X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=blobdiff_plain;f=ao_flight.c;h=ddf2d173c74e1839d9800622d48eb6c6e1d99292;hp=5998f291c42881e7c361af105b03659c0be8deb9;hb=b99315cee4ab796376458a2442cf36806fa4aed3;hpb=b32f2f0090ff967edac07ae4d7a9895ed0b96d31 diff --git a/ao_flight.c b/ao_flight.c index 5998f291..ddf2d173 100644 --- a/ao_flight.c +++ b/ao_flight.c @@ -28,7 +28,7 @@ __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_time; /* time of launch detect */ +__pdata uint16_t ao_launch_tick; /* time of launch detect */ __pdata int16_t ao_main_pres; /* pressure to eject main */ /* @@ -46,9 +46,7 @@ __pdata int16_t ao_interval_min_pres; __pdata int16_t ao_interval_max_pres; __data uint8_t ao_flight_adc; -__xdata int16_t ao_accel, ao_prev_accel, ao_pres; - -#define AO_INTERVAL_TICKS AO_SEC_TO_TICKS(5) +__pdata int16_t ao_raw_accel, ao_raw_accel_prev, ao_raw_pres; /* Accelerometer calibration * @@ -63,13 +61,18 @@ __xdata int16_t ao_accel, ao_prev_accel, ao_pres; * * 26.67 mV/g * 32767/3300 counts/mV = 264.8 counts/g * - * Zero g was measured at 16000 (we would expect 16384) + * 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 ACCEL_G 265 #define ACCEL_ZERO_G 16000 #define ACCEL_NOSE_UP (ACCEL_ZERO_G - ACCEL_G * 2 /3) -#define ACCEL_BOOST (ACCEL_NOSE_UP - ACCEL_G * 2) +#define ACCEL_BOOST ACCEL_G * 2 #define ACCEL_LAND (ACCEL_G / 10) /* @@ -80,7 +83,7 @@ __xdata int16_t ao_accel, ao_prev_accel, ao_pres; * 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 @@ -92,10 +95,11 @@ __xdata int16_t ao_accel, ao_prev_accel, ao_pres; */ #define BARO_kPa 268 -#define BARO_LAUNCH (BARO_kPa / 5) /* .2kPa */ -#define BARO_APOGEE (BARO_kPa / 10) /* .1kPa */ -#define BARO_MAIN (BARO_kPa) /* 1kPa */ -#define BARO_LAND (BARO_kPa / 20) /* .05kPa */ +#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_LAND (BARO_kPa / 20) /* .05kPa, or about 5m */ /* We also have a clock, which can be used to sanity check things in * case of other failures @@ -109,68 +113,98 @@ __xdata int16_t ao_accel, ao_prev_accel, ao_pres; * it's scaled by 100 */ __data int32_t ao_flight_vel; +__xdata int32_t ao_raw_accel_sum, ao_raw_pres_sum; +#define GRAVITY 9.80665 /* convert m/s to velocity count */ -#define VEL_MPS_TO_COUNT(mps) ((int32_t) ((int32_t) (mps) * (int32_t) 100 / (int32_t) ACCEL_G)) +#define VEL_MPS_TO_COUNT(mps) ((int32_t) (((mps) / GRAVITY) * ACCEL_G * 100)) + +/* 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(10) void ao_flight(void) { __pdata static uint8_t nsamples = 0; - + ao_flight_adc = ao_adc_head; - ao_prev_accel = 0; - ao_accel = 0; - ao_pres = 0; + ao_raw_accel_prev = 0; + ao_raw_accel = 0; + ao_raw_pres = 0; + ao_interval_cur_min_pres = 0x7fff; + ao_interval_cur_max_pres = -0x7fff; + ao_interval_cur_min_accel = 0x7fff; + ao_interval_cur_max_accel = -0x7fff; for (;;) { ao_sleep(&ao_adc_ring); while (ao_flight_adc != ao_adc_head) { - ao_accel = ao_adc_ring[ao_flight_adc].accel; - ao_pres = ao_adc_ring[ao_flight_adc].pres; + 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_vel += (int32_t) (((ao_accel + ao_prev_accel) >> 4) - (ao_ground_accel << 1)); - ao_prev_accel = ao_accel; + /* all of our accelerations are negative, so subtract instead of add to get speed */ + ao_flight_vel -= (int32_t) (((ao_raw_accel + ao_raw_accel_prev) >> 1) - ao_ground_accel); + ao_raw_accel_prev = ao_raw_accel; ao_flight_adc = ao_adc_ring_next(ao_flight_adc); } ao_flight_accel -= ao_flight_accel >> 4; - ao_flight_accel += ao_accel >> 4; + ao_flight_accel += ao_raw_accel >> 4; ao_flight_pres -= ao_flight_pres >> 4; - ao_flight_pres += ao_pres >> 4; - + ao_flight_pres += ao_raw_pres >> 4; + if (ao_flight_pres < ao_min_pres) ao_min_pres = ao_flight_pres; + 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; } - + switch (ao_flight_state) { case ao_flight_startup: + + /* startup state: + * + * Collect 100 samples of acceleration and pressure + * data and average them to find the resting values + */ if (nsamples < 100) { + ao_raw_accel_sum += ao_raw_accel; + ao_raw_pres_sum += ao_raw_pres; ++nsamples; continue; } - ao_ground_accel = ao_flight_accel; - ao_ground_pres = ao_flight_pres; - ao_min_pres = ao_flight_pres; + ao_ground_accel = (ao_raw_accel_sum / nsamples); + ao_ground_pres = (ao_raw_pres_sum / nsamples); + ao_min_pres = ao_ground_pres; ao_main_pres = ao_ground_pres - BARO_MAIN; ao_flight_vel = 0; - + ao_interval_end = ao_flight_tick; - + /* Go to launchpad state if the nose is pointing up */ if (ao_flight_accel < ACCEL_NOSE_UP) { 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 - * This also happens to bring the USB up for the TI board */ ao_led_on(AO_LED_GREEN); ao_timer_set_adc_interval(100); @@ -184,12 +218,18 @@ ao_flight(void) /* pad to boost: * * accelerometer: > 2g + * 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 < ACCEL_BOOST || - ao_flight_pres + BARO_LAUNCH < ao_ground_pres) + if (ao_flight_accel < ao_ground_accel - ACCEL_BOOST || + ao_flight_pres < ao_ground_pres - BARO_LAUNCH) { ao_flight_state = ao_flight_boost; + ao_launch_tick = ao_flight_tick; ao_log_start(); ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); break; @@ -200,25 +240,36 @@ ao_flight(void) /* 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_time) > BOOST_TICKS_MAX) + (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; + /* fall through ... */ case ao_flight_coast: - - /* coast to apogee detect: - * + + /* boost/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. For slow flights (<200m/s) + * we expect to transition right through this stage to + * apogee detect. */ if (ao_flight_vel < VEL_MPS_TO_COUNT(200) || - ao_flight_pres - (5 * BARO_kPa) > ao_min_pres) + ao_flight_pres > ao_min_pres + BARO_COAST) { ao_flight_state = ao_flight_apogee; ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); @@ -229,7 +280,15 @@ ao_flight(void) /* apogee to drogue deploy: * * accelerometer: integrated velocity < 10m/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 (ao_flight_vel < VEL_MPS_TO_COUNT(-10) || ao_flight_pres - BARO_APOGEE > ao_min_pres) @@ -238,12 +297,13 @@ ao_flight(void) ao_flight_state = ao_flight_drogue; ao_wakeup(DATA_TO_XDATA(&ao_flight_state)); } - break; + break; case ao_flight_drogue: - + /* drogue to main deploy: * * accelerometer: abs(velocity) > 50m/s + * OR * barometer: reach main deploy altitude */ if (ao_flight_vel < VEL_MPS_TO_COUNT(-50) || @@ -260,9 +320,10 @@ ao_flight(void) /* drogue/main to land: * * accelerometer: value stable + * AND * barometer: altitude stable */ - if ((ao_interval_max_accel - ao_interval_min_accel) < ACCEL_LAND || + if ((ao_interval_max_accel - ao_interval_min_accel) < ACCEL_LAND && (ao_interval_max_pres - ao_interval_min_pres) < BARO_LAND) { ao_flight_state = ao_flight_landed;