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author | Lorenz Meier <lm@inf.ethz.ch> | 2014-04-05 09:03:23 -0700 |
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committer | Lorenz Meier <lm@inf.ethz.ch> | 2014-04-05 09:03:23 -0700 |
commit | be6c0d2ece235077f067f4db10689b8ad3d9c5b1 (patch) | |
tree | 21a42edb73c6dc401f817df5b84876e656c672b6 | |
parent | 3e5f0813a88817418cc259a5574372e5edca0432 (diff) | |
parent | a1a4013d02ca7ec3f62c6c3f2e4b95181f365c35 (diff) | |
download | px4-firmware-be6c0d2ece235077f067f4db10689b8ad3d9c5b1.tar.gz px4-firmware-be6c0d2ece235077f067f4db10689b8ad3d9c5b1.tar.bz2 px4-firmware-be6c0d2ece235077f067f4db10689b8ad3d9c5b1.zip |
Merge pull request #803 from PX4/airspeed_scaling
Airspeed scaling
-rw-r--r-- | src/drivers/meas_airspeed/meas_airspeed.cpp | 128 | ||||
-rw-r--r-- | src/lib/mathlib/math/filter/LowPassFilter2p.cpp | 7 | ||||
-rw-r--r-- | src/lib/mathlib/math/filter/LowPassFilter2p.hpp | 20 | ||||
-rw-r--r-- | src/modules/commander/airspeed_calibration.cpp | 14 | ||||
-rw-r--r-- | src/modules/sdlog2/sdlog2.c | 1 | ||||
-rw-r--r-- | src/modules/sdlog2/sdlog2_messages.h | 3 | ||||
-rw-r--r-- | src/modules/sensors/sensors.cpp | 5 | ||||
-rw-r--r-- | src/modules/uORB/topics/airspeed.h | 5 | ||||
-rw-r--r-- | src/modules/uORB/topics/differential_pressure.h | 9 |
9 files changed, 159 insertions, 33 deletions
diff --git a/src/drivers/meas_airspeed/meas_airspeed.cpp b/src/drivers/meas_airspeed/meas_airspeed.cpp index 2c3efdc35..1ad383ee0 100644 --- a/src/drivers/meas_airspeed/meas_airspeed.cpp +++ b/src/drivers/meas_airspeed/meas_airspeed.cpp @@ -87,6 +87,7 @@ #include <uORB/uORB.h> #include <uORB/topics/differential_pressure.h> #include <uORB/topics/subsystem_info.h> +#include <uORB/topics/system_power.h> #include <drivers/airspeed/airspeed.h> @@ -121,6 +122,14 @@ protected: virtual int collect(); math::LowPassFilter2p _filter; + + /** + * Correct for 5V rail voltage variations + */ + void voltage_correction(float &diff_pres_pa, float &temperature); + + int _t_system_power; + struct system_power_s system_power; }; /* @@ -129,10 +138,11 @@ protected: extern "C" __EXPORT int meas_airspeed_main(int argc, char *argv[]); MEASAirspeed::MEASAirspeed(int bus, int address, const char *path) : Airspeed(bus, address, - CONVERSION_INTERVAL, path), - _filter(MEAS_RATE, MEAS_DRIVER_FILTER_FREQ) + CONVERSION_INTERVAL, path), + _filter(MEAS_RATE, MEAS_DRIVER_FILTER_FREQ), + _t_system_power(-1) { - + memset(&system_power, 0, sizeof(system_power)); } int @@ -194,19 +204,48 @@ MEASAirspeed::collect() dp_raw = 0x3FFF & dp_raw; dT_raw = (val[2] << 8) + val[3]; dT_raw = (0xFFE0 & dT_raw) >> 5; - float temperature = ((200 * dT_raw) / 2047) - 50; + float temperature = ((200.0f * dT_raw) / 2047) - 50; - /* calculate differential pressure. As its centered around 8000 - * and can go positive or negative, enforce absolute value - */ + // Calculate differential pressure. As its centered around 8000 + // and can go positive or negative const float P_min = -1.0f; const float P_max = 1.0f; - float diff_press_pa = fabsf((((float)dp_raw - 0.1f * 16383.0f) * (P_max - P_min) / (0.8f * 16383.0f) + P_min) * 6894.8f) - _diff_pres_offset; + const float PSI_to_Pa = 