void navigation_setangleerror(unsigned char gotnewgpsreading,fixedpointnum *angleerror)
{ // calculate the angle errors between our current attitude and the one we wish to have
// and adjust the angle errors that were passed to us. They have already been set by pilot input.
// For now, we just override any pilot input.
// keep track of the time between good gps readings.
navigation_time_sliver+=global.timesliver;
if (gotnewgpsreading)
{
// unshift our timesliver since we are about to use it. Since we are accumulating time, it may get too large to use while shifted.
navigation_time_sliver=navigation_time_sliver>>TIMESLIVEREXTRASHIFT;
// get the new distance and bearing from our current location to our target position
global.navigation_distance=navigation_getdistanceandbearing(global.gps_current_latitude,global.gps_current_longitude,target_latitude,target_longitude,&global.navigation_bearing);
// split the distance into it's ontrack and crosstrack components
// see the diagram above
fixedpointnum angledifference=global.navigation_bearing-navigation_starttodestbearing;
fixedpointnum crosstrack_distance=lib_fp_multiply(global.navigation_distance,lib_fp_sine(angledifference));
fixedpointnum ontrack_distance=lib_fp_multiply(global.navigation_distance,lib_fp_cosine(angledifference));
// accumulate integrated error for both ontrack and crosstrack
navigation_crosstrack_integrated_error+=lib_fp_multiply(crosstrack_distance,navigation_time_sliver);
navigation_ontrack_integrated_error+=lib_fp_multiply(ontrack_distance,navigation_time_sliver);
lib_fp_constrain(&navigation_crosstrack_integrated_error,-NAVIGATIONINTEGRATEDERRORLIMIT,NAVIGATIONINTEGRATEDERRORLIMIT);
lib_fp_constrain(&navigation_ontrack_integrated_error,-NAVIGATIONINTEGRATEDERRORLIMIT,NAVIGATIONINTEGRATEDERRORLIMIT);
// calculate the ontrack and crosstrack velocities toward our target.
// We want to put the navigation velocity (change in distance to target over time) into a low pass filter but
// we don't want to divide by the time interval to get velocity (divide is expensive) to then turn around and
// multiply by the same time interval. So the following is the same as the lib_fp_lowpassfilter code
// except we eliminate the multiply.
// note: if we use a different time period than FIXEDPOINTONEOVERONE, we need to multiply the distances by the new time period.
fixedpointnum fraction=lib_fp_multiply(navigation_time_sliver,FIXEDPOINTONEOVERONE);
navigation_crosstrack_velocity=(navigation_last_crosstrack_distance-crosstrack_distance+lib_fp_multiply((FIXEDPOINTONE)-fraction,navigation_crosstrack_velocity));
navigation_ontrack_velocity=(navigation_last_ontrack_distance-ontrack_distance+lib_fp_multiply((FIXEDPOINTONE)-fraction,navigation_ontrack_velocity));
navigation_last_crosstrack_distance=crosstrack_distance;
navigation_last_ontrack_distance=ontrack_distance;
// calculate the desired tilt in each direction independently using navigation PID
fixedpointnum crosstracktiltangle=lib_fp_multiply(usersettings.pid_pgain[NAVIGATIONINDEX],crosstrack_distance)
+lib_fp_multiply(usersettings.pid_igain[NAVIGATIONINDEX],navigation_crosstrack_integrated_error)
-lib_fp_multiply(usersettings.pid_dgain[NAVIGATIONINDEX],navigation_crosstrack_velocity);
fixedpointnum ontracktiltangle =lib_fp_multiply(usersettings.pid_pgain[NAVIGATIONINDEX],ontrack_distance)
+lib_fp_multiply(usersettings.pid_igain[NAVIGATIONINDEX],navigation_ontrack_integrated_error)
-lib_fp_multiply(usersettings.pid_dgain[NAVIGATIONINDEX],navigation_ontrack_velocity);
// don't tilt more than MAX_TILT
lib_fp_constrain(&crosstracktiltangle,-MAX_TILT,MAX_TILT);
lib_fp_constrain(&ontracktiltangle,-MAX_TILT,MAX_TILT);
// Translate the ontrack and cross track tilts into pitch and roll tilts.
