ArduPilot开源代码之AP_RangeFinder

原创已于 2023-10-04 07:50:05 修改 · 617 阅读

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于 2023-10-03 13:22:46 首次发布

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本文结合代码研读Ardupilot中AP_RangeFinder的应用，其主要用于测量对地距离。介绍了框架设计，包括启动代码对传感器检测初始化、任务代码循环遍历更新数据；还提及重要例程，如状态更新和传感设备检测，最后指出传感器因总线和协议有差异，在驱动代码实现。

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1. 源由

AP_RangeFinder的应用的主要用途是用于测量对地距离的，这个与大家通常理解的障碍物避障还是有比较大的差异的。

主要的应用有：

其他应用有：

本次结合代码进行研读，其中也请注意两个应用类型的传感器：upward facing rangefinder和downward facing rangefinder。

2. 框架设计

启动代码：

Copter::init_ardupilot
 └──> Copter::init_rangefinder
     └──> rangefinder.init

任务代码：

SCHED_TASK(read_rangefinder,      20,    100,  33),
 └──> Copter::read_rangefinder
     └──> rangefinder.update

2.1 启动代码

主要作用是对传感器设备进行检测和初始化。

RangeFinder::init
 ├──> <num_instances != 0> // don't re-init if we've found some sensors already
 │   └──> return
 ├──> <uint8_t i=0; i<RANGEFINDER_MAX_INSTANCES; i++> // set orientation defaults
 │   └──> params[i].orientation.set_default(orientation_default)
 ├──> <uint8_t i=0, serial_instance = 0; i<RANGEFINDER_MAX_INSTANCES; i++>
 │   │  // serial_instance will be increased inside detect_instance
 │   │  // if a serial driver is loaded for this instance
 │   ├──> WITH_SEMAPHORE(detect_sem);
 │   ├──> detect_instance(i, serial_instance);
 │   └──> <drivers[i] != nullptr>
 │       │  // we loaded a driver for this instance, so it must be
 │       │  // present (although it may not be healthy). We use MAX()
 │       │  // here as a UAVCAN rangefinder may already have been
 │       │  // found
 │       └──> num_instances = MAX(num_instances, i+1);
 └──> [initialise status]
     ├──> state[i].status = Status::NotConnected;
     └──> state[i].range_valid_count = 0;