6894.757f; + /* + this equation is an inversion of the equation in the + pressure transfer function figure on page 4 of the datasheet - if (diff_press_pa < 0.0f) { - diff_press_pa = 0.0f; - } + We negate the result so that positive differential pressures + are generated when the bottom port is used as the static + port on the pitot and top port is used as the dynamic port + */ + float diff_press_PSI = -((dp_raw - 0.1f*16383) * (P_max-P_min)/(0.8f*16383) + P_min); + float diff_press_pa_raw = diff_press_PSI * PSI_to_Pa; + // correct for 5V rail voltage if possible + voltage_correction(diff_press_pa_raw, temperature); + + float diff_press_pa = fabsf(diff_press_pa_raw - _diff_pres_offset); + + /* + note that we return both the absolute value with offset + applied and a raw value without the offset applied. This + makes it possible for higher level code to detect if the + user has the tubes connected backwards, and also makes it + possible to correctly use offsets calculated by a higher + level airspeed driver. + + With the above calculation the MS4525 sensor will produce a + positive number when the top port is used as a dynamic port + and bottom port is used as the static port + + Also note that the _diff_pres_offset is applied before the + fabsf() not afterwards. It needs to be done this way to + prevent a bias at low speeds, but this also means that when + setting a offset you must set it based on the raw value, not + the offset value + */ + struct differential_pressure_s report; /* track maximum differential pressure measured (so we can work out top speed). */ @@ -219,6 +258,13 @@ MEASAirspeed::collect() report.temperature = temperature; report.differential_pressure_pa = diff_press_pa; report.differential_pressure_filtered_pa = _filter.apply(diff_press_pa); + + /* the dynamics of the filter can make it overshoot into the negative range */ + if (report.differential_pressure_filtered_pa < 0.0f) { + report.differential_pressure_filtered_pa = _filter.reset(diff_press_pa); + } + + report.differential_pressure_raw_pa = diff_press_pa_raw; report.voltage = 0; report.max_differential_pressure_pa = _max_differential_pressure_pa; @@ -288,6 +334,62 @@ MEASAirspeed::cycle() } /** + correct for 5V rail voltage if the system_power ORB topic is + available + + See http://uav.tridgell.net/MS4525/MS4525-offset.png for a graph of + offset versus voltage for 3 sensors + */ +void +MEASAirspeed::voltage_correction(float &diff_press_pa, float &temperature) +{ +#ifdef CONFIG_ARCH_BOARD_PX4FMU_V2 + if (_t_system_power == -1) { + _t_system_power = orb_subscribe(ORB_ID(system_power)); + } + if (_t_system_power == -1) { + // not available + return; + } + bool updated = false; + orb_check(_t_system_power, &updated); + if (updated) { + orb_copy(ORB_ID(system_power), _t_system_power, &system_power); + } + if (system_power.voltage5V_v < 3.0f || system_power.voltage5V_v > 6.0f) { + // not valid, skip correction + return; + } + + const float slope = 65.0f; + /* + apply a piecewise linear correction, flattening at 0.5V from 5V + */ + float voltage_diff = system_power.voltage5V_v - 5.0f; + if (voltage_diff > 0.5f) { + voltage_diff = 0.5f; + } + if (voltage_diff < -0.5f) { + voltage_diff = -0.5f; + } + diff_press_pa -= voltage_diff * slope; + + /* + the temperature masurement varies as well + */ + const float temp_slope = 0.887f; + voltage_diff = system_power.voltage5V_v - 5.0f; + if (voltage_diff > 0.5f) { + voltage_diff = 0.5f; + } + if (voltage_diff < -1.0f) { + voltage_diff = -1.0f; + } + temperature -= voltage_diff * temp_slope; +#endif // CONFIG_ARCH_BOARD_PX4FMU_V2 +} + +/** * Local functions in support of the shell command. */ namespace meas_airspeed @@ -409,7 +511,7 @@ test() } warnx("single read"); - warnx("diff pressure: %8.4f pa", (double)report.differential_pressure_pa); + warnx("diff pressure: %d pa", (int)report.differential_pressure_pa); /* start the sensor polling at 2Hz */ if (OK != ioctl(fd, SENSORIOCSPOLLRATE, 2)) { @@ -437,7 +539,7 @@ test() } warnx("periodic read %u", i); - warnx("diff pressure: %8.4f pa", (double)report.differential_pressure_pa); + warnx("diff pressure: %d pa", (int)report.differential_pressure_pa); warnx("temperature: %d C (0x%02x)", (int)report.temperature, (unsigned) report.temperature); } diff --git a/src/lib/mathlib/math/filter/LowPassFilter2p.cpp b/src/lib/mathlib/math/filter/LowPassFilter2p.cpp index 3699d9bce..6f640c9f9 100644 --- a/src/lib/mathlib/math/filter/LowPassFilter2p.cpp +++ b/src/lib/mathlib/math/filter/LowPassFilter2p.cpp @@ -69,7 +69,7 @@ float LowPassFilter2p::apply(float sample) // do the filtering float delay_element_0 = sample - _delay_element_1 * _a1 - _delay_element_2 * _a2; if (isnan(delay_element_0) || isinf(delay_element_0)) { - // don't allow bad values to propogate via the filter + // don't allow bad values to propagate via the filter delay_element_0 = sample; } float output = delay_element_0 * _b0 + _delay_element_1 * _b1 + _delay_element_2 * _b2; @@ -81,5 +81,10 @@ float LowPassFilter2p::apply(float sample) return output; } +float LowPassFilter2p::reset(float sample) { + _delay_element_1 = _delay_element_2 = sample; + return apply(sample); +} + } // namespace math diff --git a/src/lib/mathlib/math/filter/LowPassFilter2p.hpp b/src/lib/mathlib/math/filter/LowPassFilter2p.hpp index 208ec98d4..74cd5d78c 100644 --- a/src/lib/mathlib/math/filter/LowPassFilter2p.hpp +++ b/src/lib/mathlib/math/filter/LowPassFilter2p.hpp @@ -52,18 +52,30 @@ public: _delay_element_1 = _delay_element_2 = 0; } - // change parameters + /** + * Change filter parameters + */ void set_cutoff_frequency(float sample_freq, float cutoff_freq); - // apply - Add a new raw value to the filter - // and retrieve the filtered result + /** + * Add a new raw value to the filter + * + * @return retrieve the filtered result + */ float apply(float sample); - // return the cutoff frequency + /** + * Return the cutoff frequency + */ float get_cutoff_freq(void) const { return _cutoff_freq; } + /** + * Reset the filter state to this value + */ + float reset(float sample); + private: float _cutoff_freq; float _a1; diff --git a/src/modules/commander/airspeed_calibration.cpp b/src/modules/commander/airspeed_calibration.cpp index 6039d92a7..c8c7a42e7 100644 --- a/src/modules/commander/airspeed_calibration.cpp +++ b/src/modules/commander/airspeed_calibration.cpp @@ -1,6 +1,6 @@ /**************************************************************************** * - * Copyright (C) 2013 PX4 Development Team. All rights reserved. + * Copyright (c) 2013, 2014 PX4 Development Team. