Variable Radius Inspection Using Sweeping Linear Array

Abstract

Method and apparatus for enabling ultrasonic inspection of a changing, insufficiently defined or unknown shape (e.g., a variable radius or a noncircular radius caused by the use of soft tooling) at a rate that meets production requirements. The apparatus comprises a linear ultrasonic array (i.e., sensor) incorporated in a toppler, which in turn is slidably supported by an oscillating sensor mechanism carried by a traveling trailer vehicle. As a result of this arrangement, the sensor can undergo a back-and-forth sweeping motion coupled with motion along the spar radius. The sensor is further able to displace radially relative to a sweep pivot axis and rotate (hereinafter “topple”) about a topple pivot axis. In this manner, the orientation of the sensor can adjust to the contour of the inspected surface as the sensor scans.

1 . A method for scanning a filleted join region of a hollow structure, comprising:
 (a) placing a first mobile platform inside the hollow structure with a first sensor proximate to the filleted join region, the first sensor being supported on a first pivotable assembly of the first mobile platform;   (b) actuating a first motor to cause the first mobile platform to travel along a path substantially parallel to the filleted join region;   (c) controlling a second motor to cause the first pivotable assembly to oscillate through a range of sweep angles;   (d) controlling the first sensor so that it directs ultrasound toward the filleted join region; and   (e) urging a first slidable subassembly of the first mobile platform that holds the first sensor toward the filleted join region,   wherein at least steps (b), (c) and (e) are performed concurrently.   
     
     
         2 . The method as recited in  claim 1 , wherein an orientation of the sensor is adjusted to a contour of the filleted join region 
     
     
         3 . The method as recited in  claim 1 , wherein the sensor is a linear ultrasound transducer array that is parallel to a direction of travel of the first mobile platform. 
     
     
         4 . The method as recited in  claim 3 , wherein an orientation of the linear ultrasound transducer array is adjusted to a contour of the filleted join region such that the sound waves enter normal to the front surface of the radius. 
     
     
         5 . The method as recited in  claim 4 , wherein normality of the sound waves is an average of a local surface variation. 
     
     
         6 . The method as recited in  claim 3 , wherein a resulting motion of the linear ultrasound transducer array is a sawtooth path with rounded peaks and valleys due to acceleration/deceleration. 
     
     
         7 . The method as recited in  claim 6 , wherein the first mobile platform travels along a path that is in close proximity and parallel to the filleted join region with a velocity that is a function of a cycle rate of the oscillations of the first pivotable subassembly, an angular motion range of the oscillations, desired overlap amount, and a length of the linear ultrasound transducer array. 
     
     
         8 . The method as recited in  claim 3 , further comprising:
 measuring a distance traveled by the first mobile platform along the filleted join region;   measuring an angle swept by the linear ultrasound transducer array as the first mobile platform travels along the filleted join region; and   correlating acquired ultrasonic data with position information produced during the measuring steps.   
     
     
         9 . The method as recited in  claim 1 , further comprising:
 placing a second mobile platform outside the hollow structure and separated from the first mobile platform by a skin of the hollow structure; and   magnetically coupling the first mobile platform to the second mobile platform through the skin,   wherein the first motor is mounted to the second mobile platform.   
     
     
         10 . The method as recited in  claim 9 , further comprising:
 placing a third mobile platform inside the hollow structure and separated from the first mobile platform by a web of the hollow structure; and   magnetically coupling the third mobile platform to the first and second mobile platforms through the skin and web so that the third mobile platform travels along the filleted join region when the first motor is activated.   
     
     
         11 . The method as recited in  claim 1 , wherein the hollow structure is an integrally stiffened wing box. 
     
