Method for controlling movement of a robot

Patent metadata

Field	Value
Publication number	US-11717962-B2
Application number	US-202117170911-A
Country	US
Kind code	B2
Filing date	Feb 9, 2021
Priority date	Aug 10, 2018
Publication date	Aug 8, 2023
Grant date	Aug 8, 2023

Abstract

A method for controlling movement of a robot having a plurality of links connected by rotatably driven joints includes the steps of: a) defining a target speed vector of a reference point of the robot in Cartesian space; b) determining rotation speeds ({dot over (q)}ref) of the joints which minimize a weighted sum, the weighted sum having for summands i) a discrepancy (∥{dot over (x)}refk−J{dot over (q)}refk∥Wx) between the target speed vector ({dot over (x)}ref) and an actual speed vector ({dot over (x)}act) calculated from actual rotation speeds of the joints; and ii) a rate of change(1TS⁢q.refk-q.refk-1Wa)of the target rotation speeds; and c) setting the rotation speeds ({dot over (q)}ref) determined in step (b) as target rotation speeds of the joints.

First claim

What is claimed is:

1. A method for controlling movement of a robot comprising a plurality of links connected by rotatably driven joints, the method comprising the steps of:
a) defining a target speed vector of a reference point of the robot in Cartesian space;
b) determining rotation speeds ({dot over (q)} ref ) of the joints which minimize a weighted sum, the weighted sum having for summands
i) a discrepancy ((∥{dot over (x)} ref k −J{dot over (q)} ref k ∥ W x ) between the target speed vector ({dot over (x)} ref ) and an actual speed vector ({dot over (x)} act ) calculated from actual rotation speeds of the joints; and
ii) a rate of change

(

1

T
S

⁢



q
.

ref
k

-

q
.

ref

k
-
1



W
a

)

 of the target rotation speeds; and
c) setting the rotation speeds ({dot over (q)} ref ) determined in step (b) as target rotation speeds of the joints.

2. The method of claim 1 , wherein the discrepancy (∥{dot over (x)} ref k −J{dot over (q)} ref k ∥ W x ) between the target speed vector ({dot over (x)} ref ) and an actual speed vector ({dot over (x)} act ) is weighted by direction of translation and/or rotation.

3. The method of claim 1 , wherein a movement of the robot approaches a workpiece surface, and a discrepancy in a direction perpendicular to the workpiece surface is weighted more than a discrepancy in a direction parallel to the workpiece surface.

4. The method of claim 1 , wherein the rate of change

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1

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S

⁢



q
.

ref
k

-

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ref

k
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1

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is weighted by joint.

5. The method of claim 4 , wherein an angular acceleration in a proximal joint is weighted more than an angular acceleration in a distal joint.

6. The method of claim 1 , wherein the discrepancy comprises a scalar product of a vector difference ({dot over (x)} ref k −J{dot over (q)} ref k ) between the target speed vector ({dot over (x)} ref ) in Cartesian space and a speed vector (J{dot over (q)} ref k ) in Cartesian space calculated from the determined rotation speeds, and the vector difference ({dot over (x)} ref k −J{dot over (q)} ref k ) multiplied by a weighting matrix (W x ).

7. The method of claim 1 , wherein the rate of change (∥{dot over (q)} ref k −{dot over (q)} ref k-1 ∥ W x ) of the target rotation speeds is calculated as the scalar product of a vector difference between a vector of the target rotation speeds ({dot over (q)} ref k ) and the vector of rotation speeds ({dot over (q)} ref k-1 ) at a previous instant (k−1) multiplied by a weighting matrix (W α W).

8. The method of claim 1 , wherein an angle range of at least one of the joints is limited, and a third summand (γΨ T {dot over (q)} ref k ) of the weighted sum is neutral when the at least one of the joints is far from a limit of the angle range and is high when the at least one of the joints is close to and approaching the limit and/or which is low when the when the at least one of the joints is close to and moving away from the limit.

9. The method of claim 8 , wherein the third summand (γΨ T {dot over (q)} ref k ) diverges at the limit.

Assignees

• Abb Schweiz Ag

Inventors

• Groth Tomas
• Wahrburg Arne

Classifications

• B25J9/1651 Primary

  acceleration, rate control · CPC title

• B25J9/06

  characterised by multi-articulated arms · CPC title

• G05B2219/39322

  Force and position control · CPC title

• G05B2219/43188

  Vector speed with feedback · CPC title

• G05B2219/50391

  Robot · CPC title