Update flight algorithm based on data collected from SN-1 Flight 1

This now correctly sequences through the flight data collected from the
first TeleMetrum test flight.

This also completes up the flight algorithm test harness (ao_flight_test),
which runs the flight algorithm on the Linux host from a captured data log.

1 files changed, 103 insertions, 42 deletions

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;