Tolerance based motion control system

Abstract

The present invention involves a tolerance based motion controller. The controller is capable of processing a group of tolerance constraints. The tolerance constraints specify where and when each tolerance constraint is to be applied, along with the information specifying the desired trajectory of motion. There are also a group of velocity constraints, specifying the maximum allowable velocity at each point along the desired trajectory. This information along with sensor feedback is used to modify the velocity along the actual trajectory of motion. This results in the time required traverse the trajectory being as short as possible. Also, the actual trajectory of motion should never exceed the permissible deviation from the desired trajectory, as specified by the tolerance constraints, with the velocity always being bounded by the specified velocity constraint.

1. A method of NC tolerance based motion control for a motion device based on feedrate parameters comprising the steps of:
 specifying where and when what NC tolerance is requested by using NC tolerance commands  for a desired trajectory a plurality of NC tolerances from the desired trajectory;  
 obtaining thegenerating motion commands, including itsbased on the desired trajectory and the feedrate parameters;  
 calculating feedrate limitations by mappings from desired trajectory of  said motion commands and at least a first NC tolerance requirement commands  from the desired trajectory;  
 modifying thedetermining a commanded feedrate by using thesaid feedrate limitations; and  
 executing themoving said motion device based on said motion commands according to modifiedand said commanded feedrate so that the requested, whereby the at least a first NC tolerance may befrom the desired trajectory is satisfied by moving said motion device based on said motion commands and said commanded feedrate.  
 
     
     
       2. An apparatus for performing NC tolerance based motion control for a machine tool using , said apparatus having access to a part program and a desired error tolerance , said apparatus comprising:
 parsing means for parsinga parser adapted to parse the part program into at least one segment, each said segment including an associated trajectory and an error tolerance informationrange from the associated trajectory;  
 calculating means for determininga processor adapted to determine a modified feedrate value for each said segment based on the associated trajectory and the error tolerance informationrange from the associated trajectory, the modified feedrate value being based at least in part on a predicted deviation of the motion device from the associated trajectory; and  
 executing means for operatinga control configured to provide signals to operate the machine tool according to said modified feedrate value so that the desiredfor each said segment, whereby the error tolerance may berange from the associated trajectory is satisfied by operating the machine tool according to said modified feedrate.  
 
     
     
       3. A method of NC tolerance based motion control comprising the steps of:
 specifying where and when what NC tolerance is requested by using NC tolerance commands;    obtaining the motion commands, including its desired trajectory and feedrate;    calculating feedrate limitations by mappings from desired trajectory of motion commands and NC tolerance requirement commands;    modifying the commanded feedrate by using the feedrate limitations;    executing the motion commands according to modified feedrate so that the requested NC tolerance may be satisfied.    
     
     
       4. An NC motion control system capable of processing NC tolerance requirements and motion commands with associated feedrates for a motion device and modifying feedrates according to the  a desired trajectory of the motion command  commands and said NC tolerance commands so that the NC tolerance  requirements may be satisfied , said system comprising:
 a motion command meansunit adapted to store a set of said motion commands, including relatedsaid associated feedrates;  
 a tolerance command meansunit adapted to store a set of NC tolerance commands specifying where and when an NC tolerance range is requested;  
 a feedrate mappings meansmapper adapted to calculate a set of feedrate limitation mappings that maplimitations mapped from the desired trajectory of said motion commands and said NC tolerance commands to the feedrate limitations that allows the motion command to be executed within themaintain a position of the motion device within a specified NC tolerance range from the desired trajectory;  
 a processor capable of modifying  configured to modify the feedrate in the motion commands  associated feedrates of the motion device based on the set of feedrate limitation mappings, the motion command to be executed and the NC tolerance requirement for the said motion command, capable of reading position feedback signals, and capable of calculating motion signals according to the said motion command, the position feedback and the modified feedrate  limitations and to move the motion device based on the modified associated feedrates.  
 