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions @@ -64,9 +64,9 @@ int do_airspeed_calibration(int mavlink_fd) { /* give directions */ mavlink_log_info(mavlink_fd, CAL_STARTED_MSG, sensor_name); - mavlink_log_info(mavlink_fd, "don't move system"); + mavlink_log_info(mavlink_fd, "ensure airspeed sensor is not registering wind"); - const int calibration_count = 2500; + const int calibration_count = 2000; int diff_pres_sub = orb_subscribe(ORB_ID(differential_pressure)); struct differential_pressure_s diff_pres; @@ -85,13 +85,15 @@ int do_airspeed_calibration(int mavlink_fd) if (fd > 0) { if (OK == ioctl(fd, AIRSPEEDIOCSSCALE, (long unsigned int)&airscale)) { paramreset_successful = true; + } else { + mavlink_log_critical(mavlink_fd, "airspeed offset zero failed"); } close(fd); } if (!paramreset_successful) { - warn("WARNING: failed to set scale / offsets for airspeed sensor"); - mavlink_log_critical(mavlink_fd, "could not reset dpress sensor"); + warn("FAILED to set scale / offsets for airspeed"); + mavlink_log_critical(mavlink_fd, "dpress reset failed"); mavlink_log_info(mavlink_fd, CAL_FAILED_MSG, sensor_name); return ERROR; } @@ -107,7 +109,7 @@ int do_airspeed_calibration(int mavlink_fd) if (poll_ret) { orb_copy(ORB_ID(differential_pressure), diff_pres_sub, &diff_pres); - diff_pres_offset += diff_pres.differential_pressure_pa; + diff_pres_offset += diff_pres.differential_pressure_raw_pa; calibration_counter++; if (calibration_counter % (calibration_count / 20) == 0) diff --git a/src/modules/sdlog2/sdlog2.c b/src/modules/sdlog2/sdlog2.c index d2cf6d662..e62b0fafc 100644 --- a/src/modules/sdlog2/sdlog2.c +++ b/src/modules/sdlog2/sdlog2.c @@ -1193,6 +1193,7 @@ int sdlog2_thread_main(int argc, char *argv[]) log_msg.msg_type = LOG_AIRS_MSG; log_msg.body.log_AIRS.indicated_airspeed = buf.airspeed.indicated_airspeed_m_s; log_msg.body.log_AIRS.true_airspeed = buf.airspeed.true_airspeed_m_s; + log_msg.body.log_AIRS.air_temperature_celsius = buf.airspeed.air_temperature_celsius; LOGBUFFER_WRITE_AND_COUNT(AIRS); } diff --git a/src/modules/sdlog2/sdlog2_messages.h b/src/modules/sdlog2/sdlog2_messages.h index 354bb08e8..a1a5856bc 100644 --- a/src/modules/sdlog2/sdlog2_messages.h +++ b/src/modules/sdlog2/sdlog2_messages.h @@ -174,6 +174,7 @@ struct log_OUT0_s { struct log_AIRS_s { float indicated_airspeed; float true_airspeed; + float air_temperature_celsius; }; /* --- ARSP - ATTITUDE RATE SET POINT --- */ @@ -338,7 +339,7 @@ static const struct log_format_s log_formats[] = { LOG_FORMAT(STAT, "BBfBB", "MainState,ArmState,BatRem,BatWarn,Landed"), LOG_FORMAT(RC, "ffffffffB", "Ch0,Ch1,Ch2,Ch3,Ch4,Ch5,Ch6,Ch7,Count"), LOG_FORMAT(OUT0, "ffffffff", "Out0,Out1,Out2,Out3,Out4,Out5,Out6,Out7"), - LOG_FORMAT(AIRS, "ff", "IndSpeed,TrueSpeed"), + LOG_FORMAT(AIRS, "fff", "IndSpeed,TrueSpeed,AirTemp"), LOG_FORMAT(ARSP, "fff", "RollRateSP,PitchRateSP,YawRateSP"), LOG_FORMAT(FLOW, "hhfffBB", "RawX,RawY,CompX,CompY,Dist,Q,SensID"), LOG_FORMAT(GPOS, "LLfffffB", "Lat,Lon,Alt,VelN,VelE,VelD,BaroAlt,Flags"), diff --git a/src/modules/sensors/sensors.cpp b/src/modules/sensors/sensors.cpp index