VISION CORRECTION METHOD FOR TOOL CENTER POINT OF A ROBOT MANIPULATOR

• US 20130035791A1
• Filed: 03/08/2012
• Published: 02/07/2013
• Est. Priority Date: 08/05/2011
• Status: Active Grant

• Current Assignee: Fulian Yuzhan Precision Technology Company Limited, Cloud Network Technology Singapore Pte. Ltd. (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. (Hon Hai Precision Industry Co., Ltd.), Hon Hai Precision Industry Co., Ltd.
• Inventors: CHIU, LONG-EN, FU, SHU-JUN, ZHAO, GANG
• Granted Patent: US 9,043,024 B2
• Time in Patent Office: Days
• US Class Current: 700/253
• CPC Class Codes: B25J 9/1692 Calibration of manipulator
• CPC Class Codes: G05B 2219/39026 Calibration of manipulator while tool is mounted

Abstract

A vision correction method for establishing the position of a tool center point (TCP) for a robot manipulator includes the steps of: defining a preset position of the TCP; defining a preset coordinate system T_G with the preset position of the TCP as its origin; capturing a two-dimensional picture of the preset coordinate system T_G to establish a visual coordinate system T_V; calculating a scaling ratio λ of the vision coordinate system T_V relative to the preset coordinate system T_G; rotating the TCP relative to axes of the preset coordinate system T_G; capturing pictures of the TCP prior to and after rotation; calculating the deviation ΔP between the preset position and actual position of the TCP; correcting the preset position and corresponding coordinate system T_G using ΔP, and repeating the rotation through correction steps until ΔP is less than or equal to a maximum allowable deviation of the robot manipulator.

Claims

1. A vision correction method for tool center point (TCP) of a robot manipulator, the robot manipulator comprising a main body, a drive mechanism, a controller for controlling the drive mechanism, a tool assembled to a distal end of the main body and having the TCP, and a vision lens positioned to one side of the tool;

the robot manipulator predefining a basic coordinate system having three axes, the vision correction method comprising the following steps;

defining a preset position P₀ of the TCP and establishing a preset coordinate system T_G based on the preset position P₀, defining the actual position of the TCP as P₁;

capturing a picture of the actual TCP and establishing a two-dimensional visual coordinate system T_V based on the picture, defining the corresponding coordinate of the actual TCP formed within the two-dimensional visual coordinate system T_V as P₁′

;

calculating a scaling ratio λ

of the vision coordinate system T_V relative to the preset coordinate system T_G;

driving the tool to rotate relative to one axis of the preset coordinate system T_G by θ

₁ degrees, and obtaining the coordinate value P₂ of the TCP of the tool;

capturing a picture of the actual TCP and obtaining the corresponding coordinate P₂′

of the actual TCP formed within the visual coordinate system T_V;

driving the tool to rotate relative to another axis of the preset coordinate system T_G by θ

₂ degrees, and then obtaining the coordinate value P₃ of the TCP of the tool;

capturing a picture of the actual TCP and obtaining the corresponding coordinate P₃′

of the actual TCP formed within the visual coordinate system T_V;

calculating a deviation Δ

P between the preset position P₀ and the actual position P₁ of the TCP, and then comparing the deviation Δ

P with a maximum allowable deviation of the robot manipulator;

wherein, if the deviation Δ

P is less than or equal to the maximum allowable deviation of the robot manipulator, the preset position P₀ of the TCP is thereby considered as the actual position P₁ of the TCP and finishing the coordinate correction work;

if the deviation Δ

P is greater than the maximum allowable deviation of the robot manipulator, then, amending the position parameters of the preset position P₀ of the TCP, and repeating the vision correction method for tool center point till the final deviation is less than or equal to the maximum allowable deviation of the robot manipulator.

2. The vision correction method of claim 1, wherein the origin of the basic coordinate system T₀ is established at the distal end of the main body, the preset position P₀ is an estimated position close to the actual position of the TCP of the tool.

3. The vision correction method of claim 2, wherein the robot manipulator further comprises a base, the drive mechanism is mounted in the main body and connected with the controller, the controller comprises a preset control software installed therein for driving and controlling the drive mechanism to work.

4. The vision correction method of claim 1, wherein the drive mechanism is a multi-axis drive mechanism, and the tool is a cutting tool.

5. The vision correction method of claim 2, wherein the preset coordinate system T_G comprises three coordinate axes X_G-axis, Y_G-axis and Z_G-axis positioned parallel to the corresponding three coordinate axes X-axis, Y-axis and Z-axis of the basic coordinate system T₀ respectively, the coordinate value of the origin P₀ of the preset coordinate system T_G is stored into the controller.