     
     
       5. A method of operating a tolerance based computer-controlled machine tool Numerical Controller (NC) to control the operation of a motion device, said method comprising the steps of:
 having the operator specify the intendedspecifying a desired NC tolerance level and generating NC tolerance commands therefrom;  
 obtainingspecifying a set of motion commands, the motion commands  including a desired trajectory and feedrate;  
 in a computer,  calculating feedrate limitations by mappings from thesaid desired trajectory of motion commands and theand said NC tolerance requirement  commands;  
 modifying the set of feedrate  said motion commands based upon  on said feedrate limitations; and  
 executing the  said motion commands, according to the set of  said modified feedrate commands, so that the NC tolerance may be reduced to the intended level; thereby improving the control quality  to move of the motion device, whereby the motion device is maintained within the NC tolerance level as the motion device is moved.  
 
     
     
       6. The method described in  of  claim 5  wherein the NC tolerance commands are in the form of specialized G and M codes. 
     
     
       7. The method of  claim 1 , wherein each of the plurality of NC tolerances is a dimensional tolerance. 
     
     
       8. The method of  claim 1 , wherein the motion device is a machine tool. 
     
     
       9. The apparatus of  claim 2 , wherein the error tolerance range is a dimensional tolerance range. 
     
     
       10. The method of  claim 4 , wherein the motion device is a machine tool. 
     
     
       11. The method of  claim 5 , wherein the NC tolerance level is a dimensional tolerance level. 
     
     
       12. A method of operating a motion controller for controlling a motion device within an acceptable deviation range from a desired trajectory, the acceptable deviation range from the desired trajectory being non- uniform, the method comprising:      determining a first uniform acceptable deviation range corresponding to a first desired trajectory segment of the desired trajectory for the motion device;        obtaining a first velocity for the motion device;        determining a maximum velocity for the motion device based on said first uniform acceptable deviation range from the first desired trajectory segment, the maximum velocity being greater than the first velocity; and        operating the motion controller based on said determined maximum velocity to influence a movement of the motion device at a second velocity greater than the first velocity, whereby the movement of the motion device is maintained within the first acceptable deviation range from the first desired trajectory segment.     
     
     
       13. The method of  claim 12 , wherein said first uniform acceptable deviation range is specified by a user. 
     
     
       14. The method of  claim 12 , further comprising the step of:
   determining a predicted deviation of said motion device from the first desired trajectory segment, wherein said maximum velocity is further based on said predicted deviation.     
     
     
       15. The method of  claim 14 , wherein said first desired trajectory segment is specified by a user. 
     
     
       16. The method of  claim 14 , wherein said first desired trajectory segment is calculated. 
     
     
       17. The method of  claim 14 , wherein said predicted deviation is based on prior performance of said motion device. 
     
     
       18. The method of  claim 14 , wherein said predicted deviation is based on experimentation. 
     
     
       19. The method of  claim 12 , wherein said second velocity is based in part on real- time monitoring of a performance of said motion device.   
     
     
       20. The method of  claim 19 , wherein the performance of said motion device includes a current position of the motion device. 
     
     
       21. The method of  claim 12 , wherein said acceptable deviation range from the desired trajectory includes a plurality of uniform acceptable deviation values corresponding to a plurality of trajectory segments of said desired trajectory. 
     
     
       22. The method of  claim 12 , wherein the first uniform acceptable deviation range is a dimensional deviation range and the velocity is the maximum velocity. 
     
     
       23. The method of  claim 12 , wherein the motion device is a machine tool. 
     
     
       24. A method of controlling a machine tool with a controller, said method comprising:
   selecting an operation for the machine tool;        associating a first feedrate and an acceptable deviation range from a desired trajectory with said operation;        determining a maximum machine tool feedrate for said operation based on said acceptable deviation range from the desired trajectory; and        providing control signals to move the machine tool at a second feedrate being greater than the first feedrate, the maximum machine tool feedrate being greater than the first feedrate, whereby the maximum machine tool feedrate is determined to maintain the machine tool within the acceptable deviation range from the desired trajectory.     
     
     
       25. The method of  claim 24 , wherein said acceptable deviation range from the desired trajectory includes a plurality of values corresponding to a plurality of segments of said desired trajectory. 
     
     
       26. The method of  claim 24 , wherein said operation is characterized by at least one of the first velocity, the desired trajectory, a curvature of the desired trajectory, a turning angle of the desired trajectory, an acceleration, and a deceleration. 
     
     
       27. The method of  claim 24 , further comprising the step of determining a predicted deviation of the machine tool from the desired trajectory for said operation and wherein said maximum machine tool feedrate is further based on said predicted deviation of the machine tool from the desired trajectory. 
     
