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Diffstat (limited to 'src/ao_flight.c')
| -rw-r--r-- | src/ao_flight.c | 484 |
1 files changed, 484 insertions, 0 deletions
diff --git a/src/ao_flight.c b/src/ao_flight.c new file mode 100644 index 00000000..c0f56830 --- /dev/null +++ b/src/ao_flight.c @@ -0,0 +1,484 @@ +/* + * Copyright © 2009 Keith Packard <keithp@keithp.com> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; version 2 of the License. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. + */ + +#ifndef AO_FLIGHT_TEST +#include "ao.h" +#endif + +/* Main flight thread. */ + +__pdata enum ao_flight_state ao_flight_state; /* current flight state */ +__pdata uint16_t ao_flight_tick; /* time of last data */ +__pdata uint16_t ao_flight_prev_tick; /* time of previous data */ +__pdata int16_t ao_flight_accel; /* filtered acceleration */ +__pdata int16_t ao_flight_pres; /* filtered pressure */ +__pdata int16_t ao_ground_pres; /* startup pressure */ +__pdata int16_t ao_ground_accel; /* startup acceleration */ +__pdata int16_t ao_min_pres; /* minimum recorded pressure */ +__pdata uint16_t ao_launch_tick; /* time of launch detect */ +__pdata int16_t ao_main_pres; /* pressure to eject main */ + +/* + * track min/max data over a long interval to detect + * resting + */ +__pdata uint16_t ao_interval_end; +__pdata int16_t ao_interval_cur_min_accel; +__pdata int16_t ao_interval_cur_max_accel; +__pdata int16_t ao_interval_cur_min_pres; +__pdata int16_t ao_interval_cur_max_pres; +__pdata int16_t ao_interval_min_accel; +__pdata int16_t ao_interval_max_accel; +__pdata int16_t ao_interval_min_pres; +__pdata int16_t ao_interval_max_pres; + +__data uint8_t ao_flight_adc; +__pdata int16_t ao_raw_accel, ao_raw_accel_prev, ao_raw_pres; + +/* Accelerometer calibration + * + * We're sampling the accelerometer through a resistor divider which + * consists of 5k and 10k resistors. This multiplies the values by 2/3. + * That goes into the cc1111 A/D converter, which is running at 11 bits + * of precision with the bits in the MSB of the 16 bit value. Only positive + * values are used, so values should range from 0-32752 for 0-3.3V. The + * specs say we should see 40mV/g (uncalibrated), multiply by 2/3 for what + * the A/D converter sees (26.67 mV/g). We should see 32752/3300 counts/mV, + * for a final computation of: + * + * 26.67 mV/g * 32767/3300 counts/mV = 264.8 counts/g + * + * Zero g was measured at 16000 (we would expect 16384). + * Note that this value is only require to tell if the + * rocket is standing upright. Once that is determined, + * the value of the accelerometer is averaged for 100 samples + * to find the resting accelerometer value, which is used + * for all further flight computations + */ + +#define GRAVITY 9.80665 +/* convert m/s to velocity count */ +#define VEL_MPS_TO_COUNT(mps) ((int32_t) (((mps) / GRAVITY) * ACCEL_G * 100)) + +#define ACCEL_G 265 +#define ACCEL_ZERO_G 16000 +#define ACCEL_NOSE_UP (ACCEL_G * 2 /3) +#define ACCEL_BOOST ACCEL_G * 2 +#define ACCEL_INT_LAND (ACCEL_G / 10) +#define ACCEL_VEL_LAND VEL_MPS_TO_COUNT(10) +#define ACCEL_VEL_MACH VEL_MPS_TO_COUNT(200) +#define ACCEL_VEL_APOGEE VEL_MPS_TO_COUNT(2) +#define ACCEL_VEL_MAIN VEL_MPS_TO_COUNT(100) +#define ACCEL_VEL_BOOST VEL_MPS_TO_COUNT(5) + +/* + * Barometer calibration + * + * We directly sample the barometer. The specs say: + * + * Pressure range: 15-115 kPa + * Voltage at 115kPa: 2.82 + * Output scale: 27mV/kPa + * + * If we want to detect launch with the barometer, we need + * a large enough bump to not be fooled by noise. At typical + * launch elevations (0-2000m), a 200Pa pressure change cooresponds + * to about a 20m elevation change. This is 5.4mV, or about 3LSB. + * As all of our calculations are done