vel_control.c

/*
**************************************************************

 Current regulation - Pontus Giselsson, Per-Ola Larsson 18/02/09
           for LTH - reglerteknik

***************************************************************
*/
#include <avr/twi.h>
#include <avr/io.h>
#include <avr/signal.h>
#include <avr/interrupt.h>
#include <inttypes.h>

#include "pccom.h"
#include "vel_control.h"


// reference variables
volatile int32_t ref = 0;        // 11 frac bits
volatile int32_t refCtrl = 0;    // ref used in ctrl-loop (=ref sent from simulink)


// velocity control variables
volatile int32_t u = 0;          // 11 frac bits
volatile int32_t uSend = 0;      // ctrl sent to simulink
volatile int32_t v = 0;          // 11 frac bits
volatile int32_t vSat = 0;
volatile int8_t brake = 0;       // brake variable if pos-sample missed
volatile int32_t I = 0;          // 11 frac bits
volatile int32_t e = 0;          // 11 frac bits
volatile int8_t intCond = 0;


volatile int32_t K = 807;       // 6 frac bits, prop constant
volatile int32_t Ke = 13;        // 6 frac bits, integral constant
volatile int8_t fr_comp = (10<<3);
#define V_MAX (120<<4)
#define V_MIN (-120<<4)


// encoder variables
#define ENCODERY  (PIND&0x04)        //Positional encoder pins
#define ENCODERX  ((PINB&0x02)<<1)   //Positional encoder pins (shift one step for faster comparison with Y)

// position variables
volatile int16_t pos = 0;        // position in tics
volatile int16_t posTemp = 0;    // position sent to simulink
volatile int16_t posCtrl = 0;    // position used in ctrl-loop
volatile int16_t oldPos = 0;     // previous pos used for velocity estimation
volatile int8_t newX;            // encoder signal
volatile int8_t newY;            // encoder signal
volatile int8_t oldX;            // previous encoder signal
volatile int8_t oldY;            // previous encoder signal

// velocity estimation parameters
volatile int32_t velEst = 0;     // vel-estimate, 5 frac bits
volatile int32_t velEstSend = 0; // vel-estimate sent to simulink
int16_t a = 116;                 // 7 frac bits (parameter in velocity estimate)
int16_t b = 152;                 // 5 frac bits (parameter in velocity estimate)

// adc measurement variables
volatile int16_t low;            // temporary variable for ad-reading
volatile int16_t high;           // temporary variable for ad-reading
volatile int16_t angleOffset = 0;

/* return position (in tics) */
int32_t getPosition() {
  cli();
  posTemp = pos;
  sei();
  return ((int32_t) posTemp);
}


/* return velocity (in mm/s) */
int32_t getVelocity() {
  return velEstSend;
}


/* return last angle measurement */
int16_t getAngle() {
  low = inp(ADCL);
  high = inp(ADCH);
  return (((int16_t) ((high<<8) | low) - 512)-angleOffset);
}


/* return current-reference */
int32_t getCurrentRef() {
  return uSend;
}


/* Set new reference value */
void setRef(int32_t newRef) {
  ref = newRef;
}

/* Routine used to initialize the positional encoders */
void initPos()
{
  oldX = ENCODERX;
  oldY = ENCODERY;
}

/* Timer 2, Encoder counter, 73 kHz updates position variable */
SIGNAL(SIG_OUTPUT_COMPARE2) {

  // Update position from encoder
  newX = ENCODERX;
  newY = ENCODERY;
  if((newX != oldX) || (newY != oldY)) {                            //Check if any value changed
      /*
      sum = (oldX<<2)+oldY+newX+(newY>>2);  
      if (sum == 2 || sum == 4 || sum == 11 || sum == 13) {
	pos = pos+1;
      } else if (sum == 1 || sum == 7 || sum ==  8 || sum == 14) {
	pos = pos-1;
      } else {
	brake = 1; // emergency brake
      }
      */
    // Works like if-clauses above, but faster!
      if ((oldX == newY) && (oldY != newX)) {
	pos = pos+1;
      } else if ((oldX != newY) && (oldY == newX)) {
	pos = pos-1;
      } else {
	brake = 1;
      }
      oldX = newX;
      oldY = newY;
  }

}


/* Timer 0, serial communication with simulink */
SIGNAL(SIG_OUTPUT_COMPARE0) {

  TIMSK &= ~(BV(OCIE0)|BV(OCIE1A));   // Disable communication and ctrl-interrupts

  sei(); // enable interrupts from encoder-counter
  
  // Poll UART receiver
  uint8_t status = UCSRA;
  if (status & (1<<RXC)) {
    char ch = UDR;
    pccom_receiveByte(ch);
    
    if (status & ((1<<FE)|(1<<DOR)|(1<<PE))) { 
      //main_emergencyStop(); // stop on USART error
    }     
  }
  
  // Poll UART sender
  if (UCSRA & (1<<UDRE)) {
    int16_t toSend = pccom_getNextByteToSend();
    if (toSend >= 0) UDR = (char)toSend;
  }

  TIFR = (1<<OCF0);        // skip pending interrupts from serial comm, (but not from ctrl)

