models/johnpye/spring.a4c

REQUIRE "ivpsystem.a4l";
REQUIRE "atoms.a4l";

(* spring oscillation model. Intended to demonstrate second-order ODE *)
MODEL spring;
    x IS_A distance;
	v_x IS_A speed;
	a_x	IS_A acceleration;

	t IS_A time;

	(* equations of motion *)
	F IS_A force;
	k IS_A stiffness;
	m IS_A mass;
	F = -k*x;
	F = m*a_x;
	DIFF(v_x) = a_x;
METHODS
METHOD specify;
	FIX m, k;
END specify;

METHOD default_self; (* dynamic vals *)
	x := 1 {m};
	v_x := 0 {m/s};
	a_x := -1 {m/s^2};
END default_self;

METHOD values; (* fixed vals *)
	m := 1 {kg};
	k := 5 {N/kg};
	t := 0 {s};
	x := 1 {m};
	v := 0 {m/s};
END values;

METHOD set_ode; (* this is where the current implementation sux *)
	x.ode_id := 1;   x.ode_type := 1;
	v_x.ode_id := 1; v_x.ode_type := 2;
	a_x.ode_id := 1; a_x.ode_type := 3; 

	t.ode_type :=-1;
END set_ode;

METHOD set_obs; (* this sux also *)
	x.obs_id := 1;
	v_x.obs_id := 2;
	a_x.obs_id := 3;
END set_obs;

METHOD on_load;
	RUN default_self;
	RUN reset;
	RUN specify;
	RUN set_obs;
	RUN set_ode;
END on_load;

END spring;
1	REQUIRE "ivpsystem.a4l";
2	REQUIRE "atoms.a4l";
3
4	(* spring oscillation model. Intended to demonstrate second-order ODE *)
5	MODEL spring;
6	x IS_A distance;
7	v_x IS_A speed;
8	a_x IS_A acceleration;
9
10	t IS_A time;
11
12	(* equations of motion *)
13	F IS_A force;
14	k IS_A stiffness;
15	m IS_A mass;
16	F = -k*x;
17	F = m*a_x;
18	DIFF(v_x) = a_x;
19	METHODS
20	METHOD specify;
21	FIX m, k;
22	END specify;
23
24	METHOD default_self; (* dynamic vals *)
25	x := 1 {m};
26	v_x := 0 {m/s};
27	a_x := -1 {m/s^2};
28	END default_self;
29
30	METHOD values; (* fixed vals *)
31	m := 1 {kg};
32	k := 5 {N/kg};
33	t := 0 {s};
34	x := 1 {m};
35	v := 0 {m/s};
36	END values;
37
38	METHOD set_ode; (* this is where the current implementation sux *)
39	x.ode_id := 1; x.ode_type := 1;
40	v_x.ode_id := 1; v_x.ode_type := 2;
41	a_x.ode_id := 1; a_x.ode_type := 3;
42
43	t.ode_type :=-1;
44	END set_ode;
45
46	METHOD set_obs; (* this sux also *)
47	x.obs_id := 1;
48	v_x.obs_id := 2;
49	a_x.obs_id := 3;
50	END set_obs;
51
52	METHOD on_load;
53	RUN default_self;
54	RUN reset;
55	RUN specify;
56	RUN set_obs;
57	RUN set_ode;
58	END on_load;
59
60	END spring;