Digital position encoder and data optimizer

• US 5,126,948 A
• Filed: 11/08/1989
• Issued: 06/30/1992
• Est. Priority Date: 11/08/1989
• Status: Expired due to Fees

• Current Assignee: Vought Aircraft Company
• Original Assignee: LTV Aerospace and Defense Company
• Inventors: Rice, Mark, Mitchell, Lee D.
• Primary Examiner(s): RUGGIERO, JOSEPH F
• Application Number:
  US07/434,983
• Time in Patent Office: 965 Days
• Field of Search: 364/474.03, 364/474.37, 364/513, 364/560, 364/561, 364/191-193, 318/577, 318/578, 318/568.1, 33/503, 33/504, 33/505, 901/3-5, 395/80, 395/99
• US Class Current: 700/161
• CPC Class Codes: G05B 19/408 characterised by data handling or data format, e.g. reading, buffering or conversion of data
• CPC Class Codes: G05B 19/4207 in which a model is traced or scanned and corresponding data recorded

Abstract

A digitizing system for automatically recording data points representative of, for example, sheet metal templates having varying shapes is disclosed. A stylus connected to a tracing arm is guided along the edge of a template. As the arm moves, digital scales generate a stream of encoded electrical pulses which yield direction and distance information. These pulses are then decoded, counted, and stored. If the operator has selected the automatic digitize mode, a data point is automatically stored each time the stylus moves a predetermined distance in the X, Y, or Z direction. The present invention also provides an improved method of optimizing or compressing the stored set of data points.

Claims

1. A digitizing system for generating, recording, and optimizing coordinate data representative of a traced path comprising:

a) a digitizer support structure;

b) a stylus assembly functionally supported by said support structure and displaceable in a first dimension and in a second dimension;

c) a scaling network functionally interconnected with said stylus assembly and responsive to stylus movement for generating stylus displacement signals indicating stylus movement in said first and second dimensions;

d) a first circuit responsive to said stylus displacement signals for generating count signals representing the displacement of said stylus relative to a predetermined starting point;

e) initiating means responsive to said count signals for generating an initiating signal whenever said stylus travels a predetermined distance;

f) a second circuit responsive to said initiating signal and to said count signals for generating coordinate data representative of said count signals; and

g) a data processor for receiving and processing said coordinate data, said data processor including;

i) memory means for storing said coordinate data thereby resulting in an ordered set of data points P_a, P_b, . . . , (P_i), . . . , P_n, where P_n is the last data point in the set; and

ii) optimizing means for optimizing the stored coordinate data;

wherein said optimizing means comprises;

a) means for establishing a direction vector through points P_a and P_b, where P_a is the base point for said direction vector;

b) means for establishing a tolerance band of predetermined width on either side of and parallel to said direction vector;

c) means for identifying a point P_i, if any, following the base point that falls outside said tolerance band;

d) data discarding means responsive to the existence or nonexistence of P_i for discarding substantially all points between the base point and a point P_h, which is a point within said tolerance band preceding the point P_i in said ordered set of data points, only if P_i exists, otherwise, if P_i does not exist, said means functioning to discard substantially all data points between the base point and the last data point, P_n, in which case said set of data points has been completely optimized;

e) means continually operable until said set of data points has been completely optimized for determining whether said set of data points has been completely optimized and if said set has not been completely optimized said means further functioning to;

(i) establish a new direction vector through the point P_h and point P_i, where P_h is the base point for said new direction vector,

(ii) establish a new tolerance band of predetermined width on either side of and parallel to said new direction vector,

(iii) identify a new point Phd i, if any, following the base point that falls outside said new tolerance band, and then

(iv) employ said data discarding means.

2. The system of claim 1 wherein said second circuit further functions to generate coordinate data without interrupting the function of said first circuit.

3. The system of claim 2 further comprising means for associating the correct sign, either positive or negative, with said coordinate data.

4. The system of claim 1 wherein said stylus assembly is also displaceable in a third dimension and wherein said scaling network further functions to generate stylus displacement signals indicating stylus movement in said third dimension.

5. The system of claim 4 wherein said second circuit further functions to generate coordinate data without interrupting the function of said first circuit.

6. The system of claim 5 further comprising means for associating the correct sign, either positive or negative, with said coordinate data.