     
       28. The method of  claim 27 , wherein said step of determining said predicted deviation of the machine tool from the desired trajectory includes measuring previous machine tool performance. 
     
     
       29. The method of  claim 27 , wherein said predicted deviation of the machine tool from the desired trajectory is based on at least one of a function and a data set based on at least one of the first velocity, the desired trajectory, a curvature of the desired trajectory, a turning angle of the desired trajectory, an acceleration, and a deceleration. 
     
     
       30. The method of  claim 24 , wherein said determining step occurs in real- time while said controller controls said machine tool.   
     
     
       31. The method of  claim 24 , wherein said acceptable deviation range from the desired trajectory is at least one of a dimensional deviation and a geometric deviation. 
     
     
       32. The method of  claim 24 , wherein the acceptable deviation range is a dimensional deviation range. 
     
     
       33. The method of  claim 24 , wherein said determining step includes the step of monitoring a current position of the machine tool and the second feedrate is further based on a current deviation of the machine tool from the desired trajectory. 
     
     
       34. A method of operating a motion control device to control the movement of a motion device within an acceptable deviation range, the motion control device having at least one variable parameter, the method comprising the steps of:
   obtaining a motion profile for the motion device;        associating the acceptable deviation range with said motion profile;        determining a predicted deviation of the motion device from said motion profile;        determining a value for the at least one variable parameter based on said predicted deviation of the motion device from said motion profile and said acceptable deviation range associated with said motion profile, the value of the at least one variable parameter to maintain the motion device within the acceptable deviation range associated with said motion profile; and        providing control signals to move the motion device based on the value for the at least one variable parameter.     
     
     
       35. The method of  claim 34 , wherein said at least one variable parameter includes at least one velocity parameter. 
     
     
       36. The method of  claim 34 , wherein said acceptable deviation range associated with said motion profile includes a plurality of values corresponding to a plurality of segments of said motion profile. 
     
     
       37. The method of  claim 34 , wherein the value of the at least one variable parameter minimizes the time required to traverse said motion profile within said acceptable deviation range associated with said motion profile. 
     
     
       38. The method of  claim 34 , further comprising the step of monitoring a current position of the motion device, wherein said predicted deviation of the motion device from said motion profile is determined based in part on the current position of the motion device. 
     
     
       39. The method of  claim 34 , wherein the acceptable deviation range is a dimensional deviation range. 
     
     
       40. The method of  claim 34 , wherein the motion device is a machine tool. 
     
     
       41. The method of  claim 34 , wherein the at least one variable parameter includes a first velocity parameter corresponding to a first direction of travel of the motion device, a second velocity parameter corresponding to a second direction of travel of the motion device, and a third velocity parameter corresponding to a third direction of travel of the motion device. 
     
     
       42. The method of  claim 34 , wherein the motion profile is provided in a part program. 
     
     
       43. The method of  claim 42 , wherein the part program further includes information about the acceptable deviation range. 
     
     
       44. The method of  claim 34 , wherein the step of associating the acceptable deviation range with said motion profile includes the steps of:
   parsing the motion profile into a plurality of segments based on the acceptable deviation range, the acceptable deviation range having a plurality of values and each segment having a constant value for that segment; and        storing the plurality of segments and associated constant value acceptable deviation ranges on a computer readable medium.     
     
     
       45. An apparatus for control of a motion device capable of movement according to a desired motion, the apparatus comprising:
   a processor adapted to receive data relating to said desired motion, a first acceptable deviation for said desired motion associated with a first  3 D region of space, and a second acceptable deviation for said desired motion associated with a second  3 D region of space, said processor further adapted to determine a control signal including a first motion device velocity information based on the first acceptable deviation for a first portion of said desired motion in the first  3 D region of space and based on a first predicted deviation of the motion device from the first portion of the desired motion and a second motion device velocity information based on the second acceptable deviation for a second portion of said desired motion in the second  3 D region of space and based on a second predicted deviation of the motion device from the second portion of the desired motion; and        a device coupled to said processor and configured to provide said control signal to the motion device.     
     
     
       46. The apparatus of  claim 45 , wherein said first motion device velocity information corresponds to a maximum velocity of the motion device while maintaining the motion device within the first acceptable deviation for the first portion of the desired motion. 
     