in 16 bits, we'll actually see a change + * of 16 times this though + * + * 27 mV/kPa * 32767 / 3300 counts/mV = 268.1 counts/kPa + */ + +#define BARO_kPa 268 +#define BARO_LAUNCH (BARO_kPa / 5) /* .2kPa, or about 20m */ +#define BARO_APOGEE (BARO_kPa / 10) /* .1kPa, or about 10m */ +#define BARO_COAST (BARO_kPa * 5) /* 5kpa, or about 500m */ +#define BARO_MAIN (BARO_kPa) /* 1kPa, or about 100m */ +#define BARO_INT_LAND (BARO_kPa / 20) /* .05kPa, or about 5m */ +#define BARO_LAND (BARO_kPa * 10) /* 10kPa or about 1000m */ + +/* We also have a clock, which can be used to sanity check things in + * case of other failures + */ + +#define BOOST_TICKS_MAX AO_SEC_TO_TICKS(15) + +/* This value is scaled in a weird way. It's a running total of accelerometer + * readings minus the ground accelerometer reading. That means it measures + * velocity, and quite accurately too. As it gets updated 100 times a second, + * it's scaled by 100 + */ +__pdata int32_t ao_flight_vel; +__pdata int32_t ao_min_vel; +__pdata int32_t ao_old_vel; +__pdata int16_t ao_old_vel_tick; +__xdata int32_t ao_raw_accel_sum, ao_raw_pres_sum; + +/* Landing is detected by getting constant readings from both pressure and accelerometer + * for a fairly long time (AO_INTERVAL_TICKS) + */ +#define AO_INTERVAL_TICKS AO_SEC_TO_TICKS(20) + +#define abs(a) ((a) < 0 ? -(a) : (a)) + +void +ao_flight(void) +{ + __pdata static uint16_t nsamples = 0; + + ao_flight_adc = ao_adc_head; + ao_raw_accel_prev = 0; + ao_raw_accel = 0; + ao_raw_pres = 0; + ao_flight_tick = 0; + for (;;) { + ao_sleep(&ao_adc_ring); + while (ao_flight_adc != ao_adc_head) { + __pdata uint8_t ticks; + __pdata int16_t ao_vel_change; + ao_flight_prev_tick = ao_flight_tick; + + /* Capture a sample */ + ao_raw_accel = ao_adc_ring[ao_flight_adc].accel; + ao_raw_pres = ao_adc_ring[ao_flight_adc].pres; + ao_flight_tick = ao_adc_ring[ao_flight_adc].tick; + + ao_flight_accel -= ao_flight_accel >> 4; + ao_flight_accel += ao_raw_accel >> 4; + ao_flight_pres -= ao_flight_pres >> 4; + ao_flight_pres += ao_raw_pres >> 4; + /* Update velocity + * + * The accelerometer is mounted so that + * acceleration yields negative values + * while deceleration yields positive values, + * so subtract instead of add. + */ + ticks = ao_flight_tick - ao_flight_prev_tick; + ao_vel_change = (((ao_raw_accel >> 1) + (ao_raw_accel_prev >> 1)) - ao_ground_accel); + ao_raw_accel_prev = ao_raw_accel; + + /* one is a common interval */ + if (ticks == 1) + ao_flight_vel -= (int32_t) ao_vel_change; + else + ao_flight_vel -= (int32_t) ao_vel_change * (int32_t) ticks; + + ao_flight_adc = ao_adc_ring_next(ao_flight_adc); + } + + if (ao_flight_pres < ao_min_pres) + ao_min_pres = ao_flight_pres; + if (ao_flight_vel >= 0) { + if (ao_flight_vel < ao_min_vel) + ao_min_vel = ao_flight_vel; + } else { + if (-ao_flight_vel < ao_min_vel) + ao_min_vel = -ao_flight_vel; + } + + switch (ao_flight_state) { + case ao_flight_startup: + + /* startup state: + * + * Collect 1000 samples of acceleration and pressure + * data and average them to find the resting values + */ + if (nsamples < 1000) { + ao_raw_accel_sum += ao_raw_accel; + ao_raw_pres_sum += ao_raw_pres; + ++nsamples; + continue; + } + ao_ground_accel = (ao_raw_accel_sum / nsamples); + ao_ground_pres = (ao_raw_pres_sum / nsamples); + ao_min_pres = ao_ground_pres; + ao_config_get(); + ao_main_pres = ao_altitude_to_pres(ao_pres_to_altitude(ao_ground_pres) + ao_config.main_deploy); + ao_flight_vel = 0; + ao_min_vel = 0; + ao_old_vel = ao_flight_vel; + ao_old_vel_tick = ao_flight_tick; + + /* Go to launchpad state if the nose is pointing up */ + ao_config_get(); + if (ao_flight_accel < ao_config.accel_zero_g - ACCEL_NOSE_UP) { + + /* Disable the USB controller in flight mode + * to save