Method of curvature controlled data smoothing

• US 7,693,588 B2
• Filed: 03/23/2006
• Issued: 04/06/2010
• Est. Priority Date: 03/23/2005
• Status: Active Grant

• Current Assignee: Hurco Companies, Inc.
• Original Assignee: Hurco Companies, Inc.
• Inventors: Hong, Jiawei, Tan, Xiaonan
• Primary Examiner(s): Rodriguez; Paul L
• Assistant Examiner(s): Rodriguez; Carlos Ortiz
• Application Number:
  US11/277,286
• Publication Number:
  US 20070085850A1
• Time in Patent Office: 1,475 Days
• Field of Search: 345/474, 700/33, 700/44, 700/61, 700/98, 700159-161, 700/164, 700186-189, 700/192, 700/252, 702/94, 702/95, 702/155, 702/157, 702/158, 702/168
• US Class Current: 700/61
• CPC Class Codes: G05B 19/41 characterised by interpolation, e.g. the computation of intermediate points between programmed end points to define the path to be followed and the rate of travel along that path G05B19/25, G05B19/31, G05B19/37, G05B19/39, G05B19/40 take precedence
• CPC Class Codes: G05B 19/4103 Digital interpolation
• CPC Class Codes: G05B 19/416 characterised by control of velocity, acceleration or deceleration G05B19/19 takes precedence
• CPC Class Codes: G05B 19/4163 Adaptive control of feed or cutting velocity without NC B23Q15/12
• CPC Class Codes: G05B 2219/34171 Generate polynomial fitting in tolerance zone around polygon
• CPC Class Codes: G05B 2219/34175 Overlap, between two blocks, continuous, smooth speed change, movement
• CPC Class Codes: G05B 2219/43057 Adjust acceleration, speed until maximum allowable moment for axis
• CPC Class Codes: G05B 2219/43199 Safety, limitation of feedrate
• CPC Class Codes: G05B 2219/43203 Limitation of speed, permissible, allowable, maximum speed
• CPC Class Codes: G05B 2219/50179 Dynamic tolerance, limit values as function of speed, type of command

Abstract

The present invention relates to navigation of a path by a moving object, and, more particularly, to motion control systems for computer-controllable machine tools.

Claims

1. A method of generating a trajectory for a body, including the steps of:

identifying a plurality of line segments included within the trajectory;

compressing at least a portion of the plurality of line segments;

smoothing at least a portion of the plurality of line segments by converting the portion of line segments into a plurality of arcs which remain within a tolerance relative to the trajectory, wherein the portion of the plurality of line segments includes at least two line segments, wherein the body is a cutting tool of a CNC machine, wherein the compressing step includes the steps of determining a starting point of a first line segment, determining an ending point of a second line segment, replacing the first line segment and the second line segment with a third line segment that begins at the starting point and ends at the ending point if a plurality of conditions are satisfied; and

moving the cutting tool of the CNC machine based on the plurality of arcs.

2. The method of claim 1, wherein the plurality of conditions includes a distance limit between the starting point and the ending point.

3. The method of claim 1, wherein the plurality of conditions includes an angle limit on an angle formed by the first line segment and the second line segment.

4. The method of claim 1, wherein the plurality of conditions includes a tolerance requirement for tolerances associated with the starting point, the ending point, and a common point.

5. The method of claim 1, wherein the plurality of conditions includes a perpendicular distance limit on the perpendicular distance between a common point and the third line segment.

6. The method of claim 5, wherein the perpendicular distance limit is smaller than a tolerance associated with the common point.

7. A method of generating a trajectory for a body, including the steps of:

identifying a plurality of line segments included within the trajectory;

smoothing at least a portion of the plurality of line segments by converting the portion of line segments into a plurality of arcs which remain within a tolerance relative to the trajectory, wherein the portion of the plurality of line segments includes at least two line segments, wherein the body is a cutting tool of a CNC machine, wherein the smoothing step includes the steps of identifying a plurality of points that define the plurality of line segments, and adjusting the position of at least a portion of the plurality of points such that the plurality of arcs pass through the plurality of points and define a portion of the trajectory, the portion of the trajectory having a gradually changing curvature; and

moving the cutting tool of the CNC machine based on the plurality of arcs.

