FOR ROBOTIC INSPECTION AND ASSEMBLY

THE DEVELOPMENT OF A PROXIMITY SENSOR FOR USE IN AUTOMATED ASSEMBLY AND INSPECTION OPERATIONS IS PROPOSED. A TWO-DIMENSIONAL ARRAY OF SMALL CAPACITIVE PROXIMITY SENSORS DETECTS THE DISTANCE BETWEEN EACH SENSOR TIP AND THE TARGET OBJECT. WHEN OPERATING AT A CLOSE DISTANCE TO THE OBJECT (LESS THAN 10 MM), AN IMAGE OF THE SURFACE CONTOUR IS OBTAINED IN ADDITION TO THE DISTANCE INFORAMTION. THE SENSING PROCESS IS CONTROLLED BY A LOCAL MICROPROCESSOR, WHICH ADDRESSES THE SENSORS IN SERIAL ORDER THROUGH A MULTIPLEXER, SAMPLES THE DATA AND LINEARIZES THEM ACCORDING TO THE CALIBRATION CURVE. THE SENSOR ARRAY CAN BE ATTACHED TO A ROBOT END-EFFECTOR. EACH SENSOR ELEMENT CONSISTS OF A THIN SHORT LEAD (LINE CAPACITANCE) EMBEDDED IN A HARD CERAMIC SUBSTRATE. THE SENSORS ARE THEREFORE RUGGED AND CAN, DUE TO THEIR SMALL SIZE, BE MOUNTED AT ALMOST ANY LOCATION ON TEH END-EFFECTOR. THE IMAGING CAPABILITIES OF THE SENSOR ARRAY ARE COMPARABLE TO AN "EYE-IN-HAND" CLOSE DISTANCE VISION SYSTEM; THE ARRAY, HOWEVER, CAN OPERATE AT ARBITRARILY CLOS DISTANCES WITHOUT ALIGNMENT OR ILLUMINATIONPROBLEMS. IT OFFERS POTENTIALLY HIGHER ACCURACY AND RESOLUTION WHILE REQUIRING MUCH SIMPLER COMPUTATIONS. FROM THE MEASURED DATA, GEOMETRICAL PARAMETERS CAN BE DETERMINED,SUCH AS MEAN DISTANCE BETWEEN END-EFFECTOR AND WORKPIECE, LOCATINOS OF HOLES AND EDGES AND SPATIAL ANGLES OF THE SURFACE RELATIVE TO THE END-EFFECTOR. THE ACCURACY OF DISTANCE MEASUREMENTS IS BETTER THAN 1 M; THE ACCURACY OF EDGE DETECTION IS BETTER THAN 100 M. COMPARED TO TOUCH SENSORS, THE CAPACITIVE SENSOR OPERATES WITHOUT PHYSICAL CONTACT, REDUCING WEAR, AND OFFERS HIGHER PACKAGE DENSITY AND RESOLUTION.