Method and system for calculating weight and center of gravity of object lifted by robot

Patent metadata

Field	Value
Publication number	US-9399293-B2
Application number	US-201414501586-A
Country	US
Kind code	B2
Filing date	Sep 30, 2014
Priority date	Jun 11, 2014
Publication date	Jul 26, 2016
Grant date	Jul 26, 2016

Abstract

A method for calculating weight and center of gravity of an object lifted by a robot includes lifting an object, measuring a change in angle of each joint through an angle sensor provided for each joint of the gripper in the event of the lifting, and calculating angular velocity and acceleration of each joint, calculating, via a controller, acceleration of the object, measuring an upper pressing force and a lower pressing force using force sensors installed on the joints, and calculating, via the controller, the weight of the object using a vertical component of the acceleration of the object, gravitational acceleration, and the upper and lower pressing forces.

First claim

What is claimed is:

1. A method of controlling a system for calculating weight and/or center of gravity of an object for a robot, the method comprising:
pressing respective upper and lower surfaces of the object via upper and lower parts of a robotic gripper to grip the object;
lifting the object with the gripper;
measuring, during lifting of the object, a change in angle of each joint of the gripper through an angle sensor provided for each joint of the gripper and calculating angular velocity and angular acceleration of each joint;
calculating, via a controller, acceleration of the object using the angular velocity, the angular acceleration and a Jacobian matrix of the gripper;
measuring an upper pressing force with which the upper part of the gripper presses the upper surface of the object and a lower pressing force with which the lower part of the gripper presses the lower surface of the object using force sensors installed on the joints;
calculating, via the controller, the weight of the object using a vertical component of the acceleration of the object, a gravitational acceleration and the upper and lower pressing forces;
calculating, via the controller, an angular acceleration at which the object rotates around the center of gravity from positional changes of points at which the upper and lower parts of the gripper come into contact with the respective upper and lower surfaces of the object; and
calculating, via the controller, the center of gravity of the object from the calculated weight of the object, the calculated angular acceleration, the calculated upper and lower pressing forces, and positions of the points at which the upper and lower parts of the gripper come into contact with the respective upper and lower surfaces of the object.

2. The method according to claim 1 , wherein the controller calculates the acceleration of the object via the following equation:
{umlaut over (x)}=J{dot over (θ)}+J {umlaut over (θ)}

where {umlaut over (x)}=the acceleration of the object, J=the Jacobian matrix of the gripper, and θ=the angle of each joint of the gripper.

3. The method according to claim 1 , wherein the controller calculates the weight of the object via the following equation:

m
=

R
B

-

R
A

a
y

+
g

where m=the weight of the object, R A =the upper pressing force, R B =the lower pressing force, a y =the vertical component of the acceleration of the object, and g=the gravitational acceleration.

4. The method according to claim 1 , wherein, when a y <k 1 ×g, where a y is the vertical component of the acceleration of the object, k 1 is a setting coefficient, and g is the gravitational acceleration, the controller calculates the weight of the object via the following equation:

m
=

R
B

-

R
A

g

where m=the weight of the object, R A =the upper pressing force, R B =the lower pressing force, and g=the gravitational acceleration.

5. The method according to claim 1 , wherein the controller calculates the center of gravity of the object via the following equation:

-

1
12

⁢

mar
G
2

+

(

R
A

-

R
B

)

⁢

r
G

+

(

-

R
A

⁢

r
A

+

R
B

⁢

r
B

)

=
0

where m=the weight of the object, α=the angular acceleration of the object, r G =the center of gravity of the object, R A =the upper pressing force, R B =the lower pressing force, r A =the position at which the upper part of the gripper comes into contact with the upper surface of the object, and r B =the position at which the lower part of the gripper comes into contact with the lower surface of the object.

6. The method according to claim 1 , wherein, when α<k 2 , where α is the angular acceleration of the object, and k 2 is a setting coefficient, the controller calculates the center of gravity of the object in the process of calculating the center of gravity of the object via the following equation:

r
G

=

(

R
A

⁢

r
A

-

R
B

⁢

r
B

)

(

R
A

-

R
B

)

where r G =the center of gravity of the object, R A =the upper pressing force, R B =the lo

Assignees

• Hyundai Motor Co Ltd

Inventors

• Shin Wan Jae

Classifications

• B25J9/1638 Primary

  compensation for arm bending/inertia, pay load weight/inertia · CPC title

• G05B2219/39224

  Jacobian transpose control of force vector in configuration and cartesian space · CPC title

• G05B2219/40549

  Acceleration of end effector · CPC title

• B25J13/088

  with position, velocity or acceleration sensors · CPC title

• B25J19/028

  Piezoresistive or piezoelectric sensing devices · CPC title