--- /dev/null
+#!/usr/bin/env nickle
+
+/*
+ * Pressure Sensor Model, version 1.1
+ *
+ * written by Holly Grimes
+ *
+ * Uses the International Standard Atmosphere as described in
+ * "A Quick Derivation relating altitude to air pressure" (version 1.03)
+ * from the Portland State Aerospace Society, except that the atmosphere
+ * is divided into layers with each layer having a different lapse rate.
+ *
+ * Lapse rate data for each layer was obtained from Wikipedia on Sept. 1, 2007
+ * at site <http://en.wikipedia.org/wiki/International_Standard_Atmosphere
+ *
+ * Height measurements use the local tangent plane. The postive z-direction is up.
+ *
+ * All measurements are given in SI units (Kelvin, Pascal, meter, meters/second^2).
+ * The lapse rate is given in Kelvin/meter, the gas constant for air is given
+ * in Joules/(kilogram-Kelvin).
+ */
+
+const real GRAVITATIONAL_ACCELERATION = -9.80665;
+const real AIR_GAS_CONSTANT = 287.053;
+const int NUMBER_OF_LAYERS = 7;
+const real MAXIMUM_ALTITUDE = 84852;
+const real MINIMUM_PRESSURE = 0.3734;
+const real LAYER0_BASE_TEMPERATURE = 288.15;
+const real LAYER0_BASE_PRESSURE = 101325;
+
+/* lapse rate and base altitude for each layer in the atmosphere */
+const real[NUMBER_OF_LAYERS] lapse_rate = {
+ -0.0065, 0.0, 0.001, 0.0028, 0.0, -0.0028, -0.002
+};
+const int[NUMBER_OF_LAYERS] base_altitude = {
+ 0, 11000, 20000, 32000, 47000, 51000, 71000
+};
+
+
+/* outputs atmospheric pressure associated with the given altitude. altitudes
+ are measured with respect to the mean sea level */
+real altitude_to_pressure(real altitude) {
+
+ real base_temperature = LAYER0_BASE_TEMPERATURE;
+ real base_pressure = LAYER0_BASE_PRESSURE;
+
+ real pressure;
+ real base; /* base for function to determine pressure */
+ real exponent; /* exponent for function to determine pressure */
+ int layer_number; /* identifies layer in the atmosphere */
+ int delta_z; /* difference between two altitudes */
+
+ if (altitude > MAXIMUM_ALTITUDE) /* FIX ME: use sensor data to improve model */
+ return 0;
+
+ /* calculate the base temperature and pressure for the atmospheric layer
+ associated with the inputted altitude */
+ for(layer_number = 0; layer_number < NUMBER_OF_LAYERS - 1 && altitude > base_altitude[layer_number + 1]; layer_number++) {
+ delta_z = base_altitude[layer_number + 1] - base_altitude[layer_number];
+ if (lapse_rate[layer_number] == 0.0) {
+ exponent = GRAVITATIONAL_ACCELERATION * delta_z
+ / AIR_GAS_CONSTANT / base_temperature;
+ base_pressure *= exp(exponent);
+ }
+ else {
+ base = (lapse_rate[layer_number] * delta_z / base_temperature) + 1.0;
+ exponent = GRAVITATIONAL_ACCELERATION /
+ (AIR_GAS_CONSTANT * lapse_rate[layer_number]);
+ base_pressure *= pow(base, exponent);
+ }
+ base_temperature += delta_z * lapse_rate[layer_number];
+ }
+
+ /* calculate the pressure at the inputted altitude */
+ delta_z = altitude - base_altitude[layer_number];
+ if (lapse_rate[layer_number] == 0.0) {
+ exponent = GRAVITATIONAL_ACCELERATION * delta_z
+ / AIR_GAS_CONSTANT / base_temperature;
+ pressure = base_pressure * exp(exponent);
+ }
+ else {
+ base = (lapse_rate[layer_number] * delta_z / base_temperature) + 1.0;
+ exponent = GRAVITATIONAL_ACCELERATION /
+ (AIR_GAS_CONSTANT * lapse_rate[layer_number]);
+ pressure = base_pressure * pow(base, exponent);
+ }
+
+ return pressure;
+}
+
+
+/* outputs the altitude associated with the given pressure. the altitude
