Dynamical system-based robot velocity control

Patent metadata

Field	Value
Publication number	US-2016000511-A1
Application number	US-201414323047-A
Country	US
Kind code	A1
Filing date	Jul 3, 2014
Priority date	Jul 3, 2014
Publication date	Jan 7, 2016
Grant date	—

Abstract

A robotic system includes an end-effector and a control system. The control system includes a processor, a dynamical system module (DSM), and a velocity control module (VCM). Via execution of a method, the DSM processes inputs via a flow vector field and outputs a control velocity command. The inputs may include an actual position, desired goal position, and demonstrated reference path of the end-effector. The VCM receives an actual velocity of the end-effector and the control velocity command as inputs, and transmits a motor torque command to the end-effector as an output command. The control system employs a predetermined set of differential equations to generate a motion trajectory of the end-effector in real time that approximates the demonstrated reference path. The control system is also programmed to modify movement of the end-effector in real time via the VCM in response to perturbations of movement of the end-effector.

First claim

1 . A robotic system comprising:
an end-effector; and a control system in communication with the end-effector, including:
a processor;
a dynamical system module (DSM) which processes a set of inputs via a flow vector field and outputs a control velocity command, wherein the set of inputs includes an actual position of the end-effector, a desired goal position of the end-effector, and a demonstrated reference path of the end-effector; and
a velocity control module (VCM) in communication with the dynamical system module, wherein the velocity control module receives an actual velocity of the end-effector and the control velocity command as inputs, and generates a motor torque command to the end-effector as an output command;
wherein the control system employs a predetermined set of differential equations to generate a motion trajectory of the end-effector in real time that approximates the demonstrated reference path, and wherein the control system is programmed to adapt or modify a movement of the end-effector in real time via the velocity control module in response to perturbations of movement of the end-effector.

2 . The robotic system of claim 1 , wherein the dynamical system module includes a path transformation module programmed to transform a frame of reference of the flow vector field, and a path blending module that incorporates a tunable linear interpolation term into the differential equations so as to blend together a path of the end-effector drawn forward from a start position with a path drawn backward from a goal position.

3 . The robotic system of claim 2 , wherein the control system is operable to append a flow vector field function defining the flow vector field with a transform that rotates a frame of reference of the flow vector field function to match an orientation of the demonstrated path with an orientation of the new start and goal positions.

4 . The robotic system of claim 1 , wherein the end-effector is a robotic gripper.

5 . The robotic system of claim 1 , wherein velocity control module operates at a cycle rate that is at least 5× higher than a cycle rate of the dynamical system module.

6 . The robotic system of claim 6 , wherein the cycle rate of the dynamical system module is 20-40 Hz and the cycle rate of the velocity control module is 100-1000 Hz.

7 . A method comprising:
processing a set of inputs via a dynamical system module (DSM) having a predetermined flow vector field, including an actual position of an end-effector of a robotic system, a desired goal position of the end-effector, and a demonstrated reference path of the end-effector, including employing a predetermined set of differential equations to generate a motion trajectory of the end-effector in real time to approximate the demonstrated reference path; outputting a control velocity command via the dynamical system module; receiving and processing an actual velocity of the end-effector and the control velocity command from the dynamical system module via a velocity control module (VCM); and generating a motor torque command to the end-effector via the velocity control module to thereby adapt or modify a movement of the end-effector in real time in response to perturbations of movement of the end-effector.

8 . The method of claim 7 , further comprising transforming a frame of reference of the flow vector field via a path transformation module of the control system, and incorporating a tunable linear interpolation term into the differential equations via a path blending module of the control system so as to blend together a path of the end-effector drawn forward from a start position with a path drawn backward from a goal position.

9 . The method of claim 7 , further comprising appending a flow vector field function defining the flow vector field with a transform that rotates a frame of reference of the flow vector field function to thereby match an orientation of the demonstrated path with an orientation of the new start and goal positions.

10 . The method of claim 7 , wherein transmitting a motor torque command to the end-effector includes transmitting a motor torque command to a robotic gripper.

11 . The method of claim 7 , further comprising operating the velocity control module at a cycle rate that is at least 5× higher than a cycle rate of the dynamical system module.

12 . The method of claim 11 , wherein the cycle rate of the dynamical system module is 20-40 Hz and the cycle rate of the velocity control module is 100-1000 Hz.

Assignees

• Gm Global Tech Operations Inc

Inventors

• Hoffmann Heiko
• Payton David W
• Mitchell Derek

Classifications

• A61B2560/02

  Operational features · CPC title

• A61B19/2203 Primary

  Human Necessities · mapped topic

• G05B19/19

  characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path · CPC title

• B25J9/1628 Primary

  characterised by the control loop · CPC title

• A61B34/30

  Surgical robots · CPC title