7. A digitizing system for generating, recording, and optimizing coordinate data representative of a traced path comprising:

a) a digitizer support structure;

b) an arm assembly slidably connected to said support structure and displaceable in a first dimension only;

c) a stylus assembly slidably connected to said arm assembly and displaceable in said first dimension and in a second dimension;

d) scaling network means functionally interconnected with said arm assembly and said stylus assembly and responsive to stylus movement for generating stylus displacement signals indicating stylus movement in said first and second dimensions;

e) means for converting said stylus displacement signals into direction count pulses;

f) counting means responsive to said direction count pulses for generating count signals representing the displacement of said stylus relative to a predetermined starting point;

g) initiating means responsive to said count signals for generating an initiating signal whenever said stylus travels a predetermined distance;

h) data coordinate generating means responsive to said initiating signal and to said count signals for generating coordinate data representative of said count signals; and

i) data processing means for receiving and processing said coordinate data, said data processing means including;

(i) a memory;

(ii) means for successively storing said coordinate data in said memory thereby resulting in an ordered set of data points P_a, P_b, . . . , (P_i), . . . , P_n, where P_n is the last data point in the set; and

(iii) optimizing means for optimizing the stored coordinate data;

wherein said optimizing means comprises;

a) means for establishing a direction vector through points P_a and P_b, where P_a is the base point for said direction vector;

b) means for establishing a tolerance band of predetermined width on either side of and parallel to said direction vector;

c) means for identifying a point P_i, if any, following the base point that falls outside said tolerance band;

d) data discarding means responsive to the existence or nonexistence of P_i for discarding substantially all points between the base point and a point P_h, which is a point within said tolerance band preceding the point P_i in said ordered set of data points, only if P_i exists, otherwise, if P_i does not exist, said means functioning to discard substantially all data points between the base point and the last data point, P_n, in which case said set of data points has been completely optimized;

e) means continually operable until said set of data points has been completely optimized for determining whether said set of data points has been completely optimized and if said set has not been completely optimized said means further functioning to;

(i) establish a new direction vector through the point P_h and point P_i, where P_h is the base point for said new direction vector,

(ii) establish a new tolerance band of predetermined width on either side of and parallel to said new direction vector,

(iii) identify a new point P_i, if any, following the base point that falls outside said new tolerance band, and then

(iv) employ said data discarding means.

8. The system of claim 7 wherein said data coordinate generating means further function to generate coordinate data without interrupting the function of said counting means.

9. The system of claim 8 wherein said data coordinate generating means function to generate said coordinate data in the form of ASCII text characters.

10. The system of claim 9 wherein said data processing means includes an "IBM" compatible personal computer.

11. The system of claim 7 wherein said stylus assembly is also displaceable in a third dimension.

12. The system of claim 11 wherein said scaling network means further function to generate stylus displacement signals indicating stylus movement in said third dimension.

13. The system of claim 12 wherein said data coordinate generating means further function to generate coordinate data without interrupting the function of said counting means.

14. The system of claim 13 wherein said data coordinate generating means function to generate said coordinate data in the form of ASCII text characters.

15. The system of claim 14 wherein said data processing means includes an "IBM" compatible personal computer.

16. A digitizing system for generating, recording, and optimizing coordinate data representative of a traced path comprising:

a) a digitizer table;

b) an arm assembly slidably connected to said table and displaceable in a first dimension;

c) a stylus assembly slidably connected to said arm assembly and displaceable in said first dimension and in a second dimension;

d) scaling network means functionally interconnected with said arm assembly and said stylus assembly and responsive to stylus movement for generating stylus displacement signals indicating stylus movement in said first and second dimensions;

e) manual entry means for generating function request signals;

f) a digital computer including a memory means;

g) a digitizer card functionally connected to said digital computer, to said scaling network means, and to said manual entry means, said digitizer card comprising;

(i) means for receiving said stylus displacement signals and for converting said signals into direction count pulses;

(ii) counting means responsive to said direction count pulses for generating count signals representing the displacement of said stylus relative to a predetermined starting point;

(iii) initiating means responsive to said count signals for generating an initiating signal whenever said stylus travels a predetermined distance in either said first or second dimensions;

(iv) data coordinate generating means responsive to said initiating signal and to said count signals for generating coordinate data, said coordinate data being in the form of ASCII text characters and representative of said count signals;

