Continuous high resolution surface profiling apparatus and method

Abstract

A surface profiler including at least one front support wheel and at least one rear support wheel for travelling along the surface of a profile to be measured, the rotational axes of said wheels being longitudinally spaced, and the wheels contacting the surface being profiled in a collinear manner. A frame carried on the wheels carries at least one inclinometer and at least two vertical distance measuring apparatus such as lasers, and may also carry an optical encoder. The lasers are collinear with each other and with the wheels. Incremental to measurements of inclination angles provided by the inclinometer, together with incremental measurements of distance to the surface being measured provided by the lasers, produce a continuous, high resolution mathematical series of elevations representing the surface profile, including reproduction of surface features that are smaller than the distance between the wheels.

What is claimed is: 
     
       1. A surface profiling apparatus comprising:
 a frame;   a plurality of wheels supporting said frame, at least two of said wheels being separated by a distance W and being aligned to contact a surface being profiled in a longitudinally collinear manner;   a longitudinal distance measuring apparatus supported by said frame;   a longitudinal inclination measuring apparatus supported by said frame to measure an angle α between said frame and said surface; and   at least two vertical distance measuring devices, said vertical distance measuring devices being collinear with said collinear wheels and separated by a distance L.   
     
     
       2. The surface profiling apparatus of  claim 1  wherein said vertical distance measuring devices are equidistant from the mid-point of said frame. 
     
     
       3. The surface profiling apparatus of  claim 1  wherein each of said vertical distance measuring devices is a laser. 
     
     
       4. The surface profiling apparatus of  claim 3  wherein said lasers are attached to said frame at a specified separation, and wherein said separation is shorter than the distance W. 
     
     
       5. The surface profiling apparatus of  claim 3  wherein said lasers are equidistant from the mid-point of said frame. 
     
     
       6. The surface profiling apparatus of  claim 1 , wherein said longitudinal distance measuring apparatus is positioned between said collinear wheels. 
     
     
       7. The surface profiling apparatus of  claim 1  wherein said longitudinal distance measuring apparatus is positioned between said vertical distance measuring apparatuses. 
     
     
       8. The surface profiling apparatus of  claim 1 , wherein said longitudinal distance measuring apparatus is rotationally linked to an axle of one of said wheels. 
     
     
       9. The surface profiling apparatus of  claim 8  wherein said longitudinal distance measuring apparatus is an optical encoder. 
     
     
       10. The surface profiling apparatus of  claim 1  wherein said longitudinal inclination measuring apparatus is an inclinometer. 
     
     
       11. The surface profiling apparatus of  claim 1  further comprising a motorized drive adapted to move the profiling apparatus along the surface to be profiled. 
     
     
       12. The surface profiling apparatus of  claim 1  further comprising attachment means by which the apparatus may be attached to a motorized vehicle to move the apparatus along the surface to be profiled. 
     
     
       13. The surface profiling apparatus of  claim 1 , further comprising an operator interface to control said profiling apparatus. 
     
     
       14. The surface profiling apparatus of  claim 13  wherein said interface is associated with a cabinet associated with said frame. 
     
     
       15. The surface profiling apparatus of  claim 14  wherein said cabinet houses operational equipment, said operational equipment being selected from the group consisting of: one or more internal sensors, a power supply, power level monitor, signal conditioning equipment, real time clock, distance pulse counters, digital input/output and multi-channel 16 bit analog to digital converter, computer and non-volatile memory. 
     
     
       16. The surface profiling apparatus of  claim 1 , further comprising a transverse inclination measuring apparatus, supported by said frame and oriented substantially perpendicular to said longitudinal inclination measuring apparatus, to measure a transverse angle χ between said frame and said surface. 
     
     
       17. A method of profiling a surface using a surface profiling apparatus mounted on a plurality of wheels, at least two of said wheels being aligned to contact the surface in a longitudinally collinear manner, the method comprising:
 acquiring data relating to:
 a longitudinal distance ΔD travelled by said profiler surface profiling apparatus from a longitudinal distance measuring apparatus mounted on said profiler surface profiling apparatus; 
 an angle α of said profiler surface profiling apparatus relative to a horizontal plane intersecting said surface at a location of one of said wheels where a point of the wheel, a vertical line and a line collinear with a diameter of the wheel intersect, from a longitudinal inclination measuring apparatus comprising a first inclinometer mounted on said profiler surface profiling apparatus; and 
 a vertical distance L f  between said profiler surface profiling apparatus and said surface from a first vertical distance measuring apparatus mounted on said profiler surface profiling apparatus; 
 a vertical distance L r  between said frame and said surface from a second vertical distance measuring apparatus mounted on said profiler surface profiling apparatus; 
 said first and second vertical distance measuring apparatuses being mounted collinearly with said wheels and separated by a distance L; 
 
 calculating an incremental change in surface elevation ΔE, using the formula: 
 