b171b995d..4083b8b4f 100644 --- a/src/modules/sensors/sensors.cpp +++ b/src/modules/sensors/sensors.cpp @@ -1025,12 +1025,13 @@ Sensors::diff_pres_poll(struct sensor_combined_s &raw) raw.differential_pressure_timestamp = _diff_pres.timestamp; raw.differential_pressure_filtered_pa = _diff_pres.differential_pressure_filtered_pa; - float air_temperature_celcius = (_diff_pres.temperature > -300.0f) ? _diff_pres.temperature : (raw.baro_temp_celcius - PCB_TEMP_ESTIMATE_DEG); + float air_temperature_celsius = (_diff_pres.temperature > -300.0f) ? _diff_pres.temperature : (raw.baro_temp_celcius - PCB_TEMP_ESTIMATE_DEG); _airspeed.timestamp = _diff_pres.timestamp; _airspeed.indicated_airspeed_m_s = calc_indicated_airspeed(_diff_pres.differential_pressure_filtered_pa); _airspeed.true_airspeed_m_s = calc_true_airspeed(_diff_pres.differential_pressure_filtered_pa + raw.baro_pres_mbar * 1e2f, - raw.baro_pres_mbar * 1e2f, air_temperature_celcius); + raw.baro_pres_mbar * 1e2f, air_temperature_celsius); + _airspeed.air_temperature_celsius = air_temperature_celsius; /* announce the airspeed if needed, just publish else */ if (_airspeed_pub > 0) { diff --git a/src/modules/uORB/topics/airspeed.h b/src/modules/uORB/topics/airspeed.h index a3da3758f..d2ee754cd 100644 --- a/src/modules/uORB/topics/airspeed.h +++ b/src/modules/uORB/topics/airspeed.h @@ -52,9 +52,10 @@ * Airspeed */ struct airspeed_s { - uint64_t timestamp; /**< microseconds since system boot, needed to integrate */ + uint64_t timestamp; /**< microseconds since system boot, needed to integrate */ float indicated_airspeed_m_s; /**< indicated airspeed in meters per second, -1 if unknown */ - float true_airspeed_m_s; /**< true airspeed in meters per second, -1 if unknown */ + float true_airspeed_m_s; /**< true airspeed in meters per second, -1 if unknown */ + float air_temperature_celsius; /**< air temperature in degrees celsius, -1000 if unknown */ }; /** diff --git a/src/modules/uORB/topics/differential_pressure.h b/src/modules/uORB/topics/differential_pressure.h index ff88b04c6..01e14cda9 100644 --- a/src/modules/uORB/topics/differential_pressure.h +++ b/src/modules/uORB/topics/differential_pressure.h @@ -52,13 +52,14 @@ * Differential pressure. */ struct differential_pressure_s { - uint64_t timestamp; /**< microseconds since system boot, needed to integrate */ - uint64_t error_count; + uint64_t timestamp; /**< Microseconds since system boot, needed to integrate */ + uint64_t error_count; /**< Number of errors detected by driver */ float differential_pressure_pa; /**< Differential pressure reading */ + float differential_pressure_raw_pa; /**< Raw differential pressure reading (may be negative) */ float differential_pressure_filtered_pa; /**< Low pass filtered differential pressure reading */ float max_differential_pressure_pa; /**< Maximum differential pressure reading */ - float voltage; /**< Voltage from analog airspeed sensors (voltage divider already compensated) */ - float temperature; /**< Temperature provided by sensor, -1000.0f if unknown */ + float voltage; /**< Voltage from analog airspeed sensors (voltage divider already compensated) */ + float temperature; /**< Temperature provided by sensor, -1000.0f if unknown */ }; |