Robot calibration system

A method of dynamically calibrating a robot that is moved along a path between an initial orientation and a destination orientation where the robot orientation is dictated by robot joint positions, comprising the steps of:

• (A) determining a calibration factor using joint position information from a plurality of robot orientations;
• (B) moving the robot joints into default positions;
• (C) moving the robot into the initial orientation by applying the calibration factor to the default positions;
• (D) determining a next desired robot orientation having a plurality of joint positions;
• (E) determining a target robot orientation by applying the calibration factor to the joint positions of the next desired robot orientation;
• (F) moving the robot into the target robot orientation;
• and
• (G) repeating steps (D) through (F) until the robot is moved into the destination orientation.

A robot calibration system, comprising:

• a robot base;
• a robot arm supported on said base and including a plurality of joints that are moveable into a plurality of joint positions to provide a plurality of orientations of said robot arm;
• a signal generator that generates an electrical signal;
• a controller that controls movement of said joints to move said robot arm among said plurality of orientations, said controller determining each said joint position for each orientation of said robot arm responsive to said signal;
• and
• a calibration member having a calibration length, a first end near a first reference location that remains fixed relative to said robot base and a second end near a second reference location on said robot arm, said calibration member being taut and activating said signal generator whenever said robot arm is moved into one of said robot arm orientations where a distance between said second reference location and said first reference location equals said calibration length.

A robot calibration system, comprising:

• a robot base;
• a robot arm supported on said base and including a plurality of joints that are moveable into a plurality of joint positions to provide a plurality of orientations of said robot arm;
• a controller that controls movement of said joints to move said robot arm among said plurality of orientations;
• and
• a calibration sensor that defines a first reference location that remains fixed relative to said robot base and generates a signal each time that a second reference location on said robot arm is a fixed distance away from said first reference location;
• and wherein
• said controller determines each joint position of each said joint responsive to said electrical signal and uses said determined joint positions to determine a calibration factor.

A method of calibrating a robot system having a robot arm that is supported on a base and includes a plurality of joints that have default positions and are moveable into a plurality of joint positions to provide a plurality of robot arm orientations, comprising the steps of:

• (A) establishing a first reference location that remains fixed relative to the robot base;
• (B) establishing a second reference location on the robot arm;
• (C) establishing a plurality of robot orientations;
• (D) establishing a starting robot orientation such that a fixed distance between the first reference location and the second reference location is achieved by moving the robot from the starting robot orientation towards one of the plurality of robot orientations;
• (E) moving the robot to the starting orientation;
• (F) moving the robot from the starting orientation towards the one of the plurality of robot orientations;
• (G) determining when the second reference location is at the fixed distance from the first reference location;
• (H) storing each joint position associated with each orientation where the second reference location is the fixed distance from the first reference location;
• (I) repeating steps D through H for each one of the plurality of robot orientations;
• and
• (J) determining a calibration factor by comparing the default positions with the joint positions of step H.

A method of providing real-time error correction to the joint positions of a robot that is moved along a programmed path between an initial orientation and destination orientation where the robot orientation is dictated by robot joint positions, comprising the steps of:

• (A) determining a calibration factor using joint position information at a plurality of robot orientations;
• (B) commanding the robot to move along the programmed path;
• (C) determining an intermediate robot orientation at a selected time interval;
• (D) determining the joint positions for the intermediate robot orientation at the selected time interval;
• (E) applying the calibration factor to the joint positions at the selected time interval to obtain a corrected intermediate robot orientation along the programmed path;
• (F) moving the robot to the corrected intermediate orientation;
• and
• (G) repeating steps (C) through (F) until the robot is moved into the destination orientation.