Method for robot to automatically find bending position

A method for automatically finding a bending position by a robot, comprising the steps of:

• step 1:
• establishing a tool coordinate system (TX, TY, TZ) of a robot gripper, wherein the TZ direction is a normal vector at an end of a flange of the robot and its positive direction is the lead-out direction of the flange, the TX direction is the same as the X direction of the robot, the TY direction is determined according to the right-hand rule, and the origin O of the coordinate system is an intersection point between the center of the flange in the TZ direction and the plane of a workpiece to be grabbed;
• and translating a TCP of the robot from the center of the flange to the newly established tool coordinate system;
• step 2:
• determining respective user coordinate systems (XA, YA, ZA;
• XB, YB, ZB) of two rear retaining fingers:
• wherein the X axis is parallel to a center line M of a lower mold of a bending machine, the Z axis is parallel to the moving direction of an upper mold of the bending machine, the positive direction of the Z axis is the same as the downward moving direction of an upper slider, the Y axis is perpendicular to the X axis, the positive direction of the Y axis is a direction in which the rear retaining finger points to the lower mold of the bending machine, and an intersection point between a center line of the rear retaining finger and an edge of the lower mold is the origin O of the user coordinate system of the rear retaining finger;
• step 3:
• selecting the user coordinate system of one rear retaining finger, and calculating a correction translation matrix of the robot along the X direction in the user coordinate system:
• T
• =
• [
• 1
• 0
• 0
• p
• x
• 0
• 1
• 0
• 0
• 0
• 0
• 1
• 0
• 0
• 0
• 0
• 1
• ]
• ,
• where px is the translation distance of the robot in the user coordinate system;
• and
• performing the translational motion of the robot gripper based on the correction translation matrix, acquiring the information of rear retaining finger sensors in real time during motion, stopping the translational motion of the robot gripper when one of the rear retaining finger sensors is detected, and recording the current position and posture of the robot;
• and
• step 4:
• judging the information state of the rear retaining finger sensors, calculating a rotation matrix of the robot gripper in the user coordinate system of the rear retaining finger whose rear retaining finger sensor information is detected, and performing rotary motion by the robot gripper around the origin of the user coordinate system of the rear retaining finger whose information is detected based on the correction rotation matrix:
• if the information of the two rear retaining finger sensors is detected simultaneously, then the robot gripper is in a standard bending position;
• and
• if only the information of one rear retaining finger sensor is detected and the information of the other rear retaining finger sensor is not detected, calculating a correction rotation matrix of the robot in the user coordinate system of the rear retaining finger whose rear retaining finger sensor information is detected, performing the rotary motion of the robot gripper based on the correction rotation matrix, rotating the robot gripper around the origin of the user coordinate system of the rear retaining finger whose rear retaining finger sensor information is detected, and stopping the rotary motion of the robot gripper until the other sensor is detected;
• then the robot gripper is in a standard bending position.