models/johnpye/fourbar.a4c

REQUIRE "atoms.a4l";

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