A Methodology for tele-operating mobile manipulators with an emphasis on operator ease of use

Robotica ◽  
2012 ◽  
Vol 31 (3) ◽  
pp. 331-344 ◽  
Author(s):  
M. Frejek ◽  
S. B. Nokleby
Keyword(s):  
Degrees Of Freedom ◽  
Ease Of Use ◽  
Mobile Manipulator ◽  
Mobile Manipulators ◽  
Test Results ◽  
End Effector ◽  
Optimization Routine ◽  
Singular Configuration ◽  
6 Degrees Of Freedom ◽  
Mobile Base

SUMMARYAn algorithm for the tele-operation of mobile-manipulator systems with a focus on ease of use for the operator is presented. The algorithm allows for unified, intuitive, and coordinated control of mobile manipulators. It consists of three states. In the first state, a single 6-degrees-of-freedom (DOF) joystick is used to control the manipulator's position and orientation. The second state occurs when the manipulator approaches a singular configuration, resulting in the mobile base moving in a manner so as to keep the end-effector travelling in its last direction of motion. This is done through the use of a constrained optimization routine. The third state is entered when the operator returns the joystick to the home position. Both the mobile base and manipulator move with respect to one another keeping the end-effector stationary and placing the manipulator into an ideal configuration. The algorithm has been implemented on an 8-DOF mobile manipulator and the test results show that it is effective at moving the system in an intuitive 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.

Simplified Tele-Operation of Mobile-Manipulator Systems Using Knowledge of Their Singular Configurations

2009 ◽  
Author(s):  
Michael C. Frejek ◽  
Scott B. Nokleby
Keyword(s):  
Mobile Manipulator ◽  
End Effector ◽  
Control Approach ◽  
Singular Configurations ◽  
The Third ◽  
Preliminary Version ◽  
Optimization Routine ◽  
Position And Orientation ◽  
Singular Configuration ◽  
Mobile Base

An algorithm for the simplified tele-operation of a mobile-manipulator system is presented. It allows for unified, intuitive, and coordinated control. Unlike other approaches, the mobile-manipulator system is modelled and controlled as two separate entities rather than as a whole. The algorithm consists of three states. In the first state, a joystick is used to freely control the manipulator’s position and orientation. The second state occurs when the manipulator approaches a singular configuration. This causes the mobile base to proceed in such a way as to keep the end-effector moving in its last direction. This is done through the use of a simple optimization routine. The third state is triggered by the user: once the end-effector is in the desired position, the mobile base and manipulator both move with respect to one another keeping the end-effector stationary and placing the manipulator into an ideal configuration. The proposed algorithm avoids the problems of algorithmic singularities and simplifies the control approach. A preliminary version of the algorithm has been implemented on the Jasper mobile-manipulator system with success.

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.

Rate Kinematics for Mobile Manipulators

1992 ◽  
Author(s):  
Chau-Chang Wang ◽  
Nilanjan Sarkar ◽  
Vijay Kumar
Keyword(s):  
Nonholonomic Constraints ◽  
Mobile Manipulators ◽  
Weighted Norm ◽  
End Effector ◽  
Serial Chain ◽  
Mobile Base

Abstract When a serial-chain manipulator is mounted on a mobile base, the end-effector motion must be decomposed into the motion of the base and the motion of the manipulator. The problem of determining the actuator rates for a given end-effector motion is typically under constrained. A compact, analytical inverse rate kinematics solution is presented in which a weighted-norm of the joint rates is minimized. The method is capable of accomodating any type of joint as well as nonholonomic constraints. This framework allows the allocation of the end-effector motion between the manipulator and its mobile base according to user-prescribed preferences.

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.

scholarly journals A New Kinematic Model and Control Strategy for a Mobile Platform for Transporting Lightweight Manipulators

Electronics ◽  
2018 ◽  
Vol 7 (12) ◽  
pp. 441
Author(s):  
Daniel Feliu-Talegon ◽  
Andres San-Millan ◽  
Vicente Feliu-Batlle
Keyword(s):  
Control Strategy ◽  
Mechanical Design ◽  
Kinematic Model ◽  
Mobile Platform ◽  
Mobile Manipulator ◽  
Mobile Manipulators ◽  
The Real ◽  
And Control ◽  
Mobile Base

This work is concerned with the mechanical design and the description of the different components of a new mobile base for a lightweight mobile manipulator. These kinds of mobile manipulators are normally composed of multiple lightweight links mounted on a mobile platform. This work is focused on the description of the mobile platform, the development of a new kinematic model and the design of a control strategy for the system. The proposed kinematic model and control strategy are validated by means of experimentation using the real prototype. The workspace of the system is also defined.

