Fixed Pitch RC Helicopters Explained-固定螺距直升机原理

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原文内容链接：http://www.rctoys.com/pr/2008/04/18/learn-about-fixed-pitch-rc-helicopters/

Fixed Pitch RC Helicopters Explained
固定螺距直升机原理



All RC helicopters need a way to control their altitude and direction. In most cases, this is accomplished by altering the angle (pitch) of each rotor blade. The resulting change in airflow from the blades causes the RC helicopter to move in the desired direction. Changing the pitch of the rotors provides very fine control. There are ways that an RC helicopter can be built that eliminate the need for pitch control. These fixed pitch RC helicopters are a great way to start flying rc helicopters, because of their simplified controls and low cost. In this article we will look at how they work, and see some good examples of this design in actual RC helis.

所有遥控直升机都需要一种方法控制他们的高度和方向，绝大多数是通过改变每个旋翼的角度(螺距)实现，改变了旋翼升力控制飞行的方向。改变旋翼的螺距是非常好的控制方法。还有一些没有使用改变螺距的来控制，这些固定螺距的直升机是非常好的入门机。因为他们控制简单，飞行成本低。这里我们将了解他们的工作原理，有一些很好的设计范例。

How Fixed Pitch RC Helis Work
固定螺距直升机原理

In order to understand how fixed pitch RC helicopters work, it is useful to consider a fixed wing aircraft. Airplanes can fly because air moves over the wings, resulting in a difference in air pressure between the top and bottom, which causes lift. To increase the lift we can do one of two things. The speed of the air moving over the wings can be increased, or the curve of the wing can be made steeper. If we think of the rotors on a RC helicopter like the wings on a plane, the easiest way to increase lift is to cause them to spin faster. This will send the helicopter upwards. When the helicopter needs to descend the rotor speed is decreased.

为了理解固定螺距直升机的原理，思考一下固定翼飞机的原理会有帮助。飞机能够飞行是因为机翼相对于气流的运动，形成机翼上下不同的压力差产生的升力。我们使用2种方法中的1个都可以增加升力。提高机翼与气流的相对速度，或者增加机翼的弯度使其更陡峭。如果我们把直升机的旋翼看作是飞机的机翼，那么最简单的增加升力的方法是提高旋翼的旋转速度。这使直升机上升，当要下降时，减低旋翼的转速。


Quad Rotor RC Helicopter Design
4旋翼直升机




Some RC helicopters are built using four main rotors, each mounted at a right angle to the aircraft. This design allows four channel control, without the complexity of variable pitch. A flight computer can read the input from a radio receiver and then change the speed of each motor accordingly. Using a flight computer also allows automatic stabilization of the helicopter. The flight computer is a sophisticated circuit board, which is capable of changing the motion of the helicopter under different conditions. This makes quad rotor helicopters perfect for aerial video and surveillance. The Draganflyer helicopters use this design, and are available in several different models.

有些遥控模型直升机使用4个主旋翼，每个成直角安装在飞机上。这样的设计允许使用4个通道控制，没有复杂的可变螺距结构。一个飞行电脑(飞控系统)接受来自接收机的信号，然后相应地改变每一个马达的转速(旋翼的转速)。飞控系统也可以自动控制直升机的稳定。飞控系统是复杂的电路系统，能够在各种状态下可控制直升机的动作。这使4旋翼直升机非常适合航拍和空中监视。

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Conventional RC Helicopter Design
传统设计的遥控直升机



There are two ways in which a fixed pitch RC helicopters direction of travel can be changed . If we include a rear rotor, which is mounted at a right angle to the fuselage (body of the helicopter), we can use it to push the helicopters nose in the desired direction. Our Mini Bell Helicopters are a good example of this design, and are able to be built to very small dimensions because of the reduced complexity.

有2种方法改变固定螺距直升机的飞行方向。如果有一个尾马达，垂直安装于机身，我们看能够用他来推动机头到要求的方向。

Coaxial RC Helicopter Design
共轴直升机


We can also use two main rotors, each linked to a separate motor to turn the helicopter. By spinning each rotor at a different rate, the yaw (direction) of the helicopter can be controlled. Our Bladerunner Series and Lama V4 R/C helicopters use this fixed pitch coaxial design. Each rotor can be placed on the same axial. This reduces the size of the helicopter, so that they can be flown indoors. Learn more about coaxial helicopters.

我们也可以用2个主旋翼，每个旋翼有独立的马达驱动。每个主旋翼在不同的旋转速率下，可以控制直升机的旋转(方向)。




Another benefit of the fixed pitch coaxial design is that it frees an extra channel of control. If we don’t need to control the direction (pitch or yaw, depending on application) of the RC helicopter with the tail rotor, we can mount it in the same direction as the main rotor blades, allowing pitch control. This design is found in our Micro Mosquito RC helicopter, where two main rotors are complemented by a tail rotor.

这个设计另外一个好处是可以省下一个额外的通道。如果我们不需要控制俯仰或者旋转(根据应用需要)，我们可以把尾电机固定在和主旋翼一样的方向上，当作主旋翼。