       
         
           
             
               
                 
                   Δ 
                   ⁢ 
                   E 
                 
                 = 
                 
                   ΔDsin 
                   ⁡ 
                   ( 
                   
                     α 
                     + 
                     
                       
                         tan 
                         
                           - 
                           1 
                         
                       
                       ( 
                       
                         
                           ( 
                           
                             
                               L 
                               f 
                             
                             - 
                             
                               L 
                               r 
                             
                           
                           ) 
                         
                         L 
                       
                       ) 
                     
                   
                   ) 
                 
               
               ; 
               and 
                 
             
           
         
         adding said incremental change to an accumulated elevation series which represents a profile of said surface. 
       
     
     
       18. The method of  claim 17 , wherein said method is applied at periodic intervals. 
     
     
       19. The method of  claim 18  wherein said periodic intervals are at time increments, Δt. 
     
     
       20. The method of  claim 19  wherein Δt is 1 millisecond. 
     
     
       21. The method of  claim 18  wherein said periodic intervals are at longitudinal distance increments, ΔD. 
     
     
       22. The method of  claim 21  wherein ΔD is 1 millimeter. 
     
     
       23. The method of  claim 17 , wherein said step of acquiring data further comprises acquiring data relating to a transverse angle χ of said profiler relative to surface profiling apparatus between a horizontal plane above said surface and a line transverse to a longitudinal axis of a frame of said surface profiling apparatus, from a transverse inclination measuring apparatus comprising a second inclinometer supported by mounted on said profiler surface profiling apparatus to correct said angle α for cross-axis error. 
     
     
       24. The method of  claim 23 , wherein said method is applied at periodic intervals. 
     
     
       25. The method of  claim 24  wherein said periodic intervals are at time increments, Δt. 
     
     
       26. The method of  claim 25  wherein Δt is 1 millisecond. 
     
     
       27. The method of  claim 24  wherein said periodic intervals are at longitudinal distance increments, ΔD. 
     
     
       28. The method of  claim 27  wherein ΔD is 1 millimeter. 
     
     
       29. A method of profiling a surface using a surface profiling apparatus mounted on a plurality of wheels, at least two of said wheels being aligned to contact the surface in a longitudinally collinear manner, the method comprising:
 moving the profiler surface profiling apparatus a longitudinal distance increment ΔD; 
 obtaining a vertical distance L f  between said surface profiling apparatus and said surface from a first vertical distance measuring device, and a vertical distance L r  between said surface profiling apparatus and said surface from a second vertical distance measuring device, said first and second vertical distance measuring apparatuses being mounted on said surface profiling apparatus collinearly with said at least two wheels and separated by a distance L; 
 calculating a first angle β between said vertical distances L f , L r  and said distance L using the formula: 
 
       
         
           
             
               
                 β 
                 = 
                 
                   
                     tan 
                     
                       - 
                       1 
                     
                   
                   ( 
                   
                     
                       ( 
                       
                         
                           L 
                           f 
                         
                         - 
                         
                           L 
                           r 
                         
                       
                       ) 
                     
                     L 
                   
                   ) 
                 
               
               ; 
             
           
         
         obtaining an angle α of said profiler surface profiling apparatus relative to a horizontal plane intersecting said surface at a location of one of said wheels where a point of the wheel, a vertical line and a line collinear with a diameter of the wheel intersect, from a longitudinal inclination measuring apparatus comprising a first inclinometer mounted on said profiler surface profiling apparatus; 
         calculating an incremental change in surface elevation ΔE, using the formula:
   ΔE =ΔD sin(α+β);
 
 
         and adding said incremental change to an accumulated elevation series which represents a profile of said surface. 
       
     
     
       30. The method of  claim 29 , wherein said method is applied at periodic intervals. 
     
     
       31. The method of  claim 30  wherein said periodic intervals are at time increments, Δt. 
     
     
       32. The method of  claim 31  wherein Δt is 1 millisecond. 
     
     
       33. The method of  claim 30  wherein said periodic intervals are at longitudinal distance increments, ΔD. 
     
     
       34. The method of  claim 33  wherein ΔD is 1 millimeter. 
     
     
       35. The method of  claim 29  comprising the further step of correcting said angle α for cross-axis error using a transverse angle χ, said transverse angle χ being obtained from a transverse inclination measuring apparatus supported by comprising a second inclinometer mounted on said profiler surface profiling apparatus.