// Set angledifference equal to the difference between the aircraft's heading (the way it's currently pointing)
// and the angle between waypoints and rotate our tilts by that much.
angledifference=global.currentestimatedeulerattitude[YAWINDEX]-navigation_starttodestbearing;
fixedpointnum sineofangle=lib_fp_sine(angledifference);
fixedpointnum cosineofangle=lib_fp_cosine(angledifference);
navigation_desiredeulerattitude[ROLLINDEX]=lib_fp_multiply(crosstracktiltangle,cosineofangle)-lib_fp_multiply(ontracktiltangle,sineofangle);
navigation_desiredeulerattitude[PITCHINDEX]=lib_fp_multiply(crosstracktiltangle,sineofangle)+lib_fp_multiply(ontracktiltangle,cosineofangle);
// for now, don't rotate the aircraft in the direction of travel. Add this later.
navigation_time_sliver=0;
}
// set the angle error as the difference between where we want to be and where we currently are angle wise.
angleerror[ROLLINDEX]=navigation_desiredeulerattitude[ROLLINDEX]-global.currentestimatedeulerattitude[ROLLINDEX];
angleerror[PITCHINDEX]=navigation_desiredeulerattitude[PITCHINDEX]-global.currentestimatedeulerattitude[PITCHINDEX];
// don't set the yaw. Let the pilot do yaw
// angleerror[YAWINDEX]=navigation_desiredeulerattitude[YAWINDEX]-global.currentestimatedeulerattitude[YAWINDEX];
// don't let the yaw angle error get too large for any one cycle in order to control the maximum yaw rate.
// lib_fp_constrain180(&angleerror[YAWINDEX]);
// lib_fp_constrain(&angleerror[YAWINDEX],-MAXYAWANGLEERROR,MAXYAWANGLEERROR);
}
// It all starts here:
int main(void) {
// start with default user settings in case there's nothing in eeprom
default_user_settings();
// try to load settings from eeprom
read_user_settings_from_eeprom();
// set our LED as a digital output
lib_digitalio_initpin(LED1_OUTPUT,DIGITALOUTPUT);
//initialize the libraries that require initialization
lib_timers_init();
lib_i2c_init();
// pause a moment before initializing everything. To make sure everything is powered up
lib_timers_delaymilliseconds(100);
// initialize all other modules
init_rx();
init_outputs();
serial_init();
init_gyro();
init_acc();
init_baro();
init_compass();
init_gps();
init_imu();
// set the default i2c speed to 400 KHz. If a device needs to slow it down, it can, but it should set it back.
lib_i2c_setclockspeed(I2C_400_KHZ);
// initialize state
global.state.armed=0;
global.state.calibratingCompass=0;
global.state.calibratingAccAndGyro=0;
global.state.navigationMode=NAVIGATION_MODE_OFF;
global.failsafeTimer=lib_timers_starttimer();
// run loop
for(;;) {
// check to see what switches are activated
check_checkbox_items();
// check for config program activity
serial_check_for_action();
calculate_timesliver();
// run the imu to estimate the current attitude of the aircraft
imu_calculate_estimated_attitude();
// arm and disarm via rx aux switches
if (global.rxValues[THROTTLE_INDEX]<FPSTICKLOW) { // see if we want to change armed modes
if (!global.state.armed) {
if (global.activeCheckboxItems & CHECKBOX_MASK_ARM) {
global.state.armed=1;
#if (GPS_TYPE!=NO_GPS)
navigation_set_home_to_current_location();
#endif
global.home.heading=global.currentEstimatedEulerAttitude[YAW_INDEX];
global.home.location.altitude=global.baroRawAltitude;
}
} else if (!(global.activeCheckboxItems & CHECKBOX_MASK_ARM)) global.state.armed=0;
}
#if (GPS_TYPE!=NO_GPS)
// turn on or off navigation when appropriate
if (global.state.navigationMode==NAVIGATION_MODE_OFF) {
if (global.activeCheckboxItems & CHECKBOX_MASK_RETURNTOHOME) { // return to home switch turned on
navigation_set_destination(global.home.location.latitude,global.home.location.longitude);
global.state.navigationMode=NAVIGATION_MODE_RETURN_TO_HOME;
} else if (global.activeCheckboxItems & CHECKBOX_MASK_POSITIONHOLD) { // position hold turned on
navigation_set_destination(global.gps.currentLatitude,global.gps.currentLongitude);
global.state.navigationMode=NAVIGATION_MODE_POSITION_HOLD;
}
} else { // we are currently navigating
// turn off navigation if desired
if ((global.state.navigationMode==NAVIGATION_MODE_RETURN_TO_HOME && !(global.activeCheckboxItems & CHECKBOX_MASK_RETURNTOHOME)) || (global.state.navigationMode==NAVIGATION_MODE_POSITION_HOLD && !(global.activeCheckboxItems & CHECKBOX_MASK_POSITIONHOLD))) {
global.state.navigationMode=NAVIGATION_MODE_OFF;
// we will be turning control back over to the pilot.
reset_pilot_control();
}
}
#endif
// read the receiver
read_rx();
// turn on the LED when we are stable and the gps has 5 satelites or more
#if (GPS_TYPE==NO_GPS)
lib_digitalio_setoutput(LED1_OUTPUT, (global.state.stable==0)==LED1_ON);
#else
lib_digitalio_setoutput(LED1_OUTPUT, (!(global.state.stable && global.gps.numSatelites>=5))==LED1_ON);
#endif
// get the angle error. Angle error is the difference between our current attitude and our desired attitude.