2.2 任务代码

以固定的频率进行循环遍历，得到相应的数据更新。

// return rangefinder altitude in centimeters
Copter::read_rangefinder
 ├──> <RANGEFINDER_ENABLED != ENABLED>
 │   ├──> [downward facing rangefinder]
 │   │   ├──> rangefinder_state.enabled = false;
 │   │   ├──> rangefinder_state.alt_healthy = false;
 │   │   └──> rangefinder_state.alt_cm = 0;
 │   ├──> [upward facing rangefinder]
 │   │   ├──> rangefinder_up_state.enabled = false;
 │   │   ├──> rangefinder_up_state.alt_healthy = false;
 │   │   └──> rangefinder_up_state.alt_cm = 0;
 │   └──> return
 ├──> rangefinder.update();
 ├──> <RANGEFINDER_TILT_CORRECTION == ENABLED>
 │   └──> const float tilt_correction = MAX(0.707f, ahrs.get_rotation_body_to_ned().c.z);
 ├──> <RANGEFINDER_TILT_CORRECTION != ENABLED>
 │   └──> const float tilt_correction = 1.0f;
 │
 │
 │  // iterate through downward and upward facing lidar
 │  struct {
 │      RangeFinderState &state;
 │      enum Rotation orientation;
 │  } rngfnd[2] = {{rangefinder_state, ROTATION_PITCH_270}, {rangefinder_up_state, ROTATION_PITCH_90}};
 │
 └──> <for (uint8_t i=0; i < ARRAY_SIZE(rngfnd); i++)>
     ├──> [local variables to make accessing simpler]
     │   ├──> RangeFinderState &rf_state = rngfnd[i].state;
     │   └──> enum Rotation rf_orient = rngfnd[i].orientation;
     ├──> [update health]
     │   └──> rf_state.alt_healthy = ((rangefinder.status_orient(rf_orient) == RangeFinder::Status::Good) &&
     │                          (rangefinder.range_valid_count_orient(rf_orient) >= RANGEFINDER_HEALTH_MAX));
     ├──> [tilt corrected but unfiltered, not glitch protected alt]
     │   └──> rf_state.alt_cm = tilt_correction * rangefinder.distance_cm_orient(rf_orient);
     ├──> [remember inertial alt to allow us to interpolate rangefinder]
     │   └──> rf_state.inertial_alt_cm = inertial_nav.get_position_z_up_cm();
     ├──> [glitch handling] 
     │   //rangefinder readings more than RANGEFINDER_GLITCH_ALT_CM from the last good reading
     │   // are considered a glitch and glitch_count becomes non-zero
     │   // glitches clear after RANGEFINDER_GLITCH_NUM_SAMPLES samples in a row.
     │   // glitch_cleared_ms is set so surface tracking (or other consumers) can trigger a target reset
     │   ├──> const int32_t glitch_cm = rf_state.alt_cm - rf_state.alt_cm_glitch_protected;
     │   ├──> bool reset_terrain_offset = false;
     │   ├──> <if (glitch_cm >= RANGEFINDER_GLITCH_ALT_CM)>
     │   │   └──> rf_state.glitch_count = MAX(rf_state.glitch_count+1, 1);
     │   ├──> <else if (glitch_cm <= -RANGEFINDER_GLITCH_ALT_CM) >
     │   │   └──> rf_state.glitch_count = MIN(rf_state.glitch_count-1, -1);
     │   ├──> <else>
     │   │   ├──> rf_state.glitch_count = 0;
     │   │   └──> rf_state.alt_cm_glitch_protected = rf_state.alt_cm;
     │   └──> <abs(rf_state.glitch_count) >= RANGEFINDER_GLITCH_NUM_SAMPLES> // clear glitch and record time so consumers (i.e. surface tracking) can reset their target altitudes
     │       ├──> rf_state.glitch_count = 0;
     │       ├──> rf_state.alt_cm_glitch_protected = rf_state.alt_cm;
     │       ├──> rf_state.glitch_cleared_ms = AP_HAL::millis();
     │       └──> reset_terrain_offset = true;
     ├──> [filter rangefinder altitude]
     │   ├──> uint32_t now = AP_HAL::millis();
     │   ├──> const bool timed_out = now - rf_state.last_healthy_ms > RANGEFINDER_TIMEOUT_MS;
     │   ├──> <rf_state.alt_healthy>
     │   │   ├──> <if (timed_out)>
     │   │   │     // reset filter if we haven't used it within the last second
     │   │   │   ├──> rf_state.alt_cm_filt.reset(rf_state.alt_cm);
     │   │   │   └──> reset_terrain_offset = true;
     │   │   └──> <else >
     │   │       └──> rf_state.alt_cm_filt.apply(rf_state.alt_cm, 0.05f);
     │   └──> rf_state.last_healthy_ms = now;
     ├──> <reset_terrain_offset> // handle reset of terrain offset
     │   ├──> <if (rf_orient == ROTATION_PITCH_90)> // upward facing
     │   │   └──> rf_state.terrain_offset_cm = rf_state.inertial_alt_cm + rf_state.alt_cm;
     │   └──> < else > // assume downward facing
     │       └──> rf_state.terrain_offset_cm = rf_state.inertial_alt_cm - rf_state.alt_cm; 
     └──> <HAL_PROXIMITY_ENABLED> <rf_orient == ROTATION_PITCH_270> <rangefinder_state.alt_healthy || timed_out>
	     │  // send downward facing lidar altitude and health to the libraries that require it
         └──> g2.proximity.set_rangefinder_alt(rangefinder_state.enabled, rangefinder_state.alt_healthy, rangefinder_state.alt_cm_filt.get());

3. 重要例程

3.1 状态更新

针对当前传感器数据有效性进行状态更新。

NotConnected
NoData
OutOfRangeLow
OutOfRangeHigh
Good

RangeFinder::update
 ├──> <uint8_t i=0; i<num_instances; i++>
 │   └──> <drivers[i] != nullptr>
 │       ├──> <(Type)params[i].type.get() == Type::NONE> // allow user to disable a rangefinder at runtime
 │       │   ├──> state[i].status = Status::NotConnected
 │       │   ├──> state[i].range_valid_count = 0
 │       │   └──> continue
 │       └──> drivers[i]->update()
 └──> <HAL_LOGGING_ENABLED>
     └──> Log_RFND()