(v) means for associating the correct sign, either positive or negative, with said coordinate data; and

(vi) buffer means for temporarily storing said coordinate data until read by the digital computer, for receiving and temporarily storing said function request signals until read by the digital computer, and for receiving command signals from said digital computer;

h) means for successively storing said coordinate data in said memory thereby resulting in an ordered set of stored data points P₁, P₂, . . . , (P_i), . . . , P_n is the last data point in the set; and

i) optimizing means for optimizing said stored set of data points wherein said optimizing means includes;

(i) means for establishing a direction vector through the first two points P₁ and P₂, where P₁ is the base point for said direction vector;

(ii) means for establishing a tolerance band of predetermined width on either side of and parallel to said direction vector;

(iii) means for identifying the first point P_i, if any, following the base point that falls outside said tolerance band;

(iv) data discarding means responsive to the existence or nonexistence of P_i for discarding all points between the base point and a point P_i-1, which is the point immediately preceding the point P_i, if P_i exists, otherwise, if P_i does not exist, said means functioning to discard all data points between the base point and the last data point, P_n, in which case said set of data points has been completely optimized; and

(v) means continually operable until said set of data points has been completely optimized for determining whether said set of data points has been completely optimized and if said set has not been completely optimized said means further functioning to;

(1) establish a new direction vector through point P_i-1 and point P_i, where P_i-1 is the base point for said new direction vector,

(2) establish a new tolerance band of predetermined width on either side of and parallel to said new direction vector,

(3) identify a new point P_i, if any, following the base point that is the first point to fall outside said new tolerance band, and then

(4) employ said data discarding means.

17. The system of claim 16 wherein said stylus assembly is also displaceable in a third dimension.

18. The system of claim 17 wherein said scaling network means further function to generate stylus displacement signals indicating stylus movement in said third dimension.

19. The system of claim 18 wherein said initiating means further functions to generate an initiating signal whenever said stylus travels a predetermined distance in said third dimension.

20. The system of claim 16 wherein said digital computer is an "IBM" compatible personal computer.

21. The system of claim 19 wherein said digital computer is an "IBM" compatible personal computer.

22. A method of generating, recording, and optimizing coordinate data representative of a path traced by a digitizing system wherein said digitizing system includes a digitizer support structure, a stylus assembly functionally supported by said support structure and displaceable in two or three dimensions, and a scaling network functionally associated with said stylus assembly and responsive to stylus movement for generating stylus displacement signals;

comprising the steps of;

a) generating stylus displacement signals by tracing a path with said stylus assembly;

b) converting said stylus displacement signals into direction counts;

c) counting said direction counts relative to a predetermined starting point;

d) generating coordinate data indicative of the displacement of said stylus relative to said starting point whenever said stylus travels a predetermined distance;

e) successively storing said coordinate data in a memory so that an ordered set of data points P₁, P₂, . . . , (P_i), . . . , P_n representative of said traced path is created where P_n is the last data point in the set; and

f) reducing the total number of points in said ordered set without substantially altering the representation of said traced path thereby to optimize said set of data points by;

1) establishing a direction vector through the first two points P₁ and P₂, where P₁ is the base point for said direction vector;

2) establishing a tolerance band of predetermined width on either side of and parallel to said direction vector;

3) identifying the first point P_i, if any, following the base point that falls outside said tolerance band;

4) if P_i exists, discarding all points between the base point and a point P_i-1 which is the point immediately preceding the point P_i, otherwise, if no point P_i exists which falls outside said tolerance band, then discarding all points between the base point and the last data point, P_n, thereby defining completion of said optimization step;

5) if the optimization procedure is not complete, then

(i) establishing a new direction vector through point P_i-1 and point P_i, where P_i-1 is the base point for said new direction vector;

(ii) establishing a new tolerance band of predetermined width on either side of and parallel to said new direction vector;

(iii) identifying a new point P_i, if any, following the base point that is the first point to fall outside said new tolerance band;

(iv) repeating steps (4) through (5)(iii) until optimization is complete.

23. The procedure of claim 22 wherein said step of determining the first point P_i, if any, following the base point that falls outside said tolerance band further includes successively determining the perpendicular distance from each point following the base point in said ordered set of data points to said direction vector and then comparing each said perpendicular distance with the predetermined width of said tolerance band.