Path contriving system for look-ahead sensor in a robotic control system

• US 4,843,287 A
• Filed: 12/31/1987
• Issued: 06/27/1989
• Est. Priority Date: 12/31/1987
• Status: Expired due to Fees

• Current Assignee: Westinghouse Electric UK Holdings Limited (Fluor Corporation)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Taft, Jeffrey D.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): MARTIN, DAVID S
• Application Number:
  US07/140,262
• Time in Patent Office: 544 Days
• Field of Search: 318/568-573, 318/574-577, 318/586, 318/567, 219/124.1, 219/124.22, 219/124.32, 219/124.34, 901/9-10, 901/42, 901/47, 358/107, 356/1-2, 356/376, 356/303-304, 364/167-169, 364/513
• US Class Current: 318/568.16
• CPC Class Codes: B23Q 35/128 Sensing by using optical means
• CPC Class Codes: G05B 19/425 Teaching successive positions by numerical control, i.e. commands being entered to control the positioning servo of the tool head or end effector
• CPC Class Codes: G05B 2219/36417 Programmed coarse position, fine position by alignment, follow line, path adaptive

Abstract

A look-ahead sensor attached to the its effector end deviates upon each control action upon the robot toward a new position along the seam path. The chord across the seam path from the present effector end to the contemporaneously sensed seam path location is determined and used with the present orientation of the effector end to determine an additional yaw angle compensating for the deviation. As a result, the look-ahead sensor is constantly brought back on track.

Claims

1. In a robotic system controlling about position coordinate and orientation axes an effector end;

said orientation axes including a yaw axis;

the robotic system including;

a look-ahead seam sensor mounted on said effector end a distance therefrom;

said effector end being movable into position about said coordinate axes and orientable in relation to said orientation axes;

said look-ahead sensor being movable with said effector end at said distance about said yaw axis;

said look-ahead seam sensor being adapted, when tracking a seam path for said effector end, to sense seam path locations at said distance away from the effector end; and

the coordinates characterizing each sensed seam path location being stored successively to provide seam path location indicative samples;

the combination of;

means for controlling the effector end from a present operative position to a new operative position corresponding to one of said sensed seam path locations and to one of said seam path stored location indicative samples;

said look-ahead seam sensor and effector end having for said present operative position a common orientation about said yaw axis in accordance with a previous controlling operation of said robotic system upon said effector end;

means responsive to the location of said effector end in terms of said coordinate axes for said present operative position and to the contemporaneously sensed and stored seam path location sample for determining the chord across the seam path between said present operative position and said contemporaneously sensed sample;

means for determining in relation to said chord and said common orientation the yaw angle therebetween; and

means operative upon said effector end concurrently with said controlling means for minimizing said yaw angle, whereby the look-ahead sensor is contrived to follow the seam path at said distance ahead of the effector end.

2. The robotic system of claim 1 with said controlling means including:

means for iteratively calculating and storing in response to said controlling means the elapsed distance of the effector end from a first position thereof to the present position;

means associated with said look-ahead seam sensor for iteratively calculating and storing the elapsed distances from a first sensed seam location to said contemporaneously sensed location;

means operative from said present effector end and from a last effector end position for extrapolating to an anticipated position as said new position, and for deriving an anticipated elapsed distance;

means for correlating said anticipated elapsed distance with said corresponding stored location to derive corresponding position coordinates and orientation axes for the effector end at said new position;

said effector end being controlled about its orientation axes in accordance with said coordinate axes, and concurrently about its yaw axis in accordance with said yaw angle.