power + */ + ao_usb_disable(); + + /* Turn on telemetry system + */ + ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_PAD); + + ao_flight_state = ao_flight_launchpad; + ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); + } else { + ao_flight_state = ao_flight_idle; + + /* Turn on the Green LED in idle mode + */ + ao_led_on(AO_LED_GREEN); + ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); + } + /* signal successful initialization by turning off the LED */ + ao_led_off(AO_LED_RED); + break; + case ao_flight_launchpad: + + /* Trim velocity + * + * Once a second, remove any velocity from + * a second ago + */ + if ((int16_t) (ao_flight_tick - ao_old_vel_tick) >= AO_SEC_TO_TICKS(1)) { + ao_old_vel_tick = ao_flight_tick; + ao_flight_vel -= ao_old_vel; + ao_old_vel = ao_flight_vel; + } + /* pad to boost: + * + * accelerometer: > 2g AND velocity > 5m/s + * OR + * barometer: > 20m vertical motion + * + * The accelerometer should always detect motion before + * the barometer, but we use both to make sure this + * transition is detected + */ + if ((ao_flight_accel < ao_ground_accel - ACCEL_BOOST && + ao_flight_vel > ACCEL_VEL_BOOST) || + ao_flight_pres < ao_ground_pres - BARO_LAUNCH) + { + ao_flight_state = ao_flight_boost; + ao_launch_tick = ao_flight_tick; + + /* start logging data */ + ao_log_start(); + + /* Increase telemetry rate */ + ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_FLIGHT); + + ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); + break; + } + break; + case ao_flight_boost: + + /* boost to coast: + * + * accelerometer: start to fall at > 1/4 G + * OR + * time: boost for more than 15 seconds + * + * Detects motor burn out by the switch from acceleration to + * deceleration, or by waiting until the maximum burn duration + * (15 seconds) has past. + */ + if (ao_flight_accel > ao_ground_accel + (ACCEL_G >> 2) || + (int16_t) (ao_flight_tick - ao_launch_tick) > BOOST_TICKS_MAX) + { + ao_flight_state = ao_flight_coast; + ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); + break; + } + break; + case ao_flight_coast: + + /* coast to apogee detect: + * + * accelerometer: integrated velocity < 200 m/s + * OR + * barometer: fall at least 500m from max altitude + * + * This extra state is required to avoid mis-detecting + * apogee due to mach transitions. + * + * XXX this is essentially a single-detector test + * as the 500m altitude change would likely result + * in a loss of the rocket. More data on precisely + * how big a pressure change the mach transition + * generates would be useful here. + */ + if (ao_flight_vel < ACCEL_VEL_MACH || + ao_flight_pres > ao_min_pres + BARO_COAST) + { + /* set min velocity to current velocity for + * apogee detect + */ + ao_min_vel = abs(ao_flight_vel); + ao_flight_state = ao_flight_apogee; + ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); + } + break; + case ao_flight_apogee: + + /* apogee detect to drogue deploy: + * + * accelerometer: abs(velocity) > min_velocity + 2m/s + * OR + * barometer: fall at least 10m + * + * If the barometer saturates because the flight + * goes over its measuring range (about 53k'), + * requiring a 10m fall will avoid prematurely + * detecting apogee; the accelerometer will take + * over in that case and the integrated velocity + * measurement should suffice to find apogee + */ + if (/* abs(ao_flight_vel) > ao_min_vel + ACCEL_VEL_APOGEE || */ + ao_flight_pres > ao_min_pres + BARO_APOGEE) + { + /* ignite the drogue charge */ + ao_ignite(ao_igniter_drogue); + + /* slow down the telemetry system */ + ao_telemetry_set_interval(AO_TELEMETRY_INTERVAL_RECOVER); + + /* slow down the ADC sample rate */ + ao_timer_set_adc_interval(10); + + /* + * Start recording min/max accel and pres for a while + * to figure out when the rocket has landed + */ + /* Set the 'last' limits to max range to prevent + * early resting detection + */ + ao_interval_min_accel = 0; + ao_interval_max_accel = 0x7fff; + ao_interval_min_pres = 0; + ao_interval_max_pres = 0x7fff; + + /* initialize interval values */ + ao_interval_end = ao_flight_tick + AO_INTERVAL_TICKS; + + ao_interval_cur_min_pres = ao_interval_cur_max_pres = ao_flight_pres; + ao_interval_cur_min_accel = ao_interval_cur_max_accel = ao_flight_accel; + + /* and enter drogue state */ + ao_flight_state = ao_flight_drogue; + ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); + } + + break; + case ao_flight_drogue: + + /* drogue to main deploy: + * + * barometer: reach main deploy altitude + * + * Would like to use the accelerometer for this test, but + * the orientation of the flight computer is unknown after + * drogue deploy, so we ignore it. Could also detect + * high descent rate using the pressure sensor to + * recognize drogue deploy failure and eject the main + * at that point. Perhaps also use the drogue sense lines + * to notice continutity? + */ + if (ao_flight_pres >= ao_main_pres) + { + ao_ignite(ao_igniter_main); + ao_flight_state = ao_flight_main; + ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); + } + + /* fall through... */ + case ao_flight_main: + + /* drogue/main to land: + * + * accelerometer: value stable + * AND + * barometer: altitude stable and within 1000m of the launch altitude + */ + + if (ao_flight_pres < ao_interval_cur_min_pres) + ao_interval_cur_min_pres = ao_flight_pres; + if (ao_flight_pres > ao_interval_cur_max_pres) + ao_interval_cur_max_pres = ao_flight_pres; + if (ao_flight_accel < ao_interval_cur_min_accel) + ao_interval_cur_min_accel = ao_flight_accel; + if (ao_flight_accel > ao_interval_cur_max_accel) + ao_interval_cur_max_accel = ao_flight_accel; + + if ((int16_t) (ao_flight_tick - ao_interval_end) >= 0) { + ao_interval_max_pres = ao_interval_cur_max_pres; + ao_interval_min_pres = ao_interval_cur_min_pres; + ao_interval_max_accel = ao_interval_cur_max_accel; + ao_interval_min_accel = ao_interval_cur_min_accel; + ao_interval_end = ao_flight_tick + AO_INTERVAL_TICKS; + ao_interval_cur_min_pres = ao_interval_cur_max_pres = ao_flight_pres; + ao_interval_cur_min_accel = ao_interval_cur_max_accel = ao_flight_accel; + } + + if ((uint16_t) (ao_interval_max_accel - ao_interval_min_accel) < (uint16_t) ACCEL_INT_LAND && + ao_flight_pres > ao_ground_pres - BARO_LAND && + (uint16_t) (ao_interval_max_pres - ao_interval_min_pres) < (uint16_t) BARO_INT_LAND) + { + ao_flight_state = ao_flight_landed; + + /* turn off the ADC capture */ + ao_timer_set_adc_interval(0); + + ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); + } + break; + case ao_flight_landed: + break; + } + } +} + +#define AO_ACCEL_COUNT_TO_MSS(count) ((count) / 27) +#define AO_VEL_COUNT_TO_MS(count) ((int16_t) ((count) / 2700)) + +static void +ao_flight_status(void) +{ + printf("STATE: %7s accel: %d speed: %d altitude: %d main: %d\n", + ao_state_names[ao_flight_state], + AO_ACCEL_COUNT_TO_MSS(ACCEL_ZERO_G - ao_flight_accel), + AO_VEL_COUNT_TO_MS(ao_flight_vel), + ao_pres_to_altitude(ao_flight_pres), + ao_pres_to_altitude(ao_main_pres)); +} + +static __xdata struct ao_task flight_task; + +__code struct ao_cmds ao_flight_cmds[] = { + { 'f', ao_flight_status, "f Display current flight state" }, + { 0, ao_flight_status, NULL } +}; + +void +ao_flight_init(void) +{ + ao_flight_state = ao_flight_startup; + ao_interval_min_accel = 0; + ao_interval_max_accel = 0x7fff; + ao_interval_min_pres = 0; + ao_interval_max_pres = 0x7fff; + ao_interval_end = AO_INTERVAL_TICKS; + + ao_add_task(&flight_task, ao_flight, "flight"); + ao_cmd_register(&ao_flight_cmds[0]); +} |