Here are some suggestions how to setup Pixhawk to work with FBL-systems like VBar, Microbeast, GT5.2, etc.
Arducopter Heli Version 3.3.3
Tip: calibration of accelerometer is much easier before you put the Pixhawk in the helicopter.
WARNING !!! Remove blades or pinion or motor wires NOW.
Insert the Pixhawk between RX and FBL. RC1 = aileron, RC2 = elevator, RC3 = collective pitch, RC4 = rudder, RC8 = ESC, RSC, throttle
If necessary change the TX output (channel number, servo direction) to achieve the correct movements in Radio Calibration. TX must send 100% on each channel, trim at 0.
In Radio Calibration make sure the bars move with your stick left and right for aileron and rudder.
The collective pitch is called throttle and should correspond to your stick movement as well.
The elevator must go down (lower numbers) for helicopter nose down stick movement and must go up (higher numbers) for nose up stick movement.
WARNING !!! MissionPlanner tries to help you and changes your input to the recommended minimum or maximum value. Unfortunately These values are most of the time for multicopters and not for helicopters. Therefore it is recommended to use Full Parameters List/Tree, Write and Refresh commands to check if the value is what YOU want.
http://ardupilot.org/copter/docs/parameters.html
H_FLYBAR_MODE = 1
H_SWASH_TYPE = 1
H_TAIL_TYPE = 1
ACRO_TRAINER = 0 (this gives the FBL-unit full control in ACRO mode)
H_SV1_POS = 90 (aileron)
H_SV2_POS = 0 (elevator)
H_SV3_POS = 180 (collective pitch)
HS(1,2,3,4)_TRIM = 1500 (adjust as needed to trim the input of your FBL to center,
DO NOT trim the swash plate !
Any trim of the swash plate must be done in the FBL-unit !)
The Pixhawk should act now similar to a RX, Main Out 1 = aileron, Main Out 2 = elevator, Main Out 3 = collective pitch,
Main Out 4 = rudder, Main Out 8 = ESC for H_RSC_MODE = 1
These Main Out signals are the input for FBL-units that understand Standard RX. Some newer FBL-units only read ‘Singlewire’ signals.
For these FBL-units you can provide SBUS signals from the Pixhawk SBUS port.
If you use SBUS, set BRD_SBUS_OUT = 1 (or higher ?) and RSSI_PIN = 103 (needs power cycle) to get SBUS signal from Pixhawk to FBL-unit.
In your FBL-unit you must be able to make channel assignment. For standard input you switch wires until it fits, for SBUS input you need to set it with the software of your FBL-unit (check manual before you buy it).
Once the channels are assigned you need to scale the amount of input for your FBL-unit either by doing it with the software of your FBL-unit or by controlling output of Pixhawk.
H_CYC_MAX = 4500 (this is your aileron + elevator input to the FBL-unit, you can adjust this to limit the output to your FBL-unit)
H_COL_MAX = 1900, H_COL_MIN = 1100 (this is your collective pitch input into the FBL-unit, you can adjust this to limit the output to your FBL-unit)
Check the input channels of your FBL-unit to show the correct direction of aileron, elevator, collective pitch and rudder.
Adjust as needed using HS1/2/3/4_REV = 1 / -1 (1 or -1 to change direction)
DO NOT use the TX to reverse servo direction !
All trim settings must be done in the FBL-unit, disable trim on your TX !!!
The Expo settings on your FBL-unit should be 0, use your TX to set Expo because this is for your fingers, Pixhawk needs linear response.
Check rudder and swash movement (collective, aileron, elevator) and adjust as needed using your FBL-unit. Basically do a FBL-unit Setup according to the manual (just as you would without the Pixhawk and a RX instead).
You must not have two control Loops - as you have the FBL-unit, you must disable the Pixhawk PID loop.
RATE_PIT_P/I/D = 0, RATE_RLL_P/I/D = 0, RATE_YAW_P/I/D = 0 … we have external FBL, therefore everything 0
RATE_PIT_FF = 0.05, RATE_RLL_FF = 0.05, RATE_YAW_FF = 0.05 … we want manual input in Stabilize etc., adjust to your taste 0.05 - 0.25 should be o.k… Check for similar stick reactions in Acro and Stabilize mode !
ACCEL_Z_P = 0.3 (adjust as needed, many helicopters oscillate on collective using standard value 0.5)
H_LAND_COL_MIN = 300 (adjust to your taste, should give you about 3°-4° negative collective using symmetrical blades. If the H_LAND_COL_MIN is set too high, such that the helicopter cannot descend at the target landing rate, then it will think it has landed and might disarm in the air.)
Edit read: http://discuss.ardupilot.org/t/novaerial-robotics-ac3-4-heli-review-and-issues-list/13485/6
DISARM_DELAY = 0 (only if you can’t arm because after arming software disarms and other settings don’t work, otherwise keep this safety feature)
RC1,2,3,4_DZ = 5 (if your TX is good and you like small inputs), RC_SPEED = 125(?), RC_FEEL_RP = 50 (adjust to your taste)
WARNING !!! Remove blades or pinion or motor wires NOW.
Check FAIL SAFE, what happens with TX off, what happens with RX off and Pixhawk on (no connection Pixhawk to RX), what happens if you loose connection Pixhawk to FBL-unit, etc.
SBUS sends Failsafe flag, PPM input is usually best handled using OFF (no signal) in the fail safe settings of the RX. Walk with your heli around (away from home) to see RTL or LAND servo movements etc.
Check stick movements before EVERY flight !
Check ACRO mode FBL correction direction before EVERY flight !
Check STABILIZE mode correction direction before EVERY flight !