Singularity, isotropy, and velocity transmission evaluation of a three translational degrees-of-freedom parallel robot

Robotica ◽  
2012 ◽  
Vol 31 (2) ◽  
pp. 193-202 ◽  
Author(s):  
Yongjie Zhao
Keyword(s):  
Performance Evaluation ◽  
Angular Velocity ◽  
Degrees Of Freedom ◽  
Jacobian Matrix ◽  
Parallel Robot ◽  
End Effector ◽  
Transmission Index ◽  
Delta Robot ◽  
Singular Configuration ◽  
Velocity Transmission

SUMMARYPerformance evaluation of a parallel robot is a multicriteria problem. By taking Delta robot as an object of study, this paper presents the kinematic performance evaluation of a three translational degrees-of-freedom parallel robot from the viewpoint of singularity, isotropy, and velocity transmission. It is shown that the determinant of a Jacobian matrix cannot measure the distance from the singular configuration due to the existing inverse kinematic singularity of a Delta robot. The determinants of inverse and direct kinematic Jacobian matrices are adopted for the measurement of distance from the singular configuration based on the theory of numerical linear dependence. The denominator of the Jacobian matrix will be lost in the computation of the condition number when the end-effector is on the centerline of the workspace, so the Delta robot may also be nearly at a singular configuration when the condition number of the Jacobian matrix is equal to 1. The velocity transmission index whose physical meaning is the maximum input angular velocity when the end-effector translates in the unit velocity is presented. The evaluation of singularity, isotropy, and velocity transmission of a Delta robot is investigated by simulation. The velocity transmission index can also be used for the velocity transmission evaluation of a parallel robot with pure rotational degrees-of-freedom based on the principle of similarity. The physical meaning is modified to be the maximum input velocity when the end-effector rotates in the unit angular velocity.

scholarly journals Optimal Image-Based Guidance of Mobile Manipulators using Direct Visual Servoing

Electronics ◽  
2019 ◽  
Vol 8 (4) ◽  
pp. 374 ◽  
Author(s):  
Álvaro Belmonte ◽  
José Ramón ◽  
Jorge Pomares ◽  
Gabriel Garcia ◽  
Carlos Jara
Keyword(s):  
Visual Servoing ◽  
Degrees Of Freedom ◽  
Mobile Manipulator ◽  
Robot Dynamics ◽  
Mobile Manipulators ◽  
Control Force ◽  
Robot Arm ◽  
Dynamical Behaviors ◽  
Control Framework ◽  
Image Trajectories

This paper presents a direct image-based controller to perform the guidance of a mobile manipulator using image-based control. An eye-in-hand camera is employed to perform the guidance of a mobile differential platform with a seven degrees-of-freedom robot arm. The presented approach is based on an optimal control framework and it is employed to control mobile manipulators during the tracking of image trajectories taking into account robot dynamics. The direct approach allows us to take both the manipulator and base dynamics into account. The proposed image-based controllers consider the optimization of the motor signals sent to the mobile manipulator during the tracking of image trajectories by minimizing the control force and torque. As the results show, the proposed direct visual servoing system uses the eye-in-hand camera images for concurrently controlling both the base platform and robot arm. The use of the optimal framework allows us to derive different visual controllers with different dynamical behaviors during the tracking of image trajectories.

scholarly journals EyeRobot: enabling telemedicine using a robot arm and a head-mounted display

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Kevin Yu ◽  
Thomas Wegele ◽  
Daniel Ostler ◽  
Dirk Wilhelm ◽  
Hubertus Feußner
Keyword(s):  
Pose Estimation ◽  
Degrees Of Freedom ◽  
Robot Arm ◽  
End Effector ◽  
Head Mounted Display ◽  
Local Site ◽  
Head Mounted Displays ◽  
Time Critical ◽  
6 Degrees Of Freedom ◽  
First Contact

AbstractTelemedicine has become a valuable asset in emergency responses for assisting paramedics in decision making and first contact treatment. Paramedics in unfamiliar environments or time-critical situations often encounter complications for which they require external advice. Modern ambulance vehicles are equipped with microphones, cameras, and vital sensors, which allow experts to remotely join the local team. However, the visual channels are rarely used since the statically installed cameras only allow broad views at the patient. They neither allow a close-up view nor a dynamic viewpoint controlled by the remote expert. In this paper, we present EyeRobot, a concept which enables dynamic viewpoints for telepresence using the intuitive control of the user’s head motion. In particular, EyeRobot utilizes the 6 degrees of freedom pose estimation capabilities of modern head-mounted displays and applies them in real-time to the pose of a robot arm. A stereo-camera, installed on the end-effector of the robot arm, serves as the eyes of the remote expert at the local site. We put forward an implementation of EyeRobot and present the results of our pilot study which indicates its intuitive control.

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