     
         12 . A system for scanning a filleted join region of a hollow structure, comprising a first mobile platform disposed inside the hollow structure and a second mobile platform disposed outside the hollow structure and magnetically coupled to the first mobile platform through a skin of the hollow structure, wherein the first mobile platform comprises:
 a probe body comprising a plurality of wheels configured to enable the probe body to move along a radius that connects a flange of the hollow structure to a web of the hollow structure when first wheels of the plurality of wheels are in contact with the flange and second wheels of the plurality of wheels are in contact with the web;   a sweeper which is rotatably coupled to the probe body so that a sweep axis of the sweeper will be generally parallel to the radius when the first wheels are in contact with the flange and the second wheels are in contact with the web, wherein the sweeper comprises:   first and second sweep drive axles aligned with the sweep axis and rotatably coupled to the probe body;   first and second sweep drive flanges respectively affixed to the first and second sweep drive axles;   a sensor position adjustment subassembly which is translatably mounted to the first and second sweep drive flanges so that a direction of translation of the sensor position adjustment subassembly is transverse to the first and second sweep drive axles, wherein the sensor position adjustment subassembly comprises a toppler that is rotatable about a topple pivot axis that is generally parallel to the sweep axis; and   a sensor that is held by the toppler.   
     
     
         13 . The system as recited in  claim 12 , wherein the sensor pivots about the topple pivot axis when the toppler pivots, the toppler translates in the direction of translation when the sensor position adjustment subassembly translates, and the sensor position adjustment subassembly pivots about the sweep axis when the sweeper pivots. 
     
     
         14 . The system as recited in  claim 12 , wherein the sensor comprises a linear ultrasonic transducer array disposed parallel to the sweep axis. 
     
     
         15 . The system as recited in  claim 12 , further comprising:
 a first motor mounted to the probe body of the first mobile platform and mechanically coupled to the sweeper, the first motor driving pivoting of the sweeper when actuated;   a second motor mounted to the second mobile platform for driving movement of the second mobile platform along the filleted join region; and   a motor controller configured to control the first and second motors to operate in a synchronized manner such that a speed of the first mobile platform depends on a length of the sensor and a cycle rate and sweep angle range of the sweeper.   
     
     
         16 . The system as recited in  claim 15 , wherein the motor controller is configured to control the first and second motors so that the sweeper oscillates about the sweep axis while the probe body moves along a path substantially parallel to the filleted join region. 
     
     
         17 . A system for scanning a filleted join region of a hollow structure, comprising a first mobile platform disposed inside the hollow structure and a second mobile platform disposed outside the hollow structure and magnetically coupled to the first mobile platform through a skin of the hollow structure, wherein the first mobile platform comprises:
 a probe body;   a sweeper bridge assembly pivotably coupled to the probe body for pivoting about a sweep axis, the sweeper bridge assembly comprising first and second sweep drive axles each having first and second ends and a common axis, the first ends of the first and second sweep drive axles being pivotably coupled to the probe body, a first sweep drive flange attached to the second end of the first sweep drive axle, a second sweep drive flange attached to the second end of the second sweep drive axle, and a sensor position adjustment subassembly which is linearly movable relative to the first and second sweep drive flanges only in a direction which is normal or nearly normal to the sweep axis; and   a sensor supported by the sensor position adjustment subassembly,   wherein the sensor position adjustment subassembly comprises:   first and second bridge towers which are translatable relative to the first and second sweep drive flanges in the direction normal to the sweep axis;   a bridge connecting the first and second bridge towers; and   a sensor holder that holds the sensor and is pivotable relative to the sensor position adjustment subassembly only about a topple pivot axis which is generally parallel to the sweep axis.   
     
     
         18 . The system as recited in  claim 17 , wherein the sensor holder further comprises first and second toppler pivot axles, the first and second bridge towers respectively comprise first and second toppler pivot bearings, and respective first portions of the first and second toppler pivot axles are respectively seated in the first and second toppler pivot bearings. 
     
     
         19 . The system as recited in  claim 17 , wherein the sensor comprises a linear ultrasonic transducer array. 
     
     
         20 . The system as recited in  claim 17 , wherein the first and second bridge towers comprises first and second pins which limit pivoting motion of the sensor holder relative to the sensor position adjustment subassembly.