Sensors

PX4-based systems use sensors to determine vehicle state (needed for stabilization and to enable autonomous control). The vehicle states include: position/altitude, heading, speed, airspeed, orientation (attitude), rates of rotation in different directions, battery level, etc.

The system minimally requires a gyroscope, accelerometer, magnetometer (compass) and barometer. A GPS or other positioning system is needed to enable all automatic modes, and some assisted modes. Fixed wing and VTOL-vehicles should additionally include an airspeed sensor (very highly recommended).

The minimal set of sensors is incorporated into Pixhawk Series flight controllers (and may also be in other controller platforms). Additional/external sensors can be attached to the controller.

Below we describe some of the sensors. At the end there are links to information about sensor wiring.

GPS & Compass

PX4 supports a number of global navigation satellite system (GNSS) receivers and compasses (magnetometers). It also supports Real Time Kinematic (RTK) GPS Receivers, which extend GPS systems to centimetre-level precision.

The Pixhawk internal compass is close to other electronics, and may be susceptible to electromagnetic noise. An external compass/GPS mounted on a pedestal or wing (for fixed-wing) away from the rest of the system is recommended.

Common GPS/compass hardware options are listed in: GPS/Compass.

GPS + Compass

Airspeed

Airspeed sensors are highly recommended for fixed-wing and VTOL frames.

They are so important because the autopilot does not have other means to detect stall. For fixed-wing flight it is the airspeed that guarantees lift not ground speed!

Digital airspeed sensor

For more information and recommended hardware see: Airspeed Sensors.

Distance

Distance sensors are used for precision landing, object avoidance and terrain following.

PX4 supports many affordable distance sensors, using different technologies, and supporting different ranges and features. For more information see: Distance Sensors.

Optical Flow

PX4Flow is an optical flow smart camera that can track motion, and has as integrated sonar sensor. PX4 blends the sensor output with information from other position sources (e.g. GPS) to provide a more accurate position lock. This sensor can be used indoors, when no GPS signal is available.

px4flow-bottom

Some options include:

Sensor Wiring

Sensor wiring information is usually provided in manufacturer documentation for flight controllers and the sensors themselves.

In addition, see:

  • Basic Assembly contains flight controller quick start guides. These cover wiring of the core sensors to specific flight controller hardware.
  • Flight Controller topics often contain wiring information.
  • Peripheral Hardware contains documentation for other sensors.
© PX4 Dev Team. License: CC BY 4.0            Updated: 2018-09-19 17:51:39

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