UAV Sensors and Communication Systems. Using a UAV to deliver aerial video to searchers has potential to support search and rescue efforts, but a number of technology and human factors problems must be overcome to make this practical (Cooper, 2008). The

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SENSORS

Introduction

Search and rescue is a challenging problem because of the large areas and often rough terrain that must be searched. Using a UAV to deliver aerial video to searchers has potential to support search and rescue efforts, but a number of technology and human factors problems must be overcome to make this practical (Cooper, 2008). The biggest problem is how to manage flying the UAV from the ground station while simultaneously intepreting the information from all the sensors being relayed from the UAV to the ground station.

Typically, a UAV engaged in a search task requires either two operators or a single operator to fill two roles: a pilot, who “flies” the UAV, and a sensor operator, who interprets the imagery and other sensors (Cooper, 2008).

Search and rescue is a big challenge because it involves covering a vast area while looking for just a specific target. This is where the UAV plays a vital role. Using all the latest onboard sensors it helps a lot in search and rescue. In this part of the report I am going to look at these sensors in depth and how they help the sensor operator on the ground, who is responsible for analysing imagery and localizing potential signs of the target of the search and rescue mission.

The primary autonomous sensing methods used by the Unmanned Aerial Vehicle are:

  • Air data sensors
  • Inertial sensors
  • Imaging sensors
  • Radar sensors

All these sensors aid the navigation system to achieve optimal performance. As we are going to see the capabilities of the UAVs integrated navigation system blend the inputs of multisensory types to attain high levels of accuracy that allow new navigation and approach procedures to be used. This is important especially in today’s world where the sky is getting more and more traffic. This integrated system will assure safe and smooth traffic flow.

Let’s look at each of these sensors in more detail.


Air Data Sensor

Air data, as the name suggests, involve the sensing of the medium through which the aircraft is flying. Typical sensed parameters are dynamic pressure, static pressure, rate of change of pressure and temperature (Moir & Allan, 2003). The pressure parameters are sensed by two instruments known as pitot static probes and static sensors. These static probes are positioned on the side of the UAV to deal with the errors that may arise when the aircraft yaws or changes its angle of attack.

The temperature is sensed by positioning a device known as the total temperature probe in the airflow and sensing the change in resistance associated with temperature. It is important for the sensor operator to know the outside air temperature because it directly affects the aircraft’s performance. During take-off it directly affects the thrust available from the engine and the lift due to air density both of which are affect significantly the UAVs take-off distance and operational margins. In the cruise, engine performance and fuel consumption are affected (Moir & Allan, 2003).

These instruments are connected to an air data computer (ADC) which centrally measures air data and provides corrected data to the recipient subsystems. It can determine calibrated airspeed, Mach number, altitude, and altitude trend data from an aircraft's pitot-static system. It also measures the static air pressure and true air speed from the input of total air temperature.

The air data computer will be displayed on the ground station where the sensor operator will interpret the information given and use it for the safe operation of the aircraft.

Inertial Sensors

The UAV is fitted with what is known as the inertial navigation system (INS) which is essentially a navigation aid that uses a computer, accelerometers and gyroscopes to continuously calculate the position, orientation and velocity of the aircraft by means of dead reckoning. It is very suitable because it does not require any external references for it to determine the position, orientation or velocity of the UAV.

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Inertial navigation is accomplished by integrating the output of a set of sensors to compute position, velocity, and attitude. The sensors used are gyroscopes and accelerometers. Gyroscopes measure angular rate with respect to inertial space, and accelerometers measure linear acceleration, again with respect to an inertial frame (Stovall, 1997).

The UAV will use what is known as the strapdown system. In this system, the inertial sensors are mounted directly to the aircraft’s structure and no gimballed platform is required. The inertial sensors are resolved mathematically using a computer prior to performing the necessary navigation calculations. The removal of the stabilized platform ...

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