+ returned is measured with respect to the mean sea level */
+real pressure_to_altitude(real pressure) {
+
+ real next_base_temperature = LAYER0_BASE_TEMPERATURE;
+ real next_base_pressure = LAYER0_BASE_PRESSURE;
+
+ real altitude;
+ real base_pressure;
+ real base_temperature;
+ real base; /* base for function to determine base pressure of next layer */
+ real exponent; /* exponent for function to determine base pressure
+ of next layer */
+ real coefficient;
+ int layer_number; /* identifies layer in the atmosphere */
+ int delta_z; /* difference between two altitudes */
+
+ if (pressure < 0) /* illegal pressure */
+ return -1;
+ if (pressure < MINIMUM_PRESSURE) /* FIX ME: use sensor data to improve model */
+ return MAXIMUM_ALTITUDE;
+
+ /* calculate the base temperature and pressure for the atmospheric layer
+ associated with the inputted pressure. */
+ layer_number = -1;
+ do {
+ layer_number++;
+ base_pressure = next_base_pressure;
+ base_temperature = next_base_temperature;
+ delta_z = base_altitude[layer_number + 1] - base_altitude[layer_number];
+ if (lapse_rate[layer_number] == 0.0) {
+ exponent = GRAVITATIONAL_ACCELERATION * delta_z
+ / AIR_GAS_CONSTANT / base_temperature;
+ next_base_pressure *= exp(exponent);
+ }
+ else {
+ base = (lapse_rate[layer_number] * delta_z / base_temperature) + 1.0;
+ exponent = GRAVITATIONAL_ACCELERATION /
+ (AIR_GAS_CONSTANT * lapse_rate[layer_number]);
+ next_base_pressure *= pow(base, exponent);
+ }
+ next_base_temperature += delta_z * lapse_rate[layer_number];
+ }
+ while(layer_number < NUMBER_OF_LAYERS - 1 && pressure < next_base_pressure);
+
+ /* calculate the altitude associated with the inputted pressure */
+ if (lapse_rate[layer_number] == 0.0) {
+ coefficient = (AIR_GAS_CONSTANT / GRAVITATIONAL_ACCELERATION)
+ * base_temperature;
+ altitude = base_altitude[layer_number]
+ + coefficient * log(pressure / base_pressure);
+ }
+ else {
+ base = pressure / base_pressure;
+ exponent = AIR_GAS_CONSTANT * lapse_rate[layer_number]
+ / GRAVITATIONAL_ACCELERATION;
+ coefficient = base_temperature / lapse_rate[layer_number];
+ altitude = base_altitude[layer_number]
+ + coefficient * (pow(base, exponent) - 1);
+ }
+
+ return altitude;
+}
+
+real feet_to_meters(real feet)
+{
+ return feet * (12 * 2.54 / 100);
+}
+
+real meters_to_feet(real meters)
+{
+ return meters / (12 * 2.54 / 100);
+}
+
+/*
+ * Values for our MP3H6115A pressure sensor
+ *
+ * From the data sheet:
+ *
+ * Pressure range: 15-115 kPa
+ * Voltage at 115kPa: 2.82
+ * Output scale: 27mV/kPa
+ *
+ *
+ * 27 mV/kPa * 2047 / 3300 counts/mV = 16.75 counts/kPa
+ * 2.82V * 2047 / 3.3 counts/V = 1749 counts/115 kPa
+ */
+
+real counts_per_kPa = 27 * 2047 / 3300;
+real counts_at_101_3kPa = 1674;
+
+real count_to_kPa(real count)
+{
+ return (count / 2047 + 0.095) / 0.009;
+}
+typedef struct {
+ int type;
+ int time;
+ int a;
+ int b;
+} flight_record;
+
+flight_record
+read_record(file in) {
+ flight_record r;
+ File::fscanf(in, "%c %x %x %x\n",
+ &r.type, &r.time, &r.a, &r.b);
+ return r;
+}
+
+real g_count = 264.8;
+#real g_count = 262;
+#real g_count = 400;
+int g_base = 15735;
+
+real
+count_to_g(real count)
+{
+ return (g_base + g_count - count) / g_count;
+}
+
+real base_alt = 0;
+real base_sec = 0;
+real last_alt;
+real last_sec;
+real last_alt_speed;
+real accel_speed;
+real accel_meters;
+
+real[...] barometer;
+real[...] accelerometer;
