Robot controlling method and apparatus using laser sensor

A method of controlling a welding robot for performing multi-layer welding on a workpiece by repeatedly executing a moving cycle of a welding torch mounted on the welding robot while consecutively modifying a taught path designated by an operation program, using an output from a laser sensor which has a sensing area in the vicinity of and in a moving direction of the welding torch, said method comprising the steps of:

• (a) obtaining data representing a position of the workpiece by said laser sensor during the playback operation of the operation program to operate the robot;
• (b) calculating a reference position for determining a target position of the robot movement based on said data obtained in said step (a);
• (c) determining a shift direction and a shift amount with respect to said reference position in accordance with a position shift pattern designated by the operation program;
• (d) calculating the target position by shifting said reference position in said shift direction determined by said step (c) and by said shift amount determined in said step (c);
• and
• (e) modifying said taught path based on said target position determined in said step (d),
• wherein said steps (a)-(e) are periodically executed and said step (c) includes a step of reading data stored in one position shift pattern register, designated by the operation program, of a plurality of position shift pattern registers for storing said shift direction and shift amount with respect to said reference position, in dependence upon the current moving cycle of the welding torch for the corresponding layer of the multi-layer welding.

A method of controlling a welding robot for performing multi-layer welding on a workpiece by repeatedly executing a moving cycle of a welding torch mounted on the welding robot while consecutively modifying a taught path designated by an operation program, said method comprising the steps of:

• (a) determining positions of first and second workpieces by irradiating light beams from a laser sensor in a vicinity of and in a moving direction of the welding torch;
• (b) determining a reference position based on the positions determined in said step (a), wherein the reference position is a position of a corner line on a cross section of the first and second workpieces;
• (c) determining a shift direction and a shift amount relative to said reference position in accordance with a preset position shift pattern designated by the operation program;
• (d) determining a target position of the robot movement by shifting the reference position based upon the shift direction and shift amount;
• (e) modifying the taught path based upon said target position determined in said step (d);
• and
• (f) repeating said steps (a)-(e) for a plurality of moving cycles of the welding torch, wherein each moving cycle produces another layer of the multi-layer welding.

A method of controlling a welding robot for performing multi-layer welding on a workpiece by repeatedly executing a moving cycle of a welding torch mounted on the welding robot while consecutively modifying a taught path designated by an operation program, said method comprising the steps of:

• (a) determining a position of a workpiece by irradiating light beams from a laser sensor in a vicinity of and in a moving direction of the welding torch;
• (b) determining a reference position based on the position determined in said step (a), wherein the reference position is a welding-line position of the welding torch;
• (c) determining a shift direction and a shift amount relative to said reference position in accordance with a preset position shift pattern designated by the operation program;
• (d) determining a target position of the robot movement by shifting the reference position based upon the shift direction and shift amount;
• and
• (e) modifying the taught path based upon said target position determined in said step (d);
• and
• (f) repeating said steps (a)-(e) for a plurality of moving cycles of the welding torch, wherein each moving cycle produces another layer of the multi-layer welding.

A sensor for controlling a welding robot which performs multi-layer welding on a workpiece by repeatedly executing a moving cycle of a welding torch mounted on the welding robot while consecutively modifying a taught path designated by an operation program, the sensor comprising:

• a laser generator to produce laser light;
• a pivotal mirror which pivots to scan the laser light on the workpiece;
• an optical system to receive and focus the laser light reflected from the workpiece;
• a light receiving element to receive the focused laser light passing through the optical system;
• a controller to control the laser generator and the pivotal mirror;
• wherein a coordinate position (X,Y) at which the laser light strikes and the workpiece is determined by the following equations:
• ##EQU2## wherein L1 is a distance from an origin of the sensor to a center of the optical system, L2 is a distance from the center of the optical system to a center point of the light receiving element, D is a distance from the origin to a pivot point of the pivotal mirror in the X axis direction, L0 is a distance from the origin to the pivot point in the Y axis direction, .theta. is an angle between the laser light reflected from the workpiece and a Y-axis, and xa is a light receiving position on the light receiving element in the X axis direction.