// PID-control of a DC servo process.//// This example shows four ways to implement a periodic controller// activity in TrueTime. The task implements a standard// PID-controller to control a DC-servo process (2nd order system). #define S_FUNCTION_NAME servo_init#include "ttkernel.cpp"// PID data structure used in Implementations 1a, 2, and 3 below.class PID_Data {public:  struct { // states    double u, Iold, Dold, yold, t; // t used only in Implementation 2 below   } s;    struct { // params    double K, Ti, Td, N, h;    int rChan, yChan, uChan;   } p;};// calculate PID control signal and update statesvoid pidcalc(PID_Data* d, double r, double y) {  double P = d->p.K*(r-y);  double I = d->s.Iold;  double D = d->p.Td/(d->p.N*d->p.h+d->p.Td)*d->s.Dold+d->p.N*d->p.K*d->p.Td/(d->p.N*d->p.h+d->p.Td)*(d->s.yold-y);   d->s.u = P + I + D;  d->s.Iold = d->s.Iold + d->p.K*d->p.h/d->p.Ti*(r-y);  d->s.Dold = D;  d->s.yold = y;};// Variables used in Implementation 1b below.const int nInp = 2;                 // nbr of inputs to controller block const int nOutp = 2;                // nbr of outputs to controller block static double inp[] = {0.0, 0.0};   // block inputs static double outp[] = {0.0, 0.0};  // block outputs // ---- PID code function for Implementation 1a ----double pidcode1(int seg, void* data) {  double r, y;  PID_Data* d = (PID_Data*) data;  switch (seg) {  case 1:      r = ttAnalogIn(d->p.rChan);    y = ttAnalogIn(d->p.yChan);    pidcalc(d, r, y);     return 0.002;  case 2:        ttAnalogOut(d->p.uChan, d->s.u);    return FINISHED;  }}// ---- PID code function for Implementation 1b ----double blockcode(int seg, void* data) {  switch (seg) {  case 1:     inp[0] = ttAnalogIn(1);    inp[1] = ttAnalogIn(2);    ttCallBlockSystem(nOutp, outp, nInp, inp, "controller");    return outp[1];     // execution time returned from block   case 2:        ttAnalogOut(1, outp[0]);    return FINISHED;  }}// ---- PID code function for Implementation 2 ----double pidcode2(int seg, void* data) {  double r, y;  PID_Data* d = (PID_Data*) data;  switch (seg) {  case 1:    d->s.t = ttCurrentTime();    return 0.0;  case 2:      r = ttAnalogIn(d->p.rChan);    y = ttAnalogIn(d->p.yChan);    pidcalc(d, r, y);     return 0.002;  case 3:        ttAnalogOut(d->p.uChan, d->s.u);    // Sleep    d->s.t += d->p.h;    ttSleepUntil(d->s.t);    return 0.0;  case 4:    ttSetNextSegment(2); // loop    return 0.0;  }}// ---- PID code function for Implementation 3 ----double pidcode3(int seg, void* data) {  double r;  double *y;  PID_Data* d = (PID_Data*) data;  switch (seg) {  case 1:      r = ttAnalogIn(d->p.rChan);    y = (double*) ttTryFetch("Samples");    pidcalc(d, r, *y);     delete y;    return 0.0018;  case 2:        ttAnalogOut(d->p.uChan, d->s.u);    return FINISHED;  }}// ---- Sampler code function for Implementation 3 ----double samplercode(int seg, void* data) {  double y;  int* d = (int*) data;  switch (seg) {  case 1:      y = ttAnalogIn(*d);    ttTryPost("Samples", new double(y)); // put sample in mailbox    ttCreateJob("pid_task");  // trigger task job    return 0.0002;  case 2:        return FINISHED;  }}#define NBROFINPUTS 2#define NBROFOUTPUTS 1#define SCHEDULER FPPID_Data *d;double *d2 = NULL;int *hdl_data = NULL;void init() {    // Initialize TrueTime kernel  ttInitKernel(NBROFINPUTS, NBROFOUTPUTS, SCHEDULER);  // Task attributes  double period = 0.006;  double deadline = period;  double offset = 0.0; // start of first task instance  double prio = 1.0;  // Create task data (local memory)  d = new PID_Data;  d->p.K = 0.96;  d->p.Ti = 0.12;  d->p.Td = 0.049;  d->p.N = 10.0;  d->p.h = period;  d->s.u = 0.0;  d->s.t = 0.0; // only used in Implementation 2 below  d->s.Iold = 0.0;  d->s.Dold = 0.0;  d->s.yold = 0.0;  d->p.rChan = 1;  d->p.yChan = 2;  d->p.uChan = 1;  // IMPLEMENTATION 1a: using the built-in support for periodic tasks  //  ttCreatePeriodicTask("pid_task", offset, period, prio, pidcode1, d);  // IMPLEMENTATION 1b: calling Simulink block within code function  //  // d2 = new double(0.0); // Only the control signal needs to be                            // stored between segments. Controller                            // states are stored internally by TrueTime.  // ttCreatePeriodicTask("pid_task", offset, period, prio, blockcode, d2);  // IMPLEMENTATION 2: sleepUntil and loop back  //  // ttCreateTask("pid_task", deadline, prio, pidcode2, d);  // ttCreateJob("pid_task");    // IMPLEMENTATION 3: sampling in timer handler, triggers task job  //  // hdl_data = new int(2); // y_chan for reading samples  // ttCreateInterruptHandler("timer_handler", prio, samplercode, hdl_data);  // ttCreatePeriodicTimer("timer", offset, period, "timer_handler");  //  // ttCreateMailbox("Samples", 10);  //  // ttCreateTask("pid_task", deadline, prio, pidcode3, d);}void cleanup() {   delete d;  if (d2) delete d2;  if (hdl_data) delete hdl_data;}