3.2 传感设备检测

除了AP_RangeFinder里面使用到的传感器外，衍生阅读可看下360度雷达以及视觉传感，详见Rangefinders (landing page)。

ANALOG
MBI2C
PLI2C
PX4_PWM
BBB_PRU
LWI2C
LWSER
BEBOP
MAVLink
USD1_Serial
LEDDARONE
MBSER
TRI2C
PLI2CV3
VL53L0X
NMEA
WASP
BenewakeTF02
BenewakeTFmini
PLI2CV3HP
PWM
BLPing
UAVCAN
BenewakeTFminiPlus
Lanbao
BenewakeTF03
VL53L1X_Short
LeddarVu8_Serial
HC_SR04
GYUS42v2
MSP
USD1_CAN
Benewake_CAN
TeraRanger_Serial
Lua_Scripting
NoopLoop_P
TOFSenseP_CAN
NRA24_CAN
SIM

RangeFinder::detect_instance
 ├──> <!AP_RANGEFINDER_ENABLED>
 │   └──> return
 ├──> AP_RangeFinder_Backend_Serial *(*serial_create_fn)(RangeFinder::RangeFinder_State&, AP_RangeFinder_Params&) = nullptr;
 ├──> const Type _type = (Type)params[instance].type.get();
 ├──> <case PLI2C/PLI2CV3/PLI2CV3HP> <AP_RANGEFINDER_PULSEDLIGHTLRF_ENABLED>
 │   ├──> _add_backend(AP_RangeFinder_PulsedLightLRF::detect
 │   └──> break;
 ├──> <MBI2C> <AP_RANGEFINDER_MAXSONARI2CXL_ENABLED>
 │   ├──> uint8_t addr = AP_RANGE_FINDER_MAXSONARI2CXL_DEFAULT_ADDR;
 │   ├──> <params[instance].address != 0>
 │   │   └──> addr = params[instance].address;
 │   ├──> _add_backend(AP_RangeFinder_MaxsonarI2CXL::detect
 │   └──> break;
 ├──> <LWI2C> <AP_RANGEFINDER_LWI2C_ENABLED>
 │   ├──> <params[instance].address> // the LW20 needs a long time to boot up, so we delay 1.5s here
 │   │   ├──> <HAL_RANGEFINDER_LIGHTWARE_I2C_BUS>
 │   │   │   └──> _add_backend(AP_RangeFinder_LightWareI2C::detect
 │   │   └──> <!HAL_RANGEFINDER_LIGHTWARE_I2C_BUS>
 │   │       └──> _add_backend(AP_RangeFinder_LightWareI2C::detect
 │   └──> break;
 ├──> <TRI2C> <AP_RANGEFINDER_TRI2C_ENABLED>
 │   ├──> <params[instance].address>
 │   │   └──> __add_backend(AP_RangeFinder_TeraRangerI2C::detect
 │   └──> break;
 ├──> <VL53L0X/VL53L1X_Short> 
 │   ├──> <AP_RANGEFINDER_VL53L0X_ENABLED>
 │   │   └──> _add_backend(AP_RangeFinder_VL53L0X::detect
 │   ├──> <AP_RANGEFINDER_VL53L1X_ENABLED>
 │   │   └──> _add_backend(AP_RangeFinder_VL53L1X::detect
 │   └──> break;
 ├──> <BenewakeTFminiPlus> <AP_RANGEFINDER_BENEWAKE_TFMINIPLUS_ENABLED>
 │   ├──> uint8_t addr = TFMINIPLUS_ADDR_DEFAULT;
 │   ├──> <params[instance].address != 0>
 │   │   └──> addr = params[instance].address;
 │   ├──> _add_backend(AP_RangeFinder_Benewake_TFMiniPlus::detect
 │   └──> break;
 ├──> <PX4_PWM> <AP_RANGEFINDER_PWM_ENABLED>
 │   │  // to ease moving from PX4 to ChibiOS we'll lie a little about
 │   │  // the backend driver...
 │   ├──> <AP_RangeFinder_PWM::detect()>
 │   │   └──> _add_backend(new AP_RangeFinder_PWM(state[instance], params[instance], estimated_terrain_height), instance);
 │   └──> break;
 ├──> <BBB_PRU> <AP_RANGEFINDER_BBB_PRU_ENABLED>
 │   ├──> <AP_RangeFinder_BBB_PRU::detect()>
 │   │   └──> _add_backend(new AP_RangeFinder_BBB_PRU(state[instance], params[instance]), instance);
 │   └──> break;
 ├──> <LWSER> <AP_RANGEFINDER_LIGHTWARE_SERIAL_ENABLED>
 │   ├──> serial_create_fn = AP_RangeFinder_LightWareSerial::create;
 │   └──> break;
 ├──> <LEDDARONE> <AP_RANGEFINDER_LEDDARONE_ENABLED>