// It can be set by navigation, or by the pilot, etc.
fixedpointnum angleError[3];
// let the pilot control the aircraft.
get_angle_error_from_pilot_input(angleError);
#if (GPS_TYPE!=NO_GPS)
// read the gps
unsigned char gotNewGpsReading=read_gps();
// if we are navigating, use navigation to determine our desired attitude (tilt angles)
if (global.state.navigationMode!=NAVIGATION_MODE_OFF) { // we are navigating
navigation_set_angle_error(gotNewGpsReading,angleError);
}
#endif
if (global.rxValues[THROTTLE_INDEX]<FPSTICKLOW) {
// We are probably on the ground. Don't accumnulate error when we can't correct it
reset_pilot_control();
// bleed off integrated error by averaging in a value of zero
lib_fp_lowpassfilter(&global.integratedAngleError[ROLL_INDEX],0L,global.timesliver>>TIMESLIVEREXTRASHIFT,FIXEDPOINTONEOVERONEFOURTH,0);
lib_fp_lowpassfilter(&global.integratedAngleError[PITCH_INDEX],0L,global.timesliver>>TIMESLIVEREXTRASHIFT,FIXEDPOINTONEOVERONEFOURTH,0);
lib_fp_lowpassfilter(&global.integratedAngleError[YAW_INDEX],0L,global.timesliver>>TIMESLIVEREXTRASHIFT,FIXEDPOINTONEOVERONEFOURTH,0);
}
#ifndef NO_AUTOTUNE
// let autotune adjust the angle error if the pilot has autotune turned on
if (global.activeCheckboxItems & CHECKBOX_MASK_AUTOTUNE) {
if (!(global.previousActiveCheckboxItems & CHECKBOX_MASK_AUTOTUNE)) {
autotune(angleError,AUTOTUNE_STARTING); // tell autotune that we just started autotuning
} else {
autotune(angleError,AUTOTUNE_TUNING); // tell autotune that we are in the middle of autotuning
}
} else if (global.previousActiveCheckboxItems & CHECKBOX_MASK_AUTOTUNE) {
autotune(angleError,AUTOTUNE_STOPPING); // tell autotune that we just stopped autotuning
}
#endif
// This gets reset every loop cycle
// keep a flag to indicate whether we shoud apply altitude hold. The pilot can turn it on or
// uncrashability/autopilot mode can turn it on.
global.state.altitudeHold=0;
if (global.activeCheckboxItems & CHECKBOX_MASK_ALTHOLD) {
global.state.altitudeHold=1;
if (!(global.previousActiveCheckboxItems & CHECKBOX_MASK_ALTHOLD)) {
// we just turned on alt hold. Remember our current alt. as our target
global.altitudeHoldDesiredAltitude=global.altitude;
global.integratedAltitudeError=0;
}
}
fixedpointnum throttleOutput;
#ifndef NO_AUTOPILOT
// autopilot is available
if (global.activeCheckboxItems & CHECKBOX_MASK_AUTOPILOT) {
if (!(global.previousActiveCheckboxItems & CHECKBOX_MASK_AUTOPILOT)) {
// let autopilot know to transition to the starting state
autopilot(AUTOPILOT_STARTING);
} else {
// autopilot normal run state
autopilot(AUTOPILOT_RUNNING);
}
} else if (global.previousActiveCheckboxItems & CHECKBOX_MASK_AUTOPILOT) {
// tell autopilot that we just stopped autotuning
autopilot(AUTOPILOT_STOPPING);
} else {
// get the pilot's throttle component
// convert from fixedpoint -1 to 1 to fixedpoint 0 to 1
throttleOutput=(global.rxValues[THROTTLE_INDEX]>>1)+FIXEDPOINTCONSTANT(.5)+FPTHROTTLETOMOTOROFFSET;
}
#else
// get the pilot's throttle component
// convert from fixedpoint -1 to 1 to fixedpoint 0 to 1
throttleOutput=(global.rxValues[THROTTLE_INDEX]>>1)+FIXEDPOINTCONSTANT(.5)+FPTHROTTLETOMOTOROFFSET;
#endif
#ifndef NO_UNCRASHABLE
uncrashable(gotNewGpsReading,angleError,&throttleOutput);
#endif
#if (BAROMETER_TYPE!=NO_BAROMETER)
