Device and method for correction of robot inaccuracy

A method for improving orientation and/or location accuracy of a programmable robot with respect to a target, said method comprising the steps of:

• (a) positioning the robot with respect to the target, said robot having a terminal operating end-effector, said robot being capable of movement between a variety of different positions with respect to the target;
• (b) identifying a plurality of separated reference positions external from the robot;
• (c) developing identification data defining geometries and spatial data of the separated reference positions relative to the target;
• (d) storing the identification data for each respective reference position within a data processing unit for recall and comparison by the robot upon later excursion to a location near such reference position;
• (e) moving the robot end-effector to a first location near one of the reference positions, referred to herein as the calibration position, wherein a sensor coupled to the robot detects the presence of the calibration position;
• (f) comparing the detected calibration position with the originally stored information data relating to that position;
• (g) developing a rigid body error correction based on position differences detected in the previous comparison step, said correction to be used with respect to later moves of the robot relative to the calibration position;
• (h) storing the rigid body error correction within the data processing unit;
• (i) moving the end-effector to a second reference position utilizing the originally stored identification data regarding the second reference position and applying the rigid body correction developed with respect to the calibration position to more accurately predict proper placement of the robot in approximate vicinity to the second reference position.

A method for mapping robot inaccuracy of a programmable robot, said method comprising the steps of:

• (a) preparing a target object having a plurality of identifiable features thereon which can serve as reference points for mapping;
• (b) developing a feature database defining geometries and spatial relationships of the features on the object in sufficient detail to enable individual recognition of each feature;
• (c) storing the feature database in a computer for later recall and comparison;
• (d) positioning the target object within operational reach of a distal link of the robot;
• (e) attaching sensing means at the distal link capable of detecting the stored features based on a comparison of sensory data with data in the feature database;
• (f) calibrating the sensing means with respect to the distal link to accurately define relative positioning of a distal frame with respect to a terminal control frame of the sensing means;
• (g) storing the calibrated terminal control frame position within the computer for later recall and comparison;
• (h) preparing a routine which correlates stored feature database information with the calibrated terminal control frame position and provides drive commands to the robot for moving the sensing means sequentially to predicted positions of the respective features;
• (i) activating the routine to move the sensing means to a calibrating feature comprising one of the stored features on the target object;
• (j) defining the relative pose error of the actual position of the sensing means with respect to the predicted position to provide rigid body correction data;
• (k) storing the rigid body correction data within the computer for later recall and comparison;
• (l) correlating the stored rigid body correction data with the prepared routine to define a new predicted position for a next feature to which the sensing means will be moved;
• (m) moving the sensing means to the new predicted location of next feature;
• (n) defining the relative pose error of the actual position of the sensing means with respect to the new predicted position;
• (o) storing the error data of step "n" within the computer for later recall and comparison;
• (p) repeating steps l through o with respect to each subsequent feature to develop a map of the target object based on error data measured;
• (q) processing the map error data to define an expression representing robot inaccuracy.

A method for improving orientation and/or location accuracy of a programmable robot with respect to an operation to be performed on a target object, said method comprising the steps of:

• (a) preparing a routine which provides drive commands to the robot for moving an attached sensing means to an approximate position of a desired feature on the target object;
• (b) calibrating a sensory reference frame which defines a relative position for the sensing means with respect to the robot;
• (c) activating the routine such that the robot sensing means detects the feature and produces sensory data regarding feature position;
• (d) develop a transformation matrix which relates position of the feature to the sensory reference frame;
• (e) determine a sensory frame pose for the robot based on the matrix of step "d", sensory reference frame position and geometry of the feature;
• (f) determine a set of joint coordinates for the robot corresponding to the sensor frame pose;
• (g) identifying control points along a path of operation representing regions of movement limitation for the robot;
• (h) modifying the routine and defined path of operation with control points to maintain path conformity for free movement of the robot;
• and
• (i) activating the modified routine to perform the operation.

A method for improving orientation and/or location accuracy of a programmable robot with respect to a target, said method comprising the steps of:

• (a) calibrating the position of a terminal control frame of a robot end-effector which is coupled to a robot distal link having a robot distal frame to define their relative position and orientation;
• (b) identifying a plurality of separated reference positions external from the robot;
• (c) developing identification data defining geometries and spatial data of the separated reference positions relative to the target;
• (d) storing the identification data for each respective reference position within a data processing unit for recall and comparison by the robot upon later excursion to a location near such reference position;
• (e) moving the robot end-effector to a first location near one of the reference positions, referred to herein as the calibration position, wherein a sensor coupled to the robot detects the presence of the calibration position;
• (f) comparing the detected calibration position with the originally stored information data relating to that position;
• (g) developing a rigid body error correction based on position differences detected in the previous comparison step, said correction to be used with respect to later moves of the robot relative to the calibration position;
• (h) storing the rigid body error correction within the data processing unit;
• (i) moving the end-effector to a second reference position utilizing the originally stored identification data regarding the second reference position and applying the rigid body correction developed with respect to the calibration position to more accurately predict proper placement of the robot in approximate vicinity to the second reference position.