 │   ├──> serial_create_fn = AP_RangeFinder_LeddarOne::create;
 │   └──> break;
 ├──> <USD1_Serial> <AP_RANGEFINDER_USD1_SERIAL_ENABLED>
 │   ├──> serial_create_fn = AP_RangeFinder_USD1_Serial::create;
 │   └──> break;
 ├──> <BEBOP> <AP_RANGEFINDER_BEBOP_ENABLED>
 │   ├──> <AP_RangeFinder_Bebop::detect()>
 │   │   └──> _add_backend(new AP_RangeFinder_Bebop(state[instance], params[instance]), instance);
 │   └──> break;
 ├──> <MAVLink> <AP_RANGEFINDER_MAVLINK_ENABLED>
 │   ├──> <AP_RangeFinder_MAVLink::detect()>
 │   │   └──> _add_backend(new AP_RangeFinder_MAVLink(state[instance], params[instance]), instance);
 │   └──> break;
 ├──> <MBSER> <AP_RANGEFINDER_MAXBOTIX_SERIAL_ENABLED>
 │   ├──> serial_create_fn = AP_RangeFinder_MaxsonarSerialLV::create;
 │   └──> break;
 ├──> <ANALOG> <AP_RANGEFINDER_ANALOG_ENABLED>
 │   ├──> <AP_RangeFinder_analog::detect(params[instance])> // note that analog will always come back as present if the pin is valid
 │   │   └──> _add_backend(new AP_RangeFinder_analog(state[instance], params[instance]), instance);
 │   └──> break;
 ├──> <HC_SR04> <AP_RANGEFINDER_HC_SR04_ENABLED>
 │   ├──> <AP_RangeFinder_HC_SR04::detect(params[instance])>  // note that this will always come back as present if the pin is valid
 │   │   └──> _add_backend(new AP_RangeFinder_HC_SR04(state[instance], params[instance]), instance);
 │   └──> break;
 ├──> <NMEA> <AP_RANGEFINDER_NMEA_ENABLED>
 │   ├──> serial_create_fn = AP_RangeFinder_NMEA::create;
 │   └──> break;
 ├──> <WASP> <AP_RANGEFINDER_WASP_ENABLED>
 │   ├──> serial_create_fn = AP_RangeFinder_Wasp::create;
 │   └──> break;
 ├──> <BenewakeTF02> <AP_RANGEFINDER_BENEWAKE_TF02_ENABLED>
 │   ├──> serial_create_fn = AP_RangeFinder_Benewake_TF02::create;
 │   └──> break;
 ├──> <BenewakeTFmini> <AP_RANGEFINDER_BENEWAKE_TFMINI_ENABLED>
 │   ├──> serial_create_fn = AP_RangeFinder_Benewake_TFMini::create;
 │   └──> break;
 ├──> <BenewakeTF03> <AP_RANGEFINDER_BENEWAKE_TF03_ENABLED>
 │   ├──> serial_create_fn = AP_RangeFinder_Benewake_TF03::create;
 │   └──> break;
 ├──> <TeraRanger_Serial> <AP_RANGEFINDER_TERARANGER_SERIAL_ENABLED>
 │   ├──> serial_create_fn = AP_RangeFinder_TeraRanger_Serial::create;
 │   └──> break;
 ├──> <PWM> <AP_RANGEFINDER_PWM_ENABLED>
 │   ├──> <AP_RangeFinder_PWM::detect()>
 │   │   └──> _add_backend(new AP_RangeFinder_PWM(state[instance], params[instance], estimated_terrain_height), instance);
 │   └──> break;
 ├──> <BLPing> <AP_RANGEFINDER_BLPING_ENABLED>
 │   ├──> serial_create_fn = AP_RangeFinder_BLPing::create;
 │   └──> break;
 ├──> <Lanbao> <AP_RANGEFINDER_LANBAO_ENABLED>
 │   ├──> serial_create_fn = AP_RangeFinder_Lanbao::create;
 │   └──> break;
 ├──> <LeddarVu8_Serial> <AP_RANGEFINDER_LEDDARVU8_ENABLED>
 │   ├──> serial_create_fn = AP_RangeFinder_LeddarVu8::create;
 │   └──> break;
 ├──> <UAVCAN> <AP_RANGEFINDER_DRONECAN_ENABLED>
 │   │  /*
 │   │    the UAVCAN driver gets created when we first receive a
 │   │    measurement. We take the instance slot now, even if we don't