     
       47. The apparatus of  claim 45 , wherein the motion device includes a machine tool. 
     
     
       48. The apparatus of  claim 45 , wherein the data related to the desired motion is based on a part definition which specifies the first specified velocity, wherein the velocity of the motion device is maximized. 
     
     
       49. The apparatus of  claim 45 , wherein the acceptable deviation range is a dimensional deviation range. 
     
     
       50. An apparatus for control of a motion device capable of movement according to a desired motion, the apparatus comprising:
   a processor adapted to receive data relating to said desired motion and an acceptable deviation range for said desired motion passing through a first  3 D region, said processor further adapted to determine a control signal, wherein said control signal includes motion device velocity information; and        a device coupled to said processor and adapted to provide said control signal to the motion device, whereby the determination of said control signal increases a velocity of the motion device relative to a first specified velocity while maintaining said motion device within said acceptable deviation range for said desired motion passing through the first  3 D region.     
     
     
       51. The apparatus of  claim 50 , wherein said control signal is further based on an actual position of the motion device. 
     
     
       52. The apparatus of  claim 50 , wherein the acceptable deviation range is a dimensional deviation range. 
     
     
       53. The method of  claim 52 , wherein the motion device is a machine tool. 
     
     
       54. An apparatus for motion control for a motion device capable of receiving commands associated with a desired velocity, a trajectory, and an acceptable deviation range from the trajectory, the apparatus comprising:
   a calculating means for determining a velocity parameter, the velocity parameter based on the trajectory, a predicted deviation from the trajectory, and the acceptable deviation range from the trajectory to maintain the motion device within the acceptable deviation range from the trajectory; and        a control means for operating the motion device, whereby the control means operates the motion device in accordance with the velocity parameter to maintain the motion device within the acceptable deviation range from the trajectory.     
     
     
       55. The apparatus of  claim 54 , wherein said velocity parameter corresponds to a velocity of the motion device and determining said velocity parameter includes maximizing the velocity of the motion device while keeping the predicted deviation from the trajectory of the motion device within the acceptable deviation range from the trajectory. 
     
     
       56. The apparatus of  claim 55 , further comprising a parsing means for receiving a part definition and for parsing said part definition into at least one segment, each said segment including an associated trajectory and an associated acceptable deviation range from the associated trajectory. 
     
     
       57. The apparatus of  claim 56 , wherein a first segment includes a first associated deviation range and a second segment includes a second associated deviation range, the second associated acceptable deviation range differing from the first acceptable deviation range. 
     
     
       58. The method of  claim 54 , wherein the motion device is a machine tool. 
     
     
       59. A method of tolerance based motion control of a motion device comprising the steps of:
   receiving a desired trajectory for the motion device and an acceptable deviation range from the desired trajectory for the motion device;        determining at least a first velocity limitation of the motion device, the first velocity limitation being based on the desired trajectory and the acceptable deviation range from the desired trajectory;        monitoring an actual deviation of the motion device from the desired trajectory;        determining a commanded velocity of the motion device based on at least the first velocity limitation and the actual deviation to maintain a predicted position of the motion device within the acceptable deviation range from the desired trajectory; and        providing signals to move the motion device at the commanded velocity.     
     
     
       60. The method of  claim 59 , wherein the commanded velocity corresponds to a maximum velocity to move the motion device while maintaining the motion device within the acceptable deviation range from the desired trajectory. 
     
     
       61. The method of  claim 59 , wherein the motion device is a machine tool. 
     
     
       62. The method of  claim 61 , wherein the step of receiving the desired trajectory and the acceptable deviation range from the desired trajectory includes the step of receiving a part program including a plurality of motion commands which specify the desired trajectory and a plurality of tolerance commands which specify the acceptable deviation range from the desired trajectory. 
     
     
       63. The method of  claim 62 , further comprising the steps of:
   parsing the plurality of motion commands based on the plurality of tolerance commands to generate a plurality of motion command segments, each motion command segment having a uniform acceptable deviation range, a first motion command segment having a first uniform acceptable deviation range from a first desired trajectory segment and a second motion command segment having a second uniform acceptable deviation range from a second desired trajectory segment different from the first uniform acceptable deviation range from the first desired trajectory segment; and        storing the plurality of motion command segments on a computer readable medium.     
     
