models/johnpye/fourbar.a4c

REQUIRE "atoms.a4l";

IMPORT "johnpye/extpy/extpy";
IMPORT "johnpye/fourbarplot";

(* 
	Model of a four-bar linkage
	
	The pivots are at A, B, C, D. Sides are named after the
	end points. The 'default' configuration being modelled is
	of a quadrilater with A and D fixed and B and C free.
	The angle at A, alpha (to the positive x axis) will also be fixed
	
*)

MODEL fourbar;
	x_A,y_A IS_A delta_distance;
	x_B,y_B IS_A delta_distance;
	x_C,y_C IS_A delta_distance;
	x_D,y_D IS_A delta_distance;
	
	AB,BC,CD,DA IS_A distance;
	alpha, beta, gamma, delta IS_A angle;
	
	x_B = x_A + AB*cos(alpha);
	y_B = y_A + AB*sin(alpha);
	
	(x_C-x_B)^2 + (y_C-y_B)^2 = BC^2;
	beta = arctan((y_C-y_B)/(x_C-x_B));
	
	x_D = x_C + CD*cos(gamma);
	y_D = y_C + CD*sin(gamma);
	
	x_A = x_D + DA*cos(delta);
	y_A = y_D + DA*sin(delta);
	
METHODS
METHOD default_self;
	y_B := 0.5 {m}; x_B := 0.8 {m};
	y_C := -0.5{m}; x_C := 1.2 {m};
	x_D := 2 {m}; y_D := 0 {m};
END default_self;

METHOD specify;
	FIX x_A, y_A;
	FIX AB, BC, CD, DA;
	FIX alpha, delta;
END specify;
METHOD values;
	x_A := 0 {m};
	y_A := 0 {m};
	delta := 180 {deg};
	AB := 1 {m};
	BC := 1 {m};
	CD := 1 {m};
	DA := 2 {m};
	
	alpha:= 30 {deg};
END values;
METHOD fancyplot;
	EXTERNAL fourbarplot(SELF);
END fancyplot;

METHOD on_load;
	RUN reset;
	RUN values;
	RUN default_self;
END on_load;
END fourbar;
	
1	REQUIRE "atoms.a4l";
2
3	IMPORT "johnpye/extpy/extpy";
4	IMPORT "johnpye/fourbarplot";
5
6	(*
7	Model of a four-bar linkage
8
9	The pivots are at A, B, C, D. Sides are named after the
10	end points. The 'default' configuration being modelled is
11	of a quadrilater with A and D fixed and B and C free.
12	The angle at A, alpha (to the positive x axis) will also be fixed
13
14	*)
15
16	MODEL fourbar;
17	x_A,y_A IS_A delta_distance;
18	x_B,y_B IS_A delta_distance;
19	x_C,y_C IS_A delta_distance;
20	x_D,y_D IS_A delta_distance;
21
22	AB,BC,CD,DA IS_A distance;
23	alpha, beta, gamma, delta IS_A angle;
24
25	x_B = x_A + AB*cos(alpha);
26	y_B = y_A + AB*sin(alpha);
27
28	(x_C-x_B)^2 + (y_C-y_B)^2 = BC^2;
29	beta = arctan((y_C-y_B)/(x_C-x_B));
30
31	x_D = x_C + CD*cos(gamma);
32	y_D = y_C + CD*sin(gamma);
33
34	x_A = x_D + DA*cos(delta);
35	y_A = y_D + DA*sin(delta);
36
37	METHODS
38	METHOD default_self;
39	y_B := 0.5 {m}; x_B := 0.8 {m};
40	y_C := -0.5{m}; x_C := 1.2 {m};
41	x_D := 2 {m}; y_D := 0 {m};
42	END default_self;
43
44	METHOD specify;
45	FIX x_A, y_A;
46	FIX AB, BC, CD, DA;
47	FIX alpha, delta;
48	END specify;
49	METHOD values;
50	x_A := 0 {m};
51	y_A := 0 {m};
52	delta := 180 {deg};
53	AB := 1 {m};
54	BC := 1 {m};
55	CD := 1 {m};
56	DA := 2 {m};
57
58	alpha:= 30 {deg};
59	END values;
60	METHOD fancyplot;
61	EXTERNAL fourbarplot(SELF);
62	END fancyplot;
63
64	METHOD on_load;
65	RUN reset;
66	RUN values;
67	RUN default_self;
68	END on_load;
69	END fourbar;
70