Foamboard Tail Sitter
I was thrilled to find this thread! The firmware seems to be moving forward very quickly and it’s exciting to see that there are people flying various configurations.
In hopes of making things more approachable to others, here’s quick rundown of how I put together a dual fixed-motor out of foam-board that seems to be fairly manageable in hovering and forward flight modes on the default parameter values. I’ll be very grateful for your corrections and feedback, especially regarding the log file analysis for tuning.
All the files mentioned below (airframe plans, parameters, log files, photos, and videos) are in this Dropbox directory:
Inspired by @ag-sys in this post (http://discuss.ardupilot.org/t/dual-motor-tailsitters/15302/292), I started with a FliteTest Spear and added dual motor pods. The Spear has plenty of space in side the fuselage for electronics and battery, bringing the vertical location of the CG into good alignment with the motors.
Motors from FliteTest Power Pack D
Left : CCW
Battery: 3s 2200mAh
Takeoff weight is 835 grams.
Wiring for Pixhawk1, HolyBro version
All external module connections as normal. No airspeed sensor.
Output 1: ESC Right
Output 2: ESC Left
Output 5: Elevon Right
Output 6: Elevon Left
Place aircraft in fixed wing flight orientation.
Install firmware ArduPlane V3.8.0beta5
Setup Accel, Compass, Radio as normal
Q_ENABLE=1 (was default value)
Q_TAILSIT_INPUT = 0 (was default value)
Write and refresh parameters
ELEVON_OUTPUT=3 (frame specific)
Reverse pitch axis with checkbox in Mission Planner > Radio Cal. (Not sure what parameter this flips.)
SERVO1_FUNCTION=74 (right motor)
SERVO2_FUNCTION=73 (left motor)
SERVO5_FUNCTION=4 (right elevon)
SERVO6_FUNCTION=19 (left elevon)
FLTMODE_CH = 5 (your preference, using 3-position switch)
FLTMODE1 = 17 (QSTABILIZE)
FLTMODE4 = 18: (QHOVER)
FLTMODE6 = 5 (FBWA)
Save parameter file (TS1-V7.param)
ARMING_CHECK = 0 (Disabled for testing)
ARMING_RUDDER = 2 (your preference)
Check for reasonable output
Upon boot, right aileron sometimes goes full down for 2-5 seconds, then returns to neutral.
Mode: FBWA, lay plane on it’s belly
Control surfs: yes
Motors: Disarmed, nothing. Armed with zero throttle, nothing. Armed with throttle, normal throttle response. No differential throttle.
Mode: QSTABILIZE, stand plane on tail
Control surfs: upon pressing safety button, deflect a bit, then stabilize. Sometimes wind up over time and sit against stops. Respond to sticks. Respond to picking up and moving aircraft around each axis.
Motors: Disarmed, nothing. Armed with zero throttle, nothing. Armed with throttle, normal throttle response. Motors spinning, pick up and move aircraft, differential response as expected.
Investigate QSTABILIZE arming motor behavior. Default values
Increased these to 0.2 and 0.25. Motors still don’t spin upon arming. Returned to default values.
ARMING_CHECKS = 1
FLTMODE6 = 19 (QLOITER)
- Should motors spin upon arming?
- Question: Does the output number matter, if the correct SERVO#_FUNCTION value is assigned?
- Why does right aileron go full down on boot? Maybe choose another output channel?
This is pretty long, so I’ll post the testing notes separately.