feng ◽  
Yu-Cheng Lai ◽  
Hsiang-Yun Chen
Keyword(s):  
Point Cloud ◽  
Null Space ◽  
Robot Manipulator ◽  
Search Algorithm ◽  
Movement Control ◽  
Control Policy ◽  
Device Management ◽  
Redundant Robot ◽  
Better Regulation ◽  
The Right

This paper designed a 7-DOF redundant robot manipulator that can flexibly and efficiently pick-up random objects. The developed 7-DOF machine with an additional redundancy achieved great progress in terms of flexibility and efficiency in the operational space. A robot operating system (ROS) was used to configure the manipulator system’s software modules, supporting convenient system interface, appropriate movement control policy, and powerful hardware device management for better regulation of the manipulator’s motions. A 3D type Point Cloud Library (PCL) was utilized to perform a novel point cloud image pre-processing method that did not only reduce the point cloud number but also maintained the original quality. The results of the experiment showed that the estimation speed in object detection and recognition procedure improved significantly. The redundant robot manipulator architecture with the two-stage search algorithm was able to find the optimal null space. Suitable parameters in D-H transformation of forward kinematics were selected to efficiently control and position the manipulator in the right posture. Meanwhile, the reverse kinematics estimated all angles of the joints through the known manipulator position, orientation, and redundancy. Finally, motion panning implementation of manipulator rapidly and successfully reached the random object position and automatically drew it up to approximate the desired target.

DEVELOPMENT OF AN ARTICULATION ROBOT ARM

2017 ◽  
Vol 41 (3) ◽  
pp. 443-455
Author(s):  
Kuo-Lan Su ◽  
Jian-Fu Weng ◽  
Jr-Hung Guo ◽  
Kai-Lu Cai
Keyword(s):  
Control System ◽  
Vision System ◽  
Motion Trajectory ◽  
Robot Arm ◽  
Plc Control ◽  
Plc Control System

This article describes the design of an articulation robot arm with seven joints. The control core of the robot arm is the module-based system built using the Mitsubishi Q series programming logical controller (PLC). The robot arm contains seven AC servomotors, seven driver devices, a vision system and a PLC control system. The PLC-based controller programs the motion trajectory of the gripper to catch or hold the objects and finish the assigned tasks. Kinect system (Asus Xtion Pro-Live, or called RGB-D sensor) acts as the vision system to recognize shape and color of each object. During the experiments, we found that the robot arm recognizes the shape and color of each object, and catches each object moving to the assigned box with the same color.

scholarly journals Reference trajectory tracking for a multi-DOF robot arm

2015 ◽  
Vol 25 (4) ◽  
pp. 513-527 ◽  
Author(s):  
Róbert Krasňanský ◽  
Peter Valach ◽  
Dávid Soós ◽  
Javad Zarbakhsh
Keyword(s):  
Data Exchange ◽  
Iterative Solution ◽  
Reference Trajectory ◽  
Robot Arm ◽  
Task Space ◽  
Joint Configuration ◽  
Matlab Simulink ◽  
Stepper Motors ◽  
Homogeneous Transformation Matrix ◽  
Kinematic Transformation

Abstract This paper presents the problem of tracking the generated reference trajectory by the simulation model of a multi-DOF robot arm. The kinematic transformation between task space and joint configuration coordinates is nonlinear and configuration dependent. To obtain the solution of the forward kinematics problem, the homogeneous transformation matrix is used. A solution to the inverse kinematics is a vector of joint configuration coordinates calculated using of pseudoinverse Jacobian technique. These coordinates correspond to a set of task space coordinates. The algorithm is presented which uses iterative solution and is simplified by considering stepper motors in robot arm joints. The reference trajectory in Cartesian coordinate system is generated on-line by the signal generator previously developed in MS Excel. Dynamic Data Exchange communication protocol allows sharing data with Matlab-Simulink. These data represent the reference tracking trajectory of the end effector. Matlab-Simulink software is used to calculate the representative joint rotations. The proposed algorithm is demonstrated experimentally on the model of 7-DOF robot arm system.

EVALUATION OF THE TECHNICAL CONDITION OF THE FLAPE BEARING WITH ADJUSTABLE RIGIDITY

2020 ◽  
Vol 6 ◽  
pp. 101-105
Author(s):  
A.V. SYTIN ◽  
N.V. TOKMAKOV ◽  
A.V. GORIN ◽  
М.А. TOKMAKOVA
Keyword(s):  
Control System ◽  
Block Diagram ◽  
Technical Condition ◽  
Qualitative Assessment ◽  
Schematic Diagram ◽  
Constructive Solution ◽  
Experimental Stand ◽  
Bearing Stiffness ◽  
Stiffness Control

The article considered the assessment of the technical condition of a petal bearing with adjustable stiffness. A schematic diagram of bearing stiffness control is presented. Revealed a constructive solution providing rigidity adjustment. For a qualitative assessment of the technical condition, a petal bearing was modeled in the VATCAD environment. The schematic diagram and block diagram of the control system of the experimental stand for assessing the technical condition of the petal bearing are described. Recommendations are given for the further application of the concept of assessing the technical condition of petal bearings.

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