8. The method of claim 7, wherein a first arc of the plurality of arcs joins a second arc of the plurality of arcs at a point wherein the first and second arcs are mutually tangential.

9. The method of claim 7, further including the steps of:

calculating the trajectory;

calculating the tolerance; and

calculating a feedrate associated with the trajectory.

10. The method of claim 9, wherein the calculating the trajectory step includes the steps of reading from a part program locations of a plurality of points and interpolating between the plurality of points to define the trajectory.

11. The method of claim 10, wherein the part program includes a plurality of NC motion commands and a plurality of NC tolerance commands.

12. A method of generating a trajectory for a body, including the steps of:

identifying a plurality of line segments included within the trajectory;

smoothing at least a portion of the plurality of line segments by converting the portion of line segments into a plurality of arcs which remain within a tolerance relative to the trajectory, wherein the portion of the plurality of line segments includes at least two line segments, wherein the body is a cutting tool of a CNC machine, wherein the smoothing step includes the steps of identifying a plurality of points that define the plurality of line segments, and adjusting a position of at least a portion of the plurality of points such that the plurality of arcs pass through the plurality of points and define a portion of the trajectory, the plurality of arcs being circular arcs; and

moving the cutting tool of the CNC machine based on the plurality of arcs.

13. A method of generating a trajectory for a body, including the steps of:

identifying a plurality of line segments included within the trajectory;

smoothing at least a portion of the plurality of line segments by converting the portion of line segments into a plurality of arcs which remain within a tolerance relative to the trajectory, wherein the portion of the plurality of line segments includes at least two line segments, wherein the body is a cutting tool of a CNC machine; and

moving the cutting tool of the CNC machine based on the plurality of arcs,

wherein the smoothing step includes the steps of preparing for smoothing, adjusting for smoothing, and smoothing using a double arc algorithm and the preparing for smoothing step includes the steps of

identifying a first point, a second point adjacent the first point, and a third point adjacent the second point that together define a portion of the trajectory,

determining an arc that passes through the points,

determining a first line segment between the first and second points,

calculating a first shortest distance between a midpoint of the first line segment and the arc,

determining a second line segment between the second and third points,

calculating a second shortest distance between a midpoint of the second line segment and the arc, and

marking the second point for smoothing if the first and second shortest distances are both less than a predetermined distance, and an angle formed by the first and the second line segments is greater than a predetermined angle.

14. The method of claim 13, wherein the preparing for smoothing step includes the step of marking points that together define a portion of the trajectory as either suitable for smoothing or unsuitable for smoothing, depending upon whether a plurality of conditions are satisfied.

15. A method of generating a trajectory for a body, including the steps of:

identifying a plurality of line segments included within the trajectory;

smoothing at least a portion of the plurality of line segments by converting the portion of line segments into a plurality of arcs which remain within a tolerance relative to the trajectory; and

moving the cutting tool of the CNC machine based on the plurality of arcs,

wherein the smoothing step includes the steps of preparing for smoothing, adjusting for smoothing, and smoothing using a double arc algorithm and wherein the adjusting for smoothing step includes the steps of;

identifying four adjacent points that together define a portion of the trajectory,

determining a first construction arc that passes through the first, second, and fourth points and lies in a first plane,

determining a second construction arc that passes through the first, third and fourth points and lies in a second plane,

determining a first vector extending from the second point to a first end point on the second construction arc that is closest to the second point,

determining a second vector extending from the third point to a second end point on the first construction arc that is closest to the third point,

adjusting the second point a first adjustment distance along the first vector if the second point has been marked as suitable for smoothing and at least one of the first and third points has been marked as suitable for smoothing, and

adjusting the third point a second adjustment distance along the second vector if the third point has been marked as suitable for smoothing and at least one of the second and the fourth points has been marked as suitable for smoothing, wherein the body is a cutting tool of a CNC machine.

16. The method of claim 15, wherein the step of determining a first vector includes the steps of

determining a first center point of a circle defined by the second construction arc,

determining a first projection point that defines a line with the second point that is perpendicular to the second plane, and

locating the first end point by determining a line that passes through the first center point and the first projection point and intersects the second construction arc.

17. The method of claim 15, wherein the step of determining a second vector includes the steps of

determining a second center point of a circle defined by the first construction arc,

determining a second projection point that defines a line with the third point that is perpendicular to the first plane, and

locating the second end point by determining a line that passes through the second center point and the second projection point and intersects the first construction arc.

