US 5,550,953 AGranted

On-line method and apparatus for coordinated mobility and manipulation of mobile robots

AssigneeThe United States of America as represented by the Administrator of the National Aeronautics and Space Administration

InventorHomayoun Seraji

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Abstract

A simple and computationally efficient approach is disclosed for on-line coordinated control of mobile robots consisting of a manipulator arm mounted on a mobile base. The effect of base mobility on the end-effector manipulability index is discussed. The base mobility and arm manipulation degrees-of-freedom are treated equally as the joints of a kinematically redundant composite robot. The redundancy introduced by the mobile base is exploited to satisfy a set of user-defined additional tasks during the end-effector motion. A simple on-line control scheme is proposed which allows the user to assign weighting factors to individual degrees-of-mobility and degrees-of-manipulation, as well as to each task specification. The computational efficiency of the control algorithm makes it particularly suitable for real-time implementations. Four case studies are discussed in detail to demonstrate the application of the coordinated control scheme to various mobile robots.

Claims14

Dependent claims

A method of controlling a mobile robot, the robot of the type having a mobile base having at least one degree of mobility and a manipulatable arm having at least one degree of manipulation;

the method comprising the steps of:
(a) generating a forward kinematic model that relates arm and base joint coordinates to end-effector coordinates;
(b) generating a differential kinematic model that relates end-effector velocity to arm and base joint velocities including Jacobian matrices of the arm and base, respectively;
(c) augmenting by column the arm Jacobian matrix with the base Jacobian matrix to obtain an overall end-effector Jacobian matrix where the availability of base mobility appears as extra columns in the end-effector Jacobian matrix because of effectively increasing the dimension of the joint space;
(d) augmenting by row the end-effector Jacobian matrix of step (c) with a constraint Jacobian matrix which relates to a user-defined additional task to be accomplished due to kinematic redundancy where said additional task results in extra rows in the end-effector Jacobian matrix due to an increase of the task space;
(e) selecting end-effector and constraint task weighting factors and arm and base joint velocity weighting factors;
(f) finding the optimal arm and base motions using a closed-loop damped-least-squares approach;
and
(g) moving the arm and base of said robot in accordance with the optimal motions resulting from carrying out steps (a) through (f).

6 more elements

A method for on-line, real-time control of a mobile robot having a mobile base and a manipulatable arm mounted on the base to provide a number of degrees-of-freedom equal to the sum of the number of degrees-of-base-mobility and the number of degrees-of-arm-manipulation, the robot operating in a multi-dimension task space wherein the number of task-space-dimensions is less than the degrees-of-freedom;

the method comprising the steps of:
(a) generating a forward kinematic model that relates arm and base joint coordinates to end-effector coordinates;
(b) generating a differential kinematic model that relates end-effector velocity to arm and base joint velocities including Jacobian matrices of the arm and base, respectively;
(c) augmenting by column the arm Jacobian matrix with the base Jacobian matrix to obtain an overall end-effector Jacobian matrix where the availability of base mobility appears as extra columns in the end-effector Jacobian matrix because of effectively increasing the dimension of the joint space;
(d) augmenting by row the end-effector Jacobian matrix of step (c) with a constraint Jacobian matrix which relates to a user-defined additional task to be accomplished due to kinematic redundancy where said additional task results in extra rows in the end-effector Jacobian matrix due to an increase of the task space;
(e) selecting end-effector and constraint task weighting factors and arm and base joint velocity weighting factors;
(f) finding the optimal arm and base motions using a closed-loop damped-least-squares approach;
and
(g) moving the arm and base of said robot in accordance with the optimal motions resulting from carrying out steps (a) through (f).

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/231,597Filed 20 Apr 1994
Granted: 27 Aug 1996
Term ends: Not estimatedThe source records don’t support an estimate.

Classification12 codes

B25J 9/162
Characterised by special kind of manipulator, e.g. planar, scara, gantry, cantilever, space, closed chain, passive/active joints and tendon…
G05B 2219/39081
Robotics, robotics to robotics hand: inexact solution for orientation or other DOF with relation to type of task
G05B 2219/39172
Robotics, robotics to robotics hand: vehicle, coordination between manipulator arm and its moving vehicle
G05B 2219/39174
Robotics, robotics to robotics hand: add DOFs of mobility to DOFs of manipulator to add user defined tasks to motion