     
       64. The method of  claim 63 , wherein the plurality of tolerance commands each specify at least one of a time and an area wherein the acceptable deviation range of the tolerance command is active. 
     
     
       65. The method of  claim 59 , wherein the first velocity limitation of the motion device is further based on at least one of a desired velocity, the desired trajectory, a curvature of the desired trajectory, a turning angle of the desired trajectory, and a rate of change in velocity. 
     
     
       66. The method of  claim 59 , wherein the first velocity limitation of the motion device is based further on a desired velocity and the commanded velocity is based on a maximum velocity to move the motion device while maintaining the motion device within the acceptable deviation range from the desired trajectory, the commanded velocity being greater than the desired velocity. 
     
     
       67. The method of  claim 66 , wherein the commanded velocity is the maximum velocity to move the motion device while maintaining the motion device within the acceptable deviation range from the desired trajectory. 
     
     
       68. The method of  claim 59 , wherein the acceptable deviation range is a dimensional deviation range. 
     
     
       69. A method of tolerance based motion control of a motion device comprising the steps of:
   specifying a first tolerance for a first  3 D region of space;        specifying a second tolerance for a second  3 D region of space;        specifying a trajectory which passes through both the first  3 D region of space and the second  3 D region of space; and        controlling a velocity of the motion device to maintain the motion device within the first tolerance from the trajectory in the first  3 D region of space and to maintain the motion device within the second tolerance from the trajectory in the second  3 D region of space.     
     
     
       70. The method of  claim 69 , further comprising the step of providing a part program including a plurality of program instructions, wherein the plurality of program instructions, specify the first  3 D region of space, specifying the first tolerance; specify the second  3 D region of space, specify the second tolerance, and specify the trajectory. 
     
     
       71. The method of  claim 70 , wherein the second tolerance value is less than the first tolerance value. 
     
     
       72. The method of  claim 69 , wherein the first tolerance is specified for a first phase of the movement of the motion device and the second tolerance is specified for a second phase of the movement of the motion device, the second phase occurring after the first phase, wherein the second  3 D region overlaps at least a portion of the first  3 D region. 
     
     
       73. The method of  claim 72 , wherein the velocity of the motion device is controlled to maintain the motion device within the first tolerance value for a first portion of the trajectory passing through the first  3 D region of space during the first phase and to maintain the motion device within the second tolerance for a second portion of the trajectory passing through the second  3 D region of space during the second phase. 
     
     
       74. The method of  claim 69 , further comprising the steps of:
   increasing the velocity of the motion device for a first portion of the trajectory based on the first tolerance and a first calculated machining error from the trajectory for the motion device; and        decreasing the velocity of the motion device for a second portion of the trajectory based on the first tolerance and a second calculated machining error from the trajectory for the motion device.     
     
     
       75. A method of tolerance based motion control of a motion device comprising the steps of:
   associating for a first  3 D region of space a first tolerance;        associating for a second  3 D region of space a second tolerance, the second  3 D region of space overlapping at least a portion of the first  3 D region of space;        determining if a desired trajectory is contained in both of the first  3 D region of space and the second  3 D region of space and if so then dividing the desired trajectory into at least two trajectory segments, a first trajectory segment being contained in the first  3 D region of space and a second trajectory segment being contained in the second  3 D region of space;        determining at least a first velocity limitation of the motion device for the first trajectory segment based on the first tolerance; and        determining a commanded velocity of the motion device based at least on the first velocity limitation to maintain a predicted position of the motion device in the first  3 D region of space within the first tolerance.     
     
     
       76. The method of  claim 75 , further comprising determining a second velocity limitation of the motion device for the second trajectory segment based on the second tolerance, wherein the commanded velocity of the motion device is further based on the second velocity limitation to maintain a predicted position of the motion device in the second  3 D region of space within the second tolerance. 
     
     
       77. The method of  claim 76 , wherein the predicted position of the motion device in the first  3 D region of space and the predicted position of the motion device in the second  3 D region of space are based on feedback of an actual position of the motion device. 
     
     
       78. The method of  claim 77 , wherein the motion device is a machine tool, the first  3 D region of space is a first machining space, and the second  3 D region of space is a second machining space.