  TIMSK |= (BV(OCIE0)|BV(OCIE1A)); // reenable communication and ctrl-interrupts

}



/* Timer 0, control loop , 1 kHz */
SIGNAL(SIG_OUTPUT_COMPARE1A) {
  
  posCtrl = pos; // store pos to use in this loop

  sei(); // to enable interupts from encoder counter and communication

  // velocity estimation in mm/s
  velEst = (((a*velEst+64)>>7)+b*(posCtrl-oldPos));  // 5 fracbits on velEst
  oldPos = posCtrl;
  
  // store velEst and ref to be sent/used here
  cli();
  velEstSend = velEst;
  refCtrl = ref;
  // ref = ref*(1-brake); // emergency stop
  sei();

  // control error
  e = refCtrl-((velEst+16)>>5);  // mm/s

  // temporary ctrl-signal
  v = (((K*e+(1<<5))>>6)+((I+(1<<3))>>4));

  // friction compensation
  if (refCtrl > 0) {
    v = v+fr_comp;
  } else if (refCtrl < 0) {
    v = v-fr_comp;
  }

  // variable that decides if I-part should be updated
  intCond = 1;
  
  // saturation of v
  if (v > V_MAX) {
    vSat = V_MAX;
    if (e > 0)
      intCond = 0;
  } else if (v < V_MIN) {
    vSat = V_MIN;
    if (e < 0)
      intCond = 0;
  } else {
    vSat = v;
  }
  
  if (intCond)
    I = I + (((Ke*e)+(1<<1))>>2);

  // scale ctrl-signal to send over twi
  u = (vSat+8)>>4; // u=127 gives current = 6.75 A, vSat makes u saturate at 114

  // u that is sent to simulink
  cli();
  uSend = u;
  sei();


  // TWI-communication to set current reference on the other atmel
  // send start command
  outp(BV(TWINT)|BV(TWEN)|BV(TWSTA),TWCR);
  while (!(TWCR&BV(TWINT))) {}
    
  // Contact slave  
  outp(0x02,TWDR);  // slave is 0x02 (sla+w)
  outp(BV(TWINT)|BV(TWEN),TWCR);
  while (!(TWCR&BV(TWINT))) {}
 
  // Send reference byte to slave
  outp((int8_t)u,TWDR);  // send 8 bits reference
  outp(BV(TWINT)|BV(TWEN),TWCR);
  while (!(TWCR&BV(TWINT))) {}
    
  // stop transmission
  outp(BV(TWINT)|BV(TWEN)|BV(TWSTO),TWCR);

}


int main()
{
  cli();
  
  //Port directions
  //outp(0x80,DDRB);   // Led output
  outp(0x10,DDRC);  // timer calculation port
  PORTD = 0x40;  // pull up on reset switch


  /* Timer section */
  // Enable timer0, timer1, timer2 compare match interrupts
  outp(BV(OCIE0)|BV(OCIE1A)|BV(OCIE2),TIMSK);
  
  /* Timer 2, 73 kHz Prescaler 1, encoder counter for position measurement */
  outp(BV(WGM21)|BV(CS20),TCCR2);
  outp(200,OCR2);
  /* Reset timer 2 */
  outp(0,TCNT2);
  
  /* Timer 1, 1 kHz , prescaler 1, ctrl-loop */
  outp(BV(WGM12)|BV(CS10),TCCR1B);
  outp(0x39,OCR1AH);
  outp(0x7f,OCR1AL);
  outp(0,TCNT1H);
  outp(0,TCNT1L);
  

  /* Timer 0, 40 kHz, Prescaler 8, serial communication */
  outp(BV(WGM01)|BV(CS01),TCCR0);
  //outp(184-1,OCR0); // 10 kHz
  outp(46-1,OCR0); // 40 kHz
   /* Reset timer 0 */
  outp(0,TCNT0);


  // syncronization (ctrl interrupt 34 micros before communication interrupt)
  TCNT1 = TCNT0*8+500;
  
  
  //Serial communication initialization
  outp(0x00, UCSRA);	// USART:
  outp(0x18, UCSRB);	// USART: RxEnable|TxEnable
  outp(0x86, UCSRC);	// USART: 8bit, no parity
  outp(0x00, UBRRH);	// USART: 115200 @ 14.7456MHz
  outp(7,UBRRL);	// USART: 115200 @ 14.7456MHz 
  
  
  /* AREF (AREF is 5V) pin external capacitor, ADC3 for pendulum angle */
  outp(BV(REFS0)|BV(MUX0)|BV(MUX1),ADMUX);
  
  // Enable ADC on adc3, start first conversion, prescaler 128, free running mode
  outp(BV(ADEN)|BV(ADSC)|BV(ADATE)|BV(ADPS2)|BV(ADPS1)|BV(ADPS0),ADCSRA);


  // Initialize Master TWI
  outp(0x10,TWBR);  // set SCL-frequency CPU-freq/(16+2*16)
  outp(BV(TWEN),TWCR); // enable TWI

  // initialize position measurements
  initPos();

  // initialize pc-communication
  pccom_init();
  
  //Enable interrupts
  sei();

  // loop
  while (1) {
    // reset position, velocity estimate and integral part of ctrl if reset button pushed
    if (!(PIND & 0x40)) {
      cli();
      low = inp(ADCL);
      high = inp(ADCH);
      pos = 0; // reset position
      angleOffset =  ((int16_t) ((high<<8) | low) - 512);
      oldPos = 0;
      velEst = 0; // reset velocity estimate
      I = 0; // reset integral part of controller
      u = 0; // reset ctrl signal
      sei();
    } 
  }
}