+
+real sinc(real x) = x != 0 ? sin(x)/x : 1;
+
+real gaussian(real x) = exp(-(x**2)/2) / sqrt(2 * pi);
+
+load "filter.5c"
+
+real[...] convolve(real[...] d, real[...] e) {
+ real sample(n) = n < 0 ? d[0] : n >= dim(d) ? d[dim(d)-1] : d[n];
+ real w = (dim(e) - 1) / 2;
+ real c(int center) {
+ real v = 0;
+ for (int o = -w; o <= w; o++)
+ v += sample(center + o) * e[o + w];
+ return v;
+ }
+ return (real[dim(d)]) { [n] = c(n) };
+}
+
+real sum(real[...] x) { real s = 0; for(int i = 0; i < dim(x); i++) s += x[i]; return s; }
+
+real[...] kaiser_filter(real[...] d, int half_width) {
+# real[half_width * 2 + 1] fir = { [n] = sinc(2 * pi * n / (2 * half_width)) };
+ real M = half_width * 2 + 1;
+ real[M] fir = { [n] = kaiser(n, M, 8) };
+ real fir_sum = sum(fir);
+ for (int i = 0; i < dim(fir); i++) fir[i] /= fir_sum;
+ return convolve(d, fir);
+}
+
+int[...] int_filter(int[...] d, int shift) {
+ /* Emulate the exponential IIR filter used in the TeleMetrum flight
+ software */
+
+ int v = d[0];
+ int n;
+ int[dim(d)] ret;
+
+ for (n = 0; n < dim(d); n++) {
+ v -= (v + (1 << (shift - 1))) >> shift;
+ v += (d[n] + (1 << (shift - 1))) >> shift;
+ ret[n] = v;
+ }
+ return ret;
+}
+
+real gravity = 9.80665;
+
+int[...] pressure_value, accelerometer_value;
+real[...] clock;
+
+void readsamples_log(file in) {
+ setdim(pressure_value, 0);
+ setdim(accelerometer_value, 0);
+ while (!File::end(in)) {
+ flight_record r = read_record(in);
+ if (r.type == 'F') {
+ g_base = r.a;
+ }
+ if (r.type == 'A') {
+ clock[dim(clock)] = r.time / 100;
+ pressure_value[dim(pressure_value)] = r.b;
+ accelerometer_value[dim(accelerometer_value)] = r.a;
+ }
+ }
+}
+
+typedef struct {
+ int time;
+ int accel;
+ int pressure;
+ string state;
+} telem_record;
+
+autoimport String;
+
+telem_record read_telem(file in) {
+ string[*] r = wordsplit(chomp(fgets(in)), " ");
+ static int line = 0;
+
+ line++;
+ if (dim(r) < 15) {
+ printf ("invalid record line %d\n", line);
+ return read_telem(in);
+ }
+ return (telem_record) {
+ .time = string_to_integer(r[10]),
+ .accel = string_to_integer(r[12]),
+ .pressure = string_to_integer(r[14]),
+ .state = r[9]
+ };
+}
+
+void readsamples_telem(file in) {
+ telem_record[...] telem;
+
+ setdim(telem, 0);
+
+ setdim(clock, 0);
+ setdim(pressure_value, 0);
+ setdim(accelerometer_value, 0);
+ real clock_bias = 0;
+
+ telem_record[...] save = {};
+
+ setdim(save, 0);
+ while (!File::end(in)) {
+ save[dim(save)] = read_telem(in);
+ if (save[dim(save)-1].state == "boost")
+ break;
+ }
+ int start = dim(save) - 4;
+
+ int accel_total = 0;
+ for (int i = 0; i < start; i++)
+ accel_total += save[i].accel;
+ g_base = accel_total // start;
+
+ for (int i = start; i < dim(save); i++)
+ telem[dim(telem)] = save[i];
+
+ while (!File::end(in)) {
+ int n = dim(telem);
+ telem[n] = read_telem(in);
+ telem[n].time += clock_bias;
+ if (n > 0 && telem[n].time < telem[n-1].time) {
+ clock_bias += 65536;
+ telem[n].time += 65536;
+ }
+ }
+ int clock_start = telem[0].time;
+ int clock_end = telem[dim(telem)-1].time;
+ int samples = clock_end - clock_start;
+
+ int j = 0;
+ for (int i = 0; i < samples; i++) {
+ clock[i] = i / 100;
+ pressure_value[i] = telem[j].pressure;
+ accelerometer_value[i] = telem[j].accel;
+ if (j < dim(telem)-1) {
+ int cur_time = clock_start + i;
+ if (cur_time - telem[j].time > telem[j+1].time - cur_time)
+ j++;
+ }
+ }
+}
+
+readsamples_log(stdin);
