Listing 4.

Modified simulation, version 3.

1	import jtt.*; // Import the JTT package
2	public class MyProcess {
3	// Initialize the process
4	public MyProcess ( ) {
5	// create a task (a PID controller)
6	Task task = new Task ( );
7	task.setPeriod (0.012); // period = 12 ms
8	// add code to task
9	task.addCode (new CodeSegment ( ) {
10	public double code ( ) {
11	controlAction = calculate (reference, output);
12	return 0.02; // 20 ms
13	}
14	});
15	task.addCode (new CodeSegment ( ) {
16	public double code ( ) {
17	input = controlAction;
18	return 0; // 0 ms
19	}
20	});
21	// create kernel and add it the task . . .
22	}
23	// Gets rate of the ODE model
24	public void getRate (double [] state, double [] rate) {
25	rate [0] = state [1];
26	rate [1]= − state [1] + 1000 * input;
27	rate [2] = 1;
28	}
29	// Step the process for an increment of time
30	public void step (double dt) {
31	getRate (state, rates1);
32	for (int i = 0; i <numEqn; i++)
33	k1 [i]= state [i]+ stepSize * rates 1 [i]/2.0;
34	getRate (k1, rates 2);
35	for (int i = 0; i <numEqn; i++)
36	k2 [i]= state [i]+ stepSize * rates 2 [i]/2.0;
37	getRate (k2, rates 3);
38	for (int i = 0; i <numEqn; i++)
39	k3 [i]= state [i]+ stepSize*rates3 [i];
40	getRate (k3, rates4);
41	for (int i = 0; i <numEqn; i++)
42	state [i]= state [i]+stepSize*(rates1[i]+2*rates2[i]+2*rates3[i]+rates4[i])/6.0;
43	}
44	// Computes the PID
45	public double calculate (r, y) {
46	P = Kp*(beta*r−y); I = Iold; D = Td/(N*h+Td)*Dold+N*Kp*Td/(N*h+Td)*(yold−y);
47	Iold = Iold + Kp*h/Ti*(r−y); Dold = D; yold = y;
48	return (P + I + D);
49	}
50	// Simulate the process
51	. . .
52	} // end of class