6. The vision correction method of claim 5, wherein the two-dimensional visual coordinate system T_V is established by the following steps:

adjusting the vision lens to aim at and being parallel to an X_GZ_G plane of the preset coordinate system T_G;

capturing a two-dimensional picture of the X_GZ_G plane via the vision lens; and

establishing the two-dimensional visual coordinate system T_V based on the two-dimensional picture of the X_GZ_G plane of the preset coordinate system T_G.

7. The vision correction method of claim 6, wherein, the vision correction method further includes driving the TCP of the tool to move back to its original position P₁ before rotating the tool to rotate about another axis of the preset coordinate system T_G by θ

₂ degrees.

8. The vision correction method of claim 1, wherein, the vision lens comprises a picture analysis unit for recognizing the TCP and calculating the scaling ratio λ

of the vision coordinate system T_V relative to the preset coordinate system T_G.

9. A vision correction method for tool center point of a robot manipulator, the robot manipulator comprising a main body, a drive mechanism, a tool assembled to a distal end of the main body and having a tool center point (TCP), and a vision lens positioned aside of the tool;

the robot manipulator predefining a basic coordinate system T₀, the vision correction method comprising the following steps;

defining a preset position P₀ of the TCP and establishing a preset coordinate system T_G based on the preset position P₀, defining the actual position of the TCP as P₁;

defining the deviation between the preset position P₀ of the TCP and the actual position P₁ of the TCP as Δ

P (Δ

x, Δ

y, Δ

z);

the preset coordinate system T_G comprising three coordinate axes X_G-axis, Y_G-axis and Z_G-axis positioned parallel to the corresponding three coordinate axes X-axis, Y-axis and Z-axis of the basic coordinate system T₀ respectively, the coordinate value of the origin P₀ of the preset coordinate system T_G being stored into the controller;

capturing a picture of the actual TCP and establishing a two-dimensional visual coordinate system T_V based on the picture, defining the corresponding coordinate of the actual TCP formed within the two-dimensional visual coordinate system T_V as P₁′

;

calculating a scaling ratio λ

of the vision coordinate system T_V relative to the preset coordinate system T_G;

driving the tool to rotate relative to the Z_G-axis direction of the preset coordinate system T_G by about 180 degrees, capturing a picture of the TCP of the tool thereby obtaining the coordinate value of the TCP of the tool relative to the vision coordinate system T_V, and then calculating the value of Δ

x;

driving the tool to move back to its original position, and rotating the tool relative to the Z_G-axis direction of the preset coordinate system T_G by about 90 degrees, capturing a picture of the TCP of the tool thereby obtaining the coordinate value of the TCP of the tool relative to the vision coordinate system T_V, and then calculating the value of Δ

y;

driving the tool to move back to its original position, and rotating the TCP of the tool relative to the Y_G-axis direction of the preset coordinate system T_G by about 90 degrees, capturing a picture of the TCP thereby obtaining the coordinate value of the TCP relative to the vision coordinate system T_V, and then calculating the value of Δ

z;

calculating the deviation Δ

P (Δ

x, Δ

y, Δ

z) and comparing the deviation Δ

P with a maximum allowable deviation of the robot manipulator;

wherein, if the deviation Δ

P is less than or equal to the maximum allowable deviation of the robot manipulator, the preset position P₀ of the TCP is then considered as the actual position P₁ of the TCP thereby finishing the coordinate correction work;

if the deviation Δ

P is greater than the maximum allowable deviation of the robot manipulator, then, amending the position parameters of the preset position P₀ of the TCP, and repeating the vision correction method for tool center point till the final deviation is less than or equal to the maximum allowable deviation of the robot manipulator.

10. The vision correction method of claim 9, wherein the origin of the basic coordinate system T₀ is established at the distal end of the main body, the preset position P₀ is an estimated position close to the actual position of the TCP of the tool.

11. The vision correction method of claim 10, wherein the robot manipulator further comprises a base, the drive mechanism is mounted in the main body and connected with the controller, the controller comprises a preset control software installed therein for driving and controlling the drive mechanism to work.

12. The vision correction method of claim 9, wherein the drive mechanism is a multi-axis drive mechanism, and the tool is a cutting tool.

13. The vision correction method of claim 9, wherein, the vision lens comprises a picture analysis unit for recognizing the TCP and calculating the scaling ratio λ

of the vision coordinate system T_V relative to the preset coordinate system T_G.