18. The method of claim 15, wherein the adjusting for smoothing step is performed a plurality of times on a plurality of sets of four adjacent data points, each set sharing three data points with a prior set and a subsequent set.

19. The method of claim 15, wherein the first adjustment distance is a product of a first value times a length of the first vector if only one of the first and third points has been marked as suitable for smoothing, and the first adjustment distance is a product of a second value times the length of the first vector if both of the first and third points have been marked as suitable for smoothing, the second value being smaller than the first value.

20. The method of claim 19, wherein the first value is approximately equal to 0.5 and the second value is approximately equal to 0.19.

21. A method of generating a trajectory for a body, including the steps of:

identifying a plurality of line segments included within the trajectory;

smoothing at least a portion of the plurality of line segments by converting the portion of line segments into a plurality of arcs which remain within a tolerance relative to the trajectory; and

moving the cutting tool of the CNC machine based on the plurality of arcs,

wherein the smoothing step includes the steps of preparing for smoothing, adjusting for smoothing, and smoothing using a double arc algorithm and wherein the smoothing using a double arc algorithm step includes the steps of

determining a desired tangent vector for each of a plurality of points processed by the adjusting for smoothing step, and

generating double arcs to replace a first line segment between a first point and a second point and a second line segment between the second point and a third point, wherein a first arc of the double arcs is tangent to a first desired tangent vector at the first point and a second arc of the double arcs is tangent to a second desired tangent vector at the third point, the first arc and the second arc being tangent to each other, wherein the body is a cutting tool of a CNC machine.

22. The method of claim 21, further including the step of determining whether the double arcs are valid by comparing a distance from the second point to a closest arc of the double arcs to a predetermined distance.

23. The method of claim 22, wherein if the double arcs are not valid, then generating a second pair of arcs that pass through the first point, the second point, and an intermediate point between the first and second points.

24. The method of claim 23, further including the step of determining whether the second pair of arcs are valid by comparing a distance from the intermediate point to a line segment extending between the first and second points to a predetermined distance.

25. The method of claim 24, wherein if the second pair of arcs are not valid, then defining a portion of the trajectory between the first and second points as a line segment.

26. A method of generating a trajectory for a body, including the steps of:

identifying a plurality of line segments included within the trajectory;

smoothing at least a portion of the plurality of line segments by converting the portion of line segments into a plurality of arcs which remain within a tolerance relative to the trajectory, wherein the smoothing step includes the steps of preparing for smoothing, adjusting for smoothing, and smoothing using a double arc algorithm and wherein the adjusting for smoothing step includes the steps of;

identifying four adjacent points that together define a portion of the trajectory,

determining a first construction arc that passes through the first, second, and fourth points and lies in a first plane,

determining a second construction arc that passes through the first, third and fourth points and lies in a second plane,

determining a first vector extending from the second point to a first end point on the second construction arc that is closest to the second point,

determining a second vector extending from the third point to a second end point on the first construction arc that is closest to the third point,

adjusting the second point a first adjustment distance along the first vector if the second point has been marked as suitable for smoothing and at least one of the first and third points has been marked as suitable for smoothing, and

adjusting the third point a second adjustment distance along the second vector if the third point has been marked as suitable for smoothing and at least one of the second and the fourth points has been marked as suitable for smoothing, and

moving the body based on the plurality of arcs, wherein the body is a cutting tool.

27. A method of generating a trajectory for a body, including the steps of:

identifying a plurality of line segments included within the trajectory; and

smoothing at least a portion of the plurality of line segments by converting the portion of line segments into a plurality of arcs which remain within a tolerance relative to the trajectory, wherein the smoothing step includes the steps of preparing for smoothing, adjusting for smoothing, and smoothing using a double arc algorithm and wherein the smoothing using a double arc algorithm step includes the steps of

determining a desired tangent vector for each of a plurality of points processed by the adjusting for smoothing step,

generating double arcs to replace a first line segment between a first point and a second point and a second line segment between the second point and a third point, wherein a first arc of the double arcs is tangent to a first desired tangent vector at the first point and a second arc of the double arcs is tangent to a second desired tangent vector at the third point, the first arc and the second arc being tangent to each other, and

moving the body based on the double arcs, wherein the body is a cutting tool.