地面效应和起飞不平稳的问题

Bitcraze圣诞之前将crazyflie2.0的制作流程共享在官网上，并且配有视频，真是很赞；参考网址：
https://www.bitcraze.io/getting-started-with-the-crazyflie-2-0/
很多内容之前已经有了，这里列出来一些值得记录的内容：

normal flight

When thrusting without touching any other controls, this is what it might look like. The Crazyflie usually drifts in some direction
if not compensated for, that is completely normal.

这里大概在讲在飞行器刚开始升起的时候，遥控器上的Roll，Pitch和Yaw不要动，我们只要提供推力（thrust），官网有相关视频参考；blob:https%3A//vine.co/8cdc6fce-358a-4085-a024-82b0fd7af6cc；如果在Roll和Pitch上做矫正，那Crazyflie通常会在某些方向上漂移；这很正常。如果无法忍受这种漂移，可以在PC
client的Trim框里面调整为非零的值，再尝试飞下，直到不会漂移为止。

地面效应the ground effect

When the copter is flying close to the ground (less than a few decimeters above the ground) it is effected by what is called
the ground effect. The feeling is that the air is slippery, almost as if it is gliding on ice. To avoid this, particularly when learning to fly, use a lot of thrust just when taking off and then ease off for level flight.

当飞行器离地面很近的时候（高于地面在几分米左右），会受到地面的影响，暂且叫做地面效应；感觉像是空气非常的润滑，仿佛滑在冰上。为了避免这种现象，特别是当学习飞行的时候，刚开始起飞要用大量的推力，也就是一开始就加大油门（但是别过猛了），等快速离开地面之后，将推力慢慢收回来，只要能抵抗重力，平稳飞行就可以了。

这点相信刚开始飞的人都有这种感觉，我第一次飞也不敢加大油门，受到地面影响特别不容易垂直飞起来，百分之八九十都会偏向某个方向，如果你推力还是很小，就会不停的漂，索性我们刚开始把推力加大，飞起来之后就不会存在这种问题；如果还是漂移那证明你电池或者某个方向重量上不均匀导致的。

if the Crazyflie is unbalanced

If your Crazyflie drifts a lot when taking off, there are two thing you should check.
Make sure the battery is centerd. If it has slipped too far to either side, the Crazyflie might have a hard time compensating for it.
Check that the propelles are spinning freely. Blow lightly on them, one by one, and verify that they turn. A a common problem is that hair is jammed between the propeller and motor. If this is the problem. just pull the propeller
off from the motor, remove the hair and reinstall the propeller.

当起飞的时候，如果Crazyflie不平衡，两件事情需要检查：
（1）确保电池放在飞行器中心位置，如果重量过于偏向某个方向，Crazyflie利用对应电机提升转速来提高推力弥补是很困难的

（2）检查螺旋桨是不是平衡的。