Apollo application and source code analysis: Monitor monitoring-hardware monitoring-GPS

Hardware Architecture Diagram

You can see that the "GNSS positioning module" in the lower left corner is actually composed of IMU and GPS Antenna.

perform analysis

the code

class GpsMonitor : public RecurrentRunner {
 public:
  GpsMonitor();
  void RunOnce(const double current_time) override;
};

void GpsMonitor::RunOnce(const double current_time) {
  auto manager = MonitorManager::Instance();
  Component* component = apollo::common::util::FindOrNull(
      *manager->GetStatus()->mutable_components(), FLAGS_gps_component_name);
  if (component == nullptr) {
    // GPS is not monitored in current mode, skip.
    return;
  }
  ComponentStatus* component_status = component->mutable_other_status();
  component_status->clear_status();

  static auto gnss_best_pose_reader =
      manager->CreateReader<GnssBestPose>(FLAGS_gnss_best_pose_topic);
  gnss_best_pose_reader->Observe();
  const auto gnss_best_pose_status = gnss_best_pose_reader->GetLatestObserved();
  if (gnss_best_pose_status == nullptr) {
    SummaryMonitor::EscalateStatus(ComponentStatus::ERROR,
                                   "No GnssBestPose message", component_status);
    return;
  }
  switch (gnss_best_pose_status->sol_type()) {
    case SolutionType::NARROW_INT:
      SummaryMonitor::EscalateStatus(ComponentStatus::OK, "", component_status);
      break;
    case SolutionType::SINGLE:
      SummaryMonitor::EscalateStatus(
          ComponentStatus::WARN, "SolutionType is SINGLE", component_status);
      break;
    default:
      SummaryMonitor::EscalateStatus(ComponentStatus::ERROR,
                                     "SolutionType is wrong", component_status);
      break;
  }
}

analyze

The core content of gps monitor is only 70 line code

The basic idea is as follows:

1. Find out whether GPS is a configured monitoring component from the configuration file
2. If yes, subscribe to GnssBestPose topic and receive data
3. Get the latest data, if the latest data is null, issue an ERROR level fault
4. If the obtained data type is NARROW_INT, it means normal
5. If the obtained data type is SINGLE, it means WARN
   1. Here, according to Apollo's positioning algorithm design and hardware architecture, it is not difficult to guess that SINGLE means IMU inertial unit or GPS has no normal output data
   2. If the obtained data type is other cases, it means ERROR

Both GnssBestPose and SolutionType are defined from GNSS driver.

modules/drivers/gnss/proto/gnss_best_pose.proto

enum SolutionType {
  NONE = 0;
  FIXEDPOS = 1;
  FIXEDHEIGHT = 2;
  FLOATCONV = 4;
  WIDELANE = 5;
  NARROWLANE = 6;
  DOPPLER_VELOCITY = 8;
  SINGLE = 16;
  PSRDIFF = 17;
  WAAS = 18;
  PROPOGATED = 19;
  OMNISTAR = 20;
  L1_FLOAT = 32;
  IONOFREE_FLOAT = 33;
  NARROW_FLOAT = 34;
  L1_INT = 48;
  WIDE_INT = 49;
  NARROW_INT = 50;
  RTK_DIRECT_INS =
      51;  // RTK filter is directly initialized from the INS filter.
  INS_SBAS = 52;
  INS_PSRSP = 53;
  INS_PSRDIFF = 54;
  INS_RTKFLOAT = 55;
  INS_RTKFIXED = 56;
  INS_OMNISTAR = 57;
  INS_OMNISTAR_HP = 58;
  INS_OMNISTAR_XP = 59;
  OMNISTAR_HP = 64;
  OMNISTAR_XP = 65;
  PPP_CONVERGING = 68;
  PPP = 69;
  INS_PPP_CONVERGING = 73;
  INS_PPP = 74;
}