+
+int[...] int_integrate(int[...] d, int base) {
+ int v = 0;
+ int[dim(d)] ret;
+
+ ret[0] = 0;
+ for (int i = 1; i < dim(d); i++)
+ ret[i] = (v += (d[i-1] + d[i] + 1) // 2);
+ return ret;
+}
+
+int[...] int_differentiate(int[...] d) {
+ return (int[dim(d)]) { [n] = n == 0 ? 0 : d[n] - d[n-1] };
+}
+
+int average(int[...] d, int n) {
+ int sum = 0;
+ for (int i = 0; i < n; i++)
+ sum += d[n];
+ return sum // n;
+}
+
+int[...] rebase(int[...] d, int m, int a) = (int[dim(d)]) { [n] = d[n] * m + a };
+
+int size = dim(accelerometer_value);
+
+real[...] do_low_pass(real[] data, real ωpass, real ωstop, real error) {
+ real[*] fir = low_pass_filter (ωpass, ωstop, error);
+ File::fprintf (stderr, "low pass filter is %d long\n", dim(fir));
+ return convolve(data, fir);
+}
+
+if (false) {
+ accelerometer_value = rebase(accelerometer_value, -1, g_base);
+ int accel_i0_base = average(accelerometer_value, 30);
+ int[size] pres_d0 = int_filter(pressure_value, 4);
+ int[size] accel_i0 = int_filter(accelerometer_value, 4);
+ int[size] pres_d1 = int_filter(int_differentiate(pres_d0), 4);
+ int[size] accel_i1 = int_integrate(accelerometer_value, accel_i0_base);
+ int[size] pres_d2 = int_filter(int_differentiate(pres_d1), 4);
+ int[size] accel_i2 = int_integrate(accel_i1, 0);
+
+ real count_to_altitude(int count) = pressure_to_altitude(count_to_kPa(count / 16) * 1000);
+
+ for (int i = 0; i < size; i++)
+ printf("%g %g %g %g %g %g %g %g %g\n",
+ clock[i] - clock[0],
+ count_to_altitude(pres_d0[i]) - count_to_altitude(pres_d0[0]), accel_i2[i] / 10000 / g_count * gravity,
+ pres_d1[i] * 100, accel_i1[i] / 100 / g_count * gravity,
+ pres_d2[i] * 10000, accel_i0[i] / g_count * gravity,
+ count_to_altitude(pressure_value[i]) -
+ count_to_altitude(pressure_value[0]), accelerometer_value[i]
+ / g_count * gravity);
+
+} else {
+ real[size] accelerometer = { [n] = gravity * (count_to_g(accelerometer_value[n]) - 1.0) };
+ real[size] barometer = { [n] = pressure_to_altitude(count_to_kPa(pressure_value[n] / 16) * 1000) };
+ real[size] filtered_accelerometer = do_low_pass(accelerometer,
+ 2 * π * 5/100,
+ 2 * π * 8/100,
+ 1e-8);
+ real[size] filtered_barometer = do_low_pass(barometer,
+ 2 * π * .5 / 100,
+ 2 * π * 1 / 100,
+ 1e-8);
+
+ real[...] integrate(real[...] d) {
+ real[dim(d)] ret;
+ for (int i = 0; i < dim(ret); i++)
+ ret[i] = i == 0 ? 0 : ret[i-1] + (d[i-1] + d[i]) / 2 * (clock[i] - clock[i-1]);
+ return ret;
+ }
+
+ real[...] differentiate(real[...] d) {
+ real[dim(d)] ret;
+ for (int i = 1; i < dim(ret); i++)
+ ret[i] = (d[i] - d[i-1]) / (clock[i] - clock[i-1]);
+ ret[0] = ret[1];
+ return ret;
+ }
+
+ real[size] accel_speed = integrate(accelerometer);
+ real[size] accel_pos = integrate(accel_speed);
+ real[size] baro_speed = differentiate(filtered_barometer);
+ real[size] baro_accel = differentiate(baro_speed);
+
+ printf("%7s %12s %12s %12s %12s %12s %12s %12s %12s\n",
+ "time",
+ "height(baro)",
+ "height(accel)",
+ "speed(baro)",
+ "speed(accel)",
+ "accel(baro)",
+ "accel(accel)",
+ "raw(baro)",
+ "raw(accel)");
+ for (int i = 0; i < size; i++)
+ printf("%7.2f %12.6f %12.6f %12.6f %12.6f %12.6f %12.6f %12.6f %12.6f\n",
+ clock[i] - clock[0],
+ filtered_barometer[i] - filtered_barometer[0], accel_pos[i],
+ baro_speed[i], accel_speed[i],
+ baro_accel[i], filtered_accelerometer[i],
+ barometer[i] - barometer[0], accelerometer[i]);
+}
projects / fw / tmflights / blobdiff