One big change we’ve made this version is the addition of some advanced control code to the blades, to help you build helicopters and quad copters that work like the real thing.
This blog will help you understand what the new functionality does and how you can use it.
Advanced Blade Controls
When you enable Pitch/Yaw/Roll control on a rotating blade now, the blades themselves will make a decision on whether the blade needs to be in cyclic or collective mode - on a per axis basis.
Image 1: Blade COM alignment
For this craft above, the blades are aligned with the center of mass in the forward direction - so they’ll use cyclic mode for pitch. They’re far apart horizontally, so they’ll use collective mode for roll. And because their axis of rotation is flat, they won’t attempt to provide any control input in yaw.
Cyclic mode: Cyclic mode is what a normal helicopter’s main rotor does to control the pitch and roll of the helicopter. They will change their pitch - by the limits you set in the authority limiter control of the blade - as they spin around. This creates more or less lift to one side or the other of the blade’s disc of rotation.
Image 2: Cyclic Mode Pitch
Collective mode: Collective mode is what a normal helicopter does when it wants to change how much overall lift is created. But as you can see in the picture below, adjusting the relative lift on the two different sets of rotors will cause the craft to roll.
Image 3: Collective Mode Roll
Summary and Videos:
So that’s what our blades now do in a nutshell. However, understanding these topics can be pretty complicated. I really recommend checking out some of these excellent Youtube videos for further study.
Smarter Everyday’s series on Helicopters - Dustin’s videos are fantastic, and these are no different:
Craft Building Tips:
Here are a few tips to help you build your helicopters/quad-copters/etc.
- Make sure to set your authority limiter pretty low. One of the potential trouble spots you can have is if the blade pitches too much trying to generate control - if it goes OVER the stall limit and starts generating less lift, you’ll get the opposite of what you wanted. 2 or 3 degrees will often be enough.
- Helicopters can be finicky to control. Even if you’ve got everything right, any change in a helicopters forward or vertical motion affects the lift on the blades, which generate input coupling. If flying a plane is like driving a car, then flying a helicopter is like riding a unicycle - don’t be surprised if you have to constantly adjust inputs.
- Chinook-style craft will generate interesting and unpredictable effects due to axis coupling effects. If you want to build a really stable Chinook style craft, consider looking into how those are actually built - they adjust their whole rotor assembly plane of rotation, rather than just using cyclic/collective. http://www.chinook-helicopter.com/standards/Army_D_Model_AQC_Classes/Flight_Controls.pdf
- The blade controls will work well for using a tail rotor, blades rotating in any axis will respond appropriately. That said - it’s still easier to manage a helicopter with two counter rotating blades.
Finally - if you decide none of this is for you and you just want a helicopter without worrying about the physics so much, feel free to just turn off the Pitch/Yaw/Roll blade controls, and use a reaction wheel to generate the torque you want - no one on the dev team will accuse you of cheating, we promise!