// check for altitude hold and adjust the throttle output accordingly
if (global.state.altitudeHold) {
global.integratedAltitudeError+=lib_fp_multiply(global.altitudeHoldDesiredAltitude-global.altitude,global.timesliver);
lib_fp_constrain(&global.integratedAltitudeError,-INTEGRATED_ANGLE_ERROR_LIMIT,INTEGRATED_ANGLE_ERROR_LIMIT); // don't let the integrated error get too high
// do pid for the altitude hold and add it to the throttle output
throttleOutput+=lib_fp_multiply(global.altitudeHoldDesiredAltitude-global.altitude,settings.pid_pgain[ALTITUDE_INDEX])-lib_fp_multiply(global.altitudeVelocity,settings.pid_dgain[ALTITUDE_INDEX])+lib_fp_multiply(global.integratedAltitudeError,settings.pid_igain[ALTITUDE_INDEX]);
}
#endif
#ifndef NO_AUTOTHROTTLE
if ((global.activeCheckboxItems & CHECKBOX_MASK_AUTOTHROTTLE) || global.state.altitudeHold) {
if (global.estimatedDownVector[Z_INDEX]>FIXEDPOINTCONSTANT(.3)) {
// Divide the throttle by the throttleOutput by the z component of the down vector
// This is probaly the slow way, but it's a way to do fixed point division
fixedpointnum recriprocal=lib_fp_invsqrt(global.estimatedDownVector[Z_INDEX]);
recriprocal=lib_fp_multiply(recriprocal,recriprocal);
throttleOutput=lib_fp_multiply(throttleOutput-AUTOTHROTTLE_DEAD_AREA,recriprocal)+AUTOTHROTTLE_DEAD_AREA;
}
}
#endif
#ifndef NO_FAILSAFE
// if we don't hear from the receiver for over a second, try to land safely
if (lib_timers_gettimermicroseconds(global.failsafeTimer)>1000000L) {
throttleOutput=FPFAILSAFEMOTOROUTPUT;
// make sure we are level!
angleError[ROLL_INDEX]=-global.currentEstimatedEulerAttitude[ROLL_INDEX];
angleError[PITCH_INDEX]=-global.currentEstimatedEulerAttitude[PITCH_INDEX];
}
#endif
// calculate output values. Output values will range from 0 to 1.0
// calculate pid outputs based on our angleErrors as inputs
fixedpointnum pidOutput[3];
// Gain Scheduling essentialy modifies the gains depending on
// throttle level. If GAIN_SCHEDULING_FACTOR is 1.0, it multiplies PID outputs by 1.5 when at full throttle,
// 1.0 when at mid throttle, and .5 when at zero throttle. This helps
// eliminate the wobbles when decending at low throttle.
fixedpointnum gainSchedulingMultiplier=lib_fp_multiply(throttleOutput-FIXEDPOINTCONSTANT(.5),FIXEDPOINTCONSTANT(GAIN_SCHEDULING_FACTOR))+FIXEDPOINTONE;
for (int x=0;x<3;++x) {
global.integratedAngleError[x]+=lib_fp_multiply(angleError[x],global.timesliver);
// don't let the integrated error get too high (windup)
lib_fp_constrain(&global.integratedAngleError[x],-INTEGRATED_ANGLE_ERROR_LIMIT,INTEGRATED_ANGLE_ERROR_LIMIT);
// do the attitude pid
pidOutput[x]=lib_fp_multiply(angleError[x],settings.pid_pgain[x])-lib_fp_multiply(global.gyrorate[x],settings.pid_dgain[x])+(lib_fp_multiply(global.integratedAngleError[x],settings.pid_igain[x])>>4);
// add gain scheduling.
pidOutput[x]=lib_fp_multiply(gainSchedulingMultiplier,pidOutput[x]);
}
lib_fp_constrain(&throttleOutput,0,FIXEDPOINTONE); // Keep throttle output between 0 and 1
compute_mix(throttleOutput, pidOutput); // aircraft type dependent mixes
#if (NUM_SERVOS>0)
// do not update servos during unarmed calibration of sensors which are sensitive to vibration
if (global.state.armed || (!global.state.calibratingAccAndGyro)) write_servo_outputs();
#endif
write_motor_outputs();
}