 │   │    yet have the driver
 │   │   */
 │   ├──> num_instances = MAX(num_instances, instance+1);
 │   └──> break;
 ├──> <GYUS42v2> <AP_RANGEFINDER_GYUS42V2_ENABLED>
 │   ├──> serial_create_fn = AP_RangeFinder_GYUS42v2::create;
 │   └──> break;
 ├──> <SIM> <AP_RANGEFINDER_SIM_ENABLED>
 │   ├──> _add_backend(new AP_RangeFinder_SITL(state[instance], params[instance], instance), instance);
 │   └──> break;
 ├──> <MSP> <HAL_MSP_RANGEFINDER_ENABLED>
 │   ├──> <AP_RangeFinder_MSP::detect()>
 │   │   └──> _add_backend(new AP_RangeFinder_MSP(state[instance], params[instance]), instance);
 │   └──> break;
 ├──> <USD1_CAN> <AP_RANGEFINDER_USD1_CAN_ENABLED>
 │   ├──> _add_backend(new AP_RangeFinder_USD1_CAN(state[instance], params[instance]), instance);
 │   └──> break;
 ├──> <Benewake_CAN> <AP_RANGEFINDER_BENEWAKE_CAN_ENABLED>
 │   ├──> _add_backend(new AP_RangeFinder_Benewake_CAN(state[instance], params[instance]), instance);
 │   └──> break;
 ├──> <Lua_Scripting> <AP_SCRIPTING_ENABLED>
 │   ├──> _add_backend(new AP_RangeFinder_Lua(state[instance], params[instance]), instance);
 │   └──> break;
 ├──> <NoopLoop_P> ,AP_RANGEFINDER_NOOPLOOP_ENABLED>
 │   ├──> serial_create_fn = AP_RangeFinder_NoopLoop::create;
 │   └──> break;
 ├──> <TOFSenseP_CAN> <AP_RANGEFINDER_TOFSENSEP_CAN_ENABLED>
 │   ├──> _add_backend(new AP_RangeFinder_TOFSenseP_CAN(state[instance], params[instance]), instance);
 │   └──> break;
 ├──> <NRA24_CAN> <AP_RANGEFINDER_NRA24_CAN_ENABLED>
 │   ├──> _add_backend(new AP_RangeFinder_NRA24_CAN(state[instance], params[instance]), instance);
 │   └──> break;
 ├──> <serial_create_fn != nullptr> <AP::serialmanager().have_serial(AP_SerialManager::SerialProtocol_Rangefinder, serial_instance)>
 │   ├──> auto *b = serial_create_fn(state[instance], params[instance]);
 │   └──> <b != nullptr>
 │       └──> _add_backend(b, instance, serial_instance++);
 └──> <drivers[instance] && state[instance].var_info>  // if the backend has some local parameters then make those available in the tree
     ├──> backend_var_info[instance] = state[instance].var_info;
     ├──> AP_Param::load_object_from_eeprom(drivers[instance], backend_var_info[instance]);      
     └──> AP_Param::invalidate_count(); // param count could have changed

4. 总结

各传感器设备因设备总线以及协议的差异，存在一定的差异化，在相应的驱动代码中实现，可参考：ArduPilot之开源代码Library&Sketches设计。

作为RangeFinder传感器主要的目的是检测飞机与地面之间的距离

    // The RangeFinder_State structure is filled in by the backend driver
    struct RangeFinder_State {
        float distance_m;               // distance in meters
        uint16_t voltage_mv;            // voltage in millivolts, if applicable, otherwise 0
        enum RangeFinder::Status status; // sensor status
        uint8_t  range_valid_count;     // number of consecutive valid readings (maxes out at 10)
        uint32_t last_reading_ms;       // system time of last successful update from sensor

        const struct AP_Param::GroupInfo *var_info;
    };

注：不同设备更新频率方面主要在驱动中进行数据采集更新，详见驱动代码的init方法中如何挂定时回调钩子函数。