Feature based method of designing automotive panels

• US 5,119,309 A
• Filed: 03/25/1991
• Issued: 06/02/1992
• Est. Priority Date: 04/26/1989
• Status: Expired due to Fees

• Current Assignee: General Motors Corporation (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Marin, Samuel P., Cavendish, James C., Ross, Giles L.
• Primary Examiner(s): Harkcom, Gary V.
• Assistant Examiner(s): Bayerl, Raymond J.
• Application Number:
  US07/675,108
• Time in Patent Office: 435 Days
• Field of Search: 364/522, 364/191, 364/192, 364/474.01, 364/474.05, 364/474.22, 364/474.24, 364/474.29
• US Class Current: 700/182
• CPC Class Codes: G05B 19/4099 Surface or curve machining, making 3D objects, e.g. desktop manufacturing
• 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 2219/34098 Slope fitting, fairing contour, curve fitting, transition
• CPC Class Codes: G06F 30/15 Vehicle, aircraft or watercraft design
• CPC Class Codes: G06T 17/20 Finite element generation, e.g. wire-frame surface description, tesselation

Abstract

A method of forming a composite surface which is comprised of a base or primary surface and a number of features, and which satisfies certain functional objectives or requirement. Implemented in a Computer Aided Design system employed to assist in the design of automobile inner panels, the method accepts as input a feature-based information which describes the geometry of a particular inner panel, and produces as an output, a composite surface with a user-specified degree of smoothness. The method permits interactive design and modification of complex inner panel surfaces, and significantly simplifies attendant aspects of the panel design process such as numerically controlled machining.

Claims

1. A method of creating and machining a three dimensional composite surface on a workpiece using a computer, said composite surface being defined by a function z=g₁ (x,y) containing a primary surface S₀ defined by a function z=f₀ (x,y), a secondary surface S₁ defined by a function z=f₁ (x,y), and which makes a smooth transition between S₀ and S₁, comprising the steps of:

a. entering into said computer a plurality of coordinate data points x_j, y_j,j=1,2, . . . N

b. connecting said data points in the xy-plane with straight lines and rounding the j^th corner of the thereby defined polygon with a circle of radius r_j to define a smooth closed curve C₁,

c. offsetting C₁ by a predetermined amount R to define a closed curve C₀,

d. generating output data which defines the composite surface as coinciding with S₀ in the region outside the curve C₀, coinciding with S₁ in the region inside the curve C₁, and making a smooth transition from S₀ to S₁ in the region between C₀ and C₁,

e. machining the workpiece in accordance with said output data.

2. The method as defined in claim 1 in which the workpiece is used to manufacture an automotive inner panel.

3. A method of creating a three dimensional composite surface and machining the surface on a workpiece using a computer, said composite surface defined by a function z=g₁ (x,y) and comprising a primary surface S₀ defined by the function z=f₀ (x,y), joined smoothly to a secondary surface S₁ defined by the function z=f₁ (x,y), comprising the steps of:

a. inputting a plurality of coordinate data points (x_j,y_j), j=1,2, . . . N, inputting corner radius values r_j, j=1,2, . . . N, and inputting an offset distance R,

b. connecting the data points with straight lines, and rounding the j^th corner (j=1,2, . . . N) of the thereby defined polygon with a circle of radius r_j to define a smooth curve C₁,

c. defining a smooth closed curve C₀ by offsetting C₁ in the xy-plane a distance R,

d. processing the data input from step a to define a transition function Z=Φ

(x,y) having values Z=1 for xy-coordinates inside C₁, Z=0 for xy-coordinates outside C₀, and values of Z that increases from 0 to 1 for coordinates inside the region existing between the two curves C₀ and C₁ in the xy-plane,

e. generating output data defining the composite surface which coincides with S₀ for xy-coordinates in the region outside the curve C₀, coincides with S₁ for xy-coordinates int eh region inside the curve C₁ and makes a smooth transition between S₀ and S₁ in the region between the two curves C₀ and C₁ in accordance with the formula

space="preserve" listing-type="equation">g1(x,y)=(1-Φ

(x,y))f.sub.0 (x,y)+Φ

(x,y)f.sub.1 (x,y)

f. machining the workpiece in accordance with said output data.

4. The method defined by claim 3 comprising the further step of iteratively performing steps a-e to generate a collection of secondary surfaces defined by Z =f_i (x,y), i=1,2, . . . N, transition regions Ω

^T_i, i=1,2, . . . N and transition functions Z=Φ

_i (x,y) all for the purpose of generating composite surfaces defined by Z=g_i (x,y), each said surface containing exactly i features in accordance with the formula;

space="preserve" listing-type="equation">g.sub.i (x,y)=(1-Φ

.sub.i (x,y))g.sub.i-1 (x,y)+Φ

.sub.i (x,y)f.sub.i (x,y)

space="preserve" listing-type="equation">i=1,2, . . . N

where g₀ (x,y)=f₀ (x,y)=primary surface.

5. The method as defined in claim 4 in which the workpiece is used to manufacture an automotive inner panel.

6. The method defined by claim 3 comprising the further step of iterativley performing steps a-e to generate a collection of secondary surfaces defined by Z=f_i (x,y), i=1,2, . . . N, transition regions Ω

^T_i, i=1,2, . . . N and transition functions Z=Φ

_i (x,y) all for the purpose of generating composite surfaces defined by Z=g_i (x,y), each said surface containing exactly i features in accordance with the formula;

space="preserve" listing-type="equation">g.sub.i (x,y)=(1-Φ

.sub.i (x,y)g.sub.i-1 (x,y)+Φ

.sub.i (x,y)f.sub.i (x,y) +Ψ

.sub.i (x,y)

space="preserve" listing-type="equation">i=1,2, . . . N

where g₀ (x,y)=f₀ (x,y)=primary surface and Ψ

_i (x,y) is any smooth function whose value is non zero only in the transition region Ω

^T_i.

7. The method as defined in claim 6 in which the workpiece is used to manufacture an automotive inner panel.

8. The method as defined in claim 3 in which the workpiece is used to manufacture an automotive inner panel.

9. A method of creating a three dimensional composite surface and machining the surface on a workpiece using a computer, said composite surface being defined by a function Z=g₁ (x,y) and comprising a primary surface S₀ defined by the function z=f₀ (x,y), joined smoothly to a second lay surface S₁ defined by the function z=f₁ (x,y) comprising the steps of:

a. inputting a plurality of coordinate data points (x_j, y_j) j=1,2. . . N, inputting corner radius values r_j, j=1,2. . . N, and inputting an offset distance R,

b. connecting the data points with straight lines and rounding the jth corner (j=1,2, . . . N) of the thereby defined closed polygon,

c. defining a smooth closed curve C₀ by offsetting C₁ in the xy-plane a distance R,

d. processing the data input from step a. to define a transition function Z=Φ

(x,y) that is defined by;

##EQU8## where Ω

⁰ is the region in the xy-plane outside the curve C₀, Ω

¹ is the region in the xy-plane inside the curve C₁, Ω

^T is the transition region in the xy-plane between the two curves C₀ and C₁, r is the radial offset distance from the xy-coordinate to the curve C₁, and where

space="preserve" listing-type="equation">h(r)=((R-r)/R).sup.2 (-2((R-r)/R))

e. generating output data defining the composite surface in accordance with the formula;

space="preserve" listing-type="equation">g.sub.i (x,y)=(1=Φ

(x,y))f.sub.0 (x,y)+Φ

(x,y)f.sub.1 (x,y)

f. machining the workpiece in accordance with said output data.

10. The method as defined in claim 9 in which the workpiece is used to manufacture an automotive inner panel.