LifeOverflow

This is the first of the multi-part article series describing the various options available for every module required in developing your own Unmanned Aerial Vehicle. The article is not for beginners, therefore, commonly used terms are not explained in the text. The article aims are intermediate to expert level designers looking for various options in terms of available hardware and/or software in the field of interest. 

For the first part of the article, I am going to start with the inertial management unit (IMU) required by a UAV.

An intertial management unit is the main component of a intertial navigation system used in UAVs. The IMU senses its rate and direction of motion with the help of accelerometers and gyroscopes, providng the computer with enough data about its orientation etc in space. There are 3 rotational attributes that you must be aware of - yaw, pitch and roll. This data is then fed into a guidance computer, which uses the data to calculate the current position. The IMU detects accelerations which are integrated by a guidance computer to deduce the position and velocity of the vehicle.

 1. Crossbow NAV420

• Environmentally Sealed

 Datasheet

2. UNAV 3500 FW (fixed wing)

The UNAV3500 is our “full-featured” autopilot, with an onboard sensor suite and MEMS IMU.
It includes a tightly integrated groundstation ( software ) that provides a full-duplex data link with the autopilot.

• Small Size: 4.0” x 2.0” x 0.75”
• PCB weight: 1.2 oz 
• GPS weight: 1.6oz
• Low Power: 5.0v-7.0v @ 100ma
• Control Loop: 30Hz
• ( 7 ) RC input channels
• ( 7 ) RC servos: (4) flight control,  (3) payload
• 6DOF IMU (electronic gyro) 
• Onboard sensors:  ( 8 )
• User A/D inputs:  ( 5 ) 
• Onboard servo switching: electronic servo command transfer
• GPS waypoint navigation: accepts NMEA0183 (GGA & RMC) from any GPS receiver
• Smart Waypoint sequencer: ignores invalid waypoint data or SPD & ALT out of limits
• Waypoints:  64 non-volatile waypoint storage ( LON, LAT, ALT, SPD )
• Data logging: All downlinked data stored to file for playbeack on the FDR (flight data recorder)
• Program storage: allows embedded program to be updated in the field
• Sensor Calibration: on command sensor calibration stored in FLASH
• Robust design: All data backed in FLASH, transparent recovery from a power failure in 1 sec
• Fault detection: fault detection, reporting and compensation
• Payload Trigger (2): Triggers can be controlled from groundstation or waypoint proximity
• Payload Servo control (3): integrated camera mount stabilization as well as full manual control
• Semi-autonomous mode: autopilot stabilizes airplane, ground pilot controls flight path
• Moving Map: ½ screen display permits simultaneous use of  most moving map programs.

3. UNAV 3500 HL (Helicopter)

• Small Size: 4.0” x 2.0” x 0.75”
• PCB weight: 1.2 oz 
• GPS weight: 1.6oz
• Range Finder  weight: 8.0 oz 
• Low Power: 5.0v-7.0v @ 100ma
• Control Loop: 30Hz
• Laser range-finder
• Altitude hold: +/- 2 ft
• Altitude range: 3000ft AGL
• Programmable on-board, non-volatile route date: 64 WPs
• GPS waypoint navigation: accepts NMEA0183 (GGA & RMC) from any GPS receiver
• programmable GPS data:  64  ( LON, LAT, ALT, SPD )
• programmable altitude hold for each leg: 64
• programmable airspeed hold for each leg: 64 
• ( 7 ) RC input channels
• ( 7 ) RC servos: (6) flight control,  (1) payload
• 6DOF IMU (electronic gyro) 
• Onboard sensors:  ( 8 )
• User A/D inputs:  ( 5 ) 
• Onboard servo switching: electronic servo command transfer
• Smart Waypoint sequencer: ignores invalid waypoint data or SPD & ALT out of limits
• Data logging: All downlinked data stored to file for playbeack on the FDR (flight data recorder)
• Program storage: allows embedded program to be updated in the field
• Sensor Calibration: on command sensor calibration stored in FLASH
• Robust design: All data backed in FLASH, transparent recovery from a power failure in 1 sec
  Fault detection: fault detection, reporting and compensation
• Payload Trigger (2): Triggers can be controlled from groundstation or waypoint proximity
• Payload Servo control (3): integrated camera mount stabilization as well as full manual control
• Semi-autonomous mode: autopilot stabilizes airplane, ground pilot controls flight path
• Moving Map: ½ screen display permits simultaneous use of  most moving map programs.

If there are other useful IMUs that I have missed, please let me know.