New addition to the fleet – AutoQuad X8 multirotor

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Since 2011 I’m a teammember of the AutoQuad team, a group of enthousiasts that develop en built AutoQuad hardware and software. At the time of writing (dec 2014) the AutoQuad team has developed the:

  • AutoQuad 6 flightcontroller,
  • the AutoQuad M4 flightcontroller,
  • the AutoQuad 7 flightcontroller (development study),
  • the ESC32 v2 and
  • ESC32 v3 (not in production yet).
  •  the AutoQuad PDB, a motherboard with 150A+ powerdistribution, 16 CAN ports, 14 PWM ports, high power LED ports, OSD, 150A current sensor, 3 serial ports, 2 video switches, audio out, 2 x I2C and all connected via dual CAN ports to the AutoQuad FC’s

Besides a HEXA and an Quad, an redundant mutli rotor platform was needed and decided to use all the prototypes now available as a showcase. A suitable frame was not found so a set of centerplates was made from GFK material using a simple dremel powertool.

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Centerplates with AutoQuad PDB

An X8 is basically a dual QUAD in coax mode. Rotors on top and bottom. It will provide basic redundancy so a part of the thrust may be lost. ie an motor, prop etc but not two on the same arm. Most X8 configurations can loose one propulsion but more will require intervention from the flightcontroller. The flightcontroller will need to know with of the arms is losing thrust so it can adapt. AutoQuad using ESC32 will now the status of the ESC/motor/prop 400 times per second and the Quatos adaptive controller algoritms   can adapt to it. Well, that is the idea anyway.

The ESC32 v2 will be replaced by the v3, the v3 enhancements are: up to 10S, onboard switching bec for the logics, usb port, can, i2c, pwm. It uses a powerfull stm32f307 mcu and amongst features are voice output through the motor wiring (how cool is that).

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All esc32′s are connected on the CAN bus through the PDB. Both the PDB and Flightcontroller will have the telemetry information from the ESC32′s.

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AutoQuad PDB with bluetooth
xBee adapter
Bluetooth, the telemetry through
bluetooth is running via the CAN bus
Wiring the bottom layer

The X8 is intended to use the nano size M4 but that is currently occupied in another frame so I installed the AutoQuad 7 FC that is still in development study. I dont use all of its new features because a lot of it is done by the PDB. The only connection between the PDB and the AutoQuad 7 is done with the CAN bus. The AutoQuad 7 fc is only using power, can bus and the direct connection from the (Graupner HoTT) receiver. The HoTT Telemetry is also run on the PDB.

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AutoQuad 7 flightcontroller Not a lot of connections:) power and CAN bus HoTT telemetry, ESC32 v3 detected

So, now for the configuration. Is is using my HoTT firmware so all telemetry data is send to the HoTT transmitter. The PDB firmware is enhanced to accept CAN messages for the signaling, the ESC32′s telemetry and pwm signal passthrough. That is needed so the flightcontroller can use the CAN bus to control LEDS and the gimbal tilt/pitch/roll.
The Quatos adaptive controller is using the custom profile from this X8 so it nows its inertia momentum and geometric configuration. A lot os tuning wend into it but after that is is only an 4 param dial instead of the numerous possibilities of an PID controller.

Maiden flight. For the maiden I needed to test the redundancy and the firmware was temporary changed to allow shutdown motors in flight.

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All up weight with 4S6200mAh
and gopro+gimbal 2343gram

For the motors a custom made PDB was made for the leds and easy wiring to the motors.

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First flight.

Well, simply said: Uneventful. Everything worked as designed, redundancy test showed good recovery even with 2 motors out. With a 3rd motor it suffered from altitude loss but that was to be expected. A lot of firmware changes are still needed to allow more control via the CAN bus but for now it behaves like all components are directly attached to the flightcontroller while the only connection in fact is the two wire CAN bus.

The X8 is designed to carry a bigger gimbal with a large compact camera. The gi,bal was a good deal on rctimer ($95,-) and as controller the STorM32 opensource controller. Working great!.

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With GoPro gimbal 18 min flighttime With larger gimbal and compact cam All weight up flying 2774 gram / 14min flighttime

 

Features (dec 2014)

  • Superb stability and recovery using Quatos
  • all CAN bus communication, only 2 wires between components
  • full telemetry to the transmitter, transmitter also functions as limited groundstation (setting can be changed and send to flightcontroller)
  • unlimited waypoints
  • voltage, current, capacity used, current/rpm/temperature/duty cycle telemetry per ESC
  • android, OSx, Windows groundstation
  • follow me, fly to using android device with gps
  • gps position hold up to <10 cm accuracy using SKF (scented  kalman filtering) fusion between GPS and IMU sensors
  • GPS raw data output for diagnostics
  • geofence and ceiling for safety (can be enabled or disabled)
  • waypoint recording in flight or using android app.
  • waypoint can be stored on internal uSD, on android app or ground station