I think I might have missed something whilst reading this long thread since last time I posted here.
Does your aircraft use differential front motor winkel for yaw control, or do you still use an extra rear rotor with tilt servo for yaw control in hover?
I was thinking (maybe hoping?) you were using differential tilt to control hover yaw, as that is what I need to do.
Eventually I’d like to add wings, however, to get there will require a functional control system with differential yaw in hover, which we’re trying to develop on a tilt-tricopter separate from the wing components. The reason for this is it’s possible the wings could become “optional” ie the same vehicle could fly with and without wings.
There’s a couple of things we’re trying to “hybridize” into the design. Things like optimizing forward prop pitch on the tilt motors whilst optimizing and increasing the size of the static tail rotor for hover, to the point that some 70-80% of lift comes from the rear rotor in hover. Then there’s some expected gyrocopter effects in transition between hover and forward cruise that we want to take advantage of as well. All whilst reducing the required wing area to the absolute minimum to sustain forward flight in cruise. (and by only using 3 motors and two servo’s all together to do so, for both hover and forward flight)
I really like your progress so far, and have been meaning to post here again for some time. I might have to give your idea a go using Arducopter…wouldn’t be the first time I’ve used that to go forwards without pitching it forwards. It actually was part of my first attempt at quadplanes in 2014, where I used a small hexacopter with a pusher prop on the rear. It hovered with about 14A, but flew forwards at +90kmh on 18A using the pusher prop because the hover props autorotated in flight and produced lift. Was fun, like driving an airborne hovercraft in alt hold, to turn you’d yaw and throttle up until you got the desired rate of turn…no banking required.
I’m working on changes to avoid the need for that, so we control yaw in hover by differential tilt of the front motors. That is needed for the eflite convergence, but also makes sense for any tilt-tri-quadplane as it saves you a servo output and makes the rear motor mount simpler.
The only real downside is you need to be able to go past vertical on the tilt of the motors, or you will tend to drift forward in hover.
Cheers, Tridge
Can Arducopter be configured for a reverse Y6 such as two motors on the front of the aircraft and the other four to the rear. If so, how would that be configured? Thanks for all your effort!
I was hoping you were going to say that! That would be great!
Can you also have a look at my previous post further above addressed to you regarding setup and keeping the rear hover motor continuously on whilst tilting the other two forwards? Thx.
@Tridge
Clockwise from which point of view ? The pictures of copter-wiki suggests from above. If cw/ccw means cw/ccw seen from above we have this situation:
Increasing power on front right motor leads to roll-feedback in direction of the red arrow - the wrong way round ? In this case we have to change the front motor direction
We will probably design a new tilt mechanism for vectored yaw… So we can fly without the rear tiltservo.
.
Today we was happy with your improvements of the forwardtransition: Perfect- thanks a lot
Roughly how much rearwards tilt angle do you need from vertical on the tiltrotors for effective yaw control? From the video yaw control authority looks really good.
Is it possible to fly in reverse in hover?
If I have a tiltrotor tricopter without any wings; how do I make the rear hover motor remain on throughout the flight, even in forward flight, and is there currently a way to limit the tilt motor forward angle, so it produces a minimum in hover lift?
(Note our intention is to have wings eventually, but we’d like to configure the copter etc first and experiment how much wing is required to maintain forward cruise winged flight)
I don’t know if this will work at all, but you could try setting the SERVOn_MIN/MAX values to prevent the motors moving all the way forward, and then set Q_TILT_MAX=90 and set Q_ASSIST_SPEED=100.
I haven’t tried it though.
A quick note on how to configure tilt-quadplanes with vectored yaw.
The two key parameters are:
Q_TILT_TYPE=2
Q_TILT_YAW_ANGLE=10
The Q_TILT_TYPE=2 means that you have a tilt rotor that uses motor tilt for yaw (ie. vectored yaw).
The Q_TILT_YAW_ANGLE is the angle in degrees that the tilt motors are tilted back when at their full up value (as set with SERVOn_MIN or SERVO_n_MAX if the servo is reversed).
For my convergence I set Q_TILT_YAW_ANGLE=10 as the motors tilt back about 10 degrees when fully up. This parameter allows the code to work out what PWM value to use for the motors to be straight up, and also to work out what range of movement to use in controlling yaw when hovering.
The only other unique setup for this type of vehicle is you need to tell ArduPilot which servo output controls tilt of the left motor, and which controls tilt of the right motor. The SERVOn_FUNCTION for left motor tilt is 75 and for right motor tilt it is 76.
So I have:
SERVO3_FUNCTION 75
SERVO3_MAX 2050
SERVO3_MIN 1000
SERVO3_REVERSED 0
and
SERVO4_FUNCTION 76
SERVO4_MAX 2000
SERVO4_MIN 950
SERVO4_REVERSED 1
that sets up the aircraft so that servo output 3 is the left motor tilt, and servo output 4 is the right motor tilt. The MIN/MAX values and have been adjusted to point the motors straight forward in manual, and so they are centred on being straight up in QSTABILIZE mode. Notice that for the convergence the right motor tilt is reversed (which is why SERVO4_REVERSED is 1).
Another note on the EFlite Convergence. The wires going into the ESCs can be very confusing. It uses reasonably thick 3 wire cables, which correspond to power, ground and signal (signal as PWM). The colours are very confusing though, and there is a hidden connector inside the wing cavity which on my plane swapped colours. So white went in on the fuselage side, but it emerged as black at the ESC. It is really baffling when setting it up until you pull out the wire and see there is the hidden connector inside the wing cavity which swaps the colours.
Make sure you trace the connections carefully with a multimeter.
When we discovered this we wondered if the people in the factory were just trying to confuse DIY people
Could vector control of the front motors be used not only for yaw but also for forward flight ? This could reduce battery consumption:
It costs a lot of power to fight nose down against the wind due to downforce on the wings. Here is an example, as at 15 kph headwind the climbing ability decreased to zero and current inreased significantly. I then let the VTOL drift backwards with the wind and was thus able to win a safe height for forwardtransition.
Especially at the end of the flight with an almost empty battery vector control could save time (and batterycapacity) while exact reaching the desired landingpoint in windy conditions. We ask from expirience at the end of today’s flight (Backtransition at 09:05)
yes, that’s a good idea. It could be linked to Q_VFWD_GAIN. The question is really what angle limit to apply to retain stability. Maybe just Q_TILT_MAX ?
I can try it on the convergence and see how it goes.
Thanks for the suggestion!